Patent ID: 7931376

Claim:
A beam combining device adapted to a projector, the projector comprising a first color light source, a second color light source and a third color light source for respectively emitting a first color beam, a second color beam and a third color beam in a first polarization state, the beam combining device comprising: a polarization state converting module arranged in the propagating paths of the first color beam, second color beam and third color beam for converting the first color beam, second color beam and third color beam in the first polarization state into a second polarization state, wherein the second beam and the third color beam are permitted to be transmitted through the polarization state converting module but the first color beam is permitted to be reflected by the polarization state converting module; a color separation unit disposed at a side of the polarization state converting module and arranged in the propagating paths of the second color beam and the third color beam, wherein the second color beam is permitted to be transmitted through the color separation unit but the third color beam is permitted to be reflected by the color separation unit, so that the second color beam and the third color beam are directed to the polarization state converting module; and a polarization beam splitter disposed at another side of the polarization state converting module and arranged in the propagating paths of the first color beam, the second color beam and the third color beam, wherein the first color beam in the first polarization state is permitted to be transmitted through the polarization beam splitter and directed to the polarization state converting module, and the first color beam, the second color beam and the third color beam that are converted into the second polarization state by the polarization state converting module are reflected by the polarization beam splitter.