| 摘要 |
Provided are a color combining optical element capable of forming a good projected image on a screen surface while permitting scaling-down of entire apparatus and a projection image display apparatus using it. A color combining optical element is constructed of three or more prisms and in such structure that it has a prism provided with a surface as a surface serving as a total reflection surface and as a transmissive surface on the extreme exit side and two dichroic mirror layers for reflecting light of mutually different wavelength regions, that the two dichroic mirror layers are located so as not to cross each other, that an outline of a cross section of a prism placed between the two dichroic mirror layers, cut by a plane along a color composition direction, is comprised of four or more segments, and that at least one of flection points in the cross section of surfaces without the dichroic mirror layers is present at an inner position of the color combining optical element with respect to a segment connecting two ends of segments in the cross section of surfaces with the two dichroic mirror layers.
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