Patent ID: 7021770

Claim:
A rear projection optical system comprising a projection optical system for projecting an image displayed on a display surface onto a screen surface, wherein the projection optical system includes at least four curved-surface reflecting mirrors, and wherein assuming that a ray of light that travels from a center of the panel display surface to a center of the screen surface is called a screen center ray, the following condition is fulfilled: 0.5< DL/HL< 3.5, 10<θ<70, Fnoy≦3.5, and Fnoz≦3.4, where: DL represents an optical distance traveled by the screen center ray from a last surface of the projection optical system to the screen surface, HL represents a dimension of the screen surface in a direction parallel to a plane formed at the center of the screen surface by a normal to the screen surface and the screen center ray, θ represents an angle of incidence at which the screen center ray is incident on the screen surface, Fnoy represents an f-number in a direction corresponding to the height direction of the display surface, and Fnoz represents an f-number in a direction corresponding to the width direction of the display surface.