| 摘要 |
PURPOSE:To correctly recognize an area of a reference mark by automatically changing a binary threshold level when a binary operation area of the reference mark of a substrate is out of tolerance. CONSTITUTION:A picture of a reference mark 12 picked up by a camera on a substrate 11 is given binary treatment on the threshold level set up by a control means to operate an area of the reference mark. Then, this operation area is compared with a range of a preset reference value, for instance, when the operation area of the reference mark 12 is off the range of the preset reference value, the threshold levels A to C may be automatically changed. Accordingly, an operation area can be set within the preset tolerance. Thereby, the area of the reference mark can be correctly recognized. |
