Abstract of Disclosure The present invention mainly includes an illumination system and an imaging system, wherein the illumination system generates an incident light beam, and, by means of reflection with a reflecting lens, projects it from above in front of the field lens, into the first surface of the field lens fronting the projection lens set, then through the field lens, and onto the light valve of the imaging system, wherein the geometric center of the light valve is located at the underside of the optical axis of the second surface adjacent to the corresponding side of the first surface of the field lens, allowing the geometric center of the transmissive area created by the projection of the light beam into the field lens to be much closer to the optical axis of the field lens than the geometric center of the light valve is, thus ensuring that the transmissive area is contained within the optimized area on the field lens, while reducing the amount of distortion generated in the light spot by the light beam coming in through the field lens, wherein the said light beam is then further reflected, by means of reflection with the array of micro-mirrors poised on the light valve to differentiate the angles of reflection at ON-state or OFF-state, through the field lens, then into or away from the projection lens set, and is selectively projected onto the screen, so as to improve illumination efficiency, while lowering the cost and reducing the volume.