| 摘要 |
PURPOSE:To hold lighting intensity constant and to take a copy stably by controlling the input to a slit light emission type not-cathode ray fluorescent tube according to the intensity of irradiation light detected by a photodetector provided near the hot-cathode ray fluorescent tube. CONSTITUTION:The fluorescent tube 1 is sealed with a face glass plate 2, two strip-shaped fluorescent bodies 4 are arranged on a strip anode 3 across a slit 5, and hot-cathode ray filaments 6 are arranged thereupon successively. When the filaments 6 are heated to apply +DC to the anode 3 on the basis of the filaments 6, the fluorescent bodies 4 are excited as shown by an arrow to emit light, and an original 7 conveyed by a roller 8 on the top surface of the face glass 2 is lighted through the slit; and the reflected light is passed through the slit 5 and guided to an image formation optical system 9 to form an image on a semiconductor sensor 10. A photodetecting element 11 is fitted onto the face glass and outputs a detection signal proportional to the brightness of the fluorescent bodies 4. The filament voltage or DC voltage of the anode 3 is controlled with the detection signal to hold the intensity of light emission constant. |
