Patent ID: 8087785

Claim:
A projection display apparatus, comprising: at least one light source, capable of emitting an illumination beam; a polarization beam splitter, disposed in the optical path of the illumination beam and transmitting the illumination beam emitted from the light source; a polarization changing device, disposed in the optical path of the illumination beam for changing the polarization direction of the illumination beam transmitted from the polarization beam splitter and reflecting the illumination beam back to the polarization beam splitter; an optical uniformizing element, disposed in the optical path of the illumination beam and between the polarization beam splitter and the polarization changing device for uniformizing the illumination beam, wherein the illumination beam sequentially passes through the polarization beam splitter and the optical uniformizing element and is reflected by the polarization changing device, and the illumination beam reflected by the polarization changing device again passes through the optical uniformizing element to reach the polarization beam splitter, such that the optical uniformizing element uniformizes the illumination beam twice; a light valve module, disposed in the optical path of the illumination beam, and converting the illumination beam reflected by the polarization changing device via the polarization beam splitter into an image beam transmitting to the polarization beam splitter; and a projection lens, disposed in the optical path of the image beam and projecting the image beam from the polarization beam splitter into a frame.