Design of miniaturized optoelectronic systems using resonant microscanning mirrors for projection of full-color images

Abstract

Projection systems comprising micromechanical scanning mirrors are a promising approach for information display of any kind. If combined with advanced laser diodes as light sources, ultra-compact projection heads can be realized, as it will be shown in this contribution. Besides the laser, key component of the system is a special MEMS device, a twodimensional resonant micro scanning mirror. The laser beam formed by collimator optics is directed onto the micro scanning mirror. Then, the reflected beam describes a highly complicated Lissajous figure on the projection screen with flare angles of up to 20 degrees. By driving the mirror and electrically modulating the intensity of the laser beam in a synchronous manner, projection of images can be achieved. Advanced techniques that guarantee improved image quality and allow compensation of artifacts because of relative movement between projection head, screen, and human observer will be described. Based on these principles, several optoelectronic systems have been designed. A monochrome projection head that incorporates the laser diode, optics and the micro mirror could be reduced to a volume of 15mm x 7 mm x 5mm. A slightly larger head is attached to a laser unit with red, green, and blue lasers via glass optical fiber for projection of full color images and video streams. All systems have VGA (640 x 480 pixels) resolution. They operate with 8 bit color depth per pixel and 50 frames per second. These key features in combination with the miniaturized size allow their use for a broad range of applications.