OPTICAL CHARACTERISTICS OF AN OPTICALLY ADDRESSED SPATIAL LIGHT-MODULATOR FOR NONLINEAR JOINT TRANSFORM CORRELATION

The specifications supplied for a GEC-Marconi optically addressed spatial light modulator were investigated and extended with the aim of using the device in a joint transform correlator. This device showed three important characteristics which would affect its performance for correlation applications; (i) a novel ability to show two different modes of operation of the nonlinear input-output relationship (accessible by changing the operating voltage), (ii) the resolution and contrast were approximately constant over a wide range of operating frequencies but showed a sharp fall-off at low frequency, and (iii) the contrast increased as the read intensity decreases whilst the limiting resolution remains unchanged. The maximum limiting resolution and contrast ratio were measured and are almost-equal-to 90 lp/mm and > 1500:1, respectively. From the measured device characteristics the SLM can now be optimised for use in correlation experiments.