Abstract: A light source such as a metal halide lamp is effectively cooled in an optical apparatus such as a liquid crystal projector. In an optical apparatus which includes a concave mirror 11, a light emitting section 12 arranged in a concave portion of the concave mirror along the optical axis and a cooling structure for cooling a periphery of the light emitting section, the cooling structure is provided with a means for generating an air flow 4, the direction of which is approximately perpendicular to the optical axis of the concave mirror 11, and a means for generating an air flow 5 circulating into the concave portion of the concave mirror 11.

Abstract: A projector comprising liquid crystal display panels and a projection lens for projecting the modulated light to a screen. A back surface reflection mirror including a transparent plastic sheet and a reflecting film is arranged between the projection lens and the screen. The mirror is thin and light and may have optical anisotropy. In order to eliminate an uneven pattern appearing in the screen caused by optical isotropy of the mirror and the difference between the light distribution characteristics in the screen for P- and S-polarized light, the projection lens and the back surface reflection mirror are arranged in such a relationship that a wave normal vector of an arbitrary component of the light projected by the projection lens and made incident to the back surface reflection mirror is not parallel to the optical axis of the plastic sheet.