Patent ID: 6951394

Claim:
A digital light processing projection system comprising: an illuminating device having a light source outputting a light beam; an optical-path-switching element having a plurality of micro-mirrors for receiving the light beam and reflecting the light beam under a first state and a second state, respectively; a projection device having a projection lens for receiving the light beam reflected from the optical-path-switching element under the first state; and a prism set arranged between the illuminating device, the optical-path-switching element, and the projection device, having a plurality of prisms in which an air gap exists between any two adjacent prisms; wherein, the light beam output from the illuminating device directly passes through the prisms and air gaps of the prism set before being received by the optical-path-switching element; the light beam reflected from the optical-path-switching element is totally reflected at an interface between one of the prisms and one of the air gaps before being received by the projection lens under the first state; and the light beam reflected from the optical-path-switching element is totally reflected back and forth within one of the prisms being adjacent to the optical-path-switching element under the second state.