Theoretical and finite element analysis of dynamic deformation in resonating micromirrors

Abstract

Dynamic deformation is one of the limiting

factors in the design of high frequency resonating micro-scanners that are intended for high definition raster scanning display applications. Out-of-plane deformation resulting from high acceleration loads causes beam divergence,

which will in turn reduce the optical resolution. This paper presents a detailed analysis on the mechanical design aspects contributing to dynamic deformation such as the micromirror layout and the micromirror-spring linkage

design. The applicability of one-dimensional plate bending theory in evaluating micromirror deformation due to

inertial loads is investigated using finite element analysis. Improved analytical dynamic deformation predictions, which take into consideration the two-dimensional mirror plate twist, will also be presented. A comparison among a number of layout designs was carried out with the aim of increasing micromirror bending stiffness in a direction parallel to the axis of rotation. Moreover, spring-linkage effects were also addressed and a significant improvement in dynamic deformation was achieved with the inclusion of a gimbal structure between the micromirror and the torsion springs. A parametric analysis was also carried out in order to optimise the gimbal frame design in order to comply with the Rayleigh diffraction limit criterion.