Patent ID: 6310698
Filing Date: 2001-10-30
Classification: H04N

Abstract:
A method for deriving a calibration curve for a halftone imaging apparatus comprising:A) requesting said imaging apparatus to produce on an imaging medium at a first screen ruling a requested halftone dot test pattern comprising at least two different requested halftone gray values, each halftone gray value comprising dots having a requested dot diameter and a requested dot area, said gray value representing the portion of a unit cell area covered by the dot area;B) producing with said imaging apparatus on said imaging medium a imaged test pattern corresponding to said requested test pattern;C) measuring said imaged test pattern dot areas and calculating an imaged dot diameter for each of said distinct imaged dot areas in said imaged test pattern;D) calculating a dot diameter change as a difference between said requested dot diameter and said imaged dot diameter for each of said different halftone gray values of said requested and second test pattern;E) deriving a first function representing said calculated dot diameter change as a function of requested dot diameter;F) using said first function, to predict a predicted dot diameter change for any requested dot diameter;G) using said predicted dot diameter, calculating a predicted dot area and a predicted dot value representing the proportion of the area of any unit cell covered by the predicted dot area;H) using a plurality of such predicted dot values as a function of requested dot values to derive a calibration curve for a halftone imaging apparatus.