The deviations from flatness of a set of three surfaces can be mapped by averaging the results of intercomparisons of these surfaces, taken two at a time, with both the surfaces rotated in their own plane in a series of steps. This procedure makes it possible to separate the surface errors into their rotationally invariant and rotationally dependent components. The errors of the individual surfaces can then be obtained directly from the differences of these averages. Averaging techniques can also be used for direct measurements of small- scale surface irregularities (ripples), with very small amplitudes, on high-quality surfaces. These techniques can be extended to make measurements on highly reflecting surfaces, as well as to obtain, directly, the spatial frequency spectrum of such surface irregularities.

Geometrically desensitized interferometry uses two beams at different incident angles to generate an interference pattern with an equivalent wavelength of 5 to 20 micrometers. Unlike conventional interferometers, the fringe contrast is primarily a function of the optical geometry, rather than the spectral properties of the source light. In particular, a line-shaped source provides either a narrow or broad contrast envelope, depending on the orientation of the line with respect to the plane of incidence. This adjustable coherence depth is useful for initial system alignment, depth scanning and for separating surfaces of transparent flat parts.

Parallel and absolute measurement of surface shape using wavelength scanning interferometry has been applied to various objects including diffuse surfaces and milled ones having discontinuities such s steps, dips, and protrusions. We have employed not only the Michelson setup but also the Fizeau one newly introduced. The behaviors of interference signals arising from these objects are experimentally compared. Spiky noises have been observed from the milled surfaces and the defocused diffuse surface. In spite of the noise we succeeded in measuring steps and narrow dips on a mirror and a milled surface, as well as a cylindrical protrusion on a diffuse surface. With a dye laser of tuning range of 4.2 nm we attained the resolution of 39 micrometer within the depth of 3 mm.

A variety of technical applications require surface roughnesses to be measured and characterized over a wide range of scale. In order to meet these requirements it is inevitable to combine different measurement techniques by using an assembled PSD. As an example the white light interferometry (WLI) is compared to the atomic force microscopy (AFM) by measuring a binary grating. The results show a good correspondence of the profiles and power spectral densities (PSD). Furthermore, rough surfaces are measured by WLI and AFM and combined by means of the PSD in a wide range of scale covering up to 5 orders of magnitude. It will be shown, that in some cases only the combined PSD will give the right results to describe the surface by a model PSD. It turns out that either the fractal or the ABC-model are very well suited.

To achieve a measurement with high spatial resolution over a large area, we stitch together multiple high spatial resolution maps obtained from an interferometric microscope with or without a motorized stage. These maps have a high height precision and a lateral resolution as high as 0.11 micron/pixel. They can be stitched together with acceptable accuracy as long as each of their adjacent areas has enough overlapping pixels. The stitching technique we have developed is based on a computed probability that gives a quantitative measure for the goodness of the chi-square fitting. It is insensitive to the piston and tilt changes of each map. It is also insensitive to the lateral shift and/or rotation between the overlapping maps. This technique is robust and flexible. It is able to give a satisfactory measurement without relying on the accuracy of the stage movement. The map stitching expands the field of view available to an objective lens, which makes it possible to measure a large area without losing high-slope surface features.

Recently, the digital shearography, a combination between the laser optical measurement and the digital image processing, has been developed as an industrial measuring method for strain measurement. With the support of the digital image processing, the flexural strains ((delta) ²w/(delta) x², (delta) ²w/(delta) y² and (delta) ²w/(delta) x (delta) y) can be determined by using one illuminating beam. The inplane strains ((delta) u/(delta) x, (delta) v/(delta) y, (delta) u/(delta) y and (delta) v/(delta) x) can also be measured using two alternate illuminating beams. However, a detailed analysis of measuring precision using the shearographic strain measurement method has not been reported. This paper will focus on the analysis of the factors which influence the measuring accuracy, such as the shearing amount, the sensitivity vector, the errors of phase shifting, the relatively large rigid body motion etc. The relationship between these factors and the measuring precision are presented.

Several proposed space-based interferometry missions require positional knowledge of their optical elements to very high precision. To achieve the desired stellar position measurement precision, the internal optical path difference of the stellar interferometer must be measured to within 10 picometers. This knowledge can be provided by a metrology system based on a laser interferometer incorporating the spacecraft optics. We present results from fabrication and testing of a lab-based frequency-modulated (FM) Michelson interferometer intended to maintain length stability to a few picometers. The instrument can be used to make precise relative distance measurements or it can be used to characterize orientation and polarization effects of system components commonly used in metrology gauges. External frequency modulation of a frequency- stabilized laser source and phase-sensitive detection are used to detect changes in the arm length difference of the interferometer. Arm length adjustments are made via a closed loop feedback system. A second system having a shared beampath with the primary system monitors the performance of the primary system. Preliminary data, operating in an ambient lab environment, demonstrate control to roughly 6 picometers rms for measurement times around 10 seconds.

In the paper the creation of a virtual object on the base of optical measurement of 3D object by fringe projection technique coupled with the capabilities of CAD systems is presented. Basic stages of that task, being the most important part of the reverse engineering process, are discussed and the procedure is formulated by terms and definitions of theory of optimal algorithms. The quality criteria of a virtual object are defined and the influence of consecutive stages of the task on the quality of the virtual object is discussed.

For sensing applications like absolute distance measurement using the self-mixing effect, the laser diode is modulated by a triangular signal in order to produce an excursion of the optical frequency. The optical beam back-scattered by a non- cooperative target into the laser diode active cavity causes strong variations of the optical output power, these variations being counted in order to determine distances. In this paper, some intrinsic limitations of a feedback interferometric absolute distance measurement system are analyzed. The spectral characteristics, the wavelength or the optical power of the laser diode are disturbed by the optical feedback. These changes modify parameters like the coherence length (i.e. the maximum range of the sensor) or the value of the injection current to be modulated. So, laser diodes have to be characterized in terms of spectral linewidth. In the case of strong feedback, the optical power is also disturbed by the hysteresis. The influence of the thermal effects is analyzed and a solution is proposed to improve the accuracy of the sensor.

We describe a fringe locking phenomenon that is observed in a two beam interferometer using a laser diode. We found that the fringes were locked even when one mirror of the interferometer was vibrated at an amplitude of several wavelengths. The phenomenon is caused by optical feedback from the interferometer to the laser diode so that oscillation wavelength of the laser can be changed by mirror movement to compensate for the resultant change in the path difference. The phenomenon occurs if a fraction at least 0.1% of LD output power is returned. The degree of fringe locking depends on optical path difference periodically with a period of optical laser cavity length. The locking has also been observed for the mirror vibration at two wavelengths in amplitude and 10 kHz in frequency limited by the PZT driver. The wavelength shift caused by the mirror movement has been calculated using an equivalent Fabry-Perot cavity model for the laser diode interferometer and showed good agreement with experimental results.

In the COXI (Combined Optical and X-ray Interferometer) system, optical and x-ray interferometers are combined to provide a means for the calibration of transducers with the traceability to the standards of length in the sub-nanometer region. The COXI mainly comprises a laser interferometer, an x-ray interferometer, and a precision translation stage. The laser interferometer used for the COXI instrument was a Michelson type, differential heterodyne interferometer having common optical path. A monolithic x-ray interferometer was made from a silicon single crystal. We have designed a control procedure to operate the COXI instrument for the calibration of nano-transducers and developed a phase demodulator for use with the laser interferometer. The bandwidth, phase resolution, and the measurement uncertainty of the interferometer were found 1 kHz, 0.01 degree, and 0.1 degree, respectively.

Micro-systems engineering is a fast growing technology with a wide variety of different materials. The task to ensure reliability and precision of the products needs the precise knowledge of the materials' properties, which is too less in dimensions smaller than one millimeter at the moment. Because properties determined at much larger specimen cannot be scaled down without any experimental result, simple and robust methods to analyze the materials' shape and deformation under a given load must be developed. Holographic interferometry and optical contouring techniques are widely used as highly sensitive and contactless methods for deformation and shape analysis. To get a full 3d-information of the object's surface, however, requires a complex optical setup with at least three illumination directions. Especially when small objects like micro-components have to be examined, the ordinary use of conventional holography becomes more and more a problem. In that case digital Holography can be used as a fast, simple and robust method. It replaces the classic holographic recording media by a CCD matrix. The whole reconstruction process of the interference phase is done by computer. Compact and very simple setups can be achieved by use of fiber optics. Several experiments realized in an optimized setup by using four illumination directions are presented to show the advantages of digital holography for the investigation of microsystems. This new technique is applied to components with lateral extensions from 0.1 m to 0.001 m to examine their shape and their full three dimensional deformation under a given mechanical load. The results are compared with computer simulations using FEM. For compound Si/Ni microbeams Young's modulus was determined as an example for this technology of measurement.

In the Pole Tip Recession (PTR) measurement using a Phase Shifting Interferometer (PSI), the phase shift due to the reflection at the air/thin film/dissimilar substrate interfaces will certainly cause incorrect PTR measurement. In this paper the effects of the variations in the refractive index of the materials and of coating thickness on the PTR measurement have been analyzed, and the PTR offsets and their errors have been calculated.

This paper presents the test results on a compact, off-axis telescope which is the precursor projector/receiver for a NASA Shuttle-based coherent lidar system operating at a wavelength of 2 microns to measure atmospheric wind profiles. The afocal telescope has an entrance pupil diameter of 25 cm, and an angular magnification of 25x. To determine the transmitted and returned optical wavefront quality, the telescope was tested in a Twyman-Green configuration at the operational wavelength. Interferograms were obtained via an infrared camera, and analyzed using a digitizing tablet and WYKO WISP software. Interferograms were obtained with and without an 11.7 degree wedged silicon window located in the entrance pupil. This window, which rotates orthogonal to the telescope optical axis, serves as the lidar system scanner. The measured wavefront information from the interferometer was used in a GLAD heterodyne receiver model to predict the effect of the optical system on the lidar performance. The experimental setup and procedures will be described, and the measurement results of the coherent lidar optical subsystem will be presented in this paper.

A new method is presented to extract quantitative information of Moire fringes. It is different from the method of phase shift. Instead of changing the phase of Moire fringe, it changes the frequency of the Moire fringe. The theoretical formula is introduced for a special relationship of three frequencies. For unwrapping the phase image, the first step is to expand the cosine value range from (0, (pi) ) to (0,2 (pi) ) to avoid the indetermination of 'plus' or 'minus.' The experiment result is given and the effect of the position of light source on measuring results is also discussed.

New generations of microelectronics and microsystem devices call for the utilization of a variety of new materials and the combination of materials with a widespread of their mechanical and thermal characteristics. Thermo-mechanical reliability issues as well as functional aims bear a big challenge to understand and to design mechanical behavior of devices and components. Laser interferometric and related measurement techniques with their capability to analyze mechanical properties of complex systems are essential tools accompanying the R&D process. At the IZM Berlin different kinds of laser methods have been used to analyze surface characteristics of components like surface profiles and roughness, deformation behavior due to thermo-mechanical load, and functional performance of systems. In particular, methods like interference microscopy, auto focus profilometry, speckle and holographic interferometry, speckle photography, interferometry on specular surfaces, Moire and microDAC have been applied. With regard to finite element based mechanical reliability studies of microtechnology devices deformation measurement methods are being introduced to verify simulation findings. Consequently, uncertainties in constitutive modeling of mechanical behavior or in material properties used can be significantly reduced. Measurement examples of experimental deformation analysis applied to advanced packaging like flip chip technology, chip scale packaging, new interconnect techniques and glob top encapsulation are demonstrated. Different kinds of laser optical measurements on printed circuit boards, micro coolers, actuator arrays, ball grid arrays illustrate the usefulness of mentioned methods for microelectronics and microsystem research and development. Integration of laser optical methods into future production lines is one of the project aims reported here.

The diffraction pattern of a textile fiber observed in the back focal plane of the polarizing microscope is used to measure its birefringence. The mathematical model of the phenomenon and the automatic pattern analysis are described.

In this paper, we applied phase-shifting digital holography to microscopy. The digital holograms are recorded by a video camera from the superposition of a plane reference beam and the object beam passed through a microscopic objective. The distribution of complex amplitude of the object wave is derived by using the phase-shifting algorithm and then Fresnel transformed in a computer to reconstruct images at arbitrary planes. After relationships between object position and position of focused image and magnification are discussed, those are applied to determine the sizes and positions of small particles by image processing technique.

Interferometry is an essential field of optical metrology and is adapted in many applications in optics, crystal growth, and industry. Crystal growth rate is one of the critical parameters for the growth of optical quality single crystals. A laser interferometry technique has been developed and applied successfully for crystal growth rate measurement from solution. A He-Ne laser at the wavelength of 633 nm with an output power of 1.5 mW was used in this experiment. The beam was incident on the crystal growing from solution. As the crystal is growing, the path length of the front and back surface reflected beams changes hence the phase factor of the detector output signal changes continuously. This phase change is directly related to the growth of crystal. The growth rate of the LAP crystal was found to be 6.5 plus or minus 0.1 nm/s. A Mach-Zehnder interferometer, also, has been applied to study the variation of concentration at the interface of the growing crystal from solution.

The technique of optical-time domain reflectometry (OTDR) is analyzed to determine the effect of an optical phase modulation on light backscattered in an optical fiber. It is shown that the spatial distribution, along the fiber, of an external phase modulation can be measured with a spatial resolution close to that of the OTDR. A distributed interferometric sensor arrangement employing this technique has been investigated experimentally, and a satisfactory interrogation of more than one thousand resolution intervals has been demonstrated.

In this paper in-fiber Bragg gratings (IFBGs) were embedded in epoxy resin carbon fiber composite coupons, and these coupons were subjected to transient events such as impacts. The IFBGs were demodulated using a fiber Fabry-Perot interferometer and an interference filter. In addition to the IFBGs, two other types of sensors were used. These were a force transducer mounted in the impact rig, and resistive foil strain gauges mounted on the surface of the test coupons. Comparisons of the data obtained using these sensors have been made. The IFBGs have successfully survived the impacts and have been used to record strain transients that characterize typical fracture events.

A tomographic imaging system based on the principle of an optical frequency domain reflectometry is presented. The light source is a tunable laser diode whose optical frequency is scanned over 6.3 THz during 5.76 s, and the photosensor is a CCD camera of wide dynamic range. The main performance of this system can measure simultaneously the 3-D information of reflectivity through scattering media without the need for mechanical scanning.

Fiber Bragg grating (FBG) sensors have been used to monitor the axial and radial strain induced in a 30 mm caliber gun barrel by the passage of a projectile with a muzzle velocity of greater than 1 km/s. The performance of the sensors is compared with that of conventional resistive foil strain gauges. The FBG sensors were used to monitor transient strain signatures of duration less than 100 microseconds with rise times less than 10 microseconds and magnitude 10,000 micrometers/m.

In quality control nondestructive techniques gain more and more importance. Optical methods as for instance holographic interferometry have the advantage of being sensitive and can be used contactless for inspection of technical components. The acquired interferogram contains fringe patterns, that hold information about the surface deformation subjected to the applied load. The detection of faulty parts is, usually done by an expert who is used to interpret the interferogram and to decide the criticality of the detected flaws. The automation of this procedure raises several problems, since the diversity of pattern produced by different objects and flaws makes an effective processing very complicated. This paper describes a method for the recognition of fault indicating patterns by synthesis of the interferograms, the comparison with the real pattern and modification of the simulation strategy with respect to the classification of the flaw. Taking into account the experimental conditions and a first hypothesis about the type of flaw within the object, a synthesized image of the fringes can be generated and compared to the experimental image. In case the synthesized and experimental patterns differ, this indicates that the assumed hypothesis wasn't correct and have to be modified. This process is repeated until both patterns correspond, and so the supposed hypothesis about the flaw was verified. This new approach was proposed earlier for holographic interferometry and a simple object. Here we demonstrate new results at a copy of satellite tank using holographic interferometry and show the advantage with respect to robustness of detection and the classification of the voids.

A novel optical diagnostic technique, namely, a dual hologram shearing interferometry with regulated sensitivity, is proposed for visualization and measuring the density gradients of compressible flows in wind tunnels. It has advantages over conventional shearing interferometry in both accuracy and sensitivity. The method is especially useful for strong turbulent or unsteady regions of the flows including shock flows. The interferometer proved to be insensitive to mechanical vibrations and allowed to record holograms during the noisy wind tunnel run. The proposed approach was demonstrated by its application to a supersonic flow over spherically blunted and sharp nose cone/cylinder models. It is believed that the technique will become an effective tool for receiving optical data in many flow facilities.

In this paper, an analysis theory of real-time stroboscopic holographic interferometry with fringe drift counting technique is discussed. Based on the theory, a real-time auto- analysis system for stroboscopic interferometry is researched. The system can be used to analyzing object's vibration. The difficulty of identifying the node-locus in stroboscopic interference pattern is disposed. And the influence of primitive fringe on the quantitative analysis of the real-time holography is also eliminated.

The process of fringe formation under simultaneous illumination in two orthogonal directions is analyzed. Procedures to extend the applicability of this technique to large deformation and high density of fringes are introduced. The proposed techniques are applied to a number of technical problems. Good agreement is obtained when the experimental results are compared with results obtained by other methods.

Deformations of thermally loaded composite tubes are studied by means of Finite-Element-Analyses and interferometric measurement techniques. Of particular interest are the differences in the deformation behavior of the two investigated anisotropic tubes in comparison to isotropic tubes. Two characteristic bending phenomena appear at the frontal and the shell surface of the tubes, owing to the three-dimensional stress state near the edges. These simulated phenomena are experimentally verified by means of holographic as well as speckle interferometry. The results of this work show that in most cases the implemented micro- and macro- mechanics of the used Finite-Element models enable to properly predict the thermal deformation of composite tubes. Nevertheless, especially for very thin tubes, significant discrepancies between the simulated and the measured deformations could appear, due to the disregarding of the complex microscopic structure in the simulation. Thus, experimental verifications of the simulated thermal deformation of composite tubes are necessary. Generally, these verification measurements should be performed with fieldwise experimental methods, like the presented interferometric measurement techniques.

An experimental technique is developed to measure the radial displacement component of cylindrical surfaces using a conical mirror for normal illumination and observation. Single illumination ESPI is used to obtain fringe patterns related to the radial displacement field. Some data processing strategies are presented and discussed to properly extract the measurement data. Data reduction algorithms are developed to quantify and compensate the rigid body displacements: translations and rotations. The displacement component responsible for shape distortion (deformation) can be separated from the total displacement field. The thermal radial deformation of an aluminum engine piston with a steel sash is measured by this technique. A temperature change of about 2 degrees Celsius was applied to the engine piston by means of an electrical wire wrapped up in the first engine piston grove. The fringe patterns are processed and the results are presented as polar graphics and 3D representation. The main advantages and limitations of the developed technique are discussed.

Theoretical and experimental results of studies on a stability of slow-speed motion generated by different type rotating platforms designed for an investigation of angular velocity meters are presented. On the basis of simulation, the possibilities to obtain smooth rotary motion have been analyzed. The main attention has been paid to low angular velocity, order of Earth revolution velocity. Slow-speed platforms constructed nowadays exhibit many technical problems caused mainly by wide range of revolution velocity. Very often angular velocity generated by them exhibits large disturbances caused by mechanical principle of action. These disturbances cause oscillations of instantaneous velocity which increase for decreasing mean value of generated angular velocity of rotary motion. In theoretical simulation the role of sub- assemblies workmanship has been discussed. Moreover, the effect of this workmanship on the level of generated rotation velocity oscillations has been estimated. In experimental part, an application of fiber optic gyroscope enabling experimental verification of obtained theoretical results is presented. According this application, the instabilities of angular velocity produced by different rotation platforms have been well visualized and measured.

The semiconductor industry has been demanding film thickness reference material for films other than thermally grown silicon dioxide for sometime. To meet this challenge, Nitride Film Thickness Standard (NFTS) has been developed in four nominal thickness values, 20.0 nm, 90.0 nm, 120.0 nm and 200.0 nm. These are silicon nitride (Si₃N₄) films on silicon crystal substrate. Work is underway to develop a 9.0 nm standard. Thin nitride films are particularly needed for calibration of the thickness of nitride layers in capacitors and isolation masks for LOCOS (local oxidation of silicon). The reference material is certified for derived film thickness. The study consists of measurements made on four different sets of wafers that included patterned and unpatterned wafers. The measurements made on these wafer sets were used for answering issues related to film stability and cleaning. The stability study includes the search for a cleaning process that will restore a prior surface condition. On two sets of wafers two different types of cleaning procedures were used. Results indicate that a sulfuric acidmegasonic clean will etch the nitride film while an isopropyl alcohol clean followed by a deionized water rinse can be used over and over again. The third set of wafers was never cleaned and measurements were made on these over a period of two years. The last set of wafers is patterned. These are cleaned prior to measurement. Results show that LPCVD silicon nitride films are stable and can be used with confidence over a long period of time for calibrating optical metrology instruments.

We describe a simple method for measuring a long radius of curvature based on the rotatable wedge plate shearing interferometer and a digital moire method. Detailed analysis of the principle of measurement and a description of the experiment are presented. The achievable accuracy of the measurement and the experimental results are discussed.

With the renewed interest in hypervelocity vehicles, component testing in extreme thermoacoustic and thermovibration environments is now required. This requires new test facilities and new instrumentation techniques be developed to test and evaluate these new structures, components and sub- components. To collect data in these extreme environments new instrumentation is needed. In a dynamic test environment use of strain gages is limited to low temperature testing. This paper describes how room temperature and high temperature (greater than 2000 degrees F) strain data is collected, using a laser vibrometer, on cantilevered coupons. This paper also describes the use of a laser vibrometer to obtain mode shapes and damping information. With new structural components, many manufactured from new composite materials such as ceramic matrix composites (CMC), there is a need to acquire accurate mode shapes and damping information. Traditionally modal analysis is done using accelerometers to map out the responses of a structure. This is time consuming, expensive and on small structures the weight of the accelerometers could affect the results. Through the use of a laser vibrometer accurate mode shapes can be obtained quickly. This information can be used to validate finite element models and to determine instrumentation locations on test components. With complex structures it is essential to determine the correct locations to install instrumentation when performing high level dynamic testing, the vibrometer is ideally suited for this. While the mode shapes are being mapped using a vibrometer it is an easy and logical step to calculate the damping of the structural component. Damping is calculated using the half-power bandwidth method that provides accurate results when using a vibrometer.

To measure three dimensional coordinate we have been developing a laser tracking interferometer system (LTS). Four laser interferometers chase the movement of a target cat's eye and measure the change in distance between them. The position of the cat's eye is determined from the measured distances based on the principle of trilateration. Taking advantage of measurement redundancy produced by the fourth tracker, the position of the trackers and the initial position of the cat's eye can be estimated by a self-calibration algorithm. A restriction on the arrangement of the laser trackers to perform the self-calibration algorithm is theoretically studied. Finally a preliminary experiment was made to show the measurement error of about 40 micrometers for a 1 m measurement.

In the present investigation, holographic interferometry was utilized for the first time to measure the electrical resistance of aluminum samples during the initial stage of anodization processes in aqueous solution without any physical contact. The anodization process (oxidation) of the aluminum samples was carried out chemically in different sulpheric acid concentrations (0.5 - 3.125% H2SO4) at room temperature. In the mean time, a method of holographic interferometric was used to measure the thickness of anodization (oxide film) of the aluminum samples in aqueous solutions. Along with the holographic measurement, a mathematical model was derived in order to correlate the electrical resistance of the aluminum samples in solutions to the thickness of the oxide film of the aluminum samples which forms due to the chemical oxidation. The thickness of the oxide film of the aluminum samples was measured by the real time-holographic interferometry. Consequently, holographic interferometric is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film as well as the electrical resistance of the aluminum samples can be determined in situ. In addition, a comparison was made between the electrical resistance values obtained from the holographic interferometry measurements and from measurements of electrochemical impedance spectroscopy. The comparison indicates that there is good agreement between the data from both techniques, especially when an electromagnetic coefficient was introduced to make the values of the electrical resistance from both technique are nearly the same.

We propose an interferometric method for absolute distance measurement. This method uses the fact that the wavelength of a laser diode can be tuned continuously, by addition of an external cavity. The laser system, which has a small linewidth and therefore a large coherence length, is used to feed two interferometers. One of them serves as a reference distance. The phase variation of the signal is extracted by the Fourier transform technique. The magnitude of phase variation is proportional to the rate of measuring and reference distances. If the reference distance is known, a measuring distance can be obtained from measurement of the phase variation. We have done some fundamental experiments and shown that the precision is essentially limited by calibration of reference distance. The application of this technique has already allowed to measure distance of 3 m with relative accuracy of 1.8 10^-4.

We describe a technique that is used for the real-time measurement of the vibration of an object point. The technique can be used when the vibration is characterized by a large amplitude, i.e. several millimeters. The technique shows the additional advantages that it requires no special surface treatment and is insensitive to inplane object displacements. In this technique an object point is illuminated by a small diameter beam (at an angle) that is structured with straight parallel fringes. The illuminated object point is then imaged onto a Ronchi ruling. The total light transmitted through the Ronchi ruling is then used to recover the vibration of the object point, in real time, by using well known servo techniques.

This paper describes the theory of determination of small deformation tensor by means of the method, availing of statistical properties of the speckle field in an optically free space geometry or in a near image field. The small deformation tensor and a correlation function are briefly mentioned, and the main emphasis is aimed on theoretical derivation of the relationship between the correlation function of two speckle intensities, being recorded before and after deformation. This results in the relationship theoretically enabling a determination of all components of the small deformation tensor by means of a relatively simple optical arrangement in connection with computer and linear CCD detectors. Further, a compilation of all completed experimental results are briefly mentioned. An accuracy and sensitivity of this measurement methods are analyzed by theory of errors. As it flows from theory, the exact results at stress deformation, body displacement and rotation depend in crucially upon the geometrical arrangement of the optical system. The emphasis on the analysis of accuracy and sensitivity of individual geometrical parameters of assembly are given, with the aim to find an optimized geometry of experimental arrangement. The feasibility of an easy realization in practice and most importantly achieving satisfactory results of measurements are the important criteria. The conclusion presents some results obtained at concrete measurement with proposed experimental assembly.

In-fiber Bragg gratings (IFBGs) and dielectric sensors have been embedded in the same carbon fiber epoxy composite and have been used together during the curing process to make in- situ measurements of two cure parameters, namely internal strain and conductivity. This was performed using an automated acquisition system, part of which could use real-time measurements to estimate and predict cure parameters. The IFBGs were demodulated using a scanning fiber Fabry-Perot interferometer. The results obtained using this combined cure monitoring system demonstrate that it is possible to monitor the strain levels in the optical fiber resulting from the onset of liquification, gelation, and vitrification within the surrounding resin matrix.