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We present a dual-imaging technique combining laser speckle contrast imaging and spectral-domain Doppler optical coherence tomography to enable quantitative characterization of local cerebral blood flow (CBF) changes in rat cortex in response to drug stimulus (e.g., cocaine) at high spatiotemporal resolutions. To examine the utility of this new technique, animal experiments were performed to study the influences of anesthetic regimes (e.g., isoflurane, [alpha]-chloralose) on the pharmadynamic effects of acute cocaine challenge. The results showed that cocaine-evoked CBF patterns (e.g., increases in [alpha]-chloralose and decreases in isoflurane regimes) were quantitatively characterized, thus rendering it a potentially useful tool for imaging studies of brain functions. OCIS codes: 170.2655, 170.3340, 170.4500, 110.6150.

Ultrasound-modulated optical tomography based on the measurement of laser-speckle contrast was investigated. An ultrasonic beam was focused into a biological-tissue sample to modulate the laser light passing through the ultrasonic column inside the tissue. The contrast of the speckle pattern formed by the transmitted light was found to depend on the ultrasonic modulation and could be used for imaging. Variation in the speckle contrast reflected optical inhomogeneity in the tissue. With this technique, two-dimensional images of biological-tissue samples of as much as 25 mm thick were successfully obtained with a low-power laser. The technique was experimentally compared with speckle-contrast-based, purely optical imaging and with parallel-detection imaging techniques, and the advantages over each were demonstrated. OCIS codes: 170.3880, 120.6150, 110.7050, 110.7170.

A metrology system is presented that measures internal three-dimensional (3-D) displacement fields. The system uses a stereo pair of flash x-ray heads and correlation analysis to measure the true deformation of a layer of x-ray-absorbent particles inside the specimen. The 3-D deformation field inside blocks of polyester was determined. The polyester blocks were impacted by a 9-mm steel ball bearing fired from a 9-mm-bore gas gun at a speed of 373.5 +/- 3.0 m s(super -1). At a given time after impact, a short-duration (30 ns) flash x-ray pulse exposes the x-ray radiographs and freezes the events during impact. Thereafter, the x-ray radiographs are scanned into a personal computer and analyzed as in digital speckle photography.

The changes in the microtopography of a metal surface during a corrosion process are measured by decorrelation of the scattered speckle fields under coherent illumination. For that purpose a quantitative relation between the decorrelation of the scattered light fields and the rate of corrosion is established in a theoretical model, based on the statistics of phase and reflectivity changes of point scatterers at the surface. The speckle fields are recorded by a CCD camera and processed numerically in a computer, yielding the standard deviation of the topography changes with nanometer sensitivity. From the analysis of a series of images taken at equal time intervals during the corrosion process, the degree of interrelation among subsequent topography changes is calculated.

We have used a computer-generated holographic optical element (HOE) with electronic speckle pattern interferometry to calculate the interference phase corresponding to the deformation of a test object from a single TV frame. The HOE is a modified crossed phase grating that introduces a known phase change between the +/- 1 diffracted orders, without being translated. The progressive propagation of transient mechanical waves was measured with an rms precision of 2(pi)/30.

Speckle filtering in synthetic aperture radar (SAR) images is a key point to facilitate applicative tasks. A filter aimed at speckle reduction should energetically smooth homogeneous regions, while preserving point targets, edges, and linear features. A compromise, however, should be arranged on textured areas. In this work, a ratio Laplacian pyramid (RLP) is introduced to match the signal-dependent nature of speckle noise. Local statistics filtering is applied to the different spatial resolutions of the RLP of a speckled image. For natural scenes, each pyramid layer is characterized by an signal-to-noise ratio (SNR) increasing as resolution decreases. Thus, each filter may be adjusted to achieve adaptivity also across scales. In addition, the estimation of the local statistics driving the filter is more accurate thanks to the multiresolution framework. A complete procedure is setup, and a general formulation, in which the variance of speckle is theoretically derived at each resolution, is developed. Experiments carried out on remotely sensed optical images corrupted with synthetic speckle, as well as on true SAR images, show the potentiality of the pyramid-based approach compared with other established despeckle algorithms, in terms both of SNR improvements and of enhancement in visual quality. Index TErms - Laplacian pyramid, local statistics filtering, multiresolution analysis, speckle, synthetic aperture radar (SAR) images.

I report on a new optical technique that uses the principles of speckle photography and wave-front shearing to obtain the measurement of surface strains. The strain information stored at each point on the object surface is read out on a point-wise basis. The method is developed from a theoretical point of view, and experimental results are presented.

A robust procedure for analyzing fringe patterns obtained from speckle interferometric techniques is proposed. The fringes generally are observed only in a region S of a rectangular lattice L. We give a method for computing (from S) the region R, where the unwrapped phase is to be computed; this computation is done by use of a morphological filter (in particular, a closing filter). We then use a fast-unwrapping algorithm to compute the phase: a preconditioned conjugate-gradient algorithm that uses the discrete Fourier transform. Key words: Inverse problems, regularization, morphological filters, phase unwrapping.

Local decorrelation of speckle patterns scattered by a surface is used for nondestructive evaluation of the state of conservation of wooden artifacts. Some experiments have been carried out on models with simulated internal flaws and on real, ancient, wooden panel paintings. The setup is very simple and can easily be used by nonoptically skilled operators. Key words: Nondestructive testing, artwork diagnostics, speckle correlation.

In holography and speckle interferometry the measurement range is generally limited by the greatest number of fringes that can be resolved in a single image. As a result these techniques have been generally confined to small displacement measurement applications. In the case of out-of-plane measurements one can overcome this limitation by simply adding incremental measurements at individual detector pixels. In the case of in-plane measurements, however, summing incremental measurements is not a straightforward procedure since the interference pattern moves laterally across the detector as the material deforms. We describe a modeling technique based on finite elements which solves this problem. In combination with a full field method such as holography or speckle interferometry, it provides a very sensitive measurement technique with dense spatial sampling and large dynamic range. Experimental results of speckle interferometry operating in transmission to measure in-plane displacements of biological membranes are presented, where total material displacements are of the order of millimeters. The results also demonstrate how the finite strain tensor is calculated analytically from the data at any point on the material. Key words: Speckle, interferometry, finite elements, membranes.

This paper describes an apparatus designed to study large mechanical deformations in biological membranes. The task of mechanically characterizing biological membranes is challenging because of the anisotropic and nonlinear nature of their material properties. The apparatus described here is well suited to the task because it uses speckle interferometry to measure in-plane displacements in a distributed fashion and has multiple degrees of freedom in the applied stress mechanism. In this way few a priori assumptions or restrictions are imposed on the applied stress and strain fields. The interferometer operates in transmission mode to increase the light efficiency of the system since the sample biological membranes are translucent and reflect little light. The experimental results confirm that the strain fields in the biological membranes that are generated in the experiments are highly nonuniform and cannot be properly estimated from a small number of point measurements. Key words: Speckle, interferometry, membranes, mechanical testing.

Spectral analysis of a time-evolving speckle pattern is used to provide motion-resolved detection of moving objects embedded within scattering media. Results show that the ability to detect small non-stationary scattering objects and to discriminate between objects moving at different rates is greatly enhanced. Key words: Speckle, first-arriving light, holography, scattering media, imaging, speckle velocimetry.

The use of electronic speckle pattern interferometry (ESPI) to monitor and measure the surface movement of plants is presented. We chose to study the gravitropical response of a coleoptile (the shoot from a growing seed) to illustrate the potentials of the technique for botanical measurements. A coleoptile represents a very fast growing translucent biological object, a difficult object to record interferometrically. Traditional holographic interferometry is not suited to the study of objects with such rapid fringe decorrelation. However, ESPI with its short exposure time, fast sampling rate, and high sensitivity makes it possible to obtain fringes even on the very tip of the coleoptile where the microstructure changes most rapidly. Key words: Electronic speckle pattern interferometry, speckle decorrelation, coleoptiles, gravitropism, plant measurement, TV holography, electronic holography.

We present a robust method of phase unwrapping that was designed for use on noisy phase images with arbitrary fringe patterns. The method proceeds by first identifying distinct regions between fringe boundaries in an image and then phase shifting the regions with respect to one another by multiples of 2[Pi] to unwrap the phase. Image pixels are segmented between interfringe and fringe boundary areas by fitting a plane model using least squares to overlapping domains centered on all pixels. The method is tolerant of fringe gradient degradation caused by noise, filtering artifacts, and finite instrumentation bandwidth. Key words: Phase unwrapping, interferometry, speckle, holography, moire.

We carried out real-time optical image subtraction and edge enhancement based on a speckle modulation technique by using ferroelectric liquid-crystal polarization switches and a ferroelectric liquid-crystal spatial light modulator. A ferroelectric liquid-crystal spatial-light modulator is employed as a real-time and multiple-exposure optical device, and successful results are obtained from three-exposure images modulated by speckles. Thus, image subtraction and edge enhancement are realized in real time. The whole operation is performed within several milliseconds with modest operating conditions. Because the spatial light modulator has a high resolution of greater than 100 line pairs/mm and can store fine speckle patterns, the image qualities we obtained are quite satisfactory.

Spatial-frequency filtering of laser-speckle patterns has proved to be a useful tool in the measurement of the modulation transfer function for focal plane arrays. Intensity thresholding of the laser-speckle patterns offers nearly an order of magnitude savings in digital storage space. The effect of this thresholding on the spatial-frequency power spectral density of the speckle pattern is investigated. An optimum threshold level is found that minimizes distortion of the power spectrum for the classes of speckle data used for modulation transfer function testing.

A study was conducted to evaluate natural convection heat transfer characteristics in converging vertical channel flows. The study developed nonintrusive measurements of wall temperature gradients by applying laser specklegram methods. Results show that correlations for local and average Nusselt numbers can be described as functions of the Grashof number. In addition, deviations from both Nusselt numbers generated vital heat transfer reductions.

We report a method for noninvasively evaluating blood flow at the ocular fundus by using laser speck phenomena. The intensity fluctuation of speckles scattered from a 1-mm-diameter illuminated area at the fundus is detected and analyzed by the photon-correlation technique, which gives us the relative degree of total blood flows within the probe area. The method is used to evaluate blood flows at the ocular fundus of a rabbit and normal human volunteers. The experimental results show that the presen laser speckle method is useful for the relative evaluation of blood flows in the ocular fundus tissu

A laser speckle shearing interferometric technique is used for measuring the temperature profile inside a gaseous flame. The experimental results are compared with the values obtained by a thermocouple and also by speckle photography. Good agreement is seen among the temperatures measured by speckle shearing interferometry, speckle photography, and the thermocouple. Speckle shearing interferometry is easier to implement than speckle photography. This is because in speckle shearing interferometry the accurate positions of the fringes can be known without point-by-point analysis and correction for the halo effect.