A transparency viewing device including a faceplate adapted for mounting at least one transparency thereon, an LCD array defining an array of pixels, a driver which selectively varies the transparency of the pixels, a source of back illumination for the LCD array wherein the LCD is substantially effective...http://www.google.com.tw/patents/US5859676?utm_source=gb-gplus-share專利 US5859676 - Self-masking viewing apparatus
