Haruyoshi Toyoda

1 ms column parallel vision system and its application of high speed target tracking

We have developed a 1 ms vision system, to provide a much faster frame rate than that of the conventional systems. Our 1 ms vision system has a 128/spl times/128 PD array and an all parallel processor array connected to each other in a column parallel architecture, so that the bottleneck of an image transfer is solved. 1 ms visual feedback has been realized in this system, in which the image feature value is extracted in 1 ms cycle-time for visual servoing. We have also developed a high speed active vision system (AVS)-II. Finally, we provide a detail discussion on our 1 ms vision system and its performance through some experiments.

Diffraction efficiency analysis of a parallel-aligned nematic-liquid-crystal spatial light modulator.

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator is developed for applications in optical information processing and interferometry. Its performance, including diffraction efficiency, is measured, and a theoretical analysis of diffraction efficiency is performed. A comparison between the experimental results and the theoretical analysis shows good agreement. The diffraction efficiency of near-sinusoidal gratings written on the device is of the order of 30%, which is close to theoretical maximum.

Optical associatron: a simple model for optical associative memory.

A new neural network architecture for optical computing is proposed. This architecture can be used for implementing a simple system based on a modified theory of the associative memories. It is shown that the memorized patterns can be recalled perfectly by an experimental system using two microchannel spatial light modulators. The modified theory and principle of operation of the optical associatron system are discussed, and the system itself and basic experimental results are also described.

Lossless light projection

A new technique for energy-preserving phase-only light projection is demonstrated. The phase-only encoding is based on an extension of the Zernike phase-contrast method into the domain of full-range [0; 2pi ] phase modulation, breaking the usual small-phase-angle limitation. Controlling the spatial average value of the input-phase pattern and choosing appropriate phase retardation at the phase-contrast filter yield pure-phase-based image formation. Experimental results demonstrate close to 90% energy efficiency. Output intensity levels with magnitudes more than 3.5times that of the input intensity level were measured in the brightest regions of the projected images.

A high-speed CMOS image sensor with profile data acquiring function

We have developed a Profile Imager aimed at high-speed automatic target tracking. The Profile Imager can perform both target tracking within a 512 /spl times/ 512-pixel entire image area and acquisition of partial images simultaneously and independently. Experimental results of capturing 128 /spl times/ 128-pixel partial images of an automobile license plate at 1620 frames/s are presented. In addition, results of integrating 89 partial images demonstrate the capability of the device as a high-speed, high-resolution, high-dynamic-range image tracker. A 0.6-/spl mu/m two-poly three-metal CMOS process is used to implement a 13.0 mm /spl times/ 14.3 mm imager.

Reconfigurable optical interconnections for parallel computing

We describe our research on optically interconnected optoelectronic parallel computing systems. Our architecture is based on a multilayer pipeline of two-dimensional optoelectronic device arrays in which each pixel is composed of an optical input channel, a general-purpose programmable processor, local memory, and a surface-emitting laser diode as an optical output channel. Free-space optics provides parallel, global communication between layers in the pipeline via optical paths that are dynamically reconfigurable. Design and initial realization of a system are described.

A 3.2 kHz, 14-Bit Optical Absolute Rotary Encoder With a CMOS Profile Sensor

We have developed a 3.2 kHz, 14-bit optical absolute rotary encoder system using a profile sensor and a slit disc. The profile sensor, which we have designed for this purpose, is a unique CMOS area image sensor aimed at high-speed position detection of X and Y axes. Y axis profile data from the profile sensor is used for recognition of an index code on the slit disc, and X axis profile data is used for position detection of the index code. This combination of two-axis information enables high resolution even with a small number of index codes (64 indexes) and a small amount of digital calculations. Experimental results show that this system can detect rotation with an angular resolution of 14 bits (0.022deg) and a maximum detection speed of 3.2 kHz.

Experimental studies on learning capabilities of optical associative memory

The learning capabilities of optical associative memory called the optical associatron are experimentally shown. The experimental system has a simple architecture for optical associative memory; in particular, the system has versatile adaptive learning capabilities implemented with microchannel spatial light modulators. In this paper, various experimental results of learning and recalling processes on the system are shown. Based on the results, the behavior of learning on the optical associative memory is discussed. In addition, a modified method of learning is proposed and verified on the system. A method for implementation of error backpropagation is also proposed.

Development of an optical joint transform correlation system for fingerprint recognition

Yuji KobayashiHaruyoshi ToyodaCentral Research LaboratoryHamamatsu Photonics K.K.5000, Hirakuchi, HamakitaShizuoka 434-8601, JapanE-mail: kobayasi@crl.hpk.co.jp,toyoda@crl.hpk.co.jpAbstract. A compact joint transform correlator is designed and con-structed to test the properties of a practical application and is applied tofingerprint recognition. The system performance is evaluated on finger-print recognition accuracy under thermal conditions ranging from 0 to40°C and is found to provide a high level of identification and rapidprocessing abilities under actual environmental conditions.

Correlation matching method for high-precision position detection of optical vortex using Shack–Hartmann wavefront sensor

We propose a new method for realizing high-spatial-resolution detection of singularity points in optical vortex beams. The method uses a Shack-Hartmann wavefront sensor (SHWS) to record a Hartmanngram. A map of evaluation values related to phase slope is then calculated from the Hartmanngram. The position of an optical vortex is determined by comparing the map with reference maps that are calculated from numerically created spiral phases having various positions. Optical experiments were carried out to verify the method. We displayed various spiral phase distribution patterns on a phase-only spatial light modulator and measured the resulting singularity point using the proposed method. The results showed good linearity in detecting the position of singularity points. The RMS error of the measured position of the singularity point was approximately 0.056, in units normalized to the lens size of the lenslet array used in the SHWS.