Method and Apparatus for Verifying Two Dimensional Mark Quality

• US 20080004822A1
• Filed: 06/29/2006
• Published: 01/03/2008
• Est. Priority Date: 06/29/2006
• Status: Active Grant

• Current Assignee: Cognex Corporation
• Original Assignee: Cognex Corporation
• Inventors: Gopalakrishnan, Venkat K., Nadabar, Sateesha, Gerst, Carl W.
• Granted Patent: US 8,108,176 B2
• Time in Patent Office: Days
• US Class Current: 702/81
• CPC Class Codes: G06K 5/00 Methods or arrangements for verifying the correctness of markings on a record carrier; Column detection devices

Abstract

A method and system for applying a two dimensional mark on a first surface of a component and assessing mark quality, the method including the steps of positioning a component with a first surface at a first station, applying a two dimensional mark to the first surface at the first station wherein the applied mark is intended to codify a first information subset, obtaining an image of the applied two dimensional mark at the first station, performing a mark quality assessment on the obtained image and performing a secondary function as a result of the mark quality assessment.

Claims

1. A method for applying a two dimensional mark on a first surface of a component and assessing mark quality, the method comprising the steps of:

positioning a component with a first surface at a first station;

applying a two dimensional mark to the first surface at the first station wherein the applied mark is intended to codify a first information subset;

obtaining an image of the applied two dimensional mark at the first station;

performing a mark quality assessment on the mark in the obtained image; and

performing a secondary function as a result of the mark quality assessment.

5. The method of claim 1 wherein the step of performing a mark quality assessment includes attempting to decode the image of the mark and when the image is successfully decoded, gleaning other mark quality characteristics from the mark in the obtained image.

6. The method of claim 5 wherein the step of gleaning other mark quality characteristics includes gleaning at least a subset of geometric characteristics of the mark, mark size, mark color, mark shading, symbol contrast, axial non-uniformity of the mark, grid non-uniformity of the mark, extreme reflectance, angle of distortion, dot diameter, dot ovality, dot position, image sharpness and background uniformity.

7. The method of claim 5 wherein the step of gleaning other mark quality characteristics includes obtaining information from the mark in the obtained image indicative of the degree of at least one irregularity in the obtained image, the step of performing a mark quality assessment further including, where the degree of the at least one irregularity in the image exceeds a tolerable level, at least in part compensating for the irregularity thereby generating a compensated mark, gleaning mark quality characteristics from the compensated mark and generating an applied mark quality value as a function of the gleaned characteristics from the compensated mark.

8. The method of claim 7 wherein the step of performing a mark quality assessment further includes comparing the applied mark quality value to a baseline assessment value, the secondary function including, when the applied mark quality value is below the baseline value, indicating a low mark quality level.

9. The method of claim 8 wherein the secondary function further includes, when the applied mark quality value is at least equal to the baseline value, indicating a high mark quality level.

10. The method of claim 7 wherein the first surface may be warped, the at least one irregularity including at least a subset of non-optimal lighting, first surface warping, lens/optical distortion, perspective distortion, and perceived background texture.

11. The method of claim 7 wherein the at least one irregularity is geometric distortion, the step of compensating including using the decoded information to generate a synthetic ideal mark model and using the ideal mark model to compensate for the geometric distortion.

12. The method of claim 11 further including the step of providing known mark characteristics, the step of generating a synthetic ideal mark model including using both the provided known mark characteristics and the decoded information.

13. The method of claim 11 wherein the step of using the ideal mark model includes using the ideal mark model and the mark in the obtained image to generate a difference map and using the difference map to compensate for the irregularity in the mark in the obtained image.

14. The method of claim 1 wherein the step of performing a mark quality assessment includes attempting to decode the image of the mark and when the image is successfully decoded, unwarping the mark to at least in part compensate for mark distortion thereby generating an unwarped mark, gleaning mark quality characteristics from the unwarped mark, generating an applied mark quality value as a function of the gleaned characteristics from the unwarped mark and comparing the applied mark quality value to a baseline assessment value, the secondary function including, when the applied mark quality value is below the baseline value, indicating a low mark quality level.

15. The method of claim 14 wherein the step of unwarping the mark thereby generating an unwarped mark includes using the decoded information from the mark to generate a synthetic ideal mark model, comparing the synthetic ideal mark model to the mark in the obtained image to generate a deformation map and unwarping the mark using the deformation map to generate the unwarped mark.

16. The method of claim 1 wherein the step of obtaining an image at the first station includes supporting a handheld mark reader adjacent the first station.

17. The method of claim 1 wherein the step of performing a mark quality assessment on the obtained image includes decoding the mark in the obtained image, using the decoded information to generate a synthetic ideal mark model, using the ideal mark model and the mark in the obtained image to generate a difference map and using the difference map to compensate the mark obtained in the image for at least a subset of non-optimal lighting, first surface warping, lens/optical distortion, perspective distortion, and perceived background texture.

18. The method of claim 5 wherein the step of gleaning other mark quality characteristics includes obtaining information from the mark in the obtained image indicative of the degree of at least one irregularity in the obtained image and., when the degree of the at least one irregularity exceeds a tolerable level, providing a feedback signal indicating that the degree or irregularity is intolerable.

2-4. -4. (canceled)

19. A method for assessing quality of a two dimensional mark that is applied to a first surface of a component, the method comprising the steps of:

a. providing a two dimensional mark on a first surface of a component;

b. providing a handheld mark reader that includes a field of view;

c. positioning the handheld reader with respect to the component such that the first surface is in the field of view;

d. obtaining an image of the two dimensional mark;

e. attempting to decode the image to obtain an applied mark information subset;

f. when the image is successfully decoded;

i. assessing the degree of at least one irregularity in the mark in the obtained image; and

ii. when the degree of the at least one irregularity exceeds a tolerable level, providing a feedback signal indicating that the handheld reader should be repositioned.

20. The method of claim 19 further including the step of, when the image decoding is unsuccessful, providing at least one of audible and visual feedback signal to a handheld user indicating that the handheld reader should be repositioned with respect to the first surface.

21. A method for assessing quality of a two dimensional mark that is applied to a first surface of a component, the method comprising the steps of:

a. providing a two dimensional mark on a first surface of a component;

b. providing a handheld mark reader that includes a field of view;

c. positioning the handheld reader with respect to the component such that the first surface is in the field of view;

d. obtaining an image of the two dimensional mark;

e. attempting to decode the image to obtain an applied mark information subset;

f. when the image is successfully decoded;

i. assessing the degree of at least one irregularity in the mark in the obtained image; and

ii. when the degree of the at least one irregularity exceeds a tolerable level, attempting to compensate at least in part for the irregularity thereby generating a compensated mark, gleaning mark quality characteristics from the compensated mark and using the gleaned characteristics to calculate an applied mark quality value.

22. The method of claim 21 wherein the step of performing a mark quality assessment further includes comparing the applied mark quality value to a baseline quality assessment value, the secondary function including, when the applied mark quality value is below the baseline value, indicating a low mark quality level.

23. The method of claim 22 wherein the secondary function further includes, when the applied mark quality value is at least equal to the baseline value, indicating a high mark quality level.

24. The method of claim 21 wherein the first surface may be warped and the at least one irregularity includes at least a subset of non-optimal lighting, first surface warping, lens/optical distortion, perspective distortion, and perceived background texture.

25. The method of claim 21 wherein the at least one irregularity is geometric distortion, the step of compensating including using the decoded information to generate a synthetic ideal mark model and using the ideal mark model to compensate for the geometric distortion.

26. The method of claim 25 wherein the step of using the ideal mark model includes using the ideal mark model and the mark in the obtained image to generate a difference map and using the difference map to compensate the mark obtained in the image.

27. A method for assessing the quality of a two dimensional mark applied to a first surface of a component using a handheld reader that includes a field of view, the method comprising the steps of:

(a) providing a component with a two dimensional mark on a first surface wherein the applied mark is intended to codify a first information subset;

(b) positioning the handheld reader with respect to the component such that the first surface is in the field of view;

(c) obtaining an image of the mark using the handheld reader;

(d) performing a mark quality assessment on the obtained image to generate an applied mark quality value;

(e) where the applied mark quality value is lower than a baseline assessment value, providing at least one of an audible signal and a visual signal to a handheld reader user indicating that the reader should be repositioned;

after the reader is repositioned, repeating steps (c) through (e) until an applied mark quality value is at least equal to the baseline assessment value; and

when the applied mark quality value is at least equal to the baseline assessment value, providing at least one of an audible signal and a visual signal to the reader user indicating that the applied mark quality value is at least equal to the baseline assessment value.

28. The method of claim 27 wherein the step of providing one of an audible signal and a visual signal to a handheld reader user indicating that the reader should be repositioned includes providing a changing one of an audible and a visual signal where the signal changes as a function of whether or not the applied mark quality value is increasing or decreasing between consecutive quality assessment processes.

29-35. -35. (canceled)

36. A system for assessing the quality of a two dimensional mark applied to a first surface of a component, the system comprising:

a handheld reader including a field of view, the reader for obtaining an image of the two dimensional mark when the mark is within the reader field of view;

a processor for receiving reader generated images and programmed to perform a mark quality assessment process on the obtained images to generate quality assessment values associated with the images, when the quality assessment value is lower than a baseline assessment value, the processor providing one of an audible signal and a visual signal to a handheld reader user indicating that the reader should be repositioned so that a new image can be obtained and, when a quality assessment value is at least equal to the baseline assessment value, providing one of an audible signal and a visual signal to the handheld reader user indicating that the quality assessment value is at least equal to the baseline assessment value.

37. The system of claim 36 wherein the processor provides one of an audible signal and a visual signal to a handheld reader user indicating that the handheld should be repositioned by providing a changing one of an audible and a visual signal where the signal changes as a function of whether or not the quality assessment value is increasing or decreasing between consecutive quality assessment processes.

38. A method for assessing quality of a two dimensional mark that is applied to a first surface, the method comprising the steps of:

obtaining an image of the applied two dimensional mark;

decoding the mark in the obtained image to generate a first information subset;

using the first information subset to generate a synthetic ideal mark model;

comparing the synthetic ideal mark model to the mark in the obtained image to generate a difference map;

using the difference map to at least in part compensate for at least one irregularity in the mark in the obtained image thereby generating a compensated mark; and

assessing the quality of the compensated mark.

39-41. -41. (canceled)