| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect the outer circumferential position of a transparent substrate without specially working the outer circumference of the transparent substrate. SOLUTION: A light-emitting means 1 is faced with a light-receiving means 2. The outer circumferential position of a transparent substrate 5 which is placed between the light-emitting means 1 and the light-receiving means 2 is detected by a quantity of light which is received by the light-receiving means 2. At this time, a first slit 3, a first optical means 6 by which the image of the light-emitting means 1 is formed on the first slit 3 and a second optical means 7 by which transmitted light from the first slit is image-formed on the face of the substrate are arranged between the first light-emitting means 1 and the substrate face of the transparent substrate 5. A second slit 4 and a third optical means 8 by which the image of the substrate face is formed on the second slit 4 in a state that the transparent substrate 5 does not exist are arranged between the substrate face and the light-receiving means. Then, transmitted light from the transparent substrate 5 is not image-formed on the second slit 4 due to a change in its optical path length, a part is shaded by the slit 4, and a quantity of light at the light-receiving means 4 is dropped. By making use of its drop, the outer circumferential position of the transparent substrate 5 is detected.</p> |
