Scanner characterization for color measurement and diagnostics

Abstract

We propose a novel scanner characterization approach for applications requiring color measurement of hardcopy output in calibration, characterization, and diagnostics applications. The method is advantageous for common practical color printing sys- tems that use more than the minimum of three colorants necessary for subtractive color reproduction; printing with cyan (C), magenta (M), yellow (Y), and black (K) is the most prevalent example we use in our description. The proposed method exploits the fact that for the scenarios in consideration, in addition to the scanner RGB values for a scanned patch, the CMYK control values used to print the patch are also available and can be exploited in characterization. An indexed family of 3D scanner characterizations is created, each characterization providing a mapping from scanner RGB to CIELAB for a fixed value of K, the latter constituting the index for the char- acterization. Combined together, the family of 3D characterizations provides a single 4D characterization that maps scanner RGB ob- tained from scanning a patch and the K control value used for print- ing the patch to a colorimetric CIELAB measurement for the patch. A significant improvement in the robustness of the method to varia- tions in printing is obtained by modifying the K index to utilize the scanned output for a black-only patch printed with the correspond- ing K value instead of directly utilizing the control K value used at the printer. Results show that the proposed 4D scanner character- ization technique can significantly outperform standard 3D ap- proaches in the target applications. © 2007 SPIE and IS&T.