Since 1970 The Center for Industrial Research and Norwave in Oslo have been heavily engaged in research in wave physics. This work includes projects in Computer holography Seismic holography and Holographic lenses for acoustical cameras. The largest of the " wave projects" however is devoted to the extraction of useful energy from ocean waves. This work has been concentrated around the development of two new pieces of hardware. The first is a holographic lens for focusing ocean waves. The second is a horn-shaped chute for collection of water wave energy. In both cases the pieces of hardware are small compared to the wavelength. This fact invalidates many of the approximations that are in routine use in design and evaluation in optical work. The lecture will concentrate on a visual presentation on how these pieces work in practise. I will also try to point out where the techniques may be of utility for other wave phenomena. ARE WATER WAVES WAVES? The question posed in the heading is not stupid since as we shall see the flow is governed by Laplace''s equation which is an elliptic rather than a hyperbolic differential equation. We start out with a presentation of the governing equations for an inviscid irrotational and incompressible liquid with a free surface (the ocean). The flow inside the water is described by means of a velocity potential 4(x while the surface elevation given by i(x t). The depth is h(x atz 1. 2 + (V4) +g 0 at z 2. V2c0 3. ah4 aha4 atz 4. Physical quantities are derived from the potential via the following equations: v 5. 1 2 P Po+ (V4) +gz)p -h 6. 2 / SPIE Vol. 1319 Optics in Complex Systems (1990)
We describe an optical method for obtaining inregister incoherent superposition of 2D diffraction patterns in all the planes parallels to the exit pupil. This means that the consonance is independent of the plane of detection. 1 . DISCUSSION If we illuminate with a point source a screen with an aplitud transmittance propor tional to the Montgomery rings'' then its Fraunhofer diffraction pattern will appear pen dicaly along the optical axis2 . A second incoherent point source illuminating the same screen on axis but in a different position will produce another set of self images. Is easy to show that if its position fits with one of the self images of the first point source then both sets are in consonance. Exactly the same procedure can be applied to a third source a fourth source an so on. More over not only the self images are in con sonance but all the diffraction patterns associated with the screen. This means that there are different position for a point source along the axis that produces exactly the same diffraction field of these screen. If we multiply the Montgomery ring by a second amplitud screen then the resultant pat tern will exhibits the same behavior. We call Montgomery patterns to the diffraction pat terns produced in both cases. In this sense if we choose one of those screens (Montgome ry rings x amplitud screen)
Resolution substantially greater than conventional diffraction limits can be achieved by spacing the diffracting and receiving planes by a few wave lengths. An optical encoder exploiting this fact was successfully manufactured thus highlighting possibilities for other practical systems and devices.
Author(s): Jun Uozumi; Hiroyuki Kimura; Toshimitsu Asakura
Since the introduction of the concept of fractal by Mandelbrot1, diffraction phenomena
by fractal objects have attracted several researchers26. Some of them have treated
the diffraction from random phase screens with fractal properties24. Others have discussed
the diffraction by simple regular fractals. In a recent paper7, we reported the
Fraunhofer diffraction by Koch curves which are more complicated fractals in the sense
that they may contain a rotational operation in their generation. In this paper, we discuss
the dimensionality of regular Koch curves and their diffraction patterns, and extend
the discussion to the randomized Koch curves and their diffraction patterns.
The properties of complex systems of integrated optics
depend mainly on the nearfields of the components,
if their distances are less than a few wavelengths.
For field-calculations the Kirchhoff and the
Rayleigh-Sommerfeld diffraction theories may be
applied also to phase objects. Usually these are assumed
to be "thin" ; then in the "object plane" the
incident wave may be multiplied with the complex
object transmittance (Kirchhoff's boundary conditions).
But, in general, this approximation leads to
deviations; these are investigated for small phase
objects (n-i << 1, Ac < 20°) of finite thickness.
In the earlier work, Wolf has presented a new version of coherence theory that
based on ensemble averages of modal components of field. Its use allows the coherence properties of partilly coherent light to be defined, understood and. studied
with ease an a clear un&eratanding of physical processes involved. In this paper,
we apply Wolf's coherence theory to represent the propagation of partially coherent
beams through first-order optical system that ray matrix is...
Formulae and computer programs were developed for surface contributions to high order aberrations coefficients using the Aldis theorem and Andersen algor ithms for a symmetr ical optical system. 2. THEORY Using the algorithms developed by T. B. Andersent which allow to calculate the high order aberrations coefficients of an optical system. We were able to obtain a set of equations for the contributions of each surface of a centered optical system to such aberration coefficiets by using the equations of Andersen and the so called Aldis theorem 3. COMPUTER PROGRAMS AND EXAMPLES. The study for the case of an object at infinite has been completed and more recently the object to finite distance case has been also finished . The equations have been properly programed for the two above mentioned situations . Some typical designs of optical systems will be presented and some advantages and disadvantages of the developed formulae and method will be discussed. 4. CONCLUSIONS The algorithm developed by Anderson has a compact notation and structure which is suitable for computers. Using those results obtained by Anderson together with the Aldis theorem a set of equations were derived and programmed for the surface contributions of a centered optical system to high order aberrations. 5. REFERENCES 1. T . B. Andersen App 1. Opt. 3800 (1980) 2. A. Cox A system of Optical Design Focal Press 1964 18 / SPIE
Generalized methods for efficiently calculating Fraunhofer diffraction intensity
fields resulting from diffraction through complex two-dimensional apertures, with complex
aperture functions, have been recently developed by this author (Ref. 1) which are based on
nine-node bi-quadratic isoparametric finite elements (Ref. 2) and on Fourier and
In this contribution quantum-effects in the radiation-atom interaction will be reviewed. It is well known that most of the phenomena involving laser light can be described by semi-classical methods however phenomena such as laser noise the spectra and photon statistics of resonance fluorescence and the interaction of atoms in the single-atom maser require a quantization of the radiation field. In this paper we will describe results on the latter two effects. We will start with the discussion of resonance fluorescence. 1. RESONANCE FLUORESCENCE The resonant interaction of laser light with atomic systems has received considerable theoretical and experimental attention over the past decade. Until the advent of the laser light sources for spectroscopy consisted of ordinary spectral lamps excited by DC or RF discharges and produced light having a very broad spectral width and hence very short correlation time and a relatively low intensity. For such fields both the experimental and theoretical results are in general well understood. However the development of the laser made available light sources which are sufficiently intense that an atomic (or molecular) transition can be very easily saturated. In addition the lasers are highly monochromatic having a coherence time much greater than typical natural lifetimes of excited atomic states and finally tunable making it possible to selectively excite particular atomic transitions. The theoretical analysis of this physical situation requires the use of techniques more general than
Recently the statistical properties of the third-order nonlinear
dissipative oscillator have been determined exactly to an approximation
respecting non-zero reservoir temperatures for a most general input state.1 Later the assumption of zero-'temperature heat bath has been removed,
but the initial coherent state has been considered. In this coinmunication we present the statistical characteristics of the third-order non
linear dissipative oscillator responsive to the requirements of quantum
optics and established without any restrictions on the initial state.
Author(s): Ziaohu Zhang; Xiping Zheng; Xiaoping Yang
The Photonnusber eigenstate (PNE state) generated in a oneatos sphoton sicrolaser systes via the atosic seasuresent for the outofresonance case is shown. The effect of detuning on the probability of obtaining state after having k atoss passed the cavity is discussed. THEORY A beau of lowdensity twolevel atoss is injected into ahighQ cavity at such a low rate that at lost one atos at a t lie is present inside the cay i ty. The cavi ty loss is negi igible. Consider a twolevel atos interacting with a singlesode field via the iphoton transition for the near ly resonant case. The effect i ye Has i lton ian for th is systes in the RWA is Hf cact + q/2)+i1 A q/2+t1g( a'' cy. . Q" ( 1) where L(. )i() is the detuning and ''fi is the energy difference between the two levels of atos g is the iphoton transition atosfield coupling constant Q and *'' are the annihilation and creation operators of the field and ca is the frequency of field a3 and a. are the Pauli spin operators. Assuse that the field is in PNE state at a tue t1 in which the ith excited atol is just going to be injected. r is the tile for the ith atoi to pass through the cavity. The density operator p (t+t ) is p (t+t )U( i: ) p
An approximate analysis of the relaxation oscillations in Fabry Perot laser cavities is presented. A linear smallsignal perturbation solution of the coupled laser rate equations is generalized by including transverse1 as well longitudinal field dependence2. By the threshold field approximation3 we obtain an expression relating the frequency 0 and damping rate X of the relaxation oscillations to the laser parameters such as steadystate output power P0/Pq normaliezed to the saturation power P distributed losses a L'' poin losses at the mirrors a1 and a arbitrary relectivities o the mirrors r1 and r2 spontaneous liftime ''r of the active medium and geometry o the resonator. 2. THEORY The couppled laser rate equations for single mode can be written in the following form dN I(r) N N dQ I(r) N Q --- ---- (1) dt I ''r #r dt I -r 5 S Q where N denotes the inversion density I (r) describes the total intensity of the nmth laser mode in the cavity I is the saturation in tensity p is the exatation rate Q denotes the number of the photons in the nmth laser mode and ''r is the cavity lifetime. An approximate expressions for the spatial dependence of the electric fields for the forward and backward amplitudes of the nmth laser mode in our approach can be written as R AUR(t) f(x e''TZ S A(r) f(x
Many applications of high-power semiconductor lasers require a highly stable, single-mode, nearly diffractionlimited
output beam. However, most existing devices tend to oscillate in several lateral modes. In the case of
phased-array lasers, high-order supermodes with twin-lobed far-fields are usually dominant. Even when single-lobed
operation is obtained, the far field is often much broader than the diffraction limit.
For application in coherent free-space optical communication a high-power (500mW) singIe-frequency diode-laser-pumped Nd:YAG laser has been developed. By active frequency stabilisation a linewidth of less then 10 kHz has been achieved. L EXPERIMENTS A twisted-mode (TMC) technique1''2 has been applied to obtain a high-power singlefrequency laser radiation at 1. 064 zm wavelength3''4 . The output power of 500 mW was only limited by the available diode-laser pump power. The linewidth of the free-running TMC-Nd:YAG-Iaser was about 100 kHz. Three different frequency stabilisation schemes have been applied to the TMC-laser to get a better frequency stability. By frequency offset locking of the TMC-laser to a frequency stable low-power reference laser5 a heterodyne linewidth of less than 10 kHz could be achieved. The excellent spectral properties of the reference laser were transferred to the high-power laser. By a heterodyne technique with a second low-power laser a optical communication DPSK system of 565 Mbit/s could be demonstrated. By locking the TMClaser to an external ultrastable cavity a linidth in the subkilo hertz region can be achieved6''7. This frequency-stable laser has been taken as a masteroscillator for a 18 W single-frequency Nd:YAG-laser which should be used to measure gravitational waves by interferometry. Locking to a molecular resonance line leads to an absolute frequency reference laser. To get data about Cesium lines high-resolution measurements have been made in comparison to Iodine lines which were measured by
Exact methods derived from Maxwell equations and based on 4X4 matrix algebra for studing stratified homogeneous uniaxial media are used to analyze tilted birefringent filters when they operate as intracavity wavelength selectors. The transmission spectrum and the tuning curves of different tilt angles are obtained. A detailed analysis of the " Brewster''s angle" effect is also presented. Spectroscopy devices such as gratings Fabry-Perot birefringents filters etc. have proved to be suitable for continuously varying the wavelength in dye-laser cavities. A theoretical and experimental analysis ofFabry-Perot type tuning elements has already been made by Bemebeu et al. 1''2 In the present work we show a theoretical study of birefringent filters as tuning elements by analyzing the transmission factor in terms of the wavelength and other parameters characterizing the filter (angle of incidence tune angle thickness refraction indices etc). A birefringent filter usually consists of one or several tilted birefringent plates of crystalline quartz with the optical axis parallel to the surfaces of the plate. Inside the plate the laser beam whose polarization is parallel to the plane of incidence is split into an ordinary and an extraordinary beam with different indices. Since the retardation by the plate is different for the two beams the linear polarization is generally transformed into an elliptical polarization behind the plate so additional losses occur. Only when the optical path difference between the two beams is an
The gain saturation in hollow waveguide lasers is theoretically analyzed for various resonator arrangements. The presented simple formula facilitates the laser designing process. A mode inversion phenomenon is predicted and strong dependence of the gain saturation on the mode structure is observed. 1.
In laser systems where it is impossible or impractical to use
lamps and rod whose effective perimeters are matched, some elements of
construction of cavities using nonimaging optical concentrators can be
used to achieve improved designs in regard to efficiency and pumping uniformity.
Author(s): Alexander V. Churenkov; Stanislav M. Kozel; Vladimir N. Listvin
Recently interest has grown to the physical quantities
fibre-optic sensors in which a micromachined resonator acts
as a sensitive element. This resonator can change the
resonant frequency when acted upon by an outside force.
Energy supply necessary for the resonator excitation and
transfer of information about the outer action are
accomplished by optical fibres, that can be present in the
zone of a higher aggressiveness, strong electromagnetic
interferences atc. The frequency output of such sensors is
easily processed by digital systems and is insensitive to
By feeding back the output intensity of a laser diode interferoater together with
an external modulated light input to the injection current of the laser diode, we have
observed the optical bistability and multistability without using cut-off or saturation
effect of the gain mediin. We have pointed out that optical chaos can be realized
when an appropriate time delay is introduced in the feedback circuit because of the
non-l I near property of the interference signal . 1
In this report, optical bistability, multistability, and chaos in active interferometer
are presented when the system has a delayed feedback . It is shown that the
optical instability occurs at certain corIitions arid this instability is verified to be
The optical Stark-effect consits of a zlift of spectral lines due to the influence of an external electric field that oscillates with some
optical frequency w . If one exposes an oriented molecule to two fields oscillating with frequencies w and 2w a part of the shift
will become dependent on the relative phase of the two external
oscillations. We call this phase dependent shift of spectral lines the
second harmonic Stark-effect. It is liRely that the irreversible changes
that occur in glass optical fibers during the preparation process of
second harmonic generation are related to the second harmonic Stark-
There is an implicit assumption in all of spectroscopy that the relative energy distribution in
the spectrum of radiation which propagates in free space is independent of the location of the
observer, provided that the observer and the source are at rest relative to each other. That this
assumption is not valid, in general, was suggested by the results of an investigation of Mandel111,
carried out almost thirty years ago. Mandel showed that when light beams from two small
correlated sources which have the same normalized spectra are superposed, the normalized
spectrum in the region of superposition will differ, in general, from the normalized spectrum of
each source. More recently it was predicted theoretically2 and confirmed experimentally soon
therwards3 that the normalized spectrum of light produced by an extended source, will, in
general, differ from the normalized source spectrum (assumed to be the same at every source
point); and that it will depend on the location of the point of observation. The spectral changes
were shown to depend on the correlation properties of the source.
Energy conservation laws for statistical wavefields are first reviewed based on the following three models: electromagnetic theory scalar wave theory and radiometiy. These laws apply whether or not the coherence properties of the source generate shifts of spectral lines in the emitted radiation. Some subtleties are then noted which indicate why the spectrum of light is in general not conserved on propagation. We illustrate the results by considering fields produced by planar quasi-homogeneous secondary sources and by spherically symmetric sources of different states of coherence. * Research supported by the Department of Energy under grant # DE-FGO2-9OER 14119. The views expressed in this article do not constitute endorsement by DOE. ** Alsowith The Institute of Optics University of Rochester. SPIE Vol. 1319 Optics in Complex Systems (1990) / 59
In recent years coherent optical techniques have become of growing interest, which require a full three-dimensional analysis
of the encountered light distributions, which often show random fluctuations known as speckle. The geometrical properties
of such speckle fields are usually determined by the intensity autocorrelation function (ACF) or equivalently by its corresponding
counterpart in Fourier-space, the spatial power spectral density (PSD)' . It is well-known that spatial stationarity
of the underlying quantities is only given for monochromatic fully developed gaussian fields in planes transversal to the main
propagation direction. In the more general 3D case, or for non-monochromatic or time-dependent speckle fields (as one
is concerned with for example in vibration analysis, rough surface interferometry and other multi-wavelength techniques)
a straightforward analysis is only possible if at least local stationarity may be assumed. This requires, that the diffusing
object is modelled (at least picewise) as a quasi-homogeneous planar source, for which the object mutual intensity separates
into a product of the macroscopic source intensity distribution and the autocorrelation of its microroughness.
In this paper we consider a completely incoherent, finite sized, quasi-monochromatic polarized
optical source located in an input plane and assume that an arbitrary paraxial optical system,
characterized by a complex ABCD matrix, occupies the space between the primary source and an
observation plane. By using a Huygens-Fresnel integral formulation whose kernel is a function of the
system ABCD matrix elements one can obtain expressions for the complex optical field in the
Author(s): Antonio Ruiz Garcia; M. C. Vazquez; R. Fernandez; M. Alvarez-Claro
In the application of speckle velocimetry to real physical situations in phisics of
fluids (fundamentally, in the PIV mode) several problems arise. The analysis of the information stored in a specklegram only is reasonably available if a automatic method is
carried out. The fundamental problem is however the quantity and quality of such information. The research has followed fundamentally two approach, one in which the principal
task is the automatic adquisition of information from the fringe pattern and other in
which the principal goal is the formation of reasonably good fringe pattern. In this line, two methods, the multiple exposure and the two-step or copy one has been implemented
that show a good performance. There are however certain physical situations in which a
ntmiber of problems arise , between them , the apparition of non regular fringe pattern. The experiment proposed here try to reach a more profund insight into de problem so as a
systematic research about the relation between speckle photography (SP) and holographic
The phase conjugate (PC) mirror system consisting of a rod amplifier and a nonlinear medium is presented and the theoretical analysis of the enhanced PC wave in the system is derived by taking into account of the overlap of the probe and counterpropagating PC wave in the amplifier. In order to examine experimentally the enhanced PC reflectivity in degenerate four wave mixing (DFWM) an amplifier is placed in the probe beam path. Experimental result of maximal R/R 90. 25 is obtained where R and R are PC reflectivities in the absence and presence of the amplifier respectively. The experimental results agree within 5 with the theoretical values. 1. THEORETICAL ANALYSIS Schematic digram of the PC mirror system consisting of an amplifier and a nonlinear medium is shown in Fig. 1. The phase distortion 4 is due to several effects such as inhomogemous pumping stress gain saturation thermal leasing and self-focusing/defocusing in the amplifier. 1 The amplifier is palced near the nonlinear medium so that the changes in phase (4) and gain (g) are negligible during the round trip time. Considering phase conjugation at the nonlinear medium the output signal SA8 over the input probe bA. is expressed as 8A ge+/ (ge14''A) J where R is PC reflectivity of nonlinear medium. There is no phase distortion term in output signal. Thus we obtain the following expression for the signal 6M photons/ 2
Polarization dependence of phase-conjugate reflectivity by degenerate four-wave mixing is clarified theoretically and experimentally in a saturable-dye-doped polymer film. 1. _INTRODUCTLON A dyedoped film in which optically anisotropic saturable dye molecules are rigidly fixed and are randomly oriented has been used as a nonlinear material which can generate a phase-conjugate (PC) wave by degenerate four-wave mixing13 (DFWM). Such a film can generate a PC wave which has the same polarization state as the probe wave even for a probe wave orthogonally polarized to two pump waves. Tompkin et. al. 4 showed that in such a phase conjugator the nearly perfect vectorial phase conjugation can be obtained at the pump intensity near the saturation intensity of the phase conjugator. In this work following the analysis of Tompkin et. al. 4 closed-form solutions for the PC reflectivities in the dye-doped film are derived for two states of the polarization: the probe wave is polarized parallel and perpendicular to the pump waves. Some experimental results are also demonstrated in an eosin-Y-doped poly-vinyl alcohol (PVA) film and are compared with the theoretical results. 2. POLARIZATION DEPENDENT PC REFLECTIVITIES Dye molecules are modeled as dipoles which are randomly and uniformly oriented and are rigidly fixed in a solid matrix. We assume that each dye molecule has only one component of transition dipole moments at a wavelength considered5. An induced dipole moment of each dye molecule by
Author(s): Christos Flytzanis; Francois Hache; Maurice C. Klein; Daniel Ricard
We discuss certain features of the three dimensional quantum confmement in semiconductors and its impact on the nonlinear optical properties of semiconductor nanocrystals. We cursively present results on spectral hole burning and saturation spectroscopy on optical Kerr effect and on electroabsorption close to quantum confined resonances in these nanocrystals. 1.
Wavelength shifts in optical signals as high as some nanometers originating from signal purTp interaction in semiconductors and organic polymers can be applied for optical swit ching impressing infornation onto signals and pulse compression. 1.
Author(s): Norbert N. Neuroth; K. E. Remitz; Burkhard Speit
During the last years there is an increasing interest in materials dealing
with nonlinear optical effects. Besides semiconductors, crystals and organic materials
attention has also been paid to silicate glasses in which a CdSxSei. microcrystalline
phase is thermally developed. These glasses are the basis for a comercially available
set of yellow-to-red "short wavelength cut" filters. Although these glasses have not
been optimized for nonlinear behaviour by now they already show large nonlinear
Author(s): Peter Maly; Jaroslav Pantoflicek; A. Svoboda
We have studied the temporal response of four-wave mixing in
silicon to study the coherence of picosecond pulses and the diffusion of free carriers. The measurements were done at room temperature. The sample used was an N-type monocrystalline silicon
with the impurity density of 5 1O15 cm-3.
Several methods for detection of a moving object against static bkground in photorefrtive terials
(e. g. BSO and BaTiO3) have been reported by using optical phase conjugation or two wave mixing ' 2) Here we
donstrate the real-time detection of the moving object using optical phase conjugation in a methyl-orangedopxi
polyvinyl alcohol (MO-PVA) film, in which trans-cis photo-isomorization induces optical anisotropy. The
present method es two cross-polarized components of the phase conjugate (PC) wave at a wavelength of 515 r.
Author(s): Richard M. Kowarschik; G. Rodriguez-Zurita
The nonlinear optical phase conjugation (NOPC) is an important
field of modern optics with applications in the compensation of
aberrations in laser systems, image processing, and optical measuring
systems. Interferometers with PC-mirrors (PCM) offer a higher
accuracy of measurement and the possibility of phase measurement
with no additional reference waves. The successful application of
NOPC very strongly depends on the PC-materials. So, for example,
photorefractive materials like BCO-crystals have a high sensitivity
connected with low response times, but their applications as
PCM's in interferometers requirers the exact knowledge and characterization of the quality of the phase conjugation process both
with respect to the amplitudes and the phases of the signal Wayes
and the correspondend spatial and temporal behavior.
RareEarth doped silica fibers are interesting light sources for optical communications and sensor applications. Their broad fluorescence linewidth and the long spontaneous lifetime of the upper laser level otter the possibility to produce short and intense light pulses. We demonstrate pulsed operation of a Nddoped fiber laser with an asymmetric switched directional coupler operating as an intracavity intensity . modulator. 1 . Fiberlaser configuration The fiberlaser arrangement is shown in Fig. 1 . The prepared modulator is an xcut LiNbO3substrate with a pair of indiffused Tistripe waveguides of 5 pm width which are singlemode at the lasing wavelength A 1088 nm. The minimum waveguide separation is 2 im and has 8 mm length. One single pair of 8 mm long Alelectrodes with a 10 pm gap deposited onto the substrate surface is placed asymmetrically relative to the waveguides. This electrode arrangement provides electrooptic modulation of the phase mismatch between the two waveguides via the strong electrooptic coefficient rss of the LiNbO3 crystal. The modulator chip is Lw 20 mm long. The singlemode Ndfiber with LF 3. 485 m is pumped at a wavelength A 825 nm and butt coupled to the modulator. At the buttjoint the faces are angledcut with angles Yr 1 1. and yp. 7. 5 so no residual cavities exist within the laser resonator. The laser cavity is defined by dielectric coatings on the free ends of
One challenge to the electrical engineer consists in remodelling and
solving Maxwell's equations in the complicated boundary conditions of
a real optical waveguide. Much progress has been reported in this field
and was embodied in the design and manufacture of advanced optical fibers,
but the obscure process of obtaining these great results makes it desirable
to find more obvious and simpler ways of getting insight intO the behaviour
of light in the confined geometry of a fiber. In this paper we use the
concept of topological phases to estimate the phase shift of the light
wave due to winding of the optical fiber in a cable.
Author(s): Adam E. Heimrath; Leslaw Bielak; Dariusz Swierk
The problem of randomly distributed imperfections of multimode gradient-index fibers and their influence on signal dispersion is discussed. The measured data are analyzed and the numerical modelling of the response to the impuk''e is presented. 1.
Author(s): S. Maneuf; Alain Barthelemy; Bernard Colombeau; Claude Froehly; Michel Vampouille
Unstable self-focusing of high power laser beams may be prevented not only by their shaping into soliton patterns but also by their one dimensional or two-dimensional modulation by fine periodic interference fringes. 1 -
cisterberg and W. Harguliz have demonstrated efficient generation of
second harmonic waves in Ge-doped glass fibers with 1O64 nm light (1).
This process is acompanied by an irreversible modification of the glass
material tflat enhences the generation of Uie second harmonic and is
induced by the presence of the second harmonic wave. We suggest a
microscopic mechanism for the irreversible process.
Nonlinear interaction due to Kerr effect between two
linearly polarized modes in a single mode optical fiber and
its various manifestations have been investigated very
intensively (see e.g. ), solely using the classical
treatment. To describe nonclassical effects it is necessary
to use the methods of quantum optics.
The picosecond solitons dynamics in an elliptical core fiber
can be described by nonlinear combined equations according to two-
dimensional model of a waveguide. Averaging over the transverse
dimensions, neglecting the oscillatory term and keeping the core
ellipticity and the spectrum dependence of waveguide's characteristics terms, we find an analitical solution of these equations
because of just integrable. Our consideration is acceptable for
various situations when the core ellipticity is high enough and a
spetial period of polerisation beating is much less than soliton
forming length .
Soliton propaqation in nonlinear Kerr media gives rise to pulse or beam interactions. In the spatial domain, separate in phase fundamental solitons merge after an appropriate propagation length. Using this beam defliction we propose an AND logical optical gate that would work in the picosecond range.
The fiber exhibits a number of features that make it extremely
attractive for use in optical information processing systems. Among
them are the huge bandwidths and high efficiencies of nonlinear pile-
nomena achieved at relatively low powers of laser radiatioui. In addi
tion, the problem of overheating is obviated here because heat is
removed through fairly large lateral surfaces.
The systems suggested so far rely on two nonlinear rfiechanisms.
The principles of the use of SRS were discussed in /1-3/. Prom the
estimates, the pulse repetition frequency in the SRS-device can be
as high as io12 Hz for pulse energies of i012 A variety
of logic elements operating through light-induced refractive-index
variations were also suggested /4-6/. They provide the pulse repetition frequencies up to 1013-i014 Hz.
Lu this paper we discuss different versions of optical signal
We present a method , based on the variatiml principle , for Obtaining equivalent
1-D profile for the given 2-D profile of a veguide. The method leads to a better
equivalent profile in ccniparison to other existing methods.
Author(s): Heihachi Sato; Yuji Azumai; Manabu Kishimoto; Iwao Seo
Using an amorphous like VDCN/VAc copolymer a second harmonic generation (SHG) has
been observed at both Nd: YAG 1.06 im and Er: YAG 2.94 μm laser lines. Here, we try to
enhance the SHG power with a slab waveguide scheme under the phase-matching condition.
Author(s): Ton Ko; Chen-Hsing Chao; Pai-Sheng Shen; Ching T. Lee
The unwanted amplitude undulation (AM)
content in the output of a waveguide E-O phase
modulator has been observed. Which would come
from either the misaligoment between the polarization analyser azimuth (or birefringent
ares of a polarization maintaining fiber,PNF)
and the principal aces of the modulator 
or the inherent multi-modes due to the waveguide
structure [2J[31 , or the multiple beam
reflections in between both ends of the waveguide.
A simple way with the polarimetric
detection rather than the usual two or more
light paths interferometer has been made in
checking with such residual AM-effect. For
simplicity, we may ignore the multiple light
ref'ections effect which will be small either
by the antireflection coating or by
liqued cutting of the end facets of
Author(s): Norbert Hensel; Guido Sawade; Gert Sinn
The dimensions of integrated optics components are
usually of the order of light-wavelength. Hence
systematic investigations of form, tolerance and geometric
variations by light experiments are far more
difficult than by electro-magnetic waves (A 6 mm)
in correspondingly enlarged model structures. Fielddistributions
in dielectric strip-waveguides of rectangular
cross-sections are measured in the evanescent
fields near the waveguide surface with a hollowwaveguide-
probe. Results are compared with calculations
by the Beam-Propagation-Method (BPM).
Statistical studies are made of the phase fluctuations of all the guided modes including
cross-coupled modes, propagating in a highly birefringent PANDA fiber. The fluctuating
phases are demodulated from the generated beat-photocurrents and processed to give their
cross-power spectra. For the dynamic sensing by a fiber-optic sensor, it is essential to
clarify the dynamic propagation characteristics of all the guided modes in the presence
of environmental perturbations. The present work is amid at studying statistics for the
phase fluctuations of the modes guided in the fiber under lateral forced vibrations.
One of the guided modes, as a signal beam, is mixed with a local oscillator beam to
generate a beat-photocurrent from which the fluctuating phases can be demodulated and
For the first time we investigate the properties of transverse electric polarized nonlinear guided waves propagating in an asymmetric N-channel waveguide surrounded on both sides by Kerr-like nonlinear media. We use a transfer matrix formalism that allows the exact calculation of the stationary field distribution and the nonlinear dispersion relation. The propagation wavevector and field distribution of surface and guided electromagnetic waves become power - dependent when one or both of the semi-infinite media bounding a single interface r a thin dielectric film exhibit intensity - dependent refractive indices''4. The aim of this work is to give an analytical treatment for the general N-channel asymmetric waveguide surrounded on both sides by Kerr-like optically nonlinear media. For a single channel wavegide (N with nonlinear bounding media we recover the results reported mD. By using the transfer matrix technique adapted for periodic multilayer linear dielectric structures in contact with nonlinear media6 the stationary field distribution and the rich structured nonlinear dispersion curve are obtained exactly. Numerically we investigated the TE-polarized nonlinear guided waves is a periodic stratified dielectric structure with five unit cells (ten dielectric layers) surrounded on both sides by nonlinear media with either equal or unequal Kerr-like self-focusing optical nonlinearities. The complex variations in the effective refractive index with guided wave power in the case of self-focusing optical nonlinearities suggest a new class of potentially useful optical devices particularly upper and
The intensity distribution of a gaussian beam propagating through GRIN media that has been truncated by a centered circular aperture is calculated by Fresnel-Kirchoff theory. On axis intensity is evaluated. 1 MATHEMATICAL TREATMENT AND DISCUSSION. The circular aperture in an opaque screen is located at z r is the radial coordinate. In the z half-space the medium has a refractive index profile given by 2 2 2 2 n (r (z)r ). For the z half-space the medium is considered to be homogeneous with n''l. The diffracted field in the z region when a gaussian beam source at z0 in the z region is evaluated in terms of Bessel functions. The beam at z can be represented in terms of its waist size and its half-width w(z0) and curvature radius R(z0) at the aperture plane. The Huygens-Fresnel diffraction formula with the Fresnel approximation can be evaluated as an infinite sum yielding: S 2 Akwn iknHr 2 J(aa) 00 01 1 1 2 n u(r w(z )JexP[ 2H JJ : exp(a C) (1) 1 0 1 n 2n! (aa) where H(z) and H2(z) are respectively the axial and the field rays1 a and C intensity distribution in the diffraction pattern is given by I(r This treatment predicts for the on axis intensity: I 2 2 nH 1 I I a 1 ia ki 1 0 2 I (z)cx . coshi
A recognized model for a digital optical computer consists of arrays of optical logic gates interconnected in free space with regular patterns. This model simplifies optical hardware but complicates the process of designing digital circuits since connections cannot be abstracted away until a final layout is required as is the case for conventional digital electronics technology. The Rutgers Optical Computing Project explores digital design problems for optical computing and provides computer-aided design tools that assist the computer designer. Two areas of interest are considered here: digital optical circuit design and avoiding device faults. Background For an all-optical digital computer optical logic gates are needed as well as optical interconnects. One particular optical logic gate is considered here the self electro-optic effect device (SEED)  shown in Figure 1. The SEED is based on an electrically coupled optical modulator and detector pair and is made up of approximately 1200 alternating layers of GaAs and GaA1As in an 8im thick quantum well structure placed inside a PIN photodiode detector as shown in Figure 1. When light is applied to the detector a current is generated that reduces the potential across the quantum well. When a strong enough current is created the positive feedback allows the device to retain its state after the light source is removed. A variation of the SEED is the symmetric-SEED (SSEED)  which is used in a testhed all-optical
We demonstrate tI design and fabrication ofarange of space-variant holographic elements(SVHOEs) in dzhromated gelatin
(Dcci). These include: a half cmss-over, a perfect shuffle and several butterfly based networks. High diffraction efficiencies (>90%)
and near diffractkin limited perfmnance have been hieved. The interconnects link point to point and can be nither on or off-axis in
Optical interconnects of arbitrary design require space-variant optics. Planar holographic optical elements (HOE) offer a high flexibility and ease of production. HOE work via diffraction causing chromatic aberrations. This problem becomes serious if semiconductor lasers with poor wavelength stability should be used. Estimates for the number of independent space-variant interconnects their spatial tolerances and their wavelength stability will be considered. 1 . INTRODUC liON Optical interconnects enable the transmission of signals with ultra high frequencies with small crosstalk and rather low waste energy per transmission line. Two fields of application for optical wiring concepts can be discerned i. e. fixed pattern chip to chip (or board to board) interconnects and reconfigurable switching networks or bus systems where the interconnect path is selected out of a number of fixed interconnects by means of e. g. so-called exchange bypass modules (EBM)1''2. 2. INTERCONNECT CONCEPTS A general feature of optical interconnects is the fact that the light has to leave the board/chip-plane in order to give room for the interconnect fabric i. e. the light leaves the board-plane perpendicularly The necessary optical means are: collimating or focussing elements deflectors and beamsplitters(fanout). Gratings or more general holograms seem the most promising optical elements. These elements may be planar and can be configurated in an arbitrary manner. HOE3 can be used for the above mentioned purposes . Efficient HOE can be obtained either by using thick
An interconnection network has three elementary functions: fan-out, shift and fan-in. Signals from input
nodes are first split into several interconnections and are then shifted and routed to destination nodes.
Interconnections from several input nodes are then combined onto a detector. In an optical free space
system, these basic functions can be accomplished by multiple imaging.
A new technique for the three dimensional integration of optical components is presented. It is based on diffusion techniques and photoinitiated polymerization. Initial experimental results demonstrate the feasibility and efficiency. DIFFUSION jQ PHOTOINITIATED POLYMERISA11ON We want to combine diffusion with photoinitiated polymerization in order to form passive elements which are necessary for three dimensional integration of optical components for microoptical systems1''2. The production of optical elements by photopolymerization consists of two main steps. First the PMMA is sensitized to ultraviolet light by diffusing a photoinitiator into the substrat. Then the exposure by UV light causes an increase in the thickness and in the refractive index. The structuring can be achieved either by local diffusion and global exposure for stabilization or by global diffusion and local exposure. In the first case metal-masks for the diffusion process are necessary whereas in the second case photo-masks can be used. OPTICAL INTERCONNECFION For realizing a flexible optical interconnection plate3''4 the necessary functions are: light collimation light deflection and beam splitting. Collimation can be achieved by microlenses. For deflection we use a miniaturized prism. For beam splitting an index grating can be used. The components are integrated within a planar PMMA plate. EXPERIMENTAL RESULTS By measuring the phase profile of diffused lenses and prisms we demonstrated that phase shifts of several wavelengths can be achieved by polymerization and diffusion techniques. The main effect results from the
Author(s): L. Cescato; Ekkehard Gluch; Wilhelm Stork; Norbert Streibl
High frequency surface relief structures are optically anisotropic and show interesting polarisation properties 1 . These properties can be used to produce polarizations components such as wave plates polarizers. polarizing beamsplitters etc. Our experimental results show that even gratings with relatively low spatial frequency ( periods A ) exhibit a strong phase retardation and can be used as quarter-wave plates. k INTRODUC11ON The artificial birefringence exhibited by ultrahigh frequency gratings of dielectric materials can be used to produce various polarization components2 . Such components have applications in integrated optics as well as in free space optics. In order to produce the high spatial frequencies complex processes such as electron-beam lithography and reactive ion etching are needed. We show in this paper that sinusoidal holographic gratings in photoresist exhibit also a strong phase ret even at relatively long periods. L EXPERIMENTAL MEASUREMENTS To obtain the phase retardation of a lower frequency ( period A ) grating a simple setup as used by Enger and 2 can be applied. In our case however there are three measurements necessary to obtain the phase retardation because transmission of the two perpendicularly polarized beams is different from each other. I GRATING PRODUCTION grating 2 3 4 5 6 7 8 9 period (pmj 0. 74 0. 74 0. 61 0. 54 0. 46 0. 32 0. 54 0. 54 0. 54 ne (sec) 60
We analyze the exact Fresnel diffraction in a GRIN Fiber Lens (GFL) due to its finite extent when it is illuminated by a modal gaussian illumination. Its influence in Single Mode Fibers (SMF) interconnections is shown.
A new photo-electronic optical data storage system is described which has the potential for exceeding key performance characteristics of current magnetic systems and other optical systems currently in development and production.
The reading signal of an optical disk relays on phase, amplitude and/or polarization changes induced on a
focused coherent light beam at the written (stored) domain boundaries (data) [1, 2, 3]. The interaction of light
with these storage media are usually treated under the assumption of plane wave illumination since an exact
mathematical analysis of focused beams is quite difficult . In this work we show that very useful results can
be obtained by solving the scalar diffraction integral in the vicinity of a complex step function.
Results on complete storage and reconstruction of an optical signal are presented and possible applications on ultrafast parallel data processing are discussed. Separation of the segment from the signal event to be recorded and pulse shaping by coherent responses of synthesized linear frequencyselective filters are also investigated. 2 .
Author(s): Mark Aizengendler; Ivan Dolindo; Ilmo Sildos
Due to the birefringence of sapphire the 36O 450 rim phototransformation of the absorption spectrum of a neutron-coloured u-A12O3 leads to the persistent spatial modulation of defects concentration in both absorption bands. Spectral-spatial structures were detected by means of the luminescence of the photoproduct and by a direct observation the Bragg diffraction of light. After neutron irradiation and the subsequent thermal annealing of sappire one can find a number of polarized bands in its absorption spectrum. The aim of the present report is to study a persistent spectralspatial modulation in an optically anisotropic crystal neutronirradiated a-Al203 created by the 360* 450 nm laser phototransformation. Sapphire is a negative uniaxial crystal A fragment of the crystal structure and a model of anisotropic defects are shown in Fig. la. For photobleaching in the 360 nm absorption band a linearly polarized light with E''[OOOl] propagating in the direction k II  was used. Due to birefringepce of sapphire this beam changes its polarization state periodically. The concentration of the defects in the 360 nm absorption band decreases due to the phototransformation of the defects and forms a periodical spatial structure. 0 100 200 r Fig. l. (a) A fragment of the a-A12O3 structure where d mdicates the arrangement of the anisotropic defect. On the left the direction of the laser beam for bleaching (or for exciting luminescence) is shown. In the upper part condition
The low temperature spectra of absorption and luminescence
of a wide variety of impurity doped organic and inorganic solids
comprise very narrow (io 1O cm1) and intense zero-phonon
lines (zPL). They arise from the purely electronic transistions
in the impurities i.e. from the changes of the electronic state
not accompanied by creation or annihilation of the phonons of the
host solid. (ZPL may be called the optical analog of the M5sbauer
line), Because of their narrowness ZPL's are very sensitive to
even very slight differences in the crystal fields at the 1oca
tions of impurities and the ZPL spectruim of a body of impu.rities
displays a large inhomogeneous broadening (formula available on paper).
To achieve an extremely high productivity and accuracy the
processor can be based on digital optics. The investigations in
this area are directed both on essential increasing of the informative
capacity as well as speed of memory devices operation and
also for functional completness ensuring of optical systems. A fruitful approach to these problems implies the application of low
loss single-mode fibers. In this case the data storage device consists
of the fiber loop and a few regenerators. The binary coded
array of optical pulses applies the input in order to circulate
through the fiber loop and to recover their parameters in regenerator. The typical pulse duration is reached 1O- 1Os and
or such extreme time intervals the ultrashort pulses dynamics
becomes important. Passing through various elements of data storage
device the ultrashort pulses do not conserve their own parsmeters
and therefore the problem of dynamic stable informative
carriers csnies up. Under certain conditions the stationary optical
solitons are perfectly suitable and reliable ultrashort carriers
of digital information.
A criterion to evaluate the correlation between two binary, unipoar vectors is presented. An combinary vector optical associative memory, based on this criterion, which can effectively overcome the false recall, is implemented.
The main disadvantages of standard Hopfield model of associative memory are:
limited storage capacity and possibility
of convergence to a false memory or even
lack of convergence of retrieval process.
In this paper we will present certain results concerning almost necessary conditions
for quantification of distances
between stored vectors.
Tomographic alogithms are modified in order to reconstruct the inf ormation previously stored by focusing laser radiation in a volume of photosensitive media. Apriori information about the position of bits of inf ormation is used. 1. THE PRINCIPLES OF TOMOGRAPHIC MEMORIES Tomographic principles can be used to store and reconstruct the inf ormation artificially stored in a bulk of a photosensitive media 1 The information is stored by changing some characteristics of a memory material (e. g. refractive index). Radiation from the two independent light sources (e. g. lasers) is f ocused inside the memory material. In this way the intensity of the light is above the threshold only in the localized point where the light rays intersect. By scanning the material the information can be stored in binary or nary format. When the information is stored it can be read by tomographic methods. However the situation is quite different from the classical tomographic problem. Here a lot of apriori information is present regarding the p0- sitions of the bits of information profile representing single bit and a mode of operation (binary or n-ary). 2. ALGORITHMS FOR THE READOUT OF THE TOMOGRAPHIC MEMORIES Apriori information enables efficient reconstruction of the memory contents. In this paper a few methods for the information readout together with the simulation results will be presented. Special attention will be given to the noise considerations. Two different
Holographically generated conjugate wavefront has been used for realising optical associated memory elements which can reporduce complete stored information when addressed only by a partial information.
An optical three-dimensional multilayer memory device based on the effipsometric principle is presented. The possibilty to utilize the flexibility of organic layers e. g. conducting polymers will be discussed. PRINCIPLES A concept of an optical three-dimensional memory device based on the ellipsometric principle1 is presented. This " effipsometric" memory is a thin film multilayez device with an optical read-out. The information is contained in the optical properties of thin films and is read by analyzing the state of polarization ofa polarized light beam reflted at oblique incidence from a memory cell. The device is here examplified with the case of two layers on a substrate which is equivalent to a memory cell capable of storing one 2-bit word. If the optical properties of the two layers can be controlled independently we can generate 4 different states of polarization in the reflected beam corresponding to the " logical states" (0 (0 (1 and (1 ofthe memory cell. In a generalization to n layers it is possible to have 2fl different states. In other words an n-bit word can be stored at one location. Fig. 1. An optical memory device having 2-bit memory cells. With an ellipsometric read-out the state of polarization in the reflected beam is described by the two ellipsometric angles and These angles can be determined with a precision better than 0. 01''. The lateral resolution limiting the memory
Optical logic gates and free space interconnects have been used to implement optical systems modules. These modules have been assembled to implement a circular optical pipeline. The design performance and motivation behind this optical pipeline are discussed. BASICSTRATEGY In the field of computers there is the concept of a platform. A platform is a set of standards used to minimize risk and maximize flexibility. An IBM personal computer is an example of a platform. By setting standards for the hardware backplane and software operating system many smaller vendors could with relatively little risk develop boards and programs for this computer. The users were also pleased by the variety and lower cost. We have actively been trying to establish such a platform for optics. A DIGITAL INTERFACE The most important standard which we have been trying to establish has been a digital interface. Optical systems have traditionally been analog. The problems with this approach is that it is increasingly difficult to build complexity and there was very little reuse of sub-systems because of their specialized nature. Our approach was digital. This initially made things more difficult however we have already noticed several benefits. It allowed use to decouple work on the logic gates from the optics and architecture. The architecture didn''t depend on some novel aspect of physics while the devices weren''t applicable to only one architecture. This minimiZed the risk for
A new type of nonlinear image processor based on morphological processing is demonstrated. Morphological image processing is based on the successive binary convolution of an image with a selectable convolution kernel. Its field of application includes numerical optical computing and binary image processing. Simple serial commands from a small electronic computer control the selection of the convolution kernels for a given iteration and consequently the parallel processing of very large optical data planes. 1.
Basic operators of mathematical morphology can be implemented optically by using properties of Fourier optics and holography. We ifiustrate this principle presenting cxperimental results of an optical dilation and comparing them to the theoretical values. We emphasize the use of a novel truly bistable optically addressed spatial light modulator. 1.
Digital optical processors are designed to combine ultra-
parallel data procesing capabilities of optical aystems
cnd high accur&cy of performed computations. The ultimate limit
of the processing rate can be anticipated from all-optical parcllel
erchitecturea based on networks o logic gates using materials exibiting strong electronic nonlinearities with response
times less than 1O seconds1.
Interest in optical computing is fueled by several attributes of optical processors that are superior to conventional electronic computers. To keep expectations within reasonable bounds in this paper an attempt is made to assess the limitations imposed on some of these attributes by fundamental processes. 1.
Author(s): Iyad Seyd-Darwish; Pierre H. Chavel; Jean Taboury; Francis Devos; Roger Reynaud; Thierry Maurin
FRANCE We describe an opto-electronic parallel cellular automaton for a particular application: " Lattice-gas" . We use an array illuminator hologram for parallel distribution of optical informations to an electronic circuit and suggest to use an array of MQW modulators as parallel output of the results. 2 .
Stochastic algorithms such as simulated annealing in its various applications1
or Monte Carlo schemes may be implemented in parallel. Integration of many
hundreds, perhaps thousands of processing elements (P.E.) on single VLSI chips is
being investigated . However, such chips encounter great difficulties in the
generation of the random number arrays required for these algorithms: typical
requirements are thousands of spatially independent random numbers, each with a
temporal correlation in the microsecond range. Optical solutions using speckle may
Whereas the literature mainly investigates 2-moving-diffusers methods3'4 , we
show here that a method based on the statistical properties of Nmodal noise", i.e.
speckle patterns created by a step index multimode fiber, is well suited to the
We introduce a novel architecture modelled on biological information processing concepts. The architecture is highly parallel has distributed control and is comprised a large number of identical simple components. This makes it a candidate for a general purpose optical computer based on free-space/SEED optical computing technology. 1.
The high data transfer requirements in digital computing demand the use of optics. The next step is to perform data
processing by optical or opto-clectronic devices. As with electronic computing this computer architecture needs computer
skied support. We present a software system which allows interactive design, simulation and evaluation of such computer
architectures. With this system, we have developed arithmetic units based on systolic arrays.
Author(s): Kashiko Kodate; Jing Li Chen; Eriko Tokunaga; Takeshi Kamiya
A newconfigurationof two-dimensional spatially divided beam splitter using fresnel
zone plate arrays is proposed. Feasibility of applying this to OEIC and parallel opto-
electronic computing scheme is examined.
We are actually studying the problem of interconnecting a
Gaussian beam with a 2-D optical logic gate array. The
optical logic devices are reflective bistable (non-linear)
Fabry-Perot etalons. The Gaussian beam is either a high
power laser operating as bias power supply (illumination
of all the logic gates required) or a low power laser
operating as logic signal (illumination of a small subset of
the logic gates reqjiired). We decide in favour of a freespe,
space-variant, diffrtive optical element (DOE).
The DOE is a kinoform (phase encoded phase hologram),
synthesized with a modified iterative phase-retrieval
algorithm (IPR) applied in the Fresnel diffrtion regime.
IPR offers the possibility to solve the general problem of
beamshaping and to create non regular light pau&ns. It is a
usefull algorithm in the design of space-variant
The dynamics of an electrooptic hybrid bistable device with feedback is analized when a discrete signal is used. Experimental results show be and eultistability period doubling chaos and type I intermittence. Numerical results of a model without aproximations show a very good agreement with the experiment. 1 . DESCRIPTION Feedback is used in control engineering to stabilize the output in a position defined by a control parameter. Non linear dynaMic analisys shows that systems with feedback can be chaotic when the control parameter is changed. Gibbs and co workers (1) have shown for tt first time the bistability behavior in a hybrid system with a delayed feedback signal. Later on a lot of work was done in systems with other devices like liquid crystals and acustooptic modulators. We have changed the system introducing a digital signal (pulsed) and delaying the feedback until the next pulse was present at the modulator. In this way the output is controled by the feedback loop and can be described without any aproximations (like small signal modulation) by a recurrence equation. Xn+1 A E I + cos ( R. Xn + B ) 3 (1) In order to analize completely the system three control parameters were introduced experimentally to have all the possible changes of an unidimensional map: a multiplicative parameter of amplitude (like in the logistic map) and two aditional parameters in the argument of
An array of logic modules by regular interconnection' is a potential
technique in order to implement optical logic circuits. In this
investigation, we propose an implementation of a logic module array by
use of holograms.
Author(s): Robert H. Jones; Marios G. Hadjinicolaou; G. Musgrave
This paper presents a novel approach in the design of Optical Logic Array Structures ( OLAS ) for the implementation of two - level Boolean functions using optical coupling techniques and waveguides. 1.
We describe a hybrid processing real time optical correlator that uses programmable
liquid crystal teleiesion (LcTr) spatial optical modulator. A joint transform optical
correlator with a photorefractive crystal BSO has been successfully applied to real time
object recognition. Hoerer, a major shortcoming of this optical correlator is its sensitivity to the scale and orientation of the test image. Thus, its application is restricted. We present a scale- and rotational-invariant correlation hybrid processing system,
namely a joint transform digital-optical correlator using photorefractive crystal BSO
and programmable LCT spatial light modulator.
A general approach for making up fully parallel optical matrix multiplier is described. The necessary conditions of triple matrix multiplier (TMM) are induced based on Gaussian optics. Two typical configurations of TMM is discussed. 1 .
Symbolic substitution was firet proposed by Haung as a mean of utilising the parallelism of optics to perform
digital computing. Essentially, it is a combination of recognition and substitution phase. In addition,
although synibolic substitution is not restricted to space invariant operations, it is indeed based on the space
invariant connectivity of optics. Therefore, holographic associative memory techniques may be alternatively
applied to implement a symbolic substitution logic system.
A digital optical pipeline adder based on symbolic substitution is presented. We have developed an optoelectronic device as the nonlinear array. Experimental results are demonstrated. 1. OPTICAL ARCHITECTURE We demonstrate a ripple carry adder in a pipeline architecture. A pair of 8 bit numbers is accepted by the system input for every clock cycle. All numbers are dual rail coded. The sum of these numbers reaches the output 8 clock cycles later. The system is designed for active devices i. e. light emitting devices. We use a self-developed optoelectronic inverter array (OEI) as the nonlinearity. The operation is realized by applying four symbolic substitution (Symsub) rules in parallel to a 16 by 16 data plane. This plane contains the pair of input numbers an area with intermediate data and the sum output. The plane is split into four copies one for each rule. These copies enter the recognition stages. The recognition output of the Symsub stages is imaged onto a mask to perform space variant operation. The mask''s output is fed to the substitution parts of the system. The result reaches the OEI where it is amplified and normalized to binary values. The OEI''s output is fed back as the new data plane. 2. THE OPTOELECTRONIC INVERTER ARRAY The OEI is a hybrid optoelectronic system that can process 16x16 pixels at a video frame rate on an area of 13x13 m.
Let p(;y) be a pulse field of identical pulses.
By modulating the pulse density of this field, we
can shape its spectrumS In this manner we can
approximate the spectrum of a given intensity
distribution in a certain frequency band.
Upper arid lower bounds on the number of bits of accuracy achievable are determined by applying a seconth-ortler statistical model to the linear algebra processor. The use of bounds was found necessary due to the strong signal-dependence of the noise at the output of the optical linear algebra processor (OLAP). 1 1. ACCURACY BOUNDS One of the limiting factors in applying OLAPs to real world problems has been the poor achievable accuracy of these processors. Little previous research has been done on determining noise sources from a systems perspective which would include noise generated in the multiplication ard addition operations spatial variations across arrays and crosstalk. We have previously examined these noise sources and determined a general model for the output noise mean and variance. The model demonstrates a strony signaldependency in the noise at the output of the processor which has been confirmed by our experiments. 1 We define accuracy similar to its definition for an analog signal input to an analog-to-digital (ND) converter. The number of bits of accuracy achievable is related to the log (base 2) of the number of separable levels at the P/D converter output. The number of separable levels is fouri by dividing the dynamic range by m times the standard deviation of the signal a. 2 Here m determines the error rate in the P/D conversion. The dynamic range can be expressed as the
The Inverted Neural Network (INN) model especially designed for optical implementation is presented. This model takes into account the physical constraints imposed by conventional optical components and ensures that all the connections are positive. Thus subtraction of light intensities is not required for implementation nor are electronic computations. In the laboratory realization of the INN model a liquid crystal light valve fulfills the function of an array of neurons while an array of subholograxns serves as the interconnects. The overall network was tested with 64 neurons and four stable states. 1. INTRODTJCTION Several problems have to be solved in order to realize neural network models optically. The first problem stems from the fact that most models consist of both positive and negative interconnects. Conventional solutions to this problem usually involve electronic subtractions or dynamic threshold levels. It has been recently shown1''2 how the Hopfleld model can be modified into a model with positive values only. An all-optical realization of the modified model for 16 neurons and two stable states has also been demonstrated1 . The second problem that has to be considered is the fact that most of the optical devices that are used for realizing the neurons cannot exhibit very sharp thresholding. Although neurons with graded response have collective computational properties like those of two state neurons the memory capacity of Hopfield-type networks decreases as the slope of the neural
Author(s): Bernard H. Soffer; Yuri Owechko; Gilmore J. Dunning
This paper discusses holographic neumi netwrk architectures in which the connection weights between neurons are implemented
as gratings in a photorefrtive crystal. In particular, it will discuss the self-pumped optical neural network (SPONN), which is a fineed
optical architecture which features massive parallelism and a much greater degree of interconnectivity than bus-oriented or
hypercube electronic architectures.Connecüons between neurons are implemented as sets of angularly and spatially multiplexed volume
phase gratings. SPONN is potentially capable of implementing neural networks consisting of 1O1O6 neurons with 109.1010
interconnections. The mapping of neural network models onto the architecture occurs naturally without the need for multiplexing
neurons or dealing with the contention, muting, and communication bottleneck problems of electronic parallel computers. This
simplifies the programming of the optical system.
Neural Networks are part of a revived technology which has received a lot of hype in recent years.
As is apt to happen in any hyped technology, jargon and predictions make its assimilation and application
difficult. Nevertheless, Neural Networks have found use in a number of areas, working on non-trivial and noncontrived
problems. For example, one net has been trained to "read", translating English text into phoneme
sequences. Other applications of Neural Networks include data base manipulation and the solving of muting
and classification types of optimization problems.
Neural Networks are constructed from neurons, which in electronics or software attempt to model but
are not constrained by the real thing, i.e., neurons in our gray matter. Neurons are simple processing units
connected to many other neurons over pathways which modify the incoming signals. A single synthetic neuron
typically sums its weighted inputs, runs this sum through a non-linear function, and produces an output. In
the brain, neurons are connected in a complex topology: in hardware/software the topology is typically much
simpler, with neurons lying side by side, forming layers of neurons which connect to the layer of neurons
which receive their outputs. This simplistic model is much easier to construct than the real thing, and yet can
solve real problems.
The information in a network, or its "memory", is completely contained in the weights on the
connections from one neuron to another. Establishing these weights is called "training" the network. Some
networks are trained by design -- once constructed no further learning takes place. Other types of networks
require iterative training once wired up, but are not trainable once taught Still other types of networks can
continue to learn after initial construction.
The main benefit to using Neural Networks is their ability to work with conflicting or incomplete
("fuzzy") data sets. This ability and its usefulness will become evident in the following discussion.
A compact size optical neural network using high resolution liquid crystal televisions (LCTVs) has been constructed. System design consideration and an experimental demonstration of the LCTV neural network are provided. 1.
The possibility to compensate losses and aberrations in optical networks by means of phaseconjugating elements will be illustrated on the example of an active multichannel feedback system. Phase conjugating elements can be used for the compensation of aberrations and losses in optical systems. The realization of new optical transmitting and processing systems by using PC elements for several purposes - like e. g. multichannel optical operational amplifiers delay lines computing and neural networks - is possible. In particular optical feedback systems show interesting properties for applications in this field. The implementation of nonlinear and active elements e. g. optical image amplifiers results in a wide variety of achievable transfer functions. In this paper we present a coherent optical feedback system which is capable to process a large number of channels entirely in parallel. The system consists of a ring-resonator with a phase-conjugating mirror (PCM) as an image amplifier. The aberration compensating property of optical phaseconjugation allows us to realize a feedback system with space-bandwidth product up to iO which would hardly be achievable otherwise. In addition optical resonators employing PCM''s show spatial and temporal properties different from conventional resonators. The key element is a photorefractive BaTiO3 crystal in a degenerated fourwave mixing scheme. The 6. 3x2. 4x3. 6 mm crystal with the optical axis parallel to the long edge is operating at room temperature and without any applied electrical field. An
Author(s): Stanley C. Ahalt; Stuart A. Collins, Jr.; Ashok K. Krishnamurthy; D. Stewart
In this paper we present a design for an optical system which performs Closest Vector Selection (CVS)
and which could be competitive with present electronic approaches. The application of closest vector
selection has been an important one in communications. The incorporation of closest vector selection into
neural nets, which have the capability of learning, yields a very powerful tool. The optical implementation
has a potential capability better than that obtainable with electronic computers. In this paper, first the
background will be presented and then the device itself will be described.
Optical neural networks are imitative of human brain's handling in an associative and
parallel manner. It can recall complete and undistorted stored data when it is prompted
by a partial or distorted version of the data. It possesses excellent capability of making correction for error.
new recording algorithm of auto-associative memory is presented. The interconnection synaptic weights are determined by a linear equation system with predecided convergence probabilities as its important parameters.
We present a feedback system where a picture u(t) circulates under successive application of a convolution operation
with the kernel h and of a nonlinearity NL:
t1(t + 1) = NL((u(t)*h)1) . (1)
This system represents a special class of neural networks: it is space invariant. In comparison to space variant neuronal
networks it can be implement much easier, for example by Fast Fourier Transform, or even optically. Nevertheless, it
exhibits a broad spectrum of behavior: there may be deterministic chaos in space and time, i. e. the system is unpredictable
in principle and displays no fixed points, or stable structures may evolve.' Certain convolution kernels may lead to the
evolution of stable structures, i. e. fixed points, that look like patterns from nature, for example like crystals or like
magnetic domains.' In experiments described in 2 we observed that the stable structures can be disturbed quite heavily and
are yet autoassociativly restored during a couple of iteration cycles. Here we show how to adjust the kernel h in order to
obtain a certain desired stable state u of eq. 1, and how to apply the system to shift invariant pattern recognition.
Heterodyne interferometry using both spatial and temporal carrier frequencies is proposed. Combined with the multi-dimensional Fourier transform method of fringe-pattern analysis the technique enables the measurement of a phase distribution with a wider spatio-temporal bandwidth. 1.
Author(s): Shuko Yokoyama; I. Nishihara; A. Okamoto; Tsutomu Araki; Norihito Suzuki
In conventional heterodyne interferometer it Is necessary to provide a high-beat frequency laser when measurement for a high-speed target Is required1 . But use of the high-beat frequency laser makes the " nanometerdivisions" difficult. We have developed a novel interferometer system that has a sufficient response to high-speed movement of the target without Increase of the laser beat frequency. In this work a two frequency laser light passes through the same optical path of the interferometer so that two conjugate beat signals are obtained. By processing the multiple beat signals with a newly developed signal processor the above methodological contradiction is solved. l. OPTICS FOR LINEAR DISTANCE MEASUREMENT Optical system of the interferometer Is shown In Flg. l in which two frequency lights Fl and F2 (freq. f and f2) of orthogonally linear-polarized components of a two mode laser are used. A reference beat signal R (freq. r ) is generated from Fl and F2. Fl and F2 are passed through exactly the same path of the interferometer. A half power of Fl and F2 Is reflected and the rest Is transmitted In the beam splitter ( BS ). Polarization direction of the reflected beam is rotated for ir/2 after passing the X/4 plate twice. The transmitted beam Is reflected by a moving mirror (MM) mounted on the moving target so that frequency of the reflected beam Is shifted by Doppler
Interferometric systems in general are sensitive with the wavelength of the optical signal. For many applications this extreme
sensitivity is of hindrance instead of help. Dual-wavelength interferometry employs two adjacent laser lines and X 2and uses
the beat frequencybetween both signals. Thus, sensitivity and ambiguity are reduced from the optical wavelength X to a "synthetic"
wavelength (formula available on paper). Dual-wavelength interferometry was previously applied by TiZiani' for surface inspection and by Dändliker et aL2 for superheterodyne
range measurements. Our approach was to replace the commonly used gas lasers by semiconductor lasers (to reduce
volume and weight) and to use optical fibers for the signal distribution (to be more compact and to get rid of alignment and optical
cross-talk problems). A demonstration model for precise ranging to 10 m distant, reflective and rough targets was built and tested.
An interferometer for the precise measurement of rough surface deformation is described. The interferometer uses a liquid crystal phase only SLM controlled by computer in place of the usual hologram. The panel acts as a kinoform which phase modulates light scattered from the test object. Digital phase shifting techniques are used to measure both the initial phase distribution of light from the object and the phase of the interference fringes which appear when it is stressed. Surface deformations may be measured with a resolution of about 1/30 wavelength. 1 .
A stroboscopic holographic interferometry technique has been developed and used to measure the modal behaviour of ultrasonic transducers. Displacements of a few nanometres at frequencies into the megahertz region can be measured over the entire surface simultaneously. 1.
We have constructed a Zeeman interferometer with an interferometric resolution of AJ12000 where 632. 8 nm. With a 5 cm pathlength typical stability is AJ1500 per hour. There are a number of interesting applications. 1.
A new type of speckle shearing interferometer is proposed and studied experimentally. In the method a liquid-crystal is employed as a phase shifter to apply the phase shifting method for the conventional speckle shearing interferometer. The phase of the transmitted light is changed due to its birefringent property for the applied electric field. It is shown from the measurements of the fundamental properties of the liquid-crystal that the additional phase introduced between the sheared two images can be precisely controlled up to about 2ir by changing the applying voltage. From the experiments to measure the deformation of an object having a rough surface usefulness of the method is confirmed. 1.
Phaseshifting interferometry applied to speckle fields is described. Experimental cases of both weak and strong scatterers are investigated. Statistical parameters are sought on timing of the polishing process of optical sample surfaces. 1 .
By using a cyclic design as a double-focus element a common-path interferometer can be realized. No special optical elements but a lens of short focal length a half-mirror and two flat mirrors are required in the cyclic design. 1.
This paper describes a generalized phase shifting interferometiy where the reference phase instead of being set to predetermined values is directly evaluated at each time the interference fringe data are read. The evaluation of the phase shifted is achieved by introducing the FF1'' method for analyzing additional straight fringes on the interfering plane. The repeatability in the measurements of an optical surface is V500 when the generalized algorithm with 8 data acquisitions is used. 1.
A Twyman-Green phase-measuring feedback interferometer is constructed to calibrate a phase shift which affects the measurement accuracy given by a frequency tuning of a laser diode source. PHASE-SHIFTING LASER-DIODE FEEDBACK INTERFEROMETER Laser diodes (LDs) have been proved to be useful light sources in optical interferornetry for a single-mode operation and a frequency tunability. In contrast to using a phase shifter such as a piezoelectric transducer a phase-measuring LD interferometry can be realized by changing the un?alanced optical path length of the interferorneter with the frequency-modulated (FM) LD. The principle of the phase-measuring technique into practical LD interferometer together with the LD operation and the digital fringe data processing is shown in Fig. 1. The problem with the measurement is that the deviations of phase shift from its nominal value due to mode instability of LD violate the assumption of known phase shift in the phaseextracti9n algorithm causing less accuracy. To avoid this difficulty a feedback interfe rometer with TTL electronics is made to stabilize the phase shift using the frequency tuning of LD. The selection of LDs suitable for the interferometric experiment may be followed by the requirement of the singlemode behavior yielding the long coherence length. The light source such as an AlGaAs channeled-substrate planar-type LD operated at 780-nm wavelength is available for the interferometric use. The wavelength is controlled by the current such that the temperature must be kept
Three optical methods for contourmapping of phase objects are introduced. They are based on the partially coherent diffraction effect the joint Talbot effect and logic operated moire phenomenon and the Fourier filtering. 1. PARTIALLY COHERENT DIFFRACTION EFFEOS The Lau effect and the Talbot effect are interference phenomena relating to the selfimaging of periodic objects. It is known that the same specific distanceis needed for the both effects but the two effects differ in their modes of illumination spatially incoherentorcoherent. It is thus of great interest to look for new spatially partially coherent diffraction effects. 1. 1. Partially coherent effect between Lau and Talbot effects'' The observation of partially coherent effect can be achieved by illuminating the conventional Lau setup with a source slit of changable width. The spatially coherent state of illumination on the first grating can be varied continuously by the adjustment of the slit width. If the slit width is controlled to approach zero illumination is approximately coherent and the Talbot effect can be seen. If the slit is opened wide enough the illumination is incoherent resulting the Lau effect. A general formula is achieved as a joint correlation among the three functions of the source slit and the two gratings for an exact description of the fringes yielded by any state of illumination coherence. It is concluded that the fringe pattern changes in its profile not only as
The signal I of Fizeau interferences observed at two approximately parallel surfaces in reflection is symmetrical
in dependence on the interference phase , if the first surface is non-absorbing: (formula available in paper). where = 4nd/X is the interference phase, d the separation of the plates and r1 or r2 the reflection factors
of the Fizeau plates.
An evaluation of these type of Fizeau interferences by means of a common two-beam algorithm /1/
generates errors even in the case of low reflection factors of uncoated surfaces, which cannot be neglected.
These can be reduced for surfaces of low reflectance by means of a modified two-beam algorithm /2/. This
approximation is not sufficient in the case of interferences taken from plates with higher reflectance. A new
algorithm for symmetrical Fizeau interferences /3/ yields an exact solution of the interference phase
independent of the magnitude of the reflectance.
Numerical calculations and experimental investigations were carried out, to give an estimation of the
deviations, which result from the evaluation of a Fizeau interference with a common two-beam algorithm,
and to determine the dependence of the Fizeau algorithm on an imperfect step width of the phase shift.
New experimental set-ups are presented which allow multidirectional analysis of inhomogene - ous phase objects by high resolution holographic interferometry. The applicability of these arrangements is tested in a first step. After this check of the method different kinds of plasmas are investigated. In order to obtain more sensitivity the techniques of resonance heterodyne holographic interferometry are applied. Knowing the relations between refractive index in the vicinity of a resonance line and the corresponding number density of ground state atoms this number density can be determined. 1.
An heterodyne interferoaeter is constructed with a sodulated laser diode (LD) in a Michelson interferoaeter. Phase drift of beat frequency with teiperature and its affection aechanis is discussed and a method elisinating the affection aentioned above is proposed. 1 . OPTICAL HETERODYNE INTERFEROMETER Optical frequency of laser diode can be linearly aodulated by an injection current. An optical heterodyne interferoseter is constructed with a modulated laser diode in a Michelson interferoseter. If a difference exists between two arms in the interferometer a optical beat frequency phenoaenon will be forRed. The beatfrequency signal can be detected with a photoelectric device. The output signal can be described by the following equation: 1g10[1+cos(2xfbt+t)J (1) and fb is given by fb 6f''8Lf. I C (2) Where f is the aaxiRua optical frequency variation value of wxiulated laser fb the beat frequency value fa the odulated signal frequency L the optical path difference between two aras in the interferoaeter C optical wave speed. 2. VARIATION OF BEAT FREQUENCY PHASE WITh TEMPERATURE It is well known that the optical frequency of a laser diode is affected by the tesperature (in the equation (1)) ay be changed with the variation of central wavelength of . odulated optical frequency. t aay be expressed in the for. : Li A242Ai t 2ir( ) (3) AiA2 The plus and ainus . arks in the equation above are corresponding to the upward
Many Methods have been developed to .easure displace.ent with high accuracy, for
exap1e, with a dual frequency laser interferometer (AC interferometer) and an classic
interferoseter (DC interferoeter) which use a stabilized laser and fringe counter, and
an AC interfero.eter has ore advantage over the DC one.
An AC interfero.eter with a Zee.an laser can get a high resolution, in the order of
nanoMeters, but its resolution extension liRited by nonlinear relation between phase and
displace.ent which caused by the two-frequency coRponents in interferoaeter. Because
the fundaaental length scale of the interferometer is the wavelength of the light source
in the air. The accuracy of an interferoeter is li.ited by the operating envireaent,
teRperature, husidity, pressure, etc. because the aiRs of interferoseters expose in the
air. A high resolution optical fiber heterodyne interfermeter is described in the paper.
Holographic interferometry is a well-established diagnostic technique with numerous applications. Spatial distributions of
refractive index can be conveniently visualized using this approh. For example, heat transfer from electronic chips, air flow in
wind tunnels, and acoustic wave propagation have been investigated by the authors using holographic interferometry. Instead of the
conventional holographic film, we use self-developing optical crystals for storage of the holograms. The use of these
(photorefractive) materials will, in our opinion, bring about significant improvements in this techno1ogy.
A holographic interferometry technique for the measurement of the refractive index of transparent liquid samples is presented. 1 . MEASURENT PROCEDURE. The liquid under study is within a tank with an optical glass wedge. The refractive index is determined by comparison withthat of the glass wedge. The immersion tank is illuminatcd with a collimated beam of light. A diffuser plate is used after the tank to avoid the noise produced by the out of focus images of the light source and the optical components before the tank (Fig. 1). After a hologram of the wavefront transmitted through the sample has been recorded the glass wedge is removed and equally spaced straight fringes (Fizeau fringes) are observed. The separation between these fringes depends on the welge angle and the refractive index difference between the sample and the immersion fluid. It is important to have a sample with a wedge angle value adequate to the index matching to obtain observable fringes. It can he shown (Ref. 1) that the refractive index of the liquid can be determined using: N x tan a where N'' is the refractive fringes associated with the this technique depends on determined. index of the glass wedge used as reference n the number of spacement AX and is the wedge angle. The accuracy of the accuracy with which the spacing between fringes is Fig. 1. Hologram interferometer diagram. In
Author(s): Gennady R. Lockshin; Stanislav M. Kozel; V. E. Bielonuchkin
The objects which are investigated which are
investigated with the help of the holographic
interferometry methods as a rule scatter light diffusely,
therefore the two-expositional hologram reconstructs the
result of interference of the speckle-fields f ('4 and
f() scattered by th object at the initial (1) and final
Author(s): Shun-ichi Himeno; M. Seki; Y. Hamamoto; K. Uda
Holographic interferometry of optical fibers or liquid semiconductors a numerical method for their refractive indices a method of laser interferometric detection of gravitational waves are presented in this paper. 1.
Dye-sensityzed photopolymer(1) material
consists of a mixture of water-soluble acxylic
monomers, a catalyst and a sensitizing dye.
Photoexcited dye molecules react with the
catalyst, producing free radicals which initiate
polymerization of monomers. The molecular
diffusion phenomena are involved in the
formation of the refractive index modulation.
A system has been developed which is capable of interferometrically measuring optical path length
changes, with high spatial and temporal resolutions. The capability to freeze fast motion is provided
by the pulse length of the laser, the frame rate is determined by the laser and camera, and the spatial
resolution is determined by the camera and data resorder. The system has been applied to measuring
the optical disturbance through an aerocurtain, a shock wave produced by a supersonic projectile,
thermodynamic gas flow, and membrane mirror surfaces. The choice of interferometer type is
determined by environmental and optical considerations such as expected jitter and magnitude of
aberrations. The phase at each point is determined by taking intensity values of the interference
pattern at three sequential pixels, labled A, B, and C, after introducing large amount of tilt fringes and
applying the spatial phase shifting algorithm: 0 = arctan((C-B)/(A-B)}. The current system uses
100 ns pulse at any desired repetition rate or a 10 ns pulse at 30 Hz. The camera and recorder
provide a resolution of 510x480 pixels at 30 Hz or 248x192 pixels at 2000 Hz.
In this paper, we discuss the performance parameters of some hologra
phic interferometers that employ photorefractive crystals (PRC) as reusable
recording materials and computer image processing for rapid and
prece interpretation of the fringe patterns.
A fundamental study on the effect of deformation on the electrochemical
behavior of polarized metallic electrodes in aqueous solution has been conducted. The
study was successful in developing a novel technique for studying the electrochemical
behavior of the electrodes under static or cyclic deformation. The development of the
tecinique was established based on incorporating experimental methods of
electrochemistry and with those of holographic interferometry. In other words, the
new technique is capable of simultaneously measuring the anodic or cathodic current of
the electrodes as a function of static or cyclic deformations in term of interference
fringes. As a result, a relationship between deformation and current was developed
for a number of metallic electrodes/aqueous solution systems. Data on Nickel
electrodes in iN H2S04 and Molybdenum electrodes in O.75N KU will be presented at
the meeting. For further details on the technique, the reader is strongly encouraged to
refer to the literature elsewhere.
Author(s): Juergen Kross; Falko Gretzschel; Frank Guse
Abstract: A new strategy for the quantitative analysis of interferograms is introduced. It is
based on optimization strategies which were developped for lens design purposes. The
application of that strategy shows that rather accurate results are obtained very fast.
The performance of interferometers is strongly affected by thermal drift and mechanical
vibrations. These induce fluctuations in the fringe positions and fringe densities
causing a fluctuating interference pattern with a reduced visibility. The amount of fluctuations
induced by these effects depends on the type of interferometer. Here we introduce a new class of interferometers, the double beam circular interferometers (DBCI),
which are extremely insensitive to the fluctuations described above.
In holographic interfeiometry nearly straight and equally spaced fringes can be produced by a lateral displacement of a diffuser plate. This fringes can be used as carrier fringes for visual inspection of interferograms when studying phase objects. 1. FIZEAU CARRIER FRINGES Several geometries have been used to produce Fizeau fringes as carrier fringes in holographic interferometry (Ref. 1 Nevertheless in many cases these fringes are not recommendable since the tilt introduced to generate them might produce non corresponding sections of the object wavefront to be under comparison. When this problem is present the results may include imperfections due to the optical components in addition to the changes under study. These unwanted variations might be comparable to the path differences under study since quality optics is not used. 2 . YOUNG FRINGES OBSERVATION GEOMETRY If a diffuser plate whithin an holographic interferometer is laterally displaced interference occurs just between homologous points. Straight and equally spaced fringes perpendicular to the displacement direction are observed. Using exact ray tracing it can be shown that the position of the m-th bright fringe is: r 2 a a rn 4R+2d -riL. '' I x '' [1+ ir d2m27''. 2 j (1) where d is the lateral displacement of the diffuser X the wavelength of light and a is the interference order (Ref. 3). Using Eq. 1 the positions of the fringes caii lie calculated
Author(s): Mario Garavaglia; Hector J. Rabal; E. Aguirre
We present a simple optoelectronical fringe projection method for topographic or deformation study of objects. Programmed positioning and repositioning can also be performed. 1. DESCRIPTION An incoherent method for fringe projection operations was recently reported'' using photographic procedures. It is extended now to real time operation using an LCD video projector and a CCD camera. Fringes consisting in Rbnchitype rulings are generated in a personal computer and projected onto an object by using a Kodak LCD colour video projector. Its image is then read by a SVHS-CCD Panasonic camera and electronically memorized. This fringe pattern contains information concerning the position and topography of the object stored as fringe phase modulation. A standard state of the object can be frozen in the screen of a monitor and its evolution deformation or misspositioning followed through the Moire between current and stored fringes. Topography of the object expressed as a mathemati cal functi on h ( x y) and its time evolution can alsO be determined from the memorized data. . Besides a conjugated grid can be generated so that when the latter is projected onto the object the observed fringes are corrected to straight lines resembling the original Ronchi rul ings i. e. distortion produced by object topography is cancelled out. Deformations with respect to this state are straightforwardly interpreted by an observer both in magnitude and sign. The system can be made
The effect of finite dynamic range, electronic noise and sample rate of the TV-
camera on the recognition accurecy of speckle Young's fringe given by pointwise
filtering technique in speckle photography is investigated experimentally.
In the particle image velocimetry' for
fluid flow measurement, Young's fringes are
accompanied with speckle noises generated
by random interferences of scattered lights
from particle images and the photographic
negative, which generally obstruct the
fringe analysis. These speckle noises have
high spatial frequencies and their spatial
distribution is at random. Taking the
characteristics of the noises into
account,we have designed a new system for
analysing the fringes by means of spatial
modulations with a slit and a grating
displayed on a transparent liquid-crystal
In this paper a laser interferoeter for measuring small angles with an accuracy better than 0. 01 arcsecond is proposed. 1 THEORY The diagram of the interferometer is shown in Fig. 1. When the angle 1--laser 2--beam-expanding lens 3--pin--hole filter 4--collimating lens 5--aperture 6-- beam-splitter 7-CCD component 8--detector for stabilizing laser Mirrors A B--measuring reflectors Mreference mirror composed by mirrors A B is equal to X/(2m1) m1 . . the mirrorimages of Fig. 1 mirrors A B are in the same plane equal spacings on both sides of the visual field will be formed. When A rotates about 0 a small angle 4 the mirrorimages A B are not same plane and fringe spacings on two sides of the visual field be unequal. Plus sign is taken when mirror A rotates clockwisely sign for counterclockwise rotation. We have 4A(1/e 1/ca )/(4m2) (1) where e e1 are shown in Fig. 1. In order to get adequate interferometric field keep fringe straight enhance the contrast of the fringe and keep the contrast constant the lengths of mirrors A B should be long enough R:T ratio of splitter should be determined according to how many times the incident beam being reflected between mirrors A B and the reflective index of mirrors A B and the interferometer should satisfy the equivalent sine condition/''- Definite Fourie Transfer mode of processing interferometric fringe is adopted in this
We present an analysis of the Savart interferoineter calculating the interference fringes produced by the superposition of the wavefronts from the geometrical images formed by the birefringent element. 1. INTERFERENCE FRINGES FROM THE SAVART PLATE In this work we propose a procedure for analyzing the Savart interferometer including the zone of the field that is not used as a working zone. Using the ray tracing metho the images formed by a plane parallel birefringent plate were obtained . These are: an ordinary image without first order aberrations and an extraordinary one astigmatic to firs: order. In the Savart plate the two images that are formed by the rays that are extraordinary in the one plate an ordinary in the other are astigmatic. The rays that are ordinary in both plates give a point image without first order aberrations and those that are extraordinary in both plates do not exhibit first order aberrations either because the astigmatism is coinpensed. To obtain the interference fringes the forms of the wavefronts corresponding to the images are calculated and from these the corresponding phase shifts are found. The figure shows the pattern generated by the interference between the following images: OE (ordinary in the first and extraordinary in the second plate) with EO giving rise to the system that is sharp in the center of the field 00 with OE and EO which give fringes
According to the fact that a shearing interferogram cou''d be observed from the commercial test tubes and bottles the theoretical and experimental work have been performed for the cylindrical shearing interference to examine the thickness and distortion of the glass test tubes and bottles. An interferogram can be observed in reflected direction while a He-Ne laser beam is incident upon the surface of a commercial test tube or bottle. The interferograms are changed with the diameters and thicknesses of the test tubes and bottles. Some of tubes and bottles can generate a clear series of the interfertnce fringes and some can only gencrate a indistinct fringe series. Some tubes and bottles even can not generate any interfence fringes. These phenomena led to our interest in studing the cylindrical wavefront shearing interFerence and in examining the optical quality of the commercial glass test tubes and bottles. Suppose that a parallel plane wave is incident upon a test tube. This parallel pline wave will split into tWO divergent cylindrical waves after reflection from the outside and inside surfaces ul the test tube. The cylindrical centers of these tWO waves are located at two focussed lines which are formed by the two surfaces. These two cylindrical waves are coherent and will form an interferogram due to the wavfront shearing interference because of the difrerence in the wavefront radii. According to this model a expression
Interferometric tests are widely used to test high precision optical systems. This kind of testing is about
the only way to assure the desired accuracy and performance of those systems. In this paper a new
lateral shearing interferometer (LSI) will be presented originally designed to test infinity corrected microscope
**Fuji Photo Optical Co. Limited Ooiniya-shi Saitama-ken Japan A new type of shearing interferometer has been developed in which sharp multiple beam interference fringes which directly represent the lateral aberration of the lens under test are produced holographically. 1 .
It is sometimes important to investigate the 3D structure of a small transparent
object, such as biological cells or optical fibers. Here we describe an interference
microscope with digital image processing systems, in which the interferograms of a small
phase-object projected in various directions are measured and then the internal structune of the object is digitally reconstructed by technique of computer tomography.
Since electronic speckle pattern interferometry (ESPI) was presented near 20
years ago , some important applications have been found, and at least two kinds
of ESPI instrument have been produced. In an ESPI system, imaging lens is one of key
parts. In this paper, authors will study the effect of the resolving power of lens
on ESPI fringe patterns, so as to find what lens the ESPI system needs. This research
would be significant for designing an economical lens fitting to the ESPI system.
ESPI was originally developed(1) for the measurement of in-plane strains in static components. New developments at
City University are extending the application to rotating components. A pulsed laser of 20 ns duration freezes the
component motion. Two beam oblique illumination of the component surface gives a displacement sensitivity direction in
the plane of the illuminating beams. A high resolution speckle tv-camera and digital storage yields clear high-contrast
interference fringe patterns on initial state, live-load speckle image subtraction. High precision laser triggering provides the
correct register of the speckle images for satisfactory image subtraction. Where component deformation is predominantly
speed dependent. allowance must be made for variation in the response time to the component position at different speeds.
An ap1ication of holcgraphic interferartry to investigate the residual
deformations izi1uc1 in nitrogen implantel specirrens by a plana focus device is reported.
ExperilTental results Obtained for AISI 304 stainless steel specinns are presented.
Interferometry of laser-supported absorption waves and the resulting gas dynamic
disturbances are studied. It is possible to show the propagation of shock, geometri
cal shapes of the waves and vaporization of target material.
Recent advances in the design and recording of holographic optical elements are illustrated by means of two representative examples - focussing lens and multiple beam grating. The focussing lens design method is based on an analytic ray-tracing procedure that yields an analytic solution for the diffractive grating function. It will be elucidated by describing the recording and testing ofaspheric low 1 number focussing elements for 10. 6 microns wavelength having diffraction - limited performance over a broad range of incidence angles. The design of the multiple beam grating is based on solving a set of nonlinear equations to obtain a grating structure that can convert one incident beam into a set of specified output beams. Both the lens and the multiple grating elements are recorded with binary optics that involve computer generated plots with high resolution laser printer and plotolithographic techniques. Reflective and trismissive elements are formed by either etching reflective metal layers or GaAs substrates. 1.
Author(s): Jean J. Couture; Roger A. Lessard; Rupak Changkakoti
Dye polymer systems are seen as promising holographic recording media in application
of holography and nonlinear optics. Holographic characteristics of Fluorescein dye/PVA
and Eosin Y dye/PVA systems have been investigated.
Author(s): Kondragunta S. S. Rao; Prakash C. Mehta
Apochromatic Holographic Optical Elements (AHOEs) have been designed and developed using 633 nm wavelength in red sensitive photographic emulsion to work at 633 nm 5 14 nm and 488 nm with same focal lengths and equal efficiencies at each wavelength. These AHOES have been used for recognition of coloured targets and pseudocolouring.
One of the main directions in the development ot present-day
systems Of information processing is the creation of neural net-
works. In holography neural networks are amply long known: as
early as in 1963 P.I.Van Heerden showed that the coupling by means
of 3-D gratings which are recorded in a deep 3-D hologram is purely
unambiguous In particular, the grating recorded in the hologram
by the radiation of two arbitrary points interacts only
with the radiation of its 'own' points and ignores that of all
other ones during the reconstruction. But most unfortunately, a
deep 3-D hologram is not a convenient element when used in practice. In particular, in this case it is very difficult to choose
a suitable light-sensitive material and to control each separate
grating among a great number of similar gratings which are superimposed
in the hologram volume.
The report is devoted to the consideration of so-called
pseududeep holograms the properties of which are similar to those
of 3-D deep holograms, and which are free of the above-mentioned
Kinoform for irregular space-variant nonparaxial optical interconnection (01) was calculated by the generalized error-reduction algorithm (ERA). Diffraction limited spots easy to align for detectors of 10 im width and diffraction efficiency r 34 were obtained for the binary kmoform case. This approach is fast takes into account the incident beam intensity distribution and an equalization of the intensity between spots is easy. However the resulted surface relief is complicated. NONPARAXIAL KINOFORM SYNTHESIS Free-space Ols for clock distribution will require a low f-number (F/i) holograms due to expected detector sizes of 10 m x 10 im and typical laser diode (LD) light divergence angles of 30 and iS . Large field angles needed to obtain large fanouts and to deflect beams towards detectors located near the chip boundary also cause that paraxial conditions are not satisfied. Kinoforms which are computer generated phase holograms afford possibilities for Ols with complicated detector patterns and high . Free-space nonparaxial propagation can be described by the operator N FT QFI where Fr U f Uexp(-ikcxx1 ) dx1 U(x1) is the complex amplitude in the kinoform plane Q is the spectrum phase shift operator QFJ'' U exp ( ikz I 1 - 2 ) j''U k 2 vt/A X is the wavelength is the normalized spatial frequency and z is the separation between planes. N is an unitary transform because we may neglect evanescent waves in
A new fast approach to computer-generated holography for 3-D objects points in arbitrary positions in 3-D space is presented. The approach is based on fast computation of weighted zero-crossings their accumulation and thresholding to achieve a coded hologram to be physically generated. 1.
If an iaage is reconstructed floating above the holorai plane it gives strong three dilensional lipression. A holograi having the shape of corn is suitable for this purpose and this paper presents the iethod for uaking conical holographic stereograis 1.
Space-invariant kinoform-type array generators with discrete phase levels high 2D diffraction efficiency 90) and low reconstruction noise are designed using a novel algorithm and their fabrication error tolerances are analyzed. L
Two-element combinations of holographic optical elements (HOEs) consisting of a rotating
HOE and a fixed HOE are considered, and optimum conditions are obtained for aberration-
free, straight and constant-velocity scannings.
Noveldesigns for forming space variant holographic ifiters that perform general types ofcoordinate transformations on two dimensional pictures are presented. The designs are without any paraxial approximations and include planar and curved filter configurations. The experimental results indicate that high quality transformations can be obtained. 1.
Variations in the average refractive index
and thickness of the holographic recording
material are present due to chemical processing.
These changes produce a reordering of the
internal structure of the interference fringes so
we can see that the processed material and the
registered material are different. In this paper
we have analyzed the influences of exposure and
geometric disposition of the recording beams on
the variations of the maximum diffraction
Our previous resarch1 has shown that the
parameter used to analyze the influences of the
thickness and index variations is defined as:
(formula available on paper)
where T = t/t and N =QR(t and n represent
the thickness and the refractive index of the
medium, respectively); aR, and a the
angles in relation to the normal for holograms.
Renesse and Bouts represented the phase variations of holograms formed by conventional bleaches
in which the hologram is bleached after development and fixing as a function of original density.
They showed that the phase variations are determined mainly by the volume of the molecules of silver
halide formed in the bleach bath. They formulated the nuer of silver halide as function of the
The measurement of 3D objects involves complex
systems of various types. The results are often
acquired, processed and stored by a computer in
the form of digital data. The display (computer/
human interface) relies on mature 2D display
techniques. The loss of depth information is
partially compensated for by rotation or sequential
To display 3-D images stored in computer, cylindrical holographic stereograms with
white light illumination (CHS) is useful because of both one step synthesis and wide
viewing angle in the horizontal direction. But it has been difficult to make the vertical
size of reconstructed images larger than 20 cm, because conventional optical system for
synthesizing CHS requires a high-power cylindrical lens larger than the size of the
reconstructed images 1
We show a new anamorphic optical system, which
enlarges the size of images reconstructed from CHS.
LI the photolithography is combined with holography a new phaseonly relief hologram can be produced. The method that increase modulation index and diffraction efficiency by controlled the etching condition and experiment result are reported in this paper. This method has new application prospects. i
We describe an experimental method to produce image holograms that reproduces an im--- age with an specific color code. First we codify the scene using the theta modulation technique. Then a 4f optical image processor is used to decodify the information. Fi nally the decoded image is recorded holographically using a different reference beam an gle for each different scene. We take special care to make sure that the area illumi nated by the reference beam is the same area of the decoded image. In this way we have a multiple hologram which reproduces the image with the selected color code with a very high efficiency. 2. BASIC ThEORY When we illuminate a diffraction grating with a monocromatic plane wave with normal incidence the amplitud distribution after the grating will be equal to a set of plane waves with angular directions related by: dsenOm mA (1) Where d is the period of the grating A is the wave length of the incident radiation and m is the order of interference. For any particular value of m (m o) the regular desviation or direction of propagation depends directly of A. That is for: X A2 0 0 2'' We are interested in observe in the same direction (m constant) different wve legths when we illuminate our grating with a polycromatic plane wave. According to Ec. (1) the only
Author(s): Andrey G. Zhiglinskiy; Alexandre M. Izmailov; Galina G. Kund; Alexander O. Morozov; Alexander N. Samokhin
Holography is one of the most informative optical methods of the investigation
of spatially inhomogeneous , nonstationary, bright self- luminous
objects. However, most natural objects (plasmas, vapous, liquids, solids,
biological objects, etc.) have a complicated composition and structure,
which are revealed in the specific spectral dependences of the object's
refractive index, absorption, scattering and reflection. This circumstance
requies the development of the polychromatic type of holography, which is
realised with a large number of wavelengths simultaneously, for the diagnostic
of such objects.
A special code rainbow holography is presented. By dividing the code image and recording with special method the rainbow holograms which can hardly be counterfeited have been obtained. iINTRODUCTION The optical holography is an important means in security and anticounterfeiting . Up to now some secu. rity methods ofhologrophy have already been proposed. In these methods embossed rainbow hologram tech. nique is the main means. However with the popularity and improvement of rainbow holography emulating and counterfeiting of the holograms which contain information about simple images is quite possible. In this paper a new puzzling colour code method ofrainbow holograms is presented. . THEORY The puzzling colour image makes up of a obct image which is constructed with a certain colour spots and a large number of other colour noise spots used for feigning. When we make the hologram we divide the background noise spots used for feigning as well as the object image which is going to be coded into several parts and record each part on the same recording film with different angle of reference beam and corresponding different slit position respectively so reconstruction conditons are restricted seriously by recording conditions. Under common reconstruction conditions except for getting some colour spots in disorder in dif. ferent viewing direction one is unable to obtain the complete coded object image in distinguishable. This is called puzzling colour code method. . EXPERIMENT
A simple method of making true color rainbow hologram of 2D image with HeNe laser is presented. The advantage ofthis method are simple optical arrangement large viewing angle high energy utilization and high fringe visibility. Satisfactory result is obtained and main problems in color reproduction is discussed. i
In 1963 Glauber /Phys. Rev. 130, 2529 and 131, 2766/ published a
basic theoretical study that revealed the broad variety of possible
photon states. Later on a quantum-statistical analysis showed that
states with classical analog (this light Is termed classical light)
as well as states without classical analog (so-called nonclassical
light) can occur. Following the definition given by Teich, Saleh, and
Perina /JOSAB2 (1985) 275) nonclassical light exhibits one or more
of the attributes squeezed, antibunched, sub-Poissonian, what is
connected with a negative value of the field-fluctuation excess, the
bunching excess, or the Poisson excess. These negative values mean
quantum fluctuations below the classical standard quantum limits of
ideal laser light; thus, nonclassical light may yield an essential
improvement of the optical measurement accuracy, in particular of the
signal-to-noise ratio. There exists a common property of the three
attributes concerning the Glauber-Sudarshan representation P(c ),
which is the real weight function belonging to the incoherent mixture
(density operators) of Glauber states with different complex amplitudes. In the case of classical light P(oç ) is a positive definite
function, whereas nonclassical light requires a nonpositive definite
function P(o.), which cannot be interpreted as a proper probability
distribution - as it is possible in the case of light with a classical analog /M. Schubert, Ann. d. Phys. 4k (1987) 53/. In addition to
its possible important applications nonclassical light yields a deep
insight into the quantum nature of the radiation field.
Interferometric optical profilers have a spatial resolution which is either limited by the detector array sample spacing and element size or by the optical resolution of the system. To test the working spatial resolution of an optical profiler a sinsusoidal grating with 300 lines/mm was measured using an optical profiler at lOx 2Ox 40x and 200x with detector arrays having element-to-element spacings of 6. 8 j. tm and 40 tm. The highest magnification gave the greatest and most accurate depth for the grating for all of the detectors. At 40x as long as there were more than about 8 sample points per cycle as there were with the two smaller detector spacings the grating depth can be measured quite accurately. With fewer points the peak-to-valley height measurement of the grating is too low even though the optical resolution of the system is sufficient enough to resolve the grating. The results of this work show that for accurate representation of surface heights containing high frequency structures oversampling is desirable. Summary The spatial resolution of an interferometric optical proffler depends upon both the optical resolution of the system and the characteristics of the detector array used to sample the image. The limiting resolution wifi be the larger of the optical and detector resolution. One means of defining optical resolution is the Sparrow criterion which states that the image of two points is just
The use of the evanescent wave produced in the second aediua vhen total reflection occurs at a boundary enables thickness ieasureents on a uanoetre scale to be aade sisultaneously with the highest lateral sagnification. The second aediun contains a siall concentration of fluorophores and the fluorescent . ission is measured. 2. DEPTH DEPENDENCE OF FLUORESCENCE Although the existence of fluorophores in the second sedius inevitably ieans a non-vanishing extinction coefficient K the very low concentration needed leads to an extinction coefficient of less than - iO. In calculating the electric field strength E in the evanesent wave no appreciable error results in putting K equal to zero. If the refractive index of the incident iediun is n1 that of the second zediun n2 and the angle of incidence e then for incident light with the electric vector perpendicular to the plane of incidence (''s''coiponent) the electric field at a depth z is given by: 1 5(z) . 2n1y1 e$2Z (1) 1n2$2 - n1y1 . SI 1. 7O where V1 n1k0 cos e $ nksin2e1 - nk and k0 2n/A where _1. 33 A is the wavelength in vacuo. The fluorescent flux frog a slab of thickness dx is proportional to Idz (Gingell et al'') so that the total signal 5T froa the unobstructed evanescent wave is given by SiO I 4n)je22dz 2n 5T (n$ + nvf) $2(n + nj) (2) Figure
An improvement in the accuracy of the axial distance measurement between two planes using a simple zone plate interferometer is proposed. In this case a Fresnel zone plate with initial phase shift between the 0th and 1st diffracted orders must be designed. 1. ZONE PLATE INTERFEROMETER. A simple method of measuring angular and axial misalignments between two different planes is possible by using a common-path zone plate /ZP/ interferometer. One plane is associated with a transmission Fresnel ZP being a reference plane whereas the second is connected with a plane mirror directing diffracted beams back to the ZP. When the ZP is illuminated by a plane wave the light passing throughout it is divid ed into several diffraction orders. After freespace propagation they are reflected by a plane mirror and go back to the ZP producing now a new set of diffracted orders for each one of the incidents. With a proper spatial filter system we select only two //O of the output wavefronts in order to observe the interference pattern produced by them. One of these two waves is generated by the virtual focus of the ZP and the other by the real focus. The positions of both focii depends variously on the relative orienta tion and position of the mirror in respect to the ZP plane. The shape and the frequency of'' the fringes in the interferometric pattern give
Author(s): Gang Ye; Mang Cao; Jia Wang; Dacheng Li
A method for non-contact on-line measuring large shaft diaseter using laser beas scanning technique is presented in this paper. Diaaeter froa 500 to 2000 s can be Measured by the aethod over large seasuring range resolution is 0. 005 ii accuracy of variation over 700 0. 02 s. 1 .
A twodimension acoustic speckle pattern (ASP) as a whole is shown for the first time by the liquid relief method. An ''acoustic diffuse? and basic use ofASP for measuring underwater object''s displacement are given. 1.
On freepropagation some optical wavefields exhibit longitudinal quasiperiodicity. We discuss the relationships between multiple impulse responses in the Fourier domain and periodicity or quasiperiodicity. 1.
Author(s): L. Cescato; Ekkehard Gluch; Helmut Haider; Norbert Streibl
Form birefringence can be observed in dielectric coatings and in relief gratings. We compare the form birefringence of dielectric coatings and relief gratings. Using the simplified model of parallel the form birefringence of both dielectric coatings and relief gratings can be calculated and its angular dependence can be evaluated using the analogy with negative uniaxial crystals. k
The moire interference phenomenon caused by the circular diffraction gratings under
coherent illumination is studied to utilize it for precise alignment. The phenomenon
is investigated by the Fresnel Kirchhoff's diffraction theory. The characteristics of
the moixe signals in the diffracted beams are examined as a function of the lateral
displacement and the airgap between the gratings. The moire signal obtained in the first
order diffracted beam has been employed to the precise short-range alignment. The
alignment system consists of a phase shifted pair of circular gratings and a stage driven
by piezo-electric atuators. The system is controlled by the micro-computer to keep
the alignment position. The alignment has been carried out with the precision of few
tens of nm.
A numerical method of analyzing the scattering of light waves from lamellar gratings with anisotropic materials is presented. The analysis is based on the rigorous methods in terms of electromagnetic fields expanded by space harmonics. Numerical results for a lamellar grating show the diffraction characteristics with the resonance anomalies. 1 .
Two-wave mixing (TWM) and dynamic volume gratings are an
exciting area of research in nonlinear optics using nonlinear
optical media (photorefractive crystals) for energy coupling and
We describe a novel approach that leads to an analytical formula for shaping the power spectrum of 1-D gratings and zone plates with different opening ratios by using apodizers expressable as Legendre series. Some applications of this formulation are presented. 1.
The possibility of concentrating all the transmitted energy into one spectral order is established for a triangular groove dielectric grating for which a thin layer of per fectly conducting metal is evaporated on the small facet. The reflected energy is then only equal to the Fresnel reflectance (i. e. " 4 ). When an antireflection coating is evaporated on the large facet the transmitted efficiency can reach 100 into the first order.
The generalization of the circular zone plate with ring focus onto elements focusing light into an ellipse is proposed. The transmittance of obtained zone plate is given in explicit form basing on scaling property of Fourier transform.
Derived in the comunicate formula allows to find equation of basic grid for desired moire pattern and kind of displacement. As an illustration few examples of potentially practical application are given.
Author(s): Truman D. Black; V. A. Komotskii; Don A. Larson
The enhanced interaction of an optical probing beam with a traveling surface acoustic wave (SAW) using either a separate stationary rectangular phase or a holographic (HOE) phase reference gratings is reported. SUMMARY Grating enhanced probing of SAW using both amplitude and phase structures located on the same reflecting plane as the SAW was investigated analytically and experimentally by Koniotskii and Black) This paper extends this work to include a separation distance L between the reference grating and the plane of the SAW. A spatial frequency analysis in the Ranian-Nath diffraction regime was performed for both transmission and reflection configurations. The small signal case where the reference structure is strongly modulated in comparison to the phase modulation of the traveling space-time grating produced by the SAW is treated. The double grating interaction is found to provide a heterodyne-type sensitivity and spatial selectivity.
A method for full field 3-D surface reconstruction is proposed. The method is based on shadow moire topography and makes use of four contourograms shifted in phase by translating the object. The implementation of the method in a fully automated apparatus is described. Some application examples are given. 1.
A lenticular 3D image consisting of many parallax views can be seen without glasses in real-time. But it has sampling errors. In this paper characteristics of sampling errors caused by views of 3D image are explained with experimental confirmation. It is shown that the depth sampling errors have serious effects in the image stability phenomena. Data compression scheme using the geometrical structure of the 3D image is briefly described. 1.
We will discuss some physical limits of 3D-sensors that work on ''rough'' surfaces. An important result is that the most frequently used principles (laser triangulation and focus sensing with projected light spots) cannot achieve a better depth resolution than given by the Rayleigh depth of field. However we can achieve ''superresolution'' in depth by sacrificing lateral resolution: There is an ''uncertainty relation'' between lateral and longitudinal resolution. 1 .
We show a system for sequential distance measurement which works as a 3D-sensor. One point of the object is illuminated via an xy-scanning-system. The scattered wave carries the distance information in its curvature at the location of the sensor. We collinearly measure the radius of this wave in the sensor plane by shearing interferometry. Heterodyne modulation of the interference pattern is performed by a photoelastic modulator for high speed and robustness against environmental light. The sensor requires very small apertures for illumination and detection so shading effects and hidden points are minimized. 2.
Three dimensional images can be captured electronically by space-variant inversion or de-blurring of the intensity distribution measured in the volume behind the imaging lens. A computer simulation using a measured lens point-spread-function illustrates the effectiveness of the technique for incoherently-radiating objects with negligible internal scattering. 1 .
Author(s): Gerd Haeusler; A. Schmidt; R. Wachtler; Jorg Waldmuller
A 'diffraction-free' light distribution does not change its transverse intensity
pattern as it propagates through a homogeneous medium. Hence, it would be extremely
useful as a probe in optical metrology, specifically for 'light sectioning'. Is such a
'light plane' possible? How much confined can light be, without being spreaded by
diffraction? We discuss these questions. It turns out that a light plane cannot be
generated by monochromatic, coherent illumination. However, it is possible to generate a
light plane incoherently, by a scanning axicon beam.
Optical 3D-sensors are useful tools for automatic inspection.
But frequently they are complex and expensive.
We introduce a simple 'point sensor' for the acquisition
of 3D object data, based on a modification of the
'confocal focus sensing'. This principle was described
by Shamir et ala, for sensing microscopic, mirrorlike
objects. Our modification works for macroscopic objects
with rough surfaces. Rough surfaces introduce problems,
because, with coherent illumination, we get speckled
spot images. To reduce speckle effects,often a very high
illumination aperture is used. But when measuring macroscopic
objects one needs small apertures to get enough depth
of field and to avoid shading. We reduce speckle by using a
broadband laser diode or a white light source. Fig.l
The sensor works as follows (Fig.l): a light spot is projected
onto the object surface. Two images of this light spot are created by
the lens L and two beamsplitters. Two pinholes are located on the optical
axis, at different distances. The flux l and 2 behind the pinholes
is measured. The ratio D1/D2 encodes the object distance. 41/b2 is independent
from the object reflectivity.
Author(s): R. Duchowicz; Marcelo Trivi; Lucia B. Scaffardi; Nestor A. Bolognini
3-D data display can be classified into holographic and non-holographic.
(1]. Normally, the amount of information stored in a hologram i very
large. In this way, if only deph perception is required, the stereoscopic
techniques provide an adequate 3-D display. Among the non-holographic
method, we have developed an optical method for storing on a single
recording plate different perspectives of a 3-D scene [2). In this paper
we propose such stereoscopic method for displays of moving objects.
A new method is proposed to reconstruct a 3D free surface using its multiple
projections. It is not upon the conventional triangulation but upon a model
matching principle and does not require any reference point on the object.
A random phase shift atgorithm based on the principLe of phase-measuring profiLometry with a projected sinusoidaL grating to 360 measurement-of the surface topography of 3-D diffuse objects is presented. In contrast to phase shifting interferometry this method eLiminates the needs of vibration isoLation thus an on-Line or in-process amasurement could be executed. 1.
An optical array imaging method using digital phase conjugation has previously been proposed for diffraction-limited imaging ofobjects with no effects ofmisalignments ofarray elements. After collecting a set ofarray data this method iteratively receives the reflected wave from the object and retransmits its phase-conjugated wave until convergence is reached which are carried out all on a computer using the data. When the object has for example two points with similar maximum reflectivities however the method sometimes gives rise to doubled images. In this article the array data is selectively used in the iterative process to avoid such doubled images. Some numerical examples are presented. PRINCIPLE A schematic of optical array imaging system is shown in Fig. 1 where the object is illuminated from one of the array elements and the reflected light is received by the whole elements. The light is then interfered with a reference light to detect the complex-amplitude of the optical field. This is repeated for the illumination from each array element and a set of array data are obtained s(f JJh(f Object Array m n l . . N (1) F ig. 1 Schematic ofoptical array imaging where h(f x) is the wave propagation function o(x) is system using digital phase conjugation the coefficient of reflectivity ofthe object and effects of misalignments are included in h(f x) . The subsequent processing is carried out all on a computer.
We present an analysis of signal to noise ratios of two interferometric techniques for spectral imaging and its experimental verification. One technique makes use of interference signals detected near the pupil plane and the other uses the signals near the image plane. The experiments showed that the latter technique is superior to the former under the normal conditions. 1.
Applying the extended linear approximation'' to defocused imaging of semitransparent edges with weak phase part allows to study the influence of modulus and phase on the ima ge characteristics. It is shown that the influence of the phase part on the defocused image depends on the sign of defocusing and is a purely linear effect of the imaging pro cess. Defocusing is one of the oldest methods to detect weak phase objects. In the image of semitransparent edges a weak phase part is visible only in the defocused image too. In microlithography one might be interested in the focused image of the waver structure only but in searching for the exact focus position the remaining phase part in the object may have some influence on the intensity distribution2. Imaging surface steps on a waver the exact focus position is furthermore difficult to defines. The change of spatial symmetry from the object into the image for both the amplitude and the intensity is caused by the nonlinear transfer of both quantities in partially coherent imaging. Therefore two transfer functions (one symmetrical and one nonsymmetri cal) are used within the extended linear approximation to describe this effect. Recently *e have given the formulae for the image intensity distribution of semitransparent edges +. If these are applied to defocused imaging of semitransparent edges with a weak phase part it turns out that the difference
Author(s): Hector J. Rabal; Elisa M. Colombo; Carlos Kirschbaum
Physical parameters determining the perception of sharpness in defocused edges are searched for. A sensorial compression curve a gaussian model for the receptive fields and sensitivity to defocus are derived 1. METHODOLOGY AND RESULTS We search for significant physical parameters which determine the subjective perception of sharpness. Printed letters photographed with controlled defocusing were assessed by 7 observers according to a 7 steps scale of sharpness S (S low edge definition S10: high edge definition). Adaptation luminance was 100 cd/rn2. The density profile of the edges of the defocused letters was measured and after median window filtering the correlation coeficcients between its outstanding physical parameters and the psychophysical evaluation were calculated. Maximum and mean slope were found significant. The experimental values were then adjusted in a sensorial compression curv and its parameters calculated. From such a curve sensitivity to defocus was obtained. It was found that sensitivity is very small in both high and low sharpness sides and shows a maximum around the 6. 5 value (in a scale from 3 to 10) in perceived sharpness. Besides a gaussian receptive field model was proposed and its parameters calculated to adjust the sharpness response of the visual system to edges of arbitrary maximum slope and contrast. Two three and five gaussians were used for the receptive fields all results showing negligible differences. The edges were simulated by linear ramps and by exponentials.
In microwave systems for detecting or imaging buried dielectric anomalies, a common
technique is to search for reflectance variations by mechanically scanning an antenna over
an area. The antenna usually operates in its and the object's nearfields to reduce diffraction
spreading so that the reflectance distribution resembles the object's shape and is thus an
image. Although mechanical scanning is reliable, it is slow because data acquisition is
sequential. Data acquisition can be accelerated by an antenna array. An array provides
spatially parallel data channels. If a single transmitter and receiver unit are used, acquisition
is sequential but very fast with solid state switches. If each antenna has a transmitter and
receiver, acquisition is simultaneous, and costs increase.
In electronic halftoning binarization algorithms are applied to convert graylevel
images into binary ones. The local gray value of a binary image is given as a local
average over black and white (0 and 1) pixels. Electronic binarization algorithms allow
us to use binary working printing and display devices to present graytone images.
The arbitrary nature of similarity and invariance is examined and its implications for pattern recognition and classification are examined. Various measures of similarity are discussed and techniques for achieving invariance under translation rotation contrast and energy are briefly reviewed. We show how both matched filters and neural nets can achieve c!assification of objects into arbitrary classes. For neural nets different kinds of similarity measures can cause patho!ogica! behavior that can be avoided by using a specific normalized kind of similarity measure. Implications for unsupervised learning in certain kinds of neural networks !ike the are discussed.
We describe a complex optical system consisting of a 4f optical correlator with programmable filters that operates at video rates. Filter generation storage and management is under control of a digital on-board computer.
An optical correlator using incoherent light was exploited with a composite filter comprised of a multiplicity of sub-filters to simultaneously detect the presence of a number of objects or alternatively allow rotation and scale changes of one object. We determined that for high SNR it is necessary to record the sub-filters with diffused light. Moreover for a certain geometry of the correlator the sub-ifiters diameter can be as low as 4 mm without significantly affecting the correlation performance. 1.
An amplitude and phase filter is produced to correct and average the object spectrum of a high resolution micrograph with the help of a slow variant mask in the optical pupil of a Fourier transform system and by photographic nans in an imang holographic system.
The progress in the development and use of mirror optical systems with realfration of the adaptive methods for picture proceing is d1scued. Some ofour reenits presented in this work are connected with the examination and synthesis of a number of mirror syBtems The scientific solution of the aberration theory method and our study of the all-mirror optical systems are directed to the realirations of new complexes for adaptive picture processing. The unified mirror elements and a new module method for the synthesis of optimal optical configurations are presented. For many applications the mirror systems are more compact and qualitative. The complex binary and greyscaled images require rapid evaluation in modern devices. The new hybrid optoelectronic complexes can operate more effectively than computers and optical procors. The adaptive optical systems have some new functional possibilities for picture processing. They are used for image quality improvement contrast enhancement figure contouring interferogram analysis etc. The aim of this work is the presentation of the results obtained in the design of some complex adaptive systems for picture processing.
We introduce two new invariant transforms. The first one is invariant under shift rotation and scaling of the input pattern simultaneously. The second transform based on the Rapid Transform is fast shift invariant and invertible. Both transforms are useful for signal classification and recognition.
Optical inforriation processing has
received much attention since the sixties.
The parallel nature of optical systens,
their inherently large spacebandwidth
product and real-time processing
capacity has led to the development
of meny syst&me and techniques for opt ical
inforntion processing and optical
Author(s): David Mendlovic; Emanuel Marom; Naim Konforti
The joint transform correlator operation has been extended to include complex reference images. Such amplitude and phase images are involved when using single harmonic images (circular radial logarithmic etc. ) in correlation setup. The analysis of a rotation invariant pattern recognition system using joint transform correlators principles is described followed by experimental results that can be obtained in real time. The optical joint transform correlator is based on recording the Fourier transform simultaneously displayed by a pair of 2-D functions and then generate the transform of this pattern. Yu and Liu1 applied this technique to real time pattern recognition configurations by using spatial light modulators (SLMs) in the optical system. The joint transform correlator preserves shift invariant pattern recognition property but has high sensitivity to other invariant parameters such as rotation scale projection etc. It has been recently shown25 that the classical correlator configuration can be made invariant to one additional parameter (i. e. angular orientation scale changes projections) by using a matched filter containing only a part of the input data. We will demonstrate in this paper an invariant joint transform correlator by using a single harmonic of the stored pattern as the reference object.
Spatial filters for discrimination among the members of a training set are shown to be available with global optimum. These filters can be implemented with real bipolar point-spread function. The method is demonstrated to be effective also for rotation invariant pattern recognition. 1 .
Current methods for real-time optical correlation employing a jointFourier transform approach use a spatial light modulator (SLM) in the focal plane to store the interference intensity which is subsequently read out by coherent light. Because the resolution required for accurate representation of the image transform is extremely high the spatial light modulators which meet the specifications are prohibitively expensive. We propose a novel approach to jointFourier transform correlation (JTC). The method obviates the use of the spatial light modulator in the focal plane and still preserves the real time aspects of the measurements. The approach incorporates the use of acousto-optic technology for optical mixing SLMs for image representation and electronically tuned detection of the heterodyne optical signal.
An electrical-optical hybrid processor for the high-speed calculation of surface images from three-dimensional voxel data is proposed. The image rotation and two-dimensional interpolation which requires enormous calculation time i n digital computers are optically realized by this processor. Hybrid three-dimensional simulator can produce not only the surface image lxt the semi-transparent image by using the graylevels ofthe original three-dimensional information. Experimental results are demonstrated. 1.
Author(s): T. Sato; F. Kimura; Shigeru Izawa; S. Takahashi; Kashiko Kodate; Takeshi Kamiya
For the total system of optical cards defects on cards deteriorate their performance. We have developed an automatic inspection system of optical cards where we have applied spatial filtering technique to eliminate the periodic background pattern.
Author(s): Gerd Guelker; Olaf Haack; Klaus D. Hinsch; Claudia Hoelscher; Juergen Kuls; Winfried Platen
A videoholographic system was developed which allows three-dimensional deformation measurements. The system was applied in inyestigations of deformations occurring in the hardening process of a special restoration mortar. 1 .
It has been shown previously that the binary joint transform correlator (JTC) can produce reasonably
good correlation performance.'5 The binary JTC uses nonlinearity at the Fourier plane to binarize the Fourier
transform interference intensity to only two values, +1 and -1. The binarization is performed according to a
predetermined threshold value which is the median of the joint power spectrum histogram. The performance of
the binary JTC was compared to that of the classic JTC in the areas of light efficiency, correlation peak to
sidelobe ratio, correlation width, and cross-correlation sensitivity. It was shown that compared with the classical
correlator, the binary joint transform correlator provides significantly higher peak intensity, larger peak to
sidelobe ratio, narrower correlation width, and better cross-correlation sensitivity.
Recently, we have introduced two types of nonlinear image correlators with superior performance
com to that of the conventional linear optical corre1ators.1 The first type of nonlinear optical processor
is joint Fourier transform based which uses nonlinearity at the Fourier plane to threshold the joint power
spectrum.4 We have shown that compared with the linear correlator, the nonlinear correlator can provide a
much higher autocorrelation peak intensity, smaller correlation sidelobes, narrower correlation width, and
better discrimination sensitivity. The second type of nonlinear optical correlator is the nonlinear matched ifiter
based correlator13. The bandpass nonlinear matched filter is computed by expressing the linear matched
ifiter as an amplitude and phase modulated bandpass waveform using the amplitude and phase of the Fourier
transform of the reference function. The modulated bandpass real function is then transformed using a
general type of nonlinearity.
In this paper the interpolation and the dense sampling are used to improve PolarMellin Transform (PMT). The improved PMT can guarantee the degree of accurary of the Fourier transform and correlation processing.
Author(s): Xiaoliang Fu; ChunKan Tao; SongLing Bian; Aiming Li
Compared with traditional SDF MSF'' our new technique has greatly reduced the recorded information to the same goal in one piece. And that follows the bigmning work of a new pattern recognition system which has higher reliabilty with lower precisive treatment.
From the purpose of accuracy and convenience a new filter function is used to make optical matched filters in practical optical pattern recognition system by adopting Lohmann''s and Lee Waihon''s holography. These filters can reduce the halfwidth ofcorrelation peak improve the SNR and discrimination performance in correlation plane.
In a conventional pattern recognition system with a matched spatial filter (MSF), the filter
has been synthesized with the same pattern as used for an unknown input to be recognized. Therefore,
many reference patterns were used for synthesizing the filter even though a multiplexed MSF
(MMSF) was introduced' for recognizing many unknown patterns at a time. In this paper, we propose
and describe a new MMSF synthesized by some elemental components of the pattern which the desired
input unknown is composed of.
We propose a document analysis system to separate the graphic image and text and optical Chinese character recognition to recognize characters for processing Chinese form-document. It is a useful and efficient tool. 1.
In this paper smoothed binary phaseonly filtcr(ASBPOF) and amplitude smoothed amplitude encoded BPOF(ASAEBPOF) are presented. By computer simulation in the case of symmetrical and unsymmetrical characters it is concluded that with the BPOF and AEBPOF these filters sacrifice light efficiency due to the amplitudesmoothed factor it yield much better discrimination and a sharper autocorrelation peaks.
Polychromatic object recognition by multichannel correlation is experimentally achieved. Model objects whose shape changes with the wavelength of the illumination beam were used. Highpass matched filters were employed. The results confirm previous numerical simulations 1.
The computer generated holograms must be registered
after the codification, and all the output devices (TV, laser
printer,...) involve a quantisation to discreet values. There
are losses of information in the quantisation due to the
considerable dynamic range of the FT of the object and
the limited spatial or grey levels resolution.
Rotation invariant pattern recognition based on the holographic associative memory (HAM) is presented. Patterns are stored in HAM by using the scattered light holography in which a mother pattern is associated holographically with its several(nine in this paper) mtated patterns. In the experiment the rotated pattern is stored in different part of recording medium. For the input pattern rotated by any angle the associated mother pattern is reconstructed. Two mother patterns are stored in this manner.
Circular harionic expansion of twodiiensional
coiplex functions has proven
to be a very useful tool for the design
and experiiental realization of rotationally
invariant pattern recognition correlation
filters (1). Good practical results
iay be obtained provided that the choice
of the harionic order (nuiber of the ten
of the expansion) and the polar coordinates
origin taken are both optimized (2,3).
Author(s): Jarmo Hallikainen; Veijo Honkonen; Timo Jaeaeskelaeinen
Colors called "white' are found in a small but yet not sharply defined
region of the color space. The main characteristics of a white sample are
high ligthness, tristimulus value Y > 70 and low saturation, excitation
In this paper , we real i zed a real -time joint transform correlator .sed on speckle
clipping technique using Optic RAM detector and liquid crystal television (LCTV)
panels. A basic description of this application is that a time dependent speckle intensity
is detected by an Optic RAM detector by which the binarization of 2-dimensional
speckle intensity is performed for an arbitrary threshold level of the intensity.
Then, the clipped signa] is sent to a LCFV under the control of a microcomiter and,
finally, the correlation function of the clipped speckle intensities is obtained based
on the joint transfonn correlator (JTC).
Author(s): Santiago Vallmitjana; Ignacio P. Juvells; Salvador Bosch; J. R. de F. Moneo
When a large scale Fourier transform is
required, the main disadvantage in the
classical architecture for optical Fourier
transforiing (froi front to back focal
planes of a lens) is its length. If special
detectors (CCD caDera), spatial
sodulators (light valve) or filters (iiquid
crystal iodulator) are to be used,
the size of the transfora has to iatch the
size of the active eleient of the device.
When perforiirig optical correlation, the
final length of the set up will be about
four times the focal length of the two
lenses (if they are equal).
An offaxis farfield holography with a filter is studied. The intensity distribution in the reconstructed i*age plane is calculated. The influences of the radius and absorptive index of the filter on the form and contrast of the reconstructed image are discussed.
The Very Large Telescope, being build by the European Southern Observatory, has an
interferoetric node in which the light of the four 8 eter aperture telescopes, and of
a number of smaller telescopes, will be combined coherently to give iilliarcsecond level
angular resolution at optical wavelengths on very faint objects. This paper describes
current plans to impleMent this mode.
The angular resolution of conventional astronomical spectroscopy is limited to about 1 aresec by
the turbulent atmosphere. Much higher resolution can be obtained by
(a) objective prism speckle spectroscopy1, which yields diffraction-limited objective prism spectra, and by
(b) wideband projection speckle spectroscopy1, which yields spectrally dispersed 1-dimensional projections
of the object, i. e., object/spectrum reconstructions O(x,X) or O(x,y,X).
The resolution of conventional astronomical images made with large, ground-based telescopes is
limited to about 0.3 to 1 arcsec by atmospheric turbulence. Much higher resolution can be obtained by
the speckle masking method13 . Speckle masking yields images with diffraction-limited resolution, for
example, 0.03 arcsec resolution for a 3.6-rn telescope. In speckle masking a large number of speckle
interferograms (short-exposure photographs; exposure time 0.05 sec) has to be evaluated. The first
image processing step is the calculation of the ensemble average bispectrum or the ensemble average
triple correlation of all speckle interferograms. The speckle interferograms of faint astronomical objects
consist of only a small number of photon events. For example in the NGC 1068 experiment described
below, each of the 10 000 evaluated speckle interferograms consisted of about 400 photon events only.
As described in the next section, triple correlation or bispectrum processing can be applied to the
photon-counting speckle interferograms.
The atmosphere of the earth restricts the resolution of conventional astrophotography to " 1 arcsec.
Much higher resolution can be obtained by interferometric speckle techniques. Bispectrum analysis'3
(also called speckle masking) of many speckle interferograms (short-exposure photographs; exposure time
,,o.o5 sec) yields diffraction-limited images with, for example, 0.02 arcsec resolution for a 5-rn telescope.
After the first processing steps of speckle masking the object bispectrurn o()(u,v) is obtained up to the
cut-off frequency of the telescope. From the object bispectrum a diffraction-limited image of the object
can be reconstructed (a) by using the conventional recursive method2 (the Fourier phase of the object is
extracted recursively from O()(u,v) ) or (b) by using an iterative image reconstruction algorithm presented
in this paper. The iterative algorithm searches for the high-resolution image which has the best agreement
with the measured object bispectrum.
The average image and average energy spectrum are analyzed for a coherently illuminated deterministic object assuming complez gaussian saiisiics for the random screen. Furthermore it is shown that double passage through The same random screen can give diffraciion-limiied information about the object.
The optical systei for driving the solar Stirling engine with an output power in the kW range is described. This systei was of the Cassegranian-type and consisted of a parabolic iirror (diaieter 0 2. f/D 30 f: focal length) and a hyperbolic irror (0 . f/D 26). The parabolic airror was co. posed of 181 segiental iirrors . ade fro. glass plates and the hyperbolic iirror was iade fro. Al plate. The Stirling engine was developed by Isshiki et al. The input power of sun rays converged by the optical syste. ranged fro. 3. 0 to 3. 2kW and the output power of this engine was about 1kW. Fig. 1 The optical systea for the kW-range Fig. 2 A section of the Stirling engine. 1.
A flexible Monte Carlo program has been developed to simulate imaging through a turbulent atmosphere. We have applied this to conventional stellar speckle imaging and to the situation where an object is coherently illuminated and viewed after double passage through a random phase screen. We show that the timeaveraged image contains diffraction-limited information on the Fourier modulus of the object.
The resolution of conventional astrophotography is limited to 1 arcsec by the turbulent atmosphere of
the earth. Triple correlation analysis"2(speckle masking) of many astronomical speckle interferograms
(short-exposure photographs; exposure time 0.05 sec) yields diffraction-limited images with, for example,
0.02 arcsec resolution for a 5-m telescope.
The key advantage of confocal scanning microscopy is that it allows a high resolution image to be obtained of
a very thin slice of a thick object. This optical sectioning pmperty, which is completely absent in conventional
microscopy, arises because we adopt a scanning approach. We use a point source and a point detector in
order to image a single point of the object. An image of the whole field is then built up by scanning. It is the
presence of the point detector which leads to the rejection of detail from portions of the object outside the focal
region of the objective lenses. There are two main methods of achieving the scanning required to image the
entire field and this paper will be concerned with the factors which affect the strength of the optical sectioning
which may be achieved by these two methods.
Author(s): Takahiro Ode; Satoshi Komiya; Y. Yamauchi; Daikichi Awamura
We developed the Side Looking Confocal Microscope(SLCM) of which illmination axis and sensing axis are tilted from a perpendicular plane of an object. The standard confocal microscope has also an illmination source and a sensor which are situated on the same optical axis from an object. Its enterance angle is zero degrees. So in that case we can''t see 3-dimensional images -which are only bright field image- by means of standard confocal microscope method. SLCM which we developed is able to see 3-dimensional easily like a SEM image because of its angular illumination method.
Author(s): V. Evangelista; D. Guidarini; S. Vestri; Pier A. Benedetti
Confocal optical microscopy offers major improvements and usefull investigative capabilities, over conventional microscopical
imaging, expecially when high contrast and focal plane discrimination are required. Confocal operation implies space selective
illumination and light detection. Potential uses can be both in the field of transmitted-light analysis of absorbing specimens or with
incident-light configurations. Provisions for spatial scanning have to be included in the instrument and a variety of electromechanical
solutions have been suggested by others, adaptable to incident-light work. Point illumination and detection is typical of
proposed instruments and of their commercialy available versions, being principally suited to reflectance and fluorescence
investigations. In current designs , intermediate deflection devices provide two dimensional scanning of the object, using a spot of
concentrated light. The illuminated position of the object, is imaged back by the same optics on the spatial filter ( pin hole) placed
in front of a photo-detecting device. Instruments of this type are of limited utility, in transmitted light work, since the scanning
configuration doesn't permit to perform transmitted light confocal imaging. In fact an intrinsic limitation is due to the difficulty of
designing and constructing a scanning device that guarants precise and stable correspondence between the position illuminated and the
position detected which, in the case of transmission analysis reside on the opposite halves in the optical path, with respect to the
An optical processor is proposed in order to improve resolution in confocal scanning microscopy. It consists of a complex mask placed in the image plane followed by a Fourier lens. The design of the complex mask is based on the solution of a suitable integral equation. 1.
Author(s): Philip S. Brody; Charles G. Garvin; Arthur W. Gillman; Lian Shentu
We describe a real-time laser holographic microscope
which uses a photorefractive hologram and digital signal
processing. The new microscope produces high-contrast images
ofeven weak phase subjects. A pSeUdO-three-dimensiOnal
image type is produced which shows phase gradients like those
of"modulation contrast" or "differential interference contrast"
Mother image type shows phase retardation in a more direct
way, as in conventional "phase contrast." Still another type
shows images of moving phase elements in a field while
rejecting stationary ones.
Oil immersion microscope objective lenses have been designed and optimized to study thin, two-dimensional sections of objects that are monuted in a medium which is index-matched to the immersion oil and located immediately below the coverslip. The 3-D image formed by an objective lens will be subject to aberrations if any of the design conditions are not met. The degree of the aberrations can be calculated by comparing the optical paths of rays traveling through the microscope in a non-design system to those of correspondig rays traveling through the microscope under the design conditions.
A microscope using surface plasmon resonance is described, which images 2-D distributions of refractive
indices and/or surface proffles of dielectric specimens. Surface plasmon is excited at a metaldielectric
interface by using the Kretschmann's configuration, which consists of a glass prism deposited
with a thin silver film and a specimen. This microscope gives the distribution of the refractive
index with high sensitivity, if the specimen is in contact with the silver film. In experiments, we imaged
such objects as biological tissues and optical wave guide.
A theory of 3D- imaging of a thick object with a depth h (Fig.l ) is developed
for vertical Illumination microscopy (Fig2). The amount as well as the phase
of the Fourier spectrum which corresponds to the 3D- object is discussed in
detaiL Fig3 shows the amount tT(01 of the Fourier spectrum for different
object depth. ii (V I has zercs In the case of planar object (h0) . As the
thickness of the object is increased an enhancement of the spatial frequencies
and a shift of the Ninhia occurs. The zeri of the planar object spectrum are
Attempts to extend the range of
operation of the microscope beyond
conventional resolution limits usually
require precise control of light
intensity and carefully stabilised
laboratory environnnts. The system to
be described avoids these problems by
the use of comparator microscopy
combined with null-photometry.
Applications of this quantitative 3D
microscope are expected to be in the
quality control of microcircuit patterns
and the surfaces of precision
engineering and optical components and
This development was undertaken to see
if optical microscopy could be extended
down to the nanotechnology regime and at
the same time be suitable for industrial
applications preferably on-machine . The
first application of this system has
been for the measurement of surface
flaws such as digs and scratches which
can be of nanometre dimensions. Recent
results given here denvnstrate the
potential of the system for quantifying
line widths and measuring surface
Optical images whose resolution is not limited by diffraction can be created by recording the radiation from a point-like (subwavelength size) probe light source while raster scanning it across an object in immediate proximity. An imaging capability with resolution in the range from 1 to 50 nm has been demonstrated with various types of light sources including luminescence from an STM junction in transmission as well as in reflection emission and in a topographic mode. This paper gives a brief overview of the underlying principles followed by a discussion of a few selected results.
Two-Dimensional (2D) arrayed configuration for active microoptics wifi be introduced. Present status of planar microlens surface emitting lasers some functional devices and applied microoptic systems are discussed.
We have manufactued arrays of lenses in photoresist using a technique described by Popovic et al,(1) in which
small islands of resist are melted and take up a hemispherical form under the effect of surface tension. The
pirpose of this paper is to describe the range of lenses that can be made using this technique and to consider
the ways in which their optical properties may be measured and specified.
Combination of numerous fine-electrodes with an electro-optic (E-O) material is
much expected to be various optoelectronic key-devices.' However, since a metallic
opaque electrode has usually been used in most of the devices reported,2' the
loss of intensity due to the electrode portion is serious disadvantage. In addition,
the devices with the opaque electrode are not suitable to focusing or defocusing
function such as a lens. In the present paper proposed are two types of E-O lenses,
i.e., an E-O zoom lens and a Fresnel-zone plate (FZP) E-O lens which consist of
numerous transparent fine-electrodes on a flat E-O material, and are experimentally
demonstrated by composing the E-O lenses with the ITO transparent electrodes on a
PL7T (9/65/35) ceramic plate, in comparison with theoretical calculations.
Author(s): G. P. Pazi; P. Fabeni; Lucas Salvini; R. Linari
CsI:Tl monocrystal was studied in the range 360-630 nm to determine the decay-times of its several emission bands. The system was excited in the A-band at 308 nm by means of a Xe-Cl excimer laser. The temperature varies from 30 to 300 K. Many emission bands are observed some of which with slow and fast components. The decay-times range from 1 ns or less to some microsecond. The study of the fast components and the competition in the emission between thee and the slowest ones assumes particular interest in the possible application of this system as active medium for tunable solid state laser around 400 nm. 1 .
Author(s): H. C. Kandpal; K. C. Joshi; J. S. Vaishya
Auxillary optics used to measure the spectral properties of ions doped in crystal may play a dominant role in causing the shift of the peak frequency of the spectrum emitted by the ions. Therefore consideration has to be to the contribution to this spectral shift due to source correlation in addition to the shift caused by phonon scattering crystal field and tnperature effects etc.
Common method reported for growth of Potassium titanyl phosphate crystal are flux and hydrothermal techniques KTP grown by both methods show same crystal structure and both are used on laser system Widely. Howevee some differences have been found between them. For amplc an tra absorption peak around 2. 71-tm esists in hydrothermally grown KTP (KTh ) and recently we found that flux grown KTP (KTPr ) was blackened under a DC electric field but JcrPh not. Present work reports the observation of fluorescent spectra and the different orientations of polarizability tensors in KTP and KTP by measurements of Ranian scattering spectrum.
We have recently proposed the refractive-index profiling method using the iterative phase
retrieval method.1'2 In this report, we experimentally demonstrate the applicability of the
iterative phase retrieval method to the refractive-index profiling of the optical fiber.
Coupling efficiency optimization in a multichannel device composed by a SingleMode Fiber (51fF) array coupled to a GRIN Fiber Lens (FL) array is studied. Curves of coupling efficiency limited by diffraction in each pair GFLSMF is analyzed.
A power flow in individual guided modes
in a real multimode optical fibre can be
described by an integrodifferential equation' (forumla available on paper) is the average
power of the guided mode which makes, in
the geometric optics approximation, the angle with the z axis, v(e) is its group yelocity, (e) is its attenuation coefficient, and c'(y,) is the two-dimensional
coupling function expressing a power interaction
between y- and s-mode. For micro-
bendings and small scatterers, this function has been specified.
A fiber gyroscope usin a polarization-maintaining optical
fiber(PMF) has been studied. A phase shift of the laser beam passing
through the PMF by an ultrasonic wave has been observed In this
paper, the fiber gyroscope using the PMF and a polarization-maintaining
fiber coupler(PMC) is presented. Moreover, the Sagnac phase modulation
by the ultrasonic wave is studied.
The purpose of this paper is to calculate the radiation from bent single-code optical fibers along arbitrarily oriented
curved shape, which we call 'single-mode optical fiber antennas' (SMOFA). A generalized voluie current cethod (VCM) is used in
order to determine the radiated power of a N-iultiturn optical fiber antenna in the fore of circular helix. The resulting loss
formula reduces in the case of N1 to the well known atennuation forsula of the the bent single-code fibers.
Author(s): A. G. Alexandrov; Alexander V. Churenkov; Vladimir N. Listvin
In recent years with the creation of fibre-optic
interfvrometers the practical utilization of magnetometers
based on mechanical resontors became possible. In the
fibre-optic magnetometer in question the corstant magnetic
field magnitude wa defined by the amplitude of traversal
oscillations of the ribbon made of amorphous metal, which
wa fixed at one end. Oscillations resulted from the action
of th.i' variable moment of forces in cyclic remagnetization
of th' ribbon in thern presence of the constant field
componr'nt perpendicular to its surface. The amplitude of
oscillations was read out with the help of the
interferometer, formed by an output end of the fibre and
the reflecting surface of the ribbon.
In this paper an advanced optical fiber concentration sensor has been presented. It can eliminate influences of the fluctuation of light source the radom transmission loss of light in optical fibers etc. so the signalnoise ratio of the sensor Is increased clearly. 1.
We have developed a simple analytic method of predicting the performance of
glancing-incidence mirrors from laboratory measurements of their surface profiles and,
conversely, of specifying mirror quality in terms of practical performance requirements. We
call it the five-factor formula. This paper outlines its derivation and properties.
Author(s): Andre Marechal; Gerard Fortunato; Andre Galais
The Fourier Transform Spectrosetry can be remarkably simplified in the case of the detection of siall gaseous aolecules by taking advantage of the periodicity of the absorption spectrua. The instruient includes an interferometric device adjusted to a fixed optical path difference used as a signature of the molecule. High sensitivity and remarkable discrisination power are obtained.
A new anemometric method based on properties of the intensity correlation functions of light scattered off fluids can be used to determine average values of fluid velocities velocity gradients and correlations of these quantities. 1.
Holograms of a particle field illuminated by a set of light sheets are made simultaneously on one recording material differing each in reference beam direction and coherence properties. Each sheet can thus be evaluated separately by ordinary PlY techniques. 2.
An interferometric velocilnetry using a SLD for measuring a high particle density liquid flow is examined. The proposed scheme enables us to specify the velocity at a chosen ''depth in a multiple scattering medium which has been impossible in a conventional speckle velocilnetry. 1.
There is a growing need for passive sensors capable of
detecting low concentrations of various gasses at long
ranges (> 1 km). An electro-optical (E0) technique is
described which uses small changes in the temporal
coherence of natural light caused by the gas as the
means of detection. The theoretical principles are
described and the results of recent experiments to
detect nitrogen dioxide (NO2) are presented.
Dynamic speckles always appear when a coherent light illuminates dense scattering
media in motion. These media usually produce multiply-scattered speckles whose statistical
properties are considered to be different from those of singly-scattered norial
speckles. Several theoretical studies13 have been carried out for doubly- or multiplyscattered
speckles. However, most of these analyses deal with speckles in the far
field or image speckles in focus, and few studies have been conducted on the effect of
defocus on the dynamic properties of doubly-scattered speckles.
In the present paper we investigate the dynamic properties of time-varying speckles
formed in an imaging system by the light passing through a sequential pair of two
moving diffusers. The space-time correlation function for the Image speckle patterns
is derived to estisate the influence of the motion of each diffuser on a fluctuating
speed of the speckle intensity. Several interesting features have been deduced.
This paper presents a two-color optical path-1ength-cdulated reversible fringe-counting interferometer system for iieasuring the change of the air refractive index. By measuring the changes of the optical path for infrared and visible light the interferoieter cancels the effect of the geoietrical distance change. This system is being tested over a 235 ii path in the tunnel at NRLM. 1.
Recent progress in the development of curate asymptotic approximations to short-wavelength (semiclassical) scattering is reviewed. Complex angular momentum methods applied to Mie scattering have led to new insights into the diffraction effects associated with the standard critical situations in semiclassical scattering: near-forward diffractive scattering rainbow scattering glory scattering (forward and backward) and orbiting and resonance scauezing. A new diffraction effect near-critical scattering has also been treated. Tunneling plays an important role in all of these effects leading to a new conceptual picture of diffraction. 1.
The dependent scattering problem in dense attering media has been studied theoretically and experimentally for concentra- Lions up to 50 and for spherical scatters having the values ofka in the Mie scattering range. The agreement between theory and experiment is good. 1.
Experimental observations of the light scattered from characterized one-dimensional randomly rough diffusers have been carried out at four wavelengths 0. 633 1. 15 3. 39 and 10. 6 pm. Comparisons are made between identical metal (gold) and dielectric diffusers.
The Kirchhoff approximation (KA) is used to find the double scatter contribution to the field scattered from a random rough surface. The method is to use the same approximation for each interaction with the surface as is normally used for the single scatter term. Solution of the double scatter term using a Monte-Carlo method shows a peak in the scattered intensity in the backscatter direction. This peak is approximately a factor of 2 greater in intensity than the background intensity agreeing with a simple multiple scattering ray picture.
An alternative technique is provided to the measurement of second order correlation function g(2)(t) for low intensity scattering experiments It is based on the measurement of the Lap1e Trasform (Li'') of the time interval probability between successive photoelectrons(Q(s)). It is applied to the analysis ofboth sphere and rod solutions measuring the polarized and depolarized component of the scattered light respectively.
The angular distribution o the irregularly reflected and trans
mitted light gives informations about the deviations from an
ideal flat layer stack structure which can be assumed either as
inter'ace or surface roughnesses or as volume inhomogeneities in
the layers itseLf. In a previous paper of Bosquet et al. /1/ the
interrace roughness case has been discussed. The volume scattering case treated in the paper of Elson /2/ is only taken into
consideration for a semi-infinite substrate with a special correlation function for the permitivity fluctuations. Our work
follows the given lines of a perturbative treatment of scattered
light but without assuming any special conditions for the origin
of the scattering process. Therefore the well-known matrix description for the regurlarly reflected and transmitted light is
extended to the problem o± the transition from exciting to
scattered light defining bidirectional transmission and reflection
coeffidents for the ratio between the scattered and exciting
light waves. All four possible coefficients for the reflected or
transmitted scattered light can be summarized in a two by two
A code based on Maxwell equations has been developped in order to investigate the problem of scattering by deterministic and random rough surfaces. Numerical data on absorption and enhanced backscattering phenomena are shown.
Scattering of electromagnetic waves incident upon randomly rough metal and dielectric surfaces is numerically studied for several dielectric constants e(w) by means of the extinction theorem. A new effect concerning to light transmission through dielectric media is presented. The influence of surface polariton excitation on enhanced backscattering is also analyzed. 1.
Jn an interferometer which uses a reference surface the measured surface heights correspond to the difference between the test and reference surfaces. To determine the rms roughness of supersmooth surfaces accurately the effects of the reference surface roughness need to be removed. One technique for doing this involves averaging a number of uncorrelated measurements of a mirror in order to generate a reference surface profile which can then be subtracted from subsequent measurements so that they do not contain errors due to the reference surface. Th other technique provides an accurate rms roughness of the surface by taking two uncorrelated measurements of the surface. These two techniques for measurement of supersmooth surfaces are described and results of the measurement of a 0. 7 A rms roughness mirror are presented.
Author(s): Edgar W. Fischer; Zoran Sodnik; Thomas Ittner; Hans J. Tiziani
For interferometric topography measurements of optically rough surfaces dual wavelength heterodyne interferometry (DWHI) is a powerful tool. A DWHI system based on a two-wavelength HeNe laser and a matched grating technique is described. This set-Sup improves system stability and allows a simple heterodyne frequency generation. 1.
Supersmooth surfaces with a roughness of 0. 05 nm have been developed and characterized by Nomarski microscopy and other optical and mechanical profiling systems. Photomicro graphs of these surfaces are being discussed. 1.
A technique for measuring the surface roughness of metallic electrodes in
aqueous solution has been established. The technique was developed based on
incorporating methods of diffraction for measuring the hidez 1 refraction iI solutions
and with those of holographic interferometry for measuring the microscopic alterations
on the electrode surface. In particular, the technique utilizes the idea of the doubleexposure
holographic formation of a contour map over a diffusely reflecting surface of
arbitrary shape by using an immersion method1. As a result, the surface roughness of
a number of metallic electrodes has been determined in situe as a function of time. In
addition, a correlation between data of surface roughness and with those of
electrochemistry was developed. In general, the arrelation indicates that the surface
roughness of the electrode changes in responding to the change of the surface
electrochemistry of the electrodes. The obtained results will be presented at the
In this contribution new approximate formulae for calculating the
specular reflectance R, the transmittance T and the scatter losses 5(5 = = l-R-T) of nonabsorbing multilayer systems, the rough boundaries of which
are generated by normal stochastic processes, are presented. The formulae
are derived within the scalar theory of diffraction under assumptions that
the boundaries are mutually independent from the statistical point of view
and the standard deviations of the height irregularities are relatively
small compared with wavelengths of incident light. Moreover, it is assumed
that slopes of the irregularities on all the boundaries of the system considered
are small enough (the standard deviations of angles coresponding to
the slopes are much smaller that unity) and that conditions of the Fraunhofer
approximation are fulfilled when light is detected by a detector.
An angle speckle correlation was proposed for a measuring
of surface roughness parameters first in [1) . In this paper we
present some new results of the method which we reached for a
case of randomly rough surfaces in 2D Fresnel approximation. W
made a comparison with 2D Fraunhofer approximation results.
We describe a noncontact optical microtopographer designed to map the relief of rough surfaces with resolutions in the submicron order. The principle of operation is based on the horizontal shift of a bright light spot on an horizontal surface illuminated by an oblique light beam when that surface suffers a vertical displacement. In this system the optical mecanical and electrooptical hardware contraints are more important than the software ones in oposition to what happens in other systems namely those using fringe projection.
For the design and fabrication oioptical and semiconductor devices, an accurate and simple measurement of the refractive index and the
thickness of a thin film is important. Ellipsometry is an accurate and popular technique, but for thick films, the order of thickness
periodicity has to be known to obtain the ext value'. This limitation can be overcome by multi-angle of incidence ellipsometry2, but
it needs more complicated apparatus and more involved data analysis than fixed angle ellipsometry. In this paper, we propose a new
technique to determine the refractive index and the thickness of a thin film simultaneously by using the polarized reflectances which
are measured at oblique incident angles, which we call PRETTI method (Polarized REflectances measurement Technique for Thickness
and Index). First,we explain the new algorithm to determine the refractive index and the thickness of a thin film,and then the
measurement results on a single layer film and a double layer film are mentioned.
A novel system for mapping the spatial distribution of a time varying state of polarization (SOP) is developed on the basis of optical heterodyne detection techniques using the Fouriertransformation for fringe analyzing. A signal beam is photomixed over a photodetector array with a local oscillator beam consisting of orthogonal linearly polarized twofrequency components. The generated beat photocurrent is composed of two beatcomponents that include information about the orthogonally polarized components of the signal beam. The amplitude ratio and phase difference of these two beatcomponents can determine the spacetime variations of the SOP. 1 .
High performance digital systems will soon take advantage of optical data transmission. Optical bus
systems allow to connect electronic boards via several parallel high speed optical data links. Each board
is provided with opto-electronic converters (laser diodes or light modulators and photo diodes) for the
emission and detection of modulated optical signals. The light is confined by total internal reflection
within an optical backplane e.g. a plane-parallel glass-plate.
The optical band-elimination filter (OBEF) with narrow band is constructed from two polarizers and an optically active uniaxial crystal of AgGaSe2 for the application of Raman spectroscopy. Experimental results show that this OBEF cap eliminate sufficiently the emission of A1GaAs semiconductor laser. 1 .
The optical Kerr effect (OKE), a well known non-demolition optical method
for the investigation of matter, yields useful information concerning molecular
interactions and local fields in a medium. However, the interpretation of the results
obtained in dense media is beset with many difficulties, especially when it comes to
determine the contributions of different types of molecular interactions to the optically
induced birefringence. Due to the enhancement in sensitivity of our experimental
device,1 OKE measurements in gases and vapours, where the molecular interactions
can be pressure-controlled, have now become feasible.
Here, we report OKE measurements in liquid and gaseous carbon dioxide and
the temperature-dependence of this effect, from which some information concerning
the molecular interactions and local molecular fields of the medium can be obtained.
Observe and study that the device PROM exhibits an optical isodeusity behavior which may cause some interest in image processing. PROM is a device constructing with photorefractive crystal BSO (Bai2SiO2o) which is usually used to convert an optical image from incoherent to coherent. Recently more attention has been devoted to developing applications of PROM in the fields of optical holography optical information processing and optical computing. In this paper an optical isodensity behavior ofthe PROM device is observed and measured.
In general the temperature dependence of refractive index of coating materials is usually small. The most notable exception being the lead telluride. Thinfilm filters made of PbTe possess anomalously high nortlinearily in refractive index. We have investigated the phenomenon theoretically and experimexitally. 2 . BISTABLE CHARACTERISTICS OF INTERFERENCE FILTERS It can be proved that the transmittance and reflectance of a twin-cavity NLIF which consists of two F-B filters coupled by a single low-index are given by 2 a(1r1 )(1-r0) T --i. -. (1) -d (1r01) (1r12) (1-i-Fsin 4)(1+sin p) where a r01 F . Te phase change of the cavity 0 IS 2r0dnAI0D (2) 2k5dT 1k where the absorbtance A 00 the initial detunning of fresonance and the first term on the right side of the equation(1)-(2) the output characteristics of the NLIF can be calculated. 3 . EXPERIMENTAL CASE The interference filters suggested to be used in my research will be made by vacuum deposition with a thermal source. The filters will be made according to the prescripti The dominant mechanism responsible for d(nhl) must be the change in the refractive index. A low limit on the OB switch-on time is found to be O. 35us and switch-off time is 5. 5us. 4. REFERENCES 1. W. T. Feng " Temperature effects on properties of zinc selenide and lead telluride" to be published in Infrared Physics. 2. H. S. Carslaw Conduction
Fringe-locking is a convenient technique for recording running holograms in photorefractive crystals (1) where the phase shift i between the recorded interference fringes and
the resulting hologram is adaptively fixed to ψ = 90°. ψ = 90° means that the real part
of the complex expression for the spatial charge arising electric fields modulation
Esc (2) is fixed to zero. This condition allows computing the expression for the hologram
velocity for different applied electric field E, and compare it to experimental data from
Author(s): Jean Monin; Olivier Brevet-Philibert; Valerie Cabuil; Lionel Delaunay
We show a Faraday polarisation modulator whose frequency ranges from
20Hz to 40KHz. This device can be used, among other applications, in high
precision polarimetric and ellipsometric setups (azimuthal polarisation
For the characterization of infrared optical materials the homogeneity
of refractive index and the residual stress-birefringence distribution
are important parameters. The measurements of such properties of larger
samples using large aperture optical systems in connection with infrared
cameras result in an enhanced equipment, especially with respect to beam
splitters and polarizing components. A concept to avoid this difficulties
is the scanning method, where the sample is mounted on a table allowing
the automatic translation by computer controlled stepper motors, while
the beam has been fixed. The radiation of either a HeNe laser (3.39 pm)
or a C02 laser (10.6 pm) is usually detected by sensitive thermocouples.
Although, the data processing in the following measuring methods is
nearly the same , the optical arrangement is quite different.
Simplified formulas for the 3rd-order aberrations of an optical system which has
centering errors have been developed. These fornulas were applied to estiiiate
centering tolerances arcng rrin ccxronents of Japanese National Large Telescope
(LNLT) . The result was confirn1 by calculating spot diagrar with tha optical
arranerre, in which the relevant cononents of JNLT re given centering errors
corresporxling to tha tolerance values.
Author(s): Christiaan H. F. Velzel; Jacob L. de Meijere
Systematic improvement of the specifications of an optimized system can be realized by adding or reactivating degrees of freedom. We demonstrate examples of both methods, where we also include the analysis of mechanical tolerances.
Examples from both conventional cathode ray tube (CRT) projectors and the newly developed liquid crystal (LC) projectors show how worthwhile improvements can be made if the system is considered as a whole instead of as a number of separate components. 1.
It is proposed a process to formally linearise a constrained nonlinear susematic lens design problem formulated by the penalty function method, together with solutions given by the QR transformation method.
Author(s): Xianxin Zhong; Shaotang He; Shouyl Chen; X. Y. Chen; Xin Zhou; Shutia Chunyu; Chunhong He
A novel spectrographic system with grazing incidence grating spectrograph for studying laser produced plasmas has been developed. The complex system is composed of three units: a grazing incidence grating spectrograph 4 dimensions microadjustment equipment and an aligning system with optical fibre bundle electronic camera TV monitor and laser transit. The optical system optoelectronic machinery system experiment arrangement and results are discussed. 1.
Manufacturing of modern microelectronic circuits requires projection-
lithographic generation of submicron patterns by using high-aperture diffraction-limited UV- and DUV-lenses. Realized image quality of such high-performance leiises is mainly determined by the control of the extremly
narrowed fabrication tolerances by new developed special high technologies
for production and measurement of such lenses1. Contactless optical
precision measurement of surfacy topography, thickness, distances, and
decentring of optical elements , computer-controlled correction polishing" , manufacturing of nanometer-asperic surfaces by CNC-correction
polishing or by ion-beam etching, computer-assisted assembly , wave-
front analysis on the basis of measurement of geometrical-optical beam
aberrations, and image quality testing with near-coherent illumination
are such new techniques. The correction of such lenses is more difficult because the available optical media are limited to those which sufficiently good transmission in the UV resp. DUV region. Optical media used
in DUV-lenses are fused silica glass, calcium or barium fluoride, and
eventually fluorphosphate crown glass. This media restriction leads to
an increase in number of lenses, constructional length, and technological
difficulties in the manufacturing.
The Hartmann test to measure wavefronts is much more powerful than generally assumed. Its results need not to be worse than interferometric methods. Various authors have already demonstrated this fact and also our own work points in that direction. Here we would present an extension of the Hartmann test that increases its performance at low light levels. The traditional Hartmann test scans the aperture of the wave or lens to be measured with a single hole in an opaque screen. It is equally well possible to use a complete set of screens with any number of holes. By adequately adding the measurement results for each of the screens the contribution of each of the holes can be extracted. Thus the wave front can be reconstructed. The advantage of this method is a significant increase in signal to noise ratio provided the noise is signal independent.
The penetration depth of light into a processed surface is interferometrically ieasured by optically contacting it on a glass plate with a resolution of 3 urn. This principle is based on the ieasurement of the difference between the phase changes of light in reflections on the object and the glass plate. Also the depth is siiiultanecusly measured by an optical systeii with a phase-locked laser interferometer and an optical displacement sensor. 1 .
A porro prism used in Qswitched laser cavity has been designed to function both as retroreflector and N2 phase plate . This enables in optimising coupling of laser output . The results have been verified experimentally.
A telecentric flat field and anastigmatic four mirror optical camera system is developed for lithographic application. We have Obtained initially the analytic solutions of the four spherical mirror system free from four Seidel aberrations with reduction magnification (5x). However the systems obtained after corrections have still sizable amount of residual aberrations and small field. To overcome these shortcomings aspherization of the three mirrors is performed and it is found that it gives more improved performances.
Author(s): R. Fernandez; M. C. Vazquez; Jose H. Barcala
Simple three-component optical systems and their derivatives have been well documented. Since Berek until the present moment the volume of work on this kind of optical
system supports their importance with a range of applications that covers from spectacle to microscope lenses.
In the present work we offer a method for projecting optical systems of this kind
that also includes the selection of the glasses used for their ccxnponenets.
Author(s): Michael A. Golub; Nikolay L. Kazanskiy; Iosif N. Sisakian; Victor A. Soifer
Diffractive optical elements - compensator - permit to -form
complicated optical wavefronts for tetinci complex optical surfaces
in mirrors and lenses. In this paper the optical testing scheme has
been considered as a transformator of optical transfer function of
diffractive compensator into wavefronts with demanded form.
A broadened interest in diffractive optics has gained momentum over the last years.
The application of diffractive components offer high flexibility to shape the spatial
distribution of an electromagnetic wave. Fabrication techniques of diffractive optical
elements have been developed which are based on e-beam lithography, ion-exchange
methods and embossing procedures.
We developed formulae and numerical techniques for the corrutations of the point spread
function (PSF) and optical transfer function (GrF) in the general case of unrestricted
aberration and with the following di fferent forms of non-uniform real ariplitude : ( i ) when
the real airplitude is described by a polynomial, (ii) a Gaussian distribution of real amplitude
which corresponds to the intensity distribution of laser beam, and ( iii ) a pupil
with a central obstruction. The developed coriputer programs
were tested and used to study the influence of non-uniform
anplitude on the PSF and CITF .
An exact solution for the crosscorrelation between two different apertures of circular symmetry under defocused conditions in a two-pupil system is developed. Application to some nonstandard pupil topologies is described. Previous experimental and theoretical work demonstrates that two optical fields with different temporal frequencies when mixed through an optical heterodyne action at a photodetector can if properly preconditioned produce an electronic signal related directly to the crosscorrelation of the two corresponding pupil functions . Applying this concept several aperture topologies are proposed which lead to OTFs with bandpass and bandreject properties. The approach presented herein is to calculate without approximation the crosscorrelation of two different circular apertures in a two-pupil system. This result will serve as the essential function through which OTFs for various more complicated apertures are expressible. This approach is based on an extension of a previous analysis carried out for the autocorrelation of a circular aperture with defocus .
Imaging characteristics of optical system can be modified to achieve improved performance by making use of apodisation technique. It can be achieved by modifying either by amplitude or the phase or both over the pupil of the optical system or by using linear polarisation masks placed at different orientations over the zones of the optical system . It has been found that the performance of apodised optical systems can be improved in any desired region of spatial frequencies by varying the relative size of the zones as well as amplitude transmittances in different zones. Similar results are also obtained in case of optical systems masked with linear polarisers.
The method of wavefront analysis is based on the metrological simulation
of optical ray tracing. Many rays, selected by a pinhole, will be
analysed sequentially, so that the transverse ray aberrations measured
with a elekironic coordinate-detector can be stored in the computer. Due
to low power per ray photon counting must be applied. The aberrations are
necessary to start a mathematical analysis by the computer and the result
is the wavefront from the lens under test for one point represented by
the Niiboer-Zernike-coefficients. This method needs no addditional
optics, so it is possible to measure with ligth of any wavelength
especially with ultravioleti ligth, too.
Author(s): Rolph Hey; Christian Hofmann; Jens-Ullrich Mueller
In the process of evaluation the performance of photolithographical lenses
it is necessary to determine the image intensity distribution of submicron-patterns in relation to aberrations and the light source. Our lens
testing equipment, working with g-line systems4 , was adapted for the UV
and DUV region.
For the flatness inspection of scattering surface light contouring can
be advantageously applied with accuracies ranging from micrometers to millimeters.1 In these cases the information about the shape of object are obtamed
by phase measurement of a projected fring system as a function of
space coordinates. By means of the phasestep methodZ the phase measurements
can be performed with high accuracy.
Indian Institute of Astrophysics (IIA) has recently completed building of 2.34 M
TelescopeS Optics for the same was fabricated in the Optical shop of the Institute. The
paper describes the technology used in making 2.34 M Telescope Optics. A polarisation
shearing interferometer developed for the testing of large mirrors has also been discussed.
Author(s): Josef Humlicek; Karel Vojtechovsky; Irena Drimalova; Eva Bochnickova
We present studies of very rich polarization phenomena observed in the light diffracted from regular
geometrical patterns. The ratio of the field amplitudes for the p-and 8-polarized light is accessible in
standard ellipsometric measurements. Forward calculations based on a scalar diffraction integral predict
ellipticity and phase shifts in the specular and higher-order beams. Both one- and two-dimensional patterns
created in general planar filmed structures are dealt with. We identify effects related to propagation
of light in the film system, i.e., to the film thicknesses and their optical properties. Characteristic features
due to the in-plane geometrical arrangement are also identified, especially, the effects of the transient
regions between the neighboring plane segments.
Author(s): Victor V. Kotlyar; Igor V. Nikolsky; Victor A. Soifer
The ensemble of spherical absorbing microparticles is illuminated
by collimated beam of coherent light. The lights wavelenght is as
little as diameter of any particle. Fourierlense forms in the focal
plane spectrum pf spatial radiation scattered by microparticies. The
intensity distribution of spatial spectrum, exept for the central
part, is registered by multy-element photo-detector. If photo-detector
is a set of concentric rings the signal from each photo-sensitive rinq
is proportional to average light intensity. Registered reading of
average intensity as function from ring radius are processed by
computer. Further the algorithmes of processinç of the tneasurincj data
Author(s): Betty Kerllenevich; Enrique Chapunov; Andre Coche
Orientation and centering of a laser beam IR or visible are necessary in its various applications.
In the cases where a visual rapid positionning of the laser beam is more important than an extreme
precision, the system proposed here presents advantages described in what follows.
Author(s): Yoshikazu Kawauchi; H. Yamashita; K. Saitoh
The design of a disktype holographic scanner with a laser diode to correct for scanline deviation and scan nonlinearity and to reduce aberration is described. By dividing a hologram facet into three parts three performance functions are optimized independently. The spot diameters obtained (at l/e2) are less than 9Ojim for maximum scanline deviation of and scanlinearity error of within the scan length of 210m. 1 . I NTRODUCT I ON In designing holographic scanners it is difficult to satisfy the properties of scanline deviation scan linearity and spot diameter because there is a tradeoff relationship between aberration scan spots and scan linearity. " This paper provides a hologram facet design divided into three parts in which three performance functions are optimized independently by ray tracing and the damped leastsquares method. The calculation of waveoptical diffraction intensity is included to increase the numerical accuracy. 2. PROEDURE AND NUMERICAL RESULTS A hologram facet is divided into three unequal but symetric parts. The optimization is performed such that the center region is optimized first next the side regions are optimized and then the positions of spots in each region are adjusted. After that the scanning properties are evaluated over the whole scan length. The results of three performance functions (dotted lines) are shown in Fig. l and Fig. 2 as compared with the results for the conventional undivided facet (solid lines). The figures show
As the sagnetic steel used for the substrate of the mirror is shaped by casting, there
are some cracks and blowho].es in its interior. If the magnetic steel mirror is ground by
the traditional method, cracks and blowholes aight appear and the ground mirror would become
a waste. Besides these, magnetic steel is very easy to be corroded during the grinding period, so that there is a lot of repairing work invalved and the utilization ratio of
this magnetic steel substrate is only 25%. Whereas the magnetic steel mirror made by the
replicating aethod has no such defects; not only the productive efficiency has been increased,
but has the utilization ratio also been increased by 95%; the precision of the surface shape of each mirror has good consistence.
The Voyager cameras include unique features required by the characteristics of a mission to Jupiter Saturn Uranus and Neptune. These characteristics include low illumination levels long mission duration large communication distances and intense Jovian radiation belts. The presence of several modest programmable processors on the spacecraft has permitted the post-launch refinement of image acquisition and the development of imaging capabilities such as image motion compensation and data compression which were not originally part of the baseline experiment design. The quantity and quality of Neptune imaging data exceeds by a large factor the yield which was foreseen at the time of launch thirteen years ago. The initial expenment design is descnbed as well as its subsequent post-launch evolution. The key conclusion is that flexibility must be a design goal for imaging systems developed for remote sensing of new territory. 1.
In May/June 1989 the German Aerospace Research Establishment (DLR) Institute for Optoelectronics was involved in the first European Imaging Spectroscopy Airborne Campaign (EISAC). Test sites in various countries of the European Community were flown with the GER-Il Scanner. In the presented study the preprocessed and atmospherically corrected data was used for a spectral analysis of an old vegetation covered waste deposit. 2. THE GER-Il Scanner The GER-lI Scanner (Geophysical Environment Corp. ) is a 63 channel imaging spectrometer with three seperate line arrays of detectors which view the ground through the same aperture via a rotating mirror. It contains 31 channels in the visible I near infrared (VIS/NIR) wavelength region (470 nm - 840 nm sampling interval 12. 3 nm) 4 channels between 1440 nm to 1900 nm (sampling interval 120 nm) and another 28 channels in the short wave infrared (SWIR) wavelength region (2000 nm - 2450 nm sampling interval 16. 3 nm). The IFOV was selected to be 3. 3 mrad which leads to a pixel size of 10 m at 3000 m flying altitude. The high spectral and spatial resolution make this scanner a useful tool for environmental studies. 3. DATA PROCESSING As a first evaluation step the GER-Scanner data was preprocessed including a roll- lag- and slope-correction1. Comparison of ground vegetation spectra measured with the IRIS-Mark IV spectroradiometer (GER-Corp. ) during the time of the overflight yielded
Optical design of Air.bone liaging Spectroieter is described in this
study. A new design of push.brooi type liaging Spectroseter using lens,
prisa and CCD sensor systei is cospared to classical Isaging Spectrometers
those were composed of all reflecting optical components.
Advantage of using refracting elements against that of using mirror
and reflection grating is the design flexibility of optical components and
possibility of reducing and correcting many kind of aberrations.
Disadvantage of lens system - chromatic aberration - is reduced to
be negligibly small within 0.4 to 1.0 jim by selecting glass materials.
The purpose of Imaging pectrometer is to monitor life conditions of
vegetations from high altitudes by measuring spectral reflectance of
foliage (chiorophyl). By such purpose, wavelength was limited from
visible until near IR region.
Current electro-optical (E0) sensors are largely based upon image plane (post detector) processing. However such systems do not achieve the discrimination possibe between the sought after signal and natural interfering features in the background because they only respond to the time averaged intensity and thus throw away key information about spectral profile polarization temporal and spatial coherence phase profile etc. The paper describes techniques whereby differences in these characteristics are exploited to good effect by processing in the optical (pre-detector) domain the processing being achieved by the application of selective transformations which respond uniquely to the sought after signal''s characteristics.
The need to verify the pei1ormaixc of untended instrumentation has been recognized since scientists began sending thnse
instrumems into hostile environments to quire data. The sea floor and the stratosphere have been explored, and the quality
and cury of the data obtained vified by calibrating the instrumentalion in the laboratoiy, both jxior and subsequent to
deployment The inability to make the lau measurements on deep-space missions make the calibration vthficatkin of these
insiruments a uniclue problem.
The purpose of mesoscale atmospheric studies by means of radar radiation is ultrashort range weather forecast effective on time scales of an hour or Ilore F 1] . Different types of meteorological phenomena give characteristic shapes of radar echo . The aim of our work is to find a simple method of classification of clouds for high-speed analysis of meteorological radar gray-scale images. This is the first global stage of radar inages analysis. To get into details on precipitation the local analysis follows. In the second step images of chosen clouds can be analysed . In images impulse noise and oscillations are to be eliminated and edges of smoothed images of clouds are to be preserved .
The question of retrievieng spatial information of sea surface heights from aerial photographs
is considered. With some siiplifying assumptions, a one-dimensional model for
the problem is proposed and a numerical relation between the surface height autocorrelation
and the autocorrelation of the intensity variations in the photograph is found.
Furthermore, it is possible to invert numerically the relation to estimate the former
from the latter. The results are supported with a computer simulated example.
Optical long-baseline interferometry can yield images and spectra with fascinating angular resolution. For example, at a wavelength
of 500 nm and with a baseline of lOOm a resolution of 10 arcsec can be obtained. We have studied the dependence of
the SNR in the reconstructed image on the diluted pupil function, on wavefront aberrations and on photon noise in the interferograms.
A pulse when xopagating through nonlinear optical fiber in the normal dispersion regime after Raman-induced depletion develops an asymmetric optical wave breaking on its leading edge. Its direct observation in the spectro-temporal domain is in excellent agreement with numerical simulation. 1.
Optical interconnects are of increasing importance for high speed data communications in electronic
or all-optical digital computers [e.g., 1-4]. A problem that has not been solved yet is how to
package optical components in a way that is compatible with the small size of current VLSI sytems.
Conventional optical packaging relies on individual mechanical mounting which results in bulky
large-volume systems. Mechanical packaging is costly and causes problems with the alignment and
the stability of the system. This is especially true, if the alignment tolerances are small, i. e., in the
micron or submicron range.
Vertical-cavity, surface-emitting lasers have great potential owing to their inherent two-dimensional geometry
and very small gain nedium volumes which are essential to low threshold currents. Possible applications are
optical switching/computing, photonic interconnection, high/low power laser sources, image processing,
optical neural networks, etc. Driven by these high promises, there have been numerous reports on vertical
cavity surface emitting laser diodes using InGaAs/GaAs/A1As, GaAs/AlGaAs structures16. In this paper, we
report characteristics of discrete InGaAs microlasers and monolithic two-dimensional arrays of microlasers.
The advantages of optics for communications of data over distances longer than nearby gates have been argued
previously7. We proposed and demonstrated a photonic interconnect scheme using microlasers with planar
optics which will be robust, accurate, and easily alignable.
Efficient second-harmonic generation (SHG) was recently observed in
centrosymmetric doped glass f'ibrest'2. Two processes are important for
forming gratings in doped fibres, namely, the excitation of dopant
defects, and the creation and alignment of permanent dipoles in the fibre
core. Positively and negatively charged color centers are assumed to be
generated owing to two 3- or higher-order-photon absorption. Electric dipoles
can be created within strings of interconnected dopant defects
only3. It seems very likely that the dopant-defect strings are dominantly
oriented along the fibre due to the layer structure of dopant distribution
and the drawing process.
The Hough transform is a powerful tool for machine vision systems. In this paper by using inexpensive LCITV instead of expensive SLM as an input device a commercializable optical Hough transform processor is presented. The integration of this processor with a digit image processing system is also discussed.