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Proceedings Paper

A novel 24-kHz resonant scanner for high-resolution laser display
Author(s): Steffen Kurth; Christian Kaufmann; Ramon Hahn; Jan Mehner; Wolfram Doetzel; Thomas Gessner
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Paper Abstract

This contribution deals with design, fabrication and test of a micromachined resonant scanner usable for horizontal deflection of the laser beam in a projection display. The electrostatically driven plate is separated from the mirror in order to reduce air damping and electrostatic non linearity. The device consists of a circularly shaped mirror which is suspended by torsion beams in the center of an elastically suspended driving plate. A resonator with two rotational degrees of freedom is arranged in this way. The rotation axes of mirror and driving plate are the same. A suitable design of the properties of the two degrees of freedom resonator leads to a significant amplification of the oscillation of the mirror compared to the oscillation of the driving plate. The first resonant mode is a rotation of both plates with nearly the same magnitude at a frequency of approx. 5 kHz. The second mode with paraphase deflection at 24 kHz shows a deflection amplification by a ratio of 53 and is used for scanning operation. A supporting part made of glass carries two electrodes in the region of the driving plate and has a micro sandblasted hole beneath the mirror. Bulk micromachining KOH wet etching of the electrode gap size on the back side of the driving plate, reactive ion etching for contour shaping of the mirror, of the driving plate and of the torsion beams and anodic bonding have been used for fabrication of the mechanical structure. The mirror is evaporated by an aluminum layer. Applying a voltage of 380V results in a mechanical deflection of ± 5.5 degrees at 24 kHz at atmosphere pressure. The device shows very small dynamic warp (<100nm) of the mirror plate even though the relatively large size of 2.2 mm diameter because of the thickness of 280 µm. The measured mechanical Q-factor is 5100.

Paper Details

Date Published: 22 January 2005
PDF: 11 pages
Proc. SPIE 5721, MOEMS Display and Imaging Systems III, (22 January 2005); doi: 10.1117/12.590847
Show Author Affiliations
Steffen Kurth, Fraunhofer Institute for Reliability and Microintegration (Germany)
Christian Kaufmann, Chemnitz Univ. of Technology (Germany)
Ramon Hahn, Chemnitz Univ. of Technology (Germany)
Jan Mehner, Fraunhofer Institute for Reliability and Microintegration (Germany)
Wolfram Doetzel, Chemnitz Univ. of Technology (Germany)
Thomas Gessner, Fraunhofer Institute for Reliability and Microintegration (Germany)
Chemnitz Univ. of Technology (Germany)

Published in SPIE Proceedings Vol. 5721:
MOEMS Display and Imaging Systems III
Hakan Urey; David L. Dickensheets, Editor(s)

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