| 摘要 |
PROBLEM TO BE SOLVED: To make a projection type video display device compact and to enhance performance for increasing brightness and making quality high. SOLUTION: In the projection type video display device, a hole is formed at the central part of a reflector so that a light source is inserted and held in the reflector. Then, when the maximum radius of an almost circle obtained by projecting the hole or a light source bulb having a larger maximum outside diameter to a plane being vertical to an optical axis of the reflector is defined as r, the thickness of a light refracting plate in an optical axis direction is defined as t, the refractive index of the light refracting plate is defined as N, an angle formed by the optical axis and the light refracting plate is defined asθand the shift amount of a light beam by the light refracting plate is defined asδ, the light refracting plate constituted so that an expression (1) is satisfied by the shift amountδis used. (1) r=δandδ=tanθ+1/tan[θ-sin-1(sinθ/N)].
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