Smart pixel with four-level amplitude or phase modulation

FLC/VLSI spatial light modulators (SLMs) offer a means of implementing programmable holograms. The pixel described here offers advantages over those previously used and has the potential to be implemented in a large array. We give an initial description of a pixel which allows one of four levels of (highly stable) voltage to be driven onto the pixel mirror thus allowing four els of phase to be generated. This provides the advantages of static memory drive with those of four level phase modulation, albeit at the expense of circuit complexity.