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.
