US Patent 7576893 Correlated secondary TRC calibration method

This invention is a method of producing a set of TRC's for a color printer's secondary halftone screens that is correlated with the printer's primary halftone screens. The method makes use of the printer/screen characteristic data that is normally gathered during screen calibration. However, instead of progressing from the data to a normal calibration for the secondary screens, the method goes backward through the data starting with the finished primary screen TRC's. The method insures that for every primary screen density, the closest possible secondary screen density is used when the same digital value is specified.