High-speed telescope autofocus for UAV detection and tracking.

This paper presents the analysis, implementation and experimental evaluation of a high-speed automatic focus module for a telescope-based UAV detection and tracking system. An existing optical drone detection system consisting of two telescopes and deep learning-based object detection is supplemented by suitable linear stages and passive focus algorithms to enable fast automatic focus adjustment. Field tests with the proposed system demonstrate that UAVs flying at speeds of up to 24 m/s towards the system are successfully tracked and kept in focus from more than 4500 m down to 150 m. Furthermore, different search functions and contrast measures are evaluated and it is shown that the Tenengrad operator combined with the Hill Climbing search function achieve the best performance for focusing on fast moving small UAVs.

Camera-guided real-time laser ranging for multi-UAV distance measurement.

This paper presents the design and implementation of a scalable laser ranger finder (LRF)-based prototype system, which enables distance measurement and precise localization of multiple unmanned aerial vehicles (UAVs) in real-time. The system consists of a telescope and camera as the image acquisition components, supplemented by an LRF and a fast steering mirror (FSM) to obtain the distance measurement. By combining the optical path of the camera and the LRF through a dichroic mirror, the LRF is accurately aligned by the FSM based on the angular position of a UAV within the camera field of view. The implemented prototype successfully demonstrates distance measurements of up to four UAVs with a bandwidth of 14 Hz per object.