| 摘要 |
PURPOSE:To prevent the hunting phenomenon with a low cost, by adding a switching circuit between a motor and a circuit that drives the motor. CONSTITUTION:In case when an image is too dark, an iris signal T transmits the information to open the disphragm. Thus the current flows to an input point 14 of a motor driving amplifier 2. A motor 8 turns in the direction to open the diaphragm, and a diaphragm ring 11 moves. When the diaphragm reaches the open end, a wiper brush 19a of diaphragm end detection switch 19 touches a conduction end 19b. Thus the voltage at a point 17 becomes zero to stop the motor 8. Then the signal T transmits the information to close the diaphragm since the image is too bright. Thus the voltage of -V is produced at the point 14, and the motor 8 turns in the direction to close the diaphragm. The brush 19a touches a conduction end 19c at the diaphragm end to set the voltage of the point 19 at zero. Thus the motor 8 is stopped. In such constitution, the hunting phenomenon can be prevented with a low cost. |
