Patent ID: 7114814

Claim:
A projector comprising, a light source; a display device to modulate light emitted from the light source; a lens device to project light emitted from said light source via said display device, wherein said lens device comprises a diaphragm mechanism formed having an aperture; an ambient light illuminance detector to measure illuminance of ambient light from outside of the projector; a projected image illuminance detector to measure illuminance of an image projected on the screen; an illuminance comparator to compare an illuminance detected by said ambient light illuminance detector and an illuminance detected by said projected image illuminance detector; a diaphragm mechanism to control a size of an opening of the aperture of the diaphragm mechanism in accordance with a result of a comparison by the illuminance comparator; and an image signal controller to control an intensity of image signals input into the display device in accordance with a result of a comparison by the illuminance comparator; wherein the lens device is arranged telecentric to rays of light emitted from the display device and comprises a diaphragm mechanism having an aperture at such a position that the lens device causes principal rays of light emitted from various location on the display device to intersect with the optical axis.