Tadao Iwaki

Optical pattern recognition of letters by a joint-transform correlator using a ferroelectric liquid-crystal spatial light modulator

The use of a joint-transform correlator (JTC) as an optical pattern-recognition system for letters has been studied. The system incorporates a ferroelectric liquid-crystal spatial light modulator (LAPS-SLM). The LAPS-SLM has a high contrast ratio and a fast response time, permitting the JTC to recognize more reference letters simultaneously than a classical correlator can.

Optical pattern recognition with LAPS-SLM (II): feedback joint transform correlator using LAPS-SLM

A new algorithm of the feedback joint transform correlator ( FJTC ) was proposed. The system is made by using the ferroelectric liquid crystal spatial light modulator named LAPS-SLM. The FJTC features excellent pattern recognition characteristics and pattern associative characteristics, compared to conventional joint transform correlators ( JTC).

Effects of nonlinear parameters in feedback joint transform correlator (I)

We report that nonlinear parameters effect the characteristics of the optical pattern recognition of a feedback joint transform correlator (FJTC) which is based on a joint transform correlator (JTC). This system incorporates the optically addressed ferroelectric liquid crystal spatial light modulator named LAPS-SLM. Nonlinear parameters in the FJTC are a threshold level of the LAPS-SLM to record the binary joint power spectrum (JPS), and a feedback transfer function from the correlation plane to the input plane. It is important to control the threshold level of the binary JPS. But the FJTC does not always need the optimum condition where the FJTC recognizes the signal image correctly at the initial recognition.

Threshold characteristics of an OASLM using a a-Si:H photoconductor and a SSFLC modulator

We present the write light intensity threshold characteristics of an OASLM incorporating a hydrogenated amorphous silicon photoconductor and a surface stabilized ferroelectric liquid crystal modulator, LAPS-SLM. In this paper, we describe a new implementation which applying the two threshold characteristics of the LAPS-SLM to perform all Boolean logic by one device.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Rotation- and scale-invariant joint transform correlator using FLC-SLMs

A rotation and scale invariant joint transform correlator is described. The polar-logarithmic coordinate transformation is used as a preprocessing of input images. The resultant coordinate transformed images are interfaced to a joint transform correlator. The use of optically addressed ferroelectric liquid crystal spatial light modulators at the coordinate transform plane and at the Fourier plane allows data to be processed faster than video rate and gives the characteristics of a binary joint transform correlator. The rotation and scale invariance of the correlator is demonstrated experimentally.

Catastrophic characteristics of pattern recognition in feedback joint transform correlator

A joint transform correlator with feedbacks from the correlation outputs to the input intensity of the reference images works as a neurocomputing system. The characteristics change catastrophically with the parameters of the feedback transfer function.

Compact one lens JTC using a transmissive amorphous silicon FLC-SLM (LAPS-SLM)

A compact, FT lens binary joint transform correlator (BJTC) based on a high resolution ferroelectric liquid crystal, optically addressed spatial light modulator (FLC-OASLM) read in transmission mode is proposed. Experimental results of its implementation using two semiconductor lasers are presented. A binary and a gray scale driving operation of the SLM are introduced and good multiple object recognition capability at high frame rates is demonstrated.