| 摘要 |
<p>PROBLEM TO BE SOLVED: To make it possible to detect the state of a wafer with enough accuracy without using laser light harmful to human eyes by making up a wafer detector, in such a structure that light reflected on a mirror may be cast on a specified place of a wafer several times due to the swing of the mirror. SOLUTION: When a visible light generator 7 and a visible light detector 8 exist somewhere nearly at the same height as a wafer 1, visible light is cast on the wafer 1 several times due to the swing of a mirror 13. And, a conical signal showing that the wafer 1 is inserted right in a supporting stage section can be obtained several times for one wafer 1. By conducting the detection a plurality of times for one wafer 1, there is no failure to detect the wafer 1 even when visible light having less directivity than laser light is used. As a result, the state of a wafer can be detected with enough accuracy even if light of less directivity is used.</p> |
