Spatial correlation properties are studied for speckle patterns produced in the diffraction region behind a lens which is located at a focal distance from a diffuser with an aperture under illumination of the coherent plane-wave light. It is shown theoretically that, if a ring-slit aperture of a negligible slit width is used, the speckle field produced has a perfect correlation in the longitudinal direction. An experiment was performed using a circular aperture and ring-slit apertures having different ratios of the inner to the outer radius and the speckle pattern produced using the ring-slit aperture with the smallest slit width had the longest longitudinal correlation in all cases examined. The statistical stationarity and symmetry of the speckle field, as well as variation in the speckle size, are also discussed.

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An optoelectronic implementation of polynomial evaluation has been presented which uses a recirculating inverse perfect shuffle interconnection (IPS). The IPS interconnection is formed by a binary phase grating which permits a high density of interconnection; it can be utilized in a high order of polynomial evaluation processing system.

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Pseudo-random properties of a class of two-dimensional (2-D) 5-neighborhood cellular automata (CA), built around nonlinear (OR, AND) and linear (XOR) Boolean functions are studied. The site values at each step of the 2-D CA evolution are taken in parallel and form pseudo-random sequences, which satisfy the criteria established for pseudo random number generator (PRNG): long period, excellent random qualities, single bit error propagation (avalanche criteria), easy and fast generation of the random bits. A block-scheme for secure Stream Cipher based on 2-D CA is proposed. The 2-D CA based PRNG algorithm has simple structure, use space-invariant and local interconnections and can be easily realized in very large scale integration or parallel optoelectronic architectures.

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We show a prototype of a coding system for image compression using vector quantization with an optical inner product processor, whose accuracy is improved by the applying data transformation method. We also present compression effects for gray-scaled images by this system. The system can compress 25656 bits image data within 1.2 seconds under 0.18 compression ratio with an adequate quality.

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The spot shape on super-resolution optical disks with a photon-mode mask layer was theoretically analyzed. The spot shape was found to depend on the lifetime of the bleached state of the dyes, the light power, and the disk rotation speed. When the lifetime is short, the super-resolution spot shape is not produced at high disk speeds. On the other hand, a dye mask layer with long lifetime, such as a photochromic mask, can produce a sharp spot shape in the higher disk speed region, and therefore is suitable for obtaining a super-resolution disk with a high data transfer rate.

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A method is presented for matching apparent sharpness between digital image display devices with different characteristics. The sharpness is most precisely described by the point spread function (PSF) as opposed to dot density such as DPI (dot per inch). The difference between devices is expressed as difference between transfer functions obtained from the PSFs. In the presented method, spatial frequency filtering for one digital image is carried out where the ratio of the transfer functions or its modified version is used as filter. The modification is introduced as a clipping operation to reduce excessive enhancement when the ratio of the transfer functions has a high pass characteristic with large gain. Through computer simulation including a subjective evaluation experiment and numerical evaluation, the effectiveness of filtering operation for sharpness matching is demonstrated.

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An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only light modulation device. The phase modulation characteristics of the PAL-SLM using a liquid crystal display (LCD) as an addressing mask were investigated by analyzing diffraction efficiencies resulting from binary gratings projected from the LCD. A more than 2p phase-only modulation depth was achieved. The highest first-order diffraction efficiency of approximately 38% was also obtained; this is close to the theoretical limit. The experimental results of diffraction efficiencies depending on the phase modulation depth are in good agreement with the simulation for the system operation.

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Frequency of a 532 nm emission line of a diode-laser-pumped Nd:YAG laser is stabilized by lock of the output line to the linear absorption line of iodine molecules. The stabilization method is very simple utilizing the frequency shift caused with an acousto-optic modulator. The laser frequency was stabilized at the zero-crossing point of the second-derivative of the dispersion curve. Instability obtained by the error signal is affected by the phase-characteristics of detectors, which results in 3^*10^-8.

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We perform a transient analysis, steady-state analysis, and linear stability analysis of a nonlinear Fabry-Perot resonator in order to examine the possibility of a fiber bistable device. We here develop two iterative methods for calculating the dynamics of the Fabry-Perot resonator containing a nonlinear medium with an instantaneous response time. The treatment of the counter-propagating field within the cavity is very important in estimating the nonlinear phase shift due to propagation. A trapezoid rule and midpoint rule are used here for the numerical integration. The iterative method using the trapezoid rule gives excellent agreement with the multiple-beam method developed by Bischofberger and Shen (Phys. Rev. A 19 (1979) 1169), which is more complicated than the proposed procedure. Unfortunately it is found that the midpoint approximation is numerically unstable. Assuming a conventional optical fiber, the switching power for optical bistability is less than 1 kW for a resonator length of 1-2 cm. On the basis of the iterative method, we perform a linear stability analysis to examine whether Ikeda instability affects bistable device application or not. The stability analysis shows that the instability threshold is two orders of magnitude larger than the switching power for optical bistability.

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A position sensing interferometer is described which is able to sense the position of a specular object from a normal distance. The interferometer consists basically of a diffraction grating, a focusing lens and two plane mirrors. The grating acts as a tool to divide the incident beam and also to combine the reflected beams from an object so that they interfere with each other. An experiment was carried out to verify the principle. Interference fringe patterns caused by variation in the object position were obtained. The sensitivity obtained theoretically was confirmed by measuring the width of the fringes. As a result of theoretical comparison with conventional techniques, it was determined that this interferometric method has the advantage of the high sensitivity and the wide dynamic range being compatible with each other. The setting for sensing is simple and the analysis of the fringe patterns is easy.

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A beam profile monitoring system for synchrotron radiation, designed to evaluate the distribution of a cross section of the electron beam in a high-energy accelerator storage ring in real-time is descripted. The Shack-Hartmann wavefront sensor is adopted for the measurement of the wavefront error caused by deformation of an extraction beryllium mirror for the visible synchrotron radiation. The correction of the measured wavefront distortion is also described.

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We hypothesized that the recognized visual space of illumination (RVSI) was constructed in our brain when we grasped the state of illumination of a space. The importance about the RVSI is that it is three dimensional and is valid not only at the surfaces of the existing objects in the space, but also for the entire portion in the space where no objects exist. With this property of RVSI we are able to predict the appearance of an object surface in terms of lightness as well as of color when the object shifts from one place to the other in the space. The three dimensionality of the RVSI is proved by giving a hidden illumination within a space and by asking a subject to judge the lightness or color of a test patch placed in the area of the hidden illumination. In spite of the additional light on the test patch the subject did not recognize that the light was added but simply felt that the surface was made of a higher lightness or colored by transferring the light into an increase of the reflectance factor of the test patch. The results can be interpreted if we assume that a same RVSI exists throughout the entire space including the area of the hidden illumination.

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