寬頻消色差超穎透鏡於成像及感測之應用

Abstract

成像與感測是探索環境最直接的途徑，本論文用消色差超穎透鏡作為媒介來實現全彩成像與距離感測，我們選用氮化鎵為基材，利用集成共振單元和相位補償公式設計並製作出於可見光波段工作的寬頻消色差超穎透鏡，並在實驗上証實消色差的功能、全彩成像和距離感測的實際應用。 我們將這個寬頻消色差超穎透鏡排列成60×60的陣列應用於光場成像，捕捉拍攝場景中所有物體的各自四維光線資訊，取得光場影像原始圖像資訊經由影像處理演算法重組訊息，可以實現數位對焦、多重深度全解析的影像，更進一步的於連續拍攝中，可以得到被拍攝物的深度和速度訊息。 最後我們擴展了消色差超穎透鏡的功能，用於產生結構光光源，可投射出聚焦的光點狀陣列用以感測距離，並將結構光與光場系統整合為一體，補足了光場成像系統需要足夠的光源環境以取得良好成像品質用以分析距離的限制條件，在微弱光源甚至黑暗環境中，我們的消色差超穎透鏡陣列轉換功能，變成結構光光學系統中負責投射結構光的光學元件，經由引入一道532奈米的雷射光照射在消色差超穎透鏡上，投射出聚焦光點陣列於場景中，再經由影像擷取得影像，經由影像處理分析光點與光點之間的分散程度，來判斷物體的實際深度距離。這個光場成像與結構光的整合系統可工作於任意環境光線條件下用來感測距離。 超穎透鏡有重量輕巧、體積微小、精度高、剛性強、低能耗、厚度極薄、易於電子電路和軟件集成、能直接用半導體製程與光感測器整合等優點，此工作為機器人視覺、自動駕駛車輛、車用感測、無人飛機偵測、量子光源和虛擬實境等等應用開拓了新的方向，讓未來光學設計能更加靈活且實用。

Imaging and sensing are the most direct ways to explore the environment. In this paper, the achromatic metalens is used to achieve full color imaging and range sensing. The GaN based achromatic metalens working in visible is designed and fabricated and the achromatic property and the full color imaging are be demonstrated. We also show the light field imaging by the 60×60 achromatic metalens array which can capture the multi-dimensional information of the targets. By the imagine process, the ability to focus on arbitrary depth and all-in-focus images can be realized. Moreover, the depth information and speed information can detect. Finally, we demonstrated the new functionality of the achromatic metalens array which is structured light pattern generator to project the focused spots array. Here we combined the light field imaging system and structured light system in one optical setup by using only one achromatic metalens array which complemented each other's restrictions on lighting conditions. In the bright enough environment, the achromatic metalens array is an imaging component of the light field imaging system. In the dark environment, a 532 nm continuous wave laser was introduced to irradiate on the achromatic metalens array to project the focused spots array on the scene. This integrated system can be used to sense distance in all light conditions. The advantages of metalens are light weight, small size, accuracy, rigid and strong, low energy consumption, low profile configuration and easy electronics and software. This work opens up new directions for applications such as robot vision, autonomous vehicles, vehicle sensing, unmanned aircraft detection and virtual reality which makes future optical designs more practical.