Method of controlling a lens stop position

Claim 1

In a method for controlling the movement of a lens in an electrophotographic copying apparatus wherein the lens is driven by a stepping motor which steps in response to application of a number of pulses thereto, said number of pulses applied to said motor corresponding to the movement of said lens, an improvement thereof comprising the steps of: setting an initial control pattern for the movement of said lens to a desired position, detecting whether said lens has passed through a home position by using a sensor; detecting the amount of movement of the lens when it is detected by the sensor that the lens has passed through said home position; detecting whether the speed of movement of the lens at the home position is accelerating, decelerating or constant; and correcting the position of the lens to compensate for differences between said initial control pattern and the amount of movement detected such that, if it is detected that the speed of movement of said lens is accelerating or decelerating, said lens position is moved to said desired position only after the speed of movement of said lens becomes constant or controllable, but if it is detected that the speed of movement of said lens is constant, correcting the initial control pattern for the movement of said lens to move the lens to said desired position.