Abstract

In a joint transform correlator (JTC), the spectra of two input image functions are first recorded on a square-law detector (SLD). A readout light is then applied to produce the correlation functions at the output plane. Due to the limited dynamicrange of the SLD, the encoded power spectrum only utilizes a small portion of the device. Therefore, much of the readout power is wasted. An image sampling technique is now proposed to alleviate this problem. We assume that a 2-D sampling grating has been synthesized and is inserted at the input plane of the JTC. The joint transform power spectrum is then diffracted into multiple orders. It is also assumed that the sampling pulse width is sufficiently small compared to the dimension of the detector and that the sampling rate satisfies the Nyquist requirement. If we use only the first ±N orders of diffraction encoded on the SLD, and a quasimonochromatic, partially coherent light is utilized as the readout source, the output correlation intensity is then (1 + 2N)² times that of a conventional JTC. Since the JTC can be regarded as a generalized optical processor, the proposed technique can improve the performance in other image processing uses.

© 1989 Optical Society of America