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A resonantly excited 2D-micro-scanning-mirror with large deflection

: Schenk, H.; Dürr, P.; Kunze, D.; Lakner, H.; Kück, H.


Sensors and Actuators. A 89 (2001), Nr.1-2, S.104-111
ISSN: 0924-4247
Fraunhofer IMS, Außenstelle Dresden ( IPMS) ()
2D-micro-scanner; microscanner; electrostatic driving; filled trench; shock resistivity

We present a novel resonantly excited 2D-micro-scanning-mirror which makes use of an electrostatic driving principle. To achieve large deflection angles, the driving electrodes are located in the chip plane. With that, small electrode gaps can be used without restricting the deflection angle geometrically. The mirror plate, with an area up to 1.5 mm × 1.5 mm, is suspended by a gimbal mounting and can, therefore, be deflected along two axes. The base material for the fabrication of the device is a SOI-wafer with a top layer thickness of 30 m. A special isolation technique which is based on open and filled isolation trenches is suitable to seperate the electrical potentials on the fixed and movable parts. In particular, the filled trenches allow to excite the two oscillations independently.
The influence of the surrounding gas on the coupling of the oscillations is examined. No significant influence is observed. The investigations of the mechanical performance show that the devices have a shock resistivity of about 3.4 × 103 × g. Results of long run tests with a duration of 7 x 109 periods at a torsional angel of ± 10° show that the change of the eigenfrequency is smaller than 0.01 %.
The performance of the novel 2D-micro-scanning-mirror is demonstrated by the generation of various Lissajous patterns by the reflected laser beam. Frequency ratios of 1 : 1 up to 13 : 1 are obtained with the presented devices.