METHOD FOR JUDGING IMAGE QUALITY USING HUMAN-READABLE DEFECT-SENSITIVE PATTERNS

• US 20030122887A1
• Filed: 12/28/2001
• Published: 07/03/2003
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: Kodak Alaris Inc (KPP (no. 2) Trustees Ltd.)
• Original Assignee: Eastman Kodak Company
• Inventors: Bland, William E.
• Granted Patent: US 6,598,953 B2
• Time in Patent Office: Days
• US Class Current: 347/19
• CPC Class Codes: B41J 11/46 by marks or formations on the paper being fed
• CPC Class Codes: B41J 11/663 Controlling cutting, cutting resulting in special shapes of the cutting line, e.g. controlling cutting positions, e.g. for cutting in the immediate vicinity of a printed image
• CPC Class Codes: B41J 11/68 cutting parallel to the direction of paper feed
• CPC Class Codes: B41J 11/70 cutting perpendicular to the direction of paper feed
• CPC Class Codes: B65H 2220/01 indicating an entity as a function of which control, adjustment or change is performed, i.e. input
• CPC Class Codes: B65H 2511/10 Size; Dimensions
• CPC Class Codes: B65H 2555/30 Multi-axis
• CPC Class Codes: B65H 35/0006 Article or web delivery apparatus incorporating cutting or line-perforating devices
• CPC Class Codes: G06K 15/027 Test patterns and calibration arrangements for controlling or analysing printing mechanisms of typewriters or selective printing units B41J29/393 takes precedence; colour correction using test pattern analysis in general H04N1/6033

Abstract

A method for monitoring the condition of an inkjet printhead. A test image is printed by the printhead and a second reference printhead. The density of ink dots in the test image is selected so that each dot just contacts adjacent dots while avoiding significant overlap. A defective nozzle can produce misplaced or undersized dots, creating abnormal spacing between adjacent dots. At the selected ink dot density, the abnormal spacing is most perceptible to the eye.

Claims

1. A method of evaluating the performance of an inkjet printhead, comprising:

(a) creating a test image comprising a matrix of adjacent dots;

(b) selecting an ink dot density which causes each dot of the matrix to overlap at least one adjacent dot;

(c) printing the test image with the printhead;

(d) detecting the presence of spaces between adjacent dots; and

(e) comparing the spaces with a standard.

2. A method of evaluating the performance of an inkjet printhead, comprising:

(a) creating a test image comprising a matrix of dots;

(b) selecting an ink dot density with standard spacings between adjacent dots such that the standard spacings can include zero and non-zero spacings; and

(c) comparing actual spacings between adjacent dots with the standard spacings.

3. A method of evaluating the performance of a suspect inkjet printhead, comprising:

(a) creating a test image comprising a matrix of dots;

(b) selecting an ink dot density so that adjacent dots in the matrix are spaced apart only when one of the adjacent dots is defective;

(c) printing the test image with the printhead; and

(d) detecting the presence of spaces between dots.

4. The method of claim 3, including providing ink dots from a reference printhead in the matrix.

5. The method of claim 4, including providing in the test image a plurality of regions including a reference region.

6. The method of claim 5, including providing that each region has a different color.

7. The method of claim 5 including providing that one region is lighter than the reference region.

8. The method of claim 5 including providing that one region is darker than the reference region.

9. The method of claim 5 including providing that one region has a different hue from the reference region.

10. The method of claim 5 including providing that the regions comprise:

(a) a first region with a first color having a selected intensity and a selected hue;

(b) a second region with a color selected to be less intense than the first color;

(c) a third region with a color selected to be more intense than the first color; and

(d) a fourth region with a color selected to have a different hue from the first color.

11. The method of claim 10, including providing that the regions further comprise a graded region.

12. The method of claim 5, including providing that the reference printhead contributes to at least one region.

13. The method of claim 5, including providing that the reference printhead contributes to each region.

14. A method for evaluating the condition of a suspect inkjet printhead, comprising:

(a) using the suspect printhead and a reference printhead to produce a test print having a test image with at least one region, each region having a uniform matrix of overlapping ink dots;

(b) examining the test image for the presence of unintended spaces between ink dots; and

(c) if unintended spaces are detected, replacing the suspect printhead.

15. The method of claim 14, further comprising establishing an algorithm to determine when the test image should be printed.

16. The method of claim 15, further comprising basing the algorithm on at least one of a group of factors consisting of the age of the suspect printhead, the volume of ink printed by the suspect printhead, the time elapsed since an immediately preceding diagnostic print from the suspect printhead, and a physical evaluation of the printhead.

17. The method of claim 14, further comprising providing indicia on the test print.

18. The method of claim 14, further comprising providing indicia on the test print defining a color of the test image.