The existence of gravitational waves is predicted by the general relativity theory, but they have not yet been measured directly. The difficulty with these measurements is the very small signals expected from even the strongest sources (astrophysical events such as supernovae). Detection of gravitational waves by interferometric detectors requires resolution of very small displacements, which in turn requires very long arm lengths. In the case of the Laser Interferometer Gravitational-Wave Observatory (LIGO), Michelson interferometers with arm lengths of 4 km and position accuracy on the order of 10^-18 meters are to be employed. LIGO, funded by the US National Science Foundation, is being constructed at two sites in the United States with initial observation planned in 2002. An overview of the LIGO design requirements, configuration, and control scheme is presented. The optical configuration is discussed in general with particular attention to the characteristics of the core optics. In addition, a brief overview of large- scale gravitational wave observation projects worldwide is presented.

TAMA is a project to construct and operate a 300-m arm- length laser interferometer (TAMA300) to detect gravitational waves from astronomical sources. The detector comprises two orthogonally oriented Fabry-Perot (FP) cavities with 300-m length. Each FP cavity has a finesse of 520, and is illuminated by an injection-locked 10-W Nd:YAG laser. We are planning to start the first full operation of the detector system in March 2000.

Core optical substrates for the Laser Interferometer Gravitational Wave Observatory are being manufactured and tested at CSIRO. These substrates are for use in long baseline Michelson interferometers with Fabry Perot cavities up to 4 km in length in each arm. The optics consist of 32 high quality fused silica substrates, comprising folding mirrors, end test masses, input test masses, recycling mirrors and beamsplitters. The dimensions of the substrates are 250 mm diameter by up to 100 mm thick. The optical surfaces are either flat or curved, with radii of curvature between 7 km and 15 km and tolerance bands on the radius equivalent to variations in sag (over 200 mm) of about 20 nm.

Within a Technology Research Program funded by the European Space Agency, a team led by Alenia Aerospazio has investigated and started the development of some technologies which are considered fundamental for the achievement of the scientific objectives of the future astrometric mission GAIA. The activities have been focused on the design of a two-aperture optical interferometer and of a system for the active stabilization of its configuration within few picometers. A laboratory prototype of the active stabilization system has been implemented and tested. The results achieved in the laboratory tests proved that the very challenging requirements imposed by the GAIA astrometric goal of 10 micro-arcsec accuracy can be fulfilled.

The wide bandwidth of white-light has long been utilized for various interferometric measurements. We recently proposed dispersive coherence spectrotomography with white-light continuum to extract both range and spectral properties inside a medium. The principle of dispersive coherence spectrotomography is based on an optically spectral decomposition of the white-light interferograms. The main feature is that the dispersive coherence spectrotomography has the high dynamic range in depth and high signal-to-noise ratio making the most of extreme brightness of the white- light continuum. The white-light continuum is a new type of a broad-band and bright light source that is generated by focusing ultra-short and high-energy laser pulses into condensed media or gases. We present our experimental results related to the coherence properties of the white- light continuum and its applications to dispersive coherence spectrotomography of a multi-layered system of colored media.

Size, position, and velocity of particles or droplets in 3D- space can be measured contactlessly by in-line holography. In digital in-line holography the holograms are recorded by a CCD-array and stored digitally, the reconstruction of the complex wavefields is performed numerically in the computer. By an arrangement allowing the laser beam to pass several times through the particle field before hitting the CCD, several angular views are recorded simultaneously. In the reconstruction stage the viewed are separated by numerical focusing to the different distances, and by a tomography- related method the 3D-positions of the particles are determined. Double pulse recording enables to determine also the velocity of the particles. The paper gives a short introduction to digital holography, explains several holographic arrangements for multipass in-line holography, presents some experimental results of position and velocity measurements, and discusses some typical errors.

Digital in-line holography with numerical reconstruction has been developed in our group into a tool that routinely achieves both lateral and depth resolution at and below the micron level. The experimental and numerical procedures have been incorporated into a program package with a very fast reconstruction algorithm that is now capable of real time reconstruction. This is demonstrated for such diverse objects as fibers, suspensions of microspheres and biological samples (epithelial cells, the eye of Drosophila melanogaster larva), and the advantages are discussed by comparing the holographic reconstructions with images taken with conventional optical microscopy.

We report on a method for microstructure inspection using the `edge-birefringence', i.e. the polarization anisotropy caused by the structure edges. A liquid-crystal phase- shifter is inserted into the imaging optics of a reflection- made microscope, and the principle of phase-shifting interferometry is applied to measure phase and contrast of the TE-polarized image with the TM-polarized image as reference. This common-path interferometrical method provides a selective edge detection because the polarization difference is localized at the structure edges. It is useful for a simple but accurate measurement of microstructure linewidths. The (unwrapped) phase image can show supersteep edges that we attribute to phase singularities. Because with decreasing structure width the polarization difference increases, the method is particular apt for subwavelength line-structures. The images, however, become then strongly dependent on the experimental parameters like focus- position, structure material, -width and -depth.

The ISO 53471/1-1995 proposition of the new international standard of vibration pick-up calibration is examined theoretically and experimentally. Regression analysis method is applied for data transforming and error evaluation in sine-approximation method (SAM) for the calibration of vibration pick-ups by laser interferometry. To make a more valuable comparison of this modified SAM with other techniques, i.e. fringe counting method (FCM) and minimum point method, the resolution of the measuring system is increased by using double optical path difference homodyne interferometer. Additionally the uncertainty of FCM is suppressed by implementing the procedure of fringe phase analysis in the turn points of the vibration cycle. Theoretical analysis and the exemplary experimental results for all applied methods are given. The expanded measurement uncertainties about 0.2% of acceleration measurement and about 0.5% of sensitivity measurement (with a 99% confidence level) have been obtained.

Transparent object Wave-Front Distortion has been measured in a Mach-Zehnder interferometer employing as evaluation tool the Multiplicative Analogical Moire Phase-Shifting Method. The measuring procedure is based on the direct superimposition of a transmission grating with a phase modulated high-frequency Mach-Zehnder spatial carrier. Latter, a set of phase-shifted fringe patterns, provided by low-pass filtering of the obtained multiplicative moire patterns, is combined in a Generic Phase-Shifting Algorithm (GPSA). The interesting information is achieved once the previous procedure is carried out with and without the transparent object located at the measuring area. The Wave- Front Distortion can be calculated by subtraction of these results provided by the GPSA or directly if a Differential PSA is employed. A comparison of the results obtained with both algorithms has been done.

We previously proposed the integrated phase-shifting method for the grating projection method using a Ronchi grating to display the height distribution of an object in real-time. The method uses a correlation between a grating brightness with a rectangular distribution and a rectangular function. The brightness of the phase-shifted fringe pattern is integrated on a CCD sensor of a camera during one exposure time and the integrated values are recorded. The theory uses the integration of the brightness at each pixel point during one exposure-time. In the present study, this method is extended to fringe pattern analysis with a cosinusoidal brightness distribution. A theory of the phase-shifting method for high-speed phase shifting is proposed. By integrating the brightness during one exposure time, the equation is modified to obtain accurate phase values. The analyzed phase values from continuous four images immediately before the last exposure time are obtained at very exposure time, i.e. every 1/30 seconds. The application to small displacement analysis of a cantilever and a micro- accelerometer are shown.

The idea of scaled topometry is to organize systematically different optical measurement techniques with overlapping ranges of resolution in order to receive highly resolved surface information in a wide range of scales. In such a surface inspection system, measurements on different scales of resolution have to be combined by a discrimination algorithm which should be sensitive on faults independent on the scale of resolution. Starting from a global measurement with low resolution certain critical areas have to be detected in which a refined measurements has to be performed. This process of detection and refinement has to be repeated on different scales. The task of the discrimination algorithm should be the detection of critical structures and the determination of the necessary order of refinement in the resolution. For the reason of scale- independence a classical approach using the surface roughness is not suitable.

Phase distribution analysis of deformed gratings in moire method and grating projection method provides accurate shape of specimen. We previously proposed the phase-shifting method using correlation with a rectangular function. The phase analysis uses many images during phase shifting of the projected grating. In this paper, we propose a new real-time phase analysis method, that is, the integrated phase- shifting method using four images of phase-shifted grating patterns with a rectangular brightness distribution. The theory and some applications to shape measurement are shown.

For the absolute and shade-free shape measurement of 3D objects with large height discontinuities, a co-axial optical sensor system with a common image plane for pattern projection and observation was proposed. Experimental results are presented that demonstrate the shape measurements of objects with a deep hole and large discontinuities.

The subject of the paper is the presentation of a new measurement method with the registration of traveling fringes with the aid of a fast CCD camera and the analysis of the influence of imaging process on the measurement error. Theoretical considerations are supported by computer calculations. The harmonic approach to optical imaging of the object complex amplitude distribution is used to obtain quantitative results.

The creation of a virtual object for CAD/CAM and computer graphics on the base of data gathered by full-field optical measurement of 3D object is presented. The experimental co- ordinates are alternatively obtained by combined fringe projection/photogrammetry based system or fringe projection/virtual markers setup. The new and fully automatic procedure which process the cloud of measured points into triangular mesh accepted by CAD/CAM and computer graphics systems is presented. Its applicability for various classes of objects is tested including the error analysis of virtual objects generated. The usefulness of the method is proved by applying the virtual object in rapid prototyping system and in computer graphics environment.

The progress in high resolution CCD detector technology provides the electronic medium for digital registration of holograms. This possibility is widely used in digital holography, which allows reconstruction of numerically stored microinterferogram. This approach is very useful for optical metrology application, however it is not convenient to real time visualization of 3D object reconstruction. In the paper we propose to use only the stage of digital registration and then transfer these data to LCD matrix to form an optoelectronic version of microinterferogram. This hologram is reconstructed optically by a laser beam, giving possibility to visualize an amplitude-phase object's image. These procedures together with fast LCD and proper optical imaging system should enable to produce digital holographic films.

Contouring by electronic speckle pattern interferometry is one of the most difficult measuring problems in the range of micrometers. The requirement of the position alignment of the master wavefront (smooth or speckled) and the wavefront of the test object by interferometric accuracy is always a difficult task and prevents the application of this method for quality controlling. To overcome the difficulties, in our paper a new two-wavelength method is presented.

The methodology and tools used recently in movement measurement for animation purposes are discussed here. It includes creating realistic 3D objects and describing the models of animation in 3D space. As a solution optical methods using structured light are proposed for gathering the information about shape and out-of-plane deformation of 3D objects. The principle of movement monitoring and measurement by adaptive sinusoidal fit based method applied to variations of intensity in each pixel is described and discussed on the base of computer generated intensities. The concept described above is experimentally tested. The further works to implement this technique are discussed.

Singularities in speckle fields are single points where the phase value is not defined. Consequently phase singularities decrease the resolution of interferometric measurement methods such as ESPI or HI. In this paper the behavior of phase singularities in the image plane is investigated for the case that the illuminated object is displaced along the optical axis. The investigations have been performed by means of simulations and measurements. Both, the model used to simulate subjective speckle fields and the experimental setup to measure the phase changes in the image plane are described. To observe the appearance and the disappearance of singularities, the object displacement was divided into a series of smaller displacement steps. The lateral speckle phase in the image plane was generated numerically for each displacement step. This way the transformation of the whole phase field could be visualized and the path of the singularities could be traced. The results obtained from these simulations are verified experimentally: For each displacement step the speckle phase was measured interferometrically along a column of a CCD-sensor. The behavior of the measured speckle phase is compared to the numerical results. Based on these results the consequences for interferometric out-of-plane displacement measurements are discussed.

The retardation modulated DIC (RM-DIC) method is proposed for extracting phase information from a DIC image by analyzing the partial coherent theory, which is applied to quantitative measurements of phase objects. The experimental results using RM-DIC method are presented and the quantitative analysis of the phase grating are presented.

We compare quantitative phase-measuring techniques in ESPI, using temporal and spatial phase shifting (TPS and SPS). The latter is less susceptible to time-dependent disturbances but inherently yields higher noise in the results due to the spatial intensity and phase variations of the object speckle field. Moreover, the necessity of larger speckles limits the light efficiency in SPS. Based on an evaluation of phase errors in sawtooth images, we compare both of the methods quantitatively in various ESPI configurations. By varying quantities like speckle size and shape and sawtooth fringe density, we find out characteristic behaviors of the methods. Some strategies to optimize the accuracy of the SPS method are explored to estimate how competitive SPS can be in ESPI systems.

Combining two-wavelength interferometry with the N-point technique (also called spatial carrier phase shifting interferometry) allows for the measurement of objects with large step heights that single-wavelength, phase-shifting interferometry can not correctly resolve. This combination yields some significant advantages but entails some limitations as well. Advantages include the elimination of the need for a phase shifter and the fast measurement of large step heights. The major limitations is a decrease in the measurable slope range of the object. Other concerns include setting the correct carrier frequency of the fringes for both wavelengths and coping with the magnification of the inherent phase errors of the N-point technique. The presentation considers real as well as simulated objects.

An interferogram can be demodulated to find the wavefront shape if a radial carrier is introduced. The phase determination is made in the space domain, but the low-pass filter characteristics must be properly chosen. One disadvantage of this method is the possible removal of some frequencies from the central lobe, resulting in a misinterpretation of the true phase. Nevertheless isolating the central order by using a recursive method when a radial carrier reference is used is possible. An example of a recovered phase from a simulated interferogram is shown.

In this paper, a spatiotemporal phase unwrapping method is proposed, which combines the dynamic optic fiber interferometric fringe projection method and the phase- shifting technique. A fringe projection fiber optic phase- shifting interferometer was set up, in which the fringe spacing and rotation can be easily adjusted. In the first step of the spatiotemporal phase unwrapping method, a large effective wavelength can be chosen so that the phase jump at the discontinuous profile is less than (pi) , then the spatial phase unwrapping method can be applied. Several intermediate phase maps can be obtained by changing fringe pitch and fringe orientation, reducing the effective wavelength step by step, and unwrapping each pixel along the time axis. In the final step, a high precision result can be obtained. A minimum number of steps may be chosen for obtaining the required accuracy according to the conclusion presented in this paper. An experimental result is presented for the measurement of a discontinuous object and shows the validity of the proposed method.

There are some kinds of troubles in the processing, for example, a phase unwrapping process, an accuracy of analysis, and so on, in the case that the spatial fringe analysis method based on the moire technique is applied to a noisy fringe image. In this paper, the digital filter technique and the filter based on the probability process are applied to the spatial fringe analysis method in order to solve these problems. In the simulation for the model of the fringe image, the results show that the spatial fringe analysis method using the digital filter is strongly robust against noise, and that the method with the Kalman filter can smoothly and accurately detect the phase map for the object with a continuous phase distribution. Furthermore, the method is applied to analyze a speckle fringe image from ESPI. The results show that spatial fringe analysis method based on the moire technique can analyze accurately the phase of a speckle fringe image with only single image. The proposed method can be anticipated as the technology which accelerates the use of the ESPI.

In several optical techniques, two simultaneous events can be analyzed by coding their information in a crossed fringe pattern. In this work, we present two automatic methods for the processing of this kind of fringe patterns and compare them with previously established methods.

Many papers describe classifiers of speckle pattern images obtained as a result of interference of light going through quasi-monomode optical fiber. The feature extraction is achieved by placing in Fourier plane a computer generated hologram (CGH) which serves as ring wedge-detector (RWD). The basic advantage of using CGH instead of RWD is its potential possibility to be easily changed, and thus, optimized for current classifications. This paper presents a new method based on rough sets theory (RST) and evolutionary algorithms, aimed to obtain the optimal CGH-based feature extractor for given classification problem. The task of CGH is dimensionality reduction of different pattern, while preserving all features necessary for further classification. The goal of optimizing feature extractor in terms of RST is to find such set of conditional attributes, for which approximation quality with respect to decision attribute has maximum value. Since there is no gradient direction information involved in above indicator, use of it as an objective function, depends stochastic method, such as evolutionary optimization. In the end, neural network fed with features extracted by CGH is presented, as the experimental confirmation of good classification abilities of the whole system.

A grating interferometer for high-resolution displacement measurements is analyzed. To decrease interferometer sensitivity to inaccuracy of the grating guide, a laser diode beam is focused on the grating surface. The effect of the interferometer geometry on the direction and period of the fringes is analyzed. In addition, the influence of the system geometry on the optical path difference is evaluated. Methods of adjustment of the fringe direction and period and also the zero value of the optical path difference in the interferometer are proposed. The theoretical analysis is verified experimentally by analyzing separately the influence of selected geometrical parameters on fringe direction and fringe constant. The experimental results are compared with regression models obtained by theoretical analysis. More than 92% results variability is caused by the theoretically predicted model of functions.

In a phase-shifting interferometer, spatial non-uniformity of the phase modulation happens in such a case where an aspherical mirror is compared to the corresponding aspherical standard surface which is translated along the optical axis by a piezo electric transducer. The amount of phase shift is different from position to position across the observing aperture depending on the direction cosine of the testing surface. In another case, when the reference optical flat is translated by two or more piezo-electric transducers, we cannot ensure that the reference surface moves strictly parallel to the optical axis. When these transducers have different sensitivities, the phase modulation is not longer spatially uniform and varies across the observing aperture.

The fast and reliable localization and classification of fault indicating fringe patterns in interferometric images is a major task in holographic non-destructive testing. For the purpose of feature extraction from gray value images, wavelet transformation has proved to be a suitable tool. In contrast to the Fourier transformation the local feature information will be preserved and furthermore the applied transforming wavelet can be adapted--under certain constraints--to the given problem.

Filtering some types of fringe patterns in the spatial frequency domain enables to reconstruct a complex number distribution containing full information about the phase of the analyzed pattern. It is shown that by registering two images mutually shifted in phase by (pi) it is possible to reduce errors introduced by the filtering process mentioned above. The technique of further correction of the intrinsic phase error caused by filtering using the Hilbert transform has been recently proposed for patterns with spatial carrier frequencies in Cartesian coordinates. In this work we show that the same approach can be applied to analyze fringe patterns with radial carrier frequency (in polar coordinates). The method of efficient filtering of such patterns and the technique for correcting the intrinsic error caused by the Hilbert transform are given. The final accuracy of the presented HT-based method is very close to the one which can be obtained by applying the phase stepping method.

A family of detuning insensitive algorithms with an odd number of points and a maximum of seven is developed here following a simple algebraic approach. Detuning insensitive algorithms are quite useful because the phase error due to any possible phase shifter miscalibration can be substantially reduced. A method to evaluate the second order detuning error, that is, the frequency range over which the insensitivity to detuning remains valid, is given, so that the best algorithm can be selected. A few of the most interesting algorithms from this point of view are described. This method, if desired can be extended to any number of points.

The wavefront shape can be obtained from lateral shear interferograms even if the lateral shear is large. Many procedures have been devised in the past to achieve this purpose. However, all of them have serious practical restrictions. A method is reported here using a digital analysis of the interferogram in the Fourier space. An alternative iterative method also using Fourier transform techniques is also presented with detail. A comparison of this method with alternative existing procedures is described.

We perform the analysis of the impact of noise in the phase- shifting interferometry. The effect of the multiplicative noise is equivalent to the (pixel-variable) modulating intensity error, while the additive noise has the two-fold consequences, equivalent to the (pixel-variable) phase-shift error and the modulating intensity error. We evaluate the relative importance of the errors in the background intensity, the modulating intensity, and the phase-shift on the accuracy of the phase recovery. The phase reconstruction process is more sensitive to the phase displacement error than to the intensity error. Finally, we show that the phase reconstruction process is more sensitive to the additive noise than to the multiplicative noise.

We demonstrate the uniqueness and convergence of phase recovery from high-spatial-frequency and/or undersampled intensity data. Furthermore, this is accomplished without the ambiguities that arise in phase unwrapping and without having to employ a-priori information. The method incorporates the technique of the line integration of the phase gradient to find the first approximation to the phase and the algorithm of synthetic interferograms to find the unknown phase with a high accuracy. It may be used with any experimental method that at a certain data processing step obtains a generalized sine and cosine intensity functions.

In this work we present the application of a regularization algorithm to the processing of photoelastic fringe patterns. The method used is a modified phase tracking algorithm applied to phase-shifted images. In particular, we present an algorithm for isoclinics-isochromatics separation that uses only five images. The performance of the method is discussed and experimental results are presented.

In this work we present two methods for the analysis of moire deflectograms. The first method is a Fourier-transform technique. The second method uses a regularization based method. Both methods are applied to realistic deflectograms and their performances are discussed.

We derive the analytical expressions to demonstrate that the asymmetrical part of the wave-front aberration function may be determined with a rotational shearing interferometer. The coefficients up to the fourth order in the radial coordinate may be found. The differential rotational shearing interferometer is proposed for measurement and detection of large amounts of aberrations, such as those anticipated in testing off-axis optical systems. The number of fringes displayed across the pupil is controlled with the shearing angle; therefore, its sensitivity may be increased by decreasing the shearing angle.

To enable unified analysis and simultaneous evaluation of geometrical spin-redirection phase and Pancharatnam phase, conventional 2 X 2 Jones matrix calculation is generalized and a new scheme of 3 X 3 matrix calculation is proposed. By the proposed algorithm one can trace the polarization state changes and the geometric phase shifts caused by the beam propagation along an arbitrary optical path that involves both reflection and refraction at surfaces with Fresnel shift and birefringence.

A simple scheme is presented that enables the measurement of phase changes by recording only two phase stepped images per time frame. Such a scheme is useful for the detection of defects or to monitor vibration characteristics in constructions. The differences between the here presented method and the four recordings per time frame method are discussed. Finally some experimental results are shown.

This paper shortly discusses physical origin of the polarization interferometry phenomena in highly birefringent optical fibers and simultaneously presents the latest experimental results with new types of anisotropic liquid crystalline-core optical fibers and fiber-based structures in view of potential applications to environmental and industrial fiber optic sensing.

A simple and robust interferometer using a laser diode subject to optical feedback is presented. The mechanism of fringe locking is first explained in terms of the compound cavity composed of the laser and the interferometer. Our theoretical analysis showed that the fringe locking is caused by compensation for a change in the path difference by mode hopping between external cavity modes of the laser diode. Fringe phase can be locked by the optical feedback within less than 0.2 (pi) (peak to valley) even when the interferometer is placed on a wooden table where in the absence of optical feedback whereas the fringe fluctuation amounts to about 6 (pi) (peak to valley value). The locked fringe pattern with spatial carriers can be analyzed by a fringe analyzer at the video rate and the measured results of a spherical error showed the same values of spherical mirror and repeatability as on an optical bench.

The construction of the fiber-optic sensor for the recognition of perturbations and results of its studies are presented. As a sensor head, the sample of few-mode optical fiber is used. Changes of intermodal interference condition, caused by external perturbation, have generated changes of output speckle pattern. This output has been concerned as an intensity image and diffraction method has been applied for its recognition. The image feature extraction has been achieved by applying a computer-generated hologram in the Fourier plane of an output image. A size of ring and wedge generated by this hologram has been optimized by using the rough set theory. Then, a artificial neural network has been used to recognize the external perturbation without a necessary of troublesome analysis of intermode interactions. An additional advantage of this solution is the possibility to train the network to eliminate slow environmental perturbations.

The development of a time-division-multiplexed 3D digital shearography instrument is described. The system provides simultaneous measurement of the in-plane and out-of-plane deformation gradients, allowing full surface strain analysis. The object under investigation is sequentially illuminated from three directions by three fiber coupled high power laser diode sources, and imaged onto a CCD camera through a single shearing interferometer. The pulsing of the sources is synchronized with the camera frame rate. Phase stepping is achieved using laser diode wavelength tuning combined with a path length imbalance in the shearing interferometer. The source pulsing schedule and image acquisition are controlled from a PC. An analysis of the optimum illumination geometry is presented. The performance of the system is evaluated on laboratory test samples.

Low-coherence spectral interferometry with channelled spectrum detection, extensively used for dispersion characterizing optical fibers, utilizes the fact that the spectral interference between two modes of an optical fiber shows up at its output as a periodic modulation of the source spectrum with the period dependent on the group optical path difference (OPD) between modes. However, this measurement technique cannot be used to measure intermodal dispersion in the optical fiber for which the period of modulation is too small to be resolved by a spectrometer. We proposed and realized a new measurement technique utilizing a tandem configuration of a dispersive Michelson interferometer and the two-mode optical fiber in which the intermodal spectral interference can be resolved even if a low-resolution spectrometer is used. In the tandem configuration of the dispersive Michelson interferometer and the two-mode optical fiber, the OPD in the Michelson interferometer is adjusted close to the group OPD between modes of the optical fiber so that the low-frequency spectral modulation that can be processed is produced. Using the Fourier transform method in processing the measured spectral modulations and subtracting the effect of the dispersive Michelson interferometer, the intermodal dispersion of the two-mode optical fiber over a limited spectral region has been obtained.

Any dynamic small changes of refractive index of a measurand, which are on the level of 10^-6 and less can be detected by inserting a measured object inside a stable laser cavity. Using heterodyne detection technique these changes can be measured with high resolution.

Wavelength measurements with Michelson interferometers have major disadvantages of high costs and low measurement rates. The paper shows two alternative methods for wavelength measurement of monochromatic light that are based on spectral characteristics of optical components. The methods are illustrated for interference filters and double photodiodes.

The Fabry-Perot interferometer (FPI) is conceptually a very simple structure and, in principle, a lossless device when on resonance. Hence the FPI is a versatile and flexible component and a prime candidate for use as a narrowband spectral filter in wavelength division multiplexing systems with channel spacing of the order of nanometers. The FPI with single mode coupled fibers and liquid-crystal filter have high finesse and easy selectively changed wavelength of peak. To effect demultiplexing one of the transmission peaks is tuned to the wavelength of the required channel.

The present work offers a new method for the direct measurement of the propagation constants difference (Delta) (beta) of orthogonal modes (mode beat) of the same order in planar waveguides. The work also presents the method to determine the difference of propagation constants (mode beat) for different refractive indexes of the cover.

The aim of this paper is to extend spectral-domain measurements of fundamental characteristics and parameters of optical fibers such as the wavelength dependences of losses, the cutoff wavelengths of a single-mode regime, dispersions, etc., to include new measurement techniques of low-coherence spectral interferometry that can be used for comprehensive characterizing optical fibers.

A new type of the in-line optical fiber ellipsometer based on the Sagnac interferometer is described. The possibility of the detection of the changes of full polarization state in this system containing standard single-mode fiber by an appropriate applied modulation technique is discussed. The device uses interferometric measurement technique based on the fourth Fresnel-Arago's condition, which secures very good system accuracy and stability. The results of investigations of the system are presented.

We present the fiber heterodyne interferometer built in order to have possibility to meaure its ability to detect the phase changes of the laser light guided in fibers. Description, advantages and disadvantages of such systems are described.

A real-time system for analyzing data from speckle interferometers, and speckle shearing interferometers, is presented. Interferograms are recorded by a CCD camera at a rate of 60 frames s^-1, with temporal phase shifting carried out at the same rate by means of a PZT-mounted prism in the reference beam. The images are analyzed using a pipeline image processor consisting of two Datacube MaxVideo 250 VME boards. With a standard 4-frame phase-shifting algorithm, wrapped phase maps are calculated at 15 frames s^-1; these are then unwrapped in real time using a temporal phase unwrapping algorithm. The main advantage of temporal over spatial unwrapping methods is that unwrapping errors due to noise and specimen boundaries do not propagate spatially. Pseudo-color maps of displacement distribution are displayed throughout the measurement period in real time. The paper is illustrated by application of the technique to the rigid body motion of a flat plate under controlled conditions.

Conventional models of ESPI deformation measurement are valid only for planar objects, and then only in the paraxial region. If an object is non-planar, then accurate deformation values can only be recovered if the surface shape is also known. This is because the local sensitivity vectors of deformation are a function of both the illumination and observation directions, which vary with the 3D position of the object points. We present a compact ESPI system for measurement of both shape and deformation using a mutual optical configuration. We also introduce an efficient method of data analysis. The system is demonstrated on a vibrating cylinder, where the shape information is used to derive the true out-of-plane deformation on the cylinder surface.

We describe a system that has enabled non-harmonic deformations to be measured with microsecond(s) temporal resolution for the first time with speckle pattern interferometry. The short exposure period and high framing rate of a high-speed camera at up to 40,500 frames per second allow low-power CW laser illumination and fiber-optic beam delivery to be used. The technique has been demonstrated in the laboratory and tested in preliminary industrial trials. The ability to measure vibration with high spatial and temporal resolution, which is not provided by techniques such as scanning laser vibrometry, has many applications in manufacturing design.

Electronic Speckle Pattern Shearing Interferometry (ESPSI) is becoming a common tool for the qualitative analysis of material defects in the aerospace and marine industries. Current trends in the development of this optical metrology nondestructive testing (NDT) technique is the introduction of quantitative analysis, which attempts to detail the defects examined and identified by the ESPSI systems. Commercial systems use divergent laser illumination, this being a design feature imposed by the typically large sizes of objects being examined, which negates the use of collimated optics. Furthermore, commercial systems are being applied to complex surfaces which distort the understanding of the instrumentation results. The growing commercial demand for quantitative out-of-lane and in-plane ESPSI for NDT is determining the quality of optical and analysis instrument. However very little attention is currently being paid to understanding, quantifying and compensating for the numerous error sources which are a function of ESPSI interferometers. This paper presents work which has been carried out on the measurement accuracy due to the divergence of the illumination wavefront and associated with the magnitude of lateral shearing function. The error is measured by comparing measurements using divergent (curvature) illumination with respect to collimated illumination. Results show that the error is increased by approximately a power factor as the distance from the illumination source to the object surface decreases.

Multidirectional holographic interferometry (MHI) allows to study characteristics of phase objects using transmission computer tomography. The present paper deals with comparison of various phase-measurement interferometry techniques. On this basis two configurations of holographic interferometers were designed. Both of them can be modified according to the method used for the evaluation of the phase change. Components for MHI for imaging phase object with full and partial asymmetry were constructed.

This paper describes grating shearography as a technique for direct measurement of in-plane strains and out-of-plane slopes. This technique has many interesting features for mechanical engineering: strains are measured without numerical differentiation, so a good spatial resolution can be obtained; it is also fairly insensitive to vibrations; full in-plane and out-of-plane information can be gathered simultaneously; finally, it is easy to switch from grating shearography to grating interferometry, in order to have also the displacement field. We present the theoretical basis of the method and the preliminary measurements on a graphite/epoxy composite sample under Iosipescu shear testing. Results are compared with FEM simulation.

We present a general review of our current recording materials suitable for laser interferometry applications. The review will cover fine-grain Silver-Halide materials sensitive to the red (PFG-01) and green (VRP-M) spectral ranges. These products have characteristics very similar to the old Agfa products 8E75 and 8E56. Additionally ultra-fine grain red-sensitive and panchromatic Silver-Halide materials will be covered as well as products based on dichromated gelatin. In each case detailed characteristics of each emulsion type will be presented and recommended processing schemes will be discussed in the context of both Pulsed and CW radiation sources. The choice of commercially available substrate and material dimensions will be mentioned.

The synthesized reference beam TV holographic technique is presented in this paper. In this method synthesized reference beams are used for compensating the deformation of the investigated object. The phase-fronts of the reference beams are built from phase shifted plane waves. These phase shifted plane waves can be used periodically, so almost any phase front can be produced. The actual phase-front can be built after the measurement using recorded pictures in the computer memory. Using this technique the sensitivity of the measurement can be changed after the recording, so this feature of the method is extremely valuable in industrial measurements, where the repetition of the measurement is not always an easy task. In this way the fringe density at highly deformed points can be decreased; different components of the complicated fringe pattern can be removed; and the evaluation of the fringe system can be done more easily. This method can help to determine the sign of the deformation. A set of simulations and the results of real measurements are presented.

We describe a new type of shearing interferometer, with the capacity to control the amount and the direction of displacement shear. The vectorial shearing interferometer is based on the Mach-Zehnder configuration, by incorporating the displacement shearing system. It is composed of a pair of wedge prisms that modify with a high degree of precision the optical path length and the tilt of the sheared wave front with respect to that of the reference wave front. When the shearing direction is chosen along the CCD pixel rows and columns, a 2D derivative of the phase function is obtained, allowing its complete recovery in two-dimensions. The variable shear and tilt may be implemented along any other direction with the particularly beneficial characteristics that the number of fringes and their orientation may be controlled with the shear direction and its magnitude.

This study describes the use of diffractive optical elements (DOEs) namely phase gratings, for the simplification of typical illumination schemes employed in digital speckle pattern interferometry. The diffraction gratings are recorded in a photopolymer material that delivers by high diffraction efficiency in transmission but which requires relatively low exposure energies. A significant advantage of this material is that it is completely self-developing, allowing the recording of a custom DOE in-situ and the monitoring of grating efficiency during processing. An example of utilizing this type of DOE in a novel out-of- plane speckle interferometer with what is effectively two- beam illumination is described. A feature of this particular system is the complete insensitivity to in-plane displacement when employing highly off-axis illumination. Incorporation of these DOE's in fiber optic based speckle interferometers allows the realization of simple, compact systems immune to phase and polarization drift.