Patent ID: 7207676
Filing Date: 2007-04-24
Classification: G03B

Abstract:
1. An image projection apparatus having three reflection-type image display units using three primary color beams of red, green, and blue as illumination light, and modulating said primary color beams in accordance with image display signals to display images, a cross prism for combining the modulated primary color beams, and a projection lens for projecting the combined beam to a screen, said apparatus comprising: polarized beam filters, each arranged at an orientation forming an angle of about 45 degrees with respect to an incident face of said cross prism and a display surface of an image display unit, so that the modulated primary color image beam emitted from said image display unit is reflected and strikes the incident face of said cross prism and each passing a first polarized beam therethrough and reflecting a second polarized beam having a polarization axis orthogonal to said first polarized beam; display surfaces of said image display units being arranged so as to be substantially parallel to planes vertical to four inside surfaces of said cross prism and being substantially orthogonal to three primary color incident faces of the cross prism; and the primary color illumination beams incident from the opposite side of said image display units across said polarized beam filters illuminate said image display units; wherein, for each of two primary color beams among the three primary color beams forming primary colors by reflecting light at the reflection faces of said cross prism, a ½ wavelength plate is arranged between said cross prism and the corresponding polarized beam filter for making the light strike a reflection face of said cross prism to become an S-polarized beam.