Abstract: A system for testing a pattern recorded on a plate with a high density in relation to a reference pattern, comprising means for analyzing the pattern with a line detector and a logic circuit for processing the data supplied by the detector and data relating to the reference pattern, the two patterns being described line-by-line. The logic circuit is intended to detect the errors while admitting for each line a shift between the two patterns of one unit in a direction X or in a direction Y perpendicular to X, the maximum shift allowed for the entire pattern amounting, for example, to three units in each direction.