Patent ID: 8033669

Claim:
A projection display apparatus, comprising: a case which has a light-shielding function; a modulation light source provided in the case, for generating illumination light; a movable aperture provided in the case, for adjusting a light beam amount of the illumination light from the modulation light source; a light valve provided in the case, for adjusting a light amount based on an image signal to generate image light for forming an image from the illumination light; a projection optical system provided in the case, for enlarging a light beam of the image light from the light valve; a transmission-type screen provided in a window disposed to the case, for displaying the image based on the image light which is enlarged and projected by the projection optical system; a detecting means for detecting an abnormality with respect to one of the quantity of a light output from the light source to an exterior, and an abnormality with respect to the case and/or the transmission-type screen, that would permit light to escape from the case; a warning and alarm means for generating at least one of sound and light that indicates the abnormalities; and a control means for controlling at least one of the light valve, the movable aperture, the modulation light source, and the warning and alarm means when the abnormalities are detected, wherein the detecting means detects the abnormality when an amount of off light of the light valve is not within a predetermined range at a time when the light valve has shut off light to the projection optical system.