Novel fast laser-based auto-focusing microscope

In keeping with consumer preferences for ever more high-performance products, a requirement exists for precise and fast auto-focusing microscope systems for the inspection processes in mass production lines. Accordingly, the present study proposes a precise and fast laser-based auto-focusing microscope system in which an auto-focusing capability is achieved by using a position feedback signal from the centroid of the image of the reflected laser beam captured from a CCD sensor. The experimental results show that the proposed auto focusing microscope system is under a 1 s cycle time and ±3 μm positioning accuracy with a ±500 μm linear working range. Overall, it is shown that the proposed auto-focusing microscope system has both a fast response and high positioning accuracy.