Scanning micromirror for large, quasi-static 2D-deflections based on electrostatic driven rotation of a hemisphere

Abstract

A micromirror (mirror area 3.1mm2) for laser tracking applications is presented. The mirror, which is based on a hemisphere, is designed to achieve large quasi-static deflection around two rotational axes by adapting the principle of ultrasonic motors. Here, the deflection of the mirror is achieved by a periodic momentum transfer from a stage with electrostatically driven oscillations. Due to the periodic hemisphere-stage-contact, the system has multiple degrees of freedom and is non-linear. A simple model of stage-hemisphere-interaction is presented and verified in order to identify design rules and adequate excitation regimes.The actuator is fabricated in standard SOI-technology. The final system is excited as well in a non-resonant (2000Hz) as in a resonant mode (2900Hz). Thus excitation frequencies over a wide range are possible. For a resonant operation of the stage, a maximum quasi-static deflection of the mirror of up to +/−35.2° with a maximum angular velocity of 732°/s is demonstrated. In this case, the crosstalk (movement perpendicular to desired direction) is less than 22%. For the non-resonant operation the crosstalk is reduced significantly (less than 10%). In this case, a quasi-static deflection of +/−10.5° is found.