Full complex modulation using liquid-crystal televisions.

An optical architecture is proposed that uses two modified liquid-crystal televisions (LCTV's) to control amplitude and phase modulation independently. Two applications in pattern recognition are discussed.

Spatial-light-modulator-based electro-optical imaging system.

We describe a novel electro-optical system that can image objects over a long range of distance without involving any mechanical movement.

Effects of thresholding in joint-transform correlation.

The joint-transform power spectrum of two identical objects can be represented as a one-dimensional sinusoidal grating modulated by a Fourier transform, and the correlation peaks can be regarded as the first-order diffraction of the grating. The peak intensity and the width are then determined by the aperture and the modulation of the grating. Based on this analysis, it is shown that dc blocking, hard clipping, or binarization of the power spectrum results in higher correlation peak intensity and a narrower peak width. Direct-current blocking is also found to be preferable if the input pattern to the correlator is corrupted by noise.

Optical disk based joint transform correlator.

A joint transform correlation system based on optical disks is presented. The operation principle, system considerations, and processing speed are discussed.

Using the hybrid modulating properties of liquid crystal television.

The phase modulating capabilities of a commercially available liquid crystal television (LCTV) have been investigated and applied to the joint transform optical correlator architecture. Operating the LCTV in a phase modulating mode requires a much smaller coherent light source while still producing a good joint transform power spectrum and good correlation signals.

High-efficiency joint-transform correlator.

A technique that increases the efficiency of a conventional joint-transform correlator is proposed. By modifying the joint-transform power spectrum of the input objects by using a spatial sampling method, the readout light as well as the physical area of the square-law detector can be fully utilized. As a result, the output correlation intensity can be substantially increased. Cases of using coherent and partially coherent readout light are discussed, and experimental results are presented.