Patent ID: 8562138

Claim:
A projection display device for projecting an image on an imager, comprising: a light guiding optical system configured to guide illumination light to the imager; a projecting optical system configured to project modulated light modulated by the imager, wherein the projecting optical system includes a refracting optical system and a reflecting optical system configured to reflect the modulated light transmitted through the refracting optical system; and a polarization converting part of a polarization converting unit configured to convert a polarization direction of the modulated light, wherein the polarization converting part has a plurality of areas that together are less than a total number of areas of the polarization converting unit, each area has different directions of anisotropic axes, wherein a boundary of the areas is perpendicular to an optical axis of the refracting optical system, wherein the reflecting optical system is displaced from a center of the optical axis of the refracting optical system, and the polarization converting part is displaced from the center of the optical axis of the refracting optical system in a direction opposite to a direction to which the reflecting optical system is displaced from the center of the optical axis of the refracting optical system, and wherein the modulated light is irradiated on only the polarization converting part that corresponds to a subset of areas of the polarization converting unit, in which the subset of areas that corresponds to the polarization converting part is less than the total number of areas of the polarization converting unit, and wherein the polarization converting part converts the polarization direction of the modulated light incident thereon.