Space variance in quasi-linear coherent optical processors*

Abstract

Except when certain conditions are fulfilled, a coherent optical processor is not strictly space invariant, even in the absence of significant aberrations. Some experiments are carried out to determine the effect of space variance on the resolution of different parts of the image field. Some systems are space invariant only for a restricted class of objects: Such systems are called quasi-linear systems. Quasi-linear systems are shown to impose conditions not only upon the field of the object, but also upon its spatial-frequency content. The conditions for quasi-linearity are determined, together with the conditions that allow the maximum number of degrees of freedom in the object.