| 摘要 |
PURPOSE:To inspect defects at a high speed without comparing a large sized pattern with one plane with original picture data by reading the images of patterns from two axisymmetrical positions of the axisymmetrically formed patterns, discriminating the difference in the two read images and detecting the defect formed on the patterns. CONSTITUTION:Two image pickup devices 3, 3a are so positioned that the respective visual fields come into contact with each other with the symmetrical axis Y in-between. The image pickup sensors 3, 3a respectively have CCD line sensors and the pattern images of a dry glass plate on a stage are formed by lenses on the photodetecting surfaces of the CCD line sensors. The video signals of the two CCD line sensors enter a comparator circuit 16 by which the signals are differentially computed. The output thereof is inputted as a differential signal to a decision circuit 17. The input is decided by a set slice level in the decision circuit 17 and the signal for the presence or absence of the defect is emitted. |
