Process and apparatus for controlling the inking process in a printing machine

Printing plant comprising:

• an automatically controllable printing machine;
• an automatic control means for said printing machine, said control means controlling ink feed of the printing machine in response to input color density deviation signals;
• an acquisition means for photoelectrically measuring a test area on a printed sheet printed by said printing machine and for determining from photoelectrically measured data and from desired reference data said input color density deviation signals for said control means;
• said acquisition means being equipped for spectrophotometrical measurement of said test area and for converting spectrophotometrical measuring data into color position data;
• said acquisition means being further equipped for comparing said color position data with given reference color position data and for determining color deviation data in response to this comparison;
• and,
• said acquisition means being further equipped for converting said color deviation data into said input color density deviation signals.

A process for controlling the inking process in a printing machine comprising the steps of:

• (a) establishing desired reference color coordinates in a standardized color coordinate system wherein each coordinate value uniquely defines a particular color;
• (b) measuring color spectral characteristics of a test area printed by the printing machine to establish measured color coordinates for said test area in said color coordinate system;
• (c) determining a color deviation of said test area on the basis of the reference color coordinates and said measured color coordinates;
• and
• (d) controlling the inking process of the printing machine as a function of said color deviation.

An apparatus for producing inking control signals for a printing machine comprising:

• means for establishing desired reference color coordinates in a standardized color coordinate system wherein each coordinate value uniquely defines a particular color;
• means for measuring color spectral characteristics of a printed test area to establish measured color coordinates for said test area in said color coordinate system;
• means for determining a color deviation of said test area in response to said reference color coordinates and said measured color coordinates;
• and
• means for producing inking control signals as a function of said color deviation.