| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system for projector capable of preventing light such as OFF light and planar part reflection light causing the reduction of contrast from being made incident on a projection optical system, irrespective of a compact constitution, and also, to provide a projector apparatus using the projector optical system, and to provide a projector optical system where the light loss of the illuminating light and projection light is reduced, the miniaturization of a prism part is attained, and which is bright and improved in contrast, and suitable to attain the miniaturization of the apparatus, and to provide the projector apparatus using the optical system for projector. SOLUTION: A 2nd air gap layer 22 of the prism part 2 is set so that the illuminating light may be totally reflected toward a light valve 3 and the ON light may be transmitted through the layer 22, and a 1st air gap layer 21 is set so that the ON light may be transmitted through the layer 21 and the OFF light and the plane light may be totally reflected by the layer 21. Besides, the system satisfies a conditional expression (1) 2°<A<40°(A denotes the smallest angle among respective air angles of the OFF light and the plane light to the ON light), and also, satisfies a conditional expression (2) 1.6≤N≤1.8 (N denotes the refractive index of each of prisms 23, 24 and 25 so as to form the air gap layer 21 and the air gap layer 22). COPYRIGHT: (C)2006,JPO&NCIPI
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