A method for reducing the inaccuracy of harmonic ratios in the dynamics of a multiple-degrees-of-freedom MEMS scanning mirror

摘要

A generic mathematical and practical approach, suited for MEMS DRIE fabricated devices, which enables the elimination or significant reduction of the inaccuracy of harmonic ratios, is presented. The approach is useful for any multiple-degrees-of-freedom system in which such accuracy has an impact on performance such as resonating gyro and uniform rate scanners. The causes for inaccuracy are investigated and a mathematical solution that theoretically eliminates the inaccuracy of harmonic ratios in MEMS DRIE fabricated devices is proposed. Specifically, we demonstrate the proposed approach on a multiple-degrees-of-freedom vibrating mirror, intended for uniform rate scanning for raster scan video applications. Results of the fabricated new asymmetric 3 degrees of freedom MEMS devices are introduced and discussed. An improved device utilizing the proposed design achieved harmonic ratio accuracy in the order of 0.1% and triangular wave amplitude of about 5 degrees under an excitation voltage of only 50 V at a basic frequency of 13.396 kHz in atmospheric pressure. The proposed method and system are patent pending.