The usual moire method consists in projecting a grid, that is made of parallel straight lines, onto an object. Then a moire picture is obtained, which is made of cured fringes. In the inverse moire method, we compute a specific grid that is made of straight fringes. The object must be known, but small deformations from a known mean shape can be analyzed with very simple fringe processing. We show some examples of reconstruction by inverse moire.

The method combining moire interferometry and termovision techniques (MI/T) for thermally loaded elements testing is proposed. The methodology of the MI/T method applied for simultaneous in-plane displacement/strain and temperature distributions monitoring and measurement at electronic elements is described. The results of thermal tests performed at electronic chip UCY74S405N are presented.

We have previously proposed a phase evaluation method of multiple-beam Fizeau patterns that combines the two-beam phase-stepping algorithms with the more effect. This method is based on a multiplicative moire image formation process obtained y the direct superposition of high-frequency multiple-beam Fizeau carrier fringes on a transmission grating. In this paper the contrast between this Moire two- beam phase-stepping technique and the direct evaluation of the high-frequency multiple-beam Fizeau carrier fringes by means of the Fourier Transform Method is presented.

Interferometers with grazing incidence and visible light offer a fast and practicable solution for waviness and roughness testing in mechanical engineering without the necessity of scanning. Therefore, the possibility to use the grazing incidence of light onto the specimen is considered. The experimentally proved new optical layout for the grazing incidence interference microscope with a piezo-driven mirror for phase-shifting is based on a special optical stage with a hologram as a beam deflector. The object surface is sharply imaged onto the hologram, where an interference pattern is caused by the topography of the surface under test. Then, the diffracted light of the first order is imaged by a second optical stage onto a CCD-camera chip and the fringe pattern evaluation is carried out with a phase- shifting algorithm. Additionally a 2(lambda) -algorithm was implemented in the evaluation software. The necessary variation of (lambda) is generated by a small computer- controlled variation of angle of incident of light ont he specimen surface. First measurement results of objects with continuous and discontinuous surfaces demonstrate the possibilities and the limitations of the new experimental approach.

Fast analysis of 3D shape deviations is obtained with fringe projection combined with moire filtering. A method is presented where an object adapted fringe mask is written in a matrix LCD and projected onto the test object. The object is detected by a CCD camera. Perfect objects yield regular fringe patterns. shape deviations results in distorted fringes. For moire filtering the periodic structure of the detecting CCD chip is exploited, therefore no image postprocessing is required, testing at video frame rate is possible.

The surface metrology market today is moving towards non- contact modular computer-controlled systems for measuring and analyzing roughness, contour and topography. Since most of these systems require a great accessibility to the surface to be measured they can not be used for the metrology of surfaces with intricate geometries, difficult access and small dimensions. In this paper a new instrument concept for measuring the profiles of such difficult-to- access surfaces is demonstrated. Two different prototypes based on the confocal microscopy arrangement have been developed. A visible laser beam is focused with a high numerical aperture optical system onto the component surface that has to be measured. Depending on the prototype configuration, either the retroscattered or the reflected light signals are measured with a CCD array and analyzed with an image data processing algorithm. As an example of the application of these confocal prototypes, over 20 diamond wiring dies with different sizes and geometries have been measured and their inner profiles displayed and analyzed. All the results obtained show that the measurement method is robust enough to provide sub-micron repeatability and in the worst case the precision achieved is one order to magnitude better than the manufacturing tolerances of wiring dies.

A novel instrument is described for the optical, non-contact measurement of the waviness and figure component of the surface texture of flat surface. Here the spatial frequency range for waviness is typically chosen from 1.25/mm to 0.05/mm, whereas the global figure error contains the lower spatial frequencies. The special requirements on the dynamic range, the spatial resolution, and the signal-to-noise ratio of the measurement are discussed. The presented instrument consists of a white-light, extended-source, phase-shifting Mach-Zehnder interferometer. The special design employing low temporal and spatial coherence avoids coherent speckle noise on the measured surface maps while providing good spatial resolution. Thus in the waviness frequency band the modulation transfer function exceeds 0.75, an the RMS- precision is 0.1nm over the measurement area of 100mm in diameter. Measurement examples of typical applications, e.g. substrates for hard disks and flat panel displays, are shown.

Spectrally resolved white-light interferometry has proved to be an absolute and precise tool for measuring optical delays. Hitherto, the bidimensional interferogram in the hybrid spatial-spectral domain, has been processed row by row as function of (sigma) , in order to obtain the map of the optical delay (Delta) (y). In this way, nanometric precision is obtained in profilometric studies. In this paper we show that more information an be obtained from the same interferogram when it is additionally processed column by column. This corresponds to the analysis of a sequence of monochromatic interferograms which are free from the classical ambiguities in the phase, since the preliminary row-by-row data processing along the spectral axis removed them. The absolute phase function thus obtained for each column at constant (sigma) yields the profile z(y). Statistical treatment of the overall information provided by this row by row plus column by column data processing increases precision in one order of magnitude. This paper presents the method and experimental results as well.

A common procedure of profilometry by means of white light interferometry is to scan one interferometer arm step by step. In this way, the intensity detected for each surface point reproduces the autocorrelogram of the light source, which is used for the determination of the absolute phase between a reference position and the zero optical path difference position. Phase changes due to reflection on the inspected surface produces a shift of the interference fringes with respect to the coherence envelope. If those phase changes vary from points to points, artifacts can be introduced in the profile reconstruction. We propose to measure simultaneously the interferometric phase and the shift of the interference fringes with respect to the coherence envelope. That processing is based on a wavelet transformation of the sampled light source correlograms and leads to complementary information that describes more completely the optical behavior of surfaces.

Increasing demands for accuracy in manufacturing and international standards of quality control require faster and more precise measurement techniques. Surface inspection and shape control of technical workpieces is commonly done by tactile profilometers. A faster alternative to this mechanical tool can be realized interferometrically. Grazing incidence of laser light onto the technical surface reduces speckle-noise significantly. In our setup computer generated holograms are used both as references for the technical surfaces to be tested and as beam splitter or recombing element. Each class of workpieces requires specific computer generate holograms, e.g. phase-gratings for plane surfaces or diffractive axicons for cylindrical and conical surfaces An ideally shaped workpiece will result in a zero fringe field. Deviations from the ideal shape will be indicated by interference fringes and fringe distortions. The sensitivity of the interferometer can be adapted to technical needs. The surface deviations of the workpiece are superimposed by adjustment aberrations which can be described mathematically with sufficient accuracy and eliminated by a least square fit. We will demonstrate this measurement technique with workpieces of different shape.

There are many optical and non-optical methods to investigate surface structures and morphologies. Among the optical techniques, the speckle interferometric methods have become more and more interesting during the last 25years, and this paper shall be restricted to interferometric techniques based on the speckle effect only. The introduction of phase-shifting methods rendered the possibility to automate and to analyze measured interferograms more easily. And it was quite early when the angular (ASC) and spectral (SSC) speckle contouring methods have been proposed to measure surface shapes. As demonstrated in some earlier papers, the method to summarize phase interferogram images incrementally enlarged the measurement range of angular speckle contouring. Furthermore it has become possible now not only to measure macroscopic surface shapes by ASC, but also to map microscopic surface topographies and to determine the according surface parameters as roughness, for example. In a first investigation, the shape of a plastic cylinder is measured by ASC and SSC using the same interferometer set-up. As a practical application, the cylindricity of the object is determined by both methods. For all measurements a laser-diode is used as laser source, and in the SSC technique, the injection current is changed to realize different hopping modes yielding different laser wavelengths to be used for the contouring approach. It is the first time that phase images corresponding to different synthetic wavelengths are summarized modulo 2t in the spectral speckle contouring technique. The measurement results in form of phase maps, bias images, 3D-plots, and iD-profiles of the cylinder object are compared between the SSC and ASC method, and the results are shown to be in good agreement. In a second investigation, the 3D-structure of a reshaped composite hemisphere is measured using the ASC and the SSC method. The results are referenced again, compared to each other qualitatively and quantitatively, and they are also in good agreement. As an interesting parameter, the curvature radius of the reshaped composite hemisphere is determined by both methods. Finally the new method to measure surface roughness parameters by the ASC technique improved by the addition of incremental phase images modulo 2t is illustrated. Measurements have been carried out on side-milled Rugo test surfaces, and the angular speckle contouring results are compared with classical mechanical stylus profilometric reference data. A concrete application is further demonstrated for the evaluation of the surface roughness of painted composite aircraft structures. The surfaces of these carbon fiber-reinforced specimens with copper mesh have been treated by high-power laser beams for the periodically necessary removal of the paint. The intention of the investigation of the laser-treated surface by the speckle contouring method was to determine the surface morphology, and to find out whether there is a correlation between the roughness and the removed amount of paint. The interesting experimental result is that the roughness of the laser-treated surface is a strictly monotonous function of the number of high-power laser pulses at constant energy density. Reference measurements have been carried out by mechanical stylus profilometry and agree well with the speckle results. Of course all measurements have been carried out without the usual fine, white powder for contrast enhancement and without the usual vibration isolation, too. Keywords: Speckle Interferometry, Angular Speckle Contouring, Spectral Speckle Contouring, Shape, Roughness, Micromeasurement

Angular Speckle Contouring (ASC) allows the measurement of microscopic (roughness) and macroscopic form (shape). ASC is a fast, non-contacting and full-field measurement technique. The measurements for shape and roughness are performed for measuring a piston of internal combustion engine. All measurements have been carried out without vibration isolation of the optical tables. For the shape measurements the surface has been treated with white powder to increase the contrast, for the roughness measurements the surface hasn't been treated. The results obtained by ASC are compared with mechanic- profilometric measurements and the results are discussed.

The analysis of scattered light is a well known method for the inspection of very smooth surfaces. Some new methods of data analysis have now widened its utilization to rough and very rough surfaces. Even if no generalized solutionis available it is possible to determine any surface parameter in certain applications. Especially for process control purposes, scatterometry can be a fast, contactless and reliable method to measure deviations form rated values and to detect machining errors. In this paper, the method and its application to honed, polished and turned surfaces are presented. Amplitude as well as spatial parameters of the surfaces microtopography will be determined and compared to those obtained by other methods.

Surface measurement is an important tool for quality control In our contribution we describe a novel application of reflection ellipsometry to profile measurement and material detection. The ellipsometric parameters (Delta) and (Psi) are measured by using a PSA-ellipsometer arrangement and a 4- zone-intensity-ellipsometric algorithm. To achieve a high lateral resolution we focus the laser beam on the surface through a microscope objective with high numerical aperture. The spot diameter is in the order to 1 micrometers . The focus adjustment is carried out by an integrated autofocus system. From the ellipsometric parameters we conclude to the refractive index of the local surface material and the local surface gradients. The height profile is calculated by an integrating and filtering algorithm. The material is ascertained form the refractive index. The feasibility of our novel microellipsometric measurement system is demonstrated by several tests. Measurements of material transitions and the height profile of a glass surface standard are presented.

Several methods for the analysis of white light interferograms are presented and their performance is compared to a new method employing the wavelet transform in connection with sub-Nyquist sampling. As the result of computer simulations and experiments the wavelet method proves to be best suited to the problem. Furthermore, a method is proposed to characterize the microtopography of surfaces on the basis of fractal parameters, whereby these parameters are calculated by means of a wavelet method. The advantages of using wavelets in comparison to the well known fractal description by means of the power spectral density is, that this new method is less affected by noise and offers the ability to separate the roughness from the structure. Simulations show that even in the otherwise disturbing presence of sharp edges or spikes the separation of micro and macro structure is successfully performed by the proposed wavelet method.

We present an outline of vibration analysis techniques that we have used recently which are based on video speckle interferometry. The work described is carried and deals with the following subjects: the determination of composite vibration induced strain, with the use of both (a) speckle shearing interferometry and (b) electronic speckle pattern interferometry (ESPI); (c) two mode vibration analysis based on stroboscopic ESPI and (d) inexpensive techniques for multimode vibration analysis based on hybrid ESPI and laser velocimeter measurements.

Digital speckle pattern shearing interferometry is described as a robust measuring method due to its simple optical setup and the insensitivity against ambient noise. It has been sued in industry for nondestructive testing and strain measuring. This paper explores the possibilities for vibration analysis using digital speckle pattern shearing interferometry. The measuring device performing both time- average and stroboscopic methods is described. The time average digital speckle patten shearing interferometry in conjunction with the stroboscopic technique is suited well for both qualitative and quantitative vibration analyses. The determination of dynamic deformation and strain fields form the phase map of shearogram is demonstrated, and some preliminary results are shown.

We present a novel technique for the application of stroboscopic additive TV-holography to the measurement of vibrations using temporal phase-shifting. Based on a previous concept - contrived and developed by the same authors - that used two illumination pulses within each vibration cycle and interpulse phase modulation at the same rate that the vibration of the object, this new technique implements and analogous phase modulation scheme but between two swiftly alternating bursts of single pulses with different phase within each video frame, rather than using true double-pulses, thus allowing quantitative measurements to be performed with stroboscopic illumination keeping the characteristics of stability and temporal resolution of the double-pulse additive stroboscopic technique but with the additional benefit of reaching high vibration frequencies with low bandwidth phase modulators.

A new modal analysis using moire topography is proposed in this paper. A modal analysis with holographic interferometry is employed for vibration analysis, because non-contact and 2D measurements can be readily realized. The modal analysis using holographic interferometry is an effective measure for a vibration with small amplitude, it however, is difficult to apply to a vibration with large amplitude, such as over a few mm. In this paper, a vibration with a large amplitude is analyzed using the moire topography system. Single fringe image is grabbed by the projection moire topography system using a stroboscope whose flash timing is controlled with a computer system. The image is analyzed by the spatial fringe analysis method based on a new phase unwrapping. Consequently, the shape of vibrating object can be detected in process of the vibration. The new method can also analyze the vibration mode of an object that has a complex sharp. The vibration of some plates as simulation models of turbine blades is analyzed by this method. Modal parameters are calculated, then a visualization of the mode of the vibration can be realized. The results show that the proposed modal analysis is effective for the analysis of the vibration with a large amplitude.

Electronic speckle pattern interferometry (ESPI) with CW- lasers is well introduced in the industry. Using pulse lasers in combination with ESPI techniques expands the technical applications. The combination of double pulse lasers with the ESPI-technique is considered as essential for the industrial application. It expands the application of ESPI systems to the investigation of transient events and the vibration analysis of components under free boundary conditions. However, due to the limited resolution of the CCD-cameras the interferograms show lower signal-to-noise ratio which requests special treatment of the images and new evaluation algorithms, in particular for 3D analysis. First practical applications have already been carried out in the automotive industry.

The increasing demand for better characterisation ofmaterials and components in many cases requires ftill field information for the analysis of the mechanical behaviour. 3D Speckle Interferometry offers the possibility to obtain full field and non contact deformation and strain analysis of materials and components. The principle and theory of this technique have been well known since several years. Novel designs now offer the opportunity of easy application in the field of material and component testing.

Some recent applications of digital speckle photography in experimental mechanics are presented. Topics include the measurement of the in-plane deformation close to a triangular notch through an optical microscope, the 3D- deformation field of a sheet of paper subjected to increasing heat, the deformation of cardboard subjected to uniaxial stress, the shape of a curled sheet of paper, and the in-plane strain fields in an uniaxially stressed sheet of aluminium around a rectangular notch and a circular hole, respectively.

Electronic speckle pattern shearing interferometry (ESPSI) allows for the measurement of displacement derivative maps. To monitor the stress/strain state of an object surface and its material properties, it is necessary to measure more than one displacement derivative map. The conventional configuration of ESPSI has been modified by parallel adaptation of Michelson shearing interferometers and an optoelectronic/image processing head with the capability of simultaneous capturing of 2 images. The automatic analysis of speckle fields is performed by temporal phase stepping method with the separation of the information by orthogonal polarization states. In the paper the opto-mechanical and electronic configuration of the system is presented. The experimental results obtained in the modified ESPIS system, when applied to determination of shear strain in a tensile loaded aluminium specimen are also presented.

Laser light, when scattered from a moving object or fluid, fluctuates in intensity. These fluctuations can yield information about the velocity of the scatterers involved. Most techniques analyze the temporal fluctuations of a single speckle. For information on the spatial distribution of velocities, some form of scanning is necessary. Exceptions include speckle photography and particle image velocimetry, which are full-field, double-exposure methods for measuring lateral velocities and flow. Another full- field technique, laser speckle contrast analyses, has the additional advantages of being a relatively cheap, single- exposure technique operating in quasi-real time and sensitive to both lateral and line-of-sight motion. LASCA was originally developed to monitor blood flow, but these advantages should also be useful in industrial flow measurement.

Optically generated holograms can be recorded on CCD-arrays if the sampling theorem is obeyed. The digitized and quantized holograms are processed digitally for the reconstruction of intensity and phase of the real or virtual image. This digital reconstruction consists in a numerical realization of the diffraction integral One approach is the Fresnel approximation employing a single Fourier transform, the other is the interpretation of the diffraction formula as a convolution integral and calculation of this convolution by a double or triple Fourier transform. In this convolution approach the impulse response of free space propagation has to be defined which is then Fourier transformed or the free space transfer function is defined immediately. Impulse response as well as transfer function can be defined exactly or in an approximated version. The main difference between the Fresnel and the convolution approach is the different size of the resulting images. Furthermore in the Fresnel case this size depends on the wavelength and the distance of the object from the CCD, in the other case it does not. In this paper consequences on the reconstructed wavefields and on the interference phase distributions of holographic interferometry are indicated and demonstrated by experimental results.

A method for particle size and position measurement based on digital holography is described. A plane wave passes a particle stream and the diffracted wave is recorded directly by a CCD-sensor without any focusing optics. The reconstruction of the particle distribution from the recorded diffraction pattern is done numerically with a computer. Diffraction patterns from different directions are taken at a fixed instant of time, evaluated independently and finally the reconstructed scenes are combined by tomographic methods.

A breadboard holographic interferometer that uses a photorefractive sillenite crystal under the anisotropic diffraction configuration is presented for application of quantitative vibration measurements. After the hologram of the object at the rest is recorded, a stroboscope is used to observe the stable pattern of the vibrating object and phase-shifting is introduced for quantitative measurements. It is shown that this system can measure modal displacements of objects of typically 25 X 25 cm² with high accuracy by using a continuous YAG laser emitting 490 mW at 532 nm. The error sources are investigated and particularly a systematic error arising from the stroboscopic process can be calculated and eliminated.

This paper presents the methods of linear interpolation and polynomial curve fitting for achieving sub-pixel resolution phase difference determination by fringe pattern matching. These two methods wee examined by computer simulation and experiment. In computer simulation, the effects of the resolutions of imaging system were also discussed. The computer simulation and experimental result have shown that the method of linear interpolation and that of polynomial curve fitting can both be used to achieve sub-pixel resolution in the measurement of phase difference by fringe pattern matching. The phase difference between fringe patterns is easy to achieve by linear interpolation compared with polynomial curve fitting.

In periodic structures the Fourier peaks have to be removed in order to enhance defects. This can be done by digital image processing or by optical means. Recently we presented some new developments in microscopic defect enhancement by spatial self-filtering using B₁₂SiO₂₀ (BSO) in the Fourier plane of an optical processor. In this paper we summarize spatial filtering using photorefractive, non- linear devices and equivalent numerical techniques. We sue BSO as photorefractive medium and two different optically addressed spatial light modulators as nonlinear devices.

This paper proposes a fast phase unwrapping procedure capable of dealing with arbitrarily large phase discontinuities. Such discontinuities may be present in the phase maps obtained with the technique of profilometry by fringe projection, when the studied object presents sharp height discontinuities. In our procedure, two images are taken with high frequency projected fringes, so that spatial phase-stepping is possible. The algorithm sued eliminates the harmonics up to order 7. The fringe pitch is slightly varied between the two acquisitions, and the difference between the two obtained phase maps yields a slowing varying phase map which enables unwrapping, as it gives low frequency extra information.As compared to other proposed procedures, the present one allows to keep the high sensitivity associated with high frequency fringes, together with the large dynamic range resulting from the possibility to unwrap the phase successfully. Also, the number of frames required is less than what is needed by other techniques.

Phase shifting interferometry (PSI) is one of the more common techniques for interpolation between interference fringes. A surface-profiling PSI instrument stores CCD image frames of fringe patterns for a series of reference phases; then applies a mathematical algorithm to recover phase information.1 Because the wavefront phase itself is a linear function of the surface profile, PSI provides a high-resolution measurement of the surface figure. In the early days, computational limits restricted the number of image frames to three or four, which does not leave much room for variation. As demands for precision have increased, so have the length and variety of phase-shifting algorithms. The state of the art has advanced to 5, 7 and even 15 frame varieties. At the same time, the level of sophistication in deriving these algorithms has risen dramatically.234 This paper explores the limits of these trends, while reviewing some of the mathematical techniques that we at Zygo use to analyze PSI performance. Finally, in an attemptto predict far into the future, I present a 101-frame algorithm that is highly resistant to error sources. This somewhat extreme example highlights the practical limits on algorithm length, which are actually more relaxed than one might think, provided that we loosen the definition of PSI.

A novel light source using a laser diode is proposed for the optical heterodyne technique. This light consists of two frequency beams whose polarization directions are orthogonal without special types of laser or frequency modulators. A laser diode is easily modulated in a frequency due to the saw-toothed injection current modulation. In order to compensate the power fluctuation by injection current modulation and to keep the total power constant, a super luminescent diode is added and therefore interference beat signal is sinusoidal. The hybrid interferometer of heterodyne and low coherent measurement is proposed using this novel light source to overcome 2(pi) phase jump. Three dimensional surface profile can be measured with the range from nano to micrometer using this interferometer. This light source is suitable for practical application and can be made in a small unit compared with a Zeeman laser or an acousto-optic modulator.

The mutual interference of two beams in the spectral domain has been demonstrated experimentally at the output of the uncompensated Michelson interferometer excited by two low- coherence sources having different spectral widths. For the first, a wide-spectrum source, three spectral interferograms with the wavelength-dependent periods of modulation of the source spectrum affected by dispersion of the beamsplitter have been resolved. Using the Fourier transform method for the spectral fringe pattern analysis, good agreement between the experimental and the theoretical spectral interferograms has been achieved and characteristics such as the unmodulated spectra, which agree well with those obtained by blocking one of the arms of the interferometer, and the wavelength dependences of the group optical path differences (OPDs) have been obtained. For the second, a narrow-spectrum source, the spectral interferograms with the wavelength- independent periods of modulation of the source spectrum have been resolved and a cross-correlation procedure between the experimental and theoretical spectral interferograms has been applied in the estimate of the group OPDs between both beams corresponding to different positions of one of the mirrors of the interferometer.

Spectrally-resolved white-light interferometry (SRWLI) is used for real-time measurement of dispersion functions. SRWLI consists in the spectroscopic analysis of the interferograms which are produced when a wide, continuous- spectrum light-source is used to illuminate a 2-wave interferometric device. This produces incoherent superposition of many monochromatic interferograms, one for each resolved wavelength in the source spectrum. Each monochromatic interferogram at wavelength (lambda) stores the optical delay in the interferometer at that particular wavelength. When a transparent, dispersive specimen is introduced in the interferometer, the optical delay becomes a function of (lambda) , and this function is stored in the incoherent superposition of the whole set of monochromatic interferograms. We propose in this paper the use of a prismatic specimen with a linear variable thickness. In this way the interferometry gives rise, for each wavelength, to a classical Young fringe pattern whose spatial frequency stores the dispersion function. The spectroscope, in series with the interferometer, splits the incoherent superposition of the different monochromatic patterns. The recorded image is processed by measuring the frequency of the fringes at each resolved wavelength. Precision in refraction index is about 10^-6. The method is well adapted for measuring dispersion curves of evolving specimens because only one image is sufficient to determine the dispersion curve in the useful spectral range. Experimental results are presented for an optical glass in the visible spectrum.

A range of sources are investigated to determine their suitability for low coherence speckle interferometry. Sources include a superluminescent diode (SLD), a multimode laser diode (MMLD) and two MMLDs. The coherence lengths for each are determined using a Michelson interferometer and are then compared with those obtained from a speckle interferometer. Two MMLDs at 792nm and 812nm are found to provide a coherence length of 10.2 micrometers comparable with that of the SLD. The dual MMLD source arrangement provides ten to a hundred times greater optical power on the test object making the technique viable for large area test objects.

We present a new powerful modulation/demodulation technique for unambiguous measurements of phase changes in two-beam interferometers. The technique does not require any additional optics besides a basic interferometer setup and resolves the ambiguity of direction of phase changes by use of a simple two-tone modulation of the laser diode wavelength via injection current. The interference of two modulated light beams generates a signal at the photodetector which is similar to that of heterodyne interferometric setup. The optical phase is thus transferred to an electrical carrier frequency, which allows the phase detection by means of conventional electronic FM-signal processing. The new techniques can be used with any two-beam interferometers as e.g. the Michelson or Mach-Zehnder ones. In the present paper it was applied to a laser-diode, 'self- mixing interferometer' where a weak optical feedback from a target results in an interference with internal laser light.

Low loss fused single-mode fiber couplers for high finesse ring resonators have been manufactured for use in the BFRL. The fused fiber couplers have coupling ratios from 1.2 percent to 5 percent with excess loss less than 0.009dB. These components represent the passive part of an al-fiber Brillouin ring-laser pumped by a Nd:YAG laser at (lambda) equals 1319 nm wavelength. With FM-sideband modulation technique we stabilized the round trip wave in the ring resonator RRes, adjusting actively the laser frequency by a thermoelectric cooler and a piezoelectric element. Above pump threshold the RRes starts stimulated Brillouin backscattering. This 13GHz- frequency-shifted-BFRL light source can be used as a probe laser for Brillouin-sensing in a Brillouin optical-fiber domain analysis measurement setup.

The design operation and testing of a simple Class II laser optical fiber structural monitoring system and associated instrumentation is discussed. The response of this monitoring system was observed for optical fibers embedded in the tensile and compressive sides of a 100mm X 1500mm reinforced concrete beam during curing and laser under test load conditions. The internal temperature of the specimen was monitored throughout the curing process using thermocouples and this data correlated with the transmission intensity data obtained from the fibers. For he load tests, conventional electronic strain gauges were placed near the optical fibers; the fiber sensor system displayed a negative linear response. Thus, simple optical fiber sensor systems may be considered as possible alternatives to existing methods for monitoring the structural integrity of concrete infrastructures. The use of optical fibers have several inherent advantages in their own right including immunity form electromagnetic interference and ensuring the integrity of readings form around power cables and transformers. Also, the potential for long distributed sensor in environments such as tunnels is well suited to the deployment of optical fiber sensor technology.

An optical configuration for a new laser supported eddy current sensor was developed and tested. In the arrangement the induction of eddy currents is conventionally performed with an excitation coil above the object under test. For the detection of the magnetic field a suitable crystal, which is integrated in the excitation coil, in combination with a detection laser beam running parallel to the axis of the coil is used. In the presence of a magnetic field, the Faraday-effect in this crystal leads to a rotation of the polarization of the detection laser beam. With the help of a suitable optical arrangement this rotation of the laser polarization is transformed in a change of light intensity, which is analyzed by a photodiode. The special advantage of this arrangement is, that by a focusing of the detection laser beam a measurement of the magnetic field with a high spatial resolution can be achieved. In this paper the basic physics and the design of the sensor will be describe. First results of experimental investigations concerning the resolution power will be presented and compared with conventional eddy current sensors.

Recently a new system has been proposed for the removal of cochannel or multipath interference found in an optical heterodyne sensing system. It involves an amplitude locked loop used in conjunction with a phase locked loop in the system demodulator. Such a detector has been incorporated into a free-space Doppler vibrometer detection system. This paper presents experimental results and details of the performance of such a system suffering from interferences arising from spurious scattered light with and without the new detection circuitry. The result presented indicate a dramatic improvement over conventional demodulation systems.

THe fabrication of tunable optical devices by using Si free- space micro-optics and Ni micromirrors has demonstrated the applicability of MEMS technologies to photonic devices. Compact, multi-functional, assembly-free, micro-optical systems have been developed by using MEMS technologies to integrate optical devices and micromechanics onto the same wafer. A high aspect-ratio Si plate which works as a beam splitter has been fabricated using Si micromachining. A tunable laser diode with an external Si mirror has been fabricated and shown to have wavelength tunability. A Ni micromirror with comb-drive actuator has been developed and applied it to both a tunable optical filter and a tunable laser diode. Due to the precise motion of the micromirror, accurate optical tunability has been obtained.

Holographic interferometry is widely used as contactless method in experimental mechanics and non-destructive testing of materials and engineering components. But measuring the full 3D-deformation of the object's surface requires a complicated optical setup with at least three different illumination directions.Especially if micro-components with lateral extensions less than 10mm have to be examined the simple use of conventional holography becomes more and more a problem. Since high resolution CCD cameras are available for reasonable prices, digital holography can be used as a fast, easy and precise method for holographic interferometry. Compact and simple setups can be achieved by the use of fiber optics. Digital holography replaces the holographic plate by a CCD matrix. No additional magnifying optical components are needed to achieve lateral resolutions of about 5 micrometers and deformation resolution of 15nm. Some experiments using four illumination direction in an optimized setup are presented. They show the 3D-deformation fields of small objects under a given load. The results are compared with computer simulations to receive material parameters.

As a novelty application of Si-based integrated optics, the results of realization of a compact Mach-Zehnder interferometer will be presented. The deposition of a ZnO thin-film transducer on the reference arm of the interferometer will allow to transform this optically passive device in a device under an active sinusoidal phase modulation.

The optimization of microcomponents in nanotechnology requires the knowledge of the mechanical properties of the micromaterials used. These properties cannot simply be inferred from tests with macroscopic specimens. Therefore, experiments with microsamples must be performed. One of the most serious problems hereby is the measurement of the occurring deformation. Various methods have been sued so far, all suffering from the limitation of providing the deformation in one single point only rather than the whole deformation field. Electronic speckle pattern interferometry (ESPI) is an established method for measuring deformation fields in macroscopic objects. In this paper we show how the problems in applying ESPI to microscopical objects can be solved. We present an unusual fringe analysis technique which requires no phase demodulation. It allows to obtain phase maps with a quality that was hitherto only known from holography. Our deformation measurements on metallic microbars agreed to within 10nm with the results form the least squares template matching method and from finite element calculations. One advantage of being able to measure the whole deformation field is that the occurrence of local plastification can be detected, as our experiments suggest.

Experimental results of linear displacement measurements performed with a new type of micro-interferometer are presented. This interferometer is base don the self-mixing effect in GaAlAs or InGaAlP diode lasers. The very simple interferometer design offers a number of advantages: it is small, rugged, easy to align and it consists of only a few optical components. With a new-developed two-tone modulation technique and signal processing algorithms, a direction- dependent interference signal can be generated with high signal-to-noise ratio. We present here theoretical and experimental investigations that allow the characterization of the laser operating conditions for a stable self-mixing interference signal. Both visible and near-IR Fabry-Perot diode lasers were tested and found to be suitable for self- mixing interferometry. The nonlinearity in the fringe interpolation was experimentally evaluated for the self- mixing micro-interferometer to be less than 10 nm. Improvements in the stability of the optical setup will further reduce this figure. The stability of the laser wavelength was shown to be in the order of 1 X 10^-6. Intercomparison with other techniques, including glass scales and the 'Laser Stylus' RM600 LS, are discussed.

The 3D topography of an object is exploited in order to improve 2D positioning of noncooperative objects.By using fringe projection in combination with nonlinear joint transform correlators we are able to process dirty, textured or labelled objects against complicated backgrounds even in the presence of stray light.

A novel method for measuring arbitrary 3D states of mechanical stress in photoelastic models is presented. The theory of tensor field tomography is described and an iterative reconstruction algorithm is given, which processes the projection data received by illuminating the model for several orientations. The method generally works well for limited amount of stress, which is demonstrated by simulations. An experimental setup is presented for measuring the required projection data. It is a combination of an extended Mach-Zehnder interferometer and a polariscope.

Laser interferometric methods for measurement of refractive index profiles of thin film structure have been investigated experimentally and by computer simulation. An expression for the axial image, which incorporates multiple reflections and refractive distortion, has been derived. An algorithm for reconstruction of the profile from an axial image has been developed. The limitations of this approach have been investigated. The optical system produces a high-pass filtered reconstruction of the refractive index profile. For the approximation when multiple scattering and refractive distortion can be neglected, the results have been generalized to the problem of measurement of 3D refractive index variations from 3D images.

We study influence of wavelength on 'dynamic' Faraday effect in the ferrofluids. The applied magnetic field is parallel with the light direction, and is sinusoidal alternative. The alignment of magnetic agglomerates, in the field direction, creates some birefringence giving induced circular magneto- optic effects. We present relaxation curves. We show that the relaxation frequency is (lambda) -independent. On the other hand, we notice an alteration of this relaxation in high field frequency. It seems that the less the wavelength, the more important the alteration. In this case, (lambda) is no more important compared with the magnetic agglomerates size. Then particles can scatter the light. The effect is a little more important with the applied field amplitude. Finally we study the light polarization state versus the magnetic amplitude. It does not show a significant (lambda) - influence.

We show a 'dynamic' Cotton and Mouton effect in magnetic liquids. Experiments consist of a linear polarized light which goes through a very small quantity of liquid, and to apply a sinusoidal magnetic field, perpendicular to the light wave vector k, with a n angle (pi) /4 to light polarization direction for maximizing effects. The alignment of magnetic agglomerates in the field direction creates some birefringence giving induced transversal magneto-optic effects. Emergent light goes through an analyzer, and is detected by a Silicium photo-detector or InGaAs, according to wavelength. A lock-in amplifier measures the amplitude of harmonics in the detected signal. We study, more especially, frequency behavior of the second harmonic, for different magnetic liquids. They consist in Cobalt ferrite particles in different liquid carriers. The theoretical expression of the second harmonic component V_2f is calculated. It depends on the physical characteristics of the magnetic liquids. It depends also on the amplitude H₀ and the frequency f of the AC magnetic field H(t) equals H₀.cos2(pi) ft. According to this study, we can connect this phenomenon to the magnetic liquid Brownian relaxation. For a given frequency, we show the second harmonic behavior in a function of the magnetic field amplitude. One can deduce magnetic liquid magnetization curves. We compare the theoretical and experimental variations of V_2f with H₀ and f for various ferrofluids. We suggest a theoretical model of the ferrofluid dynamic Cotton and Mouton effect, which confirm experimental results.

Photothermal and thermoelastic microscopies are nondestructive methods using optical excitation and detection. In photothermal microscopy, the photoreflectance is used to detect the dynamic component of the surface temperature. In our microscope, the normal component of the thermoelastic displacement is also detected with a laser probe, leading to thermoelastic images. Both methods are used to image surface and subsurface inhomogeneities of the investigated object. A thermoelastic model has been developed to calculate the temperature and the displacement fields in the bulk and at the surface of an isotropic solid. Modeling is applied to the case of limited size optical excitation, corresponding to super-resolution. Theoretical temperature profiles show that the resolution essentially depends on the radius of the excitation beam. Conversely, the thermoelastic displacement provides a lower resolution. Finally, experimental devices are presented.Some images of test samples are shown to place in evidence the different resolutions obtained with thermal and thermoelastic methods in the super-resolution case. An extrapolation of this study should allow to fix the values of the experimental parameters to optimize a microscope using a nanometer sized source.

A plasmon surface wave is excited in a thin metallic layer on a dielectric, if the layer is illuminated at an incident angle larger than the critical angle of total reflection. At certain resonance angles, the major part of the incident energy is coupled into the surface wave and the total reflection is attenuated. We probed the resonance peak with a spectrum of incident waves and detected the reflected energy at two incident angles near the resonance peak simultaneously. The ratio of he detected energies is a function of the incident angle, thus facilitating angular measurements. First experimental results indicate a resolution better than 0.001 degrees in a measuring range of 1 degree.

A measurement system is described that detects the Doppler- shift of light scattered by an object surface to determine the time dependence of the velocity vector at several discrete points on the object. The scattered light is received form three non-coplanar viewing directions to get information about the complete velocity vector. From the measured data the dynamic behavior of the object is derived under certain excitation conditions. In contrast to conventional methods the measurement is performed contactless without any additional mass-load to the structure. This is a decisive advantage for measurements of surface movements of components with light dynamical mass.

Scanning near-field optical microscopy (SNOM) has proved to be a powerful tool to analyze and image surfaces with high lateral resolution. We report a hybrid microscope composed of a commercial atomic force microscope (AFM) and an apertureless SNOM, which operates both in reflection and transmission modes with several illumination and collection systems. The optical probe is a commercial AFM tip integrated on a silicon cantilever. The AFM is operated in the intermittent contact mode at the resonance frequency of the cantilever. We present the first images obtained on a grating of cylindrical dots of aluminum and we discus their optical origin.

The 1/f noise is a general phenomenon on physical systems. In this paper low-frequency noise of silicon crystal have been analyzed. Noise spectra can not be explained completely by a homogeneous band model of semiconductor. Therefore, we have developed a new tool, so called 'tunnel noise spectroscopy' permitting to localize a noise sources on the surface. Some applications of scanning tunnel microscopy and of reflection scanning near-field optical microscopy in the investigation of 1/f noise of the semiconductor surface coated by a thin gold film are also presented.

This contribution presents an application of scanning near- field microscopy to the characterization of semi-conductors. We have studied the planar homogeneity of a Au/GaAs Schottky barrier using a local illumination by a nanosource with various wavelengths. One of the main results is the interface defaults revealed by the photocurrent mapping at (lambda) equals 1.33 micrometers .

Digital speckle pattern shearing interferometry, also called digital shearography or TV-shearography, is a coherent optical method in conjunction with digital image processing. It measures displacement derivatives directly and obtains thus the strain information. As a nondestructive testing tool, this technique has many advantages compared with TV- holography. It is simple in optical setup, relatively insensitive against ambient noise and usable with a simple laser diode for illumination. This paper will focus mainly on its applications for nondestructive testing of micro- cracks. The stressing methods corresponding to the micro- cracks in different objects are proposed and some investigated examples are shown.

Imaging of surface plasmon polaritons (SPPs) with a photon scanning tunneling microscope (PSTM) combined with shear force feedback is experimentally investigated. A contrast correction factor, that accounts for spatial frequency filtration performed by an uncoated fiber tip of the PSTM, is introduced and evaluated from the measurements of a standing wave interference pattern formed by two counter- propagating evanescent waves, that are generated by total internal reflection of light beams inside a glass prism. Influence of propagating field components stemming from inelastic SPP scattering on the resultant intensity distribution and, consequently, on the near-field optical images obtained with the PSTM is discussed. Optical images taken at different tip-surface distances are used to evaluate the contribution from propagating field components in near-field optical images taken with shear force feedback. The approach developed is applied to experimental studies of elastic scattering of SPPs excited at the wavelength of 633 nm along smooth and rough surfaces of gold and silver films.

Laser diodes are very promising tools for spectroscopic applications, e.g. for the contactless analysis of gases. We describe a prototype of a laser diode spectrometer which fulfills industrial requirements. We present results obtained at a brick-kiln over a period of several months. In this special application information about the moisture of the gas in the oven was required to optimize the baking process. In order to obtain an absorption signal without strong temperature dependence a special absorption line at (lambda) equals 1303.5 nm was selected. This wavelength was generated by a distributed feedback laser diode. Due to a normalization technique we obtained stable signals even at high dust loads within the measure volume.

The analysis of process gases is an important task in process control. Optical methods like spectroscopy using laser diodes are very sensitive and work without disturbance of the process. A strong drawback of laser diodes is the appearance of mode hops which limit the tunability and often prevent the emission of the absorption line of a gas component under study. This problem can be solved by stabilizing the laser diode by the optical feedback of a grating, where laser diode and grating form an extended cavity. Usually either expensive antireflex coated laser diodes or additional optics are required to guarantee a stable operation of the extended cavity laser. This paper describes the use of uncoated laser diodes in extended cavity configurations. In order to prevent multimode oscillation the laser diode was used as both the gain medium and a single mode providing etalon. The linewidth of the laser system was in the order of 1 MHz. The laser frequency could be tuned continuously by several GHz by varying the length of the extended cavity without effecting the spectral purity. The laser system is capable to analyze gases of technical interest. As an application we present absorption signals obtained by sending its light beam through water vapor.

We report on the characterization of the refractive index homogeneity in large blanks of Czochralski-grown Germanium, for thermal imaging use. With a phase-measuring Twyman-Green interferometer working at 10.6 micrometers , a map of the index of refraction with an accuracy better than 1 10^-5 can be obtained for blanks which do not exhibit high birefringence.In the other case, principal stresses in the disks can be determined through the effect of birefringence on the interferogram, if the stresses are distributed cylinder-symmetrically in the plane of the disk. Relations between stresses, transmittance, and electrical resistivity of the material are observed.

The mutual interference of tow linearly polarized modes in the spectral domain has been demonstrated experimentally at the output of a two-mode, step-index optical fiber excited by low-coherence sources having different spectral widths. The corresponding spectral interferograms, which are characterized by the wavelength-dependent periods of modulation of the source spectrum affected by intermodal dispersion, serve as an illustration of the feasibility of a novel experimental method utilizing a high-resolution spectrometer in the evaluation of the spectral dependence of the group optical path difference (OPD) between two modes of an optical fiber. Using the Fourier transform method for the spectral fringe pattern analysis, good agreement between the experimental and the theoretical spectral interferograms has been achieved and characteristics such as the unmodulated spectra and the wavelength dependences of both the visibilities of spectral fringes and the group OPDs between modes exceeding the source coherence length have been obtained. These last two characteristics have also been compared with those obtained using the cross-correlation technique.

In this paper we demonstrate the feasibility of impact- induced transient deformations measurement by single-pulsed subtraction TV holography an the Fourier transform method with contouring fringes as spatial carrier. Fringe formation in single-pulsed subtraction TV holography and phase demodulation by the Fourier transform method are descried. Contouring fringes are proved to be well suited for introducing spatial carrier in the correlation fringe patterns. Experimental results are presented. Finally, the degree of immunity to environmental disturbances of this technique is discussed and improvements are proposed.

The absorption coefficients of nonlinear crystals for fundamental and second harmonic wave are of great importance for high average power second harmonic generation. A practical method to measure low absorption coefficients for high average power second harmonic generation. A practical method to measure low absorption coefficients is to use an interferometric laser calorimeter with high power lasers. Therefore Q-switched Nd:YAG laser systems with intracavity second harmonic generation are used. The measurements are made with optical powers up to 300 W and 45 W, respectively. Because of the high power, the resolution limit for the absorption coefficients is 0.001 percent/cm. The absorption coefficients of KTP and LBO crystals of different manufacturers are determined. The results are used for a numerical model which takes into account the decrease of conversion efficiency due to thermal effects caused by the absorption of laser power in the nonlinear crystal. This model describes saturation effects which appear in the range of 100 W in the green using a KTP crystal. A new idea for compensation of thermal effects will be presented.

The Integrated Optics Rotation SEnsor (IORS) is a rugged, lightweight, and low cost gyro instrument which is currently being sponsored by the Defense Advanced Research Projects Agency under funding from Small Business Innovative Research/Technology Reinvestment Program. It uses glass-on- silicon optical waveguide technology. The design of the IORS is quite simple, and can potentially be adapted to a number of military and commercial applications, including yaw rate sensing for an anti-skid safety device in automobiles, rotation rate sensing for robotics, weapon aiming,and guidance of smart munitions. The basic design is presented, along with preliminary performance specifications for an IORS prototype. The characteristics of the IORS is also compared to other gyros in terms of performance, size, weight, and price.