Some problems associated with surface metrology instrumentation and theory are discussed. In particular problems in Nanometrology are highlighted with reference to Markov processes and fractal analysis. A systems approach to surface characterization is suggested.

Interest in beams containing phase singularities (dark beams) is evolving as applications are being realized, in particular for high-resolution microscopy and measurements. While these dark beams are usually generated with the help of diffractive elements, in this paper two new approaches for the generation of dark beams within the laser cavity are proposed and investigated. Simulations demonstrate that distributions similar to dark beams can be obtained by various laser modes.

In earlier publications, it was shown that scanning of surfaces by dark beams can be exploited for sub-wavelength feature analysis. In this work, we present vector simulations based in Rigorous Coupled-Wave Analysis with the purpose to estimate the expected resolution of the method, both lateral (feature size) and axial (height). The dark beam used in this study has a line singularity generated by a π-phase step positioned in a Gaussian beam. Various combinations of the illumination and detection nuFmerical apertures (from NA=0.2 to NA=0.8) and different surface features were studied. Polarization effects which become significant at high numerical apetures, were considered as an additional source of information for the analysis. In the case of a sub-wavelength feature on an ideal surface, the resolution of the method is limited only by the electronics noise. In particular, under a reasonable assumption of a 10⁵ signal to noise ratio, it is possible to detect a 0.2 nm step.

Continuing improvements in the fabrication of super-smooth spherical and aspheric optical surfaces for applications such as extreme-ultraviolet lithography have given rise to the need to characterize the surface roughness of these optics to the sub-Angstrom level. Phase-shifting interference microscopes are well suited to acquire high-precision, three-dimensional surface structure rapidly, without contact, and over a wide range of spatial frequencies. This paper describes a new phase-shifting interference microscope by ADE Phase Shift, together with exemplary measurements of Angstrom-level surface roughness. The microscope was designed to measure large diameter (up to 500 mm) convex, concave and aspheric optics. To access all areas of the test surface, samples are placed symmetrically at the center of an R-theta stage. The phase-shifting microscope head pivots in the direction of the translation stage travel by ±20 degrees to match the major component of surface slope, while a second tilt control nulls minor tilt in the orthogonal direction. A 1K by 1K high-resolution, digital camera reduces random noise in the system to below 0.15 Angstrom rms for 16 averaged maps of nulled interferograms. When testing non-planar surfaces, the interference fringes cannot be nulled out, and special care has to be taken to minimize phase-dependent errors, commonly known as fringe print-through. A print-through level of less than 0.2 Angstrom rms has been achieved with a careful opto-mechanical system design in combination with an advanced phase algorithm whose filtering action suppresses higher-order harmonics caused by phase-shifter and detector non-linearity, as well as vibrations.

We present an analysis of the quality of white light interferometric measurements using an optical profiler with increased scan speeds up to 100 microns per second. A centroid approach was chosen for the white light fringe analysis because it is among the quickest to compute. The increase in speed requires a decrease in the spectral bandwidth of the illumination source. Only certain sampling rates (scanner speeds) yield suitable results for finding the position of the white light fringe envelope. Sampling rate, spectral bandwidth, noise, vibration and camera integration time all influence the quality of the measurements. Although precisely calibrating the scanner is one approach for achieving accurate measurements, our preferred method is determining the scanner speed during the measurement and then utilizing this information in the algorithm. Besides assuring highly accurate measurements this method avoids the delicacy and fine tuning that accompanies the calibration of the scanner. Our optical profiler system allows variable scan rates from 4.8 microns per second all the way up to 100 microns per second, which yields very precise measurements when a slower scan rate is used, extremely fast measurements with still high repeatability or any combination of speed and accuracy depending on the scan rate. We find that this combination of precision and speed make this system quite well suited for industrial measurement of a wide range of sample heights from hundreds of nanometers up to eight millimeters.

Difference holographic interferometry (DHI) is a holographic technique for direct optical comparative measurement of deformation, shape or refractive index distribution changes of two objects (master and test). At this procedure the test object is illuminated by reconstructed real images of the master object recorded previously. The holographic illumination is the spirit of the technique providing the unique possibility for direct optical comparison of the two objects. The differences in phases of the wave fronts belonging to the different states of the two objects lead to an interferogram that displays the difference of the measured quantities directly. The accurate comparison requires that the phases of the master and test object interference patterns should be compared at their corresponding points. There are two typical sources of error: (1) false reversing the master reference beams and (2)imperfect positioning of the test object. In the present paper a short summary of DHI is given, the above mentioned error sources are analyzed, techniques for minimizing their effects are suggested and the allowed shift of interference phase is estimated.

The paper is dealing with the technology of spatial light modulators in the field of diffractive optics. A short overview of the actual micro-display technology leads to the parameters and the performance of the implemented systems. The main goal of this paper is to demonstrate the adaptation of the digital hologram to the reconstructing device. Modulation measurements for the SLM system lead to complex modulation curves, which can be applied to the pixel matrix delivered from the recording digital camera. Here we focus onto a transfer of the linear grey scale recording of the CCD-camera to a linear phase modulation of the SLM. A second step can improve the diffraction efficiency of the phase structure by an optimized arrangement of the phase levels along the dynamic range of the SLM. This digital post-processing can improve the light efficiency of the system drastically. The applications in deformation and shape control discuss experimental realization, alignment problems and solutions found while improving the experimental system.

In digital holography the imaging process consists of two quite different techniques: physical registration using CCD camera and digital image reconstruction with specialized software. To receive the best image quality, besides diffraction limitations, the recording reference and reconstruction beams should be identical. The measurement of the reference field distribution at the hologram plane can be accomplished with a limited precision. The influence of differences between the reconstruction and recording reference beams is the subject of the paper. The analytical and experimental results are presented. It worth to emphasize that the differences mentioned influence results obtained in digital holographic interferometry as well.

A new technique is proposed that enables reconstruction of phase-shift digital holograms with unknown phase shifts. The technique is based on the phase-shift technique combined with the Fourier transform technique to have the advantages of these two techniques. First the unknown phase shifts are determined by the Fourier transform technique, and then the complex field recorded in the digital hologram is obtained by the phase shift technique using the knowledge of the phase shifts. Experimental results are presented that demonstrate the validity of the principle.

For digital reconstruction of holograms recorded in near diffraction zone, Discrete Fresnel is used as a discrete model of wave propagation. In applications where reconstruction of holograms in many observation planes is required, conventional implementation of Discrete Fresnel Transform reconstructs images of the object plane sections that are shifted with respect to each other depending on plane distance from the hologram plane. In the paper, a novel representation of Discrete Fresnel Transform, Focal Plane Invariant Discrete Fresnel Transform is suggested and illustrated which secures reconstruction of images automatically aligned with respect to the same optical axis. The transform invariance allows to substantially reduce computation burden whenever only a relatively small portion of the reconstructed wave front has to be analyzed and to ease analysis of the reconstructed wave front as a function of distance to the object.

Digital holography provides the direct access to the interference phase. This basic quantity of interferometry can be used for the measurement of 3D-coordinates and 3D-displacement fields of objects subjected to a certain kind of load. For the inspection of objects which cannot be accessed directly such as hidden surfaces inside a cavity endoscopic systems are applied. In this paper a miniaturized sensor is described that can be fixed at the distal end of a flexible endoscope. The sensor head integrates all components of a holographic interferometer including the CCD-camera as well as the beam splitting and guiding components for three illumination directions using glass fibers. An optimized design of the interferometer setup makes it possible to measure the 3D components of the measurement quantity with high accuracy. After a short introduction to the principles of digital holography and 3d-displacement measurement the basics of perturbation theory are presented. This theory is applied for the design of the interferometer and finally some consequences with respect to the statistical error analysis are discussed.

Speckle noise imposes fundamental limitation on image quality in coherent radiation based imaging and optical metrology systems. Speckle noise phenomena are associated with properties of objects to diffusely scatter irradiation and with the fact that in recording the wave field, a number of signal distortions inevitably occur due to technical limitations inherent to hologram sensors. The statistical theory of speckle noise was developed with regard to only limited resolving power of coherent imaging devices. It is valid only asymptotically as much as the central limit theorem of the probability theory can be applied. In applications this assumption is not always applicable. Moreover, in treating speckle noise problem one should also consider other sources of the hologram deterioration. In the paper, statistical properties of speckle due to the limitation of hologram size, dynamic range and hologram signal quantization are studied by Monte-Carlo simulation for holograms recorded in near and far diffraction zones. The simulation experiments have shown that, for limited resolving power of the imaging system, widely accepted opinion that speckle contrast is equal to one holds only for rather severe level of the hologram size limitation. For moderate limitations, speckle contrast changes gradually from zero for no limitation to one for limitation to less than about 20% of hologram size. The results obtained for the limitation of the hologram sensor’s dynamic range and hologram signal quantization reveal that speckle noise due to these hologram signal distortions is not multiplicative and is directly associated with the severity of the limitation and quantization. On the base of the simulation results, analytical models are suggested.

This contribution deals with measuring strategies and methods for the determination of several geometrical features, covering the surface micro-topography and the form of mechanical objects. The measuring principles used in optical surface metrology include optical focusing profilers, confocal point measuring and areal measuring sensors as well as interferometrical principles such as white light interferometry and speckle techniques. In comparison with stylus instruments optical techniques provide certain advantages such as a fast data acquisition, in-process applicability or contactless measurement. However, the frequency response characteristics of optical and tactile measurement differ significantly. In addition, optical sensors are commonly more influenced by critical geometrical conditions and optical properties of an object. For precise form measurement mechanical instruments dominate till now. One reason for this may be, that commonly the complete 360 degrees geometry of the measuring object has to be analyzed. Another point is that optical principles such as form measuring interferometry fail in cases of complex object geometry or rougher object surfaces. Other methods, e.g. fringe projection or digital holography, till now do not meet the accuracy demands of precision engineered workpieces. Hence, a combination of mechanical concepts and optical sensors represents an interesting potential for current and future measuring tasks, which require high accuracy and maximum flexibility.

We describe simultaneous determination of surface height profile and material distribution in the surface by imaging polarization detection. Starting from the single-beam case, the measurement principle based on the Stokes-Mueller formalism is deduced. This algorithm implies waviness detection of smooth as well as of rough surfaces. The basic concept of an imaging ellipsometer and its system configuration are discussed in the Stokes-Mueller formalism. Measuring the local slopes of the surface applying Fresnel's equations, the height image is deduced. Furthermore the imaging ellipsometer delivers the local complex refractive index from which the image of material distribution can be derived by a look-up table.

One of the applications, which is considered to be very difficult to carry out with most optical imaging profilers, is the shape and texture measurements of structured surfaces obtained from the superposition of various micro or sub-micrometric layers of dissimilar materials. Typical examples are the architectures of microelectronics samples made up of Si, SiO₂, Si₃N₄, photoresists and metal layers. Because of the very different values of the index of refraction of the involved materials, visible light is reflected in the various interfaces. As a result, some reflected wavefronts are superposed giving rise to interference patterns, which are difficult to understand in terms of surface topography and layer thickness. In this paper we introduce a new method based on non-contact confocal techniques to measure the shape of structured samples. The method is based on the comparison of the axial responses obtained in areas of the surface where there is a layer and in other areas where there is just the substrate. To our knowledge, this approach enables the confocal profilers to measure the thickness of layers on the sub-micrometric scale for the first time.

A novel interferometer concept will be presented which is based on an optical standing wave. This standing wave is scanned by a novel, partially transparent photodetector, which is designed as nip-photodiode and contacted with transparent conductive oxide (TCO). Two transparent photodiodes are integrated to a transparent phase-sensitive sensor. The photodiodes are longitudinally arranged on the optical axis of the standing wave and generate a sine and a cosine signal for the up- and down-counting of the intensity maxima and minima of the standing wave. The layer thickness of the transparent photodiodes has been designed so as to take appropriate coating into account. These measures are demonstrated by a number of experimental results. An incorrect phase relation between the photodiodes will be corrected using the Heydemann algorithm. The non-linearity of the interferometer at a length of <λ/2 will be discussed.

We report on the progress of the development of a three-wavelength light source for an earlier published absolute, two point source interferometer to measure absolute optical path differences (OPD) with angstrom accuracy over the range of millimeters. The light source system should produce three different wavelengths between 630nm and 640nm simultaneously, providing two synthetic wavelengths that enable the absolute OPD measurement. Due to requirements of the detection system, the frequencies of two of these lasers have to be stabilized with an accuracy of the order of 10^-7, while the third laser is stabilized to better than 10^-8. For the former, tuneable external cavity diode lasers are used, whereas the latter is a commercial frequency stabilized HeNe laser. Two different locking schemes and their relative merits are evaluated: Molecular absorption locking, guaranteeing long-term stability, versus Fabry Perot locking, with the flexibility of choice of the desired frequencies. Recent measurement results for both locking schemes are presented.

Simple polarized light implementation of the phase shifting method for analyzing fringe patterns formed in Burch's common-path scatterplate interferometer has been proposed. The systems employs circularly polarized beam at the input end, a quarter wave plate to change the rotation direction of circular polarization of the reference beam, and a rotating analyzer placed in two counter-rotating circular polarization beams at the output of the interferometer. The simplicity of our approach is proved theoretically and experimentally. Problems related to non-ideal light modulation at the interferometer output and the ways to overcome them are discussed.

We describe an oblique point-diffraction source, which is made from a single-mode optical fiber whose end is specially cut with an oblique face angle of 28.8° to the optical axis of the fiber. Analytical and empirical investigations reveal that, like ordinary fibers cut with zero face angle, the oblique fiber generates a high-quality spherical wave into free space by means of point diffraction at its end, but the diffracted wave has a propagation angle of 45° to the surface normal. This inclined nature of point diffraction is useful in many optical designs because it allows the returning wave of the original diffracted wave to be reflect at a right angle at the end face of the oblique fiber without additional optics. An exemplary use of the oblique fiber is demonstrated in an enhanced optical design of Fizeau interferometer, in which the troublesome combination of a pinhole and a beam splitter is effectively replaced only with a single oblique fiber. Another example is shown in a phase-shifting diffraction interferometer that has been specially designed for testing concave mirrors of low f-numbers. The use of oblique fibers enables to use the entire full numerical aperture of the diffracted wave from a single-mode fiber for optical testing without any overlap between the reference and the test waves.

We present a new type of Shack-Hartmann sensor. Replacing the static microlens array in a Shack-Hartmann sensor by a liquid crystal display results in a greater measurement flexibility. The liquid-crystal display in the adaptive Shack-Hartmann Sensor is used for the generation of an array of Fresnel microlenses. The design parameters of the microlenses like focal length, number of lenses, position, and aperture size can be quickly adapted to solve difficult measurement tasks. Furthermore the adaptive Shack-Hartmann sensor allows a pre-correction of the hologram to the wave-front to take care of larger aberrations and to achieve a higher measurement accuracy. We compare the adaptive sensor with a conventional Shack-Hartmann sensor and discuss new strategies to determine the wave-front that are possible with this active system.

In fringe pattern processing, quadrature operators are useful to obtain the corresponding modulating phase. In the case that a carrier exists (spatial or temporal), there are good methods for phase demodulation as Fourier analysis and asynchronous methods, for example. However, if there is no carrier or is too low, robust demodulation from a single image is a difficult task. In this work we present some recent advances in the processing of single fringe patterns with closed fringes based in a isotropic n-dimensional quadrature transform. In particular we address several problems related with the application of this quadrature operator. One of these problems is the Fringe direction, its role in the demodulation process is discussed and a practical method for its computation is presented. Fringe pattern normalization is also an important subject in the demodulation process from a singe image, taking this into account we present a technique for isotropic fringe pattern normalization based in the n-dimensional quadrature transform. All these techniques together configure a robust method for automatic demodulation of single fringe patterns. The performance and limitations of the method are discussed and illustrated by experimental results.

Liquid crystal light modulators are versatile optical elements that modulate amplitude and phase of coherent or incoherent light waves in space and time, thus enabling implementation of innovative optical processing and measurement systems. A brief introduction of the most commonly used liquid crystal effects and devices highlights the specific characteristics of "optical-grade" light modulators. These characteristics create unusual challenges for modulator designers requiring modifications of established manufacturing processes and development of new measurement concepts and systems for characterizing the liquid crystal light modulators. Specifically, a high precision measurement system for characterizing the voltage dependent complex transmissivity and a concept for extracting liquid crystal cell parameters is presented.

When conducting three-dimensional measurements with fringe projection, the quality of the grating applied for the generation of the fringes is very important. It has a direct influence on the achievable height resolution when phase-shifting algorithms are used. Hence, the created fringes should have an ideal sinusoidal intensity profile. In the past, Ronchi gratings, placed in a defocused position, or gratings written in nematic liquid crystal displays (LCDs) or generated with digital micromirror devices (DMDs) have been used. The latest developments in the field of ferroelectric liquid-crystal-on-silicon (F-LCOS) displays make these devices interesting as the fringe generating element. They offer both high speed operation and high flexibility. Unlike other devices, F-LCOS displays can also be operated under oblique incidence, still generating sufficient fringe contrast. We report on the characterization of a F-LCOS display and its application in two different setups. A comparison to Ronchi gratings and gratings written in transmissive twisted nematic LCDs is given. The achievable measurement resolutions as well as the measurement times are discussed. Results of measurements conducted on technical and medical surfaces are presented.

Due to the increasing use of aspherical optics, there is a demand for innovative measuring methods that allow the flexible testing of a wide variety of optical components. With the measuring method presented in this paper the imaging properties of the optical component under test may be determined by making it part of an imaging system consisting of an electronic camera with lens, a special grid pattern and the object itself. The grid pattern is taken as a reference object whose resulting image recorded by the camera is evaluated in order to obtain the properties of the tested optical component. In favor of a high measurement accuracy phase shifting techniques and photogrammetric methods are used in the course of the evaluation of the reference structure and the characterization of the tested optical surface. Unlike other techniques the presented measuring method does not require particular previous knowledge of the tested component and may be applied to both reflective and refractive optical surfaces. Measuring examples for reflective and refractive components are given, demonstrating the potential of the method.

Industrial- and multimedia applications need cost effective, compact and flexible 3D profiling instruments. In the talk we will show the principle of, applications for and results from a new miniaturized 3-D profiling system for macroscopic scenes. The system uses a compact housing and is usable like a camera with minimum stabilization like a tripod. The system is based on common fringe projection technique. Camera and projector are assembled with parallel optical axes having coplanar projection and imaging plane. Their axes distance is comparable to the human eyes distance altogether giving a complete system of 21x20x11 cm size and allowing to measure high gradient objects like the interior of tubes. The fringe projector uses a LCD which enables fast and flexible pattern projection. Camera and projector have a short focal length and a high system aperture as well as a large depth of focus. Thus, objects can be measured from a shorter distance compared to common systems (e.g. 1 m sized objects in 80 cm distance). Actually, objects with diameters up to 4 m can be profiled because the set-up allows working with completely opened aperture combined with bright lamps giving a big amount of available light and a high Signal to Noise Ratio. Normally a small basis has the disadvantage of reduced sensitivity. We investigated in methods to compensate the reduced sensitivity via setup and enhanced evaluation methods. For measurement we use synthetic wavelengths. The developed algorithms are completely adaptable concerning the users needs of speed and accuracy. The 3D camera is built from low cost components, robust, nearly handheld and delivers insights also into difficult technical objects like tubes and inside volumes. Besides the realized high resolution phase measurement the system calibration is an important task for usability. While calibrating with common photogrammetric models (which are typically used for actual fringe projection systems) problems were found that originate from the short focal length and the extreme opening angle of the system as well as the large depth of focus. The actual calibration method is outlined and current problems are shown. An improved calibration of the system is discussed for improved results in future.

As for any photogrammetric application, the accuracy of the derived object data is mostly dependent on the accuracy of the camera calibration. For many photogrammetric applications, use of a simple model for lens distortion in conjunction with co-linearity equations is sufficient. However, the combination of very close ranges and the large distortions typically associated with the lenses used on line scan cameras requires an extended lens model to account for variation of distortion within the object space. The fidelity of the calibration a model becomes particularly important where stringent tolerances are set, for example construction experiments or surface measurement.

We show a possibility for a rapid measurement of the shape of objects using color coding by stochastically geneated fringe patterns.

A dimensional measurement system also doing a tracking of objects movements is presented here. Especially, the method presented here permits to directly get the level curves of an object. It's an extension of the measurement methods by collimation, coupled with the use of a structured lighting with signature, formed of several luminous plans competing in a unique line. This line defines a set of points of the space at a fixed distance Z₀ of the measure head. The place of the points of the object where the lighting is reduced to a unique line is the searched level curve. The introduction of an asymmetry in the structure of the lighting permits to know the way as well as an approximate value of the value of the gap to the level curve of the position of the point of the illuminated object. The realized experiences permit to place the performances of such a system, and give the field of future applications.

In the past few years two form or topography measuring methods have been developed at PTB that are based on measuring the slope (angle) difference or the curvature, which both are intrinsic properties of the surface. In a laboratory environment the methods offer a very low uncertainty of measurement down to, or in part even below, the nanometer range. One of them is the Extended Shear Angle Difference method (ESAD), in which the angle difference signal of two surface points separated by a rather large shear is the basic measurement signal obtained with an autocollimation telescope. The other is Large Area Curvature Scanning (LACS) where the curvature values of the surface elements along a scan line are captured by a small interferometer. Error and uncertainty considerations are given for these methods which form the basis for determining the uncertainty which can be achieved under well optimized environmental conditions as necessary for tracing back and calibrating other measuring systems. Additionally, the uncertainty that can be reached in an industrial environment is discussed, and solutions are described to use these promising techniques also in such cases.

The development of eye-safe, imaging, scannerless laser radar systems based on gated viewing with a range of some hundred meters is difficult due to the lack of fast and amplifiable detector arrays for wavelengths in the near infrared (NIR). Nevertheless, one basic approach is to gate an InGaAs-FPA-camera with an electro-optical modulator (EOM) in the range of about 30 ns to achieve a sufficient resolution of depth. The laser radar works with a Nd:YAG-OPO laser of 1574 nm wavelength, 7 ns pulse length, and 25 Hz pulse frequency. Because of the EOM in conjunction with an adapted lens design and the resolution of 128 by 128 pixels FPA, the main interest is object detection. This requires imaging with optimized system performance to reach further target distances. In this paper, we present the simulation of the current system. Comparison of simulation data with indoor measurements is shown by the calculation of range images from a sequence of range slices. We discuss advantages of this simulation for range estimation, system comparison and design process.

Digital interferometry based device for measuring the thickness variations of the resin composite materials during blue light polymerization is described. The proposed device enables two types of quantitative measurements providing data for the total displacement and the dynamic behavior of displacement. The effect of the thermal expansion as well as polymerization shrinkage can be clearly resolved between different materials, curing lights and modes. The effectivness of our experimental device is illustrated with selected results obtained for a commercial dental material.

Classical triangulation sensors exhibit an orientation depend signal if the scattering properties of the work-piece are not symmetrical like at curved surface locations. This problem is avoided by rotational symmetric triangulation sensors. Due to this attractive property in a lot of applications such a sensor was introduced very recently on the market. This sensor is based on refractive optics and a special PSD detector, both custom made resulting in high costs. Additionally, the existing optical design approach does not offer an optical layout to start with, thus a good amount of trial and error is required and non-optimal solutions are probable. Therefore, there is great interest for a clear optical design strategy that results in layouts that are suitable also to use low cost commercial available detectors, such as CCD or CMOS image detectors. In this paper such a design procedure is presented for optical designs that use reflecting optical surfaces. Several solutions are depicted and discussed. The designs are not only attractive from the optical point of view and from detector considerations, but also from opto-mechanical design issues. For example designs with only one opto-mechanical part are possible. The resulting optical designs consist of aspherical surfaces which are obtained directly by using only some new relations of first order optics for off-axis objects. The designs are validated by exact ray tracing. These ray tracing results show already very good performance. Nevertheless, it was possible to further optimize the optical designs very efficiently using ray tracing software, thus yielding improved optical properties.

The future LHC experiment, ATLAS, features a muon spectrometer in which the alignment system must control the spatial position of the muon chambers with an accuracy of 30 μm and 200 μrad in a range of displacements of ± 5 mm and ± 5 mrad. The alignment system described in this paper, called praxial, fulfils these requirements. The paper reviews the relative and absolute calibration procedures and the production of the 1005 praxial sensors needed in ATLAS.

Optical 3D measurement systems are used in a lot of applications, for instance for quality control and reverse engineering. Active optical 3D measurement systems are very often based on the fringe projection technique. The key element of such a shape measurement system is the projection unit, where nowadays digital projection units based on LCD, LCoS, or DMD technology are used. Despite of a lot of opportunities these displays reveal some disadvantages for the use in fringe projection, which can reduce the phase measurement accuracy. In contrast to slide-like structures, these displays are separated in small picture elements -- so called active pixels -- with dimensions of about 8x8μm² up to 20x20μm². For this reason the cos function which has to be projected is spatially quantized. Therefore this function is not continuous. Another problem is the reproduction of the correct intensities given by the cos function in the projection. Usually, every projection engine shows some kind of gamma correction function or nonlinearity. This is either caused by the micro display itself or (in the case of video beamers) it is implemented into the beamer’s electronic to project proper visual images. All these effects will distort the intensity to be projected. All the mentioned effects cause phase measurement errors of different strength. Here we discuss different approaches to determine and compensate these influences of the projection engine to the 3D measurement. If the compensation is well accomplished, the accuracy of the measurement results may increase by up to one magnitude.

The report describes the laser goniometer intended for calibration of a circular optical encoders. This is one of the most perspective systems based on the rotating ring laser. This system provides the calibration of every line of optical encoder even if number of lines achieves one hundred thousands or more. The system operates in fully automate mode and calibration procedure takes very small time. The accuracy of calibration is on the level of 0,1 arcs. The rotation rate range is up to 5...10 revolutions per second. The important feature of the system is ability to measure dynamic error of optical encoder. The schematic of the system, analysis of errors, examples of implementation are considered in the report. The important part of the report is devoted to metrological support of calibration of an optical encoders. The angle standard based on the ring laser and the holographic optical encoder with systematic error on the level of 0,01 arcs is described also in the report.

In practical grazing incidence measurements using a commercial interferometer, repeatability and accuracy suffer from several effects related to part placement. In this paper, the authors analyzed three primary error resources in grazing incidence interferometry: incidence angle error, rotation angle error and included angle. The mathematical foundations of these errors as well as measurement results of several samples are presented showing the effects of each of these errors on. Using the test procedures described in the paper, the errors can be greatly reduced and the repeatability and accuracy increased by 20%.

For validation of forming simulations a methodology, using optical shape measurements, is here presented. In this work, the shape of a sheet metal component with complex geometry is measured using projected fringes. The component in consideration is a closed section steel profile that is formed using a forming tool. The shape is measured using the reduced temporal phase unwrapping scheme and calibration data for the calculation of absolute coordinates in the local coordinate system. Local 3-D coordinates from several measurements of this long object are merged together through a feature based stitching program. To validate the finite-element model, the final shape of the forming simulation is compared to the results from the shape measurements. Since no computer aided design model exists for the formed beam, the features in shape of the measured object are used as references when comparing results.

A novel calibration method that uses a planar object to determine the relative position and orientation between the CCD camera and the projector is developed. In this method the planar object is placed at different positions and orientations in the structured light system, the projector projects grids images on the plane, and the CCD camera takes images of the grids on the object. Using the fact that the object is planar we can recover the relative position and orientation between the CCD camera and the projector. An error model is also set up to correct the aberration of the light projector. Preliminary experiments suggest that this novel calibration method is flexible and is applicable to many shape measurement tasks.

Flat mirrors are often used for designing many optical measurement systems. These mirrors can be generally deformed with respect to environmental conditions during measurements. The detailed theory of deformation of the thin flat mirror, which vibrates in the direction of the normal to its surface, is introduced in our work. It is also derived the relation for the dynamic wave aberration. On the basis of this relation, it is carried out the calculation of the Strehl definition of the deformed mirror. Obtained results can be used for analysis of the influence of mechanical vibrations on the accuracy of optical measurement systems in various practical applications.

Monitoring biological relevant reactions on the single molecule level by the use of fluorescent probes has become one of the most promising approaches for understanding a variety of phenomena in living organisms. By applying techniques of fluorescence spectroscopy to labelled molecules a manifold of different parameters becomes accessible i.e. molecular dynamics, energy transfer, DNA fingerprinting, etc... can be monitored at the molecular level. However, many of these optical methods rely on oversimplified assumptions, for example a three-dimensional Gaussian observation volume, perfect overlap volume for different wavelength, etc. which are not valid approximations under many common measurement conditions. As a result, these measurements will contain significant, systematic artifacts, which limit their performance and information content. Based on Fluorescence Correlation Spectroscopy (FCS) and Fluorescence Lifetime Spectroscopy we will present representative examples including a thorough signal analysis with a strong emphasis on the underlying optical principles and limitations. An outlook to biochip applications, parallel FCS and parallel Lifetime measurements will be given with cross links to optical concepts and technologies used in industrial inspection.

Shearography is a full-field non-contact optical technique usually used for the investigation of defects in non-destructive testing. In shearography interferometric speckle patterns recorded before and after object deformation are correlated, often by subtraction, to yield correlation fringes sensitive to displacement gradient, a parameter closely related to surface strain. Shearography is sensitive to the component of displacement gradient that is determined by the direction of the illumination and viewing directions, the optical wavelength and by the magnitude and direction of the applied shear. To perform a multi-component measurement requires illumination, or viewing, from a minimum of three directions, followed by a coordinate transformation to obtain the in-plane and out-of-plane displacement gradient components. This would normally require the use of either multiple optical sources or multiple interferometer heads and multiple cameras. In this paper the authors use a single laser source, a single interferometer head and camera, with four views of the object ported from the camera lenses to the interferometer using a four-leg optical fibre imaging bundle. This approach allows four components of displacement gradient to be recorded simultaneously. Experimental results from the multi-component shearography instrument are presented.

The third order elastic moduli are fundamental parameters of elasticity characterizing the intrinsic nonlinear properties of solids. Their precise values are very necessary for description of nonlinear processes in materials. However, up to now many of the methods of determination of the 3d order moduli lead to reliable results mostly for crystalline solids. For isotropic materials these moduli are known with very low accuracy, that results in a necessity of new methods of their determination. We propose a new approach to determine the 3d order elastic moduli of non-crystalline materials by means of measurements of bulk strain solitary wave parameters.

This paper presents a portable optical measurement device named "optical rosette." Conical mirrors are used to make an ESPI interferometer with true radial in-plane sensitivity. Data acquired from this interferometer is used to measure in-plane rigid body translations, stresses and stresses gradients. A portable unit was developed and tested and its measurement performance is here evaluated. A modified multi-path Michelson interferometer was used as a reference measurement and rigid body translations in 2D were measured with a repeatability of ± 10 nm. Mechanical devices were used to generate a reference state stresses and stresses gradients. The performance of this unit to measure these quantities is also evaluated. Some examples involving industrial applications of this unit are also presented in this paper.

Using X-rays as information carriers it is possible to obtain data about motion inside an object that is opaque to visible light. An image correlation algorithm can be applied to a set of two X-ray images taken sequentially during a process, where the interior of the object is in motion. A displacement field describing the projected intermediate motion is thus obtained to sub-pixel accuracy. If this image set is expanded to contain several pictures separated in time, together describing the whole process, the images can be sequentially correlated to obtain a dynamic displacement field. In this paper, dynamical displacement field measurements have been carried out on two different objects, the first being a silo, where the motion of the flowing material in the center plane is investigated. In the second case, the motion in a layer of glue between two wooden plates is examined during a process where a shearing force acts on the system. The plane in which the measurements are carried out is defined by the use of a contrast agent, usually a tungsten powder seeding. The obtained displacement field, together with the known intermediate time interval between exposures, gives the velocity field in the seeded plane. The results show good agreement with the expected motion in the respective processes, but also provide evidence of behavior that would be undetectable using other existing techniques. A third experiment has also been carried out on a material requiring no contrast enhancing media. These measurements were performed on a chicken thigh being deformed by an external force. The results will be discussed in relation to their reliability and applicability. Further, the direction of future research will be indicated.

An optical measurement method is presented for the evaluation of phase objects. Pulsed TV holography in combination with digital speckle photography gives the possibility to study transient events. The phase object is placed in front of a diffuser, on which a CCD camera is focused. Holograms are recorded, with and without the phase object present. The speckle patterns are reconstructed and transformed to different imaging planes using a phase field for propagation. Speckle displacement fields are then calculated for the different imaging planes, which visualize the change of refractive index or phase gradients caused by the phase object. Together with the phase information in the hologram even more information is obtained. A flow of helium gas and a positive weak lens are used as phase objects in two test experiments.

A real-time system for analysing data from speckle interferometers, and speckle shearing interferometers, has been applied to the problem of detecting and sizing sub-surface delamination cracks in carbon fiber composite panels subjected to vacuum loading. Interferograms are continuously recorded by a CCD camera at a rate of 60 frames s^-1 with temporal phase shifting carried out at the same rate. Wrapped phase maps are calculated and displayed at 15 frames s^-1. These are unwrapped using a temporal phase unwrapping algorithm to provide a real-time display of the relevant displacement component. The damage identification procedure is formulated as an input output inverse problem through which system parameters are identified. The input of the inverse problem, the geometric moments (GM), is calculated from the surface displacement fields. The objective function of the optimization algorithm is defined as the squared difference between the GM obtained from the sample under test and that from a finite element (FE) model with a trial debonding. The optimum crack parameters are found by minimizing the objective function through the use of a novel implementation of real-coded genetic algorithms (ARGAs). The performance of the measurement procedure and analysis algorithms is evaluated using a set of carbon-fiber epoxy composite samples with systematically-varying and well-characterized defect geometries.

A new white-light interferometric technique characterized by the range of measurable distances dependent on the amount of dispersion in an interferometer is proposed. We show that processing of the spectral interferograms recorded by a low-resolution spectrometer and including so-called equalization wavelengths can be extended to precise the determination of positions or displacements of the interferometer mirror to reach sub-micron or even nanometer resolution. In contrary to standard spatial-domain white-light interferometry employing interferometers balanced for dispersion we use a dispersive Michelson interferometer with fused-silica optical element (optical sample or beamsplitter) of know thickness. Knowing both dispersion and the thickness of the interferometer optical element and using a least-squares fit of the theoretical spectral interferograms to the recorded ones we obtain the positions of the interferometer mirror. Within two different configurations of a dispersive Michelson interferometer, one with an optical sample and the other with one a beamsplitter, we show that the range of measurable displacements depends on the thickness of the optical element.

Shearography has been validated as fast and reliable inspection technique for aerospace components. Following several years phase of evaluation of the technique, meanwhile, shearography has entered the industrial production inspection. The applications basically range from serial inspection in the production line to field inspection in assembly and to applications in the maintenance and repair area. In all applications, the main advantages of shearography, as very fast and full field inspection and high sensitivity even on very complex composite materials have led to the decision for laser shearography as inspection tool. In this paper, we present examples of recent industrial shearography inspection systems in the field of aerospace. One of the first industrial installations of laser shearography in Europe was a fully automatic inspection system for helicopter rotorblades. Complete rotor blades are inspected within 10 minutes on delaminations and debondings in the composite structure. In case of more complex components, robotic manipulation of the shearography camera has proven to be the optimum solution. An industry 6-axis robot gives utmost flexibility to position the camera in any angle and distance. Automatic defect marking systems have also been introduced to indicate the exact position of the defect directly on the inspected component. Other applications cover the inspection of abradable seals in jet engines and portable shearography inspection systems for maintenance and repair inspection in the field.

A computed tomography (CT) apparatus using laser beam and photodiode is currently developed for faulty detection in transparent materials such as diamonds and crystals. Faults in diamond and crystals are hard to be detected using visual inspection. A unique and artistic feature may appear on the surface due to internal cracks or anomalies. While those are hard to be distinguished, the unique feature appeared may be more precious compare to any perfect objects. A simulation study for understanding the physics behind the phenomena has been performed. This has been followed by set-up of mechanical and sensor system along with the electronics readings. Previous results on individual testing show that we may develop a pretty optical CT system that can be used for fault detection in any transparent materials.

An inspection system is developed to replace manual inspection in a production line for car parts. The system, based on projected structured light, combining Gray code and phase shifting and using B/W CCD cameras and multi-media data projectors, provides robust height measurement images with a high resolution. By carefully observing a number of parameters, it is possible to attain this high resolution in a large measurement volume even with low-cost, off-the-shelf components. We have been able to achieve a noise floor in the phase determination of 30 mrad, which is better than the much reported 1 part in 10,000. The use of 4 cameras, 3 projectors and a turning operation allows total coverage of the complex shape part. A model of normal parts is designed using height measurement images of normal parts. This model represents both expected part dimensions in all camera views as well as normal variations. In order to compare measurements of new parts with the model, an alignment of the images is performed. The deviations between the measured part and the model are analyzed. Deviations outside the normal variation are classified as faults. The system is thus able to find geometrical faults as small as 2x2x0.25 mm in a part that measures roughly 400x400 mm and can decide whether or not to remove a part from the production line. Integrating optical metrology, image processing and robotics, we are able to design a complete system for in-line inspection of car parts with total coverage that is able to keep up with the production cycle time.

Visual features of lumber can be used to assure its quality in stiffness and strength. Specifically, the average annual ring distance of the planks and the position of the center of the annual rings of the front side supply a close relation to some quality parameters of planks. Unfortunately, it turns out to be difficult to detect the average annual ring width by simple image vision methods due to distortions in the front side image of a plank caused by the cutting process. In this paper we propose two integrating methods which are capable of being used in an industrial application. One is based on quantizations of color images, the other on local Fourier transformations to detect the main wave in an image.

A scanning laser Doppler vibrometer is used to make quantitative measurements of 2D ultrasound fields in air. The laser light traverses the measurement volume to and from a rigid reflector and determines the velocity of the change in optical path length, which with constant geometry only depends on the changes in index of refraction. Assuming adiabatic conditions, the refractive index rate is proportional to the sound pressure rate and quantitative measures of the sound field are possible to achieve. The emitted or scattered ultrasound being measured origins from a source or object outside the recording area. Using phase conjugation the sound field is then digitally reconstructed outside the recording area, and the reconstructed phase and intensity reveals the location of the source or object. The combination of several such reconstructions of ultrasound fields of different wavelengths, so called wavelength scanning, provides an intensity map that very accurately gives the position of the source. This opens many new possibilities to study hidden or unknown sound sources or scattering objects.

Quality control describes numerous methods for monitoring the quality of a production process. With respect to this it will be a growing requirement on optical 3D-measurement techniques to reach the demands of the measurement capability. Here the limitations to fulfill these demands under industrial conditions are discussed when using fringe-projection technique for 3D-measurement. The analysis is done while measuring an automotive stamping part and a 3D-gauge with a telecentric fringe projection system, as examples. In the analysis we determined some geometric features like diameter of hole and bending angles of parts of the object surface. The results demonstrate the possibility to achieve a standard deviation of lower than 1 μm within a measurement volume of 90 mm in diameter for the geometric features. Due to the low standard deviation a measurement capability has been reached like tactile measurement systems. To achieve this the influence of the locale choice of the geometric fitting procedure onto the point cloud has to be taken into account.

Optical measurement techniques are being used more and more for quality control in the production process. An important problem when trying to implement optical measurement systems, and in particular the scanning laser Doppler vibrometer (SLDV) which is considered in this paper, is that user interaction is always required. The need for user interaction implies an increase in testing time and cost and also brings an additional source of variability of the test results. In this article, a completely autonomous test procedure is developed to track the vibration behavior of a product during the production process (this includes automatic laser focusing, position calibration, object recognition, grid generation and mode estimation). The proposed procedure typically requires a few minutes only to automatically determine a high resolution model of the vibration behavior. The method will be validated on measurements of an electronic circuit board.

We report an interferometric analysis of 0.5mm thick lithium niobate crystal sample by making use of a reflective grating interferometer and a digital holographic technique. The lithium niobate wafer was subjected to electric field poling in order to obtain two antiparallel ferroelectric domains. The crystal was then mounted into one arm of the interferometer in order to study the phase map and consequently to evaluate the effects of domain reversion at the boundary. Engineering of periodically reversed domains in LN is extensively used for quasi-phase-matching applications while the ferroelectric structure investigated here is suitable for producing electro-optically controlled deflector or switch devices via total internal reflection at the domain interface. The above mentioned applications require deep knowledge of how the domain reversal process affects the optical properties of the ferroelectric crystals.

Forging and sheet metal forming tools are subject to strong, partial wear in use. On the one hand wear-protection layers are applied before use, and on the other hand worn tools are repaired by manual build-up welding after use. At present the repair of such tools is carried out in separate work processes with a small degree of automation and a high proportion of manual activity. This leads to long running times and potential sources of error. Our approach to solve these problems is to develop a repair cell which will facilitate automated repairs, beginning with measurement of the worn tool areas through to the repaired, fully operational tool. This paper will describe the overall concept of this repair cell with a special focus on optical metrology. Challenges of integration and demands for different sensor types are presented as well as the specified interfaces between different processing stages during manufacturing.

In recent years industrial photogrammetry has emerged from a highly specialized niche technology to a well established tool in industrial coordinate measurement applications with numerous installations in a significantly growing market of flexible and portable optical measurement systems. This is due to the development of powerful, but affordable video and computer technology. The increasing industrial requirements for accuracy, speed, robustness and ease of use of these systems together with a demand for the highest possible degree of automation have forced universities and system manufacturers to develop hard- and software solutions to meet these requirements. The presentation will show the latest trends in hardware development, especially new generation digital and/or intelligent cameras, aspects of image engineering like use of controlled illumination or projection technologies,and algorithmic and software aspects like automation strategies or new camera models. The basic qualities of digital photogrammetry-like portability and flexibility on one hand and fully automated quality control on the other -- sometimes lead to certain conflicts in the design of measurement systems for different online, offline or real-time solutions. The presentation will further show, how these tools and methods are combined in different configurations to be able to cover the still growing demands of the industrial end-users.

Progressive ophthalmic lenses involve high resolution technological manufacturing processes, due to the particular non-symmetrical, aspherical form of their convex surface. However, the testing of the surfaces is not usually performed using whole-field methods because of the high dynamic range and resolution required for the slope changes in the convex surface. Applying some simple enhancements, a robust Ronchi test technique can be used to obtain accurate power distribution maps of commercial progressive lenses. In this technique, a CCD detector is used as a high resolution slope map, which combined with multiple acquisition techniques, allow for high resolution measurements of both lateral displacement (10^-4 m) and slope measurements (10^-5 rad) with the required dynamic range in slope measurements for progressive power lenses. The power maps of different types of progressive lenses are presented, showing the differences between lens design and manufacturing. The ability of the enhanced Ronchi test technique to quantitatively map power variations with important slope changes is demonstrated.

This paper present new optical configurations in speckle shear photography to measure in-plan displacement and the strain in real time using photorefractive (PR) crystals as recording medium. Speckle photography studies are made using a simple two-beam coupling configuration PR beam coupling in barium titanate crystals is characterized experimentally by measuring the signal beam gain and the exponential gain coefficient at 440 nm, 632.8 nm and 780 nm. In speckle shear photography, a diffused object illuminated with two parallel narrow laser beams is imaged inside the crystal, and a pump beam is added at this plane. The speckle patterns due to each beam and the pump beam produce index gratings. When the object is deformed, the speckle patterns shift consequently. We now have four speckle fields two generated from the interaction of pump beam with the index gratings and two pertaining to deformed states directly transmitted through the crystal. Thus, the fields from respective points on the object interfere after passage through the crystal and produce the Young's fringe patterns. Due to strain, the fringes in each pattern are of different width and orientation, resulting in the generation of a moire pattern. The strain is obtained from the width and orientation of the fringes in the moire pattern. The experiments are conducted on a specimen with a notch, which is subjected to tensile loading. The above studies are carried out at three different laser wavelengths, namely, 441.6 nm, 632.8 nm and 780 nm and the results are compared.

In the metal forming processes, the sheet metals are often prone to various defects such as thinning, dents, wrinkles etc. In the present manufacturing environments with ever increasing demand of higher quality, detecting the defects of formed sheet metal using an effective and objective inspection system is the foremost norm to remain competitive in market. The defect detection using optical techniques aspire to satisfy its needs to be non-contact and fast. However, the main difficulties to achieve this goal remain essentially on the development of efficient evaluation technique and accurate interpretation of extracted data. The defect like thinning is detected by evaluating the deviations of the thickness in the formed sheet metal against its nominal value. The present evaluation procedure for determination of thickness applied on the measurements data is not without deficiency. To improve this procedure, a new evaluation approach based on medial axis transformation is proposed here. The formed sheet metals are digitized using fringe projection systems in different orientations, and afterwards registered into one coordinate frame. The medial axis transformation (MAT) is applied on the point clouds, generating the point clouds of MAT. This data is further processed and medial surface is determined. The thinning defect is detected by evaluating local wall thickness and other defects like wrinkles are determined using the shape recognition on the medial surface. The applied algorithm is simple, fast and robust.

A device has been designed for off-line optical paper inspection and quality control of stripes and holes in the cigarette paper. Hardware description is first presented including main paper characteristics to be measured. Typical paper stripe and holes structures are then discussed with image processing and analysis considerations to discriminate these structures, focusing in the problems derived from the small area of holes and of their internal structure that is analyzed with a confocal microscope. Algorithms for image processing and analysis are described. These algorithms involve equalization, binarization, stripes structure detection, holes distribution and statistics.

The speckle interferometry is an effective technique in the displacement measurement of a structure with a rough surface. However, when the fringe scanning technology is introduced to speckle interferometry for improving the measurement resolution, two speckle patterns before and after the deformation of the measurement object and another speckle pattern under different situation from two speckle patterns shown before generally are required. In this paper, the methods for introducing the fringe scanning method are proposed by controlling the phase of specklegram as a fringe image using filtering technologies. Then, the spatial and the temporal fringe analysis methods that use only two speckle patterns are proposed for speckle interferometry. As results, the high precise fringe analysis can be realized by the fringe scanning methods using only two speckle patterns in the displacement measurement with a large deformation. The results show that the possibility of the method based on spatial fringe analysis methods in practical uses would be higher than that of temporal methods.

By China's entry into the WTO, Chinese as well as German companies are facing the question, how to minimize the risk of unfamiliar cooperation partners when developing products. The rise of customer demands concerning quality, product diversity and the reduction of expenses require flexibility and efficiency with reliable component suppliers. In order to build and strengthen sino-german cooperations, a manufacturing control using homogenized and efficient measures to assure high quality is of vital importance. Lack of unifications may cause identical measurements conducted at subcontractors or customers to be carried out with different measurement processes which leads to incomparable results. Rapidly growing company cooperations and simultaneously decreasing of manufacturing scope cause substantial difficulties when coordinating joint quality control activities. "ProSens," a sino-german project consortium consisting of industrial users, technology producers and research institutes, aims at improving selected production processes by: Creation of a homogeneous quality awareness in sino-german cooperations. Sensitization for process accompanying metrology at an early stage of product development. Increase of the process performance by the use of integrated metrology. Reduction of production time and cost. Unification of quality control of complex products by means of efficient measurement strategies and CAD-based inspection planning.

A new measurement method based on digital holography is proposed. The holographic registration of interferometric fringes generated on a surface under study using CCD camera and their reconstruction allow the determination of the surface shape with the aid of a computer program. Problems related to limited resolution of CCD camera devices are considered. The results obtained by numerical means are presented. The discussion on further possibilities is given.

The method of scattering media probing with the use of partially coherent illumination and speckle contrast analysis is considered. The additional polarization discrimination of detected speckles gives the possibility to select the components of scattered field which propagate in probed medium at different distances. Theoretical analysis of the polarization-sensitive speckle contrast as being dependent on the coherence properties of probe light and probed medium parameters is caried out. Experimental results obtained with use of the considered technique for weakly ordered systems characterized by non-diffuse scattering regimes are presented.

Our work analyzes several multiframe phase-shifting algorithms with unknown values of phase shifts. The presented paper offers new algorithms for evaluation of phase values in interferometric measurements. Nonlinear multi-frame phase-shifting algorithms, which use five, six and seven intensity frames to determine phase values in interferometric measurements, are described theoretically. The proposed algorithms compensate for linear phase-shift errors, i.e. miscalibration of phase-shift, which are very common in practice of interferometric measurements. The phase-shift value is assumed unknown but constant in these algorithms, so that at least four phase shifted intensity frames have to be recorded. An advantage of the described algorithms is a possibility of pointwise phase-shift calculation. An analysis of proposed algorithms with respect to possible influences on the process of interferometric measurements is also carried out. Several important potential error sources were chosen and the sensitivity and accuracy of phase evaluation algorithms was compared. The algorithms derived in this work can be used in any phase-shifting measurement technique and they offer the advantage of insensitivity to the linear phase-shift errors.

Our paper concerns with statistical processing of digitally recorded straight equispaced fringe patterns by a numerical method based on discrete Fourier transforming (DFT) of the input data, which has the advantage of faster computation than the usual least square fitting method, that we have presented in a previous paper. This new method leads to the same accuracy as the least square fitting method and it is more convenient to use for processing fringe pattern with high harmonic order features.

The accuracy of a wave front generated by a lithography phase-shifting mask is essential for the performance of a lithography system. The main task of mask inspection is therefore to detect and quantify phase distortions caused by defects on the mask. There are three different classical ways to get the phase information generated by an object: First, interferometric techniques such as Linnik- or Mach-Zehnder-interferometry, second the method of spatial filtering, as is done in quantitative Zernike phase contrast microscopy, and third the use of phase-retrieval. The first two methods need a highly adapted set-up and are difficult to adjust. Phase retrieval, however, just needs a set of intensity images captured under different focus conditions to reconstruct the phase information. Therefore, this method is ideally suited for fast inspection in an industrial environment. We present phase measurements on MoSiN phase masks reconstructed on the basis of the transport of intensity equation. The effect of low-pass filtering inherent in this method is quantitatively investigated by numerical simulations done with our microscope simulation tool MicroSim. By systematic variation of imaging conditions as well as object-parameters we give insight to the applicability and the limits of the method. Comparison to Mach-Zehnder-interferometry allows the evaluation of the method also for partially coherent illumination conditions.

Digital holography gives new capabilities to the measurements of size, position, shape or velocity of different objects. In general in-line arrangement is used with a CCD device recording the interference pattern and the reconstruction is performed by numerical methods in computer. Some new ideas were used to improve the process of exposure and calculation techniques. The phase-shift technique is widely used in digital holography. Now it is proposed to use the two-reference-beams arrangement, which can replace the phase-shift methods at different cases. Three holograms -- the interference pattern of the object and the two reference waves and the three intensity distribution (of the beams, separately) are recorded and the phase evaluation can be done numerically. The advantage of FFT-algorithm is also applied reducing the computer running time in reconstruction of the image. We have developed another computational method for the reconstruction using Monte-Carlo simulation.

For all microrobot handling, a so called "Global Positioning system" must give the position of the robots to the robot control. At the University of Karlsruhe a position sensing system called "MPS" is currently being developed. With a resolution of 1 μm and a turn-around-time of 0.2s this system is very exact and fast. Working touchless, its measurement principle works two-staged: the first approximation step is using the photogrammetrical principle, these results based on interferometrical effect delivers the mentioned resolution of 1 μm. The freely movable robot is equipped with three marks working both as a photogrammetrical and as a Moire-based mark by having three of four coincidental cosinusodial shaped full circles printed upon it. A high-resolution CCD-camera is watching the whole scene permanently. Because of the Moire-effect, there are two grids needed to generate the Moire-fringes which have to be analyzed by the connected computer with the developed software. The first grid is the grid on the robot marks. The second grid, which is fixed to the working plate, is virtually created inside the computer (this grid is also circular and cosinusodial shaped). Merging the CCD-picture (after some image processing) with the virtual grid, the Moire-effect will appear. With a overspecified linear equation system, the centre point of the mark can be calculated then.

We report on the depth-scanning fringe projection technique (DSFP) which is an innovative triangulation method for absolute 3-D profiling of macroscopic scenes. This measurement principle combines the confocal principle with the fringe projection and phase evaluation techniques known from white light interferometry. Scanning of the focal plane and additional lateral shifting allow the phase to be determined for any desired depth range of the measurement volume. Hence, the limitations of the depth of sharpness occurring with projected light techniques can be overcome. A 3-D calibration method has been implemented in order to deal with the problem of geometrical aberrations and to provide a 3-D point cloud. The well-known direct calibration method has been adapted to our DSFP setup. It has been completed to a set of three polynomial transformations which allow to include the depth-scanning principle in the calibration of the system.

We present a novel concept of phase-shifting diffraction-grating interferometer, which is intended for the optical testing of concave mirrors with high precision. The interferometer is configured with a single reflective diffraction grating, which performs manifold functions of beam splitting, beam recombination, and phase shifting. The reference and test wave fronts are generated by means of reflective diffraction at the focal plane of a microscope objective with large numerical aperture, which allows testing fast mirrors with low f-numbers. The fiber-optic confocal design is adopted for the microscope objective to focus a converging beam on the diffractive grating, which greatly reduces the alignment error between the focusing optics and the diffraction grating. Translating the grating provides phase shifting, which enables to measure the figure errors of the test mirror to nanometer accuracy.

The expansion of the field of diffractive optics applications is accompanied by toughening performance requirements for CGHs. Optical testing sets especially high requirements, concerning wavefront accuracy and diffraction efficiency. The key point in fabrication technology is the writing system creating the photomask or the profiled pattern. The diffractive optics fabrication facility at ITO (University of Stuttgart) is based on the circular laser writing system CLWS-300. This flexible and high-accurate tool was originally designed for binary diffractive optics fabrication. This paper presents novel enhancements of this system allowing direct laser writing of a wide range of binary and continuous-relief CGHs on photoresist layers, chromium films and LDW-glass. Main topics of the enhancements were the scanning accuracy and exposure control. Many types of CGHs (binary precision holograms for optical testing, Shack-Hartmann arrays, microlens discs for confocal microscopy, diffractive interferometer objectives, doughnut generators etc.) have been manufactured using the developed algorithms and hardware.

We proposed a novel interferometer, which can measure the 3-dimensional coordinates of freely moving objects in space. The interferometer is composed of two fiber ends and three photo detectors. Frequency stabilized laser is incident into an optical fiber, and then split by the fiber beam splitter into two fiber ends. One fiber is used as the fixed reference arm, and the other as the movable test arm of the interferometer. By using servo control on one arm, the phase difference of the laser beams being emitted from the two fiber ends is forced to be kept constant. Beams from each fiber end are combined at the photo detectors on which interference fringes are formed. The displacement of the distances of the moving fiber end (MFE) from the three detectors can be measured by analyzing the interference fringe. From the measured distances of the MFE from each detector, the 3-dimensional coordinates of the MFE are obtained in real time by using the triangulation. Since the wavefront of the beam from the MFE is spherical, the displacement of the MFE is not restricted to a specific direction, which requires no guiding rail for the moving object. This interferometer could be applied to situations where 3-dimensional coordinates of freely moving objects are being measured with high precision.

The projection of fringes onto objects in some 3D-measurement systems has two main reasons: First, to solve the problem of homologous points for the camera images and second, to create a continuous metric in the object space. The second effect leads to the well-known sub-pixeling accuracy. The accuracy of such measurement systems is not limited by the pixel size of the camera. But, depending on some surface-discontinuities (i.e. steps) and the viewing direction of the camera, this principle is not valid for a certain number of pixels. When a camera is viewing "downstairs," these pixels get the phase information from the upper and the lower step. By using our very precise measurement system kolibri, this effect is evident on most complex technical surfaces and is clearly distinguished from statistical noise. We discuss the different circumstances of this effect and give a well-adapted algorithm for eliminating these errors.

We present an interferometrical setup and its application as a diameter measuring device in a machine tool. The optical setup is a folded Linnik interferometer. The proposed pen-like configuration is very space saving. The probing part of the sensor head fits bores from a diameter of 15 mm. The interferometer works with light of a short coherence length for unambiguous distance signals. The reference mirror is scanned by means of a tuning fork with a frequency of 1.1 kHz within a range of more than 0.2 mm. A design of a sensor head is given. The device can be fixed in the master chuck of a milling machine. The nominal diameter of the bores to be measured is preset to 40 mm, but it can be chosen from 20 mm to 55 mm using the given optical components by changing one internal distance. Measuring results show the capability of the device to analyze the position, the diameter and the shape of bores. The device can be used to establish a very fast quality control loop and therefore it will help to improve the efficiency of the production process.

This paper presents a combined system based on digital speckle pattern interferometry and laser annealing to determine residual stresses in ductile materials. The system allows the measurement of the radial in-plane displacement field generated when a specimen subjected to residual stresses is locally heated. This novel approach for measuring residual stresses has the advantage of being nondestructive and can be easily applied to in situ tests. The description of the combined system is followed by the presentation of preliminary results which illustrate the ability of both techniques to identify residual stress fields and also to determine their principal directions.

The rapid development of spatial light modulators in the past few years opened an exciting new area in coherent optical metrology. Commercially available liquid crystal spatial light modulators (LC SLM's) are capable to optically reconstruct digital holograms in quite good quality, so the reconstructed real image of an object can be used as a coherent illuminating mask in optical measurement methods like digital holography (DH) or Electronic Speckle Pattern Interferometry (ESPI). In our work we present experimental results of measuring the difference and sum of two displacements of an object pair (master and test object) using these two techniques. We describe the measurement setups in a DH and an ESPI arrangement, which are capable to project the real image of the master object -- using its previously recorded digital holograms in the SLM device -- onto the test object. If two digital holograms, recorded before and after the deformation of the master object, are used to illuminate the test object in its initial and deformed state, four images can be recorded either in the DH setup or in the ESPI setup. Using these four-four images, the contour fringes of the difference and sum of the master and test object displacements can be calculated. In the case of DH, these images are digital holograms, which are subject to numerical reconstruction, and in the case of ESPI the four images are plain speckled images, which can be used to obtain ESPI fringes (correlograms). As a result, we present several fringe images of our object pair made with these two methods.

The goal of this work is the development of a new application of fiber Bragg gratings sensors (FBG), in order to measure the pre-load transmitted to a couple of roll bearings, inside a high speed electro-mandrel. FBG sensors has been preferred to classical electrical strain gauges because of their intrinsic immunity to electromagnetic fields. This last are very strong in the application here considered, and moreover its effect cannot be easily filtered because it occur at the same frequency of the phenomena to observe. The mechanical component design, used to convert the preloading forces in measurable strain, is also illustrated. On this component the fiber optic sensor is installed and the load cell obtained is calibrated. An uncertainty value equal to 1% of the full scale, is obtained. The effective pre-load value induced by the tightening system on the rolling bearings has been measured with the system developed.

It was discussed the using multi-frequency YAG:Nd infrared laser for long range non-destructive acoustic vibration measuring system for structural modal analysis. It was shown both theoretically and experimentally that a coherent function of a laser with acousto-optic device has an oscillations with the period depending on a laser cavity length and a number of resonator modes. The advantages of using the acousto-optic devices in a tandem scheme were discussed. The adjustment of such system due to on-axis shift is suitable for object selection. It was shown that the coherence function has optimal form for selecting a transparent object on light beam trace and optical delay line for semiconductor laser with short resonator can tune on maximum of coherent function at long distance. Accordingly the mutli-frequency laser can be used in heterodyne optical scheme instead of more costly stable one-frequency laser. A simple scheme of velocity measuring based on a semiconductive two-mode laser was proposed. Conclusions regarding the possibility using the resonator with acousto-optic device inside with a frequency chirp beam using for interferometer phase modulation measure system are arrived at. The application of a frequency-shifted laser beam to practical optical measuring system may improve the processing efficiency without additional adjustments.

A novel compact roll angular displacement measurement system based on the use of wave retarder is presented. It utilizes the technique of common-path, heterodyne interferometry to detect the phase shift caused by roll angular displacement of a wave retarder fixed on a moving system. This novel system is set up and verified both theoretically and experimentally. Demonstrated by experiments, it can measure the roll angular displacement of a moving system down to microradian over the range of a half-degree.

Computer simulation of the interferometer combining properties of low-sensitive Talbot interferometer and high-sensitive holographic interferometer is considered. The interferometer has four output channels having different sensibility. Channel sensibility can be varied by means of space filtration. Wide range of the interferometer sensibility allows using the interferometer for investigation of complex phase objects. The base of the interferometer is the holographic Talbot effect found by authors. The basic object of the computer simulation is to find the method of decoding of complex interferometric patterns produced by the interferometer. Some results of the computer simulation are presented in report. The obtained results were compared with results obtained in optical experiments under the same conditions.

A simple technique to determine the diffusion coefficient in transparent liquids is developed. The method uses fringe projection with white light source. The diffusion coefficients obtained were compared with those obtained with other experimental methods.

In this paper, the authors present a new low-level birefringence detection (LLBD) system using photoelastic modulation technology. The LLBD system, operating at wavelength 1152 nm, determines point-by-point the magnitude and orientation (angle of fast axis) of birefringence therefore stress states in the sample. The principle of this LLBD system was described and experimentally verified. The resultant instrument shows high sensitivity and good repeatability for measurement. A sensitivity of magnitude of birefringence about 0.03° (or 0.096 nm at 1152 nm) was established for measurement. Several samples with different levels of birefringence were studied using LLBD system.

Today, the vibration analysis of laminated structures represents an important field in engineering metrology. The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. However to perform full-field, non-contact, and real-time measurement, optical methods are a preferable choice. Recently, interesting results have been obtained by Electronic Speckle Pattern Interferometry (ESPI). In this paper, we report an alternative electro-optical system based on local digital speckle correlation. This new method permits the development of an instrument that is cheap, safe and easy to use. We employ the proposed method to investigate the vibration characteristics of piezoceramic/nickel-alloy laminated plate. The circular membrane is a composite made of a nickel alloy disk with thickness 0.1 mm and diameter 30 mm, to which a piezoceramic disk, with the same thickness and a smaller diameter (24 mm) is bonded. A brief analysis of the technique and some experimental results are presented. Finally, the numerical finite element calculation is also performed, and the results are compared with the electro-optical measurements.

Theoretical resolution limits of evaluation of centroid shift in fiber optic Bragg grating sensors are analyzed. In the theoretical model, it is assumed that random additive Gaussian noise in a sensor signal acquisition equipment is the main origin of the system error. To provide noise resistant demodulation, a new optimal signal processing algorithm is suggested. It allows accurate detection of the Bragg wavelength shifts within large range and keeps resolution very close to theoretical limit imposed by a random noise. The new demodulation technique is also compared with well known centroid detection algorithm.

Fast and robust 3D quality control as well as fast deformation measurement is of particular importance for industrial inspection. Additionally a direct response about measured properties is desired. Therefore, robust optical techniques are needed which use as few images as possible for measurement and visualize results in an efficient way. One promising technique for this aim is the inverse pattern projection which has the following advantages: The technique codes the information of a preceding measurement into the projected inverse pattern. Thus, it is possible to do differential measurements using only one camera frame for each state. Additionally, the results are optimized straight fringes for sampling which are independent of the object curvature. The hardware needs are low as just a programmable projector and a standard camera are necessary. The basic idea of inverse pattern projection, necessary algorithms and found optimizations are demonstrated, roughly. Evaluation techniques were found to preserve a high quality phase measurement under imperfect conditions. The different application fields can be sorted out by the type of pattern used for inverse projection. We select two main topics for presentation. One is the incremental (one image per state) deformation measurement which is a promising technique for high speed deformation measurements. A video series of a wavering flag with projected inverse pattern was evaluated to show the complete deformation series. The other application is the optical feature marking (augmented reality) that allows to map any measured result directly onto the object under investigation. Any properties can be visualized directly on the object’s surface which makes inspections easier than with use of a separated indicating device. The general ability to straighten any kind of information on 3D surfaces is shown while preserving an exact mapping of camera image and object parts. In many cases this supersedes an additional monitor to view results and allows an operator to investigate results on the object, directly.

Speckle photography is a powerful tool adequate to determine small displacements, in micrometer range. Through this information, other characteristics of structure deformation under loads can be determined as stress and strain distribution. In this paper we present the results obtained by applying speckle photography technique to study the behavior of building model. The displacement whole field was obtained by pointwise method. Also we present the strain distribution obtained by finite element method to compare the results obtained by these techniques.

A new spectral-domain white-light interferometric technique employing a low-resolution spectrometer is used for dispersion characterization of optical fibers. The technique utilizes the fact that the spectral interference fringes are resolved at the output of a tandem configuration of the compensated (non-dispersive) Michelson interferometer and a two-mode optical fiber only in the vicinities of so-called equalization wavelengths at which the optical path difference (OPD) in the interferometer is the same as the intermodal group OPDs. Processing of these interference fringes in case of a two-mode optical fiber and measuring the OPD adjusted in the interferometer as a function of the equalization wavelength serve for dispersion characterization including the spectral dependence of both the difference between propagation constants of modes and the intermodal group OPD in the optical fiber. The white-light spectral interferometric technique is used for both circular-core and elliptical-core (highly birefringent) optical fibers. The measured dispersion characteristics of the optical fibers are compared with those corresponding to the results of an adequate theoretical analysis using the known parameters of the optical fibers.

A highly sensitive pressure sensor based on two Mach-Zender interferometers is described. The interferometer measuring and reference channels are made of single-mode W-lightguides. The measured sensitivity was shown experimentally to be 65•10^-2dB•Pa^-1 m^-1.

Our work analyzes an influence of the change of imaging conditions on the accuracy of optical and optoelectronic measurement systems, which are used in various industrial branches, e.g. in mechanical engineering, optical industry, building industry, etc. It is shown that in case of the change of position of the measured object the imaging properties of the used optical measurement instrument are changed. This position change affects the image quality. If some optical measurement system is aberration free for a specified position of the measured object, then for other object positions the optical system has aberrations. The consequence of this effect is the change of the measurement accuracy for the specific optical system. The described effect is not removable on principle and it is necessary to take account to it in high accuracy measurements.

Review of holographic terrestrial aerospace research and in-orbit holograpic investigations performed in microgravity conditions during the last century is given. Terrestrial aerospace research by means of opto-digital laser speckle metrology is considered. The prospects of holographic in-orbit research in the 21st century are regarded. Outlook for holographic research during future interplanetary missions in the 21st century is discussed. Advanced holographic techniques are presented. These innovative techniques suit ideally for monitoring of various physical processes, studying of vibrations and static deformations, testing of microelectronics and MEMS. They enable quite novel possibilities of rapid, elegant, high volume production of holograms and holographic interferograms both in the terrestrial environments (industrial, natural outdoor environments) and in microgravity outside the Earth. Advanced holographic techniques are so simple that their usage in the planetary environments of the future space missions seems quite natural. They can be used right now for holographic research aboard currently orbiting International Space Station. Advanced holographic techniques might be utilized quite soon on Mars. One of the early variants of advanced techniques invented by this author was used to obtain the first ever holograms and holographic interferograms of different physical phenomena outside the Earth aboard navigating spaceships. The unique feature of innovative techniques is the possibility to work in real time in situ. It is possible to obtain holograms and holographic interferograms in any brightly lit environment, including sunlit environments. The last might be very important in the future planetary missions. Holographic minirobot for planet-based investigations is proposed. Quite novel modifications of advanced techniques permit to process holographically tremendous amounts of data per second; far exceeding near future potentialities of sophisticated computer systems applied to the tasks of 3-dimensional imaging or to the tasks of optical metrology. Experimental data properly illustrating novel vast possibilities and prospects for the future in-orbit and interplanetary space research are presented.

The aim of this paper is to reveal the high potential which two-photon polarization spectroscopy can provide for the investigation of atomic species in combustion processes. As a first demonstration, we applied this technique to determine number densities and kinetic temperatures of atomic hydrogen in flames at atmospheric pressure. Our method, developed for laser-aided plasma diagnostics, renders possible absolute optical measurements in such dense combustion environments characterized by the presence of many kind of reacting species and a plasma state far off thermodynamic equilibrium. The measured polarization signal is caused only by the 1S-2S two-photon resonance of hydrogen atoms and not perturbed by the strong quenching rates or by the complicated radiative transfer. We performed the experiment with pulsed UV radiation of the highest spectral quality possible, i.e. single-mode laser radiation tunable around 243 nm with ns pulse duration close to the Fourier transform limit.

Local electric field strengths in low density plasmas can be measured directly by Doppler-free two-photon spectroscopy of atomic hydrogen mostly present in such discharges. This method is based on the Stark-splitting of the atomic resonance lines and causes no significant perturbation to the discharge. For this purpose, we take advantage of our advanced pulsed UV-laser spectrometers which provide not only the peak power needed for two-photon excitation but also the high spectral resolution to resolve the atomic hyperfine splitting. In a first experiment with opto-galvanic detection, atomic hydrogen was produced by thermal dissociation in a small cell filled with hydrogen gas and the Stark-splitting of the 1S-2S and the 1S-3S/D transition was measured. Electric fields as low as 200 V/cm and 30 V/cm respectively could be determined in accordance with theory. In addition, we have performed measurements in a hollow cathode discharge which provides higher electric fields in its cathode fall region and the 1S-2S spectrum was detected spatially resolved by means of opto-galvanic and polarization spectroscopy as well. Selected experimental results will be presented which clearly demonstrate the high potential of this optical method.

ELETTRA is an intermediate energy Synchrotron Light Source located in the outskirts of Trieste, Italy, open to researchers of basic and applied fields such as material and life sciences, physics, chemistry and geology. The synchrotron is operated 24 hours/day, 7 days/week with few periods of shutdown, mostly dedicated to maintenance. During one of these periods, in August 2001, ENEA Fusion Technology Division (Italy), in collaboration with ELETTRA Accelerator Sector and Paul Scherrer Institut (PSI, Switzerland), carried out the 3D dimensional survey of the storage ring using its own optical metrology system (Leica laser tracker LTD500). The aim of the survey was re-alignment of the storage ring magnets of the synchrotron. Within a two-weeks time shutdown, more than 2300 single measurements were taken on the 24 bending magnets, 108 quadrupoles and 72 sextupoles placed in the 259.2 m circumference storage ring. The overall root mean square error of the oriented network were less than 0.1 mm, thus making possible a subsequent and successful one-week alignment of one fourth of the storage ring (October 2001). This performance completely fulfilled the very demanding survey specifications in terms of accuracy, time required, and usability of the measurements. This paper illustrates the survey, the method and the instrumentation adopted and the results obtained. Moreover, it gives guidelines to be taken into account when planning the alignment of accelerators or large and heavy components.

In this paper we are presenting the prototype of laser measuring system -- namely laser liner -- for Computer Numerical Control (CNC} machine tools and for Coordinate Measuring Machines (CMM). The laser liner is an innovatory arrangement of one frequency interferometer. The two-mode HeNe laser is used as a source of radiation whereas the surface stabilized ferroelectric liquid crystal cell (SSFLCC) for stabilization of the laser frequency. Small dimensions of the arrangements facilitate mounting of the interferometer on machine tools. Worked out advanced correction procedure of length of light wave compensates in real time the influence of parameters of atmosphere on the length of laser radiation. Another possible thing is compensation of thermal expansion of a material.

In the following paper we describe arrangements of laser interferometer for investigation of screws and for inspection of ball screws. We have constructed two of them, namely: the technological setup for investigations of screw in process of production and the ball screw inspection setup. The former one is used to measure the pitch of screws. The data gathered during measurement is used to calculate the parameters for grinding machine. The later setup is used for testing parameters of complete ball screws. The software supporting this setup makes calculation of parameters of tested ball screw and creation of reports possible. Additionally, the inspection setup is the one that the torque measuring arrangements have been integrated on. Both the arrangements and the software allow for measurements of all parameters during movement of nut in full travel length of the ball screw and make charts and reports.

In order to find conditions that no bubbles occur on particle counting in liquid, the use of simultaneous detection of scattered light and fluorescence was examined. A liquid particle counter that had fluorescence sensing devices to detect the fluorescence from sample particles was used. Sample particles were dyed and from 1 to 10 micrometer in diameter. The wavelength of laser light to excite fluorescence was 488nm. The fluorescence was filtered by a dichroic mirror and two band pass color filters and detected at 525nm. Although ordinary particle counters detect only scattered light, our system is capable of detecting coincidence of scattered light and fluorescence. By making use of the fact that bubbles make no coincidence signals and particles make coincidence signals we can distinguish bubbles from particles. To evaluate the reliability of the particle counts obtained with this system, we compared them with the counts obtained with the microscopic method.

An interferometric method to test plane parallel plates both for planarity and parallelism of the end faces is reported. The method requires that the plates are reflective or temporarily metal coated. Measurements are taken by insertion of the plates in a reference cavity. The optical configuration uses a standard programmable interferometer with an external right angle prism folding back the probe beam. The prism error is determined by cavity calibration, and is subtracted at data reduction. The measuring procedure is discussed in detail, and results of a laboratory demonstration are presented.

The possibilities of numerical simulation of speckle phenomena and visualization of optical arrangements have been studied. Simulation results of objective and subjective speckle patterns in various optical setups are presented. Based on the speckle simulation program a virtual optical laboratory can be generated as an effective visualization tool.

Holographic interferometry and electrochemical impedance (E.I.) spectroscopy were used in this investigation to evaluate the performance of the corrosion inhibitor RA-41 in low concentrations. The samples used consisted of carbon steel in seawater with RA-41 concentrations between 5-20 parts per million (ppm). The low concentration of RA-41 in seawater solution has allowed the assumption that this solution is ideal dilute with respect to the inhibitor. With this assumption the hypothesis was made that the inhibitor performance would be directly proportional to its concentration in accordance to Henry’s Law. This was then verified with the results of both optical interferometry and E.I Spectroscopy tests. As a result of this observation the performance of the inhibitor can be derived analytically at low concentrations. In this study both classical and optical methods were used to determine the efficacy of RA-41 in low concentrations. To gain a quantitative measure of the efficacy of the inhibitor the current densities of the cathodic and anodic layer of the sample were obtained by classical method for concentrations of the inhibitor that ranged from 5-20 ppm. Simultaneously the optical method was also performed for the samples. However what was measured was the rate change of the fringe evolutions. The rate change of fringe evolutions in the sample represents the results of the optical corrosion meter measurements of the anodic deposition and cathodic dissolution layers. The results of the tests were obtained and have been shown to both be proportional to the inhibitor concentration.

Fatigue detection by two dimensional folding shear interferometry of subjected to cycling loading (pressure) composite vessel is presented. As the sensitivity of the applied method is higher in comparison with the other speckle-shear techniques, inspection of the small zone over the surface with magnification for the maximum permissible loading of the object is realized. The first step is measurement of a large surface area by lateral shear interferometry for selection of the zone with unusual mechanical response in loading, due to cracks, voids, impurities or other stress concentrators. At small lateral shear (1% over the object in our case) the obtained phase map modulus 2π coincides to derivatives of normal displacements. The moment hierarchy approach to time-series analysis is used for assessment of experimental results, as mechanical behavior of composite materials as a rule is non-linear and time depending. Further improvements of the techniques to application in fracture mechanics, lifetime and sudden (catastrophic) failures prediction are discussed.

University of Kassel and isi-sys have extended the application of shearography to quantitative vibration analysis and developed a portable automatic controlled shearography system. The Vibrograph is already used for vibration measurements in industry for example of electronic boards typically in combination with laboratory shakers in harmonic excitation modes. Now a small portable piezo shaker permits local excitation of the defects such as delaminations and disbonds. Vibrating in their natural mode shapes the Vibrograph detects the location of the defects within the fiber structure.