Method and apparatus for determining register differences from a multi-color printed image

A system for determining register differences in a multi-color printed image formed of a plurality of superimposed single-color printed images, the system comprising, in combination:

• a color video camera having a macro-optical system for scanning at least a part of the multi-color printed image and producing an enlarged electronic image of a size adequate to resolve individual dots making up the printed image,
• video converter means for deriving a plurality of single-color images and storing the single-color images in respective color memories,
• means for defining a register-checking location in of the printed image which include a contour comprising at least two superimposed single-colors,
• image processing means for determining contours in the respective single-color images from the information stored in the respective color memories at the register-checking location, the image processing means further including means for determining offsets between the separation contours of the respective single color images as a measure of register differences between said single color images.