Design and Experimental Validation of a Line-Laser Autofocusing System With Extended Working Range

Autofocus (AF) technology plays a critical role in applications such as microscopic measurement, 3D visual scanning, and semiconductor defect inspection.Conventional photoelectric sensor-based AF systems in microscopy face challenges in simultaneously achieving high precision and a large operational range, primarily due to distortions introduced by objective lenses.To address this limitation, this paper presents a conjugate line-laser-based autofocus method.The proposed approach employs a semicircular light-blocking diaphragm to generate a line-semi-ellipse laser spot on the sample surface.Combined with a laser spot image feature extraction algorithm and mathematical modeling, the system achieves an autofocus range of 500 m with a positioning accuracy within 1/5 of the depth of field (DOF) when using a 20 objective lens.The developed AF system offers a simple, robust, and efficient solution for high-speed, high-precision microscopic autofocusing, enabling extended range without compromising accuracy.