| 摘要 |
During a scanning operation of a camera as the camera moves along its predetermined path, it is occasionally necessary to readjust the iris of the camera due to varying light conditions occurring over a period of time. A control mechanism is incorporated within the lens system of the camera for enabling intermittent automatic adjustment of the iris at one or more predetermined positions along the path of movement of the camera or at preselected time intervals during the scanning operation. A drive motor acts for driving the iris to vary the size of the iris and such drive motor operates in response to signals received from a motor control circuit. In order to generate signals for adjusting the iris the light from the scene being viewed by the camera, e.g. the light passing through the lens, is measured and compared with a predetermined standard. When a difference exists between the light passing through the iris and the predetermined standard, a control signal is provided to the motor control circuit for generating a signal for driving the iris drive motor. However, a switch mechanism is connected to the motor control circuit and the drive motor so as to only allow operation of the drive motor when the switch circuit is in its closed position. An actuating mechanism causes the switching circuit to be closed when the camera is at a predetermined position along the path of movement of the camera or at preselected time intervals during the scanning operation.
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