Patent ID: 8045273

Claim:
A projection apparatus, comprising: a first, a second and a third light sources for respectively emitting a first, a second and a third light beams having respective colors and optical paths; a first reflective element configured to reflect the first light beam; a first dichroic mirror configured to reflect the second light beam and to transmit the first light beam transmitted from the first reflective element; a second dichroic mirror configured to reflect the first and the second light beams transmitted from the first dichroic mirror and to transmit the third light beam, so that the first, the second and the third light beams are guided to an identical optical path to form a combined light beam, wherein the first reflective element, the first dichroic mirror and the second dichroic mirror are arranged into a first row, in parallel and spaced at intervals from each other; a light-homogenizing element for receiving and then homogenizing the combined light beam; a second reflective element for reflecting the combined light beam transmitted from the second dichroic mirror, wherein the second reflective element and the light-homogenizing element are arranged into a second row spaced apart from the first row, and the combined light beam reflected by the second reflective element travels in a direction opposite to a propagation direction of the first light beam reflected by the first reflective element and the second light beam reflected by the first dichroic mirror; a light valve for receiving and then modulating the combined light beam to form an image beam; and a projection lens for receiving and then projecting the image beam, wherein the first reflective element and the first and the second dichroic mirrors are formed in a prism made of borosilicate glass and the prism has a light-receiving surface, the first, the second and the third light beams are incident on the light-receiving surface, and a first angle is formed between the first reflective element and the light-receiving surface, a second angle is formed between the first dichroic mirror and the light-receiving surface, a third angle is formed between the second dichroic mirror and the light-receiving surface, and the first the second and the third angles are each in the range of not less then than 28 degrees and smaller than 45 degrees.