Patent ID: 8613517

Claim:
An illumination system for use in a projection device, the illumination system comprising: a main optical axis; a light source providing a light beam advancing along the main optical axis; a wheel rotating according to a control signal; an optical device comprising a first lens, a second lens a third lens and a dichroic layer, the first lens, the second lens and the third lens are sequentially disposed between the light source and the wheel along the main optical axis so as to converge the light beam to a focused position on the wheel; a first wavelength transformer disposed on the wheel for receiving and transforming the light beam into a first wavelength light; and a first angle selective film disposed on the first wavelength transformer, wherein the first wavelength transformer is located between the light source and the first angle selective film, and the first angle selective film angle-selectively filters and reflects the first wavelength light; wherein the dichroic layer allowing the light beam generated from the light source to pass therethrough and reflecting the first wavelength light, and the dichroic layer is formed into a curved surface having a curvature radius, the main optical axis that passes through a portion of the optical device and the focus position has an imaging position, and a distance between the imaging position and the dichroic layer is substantially equal to the curvature radius of the dichroic layer.