| 摘要 |
PURPOSE:To vary a stop aperture while reducing a stop-down time to half by providing a stop blade rotating plate to a rotor arranged at both surface sides of a stop blade, and rotating them in the opposite directions by the same angle. CONSTITUTION:A fixed tube 1 supported on a lens barrel consists of stators 2 and 3 and rotors 4 and 5 of a stepping motor and rotating plates 8 and 9 fixed on its end surfaces, and the stop blade 10 interposed between them has a one- side pin 10a engaged with the hole of the rotating plate 8 and the other-side pin 10b engaged with the cam hole 9a of the rotating plate 9 respectively. The number of drive steps of the stepping motor is calculated from the quantity of light metered by the photodetecting element of a camera and the rotors 4 and 5 are rotated simultaneously in the opposite directions by the same angle to set the stop blade 10 to a necessary stop value. At this time, the driving speed of the stop blade 10 is increased twice, so the lens is stopped down at a high speed.
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