We report on a technique for producing a Bessel function correlation output
for an arbitrary input pattern. The central dark spot at the center of the
Bessel function correlator output is narrower than the width of the normal
correlation spot and can be extremely useful for locating the center of th
e correlation signal. The Bessel function is produced by convolution of the
extremely sharp correlation produced by an inverse filter with the Bessel
function and is encoded with a single phase-only liquid-crystal spatial lig
ht modulator. To encode amplitude information on the filter, we spatially m
odulate the phase encoded on the filter. Amplitude modulation is obtained b
y modulation of the diffraction efficiency of the phase grating. Experiment
al results are presented. (C) 1999 Optical Society of America OCIS codes: 0
70.4550, 070.5010, 190.5990, 230.3720, 230.6120.