US Patent 7401925 Image projection system

An image projector system includes an LED controller and first and second LEDs, a dichroic mirror. The LED controller controls the first and the second LED to emit first and second color lights, respectively. The second color light is of high luminance and is decomposed by a dichroic mirror into third and forth color lights having luminance close to that of the first color light. Each color light is guided through a light valves to adjust the spectral transmittance of the color light. A light-combining device, such as an x-cube, receives and combines the first color light, the third color light, and the forth color light, to form light images, and transmits the images to a display through a projector lens.