Method for correcting unadjusted printing data on the basis of colormetrically measured reference sheet

• US 7,307,755 B2
• Filed: 01/06/2004
• Issued: 12/11/2007
• Est. Priority Date: 01/21/2003
• Status: Expired due to Fees

• Current Assignee: Heidelberger Druckmaschinen Ag
• Original Assignee: Heidelberger Druckmaschinen Ag
• Inventors: Mayer, Martin, Siegeritz, Helmut, Schneider, Manfred, Heuss, Friedrich, Delang, Ulf, Utter, Bernd
• Primary Examiner(s): Rogers; Scott A.
• Application Number:
  US10/752,269
• Publication Number:
  US 20040150848A1
• Time in Patent Office: 1,435 Days
• Field of Search: 358/1.9, 358/504, 358518-523, 358/527, 358/530, 382/162, 382/167
• US Class Current: 358/1.9
• CPC Class Codes: B41F 33/0036 Devices for scanning or checking the printed matter for quality control
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• CPC Class Codes: G01J 3/462 Computing operations in or between colour spaces; Colour management systems

Abstract

A method for correcting digitized image data in the prepress stage when using printing presses having a device-independent color profile in the main printing stage, having the following method steps:

• • colorimetric measurement of a reference sheet and production of an image file in a device-independent color space,
  • conversion of an image file belonging to the reference sheet in a device-dependent color space into a further image file in a device-independent color space using the device-independent color profile belonging to the printing press to be used,
  • comparison of the two device-independent image files.
  • performing alterations on the device-dependent image file associated with the reference sheet or alteration of the printing process in the selected printing press if tolerance limits are exceeded.

Claims

1. A method for correcting digitized image data in the prepress stage when using printing presses having a device-independent color profile in the main printing stage, the method comprising the steps of:

measuring colorimetrically a reference sheet and producing a first image file in a device-independent color space;

converting a second image file associated with the reference sheet in a device-dependent color space into a third image file in a device-independent color space using a device-independent color profile belonging to the printing press to be used;

comparing the first and third image files; and

performing alterations on the second image file associated with the reference sheet or alterating a printing process in the printing press to be used if tolerance limits are exceeded.

2. The method as recited in claim 1 wherein consumable materials used in the printing press selected are changed to alter the printing process.

3. The method as recited in claim 2 wherein the materials include paper or ink.

4. The method as recited in claim 1 wherein the device-independent color profile of the printing press is an ICC profile.

5. The method as recited in claim 1 wherein measuring step includes colorimetrically measuring the reference sheet at multiple points in a uniform raster using an automatic spectrophotometer.

6. The method as recited in claim 1 wherein one of the first device-independent image files exists in a Lab image file format.

7. The method as recited in claim 6 wherein multiple pixels of the reference sheet are combined into a measured value during the colorimetric measurement and this measured value is compared to the likewise combined values of the third device-independent image file.

8. The method as recited in claim 1 further comprising sorting out measured values obtained using the colorimetric measurement and having a color difference with respect to an average value formed from the surrounding measured values exceeding a fixed limit.

9. The method as recited in claim 1 wherein, if the tolerance limits are exceeded, correction values are calculated and a mapping specification for converting the first and third image files into one another is calculated therefrom.

10. The method as recited in claim 9 wherein the mapping specification is taken into consideration in the color profile of the printing press.

11. A device for performing the method as recited in claim 1.