Patent ID: 7012747

Claim:
A polarizing beam splitter in which a first polarized light beam of light incident at a predetermined angle is transmitted and a second polarized light beam of the incident light is reflected in a direction different from the direction in which said first polarized light beam is transmitted, comprising: a polarized light beam separation film composed of a multiple-layer film which includes a basic structure film H2L consisting of an optically transparent high refractive-index layer H having a predetermined refractive index with respect to said incident light and an optically transparent low refractive-index layer 2 L having a refractive index lower than that of said high refractive-index layer H, and consists of any structure among (H2L) m , (H2L) m H, and 2L(H2L) m (where m is an integer 3 to 7), each of which is a repeated structure of said basic structure film, in which a reference wavelength (λ 0 ) is equal to approximately 550 nm, and said high refractive-index layer H has a thickness approximately equal to λ 0 /4 and said low refractive-index layer 2 L has a thickness approximately equal to λ 0 /2; and transparent substrates disposed on the light-entering surface side and on the light-outgoing surface side of said polarized light beam separation film, respectively.