Method of and apparatus for detecting initial position of easel and lens

Abstract

In a photographic apparatus for printing an original image on a photosensitive material, focusing is conducted at two different points, and the positions of an easel and a lens at the time of the second focusing are calculated according to the lens formula from the travel amounts of the easel and lens between the first and second focusing positions as well as the focal length of the lens. When the focal length of the lens is unknown, focusing is performed at three points, and the positions of the easel and lens at the time of the third focusing are determined with the lens formula. Pulse motors used to move the easel and lens are controlled by a microcomputer, which adds the number of pulses for forward rotation of the pulse motor and subtracts that for backward rotation. The microcomputer counts and stores the number of pulses indicative of the present positions of the easel and lens. Their initial positions are detected based on the second focusing positions for checking the standard mounting positions of the detectors for the easel and lens. The mounting positions of these detectors are stored in the microcomputer as the standard positions for use in the compensation for step out.