| 摘要 |
PURPOSE: To detect the end-point position of a transparent film in a noncontact manner, with high accuracy and with good responsivity irrespective of the orientation of the film by a method wherein irradiation light from a light source is shone at a specific angle range near the end-point position of the transparent film and a change in the quantity of reflected light is detected. CONSTITUTION: Irradiation light L1 from a light source 1 irradiates a part near the end-part position of a transparent film 5 over a range at an irradiation angleαof 20 to 70 deg.. At this time, the irradiation light L1 is reflected by the transparent film, and it is changed into reflected light L2 so as to reach a photodetector 3. On the other hand, the irradiation light which is incident on the outside of the end-part position of the transparent film 5 is not reflected, and it is changed into transmitted light L3 so as not to reach the photodetector 3. Consequently, a part which the reflected light L2 has reached is formed as a bright image on the photodetector 3, and parts other than the part are formed as dark images. A part in which an H-level is changed over to an L-level corresponds to the end part of the transparent film 5.
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