On behalf of the International Commission for Optics who sponsors this European Conference, I want to express my best wishes to the organizers as I believe they need a lot of encouragement. Next I wish that those who have come to participate to the meeting first of all may find here what they expect they will find - I mean the opportunity to discuss their research work and that of exchanging ideas inside a truly European Community. By the end of this week, shall we all feel like members of European Optics, nay of Optical Europe ? Wouldn't this constitute the greatest aim we all here might wish to achieve, since in this European Hall are sitting together in particular, with all our colleagues from the West, those who have also been willing to start on such a long journey, I mention the scientists from the USSR, only to refer to the geographically remotest European nation.

Basic considerations of similarity between the spatial and temporal frequencies in image formation have been developed along applications for which two classes of examples are given. a) Absolute measurements of optical paths by interferometry in white light ; applications to the determination of surface pping A channelled spectrum (1), observable at the output of a spectroscope set in cascade with a two-beam interferometer illuminated in white light, displays the local path-differences introduced along one arm of the interferometer, the other one being considered as conveying the reference. A relationship holds between the chromatic distribution scaled in temporal frequency and optical delays that are functiortsof time This suggests techniques of longftudinal measurements. Indeed one deals with Fourier transforms both in space and time, allowing to show some equivalence of the channelled spectrum with a Fourier hologram - the reconstruction of longitudinal information being performed at a transverse diffraction plane. This is illustrated in rugosimetry and in the assessient of calibrating tests. b) Statistical properties of random surfaces by spectrat analysis of scattered "Light. By analogy with conventional speckle methods, we have proposed the concept of temporal speckle as the spectrum of the incident radiation spreads over a broad band. It can be stated that no statistical model is needed for surface rugosity and evaluation of the r.m.s. for Gaussian rugosities are presented as illustration. The following text is very close to that of the original lecture and we did not feel the need for any proper introduction to it. A rough idea of the work, which has been given in the abstract, will be further recalled through the fundamentals in the first paragraph below.

Interference method of measuring distribution of refractin index continuous heterogeneities in semiconductors are described. Difference distributions of sample thickness and refracting index are calculated by scanning three interferograms and making use of computer analysis. Distributions of sample cuneiformity and refracting index gradient may also be found as well as the speed of variation of these quantities with respect to the variation of coordinates. Measuring results of silicon sample are given. Measuring accuracy 1x10^-5 may be achieved for refracting index distribution in 1 mm-thick semiconductor sample.

Modern spectrometry offers rich possibilities by convenient use either of interferometric devices (Fourier transform spectrometry) or of selective modulation (grid spectrometry).Progresses in resolution and luminosity have been spectacular in the last decade, and new domains of high resolution and low luminosity have been explored. In those cases of extreme performances, the instruments are generally highly sophisticated,delicate, and expensive. Nevertheless, Fourier transform spectroscopy is now developing for practical applications : we have examined the possibilities of interferometric devices to routine spectral analysis in chemistry, biology, pollution detection etc... and are now aware of the interesting characteristics of those mountings by the fact that they are luminous, flexible and very simple. They need no computer and are very suitable for low resolutions. We shall describe first the basic principle, and later focus on the various possibilities resulting from the direct access to the interferogram and the application of the mathematical properties of the Fourier transform : Fourier derivation, Fourier correlation with a reference spectrum, Fourier correlation of derivatives etc... All those possibilities result from techniques of matched filtering for spectral recognition, obviously similar to analog techniques for pattern recognition.

We describe two apparati: one serves to measure, the other to stabilize the rotations of light beams with a sensitivity which may surpass a hundredth of a second of arc.

We deal with an inverse scattering problem : knowing some properties of a diffracted wave, what can be said on the diffracting object ? This leads to strong mathematical difficulties. Using new methods, we show it is possible, for instance, to deduce the index profile of an inhomogeneous plate from its reflection coefficient.

An optical analyser of vibrations has been developed and produced. It permits the measurement of the amplitude and phase of the vibration of a mechanical part. It is characterized by a very small feeler area, on the order of several 2, depending on the power of the lens used. The frequency domain extends from 20 to 100,000 hz. The amplitudes measured are also a function of the power of the lens and range from 10 m to 10 . The apparatus offers 1000 measurement points. The principle of measurement is as follows: a displacement of the surface examined entails a defocusing which is expressed by the modification of the light flaw received by a differential photodiode. If the surface vibrates, the light flaw is modulated and the vibration is translated by a modulation of the photoelectric currents.

The gathering of information by optical methods permits rapid and non-disturbing intervention at the level of the elements being tested. The measurements can be made dynamically (rapid sampling) and in difficult environments. In general the data taken must be treated so as to permit exploitation in real time, and this in a flexi-ble form so as to be adaptable to different needs. The system proposed achieves an optimized synthesis of the present technological possibilities by using, as an optronic captor, point detector cameras coupled to a piloting and treatment unit using a micro-processor. The material is entirely-static. Besides its duties of dimensional testing (surveillance of production line), the system can be connected to the production tool, in order to constantly optimize the tolerances. The simultaneous control of several production lines is possible. The profitability of the system is assured by the gain in material, decrease in rejection rate and savings on laborious tasks.

We describe some properties of the two beam interferometer that we have built at the "Institut National de Metrologie" for wavelength comparison. We describe particularly the phase shifts between visible wave-lengths at zero path difference.

We describe an interferometer functioning in the region of 10 mm, developed for the examination of the homogeneity of IR materials and for the TWyman-Green testing of the wave surface of IR optical systems. This interferometer used a CO laser as source and a diffraction grating as separator. A scanning camera associated with a point detector reconstructs the interferogram on the screen of an oscilloscope. We also present a second -generation instrument recently produced in.collaboration with an industrial company as well as some typical applications of these interferameters,in evoking their possibilities of extension to the domain of common mechanics for the demonstration of the form of parts. We also present an experiment of linear reconstruction of the phase in order to directly obtain the wave surface, effected with the infrared interferometer, whose path difference is put to use.

A description is given of an interferometer capable of non-contact measurements of the displacement and velocity of solid surfaces. The interferometer may be used with any C.W. laser in the visible region and no treatment of the surface is usually necessary. To over-come the problem of directional ambiguity, the reference beam is frequency shifted electro-optically using a Kerr cell device. The output is a frequency modulated signal that may be processed to obtain instantaneous velocity by a ratemeter or more sophisticated frequency recording device. Displacement measurements may be made by counting cycles and continuously subtracting counts derived from the shift frequency. For instantaneous movement a precision of one count or a quarter of a wavelength is obtained but mean displacements may be registered with greater accuracy. In another mode of operation, the output of the interferometer is fed back to control the frequency shift to "phase-lock" the interferometer. This enables very small movements at high frequencies to be recorded in the presence of the much larger low frequency vibrations normally encountered in the laboratory. This technique has been successfully used in the calibration of ultrasonic transducers.

The characterization of materials requires the knowledge of the refractive index and its variations under the effect of a given parameter. Whether we are dealing with transmission by a transparent sub-stance or reflection on a metal surface, the measurement of the phase difference introduced between the entrance and exit waves permits us to discover this characteristic of the material. In dimensional metrology, a phase difference at transmission is as much a function of the index as of the thickness, and the metrology of length standards requires the knowledge of the loss of phase at reflection. Thus the lengths considered as possible optical paths, or even the rotations, can also be expressed as a phase difference. These phase differences, demonstrated by normal or differential interferometry, can be measured with a gain in time and sensitivity if this interferametry is done by phase modulation. The very small un-certainties permitted by this process make it particularly interesting to apply to measurements of small phase differences expressing small variations in index or thickness. Its possibilities will be illustrated by examples of characterization of photosensitive materials, determination of loss of phase at reflection, longitudinal localization of objects, dilatometry and torsionetry. This process also permits us to obtain simply the rate of the variations of complex amplitude of a phase object as a function of space or time.

We propose an imagery device presenting a double particularity: (1) one of the axes of the image space is an axis of the temporal frequencies Ov; that is, the image is inscribed in a projection of the spectrum of the white light emanating from the object; (2) the image is anamorphosable at will. The light radiated by the achromatic object is dispersed by an auxiliary grating, then projected on the entrance slit of a spectroscope. The spectroscope, in again dispersing the chromatic components removed by the slit, reproduces a unique image of the object. By playing with the position of the auxiliary grating, for example, we arbitrarily modify the geometrical dispersion of the device; it results that the size of the image in one of its dimensions (that corresponding to the Ov axis) is anamorphosable at will. Besides the possibility of anamorphosis, the realization of image spectrograms opens interesting possibilities in metrology (absolute measurements of thickness, in particular).

The difficulties of investigating thermal turbulence using a classical hot wire anemometer in flows with very high mean velocity and temperature are well known. We are thus concerned in this paper with the possibility of studying such a turbulence by means of a laser beam propagating through a heated free plane jet of air. The beam undergoes in the flow random perturbations which tend to deflect it around the path that it would have taken if it had propagated in a vacuum. A formula is derived which relates the random deflection to the random temperature fluctuations. The experimental set-up is described. The values of the mean temperature and velocity have been chosen so that comparisons between the results obtained by this optical method and thoses obtained by the classical hot wire are made possible. A close agreement between both sets of results proves the validity of the model.

Our holographic technique permits us to produce the equivalent of a photogrammetric stereomodel. The exploitation is made in two ways: -the direct method, in which we visually put a luminous point in contact with the three-dimensional holographic virtual image of the object; -the video method, in which we work with a camera on the real holographic image of the object. These methods permit the measurement of distance by successive sightings on the object with a precision better than 0.1 mm. The apparatus which we are developing presently works by successive sightings. It may evolve towards an automatic sequence of sightings, advantageously using repetitive details already existing on the object or curves drawn optically.

Various methods for the measurement of hydrostatic stress i.e. the isotropic component of the stress tensor, are presented. All these methods lead to a whole-field visualization. In two dimensional problems, the hydrostatic stress is obtained by the measurement of the relative variation of thickness, caused by loading the model ; by using the technique of double exposure holographic interferometry. The birefringence effects are eliminated by making the object beam to pass through the model, and in-between the two passes, the beam is subjected to a 900 rotation of its plane of polarization. In the case of three-Aimensional models, the method is based on the observation of the variations in the absolute index of refraction. The frozen-stress technique requires the use of those photoelastic materials which remain compressible at the "freezing" temperature ; but unfortunately, they are unavailable at present. Therefore, a non-destructive optical-slicing method is proposed and it is hoped that it shall give the required information concerning the hydrostatic stress. This method consists of an interferometric comparison of the two superimposed speckle patterns, each scattered from two neighbairing optically isolated light sheets. Further, the measurement of the in-plane strain can be carried out using either holographic or speckle pattern interferometry ; the precision is found to be the same in both cases.

Our goal was to use the technical accomplishments of the L.S.O.C.S., notably in spectros-copy of modulation in the applications undertaken in the applied optics department of this laboratory. Our efforts aimed at elaborating a system permitting us to optically compare with precision different objects. Since the problems becomes more complicated with the complexity of the form of the object, above all in the domain of curved shapes, the study of a comparator of gauge blocks was the first stage of the program. We hope that many of those who are presently using an older system of measurement will benefit from this one, which will be commercialized shortly.

Holographic interferometry applied to non destructive testing is a powerful method, usable with any structure (here, pressure spherical reservoirs) provided that it can be acted upon, mechanically or thermically, so as to present two different dimension conditions corresponding to the two superimposed holograms. By revealing the shape of the plastic zone, in the case of a breaking strength test piece acted on by a tractive effort, the method allows to validate a numerical simulation, the results of which are then introduced into a program for calculating the Rice integral, used as a criterion of the breaking point for elasto-plastic materials subjected to a plane stress.

The techniques of holographic contouring, holographic image subtraction and similar techniques are reviewed and discussed as methods for measuring minimal wear in engineering situations. These techniques enable the change in shape, size and surface micro-deformation of wear test specimens to be measured, producing results which cannot be obtained using conventional methods.

This paper presents two ways of using holographic interferometry, firstly for identification of materials such as metals as regards fatigue and failure behaviour and secondly for complete determination of the state of stress in transparent plane models. 1 - After outlining the principal parameters of the linear elastic theory of failure, we demonstrate the use of real time holographic interferometry in the quantitative determination of yield phenomena at fatigue crack tips. 2 - Under certain conditions elastic behaviour study of complex structures can be confined to analysis on two dimensional models. When the state of stress changes, each point in the model simultaneously undergoes a variation of index and thickness. The first factor can be linked to the difference in stresses whereas the second is a function of the sum of stresses. The optical effect from a double exposure holographic recording will not show a simple superposition of interference fringes of different origin but rather a complex intermodulation of different curves. On the other hand, using a specific set-up and a non-reciprocal rotatory power with a FARADAY cell, it is possible to obtain simultaneously and separately the interference fringes representing the sum and the difference of stresses.

Up till the present time characteristics of turbid medium were determined using indirect methods, such as optical fringe and photography methods as well as the following photoelectrical methods : shadowing, screening and scattering at small angles. Such contact methods as gravitational, electrical and inertial are significantly less perfect. Using the first two methods a parameter correlating with particle size and not size itself is found.

Broadly speaking, every prosthesis is intended to replace a missing or deficient organ. In odontology, there are two main types of prosthetic reconstitution : - movable devices resting on mucous membrane as support, - fixed devices attached to a dental support.

Evolving construction techniques in civil engineering during recent years have favoured the concomitant and growing extension of complex structures. The design of these structures most often calls for the introduction of basic assumptions which greatly condition the results. In certain cases difficult to analyse, it is particularly desirable to be able to infirm or confirm, on the is of other methods, the validity of the assumptions made .It is thuspossible to examine more closely the behaviour of these structures under load. In particular, the optical methods of stress analysis can help to facilitate the interpretation and utilization of design calculation data. Among the optical methods available to us, we endeavoured to develop in a quanti tative manner the use of holographic interferometry for application to certain civil engineering problems.

In electrochemical processes at solid-liquid interfaces, one of the main factors controlling mass transfer is the formation of boundary layers. These layers have a thickness between 0.15 and 0.7 mm, depending on the flow velocity of the liquid. Classical electrochemical techniques only give overall measurements of mass transfer; the aim of this study was to measure local mass transfer using holographic interferometry in real time, a technique particularly well adapted to the use of cells with complex forms. Two processes were observed: electrolysis and electrodialysis. The refractive index profile in the boundary layer was observed as a function of the liquid flow-rate and the applied difference in potential. Because of high refractive-index gradients in the boundary layer, the observed profile may be considerably distorted by light-deflection effects. Calculations have shown, however, that light-deflection errors may be kept within tolerable limits by using sufficiently dilute solutions. These solutions of limited concentration still allow useful results to be obtained.

On a brake test stand the vibration modes of the calliper frame, of the disk, and of the brake pads occuring simultaneously are made visible during squealing in an interference figure by means of double-exposure interferometric holography.

In a holographic recording and reconstruction configuration, in which the object illumination source and the center of projection of the observation system seem to coincide, the accurate measurement of the sensitivity vectors is simplified considerably. Therefore, quantitative interpretations of the holographic interferograms are obtained with relatively small effort. If a dual reference beam double-exposure set-up is used, the sense of displacement components can be found and extremes in the scalar product of displacement vector and sensitivity vector can be detected when a relative phase shift is introduced in the reconstruction beams.

A hybrid system involving analogue and digital video techniques is presented, which enables the user to determine the loci of interference fringes with high precision in double-exposure holography. Experimental results for interferometric applications are given.

In holographic interferometry, fringe control may be achieved in several manners. In this paper, the general way of reasoning is applied to the case where the two interfering wavefronts are recorded on separate holograms, one of which is moved during the reconstruction. In the first part, we investigate the image reconstructed by a hologram displaced with regard to the recording. We determine especially the position of the aberrated image of a point source. In the second part we examine the fringes produced by the interference of the wavefront coming (virtually) from an undeformed object and the wave-front coming from the same object which has been mechanically deformed and moreover "optically modified" by the movement of the hologram. We first determine the optical path difference which does depend upon the mechanical displacement of the object point and upon the motion of the hologram, but not upon the position of the images. We then calculate the derivative of this path difference and express so the fringe interspace and direction. The derivative contains in addition to the previously mentioned displacement vectors, the strain and rotation tensors of the object and the rotation tensor of the hologram. In conclusion we show how such a modification of the position of a hologram may be useful for the deformation measurement.

We present an application of holographic interferometry by double exposure to non-destructive test-ing of solid propergol engines 350 Ian in diameter and 1000 mm in length at a maximum. The apparatus in -stalled for industrial use is described. It permits us to easily visualize defecth in the adhesive of 10 rrm x 7 mm under 2.5 mm of thermic protection by application of a weak pneumatic stress (around 10 oraigl. The engine is placed in a vacuum chamber provided with an observation port. The parasitical contour fringes due to the variations in refractive index of the air with the partial vacuum can be eliminated by the use of a different gas with each of the two exposures of the hologram. Results concerning real engines are shown.

Up to now, holography has been employed industrially only in the testing of thin shells (helicopter or turbine blades, for example). The studies undertaken at SNIAS Aquitaine since 1972 have been oriented toward the testing in series of casings of ballistic engines in spun fibers. This paper presents the different stages and the results obtained. These studies permit us to favorably envisage the introduction of this technique into the testing of our products. Several conclusions are drawn as to this method.

Holographic interferometry is widely used at ONE RA for the detailed analysis of transonic flows, whose great sensitivity to perturbating effects of material probes is well known. The implementation of holographic techniques made it possible to build an interferometer presenting many advantages over the classical Mach-Zehnder instrument as regards the possible extent of the field, but also ease of use and cost of fabrication. Interferograms corresponding to the infinite fringe adjustment provide a visualization of the aerodynamic phenomena. But the quantitative study is prefe-rably carried out from interferograms presenting an initial finite fringe pattern, in order to multiply the measuring points. Processing, which makes use of an entirely automatic process, is ensured on photographic reproductions of the interferograms restituted by double exposure holograms. The negatives are explored by means of a high precision microdensitometer coupled with a data acquisition unit, comprising a minicomputer and a disc memory where the programme and intermediary data are stored. The computer ensures two functions 1 it pilots the displacements of the plate holder of the densitometer according to a preprogrammed path, and 2) it ensures the acquisition and processing of the densitometric data. The results are edited on a printer and on a tracing table. Thanks to this procedure, the processing time is considerably reduced the exploitation time of an interferogram along 25 lines comprising each 60 gas density measurements (i.e. 1500 measuring points) is less than 7 hours. The holographic bench and its acquisition unit are at present used for the systematic study of the shock wave-turbulent boundary layer interaction in tran-sonic flow at the SBA wind tunnel of the ONE RA Fluid Mechanics Laboratory of Chalais-Meudon (near Paris).

The bony structure of the human face is particularly exposed to the risk of fractures. Repair by conventional methods imposes a long and constraining immobilization of the patient. New methods, using holographic interferametry,are presently being developed in Strasbourg.

The use of a hologram in an interferometer in order to test an aspherical surface poses the problem of the choice between holograms with the carrier on the axis and holograms with inclined carrier. We compare the performances which we can expect from these two types of holograms in the case of an aspherical deformation of the 4th degree.

Heterodyne holographic interferometry is a combination of holographic infometry and opto-electronic fringe evaluation with the following outstanding properties (1,2): - fringe interpolation to better than 10^-3 of a fringe (+ 0.3° for the interference phase); - measurement with the same accuracy at any desired position in the image, therefore high spatial resolution (> 100x100 points); - independent of brightness variations across the image; - inherently direction sensitive, i.e. increase and decrease of interference phase can be distinguished; - computer readable output both for position and phase easily obtained (allows on-line data processing); - inherently less sensitive to speckle noise than fringe intensity measurements.

A speckle-pattern image method is used to determine the inclination with regard to viewing direction of a diffusing plane surface. We recorded on a photographic plate a defocused double exposure image, illuminating along the viewing direction with two neighbouring wave-lengths. In the experiments we have used, too, diffusing plane dihedrons illuminated in this way. Good agreement with the equation founded is observed.

The use of speckle pattern interferometry to detect vibration modes was reported by Archbold et al. [1], and by several others [2,3] to detect vibration amplitudes. TV detec-tion and electronic filtering have been added [4-6]to give a more flexible system: ESPI.

Holographic interferometry is a nondestructive testing technique with a growing number of industrial applications. Photosensitive plates used for coherent wavefront recording generally require processing time, and it seems of particular interest to have new reusable materials allowing in situ interferogram writing and erasure with a recording energy comparable with high resolution photographic plates. We report in this conference a particular application of highly sensitive photoconductive cubic crystals Bi12 Si020 (BSO) to double-exposure real-time interferometry.

The principal attraction of autoprocessor materials for holographic recording is their simplicity of use by comparison to classical silver emulsions; their major disadvantage resides in the great sensitivity of the latter, which is difficult to equal with other photosensitive materials. To types of material are examined: -Photopolymers, which take advantage of the change of refractive index caused by the polymerization induced by the absorption of light energy. Excellent diffraction efficiencies are obtained with satisfying sensitivity. We will present all their properties. -Organometallic materials in which the variation of index is the result of an intrinsic and reversible chemical amplification of a photoelectric phenomenon. These materials are being studied and have already shown perfect reversibility as well as a comfortable spectral sensitization.

The use of birefringent systems permits the recording, in a single exposure, of several different granularity figures. In two exposures, one with the image A, the other with the image B, we can obtain, in the focal plane of the recording plate of A and B exactly superposed, the profile of the interference fringes which would be given in fact by three exposures, made by alternating the images (A, B, A), with the respective exposure times 1/2, 1, 1/2. The signal/noise ratio is thus ten times greater than that which is given in the case of two poses in the absence of birefringent crystal.

The speckles of the image plane of an object are radially shifted and decorrelated when the object is axially translated . It will be shown that the radial shift of the corresponding speckles is removed when the pupil of the optical system is placed in the back focal plane of the imaging lens . A photographic plate twice exposed to the irradiance of image plane and laterally shifted between the exposures , exhibits , after processing , a system of Young's fringes in its Fourier plane . The contrast of these fringes , which represents the correlation degree of the recorded speckle patterns , is only a function of the relative value of the axial shift of the object in camparison with the depth of focus of the imaging lens . If the pupil of the optical system is placed in the plane of the imaging lens , the contrast of the fringes generated in the same way as above , depends on the maximum value of the radial shift suffered by the speckles with respect to their mean size in image plane .

The principe of the diffracting gauge is based on the farfield diffraction spectrum of a slit. In extensometry this gauge permits to measure easely and cheaply strain components with great sensibility and fidelity in time.

Speckle photography is a simple technique for measuring displacement in the plane of a surface, so allowing the strain field to be evaluated in two dimensions. A direct experimental comparison of speckle photography with photoelasticity and with finite element analysis on a notched tensile test specimen showed that serious errors could, however, occur due to local surface tilting and to aberrations of the imaging lens. Methods of minimising these effects and those of the speckle decorrelation that can also take place, are discussed.

We present an experiment based on speckle photography, to study the distribution of velocities in a fluid at a given instant. This technique is complementary to laser velocimetry (UDV), in which the velocity is measured at a certain point of the fluid, as function of time. A section of the fluid is lit by a laser beam widened in one direction by a cylindrical lens and an image of this section is formed on a photographic plate. When polystyrene balls are added to the fluid, the image of the section lit is speckled. The laser beam is modulated so that the section of the fluid being studied is lit by two short pulses separated by a known interval of time. The photographic plate thus records two speckles displaced from each other; this displacement is variable in the plane of the photographic plate, because of the distribution of velocities in the lighted plane. An analysis of this photographic plate permits us to construct the map of velocities of the illuminated section of the fluid.

The connecting rod, which transmits the forces due to the pressure of the gas from the piston to the crankshaft, is also subjected to great traction forces due to the inertia of the piston. Deformations caused by these forces should not be too great, in particular not in the zone of contact with the crankshaft; the lubricant layer must remain continuous to avoid excessive wear. Such deformations are created, using static simulations of the traction forces, and were measured by using double exposure speckle photography.

We study the diffraction spectrum of a population of circular objects randomly distributed. We present a rigorous study of the deconvolution of the intensity of a diffracted spectrum, permitting us to obtain the complete histogram of the distribution of sizes. (The method is applied notably to multi-modal histo-grams). The granularity term corresponding to the random positionings of diffracting objects was studied by means of a statistical model based on the independence of the positionings of the objects. We find that the size of the speckle wo is proportional to the inverse of the width of the object field studied. In the field of frequencies greater than wo we find the conventional properties of the speckle, which permits us to verify the approximations made in the complete expression of the spectral intensity recorded.

The goal of this experiment is to demonstrate local differences in surface state on a diffusing object by double speckle photography. We record on a single holographic plate two images of the diffusing object lit with coherent light; between the two exposures we slightly modify the angle of incidence of the light beam. We then use the interference fringes produced in the Fourier plane of this double photograph; their visibility characterizes the correlation between the two speckle figures, related to the local surface state. By an appropriate filtering setup it is then possible to visually localize on the image zones of different rugosity.

A method is proposed to use the speckles created in front of a curved surface to approach the slope contours of this surface. By focusing the camera on a plane in front of the surface and photographing the speckles contained in this plane before and after changing of the laser light wavelength , a speckle interferogram is obtained. Various methods of analysing speckle photographs are presented to obtain some informations related to the form of the objects. Two methods use the diffraction properties of the speckle patterns in coherent optics. A third method of viewing speckle photographs is to use a small light source which may have a limitated spatial coherence and is often polychromatic. A fourth method is suggested to observe in real time the contour lines of the object.

The sandwich speckle technique described in the paper permits to cancel the influence of uniform displacements field due to the deformation of the supports of the loaded model. On the other hand it is possible to follow the evolution in time of deformation by a step by step recording.

Moire-holograms contain a parallel-line grating recorded during the exposure process of the model grid under three-dimensional deformation. Utilizing the diffraction of a white light beam striking the holoplate, frozen moire patterns can be observed, under proper angles, directly by reflection. With a Fourier transform optical system, the reconstruction is achieved by means of a white source, filtering one among the chromatic wavefronts at the first diffracted order. If the wavefronts of two complementary colors are allowed to pass through the filter, direct derivatives of displacement fringes will appear on the planes where the images are slightly shifted, before or after overlapping. By a grounded glass the image plane is determined where the differentiation fringes exibit the neatest pattern, which may be recorded on a photographic film.

An assessment of the residual stress pattern around a butt-weld has been made using a hole-drilling technique along with a sensitive moire fringe method. The method of applying the specimen grid is described, and also the procedures for extracting stress data from the moire fringe patterns. This technique may be useful in situations where the residual stress varies rapidly, or where it is inconvenient to apply numbers of strain gauges.

Some elements of comparison are given between the projection-type Moire topography and photogrammetry. The basic mathematics of photogrammetry is applied to reconstruct the 3.D. Shape of the object from the Moire pattern. Some particular aspects of the Moire method are discussed and a general methodology is proposed. In connection with this, an opto-electro nic technique is described, which measures the Moire phase with high resolution and sign determination. The experimental results show that this technique is especially suitable for high accuracy automatic reconstruction of 3.D. Shapes.

The paper deals with the problem of dimensional testing of the limiting surfaces of objects having comparatively large frontal dimensions and transversal dimensions in the same order of magnitude.The solution is sought by an extension and generalization of the projection moire technique. A geometry is considered where two sets of curves are obtained by projecting a grid from a point light source over a master and test object respectively,while an optical system having central point at finite distance records them. The conditions are antyzed under which the moire fringes produced by the superposition of the two sets are the contours of the differences between the objects.

The analysis of shadow casting by fine grids is extended to include the effects of diffraction. The transfer function of an incoherently illuminated 'pupil' grid is derived and shown to equal the autocorrelation of a modified pupil. Achromatic image casting properties having no geometric analogue are predicted and their application to a displacement transducer is described.

We studied an optical method of diffuse wave interferometry based on a random moire principle, permitting, in real time, the measurement of very small displacements or vibrations under experimental conditions which are unusual by reason of their weakly constrain-ing character. In fact, - the field of application is that of objects with unpolished surfaces, observed perpendicularly to this surface, for displacement vectors situated in the plane of this surface; - the setup demands only ordinary precision ; it is composed of a lighting system with two coherent (laser) waves and a low-resolution imagery system followed by a detector ; - the mode of operation consists in the detection of variations of lighting in a laser image granularity spot ; under certain conditions, these variations are propor-tional to the displacement of the point corresponding to the object ; - the performances : the sensitivity is interferometric ; the theoretical limit is on the order of 0.1Å√Hz standard experimental conditions. Values close to this limit have been attained experimentally. The precision of the measurements is on the order of 1%.

Holographic transposition of ultrasonic waves into light waves can be exploited not only qualitatively, as a technique for non-destructive testing of opaque materials, but also quantitatively. In fact, as a method of visualization, acoustical holography translates the variations of acoustical transparence of the object inspected into the form of variations of lighting. Generally, the non-linearities of this process limit the accessible information solely to the contour of the variations in transparence as well as their localization, which leads to a simple dimensional metrology. It is nonetheless possible to exploit the conservation of the phase to effect, by means of optical techniques, measurements on the parameters characterizing the inhomogeneous zones of a material. The conditions of linearity of the transfer of the information by holography are examined in the case of the surface relief method and some examples of the optical treatment of the acoustical information are presented.

For the investigation of the dynamics of tiny, fast moving cavitation bubbles we devel-oped high speed holocinematographical recording techniques. In most experiments we used a multiply Q-switched ruby laser as illuminating light source. The maximum number of holograms which could be recorded in one sequence was limited to eight in this case. More recently, we examined the cavity-dumped argon ion laser for recording longer hologram series. The experimental devices operate in the range of 10 000 to 20 000 holograms per second with ruby laser illumination and at pulse rates up to two kilohertz with argon ion laser illumination. For separating successively recorded information we employed spatial multiplexing techniques in both cases. Reconstructed hologram series taken of acoustically produced cavitation bubbles demonstrate the performance of the experimental arrangements. From the recordings bubble motion can easily be evaluated.

The round table discussion, composed of two parts, had approximately sixty participants. The first part, to which the majority of time was devoted, dealt with non-silver materials presently under research and development or having recently appeared on the market. The second part was concerned with problems of choice, use and supply of silver emulsions. Due to the interest shown by the participants, the discussion of most of these products was primarily oriented around the use of sensitive surfaces in holography. Consequently certain materials, such as photochranes and europium oxide films, which have different uses, were in fact abandonned during the open discussion.

This paper describes the principles of holographic cinematography developed in NIKFI. The following ideas are underlying the principles of the holographic cinematography: 1) using lenses of large aperture, about 200 mm, for shooting and projection; 2) using a point-focusing multiplying holographic screen for projection; 3) using a holographic film with a thick emulsion layer of the order of 10 micrometres; 4) using two methods of shooting. In the first method a pulse coherent light is used for indoor shooting. In the second method a common non-coherent light is used for outdoor shooting. In the latter one a lenticular plate is put in the camera. A space colour image is stored on a colour film stock. This image is converted into a hologram film during printing.

The hologram technique initially proposed for application to a specific technical problem(1) in recent years has found increasingly wider use in the development of a new kind of art. The strange holographic pictures creating the full illusion of objects depicted are exhibited more and more frequently at the various exhibitions, museums, private collections and so on. The earliest idea of the possibility to utilize holography in this way was promoted in ref. (2) in connection with so-called holographic technique with recording in three-dimensional media. This idea was confirmed by the experiments carried out with the improved technology of Lippman colour photography (3-5).