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Proceedings Volume 0473

Symposium Optika '84

Gabor Lupkovics, Andras Podmaniczky
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Proceedings Volume 0473

Symposium Optika '84

Gabor Lupkovics, Andras Podmaniczky
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Volume Details

Date Published: 18 January 1985
Contents: 1 Sessions, 86 Papers, 0 Presentations
Conference: Symposium Optika '84 1984
Volume Number: 0473

Table of Contents

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Table of Contents

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Current Research In The Institut D'optique - Orsay
A. Marechal
I - FUNDAMENTAL PROBLEMS A. ASPECT : Non locality in wave mechanics. The Einstein-Bohr dispute and the optical test of Bell's inequalities. A. Einstein and N. Bohr had a discussion about the role of probabilities in microphysics; as is well known the location and momentum of particles cannot be known precisely but only through probabilistic expressions. Einstein thought that complementary variables (hidden variables) are unknown at the present time and that the knowledge of those variables would suppress the actual uncertainty "God does not play random games". On the contrary, Bohr advocated the fundamental role of probabilities. During the sixties J. Bell established inequalities supporting the Einstein point of view. These inequalities are in contradiction with the predictions of quantum mechanics in some very rare situations. A.Aspect designed and realised an optical experiment where the correlation of polarisation of photons emitted by a single atom was measured with a very good signal to noise ratio. Moreover the orientation of the polarisation analyser was changed during the time of flight of photons. The experimental result is in full agreement with the point of view of N. Bohr : the uncertainty on the movement of particles is a fundamental component of the laws of nature and Bell's inequalities do not hold.
Thermoplastic Holograms In Optical Metrology And Image Processing
Jumpei Tsujiuchi, Takahiro Saito
Thermoplastic photoconductor materials are conveniently used for recording holograms because of their interesting advantages, but the processing is rather delicate and making good holograms is not easy. These difficulties are surmounted by developing new techniques for processing holograms such as the post-exposure light application (PLA) method and the the solvent vapour method, and applications of thermoplastic hologram have been still more promoted. This paper presents outlines of these new techniques together with some of their applications in the field of optical metrology and image processing.
Optical Algebraic Processing Architectures And Algorithms
H. John Caulfield, William T. Rhodes
A generation of opto-electronic signal processors has been developing during the past several years. These processors are designed to perform algebraic operations like matrix-vector and matrix-matrix multiplication. In this paper key architectural developments are reviewed and major algorithmic methods and problems are discussed.
Grating Structures In Integrated Optics
G. C. Righini, G. Molesini
Grating structures for integrated optics are reviewed. Main areas of application are outlined, and special concern is devoted to coupling, focusing and filtering functions. Different structures are described acting as optical components in planar waveguides. Comparison with non-diffractive elements is provided, and links with bulk optics are considered. Current trends of research and technical development are pointed out according to the actual state of the art.
Laser Control Over Electrochemical Processes
F. V. Bunkin, B. S. Luk'yanchuk, G. A. Shafeev
A review is given of the up-to-date concepts of electrochemical processes. Electrochemical reactions induced by laser heating in absorbing liquid electrolytes are considered. It is experimentally shown that electric fields and currents are generated in an electrolyte exposed to laser radiation, which is due to the thermal diffusion of absorbing ions. The feasibility of selective deposition of a given element from the solution of its salt under laser radiation is demonstrated. Experimental findings on electrochemical reactions with semiconductors (Si, GaAs, Ge) are presented.
Analysis Of Rotating Component Strains Using Electronic Speckle Pattern Interferometry
R. W. T. Preater
The measurement of in-plane strain rather than out-of-plane displacement is a distinct advantage to engineers. Electronic speckle pattern interferometry (ESPI) rather than holographic interferometry can provide this type of information. The use of a pulsed laser in place of a c/w laser removes the otherwise rigorous stability requirements of conventional holographic techniques and freezes the component movement. Pulsed laser ESPI is a non-contact method which may be used under service environmental conditions. Initial tests using a tv-camera sensitive to low light levels have shown that in conjunction with precision laser triggering interference subtraction fringes can be recorded for component tangential velocities up to 5 ms-1. Digital storage and the recent incorporation of a high resolution tv-camera system has increased the tangential velocity range to 15 ms-1. The combination of this system with image derotation may enable components with much higher velocities to be studied.
An ESPI Contouring Technique In Strain Analysis
Svein Winther, Gudmunn A. Slettemoen
A new electronic speckle pattern interferometric (ESPI) contouring technique, which is a variation of the holographic two beam illumination method, is described. Together with necessary mathematical derivations, experimental test results are reported. The system is an integrated part of a deformation measuring system where contour data will be used in strain analysis.
Evaluation Of Holographic Interferograms By Parametric Representation Of The Displacement Vector Field
G. Szarvas, A. Adam, I. Bogar, et al.
One of the difficulties of widespread application of hologram interferometry in industry is the unsolved problem of rapid, automatic evaluation of interferograms. By means of its simplicity and accuracy the zero order fringe distinguishes itself among the other ones. The industrial application of the technique is made more difficult by the fact that interferograms recorded in factory environment do not contain the zero order fringe. There is no way to produce such a system in which the object and interferometer would not be moved to each other by an order of magnitude of the wave length of the light. So the zero order fringe technique can only be used if the fringes are calibrated i.e. if only the absolute order number of a fringe is determined. The fringes can be calibrated by holographic technique /fringe counting technique/ or by another way /using the values of displacement components measured by dial indicator or vibrometer with piezoelectrical head./ The disadvantages of that techniques are their combined nature, claim to the complicated equipment and procedures differing from the relatively simple zero order fringe method. In the present paper a method called parametric calibration of fringe order will be proposed. The absolute displacement vector of the object surface points is determined using the relative fringe order number. The suggested method is suitable for the calibration of the interference fringes /for the determination of the absolute fringe order/ in a nearly plane region of the object.
Theory And Practice In Optimization Of Holographic Interferometers
Wolfgang Osten
Simple geometries of holographic interorometers are discussed, which secure that the influence of measuring errors on the displacement vector is very small. The design of the inferometers for the zero-order-fringe and the fringe-counting-method is characterized by 360°/n-symmetry in the position of the observation points or the scanning lines over the hologram, respectively, where n means the number of equations in the evaluation system. Very simple relations are given for the calculation of the condition number and the standard deviations of the displacement components taking into account overdetermined systcms.
Holographic Interferometry Of Concrete
M. H. De Caluwe
The knowledge of the deformational behaviour of concrete is of major importance in the design of concrete constructions. This behaviour has so far only been verified under practical situations. One of the reasons therefore is, that the available mathematical models have been derived from a large number of experimental findings and are not applicable straightforwardly to different particular cases. The macroscopic deformations due to the external loads considered in those calculations are in fact the summation of microscopic deformations of the different constituents of the heterogeneous material called concrete. Up to now little information is available on the deformational behaviour of those constituents. The use of coherent optical techniques allows us to investigate microscopic deformations, and so can give us information about the interaction of the individual material components. The phenomena we investigated were: I. the influence of the deformation properties of the mortar matrix and the granulate during the creep period. 2. micro crack formation under static load. 3. the atmospheric sensitivity of different compositions after drying. The coherent optical techniques available are holography and speckle correlation; the incoherent techniques, high frequency moire, photoelasticity, and white light speckling. This article will deal only with holography and it's the intention to demonstrate its usefullness in the study of concrete, with the restriction that only hypotheses had to be derived from this general survey as a base for more extensive research.
Application Of Holographic Interferometry For Investigation Of Microroughness Of Engineering Surfaces
Marek Lech, Irena Mruk, Jacek Stupnicki
The paper describes an improved immersion method of holographic interferometry /IMHI/ adjusted for studies of roughness of engineering surfaces. Special optical arrangement, with two types of immersion cells and adequate technique of preparing transparent replicas reproducting with high fidelity details of differently machined surfaces was elaborated. It permits to obtain the contour maps of the surface asperities with intervals between the planes of succesive contour lines within a range of 1 μm. The results obtained for some engineering surfaces are given.
Difference Holographic Interferometry /DHI/: Perspectives
F. Gyimesi, Z. Fuzessy
The usual holographic interferometric techniques do not make it possible to compare the deformations or the shapes of two similar but different objects in direct interferometric way. The DHI technique overcomes this limitation by using holographically reconstructed illumination wavefronts in the usual holographic interferometric techniques. Experimental results have proved the applicability of the technique in both the deformation and the shape measurements. Although many practical problems are to be solved yet DHI can be expected to become a routine control measurement in an assembly line.
Holographic Evaluation Of Ultrasonic Stimulated Medical Instruments
G. Frankowski, V. Grosser, W. Mueller, et al.
A holographic vibration analysis of ultrasonic stiuulated 'medical instruments consisting of a piezoelectric transducer and a surgical instrument was made. All examinations were performed by means of time-average-holography. A quantitative and a qualitative interpretation of the tile-average-holograms was undertaken. Quantitative interpretation of the interferograms provided the vibration amplitudes in different points of the transducer. Qualitative interpretation was taken up to get the vibration form of the surgical instruments. A comparison between the holographic results and the theoretical computer calculation of the vibration amplitudes was made.
Investigation Of The Model Of Hydraulic Press By Means Of Holographic Interferometry
Piotr J. Wesolowski
The model of hydraulic press was investigated in workshop environment by means of holographic interferometry.The double exposure method was applied. A ruby-pulse laser was built-in the interferometer applying four observation directions. As a result of this feature ,the interferometer gives possibility for quantitative measurement of displacement field in absence of the zero order fringe. After this surface qrain and stress can be computed. The maximum area of the measured object was about lx1.5 m2 .
The Deformation Analysis Of Transversely Struck Isotropic And Anisotropic Plates By Using The Holographic Double Exposure Technique
H. Schwieger, R. Streubel
As a contribution to systematic investigations of the mechanical behaviour of struck elements, the holographic double exposure technique was used to study the dynamic response of isotropic plates and such with natural and structural anisotropy. Further, the propagation of elastic bending waves was investigated. The whole arrangement has been designed to test large plates in order to study the so called "early state", which is not influenced by the reflected waves coming back from the boundaries to the impact region. Thus, in the studied cases the maximum loading below the impact point took place within the early state. A double pulsed ruby laser with a concave expanding lens was used to illuminate the large-sized object surface, whereby the laser was controlled by the falling impact mass (steel ball), so that the first flash was triggered before the impact and the second one in desired time intervals after the beginning of contact. For studying the different deformation states, comprehensive series of moment photographs with circularly and elliptically shaped interference fringes were produced characterizing the loci of equal displacement. Especially the photographs of a stiffened duraluminium plate show an interesting distribution of the interference fringes. The higher vibration modes of a rolled brass plate were also visualized and illustrate the mechanical properties of this anisotropic material.
A New Way For Determination Polarization Parameters Of An Object Wave By Holographic Interferometry Method
I. M. Nagibina, T. A. Ilyinskaya
Method of holographic interferometry for the definition of polarized parameters of the objective wave according to interferograms is given in this article. This method is based on accounting vector characteristics of objective waves in the process of obtaining inter-ferograms.
Photorefractive Crystals For Real-Time Holographic Interferometry
A. A. Kamshilin, E. V. Mokrushina
A method for simultaneous recording and readout of volume holograms in cubic photorefractive crystals based on the phenomenon of anisotropic diffraction is suggested. A model of a holographic interferometer for visualization of vibration modes of diffuse objects employing this method is described.
An Opto-Electronic Hybride System Based Upon Frequency Plane Filtering For Prescreening Cytological Samples
Benno W. Reuter, Ulrich Schenck
Fully automated screening of cervical smears by high resolution digital image processing systems has been aimed at for more than ten years. Despite the use of sophisticated systems and a special preparation up to now no system has proved its ability to replace the cytotechnologist. The main problems are the high information content of the samples and the limited speed of sequential digital processors. As a solution to the speed problem analogue optical processing methods have been proposed. We have built an inexpensive and compact opto-electronic system that is adapted to the way a highly trained cytotechnologist screens a sample. It uses spatial frequency plane filtering for fast information reduction. Due to their limited accuracy and low flexibility sample classification by exclusive use of optical processors is not possible. Therefore our system is intended only as an interactive screening aid to facilitate human cytoscreening and leaves the classification of the slide to the cytotechnologist. In principle it can also be used to speed up digital image processing systems.
Real Time Spatial Filtering And Pseudocoloring By Light Scattering
L. R. Berriel-Valdos, E. Jara, S. Guel, et al.
There are several methods to introduce false colors into a gray level transparency using three primary colors. We emphasize here methods which makes use of the multiple scattering process inside the film. Based on this it is possible to obtain simultaneously the addition of a positive image, a low contrast reversed image, and a pseudo reversed image. This method works in real time, increases the color range variation of the gray levels, has a good continuous heu variation, and furthermore it has a low-cost implementation.
Coherent Optical Techniques For Transonic Wind Tunnel Measurements
Jahja Koka, David Casasent, Li Yong-Qing
A new technique has been proposed for deformation measurement by using moments. It is shown that changes in moments enable one to determine the model deformation with high accuracy and sensitivity. The model deformation is also measured by detecting the change in the Fourier transform of the grating printed on the model surface.
Imaging Properties Of Random Phase Diffusers For Coherent Imaging Systems
Marek Kowalczyk
A number of coherent systems exist for whichillp would be desirable to illuminate an object with a beam of randomly modulated phase. Usually for this purpose we put together the object and random phase diffuser, e.g. ground glass, at its back side. In the case of uniformly illuminated trivial object whose amplitude transmittance equals unity we observe in the image plane intensity fluctuations which correspond to some extent to the random relief of illuminating wavefront. By imaging properties of random phase diffuser we mean statistical propoerties of these fluctuations, especially their average contrast. In this work we consider imaging properties of diffusers which are set in the wide-band imaging system for which ratio, point spread function area divided by autocorrelation area of diffuser complex transmittance, is less than unity. We derive the formulae which describe intensity fluctuation in the image plane in terms of phase distribution and its first and second spatial derivatives in the object plane. Above formulae are derived for the low-pass filtering, particular case of high pass filtering, and for the case of not perfect image focusing. Then we employ these formulae for calculation the average contrast of noise pattern in the image plane when photographically formed strong diffuser with small standard deviation of surface roughness (≈ 0.58λ) is used.
Method Of Holographic Subtraction Of Images Due To Phase Shift Introduction By Means Of Object Longitudinal Displacement
I. S. Klimenko, T. V. Kuznetsova, N. N. Losevski, et al.
The method of holographic subtraction of images is describing. It make it possible to obtain high energy characteristics.
An Optical Method For Surface Curvature Testing
W. Jarisch
Inspection and measurement of surface quality play increasingly an important role in most machining and polishing processes. A typical example is the manufacturing of magnetic disks. The quality of a disk file essentially depends on the surface flatness of the substrate material. For many measurement aspects largearea topography variations are of less interest than high local changes of slope and curvature of the surface to be tested. Mathematically, the surface curvature is expressed as the second derivative of the profile function of the substrate, while the first derivative is known as the slope. Rapid local variations of the slope, that means high curvature values, cause high vertical accelerations of the magnetic head flying over the disk surface in fractions of a micrometer flight-height. Such irregularities of the substrate in the azimuthal disk direction would lead to uncontrolled fluctuations of the air gap between disk and head causing an attenuation of the write/read signal, to head vibrations, or even to a direct contact of the head with the disk (head crash). In the radial direction, the high-speed radial positioning of the head by voice coil driven motors also may cause a head crash at high local changes of the disk slope. Limits of the tolerable head accelerations, found by experience and theoretically by calculations, are listed in manufacturing specifications. For a fast, large area disk quality inspection and evaluation, a compact and highly sensitive measuring method has been developed. A testing tool based on this method displays the test area superimposed with a clear fringe pattern on a TV screen. The fringe pattern represents the surface curvature. From this, both components of the disk curvature, the azimuthal as well as the radial component, can be measured. Coherent optical interference and Moire techniques are the basic principles of the method providing the fringe pattern of the surface area under test. Each fringe interconnects locations of equal surface slopes. Consecutive, iso-slope fringes differ by a constant angular slope increment. The lateral spacing between adjacent iso-slope fringes - or generally the density of fringes - is proportional to the second derivative of the profile function of the disk and thus related to its radius of curvature. Therefore, the map of fringes indicates the areas of low and high head accelerations.
Improvement Of Optical Signal Detectibility By Means Of Multiple Observation
Karolj Skala
A detection method and electronic realization of optical detection by means of multiple observation were worked out. Improvement of the S/N ratio can be obtained by processing several images in the CCD shift register. Tho method is suitable for detection of signals from the photodetector array, which operates as a part of the optical radar.
Simultaneous Investigation Of Two Molecular Processes (Raman Scattering, Fluorescence)
Bela Nemet, Laszlo Kozma, Gabor Lupkovics, et al.
A new absolute method has been proposed for the determition of the total differential Raman scattering cross section (σR t) of solvents (e.g. water, ethanol etc.). According to this method σR,t is compared with the fluorescence cross section of dyes dissolved in these solvents. The two molecular processes of dye solutions have been investigated simultaneously at very small concentration (lo-9 -l0-9 - 10-10 M) by pulsed laser spectrofluorimeter on the range of near UV and VIS.
Measurement Of Frequency Dependence Of The Internal Amplification Of A He-Ne Laser Using A Heterodyne Method
I. Peczeli, E. Lorincz, F. Engard, et al.
A heterodyne signal was produced by backcoupling a He-Ne laser beam by means of a rotating radial grating into the active cavity of the laser. The optical mixing was observed behind the high reflectivity mirror, and was measured by a wide-band type detector. The frequency dependence of the heterodyne signal showed an unusual feature.
Surface Roughness Assessment Using The Angular Distribution Of The Back Scattered Field From A Small Laser Spot
M. A. Younes, J. R. Croft, W. J. Hill
The recent need for some in-process means to measure surface roughness has influenced many studies towards considering optical methods as a potential new tool. Till now published studies are almost all treating cases of smooth surfaces with given height distribution. The present paper presents a preliminary study of a suggested new technique where a very small laser spot interrogates the surface. In the present technique an experimental rig has been constructed, whereby the intensity of the light scattered from the laser spot interrogating the surface point by point can be scanned over a complete hemisphere. The intensity values are collected and stored for subsequent analysis. The whole system including drive of the photodetectors, drive of the test specimen and data acquisition works under computer control. Results from the optical method are compred with the theoretical intensity values calculated for the digitized height values obtained from Talysurf traces of the surface.
Ray Optical Analysis Of Backscattering By An Obliquely Illuminated Doubly Clad Fiber
Miklos Barabas, Andras Podmaniczky
We examine the far-field intensity distribution arising from the backscattering of a plane wave by a step-index fiber. Our calculations are based on the assumption that light scattered in a specified direction is the superposition of rays reflected in that direction. This geometrical optical description of scattering is extended to the case of oblique illumination and multiply clad fibers. Comparison of the computed and measured intensity shows that the ray optical treatment of scattering yields reasonable results even for a diameter to wavelength ratio as low as 20, as it is the case of an image transmitting fiber illuminated by He-Ne laser light.
Application Of Laser Interferometry For The Determination Of Optical Path Changes Of Reflecting Optical Systems
Jiri Krsek
Increased demands on geometrical accuracy and adjustment of optical elements and systems used in the laser measuring technique brought about development of new interference testing methods. The interference principle of determining optical path changes of the reflecting optical system enables the direct determination of changes of the functional arrangement of the measured optical system. The described interference methods are used for testing straightness and orthogonality of the coordinate axes of the reflecting optical system for a two-coordinate interferometer.
Laser Scanning Devices For Optical Gauging
Gyorgy Akos, Rita Csomor, Istvan Hejjas, et al.
Laser scanning devices have been constructed for measuring the outer diameter of cylindrical objects. The size measurement is based on comparing the object to a photo-lithographically fabricated grating. Both one- and two-dimensional measuring techniques are discussed.
A Two-Dimensional Diffraction pattern Sampling With Stationary Single Detector
Marek Daszkiewicz, Jacek Galas
The diffraction pattern analysis requires very well corrected lenses. The diffraction patterns are usually sampled by detector moved strictly in the Fourier plane or by especially desired multielement detectors. A new sampling method is proposed. In this method a stationary single detector is placed in the focus of transforming lens, while the sampled diffraction pattern is moved in the Fourier plane. The movement of a diffraction pattern can be obtained by illumination of the investigated structure with a parallel light beam, which changes its inclination to the optical axis of the transforming lens. Simple lenses and detectors for diffraction pattern analysis can be used. The experiments with two-dimensional samplinq have been performed. A continuous change of the illumination beam direction have been obtained by rotating, a glass wedge with variable convex angle. In this way the diffraction pattern is sampled along the Archimedean spiral trace. This type of sampling gives the light intensity distribution in the polar coordinates. Results of the experiments are presented. They show the possibility of application of this method in practice.
Laser Interferometric On-Line Measurement Of Surface Roughness Laboratory And Plant Application In Paper Industry
E. Lorincz, P. Richter, I. Peczeli, et al.
Equipment for non-contact on-line determination of surface roughness is presented. Light of a He-Ne laser scattered by the surface of a moving material (e.g.paper) is detected using an interferometer.Laboratory tests gave good correlation between the results of the optical and traditional methods. Plant application made possible to control reproducibility and observe the effect of technological processes.
Laser Photoionization Set-Up For Investigation Of Highly-Excited Atomic States
E. Vidolova-Angelova, D. Angelov
A set-up including three dye lasers pumped by a N2-laser for selective multistep ionization of atomic beam is described. The experiment is designed not only for spectroscopic investigation but for analytical use too. The application of the described set-up is briefly discussed. Some results on experimentally investigated highly-excited Rydberg states of Thulium are reported. Model potential calculations allow correct assignment of the spectra to be carried out. Non-hydrogen behaviour of the Rydberg states of rare-earth atoms is discussed.
Noncontact Optical Measuring Methods Of Silicon Wafer Deformation
L. Kocsanyi, J. Giber
Deformation measuring methods of 2", 3" diameter silicon wafers are presented. Michelson interferometer and moire method were used to determine flatness of the wafers. An in-situ interferometric measuring system was developed to measure continuously the deformation changes of a wafer during heat treatment.
Laser Interferometer Measurement Systems For Machine Tool Industry And Microelectronics
F. Petru, B. Popela, A. Stejskal, et al.
The article describes the laser interference measuring systems for machine-tool industry and microelectronics. They work on the Michelson interferometer principle with a single-frequency laser. The system for machine-tool industry measures lengths with the resolution of O,1 um, velocities, small angles, straightness and flatness. The system for microelectronics measures position in two orthogonal coordinates with the resolution of 40 nm.
High Accuracy Phase Measurement In Real Time
Johannes Schwider, Regina Burow, Karl-Edmund Elssner, et al.
Real time interferometry using the intensities at discrete reference phase values equally distributed over one fringe period is described. Principle, experimental setup and test examples (plane and spherical surfaces, optical systems) are discussed. Further, some error causes are covered, compensation techniques described and experimentally proofed
Application Of Speckle Techniques In Polymer Physics
Jaroslav Holoubek
The application of speckle techniques in the study of object displacements, speckle decorrelation and some dynamic properties of speckle patterns (SP) are discussed. The deterministic relation between the object and speckle movement is the basis of different methods of displacement measurement that find application in polymer physics. We present the application of speckle photography (based on the analysis of small-angle light scattering SP) and image speckle photography. The dynamical properties of SP are analysed by means of random phase screen theory. The structural aspects of non-Gaussian SP connected with dichromatic illumination or small number of scatterers are briefly mentioned.
Fiber Optic Sensors
A. I. Minchenko
The investigation results on phase optical sensors are presented. Phaseacoustic sensitivity of two- and three-layered (w-type) fibers with various polimeric jackets as well as without any coatings has been measured. To provide a rapid and reliable measurement of the phaseacoustic sensitivity of fibers it is suggested that a wideband acoustic noise signal should be employed. The operation of a fiber interferometer with alternating current automatic phase control (ACAPC) has been analysed. It has been shown that the detectability of this interferometer is about 1.7 times as low as that in the absence of ACAPC. Detectability characteristics of the autodyne laser sensor with a monomode fiber has been investigated.
Picosecond And Subpicosecond Pulse Generation By Travelling Wave Amplified Spontaneous Emission And Distributed Feedback Dye Laser
G. Szabo, Zs. Bor, B. Racz, et al.
A new scheme for travelling wave excitation of amplified spontaneous emission (ASE) and distributed feedback dye laser (DFDL) is presented. The method is based on the proper tilt of pumping pulse fronts by using diffraction gratings. ASE pulses emitted in the forward direction have shown a considerable pulse shortening (up to twofold) with respect to the pump duration. Travelling wave DFDL operation was also demonstrated. DFDL pulse shortening to below the resolution of the streak camera system (1.9 ps) was observed. Simultaneous measurement of the pulse spectrum and consideration of the time-bandwidth product has led to an estimate of the pulse duration Tp= 0.4 ps.
High-Voltage Copper Ion Laser With A Helical Design Of The Electrodes
M. Grozeva, N. Sabotinov
The influence of the coil pitch on the laser oscillation parameters of copper ion lines using a helical hollow cathode design are reported. A rapid growth of the laser gain with increasing the coil pitch is demonstrated. Simultaneous oscillation on seven IR copper ion lines and two krypton ion lines from 15 cm active length is obtained. A new design of a laser tube with two helical electrodes is described.
D.C. Hollow Cathode He-Kr Ion Laser
M. Janossy, K. Rozsa, P. Apai, et al.
Laser oscillation was investigated at the 469.4 nm and 431.8 nm transitions of Kr II in a d.c. excited hollow cathode He-Kr discharge. A water-cooled discharge tube was used in the experiment with an active length of 40 cm and an inner diameter of 3 mm. The laser was operated at a maximum current of 4 A, voltage being 240 V. Optimum He and Kr partial pressures were found to depend on discharge current. A gain of 6.7%/m and an output power of 5 mW was measured at 469.4 nm. Single axial mode operation was observed without using any special mode selection technics.
High Spectral Purity Narrowline Dye Laser Using Reflecting Interference Filter
M. N. Nenchev, Y. H. Meyer
The opportunity offered by the Reflecting Interference Wedge ( RIW ) of realising a new type tunable resonant cavity with narrow line of high spectral purity is reported. In addition,using only one RIW,the new simple unidirectional ring tunable laser cavity is realised.
Three-Channel Nitrogen Laser
Ludwik Pokora, Andrzej Zybura
A three channel laser designed in the S.Kaliski Institute of Plasma Physics and Laser Microtusion generates three mutually delayed radiation pulses. The solution employed had resulted in significant simplification of the optical delay line. In this paper the construction, results of theoretical analysis and introductory experimental testing of this laser, is presented.
Numerical Solving Of Boltzmann Equation In Copper Vapour Laser (CVL) Discharge Plasma
O. Marazov, St. Stoilov
A numerical technique for solving the Boltzmann equation in the CVL conditions are presented. The influence of electric field intensity and copper and neon concentrations on optimal CVL excitation conditions are investigated.
Investigation Of Spontaneous Lines From Upper And Lower Levels Of He-Ne Laser Line 632.8 nm Excited In Hollow Cathode
S. S. Cartaleva, S. V. Gateva, V. J. Stefanov
It has been found that the 632.8 nm and 1.15 - 1.20 μm He-Ne laser generations are more effective in Cu hollow cathode than in Al one.The purpose of this research was to find whether the higher efficiency of the copper hollow cathode He-Ne laser at 632.8 nm (3S2- 2P4) transition is due to higher upper laser level population or depopulation of the lower laser level. To compare the population of the laser levels in Cu and Al cathodes the intensities of some Ne spontaneous lines and reabsorbtion of Ne and He lines finishing on metastable levels have been investigated.The main results are that the upper laser and 4S0 He metastable levels are more populated in hollow Cu cathode than in Al one and there is no significant difference between the low laser neither between the 1s Ne metastable level populations in Cu and Al hollow cathodes.
Generation Of Subnanosecond Pulses By An Excimer Laser Using A Saturable Absorber
I. V. Chaltakov, Ch. G. Christov, V. L. Lyutskanov, et al.
With the aid of an-absorber, used as passive on-off switch of the excimer laser cavity Q a single high power sub nanosecond pulse is generated. Effective excimer laser pulse shortening is achieved with saturable absorber in which amplified spontaneous emission or lasing are induced.
D.C. Hollow Cathode He-Kr Discharge
P. Apai, M. Janossy, I. Palmai, et al.
Experiments carried out up to now related to the hollow cathode He-Kr laser were done using for excitation half-wave rectified a.c. pulses with a low repetition rate in order to overcome problems associated with Kr cataphoresis, impurities, unwanted transitions of the glow discharge into an arc and to avoid overheating of the discharge tube, which may cause damage of it. In the present paper a report is given on the investigations performed to develope a discharge tube for laser operation in a d.c. discharge.
Effect Of Anomalous Plasma Resistivity (APR) In Longitudinal Discharge Of Copper Vapour Laser (CVL)
O. R. Marazov, St. Stoilov
It is shown for the first time, that in longitudinal discharge copper vapour lasers an effect of anomalous plasma resistivity occurs. At the time of APR the largest part of active energy passes into the discharge. The proper understanding of APR in the conditions of CVL, would enable the correct understanding of the mechanism of exitation and laser generation as well as the further improvement of its output parameters.
Some Questions Of Thermal Stabilizing Of Injection Laser Diodes
Tamas Sziranyi
The thermal anomalies in injection laser diodes, effected by the changing of temperature are reviewed. Case assembly and mounting methods are analysed in respect of cooling. Methods for measurement of temperature of laser diodes are reviewed. Methods developed for measurement of thermal transients and compensation of their effects are showed. Knowing the mounting process and materials, and on the basis of measurement results we can choose the method of the regulating the cooling (for example in the case of thermoelectric cooling).
Physical Processes Limiting The CuBr Laser Lifetime
D. Astadjov, G. Petrash, N. Sabotinov, et al.
An experimental examination of the lifetime limiting processes in a whole-heated sealed-off CuBr laser is performed. The influence of the CuBr expenditure, the pollution of the laser windows, the recombination processes and the change of the plasma composition, especially the bromine concentration increase is investigated. Considering the experimental results a sealed-off CuBr laser of not less than 500 h of operation is designed.
Optical Bistability And Hysteresis In A Solid State Ring Laser
L. S. Kornienko, N. S. Kravtsov, A. N. Shelaev
The phenomena of optical bistability, hysteresis and memory under the interaction of oppositely directed (OD) light waves in a CW YAG:Nd3+ solid state ring laser (SRL) have been experimentally discovered. The possibilities of spontaneous or forced (with modulated SRL parameters) commutation of the radiation direction without transients at the relaxation frequency (typical for solid state lasers) have been established both in the single-mode and in the mode-locking regimes with various feedback circuits. The mode-locking band was found to be substantially broadened by more than an order of magnitude when OD light waves primarily diffracted on a standing ultrasonic wave were returned into the acousto-optical modulator. With such acousto-optical feedback the mode-locking regime has been obtained using a modulator on a running ultrasonic wave.
The Effect Of Intraresonator Nonlinear Optical And Magneto-Optical Phenomena Upon The Competitive Interaction Of Oppositely Directed Light Waves
L. S. Kornienko, N. V. Kravtsov, A. N. Shelaev
It is found experimentally that the competitive interaction of the oppositely directed (OD) light waves in YAG:Nd3+ and ruby solid-state ring lasers OIRL) can be significantly reduced due to nonlinear optical effects (second harmonic generation, stimulated Raman scattering, resonant absorption) since the nonlinear losses for the wave of lower intensity are lower. It was established that in the SRL with a resonantly absorbing medium the spatially inhomogeneous burning-out and the slowness of the relaxation of the inverted population in the solid-state active medium may result in strong phase nonreciprocity due to the frequency shift of the OD waves after their reflection from the moving lattice of the inverted population. The beat frequency strongly depends on detuning between the gain and absorption lines and may be more than two orders of magnitude less in comparison with the resonator frequency difference in the rotating SRL. The possibility has been shown of active stabilization of the bidirectional generation in the beat regime using the nonreciprocal amplitude Faraday element controlled by the external feedback circuit via the difference of the OD waves intensities.
Chemical Lasers On Photonic Branched Chain Reactions
V. I. Igoshin, S. Yu. Pichugin
The possibility of development of pure chemical pulsed laser amplifiers on photonic branched chain reaction is discussed.
A Review Of Recent Beam Propagation Method Results In Integrated Optics, Semiconductor Laser Theory And Fiber Optics
David Yevick
Research pertaining to the beam propagation method (BPM) performed by the author in collaboration with P. Danielsen (Denmark), B. Hermansson (Sweden), P. Meissner (FRG), E. Patzak (FRG), L. Thylen (Sweden) and J. Saijonmaa (Finland) is briefly summarized. First, however, heuristic deviations of two commonly-used beam propagation formalisms are given.
Coherent-Mode Representation Of Lambertian And Non-Lambertian Sources
Ari T. Friberg
The coherent-mode representation of arbitrary fluctuating optical fields is briefly reviewed and its application to the (non-lambertian) fields produced by the so-called gaussian Schell-model sources is discussed. The wavefields generated by lambertian sources are then analyzed within the framework of the coherent-mode representation. A simple and physically illustrative explanation is also obtained for the characteristic differences in the radiation properties of lambertian and spatially incoherent sources.
Evaluation Of Resonant Modes In Cascaded Holographic System
J. Slaby, T. Szoplik
Resonant modes of cascaded Fourier holograms are found with the Prony method. Lowest order symmetric eigenmode is nearly gaussian wave for two types of holographic record considered. Mode inversion is observed, nevertheless higher modes of propagation can be easily discriminated.
Achromatic And Sharp Focussing Of Laser Beams By Aspherics
Gunter Schulz
By two aspheric refracting surfaces, a two-wavelength laser beam can be focussed sharply at one axial point, that is, achromatically and without any spherical aberration. The focussing system may consist of a single lens (then one aspheric is conical at the axis) or of two single lenses with normal aspherics. The design principles for such systems are dealt with and examples of results are shown.
Time-To-Space Mapping Of Ultrashort Laser Pulses By Nonlinear Methods
J. Janszky, G. Corradi, D. S. Hamilton
Nonlinear optical phenomena as noncollinear second harmonic and sum frequency generation and also degenerate four-wave mixing can be used to obtain a one-to-one mapping of the temporal intensity distribution function of a short laser pulse on the transversal, spatial intensity distribution of an output beam. Methods for high contrast single shot measurements in the femtosecond to subnanosecond region are suggested using tilting of the wave front and/or short sampling pulses.
Nonlinear Total Internal Reflection In Nematic Layers
L. Csillag, I. Janossy, V. F. Kitaeva, et al.
It is shown that nonlinear total internal reflection can be realized in deformed nematic layers at a few mW input power. Experimental results on 5CB are presented.
A Multi-Beam Laser Film Plotter
A. Podmaniczky, S. B. Tokes
An experimental model of a drum-type film plotter is described. In the optical subunit the light source is a He-Ne laser and a multi-beam light modulator is employed to achive high recording speed and accuracy at a very moderate mechanical complexity. The system is capable to expose a 500x600 mm film in 8 minutes on 25μm raster with laser spot diameter of 40 μm.
Threshold Intensity Of Plasma Creation On Metal Surface Versus Angle Of Incidence And Polarization Of Laser Radiation
Cs. Toth, Z. Gy. Horvath
The polarization and angular dependence of the light intensity threshold for generation of plasma occuring by the interaction of ruby laser radiation with gold target was investigated. These studies were conducted in vacuum using pulsed 694,3 nm radiation from the ruby laser, operating in normal and Q-switched mode. It was found, that the component of the incident electrical field normal to the metal surface generates plasma at lower intensity, than the other component, which is parallel to the surface. A possible explanation for the obtained experimental data is given.
The Application Of The High-Energy Yield Carbon Dioxide Laser In The Surgery Of Head And Neck Cancer
F. G. Banhidy, M. Kasler
The inventions of science and technology are being rapidly introduced in the sphere of medicine, too. With the discovery of laser and later on the medical laser a new hopeful method of treatment appeared.
Investigation Of Damage Threshold Of Hard Laser Mirrors
K. Ferencz, K. Fluck, G. Szalai
Investigations were carried out to obtain the technology of production of hard laser mirrors having a high damage threshold. These mirrors are to be built into a resonator of a Nd phosphate glass laser the characteristic parameters of which are: λ=1055 nm, τ=15 ns, energy density in the resonator 3 J/cm2; the reflection coefficient of the mirrors: 99,5% and the output mirror, 32%≤R≤85%.
Absorbing Multilayers And Their Application For Laser Light Modulation
Georgy D. Zartov, Rumiana A. Peyeva, Krassimir P. Panajotov
The multilayer metal-dielectric coatings allowing the realization of electrooptical interference modulator of laser light are investigated. That type of modulators operates with driving voltage of about 100 volts. Some possibilities for application are discussed.
Investigation Of A Design Method For Optical Thin Film Systems
G. Szalai, K. Fluck
A selfrectifying design method was developed and was implemented in the form of a program package for the construction of optical thin film systems.
The Application Of CO[sub]2[/sub] And Nd:Glass Laser For The Enhancement Of The Fusion In Plasma-Focus Device
S. Denus, L. Pokora, Z. Ujda
Results of investigations of physical effects accompanying to CO2 and Nd:glass laser radiation passing through the plasma created in a Mather type plasma-focus system are presented. A number of correlations between the character of changes of measured plasma parameters and the influence of laser radiation upon the plasma have been observed. The existence of an increase of neutron yield, different values of reflecting coefficient according to laser pulse parameters, strong refraction of 1.06μm radiation have been found.
Photochemical Reaction In CdS Crystals For Holographic Information Recording
L. G. Sukhoverkhova
The change of various properties of CdS crystals due to photochemical reaction was used for reversible holographic recording. The change of CdS:Cu photosensitivity is used for holographic storage of phase gratings. It is shown that the diffraction efficiency of the grating can be controlled by the reconstructing beam intensity. The storage of the amplitude holographic gratings due to change of GLIS absorption by the illumination have been studied as well.
Holographic Optical Elements For Quantum Electronics
M. S. Soskin, V. B. Taranenko
Principles of holographic optical elements for laser beam characteristics control are given. Effective wavelength selectors for tunable lasers are described. Regime of grazing diffraction on phase volume grating with slanted fringes is analysed. Possibility of laser beam polarization control by phase volume grating is discussed. Experimental results are presented for holographic optical elements recorded in dichromated gelatin films and for tunable lasers controled by holographic wavelength selectors.
Adaptive Mirror For Large-Aperture Laser Beams
T. B. Volyak, I. K. Krasjuk, P. P. Pashinin
The measurements of the laser damage thresholds of metal-coated plastics were performed. The results have shown that the plastics could be used as laser mirrors in pulsed devices. An optical quality of the varifocal plastic mirror is comparible with that of conventional massive mirrors and of the other complex varifocal mirrors. It has shown that mylar mirrors is stable and unstable cavities of the pulsed TEA C02-laser could replace the traditional massive mirrors. Simplicity of design and easy parambter variation of adaptive plastic mirrors are advantageous for using in different laser devices.
Comparative Characteristics Of Coherent And Incoherent Radiation In The Photography Of Ulcer
V. F. Novikov, L. V. Paramonov
The efficiency of He-Ne laser radiation and incoherent radiation by red light sources with different spectral bandwidths is compared for the endoscopic phototherapy of gastric and duodenal ulcers. Coherent and incoherent radiation is determined to result in the same theraputic effect when doing the treatment of ulcer deseases. The methods of ulcer treatment is suggested with a conventional fibrogastroscope fitted with red glass filter.
The Optical Parametric Mixers With Phase Conjugating Mirrors
V. I. Bespalov, A. M. Kiseljov, G. A. Pasmanik
The method for phase conjugation oa laser radiation in a wide wavelength range is proposed. This method uses a parametric mixing of input signal with reference wave followed by conversion to another (intermediate) frequency range where phase conjugation occurs. When passing back through the parametric mixer, the phase-conjugate signal of intermediate frequency and the phase-conjugate reference wave form radiation at the frequency of the input signal with phase conjugation. The method was tested experimentally at λ = 0.53μ
Energetically Effective Sensitive Four-Wave Phase Conjugating Mirrors
N. F. Andreev, V. I. Bespalov, M. A. Dvoretsky, et al.
The method of the four-wave phase conjugation of weak light signals with a large coefficient of transformation of the pump wave energy into the conjugated wave is studied.
New Nonsilver Media For Optical Recording
E. N. Salkova
CdTe and CdHgTe absorptive semiconducting thin films for holographic recording in the red and infrared regions were used. Holographic relief diffraction gratings were recorded for the times 10-6 to 10-8 s with the following parameters: sensitivity 10-2 - 10-3J/cm2, resolution 2000 lines/mm, diffraction efficiency 20%. No additional treatment of the exposed material was required. The mechanisms of relief formation on the thin film surfaces were investigated by complex techniques. The properties of obtained gratings and their possible applications are discussed.
Single Beam Method Of Manufacturing Holographic Optical Gratings
V. P. Aksenov
Experimental results of detailed measurements of periodic surface damage induced by pulses from a Nd:YAG laser radiation on surface of Ge samples and Ge films on Si02 substrate are reported. The periodic surface structures or ripples are created by the intensity modulation on the surface which is the result of the interference of incident laser beam and a coherently scattered surface waves (surface plasmons, grazing transversal waves, surface polaritons), which may be generated by photons at a rough surface. We consider a dependence of ripples growth rate from direction of incident light polarization, form of the laser spot, direction of surface wave travelling. The coherent extension of ripples from overlapping laser spots was observed for the grating with spasing d=λ/cosθ where θ is angle of incidence of laser beam, λ is wavelength of light. The optical grating with square near 2 cm2 was manufactured.
Multilayer Dispersion Elements For X-Ray Emission At A = 17 - 100 I
S. V. Gaponov, S. A. Gusev, Yu. Ya. Platonov, et al.
It is shown that near the K edge of absorption of weak absorbers, C, Be and B, using rather light materials, Cd, Ag, Te and Cr, ,it is possible to obtain a reflectivity R ≈ 70 % at spectral resolution λ/Δλ ≈ 50 + 100.
Acoustooptic And Electrooptic Diffraction Light Modulators
David L. Hecht
This paper presents an overview of the operating principles and characteristics of acoustooptic and electrooptic diffraction light modulators. Functionally, these may be categorized into temporal light modulators, spatial light modulators, and tuneable color filters. Physically, they may be categorized by driving mechanism and by optical geometry. Acoustooptic modulators may employ traveling wave or standing wave ultrasonic fields to induce photoelastic modulation of the optical indices of refraction. Electrooptic modulators may use electrostatic fields or traveling electromagnetic waves. The three principal classifications based on optical geometry are bulk-wave, total internal reflection, and guided optical wave devices. In bulk optical devices, the optical beam interaction occurs within the active medium, largely unaffected by material interfaces. In total internal reflection devices, the optical beam can interact with a perturbation confined near surface of the active material, but otherwise maintains bulk propagation characteristics. In guided wave optical devices, the light is confined to a dielectric waveguiding structure whose optical index characteristics are further perturbed by the active modulation. For most diffraction modulators, the controlling physical principle is the conservation of momentum, which may be elaborated as wavevector matching or phase matching conditions. Spatial light modulators involve control of the wavevector components transverse to the optical propagation direction. Color filters affect the wavevector component along the optical propagation direction. Temporal modulators affect the amplitude or frequency of a light source considered as a whole: they may utilize transverse or longitudinal modulation; frequency shifts are fixed by the conservation on energy.
White Light Image Enhancement And Restoration
J. Bescos, J. Santamaria
The introduction of white light in several fields of optics such as interferometry, diffraction and optical testing, has produced many valuable contributions that frequently have led to optical techniques of present application. The use of white light in optical processing also allows to extend the capabilities of this field by including new operations and applications, besides other advantages related the reduction of noise. White light processors are able to encode through different wavelengths distinct types of information. The display of information using several wavelengths or spectral bands is specially adequated in images addressed to human observers or other colour sensitive receivers, since these receivers can take advantage of the high sensitivity of the human eye to small changes of colour. In this way different pseudocolour techniques addressed to enhance through colour distinct types of information have been recently developed . The parallel white light processors could be used to process images for direct analysis or could serve as preprocessor which derives colour encoded texture information for further processing by digital, optical or other techniques. On the other hand white light processors enable direct enhancement and restoration of colour images. Images with poor colour saturation due to inadequate illumination or registration conditions can be enhanced by spatial filtering. Also, images with spatially invariant degradations such as defocusing and chromatism, can be restored in white light by optical or digital techniques.
High Power UV Lasers
K. Hohla
During the past 8 years excimer lasers have made an enormous progress both in power and energy. Today they are the most important high power laser source in the uv-spectal range. The paper will present the basic concept of excimer lasers including the spectoroscopy and the kinetic of the lasing process. Based on these data the most practical excitation mechanism, the fast discharge, will be discussed. Limitations and technical constraints of power density and efficiency will be given. The physical properties of the excimer laser radiation i.e. bandwidth, tunability, coherence and pulse duration have been of major concern in the last few years. Concepts will be discussed by which the difficulties connected with the high gain of the laser medium can be surpassed. Today the laser radiation can be controlled within 0.2 cm-1 bandwidth and within three to four times the diffraction limited divergence angle. Inadditiorycluring the past year, devices have been developed allowing pulses with durations of several ps and 30-40 mj energy. Parallel to these physical improvements the reliability of the excimer laser has reached such a high level that they are now introduced in industrial processes. The limitations of the most critical parts of excimer lasers will be presented together with the evaluation of running costs. Finally some selected examples of applications of this new work horse of uv radiation will be discussed.
Measurement Of The Deformation Of Rail Track Fastening Clips By Holographic Interferometry
A. E. Ennos
One method of attaching railway rails to the sleepers (ties) is to use spring steel clips, mounted on either side of the rail, that exert a downward force on the foot of the rail. In service these will flex with the passing of a train. Holographic interferometry has been used to measure quantitatively the manner in which the spring clips deform when the rail is given a displacement in a prescribed direction. The information can be used both to provide data on the bending and torsion of the clip, and as a means of testing the validity of finite element analysis calculations. Measurements on three different designs of commercial clip were carried out on a section of sleeper holding a short length of rail. A controlled upward displacement of the rail was achieved pneumatically by means of plastic pipes interposed between rail and concrete sleeper. Double exposure holograms were recorded on large photographic plates, allowing views of the fringe patterns from widely spaced directions. The three components of displacement at points along the length of the clip were calculated from fringe information taken from nine directions, using least squares fit to obtain increased accuracy. Rotations of the surface were calculated from the fringe directions and spacings. In addition to deformation measurements of the clip under service conditions, information on local yielding of the clip under increasing stress was also obtained by means of real-time interferometry, using an instant hologram camera.
Population Inversion Of ARII Laser Levels In The Hollow Cathode He-Ar Discharge
P. Pramatarov, M. Stefanova, Y. Pacheva
The population of the upper laser level 4p2P3/2 of Ar11476A laser line and the triplet metastable helium atoms density are measured in a pulsed hollow cathode He-Ar discharge. The discharge tube is a "transverse" segmented type with a 6 mm inner cathode diameter. Helium pressure varies from 8 to 20 Torr while the Argon pressure - from 0,5 to 1,5 Torr. The discharge current density varies from 50 to 250 mA/cm2. The balance equation of the upper and lower laser levels and the ground state of Ar ion are qorked out for the pulse and the afterglow. Cross section value for the excitation transfer process from a helium triplet metastable atom He(23S1) to a ground state argon ion Arll is estimated. The processes leading to inversion population between the upper and lower laser levels are investigated.
Four Channel Nd:Glass Laser System For Fusion Experiments
S. Denus, A. Dubik, B. Kaczmarcyk, et al.
The laser system at the Institute of Plasma Physics and Laser Microfusion is a four beam Nd-glass laser used for the study of laser plasma phenomena and is capable of generating 40 J pulses of 20-30 GW peak power in each arm. This paper presents an overview of the system. The Nd:YAG Q-switched oscillator with its optically triggered spark gap switchout produces pulses whose duration and energy are nominally 1,5-2 ns and 2 mJ, respectively. This pulse is amplified by two of rod preamlifiers and stages of rod amplifiers. The rod amplifier stages have apertures of 12 mm, 15 mm, 20 mm, 30 mm and 45 mm respectively. Spatial filters are placed between amplifier rod stages. After leaving the amplifier stage of 12 mm of the system the beam is spatially filtered to remove the high frequency ripples imposed on the beam by the hard aperture. The spatial filter also produces an image of hard (soft) aperture, which is subsequently re-imaged by a second spatial filter and so on up to a 9-th spatial filter which 'finally relays the hard (soft) aperture image onto the main focusing lens of the system.
Non-Destructive Testing Of Optical Fibre Preforms
M. Miler, F. Osvald
The quality of the communication fibres depends directly on the quality of the preform. There exists a large number of various destructive and non-destructive methods for testing of the preforms. The methods are objective or visual. The visual methods are very useful for quick qualitative testing especially at the beginning phase of the development of the preform making method. This paper describes a visual method of preform testing which is based on examination of the shadow pattern arising by the transmission of the light beam across the preform. To obtain sufficient intensity of the picture the beam is scanned along the preform axis. Rotationally non-symmetric optical system and a vibrating mirror serve for the scanning. As a light source the He-Ne laser is used. The interpretation of the shadow pattern is given. The pattern contents dark and bright fringes. From their number, position and width one can evaluate the number, width and refractive index of the films deposited by the MCVD method.
Optical Distance Sensing For Robotics Applications
V. Gerbig
Technical possibilities and economic conditions have made robots a necessity. But most of todays "robots" lack sensors and hence they are not capable of really intelligent, flexible, adaptive and safe (but unsupervised) operation. Besides mechanical sensors for forces, moments, pressure etc., optical sensors are truly required to gain those capabilities. Optical sensing allows for fast, non-contact, force-free, remote, flexible, universally applicable, accurate, etc. measure-ments without wear of object or sensor. Optical distance sensing is a basic measurement function. Done in parallel (using moire e.g.) or performed serially (i.e. by scanning) it provides information about position, orientation, shape, dimensions, etc., and also about changes of these parameters with time (speed, vibration, etc.). Therefore, numerous applications are imaginable, esp. in robotics, e.g. tracking, approaching, grasping, guiding, assembling and inspection. Various methods for optical distance measurements will be presented. There are geometrical optical methods (like triangulation) as well as wave-optical ones (like interferometry), methods for smooth and rough targets, active and passive methods, etc. Many known and some new methods are to be discussed and evaluated in the light of robotics applications which mostly require fast, accurate, compact, robust and inexpensive systems.
Displacement Of Molten Metal Under High-Repetition-Rate Pulsed Irradiation
R. V. Arutyunyan, V. Yu. Baranov, L. A. Bol'shov, et al.
The processes occuring due to high-pulse-repetition rate laser beam interaction with metals have been studied by now very poorly both theoretically and experimentally. In the same time, first high repetition rate (HRR) pulsed laser applications to materials processing attract some interest to such a study. The investigation of possible improvement, theof the cw-laser-induced processes by using cw and HR R lasers together is also prospective. The melt removal mechanisms studied both theoretically and experimentally are the subject of the present paper. The pulse approximation of hydrodynamical equations is valid to describe the molten metal motion generated by laser puls of 1-100 μs duration. Reasonable agreement between theoretical estimations of velocity and escape time of the melt and experimental data was achieved. High-repetition rate pulsed processing was also investigated. The model of deep penetration by a HRR laser is put forward. It explaines the greater penetration ability of a HRR laser as compared to the cw laser of the same output power.
Recognition Or Identification In Optical Correlators
B. Smolinska, G. Krul
Optical correlator is an optical system able to create in the output the correlation of images of introduced optical signals. Correlation function is used as a decisive function in signal identification process. Often we are rather interested in recognizing than in exact identification of the optical signals. At first we must characterize signal features valid for recognition. Beyond a lot of signal characteristics we can discern two: the signal shape and contour sharpness (image contrast). Because the identification is carried out in the Fourier plane of ptical system we will define these features in spatial frequencies. So we discern: 1. The set of spatial frequency directions realized in the Fourier spectrum of the signal and 2. maximal spatial frequencies occouring in the Fourier spectrum. The first is connected with the shape and the second with the sharpness of contours in the input signal. The question is how will the correlator system respond to this characteristics? We tested two correlator systems: Van der Lugt correlator and quasi coherent correlator. The optical signals used in the examinations were intentionally constructed in order to emphasize the above mentioned characteristics of them, There wert: two diffraction gratings with the same grating constants and modulation deepths. They differed in the progress of the transmittance only. The tested correlators were arranged in known manner. Light intensity collected in the center of correlation image in the output of correlator system served as identity gauge of tested signals. Conclusions: In the experiments it occoured that the Van der Lugt correlator is more sensible device than the quasi in transmittance progresses can be detected sharply. The nonlinear recording of the matched filter promotes this effect. In the contrary because of better linearity of recording the matched filter and the scattering nature of diffuse illumination, the quasi coherent correlator is sensible only for the general shape of the signal. For identifying optical signals exactly, with full characteristic, the Van der Lugt correlator is unexchangeable. But when one is interested in recognizing signal shapes it is better to use the quasi coherent correlator.
Comparison Of Moire-Mismatch, Moire-Fringe Multiplication And Moire-Interferometry As A Method For Measuring In Plane Displacements
R. Beer
Traditional Moire-technique uses two equal bar-and-space gratings to get Moire-fringes by mechanical superposition. In order to measure in plane displacement a very high density of the grating is needed where as a grating frequency of 40 L/mm is usual (in Moire-technique). Mismatch as well as Fringe-Multiplication is used to overcome the difficulties arising from this fact. Sciammarella and Lurowist also introduced a method to determine fractional fringe order by an operation quite similar to Tardy's method in photoelasticity. Laterly a special case of Fringe-Multiplication was introduced by D. Post the so called Moire interferometry. That is a relatively easy technique for producing high frequeny gratings and it extends the Moire-method into a high-sensitivity domain. Moire-Interferometry works in the reflection area, therefore to perform the experimental analysis it is not necessary to use a transparent specimen or a transparent replica of the deformed specimen grating; the observation of the actual workspiece is possible. Of course the multiplicator factor is only 2, however following Post procedure it is easy to get very high frequency grating. Using two Laser-beams a virtual reference grating frequency up to 4000 L/mm have been reached, that means a sensitivity up to. 25 μm/fringe. Examples for these methods can be shown, dealing with our investigations of some repear patch problems.