Jonathan S. Kane

Edge enhancement techniques for improving the performance of binary phase-only filter pattern recognition devices

Several edge enhancement techniques are examined for improving the performance of binary phase-only filter pattern recognition devices. These include the linear techniques of blocking the lower Fourier orders and Laplacian filtering as well as the nonlinear techniques of phase extraction and phase binarization. The results indicate that the nonlinear techniques outperform the linear techniques when there is no distortion caused by aperturing the input information. However, when the input is apertured, both the linear and nonlinear techniques yield approximately the same peak-to-noise ratio.

Real-time holographic baseband frequency demodulator.

The multiplicative and low-bandpass filtering characteristics of real-time holograms in photorefractive media are used as a basis for a baseband frequency demodulator by means of holographic homodyne detection. We experimentally demonstrate the demodulation of spatial bandpass signals in the kilohertz regime and homodyne detection in the gigahertz regime.

Binary phase-only filter associative memory

An associative memory is implemented by using a binary phase-only filter as the memory element in a two-focal-length (2-f) correlator architecture. A sharp autocorrelation peak, combined with the 2-f architecture, allows the noise to be separated adequately from the signal such that a simple plane mirror can be used in the correlation plane instead of a nonlinearity.

Self-pumped optical phase conjugation with a sodium Raman laser

We report self-pumped optical phase conjugation in which the pumps are self-induced as standing waves in a linear Raman laser. Self-pumped reflectivities approaching 5% are obtained for input intensities of 20 W/cm(2). This low optical input intensity combined with predicted submicrosecond response times suggests that the resonant Raman interaction may provide the basis for a promising new class of nonlinear-optical material.

NEAR-OPTIMAL BINARY PHASE-ONLY FILTER CORRELATOR FOR OBSCURED INPUTS

The experimental and theoretical operation of the dc-blocked phase-only filter correlator is studied for obscured inputs. The performance of the nearly optimal filter is compared with the performances of other varieties of simple optimal filters that are capable of real-time implementation with spatial light modulators. Uses of these correlation filters in associative memories is investigated.

Realizing optical logic with a smart-pixel spatial light modulator

A method of implementing optical logic has been realized experimentally with a novel liquid crystal on silicon spatial light modulator with an integrated lens arrays. The device allows for three optical inputs and one optical output per pixel. The different logic functions realized, OR, and, nor, nand, and xor, are discussed.

TWO-PORT PHOTOREFRACTIVE JOINT-TRANSFORM CORRELATOR

We present what is to our knowledge the first quantitative analysis of the dual optimality that can be achieved in the all-optical two-port photorefractive joint-transform correlator. We determine the operating region where these ports have complementary performance: the first port performs well for non-Gaussian clutter noise, and the second port is optimal for additive Gaussian noise. Dual optimality is achieved without the performance compromise of the optimal trade-off filter approach.

Optoelectronic winner-take-all VLSI shunting neural network

In this paper we present an analog winner-take-all MOS VLSI (metal-oxide semiconductor/very large scale integration) optoelectronic network. By varying either the input current or circuit parameters, the circuit can evidence several different behaviors such as contrast enhancement, strict winner-take-all, or winner-take-all with hysteresis. Simulation and experimental results from the prototype circuit are also discussed.

Analysis of the dual discrimination ability of the two-port photorefractive joint transform correlator

An all-optical joint transform correlator featuring two operative correlation planes(ports) with complementary performance is presented. We present the theory of operation, derive the input-output characteristics, and demonstrate computer simulations and experimental results. The two-port joint transform correlator is based on simultaneous use of two photorefractive wave-mixing architectures. The first port uses two-beam coupling, and the second port uses four-wave mixing. The performance of the two ports depends on an experimentally controlled beam intensity ratio and the photorefractive coupling coefficient. With appropriate selection of these parameters, the first port is capable of high discrimination, while simultaneously the second offers a low discrimination output. Our results show that the two-beam coupling port can achieve peak-to-noise and signal-to-noise ratio values better than the phase-only correlator, whereas the four-wave-mixing port performs similarly to the classical joint transform correlator. This leads to a potential application in which the correlator could be set up so that in one port a general class is detected (interclass) and, in the other, the specific item in a class is detected (intraclass).

Optical processing with feedback using smart- pixel spatial light modulators

A spatial light modulator is often used as the basic element in real-time recognition architectures. However, many of the devices suffer from poor uniformity and/or nonlinearities that affect the overall perfor- mance of any real-time recognition scheme. We propose using optical feedback as a method of improving device performance. We demon- strate both positive and negative feedback separately through a mixture of on-board electronic processors and optical polarization intensity en- coding. Placing the spatial light modulator in a positive feedback system causes the system to act like a memory. Placing the spatial light modu- lator in a negative feedback system makes the spatial light modulator response more analog, which in turn leads to improved uniformity.