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Bi-resonant scanning mirror with piezo-resistive position sensor for WVGA laser projection systems

: Drabe, C.; Kallweit, D.; Dreyhaupt, A.; Grahmann, J.; Schenk, H.; Davis, W.


Schenk, H. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
MOEMS and miniaturized systems XI : 24 - 25 January 2012, San Francisco, California
Bellingham, WA: SPIE, 2012 (Proceedings of SPIE 8252)
ISBN: 978-0-8194-8895-4
Paper 825209
MOEMS and Miniaturized Systems Conference <11, 2012, San Francisco/Calif.>
Photonics West Conference <2012, San Francisco/Calif.>
Fraunhofer IPMS ()

Fraunhofer IPMS developed a new type of small-sized scanning mirror for Laser projection systems in mobile applications. The device consists of a single crystal mirror plate of 1 mm diameter in a gimbal mounting enabling a bi-resonant oscillation of both axes at a resonance frequency of about 100 Hz and 27 kHz respectively. The mechanical scan angle (MSA) achieved is ± 7° for the slow and ± 12° for the fast axis. The mirror angle position and phase can be read out via two piezo-resistive sensors located at the torsion axes. In order to allow for a minimum device size of the resonantly driven slow axis the sensor of the inner fast axis was connected by a new kind of thin silicon conductors. Those are created by means of an etch stop in TMAH etch and kept as thin as possible in order to reduce their contribution to the mechanical stiffness of the mirror-supporting structures. This new system enables to lead six (or even more) independent electrical potentials onto the mov ing parts of the device, whereas the mechanical properties are mainly determined by only 2 torsion axes. The devices were subsequently characterized and tested. Technology details, simulation results, pictures of the device and the new conductor structures as well as measurement results are presented.