DEPTH OF FOCUS AND THE MOMENT EXPANSION

We introduce the so-called moment expansion of a defocused image as a tool for analyzing and improving the depth of focus in optical imaging . It is shown that a number of previously noted defocus phenomena can be readily derived or explained in terms of moment expansion. Some pot ential applications of the moment expansion to phase-shifting mask and pupil filter design for optical lithography are also briefly noted. ( C) 1995 Optical Society of America