Optical grating, for analyzing errors in moving sheet, has correction method to correct errors due to failed optical channel, by sampling image from adjacent channels and calculating most likely error free image

摘要

The optical grating (1) has an evaluation unit for inspection of geometric features of a sheet object (2,12) by analyzing the output of the transmitting and receiving optical channels of the grating. Inhomogeneities in the object can still be recognized in the event of a failed channel, by sampling groups of adjacent channels and building up the error free image by comparing the acquired image with conversion tables.