Method for segmenting the surface of a tyre and apparatus operating according to said method

Patent metadata

Field	Value
Publication number	US-9835524-B2
Application number	US-201314416976-A
Country	US
Kind code	B2
Filing date	Jul 23, 2013
Priority date	Jul 31, 2012
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

A method for segmenting the surface of a tire including at least one groove, includes: irradiating a portion of the surface of the tire by means of electromagnetic radiation having a wavelength in the visible spectrum; acquiring an image of the irradiated portion of the surface; and processing the image so as to segment it into regions corresponding to regions of the tire which do or do not belong to the at least one groove. Additionally, processing the image so as to segment it includes: calculating a statistical quantity associated with the irradiation by electromagnetic radiation for each region of the image; and determining whether the region of the image does or does not belong to the at least one groove according to the value of the statistical quantity. Equipment for segmenting a surface of a tire including at least one groove.

First claim

The invention claimed is:

1. A method for segmenting the surface of a tyre comprising at least one groove, comprising:
irradiating a portion of said surface of said tyre with electromagnetic radiation having a wavelength in the visible spectrum;
acquiring an image of said portion of the irradiated surface; and
processing said image so as to segment said image into regions corresponding to regions of the tyre which do or do not belong to said at least one groove,
wherein the processing of said image so as to segment said image comprises:
calculating a statistical quantity associated with irradiation by said electromagnetic radiation for each region of said image, said calculating a statistical quantity for each region of said image comprising calculating a value of dispersion of data relative to a variable related to a light intensity of each region of said image; and
determining whether said region of said image does or does not belong to said at least one groove according to a value of said statistical quantity.

2. The method according to claim 1 , wherein irradiating a portion of said surface comprises:
using an almost telecentric source of said electromagnetic radiation for irradiating said portion.

3. The method according to claim 1 , wherein irradiating a portion of said surface comprises the fact that said electromagnetic radiation is essentially grazing with respect to a bottom surface of said at least one groove.

4. The method according to claim 1 , comprising:
detecting an identification code of said tyre; and
positioning said tyre for said irradiation in accordance with said identification code.

5. The method according to claim 1 , wherein a main longitudinal direction is defined in said at least one groove, and wherein segmenting said image in said regions comprises segmenting said image into regions that are essentially parallel to said main longitudinal direction.

6. The method according to claim 1 , wherein positioning said tyre comprises rotating and/or translating said tyre so as to irradiate said portion in a predetermined direction.

7. The method according to claim 1 , wherein irradiating a portion of said surface of said tyre by means of electromagnetic radiation comprises:
irradiating said portion by means of radiation having one of a plurality of main irradiation directions, and
selecting a radiation having a different main direction among said plurality.

8. The method according to claim 1 , wherein determining whether said region of said image does or does not belong to said groove comprises:
dividing said image into a plurality of regions;
calculating a value of said statistical quantity for each region of said plurality;
calculating a ratio between two values of said statistical quantity of two separate regions of said plurality; and
where one of the two regions of said plurality belongs to said groove and one does not belong to said groove when said ratio has a value outside a predetermined range.

9. The method according to claim 8 , wherein two regions of said plurality both belong to said groove or both do not belong to said groove when said ratio has a value within said predetermined range.

10. The method according to claim 1 , wherein calculating said statistical quantity for each region of said image comprises calculating a standard deviation of the data relative to a variable related to a light intensity of each region of the image of the portion of the acquired irradiated surface.

11. The method according to claim 10 , wherein calculating said statistical quantity for each region of said image comprises calculating the standard deviation of luminance of each region of the image of said portion of the acquired irradiated surface.

12. The method according claim 8 , wherein said statistical quantity is a standard deviation, said predetermined range extending from about 0.8 to about 1.25.

13. The method according to claim 1 , wherein calculating a statistical quantity associated with the irradiation for each region of said image comprises:
calculating said statistical quantity for a region of said image comprising a column of pixels having a width of at least one pixel.

14. The method according to claim 13 , wherein a mean of said statistical quantity is calculated for at least three columns of pixels.

15. The method according claim 1 , wherein said at least one groove is present on a tread band of said tyre.

16. The method according to claim 15 , wherein said at least one groove is present on a shoulder area of said tyre.

17. The method for detecting defects on a surface of a tyre, comprising the method for segmenting the surface of a tyre according to claim 1 , comprising:
processing at least one of said regions of said image belonging to said at least one groove, for the detection of defects within the surface of the tyre.

18. The method according to claim 17 , wherein said defect is greater than about 0.5 mm.

19. The method according to claim 17 , wherein said defect comprises an exposed cord.

20. The method according to claim 17 , wherein processing said region belonging to said groove comprises using a wavelet transform and/or a morphological operator.

21. Equipment for segmenting a surface of a tyre comprising at least one groove, comprising:
a source of electromagnetic radiation capable of irradiating a portion of said surface of said tyre with electromagnetic radiation having a wavelength in a visible spectrum;
a light sensor capable of acquiring an image of said portion of an irradiated surface of said tyre;
a processor capable of processing said image by dividing said image into regions which do or do not belong to said at least one groove, said processor comprising:
a calculator capable of calculating a statistical quantity associated with the irradiation by said electromagnetic radiation for each region of said image, said calculating a statistical quantity comprising calculating a value of dispersion of data relative to a variable related to a light intensity of each region of said image; and
a selector capable of determining whether said region of said image does or does not belong to said at least one groove according to a value of said statistical quantity.

22. Equipment according to claim 21 , wherein said source of electromagnetic radiation is almost telecentric.

23. Equipment according to claim 21 , wherein said electromagnetic radiation is essentially grazing with respect to a bottom surface of said at least one groove.

24. Equipment according to claim 21 , wherein a size of said groove is not less than about 2 mm.

25. Equipment according to claim 21 , wherein said light sensor comprises a linear scanning video camera.

26. Equipment according to claim 21 , wherein said radiation source comprises an LED.

27. Equipment according to claim 26 , wherein said source of electromagnetic radiation comprises a linear array of LEDs.

28. Equipment according to claim 21 , comprising a plurality of sources of electromagnetic radiation capable of irradiating with electromagnetic radiation, each source having a main direction of irradiation which differs from other sources of the plurality.

29. Equipment according to claim 21 , wherein said electromagnetic radiation comprises a radiation having a wavelength in a range from 495 nm to 570 nm.

30. Equipmen

Assignees

• Pirelli

Inventors

• Boffa Vincenzo
• Gallo Marco
• Montrucchio Bartolomeo

Classifications

• G01M17/027 Primary

  using light, e.g. infrared, ultraviolet or holographic techniques · CPC title

• B29D30/0061

  Accessories, details or auxiliary operations not otherwise provided for · CPC title

• B29D2030/0066

  Tyre quality control during manufacturing · CPC title

• G01M17/02

  Tyres · CPC title