| 摘要 |
A dental x-ray diagnostic installation has an exposure unit consisting of an x-ray tube and a cassette holder for generating a dental x-ray exposure. The exposure unit is rotatable about a patient's head by a motor. A radiation detector is attached to the cassette holder which supplies an electrical signal corresponding to the radiation dose rate to a dose rate regulator which in turn operates a voltage control unit which sets the level of high voltage supplied to the x-ray tube such that the dose rate of the radiation emitted by the x-ray tube is maintained at a value for producing an optimum film exposure. A range adjustment for the x-ray tube voltage is externally selected and limits operation of the voltage control unit such that if the dose rate regulator supplies a signal to the voltage control unit requiring a voltage which exceeds the set limit, the voltage control unit is inhibited and instead the motor speed is adjusted to maintain the optimum exposure. |
