| 摘要 |
A quarter wave plate that is a crystal plate made of an inorganic material having birefringence and optical rotatory power and has an optical axis, includes an incident surface positioned on one surface of the crystal plate; and an emitting surface positioned on another surface, which is opposed to the incident surface, of the crystal plate. In the quarter wave plate, linearly-polarized light incident from the incident surface is converted into circularly-polarized light so as to be emitted from the emitting surface, and circularly-polarized light incident from the incident surface is converted into linearly-polarized light so as to be emitted from the emitting surface. Further, in the wave plate, an angle &phgr; formed by a normal line on the incident surface and the optical axis is set in a range of 0°<&phgr;<90°, and an optical axis azimuth angle &thetas; formed by an optical axis projection line, which is formed by projecting the optical axis on the incident surface, and a polarization plane of the linearly-polarized light is set in one of a range of 0°<&thetas;<90° under &thetas;≠45° and a range of 90°<&thetas;<180° under &thetas;≠135°.
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