Patent ID: 8425052

Claim:
An illumination system for a projection device, the illumination system comprising: a light source; a color wheel; and a drive-unit for driving the light source, the color wheel comprising a plurality of color filter segments determining a color of the light emitted by the illumination system, the color wheel being configured for sequentially positioning color filter segments from the plurality of color filter segments in an optical path between the light source and a light output window of the illumination system by rotating the color wheel, a spoke of the color wheel being a boundary between two adjacent color segments, the light source comprising a first light-emitting unit and a second light-emitting unit, each emitting light towards the light output window of the illumination system, the first light-emitting unit, the second light-emitting unit and the spoke being configured for preventing the spoke when transiting the optical path between the light source and the light output window to simultaneously transit a first optical path between the first light-emitting unit and the light output window and a second optical path between the second light-emitting unit and the light output window, wherein the color wheel is disposed in the first optical path and in the second optical path, the drive-unit being configured for switching off the first light-emitting unit during a time interval when the spoke transits the first optical path.