Abstract

Vignetting by lens apertures can cause imaging systems that are space-invariant for incoherent imaging to be strongly space-variant for coherent imaging. We show that systems of this type exhibit a form of shift-invariance for coherent objects that are diffuse. The shift-invariance applies specifically to the expected value of the optical intensity of the image distribution. Conditions for shift-invariance are briefly reviewed, the quasispace-invariance principle is explained, and experimental results are presented.

© 1987 Optical Society of America