A variety of high precision optical measurement methods are presented and discussed. Noncontact optical methods are appropriate for micro- and macrostructure measurements. Time of flight and phase measuring techniques with a resolution in the order of a few mm to one mm respectively are covered. Furthermore active and passive triangulation techniques are very robust and appropriate for different applications in precision measurements. Moire techniques or projected fringe techniques are useful tools for topography measurements. Furthermore image plane locating systems can be applied to analyze the surface topometry. Recently confocal principles were studied to be applied for the measurement of the surface geometry and microstructure. Today, laser interferometry is probably one of the most commonly used techniques for very high resolution measurements in metrology. Interferometry and Moire techniques as well as image plane locating systems will be applied more frequently, when used with image processing. They are becoming useful tools for precision measurements in research and for industrial applications. Computer analysis is increasingly important for fringe analysis. The use of solid-state detector arrays, image memory boards together with microprocessors and computers for the extraction of the information from the interferograms and high-resolution graphic boards find important application in optical metrology.

Raufoss AS designs and produces air brake fittings for trucks and buses on the international market. One of the critical components in the fittings is a small, circular metal ring, which is going through 100% dimension control. This article describes a low-price, high accuracy solution developed at SINTEF Instrumentation based on image metrology and a subpixel resolution algorithm. The measurement system consists of a PC-plugg-in transputer video board, a CCD camera, telecentric optics and a machine vision strobe. We describe the measurement technique in some detail, as well as the robust statistical techniques found to be essential in the real life environment.

Final disposal casks will be stored up to 60 years in an intermediate storage facility. Unauthorized access to the radioactive content has to be detected. For this reason a short weld seam acting as a seal is applied between the cask body and the lid. The seal has to be examined using unique and reproducible features characterizing the weld seams even under the influence of aging. Relief inspection is investigated for this task. Received images are segmented into slices corresponding to different altitude levels. Every slice shows a number of objects, which are analyzed by morphometrical and contour features. The identification algorithm is basically a supervised minimum distance classifier. The initial references are learned automatically by the system when a cask is introduced into the storage. References will be updated every time a cask is inspected.

This paper presents an imaging spectrometer principle based on a novel prism-grating-prism (PGP) element as the dispersive component and advanced camera solutions for on-line applications. The PGP element uses a volume type holographic plane transmission grating made of dichromated gelatin (DCG). Currently, spectrographs have been realized for the 400 - 1050 nm region but the applicable spectral region of the PGP is 380 - 1800 nm. Spectral resolution is typically between 1.5 and 5 nm. The on-axis optical configuration and simple rugged tubular optomechanical construction of the spectrograph provide a good image quality and resistance to harsh environmental conditions. Spectrograph optics are designed to be interfaced to any standard CCD camera. Special camera structures and operating modes can be used for applications requiring on-line data interpretation and process control.

In this paper we present a software tool by which the image processing and defect classification parts of an inspection system can more easily be designed and tested. The user interface of the tool has been programmed using Microsoft Visual Basic to which the C coded development software has been liked as Windows DLL-libraries. At the moment, a texture analysis method based on sum and difference histograms has been implemented as a basic segmentation method, but the addition of other algorithms is quite straight-forward. In addition to texture analysis, the tool includes a set of classification functions for automatic generation of nearest neighbor and decision tree classifiers. Starting from raw image data, generation of an executable decision tree classifier is possible without writing a line of code. The generation of the decision tree classifiers is based on IFD3, which is an extended version of Quinlan's ID3 algorithm. In this extended version, more advanced features of the induction of fuzzy and hybrid decision trees have been introduced.

Laser-induced breakdown spectroscopy (LIBS) is able to rapidly analyze the constituents of materials without contact under atmospheric conditions. Hence this method is predestined to applications where processes have to be controlled for various compounds. Current research activities aim to improve the limits of detection of LIBS for multi-element analysis. The influence of the laser pulse structure on the emission of the laser-induced plasma is investigated. Using certified reference samples, LIBS is calibrated to perform concentration measurements of elements in an iron matrix. An overview of recent LIBS applications is given.

Fringe projection methods have been widely discussed as a method of measuring surface form or topography. This paper discusses the factors which limit the accuracy of the technique and presents methods by which such a system can be calibrated.

A rugged interferometric fiber optic instrument for non-contact profiling of optically rough, machined metal surfaces has been developed, designed for use on the machine tool. The sensor is a robust and compact interferometric probe which scans focused light across the test surface. A laser diode source and photodetector communicate with the sensor through an optical fiber, and the output is demodulated with a phase-stepping algorithm, achieved by frequency modulating the source. Operation is demonstrated with face-milled steel surfaces, with steep local gradients and local variations in reflectivity of a factor of 100,000. The measured horizontal resolution is 1.5 micrometers , and the noise-limited vertical resolution 0.3 nm/(root)Hz. Two additional manufacturing applications are demonstrated: in-situ profiling of diamond-machined surfaces and score dies.

The aspect of manufactured objects gives rise to increasing attention in the industrial world. Because of the concurrence, aspect becomes an essential commercial criteria like technical performances or cost. To fulfill the necessary aspect control, industry tries to replace traditional visual control by systematic procedures and dedicated measurement apparatus. Our work deals with that domain of metrology. This paper describes a brightness measurement method working on rough surfaces with a skin profile (or waviness) from 50 to 500 micrometers deep. In such a case, the skin profile visibility is not due to height distribution of the surface and depth sensitivity of eye, but it is due to the amount of light that each point of the surface scatters toward the observer eye. Our eye discerns the skin profile through the contrast level of the image it catches. So the brightness (or the scattering properties) measurement of surfaces is essential for evaluating the aspect quality of product surfaces. Our method predicts the scattering properties of surfaces by the scattering theory developed by Beckmann and Spizzichino and from roughness measurement. Confocal microscopy is used for profiling surfaces within two different roughness ranges. The skin profile is measured with low magnification objectives and that data is used to compute the local slope of the surface. High magnification objectives allow us to measure microroughness superimposed on the local shape. After high pass filtering, the statistical roughness parameters are used to compute the reflection coefficient of the material from the Beckmann and Spizzichino model. Then the contrast of the image that an observer catches under any illumination and observation configurations is computed from the knowledge of both the skin profile and the brightness.

Three-dimensional imaging interferometric microscopes have outstanding accuracy, provided of course that the test objects are sufficiently smooth and continuous. The present study shows that a white-light source and spatial-frequency domain analysis of the resulting interferograms can dramatically increase the range of application of interferometric surface profilers. This analysis breaks the white light up into its constituent colors and makes it possible to apply multiple-wavelength techniques to the problem of surface height measurement.

An overview is presented of recent developments in the use of laser-generated ultrasound. Until the late 1980s, implementation of laser-ultrasound instruments in industry was impeded by a lack of detection sensitivity. Various optical detection schemes were investigated, including the Michelson interferometer, interferometers incorporating phase conjugation, techniques based on heterodyne holographic interferometry and lasers using two-wave mixing in photorefractive crystals. These detectors remain within research laboratories. The first interferometers to be developed for industrial applications have been those based on the confocal Fabry-Perot interferometer (CFPI). These are capable of analyzing the frequency shift of light imposed by ultrasound when light is back-scattered from a rough surface. A description of their properties is presented, showing how their frequency response to ultrasound may be modified. Typical signals recorded for thickness measurement or for defect imaging are presented, together with ultrasonic images acquired of defects in materials such as carbon fiber composite. They have now demonstrated their relevance to industrial applications, the challenge for the future being to reduce their overall costs.

An elegant measuring setup for contouring strong aspherical surfaces is introduced. Moire deflectometry is chosen as the measuring method because the configuration is simple, robust, and variable in sensitivity. The instrument is capable of measuring height deviations between an aspherical surface and its best fitting sphere ranging from minimally 1 micrometers to maximally 30 micrometers with a relative accuracy of 10%, which is useful for the production of surfaces in infrared optics. It is possible to measure transparent as well as reflecting surfaces, both convex and concave. A CCD-camera and a PC make part of the setup to automate the measurements. The short measurement time of less than 60 seconds makes the instrument useful in the manual production of aspherical surfaces.

An interferometer based on a single multi-functional holographic optical element (HOE) is presented. The interferometer is meant for flatness testing of quite large objects, not necessarily optically polished. Other features include two beam common-path arrangement, desensitization as compared to the classical (lambda) /2) figure, white-light illumination. Emphasis is then laid on automatic fringe pattern interpretation which makes use of an ad hoc phase-shifting procedure. Results obtained with computer disks are shown.

Modern phase-shifting interferometers grew out of a traditional need for high-precision evaluation of polished optical components. The technology is very mature now, enough so that it is reasonable to look for other applications of these instruments. Some important industrial applications have been found, particularly in the data storage industry. However, there are still many applications where the speed and high accuracy of phase-shifting interferometry would be very desirable, but the surface-finish requirements to generate visible-wavelength interference fringes are impractical. One way to increase the range of surface finishes compatible with interferometric analysis is to increase the source wavelength. Improvements in the reliability and affordability of 1.55-micrometers wavelength distributed-feedback laser diodes has opened up a new wavelength region for interferometric metrology. The 2.5X increase in wavelength when compared to HeNe-based interferometers is sufficient to a variety of important parts ordinarily considered too rough or distorted for visible-wavelength interferometry.

The paper describes a simple to use and inexpensive lateral shearing interferometer for checking the symmetry of optically accurate stretchable plastic concave membrane mirrors. The same interferometer can be used for checking the optical flatness of tensional flat membranes, before they are stretched by air pressure difference into concave mirrors. The interferometer is also capable of examining a very wide range of mirror sizes and curvatures. The interferometer reveals by fringe distortion all the blemishes of the metallized mirror finish membranes. The smallest crease marks, invisible to the eye, now become visible. Dust particles can become trapped between the underside of the membrane circumference and the rim top of the membrane support frame. The particles are seen to greatly affect the fringes locally, but have no affect on the rest of the mirror. Slow changing fringes usually indicate leaks of air into the chamber behind the membrane, causing mirror curvature change; or they can indicate membrane creep. Membrane damping can be examined by shouting at the mirror from close range and noting the time for the fringes to resume their stationary positions. The same interferometer also makes a nice flow visualizer, a truly remarkable and well respected instrument.

We describe an optical noncontact microtopographer based on an active, discrete triangulation procedure, showing that this kind of triangulation based surface inspection system can be applied not only to large distance range sensing but also to smaller samples or smoother surfaces with resolutions that can be driven down to the sub-micron range. In our system the topographic information is obtained from the horizontal shift incurred by the bright spot created by an oblique collimated light beam on a surface when it is displaced vertically. A laser beam is focused onto a small diffraction limited spot on the surface and is made to scan it over the desired region. The horizontal position of the bright spot is perpendicularly imaged onto a linescan camera and the information about the individual detectors that are activated, above a certain controllable intensity threshold level, is used to compute the corresponding horizontal spot's shift on the reference plane. Thus we can compute the distance between the surface and a reference plane at each sampled point. A map of the surface topography can then be built and statistical surface characterization parameters may be calculated. Our laboratory setup's configuration is quite versatile and it has been used for different inspection tasks like: thickness measures and relief mapping of polyethylene films and thin sputtered copper, tin dioxide and silver films, several kinds of fabrics; and roughness measure and topographic inspection of polyethylene molds and graphite samples. Also presented are the portable version of our system and the setup for large distance dimensional assessment.

Testing of surface shapes by automatic interferometry is exact, quick, and comfortable, and therefore popular. It, however, suffers from drawbacks: The equipment is often quite voluminous and not exactly cheap, and the attainable accuracy is limited by the precision of the reference surface (relative testing). In cooperation with Fisba Optik AG we recently developed a matchbox-sized, cost-reduced interferometric surface shape sensor to overcome the first drawback. Furthermore we combined this sensor with methods for absolute calibration of the sensor or a reference surface resp. to clear the reference surface handicap. Absolute calibration methods are methods which measure surfaces independently from others with sufficient accuracy as compared to an ideal mathematical surface. We adapted our own developments of absolute flatness and sphericity testing for the surface shape inspection sensor. Further on we developed and adapted new methods for absolute cylindricity testing the importance of which is increasing as the usage of cylindrical surfaces of higher and certificated accuracy is rising.

The high sensitivity fringe projection automated system for shape measurement of the object with P-V ranging from 10 - 2000 micrometers is presented. The system uses the carrier-frequency phase-shifting fringe pattern analysis method which enables the proper shape determination on the basis of a single image. The system may be applied for the object with max. dimension up to 20 mm. The opto-mechanical arrangement uses white light and is not sensitive for vibrations and work in a hostile environment.

An optical fiber based Moire interferometer for surface shape measurement is described. The technique uses an optical fiber interferometer to project interference fringes and is readily phase stepped without mechanical movement of components.

A holographic configuration for the measurement of angular variations of 3D objects is described. The method is simple, accurate and provides a very wide range of sensitivity. Phase-shifting procedures can be applied to the technique for quantitative measurement purposes.

A double integrated interferometer is proposed for absolute distance and velocity measurements with directional discrimination. An injection current-modulated laser diode is used as the wavelength tunable light source. One of the interferometers is used as a reference for systematic calibration. The second one permits the test distance measuring. The calibration enables the compensation of instantaneous fluctuations of the frequency modulation, the output light power drift, the frequency deviation, the refractive index and other external environmental disturbance corrections. The system is used for distance measuring from a few millimeters to 500 mm with a resolution better than 10 micrometers .

The automation of the fringe pattern analysis of Fizeau interferences combining the Moire effect with the phase-stepping evaluation method is presented. In this case the phase modulator is a Ronchi grid placed at the interferometer's image plane forming a Moire image and the necessary phase-steps are obtained simply by translating the grid in its own plane, perpendicular to the optical axis. A detailed description of the Moire image formation as an incoherent superposition is developed. Measurements were carried out in a Fizeau interferometer built by the authors.

Holographic interferometry and contouring are two optical methods used for the characterization of mechanical properties of thin films. Therefore, a phase measurement interferometry applied to these methods is explained. These solutions are discussed in terms of accuracy and sensibility. An application on a bulge test is proposed and experimental results are compared with finite element calculation. In each case, the good agreement between theory and experience allows us to validate the apparatus.

Holographic interferometry is an optical method for measuring displacement. However, it is the first or second derivative of displacement in many cases that is of interest, rather than the displacement information. Shearography which has developed in the last twelve years permits full-field, noncontacting measurement of the first derivative of displacement, and, therefore, it is rapidly gaining acceptance by the industry. This paper presents the recent development of shearography in technique and in theory. A few applications are shown in this paper.

New materials and components are often difficult to inspect. Shearography provides full field and non contact deformation and strain measurement in video realtime with very high resolution. This possibility gives it the chance to detect defects inside the component by looking at the strain distribution on the surface of the component during a little mechanical or thermal load. For example a foamed dashboard can be inspected shearographically by putting it into a vacuum chamber and changing the pressure inside the chamber by a slight amount. The enclosed air in voids will cause the expansion of the void and show up in a small deformation of the surface of the dashboard at the void. A shearography system is detecting these deformations and displaying them on a computer monitor. In this paper the technique of shearographic nondestructive inspection and examples of applications in automotive industries, aircraft industry, and terotechnology are given.

A novel technique for out-of-plane vibration analysis combining synchronous phase-stepping with additive stroboscopic TV holography and its implementation on a fiber optic electronic speckle pattern interferometer (FOESPI) are presented. Stroboscopic pulse-to-pulse (high frequency) as well as TV frame-to-frame (low frequency) phase-stepping of the reference arm are combined, with this scheme position of additive fringes is shifted yielding a series of frames (correlograms) which are then processed using conventional phase-stepping algorithms to obtain a phase-map of the vibrating object. A restriction of this technique, taking only two contrast-inverted correlograms for sequential subtraction, is also demonstrated for real-time visibility enhancement of additive fringes.

A stroboscopically illuminated ESPI system is described for the simultaneous measurement of vibration amplitude and phase. The technique involves modulating both the illumination pulse phase relative to the vibration, and the optical phase of the interferometer reference beam to generate eight video frames which are processed to yield vibration amplitude and phase.

A simple white light fringe interferometer is described, which is capable of displaying the phase information from one plane selected in a fluid. By using the correct optics the plane thickness and its position in the fluid can be chosen. An examination of the optical principles of the Lau type interferometer produced conclusions as to how the unit will be developed in the future. Previously published Lau type interferometers have used small diameter, well corrected, relatively expensive lenses (usually with large f-number) to examine small cross sectional flows. The authors intend to use optically accurate, very large diameter, variable focus, mirror finish plastic membrane concave mirrors of any desired f-number. Such mirrors result in any desired plane thickness in any desired position, for fluid flows of very large cross section. Such an important engineering development is already underway and will be reported in future papers.

A number of aspects of the rapidly expanding field of fiber optic sensors are reviewed. The work focuses upon a review of the diversity of sensor systems and the markets related to the needs for new instrumentation systems, including fiber optics. An instrumental perspective for process control and analysis is given, together with representative examples of the technology used to make sophisticated measurements. The questions of data transmission and the environment are considered, and future directions for the technology and sensor research and investment are considered.

A homodyne interferometer is described, using a He-Ne laser source and working in Twyman- Green configuration. By means of proper retardation plates and polarizing beam splitters, three signals at 90 degree(s) phase lag are made available. Such signals are digitized and fed into a desktop computer. Fitting procedures and computing algorithms are then implemented working out a phase angle; monitoring such a phase provides information on the optical path difference between the two arms of the interferometer. The general features of the approach are reviewed; examples of application are given, monitoring the fine displacement of mechanical parts and measuring the optical thickness variation of a soap film in air.

A discussion about the photodeflection capability to detect layers and defects is presented. A 1D and 3D numerical analysis has been performed. In particular for the 3D case, a model based on the analog circuit method is applied to describe (surface or volume) defects and nonhomogeneities in materials, which can be detected through the photothermal deflection method. Experimental results are also discussed.

A holographic measurement system was combined with digital image processing for the investigation of droplet velocity and number density in the injection spray of a model diesel engine. The model engine consisted of a conventional injection pump and a test chamber that could be operated at high pressure and temperature to simulate the conditions in an operating diesel engine. The holographic images were reconstructed and fed into a PC by means of a CCD camera. Up to 30 image sections are necessary to store the information of a whole hologram. The software developed for the segmentation of the droplets and the determination of the droplet velocity is presented.

Chromatic monitoring techniques have been developed to provide rapid feedback on the state of electrically induced plasmas. These techniques have been used to provide diagnostic information, based on the plasma emissions, and also to give rapid feedback on the thickness of insulating films while being processed. It is also possible that the chromatic technique could be used to monitor other important aspects of plasma systems, such as the concentration of particulates in plasmas and substrate temperature. The chromatic monitors provide information to a knowledge based system, which also has access to data from the conventional gas flow, pressure and rf power meters. The knowledge base consists of a set of rules, obtained by interviewing processing experts, and a statistical model of the plasma chamber. As well as being able to diagnose coarse errors in the plasma chamber equipment, the knowledge based system can compensate for undesirable variations during process runs.

Out of focus images recorded separately by two CCD cameras viewing the same object field are processed to measure simultaneously the size, 3-D position, and velocity of particles. The sign ambiguity of defocusing is removed by introducing a shift on the axial location of one camera with respect to the other and by using the ratio of the Fourier transforms of two defocused images. Particle sizing procedure includes mainly a calibration of the point spread function (PSF) of the optoelectronic setup for different amounts of defocusing and the measurement of both the contrast and the width at the intensity mid-point of defocused images.

Recently a new method for temperature measurement of droplets was presented. This method determines the index of refraction of a spherical scatterer with high accuracy and utilizes the dependence of the index of refraction on the temperature to finally determine the temperature. In this paper we show that the method is likewise applicable to cylindrical scatterers with a homogeneous refractive index distribution, like liquid jets. The method can be used to optically determine the temperature of a liquid jet, or to measure other properties of the liquid that influence the index of refraction of that liquid. One such property is the concentration of one liquid in another, like that of glycerol in an aqueous solution, which was studied experimentally for assessing some properties of the proposed method. An estimation of the sensitivity of the method was gained by detecting temperature changes of a cylindrical water jet.

We describe a temperature sensor based on a tapered monomode fiber. The sensor is demodulated by a static interferometer designed to measure a phase by the coherence multiplexing technique. A comparison between experimental results, theoretical analysis, and numerical simulation is presented. The performances of the sensing device are also given.

The mirror temperature of diode lasers has been measured by means of a photodeflection method. Information on the thermal behavior of the laser during operation is also obtained.

The effect of linear birefringence modulation on the magnetoptic Faraday rotation ((Omega) ) is demonstrated to be separable by illuminating the sensor with linearly and circularly polarized light. For levels of (Omega) typically obtained in power distribution and transmission industries crosstalk levels between the two signals have been experimentally observed that enable +/- 0.1 - 1% accuracy to be obtained in (Omega) .

The wide application of thermovisual equipment in various branches of science, industry, and medicine resulted in significant increase in production volume of visual systems, simultaneously, the number of technical and scientific works are increasing. The aim of these works is the creation of firmware for the receiving and processing of thermovisual information. The demand for such systems is considerable and constant. It is explained by the high level of efficiency of such systems application and by the high level of manufacturing.

In this paper a true RGB 3-chip color line scan camera is described. The camera was mainly developed for accurate color measuring in industrial applications. Due to the camera's modularity it's also possible to use it as a B/W-camera. The color separation is made with a RGB-beam splitter. The CCD linear arrays are fixed with a high accuracy to the beam splitters output in order to match the pixels of the three different CCDs on each other. This makes the color analyses simple compared to color line arrays where line or pixel matching has to be done. The beam splitter can be custom made to separate spectral components other than standard RGB. The spectral range is from 200 to 1000 nm for most CCDs and two or three spectral areas can be separately measured with the beam splitter. The camera is totally digital and has a 16-bit parallel computer interface to communicate with a signal processing board. Because of the open architecture of the camera it's possible for the customer to design a board with some special functions handling the preprocessing of the data (for example RGB - HSI conversion). The camera can also be equipped with a high speed CPU-board with enough local memory to do some image processing inside the camera before sending the data forward. The camera has been used in real industrial applications and has proven that its high resolution and high dynamic range can be used to measure color differences of small amounts to separate or grade objects such as minerals, food or other materials that can't be measured with a black and white camera.

In measurements which are influenced by external parameters, computer control and automation can help to improve the accuracy. This is also true of basically optical measurement set-ups such as certain interferometers for measuring flatness or wavefront aberrations, or set-ups for measuring the optical transfer function of lenses, for example. For the latter, a critical external parameter is the temperature variation resulting in expansion and therefore defocusing effects. New developments and measurement principles leading to improved accuracy are discussed.

We have constructed a fully automated Raman spectroscopic headspace gas analyzer for the assaying of oxygen and nitrogen in sealed vials. A single grating spectrograph with pre-filter and multichannel detection is utilized. Visible radiation at 488 nanometers is obtained from an argon ion laser. It is used to inspect vials containing a pharmaceutical product which is freeze dried and sealed under nitrogen (N₂). This product, though buffered, is sensitive to carbon dioxide (CO₂); therefore the analyzer is utilized to reject vials which have suffered ingress of air by detecting the presence of oxygen (O₂).

Heterodyne laser probes are very sensitive noncontacting instruments which provide wide bandwidth and high resolution. Most interferometers are based on a symmetrical two-arms structure, but in all cases, bench scientists know many undesirable beams (due to various reflection) often reduce expected signal to noise ratio. So one major problem of laser probe designers consists in spurious beams elimination. In practice, the so called `spurious beams' can successfully be used for new concepts of heterodyne laser probe. We have verified most assemblies could be simplified (the second arm often becomes useless) and alignment is reduced to minimum. Moreover, optical stability is generally better when using He-Ne laser. The only apparent disadvantage seems to be a small decreasing of the signal to noise ratio (typically about 3 dB, but that value depends on the structure).

We present an active triangulation based system for 3D reconstruction of objects with large depth variations which are placed on a rotary table to obtain the entire 3D view. We project Fresnel diffraction from an edge to generate an illumination pattern with large depth of focus on the object surface. The frontier line separating dark from bright areas of the diffraction pattern is used for line sectioning of the object, and the height profile is obtained through triangulation. Three dimensional reconstructions are illustrated for various objects having 10 cm maximum depth variations: the depth measurement accuracy is 0.36 mm for an object average distance of 350 mm.

Many industrial applications of optical metrology are confined to planar configurations. In this paper an approach to monocular parameter estimation is presented which makes use of this constraint. In addition to the components camera calibration and subpixel edge point detection, the method employs a recursive algorithm for parameter estimation. The algorithm and its application to simple contours such as lines and circles as well as to arbitrary implicitly given functions is described. The paper focuses on the contour segmentation that is reached using a fast plausibility test of the algorithm's residual sequence.

In the present paper the possibility of determining a longitudinal displacement of an object based on the dynamic speckle effect is analyzed. That the sensitivity of three different methods differs in mutual displacement of an illuminator, diffuser, and photomultiplier is substantiated theoretically and compared experimentally.

In the testing technology and analysis, laser aided lightoptical methods are increasing the conventional testing methods in a multivarious way. The opto-thermal hybrid microscope is a device which gives one the possibility to reveal point imperfection; for example in surface coatings. Also a differentiation between surface- and sub-surface defects can be performed, by comparing the thermal surface radiation with the intensity of the reflected part of the exiting light.

We describe a real-time holographic interferometric set-up for the determination of dynamic deformations of reflecting surfaces. The optical storage medium used is based on the novel polymer poly(vinyl alcohol) with alkoxyazobenzencarbonyl substituent. This material does not need any development and is characterized by low costs.

For the optical flow visualization in the new high enthalpy shock tunnel of the German Aerospace Research Establishment (DLR) in Gottingen (HEG) a fully automated holographic interferometer has been installed and improved. The interferometer applies the phase shift technique, which enables computerized evaluation of the holograms, to create high quality interferograms. Because of the high resolution of the images, optical enlargement and hologram-schlieren is made possible. With the use of the simple Gladstone-Dale equation it is possible to calculate complete flow field gradients.

Dimensional measurement and deformation measurement is performed using a photogrammetric setup with 3 CCD-video cameras. Using the images of a parallel shifted reference cross grating the orientation of the cameras is determined fully automatically within some minutes on a PC. Then two software packages are available for the calculation of an arbitrary deformed cross grating and for deriving elements, e.g. circles, straight lines, cylinders, in space from their edges in the images. This can be done interactively or automatically after a teach-in process. Hence the method is well suited for production and quality control.

This work relates to the glass polishing process in optical workshops, classically based on pitch lapping of ground surfaces. The process progressively removes the asperities and lowers the surface toward the bottom of the remaining pits. According to Preston's hypothesis, the polishing rate is proportional to the velocity of the lap and to its pressure on the area of contact. A computerized imaging technique is here reported to monitor the progress of the polishing action. A Nomarski microscope with a 16X objective has been equipped with a TV camera connected to a personal computer. A frame grabber provides image data that are elaborated to work out the surface features. Statistics are obtained on the fractional area covered by the residual pits. Referring to the Preston's hypothesis, the measured parameter is related to the actual finish grade of the surface inspected.

The technique of white light interferometry (WLI) is a powerful method in optical measurement systems. It involves the combination of two interferometers, coupled in series, and a light source of short coherence length. The displacement that is induced by the measurand in the first `sensor' interferometer is then determined in the second `recovery' interferometer with the advantage of a large unambiguous measurement range. The theoretical basis of the technique and practical realizations of the signal processing are considered. The potential of the system is discussed in terms of the measurement of displacement, and the technique is then applied to the measurement of other physical parameters, indicating various potential configurations of sensor elements for use ine in WLI systems. Results are presented illustrating its application in vibration, pressure, and position measurement.

Principles of the integrated optical noninvasive inspections (or nondestructive testing) of material quality are considered. It's well known that different optical methods allow us to obtain 2-dimensional spatial distributions of parameters most required for tested materials. The aim of this contribution is to elaborate ways of comprehensively using optical techniques (photometry, reflectivity, scattering, interferometry, holography, polarization, luminescence and so on). The special feature of proposed set up is the modular construction and high flexibility in design, i.e., it is possible to adapt our equipment to different kinds of automated testing techniques. Considered methods and set up were applied to the investigation of a wide range of subjects, e.g., solid natural or artificial materials, liquid crystals, microporous or fractal matrix, solutions, and biological specimens. In this paper only the results, concerned with semiconductor wafers or film-structures, are discussed. The experimental verifications and arbitrary electrophysical measurements are included.

The superimposed holographic interferometer is described. It allows shop control of residual stresses in welds of part and structures.

Computer-based 3-D imaging of hypothetical objects as a part of 3-D imaging techniques is a complex process comprising several stages from data capture to data presentation. All practical devices for computer-based 3-D imaging of hypothetical objects are systematized into groups characterized by similar ways of data capture and presentation. Limiting factors and drawbacks of current systems are analyzed.