Design and experimental validation of novel optics-based autofocusing microscope

This study designs and characterizes a novel precise optics-based autofocusing microscope with both the large linear autofocusing range and the rapid response. In contrast to conventional optics-based autofocusing microscopes with centroid method, the proposed microscope comprises two optical paths, namely one optical path which provides a short linear autofocusing range but an extremely high focusing accuracy and a second optical path which achieves a long linear autofocusing range but a reduced focusing accuracy. The two optical paths are combined using a self-written autofocus-processing algorithm to realize an autofocusing microscope with a large linear autofocusing range, a rapid response, and a high focusing accuracy. The microscope is characterized numerically using commercial software ZEMAX and is then verified experimentally using a laboratory-built prototype. The experimental results show that compared to conventional optics-based autofocusing microscopes with centroid method and a single optical path, the proposed microscope achieves both a longer autofocusing range and a more rapid response with no reduction in the focusing accuracy. Overall, the results presented in this study show that the proposed microscope provides an ideal solution for automatic optical inspection and industrial applications.