Automatic focusing method

Abstract

An automatic focusing apparatus of a peak stop system adapted to perform focusing adjustment by: measuring contrast while moving stepwise an objective lens or an object in a direction of a focal point along an optical axis of the objective lens with a certain pitch width from a reference point to store the contrast measured at each position during the movement into a memory: comparing a difference between the contrast value measured at a present position where the objective lens or the object has been just moved and the contrast value stored at each position where the objective lens or the object has been already moved, with a preset judgment value; and judging that the position of the maximum contrast (the focal point) has been passed in relation to the gradual movement with the above pitch width when each of compared results is a positive value at each position, in order to make it possible to detect accurately the position of the maximum contrast, disregarding sub-peaks of the contrast.

Dependencies are inferred from the claim text.