Gray scale response from optically addressed spatial light modulators incorporating surface-stabilized ferroelectric liquid crystals.

We demonstrate the capability of optically addressed spatial light modulators that incorporate surfacestabilized ferroelectric liquid crystals to reproduce gray scale. This capability is based on temporal averaging and is observed in an operating mode in which the applied voltage repeatedly cycles the device between writing and erasing at operating frequencies between 100 and 2000 Hz. A gray scale response is observed for write-light intensities below a saturation level that increases from 100 microW/cm(2) at 100 Hz to 2 mW/cm(2) at 2 kHz. We develop a procedure to determine the modulation transfer function from measurements of the diffraction efficiency as a function of spatial frequency and write-light intensity in a device with a nonlinear transfer characteristic. At an operating frequency of 500 Hz, the modulation transfer function is greater than or equal to 0.50 at a spatial frequency of 40 line pairs/mm.