Improved tire shearography inspection

Abstract

A method and device to accurately construct a single image for analysis by image cropping and stitching of sector images in a post-process environment after a shearography machine completes all sector scans for a given tire casing. The use of measurements of each tire scanned enables the calculation of the correct amount to crop in each sector for any tire scanned, regardless of tire size, aspect ratio, bead width, or if the tire has remaining tread or is buffed for retreading. The resulting image then may be further processed and analyzed, such as by employing the use of an AI image analysis with improved accuracy of the analysis results.

Description

IMPROVED TIRE SHEAROGRAPHY INSPECTIONFIELD OF THE INVENTION

[0001] The present invention relates generally to the field of nondestructive testing. Specifically the present invention relates to the technique of electronic shearography. More specifically the invention relates to the use of electronic shearography to detect defects in vehicles tires by processing the shearography image for improved analysis using computer imaging analysis programs including artificial intelligence image analysis.BACKGROUND OF THE INVENTION

[0002] Tire casing inspection identifies defects in tire casings to reduce incident of tire casing failure and is used particularly in the retread process where defects that occur through use of the tire may be present. Techniques to detect hidden defects, such as voids inside the tire, include shearography techniques such as shearing interferometry or laser shearography and assure retreadability of casings for producing quality retread tires. A shearography camera is oriented to take images of the surface of the tire, such as the interior surface, and takes a series of images as found, for example in US 6,433,874, US 6,791,695. The shearography process captures a sequence of still images while the machine draws a vacuum. Generally there is at least a baseline image of the object in a first stressed condition, which may be an unstressed condition, and at least one image of the object in at least one additional stressed condition. The at least on additional stressed condition is made while a vacuum is created around the tire. The vacuum causes the tire to budge where gas has been trapped in voids beneath the surface of the tire, creating stress and deformation of the tire surface. The shearography compares the first stressed condition and the at least one additional stressed condition and creates a comparison of these two interference images to reveal information about the strain concentrations and thereby reveals the locations of voids that would otherwise be hidden beneath the surface of the tire. These voids show as fringed anomalies in the images.

[0003] The tire or the camera is then circumferentially rotated to a new image position and the process is repeated to create a plurality of images that show the defects, if present, for the entire circumferential image path of the tire. The images may be combined to allowcreate a long panoramic image creates a final sector image showing any voids as fringed anomalies. Once each sector scan image is complete, the tire indexes to the next sector, ultimately covering at least a portion of the width of the tire around all 360 degrees of the tire, usually the tire interior. The sectors overlap to assure no voids are missed across the path scanned by the machine. This frequently causes the same anomaly / anomalies to be in two adjacent sector images due to the overlap of the images. Inspection criteria for some anomalies depend on the anomaly count or circumferential length to determine rejection or acceptance of the tire casing for retreading.

[0004] Al may be employed, such as disclosed by WO 2023 / 062096 to automate the analysis of the tire. Both the Al system and human operators are susceptible to erroneous analysis and classification of the tire casings, however, when overlap of the images is present in the images. In the case of the use of an Al system, such images may be used to train the Al system for recognizing and classifying anomalies, frequency of anomalies and classifying the tire casings as being acceptable or otherwise as described in WO 2023 / 062096.

[0005] The shearography machines as currently manufactured do not appropriately crop sector images and cannot create a full tire map with no overlapping of sectors. A need exists for a shearography machine that produces a single image having no overlapping portions.SUMMARY OF THE INVENTION

[0006] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0007] In one exemplary embodiment, an apparatus is disclosed for performing an inspection of a tire carcass utilizing an image, the apparatus comprising a shearography camera for taking an interference images of the tire carcass; an at least one processor coupled to the shearography camera for receiving a plurality of interference images from the shearography camera and at least one measurement from including the carcass diameter, tire carcass width, tire carcass bead width and combinations thereof, and an actuator for positioning the shearography camera according to the actual vertical and horizontal view angles and the one or more measurements; wherein said shearography camera generates a plurality of images of the interior of the tire carcass and wherein said at least one or more processors calculate the amount of each picture to crop as a function ofthe one or more measurements and the positioning of the imaging device; wherein said at least one or more processors stitch the images together to create at least one mosaic image for further processing.

[0008] In at least one exemplary embodiment the at least one mosaic image is provided to an Al system and the Al system analyses the at least one mosaic image and profides an output of an analysis of the image.

[0009] In at least one exemplary embodiment apparatus further comprising a laser line scanner wherein the measuring the carcass performed by the laser line scanner of the tire carcass.

[0010] In at least one exemplary embodiment a method for A method of inspecting a tire carcass utilizing an image having minimal overlapping data prepared by the steps comprising: measuring the tire carcass to obtain one or more measurements at least one selected from the group consisting of the tire carcass diameter, tire carcass width, tire carcass bead width and combinations thereof; positioning a camera according to an actual vertical and an horizontal view angles and the one or more measurements; generating a plurality of images of the interior of the tire carcass; calculating the amount of each picture to crop as a function of the one or more measurements and the positioning of the camera; and stitching the images together to create at least one mosaic image for further analysis, the at least one mosaic image having no overlapping sectors.

[0011] In at least another exemplary embodiment, wherein the at least one mosaic image is provided as input to an Al system to analyze the image and output an analysis.

[0012] In at least one exemplary embodiment wherein the measuring the carcass is done by performing a laser line scan of the tire carcass.

[0013] In at least one exemplary embodiment wherein the imaging device is part of a laser shear ography system.

[0014] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0016] FIG. 1 provides a perspective view of a tire casing and two camera vectors 30 degrees apart.

[0017] FIG. 2 provides a radial section view of a tire casing taken in a plane bisecting the tire and rotation of axis of the tire and showing the position of an imaging device relative to the tire casing.

[0018] FIG. 3 provides a side view of the tire casing as shown in FIG. 1.

[0019] FIG. 4 provides a radial section view taken in a plane bisecting the tire casing and rotation of axis of the tire casing showing a portion of tire casing, camera lens and relative position of each to the axis of rotation of the tire.

[0020] The use of identical or similar reference numerals in different figures denotes identical or similar features.DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention provides an improved method and device for shearography inspection of tire casings. More specifically, the present invention allows for accurate image cropping and stitching of sector images in a post-process environment after the shearography machine acquires images and the process completes all sector scans for a given tire casing. “Stitching” as used herein means the technique of using a computer to merge images together to create a large image. In at least one embodiment of the invention, measurements of each tire scanned are used to calculate the correct amount to crop in each sector for each tire scanned, regardless of tire size, aspect ratio, bead width, or if the tire has remaining tread or is buffed for retreading. For purposes of describing the invention, reference now will be made in detail to embodiments and / or methods of the invention, one or more examples of which are illustrated in or with the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features or steps illustrated or described as part of one embodiment, can be used with another embodiment or steps to yield a still further embodiments or methods. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appended claims and their equivalents.

[0022] FIG. 1 illustrates a perspective view of a typical tire casing 10. One or more shearography cameras are used to image the interior of the tire, rotating between successive sector images until a full 360-degree circumfrencial path is imaged. Shown in FIG. 1 are a first vector 110 and a second vector 120 representing the orientation of the one or more shearography cameras, the vectors spaced 30-degrees (0.524 radians) apart. The present invention uses individual tire casing measurements, number of sectors imaged, and information about image size, to calculate precisely the amount of overlap 150 in image pixels of each image field of view of each sector image 130, 140 and then crop an appropriate amount of the overlap 150 from each sector image. The corrected sector images can then be stitched together to create a full 360-degree image map of all anomalies with correct counts and lengths of the anomalies.

[0023] In at least one embodiment the individual tire casing measurements are obtained by laser measurement of the tire casing.

[0024] In another embodiment, the 360-degree image is fed to an Al image analysis program to trained to automatically classify tires scanned by shearography. The Al application cannot be reliable if there are varying overlaps of sectors and the amount or length of anomalies does not represent reality.

[0025] Determining the Usable View Angle

[0026] As shown in FIG. 2, usable vertical view angle av, measured in radians, is known for a given lens and interferometer combination. As used herein, “vertical” is across the tire beads, same direction as the tire carcass 10 rotation axis 20. The aspect ratio for sector images is 4:3 in the instant embodiment. In another embodiment the aspect ratio may be 16:9. In other embodiments the aspect ratio may be different yet. Solving for horizontal (the circumferential direction on the tire) view angle, ah, measured in radians:

[0027] As shown in equation 1 above and illustrated in FIG. 3, the angle ah is used to determine number of sectors needed to cover at least the full circumference of the tire. In this example, each sector image is positioned at an index angle 160 of 30 degrees (0.524 radians) apart from the adjacent sector image. This would result in a total of 12 scansbeing taken to cover the 360 degree circumferential path of the tire casing. The angle avis needed to determine camera radial position, and is a key parameter for this embodiment as well as illustrated in FIG 2. In this embodiment, the angle avis provided by the shearography machine manufacturer, and is dependent on the lens and interferometer assembly chosen for the machine. In the current embodiment, a SDS laser shearography inspection machine is used as provided by SDS Systemtechnik, GmbH (Rudolf-Diesel-Str. 7; 75365 Calw; Germany), and the camera and optics 300 for the interferometer result in av= 43° (0.750 radians). This is less than the optical lens capability alone. In this embodiment, angle ahis 55.4° (0.967 radians).

[0028] To minimize the number of images being taken by the shearography machine, the camera lens face 310 is positioned a distance, Rcamfrom the tire’s center axis of rotation 20 and along the medial plane of the tire which is positioned halfway between the lateral sides of the tire as shown in FIG. 2. The shearography machine manufacturer of the current embodiment uses a rule to set camera radial position and lens focal point 105 and number of sectors to guarantee positive overlap 150, using available view angles 130, 140 and other measured data and preset parameters. The rule is that the camera radial position is set to achieve full vertical lens view angle at avat Wb-2Tb where Tb is the average bead thickness in the width direction of the tire while Wb is the tire bead width. This results in the camera’s focal point 105 being positioned from the center axis of rotation of the tire at a distance of Rcamsuch that the image’s vertical view angle avis not obstructed, or alternatively, mostly not obstructed, by the beads of the tire. Due to the inner curvature of the bead, some obstruction may be tolerated at the edges of the image.

[0029] In order to determine the amount to pixels to crop from each individual image, data of the tire’s measurements is utilized. In the current embodiment, tire measurement and scan data is reported in a text page in the metafile of all the sector scan image data. The data includes bead width, the bead thickness offset parameter, tire diameter, radial head position, and other numerical data. In the current embodiment, the data is used as follows:

[0030] The target tire map image aspect ratio, ARtarge t, after the correct cropping and stitching is the ratio of the viewing arc width at the tire crown, and the crown circumference is calculated by equation 2 below and as shown in FIG 4:

[0031] Where angle avis expressed in radians. This represents a full 360° map, with no gaps or overlaps of sectors. The camera lens viewing radius, from the focal point, Rcamis a calculation from other measurement data as follows, and referencing figure 2 below. The variable Rh posis a data record exported for each tire scan as part of the metadata file.

[0032] Where diensis the distance from the camera head tilt axis 315 to the face 310 of the lens. This is from, in the current embodiment, the SDS interferometer and camera head assembly 300 physical dimensions, and is approximately 20mm. The variable df0Cis the distance from the lens face to the optical focal point of the lens. For the lens used in the current embodiment, df0Cis 53mm. With avexpressed in radians which calculates vertical arc length at the crown as shown in equation 4 below:

[0033] Next, the aspect ratio ARraw, is based on the stitching of all uncropped sector images together. For the current embodiment, the actual number of image scan sectors varies with tire size and is designated as a whole number, Ns, typically in the range of 5 to 14. In another embodiment, the actual number of image scan sectors Nsis an even number where two cameras are utilized, each facing the opposite direction from other. The raw tire map image is the stitching of full 4:3 sector images x Ns. The number of pixels in these images, nvand nh, are typically 575 x 768 but could be different for other camera resolutions or aspect ratios different than 4:3. It should be understood that the current invention is device agnostic, so using the variables nvand nh, in pixels, the raw stitched tire map image aspect ratio is simply expressed as the ratio shown in equation 5 below:ARraw ^-v / ( i s) (Eq. 5)

[0034] If the shearography machine is set up correctly, ARraw> ARtarget, which means there is positive sector overlap and no sector image data is missing. If the opposite occurs, parts of the tire are not scanned between sectors and the situation must be correctedin the machine setup. When ARraw> ARtarget, then raw sector image cropping can correct redundant image data due to circumferential (horizontal) overlaps of sectors around the tire.

[0035] The number of horizontal pixels in the corrected sector image is then calculated as shown in equation 6:

[0036] The number of horizontal pixels that are to be cropped (subtracted) from each sector is:

[0037] Or using the individual calculations for each AR, the number of horizontal pixels that are to be cropped (subtracted) from each sector is calculated as:

[0038] Simplifying the above we obtain equation 9 below:

[0039] Where n is in pixels and a is in radians (n x degrees / 180). Linear dimensions are in mm, N is a count number. For the current application, the constants are nh= 768 pixels nv= 565 pixels av= 0.2389 rad dfoc = 53mm diens = 20 mm (Eq. 10)

[0040] The remaining entries for the equation are from tire scan data from the text page of the metadata file output for each tire.

[0041] Once the shearography images are cropped they then may be stitched together to form a single mosaic image of an entire 360 degree circumferential path of the interior of the tire. The image then may be fed to an artificial intelligence based image analysis program for analysis. Without the duplication of flaws along the overlapping portions of the images, the analysis is improved by eliminating false detection of unacceptably high anomaly rates resulting in more accurate analysis and less waste.

[0042] Selected combinations of aspects of the disclosed technology correspond to a plurality of different embodiments of the present invention. It should be noted that each of the exemplary embodiments presented and discussed herein should not insinuate limitations of the present subject matter. Features or steps illustrated or described as part of one embodiment may be used in combination with aspects of another embodiment to yield yet further embodiments. Additionally, certain features may be interchanged with similar devices or features not expressly mentioned which perform the same or similar function.

[0043] The terms "a," "an," and the singular forms of words shall be taken to include the plural form of the same words, such that the terms mean that one or more of something is provided. The terms "at least one" and "one or more" are used interchangeably.

[0044] The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

Claims

WHAT IS CLAIMED IS:

1. A method of inspecting a tire carcass utilizing an image having minimal overlapping data prepared by the steps comprising: measuring the tire carcass to obtain one or more measurements at least one selected from the group consisting of the tire carcass diameter, tire carcass width, tire carcass bead width and combinations thereof; positioning a camera according to an actual vertical and an horizontal view angles and the one or more measurements; generating a plurality of images of the interior of the tire carcass; calculating the amount of each picture to crop as a function of the one or more measurements and the positioning of the camera; stitching the images together to create at least one mosaic image for further analysis, the at least one mosaic image having no overlapping sectors; and providing the at least one mosaic image as input to an Al system to analyze the image and output an analysis.

2. The method of claim 1 wherein the measuring the carcass is done by performing a laser line scan of the tire carcass.

3. The method of any one of the above claims wherein the imaging device is part of a laser shear ography system.

4. The method of any one of the above claims wherein the tire is divided up into a plurality of sectors and wherein the generating a plurality of images is performed by the steps comprising: capturing an image of the interior of the tire; drawing a vacuum; capturing a second image of the interior of the tire; creating a final sector image showing any voids as fringed anomalies; and indexing to the next sector and repeating the process until a final sector image is created for each sector.

5. The method of any one of the above claims wherein the at least one mosaic image forms an image that represents a 360 degree image of the full circumference of the interior of the tire.

6. The method of claim 3 wherein the number of sectors are calculated as a function of the vertical view angle, the bead width, the diameter of the tire and the aspect ratio of the plurality of images.

7. The method of claim 2 wherein calculating the number of sectors is done using at least one measurements obtained by the laser line scanner.

8. An apparatus for performing an inspection of a tire carcass utilizing an image comprising: a shearography camera for taking an interference images of the tire carcass; an at least one processor coupled to the shearography camera for receiving a plurality of interference images from the shearography camera; wherein the at least one processor receives an at least one measurement from the group consisting of the tire carcass diameter, tire carcass width, tire carcass bead width and combinations thereof; an actuator for positioning the shearography camera according to an actual vertical and an actual horizontal view angles and the one or more measurements; wherein said shearography camera generates a plurality of images of the interior of the tire carcass; wherein said at least one or more processors calculate the amount of each picture to crop as a function of the one or more measurements and the positioning of the imaging device; and wherein said at least one or more processors stitch the images together to create at least one mosaic image for analysis, the at least one mosaic image having no overlapping sectors.

9. The apparatus of claim 8 further comprising a laser line scanner wherein the measuring the carcass performed by the laser line scanner of the tire carcass.

10. The apparatus of claim 8 or 9 wherein the imaging device is part of a laser shearography system.

11. The apparatus of claim 8, 9 or 10 wherein the tire is divided up into a plurality of sectors and wherein the apparatus carries out the steps comprising: capturing an image of the interior of the tire; drawing a vacuum; capturing a second image of the interior of the tire; creating a final sector image showing any voids as fringed anomalies; andindexing to the next sector and repeating the process until a final sector image is created for each sector.

12. The apparatus of claim 11 wherein the images of each sector overlap.

13. The apparatus of any one claim 8 through 12 wherein the at least one mosaic image forms an image that represents a 360 degree image of the full circumference of the interior of the tire.

14. The apparatus of claim 11 wherein the number of sectors are calculated as a function of the vertical view angle, the bead width, the diameter of the tire and the aspect ratio of the plurality of images.

15. The apparatus of claim 9 wherein calculating the number of sectors is done using at least one measurements obtained by the laser line scanner.

16. The apparatus of any of claims 9 through 15 further comprising an Al system receiving the at least one mosaic image and analyzing the image and providing an output of an analysis of the image.

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