Method for compensating for tone value fluctuation in an inkjet printing machine

Patent metadata

Field	Value
Publication number	US-10277775-B2
Application number	US-201815938033-A
Country	US
Kind code	B2
Filing date	Mar 28, 2018
Priority date	Mar 31, 2017
Publication date	Apr 30, 2019
Grant date	Apr 30, 2019

Abstract

A method for compensating tone value fluctuation in inkjet printing includes generating multi-bit halftone images of pixels on a computer during prepress screening for color separations with multiple tone values out of print image data, forwarding multi-bit halftone images to a control unit of an inkjet printing machine, and printing the multi-bit halftone on the machine, wherein encoded binary values of multi-bit halftone images correspond to ink drop sizes to be generated by the machine. The computer introduces additional binary values of multi-bit halftone images not corresponding to ink drop sizes in pixel positions of multi-bit halftone images where occurring tone value fluctuations are to be compensated for by modified ink drop sizes, causing additional binary values to be ignored by the machine in a regular print mode, and assigning additional binary values to modified ink drop sizes in a correction print mode.

First claim

The invention claimed is:

1. A method for compensating for occurring tone value fluctuation in an inkjet printing operation of an inkjet printing machine by using a computer, the method comprising the following steps:
generating a multi-bit halftone image of pixels on a computer during a screening process of a preprint process for every color separation with multiple tone values out of print image data;
then forwarding the multi-bit halftone image to a control unit of the inkjet printing machine, and printing the multi-bit halftone on the printing machine, with every encoded binary value of the multi-bit halftone image corresponding to an ink drop size that may be generated by the inkjet printing machine; and
introducing, by using the computer, additional binary values of the multi-bit halftone image not corresponding to any ink drop size in pixel positions of the multi-bit halftone image where occurring tone value fluctuations are to be compensated for by modified ink drop sizes, causing the additional binary values to be ignored by the inkjet printing machine in a regular print mode, and assigning the additional binary values to the modified ink drop sizes in a correction print mode.

2. The method according to claim 1 , which further comprises:
generating the multi-bit halftone image in the screening process using multi-bit masks each corresponding to a corresponding tone value; and
inserting the additional binary values into the multi-bit masks by the computer, causing the additional binary values to be incorporated into the multi-bit halftone in the screening process.

3. The method according to claim 1 , wherein each one of the additional binary values in the multi-bit halftone image being necessary for compensating for occurring tone value fluctuation, corresponds to an increased or reduced ink drop size.

4. The method according to claim 3 , wherein when tone value fluctuation with increased ink drop sizes is to be compensated for, the ink drop sizes of pixels of the multi-bit halftone image may only be increased or remain the same.

5. The method according to claim 4 , wherein when tone value fluctuation with decreased ink drop sizes is to be compensated for, the ink drop sizes of pixels of the multi-bit halftone image may only be reduced or remain the same.

6. The method according to claim 1 , which further comprises using sensors in the inkjet printing machine to detect occurring tone value fluctuations to be forwarded to the control unit of the inkjet printing machine.

7. The method according to claim 1 , which further comprises using a compensation algorithm on the control unit of the inkjet printing machine to carry out the compensation of occurring tone value fluctuations by using the additional binary values in the multi-bit halftone image.

8. The method according to claim 1 , which further comprises encoding the multi-bit halftone image with a 2-bit width, and providing the inkjet printing machine with a capability of printing three different ink drop sizes.

9. The method according to claim 1 , which further comprises encoding the multi-bit halftone image with a bit width of at least 3, and providing the inkjet printing machine with a capability of printing three different ink drop sizes.

Assignees

• Heidelberger Druckmasch Ag

Inventors

• Kirchhoff Dirk
• Stritzel Bernd
• Kaiser Michael

Classifications

• H04N1/4057 Primary

  the pattern being a mixture of differently sized sub-patterns, e.g. spots having only a few different diameters (multi-toning H04N1/40087) · CPC title

• B41J2/2132

  Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding (methods for local corrections by dot omission, image edge enhancement, or multi-pass mask selection G06K15/102; colour conversion H04N1/40) · CPC title

• H04N1/407

  Control or modification of tonal gradation or of extreme levels, e.g. background level · CPC title

• B41J2025/008

  comprising a plurality of print heads placed around a drum · CPC title

• B41J29/393 Primary

  Devices for controlling or analysing the entire machine {; Controlling or analysing mechanical parameters involving printing of test patterns} · CPC title