Precision Auto-Focusing Apparatus Based on Long-Working-Distance, Wide-Spectrum Microscope

Abstract

<jats:p>A mirror-based Schwarzschild microscope with a wide spectrum and a long working distance was investigated to perform precise assemblage of detectors. We employed a gradient square method to construct the evaluation function for realizing accurate quantitative analysis of image defocusing. By imaging a resolution target that corresponded to 228 line pairs per mm, the validity and imaging ability of the system was proven. The results of repeated focusing tests yielded a standard deviation of 0.75 μm, which indicated high performance accuracy for the focusing system. The proposed system has potential applications in industrial inspection and focusing detection.</jats:p>