Abstract

We report on the demonstration of an all-optical, closed-loop adaptive optical compensation system and white-light compensated imaging scheme using a liquid crystal light valve (LCLV) as the correction element. A typical LCLV is a two-port device consisting of a large array of equivalent pixels (approaching one million), which can be optically addressed. When illuminated by a two-dimensional image, the LCLV is photo activated via a CdS- or Si-based photoconductor. The image information is mapped within the device onto a thin liquid crystal layer via a local internal electric field. A second beam (in general) then samples the LC layer which encodes the information via phase and/or polarization changes on a pixel-by-pixel basis. These devices have application to display systems as well as to optical data processing networks. For our application, we modified a Hughes LCLV so that, upon activation, the liquid crystal readout layer imposed only local phase shifts onto an optical beam while maintaining its polarization state. Hence, the optical wavefront of the readout beam can be controlled without affecting its amplitude, thereby resembling a deformable mirror with a large number of effective actuators. The basic scheme has been employed using discrete electro-optic phase shifters,² CRT-driven LCLVs,³ and electrically driven single-pixel membrane light modulators.⁴

© 1993 Optical Society of America