| 摘要 |
PURPOSE:To avoid the detection of the concave and convex parts, on which a pattern is not described, as defective product, in checking of the mask for the printed substrate, by adjusting the scattering degree of the illuminating light for the mask. CONSTITUTION:The illuminating light 2 is applied to the mask 1 for the transparent printed substrate on which the pattern is described, and the image of the mask 1 is projected on a pattern detector 4 through a lens 3. The output 5 from the detector is processed in an image processor 6, and the defects are detected. If the concave and convex parts are present at the part where the pattern is not described on the mask, the illuminated light is refracted from the slant surfaces of said concave and convex parts and does not reach a lens. Therefore it might be regarded as the defect. By using a scattering plate 8, an angle is imparted to the incident light axis of the illuminating light to the mask so that the light can reach the lens even though it is refracted. Since the detecting capability for the concave and convex parts is determined by the degree of parallelism of the transmitted light, it is recommended that a plurality of the scattering plates having different scattering degress are prepared. |
