REFLECTIVE LIGHTING OPTICAL SYSTEM, PARTICULARLY CONCERNED WITH MINIMIZING A BACK FOCAL LENGTH(BFL) AND AN OPTICAL SYSTEM HEIGHT WHILE INCREASING LIGHTING EFFICIENCY BY DISPOSING A FLAT PBS(POLARIZED BEAM SPLITTER) IN SQUARE FORM BASED ON A SHORT DIRECTION OF AN IMAGER

摘要

PURPOSE: A reflective lighting optical system is provided to dispose a flat PBS(Polarized Beam Splitter) in square form based on a short direction of an imager, thereby minimizing a BFL(Back Focal Length) and an optical system height while increasing a lighting efficiency. CONSTITUTION: A lamp(41) radiates RGB lights. The first dichroic mirror(43) reflects the B light while transmitting the RG lights, and separates into two paths. The second dichroic mirror(44) transmits the R light while reflecting the G light. The first PBS(45a) transmits the reflected G light to the second imager(46b). The second flat PBS(45b) transmits the transmitted R light to a red relay system. The third flat PBS(45c) transmits a light passing through the red relay system for compensating for an optical path of the R light to the first imager(46a). The fourth flat PBS(45d) transmits the reflected B light to the third imager(46c). An X-prism(47) synthesizes the RGB lights, so that the synthesized RGB lights can be incident on a projecting lens(48).