The production of high quality optical components heavily relies on interferometric testing methods /1/. Before the invention of the laser proof glass methods dominated in the production line of the optical shop. Only in scientific labs or special testing laboratories Fizeau- and Twyman-Green interferometers were used. The reason was that the illuminating sources were spatially incoherent spectrum lamps or in the best case isotope lamps /2/. In order to obtain contrast-rich fringe patterns one had to stop down the light sources or in more involved cases to adapt the reference arm-length /3/. The big advantage of the fringes with partially coherent illumination was their smoothness enabling very high measuring accuracy. But extended incoherent and monochromatic sources restricted the interferometer design to the most simple devices as the Fizeau- and the Michelson-interferometer and with special precautions also to the Twyman-Green interferometer. With the invention ofthe laser interferometry became a fool proofmatter. The high spatial and temporal coherence of single mode laser radiation together with the high luminosity ofthe laser allows for total design freedom. This is of course a great advantage on the one hand but on the other the high degree of coherence is responsible for the disturbances caused by small scattering particles in the ray path which cause so called dust diffraction patterns. Through this effect the measured phase is disturbed by stochastic phase variations which limit the wavefront smoothness to the /1OO-level. Although a well designed interferometer will be almost free from the latter problem in some regions ofthe field of view in others the disturbance will remain. In two-dimensional measurements of phase distributions as in optical testing applications these disturbances can not be averaged out as in the case of simple length measuring devices /4/. There will always be a repeatability problem with varying adjustments of the interferometer. In modern interferometers CCD-detection is state of the art and therefore measurements with these devices show the problem very clearly. As will be shown, the repeatability problems with two-dimensional shape measurements result from the dimensionality and not from the ultimate sensitivity. With zero-dimensional length measurements the accuracy can be of the order I O or better since one averages over many dust diffraction patterns with the detecting area. In contrast to this two-dimensional measurements only reach iO to i04 accuracy levels with some effort.

The tertiary mirrors of the Very Large Telescope, one of the most powerful astronomical telescope systems, were manufactured and tested at Carl Zeiss. These components are lightweight elliptical plane mirrors with diameters of 1250 mm and 880 mm for the long and short axis, respectively. A particular challenge of this project was the outer rim specification of 200 nm peak-to-valley mirror surface deviation. This value had to be obtained under all operational load cases differing in the influence of gravity on the lightweight structure of the mirror. The mirror had to be tested on its support cell. For the absolute calibration of the large plane mirror surface a Ritchey- Common test was performed at two different angular positions. The test setup was adapted as close as possible to the operational position of the mirror in the telescope. A special algorithm for the calculation of the surface figure error from the wavefront data sets was developed. The results and special challenges of the absolute calibration procedure of the mirror surface will be presented and discussed.

The wavefronts in some optical systems like radial Gradient Index (GRIN) rods and aspherical lenses have large radial slopes at the circular edge of the pupil. Then some special mathematical tools are needed to represent these wavefronts. An idea of the mechanisms employed to fabricate the GRIn rods is helpful when designing these tools. In this article we propose the use of a gaussian function to represent these wavefront deformations at the edge of the pupil. This is a compact representation and it is also very convenient for radial GRIN rods. A data fitting is performed with a regularization process introducing the a priori known wavefront characteristics.

Wavelength scanning interferometry is applied for the shape measurement of tilted surfaces both diffusively reflecting and milled. We succeeded to measure those with tilt angles up to 45 degrees. We also investigated the influence of the tilt angle on accuracy and noise of the results of measurement. We found that the standard deviations of the measurement increase remarkably as the tilt angle increases owing to the more appearance of erroneous pixels. In the milled surface, the influence of the erroneous pixels is stronger than that in the diffuse surface. We also found that the accuracy of the measurement depends on the tilt angle. We compared the dependences of the standard deviations of the diffuse surface and the milled surface on the given tilt angle. We found that the tendency also depends on the surface structure.

An interferometer for VUV wavelengths was realized in order to improve the resolution and the sensitivity of optical metrology. To be able to work at wavelengths 157 nm up to 900 nm an apochromatic design was chosen using reflective optics. For the examination of the influence of the wavelength binary gratings with different periods, aspect ratios and depths, have been selected as test structures. The benefits and also the technological problems which come along with the use of VUV wavelengths are discussed. The design of this interferometer and measuring results with different wavelengths are presented.

Interferometers are used for routinely testing optical components and in engineering for the measurement of mechanical and thermal behavior of materials and components. Conventionally, for the most accurate measurements these interferometer systems are constructed from high-quality optical elements and include fine controls for precise alignment. In this new approach, all the errors of a poor quality, misaligned system are accepted then eliminated by a simple digital subtraction process. The method offers the possibility of devising very large aperture optical systems for traditional and engineering interferometers from inexpensive and basic components.

Measurement of the refractive index of liquids is of great importance in applications such as characterization and control of adulteration of liquid commonly used and in pollution monitoring. We present and discuss a fringe projection technique for measuring the index of refraction of transparent liquid materials.

Compared to the classical VanderLugt correlator, optical- hybrid frequency plane correlator systems are more flexible, but also more complicated. Implementation of the hybrid systems requires the use of addressable spatial light modulators to display contents of the input and filter planes and the use of the additional lenses to match the scalings in the system. Furthermore, hybrid systems use the optical elements such as quarter-wave plates, half-wave plates, and polarizers; which is all not needed for the classical setup. All these additional optical elements influence both amplitude and phase distortions of the wavefront that propagates throughout the system. For measuring the phase distortions of the optical elements, we have used the holographic setup with one mirror mounted on a piezo-electric transducer and controlled by a digital image processing system.

The Laser Interferometer Gravitational-wave Observatory (LIGO) core optical components have been manufactured by CSIRO. These optical substrates are optically polished on a lap surface that is made of Teflon coated onto a thick rigid faceted Zerodur base. To produce the km-scale radii (> 10 km) on these substrates the lap surface is shaped by abrading it with a fine ground silica plate whose radius of curvature corresponds to the one specified for the LIGO component. The plates are measured by a commercial phase stepping interferometer which is used in a grazing incidence arrangement. We describe the process of shaping and measuring the conditioning plates and laps.

Effects of thermal deformations of optical elements may be visualized and measured by interferometric methods. They correspond to the deformation of heated optical surface and/or deformation of the wave front of the light beam propagating through optical elements. In one of the experiments the optical effects for a single optical element heated by CO₂ laser were measured. Single element was combined with the second optical element for spherical aberration correction. The measurement stand used was composed of five modules: interferometers in Fizeau or Twyman-Green configuration (He-Ne, aperture 100 mm), CO₂ laser with the device for changing and measuring the power of the laser beam, the substrate module, thermovision camera AGEMA 470 for temperature measuring and the module for control, registration and analysis of interferometric images. The results of measurements provide the form of the wave front shape in combination with the thermal gradient of the surface. The experimental results are compared with computer simulated effects of the optical path difference and the temperature distribution calculated by the finite element method.

The cornea is the outermost segment of the eyeball. Due to it's lamellar structure the cornea indicates the optical anisotropy and effect of birefringence. We have applied phase stepping imaging polarimetry to measure birefringence of the human cornea in vivo and in vitro. Investigation of the corneal birefringence could be useful for examining the inner corneal structure, its lamellar arrangement and in medical diagnosing of corneal pathologies. There are also some potential applications of this method in transplantation of human corneas and refractive surgery procedures. The phase stepping imaging polarimetry technique used here, allows calculating azimuth angle, phase retardation and transmission coefficient of the sample. The method uses simple setup, sample at rest, and enables fast and accurate acquisition of data. The theory of the method is included. Experimental results of azimuth angle and phase retardation distribution for human cornea in vivo and in vitro are also presented.

The optical system working under the condition of a radial thermal gradient change its nominal constructional parameters, such as: radius of curvature, thickness, interlens separation and refractive index. These changes have two aspects: first one caused by pure temperature change and the second one is related to the thermal gradient distribution. In the first case well known temperature changes of constructional parameters are encountered (area of the athermalization problem) and in the second one known gradient index changes in optical material are faced. In this paper the problem of the aspherization of optical surfaces due to the radial thermal gradient is taken into account. The rapid method for evaluation of aspherical parameter CC (conic constant) applied in the optical design is presented. The obtained results are verified by the finite element method as well as the interferometric experiment.

The collected results of the refraction index profile measurement in highly anisotropic, tunable liquid crystalline waveguides are presented. The three different liquid crystal substances have been examined. Initial orientation of the liquid crystal layer is deformed by an external electric field. The initial orientations have been prepared as twisted and planar for liquid crystal material with positive dielectric anisotropy. In the liquid crystal material with negative dielectric anisotropy as initial has been examined hybrid orientation.

In this work we have introduced a new interferometric technique for measuring the nonlinear refractive index in different samples. Adopting a holographic point of view we have developed a mathematical theory for this technique which is based on the propagation of a Gaussian wave through a small phase aperture.

3D analysis of intensity distribution in the interference field of two interfering waves enables one to reconstruct the corresponding wave-vectors at each point in space. This has been exploited to specify the lens parameters, radii of curvatures, refractive index and the thickness of the lens. The technique is very suitable for lenses of small diameters and short focal lengths.

Since the initial concept of speckle interferometry was published more than 30 years ago the subject has matured to the point where it is now an engineering tool used in a wide range of applications with instrumentation available from a number of companies. The development of the technique to this level has been accomplished by making use of parallel developments in a range of technological areas. These are the laser, the PC, and the CCD camera. More recently the incorporation of optical fiber technology has also had a major impact. This paper reviews recent developments in the optoelectronic technology used in speckle interferometry instrumentation and the use made of it in a range of application areas.

This paper explores the use of a small frequency agile diode pumped pulsed laser source for Electronic Speckle Pattern Interferometry (ESPI) and Electronic Speckle Pattern Shearing Interferometry (ESPSI). The laser allows direct synchronization to the vibrating object being studied, thereby considerably reducing synchronization issues which have been prevalent in flash lamp pumped laser ESPI and ESPSI systems. The resonant characteristics of a square clamped plate have been examined using pulsed ESPI and ESPSI in order to validate the optical designs, with representative whole field plots of vibration amplitude being presented.

In this manuscript we present the development of an integrated shearography system that is able to measure the 3D deformation of an object surface. In order to determine all six displacement derivatives that may contribute to shearography results, six measurements with three different sensitivity directions and two shear directions have to be performed. The realized system is able to perform this measurement sequence in an automated way.

Shearography is a non-contact technique that measures deformation gradients, which can subsequently be used to evaluate out-of-plane strain components. In this paper orthogonal deformation gradients are measured quasi- simultaneously. The object under investigation is illuminated using linearly polarized light from an optical fiber. A polarization sensitive Michelson interferometer shears the speckle image from the object in orthogonal directions, for horizontally and vertically polarized light, allowing both displacement gradients to be measured independently. Laser diode injection current modulation provides a wavelength shift, which can be used to step between linear polarizations by using the birefringence of a highly-birefringent optical fiber. Wavelength modulation can also be used to phase step the interferograms produced, by using an unbalanced Michelson interferometer. If the wavelength modulation, optical fiber length and the pathlength imbalance are matched, then the polarization can be stepped between linear polarizations and the phase can be stepped by the same wavelength modulation. Images of the phase stepped correlation fringes and the wrapped phase maps illustrate the system operation.

The automated diffraction interferometer with scatter plate (DISP) is described. Special feature of the interferometer optical scheme is a special construction of an illuminator which permits to suppress speckle structure of interferometric picture. The basic part of the illuminator is a vibrating fiber bundle made from multimode optical fibers different lengths. The difference in fiber lengths overcomes the coherent length of multimode laser used as a radiation source in the interferometer. Mathematical model of DISP is presented. Mathematical model of DISP interferogram was derived from refined calculation of ray path. The model allows to evaluate errors of measurement in relation to parameters of a detail under control and size of scatter plate. It is shown that the finite size of scatter plate causes an additional phase shift. This additional phase shift we can be considered as a DISP systematic error. The procedure for calibration of DISP instrumental error is proposed. It is based on the analysis of an interferogram set made from the only optical detail under different orientation about interferometer optical axis. Experimental data on DISP error calibration is presented. DISP root mean square error is not over 0.005(lambda) for detail under control with relative aperture 1:7. The production procedure of a scatter plate with uniform high aperture scattering indicatrix is described. It is based on photoregistration of coherent radiation scattered on round diffuser with central obscuration. The obscuration is performed by transparency with inverse Gauss function transmission.

The paper contains a brief description of main principles of compensation speckle interferometric technique with an emphasis is made on their implementing in non-traditional fields of material testing. The main essence of optical compensation consists of the fact that routine quantitative interpretation of fringe patterns is substituted with more accurate measuring the geometrical parameters of the interferometer set up corresponding to the compensation instants. Metrological basis of this system is the electronic speckle pattern interferometer combining two speckle fields with both an object and a reference speckle pattern is created by a ground glass diffuser. A visualization of fringe patterns related to a small difference between two deflection fields of plane specimen under pure bending is performed by digital subtraction of corresponding intensity fields derived from CCD-camera. Some examples of Poisson's ratio and elasticity modulus determination for composite materials and their evolution due to internal humidity level changing are also presented.

Principle of operation of laser radiation wavelength meter based on Fabry-Perot interferometer and linear CCD camera is presented in the paper. A dependence, on the base of which laser wavelength can be calculated, is found and a way of defining of all component uncertainties of a measurement is shown. An analysis of an influence and examples of definition of uncertainties of a measurement for four wavelength meter structural sets of different objective focal lengths are presented.

We describe a new compact refractometer for air refractive index measurements. It is based on a double plane-plane Fabry Perot interferometer whose cavities of different thickness are illuminated independently by the same tunable frequency laser diode. A first one millimeter thick cavity allows unambiguous identification of the transmission peak of the second (100 mm); the laser frequency being servo- locked to the latter. This refractometer does not require any part to be evacuated during the measurement procedure. The absolute value of the refractive index of air and its fluctuations are obtained in real time by beat frequency technique combined with an optical frequency reference. Measurements provide a resolution of order 10^-10 and a relative accuracy of a few times 10^-8. We also describe how this refractometer is used to measure the fluctuations of the density of air used to make buoyancy corrections in mass standard comparisons. Other possible applications of our refractometer, in particular for the determination of the water vapor concentration in air are reviewed.

Two different sinusoidal wavelength-scanning (SWS) interferometers with a SWS light source using a superluminescent laser diode are proposed for step-profile measurement and real-time distance measurement, respectively. An optical path difference (OPD) longer than a wavelength is measured from detection of sinusoidal phase- modulation amplitude Z_b of the interference signal that is proportional to the OPD and the scanning width 2b. In step-profile measurement, if measurement error in the OPD obtained from Z_b is smaller than a half wavelength, this measured value of the OPD is combined with a fractional value of the OPD obtained from the conventional phase of the interference signal. This combination enables us to measure the OPD longer than a wavelength with a high accuracy of a few nm. In real-time distance measurement, the amplitude Z_b is kept at a specified constant value for changes of OPD by controlling the scanning width 2b of the wavelength with a feedback system. The amplitude Z_b is detected by processing the interference signal with electric circuits in real-time. The value of b is easily controlled in the SWS light source, and an OPD longer than a wavelength is measured from the value of b with an accuracy of about a wavelength.

Spectral properties of two elliptical core fibers were investigated using interferometric methods. Phase and group modal birefringences were measured versus wavelength in the spectral range from 633 nm to 830 nm. We also measured sensitivity of phase and group modal birefringence to temperature and hydrostatic pressure in the same spectral range. Strong wavelength dependence of modal birefringence and its sensitivity to external parameters was detected in investigated fibers.

An optimization of the discharge parameters of high pressure mercury lamps with respect to improved emission properties and longer lifetimes has to be performed using results of advanced model calculations. However, the reliability of these models critically depends on the availability of accurate experimental data. The aim of this work was to provide spatially resolved particle densities of neutral mercury atoms by side-on spectral interferometry. The main challenge was to find an optical arrangement that enables one to compensate for the strong wavefront distortion in the object arm caused by the extreme curvature of the bulb of the discharge lamp, a general problem in classical interferometry. The interferograms could be taken with a time-resolution of 150 microsecond(s) at any phase of the discharge current that varied with 50 Hz. The applied spectro- interferometric technique was a phase method developed at the institute. It supplies a highly resolved phase of the light wavefronts passing the plasma using FFT algorithms. By an Abel-inversion of the side-on data mercury density profiles could be presented for cross-sections ranging up to 10 mm as consequence of the specially designed test and reference beams in the used Mach-Zehnder interferometer.

Laser differential interferometer is now widely used for the study of fast dynamic phenomena. The version of this method allows to carry out the measurement both average velocity of the target and the velocity dispersion. This information provides the important data for the calculation of threshold strength in the materials and allows to determine the beginning of their destruction. In the paper we discuss the problems associated with the large velocity dispersion, in particular with the interference pattern contrast reduction that leads to the error in determination of average velocity and does not allow to follow the whole evolution of the velocity dispersion. The way to improve the contrast are discussed. The results are illustrated by experimental data.

Speckle interferometry is an interesting tool for the measurement of micro-deformations and has found application in many different fields ranging from material testing to structural assessment. This kind of applications, however, has often been confined inside optical laboratories where operational conditions are optimal. This paper is devoted to the extension of speckle interferometry to various measurements--performed not inside well protected rooms but in testing halls dedicated to experimentation in civil engineering--where the environmental conditions are severe for an interferometric method.

Holographic interferometry and speckle interferometry are currently used in the field of non-destructive testing. More particularly, they permit to detect defects in structures by analysis of their behavior under stresses. In this work we have studied the possibility of using these techniques for the detection of cracks in reinforced concrete structures. We present some results with classical double-pulse holography and with the double reference technique. We also present some results with speckle interferometry on CCD camera.

Shearography is an approved and powerful tool for the nondestructive investigation of technical components with respect to material faults and technical imperfections. Current applications are for instance the in-service inspection of aircraft components and the tire testing. Possible imperfections can be recognized as typical fringe patterns such as the well-known butterfly type. However, a reliable flaw recognition requires a sufficient clarity of the local fault indicating pattern in contrast to the global image content. Since shearography is based on the digital correlation of speckle patterns, the image quality and consequently the flaw visibility can be very poor if some essential prerequisites aren't fulfilled. Especially for the testing of large scale components the following factors should be carefully taken into account before the experiment is started: the type of the object (relevant area, surface, fixing, ...), the type of the sensor (aperture, resolution, sensitivity, ...), the way of object illumination (wavelength, illumination profile, ...) and the way of loading (mechanical, pressure, temperature, ...). With respect to an optimal adjustment of these factors this article investigates their influence on the image quality and their mutual dependency. The derived functional dependencies are verified on example of some relevant applications for aircraft and artwork inspection.

The concept, methodology and instrumentation for hybrid experimental-numerical residual stress analysis in a laser weldment are presented. Grating interferometry and digital speckle photography are applied as complementary experimental methods for determination of the residual strains and of the material properties (Young's module and Poisson ratio) at various zones of a laser weldment. These data used in basic and localized hybrid techniques enable to determine the FEM model of laser weldment. This model is used in full hybrid technique for the residual stress-state determination by comparison in a close iterative loop of the experimental and numerical results obtained in uniaxial tensile test.

The laser diffraction is a robust and precise technique to monitor wire diameters in-line. However, classical Fraunhofer diffraction formulas are not appropriate for 3D object size determination. The Babinet's principle allow to use such formulas only for angles of diffraction that tend to zero. A real diffraction measurement necessarily takes a finite angular range (approximately 10 degree(s)) and therefore, an error will be introduced if using classical formulas. The exact electromagnetic formulation is not appropriate to deal with 3D objects in a simple way. On the other hand we observed a systematic overestimation of the diameter, even very small angle of observation, in other words, a small misfit with the Babinet's principle.

An automated Fourier-transform method of phase retrieval of moire interferometric fringe pattern is presented. The method is shown to provide fast and accurate determination of the phase information by removing the carrier without shifting in frequency domain the filtered Fourier spectrum of the carrier-modulated moire fringe pattern. The principle of the method is described and moire interferometric measurements with submicron sensitivity of the in-plane displacement fields of thick carbon fiber/PEEK composite laminates are analyzed as example of application of the technique.

For one and a half decade, software for interferometric fringe evaluation has been developed and used at Technical University Graz. Within the framework of an awarded grant to one of the authors, the Austrian Government funded activities on optical metrology in mechanical engineering. In this grant these software packages on interferometric fringe evaluation had been subsumed under Windows95/98/NT and the Unix/X-Window-System. This software is made accessible via internet to the public domain (http://optics.tu-graz.ac.at). Its main features are phase- stepping, Fourier domain evaluation and unwrapping techniques as well as algorithms for Abel-inversion and tomographical reconstruction. Additionally, we implemented a bunch of tools for data manipulation, e.g. multiple file handling, filtering, and flexible visualization of data. Some of these features with examples from a multidirectional holographic measurement on a plasma discharge and from speckle interferometry are presented.

A new type of fiber-optic pressure sensor based on highly birefringent fibers is presented. To assure temperature desensitization, the sensing part of the device is composed of specially developed side-hole fiber and elliptical core fiber, which are spliced to each other with polarization axes rotated by 90 degree(s). Such sensor construction assures high sensitivity to pressure and compensation of temperature effects associated with rapid pressure changes. The sensor allows for unambiguous and fast phase-shift measurements in the range from -(pi) /2 to +(pi) /2 with a sampling rate of 5 kHz and resolution of about 0.5% of full scale (2 (DOT) 10^-3 atm). The sensor calibration procedure, responses to fast pressure change, and preliminary applications are demonstrated.

Due to the significant difference in the physical and chemical properties of ceramics and metals, the joining process of these materials provides several problems. The paper describes a hybrid experimental-numerical approach for determination of stresses in C-M joint. Automated moire (grating) interferometry is used as a full-field experimental method providing in-plane displacement/strain data, as well as the local values of Young modulus at the vicinity of the C-M joint. These data can be used as the input for the finite element analysis for full stress state determination in the joint. Analysis of Al₂O₃-FeNi42 specimens manufactured with different temperature and time of brazing was employed to determine optical technological parameters of the joining process.

In this paper we discuss the problems connected with analysis of mechanical properties of silicon microelements being basic parts of MEMS (e.g. micromembranes, microbeams). The quality of these microproducts (the reliability and the lifetime) is strongly dependent on the material properties and the mechanical design. There is also strong influence of the technology process on their performance. The best suited methods for their testing are optical full-field measuring methods. They provide data (displacements, strains, distribution of material constants) which may be easily used in the hybrid experimental-numerical methods for microelements analysis and optimization of their design.

This paper presents results of extended studies on polarization interferometry in fiber optic smart structures. The smart structures consisted of highly birefringent (Hi- Bi) bow-tie and different types of side-hole fibers embedded in a cylindrical epoxy cylinder. The objective was to investigate and compare optical properties of different types of smart structures subjected to selected deformation effects mostly induced by hydrostatic pressure (up to 300 MPa) and temperature, whereas polarization properties of the transmitted optical signal have been investigated. Furthermore, a new experimental set-up was proposed based on the use of fiber optic connectors that make the whole system easy to handle.

Experimental results of the usefulness of the fiber-optic Sagnac interferometer for a measurement of angular position as motion uniformity of slow-speed rotating objects are presented. The system contains GS-13P/SR device with modified signal processing unit. The results of an investigation of this system, and their application for rotation angle and uniformity motion of object in inertial space are shown. A new slow-speed platforms generate constant angular motion (M19-03 stand made by COBRABiD Optica) and harmonic variable motion (STW-1 stand made by AFIT) have been used as forces source. The Fourier and wavelets analyses have been used as mathematical description of GS-13P/SR application for technical diagnostic of slow- speed platforms.

CSIRO is manufacturing the `core' optical substrates for LIGO, a Michelson interferometer with arms up to 4 km in length each containing a Fabry Perot cavity. The beam splitter and input test mass mirrors (the entrance mirror to each cavity) have specifications not only for the optical surfaces but also for the radius of curvature of the wave front transmitted through the optical substrate. Our approach to manufacturing the substrates is to calculate the quadratic component of refractive index gradient (Delta) n from measurement of the transmitted wave front and the surface relief of the two substrate surfaces. After one of the surfaces (S1) is polished to specification, the radius on the second side required to achieve the specification on the transmitted wave front is calculated (using the measured value of (Delta) n, the actual value of S1 and the target value of the transmitted wave front). Results of this work and complications of the measurement procedure due to the thermal inertia and poor thermal conductivity of the silica substrates will be presented.

There are some topical mechanical problems in solving of which remarkable features of various holographic interferometric techniques are capable of ensuring an actually new level of data obtained comparing with other experimental methods. One of these problems is a detailed quantitative description of local elasto-plastic strain history in contact interaction zone. Holographic interferometry is still a very complex and time-consuming method for strain/stress analysis, even if modern tools for computer-aided fringe patterns evaluation are available. That is why in most cases holographic techniques using for a predictive strain/stress analysis have to be supplemented with corresponding numerical techniques thus forming so- called combined or hybrid approach. The presentation is devoted to main questions related to a choice of appropriate numerical models which are capable of high-accurate reproducing a local strain history under regular cyclic loading. The main objective of constructing such a model is a determination of 3D local strain fields to within 3% in order to ensure developing new refined techniques for evaluation of fatigue damage accumulation. Holographic interferometry data are consecutively used during a whole step-by-step procedure, first, to choose an initial model and, then, to construct and to validate a set of advanced models.

A new optical technique based on color holographic interferometry is presented in this paper. Experiments on color interferometry in real time and by double exposure are carried out using three coherent wavelengths (blue, green and red) produced by c.w. lasers. Holograms are recorded on single-layer panchromatic silver-halide Slavich PFG 03C plates. As an example, a photograph of a colored Lippmann- Denisyuk interferometric hologram is presented, showing the mechanical deformations of a metallic sample. A video film on real-time trichromatic interferometry is presented. The video film, recorded at 25 frames per second, shows colored interference fringes produced by phase objects.

Buried mine detection is a very complex problem. Many types of mines contain few metallic parts, which complicates the detection with classical electromagnetic systems. In this work we have studied the application of holographic interferometry techniques to the visualization of seismic wave propagation. Perturbations of the wave propagation can reveal the presence of a buried object. At first, classical holographic interferometry is tested to follow the propagation of the seismic wave. To make the holographic acquisition system more portable, we have also tested the speckle interferometry technique. Results concerning both methods are shown and discussed.

For Digital Speckle Interferometry, the Fast Fourier analysis usually applied to interference fringe systems suffers from a limited spatial resolution because of the inherent granulation disturbance. Contrary, phase stepped interferometry is less influenced by speckle noise, but needs at least three phase-shifted frames at reference and object condition, or one frame with accordingly reduced resolution. For instationary objects, like an arc discharge, the phase stepping method is problematic since the phase- shifted interferograms are produced in an interferometrically unstable environment. Investigations of arc discharges showed that this problem can be solved by recording only one speckled object wavefront and referencing it with phase-stepped reference wavefronts. After low-pass- filtering, the resulting secondary speckle interferograms are treated with the common phase stepping algorithms. This technique was tested by a measurement of a deformation and was also applied to an end-on investigation of the `mini- arc', an argon arc discharge used for a secondary spectral reference.

Some methodological and metrological problems related to both high-quality fringe patterns recording at a proximity of fatigue crack of different length and following local strain fields determination are the first subject of the paper. The second question considered is a choice of the way of local strains representation in a form which is the most suitable for a determination of fracture mechanics parameters making emphasis on J-integral evaluation.

The technique of stresses determination on the outline of the non-loaded hole in a bending plate on the basis of absolute fringes orders and form analysis on holographic interferogram is considered.

In this paper the applications of holographic interferometry to ionizing radiation dosimetry are presented. The determination of the accurate value of dose delivered by an ionizing radiation source (released energy per mass unit) is a complex problem which imposes different solutions depending on the experimental parameters and it is solved with a double exposure holographic interferometric method associated with an optoelectronic interface and Z-80 microprocessor. The method can determine the integral absorbed dose as well as the tridimensional distribution of dose in a given volume. The paper presents some results obtained in radiation dosimetry. Different transparent liquids were used as ionizing radiation transducers. Integral dose and spatial dose-distribution were recorded for equivalent tissue liquids and blood plasma. Boundary phenomena, during a irradiation of successive layers of liquids having different atomic numbers, were investigated.

The semiconductor industry is continually moving towards more complex processor designs. The new chips occupy bigger areas and surface properties of silicon wafers used in manufacturing, such as PV and RMS, become critical. One of most important characteristics of wafers is their site flatness, defined as height parameters over area occupied by the projected semiconductor chip. Smaller critical dimensions, shorter wavelength, and higher numerical aperture steppers impose more stringent requirements on PV and RMS of the site's profile. As the wafer goes through the manufacturing process, its value increases, so detecting defective sites is essential to lowering the production costs. To resolve this problem Veeco Process Metrology has designed the RTI 4100--a high performance laser Fizeau interferometer especially suited for inspection of site wafer flatness. High accuracy data taken y the instrument is analyzed by automated software package that performs evaluation of the user selectable sites and qualifies them using various user defined rejection criteria. In this paper, we present some aspects of the instruments' design and its measurement capabilities with interest to the semiconductor industry.