Power zoom lens and camera having same

摘要

A lens position detecting apparatus including an optical system which has a lens group that is movable in an optical axis direction, a lens moving mechanism for holding the lens group in a manner which permits the lens group to be movable in the optical axis direction, and a motor for driving the lens moving mechanism. The lens position detecting apparatus further includes a code reading mechanism which has a code plate with codes which represent the position of the lens group, and a code detecting member for detecting the bodes of the code plate, at least one of either the code plate or the detecting member being movable in association with the movement of the lens group. The lens position detecting apparatus also includes a counting mechanism for counting pulses corresponding to the amount of drive of the motor with reference to an initial value corresponding to a specific position of the lens group, a position detector for detecting the position of the lens group in accordance with the counted value counted by the counting mechanism, a reference value storing mechanism for storing reference values representing the positions of the lens group when the code detecting member detects switching points of the codes, and a correcting mechanism for correcting the counted value by comparing the counted value, counted by the counting mechanism, with the reference value, corresponding to the switching point of the codes, every time the code reading mechanism detects the switching point of the codes.