| 摘要 |
PURPOSE:To protect a photomultiplier tube by decreasing a supply voltage, when the beam light is scanned in two-dimension and the output of the photomultiplier tube is a prescribed value or over at the outside of the sheet, in a picture scanning reader taking the photomultiplier tube as a photodetector. CONSTITUTION:The laser light 2 from the laser light source is performed for the main scanning in the amplitude larger than that of a storage phosphor sheet 4 by a mirror 3, the sheet 4 is moved toward the subscanning direction B for two-dimensional scanning, the light generated from the scanning is given to the photomultiplier tube 6 via a light transmission member 5. The output current of the photomultiplier tube 6 is amplified at an amplifier 9 and outputted, and inputted to a comparator 10, compared with a reference level SL. When the level is larger than the reference level SL, the output is applied to an AND gate 11. A pulse S6 representing the timing placing the main scanning position of the laser light 2 to the outside of te sheet 4 with the mirror 3 is applied to the other input of the gate 11, and when the output is generated from the gate 11 with the pulse S6, then a switch 12 provided between a power supply 7 and a booster 8 for the photomultiplier tube 6 is turned off. |
