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MOEMS translatory actuator characterisation, position encoding and closed-loop control

: Lenzhofer, M.; Tortschanoff, A.; Frank, A.; Sandner, T.; Schenk, H.; Kraft, M.; Kenda, A.


Microsystem Technologies 16 (2010), No.5, pp.901-907
ISSN: 0946-7076
Journal Article
Fraunhofer IPMS ()

Recent developments in optical micro-electro-mechanical systems (MEMS) have produced rapidly oscillating translatory micro-mirrors with out-of-plane mirror displacements exceeding ±100 m, which have a great potential for various applications requiring high-speed optical path difference modulation. A key factor affecting their practical applicability is a reliable operation control of the MEMS element. Presented here is a pro-active solution combining a laser reference interferometer with a novel position detection scheme and a dedicated control circuitry. By demodulating and processing the laser reference signal, the zero-crossing point of the moving MEMS device can be detected with an accuracy of one interference fringe only. This allows generating a highly accurate mirror control signal in real-time, enabling the implementation of a unique closed-loop control of such MEMS devices and thus ensuring optimally stable MEMS operation and maximal mechanical amplitudes even under varying environmental conditions. The presented solution so provides a vital step forward in the real-world deployment of optical systems using translatory micro-devices.