Wide Angle and High Frequency Resonant Piezoelectric MEMS Mirror for Laser Beam Scanning Application

This study designs and realizes a piezoelectric MEMS scanning mirror with large scan angle and high frequency for high-resolution laser beam scanning displays. In Fig. 1 a, this design has three merits: (1) wing-shaped actuators: to serve as the pure torque generator to drive the torsional spring and mirror (1.2mm) with good linearity (since no axial/transverse loads), (2) wing-shaped actuators: to localize the energy at torsional-spring and mirror to achieve large scan angle (at the scanning mode); (3) optimal supporting spring: to suppress the mode coupling and further to lower the stress during scanning. Thus, large scan angle at high scanning frequency is achieved. Measurements demonstrate the scanner has an optical scan angle of 70-degree (mechanical scan angle of ±17.5-degree) at the resonant frequency of 37.7kHz (no vacuum required), which can reach target resolution 1080P, with a unipolar driving voltage of 20V. As summarized in Fig. 7, compared with existing scanners, the performance of the presented one is competitive in FOM (optical scan angle (θ) × mirror size (D)) when driving at resonant frequency.

INTRODUCTION

Scanning micro-mirror can find various applications in laser beam scanning displays, such as LiDAR (light detecting and ranging) [1], pico-projectors [2], AR glasses [3], etc. The MEMS micro-mirror is a competitive option to realize LiDAR and projection system, owing to the features of miniaturization and batch fabrication. In general, the wide Field of View (FOV) and high resolution are important specifications for display applications. Thus, wide scan angle and high scanning frequency are preferred for micro-mirror design. Using high-definition display as an example, the scanning frequency should be higher than 36 kHz and the optical scan angle should achieve 40-degree [4]. However, these two key performance indices of MEMS mirror, scan angle and operating frequency, are trade-off in the design.