| 摘要 |
PURPOSE:To detect a surface defect at high speed and with high accuracy, by dark-field illuminating a surface on which a pattern having directional properties has been formed, with rays different in wavelength which are respectively applied in a direction parallel to the pattern direction and in a direction intersecting the same. CONSTITUTION:When a patterned surface is subjected to dark-field illumination with the light radiated from a light source, the red light Lr passing through a red-light transmissible filter in a slit 12r becomes parallel rays having no Y-axis component, which radiate the patterned surface from a diagonal upper side along an X-direction line 21. Similarly, the blue light Lb radiates the patterned surface from a diagonal upper side along a Y-direction line 22. A color ITV picks up the image of the patterned surface through a microscope and separately outputs red and blue video signals to respective binary-coding circuits. In an AND circuits, each set of corresponding picture elements is subjected to anding operation, therefore, the output takes ''1'' only when signals representing the corresponding picture elements both take ''1''. The images of the lines 21, 22 disappear and only the image corresponding to a defect appears in a judgement circuit. |
