US Patent 7404643 Projector having polarization conversion element

A projector has an illumination system, an electro-optical modulator, a projection optical system, and a scanning system. The illumination system has a light source, a first lens array, a second lens array, a polarization conversion element and a superposing lens. The polarization conversion element includes a polarized light separating element and a phase plate. The polarized light separating element includes a plurality of polarized light separating prisms each of which has a polarized light separating surface and a reflection surface. The plurality of polarized light separating prisms are arranged along the one direction, and polarized light separating surfaces in the polarized light separating prisms at both ends of the polarized light separating element in one direction are constituted so as to reflect the luminous flux involving the second polarized light component in a direction approaching the illumination optical axis.