Photographing lens switchable between manual focus and auto focus modes

摘要

A focusing device of a photographing lens for focusing by rotating a rotary tube relative to a stationary tube comprises a set-hold unit including a to-be-detected unit movable with the rotary tube and a detection unit movable to the to-be-detected unit; a first drive unit for driving the detection unit relative to the to-be-detected unit; the detection unit producing a distance signal representing a distance between the detection unit and the to-be-detected unit; a first drive control unit for controlling the first drive unit to keep the relative distance between the detection unit and the to-be-detected unit to a predetermined relation in accordance with the distance signal from the detection unit; a command unit for issuing a command signal; a second drive unit for driving the rotary tube; and a second drive control unit for controlling the second drive unit in response to the command signal from the command means to keep the relative distance between the detection unit and the to-be-detected unit to a predetermined relation in accordance with the distance signal from the detection unit.