Patent ID: 7396169

Claim:
A light quantity adjusting device, comprising: a base plate with a ring shape having an exposure aperture at a center thereof, a first light quantity adjusting blade arranged in the exposure aperture, a first drive device for opening and closing the first light quantity adjusting blade, said first drive device having a first magnet rotor with a ring shape, a first exciting coil with a ring shape, and a first guiding member for guiding a magnetic field generated in the first exciting coil to a position facing a magnetic pole formed on a circumference side of the first magnet rotor, said first magnet rotor and said first exciting coil being arranged on an inner circumferential edge of the exposure aperture in a stacked state, a second light quantity adjusting blade arranged in the exposure aperture, and a second drive device for opening and closing the second light quantity adjusting blade, said second drive device having a second magnet rotor, a second exciting coil, and a second guiding member for guiding a magnetic field generated in the second exciting coil to a position facing a magnetic pole formed on a circumference side of the second magnet rotor, said second magnet rotor and said second exciting coil being arranged on a portion of an outer circumferential edge of the exposure aperture.