Method of automatically adjusting focus conditions

摘要

A method of automatically adjusting focus conditions of photographic optical system is disclosed. In the method at least a part of optical image formed on a predetermined focal plane by an optical system is projected onto first and second photocell arrays in the front and the rear of a surface conjugated to the predetermined focal plane, and onto at least one of other photocell arrays arranged between the first and second photocell arrays. Outputs of first, second and other photocell arrays are arithmetically operated in accordance with respective given evaluation functions thereby obtaining first, second and other evaluation values. These evaluation values are compared with each other and the optical system is intermittently shifted in the optical axis direction with first or second moving step in the case of decision from the compared result that the optical system is positioned within or outside a predetermined range including the in-focused position.