Phase quantization of diffractive elements usually requires uniformly
distributed phase levels in the domain [0,2 pi]. In this paper we disc
uss two alternate quantization schemes. In the first one the phases ar
e uniformly distributed in a domain [0,phi(o)], with phi(o),<2 pi. The
second scheme employs non-equidistant levels in the phase domain [0,2
pi]. Both schemes are useful to reduce quantization errors in diffrac
tive elements, without increasing fabrication complexity. (C) 1997 Els
evier Science B.V.