Method for qualitatively evaluating material

• US 7,184,584 B2
• Filed: 06/25/2002
• Issued: 02/27/2007
• Est. Priority Date: 07/05/2001
• Status: Active Grant

• Current Assignee: Koenig & Bauer AG
• Original Assignee: Koenig & Bauer AG
• Inventors: Willeke, Harald Heinrich, Sacher, Jo
• Primary Examiner(s): Mancuso; Joseph
• Assistant Examiner(s): Akhavannik; Hadi
• Application Number:
  US10/482,159
• Publication Number:
  US 20040179724A1
• Time in Patent Office: 1,708 Days
• Field of Search: 382/173, 382141-145
• US Class Current: 382/141
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 10/28 Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns
• CPC Class Codes: G07D 7/206 Matching template patterns

Abstract

A method for qualitatively evaluating material with at least one identification characteristic, whose position can vary within an expectation range designated by tolerance limits, involves the use of at least one illuminating device, at least one photoelectric sensor and an evaluating device. At least one background reference value and at least one mask reference are stored in the evaluating device. The background reference represents the characteristics of a printed image, particularly the gray scale value, in at least one portion which surrounds the identification characteristic. The mask reference represents the geometrical contour of the identification characteristic. During inspection of the printed material, differential image data is found, at least from the expectation range, from the actual image data, and from the background reference value in the evaluating device. The actual position of the identification characteristic is subsequently derived in the evaluating device.

Claims

1. A method for qualitatively evaluating a material including;

providing at least one identification characteristic on a material to be evaluated;

providing an evaluation device;

determining at least one background reference value representing properties of a material to be evaluated in at least a part of a surrounding area of a material to be evaluated extending around said at least one identification characteristic;

providing at least one mask reference representing one of a geometric outline of said at least one identification characteristic and a relative arrangement of said at least one identification characteristic and a second identification characteristic;

storing said at least one background reference value and said at least one mask reference in said evaluation device;

inspecting a material to be evaluated and determining actual image data of the material to be evaluated;

forming a difference image using said actual image value and said background reference value;

comparing said difference image and said at least one mask reference in said evaluation device and determining an actual position of said identification characteristic of a material to be evaluated; and

using said actual position of said identification characteristics and blanking out areas of a material to be evaluated corresponding to said determined location of said actual position of said identification characteristic in a subsequent qualitative evaluation of a material to be evaluated.

4. The method of claim 1 further including locating said at least one identification characteristic within an area of expectation defined by tolerance limits.

6. The method of claim 1 further including storing a digitizing threshold in said evaluation unit and filtering out all image data having values lying below said digitizing threshold.

8. The method of claim 1 further including shifting said mask reference and determining a maximum congruence between said mask reference and said difference image in response to said shifting of said mask reference.

10. The method of claim 8 further including calculating a concentration of an optical distribution of image points of said mask reference and a concentration of an optical distribution of image points of said difference image and comparing said concentrations for determining said maximum congruence.

12. The method of claim 10 further including determining said maximum congruence when a minimum deviation results from comparing said concentrations of said mask reference and said difference image.

13. The method of claim 10 further including determining said maximum congruence when a minimum deviation results from comparing said concentrations of said mask reference and said difference image.

14. The method of claim 1 further including providing said identification characteristic in a strip shape.

16. The method of claim 1 further including embodying said identification characteristic as a security characteristic of a bank note.

18. The method of claim 16 further including selecting said security characteristic as one of a window thread, a perforated window thread, a hologram and a kinegram.

20. The method of claim 1 further including determining background reference values for different areas of a material to be evaluated.

22. The method of claim 1 further including projecting each of said at least one mask reference and said difference image onto at least one projection line, and deriving said actual position of said identification characteristic in a linear direction of said at least one projection line by comparing projection data of said mask reference and said difference image.

23. The method of claim 1 further including performing an evaluation of a material in said evaluation device using mathematical operations of digitized input data.

2. A method for qualitatively evaluating a material including;

providing at least one identification characteristic on a material to be evaluated;

providing an evaluation device;

determining at least one background reference value representing properties of a material to be evaluated in at least a part of an area of a material to be evaluated extending around said at least one identification characteristic;

providing at least one mask reference representing one of a geometric outline of said at least one identification characteristic and a relative arrangement of said at least one identification characteristic and a second identification characteristic;

storing said at least one background reference value and said at least one mask reference in said evaluation device;

inspecting a material to be evaluated and determining actual image data of the material to be evaluated;

forming a difference image using said actual image value and said background reference value;

comparing said difference image and said at least one mask reference in said evaluation device and determining an actual position of said identification characteristic of a material to be evaluated;

projecting each of said at least one mask reference and said difference image onto at least one projection line; and

deriving said actual position of said identification characteristic in a linear direction of said projection line by comparing projection data of said mask reference and said difference image.

3. The method of claim 2 further including blanking out an area of a material to be evaluated using said actual position of said identification characteristic in a subsequent evaluation step for the qualitative evaluation of a material to be imprinted.

5. The method of claim 2 further including locating said at least one identification characteristic within an area of expectation defined by tolerance limits.

7. The method of claim 2 further including storing a digitizing threshold in said evaluation unit and filtering out all image data having values lying below said digitizing threshold.

9. The method of claim 2 further including shifting said mask reference and determining a maximum congruence between said mask reference and said difference image in response to said shifting of said mask reference.

11. The method of claim 9 further including calculating a concentration of an optical distribution of image points of said mask reference and a concentration of an optical distribution of image points of said difference image and comparing said concentrations for determining said maximum congruence.

15. The method of claim 2 further including providing said identification characteristic in a strip shape.

17. The method of claim 2 further including embodying said identification characteristic as a security characteristic of a bank note.

19. The method of claim 17 further including selecting said security characteristic as one of a window thread, a perforated window thread, a hologram and a kinegram.

21. The method of claim 2 further including determining background reference values for different areas of a material to be evaluated.

24. The method of claim 2 further including performing an evaluation of a material in said evaluation device using mathematical operations of digitized input data.