Design optimization of a high frequency resonating micro-mirror with low dynamic deformation

Abstract

One of the main design limitations of resonant micro-mirrors intended for visual projection display applications is inertia-driven dynamic deformation. Micro-mirrors used for high frequency (20-30 kHz) laser beam scanning are typically operated at resonance in the region of their torsional modal frequency in order to achieve high scan angles. Although the optical resolution of the projected image is defined by the micro-mirror frequency, maximum scan angle and dimensions, significant dynamic deformation (> 1/10 of the incident wavelength) results in a loss in contrast between adjacent projected spots. This paper presents a structural design optimization scheme for a one directional resonant micro-mirror intended for laser projection with XGA optical resolution. The minimization of dynamic deformation is considered as one of the partial objectives together with other micro-mirror performance and reliability characteristics. The optimization scheme is performed using the response surface method and multi-objective genetic algorithms. This design process demonstrates the technical feasibility of including features, such as a gimbal structure, that improve the dynamic mirror flatness without compromising on the target scanning frequency, mode separation and maximum shear stress.