| 摘要 |
<p>PURPOSE:To enable defects to be inspected at high speed and easily by allowing one image pickup pattern which was divided in a direction symmetrical in reference to a line to be subject to mirror inversion and to allow it to be compared with the other pattern. CONSTITUTION:A mask to be inspected is scanned by laser beam, laser beam which penetrates through the mask is detected by a photosensor 18 and is AD converted 41, and is stored in an image memory 42. The main direction of scanning should be in a direction which is at right angle in reference to the center line (symmetrical in reference to a line) of the mask. One of patterns which are symmetrical in reference to a line (from one edge of mask to the center line) is stored in the image memory for each main scanning line. When the other pattern (from the center line to the other edge) is output from the photosensor 18, the image memory 42 is read in reverse and is compared by a comparison circuit 48. Then, the defect of mask can be inspected in real time with less memory capacity for a large mask such as shadow mask of CRT.</p> |
