Apparatus and method using a mask producing a halftone image with centroids of clusters distributed stochastically and bridged-cluster combinations depending on threshold lightness levels

Patent metadata

Field	Value
Publication number	US-9749497-B2
Application number	US-201515109635-A
Country	US
Kind code	B2
Filing date	Jan 22, 2015
Priority date	Jan 22, 2014
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

There is provided an ink-deposition device suitable for depositing ink on a target surface and a printing system comprising the same. In operation in a printing system, the ink-deposition device can convert digital images into ink images on the target surface using pixel-masks and methods as disclosed herein. Advantageously, the ink-deposition device, the printing system comprising it and the methods of using the same can reduce or prevent the occurrence of some undesired ink-formations typically governed by the respective physical and/or chemical properties of the surface and ink being used or mitigate their effect on print quality. Application of the pixel-image mask yields a binary image that exhibits pixel-clusters with stochastically distributed centroids.

First claim

What is claimed is:

1. A method of digital printing comprising:
a. electronically applying an N×M pixel-image mask to a target non-binary multi-level digital image to obtain therefrom a target binary digital image; and
b. converting the target binary digital image into an ink image by ink deposition onto a target surface, wherein variables L, M, N, r, s, p, y are defined such that L is a positive integer equal to at least 64, M and N are each positive integers that are each equal to at least 16, s is a positive integer having a value between 1 and y*L, p is a positive number having a value of at least 30, y is a positive number having a value of at most 0.05, and r is a positive number having a value of at least 0.5, and wherein the N×M pixel-image mask has all of the following properties:
i. a total number of lightness levels of the pixel-image mask is at least L;
ii. at sub-threshold lightness levels below a threshold lightness level, application of the pixel-image mask to a uniform-lightness N×M digital image yields a sub-threshold-lightness-level binary image characterized by an array of pixel-clusters, centroids of clusters of the array being spatially distributed according to a stochastic pattern;
iii. at the threshold lightness level, application of the pixel-image mask to a uniform-lightness N×M digital image yields a threshold-lightness-level binary image characterized by an array of pixel-clusters, centroids of clusters of the array being spatially distributed according to a stochastic pattern, the threshold-lightness-level binary image being further characterized such that, within an ink-image-space defined according to the ink-deposition process of step (b), at least p % of all pixels-clusters of the array of pixel-clusters nearly touch a neighboring pixel-cluster without touching;
iv. at a threshold-succeeding lightness level that is s lightness levels above the threshold lightness level, application of the pixel-image mask to a uniform-lightness N×M digital image yields a threshold-succeeding binary image characterized, within the ink-image-space, by a ratio r between (i) a number of 3+-bridged-cluster combinations and (ii) a number of 2-bridged-cluster combinations.

2. The method of claim 1 , wherein a value of p is at least 40.

3. The method of claim 1 , wherein a value of r is at least 0.6.

4. The method of claim 1 , wherein a product of N and M is at least 250.

5. The method of claim 1 , wherein at least a majority, or at least a substantial majority, or all of the pixel-clusters of the threshold-lightness-level binary image are of substantially the same size.

6. The method of claim 1 , wherein the stochastic pattern is a blue-noise pattern.

7. The method of claim 1 , wherein the target surface is a surface of an intermediate transfer member (ITM), the method further comprising transferring the ink-image from the surface of the ITM to a printing substrate.

8. The method of claim 1 , wherein the N×M pixel-image mask is defined so that the threshold-lightness-level binary image comprises at least 10 pixel-clusters.

9. The method of claim 1 , wherein the N×M pixel-image mask is defined so that the threshold-lightness-level binary image comprises at least 10 pixel-clusters.

10. The method of claim 1 , wherein the ink is aqueous and/or the target surface is hydrophobic.

11. The method of claim 1 , wherein the ink substantially does not penetrate into the target surface.

12. A printing system for converting digital images into ink-images, the printing system comprising:
a. an ink-deposition device capable of depositing ink on a target surface to form the ink-images thereon;
b. an electronic controller for regulating the ink depositing by the ink-deposition device so that the printing system converts digital images into the ink-images according to a N×M pixel-mask such that wherein variables L, M, N, r, s, p, y are defined such that L is a positive integer equal to at least 64, M and N are each positive integers that are each equal to at least 16, s is a positive integer having a value between 1 and y*L, p is a positive number having a value of at least 30, y is a positive number having a value of at most 0.05, and r is a positive number having a value of at least 0.5, and wherein the N×M pixel-image mask has all of the following properties:
i. a total number of lightness levels of the pixel-image mask is at least L;
ii. at sub-threshold lightness levels below a threshold lightness level, application of the pixel-image mask to a uniform-lightness N×M digital image yields a sub-threshold-lightness-level binary image characterized by an array of pixel-clusters, centroids of clusters of the array being spatially distributed according to a stochastic pattern;
iii. at the threshold lightness level, application of the pixel-image mask to a uniform-lightness N×M digital image yields a threshold-lightness-level binary image characterized by an array of pixel-clusters, centroids of clusters of the array being spatially distributed according to a stochastic pattern, the threshold-lightness-level binary image being further characterized such that, within an ink-image-space defined by the ink-deposition device, at least p % of all pixels-clusters of the array of pixel-clusters nearly touch without touching;
iv. at a threshold-succeeding lightness level that is s lightness levels above the threshold lightness level, application of the pixel-image mask to a uniform-lightness N×M digital image yields a threshold-succeeding binary image characterized, within the ink-image-space, by a ratio r between (i) a number of 3+-bridged-cluster combinations and (ii) a number of 2-bridged-cluster combinations.

13. The system of claim 12 , wherein a product of N and M is at least 250.

14. The system of claim 12 , wherein at least a majority, or at least a substantial majority, or all of the pixel-clusters of the threshold-lightness-level binary image are of substantially the same size.

15. The system of claim 12 , wherein the stochastic pattern is a blue-noise pattern.

16. The system of claim 12 , wherein the surface is an intermediate transfer member (ITM), the system further comprising an impression station configured to transfer the ink-images from the surface of the ITM to a printing substrate.

17. The system of claim 12 , wherein the threshold-lightness-level binary image comprises at least 10 pixel-clusters.

18. The system of claim 12 , wherein the threshold-lightness-level binary image comprises at least 10 pixel-clusters or at least 20 pixel-clusters.

19. The system of claim 12 , wherein the ink is aqueous and/or the target surface is hydrophobic.

20. The system of claim 12 , wherein the ink substantially does not penetrate into the surface.

Assignees

• Landa Corp Ltd

Inventors

• Litvak Mattetyahu
• Klinger Shahar
• Siman Tov Alon
• Guttman Avraham

Classifications

• H04N1/405

  Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels · CPC title

• H04N1/4055 Primary

  producing a clustered dots or a size modulated halftone pattern · CPC title

• G06K15/1881

  Halftoning (halftoning of still images in general H04N1/405, H04N1/52) · CPC title

• H04N1/4051 Primary

  producing a dispersed dots halftone pattern, the dots having substantially the same size (different sizes H04N1/4057) · CPC title

• H04N1/409

  Edge or detail enhancement; Noise or error suppression · CPC title