VERFAHREN UND VORRICHTUNG ZUR BESTIMMUNG DER BILDKLARHEIT EINER OBERFLÄCHE

PCT No. PCT/EP91/00932 Sec. 371 Date Nov. 18, 1992 Sec. 102(e) Date Nov. 18, 1992 PCT Filed May 17, 1991 PCT Pub. No. WO91/18278 PCT Pub. Date Nov. 28, 1991.Method for determining the image clarity of a surface of a sheet strip or similar, including projection of an image on the surface, detection of a virtual image of the image projected onto the surface and the processing of the detected virtual image into a signal which is presented as a measure for the image clarity of the surface, wherein the image reflected onto the surface is composed of a two-dimensional array of distinct light spots, whereby the processing of the detected virtual image includes the steps of (i) digitizing the detected virtual image with reference to at least one greyness discriminator value, and (ii) determining, for the greyness discriminator value, the number of distinct light spots in the digitized detected virtual image, and from steps (i) and (ii) obtaining a signal measuring image clarity of the whole area of the surface illuminated by the image projected onto the surface.