Swiss Aluminium Ltd.

Gilbert Dolveck

The invention relates to the printing industry, and is based on the comparison of a reproduction under inspection with a reference polychrome graphic representation. Respective reference axes (A.sub.1, A.sub.2) are defined for the reference representation and the reproduction under inspection. These axes are normal to and go through an equivalent point of the representation and reproduction, respectively. The two latter are rotated around their reference axes, producing whirling images (D.sub.1, D.sub.2) formed of concentric color rings (a.sub.1, a.sub.2, . . . a.sub.n and a'.sub.1, a'.sub.2, . . . a'.sub.n) each having a set width and shade, and forming a basis for detecting a possible color drift.

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St. Sorlin En Valloire, France

Gilbert Dolveck