| 摘要 |
PURPOSE:To raise the accuracy of detection, by generating scanning beams which proceed in parallel with one another on a horizontal plane and by irradiating the scanning beams upon the surface of a sheet and providing a light receiver to detect the change the quantity of reflected or transmitted light. CONSTITUTION:A light beam is irradiated from a gas laser 4 upon a rotary mirror 3 provided on the focus of a parabolic reflector 7, thereby generating scanning beams L which proceed in parallel with one another on a horizontal plane. The scanning beams L are irradiated upon the surface of a sheet 2 by a slender oblique reflector 8 which is moved near the surface of a sheet 2. The change in the quantity of reflected or transmitted light is detected by a light receiver 5. The oblique reflector 8 is Attached to a movable frame 9 which slides in a direction (b) perpendicular to the conveyance direction (a) of the sheet 2. As a result, the angle of incidence to the surface of the inspected sheet is kept constant. Therefore, the level of received light from the end of the sheet does not fall and a flaw or the like can be detected with high accuracy. |
