<title>Projection display device based on CRT-optically addressed SLM-combination</title>

Abstract

The system based on combination "CRT -Optically Addressed Liquid Crystal Spatial Light Modulator (LC SLM)" is constructed for application as projection display and device for laser beam controlling device in adaptive optics and optical image processing. LCSLM IN PROJECTION DISPLAYSThe optically addressed liquid crystal spatial light modulators are based on the photosensitive structures --"photoconductor electrooptical layer". Liquid crystals attach to these structures such a feature as high sensitivity, good dynamic properties, high resolution, etc. These features are arising from the nature of the electrooptical effects in LC: drastically changes of optical index (up to 0.3) in very thin layer (typical value is 2-5 micron) under controlling voltages as low as a few Volts. Ability to modulate light within whole visible region with contrast determined mostly by external optics quality made these electrooptical materials obligatory in the design ofthe many ofprojection displays.Two main types ofLC SLM are used now widely --electrically addressed and optically addressed ones. Our work is concerned with the application of optically addressed LC SLM for projection technique (so this abbreviation LC SLM will used below in this meaning only). PROJECTION SCHEMEThe CRT source is used for the input of image in the projection setup because of availability of large number of CRT with different electrical and luminescence parameters, as well as in variety of sizes. Developed electronic circuitry technique for video signal processing and amplification is very important too.Well-known idea of the optical connection via fiber plates' pair has been applied for the image transfer from the CRT screen to the photosensitive layer of the SLM. The principal scheme for reported projection device is shown in Fig. 1 as a result of mentioned approach. LC SLM PRINCIPLESThrough various constructions of the LC SLM --one could distinguish ones with electrical structures metal --insulator --semiconductor --LC --metal, i.e., electrically symmetrical structures in which photosensitive semiconductor is surrounded by dielectric layers (LC is considered here as insulator, and this assumption is quite reasonable for the tasks, important for projection displays). How these structures work?The electrical structure of this SLM is pictured in Fig.2, where the reflective SLM is shown. Principally the transmissives SLMs can be and really are used for the projection, and in this case regular optics is used for image transfer from the CRT screen to LC SLM.These structures are principally operated under AC supplied voltage. When the voltage pulse is applied to the structure, it is distributed between semiconductor and LC layer --but only if amplitude of this pulse is enough to deplete fully the entire volume of the semiconductor. This condition arises from the fact, that in the moment of the voltage pulse application electrical carriers existing in the volume of the semiconductor begin move under influence of applied voltage --in the external electrical circu...