System for checking printed condition of printed sheet matters

摘要

A system for checking the printed condition of a stack of multicolor printed sheets in which at least one corner of each of the sheets has a check mark including stripes corresponding to each color printed. A counting machine separates the sheets one by one and exposes the corner having the check mark so that a density signal generator can scan the mark by means of a photoelectric element by detecting reflected light therefrom produced by a strobe flash synchronized with the separating operation. The resulting density signal output is analyzed and processed by a density signal processor which generates a pulse output indicating the respective positions of the check mark stripes. A computer operates to inspect for presence of the pulse signal from the density signal processor and any time lag thereof to thereby detect missing print and shear in printing, respectively. The system output then indicates the sheet having the faulty print.