Liquid Crystal Light Valve Color Projection System
The trend of research and development of liquid crystal light valve color projection system is presented, firstly. Then, the two types of projection systems developed in our laboratory are given. One of the systems is based on a high-brightness, highresolution, electrically addressed, reflectively reading CR.T-LCLV spatial light modulators (SLMs). The other employs three transmitting-readout si-TFTLCLVs. The design features of the two types of the projection systems are demonstrated and the performance of the systems are given. applications. A variety of liquid crystal color projection systems [11--[51 have been produced. In this paper, we demonstrate the main design features of the two 111 color projection systems developed in our laboratory. Firstly, the color projection system is based on three electrically addressed, reflectively readout cathode-ray tube-liquid crystal light valve(CRT-LCLV) made in our laboratory. Secondly, the color projection system employs a long lifetime xenon arc lamp to photoactivate three highbrightness, high-resolution, transmissively readout liquid crystal light valves(LCLVs). The main design features and the performance characteristics are presented.
1280 x 1024 video rate laser-addressed liquid crystal light valve color projection display
An all solid-state 1280 x 1024 laser raster scanner (LRS) system conforming to the EIA RS-343 television standard with a limiting resolution of 1300 TV lines has been developed. The laser scanner incorporates acousto-optic devices to perform video modulation and X-Y deflection and is used in a time-multiplexed mode to photoactivate three liquid crystal light valves to project full-color, video-rate, large-screen images. Analysis ofthe LRS optical system, projection optics, electronics, and light valve characteristics is presented.
A Liquid-Crystal Video Stereoscope With High Extinction Ratios, A 28 % Transmission State, And One-Hundred-Microsecond Switching
A liquid-crystal pi-cell is an ideal choice for fabricating a video stereoscope because it can switch between states at speeds that approach vertical blanking times on a standard display monitor. Initial applications, although very good compared with alternative technologies, revealed several areas for improvement. First, extinction ratio measurements made from 470 to 630 nanometers varied between 20:1 and 35:1. This range of ratios falls far short of dichroic polarizer capability. Second, a noticeable color shift can occur in the transmissive state as the image is rastered down the screen. For instance, a white image can appear bluish white at the top and yellowish near the bottom. The problems associated with less than perfect extinction ratios are due to boundary-layer optics of the liquid-crystal device and with the drive waveforms applied to the liquid-crystal device. The coloration in the transmissive state occurs because the switching time from the extinction state to the transmission state is 2 to 4 msec, which exceeds typical submillisecond vertical blanking times. A second compensating liquid-crystal cell was introduced to cancel the two extinction-state problems. The compensating cell arrangement also allows simultaneous cell switching without changing the net optical state of the device. By pre-switching both cells prior to vertical blanking, a drive scheme was devised that allows less than 100 Asec switching to either the extinction or transmis-sion state. Although increased by two to three times, extinction ratios still failed to meet expectations. However, the double cell arrangement accentuated substrate index mismatches that accounted for the last bit of light leakage. Correcting this problem brought the extinction values near the limits of the polarizers and improved the transmission state to 28% .