Image processing device and printing apparatus for performing bidirectional printing

• US 8,379,271 B2
• Filed: 02/25/2011
• Issued: 02/19/2013
• Est. Priority Date: 02/09/2005
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kakutani, Toshiaki
• Primary Examiner(s): TRAN, DUNG D
• Application Number:
  US13/035,361
• Publication Number:
  US 20110141527A1
• Time in Patent Office: 725 Days
• Field of Search: None
• US Class Current: 358/3.06
• CPC Class Codes: H04N 1/4015 of the reproducing head
• CPC Class Codes: H04N 1/4051 producing a dispersed dots halftone pattern, the dots having substantially the same size different sizes H04N1/4057

Abstract

A printing apparatus performs printing on a print medium. The printing apparatus includes: a dot data generator that performs a halftone process on image data, wherein the print image is formed by mutually combining print pixels belonging to each of a plurality of pixel position groups for which a physical difference is assumed at a formation of dots by the print image generator, in a common print area, and the halftone process is configured to determine the status of dot formation on each of the print pixels on an assumption of the physical difference.

Claims

1. A printing apparatus that performs printing on a print medium, comprising:

a dot data generator that performs a halftone process on image data representing a tone value of each of pixels constituting an original image to determine a status of dot formation on each of print pixels of a print image to be formed on the print medium, for generating dot data representing the determined status of dot formation, and

a print image generator that forms a dot on each of the print pixels for generating a print image according to the dot data, wherein

the print image is formed by mutually combining print pixels belonging to each of a plurality of pixel position groups for which a physical difference is assumed at a formation of dots by the print image generator, in a common print area, and

the halftone process is configured to generate the dot data, so that a pattern of dots belonging to each of the plurality of pixel position groups has either blue noise characteristics or green noise characteristics.

2. The printing apparatus according to claim 1, wherein

the physical difference includes a displacement of timing of dot formation for each of the plurality of pixel position groups.

3. The printing apparatus according to claim 2, wherein

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient of at least 0.7.

4. The printing apparatus according to claim 1, wherein

the physical difference includes a relative shift of dot position for each of the plurality of pixel position groups.

5. The printing apparatus according to claim 4, wherein

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient of at least 0.7.

6. The printing apparatus according to claim 1, wherein

the halftone process is further configured to provide each dot pattern with specified characteristics, each dot pattern including dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups.

7. The printing apparatus according to claim 4, wherein

the halftone process is further configured to provide a hypothetical print image on an assumption of none of the relative shift of dot position with specified characteristics.

8. The printing apparatus according to claim 4, wherein

the halftone process is further configured to provide a plurality of hypothetical print images with specified characteristics, the plurality of hypothetical print images including a first hypothetical print image on an assumption of the relative shift of dot position and a second hypothetical print image on an assumption of none of the relative shift of dot position.

9. The printing apparatus according to claim 1, wherein

the print image generator has a printing head and generates a print image by forming dots on each of the print pixels during forward scan and backward scan of the printing head, while performing a main scan of the printing head, and

the plurality of pixel position groups includes a first pixel position group for which dots are formed during the forward scan of the printing head and a second pixel position group for which dots are formed during the backward scan of the printing head.

10. The printing apparatus according to claim 1, wherein

the print image generator has a printing head and generates a print image by forming dots on each of the print pixels while repeating a pass of the printing head N times according to the dot data,

wherein N is an integer of 2 or more and is determined by a nozzle pitch, and wherein each of the plurality of pixel position groups is formed by two passes.

11. The printing apparatus according to claim 1, wherein

the print image generator has a plurality of printing heads and generates a print image by forming dots on each of the print pixels according to the dot data, while performing a main scan of the plurality of printing heads, and

the plurality of pixel position groups includes a plurality of pixel position groups for which each of the plurality of printing heads is in charge of the dot formation of each of the plurality of pixel position groups.

12. The printing apparatus according to claim 1, wherein

the print image generator has a plurality of printing heads and generates a print image by forming dots on each of the print pixels according to the dot data, while performing a sub-scan of the print medium, and

the plurality of pixel position groups includes a plurality of pixel position groups for which each of the plurality of printing heads is in charge of the dot formation of each of the plurality of pixel position groups.

13. The printing apparatus according to claim 9, wherein

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient.

14. The printing apparatus according to claim 9, wherein

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient of at least 0.7.

15. The printing apparatus according to claim 9, wherein

the halftone process is configured such that any first correlation coefficients are higher than any of second correlation coefficients at least for tone levels with relatively low dot density, wherein

the first correlation coefficients are coefficients between each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distribution of the print image, and

the second correlation coefficients are correlation coefficients between each of spatial frequency distributions of dot patterns formed on print pixels belonging to each of any of other of the plurality of the pixel position groups that form print images by mutually combining in a common print area and the spatial frequency distribution of the print image.

16. The printing apparatus according to claim 9, wherein

the halftone process is configured such that a RMS granularity of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups is lower than the RMS granularity of dot patterns formed on the print pixels belonging to each of any of other of the plurality of pixel position groups that form print images by mutually combining in a common print area, at least for tone levels with relatively low dot density.

17. A printing method of printing on a print medium, comprising:

performing a halftone process on image data representing a tone value of each of pixels constituting an original image to determine a status of dot formation on each of print pixels of a print image to be formed on the print medium, for generating dot data representing the determined status of dot formation, and

forming a dot on each of the print pixels for generating a print image according to the dot data, wherein

the print image is formed by mutually combining a plurality of pixel position groups for which a physical difference is assumed at a formation of dots by the print image generator, in a common print area, and

the halftone process is configured to generate the dot data, so that a pattern of dots belonging to each of the plurality of pixel position groups has either blue noise characteristics or green noise characteristics.

18. The printing method according to claim 17, wherein

the physical difference includes a displacement of timing of dot formation for each of the plurality of pixel position groups, and

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient of at least 0.7.

19. The printing method according to claim 17, wherein

the physical difference includes a relative shift of dot position for each of the plurality of pixel position groups, and

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient of at least 0.7.

20. A computer program product for causing a computer to generate print data to be supplied to a print image generator for generating a print image by forming dots on a print medium, the computer program product comprising:

a non-transitory computer readable medium; and

a computer program stored on the non-transitory computer readable medium, the computer program comprising a program for causing the computer to perform a halftone process on image data representing a tone value of each of pixels constituting an original image to determine a status of dot formation on each of print pixels of a print image to be formed on the print medium, for generating dot data representing the determined status of dot formation, wherein

the print image is formed by mutually combining print pixels belonging to each of a plurality of pixel position groups for which a physical difference is assumed at a formation of dots by the print image generator, in a common print area, and

the halftone process is configured to generate the dot data, so that a pattern of dots belonging to each of the plurality of pixel position groups has either blue noise characteristics or green noise characteristics.

21. The computer program product according to claim 20, wherein

the physical difference includes a displacement of timing of dot formation for each of the plurality of pixel position groups, and

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient of at least 0.7.

22. The computer program product according to claim 20, wherein

the physical difference includes a relative shift of dot position for each of the plurality of pixel position groups, and

the halftone process is configured such that each of spatial frequency distributions of dot patterns formed on the print pixels belonging to each of the plurality of pixel position groups and spatial frequency distributions of the print image have a mutually positive correlation coefficient of at least 0.7.

23. A printing apparatus that performs printing on a print medium, comprising:

a dot data generator that performs a halftone process on image data representing a tone value of each of pixels constituting an original image to determine a status of dot formation on each of print pixels of a print image to be formed on the print medium, for generating dot data representing the determined status of dot formation, and

a print image generator equipped with a printing head configured to generate a print image by forming dots on each of the print pixels during forward scan and backward scan of the printing head, while performing a main scan of the printing head, wherein

the print image is formed by mutually combining print pixels belonging to each of a plurality of pixel position groups including a first pixel position group for which dots are formed during the forward scan of the printing head and a second pixel position group for which dots are formed during the backward scan of the printing head,

the halftone process is configured to generate the dot data, so that a pattern of dots belonging to each of the plurality of pixel position groups has either blue noise characteristics or green noise characteristics, and

the halftone process is configured such that any of mutual correlation coefficients between a plurality of spatial frequency distributions consisting of spatial frequency distributions of dot patterns formed on the print pixels belonging to the first pixel position group, spatial frequency distributions of dot patterns formed on the print pixels belonging to the second pixel position group, and spatial frequency distributions of the print image is at least 0.7, at least for the tone level with relatively low dot density.

24. A printing method of printing on a print medium, comprising:

performing a halftone process on image data representing a tone value of each of pixels constituting an original image to determine a status of dot formation on each of print pixels of a print image to be formed on the print medium, for generating dot data representing the determined status of dot formation, and

forming dots on each of the print pixels during forward scan and backward scan of a printing head, while performing a main scan of the printing head, for generating a print image according to the dot data, wherein

the print image is formed by mutually combining print pixels belonging to each of a plurality of pixel position groups including a first pixel position group for which dots are formed during the forward scan of the printing head and a second pixel position group for which dots are formed during the backward scan of the printing head,

the halftone process is configured to generate the dot data, so that a pattern of dots belonging to each of the plurality of pixel position groups has either blue noise characteristics or green noise characteristics, and

the halftone process is configured such that any of mutual correlation coefficients between a plurality of spatial frequency distributions consisting of spatial frequency distributions of dot patterns formed on the print pixels belonging to the first pixel position group, spatial frequency distributions of dot patterns formed on the print pixels belonging to the second pixel position group, and spatial frequency distributions of the print image is at least 0.7, at least for the tone level with relatively low dot density.