Patent ID: 7369186

Claim:
A polarizing beam splitter comprising: a plane-parallel plate; a polarization splitting layer formed on the plane-parallel plate to split incident light into reflected light and transmitted light according to the polarization directions thereof, the polarization splitting layer including stacked one-dimensional grating layers, the stacked grating layers being an alternation of at least one H layer having an effective refractive index n H for p-polarized light and at least one L layer having an effective refractive index n L for p-polarized light; and a first optical member having a light entrance surface, a light exit surface that transmits the light reflected by the polarization splitting layer, and a surface in contact with the plane-parallel plate, the polarizing beam splitter satisfying the following equation: 0.7 < n H 2 ⁢ n L 2 sin 2 ⁢ θ 1 ⁡ ( n H 2 + n L 2 ) / n p < 1.3 wherein n p is the refractive index of the material for the plane-parallel plate; and θ 1 is the angle between the light entrance surface of the first optical member and the polarization splitting layer, wherein said polarization splitting layer reflects s-polarized light that is made incident onto the polarization splitting layer at an angle θ 1 by total reflection and transmits p-polarized light that is made incident onto the polarization splitting layer at an angle θ 1 , and wherein angle θ 1 is equal to or larger than a critical angle for the s-polarized light and angle θ 1 is smaller than the critical angle for the p-polarized light.