Light-amount controlling apparatus

摘要

In a light amount controlling apparatus, there are provided a circular-shaped bottom plate having an opening at a center thereof, for supporting a diaphragm blade in such a manner that the diaphragm blade can be opened and closed to control an amount of light passing through the opening; base plate mounted to the bottom plate being arc-shaped so that the base plate is not projected to the opening and from a circular contour thereof; a magneto rotor rotatably supported by the base plate and having a drive lever for driving the diaphragm blade; a stator positioned and supported by the base plate, whose both poles are located opposite to each other while sandwiching the magneto rotor therewith; an electromagnetic coil surrounding the stator; and a cover member positioned and supported by the stator, and having a bearing portion for rotatably supporting the magneto rotor, and a coupling means for coupling the base plate with the cover member. The light-amount controlling apparatus further includes a Hall element for detecting magnetic force produced by the magneto rotor, and a drive control circuit for controlling an amount of a current supplied to the electromagnetic coil in order that the magnetic rotor is driven to a predetermined angular position based upon the detection result of the Hall element.