Micro Projector Lighting Light Path Design

The pico-projector has become one of the most popular areas these times due toits small volume and good portability. Also, it has broad market prospect for developing.The illumination optical system is the core of the entire pico-projection display system,since it has a direct impact on the brightness, contrast, size, weight and other importantparameters. At present, the illumination optical system of pico-projector has two maindevelopment directions: First, improving light utilization efficiency. In order to improvethe brightness of the projector, the illumination system should collect and utilize thelight energy of the light source as much as possible. Second, improving the uniformityof the light spot by converting the non-uniform round spot into a uniform rectangularlight spot.In this article, a non-telecentric DLP illumination optical system based on LEDlight source has been studied and designed. Based on this design, illumination systemswith light-pipe, double fly-eye lens arrays and integrated fly-eye lens arrays wereseparately simulated using TracePro and ZEMAX. The results of simulation and testshowed that this compact design can achieve high light utilization efficiency as well asgood uniformity. Certain conclusions have been achieved as follows:1. Three typical kinds of the display technology of micro-projection werecompared. Two main integrated device Light-pipe and Fly-eye lens arrays were alsocompared based on the study of non-imaging optical theory.2. The Light-pipe illumination systems both in forward and backward placementwere modeled and simulated by using the optical software TracePro. The simulationresults showed that the forward placement system can achieve higher utilizationefficiency, while the backward placement system can achieve higher illuminationuniformity.3. The Fly-eye lens arrays illumination systems both with single ideal point sourceand single ideal surface source were modeled and simulated by using the opticalsoftware ZEMAX. Telephoto lens pairs were used to replace the converging lens in order to reduce the system size.4. An compact non-telecentric DLP illumination system based on the LED lightsource was designed with the application of the band-pass filters and telephoto lensgroup. And this system was modeled and simulated with the optical software TracePro.5. The Fly-eye lens arrays illumination system using DMD chip of4:3aspect ratiowas modeled and simulated with the optical software TracePro. Systems with DoubleFly-eye lens arrays and Integrated Fly-eye lens arrays were separately simulated. Theutilization efficiency of Double arrays illumination system with ideal surface source isabove60%. Using realistic light source instead of ideal source, the system withIntegrated Fly-eye lens-arrays can achieve29%total system efficiency and79%illumination uniformity.6. The Fly-eye lens arrays illumination system using DMD chip of16:9aspectratio was modeled and simulated with TracePro. When using the ideal point source, theillumination system can achieve more than88%utilization efficiency and about83%illumination uniformity. With the realistic light source, the total system efficiency isbetween25%to29%. The simulation results showed the Japanese illuminationuniformity is about80%~91%, and the ANSI uniformity is between-29%to+18%.7. The illumination system using DMD chip of16:9aspect ratio was processed andtested. The experiment result showed that the light utilization efficiency of this systemis about62.17%, Japanese uniformity is80%~83%, ANSI uniformity is between-15%and+16%.