| 摘要 |
The invention relates to an illumination system (21) for supplying a polarized radiation beam. The illumination system (21) successively comprises a radiation source unit (3) for supplying at least one radiation beam and an optical system for concentrating the radiation to a beam, a polarizing system (11) for splitting a radiation beam (bI, bII) generated by the radiation source unit (3) into linearly polarized sub-beams, and at least one polarization-rotating element (35). The polarizing system comprises at least one optically transparent plate (11) having a refractive index n0 and a first face and a second face. At least one of these faces is provided with an optically thin layer having a refractive index n1 which is larger than n0. The light path of the sub-beams whose directions of polarizations are not to be converted incorporates a reflector (41, 43) for reflecting the sub-beams into the same direction of propagation as that of the other sub-beams. The chief ray of these beams and the normal on the plate (11) enclose an angle which is substantially equal to the Brewster angle which holds for the interface between the optically thin layer and a medium surrounding the polarizing element (11). The radiation source unit (3) comprises two radiation sources (23, 25), and such a polarizing system is associated with each radiation source (23, 25). The invention also relates to an image projection device (45) comprising such an illumination system (21). |
