Achromatic design in the illumination system for a mini projector with LED light source.

We provide a novel achromatic design in the illumination system for a mini projector with an LED light source. The lateral color aberration at the corners of the DMD active area can be reduced to 0.48 μm by our compact ATIR prism. The total prism size is 4091 mm(3). The spot sizes at the corner and the edge are also controlled under 198 μm. Moreover, we use a light pipe for color uniformity at the center of the DMD active area. Under the two components for color uniformity, the Δu' v' is well controlled under 0.016 by a 20 mm length of light pipe. The illuminance uniformity at the active area of the DMD chip is higher than 92.8%. The optical efficiency of the light pipe is 94.1%.