Patent ID: 7057815

Claim:
A polarizing beam splitter comprising: a light-transmissive substrate; and a dielectric multilayer film disposed on the substrate, the dielectric multilayer film comprising, at least, a first dielectric multilayer film and a second dielectric multilayer film having two design reference wavelengths λ 1 and λ 2 , respectively, which are different from each other, each of the first and second dielectric multilayer films comprising: an alternate layer comprising an n-cycle (n: an integer) laminate of a basic cycle of a two-layer structure of a high-refractive index layer and a low-refractive index layer each having an optical film thickness of λ 1 /4 or λ 2 /4 respectively at the reference wavelength λ 1 or λ 2 ; and a thin-film adjusting layer comprising each one of the high-refractive index layer or the low-refractive index layer having an optical film thickness of λ 1 /8 or λ 2 /8 disposed on both sides of the alternate layer; wherein the alternate layers of the first and second dielectric multilayer films respectively comprise different combinations of substances.