應用微機電反射鏡之廣角光達系統設計與實現

Abstract

Light Detection and Ranging (LiDAR)傳感器技術是自動化運輸的主要推動力。透過融合LiDAR的傳感器數據、雷達以及相機鏡頭就可以全面而穩健的感知周圍環境。但是，現今的LiDAR解決方案大多非常複雜且成本高昂，且無法有效的實現大視場的掃描，因此無法廣泛的應用到車輛與機器人中。 我們模擬並演示了完整的LiDAR系統，並透過將微機電反射鏡(MEMS mirror)加入掃瞄系統中，實現低成本、小體積、大視場掃描的LiDAR系統。首先，應用ZEMAX OpticStudio光學模擬軟體設計整個LiDAR掃描系統，包含準直透鏡、MEMS mirror、反射訊號接收透鏡，並在掃描擴角光學上設計一組非球面的光學系統，達到擴大光達掃描角度的目的。雷射光束經過此組廣角透鏡後掃描角度可以擴大4倍，達到100度。廣角透鏡的distortion控制在3%以下，讓掃描畫面更接近真實情況。第二，為了演示低成本、小體積MEMS掃描光達，使用了模組化雷射測距儀(LRF)並加入MEMS mirror。整個系統架設在自行設計與製作的支撐具上。完整的LiDAR掃描儀原型體積小於150mm*50mm*30mm。重量小於250公克。在2 klux的自然光環境中對於wide-angle LiDAR進行測量分析，最大的誤差為4.1cm，因此誤差為2%以內。最後使用自行撰寫的影像處理程式，將掃描數據轉換為3D點雲圖，生成的圖像證明了LiDAR的完整功能。

Light Detection and Ranging (LiDAR) sensor technology will become the main driving force for automated transportation. Through the fusion of LiDAR sensor data, radar and camera lens, the surrounding environment can be fully and robustly sensed. However, most of today's LiDAR solutions are very complex and costly, and cannot effectively achieve large field of view scanning, so they cannot be widely used in vehicles and robots. We simulated and demonstrated a complete LiDAR system, and by adding Microelectromechanical Systems(MEMS) mirror to the scanning system, we created a low-cost, small size, and large field of view scanning LiDAR system. First, use ZEMAX OpticStudio optical simulation software to design the entire LiDAR scanning system, including collimating lens, MEMS mirror, and reflection signal receiving lens. And design a group of aspherical optical systems on the scanning angle expansion optics to achieve the purpose of expanding the scanning angle of light. After the laser beam passes through this group of wide-angle lenses, the scanning angle can be expanded 4 times to 100 degrees. The distortion of the wide-angle lens is controlled below 3%, making the scanned image closer to the real situation. Second, in order to demonstrate low-cost, small-volume MEMS scanning LiDAR, an OEM module laser rangefinder (LRF) was used and MEMS mirror was added. The entire system is erected on a self-designed and manufactured support. The complete prototype of LiDAR scanner is less than 150mm*50mm*30mm. The weight is less than 250 grams. In the 2 klux natural light environment for wide-angle LiDAR measurement and analysis, the maximum error is 4.1cm, so the error is within 2%. Finally, a self-written image processing program was used to convert the scanned data into a 3D point cloud image, and the generated image proved the complete function of LiDAR.