STRUCTURE OF PHOTOGRAPHIC LENS DRIVEN BY ELECTROMAGNETIC FORCE

摘要

PURPOSE:To drive an aperture device arranged in a photographic lens with the driving force of a motor, by controlling the operation of the operating member of the aperture device by the electromagnetic induction action and detecting a value corresponding to the diameter of aperture blades as an electric signal. CONSTITUTION:The aperture device of a lens structure is normally held in the fully opened position by a spring stretched on an aperture operating member. A proper aperture value is calculated in an operating circuit on the basis of a release operation; and when power is supplied to a field coil 20 through an electric signal terminal 24 and a lead wire 26, the electromagnetic induction acts across the coil 20 and a permanent magnet, and a movable ring member 22 is turned around the optical axis through an arm 22a to turn the aperture operating member. The size of the aperture diameter of aperture blades is detected as an electric signal proportional to it by a rotation position detecting means 30 or the like, and the turning of the aperture operating member is stopped on the basis of the output signal of this detecting means.