Low-voltage, large-range MEMS optical scanners and their applications .

摘要

Advanced imaging techniques including optical coherence tomography/microscopy (OCT/OCM), nonlinear optical (NLO) imaging and confocal microscopy demonstrate powerful resolution and optical-sectioning capabilities; therefore can potentially replace conventional biopsy diagnosis procedures for early cancer detections. To realize in vivo, noninvasive clinical endoscopic imaging, miniature endoscopes integrated with small, versatile and large range optical scanners including 1-D, 2-D transverse and full-circumferential scan micromirrors, as well as large-axial-scan microlens scanners must be developed. The objective of this research is to develop miniature optical scanners by Microelectromechacnial Systems (MEMS) technology and the MEMS-based in vivo biomedical imaging endoscopes.;Several novel actuators based on electrothermal bimorph actuation are developed in this work that solve problems in previous generations including large mirror center shift, large initial tilting and elevation, complicated mirror control, and low fill factor. The lateral-shift-free (LSF) large-vertical-displacement (LVD) actuator realizes versatile optical scanners including tip-tilt-piston (TTP) mirrors, lens scanners and large-aperture mirrors with large axial scan. The TTP mirror demonstrates 2-D tip-tilt scan >60° and piston scan >0.6 mm at 5 Vdc with an improved fill-factor of 25%. Over 0.9 mm large axial scan mirrors and lens scanners with small tilting below 0.4° are also presented. The dual-folded-bimorph (DFB) actuator realizes over 90° mechanical rotation up to 60 Hz with a stationary center rotation axis and a flat, un-elevated initial mirror position, full-circumferential scan at real time imaging speed is achieved by the DFB-based dual-reflective micromirror. A novel self-aligned deep-trench process is also developed to fabricate the dual-reflective miromirror and light-weight large-aperture mirrors.;MEMS imaging endoscopes for both OCT and NLO are developed; 3-D in vivo imaging results are successfully demonstrated. Other potential applications are also investigated. A 4x4 TTP mirror array with sub-aperture size of 0.9 mm and a fill-factor of 65% is presented for optical phased array application. MEMS mirror with large aperture up to 10 mm, tip-tilt scan of ∼10° and resonance in the order of 100 Hz are demonstrated for free-space optical communications. The prototypes of miniature Fourier transform spectrometer (FTS) are demonstrated, the large-axial-scan MEMS mirror combined with a novel mirror-tilt-insensitive FTS system has achieved a high spectral resolution of 8.1 cm-1. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)