藉由扭轉軸設計提升壓電式單軸微掃描面鏡之光達性能

Design of Torsional Spring for the LiDAR Performance Enhancement of Single Axis Piezoelectric MEMS Scanning Mirror

王銘瑋(Ming-Wei Wang)

指導教授 ： 方維倫 ； 賴梅鳳

國立清華大學/工學院/奈米工程與微系統研究所/碩士(2021年)

摘要

隨著智慧車輛的發展，各式車用感測器的需求大增，而其中光學雷達(Light Detection and Ranging, LiDAR)比起傳統車用雷達可更快速感測周遭的人、物，讓駕駛做更即時的反應。微掃描面鏡在光學雷達系統中可作為入射光之掃描工具，而優值(Figure of Merit, FoM)為評鑑微掃描面鏡的重要指標，於光學雷達的應用上較高的優值可有較好的性能。
本研究主要利用PZT壓電薄膜搭配SOI晶圓之製程平台進行壓電式單軸微掃描面鏡的製作與實現，並藉由扭轉軸的設計提升微掃描面鏡的光學雷達性能。完成後首先萃取各項PZT參數，而後進行元件之光學量測。結果顯示具有扭轉軸結構之微面鏡於5 VPP電壓之共振頻(4.57 kHz)狀態下，可有7.33°之掃描角，相比於無扭轉軸之純致動彈簧結構微面鏡，能在相同操作電壓下，提升12%的FoM，亦即可有較好之光達性能；與此同時，可有將扭轉模態與出平面模態之共振頻差距拉開之效果，以此可減低模態耦合發生之可能性。

關鍵字

微機電 ； 單軸 ； 微掃描面鏡 ； 壓電式微掃描面鏡 ； 壓電致動器 ； 鋯鈦酸鉛 ； 光學雷達 ； 優值

並列摘要

With the development of smart cars, the demand for various automotive sensors has increased. Among them, Light Detection and Ranging (LiDAR) which is also known as the eyes of the car can sense faster than traditional automotive radars. This ability can let drivers react to the surrounding people and objects more instantly. The micro scanning mirror made by MEMS process is used as a scanning tool for incident light. Figure of Merit (FoM) is an important index for evaluating micro scanning mirrors, and higher FoM can have better performance in the application of LiDAR.
This study utilizes PZT platform to implement a novel piezoelectric single-axis micro scanning mirror. By designing a pair of torsional springs at the central of the mirror, FoM can be boosted. By measurement, it can perform 7.33° scanning angle under 5 VPP voltage and 4.57 kHz resonant frequency, which enhances 12% LiDAR performance in contrast with the reference type without torsional springs. Also, material properties of PZT have been well measured in this study to estimate possible operation range. At the same time, the resonant frequency difference between torsional mode and piston has increased by the additional effect of the torsional spring. It could reduce the possibility of mode coupling.

並列關鍵字

MEMS ； Single Axis ； Micro Scanning Mirror ； Piezoelectric Micro Scanning Mirror ； Piezoelectric Actuators ； Lead Zirconate Titanate ； PZT ； LiDAR ； Figure of Merit ； FoM

參考文獻

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[4] BorgWarner, https://www.borgwarner.com/technologies

[5] Infineon Technologies, https://www.infineon.com/