| 摘要 |
PURPOSE:To provide a polarization converting optical system constituted so that the luminance of a picture projected by a projection type liquid crystal display device is improved. CONSTITUTION:Aspherical reflecting mirrors 2 are adjacently arranged to two polarizing beam splitters(PBS) 1 whose polarization and separation surfaces are mutually orthogonally crossed. When light is made incident on the PBS 1 from a light source 4, (p) polarized light is transmitted and (s) polarized light is reflected. The aspherical surfaces of the mirrors 2 are formed so that the reflected light out of the (s) polarized light reflected, whose optical path after reflection on the mirror 2 is at a position near to the PBS 1, becomes almost in parallel with the transmitted light of the PBS 1 and the reflected light whose optical path is at a position distant from the PBS 1 becomes focusing light with respect to the transmitted light of the PBS 1. By such constitution, a focusing beam by the polarized light is obtained with respect to the reflected light among luminous fluxes at the central part of the light source 4 on the polarization and separation surfaces at the position near the PBS 1 without allowing the PBS 1 to obstruct the optical path. |
