Abstract
An integrated position sensor for a dual-axis electromagnetic tilting mirror is presented. This tilting mirror is composed of a silicon based mirror directly assembled on a silicon membrane supported by flexible beams. The position sensors are constituted by 4 Wheatstone bridges of piezoresistors which are fabricated by doping locally the flexible beams. A permanent magnet is attached to the membrane and the scanner is mounted above planar coils deposited on a ceramic substrate to achieve electromagnetic actuation. The performances of the piezoresistive sensors are evaluated by measuring the output signal of the piezoresistors as a function of the tilt of the mirror and the temperature. White light interferometry was performed for all measurement to measure the exact tilt angle. The minimum detectable angle with such sensors was 30μrad (around 13bits) in the range of the minimum resolution of the interferometer. The tilt reproducibility was 0.0186%, obtained by measuring the tilt after repeated actuations with a coil current of 50mA during 30 min and the stability over time was 0.05% in 1h without actuation. The maximum measured tilt angle was 6° (mechanical) limited by nonlinearity of the MEMS system.
Highlights
In this work, the system was improved to achieve higher scanning speed using a position feedback control, achieved with doped silicon piezoresistors configure as 4 Wheatstone bridges around the MEMS deformable part
An integrated position sensor for a dual-axis electromagnetic tilting mirror is presented. This tilting mirror is composed of a silicon based mirror directly assembled on a silicon membrane supported by flexible beams
The position sensors are constituted by 4 Wheatstone bridges of piezoresistors which are fabricated by doping locally the flexible beams
Summary
The system was improved to achieve higher scanning speed using a position feedback control, achieved with doped silicon piezoresistors configure as 4 Wheatstone bridges around the MEMS deformable part. To investigate the sensor performances, the signal output was measured as a function of tilt angle as well as noise level
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