Direct Phase Correction in Phase Locked Loop for Robust Lissajous Scanning of Resonant MEMS Mirrors

Abstract

This paper proposes the direct phase correction phase locked loop (DPCPLL) for simple and robust synchronization of two resonant MEMS mirrors for a Lissajous scan. The DPCPLL, used in a master-slave synchronization structure, runs the slave mirror at the reference frequency and uses the phase of the driving signal to compensate for the synchronization error directly. The DPCPLL merges synchronization control and a PLL, allowing a simple SISO control. The performance of the proposed DPCPLL is assessed based on the vibration immunity of the synchronization. A PID-based DPCPLL and an LQG-based DPCPLL achieve RMS synchronization errors of 87 ns and 69 ns, respectively, which are improvements compared to 118 ns achieved by the conventional structure with a synchronization controller on top of a PLL-operated mirror. The increase of the stability of the Lissajous pattern under a vibration has benefits in applications such as scanning time of flight lidars or Doppler wind lidars.