Tire shape inspection method and tire shape inspection apparatus

• US 9,109,974 B2
• Filed: 10/02/2012
• Issued: 08/18/2015
• Est. Priority Date: 11/07/2011
• Status: Active Grant

• Current Assignee: Klaus Schmidt
• Original Assignee: Kobe Steel Limited
• Inventors: Takahashi, Eiji, Tsuji, Toshiyuki, Kannaka, Masato
• Primary Examiner(s): AHMED, SAMIR ANWAR
• Application Number:
  US14/351,933
• Publication Number:
  US 20140283591A1
• Time in Patent Office: 1,050 Days
• Field of Search: 382/141, 382/143, 356/237.1, 356/237.2, 356/614, 356625-640, 348/86
• US Class Current: 1/1
• CPC Class Codes: B60C 13/003 characterised by sidewall curvature
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50
• CPC Class Codes: G01B 11/2522 the position of the object changing and being recorded
• CPC Class Codes: G01M 17/02 Tyres
• CPC Class Codes: G01M 17/027 using light, e.g. infrared, ultraviolet or holographic techniques
• CPC Class Codes: G01N 2021/8887 based on image processing techniques
• CPC Class Codes: G01N 21/9515 Objects of complex shape, e.g. examined with use of a surface follower device measuring contours and curvatures G01B11/24
• CPC Class Codes: G06T 2207/30108 Industrial image inspection
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

A tire shape inspection method executes the following steps: first, as a teaching operation step, boundary lines of the bulge and dent marks are detected in a sample source image of a sample tire, a mask image is generated which denotes the boundary lines, regions are removed from the sample source image which correspond to the boundary lines which are denoted in the mask image, and a height offset image is generated which represents the heights of the remaining regions with one or more offset values. Next, as an inspection operation step, the height offset image is subtracted from an inspection image of the inspection tire, the boundary regions which the mask image represents are removed, and, on the basis of the obtained bulge/dent removal image, shape defects of the sidewall surfaces of the inspection tire are inspected.

Claims

1. A tire shape inspection method that inspects a sidewall surface of an inspection tire for shape defects by using an image of a sidewall surface of a sample tire having uneven marks in the sidewall surface thereof, the tire shape inspection method comprising:

at least one processor configured to implement;

a teaching operation process including

a mask image generating step of detecting boundary lines which are contours of the uneven marks in a sample original image which is a two-dimensional image of the sidewall surface of the sample tire, and generating a mask image showing positions of the boundary lines, and

a height offset image generating step of removing, from the sample original image, regions corresponding to the positions of the boundary lines shown in the mask image, and generating a height offset image by expressing heights of the remaining regions using one or a plurality of offset values; and

an inspection operation process including

a subtraction processing step of subtracting the height offset image from an inspection image which is a two-dimensional image of the sidewall surface of the inspection tire, and removing boundary regions shown by the mask image, and

a shape defect detecting step of inspecting the sidewall surface of the inspection tire for shape defects on the basis of an unevenness-removed image obtained as a result of the subtraction processing step,

wherein the height offset image generating step generates, in the sample original image, an offset profile that approximates a base surface which is a sidewall surface having no uneven marks, extracts the uneven marks from the sample original image on the basis of the generated offset profile, and sets heights of the extracted uneven marks as the offset values

wherein the height offset image generating step performs;

(I) extracting line data along a tire circumferential direction in the sample original image;

(II) extracting a base line of the sample tire on the basis of the line data;

(III) generating unevenness line data of the uneven marks by subtracting the base line data from the line data; and

(IV) setting heights of the generated unevenness line data as offset values of the uneven marks;

wherein the step (IV) performs;

(IV-1) setting an evaluation window having a predetermined width in a height direction of an uneven mark portion;

(IV-2) determining an average value of unevenness line data included in the evaluation window while shifting the evaluation window in a height direction of the unevenness line data; and

(IV-3) substituting the determined average value with a height of the uneven marks in the unevenness line data and using the height as the offset value.

2. The tire shape inspection method according to claim 1, wherein in the mask image generating step,

a differential image that emphasizes boundary line portions of the uneven marks is obtained by applying a differential filter;

and

the mask image is generated by binarizing the obtained differential image through application of a predetermined threshold value to the differential image.

3. The tire shape inspection method according to claim 2, wherein before application of the differential filter,

an undetected point in the sample original image is removed by interpolation;

and

the image from which the undetected point has been removed is planarized by removing curvature components of the sidewall surface from the image from which the undetected point has been removed, on the basis of a profile shape of the sidewall surface.

4. A tire shape inspection apparatus that inspects a sidewall surface of an inspection tire for shape defects by using an image of a sidewall surface of a sample tire having uneven marks in the sidewall surface thereof, the tire shape inspection apparatus comprising:

at least one processor configured to provide;

image picker for picking up a two-dimensional image of the sidewall surface;

mask image generator for detecting boundary lines which are contours of the uneven marks in a sample original image which is a two-dimensional image of the sidewall surface of the sample tire, and generating a mask image showing positions of the boundary lines;

height offset image generator for removing, from the sample original image, regions corresponding to the positions of the boundary lines shown in the mask image, and generating a height offset image by expressing heights of the remaining regions using one or a plurality of offset values;

subtraction processor for subtracting the height offset image from an inspection image which is a two-dimensional image of the sidewall surface of the inspection tire, and removing boundary regions shown by the mask image; and

shape defect detector for inspecting the sidewall surface of the inspection tire for shape defects on the basis of an unevenness-removed image obtained as a result of the subtraction processing step,

wherein the plurality of offset values are heights of the uneven marks obtained by generating, in the sample original image, an offset profile that approximates a base surface which is a sidewall surface having no uneven marks, and extracting the uneven marks from the sample original image on the basis of the generated offset profile

wherein the height offset image generator performs to;

(I) extract line data along a tire circumferential direction in the sample original image;

(II) extract a base line of the sample tire on the basis of the line data;

(III) generate unevenness line data of the uneven marks by subtracting the base line data from the line data; and

(IV-1) set an evaluation window having a predetermined width in a height direction of an uneven mark portion;

(IV-2) determine an average value of unevenness line data included in the evaluation window while shifting the evaluation window in a height direction of the unevenness line data; and

(IV-3) substitute the determined average value with a height of the uneven marks in the unevenness line data and using the height as the offset value.

5. The tire shape inspection apparatus according to claim 4, wherein the image picker includes

line light irradiator for irradiating the sidewall surface with one light section line;

an image pickup camera configured to pick up an image of the line light with which the sidewall surface is irradiated; and

a picked-up image memory configured to form a two-dimensional image of the sidewall surface by sequentially store one-line images picked up by the image pickup camera.