| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical element, an illumination device and a projection type image display capable of improving the efficiency of using respective color component light beams when using four kinds of color component light beams. SOLUTION: A triangular prism 1 of triangle pole-shape having a bottom surface 6, an upper surface 5, a side surface 11, a side surface 21 and a side surface 31 comprises a composite surface 41, a composite surface 42 and a composite surface 43 which are defined by respective apexes of the bottom surface 6 and the upper surface 5 and centers of the bottom surface 6 and the upper surface 5, wherein at least any composite surface of the composite surface 41, the composite surface 42 and the composite surface 43 is a PBS (polarizing beam splitter) surface which transmits a color component light beam having one polarization direction and reflects color component light beams having other polarization directions. COPYRIGHT: (C)2008,JPO&INPIT
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