Patent ID: 8215778

Claim:
A projector apparatus, comprising: a display device having an image display plane for displaying an image, a prism optical system of positive refracting power adapted to enlarge and project said image displayed on said image display plane, and a stop located on a projection side with respect to said prism optical system and adapted to restrict a thickness of a light beam to be projected, wherein: said prism optical system comprises an internal reflecting surface concave on said image display plane side, a combined optical surface adapted to transmit a normal light beam out of said image display plane and reflect a normal light beam reflected off at said internal reflecting surface, and an exit surface through which a normal light beam entering said prism optical system leaves, wherein: the normal light leaving said image display plane takes such a path that it enters said prism optical system through said combined optical surface, is then reflected off at said internal reflecting surface and then at said combined optical system, and then leaves said exit surface, arriving at a projection image through said stop, with satisfaction of the following condition (1): 0.3 <fB/fv< 1.5 where fB is a length, as calculated on an air basis, from said combined optical surface of said prism optical system to said image display plane along a center ray where said center ray is defined as a normal ray that leaves a center of said image display plane and passes through a center of said stop, and fv is a value represented by fv=hH /(tan ω H ) where, given a horizontal direction is a direction vertical to a plane including a center ray before and after reflection at said internal reflecting surface, ωH is a maximum angle of projection with respect to a center ray on a projection side in said horizontal direction, and hH is a distance from the center of said image display plane to the farthest display position in said horizontal direction.