Projection display apparatus and method

Not only abnormality of a light output to an exterior but also overturning, vibration, disassembly, deformation, or breakage of a display apparatus including a case and a screen are reliably and promptly detected. A projection display apparatus includes a light source for generating illumination light, which is provided in a case having a light-shielding function, a movable aperture for adjusting the amount of illumination light from the light source, a light valve for adjusting the amount of light based on an image signal to generate image light for forming an image from the illumination light, a projection optical system for enlarging the image light from the light valve, and a transmission-type screen for displaying the image, which is provided to a window of the case. The projection display apparatus further includes first to ninth detectors ( to ) for detecting the abnormality of the light output of the light source to the exterior and the abnormality of the case or the transmission-type screen, a warning and alarm unit for notifying the abnormality by sound or light, and a control unit for controlling an internal operation when the abnormality is detected.