Thermally actuated microprojector for optical display applications
A dual axis, raster-scanning laser display based on a monolithic micromachined scanning mirror is presented. The scanner consists of a micromirror located at the end of a thermally actuated bimorph beam. The novelty of the device is that an "L"-shape cantilever, which is simultaneously excited at non-resonance (frame scanning) and at resonance (raster scanning), gives the two orthogonal angular motions. The high sensitivity of the thermal bimorph actuator allows a low frequency (nonresonant) movement of the scanner in one direction. The second orthogonal scanning direction is a resonance torsion motion. The micro-device has a raster scanning frequency varying from 1000 Hz to 5000 Hz depending on the geometry, and if combined with a 50 Hz frame signal, has a definition of up to 100 lines. Mechanical scan amplitudes over 15 degrees in two orthogonal directions have been achieved. The typical power consumption is 5 mW. In this paper, the resolution of the scanner is discussed which is limited by the diffraction from the 500 mum to 300 mum mirror and its flatness. The performance of the new device is demonstrated by projecting a two- dimensional image using a modulated laser diode and the two orthogonal mirror deflections.
Record created on 2005-09-13, modified on 2016-08-08