Patent ID: 8770760

Claim:
An image projection device, comprising: a polarization conversion optical system which converts light from a light source into a linearly polarized light having an aligned polarization direction; a display element which displays an image by modulating incident light; at least one reflection surface which reflects light from the polarization conversion optical system to direct the light to the display element; and a projection optical system which projects an image displayed on the display element onto a projection surface, wherein the display element comprises a digital micromirror device which has a rectangular image display region in which rotation axes of mirrors functioning as pixels each form an angle of 45° with respect to a long side and with respect to a short side of the image display region; when a central light ray of a light beam traveling from the light source toward a center of the image display region of the display element is incident on a surface, assuming that a plane including the central light ray incident on the surface and a normal line of the surface at a point where the central light ray is incident thereon is an incidence plane, an incidence plane of the at least one reflection surface and an incidence plane of a mirror at a center of the image display region of the display element are parallel or perpendicular to each other; and the polarization conversion optical system has: a polarization separation element which performs polarization separation to separate light from the light source into two linearly polarized lights having different polarization directions, and a direction of the polarization separation is a direction corresponding to a long-side direction of the image display region of the display element; and a polarization controller which aligns polarization directions of the two linearly polarized lights into a polarization direction that is parallel or perpendicular to the incidence plane of the at least one reflection surface and outputs resulting linearly polarized lights.