Two-Axis Electrostatic Gimbaled Mirror Scanner With Self-Aligned Tilted Stationary Combs

Abstract

We demonstrate an electrostatic two-axis gimbaled mirror scanner with tilted stationary combs (TSCs). We fabricate the scanner using self-aligned micro-assembly to realize angular offsets between stationary and movable comb electrodes. The TSCs enabled quasi-static operation by generating sufficient scanning angles for the slow axis, whereas in-plane comb electrodes provided torsional oscillation at resonance for the fast axis. The proposed self-alignment method can enhance side stability by minimizing lateral shifts of the electrodes during the micro-assembly. We experimentally verify the fabricated mirror scanner in terms of scanning frequencies and scanning angles for finger-vein authentication. The resonant frequencies and optical-scan angles were 263 Hz and 8.5°, respectively, for the slow axis, and 1959 Hz and 24.6°, respectively, for the fast axis. We obtain high-resolution finger-vein images in transmission mode using the mirror scanner and a near infrared laser, which will possibly improve live finger identification by employing the laser Doppler technique.