Compagnie Generale Des Etablissements Michelin

Michelin Recherche Et Technique S.a.

Compagnie Generale Des Establissements Michelin

Compagnie Generale Des Etablissments Michelin

Michelin Recherche Et Techniques S.a.

Societe Detechnologie Michelin

Jean-Paul Zanella

Alexandre Joly

Guillaume Noyel

Claire Moreau

Yusi Shen

Davy Vernier

Marc Calvet

A method of rectifying an image representing a surface of a tire is provided. According to the method, a circumferential marking present on a tire is detected in an image of the tire. Based on the marking, and for each line of a plurality of lines of the image, a reference position on the tire is determined. For each of the lines of the image, a difference between the reference position on the line under analysis and a minimum value of the reference positions for all of the lines of the image is determined. For each of the lines of the image, pixels of the line under analysis are radially offset by a value of the difference.

Tire image rectifying method

A method for processing an image of a surface of a tire to be inspected is described. A three-dimensional digital image is captured of the surface, and each pixel of a plane of the image is assigned an item of information relating to an elevation of the pixel with respect to the surface. By utilizing of a morphological operator that uses a structuring element, a first transformation of the image of the surface is performed with aid of an opening and then of a closing, so as to tailor a grey level of pixels situated abnormally above or below the surface.

Analysis of the digital image of the external surface of a tyre and processing of false measurement points

A method for processing an image of a surface of a tire under inspection is described. A three-dimensional digital image of the surface is captured and, for each point of the captured image, a grey-level value corresponding to an elevation is assigned to the point. Utilizing a first morphological operator that uses a rectangular key element, a closure-type first transformation of the image of the surface is carried out. Utilizing a second morphological operator that uses a rectangular key element, an opening-type second transformation of the surface is carried out. For each point of the image, a grey-level value equal to a minimum value between a grey-level value at that point obtained in a preceding step and a grey-level value at that point is assigned, so as to eliminate false measurement points.

Analysis of the digital image of the internal surface of a tyre and processing of false measurement points

In a method for processing an image of a surface of a tire, a 3D digital image of the surface is captured, and each pixel of the captured image is assigned a grey level value proportional to an elevation of a corresponding point with respect to the surface. The pixels are placed in rows and columns. A search is made for zones of the surface that include pixels having a grey-level value lower than a given threshold. Boundaries of an encompassing box that includes one or more of the zones are determined. Inside the encompassing box, a grey-level value equal to a mean grey-level value of a set of reference pixels (K, s) positioned in a zone situated in immediate proximity to a pixel under consideration is assigned to each of the pixels whose grey-level value is lower than the given threshold.

Analysis of the digital image of the surface of a tyre and processing of non-measurement points

Method for detecting and evaluating the protrusions that appear on cords coming from a twisting/rubberizing process, by the digital processing of the image of a layer of cord formed by a number of turns wound around the core of a spool (), which method comprises the steps during which: A) the raw digital image of the surface of the layer of cord over one complete revolution of the spool is taken using a linear camera (); B) the raw image is displayed flat so as to limit the influence of the variations in lighting and in the brightness of the wires; C) the flattened image is segmented so as to reveal the dark areas that contain protrusion areas; D) the segmented image is a processed using a series of morphological processing operations in order to separate and select the shapes likely to represent protrusions and areas likely to represent shadows; and E) an evaluation value is assigned to the final image obtained and the evaluation value is compared with a threshold value.

Method and device for the automatic inspection of a cable spool

A method of determining relief markings on a tire's sidewall surface includes assigning, to each pixel of a three-dimensional image of the surface, a grey-level value proportional to an elevation point corresponding to the pixel, to obtain a starting image. Using linear structuring elements of successively increasing sizes and oriented circumferentially, a series of successive morphological openings is performed iteratively on the starting surface. An image value obtained after a morphological opening using a structuring element is subtracted from an image value obtained after a morphological opening using a structuring element of an immediately lower size, to obtain a succession of images flattened by differencing. A thresholding operation is performed on the images flattened by differencing, to obtain binary images. A set-theoretic union of values of each of the binary images is performed, to obtain a final binary image in which markings appear in relief.

Method for determining markings in relief on the outer surface of the sidewall of a tyre

A method for inspecting tire tread, having circumferentially juxtaposed elements separated by identically shaped boundaries and having patterns arranged in a predetermined sequence, includes: acquiring an image of a surface of the tire tread, the image including pixels associated with a light-intensity level; transforming the image by circumferentially offsetting pixels located axially at a same distance (x, x) from a given circumferential reference (OY), by an inverse (&#x2212;y, &#x2212;y) of a circumferential offset (y, y) with respect to an axial line (OX) of a point (P, P) located on a boundary line of known shape at the same axial distance (x, x) from the circumferential reference (OY), such that boundaries between elements appear as straight traces orientated in an axial direction; and analyzing the image to identify points located on an axially orientated straight line, the points being treated as points located on a boundary line between two elements.

Method for identifying and defining basic patterns forming the tread pattern of a tyre

A method of determining relief elements on a tire surface includes capturing a three-dimensional image of the surface and assigning to each pixel (i, j) of the image a grey-level value proportional to a topographic elevation of a point corresponding to the pixel, so as to obtain a starting image (&#x192;). The method also includes transforming the starting image (&#x192;) by a first top-hat operation, with aid of a first structuring element, so as to obtain an image (&#x192;) flattened by differencing, (&#x192;=&#x192;&#x2014;&#x3b3;(&#x192;)). The method further includes performing a thresholding operation on the image flattened by differencing, so as to obtain a segmented image, (T(&#x192;)=seg) in which relief elements appear white on a black background.

Method for determining elements in relief on the surface of a tyre

A tire tread, having circumferentially juxtaposed elements separated from one another by identically shaped boundaries and having a least one basic pattern, is inspected by: producing an image of the tire tread; identifying tread wear indicators on the image; grouping together sub-sets of the indicators according to the basic pattern(s) included in the indicators; determining a characteristic point of each of the sub-sets of the indicators; determining a sequence of distances by computing distances between the characteristics points of each of the sub-sets of the indicators; comparing and the sequence of distances with a known sequence of distances between characteristic points of the basic pattern(s) to confirm coincidence thereof; and projecting a shape of a boundary between elements of the tire tread onto a surface to be inspected according to the known sequence of distances between characteristic points of the basic pattern(s).

A device for evaluating the appearance of the surface of a tire (P) comprising a color linear camera () comprising means () for separating the light beam (F) reflected by the surface of said tire (P) and entering the camera () into at least two base colors (R, G, B) of given wavelength, so as to direct the light beam to as many sensors () capable of obtaining a basic image in gray level () for each of the base colors, as many lighting means () as base colors, said lighting means being oriented so as to light the surface to be evaluated at different angles, characterized in that each of the lighting means () emits a colored light (R, G, B) that differs from that of the other lighting means, and the wavelength of which corresponds substantially to the wavelength of one of the base colors selected by the camera.

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Clermont-Ferrand, France

Jean-Paul Zanella