US Patent 7963657 Projection display device

An imager is shifted with respect to an optical axis of a refractive optical system. Thereby, a throw distance of a projector is shortened. A wavelength-selective half wavelength plate for rotating a polarization direction of green light beams is disposed between a dichroic prism and the refractive optical system in such a manner that the polarization direction of the green light beams is in parallel to the shifting direction. Thereby, the green light beams are incident onto the refractive optical system as P-polarized beams, whereby a transmittance of the green light beams in the refractive optical system is increased, while suppressing lowering of the light amount of the green light beams, and color non-uniformity resulting from lowering of the light amount of the green light beams.