EP3580722A1

EP3580722A1 - Method for inspecting a surface

Info

Publication number: EP3580722A1
Application number: EP18707094.1A
Authority: EP
Inventors: Ahmad Kamal AIJAZI; Paul CHECCHIN; Laurent Malaterre; Laurent TRASSOUDAINE
Original assignee: Centre National de la Recherche Scientifique CNRS; Universite Clermont Auvergne; Sigma Clermont
Current assignee: Centre National de la Recherche Scientifique CNRS; Universite Clermont Auvergne; Sigma Clermont
Priority date: 2017-02-08
Filing date: 2018-02-07
Publication date: 2019-12-18
Also published as: FR3062741A1; WO2018146421A1; FR3062741B1

Abstract

The invention concerns a method for inspecting a surface, in particular the hull of a boat, comprising the following steps: a) acquiring images in two-dimensions also comprising point clouds in three dimensions of a surface to be inspected from at least two stations situated in different positions, said images having at least one area of overlap, b) constructing, in three dimensions, said surface to be inspected in a reference frame from the various acquired images, c) displaying said surface to be inspected in three dimensions from one of said stations and defining at least a first area to be processed, d) displaying said first area to be processed according to another of said stations and determining at least a second area to be processed, e) associating each of said first and second areas to be processed with at least one processing weighting coefficient, said weighting coefficient enabling the state of said first and second areas to be processed to be categorised according to quantitative and/or qualitative factors, f) determining the surface areas of said first and second areas to be processed, and, g) obtaining, at least from said determined surface areas and said first and second areas to be processed, a total surface to be processed.

Description

METHOD FOR INSPECTING A SURFACE

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to the field of surface inspection methods for identifying and defining defects. In particular, it relates to a method of inspecting a surface using a plurality of stations in order to construct the inspected surface in three dimensions and to identify the defects therein.

STATE OF THE PRIOR ART

Currently, it is known inspection methods implementing cameras generating two-dimensional images in order to build three-dimensional images by stereoscopy. Such methods are used to detect surface defects by exploiting, for example, the effect of albedo. However, using current methods, these defects are generally detected or even sized, but are not qualified according to whether they are derived from oxidation, corrosion, wear, etc. Moreover, the processes implemented today do not allow to navigate through the reconstructed images in three dimensions in order to accurately inspect the surface and identify more subtle defects that could not be detected via the albedo effect or any other effect.

OBJECTIVE OF THE INVENTION

The method of inspecting a surface of the invention aims to remedy all or part of the disadvantages of the state of the art and aims in particular to provide a suitable method for exploring the entire surface to be analyzed to accurately identify and define defects from different inspection points of view.

SUMMARY OF THE INVENTION

This objective is achieved through a method of inspecting a surface, in particular a boat hull, comprising the following steps: a) acquiring two-dimensional images further comprising three-dimensional point clouds of a surface to be inspected from at least two stations at different positions, said images having at least one overlapping zone, b) constructing in three dimensions said surface to be inspected in a reference frame from the different images acquired,

c) visualizing said surface to be inspected in three dimensions from one of said stations and defining at least a first zone to be treated, d) visualizing said first zone to be treated according to another of said stations and determining at least a second zone to be treated, e ) associating each of said first and second areas to be treated with at least one treatment weighting coefficient, the weighting coefficient making it possible to categorize the state of the first and second areas to be treated according to quantitative and / or qualitative factors,

f) determining the areas of said first and second zones to be treated,

g) obtaining, at least from said determined areas and said first and second areas to be treated, a total area to be treated.

For the purposes of the present invention, the term station, a camera or sensor capable of obtaining two-dimensional images further comprising point clouds in three dimensions.

The marker may be any reference. It is in principle linked to one of the stations, for example the first one.

For the purposes of the present invention, the term "zone to be treated" means an area comprising one or more defects that can be defined by qualitative and / or quantitative characters. For the purposes of the present invention, the first zone to be treated is defined as a zone to be treated defined according to a station. For the purposes of the present invention, the second zone to be treated is further understood to mean a zone to be treated defined according to another station different from that according to which the first zone to be treated has been defined.

For the purposes of the present invention, the term "treatment weighting coefficient" means a coefficient that makes it possible to categorize the state of the zone to be treated (whether it is a first or second zone) according to quantitative factors and / or or qualitative that may correspond to the defined area to be treated.

It should be noted that for the implementation of step a), it is necessary to use at least two stations. Thus, it is possible to observe the surface to be inspected according to different points seen. This has the advantage of being able, later on, to identify and define second zones to be treated according to a second station, different from the first station used to locate and define first zones to be treated. It should be noted that, with the aid of the second station, it is therefore possible to perceive second zones to be treated, but also to perceive at least a portion of the first zones to be treated in order to correctly associate the latter with coefficients of appropriate processing weights when there is any doubt about the treatment weighting factors to be associated.

However, the method can implement more than two stations if each station has at least one overlap area with at least one other station. It should be noted that the visualization step d) has the advantage of avoiding redefining the first or the first zones to be treated defined according to the first station, and defining one or more second zones to be treated according to the second station which could not be defined according to the first station. Advantageously, the method may further comprise, once said total surface to be treated obtained, a step of archiving said first and second areas to be treated.

This archiving step has the advantage of archiving only information relating to the areas considered to be treated, whether they are first or second areas to be treated. Thus, it frees itself from an integral storage of the surface to be inspected in three dimensions by omitting the archiving of areas not defined as areas to be treated. Advantageously, the method may further comprise a step of comparing said first and second areas to be treated according to said treatment weighting coefficients to which they are associated.

This present comparison step can be used to compare the different previously defined areas to be treated (whether these are first or second areas) as a function of weighting coefficients associated with them. This step can also make it possible to compare the totality of the zones to be treated defined during a first inspection with those obtained after a second inspection. For the purposes of the present invention, the term "first inspection" means an inspection of a surface made at a time t. For the purposes of the present invention, the term "second inspection" means an inspection of the same surface but carried out at a time t + 1.

Preferably, all of said surface to be inspected may be defined by said first and second areas to be treated.

The invention also relates to a computer program comprising instructions adapted to the implementation of each of the steps of the method described above when said program is executed on a calculating machine.

The invention also relates to a system comprising means adapted to the implementation of each of the steps of the method described above.

Other features and innovative advantages of the invention will become apparent on reading the description below, provided for information only and not limiting.

DETAILED DESCRIPTION OF AN EMBODIMENT

According to a particular embodiment of the invention, the inspection method is applied to a surface of a hull of a boat. However, it should be noted that this process can be used in the field of aeronautics, penstocks for high pressure water, metal works, surface treatment, petrochemical, building, nuclear.

For the implementation of this method, two stations are used, a first and a second, such as Leica cameras P20, P40, C10. Thus, during a first step, images of at least a portion of the surface to be inspected from a boat hull are acquired, including surface defects. These images are acquired from the two stations located at different positions, the images having at least one overlap area.

During a next step, the surface to be inspected in a reference frame, for example, at the first station, is constructed in three dimensions from the different images previously acquired. An image representing the surface to be inspected is thus obtained, this image preferably being observable on at least one screen. This image shows a three-dimensional representation and a color representation of the scene.

In a next step, the surface to be inspected in three dimensions on the screen is visualized only according to the first station. It is thus possible to precisely explore the part of the surface obtained by this first station and identify any type of surface defect.

Next, several first zones to be treated are defined, each of these first zones comprising a defect identified via the abovementioned image. The first areas to be treated were identified by an operator by clicking the four corners of a quadrilateral consistent with the defects identified. Then, this operator defines each of these first zones by assigning them weighting coefficients. For example, the weighting coefficients are associated with each of the first zones to be treated according to their type, their position, their geometry, their dimensions and their density.

The allocation of these weighting coefficients can be performed following the assignment to each of these first zones, one or more labels, or labels, illustrating one or more particular characters mentioned above. In a next step, the first zones to be treated are visualized according to the second station. In this way, it is possible to perceive differently the first zones to be treated but also to perceive new ones which were not perceptible according to the first station, these new zones being called second zones to be treated. Indeed, the use of a second station as a different point of view, may allow to observe subtleties, details, the surface not perceptible state according to the first station, and may be due to illumination or different surface orientation for example. Then, several second zones to be treated are determined and the first zones to be treated are used to characterize the targeted defects by associating them with weighting coefficients.

Then we determine the areas of said first and second areas to be treated. These areas are transformed into non-cyclic quadrilaterals whose area is calculated using a modified version of the Brahmagupta formula.

For the record, the Brahmagupta formula for a cyclic quadrilateral, that is to say a simple quadrilateral inscribed in a circle, is:

"J (a ² + b ² + c ² + d ² ) ² + 8abcd-2 (a ² + b ² + c ² + d ² ),,. . . . .

1 0 K = - with K the surface and a, b, c and d the

4

lengths of the four sides.

The version adapted to the surface area to be treated then becomes: 4] K =

are the lengths of the diagonals of the quadrilateral and s the semi-perimeter, the latter being defined as s = ^{a + b + c + d}

2

In a next step, at least from said determined areas and first and second zones to be treated, a total area to be treated is obtained.

During an optional step, once said total surface to be treated obtained, it is possible to archive the first and second areas to be treated. Thus, the storage of information relating to the areas considered to be not to be processed is dispensed with, and only the information relating to the zones is stored with a maximum resolution, for example. treat. This information may, for example, be relative to the designation of the area to be treated, the coordinates of the four corners of the quadrilateral encompassing it, the weighting coefficient or coefficients associated with it, and any additional comments added by the operator.

During an optional additional step, the first and second zones to be treated can be compared as a function of the treatment weighting coefficients to which they are associated. It should be noted that it is also possible to compare the definitions of the areas to be treated with an inventory whose results were obtained during a previous implementation of the method.

In another optional step, it is possible to define the entire surface to be inspected by the first and second areas to be treated. It should be noted that it is possible to carry out a computer program comprising instructions adapted to the implementation of each of the aforementioned steps when said program is executed on a computing machine.

It should also be noted that it is possible to implement a system comprising means adapted to the implementation of each of the aforementioned steps of the method.

The invention is described in the foregoing by way of example. It is understood that one skilled in the art is able to achieve different embodiments of the invention, for example by combining the various characteristics above taken alone or in combination, without departing from the scope of the invention. .

Claims

1. A method of inspecting a surface, particularly a boat hull, comprising the steps of:

a) acquiring two-dimensional images further comprising three-dimensional point clouds of a surface to be inspected from at least two stations at different positions, said images having at least one overlapping zone, b) constructing in three dimensions said surface to be inspected in a reference frame from the different images acquired,

c) visualizing said surface to be inspected in three dimensions from one of said stations and defining at least a first zone to be treated, d) visualizing said first zone to be treated according to another of said stations and determining at least a second zone to be treated, e associating each of said first and second zones to be treated with at least one treatment weighting coefficient, said weighting coefficient making it possible to categorize the state of said first and second zones to be treated according to quantitative and / or qualitative factors,

f) determining the areas of said first and second zones to be treated,

2. The method of claim 1, further comprising, once said total surface area to be treated obtained, a step of archiving said first and second areas to be treated.

3. Method according to claims 1 or 2, further comprising a step of comparing said first and second areas to be treated in function of said treatment weighting coefficients to which they are associated.

4. Computer program comprising instructions adapted to the implementation of each of the steps of the method according to any one of claims 1 to 3 when said program is executed on a computer machine.

5. System comprising means adapted to the implementation of each of the steps of the method according to any one of claims 1 to 3.