| 摘要 |
PURPOSE:To prevent the quantity of reflected light from variation due to the shear of paper and discriminate fine variation on a printing surface by irradiating light on the paper to be detected from both the sides of a photodetector. CONSTITUTION:A lamp 7 is set up on the center of a light body 11. Reflectors 12 are set up around the lamp 7 so as to be inclined at about 45 deg. from the center line of the light body 11. A dome-shaped prism 13 is set up on a position opposed to the lamp 7. Diffused light 14 from the lamp 7 is reflected by the reflectors 12, passed through the inside of the light body 11 and condensed by the prism 13 at the front of a folder 1 and the condensed light is irradiated to a paper surface. The light reflected by the paper surface is sent to a photodetector 8 fitted to the top of the prism 13 through the prism and converted into the quantity of electricity. Since the light is condensed in front of the paper surface and then the condensed light is expanded in accordance with the separation from the photodetector, the reduction of the quantity of reflected light which is caused by the variation of the distance is compensated and the fine variation of the paper surface can be preciesely detected. |
