Patent ID: 7178921

Claim:
An image projection apparatus comprising a projection optical system for projecting an image displayed on a display surface onto a screen, the projection optical system including at least four curved reflecting surfaces, wherein the projection optical system does not form an intermediate real image of the display surface between the display surface and the screen, and wherein, assuming that a ray of light that travels from a center of the display surface through a center of an aperture stop to a center of the screen surface is called a screen center ray, the following conditions are 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.