Generating halftones

Patent metadata

Field	Value
Publication number	US-10306108-B2
Application number	US-201816039694-A
Country	US
Kind code	B2
Filing date	Jul 19, 2018
Priority date	Feb 1, 2017
Publication date	May 28, 2019
Grant date	May 28, 2019

Abstract

A halftone comprises a first halftone screen and a second halftone screen. The first halftone screen comprises a first plurality of amplitude modulated dots arranged according to a first plurality of rows, the first plurality of rows being orientated according to a first direction and comprising a first dot spacing. The second halftone screen comprises a second plurality of amplitude modulated dots arranged according to a second plurality of rows, the second plurality of row being orientated in a second direction and comprising a second dot spacing. The first direction and the second direction define an angle of 45 degrees or less and a ratio of the second dot spacing to the first dot spacing is less than one.

First claim

What is claimed is:

1. An apparatus comprising:
a colorant deposition system to deposit a plurality of colorants on a medium;
a processor; and
a memory storing computer-executable instructions which, when executed by the processor, cause the processor to:
control the colorant deposition system to deposit a first colorant in the plurality of colorants onto the medium to form first plurality of amplitude modulated dots and to deposit a second colorant in the plurality of colorants onto the medium to form a second plurality of amplitude modulated dots;
wherein:
the second plurality of amplitude modulated dots are arranged according to an offset shift with respect to the first plurality of amplitude modulated dots, the offset shift defined by a shift vector S=[s 1 , s 2 ], wherein s 1 and s 2 are integer values that represent an offset distance for a dot in the second plurality of amplitude modulated dots from a given cell center in the first plurality of amplitude modulated dots, where S=[s 1 , s 2 ]=[(m 1 −m 2 )/2, (m 1 +m 2 )/2] and where m 1 and m 2 are integer values that represent a distance between respective cell centers in an addressable pixel grid.

2. The apparatus of claim 1 , wherein the first plurality of amplitude modulated dots are of a different color than the second plurality of amplitude modulated dots.

3. The apparatus of claim 1 , wherein the first plurality of amplitude modulated dots has a dot spacing that defines a resolution of 160 lines per inch and the second plurality of amplitude modulated dots has a dot spacing that defines a resolution of 225 lines per inch.

4. The apparatus of claim 1 , wherein the first plurality of amplitude modulated dots has a first dot spacing and the second plurality of amplitude modulated dots has a second dot spacing and wherein a ratio of the second dot spacing to the first dot spacing is ½√{square root over (2)}.

5. The apparatus of claim 1 , wherein the shift vector has an angle of 45 degrees with respect to the addressable pixel grid.

6. The apparatus of claim 1 , wherein the first plurality of amplitude modulated dots has a first resolution and the second plurality of amplitude modulated dots has a second resolution and wherein a ratio of the first resolution to the second resolution is less than one.

7. An apparatus comprising:
a colorant deposition system to deposit a plurality of colorants on a medium;
a processor; and
a memory storing computer-executable instructions which, when executed by the processor, cause the processor to:
control the colorant deposition system to deposit a first colorant in the plurality of colorants onto the medium to form first plurality of amplitude modulated dots and to deposit a second colorant in the plurality of colorants onto the medium to form a second plurality of amplitude modulated dots;
wherein the first and second plurality of amplitude modulated dots are arranged to meet a harmonic condition defined by a relative angular separation and relative resolution that minimizes moiré interference in an image composed of both pluralities of amplitude modulated dots.

8. The apparatus of claim 7 , wherein the second plurality of amplitude modulated dots are arranged according to an offset shift with respect to the first plurality of amplitude modulated dots, the offset shift defined by a shift vector S=[s 1 , s 2 ], wherein s 1 and s 2 are integer values that represent an offset distance for a dot in the second plurality of amplitude modulated dots from a given cell center in the first plurality of amplitude modulated dots, where S=[s 1 , s 2 ]=[(m 1 −m 2 )/2, (m 1 +m 2 )/2] and where m 1 and m 2 are integer values that represent a distance between respective cell centers in an addressable pixel grid.

9. The apparatus of claim 8 , wherein the shift vector has an angle of 45 degrees with respect to the addressable pixel grid.

10. The apparatus of claim 7 , wherein the first plurality of amplitude modulated dots are of a different color than the second plurality of amplitude modulated dots.

11. The apparatus of claim 7 , wherein the first plurality of amplitude modulated dots has a dot spacing that defines a resolution of 160 lines per inch and the second plurality of amplitude modulated dots has a dot spacing that defines a resolution of 225 lines per inch.

12. The apparatus of claim 7 , wherein the first plurality of amplitude modulated dots has a first dot spacing and the second plurality of amplitude modulated dots has a second dot spacing and wherein a ratio of the second dot spacing to the first dot spacing is ½√{square root over (2)}.

13. The apparatus of claim 7 , wherein the first plurality of amplitude modulated dots has a first resolution and the second plurality of amplitude modulated dots has a second resolution and wherein a ratio of the first resolution to the second resolution is less than one.

14. A method of minimizing moiré interference in an image, the method comprising:
controlling a colorant deposition system to deposit a first colorant in a plurality of colorants onto a medium to form first plurality of amplitude modulated dots and to deposit a second colorant in the plurality of colorants onto the medium to form a second plurality of amplitude modulated dots;
wherein the first and second plurality of amplitude modulated dots are arranged to meet a harmonic condition defined by a relative angular separation and relative resolution that minimizes moiré interference in an image composed of both pluralities of amplitude modulated dots.

15. The method of claim 14 , wherein:
the first plurality of amplitude modulated dots are deposited with a dot spacing in which dots are separated by five pixels in an X 1 direction and one pixel in an X 2 direction orthogonal to X 1 ; and
the second plurality of amplitude modulated dots are deposited with a dot spacing in which dots are separated by two pixels in the X 1 direction and three pixels in the X 2 direction.

16. The method of claim 14 , further comprising depositing the first plurality of amplitude modulated dots with a different colorant than the second plurality of amplitude modulated dots.

17. The method of claim 14 , further comprising depositing a third plurality of amplitude modulated dots, where an orientation of the third plurality of amplitude modulated dots is based on orientation of the first plurality of amplitude modulated dots.

18. The method of claim 14 , wherein the second plurality of amplitude modulated dots are arranged according to an offset shift with respect to the first plurality of amplitude modulated dots, the offset shift defined by a shift vector S=[s 1 , s 2 ], wherein s 1 and s 2 are integer values that represent an offset distance for a dot in the second plurality of amplitude modulated dots from a given cell center in the first plurality of amplitude modulated dots, where S=[s 1 , s 2 ]=[(m 1 −m 2 )/2, (m 1 +m 2 )/2] and where m 1 and m 2 are integer values that represent a distance between respective cell centers in an addressable pixel grid.

19. The method of claim 18 , wherein the shift vector has an angle of 45 degrees with respect to the addressable pixel grid.

20. The method of claim 18 , wherein the first plurality of amplitude modulated dots has a first dot spacing and the second plurality of amplitude modulated dots has a second dot spacing and wherein a ratio of the second dot spacing to the first dot spacing is ½√{square root over (2)}.

Assignees

• Hp Indigo Bv

Inventors

• Frank Tal
• Kella Dror
• Tagansky Boaz
• Haik Oren
• Ben-Shoshan Yotam
• Limonov Marina
• Dagan Ram

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

• H04N1/6008

  with primary colour signals, e.g. RGB or CMY(K) · CPC title

• H04N1/6058

  Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut · CPC title

• H04N1/52 Primary

  Circuits or arrangements for halftone screening · CPC title