Patent ID: 8531766

Claim:
A polarization-separation device comprising: a beam splitter that includes a beam-separating surface, on which a light beam that contains a first light beam and a second light beam impinges, wherein a polarization direction of the first light beam and a polarization direction of the second light beam are perpendicular to each other, and an incident angle of the first light beam and an incident angle of the second beam vary independently while incident onto the beam-separating surface; a first polarizer arranged in an optical path of transmitted light beams having transmitted through the beam splitter, and allows the first light beam to transmit therethrough; and a second polarizer arranged in an optical path of reflected light beams reflected from the beam splitter, and allows the second light beam to transmit therethrough, wherein, within an effective range of incident angle, at least any one of a value of |Ts−Tp| and a value of |Rs−Rp| obtained when an angle θ 1 and an angle θ 2 each being equal to or closest to 45 degrees is smaller than a corresponding one of a value of |Ts−Tp| and a value of |Rs−Rp| obtained when the angle θ 1 and angle θ 2 each being farthest from 45 degrees, the angle θ 1 being angle between an incidence plane of the first light beam incident on the beam-separating surface and the polarization direction of the first light beam (0°≦θ 1 ≦90°), the angle θ 2 being an angle between an incidence plane of the second light beam incident on the beam-separating surface and the polarization direction of the second light beam (0°≦θ 2 ≦90°), Tp being transmittance of p-polarized component transmitted through the beam-separating surface, Rp being reflectance of the p-polarized component reflected from the beam-separating surface, Ts being transmittance of s-polarized component transmitting through the beam-separating surface, and Rs being reflectance of the s-polarized component reflected from the beam-separating surface.