| 摘要 |
<p>Flaws may be detected by illuminating a surface with two plane beams (13, 14) of coherent light at a wavelength close to the ends of the visible spectrum. The two beams are generated, e.g., by laser diodes (11, 12) and lie in a single plane (P) that is substantially orthogonal to the product surface (2), so that a single light trace (T) is formed on said surface. In addition, said beams are angled towards one another and have substantially the same angles of incidence (i). The illumination along said trace is measured in a direction (18) orthogonal to said surface and at said wavelength, e.g. by means of a linear array camera (17). A sharp localised reduction in illumination indicates the presence of a flaw. The method may be used to detect pinholes or scratches on as-cast metallurgical products from continuous casting processes.</p> |
