Optical microscopes are frequently used in biomedical sciences to reveal fine features of a specimen, such as human tissue samples and cells, forming the backbone of pathological imaging for disease diagnosis. One of the most critical steps in microscopic imaging is autofocusing so that different parts of a sample can be rapidly imaged all in focus, featuring various details at a resolution that is smaller than one millionth of a meter. Manual focusing of these microscope images by an expert is impractical, especially for rapid imaging of a large number of specimens, such as in a pathology laboratory that processes hundreds of patient samples every day.
source https://phys.org/news/2021-01-autofocusing-microscopy-images-deep.html