Resonant micro-mirror electrical characterisation towards tunable digital drive circuit design

Resonant micro-mirrors are becoming increasingly popular in a range of consumer devices. Resonating angular vertical comb drive micro-mirror are particularly popular due to their reduced manufacturing complexity. In order to achieve maximum scanning angle for a given maximum driving voltage, it is important that the mirror is operated at its resonant frequency. Therefore, this paper proposes a novel PLL-based micro-mirror controller with a tunable phase delay which can be used to compensate for non-constant phase transfer function in the feedback angular position sensing mechanism as well as other phase delays which may be present in the system. An analysis was carried out on the effect of the drive waveform on the energy transfer into the micro-mirror and the phase between the driving waveform and the mirror angle. The PLL and the micro-mirror are modeled using FEM based electrostatic and mechanical properties for the mirror. The proposed controller was implemented and tested using an FPGA.