||This paper presents a high-efficiency projector optical design with asymmetric condenser includes an illumination system and an imaging system. In the illumination design use the asymmetric condenser to project LED light source into the lens array. Because of the numerical aperture of lens array in horizontal is different numerical aperture of lens array in vertical direction and if we want to improve the light use efficiency, the numerical aperture of lens array and the numerical aperture of asymmetric condenser must be the same. In DMD illumination area must consider the overfill of the lighting system design, then the output of lens array will be projected onto the DMD illumination area by relay lens. According to, there are three different types of DMD output, respectively On-state, Flat-state, Off-state, we need to use the TIR Prism to control the DMD output and make the light will be projected into the projection lens when DMD is On-state.|
In the imaging system optical design, the diagonal of the screen is 60 inches, the diagonal of DMD is 0.4576 inches. We can calculate the magnification is -131.12 times and the projection distance is 2.1 meters. And the effective focal length, f/#, total track of the projection lens is respectively 16.0 mm, 1.8, 2200 mm. Then, we assess resolution of the projection lens at all fields, MTF (66 lp/mm) is greater than 67.3%, lateral color is less than 2.13 m, optical distortion is less than 1.45% and the relative illumination is greater than 90.98%.
Finally, dimensions of the entire projection system are 102.9 mm×99.2 mm×36.0 mm. Assume transmittance of all the elements is 100%, the overall efficiency of red LED projected on the screen is 56.25%, green LED is 49.57%, blue LED is 46.66%. Then, we simulate the uniformity of illuminance on the screen, the average deviation of red LED is 1.78%, green LED is 2.46%, blue LED is 1.97%. And we compare the color gamut with NTSC standard, color saturation of RGB LED is 95.25%.
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