Ink jet printing apparatus performing printing with correction of image data at boundary portion of image

• US 6,033,137 A
• Filed: 09/12/1996
• Issued: 03/07/2000
• Est. Priority Date: 09/14/1995
• Status: Expired due to Term

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Ito, Yoshikuni
• Primary Examiner(s): EICKHOLT, EUGENE H
• Application Number:
  US08/715,364
• Time in Patent Office: 1,272 Days
• Field of Search: 400/74, 347/19, 395/117
• US Class Current: 400/74
• CPC Class Codes: G06K 15/102 using ink jet print heads
• CPC Class Codes: G06K 2215/0082 Architecture adapted for a particular function
• CPC Class Codes: H04N 1/4015 of the reproducing head
• CPC Class Codes: H04N 1/4078 using gradational references, e.g. grey-scale test pattern analysis

Abstract

When degree of a streak of density fluctuation is varied mainly due to variation of a printing medium to be used and/or variation of use environment of an apparatus to be impossible to correct the density fluctuation, a test pattern is first output with maintaining a second image correcting portion for correction inoperative. A correction coefficient of an image signal corresponding to ink ejection openings at end portions is then set depending upon density fluctuation ΔC_SUM on the ink ejection openings at the end portions obtained from the result of reading. By this, in an ink jet printing apparatus, the streak in a printed image can be constantly restricted irrespective of variation of the printing medium to be used and/or use environment of the apparatus.

Claims

1. An ink jet printing apparatus using a printing head having a plurality of ink ejection elements arranged in a predetermined direction and performing printing on a printing medium on a basis of image data corresponding to said plurality of ink ejection elements, said apparatus comprising:

test pattern printing means for printing a test pattern, based on the image data corresponding to the test pattern, on the printing medium to be used for printing by using the ink ejection elements of the printing head;

reading means for reading density of the test pattern printed by said test pattern printing means so as to obtain density corresponding to each of said plurality of ink ejection elements used for printing said test pattern;

setting means for setting correction data for correcting the image data corresponding to the ink ejection elements used for printing portions including at least both end portions of a printing region to be printed, on a basis of differences between the density corresponding to a first group of ink ejection elements including ink ejection elements at both end portions of the printing region and an average density value corresponding to a second group of ink ejection elements that excludes the first group of ink ejection elements;

correction means for correcting the image data corresponding to said ink ejection elements at both end portions on a basis of the correction data set by said setting means; and

controlling means for controlling correction of the image data performed by said correction means, the image data corresponding to the test pattern, when said setting means sets the correction data corresponding to the ink ejection elements, wherein said controlling means controls said correction means based on the correction data respectively corresponding to the first group of ink ejection elements and the second group of ink ejection elements.

2. An ink jet printing apparatus as claimed in claim 1, which further comprises scanning means for scanning said printing head in a direction different from said predetermined direction, and wherein said printing region is printed by said ink ejection elements to be used for printing during scanning of said printing head by said scanning means.

3. An ink jet printing apparatus as claimed in claim 2, wherein said ink ejection elements located at both end portions of said printing region are ink ejection elements at both end portions in an array of said plurality of ink ejection elements.

4. An ink jet printing apparatus as claimed in claim 1, wherein said image data is a plurality of kinds of density data, said correction means performs correction by performing matrix operation with respect to said plurality of kinds of density data, and said correction data is a coefficient for said matrix operation.

5. An ink jet printing apparatus as claimed in claim 4, wherein said coefficient for said matrix operation is obtained as a table output depending upon said plurality of kinds of density data to be corrected.

6. An ink jet printing apparatus as claimed in claim 5, wherein said plurality of kinds of density data are density data of cyan, magenta, yellow and black.

7. An ink jet printing apparatus as claimed in claim 1, wherein said correction means is one of a plurality of correction means, and further comprising a switching means for switching correction of said plurality of correction means between effective and not effective.

8. An ink jet printing apparatus as claimed in claim 7, wherein said switching means makes correction effective when the image data corresponds to the end portion of said printing region.

9. An ink jet printing apparatus as claimed in claim 8, wherein another one of said plurality of correction means performs correction for uniformly reducing the value of said image data depending upon values of said image data.

10. An ink jet printing apparatus as claimed in claim 7, wherein switching of said plurality of correction means is performed depending upon a kind of printing medium.

11. An ink jet printing apparatus as claimed in claim 1, wherein said correction means varies current correction amount depending upon a kind of printing medium.

12. An ink jet printing apparatus as claimed in claim 7, wherein the printing head has a thermal energy generating element for generating thermal energy to be utilized for ink ejection.

13. An ink jet system using a printing head having a plurality of ink ejection elements arranged in a predetermined direction and performing printing on a printing medium on a basis of image data corresponding to said plurality of ink ejection elements, said system comprising:

test pattern printing means for printing a test pattern, based on the image data corresponding to the test pattern, on the printing medium to be used for printing by using the ink ejection elements of the printing head;

reading means for reading density of the test pattern printed by said test pattern printing means so as to obtain density corresponding to each of said plurality of ink ejection elements used for printing said test pattern;

setting means for setting correction data for correcting the image data corresponding to the ink ejection elements used for printing both end portions of a printing region to be printed, on a basis of differences between the density corresponding to a first group of ink ejection elements including at least ink ejection elements at both end portions of the printing region and an average density value corresponding to a second group of ink ejection elements that excludes the first group of ink ejection elements;

correction means for correcting the image data corresponding to said ink ejection elements at both end portions on a basis of the correction data set by said setting means; and

controlling means for controlling correction of the image data performed by said correction means, the image data corresponding to the test pattern, when said setting means sets the correction data corresponding to the ink ejection elements, wherein said controlling means controls said correction means based on the correction data respectively corresponding to the first group of ink ejection elements and the second group of ink ejection elements.

14. A method of correcting a density fluctuation in an image printed in an ink jet printing apparatus using a printing head having a plurality of ink ejection elements arranged in a predetermined direction and performing printing on a printing medium on a basis of image data corresponding to said plurality of ink ejection elements, said method comprising the steps of:

printing a test pattern, based on the image data corresponding to the test pattern, on the printing medium to be used for printing by using the ink ejection elements of the printing head;

reading a density of the printed test pattern so as to obtain density corresponding to each of the plurality of ink ejection elements used for printing said test pattern;

setting correction data for correcting the image data corresponding to the ink ejection elements used for printing portions including at least both end portions of a printing region to be printed, on a basis of differences between the density corresponding to a first group of ink ejection elements including at least ink ejection elements at both end portions of the printing region and an average density value corresponding to a second group of ink ejection elements that excludes the first group of ink ejection elements;

correcting the image data corresponding to said ink ejection elements at both end portions on a basis of the set correction data; and

controlling correction of the image data performed in said correcting step, the image data corresponding to the test pattern, before said setting step sets the correction data corresponding to the ink ejection elements.

15. An ink jet printing apparatus using a printing head having a plurality of ink ejection elements arranged in a predetermined direction and performing printing on a printing medium on a basis of image data corresponding to said plurality of ink ejection elements, said apparatus comprising:

a first correction portion for correcting the image data corresponding to the ink ejection elements of end portions of the arranged ink ejection elements so that density indicated by said image data is decreased;

a second correction portion for correcting the image data corresponding to said ink ejection elements of said end portions on a basis of the density indicated by the image data corresponding to the plurality of ink ejection elements;

a print control portion for driving the printing head on a basis of the image data corrected by both said first correction portion and said second correction portion to perform printing; and

a controlling portion for controlling correction respectively performed by said first correction portion and said second correction portion.

16. An ink jet printing apparatus as claimed in claim 15, wherein said first correction portion effects gamma correction for correcting the image data.

17. An ink jet printing apparatus as claimed in claim 15, wherein said first correction portion corrects the image data using conversion characteristics that are selectable based upon the image data.

18. An ink jet printing apparatus as claimed in claim 17, wherein the conversion characteristics are predetermined stored values.

19. An ink jet printing apparatus as claimed in claim 17, wherein the conversion characteristics comprise a family of curves whose gradients vary in correspondence with the image data.

20. An ink jet printing apparatus as claimed in claim 15, wherein said second correction portion corrects the image data using correction coefficients that are selectable based upon the image data.

21. An ink jet printing apparatus as claimed in claim 20, wherein the correction coefficients are predetermined stored values.

22. An ink jet printing apparatus as claimed in claim 20, wherein the correction coefficients comprise matrix coefficients whose magnitudes vary in correspondence with the image data.

23. An ink jet printing apparatus as claimed in claim 15, further comprising switching means for switching said first correction portion and said second correction portion between being effective and not effective.

24. An ink jet printing apparatus as claimed in claim 23, wherein switching of said first and second correction portions is performed depending upon a kind of printing medium.

25. A method of correcting a density fluctuation in an image printed in an ink jet printing apparatus using a printing head having a plurality of ink ejection elements arranged in a predetermined direction and performing printing on a printing medium on a basis of image data corresponding to said plurality of ink ejection elements, said method comprising the steps of:

correcting, in a first correction step, the image data corresponding to the ink ejection elements of end portions of the plurality of ink ejection elements so that density indicated by said image data is decreased;

correcting, in a second correction step, the image data corresponding to the ink ejection elements of the end portions on a basis of the density indicated by the image data corresponding to the plurality of ink ejection elements;

driving, in a printing step, the printing head on a basis of the image data corrected in both said first correction step and said second correction step to perform printing; and

controlling correction respectively performed in said first correction step and said second correction step.

26. A method as claimed in claim 25, wherein said first correction step effects gamma correction for correcting the image data.

27. A method as claimed in claim 25, wherein said first correction step corrects the image data using conversion characteristics that are selectable based upon the image data.

28. A method as claimed in claim 27, wherein the conversion characteristics are predetermined stored values.

29. A method as claimed in claim 27, wherein the conversion characteristics comprise a family of curves whose gradients vary in correspondence with the image data.

30. A method as claimed in claim 25, wherein said second correction step corrects the image data using correction coefficients that are selectable based upon the image data.

31. A method as claimed in claim 30, wherein the correction coefficients are predetermined stored values.

32. A method as claimed in claim 30, wherein the correction coefficients comprise matrix coefficients whose magnitudes vary in correspondence with the image data.

33. A method as claimed in claim 25, further comprising a switching step for switching said first correction step and said second correction step between being executed and not executed.

34. An ink jet printing apparatus as claimed in claim 33, wherein switching of said first and second correction steps is performed depending upon a kind of printing medium.