Dynamic-Range Focal Sweep: Seamless Continuous Autofocus Based on High-Speed Vision for Magnified Object Tracking

This paper presents an innovative continuous autofocus (C-AF) approach based on high-speed vision. It consistently provides focused images with stable and sufficiently high frame rates, aiming to improve the ability to track small, fast-moving objects in a highly magnified scene. To achieve this, we propose the concept of a dynamic-range focal sweep enabled by a high-speed camera and a focus-tunable liquid lens with high adjustment capability. The focal sweep consistently covers a small range around the object’s focus position, guided by previous depth results obtained through the depth-from-focus (DFF) technique. We conducted verification experiments to thoroughly analyze the capability of the proposed C-AF approach. By integrating a 2-axis Galvano mirror, we built a high-speed C-AF active vision system with rapid focus and pan-tilt adjustments. The comprehensive experiment results highlight the advanced capabilities of our seamless C-AF in tracking magnified objects.