| 摘要 |
PURPOSE:To ensure the checking of the entire surface of a material to be checked readily by one checking work, by projecting light from a light source using a special optical mask on the surface so that the irregular reflection on the surface of the material to be checked having irregularities become uniform. CONSTITUTION:The image of the irregular surface of a material to be checked 1 is picked up, and the video signal is processed in an electronic processor. Thus the surface of the material to be checked is checked. At this time, light beams are projected on the surface of the material to be checked 1 in the slant upper directions from light sources 2A and 2B. The light sources are arranged at the slant upper positions so that their optical axes 5A and 5B are made to cross at the center O of the material to be checked 1. Then parts a', a'', b', c' and the like of the surface of the material to be checked 1, which are not reached with the light beam in the combination of the light source 2A and the optical mask 6A, are irradiated with the light by the combination of the light source 2B and an optical mask 6B. In this way, the entire surface of the material to be checked 1 is checked readily and positively by one checking work.
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