METHOD AND APPARATUS FOR DETECTING DEFECTS AT HIGH SPEEDS

摘要

In inspecting the appearance of a printed picture, picture data corrected or free of defects is selected as a reference picture, for each picture element of which a table is formed of the same number of flags as the number of levels of a picture, and an index space is formed of the flags for all the picture elements. The reference pattern is produced by turning on the flags in the index space, and inspection and determination are effected by making reference to the flags in the index space one time per each picture element depending upon the attribute value of the picture that is inspected. The allowable range of inspection is set prior to the flag propagation processing that turns on the flag in the allowable range in the index space. Further, not being limited to two values of on and off, the flag may assume many values. It is further possible to reduce the X- and Y-sizes of index space or to reduce the level axis by compressing the index space relying upon the hierarchical expression of the flag utilizing the characteristics of picture data or by avoiding the one-to-one correspondence between the standard picture and the index space.