Proceedings Volume 1038

6th Mtg in Israel on Optical Engineering

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Proceedings Volume 1038

6th Mtg in Israel on Optical Engineering

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Volume Details

Date Published: 5 July 1989
Contents: 1 Sessions, 77 Papers, 0 Presentations
Conference: Sixth Meeting of Optical Engineering in Israel 1988
Volume Number: 1038

Table of Contents

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Table of Contents

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Sprite Detectors And Staring Arrays In Hg[sub]1-x[/sub]Cd[sub]x[/sub]Te
C T Elliott
The evolution of the Sprite detector from its invention in 1974 to the present is reviewed. The use of anamorphic optics to reduce the effects of carrier diffusion, together with changes to the device shape has produced very high spatial resolution. Improved material and two-dimensional structures have further increased the thermal sensitivity. A brief description of the technology for two-dimensional, electronicaly addressed diode arrays is also given, together with a discussion of the mechanism of p to n type conversion.
Progress In The LPE of HgZnTe, An Alternative Material For IR Photon-Detector Arrays
Ariel Sher
The solid solution HgZnTe is an attractive material for IR photon detectors. The liquid phase epitaxy growth technique, used in our laboratory for HgZnTe, is briefly described. The characteristics of p type HgZnTe epilayers, before and post an annealing process in Hg atmosphere, are presented. The status of HgZnTe as an alternative material to HgCdTe for IR photon detectors is discussed.
R-and-D IN IRCCD-Focal Plane Arrays AT AEG Company
Konrad J. Stahl
The research and development status of work in monolithic as well as in hybrid IRCCD-focal plane array (FPA) detectors based on the sensor materials InSb, Cdx Hgi-x Te and Si: X (X = In, P, Ga) at the AEG Company is described. Some examples for applications in mostly civil applications are given.
Automated Visual Inspection Of Integrated Circuits
G. Noppen, A. Oosterlinck
One of the major application fields of image processing techniques is the 'visual inspection'. For a number of rea-sons, the automated visual inspection of Integrated Circuits (IC's) has drawn a lot of attention. : Their very strict design makes them very suitable for an automated inspection. : There is already a lot of experience in the comparable Printed Circuit Board (PCB) and mask inspection. : The mechanical handling of wafers and dice is already an established technology. : Military and medical IC's should be a 100 % failproof. : IC inspection gives a high and allinost immediate payback. In this paper we wil try to give an outline of the problems involved in IC inspection, and the algorithms and methods used to overcome these problems. We will not go into de-tail, but we will try to give a general understanding. Our attention will go to the following topics. : An overview of the inspection process, with an emphasis on the second visual inspection. : The problems encountered in IC inspection, as opposed to the comparable PCB and mask inspection. : The image acquisition devices that can be used to obtain 'inspectable' images. : A general overview of the algorithms that can be used. : A short description of the algorithms developed at the ESAT-MI2 division of the katholieke Universiteit Leuven.
Measurement And Inspection Using Non-Contact Electro-Optical System: Non-Contact Gauging And Measurement With Laser Triangulation
S. Alkon
The driving forces of production are: 1.increase productivity 2. reduce production cost 3. enhance quality
Fluorescence Techniques For The Characterization Of Polymeric Membranes Whose Permeability Can Be Varied In Real Time
Aryeh M. Weiss, Alan J. Grodzinsky
Characterization and control of membrane-based separation or drug delivery systems require the development of noninvasive methods for measurement of membrane hydration during the process of interest. In this paper, real time fluorescence methods which were developed in order to study such membrane systems are described, and data which demonstrate their sensitivity and speed are presented. Sensitivity and speed were sufficient that transient phenomena such as diffusion lag time and Donnan distribution effects caused by changes in fixed charge density were well resolved.
White Light Image Processing By Rotational Shear Interferometry
Erez Ribak
A passive optical-Hartley transform of white light scenes was performed by means of a rotational shear interferometer. The full visible band was utilised by employing a colour corrector which compensated for wave-length dependence of the fringes. This transform can be used for filtering, moment calculation, or for direct detection. An inverse transform was also realised, which allowed retrieval of the original object, although at a low efficiency.
Phase Cancellation Of The Correlation Peak Value In Pattern Recognition Schemes.
D. Mendlovic, E. Marom, N. Konforti
Optical correlation schemes based on circular or radial harmonics have bean recently suggested for performing pattern recognition in presence of rotation or scale variations of the object. Those schemes however are based on using a single harmonic at one time. In this paper we are presenting two approaches that overcome this restriction.
Bragg Reflection Waveguides And Directional Couplers
Gadi Lenz, Joseph Salzman
The Bragg reflection waveguide is formed by surrounding a central waveguiding region by dielectric layers with periodic variations in refractive index. The limitations imposed by resonant confinement of the guided modes (transverse Bragg reflection) are analyzed, and the unique properties of a pair of coupled-waveguides of this type are described.
Recent Advances In Silicide Detectors
I. J. Spiro, F. D. Shepherd
Early attempts to extend staring-mode sensing into the thermal infrared spectrum failed, because the resulting imagery was dominated by spatial pattern noise. The source of this noise was modulation of the infrared background by local variations in sensor responsivity. In 1973, use of internal photoemission from silicide Schottky barrier arrays was proposed as a means of achieving the photoresponse uniformity necessary to obtain useful thermal imaging capability. In the next two year, silicide tube and solid state imaging devices were demonstrated. Tube development was abandoned in 1975. Solid state efforts were directed towards extension of photo-response to longer wavelengths and fabrication of large scale arrays with small, high fill factor, pixels. Cut-off wavelengths have evolved from 2 μm to 10 μm and array sizes from 1 x 64 to 512 x 512 since that time. Current silicide cameras have sensitivity comparable with the best scanning systems. This paper will describe recent advances in silicide sensors and project future technology trends.
Tunneling And Noise Phenomena In HgCdTe Photodiodes
R. Adar, D. Rosenfeld, Y. Nemirovsky
The reverse breakdown characteristics of 8-12μm Hg1-x CdxTe photodiodes are experimentally measured and analyzed. Temperature dependence of the currents reveal that trap-assisted and direct band-to-band tunneling processes dominate the breakdown characteristics at low and high reverse bias regions respectively. The direct band-to-band characteristics are compared to theoretical predictions in implanted diodes on both gold-doped and undoped substrates. A good quantitative fit to theory is achieved based on experimental analysis of space charge density in the measured diodes depletion region using a C-V profiling technique. The direct tunneling characteristics also show empirical correlation with noise currents measured on gold-doped junctions.
Moire Deflectometry - Applications To Lens Analysis
Kathi Kreske, Eliezer Keren, Oded Kafri
Moire deflectometry, a method for ray deflection mapping, is described. Its use in lens testing for determining properties such as surface microstructure, radius of curvature, thickness, aberrations, and OTF (optical transfer function), is demonstrated. Unlike interferometry, moire deflectometry is a ray tracing technique, and therefore the analysis of three dimensional objects is greatly simplified. Although the ray tracing approach to optical systems is much older than wave theory, moire deflectometry seems to be the first attempt to apply ray tracing methods systematically to optical metrology. The technique is fully quantitative, interferometry compatible in accuracy, and has the additional advantage of tunable sensitivity.
Computer Generated Hologram Used As An Aberration Corrector
Oded Arnon, Steve Bloomberg, Dan Ophir
A Computer Generated Hologram (CGH) is used as an aberration corrector in construction optics to record Holographic Optics Elements (HOE's) with preaberrated wave-fronts. In the system described, the CGH provides enough asphericity to record the re-quired HOE, so that other lenses in the construction optics can be selected by paraxial considerations alone. The design process of the recording system is described and a comparison is made between the measured and expected performance of the final lens.
Silver Halide Sensitized Gelatin Holographic Recording Materials
V. Weiss, Y. Amitai, A. A. Friesem, et al.
New and simplified processing procedures and formulations for Silver Halide Sensitized Gelatin (SHSG) holograms of high diffraction efficiencies and signal to noise ratios are presented. holographic performance of SHSG was found to be far superiour when compared to reversal bleach experiments. Additional improvements in diffraction efficiency and scattering noise were achieved by introducing triethanolamine into the postfix soaking bath at elevated temper-atures. Finally, a holographic focussing lens with low aberrations was realized in SHSG.
Estimating Target Acquisition Search Times For Infrared Sensors In Multi-Target Scenarios
S. R. Rotman, E. S. Gordon
The standard single-target acquisition model used in military applications for human target acquisition using infrared systems has been extended to the multitarget scenario. It incorporates three possible versions depending on the underlying causes for the non-unity detection probability at infinite time and the degree of correlation between targets.
Correlation Between LWIR And SWIR Image Of Ground Terrain
K. Wilner, R. Dombrowsky, N. Ben-Yosef
Thermal images of natural terrain in the long wavelength infrared (LWIR) are due to thermal emittion of the ground. On the other hand in the short wavelength infrared (SWIR) images there is a contribution of direct sun light due to reflection. The daily evolution of the terrain thermal images with the same thermal properties in both spectral windows were performed using an IR imaging radiometer. The sun reflection and the thermal emmition will affect the correlation between the images. Measurements have shown that the cross correlation goes through a maxima and a minima depending on the sun angle. It seems that the maxima point occurs when the shadow effects are minimal.
Material Properties In Anisotropic Plates Obtained By Speckle And Hologram Interferometry
K-E Fallstrom, N-E Molin
Modes of vibration in rectangular, orthotropic, free-free plates are determined optically, using an electronic speckle pattern interferometer (an instrument called the VibraVision) as real time instrument and a double pulsed ruby laser to record the corresponding holographic interferograms. It is found that the first three modes of vibration has a strong dependence only of one of the main material parameters at a time, namely in plane shear modulus and the two Young's moduli, respectively. It is therefore a simple task to determine these material parameters with this nondestructive, noncontact optical method. Poisson contraction ratios are harder to determine. One method is to tune the sides of the plate so that the second and third modes are turned into a ring-shaped and a cross-chaped mode. The Poisson contraction number has a stronger influence on these modes and can be determined. Experimental results and theory are presented.
Wave Propagation In Plates Studied By Pulsed Hologram Interferometry
A. Wahlin, K-E Fallstrom, H. Gustaysson, et al.
Isotropic and non-isotropic plates are impacted by a ballistic pendulum. The bending waves that are generated are studied with holographic interferometry using a double pulsed ruby laser as light source. The pulse shape changes with time because of the dispersivity of the waves. Initially the fringe pattern in the isotropic case is cylindrically symmetric and determined from an initial value problem. Later, when the waves have reached the plate rim, in-and outgoing waves gradually develop fringe patterns which in the end will be a combination of eigenmodes of the plate. A solution to the corresponding Kirchhoff plate equation is presented, which in the special case when the impact is modelled as a Dirac-pulse in space and time, is shown to depend only of the distance to the impact point divided by the square root of the time after impact and a parameter containing plate parameters. From the slope of the central deflection material parameters can be determined. Another solution, assuming a finite inpact time, is shown to agree better with experiments. Results from investigations of non-isotropic materials are also presented.
Laser Diode Stabilization With External Common Path Interferometer
Jackob Guy, Chaim Gutter, Joseph Shamir, et al.
A novel method for active laser diode stabilization is described. The input for the control loop is taken from an external common path Jamin interferometer by differential detection of the fringe pattern. Theoretical and practical limitations are discussed with experimental results indicating laser stabilization capabilities better than one part in 108.
Holographic Elements For Coordinate Transformations
N. Davidson, Y. Amitai, A. A. Friesem, et al.
A novel design technique for generating holographic elements that perform general types of coordinate transformations is presented. The design, which is based on analytic ray-tracing techniques leads to a holographic grating function that can be formed either as a computer generated or as a computer originated hologram. The design procedure is illustrated for a specific holographic element that performs a logarithmic transformation. Such an element is useful for obtaining scale invariance in optical correlation.
Holographic Optical Recognition Of Multiple Patterns
S. Gorodeisky, M. Cohen, A. A. Friesem, et al.
Holographic optical correlators using incoherent light have been developed for pattern recognition. In this paper we show how multiplicity of holographic filters can be incorporated into such correlators for recognizing several patterns simultaneously. Our computer simulation and experimental results reveal that sixteen patterns can be recognized with one composite holographic filter, giving a sharp correlation peak with good peak to background ratio.
Light Weight Optics Prepared By Replication
Michael Snir
This work was conducted on purpose to find the feasibility of producing light weight, ligh aspect ratio mirrors for scanners, folding and head mirrors used in compact optical assemblies by the cost effective polymer replication technique. The work includes theoretical consideration, experimental results and implementation of empirical results in present used mirrors.
An Application Of The LILY Software Package To Defect Inspection In Unexposed Radiographic Film
P. Dewaele, P. Wambacq, A. Oosterlinck
The results of three visual inspection techniques, using laser light, for defect detection in unexposed radiographic film are presented and compared. First convolution techniques are discussed. An appropriate choice of mask coefficients is explained and the mask dimension has to be matched with the scale at which the errors occur. Second an error detection method using polynomial regression was experienced to be very effective. Finally, fourier filtering can equally well be applied but it was computationally more expensive than the convolution method for this type of inspection. Experiments have been carried out using the LILY software package for image processing.
Focus Sensing Optical Profilometer
Andrei Brunfeld, Joseph Shamir, Gregory Toker
A high sensitivity focus sensing configuration is employed in the construction of an accurate optical profilometer. The system is analyzed theoretically and experimental investigation indicates a sensitivity better than 3nm with a linear dynamic range of 50μm. The deteriorating effects of finite apertures and various misalignments are also considered and taken into account for improved measuring procedures.
A Vision System For Localization Of Textile Pieces On Light Table
Haim Garten, Margalit Raviv
The purpose of this system (Fig. 1) is to locate accurately two pieces of fabric lying on a table. The pieces are laid down on the table with an orientation accuracy of ±12° degrees and cartezian shift up to 30 mm. The location of the two pieces is then tranfered to a robot arm that will pick them up as a matched pair and trnasfer them as such to an automatic sewing machine.
Optical Fiber Up-Tapers For Self-Aligned Beam Expansion And Single-Mode Hardware - Theory And Practice
N. Amitay, H. M. Presby
Single-mode fiber is rapidly becoming the medium of choice for lightwave communications systems carrying long distance terrestrial and submarine traffic as well as local distribution and local area networks traffic. Widespread and convenient utilization of single-mode fibers requires reliable and reasonably priced hardware such as low-loss backplane and field connectors, laser-fiber couplers, and directional couplers. The main drawback of single-mode fibers, which makes fabrication of these components difficult, is their small core size, on the order of 5-10μm. All hardware constructed from and for these fibers, where two cores or light source and core have to be aligned, are inherently very sensitive to axial and transversal displacements as well as to tiny dust particles. These displacements can be induced mechanically or thermally, while the dust comes from just routine handling.
Transmission Of Images And Holograms Through Single Multimode Optical Fibre
Andrzej Kalestynski, Maciej Sypek
This paper is devoted experiments with transmission of images and holograms through single multimode optical fibre. The technique is mostly promissing because of its paralellness.
Light Transmission Through A Modified Cladding Optical Fiber - Inverse Problem Analysis
Ady Arie, Moshe Tur
A method for deriving the angular power distribution of various sources which are used to inject light into an optical fiber is suggested. This distribution can be obtained from the optical power carried by meridional bound rays in a fiber whose cladding refractive index can be modified. The theoretical analysis, which indicates that optical power measurement errors must not exceed 1% in order to obtain reasonably accurate power distributions, is augmented by experimental results. In particular, the case of lens illumination and the estimation of the mode field diameter of a single mode fiber are studied in detail.
Chalcogenide Infrared Fibers And Bundles For Special Applications
A. Bornstein
Chalcogenide glass fibers, transparent in the mid IR region, will soon find a wide range of applications, including military uses such as thermal imaging, sensing and tracking, and remote spectroscopy. We have developed chalcogenide glasses and optical fibers and bundles suitable for such military applications. Herein we describe the As2Se3 chalcogenide fibers and bundles with glassy core and TFE cladding, with a fiber diameter of 30-1000 μm. The optical loss, measured by CO2 laser and FTIR spectrometer in thee temperature range of -197'C to 100'C, is less than 1 dB/m in the 3-5 μm range and less than 10 dB/m at 10.6 μm. At longer wavelengths the attenuation is much higher. The fibers maintain their transparency in the temperature range of -40*C to 70'C (military standard range).
Selective Excitation And Transmission Of Nodes In Hollow-Core Fibers
P. Bichaan, M. Sinvani, A. Bornstein
Optical properties of hollow-core, chalcogenide glass cladding fibers, which are good candidates for power transmission, were examined. Far-field patterns - as a function of excitation conditions - of the emitted radiation of As2Se3 hollow core fibers, at 10.6 μm, are described. Results are preceded by a theoretical background. Hollow core fibers are found to guide only a small number of modes.
CO[sub]2[/sub] Laser Radiation Transmission Through Curved Hollow Fibers
J. Dror, I. Gannot, O. Mor-Haim, et al.
Hollow plastic fibers were produced by depositing metallic and dielectric films on the internal surface of plastic tubes. These fibers can transmit high CO2 laser energy with low atten-uation even in curved trajectories. A mathematical model was developed to describe the energy transmission. The energy distribution at the outlet of the fiber was measured and found to be influenced by the existence of whispering gallery mode. These fibers are suitable for surgical uses.
A Surface Roughness Measurement In The Optical Workshop
Allan Farber, Chaim Koshizky
There is an increased demand for high quality optical components with minimal surface roughness for precision optical systems. As a result, it has become necessary to determine the surface quality using an accurate, quantitative and non-destructive measurement. This has led to considerable efforts to replace stylus methods with non-contact optical methods for surface texture measurements. Several non-contact optical methods have been tried and some of these have been implemented in commercial instruments. One of these methods utilizes the principle of differential interference con-trast. The system theory and implementation are described; results and calculations are presented for polished surfaces.
Optical Neasurements Of Diamond-Turned Surfaces
Jacob Politch
We describe here a system for measuring very accurately diamond-turned surfaces. This system is based on heterodyne interfercmetry and measures surface height variations with an accuracy of 4A, and the spatial resolution is 1 micrometer. Fran the measured data we have calculated the statistical properties of the surface - enabling us to identify the spatial frequencies caused by the vibrations of the diamond - turning machine and the measuring machine as well as the frequency of the grid.
Laser Based Transduction Of Ultrasound For Practical NDT Applications
A. Aharoni, M. Tur, K. M. Jassby
Laser based techniques for the generation and the detection of ultrasonic surface waves (SAW) are described. These methods were motivated by practical ultrasonic non-destructive testing (NDT) applications and are suitable for operation on rough surfaces which are typical to engineering materials. Wide strip laser illumination is used to generate SAW waveforms by means of a thermoelastic mechanism. For detection an holographic method has been developed, achieving sensitivities of the order of 0.1 Å at 10 MHz bandwidth on rough aluminum surfaces.
Reflective Beam Expander Using A Spherical Primary
Shai Eisenberg
A simple third order analytical solution is presented for a design of a reflective beam expander using a spherical primary, parabolic secondary and an aspheric corrector plate. The third order design is also evaluated and improved by a ray trace program.
Aspheric Generation On Glass By Ion Beam Milling
N. P. Eisenberg, R. Carouby, J. Broder
Due to the progress of the diamond turning technique, the use of aspheric elements in optical systems is increasing. However, there are materials, like glass, which are not compatible with this technique especially when the shape of the aspheric element is not a simple conic. Using ion beam milling through a mask which modulates spatially the amount of ions impinging on the surface to be shaped, a piano-convex glass lens has been transformed into an aspheric element with a conical front surface. This technique is valuable for any material used either in the visible or in the IR spectrum.
Computer Aided Optical System Alignment With CODE VTM
Daniel Leigh, Dov Frieman
High accuracy optical alignment generally requires interferometric methods. A simple computer aided interferometric optical alignment procedure, for the visible, IR and other regions, utilizing the Interferogram Interface in CODE V, is described. The accuracy of visual interferometric alignment is limited and involves highly skilled personnel. To overcome these limitations, a procedure is presented that requires specification of the nominal optical system design, the alignment parameters, such as tilts and decenters in CODE V, and entering in to the latter the interferometrically measured system wavefront data of several different points in the field of view. The last step consists of predicting the alignment parameters such that the system wavefront error is reduced. This procedure is repeated until the wavefront error falls within system specifications. A numerical alignment simulation and an actual system alignment are presented for an F/10, 8 inch diameter Cassegrain objective.
Optical Model Of Eye Movements During Visual Perception
Barbara Smelinska
During seeing the eye scanns incessantly over the inspecting scene. These eye movements represent an automatic process, consisting of two phases: proper saccadic movements and fixation period during which two processes take place. These are sampling the scene and processing the visual information by the central part of the retina and next by corresponding structures of the brain. At the beginning the fixation points are randomly distributed but with time these are grouped round peculiar parts of the scene. The movements are unavoided: When the eye steps for a tine the visual perception disappeares, the subject dont see anything.
Adaptive Dynamic Range Compression For Flir Imagery
Rami Guissin
Infrared imaging sensors are characterized by extended dynamic ranges ≈ 60db due to target and background variations and increased senstivity of the sensors. The dynamic range of display devices such as video monitors is limited to approximately ≈ 40db, requiring in turn appropriate means for compression. Various compression schemes have been proposed based on the compression of the low spatial-frequency components of the image signal, while preserving (or enhancing) the high frequency signal components. The separation of low and high frequency components using various spatial filtering techniques is limited by (i) attenuation and extinction of low contrast and extended targets, and (ii) compressed signal distortions and "ringing" effects around edges. We propose an adaptive, spatial filtering scheme which largely overcomes these limitations while retaining the subjective quality of the compressed image. The adaptive nature of the operator may be tailored to expected target dimensions (in pixels), and to expected target and background contrasts.
Sub-Quantum Accuracy Of An Infra-Red Data-Gathering Sensor By Frame Integration
Denis Rozenbaum
Successive digitized measurements of constant data fluctuate over several quantum cells because of the presence of additive noise. This dispersion allows the achievement of a subquantum accuracy by signal averaging of a large number of measurements. This processing is of particular interest for infra-red signals, characterized by a wide dynamic range. This work analyses the relation between the expectation of the digital measurement and the expectation of the real (analog) value, as a function of the statistical characteristics of the noise in the signal. It is shown that sub-quantum precision can be obtained under certain conditions. Practical considerations regarding the achievable accuracy, digitization depth, measuring the noise statistics and limits of the linear subquantum interpolation are given. A practical method for measuring noise in the signal is described.
Toward A Measure Of Image Enhancement
Leo Levi
Image processing, in general, and image enhancement in particular, have been active topics for over 25 years, and much is known about them. However, it appears that quantitative measures for image enhancement, as such, have not been formulated, even though the theory necessary for such a measure has been developed. Such a measure will be presented and applied to a representative form of image enhancement. Simple enlargement may serve as a good illustration. Such phenomena as image degradation due to excessive magnification, which are well known qualitatively, are put on a quantitative basis.
Antireflective Coating On Long Borosilicate Tubes For Solar Collectors
N P. Eisenberg, Y Ben-Dor, J. P. Warschawski
In all types of solar collectors without exception, there is a protective cover between the sun rays and the active area (thermal or photovoltaic, flat or concentrating collector). For the materials most often employed the refractive index has a value around 1.5 leading to about 4% loss by reflection for each air-cover interface, giving a total loss of about 8% of the incident energy.
The Application Of Thin Films Technique To Compensate Polarization Effects On Total Internal Reflection
K. Rabinovitch
On total internal reflection (TIR) different phase shifts occur to the p- and s- states of polarization. Therefore the polarization state of the reflected light on TIR is generally elliptical polarized and differs from the state of polarization of the incoming wave. Only in cases where the entering wave has a pure p-or s- state relative to the plane of incidence these polarization states of the reflected wave are unchanged and hence are eigen-states. In optical systems where the optical path is folded via TIR by using prisms, corner-cubes, retro-prisms, etc., the state of polarization of the exit wave will usually differ from the incoming one. In cases where the polarization state should be conserved, correcting retardation elements are applied to compensate the polarization effects on TIR. Instead of these bulk correcting elements, multilayer dielectric thin films stacks could be applied on the desired surfaces. This technique is introduced and discussed. An illustration of this method is represented on a retro - roof - prism of the type 45°-60° -60°.
Optical Network Calculus
Yitzhak Weissman
A network calculus suitable for the modeling of optical networks is presented. The new calculus is based on the signal flow graph theory which is used for the modeling of electrical and microwave networks. The new element in the optical network calculus is the fact that the nodal variables and the branch transmissions are two dimensional vectors and matrices respectively, rather than complex numbers. The new calculus is applied to a simple optical network as an example.
Very Low-Loss Integrated Optics Splitters
Z. Weissman, E. Marom, A. Hardy
The design of efficient, wide-angle, dielectric optical waveguide junction splitters with two, or more, branches is outlined. The method has several degrees of freedom which can be used to optimize the device's performance to achieve: 1) Minimization of the radiation loss for a specified mode at the input, 2) Equalization of the modal losses in a dual-mode device, and 3) Controllable power splitting ratio in a multibranch splitter.
Performance Analysis Of Polarization Maintaining Fiber Directional Coupler
E. Shafir, A. Hardy, M. Tur
Commercial tunable polarization maintaining fiber couplers exhibit inadequate low polarization isolations. Utilizing a newly developed coupled mode theory, we theoretically analyze the performance of these devices, and conclude that these low values can be explained in terms of finite misalignments of few degrees between the two fibers' principal birefringent axes. We also show that for a given device with 3dB coupling ratio the polarization isolation critically depends on the transverse setting, and can vary between 18 and 40dB for the case of 5° misalignment, in a coupler composed of 3mm beatlength fibers.
Miniature Cooler/Dewar/Detector (CDD) Package For IR Applications
N. Pundak, A. Weiner
By mounting the IR detector on the cooler cold finger a significant reduction in the total heat load can be achieved. This approach is a specially fruitful when the ratio of detector heat load/dewar parasitic heat load is relatively low. Such a package which is sold under the trade name LILIT is in regular production by Ricor Ltd. Israel since 1987. This packaged system weighing about 430 grams, consumes about 5...8 W input power to maintain 80 K under 50 mW heat load. The basic design concept, typical performance data, qualification status and some typical applications are presented.
A New Process For Manufacturing Arrays Of Microlenses
N. P. Eisenberg, A. Karsenty, J. Broder, et al.
The need for microlenses with a wide-range of focal lengths from 10μ to 100mm and with a diameter varying from 10μ to 1mm lead to the development of various techniques which are able to generate these lenses in a photoresist substrate. The existing techniques are reviewed and a new one proposed. In this technique a positive or negative photoresist layer is exposed to a tailored light intensity distribution. After development of the photoresist, its surface is identical to the spatial intensity light distribution. Photoresist with an index of refraction of n=1.6 in the visible spectrum, can be used as a lens.
Photon-Limited Imaging Of Randomly Moving Objects
J C Dainty, J Kramer
Simple centroiding, cross-correlation and triple correlation techniques have been applied to the imaging of randomly translating and rotating objects at very low light levels. The results of a computer simulation show that satisfactory reconstructions can be obtained using the cross-correlation technique at photon levels on the order of 0.2 photons per pixel for pure random translation or rotation, and on the order of 0.5 photons per pixel for both random translation and rotation, with only a few hundred frames in each case.
Shift-And-Add For Astronomical Imaging
Erez Ribak, E. Keith Hege, Nicolas V Strobel, et al.
We have obtained diffraction-limited astronomical images utilising a variant of the shift-and-add method. We show that the matched filter approach for extending the weighted-shift-and-add method does indeed reduce specklegrams from extended objects and one dominated by photon noise. The method is abberation-insensitive and yields very high dynamic range results. The iterative method for arriving at the matched filter does not automatically converge in the case of photon-noisy specklegrams for objects with more than one maximum. Methods for making the procedure more "artificially intelligent" are discussed.
Astronomical Imaging By Pupil Plane Interferometry
Erez Ribak
If we compare rotational shear interferometry to standard speckle interferometry we find that it is easier in the first case to separate the atmospheric phases from the object transform phases. Phase closure and blind deconvolution should be directly applicable. Laboratory simulations were conducted to verify theoretical predictions and computer simulations for the phase closure case, and preliminary results show promise.
Contribution Of Oxygen To Attenuation In The Solar Blind UV Spectral Region
E. Trakhovsky, A. Ben-Shalom, U. P. Oppenheim, et al.
The Solar Blind Ultraviolet (SBUV) spectral region covers the interval between 230 nm and 290 nm. The lower limit of this interval is given by the edge of the Schumann-Runge band and the upper limit is determined by solar radiation penetrating the stratospheric ozone shield. The SBUV region is interesting from the experimental point of view, since the lack of solar background is favorable in such applications as lidar, atmospheric communication and remote sensing. The present models (LOWTRAN-6) include as atmospheric attenuators in this region ozone absorption, aerosol and molecular scattering. New theoretical calculations of the Herzberg I oxygen band predict significant absorption by 02. This prediction is confirmed experimentally in the present study. Field measurements at 252, 255 and 264 nm are reported over optical paths of up to 2750 m. Results show that LOWTRAN-6 is inadequate in the SBUV region, as indicated by the present extinction measurements.
Study Of Surface Polaritons And Bulk Modes Activity In In[sub]2[/sub]O[sub]3[/sub] By IR Spectroscopy
N. Haik
IR transmission spectra of 1n203 microcrystals and thin films in the range 300 - 700 cm-1 were studied. Results on band shifts support the idea that bands in microcrystals spectra correspond to surface polaritons. Anomalous clumping effects and different behavior with respect to charge carrier localization at low and high frequency bands are presented.
New Infrared Materials Incorporating Non-Radiative Energy Transfer
S. R. Rotman, F. X. Hartmann
We apply a recently developed model for non-radiative energy transfer in correlated systems to recently published data on energy transfer in garnets. We show that even in well-studied materials in which the analysis of the data appears straight forward, subtle deviations from theory and difficulty in quantitatively evaluating interaction parameters may be due to a non-random distribution of donors and acceptors in the crystal.
A Comparison Of Polycrystalline And Single Crystalline Optical Grade Germanium
M . Azoulay, G Gafni, M. Roth
The structure - properties relationship of large-grain poly-crystalline and single crystalline optical germanium, was compared in terms of electrical and optical properties. The dopant distribution and the optical properties relevant to thermal imaging showed better homogeneity of the single crystalline than the polycrystalline material.
All-Optical Modulation In Gallium Arsenide Integrated Optical Waveguides
G. McWright, B. Ross, W. Guthreau, et al.
We have investigated all-optical modulators in gallium arsenide integrated optical waveguides; these modulators use electron-hole pair generation to alter the propagation characteristics of a guided light beam.
Air Light Influence On Electro-Optical Systems - Systematic Approach
Nadav Rosenberg
For Low Light Level E/O systems, the Air Light may give the major part of a signal, but will reduce the possible resolution. Photographic envelope, defined for different imaging systems applications, must include such effects. The scattering and absorption of sunlight by atmospheric aerosols, molecules and ozone affects the quality of images and is usually described in terms of a Multiple Scattered Radiation. Such radiation, responsible for creating Air Light, is a complicated physical and computational problem, that sometimes gives very untrivial results. This paper reviews the atmospheric path radiance Air Light as a part of a system approach to E/O systems. We present the algorithm for calculation of many stage scattering processes and suggest a non sophisticated criterion for its importance.
Atmospheric Turbulence Effects On Optical Spatial Coding
K. Wilner, M. Wetzler, N. Ben-Yosef
A common use of optical spatial coding is the application for guidance and tracking concept. The spatial coding is usually implemented by a rotating reticle. The spatial coding is performed on an image, like in the case of anti-aircraft missiles, or on a laser beam projector, such as in the beam rider concept. Experience indicates that the lateral position measurement by optical spatial coding is strongly affected by the Modulated Transfer Function (MTF) of the optical channel. In our example, this channel consists of a laser beam generator, the atmosphere, an optical receiver and threshold logic. The analysis will demonstrate the influence of the turbulence affected edge response, scintillation effects and threshold dependent error on the line of sight (LOS) measurments. As a result, the feasibility of an adaptive threshold logic demonstrates improved accuracy of the location error.
Surface Emissivity Determination Of Diffuse Objects In Natural Surroundings - SEFAB Technique
L. S. Balfour, A. Ben-Shalom
An important parameter in the analysis of thermal infrared signatures is the object surface emissivity. An in-situ determination of the emissivity of diffuse objects, both natural and artificial, in the field is most desirable. In this paper we present a technique that may be employed to determine emissivities in the infrared region using a commercial thermal imager. The Surface Emissivity For Ambient Background (SEFAB) technique uses two reference surfaces of known emissivities to determine the emissivity of the desired object. The two main advantages of the present technique are: 1) The camera calibration constant is not required and 2) The individual surface temperatures are not required provided they are the same for all the surfaces during the measurement.
Absolute Measurements Of Diffuse Reflectance In The 0.8-5.5 µm Region
D. Sheffer
An absolute reflectometer for the 0.8-5.5μm region is described. It is based on integrating spheres, and utilizes the Third Taylor method in the 7°/d configuration. A new theory for the reduction of the data is presented, and results for some diffuse gold samples are given.
A Multichannel Wide FOV Infrared Radiometric System
S. Jacobson, Z. Lissak, Y. Yoav, et al.
A radiometric system which consists of five IR radiometers with a mutual data acquisition system is described. The system was designed, developed and built at IAI to conduct simultaneous IR signature measurements of a high intensity source at different aspect angles. The requirement to provide a wide FOV radiometric capability led to a technical solution based on the combination of refractive and reflective optics. Each radiometer is equipped with a ZnSe lens, elliptical mirror, mechanical chopper and a thermoelectrically cooled PbSe detector. The chopper is positioned before the entrance aperture and its blades serve as an ambient temperature reference Black Body. The reference temperature is monitored by a temperature transducer. The optical layout of the radiometers and relevant ray tracing examples are demonstrated. The radiometer sensitivity and field of view response data are presented. The data acquisition as well as software capabilities are described. The system is remotely operated. Data on source intensity, at different aspect angles, may be obtained immediately after the test.
Solar Pumped Nd:Cr:GSGG Laser
Y. Noter, M. Oron, J. Shwartz, et al.
Direct solar illumination was used to pump a 1/4" x 3" Nd:Cr:GSGG rod and achieved quasi CW laser action at average powers of 20 watt. The solar radiation was chopped at a duty cycle of 20% to avoid crystal fracture. Peak power outputs were as high as 100 watt on a clear day. Slope efficiencies, relative to the solar power reaching the crystal, were close to 10%. Near field and far field beam patterns were recorded by a TV system in order to study the thermal behavior of the crystal. At maximum irradiation levels, the output from a 25 cm long flat concave cavity, had a beam divergence on the order of 30 mrad. Details of the experimental system and the calibration procedures are given.
Phase-Conjugated Multiple-Pass Amplifiers For Low Repetition Rate, High Energy, Pulsed Nd:Glass Lasers
S. Jackel, R. Lalluz, A. Ludmirsky
Phase conjugate mirrors based on stimulated Brillouin scattering were developed for incorporation into multiple-pass Nd:glass amplifiers. These high efficiency non-linear mirrors allowed exceptional saturated performance by the multiple-pass amplifiers: gain m 1000 at saturation fluence, near diffraction limited beam quality, no self-oscillations or pre/post pulses and minimum amplified spontaneous emission, and good beam axis stability.
Kinetic Model For Material Structural Changes And Gradual Degradation In Semiconductor Lasers And Light Emitting Diodes
Yu. L. Khali, J. Salzman, R. Beserman
A new semiphenomenological statistical kinetic model for changes in the material structure and gradual degradation in semiconductor lasers and light emitting diodes is presented. In this model, the injection of a non-equilibrium electron-hole plasma, increases the probability of struc-tural changes and reduces their effective activation energy due to the interaction of carriers with material atoms hopping over energy barriers. Arrhenius like expressions for the degradation rate with the pre-exponential factor and the effective activation energy as explicit functions of the material parameters are derived. Good agreement with experimental data is obtained.
Off-Axis Folded Laser Beam Trajectories In A Strip-Line CO[sub]2[/sub] Laser
Baruch Sterman, Amnon Gabay, Shaul Yatsiv, et al.
For a hemi-confocal cavity of high Fresnel number, the conventional Hermite-Gaussian axial mode theory no longer adequately predicts the output intensity pattern. Under these conditions, off-axis beam trajectories can have higher round trip gains, and may therefore be dominant. Specific trajectories can be selected by introducing suitable blocks into the cavity. Output patterns corresponding to M shaped modes were observed experimentally in a cavity with a stop placed at the center of the full reflecting spherical mirror. A Fox and Li resonator analysis algorithm was applied to the above cavity configuration and a similar output distribution was obtained. Therefore, the general spatial properties of the M mode are determined by diffraction.
Wind Velocity Measurements By Optical Scintillations Methods
S. Tsadka, S. Shaft, Z. Azar, et al.
Scintillations-based optical techniques for the measurement of the atmospheric transverse average wind velocity are re-examined. Three different methods for the processing of the resultant time-lagged covariance function are compared to in-situ anemometer measurements. A correlation index of 0.89-0.95 is obtained between the optical and anemometer results and it tends to increasing with the measurement time constant. Some degradation in the accuracy of the optical methods is observed when the spacing between the detectors is either much smaller or much larger than the Fresnel zone [AL]1/2.
Prediction Of Image Quality Through The Desert Atmosphere
N. S. Kopeika, I. Kogan, R. Israeli, et al.
Using atmospheric modulation contrast function area (mcfa) as a single-valued numerical criterion for image quality propagated through the atmosphere, a statistical study of atmospheric imaging data has led to the determination of regression coefficients with which to quantitatively predict effects of windspeed, air temperature, and relative humidity on image quality propagated through the atmosphere as a function of wavelength for visible and near infrared wavelengths. Utilization of this procedure is quite simple. One simply plugs in expected values for windspeed, air temperature, and relative humidity in the regression coefficient expression for mcfa. The larger the expected mcfa, the better the expected image quality. Data for desert atmospheres have been presented previously. Here, an improved version of that model is presented. Preliminary experimentation indicates the accuracy of the present model is quite good.
Two-Frequency Intensity Fluctuations In A Random Medium
Boaz Lerner, Moshe Tur, Z. Azar
The two-color correlation of scintillations was experimentally measured in a laboratory-generated random medium. The aperture averaging effect was examined by measuring the normalized spectral covari-ance and the correlation coefficient for He-Ne and Argon laser beams. Measurements were taken for several strengths of the refractive index inhomogeneities but saturation was not reached. Aperture averaging was significant and its effect on the variances and covariance became more prominent as the the strength of the refractive index inhomogeneities increased. The correlation coefficient was found to increase with the aper-ture diameter from 0.8 at the smallest aperture (0.1mm) up to almost unity at a detector diameter on the order of [Wavelength-Range]1/2. Also, the correlation coefficient decreased as the wavelength difference between the lasers increased.
Variance In Image Fluctuations In Propagation Through A Turbulent Medium
Mark J. Beran, Moshe Tur
As a result of turbulence in the atmosphere, the image of an object in the focal plane of a lens fluctuates with time. In this paper we discuss the variance of the image intensity, a measure of this fluctuation. In order to calculate the variance, we require a knowledge of the fourth-order coherence function of the light impinging upon the lens. We shall assume, in our analysis, that the object is located far above the earth, emits incoherent light with Gaussian statistics and is small enough to insure isoplanicity. Under these conditions, the fourth-order coherence function is the product of two factors. The first factor is the fourth-order coherence function resulting from a point source passing through a turbulent medium. The second factor is the fourth-order coherence function of the light from the incoherent object after it propagates through free space. The fourth-order coherence function of the light emitted by a Gaussian incoherent source is easily determined. On the other hand, it is very difficult to determine the fourth-order coherence function of the light from a point source passing through a turbulent medium, unless it is possible to neglect intensity fluctuations at the lens or to use perturbation theory. Therefore, in this paper we shall discuss what is known about the general case and when approximations may be made. In conclusion, we shall calculate the variance of the image of a point source when intensity fluctuations at the lens are neglected.
High Collection Nonimaging Optics
Roland Winston
Nonimaging optics departs from the methods of traditional optical design to develop instead techniques for maximizing the collecting power of concentrating elements and systems. Designs which exceed the concentration attainable with focusing techniques by factors of four or more and approach the theoretical limit are possible (ideal concentrators). The methodology for designing high collection nonirnaging systems is described.
Luminescent Solar Concentrators Based On Dyes Incorporated In Thin Polymer Films
Renata Reisfeld, Marek Eyal, Valery Eyal, et al.
Optical efficiencies for Luminescent Solar Concentrators (LSC) based on thin films of Polymethylmethacrylate (PMMA) doped by luminescent dye BASF-241 deposited on PMMA transparent plates are measured and calculated. The influence of refractive index of optical matching material on LSC performance is analyzed. A comparison of emission anisotropy with quantum yield and self-absorption leads to optimalization of thickness and optical density of the thin doped films. Enhancement of luminescence of Rhodamine 6G (Rh6G) in the presence of silver aggregates is reported.
GASIEL- A Useful Tool For Operational Performance Predictions
Nadav Rosenberg
This review describes part of a comprehensive continuing research program of downlooking imaging systems evaluation. The main objective of this program is to develop a systematic approach to the operational performance predictions as a practical tool for obtaining an extensive environmental information quickly and economically. A computer program, GASIEL,(eneral Approach to sprstem imaging era uation) has been developed for performance predictions such as the Ground Resolved Distance and different functions of E/O scanners in the visible region under low contrast conditions. The code was derived using a systematic approach to both photographic envelopes and system parameters and includes Atmospheric conditions (atmospheric profiles, air-light etc.), Optics and Detector data, specific targets and backgrounds, all in full spectral analysis. The model is described and the application of the code is given below.
Approximate Expression For The Spherical Wave Structure Function In A Von-Karman Type Random Medium
I. Last, M. Tur
We propose a relatively simple and convenient approximate expression for the spherical structure func-tion in atmospheric turbulence having the Von-Karman spectrum. The approximation, which is accurate to within 6%, is valid for any separation between the observation points. In the asymptotic intervals 2rp«to, to«27p((Lo, 27rp))Lo the approximate expression coincides with the known analytical solutions. An approximate expression is presented also for the coherence length ρo) for the case of homogeneous tur-bulence conditions along the propagation path.
Interactive Prediction Programs For Day/Night Reconnaissance Systems.
Shalom Wilk, Yael Cohen-Saban
Two interactive, user-friendly computer programs for design and evaluation of reconnaissance systems are presented. Graphic and alpha-numeric output enable quick analysis of system capabilities to enable detection and recognition of targets under any given set of target, atmospheric and system conditions.
Amplifiers For Solar Pumped Lasers
H. Bernstein, E. Kriohman, Y. Noter, et al.
Design considerations for solar pumped laser amplifiers are presented. Various materials and geometries are evaluated and as a conclusion the "active mirror" amplifier is chosen as a preferred geometry. An experimental set up of an active mirror solar pumped amplifier and some preliminary performance data are presented. Small signal gain of 10% was measured on a 44 mm gain path in a solar pumped Nd glass disc.
Software Package For The Design Of Nonimaging Optical Elements
Yitzhak Weissman, Baruch Barnett
In this work we describe a ray-tracing software package that was created as a tool for the design and the performance analysis of nonimaging optical elements. Tne program can handle a general cylindrically symmetric envelope with a monotonic profile, and the reflecting surface can be either a metal or a dielectric interface. Reflections are treated rigorously using Fresnel formulas, thus a ray is specified by the polarization components of the electric field, rather than by the intensity only. With the help of the program, it is possible to obtain contour plots of the radiation field at any section of the element, as well as transmission functions.
Anti-Reflective Coating On Borosilicate Long Tubes Industrial Process And Quality Control
N. Eisenberg, Y. Ben-Dor, J. P. Warschawski
It has been shown that in order to improve the optical efficiency of a solar trough evacuated pipe used for Luz solar electricity generating systems, an appropriate low cost anti-reflective coating process should be implemented in the solar collector production line, and that a dip process is the optimal choice for this application. It is shown in this paper that pumping the coating solution out of the coating container rather than withdrawing the tubes is the most appropriate coating process for Luz's needs. The same method was employed for the second coating solution which was used both for mechanical abrasion resistance improvement and for increasing optical transmissivity. The measuring procedure for quality insurance of the coated tube was investigated thoroughly and an "in-house" technique, including solar simulation and spiral movement of the tested tube, was chosen in preference to the other standard procedures (spectrophotometry, reflectometry). The complete AR coating facility and production procedure is described and the results of the industrial process are analyzed.