A varifocal micromirror with pure parabolic surface using bending moment drive

Abstract

We propose a method to generate a pure parabolic surface of varifocal micromirror by applying a bending moment to the circumference of the micromirror. Pure paraboloid can focus light without aberration a one of the ideal mirror surfaces. In the conventional method, varifocal mirror generates an approximate spherical surface or a paraboloid-like surface by applying a distributed load to the central part of the mirror with parallel plate electrodes. In this study, the micromirror is deformed only by applying a bending moment to the circumference of the mirror in order to generate an ideal paraboloid. The proposed mirror was fabricated from SOI wafer. The deviation of the varifocal mirror from the ideal paraboloid was measured to be smaller than 5 nm for the 400 mum diameter mirror with the focal lengths from the infinity to 24 mm at the voltages from 0 to 215 V.