Method and device for detecting structures of a surface of a planar item (article)

摘要

A method and a device for detecting structures of a surface (13) of a planar item (12), in particular glass panes, is specified. A coherent light beam (2) is projected onto the surface (13) and components (14) of the light which are produced by beam diffraction on structures of the surface (13) are detected and investigated. It is possible to proceed from this to judge the presence or absence of specific structures. In one device, the coherent light beam (2) is focused onto a reflective coating (8) on a substrate (6) which is otherwise non-reflective and light-transmitting, and is deflected by said coating, and the reflected beam is projected via a lens (9) onto the surface (13) of the item (12) which is to be investigated. Without disturbance by a structure, the reflection takes place in such a way that focusing occurs on the coating (8). Components (14) of light which are produced by beam diffraction on structures penetrate the substrate (6) outside the coating (8) and can be projected by means of a positive (collective, converging) lens (15) onto a detector (16) and evaluated there. The mode of procedure is suitable, in particular, in assessing abrasion resistance of, or the abrasion-induced damage to, coated surfaces, in particular surfaces having thin-film coatings and/or in assessing desired or undesired unevennesses of an otherwise flat surface. <IMAGE>