| 摘要 |
PURPOSE:To adjust the focus of a photographic optical system by oscillating a photoelectric transducer along an optical axis in a sine wave shape at a specific frequency, and then controlling intervals of periodic variation in the resistance value of the element. CONSTITUTION:The amplitude of oscillation of a photoelectric transducer 3 is set covering the clearest image forming positions of an object at a very close and an infinite distance. During the oscillation of the element 3, if an object image if formed on the photosensitive surface mose clearly and the element 3, therefore, has a limit resistance value, its output is amplified at a part 7 and then supplied to a differentiating circuit 8. Its output is inputted to an FF11 through a comparator 9 and a rectifying circuit 10. Then, a reference pulse from a generator 12 and the output pulse of the FF11 are compared mutually by a differential amplifier 13. Its difference pulse is displayed on a part 16 through an integrator 14 and a servo amplifier 15. |
