| 摘要 |
PURPOSE:To automatically control X-ray tube voltage and make photographic density of film uniform by taking out signals from a detector and a reference signal generator and controlling a tetrode in a tube voltage controller with a control signal of a bias control circuit. CONSTITUTION:X-ray passed through an object 7 of an X-ray unit 5 is detected with a photoelectric element 10, and an exposure light signal S1 is outputted. The signal 1 is amplified with an amplifier 17 and inputted to a comparator 15. At the same time, photographic density reference value of a film corresponding to tomographic time is taken out from a volume 19a and a photographic density reference signal S2 is outputted through a contact 18a. The signal S2 is compared with the signal S1 with the comparator 15, and a differential signal S3 is outputted. The signal S3 is inputted to a bias control circuit 16, and a control signal S4 corresponding to the signal S3 is inputted to a tube voltage controller 4 to control grid voltage of a tetrode 3. Applied tube voltage to the X-ray unit 5 is varied depending on the value of the signal 4 to make the differential signal S3 zero. |
