This paper discusses the fracture strength study of torsion springs in MEMS microscanners, which are fabricated in silicon-on-insulator (SOI) with deep-reactive-ion-etch (DRIE) process. High performance microscanners are of particular interest for scanning laser projection displays. To produce high resolution images, scanners are required to rotate with large actuation angles (>10 degrees mechanical angle) at designated resonant frequencies. While the designs are pushed closer to material limits, it is essential to acquire knowledge of single-crystal-silicon's fracture strength. We have designed samples for fracture strength tests, which reach failure angle (> 20 degrees) with low driving voltage (< 50 volts) under vacuum. The tests are performed with real-time optical feedback to ensure resonance operations. A voltage ramp is applied to scanners until fractures occur; the ramp-rate and starting angle are chosen such that failures occur within thirty minutes of operation. Torsional stresses at fracture are calculated from failure angles via an ANSYS® model. In the experiment, forty samples from two spring designs with a cross-section of 14x30 um and a length of 240 um are tested. Because fracture angles scatter around a mean value, Weibull statistics is used to treat the characteristic behaviors of the tested samples to better interpret the test results. The Weibull characteristic fracture strengths are 2.97 GPa and 2.58 GPa. With a stress limit of less than 2 GPa, we can achieve a 86% reliability SVGA microscanner design with a 1 mm diameter, a 32 KHz resonance frequency, and a single-side mechanical scan angle of 13 degrees
We present the design and system integration of a hybrid MEMS scanning mirror (MSM) array developed for real-time three-dimensional imaging with a panoramic optical field of view (FOV) of 360 deg ×60 deg (horizontal × vertical). The pulsed time-of-flight light detection and ranging (LiDAR) system targets a distance measurement range of 100 m with a video-like frame rate of 10 Hz. The fast vertical scan axis is realized by a synchronous scanning MSM array with large receiver aperture. It increases the scanning rate to 3200 Hz, which is four times faster in comparison with state-of-the-art fast macroscopic polygon scanning systems used in current LiDAR systems. A hybrid assembly of frequency selected scanner elements was chosen instead of a monolithic MEMS array to guaranty high yield of MEMS fabrication and a synchronous operation of all resonant MEMS elements at 1600 Hz with large FOV of 60 deg. The hybrid MSM array consists of a separate emitting mirror for laser scanning of the target and 22 reception elements resulting in a large reception aperture of D eff ¼ 23 mm. All MSM are driven in parametric resonance to enable a fully synchronized operation of all individual MEMS scanner elements. Therefore, piezoresistive position sensors are integrated inside the MEMS chip, used for position feedback of the driving control. We focus on the MEMS system integration including the microassembly of multiple MEMS scanning elements using micromechanical self-alignment. We present technical details to meet the narrow tolerance budgets for (i) microassembly and (ii) synchronous driving of multiple MEMS scanner elements. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.