We previously proposed a method of mapping full-complex spatial modula
tions into phase-only modulations. The Fourier transform of the encode
d modulations approximates that of the original complex modulations. T
he amplitude of each pixel is encoded by the property that the amplitu
de of a random-phasor sum is reduced corresponding to its standard dev
iation. Pseudorandom encoding is designed for phase-only spatial light
modulators that produce 360 degrees phase shifts. Because such device
s are rare, experiments are performed with a 326 degrees modulator com
posed of two In Focus model TVT6000 liquid-crystal displays. Qualitati
ve agreement with theory is achieved despite several nonideal properti
es of the modulator. (C) 1996 Optical Society of America