| 摘要 |
PURPOSE:To cause no control error, and also to execute automatic diaphragm control whose release time lag is small, by making an operating speed of a pulse plate roughly constant. CONSTITUTION:A relative position of a bias magnet 4 and an electromagnet 5 is shifted by a 1/2 period of the arrangement period of comb-tooth 2a of a pulse plate 2. When a release button 22 is pushed in, a switch 7 is closed, and in t1 after the electromagnet 5 is electrified, detention of a detaining part 17c and a lever 19 is detached, and in a moment when the pulse plate 2 starts to rotate, an attracting force of the electromagnet 5 goes to maximum, made roughly equal to an attracting force of the bias magnet 4, and the rotation of the pulse 2 shows smooth rise. The charge of a capacitor C decreases gradually, and attains to an unbalance state in the course of running. It changes into a running resistance, negates the increasing inertia rotation, and thereafter, said plate rotates at a constant speed. A magneto-resistance element 1 outputs the number of comb-teeth of the pulse plate 2, as a pseudo sine wave voltage from an outputting circuit 35, the electrification of an electromagnet 32 is turned off through a digital comparator 56, and an interlocking lever 17 is stopped at a desired diaphragm position. |
