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US 5,489,959 AGranted
Light quantity adjusting device
AssigneeCanon Kabushiki Kaisha
InventorHiroshi Akada
Life of this patent
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AssigneeCanon Kabushiki Kaisha
InventorHiroshi Akada
Estimating the term…
A light quantity adjusting device is provided with a light blocking member for adjusting a quantity of light by moving the light blocking member and a drive source for driving the light blocking member. The drive source includes at least a rotor having a plurality of poles, a stator, a coil and a limiting part arranged to limit the rotation angle range of the rotor to an angle not exceeding 180 degrees. The drive source is arranged such that a cogging torque existing when the coil is not energized works over the whole rotation angle range to cause the rotor to rotate in one direction and, a coil torque generated when the coil is energized works over the whole rotation angle range to cause the rotor to rotate in the other direction. The peak of the coil torque is set to be obtainable within the rotation angle range, and a torque which is obtained by combining the cogging torque and the coil torque works to cause the rotor to rotate in the other direction.
A light quantity adjusting device comprising:
An optical apparatus having a light quantity adjusting device, comprising:
A driving device including at least a rotor having a plurality of poles, a stator, a coil and limiting means for limiting a rotation angle range, wherein a first torque generating irrespective of energization of said coil works over the whole rotation angle range to cause said rotor to rotate in one direction and a second torque generated when said coil is energized works over the whole rotation angle range to cause said rotor to rotate in the other direction, the peak of the second torque being set to be obtainable within the rotation angle range, and a torque which is obtained by combining the first torque and the second torque working to cause said rotor to rotate in the other direction.
Dependencies are inferred from the claim text.