US Patent 7201498 Lighting apparatus

In recent years, much attention has been paid to a projection type display apparatus using a plurality of light sources, as projection type video equipment capable of large screen display. However, in an optical system using a plurality of light sources, devices are designed so that uniform lighting can be provided assuming only the use of all the light sources. Thus, the uniformity of brightness within a display screen may be degraded if not all of the plurality of light sources are used.