Halftone process giving specified characteristics to particular dot patterns, and generating and evaluating a dither matrix therefor

• US 7,715,053 B2
• Filed: 09/13/2006
• Issued: 05/11/2010
• Est. Priority Date: 09/15/2005
• Status: Expired due to Fees

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kakutani, Toshiaki
• Primary Examiner(s): Rogers; Scott A
• Application Number:
  US11/521,232
• Publication Number:
  US 20070058204A1
• Time in Patent Office: 1,336 Days
• Field of Search: 358/1.9, 358/3.02, 358/3.06, 358 309- 317, 358/3.2, 358/3.21, 358/3.26, 358534-536, 347/15, 347/41, 347/43
• US Class Current: 358/3.06
• 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 method for performing a halftone process on image data representing input tone values of pixels constituting an original image to determine dot formation on each print pixel of a print image to be formed on a print medium, generating dot data representing the determined dot formation, and forming a dot on each of the print pixels for generating the print image according to the dot data. The step of generating the print image includes mutually combining dots formed on print pixels belonging to each of a plurality of pixel groups in a common print area, the plurality of pixel groups having a physical difference at dot formation, the dot formation being performed with respect to each of the pixel groups. A plurality of pixel groups having a physical commonality for the dot formation among the plurality of pixel groups constitute a pixel group family. The halftone process is configured to give specified characteristics with a first dot pattern being formed on print pixels of the print image, a second dot pattern being formed on print pixels belonging to each of the plurality of pixel groups, and a third dot pattern being formed on print pixels belonging to the pixel group family.

Claims

1. A printing method of printing on a printing medium, comprising:

a dot data generating step of performing a halftone process on image data representing a input 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 generating step using a printing device to form a dot on each of the print pixels for generating the print image according to the dot data, wherein

the print image generating step includes the step of generating the print image by mutually combining dots formed on print pixels belonging to each of a plurality of pixel groups in a common print area, the plurality of pixel groups having a physical difference each other at the dot formation, the dot formation being performed with respect to each of the pixel groups;

a plurality of pixel groups having a physical commonality for the dot formation among the plurality of pixel groups constitute a pixel group family; and

the halftone process is configured to give specified characteristics to all of a first dot pattern, a second dot pattern, and a third dot pattern, the first dot pattern being formed on print pixels of the print image, the second dot pattern being formed on print pixels belonging to each of the plurality of pixel groups, and the third dot pattern being formed on print pixels belonging to the pixel group family.

2. The printing method according to claim 1, wherein

the specified characteristic is a granularity evaluation value.

3. The printing method according to claim 1, wherein

the specified characteristic is either one of blue noise characteristics and green noise characteristics.

4. The printing method according to claim 1, wherein

the halftone process is constituted based on an evaluation value calculated by multiplying a specified weighting to a print image characteristics, a pixel group characteristics, and a pixel group family characteristics and summing the weighted print image characteristics, the weighted pixel group characteristics, and the weighted pixel group family characteristics, the print image characteristic being the specified characteristic of dot pattern formed on each printing pixel of the printing image, the pixel group characteristics being the specified characteristic of dot pattern formed on the print pixels belonging to each of the plurality of pixel groups, the pixel group family characteristics being the specified characteristic of dot pattern formed on the print pixels belonging to the pixel group family, and

the specified weighting is set such that a first weighting multiplied on the print image characteristics is largest, a second weighting multiplied on the pixel group characteristics is smallest, and the weighting multiplied on the pixel group family characteristics is smaller than the first weighting and the same or greater than the second weighting.

5. The printing method according to claim 1, wherein

the print image generating step includes the step of generating the print image by forming dots on each of the print pixels according to the dot data, while performing a main scan of a printing head for ejecting ink for forming dots, with both outgoing movement and return movement of the printing head, and

the pixel group family includes a first pixel group family consisting of a plurality of pixel groups for which dots are formed during the outgoing movement of the printing head, and a second pixel group family consisting of a plurality of pixel groups for which dots are formed during the return movement of the printing head.

6. The printing method according to claim 5, wherein

the halftone process is configured such that any of correlation coefficient between any of a first granularity evaluation value, a second granularity evaluation value, and a third granularity evaluation value is 0.7 or greater, the first granularity evaluation value being a granularity evaluation value of dot pattern formed on the print pixels of the print image, the second granularity evaluation value being a granularity evaluation value of dot patterns formed on print pixels belonging to the first pixel group family, the third granularity evaluation value being a granularity evaluation value of dot patterns formed on print pixels belonging to the second pixel group family.

7. The printing method according to claim 5, wherein

the halftone process is configured such that any of correlation coefficient between any of a first spatial frequency distribution, a second spatial frequency distribution, and a third spatial frequency distribution is 0.7 or greater, the first spatial frequency distribution being a spatial frequency distribution of dot pattern formed on the print pixels of the print image, the second spatial frequency distribution being a spatial frequency distribution of dot patterns formed on the print pixels belonging to the first pixel group family, the third spatial frequency distribution being a spatial frequency distribution of dot patterns formed on the print pixels belonging to the second pixel group family.

8. A dither matrix method of generating a dither matrix for determining a status of dot formation on each print pixel of a print image to be formed on a printing medium by performing a halftone process on input image data, wherein

the print image is formed by mutually combining dots formed on print pixels belonging to each of a plurality of pixel groups for which a physical difference is assumed with dot formation using the print image generating step, in a common print area, wherein

the dither matrix generating method comprises:

a focus threshold value setting step using a printing device, a dither matrix generating device, or a computer, to set a specific threshold value as a focus threshold value from among a plurality of threshold values to be stored in each of elements of the dither matrix, the specific threshold value being for which a storage element is not yet set and for which dot formation turns on most easily among the plurality of threshold values;

a matrix evaluation step of setting a comprehensive evaluation value for each assumption that the focus threshold value is stored in each of blank elements that are elements for which stored threshold values are not yet set, wherein dots are regarded as being formed on the pixels corresponding to already set elements that are elements for which the stored threshold values are already set,

a storage element setting step of setting the element for storing the focus threshold value according to the comprehensive evaluation value, and

a repetition step of repeating each of the steps from the focus threshold value setting step to the storage element setting step, for at least part of the plurality of threshold values, wherein

the matrix evaluation step comprises;

an overall evaluation value setting step of setting an overall evaluation value by evaluating the status of dot formation corresponding to all of the groups of the already set elements,

a group evaluation value setting step of setting a group evaluation value by evaluating the status of dot formation corresponding only to elements belonging to a rating group selected from among a plurality of element groups corresponding to the plurality of pixel groups among the already set elements,

a group family evaluation value setting step of setting a group family evaluation value by evaluating the status of dot formation corresponding only to elements belonging to an element group family that is a combination of the rating group and an element group having a physical commonality with the rating group for a dot formation, among the plurality of element groups, and

a comprehensive evaluation value setting step of setting a comprehensive evaluation value according to the overall evaluation value, the group evaluation value, and the group family evaluation value.

9. The dither matrix generating method according to claim 8, wherein

the comprehensive evaluation value setting step includes the step of setting the comprehensive evaluation value by multiplying a specified weighting on the overall evaluation value, the group evaluation value, and the group family evaluation value and summing the weighted overall evaluation value, the weighted group evaluation value, and the weighted group family evaluation value, and

the specified weighting is set such that the first weighting multiplied on the overall evaluation value is the largest, the second weighting multiplied on the group evaluation value is smallest, the weighting multiplied on the groups group evaluation value is smaller than the first weighting and the same or greater than the second weighting.

10. A printing apparatus for printing on a printing medium, comprising:

a dot data generator that performs a halftone process on image data representing a input 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 the print image according to the dot data, wherein

the print image generator generates the print image by mutually combining dots formed on print pixels belonging to each of a plurality of pixel groups in a common print area, the plurality of pixel groups having a physical difference each other at the dot formation, the dot formation being performed with respect to each of the pixel groups;

a plurality of pixel groups having a physical commonality for the dot formation among the plurality of pixel groups constitute a pixel group family; and

the halftone process is configured to give specified characteristics to all of a first dot pattern, a second dot pattern, and a third dot pattern, the first dot pattern being formed on print pixels of the print image, the second dot pattern being formed on print pixels belonging to each of the plurality of pixel groups, and the third dot pattern being formed on print pixels belonging to the pixel group family.