Patent ID: 8308300
Filing Date: 2012-11-13
Classification: G03B,H04N

Abstract:
1. A color separation optical system comprising: a dichroic surface that transmits light from a light source in a green wavelength band and reflects light in a red wavelength band and a blue wavelength band; a polarization beam splitting surface that transmits the light transmitted through the dichroic surface; a light modulation element that receives the light transmitted through the polarization beam splitting surface, modulates the received light, and reflects the modulated light or non-modulated light back to the polarization beam splitting surface; and a polarization plate that analyzes the modulated light reflected by the light modulation element, wherein the polarization beam splitting surface reflects the modulated light received from the light modulation element to the polarization plate, wherein, when S-polarized light impinging on the dichroic surface at an incident angle smaller than 45 degrees and then impinging on the polarization beam splitting surface at an incident angle larger than 45 degrees in an optical path for the light in the green wavelength band is referred to as first incident-angle light, a wavelength which is longer than a wavelength at the maximum transmittance of the dichroic surface for the first incident-angle light and at which the transmittance of the dichroic surface for the first incident-angle light is 10% is referred to as a wavelength Wa, and a range of wavelengths shorter than the wavelength Wa is referred to as W, wherein the polarization beam splitting surface has a characteristic in which its transmittance for the first incident-angle light in the wavelength range W is equal to or lower than 5%, and wherein a wavelength with a transmittance of 50% for the S-polarized light at an incident angle of 45 degrees on the polarization beam splitting surface is between 600 nm and 650 nm.