On the design of piezoelectric MEMS scanning mirror for large reflection area and wide scan angle

Abstract

This study designs and implements the piezoelectric MEMS scanning mirror with large scan angle and reflection area for light beam manipulating applications. In this design, the scanning mirror has a large mirror plate (3 mm in diameter) supported by two T-shape torsional springs. The U-shape piezoelectric cantilever acts as the actuator to drive the scanning mirror through the transmission spring. The analytical model is established to provide the design guideline of transmission spring to increase the scan angle. In application, the proposed designs are fabricated on the SOI (silicon on insulator) wafer deposited with the PZT film. Measurements indicate the fabricated mirror could reach an optical scan angle of 140-degree (mechanical scan angle of ±35-degree) when driving at its resonant frequency of 1.5 kHz with a unipolar driving voltage of 42 V. Moreover, no vacuum environment is required for the presented scanning mirror to achieve the above scan angle. This is an extremely large optical scan angle for the MEMS scanner with a mirror plate of 3 mm in diameter. In addition, another U-shape piezoelectric cantilever serves as the position sensor to detect the scan angle of mirror plate. The sensing signals show good linearity with the scan angles and can be exploited as the feedback control. Measurements also demonstrate that the micro scanner could withstand 1500 g shock loading, and the deviation of scan angle is less than 10% after the cycling test under 10 V pp resonant driving in 95%RH and room temperature for 0.2 billion cycles.