High contrast ratio and compact-sized prism for DLP projection system

In this paper, a novel light separator with contrast ratio enhancement but maintaining the optical efficiency of the DLP projection system is proposed. The main capability of the novel light separator is to direct the uncontrolled light away from the image system. The working theorem for the novel light separator is derived as well. Uncontrolled light is kept away from the image system by a total internal reflection surface, thereby effectively improving the image quality. Compared with the conventional contrast ratio enhancement method, the FO:FO contrast ratio can be improved from 839:1 to 48250:1, the ANSI contrast ratio can be improved from 180:1 to 306:1, while the image system efficiency remains at 76.2%.