| 摘要 |
PROBLEM TO BE SOLVED: To provide an X-ray automatic exposure control device preventing the density from being affected by the length of a high-voltage cable connected to an X-ray tube. SOLUTION: The X-rays from an X-ray tube 4 transmits a subject 3, scattered rays are removed by an X-ray grid 10, and a transmitted X-ray image is received by a cassette 1 (X-ray film, intensifying screen). An automatic exposure control X-ray detector 2 detects the X-ray dose entering the cassette 1 with a photoelectron multiplier tube 8 as the current signal ip proportional to the dose rate. The length of a high-voltage cable 5 is stored in the memory 18 of a CPU 17 in advance, and the reference voltage value Vr of a phototimer is corrected in response to the length of the high-voltage cable 5 and the values of radiographic voltage/current. The signal proportional to the X-ray intensity detected by the photoelectron multiplier tube 8 during radiographing is time- integrated by an integrator 12. When the output Vc becomes the said corrected reference voltage value Vr, a high-voltage cutoff signal is sent to an X-ray switch 16 from a comparison detector 13 via a switch 14, and X-ray radiation is automatically completed, thereby the density error of an X-ray photograph can be eliminated.
|
