METHOD AND DEVICE FOR DETECTING A TRANSPARENT OR SEMI-TRANSPARENT MATERIAL APPLIED ONTO AN ABSORBENT AND/OR SCATTERING MATERIAL

摘要

A method is described, for detecting the presence of a foreign first material (N) randomly applied on an object (BA) under examination formed by a second material, wherein the foreign first material (N) is transparent or semi-transparent and the second material is absorbent and/or scattering at at least one wavelength of an optical radiation. The method provides for lighting a first area (Zl) of the object (BA) by means of at least one optical source (1). The method also provides for framing a second area (Z2) of the object (BA) by means of an optical receiver (3). The optical receiver (3) and the optical source (1) are designed and arranged so that the first area (Zl), lighted by the optical source (1), is different from the second area (Z2) framed by the optical receiver (3). The presence of the foreign first material (N) on a surface of the object (BA) is detected through a change in the optical signal on the optical receiver (3) due to optical radiation emitted by the optical source (1) and conveyed through the foreign first material (N) from the first area (Zl) up until the second area (Z2).