ILLUMINATION OPTICAL SYSTEM AND VIDEO PROJECTING DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent unwanted reflected light from being reflected on the surface of a prism again and made incident on an illumination object surface again in an illumination optical system introducing illuminating light into a prism from a relay optical system and totally reflecting it on the surface of the prism so as to guide it to the illumination object surface, and transmitting necessary reflected light and the unnecessary reflected light between which an angle difference from the illumination object surface exists through the prism so as to guide them to the outside. SOLUTION: A transmitting member having wavelength selectivity is arranged at a part of the optical path of the illuminating light near the diaphragm of a rely optical system. When the reflected light becomes unwanted, a component made incident on the illumination object surface again when the unwanted reflected light is reflected on the surface of the prism again is removed from the illuminating light.