Existing cathode ray tube (CRT) projectors have limitations in regard to resolution and luminance. This shortcoming has been offset by recently developed liquid crystal display (LCD) projectors or digital light processor (DLP) projectors.liquid crystal on silicon (LCOS) provides higher sharpness, resolution and luminance compared to the CRT, and thus, provides better image quality. the LCOS has a light-reflective structure in which pixel electrodes are arranged on a silicon substrate, causing light emitted from a lamp to reflect.The reflective type LCOS can realize a system offering good brightness because pixel driving electrodes do not block the light and therefore increase the light transmission.It can achieve high resolution because it has pixels on a silicon substrate using a semiconductor fabrication process,high resolution because it has pixels on a silicon substrate using a semiconductor fabrication process. LCOS display device has a competitive price because existing semiconductor fabrication process can be directly used. important parameters that causes image quality deterioration in the display devices is the uniformity of cell gap between two substrates.response speed, contrast, visual angle, and luminance of the characteristics of liquid crystal cells have a close relationship with the thickness of the liquid crystal layer.conventional spacers in the LCOS display device is necessary to solve the non-uniformity problem of the cell gap.
without requiring spacers this improvement removes the disadvantages due to uneven cell gap .A liquid crystal on silicon (LCOS) device includes a wafer, glass, and walls formed at opposite ends of an upper surface of the wafer to define a predetermined cell gap between these.A thin piezo-electric layer is attached to a surface of the wafer and an electrode is applied with external power to expand or contract the thin piezo-electric layer. There is a a voltage detection unit for detecting a voltage generated by the deformation of the thin piezo-electric layer and also a feedback control unit for compensating for this deformation according to the voltage detected by the voltage detection unit. It achieves uniformity of the cell gap by adjusting the voltage level of the thin piezo-electric layer.