隨著科技發展，無人機被廣泛應用於空拍、農業、救災、空中送貨及競速等
等。然而，無論何種應用，如何防止無人機撞擊障礙物，始終是不容忽視的課題。
無人機體積縮小並輕量化是現代的趨勢，除了保留原本的攝影鏡頭之外，在不增
加其他感測元件的情況下，如何實現前方障礙物距離偵測是個值得討論的議題。
本論文針對使用單鏡頭實現無人機前方深度距離偵測。在無人機上不增加額
外感測器的情況下，提出一個使用遞迴演算法，計算第一人稱視角(First Person
View, FPV)影像中光流(Optical Flow)的擴張焦點(focus of expansion, FOE)，並利
用幾何公式計算出深度圖後，加入濾波器使量測誤差下降。驗證方面，使用Mid-
Air 資料集、KITTI 資料集、無人機室外飛行影像與速度資訊，以速度、距離與
時間為單位表示深度在每個區間的誤差。

Drones are widely used in photography, agriculture, rescue, goods delivery, and racing.
In fact, how to avoid that drone from hitting an obstacle is indispensable for any tasks.
Developing lightweight drones is the modern trend. This study focuses on how to
calculate depth map without installing other sensors. In order to use one mono camera
in the distance detection task, we proposed a recursive algorithm calculating the focus
of expansion of the image of First Person View with critical information from Optical
Flow. After computing the depth map with geometric analysis, we applied filters to
decrease the error rate. In experiments, we tested performances in several datasets
including Mid-Air, KITTI, and data we extracted from the real world.

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