The review paper will describe the present state of holographic and speckle techniques as applied to industrial measurement. The basic principles of both techniques will be outlined with special attention given to their advantages and limitations. Current developments in the field will then be described including the testing of rotating automobile tyres by holographic interferometry and a heterodyne technique to gain an insight into noise generation mechanism. Methods for real-time holographic and speckle recording to facilitate the use of the techniques in an industrial situation will be discussed.

For the evaluation of 3-D displacement and strain of non-plane objects by means of double exposure holographic interferometry, errors induced by defocussing of the object surface and distortion due to perspective have to be taken into account. The importance of these errors is discussed. Numerical methods for correction and experimental results are presented.

Using several hologram plates for measurement of 3D-displacement a problem arises that the object looks different from different directions, so that the fringes become difficult to identify. It will be shown that recording three or more interferograms on a single plate the components of displacement vector can be determined to a higher accuracy. A 3-D displacement measurement has been reported using technique of regulated path length interferometry resulting in three independent interferograms on a single plate.

In most cases experimental investigations in fracture mechanics using holographic interferometry demand a spatial resolution better than a fraction of the wavelength of light. High accuracy can be achieved by phase measurements rather than mere fringe counting. A variation of the phase is performed by heterodyne techniques using a frequency shift of the reference waves or by phase shifting of the reference waves during reconstruction. A method was proposed to determine the three dimensional deformation field of object surface points by solving three systems of equations, each one defined by the data of four phase shifted fringe patterns. By means of this method fringe pattern disturbances can be eliminated, an accurate determination of interference phases, even between fringe maxima, is performed, and the sign of the deformation vector can be achieved. Furthermore, this method is well suitable to be automated in the data generation, recording, and evaluation processes, respectively. These aspects will be discussed and for the first time results of an experimental application of this method in practice, containing all the necessary intermediate steps, are presented.

To increase the torque and power of an engine one needs to carry out form modifications and material distribution. This has been studied through different methods and especially holography. A study of the relative mouvements in the area of the helved throws of the multi-parts crankshaft, bearing on two supports in V and submitted to a deflecting force, was obtained by measuring point by point in the real image field of a double exposure hologram. The crankshaft being positioned in a cylinder-block equipped with one cylinder and one cylinder head, the gas pressure is simulated by an oil pressure slowly increasing. Real time holograms have been performed on three different cylinder-blocks and a 16 mm film (duration 10') shows how interference fringes appear in the virtual image when the oil pressure varies. This film has permitted to the motor me chanical engineer to remedy to the cylinder-block breakings during preseries.

Fringe modification is carried out so that the geometrical change is much greater than its effect on the fringe function. The equations denoting the optical path difference, the fringe vector and the fringe interspace are deduced, and then applied to determine strains and rotations on the surface of an opaque body.

The computer-based evaluation of holographic interferograms described in this paper allows a complete quantitative evaluation of the displacement field for: a) a single holographic interferogram b) holographic interferograms simultaneously taken from different points in order to compute three-dimensional displacements c) holographic interferograms reconstructed with a laser light different from that used to take the interferogram (e.g. pulsed holography with a Ruby laser reconstructed with a He-Ne laser)

With a well known holographic setup we can determine the three dimensional displacement vector with only one single holographic plate. The probe must be imaged by a lens onto the photoplate and holographically recorded with a plane reference wave. Using an unexpanded laser beam, we can reconstruct the interesting spots of the object whose displacement we want to determine. Due to the displacement we can see interference fringes on the real image. The shape of the fringes are tightly bound to the displacement of the spot that we are reconstructing. The direction and the curvature give us the three absolute coordinates of the displacement vector.

Holographic interferometry is a versatile technique for non-tactile measurement of changes in a wide variety of physical variables such as temperature, strain, position etc. It has a great potential for becoming an important metrologic technique in industrial applications. For holographic interferometry to become more attractive for industrial practice the problem of quantitative analysis of the patterns and thereby eliciting reliable values of the relevant parameters has to be addressed. In an attempt to calibrate the technique of holographic interferometry and ascertain the reliability of the subsequent digital analysis, we have chosen precisely known translations as a basis. Holographic interferograms taken from these are analysed manually and by digital techniques specially developed for such patterns. The results are promising enough to indicate the feasibility of automated digital analysis for determining translations within an acceptable accuracy. Some details of the evaluation techniques, along with a brief discussion of the preliminary results are presented.

In an attempt to approach the theoretical limits of performance, modern telescope design places higher and higher demands on the quality of the components. Digital image processing is playing an increasingly important role in at least two distinct aspects of this endeavor. On the one hand analysis of patterns from optical quality control tests e.g. interferometry, Shack-Hartmann etc., is being made more quantitative through the digital analysis. Furthermore, active-optics, to correct for some of the more important defects in the optics and telescope maintenance, is envisaged to become an integral part of the new telescopes. Digital image processing is an essential ingredient of the active-optics approach of ESO's New Technology Telescope (NTT). If its full potential is realised it would considerably relax the otherwise most stringent requirements on optical quality and the telescope maintenance infra-structure. There is thus substantial impetus given to the development of digital techniques to meet these goals. Here we shall discuss the development of digital techniques for the analysis of interferograms originating from interferometric tests conducted to check the quality of optical components. Light passing through the component is made to interfere with a coherent reference beam. The resulting interferogram is digitally analysed to yield the fringe positions and order. To this data a fit of pseudo-Zernike polynomials is made to quantitatively evaluate the various optical aberrations.

This paper describes a brief summary of applications of holographic interferometry to practical vibration study in Nagasaki Technical Institute of MHI. The applications of vibration mode measurement are concerned with steam turbine blades, compressor impeller, internal combustion engine, car body and car brake disk. The techniques of holography contained herein are (1) the time average method giving contour fringes of vibration amplitude,(2)the phase modulation method providing information on the relative phases of vibration, and(3)the double pulse method that offers the possibility of visualizing the vibration pattern of internal combustion engine in operating condition,and the transient vibration pattern of an object excited by impact force.

Since 1979, Ford Motor Company has been developing holographic interferometry to supplement more conventional test methods to measure vehicle component vibrations. An Apollo PHK-1 Double Pulse Holographic Laser System was employed to visualize a variety of complex vibration modes, primarily on current production and prototype powertrain components. Design improvements to reduce powertrain response to problem excitations have been deter-mined through pulsed laser holography, and have, in several cases, been put into production in Ford vehicles. Whole-field definition of vibration related deflections provide continuity of information missed by accelerometer/modal analysis techniaues. Certain opera-tional problems, common among pulsed ruby holographic lasers, have reauired ongoing hardware and electronics improvements to minimize system downtime. Real-time, time-averaged and stroboscopic C. W. laser holographic techniques are being developed at Ford to complement the double pulse capabilities and provide rapid identification of modal frequencies and nodal lines for analysis of powertrain structures. Methods for mounting and exciting powertrains to minimize rigid body motions are discussed. Work at Ford will continue toward development of C. W. holographic techniques to provide refined test methodology dedicated to noise and vibration diagnostics with particular emphasis on semi-automated methods for quantifying displacement and relative phase using high resolution digitized video and computers. Continued use of refined pulsed and CW laser holographic interferometry for the analysis of complex structure vibrations seems assured.

Time-averaged holography is used to display and discuss the basic natural vibrations of the crankcase of a commercial vehicle.

The double pulse holographic technique, by means of so-called holographic sampling, makes the analysis of high amplitude vibration out of the holographic measuring range possible. In this paper the principle of holographic sampling as well as calculations simulating the real situation to verify the principle will be shown.

Vibration modes of rotating objects generally show different vibration behaviour compared to modes of the stationary object. Several methods can be used for holographic vibration analysis of rotating objects: - Method with optimized holographic measuring arrangement - Method with optical image derotator - Method with laser triggering related to object location and phase of vibration - Method with holographic interferometer rotating synchronously to the object Optomechanical and optoelectronical devices developed to perform these methods as well as measurement results of vibration analysis on technical objects will be discussed.

A portable hologram interferometric system has been developed measuring 3-D displacement due to static/dynamic load in factory environment. The evaluation of interferograms is computer aided. The system is shown both statically and functionally. Two measurements (lathe bed deformation and vibration analysis of the arm of a radial drilling machine) are reported.

The development of holographic test methods has lead to a wide industrial application. Today serial tests of aircraft tyres with holography have become routine. A large chemical company is testing their plastic materials like tanks, wheels and fans with the method of holographic interferometry. In the power engine industry turbine blades are tested holographically to find an optimal shape and to test the vibration behaviour. The automotive industry is using holographic methods' for construction optimization. The economic application of these test methods was possible by using instant holography. The principle of a new hologramrecorder is presented. The application of this equipment is shown in examples of testing materials, optimizing constructions and vibration analysis.

Electrooptic and photoconductive Bismuth Silicon Oxyde (B.S.O.) crystals allows the recording of phase volume holograms through the photorefractive effect. We demonstrate applications to real time non destructive testing using holographic interferometry by double-exposure, time average and speckle technics. We also report in this paper, the possibility of using optical fibers for object and reference wavefronts generation. In fine, we show that it is possible to induce energy transfert between reference and object beams. Application to image amplification and mode pattern visualisation of 3-D diffuse object are demonstrated.

Within this report the practical uses of holography for more exact definition of the module of elasticity E for specific materials will be given. In conjunction with this theme a new holographic method "The Step Hologram" with which the measurement range of the holographic interferometry can be widered to approximatly factor 10...20 times will be discussed. The Step Hologram allows separation of the elastic-linear lines from elastic-non-linear lines respectively and from plastic deformation. As an application excample, the exact measurement of the E-module for a brittle material such as Porcelin will be given. This material has been specifically chosen for its elastic properties. Porcelin is a white plastic material which, like Gypsum presents practical usable results. Porcelin however unlike Gypsum is not so succeptable to breakage.

When holography is applied outside'the laboratory, some well known problems are experienced: vibrations, rigid body motion, stray daylight. Pulsed holography can overcome the difficulties with vibrations but the other problems are less easily solved. When the object area to be holographically tested is small, a very simple and convenient method may be employed, which was earlier described by Neumann and Penn8; they fixed the hologram holder rigidly on the object under test, thus avoiding rigid body motion of the object with respect to the hologram. In a similar configuration Denisyuk reflection holograms are made without any necessity of darkening the environment. The authors believe that the main reason that this technique is not widely used, is due to difficulties generally encountered in processing the Denisyuk hologram to good quality. A simple processing technique is described resulting in high quality reflection holograms which may be analysed by microscope up to interference fringe densities of about 30 fringes/mm. As examples the results of a projectile impact study and the study of early fatigue crack detection in a critical aeroplane structure will be presented.

The use of external osteosynthesis in the healing and the management of fractured bones is in rapid progression. The method employs an external rigid frame which is mounted to keep the fractured bones in state of immobilisation by means of percutaneous transfixing pins traversing the bones. In this paper, holographic interferometry is used to investigate the mechanical behaviour of the ball-joint - a central element in the fixation frame - sub-jected to realistic loads. Besides, the work has permitted to compare several models of this piece (of comparable handiness) as to their characteristics of rigidity and of resistance to slipping.

The movement of animal articulation depends on the drive of the muscle. It sustains changeable load. It proceeds movement of the rule of unsingle movement. It has the action of rolling motion and sliding motion itself and the ability of self growth. Many articulation performs complicated movement. The animal articulation is different remarkably from the moving pair of ordinary engineering. Therefore it is necessary to make special investigation.

The objective of this work is to find a new mean for macro and micro assessment of flat surface. The holography technique is used to get three dimensional measurement of flat surface under consideration. The holographic contour generation using two reference waves is applied. From the hologram mathematical model for the suggested assessment is established. Seven flat specimens with different machining conditions were prepared for the application of the proposed technique. The assessment parameters that are established to distinguish between the various surfaces are:- 1. The coefficient of correlation of the surface points fitted to a flat surface. 2. The mean deviation of the perpendicular distance between surface points and least square plane. 3. The true bearing area diagram (not the bearing length diagram). 4. The ratio between the volume surface topography above the reference plane and the area of the surface.

This paper is concerned with an automatic method designed to produce a series of holographic interferograms that contain the history of surface displacements of a material undergoing a deformation process. The purpose of automatic control of the hologram formation stage, is to insure that every interferogram displays similar fringe patterns, which can then be analyzed by another automatic setup for fringe counting based on digital processing of the holographic images. The formation parameters are supervised by a microcomputer that effects a decision of the exposure time. With this approach, it is possible to follow a dynamic phenomena and to produce measurements of statistical significance which, when expressed in terms of distributions, can help characterize the response behaviour of complex structured materials.

Paper reports a successful application of holographic interferometry to the shock wave research. Four topics are discussed; i) transonic flow over an aerofoil, ii) shock wave propagation and diffraction past a circular cross-sectional 90° bend and two-dimensional straight or curved wedges, iii) stability of converging cylindrical shock waves and iv) propagation and focusing of underwater shock waves. Experiments were conducted on shock tubes equipped with a double exposure holographic interferometer. In each case isopycnics around shock waves were determined and three-dimensional shock wave interactions were also observed. Results are not only bringing forth new interesting findings to the shock wave research but also showing a further potentiality of holographic interferometry to the high speed gasdynamic study.

Subpicosecond pulses have been synthetized with a dye laser. The 8000 GHz broadband source corresponds to a temporal resolution of ▵t = 1/▵ν = 0,12 ps. The holographic recording set-up proposed by N. Abramson has been used to visualize the light in flight, but the wavelength dependence of the hologram introduces a disper sion in the reconstructed image. Compensation techniques have been applied and an other recording system has been developed. Experimental results of the reconstructed holographic wavefront are presented. The interesting possibility to obtain a reconstruction in white light is compared with the coherent case. The signal-to-noise ratio of the image is discussed.

The theoretical properties of diffraction gratings formed by ultrafine grained silver particles are studied. The effectivity index of gratings is introduced and the dependence of diffraction efficiency on grain size, polydispersity, grating thickness and modulation damping in thickness is described. Some of our theoretical results have been verified on laboratory-prepared photographic emulsions, developed in a special semi-physical developer. Finally, the influence of some technological factors is treated and analysed.

The technique of image derotation allows a variety of measurements to be made on rotating components by optically compensating for their rotational motion. A description is given of a novel technique required to achieve the high level of alignment accuracy necessary for the successful implementation of holographic interferometry and laser doppler velocimentry in conjunction with the image derotator. Several recent industrial applications in the gas turbine and automobile industries are described.

A simple inexpensive, wide field schlieren system has been developed to visualise the fluid flow patterns around heated components. The system has variable sensitivity, ranging from a high sensitivity to visualise small heat flows around the human body to a low sensitivity to visualise the large heat flows around a bunsen flume. The variable sensitivity is achieved by adjusting the distances between the optics. The wide field of view is obtained by using a novel flexible membrane mirror, providing a two foot diameter collimated light beam for inspecting the disturbed fluids.

A simple and straightforward way to make projection Moire topograms is described. A grating pattern is projected on the object, which is imaged by an interline transfer (ILT) charge coupled device (CCD) television camera. High contrast Moire fringes that can be equal to topographical contours are then obtained. Experiments showing examples of this technique are presented and discussed.

The method presented in the paper permits a global observation of the contours of any diffusing object, in real time, with both a varying sensitivity able to reach 10 μm or even less, and a possible choice of the orientation of the reference plane in the same measurement. It is related to multiplicative moire methods but does not need the use of a filtering grid, nor the preliminary registration of a phase or amplitude image, but involves only interference phenomena, due to a particular use of Sagnac interferometer. Because the interchangeability of analysed objects may be carried out without any delay, and contouring of larger objects by scanning is very easy, this method is well adapted to routine controls of the topology of any small diffusing surfaces, for example rake faces of cemented carbide tool inserts. Theoretical explanations, experimental results and also theoretical and practical performances and limitations of the method are presented in this paper, so that its field of application is well determined.

The development of Electronic Speckle Pattern Interferometry (ESPI) for the analysis of in-plane strain measurement on rotating structures has been proceeding at The City University. ESPI is a technique which not only possesses the accuracy of holographic interferometry but with the ease of electronic processing of television pictures avoids the delays involved in normal photographic techniques. Using a pulsed laser to overcome the rigorous stability requirements of conventional holography gives this method the potential of an experimental technique which may be used under service environmental conditions, with little or no shut-down of costly production-line plant. The experimental results achieved so far show reasonable fringe contrast for in-plane displacements over a wide range of tangential velocities up to nearly 5 ms^-1. Both rotational speed dependent strains and strains independent of speed have been measured in the laboratory with repeatability.

When assessing the ultimate load of statically undetermined reinforced concrete beams, an exact knowledge of the bond mechanism and the rotation capability of the plastic hinges is of great importance. The size of these plastic areas is determined conclusively from the efficiency of bond between concrete and reinforcement. Experiments were carried out at the Institut air Massivbau, Hannover University, in order to measure the bond strenght and the extension of the plastic areas on models of reinforced concrete constructions. Laser-Speckle Photography was used for these investigations. The experimental devices, peculiarities affecting the application of the procedure to reinforced concrete constructions, like optical characteristics of the concrete, fracture development etc., and the results of the test series are reported on.

This paper explains the specific advantages and disadvantages of interferometric measuring and testing techniques using the example of holographic interferometry. Applications from commercial vehicle construction and mechanical engineering are given for the most important fields in which holographic measuring techniques are used. Particular attention is thereby paid to considering the techniques from the point of view of the industrial user: to their availability outside special laboratories, to their reliability in day-to-day industrial use and to their economy. The present state of the art and the expected developments in the field of automatic evaluation are also discussed.

Holographic interferometry in contradiction with conventional interferometry can work with diffusely reflecting objects as well. However, this great advantage is restricted only to the comparison of the states of the same object. The states of two diffuse objects can not be studied by purely optical methods because of their different surface microstructure. To do this, first one has to evaluate their interferograms separately and then compare the evaluated data themselves.

This report provides a brief summary of works concerning the applications of optical holography in automative industry carried out in Central Laboratory of Optics in Warsaw, during the last ten years period. These works cover applications of holographic interferometry for nondestructive testing of engine valves, holographic investigations of pneumatic tires, double-pulse interferometry of driving gear, and holographic registration of oil mist. Holography is widelly used in different areas of modern technique [1-4] and its applications in automative industry are well known [5-7] . Those investigations have a great influence on safety aspects of automative systems, so, it is clear that currently they arouse a great interest. As a result, some investigations in this area have been stazoted out in Poland. Partially, these investigations have been carried on in Central Laboratory of Optics in cooperation with different research laboratories. Some results, obtained during last ten years period are presented in this report.

The profile of an optical surface can be measured to nanometre accuracy by integrating slope values obtained by laser autocollimation. An instrument based on this principle for measuring X-ray microscope mirror surfaces of conicoid shape has been developed, and its application to monitoring precision lapping is described. A second system for the measurement of optical flats is also under development.

A coherent optical method to measure the surface characteristics of rolling material e.g. paper on line without mechanical contact in industrial enviroument is presented. This method is based on the optical heterodyne detection of light scattered into a single radiation mode by the rough surface. The detection is followed by an appropriate signal processing that makes characterization of the surface smoothness by parameters called "correlation lengths" indicating the average size of uniform surface elements. These parameters show good correlation with other, widely used static surface roughness measurement methods. Furthermore they gi're the possibility of deeper insight into the surface structure of different types of paper.

The fabrication of power transistors and thyristors involves the etching of deep grooves (30-100μm) into the Si wafers. These grooves separate electrically the individual devices from one another, and they are the site where the high collector field meets the surface and where the passivating glass and oxide layers have to be applied. Therefore, the groove depth has to be monitored and controlled in manufacturing to ∓5%. Since the dimensions are large compared to the wavelength of light, and since the surfaces can be rough (etch pits) the usual interference techniques can not be used. The light section microscope technique, used up to now, is slow, inaccurate and operator dependent. We describe an optical profilometer essentially consisting of a high-power microscope equipped with a laser attachment which automatically steers and holds the microscope focussed to the sample surface. The automatic focussing uses the beam of a He-Ne laser, which is coupled into the microscope by beam splitters and goes through the objective lens to form a fine spot (0.5)μm) on the sample surface. From there it is reflected back through the objective and projected into a focus outside the microscope. The position of this focus is a function of the sample surface height, and it is sensed by an arrangement of apertures and photodiodes, which drive a feedback servo-motor for microscope focussing. An electronic depth gauge (LVDT) resting on the shoulder of the microscope measures the vertical excursions of the microscope, which follow the sample contour. This instrument is fast, accurate (+ lμm) with a range of well over 100 humand can be connected directly to a data terminal.

A novel method is presented for the measurement of optical fibers with diameters of 10-120 μm. The method is based on the detection of resonances in the intensity of dye laser light backscattered from a fiber in the far-field when tuning the wavelength. It has been experimentally confirmed that not only a thick (-120 μm) communication fiber produces Fabry--Perot resonances, but a thin (-13 μm) doubly-clad imaging fiber as well. The obtained accuracy is better than ± 0,1 μm. Also, the basic features of the WIRE GAUGE instrument based on laser beam scanning are shortly outlined.

A number of publications concerning conventional Laser Doppler Velocimetry and showing their rich range of applications have appeared in the last decade. For various situations this technique turned out to be very difficult or not applicable. Looking for other techniques the Laser Two Focus Method has extended the situations where laser velocimetry can be applied to. Due to recent progress in this technology the range of applications continues to broaden. Some ideas of the progress of the last years is given by presenting the hardware techniques of today's instruments and by presenting selected experiments.

Gas flow speed along the combustion chamber longitudinal axis of a suddenly propagating flame into a quiescent propane-air premixed combustible gas charged inside an open combustion chamber, and ignited by the usual capacitor discharge ignitor, under the initial conditions of room temperature and atmospheric pressure, was investigated by using a one component laser Doppler velocimetry ( LDV ) equipped with a 15 mW He-Ne gas laser and a 40 MHz Bragg cell based frequency shifter and a frequency tracker of maximum dynamic slew rate of 10 MHz/msec. The measured velocity profile of pre- and post-combustion period are demonstrated with a flame front propagating shapes visualized by high speed schlieren photography. Their results show reasonable agreement if the refraction effect due to a flame front is fully considered. The flame front just approaching and passing through the LDV measuring volume has the role or effect of a suddenly moving concave lens in the optical path of the LDV system.

Electronic Speckle Pattern Interferometry - ESPI - may be described as dynamical hologram interferometry based on video recording, processing and presentation. The technique has been used to solve various problems in Norwegian industry and industrially related research. Work has been mainly concentrated on vibration testing and measurement, but recent measurements on crack opening and locations of high strains have also attracted interest.

Two laser-based techniques, Optoacoustic Laserbeam Deflection (OLD) and Frequency Modu-lation (FM) spectroscopy, were introduced for flame diagnostics. Flame temperature was measured by OLD with 1.5% precision and flame temperature profiles were taken. Ground state and excited state sodium within an aspirated flame were detected by FM-spectroscopy. Present limits of sensitivity are absorptions of 1.5 . 10^-4 and ground state sodium densi-ties of 3.3 • 10⁶ cm ^-3.

Some nondestructive techniques for measuring the refractive index of a lens have been reported. The salient feature of this innovative approach is to avoid the use of two miscible liquids as commonly used in the liquid immersion method. Wavefront shearing inteferometry and the coherent speckling phenomenon have been applied for determining the focal length of the test lens immersed in different types of liquids. The reported method is quick to perform and adequate for producing good accuracy as compared with existing techniques. Our intentions and the main objectives of our efforts are to point out that the present approach is economic as well as less time-consuming, especially when the type of glass in a lens is to be identified. The preparation and the selection of the required liquids for the miscible liquid immersion technique is a time-consuming process and moreover, it needs a large number of trials to achieve the desired results. In contrast to this, the proposed method does not need two miscible liquids. A mathematical equation has been derived for calculating the lens' index which depends upon the focal lengths of the lens in different liquids and their refractive indices. It has also been deduced that the plano-convex lens and a thin lens behave in the same way and produce identical results. For N liquids there will be N(N-1)/2 ways of calculating the lens' index. Henceforth, the present technique will be termed the nondestructive nonmiscible liquid immersion technique.

An apparatus for rapid particle size analysis has been developed, utilising the phenomenon of electric birefringence. A principle use is in analysing polydisperse colloid suspensions, where for a monomodal distribution, a complete size distribution plot is generated. This method can produce data in terms of an equivalent spherical diameter, but a unique feature is that if the particle shape is known then the results obtained give data on the true major dimension of the particles in the medium.

A new method is suggested for analysing the dynamics of fast-moving objects. The basic differences, compared with the optical rangefinders and radar equipment available, are the continuous measurement of the distance and the possibility of measuring the alteration in distance and of measuring the velocity and acceleration of the object continuously and simultaneously. The above mentioned characteristics are attained using the well-known time of flight method with an exceptionally high pulse repetition rate and with a new type of an analog time to amplitude converter (TAC). The velocity and acceleration voltages are formed by derivation from the continuous distance voltage in respect of time. Preliminary results with a simple prototype have proven the method to be highly usable in many applications, e.g. in sports training and printing technology.

This paper is described a high precise lens-centring apparatus for use with the altitude variation interferometric theory. It also analysed some basic principles for the centring accuracy. The possibility with higher cement-centring accuracy was proved in theory and obtained in practice. And the centring problem for high accuracy in manufacture and assembly of medium and large aperture was solved well.

Opto-mechanical and electronic criteria are analyzed in relation to the design of super-stable resonators and laser heads used in industrial environment. Examples of faulty design due to engineering shortcuts are demonstrated and results of such defects are presented. Influence of industrial environment on applications of lasers is studied and proper choice of support equipment such as power supplies and coolers is recommended. Comparison of most widely used power conditioning circuits and cooling methods is presented.

Lenticular arrays with near diffraction-limited performance have been generated by laser beam writing. A photoresist film is exposed in a line raster mode by scanning under an intensity-modulated focused laser beam; subsequent development of the resist film produces the desired lenticular relief profile. The writing of exposure patterns by raster scanning is analyzed, and it is shown that very precise positioning of each raster line is required to avoid unwanted modulation terms. A low cost xy positioning table with better than 20 nm dynamic positioning accuracy was constructed to satisfy this requirement, and has been used to generate high quality fine lenticular arrays with lenslets of widths down to 20 μm and relief depths up to about 4 μm.

Beside the principle setup of cutting equipment the "Riefen" structure itself as well as the specific cut-pattern obtained for metallics are discussed. A practically useful formula for nonmetallics is given. Possible instant lens destruction is cited and an explanation tried to be given.

The paper reports a systematic microscopic analysis of metallic surface defects which are in a position to determine the breakdown threshold of a gas in close vicinity of a target surface. Metallic and nonmetallic defects with a vaporization threshold lower than that of an ideal flat metal surface were evidenced which are able to cause the lowering of the gas breakdown threshold in the neighbourhood of the metallic target.

The different methods of laser drilling of cooling holes in jet engine parts are presented. The successful use of this technology in production is shown by the example of a realized machining center.

A CO2 waveguide laser in a monolithic RF excited structure has been built at S.A.T. Besides its ruggedness and simplified design this new structure warrants : - A longer lifetime for the sealed off laser without electrodes in the plasma. The laser head is fed through a light, coaxial cable and looks like a big pencil (length = 200 mm, diameter = 25 mm, weight = 200g) This uncooled low power version emits 1 to 4 W in a 30 s run. Two civilian applications have been investigated : - Medical aalicatiOn : The odontological CO, laser (in collaboration with PR J. MELCER from Paris V University). This light laser head is especially suitable for the dental surgeon working with the laser in hand : - On the decayed areas the laser beam sterilizes and hardens the dentinary surface. - On the mucous membrane the laser beam burns outgrowths. - Industrial a22lication : Splicing of optical fibers (in collaboration with the CABLOPTIC company). Due to the high absorption of silica around 10 μm, CO₂ laser light turns to be a very promising, non-contact fusing agent for optical fibers : CO₂ laser splicing technique allows improved control of localization as well as concentrati6n of energy on the area to be fused. This method limits the ionic (OH-) pollution thus improwing mechanical resistance.

Based on the photolithography process generally used to generate high resolution masks for semiconductor I.C.S, we found a very useful industrial application of laser technology.First, we have generated high resolution metrology targets which are used in industrial measurement laser interferometers as difra.ction gratings. Secondi we have generated these targets using step and repeat machine, with He-Ne laser interferometer controlled state, as a pattern generator, due to suitable computer programming.Actually, high resolution metrology target, means two chromium plates, one of which is called the" rule" the other one the "vernier". In Fig.1 we have the configuration of the rule and the vernier. The rule has a succesion of 3 μM lines generated as a difraction grating on a 4 x 4 inch chromium blank. The vernier has several exposed fields( areas) having 3 - 15 μm lines, fields placed on very precise position on the chromium blank surface. High degree of uniformity, tight CD tolerances, low defect density required by the targets, creates specialised problems during processing. Details of the processing, together with experimental results will be presented. Before we start to enter into process details, we have to point out that the dimensional requirements of the reticle target, are quite similar or perhaps more strict than LSI master casks. These requirements presented in Fig.2.

From movies showing the laser cutting process in acrylic glass, it points out that the erosion takes place at a nearly vertical plane at the momentary end of the cut. That plane is covered by a thin molten layer, that is heated by absorbed laser radiation and by reaction. The removal of material from that layer is carried out by evaporation and by ejection of molten material due to the friction between the melt and the reactive gas flow. A computer simulation of that model yields a more detailed understanding of laser cutting and agrees well with experimental investigations.

This paper covers laser thermal treatment application to large gears (e.g. in the oil pimping unit reductor) Gear irradiation methods and thermal treatment features are presented. Hardness in the range of (700/800) HVosi and thickness up to 0.7 mm were obtained. We believe the laser treatment of such gears to provide technical and economic benefits over other methods.

Oxidation of copper targets under the actkn of cm CO₂ laser radiation was studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and selected area diffraction (SAD), in conjunction with absorptivity determinations of the metallic samples before and after laser irradiation. A particular attention was paid to characterizing the different stages of the oxidation process.

Until recently, tree logging slash, which must be virtually completely removed by burn-ing to allow for regeneration growth, has been ingited by conventional techniques employing man-held drip torches, electrically-controlled igniters, or 'incendiary' matches dropped from helicopters. Whilst satisfactory in many respects, these methods suffer with regard to cost, accessibility and, in particular, safety. Lives have been endangered and indeed lost during several decades of regeneration burning. The instrument described in this paper permits the safe ignition of logging slash at distances varying between about 100 metres and 1.5 kilometres. It employs a CO₂ laser, beam expander, and Cassegrain telescope to produce a hot spot of the appropriate size and energy density at the required distance. Focussing is achieved by adjustment of the beam-expanding optics. The instrument is fully steerable.

Annealing of preheated Si-samples by Nd:YAG laser is described. A Nd:YAG laser device with and without acousto-optical Q-switching for trimming, scribing, marking, drilling and medical purposes was used. The development of a portable LiNdLa-phosphate glass laser resulting in 6 % efficiency, Q-switched by LiF with F₂color centers is discussed together with some of its applications.

The paper reports on a numerical analysis of the thermal phenomena during cw CO₂ laser annealing of implanted silicon. At the surface of the sample the nonlinear heat equation was solved together with diffusion equation for free-carriers density. The results are in a quite good agreement with the reported experimental results.