A coherent optical processing system is usually nonredundant because any attempt to secure redundancy by band-limiting the input leads to a corresponding underuse of the Fourier plane. Methods are suggested for putting additional copies of the signal into the unused region. This results in a certain departure from strict coherence but is in no case as extreme as using noncoherent methods.
© 1980 Optical Society of America
G. L. Rogers, "Modifying a coherent optical processing system to achieve a measure of redundancy," J. Opt. Soc. Am. 70, 1012-1014 (1980)