| 摘要 |
A projection-type display apparatus in which the entry of light rays to the back side of liquid crystal light valves from dichroic prism that composes optical system light synthesizer is prevented. To this end, a projection display according to the present invention preferably includes a color synthesizer for combining colored and modulated light beams, comprising: a square column dichroic prism composed of four triangle prisms having equal refractive index together whose cross sections are right isosceles triangles such that three light valves are located adjacent to three exterior peripheral surfaces of dichroic prism to receive colored and modulated light beams therefrom and; a filter for absorbing light with a specified wavelength range, leaked from surface of dichroic prism at the opposite side of incident light surface and directed to liquid crystal light valve, the filter being located between liquid crystal light valves and surface of dichroic prism. As for construction of the dichroic prism itself, specifically, of the four aforementioned triangular prisms, the first triangular prism and the aforementioned third triangular prism are mutually affixed in a condition in which there is a first step difference in the vertical direction. The first exposed side is formed on one edge of the affixed side of the first triangular prism. Similarly, the second triangular prism and the fourth triangular prism are attached to each other such that there is a second step difference on the same edge, and a second exposed side is formed on one edge of the affixed surface of the second triangular prism. Further, the first and the third triangular prisms and the second and the fourth triangular prisms are attached, with a step difference between them, in such a way that the aforementioned first exposed side and the aforementioned second exposed side are located on the edges facing the same direction; and a third exposed surface that is orthogonal to the aforementioned first and second exposed surfaces is formed between the aforementioned first triangular prism and the aforementioned second triangular prism.
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