Patent ID: 6685322
Filing Date: 2004-02-03
Classification: G03B

Abstract:
A projection-type image display device comprising:a display element for displaying a projection image, and for modulating and reflecting illumination light by the displayed projection image; a projection optical system for projecting light modulated by the display element; an optical system, disposed medially to the display element and the projection optical system, for directing illumination light to the display element and for directing light modulated by the display element to the projection optical system; said optical system comprising: a first prism having a first surface and a second surface forming an acute angle therebetween; a second prism having a third surface, said first and second prisms being positioned to form an air gap between the second surface and the third surface; wherein a cross section of said air gap, perpendicular to the first surface and the second surface has a wedge shape which is wide at a part thereof which is nearest the first surface and is narrower at a part thereof which is more distant from the first surface; and wherein the optical system is arranged such that the first surface forms a right angle to an optical axis of the projection optical system, and wherein the second surface is positioned nearer the projection optical system than is the first surface.