Topology optimization of natural frequency in rotating-mirror structure for the ultra-high-speed camera

Polyhedron rotating scanning mirror (PRM) has very important applications in the fields of ultra-high-speed cameras, ultrashort pulse micro/nano machining, laser scanning, and Q-switching. The natural frequency of PRM is crucial for PRM design. In this paper, the application of a topology-optimization technique to improve the fundamental natural frequency of PRM for ultra-high-speed cameras was proposed based on the solid isotropic material with the penalization method and the method of moving asymptotes to investigate the structural optimization design. Moreover, the internal structure of the PRM was optimized based on the pseudo-density distribution. In the optimized structure, the three sharp corners with smaller pseudo-density material were removed and replaced by three irregular holes and three circular apertures with the same radius. Under identical conditions, the first natural frequency of the optimization structure was promoted from 4, 746.3 Hz to 5, 366.1 Hz, increased by 13.1%, which represents an obvious improvement in the image quality obtained by using ultra-high-speed cameras. The topology-optimization model and corresponding methodology reported herein provide a perspective and application area to effectively improve the fundamental frequency of a PRM without changing the external structure of this component