OLED-based pico-projection system

Two pico-projection systems, a monochrome green and a full-color system, based on high-efficiency OLED microdisplays (VGA; pixel size, 12 mu m) are presented. Both optical systems are described by a numerical aperture of about 0.3, a magnification of 15x, and a working distance of 300-360 mm. The frequency limit of both systems is 42 cycles/mm at an image contrast of about 60%. The monochrome projection system with a volume smaller than 10 cm(3) consists of one green OLED and a projection lens with five elements. The measured luminance in the image plane is about 0.061 lm. The image has a diagonal of 150 mm with a working distance of about 300 mm and has a considerable image contrast of 396: 1. The second system combines three high-brightness OLEDs, red, green, and blue colored, together with a projection lens and an image-combining element, and an X-Cube to achieve full-color projection. The estimated luminance value for the three-panel projection unit with an OLED luminance of 10,000 cd/m(2) for each display will be about Phi(calculated) = 0.147 lm. In this paper, the system concepts, the optical designs, and the realized prototypes of the monochrome and full-color projection system are presented.