Abstract

A shadow casting correlator is an incoherent optical image correlator in which the point spread function (PSF) is encoded via a 2-D source (LED/laser diode) array. The shadow casting correlator is well suited for implementing image morphology where the structuring element (realized via the PSF) is binary and needs to be updated rapidly to realize complex algorithms. In this paper we analyze the performance limitations of optical shadow casting correlators in implementing image morphology in the light of the geometrical optics approximation inherent in shadow casting systems. The analysis of the optical systems suggests that the angular divergence of the sources is the crucial parameter in determining the maximum space-bandwidth products of the image and structuring element achievable with the shadow casting correlator. The angular divergence constraint is overcome by steering the different source elements. Analytical results are presented that identify a set of values for the system parameters capable of handling a 512 x 512 image and a 32 x 32 structuring element. Experimental results verifying the analytical model will also be presented.

© 1992 Optical Society of America