Very difficult microscopic observation of wafers: Because of the inclination of the wafer surface, the single field of view of microscopic observation at 20x and 50x cannot all be clearly focused, and the microscope objective lens cruises on the surface of the sample during 2D image stitching, requiring software to automatically track and focus Clear point, select a clear focus image, the Z-axis accuracy reaches 1um, and the clearest image is collected and finally stitched into a full image.