Method and apparatus for automatically selecting the best focal position from a plurality of focal positions for a focusing apparatus

摘要

A method and apparatus for selecting the best focal position of an image in a field of view is based upon pixel values located in the image that correspond to locations defining an invariant optical property of the image. In the preferred embodiment, the invariant optical property of the image are pixels that form a "halo" that surround the boundary of an object and are contiguous and immediately adjacent thereto. It has been determined that a certain relationship should exist for this "halo" that surround the boundary of an object when the best focal position is selected.