| 摘要 |
PROBLEM TO BE SOLVED: To provide a diaphragm mechanism for a camera with simple structure capable of forming a circular aperture at only minimum opening condition of the diaphragm. SOLUTION: A drive ring 12 is rotated by a rotor 10 of a stepping motor through a gear 11. Seven closing blades 14 are fastened on a base plate 1 by pins 14a, and a pin 14b is fitted in a cam groove 12a of the drive ring 12. An ND filter 13b is attached on a light limiting member 13 supported by a pivot 1q so as to cover an aperture section 13a, and a pin 13c is fitted in the cam groove 12a of the drive ring 12. If the drive ring 12 is rotated in clockwise direction, the opening is reduced by the seven closing blades 14. After the minimum opening condition controlled by the closing blade 14 is attained, the closing blade 14 is stopped, and the only light limiting member 13 is activated, and then the aperture section 13a having an aperture smaller than that in the minimum opening condition is inserted into an optical path.
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