DoF-Extended Zoomed-In Monitoring System With High-Frame-Rate Focus Stacking and High-Speed Pan-Tilt Adjustment

This article presents a novel pan-tilt-zoom (PTZ) camera with extended depth-of-field (DoF) to address the limited DoF of the images taken by the zoom lens in zoomed-in monitoring. Our concept pioneers the integration of the through-focus scanning (TFS) mechanism and the high-speed pan-tilt mechanism based on the Galvano mirror. The TFS mechanism consists of a variable zoom lens, a servo motor, and a gear mechanism, enabling the system scans at object distances between 3 and 10 m at 0.067 s per TFS process. During each TFS, the high-speed camera captures 16 frames at different focus. A high-frame-rate (HFR) focus stacking algorithm based on GPU is implemented, generating 15 frames/s DoF-extended zoomed-in images. The two-axis Galvano mirror enables ultra-fast and precise pan-tilt adjustment between adjacent TFS processes while stably remaining stationary during the TFS process. The comparative experiment showcased the advanced performance of simultaneous focus on multiple objects at varying distances. The functional experiment demonstrated its capabilities in swift pan-tilt adjustment with real-time DoF-extended zoomed-in image generation, highlighting the proposed system’s potential for small object tracking and detection.