Optimization of MOEMS Projection Module Performance with Enhanced Piezoresistive Sensitivity

• Main Authors: Huijun Yu, Peng Zhou, Kewei Wang, Yanfei Huang, Wenjiang Shen
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Micromachines
• Subjects: MOEMS micromirror; sensitivity of piezoresistive sensor; zero-crossing time; position estimation; error of the image pixel
• Online Access: https://www.mdpi.com/2072-666X/11/7/651

In scanning laser projection systems, the laser modulation time is important for the projection resolution. The modulation time needs to be matched with the motion of the micromirror. For this paper, the piezoresistive sensor was integrated on the torsion beam of the micromirror to monitor the physical position of the micromirror. The feedback signal was used to generate the zero-crossing time, which was used to estimate the physical position of the resonating mirror over time. The estimated position was affected by the zero-crossing time and the error directly influenced the definition of the projected image. By reducing the impurity concentration from 3 × 10¹⁸/cm³ to 1 × 10¹⁸/cm³ and increasing shear stress on piezoresistive sensor, the sensitivity of the piezoresistive sensor increased from 4.4 mV/V° to 6.4 mV/V° and the error of the image pixel reduced from 1.5 pixels to 0.5 pixels. We demonstrated that the image quality of an Optical-Microeletromechanical Systems (MOEMS) laser projection could be improved by enhancing the sensitivity of the piezoresistive sensor.