Improved correlation discrimination is achieved by using a fringe-adjusted joint transform correlator (JTC). This technique is found to yield significantly better correlation output than the classical and binary JTC's for input scenes involving single as well as multiple objects. It also avoids the computation-intensive Fourier-plane joint power spectrum binarization processing of a binary JTC. Two optical implementations for the proposed technique are also suggested.

A novel amplitude-modulated phase-only filter (AMPOF) is proposed for achieving improved correlation discrimination. The proposed AMPOF has an amplitude spectrum which is the inverse of a biased amplitude spectrum of the object function and a phase spectrum which is a complex conjugate of the phase spectrum of the object function. When compared with the phase-only filters, the AMPOF is found to have significantly superior correlation discrimination capability.

A new encryption technique is proposed to encrypt color images using existing optical encryption systems for gray‐scale images. The color images are converted to their indexed image formats before they are encoded. At the decryption end, the color images are recovered by converting the decrypted indexed images back to their RGB formats. The proposed single‐channel color image encryption method is more compact and robust than the multichannels methods. Since color information is added to the shape information, better verification performance can be achieved in optical security systems. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 318–323, 1999.

Edge detection schemes based on Prewitt, Sobel, and Roberts operators are realized using optical symbolic substitution. The corresponding optical systems are compared in terms of hardware and performance.

No abstract

An efficient symbolic substitution scheme for modified-signed digit arithmetic operations is introduced. In this technique, an additional bit is used along with each pair of the input bits so that the nth additional bit is a characteristic of the (n - 1)th pair of input bits. The truth table minimization thereby shows that relatively fewer minterms are to be included in the corresponding optical content-addressable memory.

A method for calculating the modulation transfer function (MTF) of charge-coupled devices (CCD) is presented. The analysis accommodates both the time- and space-variant properties of CCDs as well as input images moving with constant velocity within a scan interval. The model developed accounts for both the static and the dynamic MTF of CCD imaging systems.

No abstract