An integrated optoelectronic position sensor for MEMS scanning mirrors

Piezoresistive strain gauges are usually used to measure position and displacement for MEMS scanning mirrors with torsional silicon bars, but this method cannot be applied to gimbal-less 2-axis electrothermal bimorph micromirrors since they do not have torsional silicon bars. This paper reports an integrated optoelectronic position sensor (iOE-PS) that can measure the linear displacement and tilting angle of 2-axis electrothermally-actuated MEMS scanning mirrors. The iOE-PS integrates a laser diode and its driving circuits, a quadrant photo-detector (QPD) and its readout circuits, and a band-gap reference all on a single chip, and it has been fabricated in a standard 0.5μm CMOS process. Experimental results show that this optical sensor has a linear response when the distance between the MEMS mirror and the integrated sensor is from 4.0 mm to 4.9 mm and the tilting angle of the mirror plate scans from −1.5° to +1.5°.