Patent ID: 6328447
Filing Date: 2001-12-11
Classification: G02B,G03B

Abstract:
A projection device, comprising:an illumination device;a polarizing beam splitter that reflects light polarized in a first direction, of light emitted from said illumination device;a polarization direction changing element that reflects the light polarized in the first direction and reflected by said polarizing beam splitter, back toward said polarizing beam splitter while changing the polarization direction thereof, the polarization direction being changed according to an image to be projected,said polarizing beam splitter transmitting light polarized in a second direction, of light reflected by said polarization direction changing element; andan optical system that magnifies and projects the light reflected by said polarization changing element and passing through said polarizing beam splitter,said polarizing beam splitter being a thin-film multilayer film composed of a plurality of first layers and a plurality of second layers alternately stacked, a first refractive index of said first layers in the first direction and a second refractive index of said first layers in the second direction being almost equal to each other, and a third refractive index of said second layers in the first direction being different from a fourth refractive index of the second layers in the second direction, said second refractive index and said fourth refractive index being substantially equal to each other,said polarizing beam splitter having a reflectivity-to-transmissivity ratio of at least 62 for the light polarized in the first direction for all lights incident on the polarizing beam splitter which have an incident angle within a range of 10 degrees to 50 degrees.