This PDF file contains the editorial “Editorial: We Got Your Input, Part II” for OE Vol. 33 Issue 10

This PDF file contains the editorial “Guest Editorial: Optics in Russia: Selected Topics” for OE Vol. 33 Issue 10

We report a new method for the highly efficient transformation of a linear polarized laser beam into a beam with any required polarization. The physics of polarization conversion is based on resonant excitation of surface electromagnetic waves (SEWs) on metallic gratings with period d ~ λ (where λ is wavelength of light) and subsequent SEW rescattering into the direction of specular reflection. The parameters of such gratings (period, depth, and groove profile) are calculated by means of the developed simple analytical theory. The grating phase retarders with reflectivity R = 92 to 97% for transformation of linearly polarized CO₂ and CO laser beams into a circular polarized beam are fabricated. The efficiency of these phase converters included in a 1.5-kW CO₂ laser technology system for metal cutting is demonstrated. The converters essentially enhance the quality and velocity of cutting and their high strength to resist optical damage is shown.

A number of iterative algorithms for calculating kinoforms are discussed: a multiplicative adaptive algorithm allowing the rate of iterative process to be increased, fast algorithms for interpolating and extrapolating the kinoform phase pixels, an algorithm for calculating kinoforms forming radially symmetrical images and axial light segments, an algorithm for calculating formators of Gauss-Hermite modes in required diffraction orders, and an algorithm for calculating formators of reference wavefronts. The results of computer simulation are given.

Experimental results of a new approach to the problem of sharpness function maximization in adaptive optics are presented. The main difference from the ordinary method is in the forming of signals, proportional to the components of the sharpness function gradient, in an optical processor. This solution is very effective in the case of low light intensity, when the quantum effects of registration are essential. It is shown that, in this particular case, the scheme of the adaptive system is similar to curvature sensing system. The experimental system provides a 32-zonal correction of the wavefront in real atmospheric conditions for objects of various forms.

New simple production methods for integrated optical passive elements and the results of the investigation of their operating performance are presented. Coniform geodesic lenses obtained by pressing at heating exhibit properties of waveguide negative lenses and waveguide beamsplitters. The modified production techniques of planar input/output couplers based on tapered waveguides and elements with a 2-D refractive index gradient enable narrowing the angle width of the device beam directivity diagram three to five times to values of 15 to 30 arcmin. A new waveguide diaphragm unified for the modes of different numbers and polarizations is presented.

A model of multilayered tissue is considered. The Monte Carlo simulation technique is used to study laser beam transport through tissues with varying optical properties for each layer (absorption, scattering, scattering anisotropy factor, and refractive index). Calculations are performed for some models of the human skin and adjacent tissues for visible and UV wavelength ranges. New technology for human epidermis optical parameters determination is presented. This technology includes epidermis upper layers glue stripping; in vitro measurements of total transmission, diffuse reflection, and angular scattering of stripping samples; and using an inverse calculation technique based on four-flux approximation of radiation transport theory. The technology was successfully used for depth dependence monitoring of epidermis optical parameters. An inverse Monte Carlo technique for determining the optical properties of tissues based on spectrophotometric measurements is developed. This technique takes into account the 2-D geometry of the experiment, finite sizes of incident beam and integrating sphere ports, boundary conditions, and sideways losses of light.

Speckle intensity first-order statistics for a large-scale scattering structure is investigated. Results of computer simulation and experimental studies of coherent light diffraction by large-scale scattering objects are presented. The correlation characteristics of dynamic speckles induced by focused Gaussian beam diffraction is theoretically and experimentally analyzed.

A totally computerized multifunctional laser gas analyzer operating within the 3-μm spectral region is described. A technique and the computer program for laser gas analysis experimental data processing are proposed for the case of multicomponent gas mixtures with complex overlapping spectra. The application of this device for IR absorption high resolution spectroscopy, environmental control (long-path gas analysis), and disease diagnosis is discussed.

We have developed two coherent lidar systems based on cw and TEA CO₂ lasers. The lidars have been tested and applied for the atmospheric wind velocity measurements. We have elaborated and experimentally verified a new method of nondestructive long-range measurement of the parameters of the atmospheric turbulence with a cw Doppler lidar (DL). The method is based on certain processing of the heterodyne Doppler spectra. In addition to the wind velocity magnitude, the method yields the value of the velocity structure constant. The method has been experimentally verified. Some results of applications of the DL for detecting artificially generated vortexes (aircraft traveling vortexes) and distinguishing them from natural winds and turbulence based on a comparison of the magnitudes of the velocity structure constant are presented.

Photothermal probe beam deflection spectroscopy is used to separately measure bulk and surface absorption of transparent IR optical elements. Different approaches of this technique are considered. One approach consists in variation of the laser beam heat modulation frequency in the condition that the heating beam component is transverse to the path of the probe beam. Another approach consists in varying the heat and probe cross section measuring point position within the tested optical sample. It is theoretically and experimentally shown that in the second case, the spatial resolution and measurement locality are determined by the size of laser beam spots and the thermal diffusion length in a sample. The relative contribution of surface and bulk absorption to summary absorption can be derived from the ratio of the probe beam deflection signal, measured both near the surface and within the sample volume far from the surface, to thermal wavelength. Absolute calibration of absorption measurements can be carried out using laser calorimetry. A comparison between deflection and calorimetry data on volume absorption in a number of ZnSe laser optical elements is made and shows a good correlation.

This PDF file contains the editorial “Guest Editorial: Digital Image Recovery and Synthesis” for OE Vol. 33 Issue 10

An important consideration in regularized image restoration is the evaluation of the regularization parameter. Various techniques exist in the literature for the evaluation of this parameter, which depend on the assumed prior knowledge about the problem. These techniques evaluate the regularization parameter either at a separate preprocessing step or by iterating based on the completely restored image, therefore requiring many restorations of the image with different values of the regularization parameter. The authors propose a nonlinear frequency-domain adaptive regularized iterative image restoration algorithm. According to this algorithm a regularization circulant matrix is used that corresponds to the assignment of a regularization parameter to each discrete frequency. Therefore, each frequency component is appropriately regularized. The resulting algorithm produces more accurate results and converges considerably faster than the algorithm that uses one regularization parameter for all frequencies. The regularization matrix is updated at each iteration step, based on the partially restored image. No prior knowledge about the image or the noise is required. The development of the algorithm is based on a set-theoretic regularization approach, where bounds on the weighted error residual and stabilizing functional are updated in the frequency domain at each iteration step. The proposed algorithm is analyzed theoretically and tested experimentally. Sufficient conditions for convergence are obtained in terms of a control parameter, which is specified by the conditions for convergence and optimality of the regularization parameters at each discrete frequency location. Finally the proposed algorithm is compared experimentally with other related algorithms.

The use of information about an image in addition to measured data has been demonstrated to provide the possibility of decreasing the noise in the measured data. A new constraint, recently proposed, is that of perfect knowledge of part of an image. These results are generalized, and the usefulness of this new constraint in decreasing noise outside the region of prior knowledge is shown to be a function of the measured data noise-correlation properties. In particular, it is shown that prior high-quality knowledge is a generalization of support constraints.

We describe a new algorithm for correcting phase errors in synthetic-aperture radar data. It employs a gradient-search algorithm to minimize the energy of the image outside a support constraint. We give analytic expressions for the gradient of the error metric with respect to a point-by-point description of the phase error and with respect to the coefficients of a polynomial expansion of the phase error. These analytic gradients greatly speed the computations for the algorithm. We demonstrate successful phase-error correction for an image of a CV-580 aircraft collected with ERIM's Ground-to-Air Imaging Radar.

We present results obtained from the application of a novel phase-retrieval algorithm for recovering a complex-valued object from a set of two intensity measurements. The algorithm requires two intensity measurements at different distances from a weak scatterer, where the total transmitted field is composed of the coherent sum of an incident plane wave and the scattered wave. The algorithm is noniterative and does not have the convergence problems associated with iterative algorithms. The new technique shows great promise for inverse-scattering applications, such as optical diffraction tomography and in-line holography of complex-valued objects, with the aim of eliminating the twin-image problem. Results are presented from a computer simulation of a simple object and from experimental data obtained from a microlens array. Our results obtained using the new algorithm on experimental data compare well with those obtained with a modified form of the Gerchberg-Saxton algorithm, at a significantly reduced computational cost.

Adaptive-optics systems have been used to overcome some of the effects of atmospheric turbulence on large-aperture astronomical telescopes. However, the correction provided by adaptive optics cannot restore diffraction-limited performance, due to discretized spatial sampling of the wavefront, limited degrees of freedom in the adaptive-optics system, and wavefront sensor measurement noise. Field experience with adaptive-optics imaging systems making short-exposure image measurements has shown that some of the images are better than others in the sense that the better images have higher resolution. This is a natural consequence of the statistical nature of the compensated optical transfer function in an adaptive-optics telescope. Hybrid imaging techniques have been proposed that combine adaptive optics and postdetection image processing to improve the high-spatial-frequency information of images. Performance analyses of hybrid methods have been based on prior knowledge of the ensemble statistics of the underlying random process. Improved image-spectrum SNRs have been predicted, and in some cases experimentally demonstrated. In this paper we address the issue of selecting and processing the best images from a finite data set of compensated short-exposure images. Image sharpness measures are used to select the data subset to be processed. Comparison of the image-spectrum SNRs for the cases of processing the entire data set and processing only the selected subset of the data shows a broad range of practical cases where processing the selected subset results in superior SNR.

It is well known that the intensity interferometry of Hanbury Brown and Twiss measures the square of the absolute value of the normalized coherence function and that the phase of the function is lost. We show that the cosine and the sine of the phase can be determined using triple- and quadruple-intensity correlations. This information is used to derive the intensity distribution of the object. The procedure for the phase reconstruction described depends on the starting values of the phase function for the least separation of the mirrors or for the nearest neighbors in the two perpendicular directions of the array of mirrors. These starting values are determined by means of an amplitude correlation experiment, such as the Young's two-slit type. The procedure of intensity correlations is then used for all other separations throughout the array. Computer simulation of the proposed procedure and a simple example of reconstruction of object intensity distribution are shown.

A technique for storing high-spatial-frequency information in low-frequency, zero signal regions of an image spectrum has been implemented and evaluated. This technique can be used for sparse arrays of small telescopes acting to synthesize a larger pupil, and reduces the number of detectors required in the 2-D image focal plane by a factor of 4.

The so-called irregular sampling problem is concerned with the problem of reconstruction of an image from irregularly located samples. We have developed new algorithms for efficient reconstruction of signals from arbitrary sampling sets, which are guaranteed to converge as long as the image is bandlimited and the sampling set does not have holes that are too big. However, experimental evidence does exist that for a typical real-world image very satisfactory reconstructions can be obtained even if it is not bandlimited in the strict sense. Only a certain type of irregularities is considered, i.e., missing lines or missing rectangles in a given image. This problem occurs in practical situations where such parts may be lost during the transmission of an image or may be badly recorded by a camera. The basic idea is to solve the problem by iterative solution of 1-D subproblems, i.e., by interpolation along horizontal and then vertical lines or vice versa. The use of fast and efficient 1-D reconstruction methods is the basis for a very fast and highly parallelizable algorithm. We demonstrate the efficiency of the product ACT algorithm by typical applications.

We address the problem of reconstructing functions from their nonuniform data and zero/threshold crossings. We introduce a deterministic process via the Gram-Schmidt orthonormalization procedure to reconstruct functions from their nonuniform data and zero/threshold crossings. This is achieved by first introducing the nonorthogonal basis functions in a chosen 2-D domain (e.g., for a band-limited signal, a possible choice is the 2-D Fourier domain of the image) that span the signal subspace of the nonuniform data. We then use the Gram-Schmidt procedure to construct a set of orthogonal basis functions that span the linear signal subspace defined by the nonorthogonal basis functions. Next, we project the N-dimensional measurement vector (N is the number of nonuniform data or threshold crossings) onto the newly constructed orthogonal basis functions. Finally, the function at any point can be reconstructed by projecting the representation with respect to the newly constructed orthonormal basis functions onto the reconstruction basis functions that span the signal subspace of the evenly spaced sampled data. The reconstructed signal gives the minimum mean square error estimate of the original signal. This procedure gives error-free reconstruction provided that the nonorthogonal basis functions that span the signal subspace of the nonuniform data form a complete set in the signal subspace of the original band-limited signal. We apply this algorithm to reconstruct functions from their unevenly spaced sampled data and zero crossings and also apply it to solve the problem of synthesis of a 2-D band-limited function with the prescribed level crossings.

A hybrid digital-optical joint transform correlator has been built for recognition of objects with noise and multiple objects. The correlator uses two optically addressed LCLVs as input transducer and for intensity-recording the joint transform spectrum, two optical lenses for performing a Fourier transform, a CCD camera as active output transducer, and a digital system for postprocessing the output signal and refreshing the reference image through our object library. In our experiment, the spatially separated images are imaged onto one light valve, whose output is written on the second light valve. The output of the second light valve is optically processed to produce a correlation signal at the output transducer. The correlator is supported by a digital system so that the output can be digitized for further processing. Some experimental results for multiple-object recognition are presented and discussed.

Selectogram characteristics are analyzed. The term selectogram stands for the structure obtained by recording the interference pattern of the radiation of an object and that of an extended reference source of light on an inclined photographic plate. Unlike a hologram, the selectogram reproduces 3-D images of objects by selecting definite components out of the radiation of an extended source whose phase distribution is not correlated with that of the reference source used at the recording stage. A case for which the image of the object being recorded is focused near the surface of the selectogram is described. It is shown that in this case, the angular size of an element determining the resolving power of the image reconstructed by the selectogram is equal to the double-angular width of a horizontal slit that filters the radiation of the object. The general structure of the radiation reconstructed by the selectogram is considered. It is shown that apart from the main image being observed through an output filtering slit, the selectogram reconstructs the multiplicity of distorted images of the object, which can be observed through horizontal stripes parallel to the filtering slit. It is pointed out that the total diffraction efficiency of all images reconstructed by the selectogram does not differ from that of a hologram. At the same time, the diffraction efficiency of the main image being observed through the output filtering slit is essentially decreased because of the presence of additional images. Ways to increase the diffraction efficiency of the selectogram are studied. Experimental data that prove these regularities are presented. Possible development of this method is discussed.

The location of a single point source in infrared imaging is typically achieved through conventional methods such as centroiding. More challenging problems with multiple point sources require alternative location-finding methods with the potential of resolving closely spaced objects. The authors introduce an algorithm predicated on least-squared-error (LSE) modeling with a Gram-Schmidt orthogonalization step. Its noise performance is compared with two other high-resolution algorithms based on the eigendecomposition of the input data. Estimates obtained through the LSE modeling approached the Cramer-Rao lower bound for high signal-to-noise ratios. However, its performance is severely degraded in the presence of non-Gaussian noise. An outlier detection scheme that may be used in conjunction with the location and amplitude estimation procedure is described, Its effectiveness is demonstrated through Monte Carlo simulations.

The raw output of many scanning radiometers is a small, rapidly varying signal superimposed on a large background that varies more slowly, due to thermal drifts and 1/f noise. To isolate the signal, it is necessary to perform a differential measurement: measure a known reference and subtract it from each of the raw outputs, cancelling the common-mode background. Calibration is also a differential measurement: the difference between two outputs is divided by the difference between the two known references that produced them to determine the gain. The GOES-I Imager views space as its background subtraction reference and a full-aperture blackbody as its second reference for calibration. The background suppression efficiency of a differential measurement algorithm depends on its timing. The Imager measures space references before and after each scan line and performs interpolated background subtraction: a unique, linearly weighted average of the two references is subtracted from each scene sample in that line, cancelling both constant bias and linear drift. Our model quantifies the Gaussian noise and 1/f noise terms in the noise equivalent bandwidth, which is minimized to optimize the algorithm. We have obtained excellent agreement between our analytical predictions and Monte Carlo computer simulations.

We develop a model-based vision algorithm to estimate the aspect angle of a target in a forward-looking infrared (FLIR) image. In the preprocessing stage of the algorithm, a set of 3-D voxel-based models is created using a CAD/CAM package. These models are rotated about the vertical axis through a series of predetermined angles and then projected onto the horizontal plane. This gives us a database library of 2-D images. We select as signature from a given FLIR image and attempt to match it with the various images in the given database library of images using the normalized cross-correlation method. The angle of rotation corresponding to the image in the database library giving the best possible match is estimated to be the aspect angle of the signature (target). We use an algebraic approach to represent images and the process involves certain algebraic operations on the polynomials. An advantage of the algebraic approach is that a high speedup in the run time is possible if the fast Fourier transform is used to compute the polynominal multiplications involved in the processing.

This article begins with a brief introduction to Fabry-Pérot interferometers and goes on to describe the use of Fabry-Pérot étalons as narrow-band filters. Properties of solid étalons with fused silica, mica, and lithium niobate substrates are discussed and compared with those of the familiar Lyot birefringent filter. Examples of applications of étalon filters in high-resolution solar imaging and vector magnetography are given. Recent measurements on an experimental étalon made with Y-cut lithium niobate are reported. Each passband of the experimental étalon transmits 80% of linearly polarized light (40% of unpolarized light), and the voltage-tuning parameters are better than for the Z-cut étalon. For the o-ray passbands, only ± 1900 V is required to tune over one free spectral range, vs ± 4000 V to tune a Z-cut étalon. When used with conventional thin-film filters for order selection, the étalon filter can be tuned to any wavelength from 0.4 to 4.0 μm.

Optical phase conjugation and two-wavelength recording in a photorefractive crystal BaTiO₃ is used for real-time lateral-shear interferometry. Dispersion in uniaxial BaTiO₃ crystal is used to provide perfect phase matching for two gratings of different spatial frequencies. Theoretical predictions of possible geometries are experimentally verified. The magnification effect and modulation of diffraction efficiency due to recording-reconstruction with different wavelengths are also presented.

A method for studying the stress-induced birefringence over the area of a sample by simultaneous application of shearing interferometry and moiré techniques is dealt with. This is a method by which one can have the fringe pattern for the first and second derivative of the birefringence distribution in the form of the slope and curvature of the test wavefront. There is, however, a method of obtaining the second derivative fringe system by using a four-exposure holographic technique in which the pattern is generated by shearing of two holograms of deformed surface. This is related to stress distribution in the structure under test. In the presented method, on the other hand, the test wavefront carries the information of stress distribution in terms of birefringence. The suggested experimental setup can provide the slope and curvature of the test wavefront in a single exposure.

This paper presents a mathematical model of a pulse-pumped Nd:YAG laser. The performance of cw-pumped systems has been described by Koechner in terms of the input power and output power. The operation of Q-switched systems has been modeled by Wagner and Lengyel. To the author's knowledge, no adequate model of the pulse-pumped laser exists. The two mentioned models are examined and aspects of each combined to produce a model of the pulse-pumped laser that allows its performance to be predicted from the mirrors-only resonator to the Q-switched system. The model applies equally well to a diode-pumped laser.

The speckle effect disturbs the measurement of spatial correlation functions in solid polymer samples by light scattering. To be able to extract the desired correlations from the measurements, the speckle noise must be suppressed. This is possible by moving the sample during the measurement. In this paper we demonstrate that a sufficient reduction of speckle contrast can be achieved even in samples of restricted dimensions or with a preferential direction.

An automated, self-calibrating, active-laser-triangulation 3-D surface-measuring system has been designed and built for the acquisition of surface coordinate information. The system is driven by a 50-MHz 80486-based PC/AT computer controlling a laser, a CCD camera, a frame-grabber card, and an encoded motor-driven positioning system. A novel self-calibration procedure is executed in a matter of seconds with the use of a standard sphere and a flat plane. Data acquisition rates of 750 points/s are obtained with an overall system accuracy of ± 0.12 mm using a 75-mm compound lens. Resolutions for the system, using the 75-mm lens, are 480 parts per image width of field in the x axis, 0.6 im in the y axis, and 4096 parts per depth of field in the z axis. The system operates at a standoff of 30 cm, a depth of view of 7 cm, and a width of field of view of 4.5 cm in the close plane and 6 cm in the far plane. The theory and design of the system are presented along with the derivation and implementation of the calibration equations, followed by results of the system's application, and a brief discussion on ways of improving accuracy, resolution, and data acquisition rates.

A principle is presented that uses a longitudinal mode splitting laser to sense the microdisplacement and measure the air refractivity with very simple construction, large measurement ranges, high sensitivity, and precision. The phase differences of two power curves of the split modes can be used to judge the movement direction, and the number of the Lamb dips and mode-change dips can be used to measure micrometer displacement. Because of the anamolous dispersion, the relative variation of the beat frequency is the function of the change of cavity length, which is the basis of measuring nanometer displacement.

The problem of classifying regions in an IR cloud scene is considered using the conventional matched filter, the perceptron, and a class of neural networks known as the multilayered perception (MLP). The purpose is to determine if neural network technology is applicable for a remote-sensing application. Another goal is to illustrate graphically how the MLP generates the decision surfaces. Examples are given to show that the MLP is better than other approaches if the application requires nonlinear decision surfaces for classification. A three-dimensional classification problem is given to illustrate the MLP hidden-layer operation. The resulting nonlinear decision surface, which achieves 100% correct classification, is displayed. A seven-dimensional classification problem is given to further illustrate the need for a nonlinear decision surface. Finally, an 128 x 128-pixel IR cloud-scene example with remote objects provides a more practical indication of the benefits of MLP for point-object classification. In addition, these examples provide a tutorial on how the internal operations of the MLP produce the required decision surfaces. The results provide a rationale for consideration of the MLP for other remote-sensing applications.

A novel global shape description technique based on edge segments is applied for recognition of 3-D objects. This approach extends the boundary-based representation to generalized edge patterns that may have segments that are straight, curved, crossing, or open. A novel representation of edge moments is used for shape description, with a novel normalization. The invariant features may be formed by using standard (invariant) moments. This has led to the development of edge standard moments. The power of the method is demonstrated for the recognition of 3-D polyhedral objects.

Evaluation of laser-induced damage in optical coatings employing a surface inclusion adhesion layer model is presented. The effects of thermal and optical absorption of an inclusion adhesion layer on a coating surface irradiated by a laser pulse can induce coating damage. The effects of the adhesion layer extinction coefficient, thickness, and heat conductivity on the laser-induced damage threshold of the coating are investigated by thin-film temperature field distribution analysis. Laser-induced damage on high-reflectance (HR) multilayer and ion-beam-sputtered coatings are analyzed.

Composite TiO₂-MgF₂ films are fabricated by reactive ion-assisted coevaporation. The optical, structural, mechanical, and chemical properties of these films are systematically studied. From the analysis of x-ray diffraction and spectrophotometer data the crystallographic phase compositions and the optical properties of the composite films are found to be controlled by the relative deposition rate of two evaporation sources. The refractive index and the microhardness of the composite films behave nonlinearly with respect to the composition of the films. When the molar fraction of TiO₂ is higher than 40%, the hardness of the composite films exceeds that of pure TiO₂ and glass substrate. The surface morphologies of all composite films are featureless and very smooth. It has been shown that composite TiO₂-MgF₂ films prepared by reactive ion-assisted coevaporation are very suitable for the design and fabrication of single-layer and multilayer antireflection coatings.

Higher-order quaternary signed-digit arithmetic using optical symbolic substitution is presented. This technique allows for multi-bit carry-free addition and borrow-free subtraction via a two-step symbolic substitution scheme and leads to a compact design by incorporating more information in fewer digits. Optical implementations based on a contentaddressable memory and on a multichannel correlator are identified.

A method of performing matrix multiplication using optical processing is presented. It combines speed due to the inherent parallelism of optics and high accuracy due to the digital representation of the multiplied numbers. The multiplication of numbers is performed by spatially convolving their binary digital representations. The spatial convolution is realized by frequency-domain multiplication. Real-time recording is necessary. An architecture for vector-vector multiplication is also proposed. The real-time recording is performed by real-time holography using fourwave optical mixing.

Long data stream convolution is required by practical signal processing applications. Various algorithms for digital computers offer satisfactory results if the long processing time and large memory space are tolerable. We describe an algorithm suitable to the optoelectronic implementation of the real-time convolution of long data streams (10⁴ to 10⁶ points). Based on the Chinese remainder theorem, an N-point 1-D data sequence (N = r₁r₂, where r₁ and r₂ are mutually prime) is permuted to form a r₁ x r₂ 2-D array. The convolution of two N-point 1-D data sequences is then realized by the convolution of their corresponding 2-D arrays. Free space 2-D optical systems can offer the benefit of real-time processing. Due to the huge amount of the required interconnects, optical schemes rather than electronic schemes are preferred to perform the 1-D to 2-D data permutation. We propose to implement a high-speed optoelectronic convolver for handling the long data sequences by using a standard 2-D optical convolver sandwiched between two optoelectronic data permutation devices. A modified cathode ray tube (CRT) and a standard CRT combined with an optical geometric transformer are described as examples of such devices. Various optical implementations of the convolution operation are also described and compared for this application. The entire algorithm was computer simulated for its optical implementation. Other practical problems and the fundamental limits are also discussed.

A hit-or-miss transform architecture and a canonical Boolean logic format and threshold decomposition algorithm are proposed to process binary and gray-tone images with morphological combined operations. The transformation of morphological combined image processing functions to hit-or-miss transforms is explicit: Binary functions are formulated by a summation of hit-or-miss transforms and gray-tone functions formulated by a double summation. A simple optical hit-or-miss transform processor is suggested on the basis of incoherent two-channel correlation with dual-rail spatial coding. The hit-or-miss transforms can be realized optically in one parallel processing step. Thus, binary and gray-tone image processing functions can be implemented by the repeated use of the optical processor with different structuring elements.

The polarization properties of four-wave interaction on polymer films with bacteriorhodopsin that possess anisotropically saturating nonlinearity are studied both theoretically and experimentally. The amplitude and the polarization of the diffracted wave for recording material with anisotropically saturating nonlinearity are calculated. Low saturation intensity allows the operation of the polarization of low-intensity signals to be realized. It is shown that control of the diffractive wave polarization is possible only with the variation of the light recording intensity.

The optical second-harmonic (SH) wave generated from a crystal-cored fiber under Cerenkov-radiation-type phase matching can be collimated by an axicon and then can be focused by a spherical lens to a diffraction-limited spot. The deviation of the radiation angle of the SH wave or the angle mismatch between the radiation angle and apex angle of the axicon causes spherical aberration. However, because the focusing system using the axicon is sensitive, such a system is not practical enough. A new optical system is proposed that consists of three spherical lenses: biconvex, biconcave, and meniscus lenses. The system can collimate the SH light radiated from the fiber. The new lens system is overcorrected for spherical aberration in certain zones. When the radiation angle of the SH wave deviates from the desired angle, the aberration can be compensated by adjusting the spacing between the biconcave lens and the meniscus lens.

A noncontact temperature measurement technique based on thermal expansion of materials is presented. The technique, diffraction-order spot analysis, is based on monitoring diffraction angle variations due to grating expansion. Because of the pressing need for noncontact temperature measurements during semiconductor processing, silicon was chosen as the demonstration material. The diffraction method requires a grating of suitable spatial frequency etched onto the surface of the Si wafer. Two symmetrically disposed incident beams are used to provide a differential measurement that is independent of sample tilt to the first order. An automated data acquisition and analysis system was developed for continuous monitoring of two diffraction-order angles. From the order separation, a relative temperature change can be calculated in near real time. Image processing techniques based on centroid operation were used to calculate diffraction-order displacement with subpixel accuracy. For comparison with optical data, simultaneous temperature measurements from a thermocouple bonded to the Si sample were recorded. Good agreement between optical and thermocouple measurements was obtained. Temperature resolution was inversely proportional to the number of grating lines. A resolution of ± 0.37°C is demonstrated for a 3000-line grating over a 20 to 750°C temperature range.

The traditional qualitative Ronchi test has undergone various manifestations with efforts to produce quantifiable results. Usual schemes call for the portage of the Ronchi grating via a carriage along machined ways aligned nearly parallel with the axis of the reflecting concave surface under test. The distance the grating is moved provides the variable in the data for making the test. A new test geometry has the grating carried in a bearing that is clamped in a gauged position, and the angle of the turned grating is read on a scale to provide the data variable. Aside from an increase in accuracy, this testing geometry allows, with the reduction mathematics, a number of entry-data options. Full-surface evaluation and the testing of astigmatic surfaces are possible. Adding an accurate vernier to the angular scale on the bearing allows finding the radius of curvature for the surface under test to a fineness unmatched by the standard mechanical spherometer.

This paper describes a new, occlusion-free, monocular three-dimensional vision system. A matrix of light beams (lasers, fiber optics, etc.), substantially parallel to the optic axis of the lens of a video camera, is projected onto a scene. The corresponding coordinates of the perspective image generated on the video-camera sensor, the focal length of the camera lens, and the lateral position of the projected beams of light are used to determine the "perspective depth" z^* of the three-dimensional real image in the space between the lens and the image plane. Direct inverse perspective transformations are used to reconstruct the three-dimensional real-world scene. This system can lead to the development of three-dimensional real-image sensing devices for manufacturing, medical, and defense-related applications. If combined with existing technology, it has high potential for the development of three-dimensional television.

This PDF contains the communication on "Holographic comparison between waves scattered from two physically distinct rough surfaces."

This PDF file contains the editorial “Book Rvw: Optical Methods for Information Technologies," by Andrei L. Mikaelian for OE Vol. 33 Issue 10