Process for calibrating electronic imaging devices
AssigneeArtwork Systems, Inc.
InventorMark R. Samworth
Life of this patent
Estimating the term…
Abstract
A method for developing calibration curves and for calibrating a halftone imaging device to reproduce on an imaging medium gray scale values equal to input gray scale values entered in said imaging device. According to this method a calibration function representing a linear change in reproduced halftone dot size on said imaging medium as a function of input halftone dot size is developed by using the device to reproduce on an imaging medium at least two test input dot values representing two different % halftone dot sizes and determining a linear change between the input and the reproduced halftone dot sizes. The dot growth is used to predict dot changes for other % halftone dots and thus construct calibration curves which may be used to calibrate the imaging device.
Claims20
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.
A method for correcting original halftone dot values sent to an imaging apparatus for accurate reproduction on an output medium, the method 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 dot values, each halftone dot having a dot diameter and a dot area, said dot value representing the portion of a unit cell area covered by the dot area;
- B) producing with said imaging apparatus on said imaging medium an imaged test pattern of 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 distinct test pattern halftone dot areas;
- E) deriving a first function representing said calculated dot diameter change as a function of requested dot diameter;
- F) using said first function, predicting a dot diameter change for any requested dot diameter size requested from and generated on the output medium with said imaging apparatus;
- G) using said predicted dot diameter change, calculating a predicted dot area and a predicted dot value representing the proportion of the area of a unit cell covered by the predicted dot area;
- H) using a plurality of such predicted relative dot area values as a function of requested dot values to obtain a function predicting for any requested value a corresponding output dot value for a dot produced by said imaging apparatus on said imaging medium and
- I) using said function to alter any original dot value sent to said imaging equipment to produce an output value substantially equal to said original value on said imaging medium.
Dependencies are inferred from the claim text.