Video color projectors enable an enlarged color image to be produced from relatively small monochrome display devices which each produce respective primary color components of the composite color image, such as red, blue and green. The monochrome display devices can be cathode ray picture tubes (CRT), or illuminated thin film liquid crystal panels (LCD). The composite color image may be projected on the front of a reflective screen and viewed in reflection, or projected on the rear of a transmissive screen and viewed in transmission. Video projector systems can project images at a wide range of sizes, these systems can potentially yield larger images than conventional imaging systems such as CRTs. Video projectors modulate light beams emitted from a light source in accordance with image information and project it on an enlarged scale. In the operation of an image projection system, an image is projected from an image source to a screen, and the projected image is viewed by a viewer in front of the screen. Video projectors use a very bright light to project the image, and are capable to correct any curves, blurriness, and other inconsistencies through manual settings.

Generally, the video projector has a light reflecting mirror device driven on the basis of a bit digital video signal, and a projection lens through which light reflected by the light reflecting mirror device is projected. A projection display device basically consists of a light source lamp unit, an optical unit for optically processing a light flux emitted from the light source lamp unit so as to synthesize a color image corresponding to image information, a projection lens unit for enlarging and projecting the synthesized light flux onto a screen, a power supply unit, and a circuit substrate on which a control circuit and the like are mounted. A flat panel display device such as a liquid crystal display or a cathode ray tube of a television set is a conventional representative video display means. Recently, diversity and high quality of image information have been advanced, so that there are increased such high quality image data as typically presented in HDTV (high-definition TV) broadcasting system and SVGA (super video graphic Array) of a computer graphic system. Among those video projectors digital light processing (DLP) and LCD (liquid crystal display) are the two popular technologies currently used in projectors and video projectors.

Generally a LCD projector is constituted such that light from a light source is condensed by a focusing lens and projected on an LCD panel, a video image is produced by a video drive image being applied to the LCD panel, and the video signal is displayed on a screen through a projection lens. Liquid crystal light valve projection systems are generally either of the transmission type (active-matrix) or the reflective type. In transmission liquid crystal light valves, each liquid crystal light valve individually modulates its respective monochromatic beam over a spatial array of pixels, and the beams are then combined with a multiplexer or combining prism and projected as a single combined beam of appropriate color. In some active-matrix liquid crystal projectors, dichroic mirrors separate white light emitted by a high intensity halogen lamp into three monochromatic beams, red, blue and green. A liquid crystal panel applies an electrical video signal to the color light obtained through the color separation. The color light to which the video signal is applied is projected by a projection lens so as to be displayed on a screen as an image of which the focus is adjusted.