Abstract: A compact illumination system using a light source such as an array of light emitting diodes (LEDs) or laser diodes (LDs) having a long life span, and a projection display device employing the illumination system are provided. The illumination system includes a light source; a collimating lens array for making light emitted form the light source be parallel; an optical path conversion unit for reflecting the light incident in parallel from the collimating lens array back toward the light source to initially converge the light; and a secondary focusing lens disposed at a side where the light source is positioned, for converging the light, that has been reflected and converged through the optical path conversion unit, on a predetermined position. The illumination system reflected the light emitted from the light source back toward the light source through the optical path conversion unit so that the volumes of the illumination system can be greatly reduced to be compact.

Abstract: A compact illumination system using a light source such as an array of light emitting diodes (LEDs) or laser diodes (LDs) having a long life span, and a projection display device employing the illumination system are provided. The illumination system includes a light source; a collimating lens array for making light emitted form the light source be parallel; an optical path conversion unit for reflecting the light incident in parallel from the collimating lens array back toward the light source to initially converge the light; and a secondary focusing lens disposed at a side where the light source is positioned, for converging the light, that has been reflected and converged through the optical path conversion unit, on a predetermined position. The illumination system reflected the light emitted from the light source back toward the light source through the optical path conversion unit so that the volumes of the illumination system can be greatly reduced to be compact.