| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect the existing states of wafers placed in a wafer container under noncontact conditions with the restrictions on design greatly reduced. SOLUTION: A video camera is arranged in an oblique direction above a wafer container 1 such that it can take the images of wafers 2 (2-1 to 2-n) seen from the wafer container 1. The images (b) of the wafers 2 taken by the video camera 4 are geometrically corrected to produce aθ-z plan image (c). In theθ-z plan image (c), the edges of the wafer 2 form a group of lines arranged at equal intervals in the direction where the wafers 2 are placed and parallel to the circumferential direction of the wafer 2. It is possible to find, from this state of the lines, the presence or absence of the wafer (d), the obliquely inserted wafer (e), the projecting wafer (f), and the overlapping wafer (g).</p> |
