LIGHTING OPTICAL SYSTEM

PURPOSE:To raise the utilizing efficiency of the luminous flux of a light source and to check the occurrence of the ghost of the light source to the utmost by arranging the light source near the position of a focus on an aperture part side, which is one of two foci of an oval mirror whose inner surface is formed as a reflecting surface, utilizing the outgoing luminous flux from the aperture part and radiating an image to be projected. CONSTITUTION:In the oval mirror 2, its inner surface is formed as the reflecting surface, its long axis 11 is made to coincide with the optical axis of a projection optical system and its aperture part 3 is formed in a circle centering around one apex 12 of the long axis 11 of the oval mirror 2. The light source 1 is arranged on the position of the focus F1 closer to the aperture part 3, between two foci F1 and F2 of the oval mirror 2. The luminous flux projected from the light source 1 on the focus F1 of the oval mirror 2 is reflected on the inner surface of the oval mirror 2 to be condensed on the other focus F2 and, thereafter, it is reflected on the inner surface again to be condensed on the focus F1. Thus, most of all luminous fluxes from the light source 1 are projected from the aperture part 3 finally even if the number of times of reflection on the inner surface of the oval mirror 2 is different so that all the luminous fluxes from the light source can be utilized for lighting.