Experiments on annealed binary phase only filters fabricated with electron beam lithography.

A binary phase only filter is encoded using a simulated annealing algorithm to distinguish two similar characters. Characters that cannot be distinguished with conventional filter encoding methods are clearly distinguished with the annealed binary phase only filter in a computer simulation. Two binary phase only filters have been fabricated by use of electron beam lithography and chemical etching. One is an annealed binary phase only filter, and the other is a binary phase only filter encoded with a conventional method. Optical pattern recognition experiments using the filters agree well with computer simulation results.