Optical design for the DLP pocket projector using LED light source

The DLP [1] pocket projector can be classified into two parts according to design characteristic. One of them is illumination system. It composes of Red, Green and Blue LEDs. Each of them has a collimator to make lights illuminate dichroic filter collimated. By dichroic filters it combines three wavelengths lights together. The last part is the micro-lens array, condenser and TIR prism is used to illuminate DMD uniformly and reduce the size of illumination system. The other is imaging system. According to the standard of DMD; the angle of view, effective focal length, the relationship of imaging and object and imaging quality of the lens can be defined. By using optical simulation software, Code V and ZEMAX, the lens conform to the standards was well designed. Finally the tolerance of production was analysed. In this design, the average light efficiency of three wavelengths LED on DMD is 51.13%, and the average uniformity on DMD is 95.17%. About the screen, the average light efficiency is 44%, and the average uniformity is 87.3%.