Abstract: An image display device is arranged to irradiate a ray of light from a light source into liquid crystal display devices, form an optical image corresponding with a video signal, and expansively project the optical image. The image display device includes a reflection mirror for reflecting the ray of light irradiated onto the liquid crystal display devices, an optical sensor being located on the reflection mirror and for detecting a light intensity, a drive circuit that causes the liquid crystal display devices to be driven, and a control unit that controls the drive circuit based on the light intensity detected by the optical sensor. In operation, the image display device provides a capability of adjusting a variable reference voltage of a common electrode brought about by variation with time ascribable to the liquid crystal display devices without preventing display of an input video signal.