Quarter-wave plate, a reflection type liquid crystal display device and optical pickup device

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 phi formed by a normal line on the incident surface and the optical axis is set in a range of 0°phi90°, and an optical axis azimuth angle theta 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°theta90° under theta45° and a range of 90°theta180° under theta135°.