| 摘要 |
PURPOSE:To improve an SN ratio in a area where the transmission amount of X-rays is small, by holding the output current of a secondary electron multiplier tube invariably constant without reference to the transmission amount of X-rays. CONSTITUTION:X-rays from an X-ray source 1 penetrate an object 2 and are supplied to a secondary electron multiplier tube (photomultiplier tube) 4 via a scintillator 3 to convert said X-rays photoelectrically. The resulting output is supplied to a high-voltage power source 10 via an I/V converter 6 to control the output voltage of the power source 10, so that a voltage applied to the photomultiplier tube 4 corresponds to a photoelectric voltage output. Thus, the output of the photomultiplier tube 4 is kept constant at any time. Then, the output voltage of the high voltage power source 10 is passed through a voltage divider 11, converted by an A/D converter 7 and then supplied to an image processor 8. Thus, the output current of the photomultiplier tube is kept invariably constant to improve greatly an SN ratio in an area where the transmission amount of X-rays is small. |
