METHOD FOR RECONSTRUCTING A THREE-DIMENSIONAL SURFACE USING AN ULTRASONIC MATRIX SENSOR

Abstract

A method for reconstructing a three-dimensional surface of a part using an ultrasonic matrix sensor including scanning the three-dimensional surface using a matrix sensor at different measurement points located at the intersection of scanning rows and of increment rows at each measurement point, acquiring a temporal row image representing a reflected wave amplitude received by each element from a selected row of the matrix sensor and acquiring a temporal column image representing a reflected wave amplitude received by each element from a selected column of the matrix sensor, constructing a two-dimensional row image for each scanning row on the basis of the temporal row images constructing a two-dimensional column image for each increment row on the basis of the temporal column images, and constructing a three-dimensional image on the basis of the two dimensional row images and of the two-dimensional column images.

Claims

1. A method for reconstructing a three-dimensional surface of a part using a matrix sensor comprising a plurality of elements arranged in rows and columns, each element being arranged to be able to emit an incident wave in the direction of the part and to generate a signal representing a reflected wave received by said element, the method comprising: scanning the three-dimensional surface with the matrix sensor, the matrix sensor being moved in a plurality of measurement points, each measurement point being defined by the intersection of a scanning line, among a set of scanning lines parallel to the rows of elements of the matrix sensor, and an increment line, among a set of increment lines parallel to the columns of elements of the matrix sensor, at each measurement point, successively acquiring a temporal row image comprising emitting an incident wave by one or more elements of a selected row of the matrix sensor and generating, for each of the elements of the selected row, a temporal signal representing an amplitude over time of a reflected wave received by said element, the temporal row image being formed by all the temporal signals of the elements of the selected row, and acquiring a temporal column image comprising emitting an incident wave by one or more elements of a selected column of the matrix sensor and generating, for each of the elements of the selected column, a temporal signal representing an amplitude over time of a reflected wave received by said element, the temporal column image being formed by all the temporal signals of the elements of the selected column, for each scanning line, constructing, from all the temporal row images corresponding to said scanning line, a two-dimensional image of the row in a plane passing through the elements of the selected row, each two-dimensional image of the row being defined by a reflected wave amplitude at various points of the plane, for each increment line, constructing, from all the temporal column images corresponding to said increment line, a two-dimensional column image in a plane passing through the elements of the selected column, each two-dimensional column image being defined by a reflected wave amplitude at various points of the plane, and from the two-dimensional row images and the two-dimensional column images, constructing a three-dimensional image of the part, the three-dimensional image being defined by a reflected wave amplitude at various points of a volume containing the two-dimensional row images and the two-dimensional column images.

2. The reconstruction method according to claim 1, wherein the scanning lines are straight lines or curved lines, and/or the increment lines are straight lines or curved lines.

3. The reconstruction method according to claim 1, wherein the scanning of the three-dimensional surface is implemented with a scanning step less than a length of a row of elements of the matrix sensor and/or with an increment step less than a length of a column of elements of the matrix sensor.

4. The reconstruction method according to claim 1, wherein each acquisition of a temporal row image comprises emitting an incident wave successively by each of the elements of the selected row and generating, for each pair of elements of the selected row, the first element of the pair designating the element of the pair located at the row and at the column that emitted the incident wave, and the second element of the pair designating the element located at the row and at the column that received the reflected wave, a temporal signal representing an amplitude over time of a reflected wave received by said second element, the temporal row image being formed by all the temporal signals of the selected row.

5. The reconstruction method according to claim 1, wherein each acquisition of a temporal column image comprises the emission of emitting an incident wave successively by each of the elements of the selected column and the generation generating, for each pair of elements of the selected column, the first element of the pair designating the element located at the row and at the column that emitted the incident wave and the second element of the pair designating the element situated at the row and at the column that received the reflected wave, a temporal signal representing an amplitude over time of a reflected wave received by said second element, the temporal column image being formed by all the temporal signals of the selected column.

6. The reconstruction method according to claim 5, wherein constructing (18) each two dimensional column image comprises implementing a total focusing method.

7. The reconstruction method according to claim 1, wherein each acquisition of a temporal row image comprises successively emitting a plurality of incident waves by a plurality of elements of the selected row, each incident wave being emitted with a predetermined angle of incidence, and the generation of generating a temporal signal for each element of the selected row and for each incident wave with the predetermined angle of incidence, the temporal row image being formed by all the temporal signals of the selected row.

8. The reconstruction method according to claim 1, wherein each acquisition of a temporal column image comprises the successive emission of successively emitting a plurality of incident waves by a plurality of elements of the selected column, each incident wave being emitted with a predetermined angle of incidence, and the generation of generating a temporal signal for each element of the selected row and for each incident wave with the predetermined angle of incidence, the element designating the element located at the row m.sub.r and at the column n.sub.s that received the reflected wave, the temporal column image being formed by all the temporal signals of the selected column.

9. The reconstruction method according to claim 7, wherein constructing each two-dimensional column image comprises implementing a plane wave imaging method.

10. The reconstruction method according to claim 1, wherein constructing each two-dimensional row image comprises detecting contours, so as to determine a profile of the part in the plane of said two-dimensional row image, and/or constructing each two-dimensional column image comprises detecting contours, so as to determine a profile of the part in the plane of said two-dimensional column image.

11. The reconstruction method according to claim 1, further comprising: at each measurement point successively acquiring a plurality of temporal row images for various selected rows, each acquisition of a temporal row image comprising emitting an incident wave by one or more elements of the selected row of the matrix sensor and generating, for each of the elements of the selected row, a temporal signal representing an amplitude over time of a reflected wave received by said element, each temporal row image being formed by all the temporal signals of the elements of said selected row, and for each scanning line and for each of the selected rows constructing, from all the temporal images of the line corresponding to said scanning line and to said selected row, a two-dimensional row image in a plane passing through the elements of the selected row, each two-dimensional row image being defined by a reflected wave amplitude at various points of the plane.

12. The reconstruction method according to claim 1, further comprising: at each measurement point, successively acquiring a plurality of temporal column images for various selected columns, each acquisition of a temporal column image comprising emitting an incident wave by one or more elements of the selected column of the matrix sensor and the generating, for each of the elements of the selected column, a temporal signal representing an amplitude over time of a reflected wave received by said element, each temporal column image being formed by all the temporal signals of the elements of said selected column, and for each increment line and for each of the selected columns, constructing, from all the temporal column images corresponding to said increment line and to said selected column, a two-dimensional column image in a plane passing through the elements of the selected column, each two-dimensional column image being defined by a reflected wave amplitude at various points of the plane.

13. The reconstruction method of claim 4, wherein constructing each two-dimensional row image comprises implementing a total focusing method.

14. The reconstruction method of claim 7, wherein constructing each two-dimensional row image comprises implementing a plane wave imaging method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, details and advantages of the invention will emerge from a reading of the following description given solely by way of example and referring to the accompanying drawings, on which:

[0038] FIG. 1A shows an example of a matrix sensor, a row of which is selected for implementing the method for reconstructing a three-dimensional surface of a part according to the invention;

[0039] FIG. 1B shows the matrix sensor of FIG. 1A, a column of which is selected for implementing the reconstruction method according to the invention;

[0040] FIG. 2 shows an example of steps of the reconstruction method according to the invention;

[0041] FIG. 3A shows an example of scanning of a plane surface;

[0042] FIG. 3B shows an example of scanning of a surface forming a portion of a torus;

[0043] FIG. 4 illustrates schematically the formation of two-dimensional row images and two-dimensional column images;

[0044] FIG. 5A shows an example of a two-dimensional row image obtained for the surface in FIG. 3B at a scanning line not passing through a local deformation;

[0045] FIG. 5B shows an example of a two-dimensional row image obtained for the surface in FIG. 3B at a scanning line passing through a local deformation;

[0046] FIG. 6A shows an example of a two-dimensional column image obtained for the surface in FIG. 3B at an increment line not passing through a local deformation;

[0047] FIG. 6B shows an example of a two-dimensional column image obtained for the surface in FIG. 3B at an increment line passing through a local deformation;

[0048] FIG. 7 shows an example of a three-dimensional image obtained for the surface in FIG. 3B from two-dimensional row images and two-dimensional column images;

[0049] FIG. 8 shows an example of an extrapolated three-dimensional image obtained from the three-dimensional image in FIG. 7.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0050] FIGS. 1A and 1B show an example of an ultrasonic matrix sensor 1 able to be used in a method for reconstructing a three-dimensional surface of a part according to the invention. The matrix sensor 1 comprises a set of sixteen rows by sixteen columns of elements E(m,n), with m and n two integers such that 1≤m≤16 and 1≤n≤16. In general terms, the invention may be based on any ultrasonic matrix sensor comprising a set of M rows by N columns of elements, with M and N two integers greater than or equal to three. Each element E(m,n) of the matrix sensor 1 is arranged to be able to emit an incident signal, in the form of an incident wave, in the direction of a surface of a part to be reconstructed, and to be able to receive a reflected wave and to convert it into a signal representing an amplitude of this reflected wave over time. When the elements are considered during the emission of an incident wave, they are denoted E(m.sub.t, n.sub.t) and, when they are considered during the reception of a reflected wave, they are denoted E(m.sub.r, n.sub.r). For the reconstruction method according to the invention, one of the rows and one of the columns are selected. For the remainder of the description, the selected row is denoted m.sub.s and the selected column n.sub.s. Optionally, a plurality of rows m.sub.sk and a plurality of columns n.sub.sk may be selected successively. FIG. 1A shows the selection of the ninth row (m.sub.s=9) and FIG. 1B shows the selection of the eighth column (n.sub.s=8).

[0051] FIG. 2 shows an example of a method for reconstructing a three-dimensional surface of a part according to the invention. The method 10 comprises an iteration of the following steps for various measurement points O(i,j): a step 11 of moving the matrix sensor 1 to the measurement point O(i,j) in question, a step 12 of acquiring a temporal row image SL.sub.i,j, a step 13 of constructing a local two-dimensional row image X.sub.i,j, a step 14 of acquiring a temporal column image SC.sub.i,j, a step 15 of constructing a local two-dimensional column image Y.sub.i,j and a step 16 of checking the completeness of the scanning. After iteration of these steps 11 to 15 at each of the measurement points O(i, j), i.e. after scanning the whole of the three-dimensional surface to be reconstructed, the method comprises a step 17 of constructing two-dimensional row images X.sub.i, a step 18 of constructing two-dimensional column images Y.sub.j and a step 19 of constructing a three-dimensional image.

[0052] The steps 11 and 16 give rise to a scanning of the three-dimensional surface with the matrix sensor 1. This scanning comprises moving the matrix sensor 1 at each measurement point O(i, j) where i designates a scanning line L.sub.i among a set of scanning lines parallel to each other, and j designates an increment line L.sub.j among a set of increment lines parallel to each other. Each measurement point O(i, j) is thus defined as the intersection of a scanning line L.sub.i and of an increment line L.sub.j. The scanning lines L.sub.i and the increment lines L.sub.j are preferably adapted to the three-dimensional surface to be reconstructed.

[0053] FIG. 3A shows a first example of scanning of a three-dimensional surface by the matrix sensor 1 in the case of a substantially plane three-dimensional surface 2 and FIG. 3B shows a second example of scanning in the case of a three-dimensional surface 3 forming a portion of a torus. The three-dimensional surface 3 includes a zone 4 locally deformed by a hollow. In each case, this movement made by the matrix sensor 1 for passing through the various measurement points O(i, j) successively follows the various scanning lines L.sub.i, the acquisition steps 12 and 14 being implemented after each movement of the matrix sensor by an increment step p.sub.j. At the end of each scanning line L.sub.i, the matrix sensor is moved to a following scanning line L.sub.i+1, the adjacent scanning lines L.sub.i being separated by a scanning step p.sub.i, shown in FIG. 4. In FIG. 3A, the scanning lines L.sub.i are straight lines parallel to each other and to the rows of elements E(m,n) of the matrix sensor 1, and the increment lines L.sub.j are straight lines parallel to each other and to the columns of elements E(m, n) of the matrix sensor 1. In FIG. 3B, the scanning lines L.sub.i form portions of a circle centred on the axis of revolution of the major radius of curvature of the torus and the increment lines L.sub.i form portions of a circle centred on the axis of revolution of the minor radius of curvature of the torus. Having regard to the respective dimensions of the matrix sensor 1 and of the torus, the scanning lines L.sub.i can be considered to be parallel to the rows of elements E(m, n) of the matrix sensor 1 and the increment lines L.sub.1 can be considered to be parallel to the columns of elements E(m,n). It may be noted that the matrix sensor 1 does not physically follow the increment lines L.sub.j during the scanning. Nevertheless, the matrix sensor 1 being moved with a regular increment step p.sub.j along the scanning lines L.sub.i, it passes through each of the measurement points O(i, j) following the increment lines L.sub.j. The increment step p.sub.j, shown in FIG. 4, thus defines a distance between two adjacent increment lines.

[0054] The step 12 of acquiring a temporal row image SL.sub.i,j for the measurement point O(i, j) in question comprises emitting an incident wave successively by each of the elements E(m.sub.s, n.sub.t) of a selected row m.sub.s of the matrix sensor 1, and generating a temporal signal SL.sub.i,j(m.sub.s, n.sub.t, n.sub.r, t) for each pair of elements {E(m.sub.s, n.sub.t); E(m.sub.s, n.sub.r)} of the selected row m.sub.s, the element E(m.sub.s, n.sub.t) designating the element located at the row m.sub.s and at the column n.sub.t that emitted the incident wave and the element E(m.sub.s, n.sub.r) designating the element situated at the row m.sub.s and at the column n.sub.r that received the reflected wave. The signal SL.sub.i,j(m.sub.s, n.sub.t, n.sub.r, t) represents an amplitude over time t of the reflected wave received by the element E(m.sub.s, n.sub.r) and resulting from a reflection of the incident wave emitted by the element E(m.sub.s, n.sub.t). The temporal row image for the measurement point O(i, j), denoted SL.sub.i,j(m.sub.s, t) and abbreviated to SL.sub.i,j, is formed by all the temporal signals SL.sub.i,j(m.sub.s, n.sub.t, n.sub.r, t) generated for the various pairs of elements {E(m.sub.s, n.sub.t); E(m.sub.s, n.sub.r)} of the selected row m.sub.s.

[0055] The step 13 of constructing a local two-dimensional row image X.sub.i,j for the point O(i,j) in question comprises determining, from the corresponding temporal row image SL.sub.i,j(m.sub.s, t), a reflected wave amplitude at various points of a plane P.sub.i(m.sub.s) passing through the elements E(m.sub.s, n) of the selected row m.sub.s. The plane P.sub.i(m.sub.s) is perpendicular to the columns of the matrix sensor 1. According to a particular embodiment, the local two-dimensional row image X.sub.i,j is constructed by a total focusing method (TFM).

[0056] The step 14 of acquiring a temporal column image SC.sub.i,j for the measurement point O(i, j) in question comprises sending an incident wave successively by each of the elements E(m.sub.t, n.sub.s) of a selected column n.sub.s of the matrix sensor 1, and generating a temporal signal SC.sub.i,j(m.sub.t, m.sub.r, n.sub.s, t) for each pair of elements {E(m.sub.t, n.sub.s); E(m.sub.r,n.sub.s)} of the selected column n.sub.s, the element E(m.sub.t, n.sub.s) designating the element located at the row m.sub.t and at the column n.sub.s that emitted the incident wave and the element E(m.sub.r, n.sub.s) designating the element located at the row m.sub.r and at the column n.sub.s that received the reflected wave. The signal SC.sub.i,j(m.sub.t, m.sub.r, n.sub.s, t) represents an amplitude over time t of the reflected wave received by the element E(m.sub.r, n.sub.s) and resulting from a reflection of the incident wave emitted by the element E(m.sub.t, n.sub.s). The temporal column image for the measurement point O(i, j), denoted SC.sub.i,j(n.sub.s,t) and abbreviated to SC.sub.i,j, is formed by all the temporal signals SC.sub.i,j(m.sub.t, m.sub.r, n.sub.s, t) generated for the various pairs of elements {E(m.sub.t, n.sub.s); E(m.sub.r, n.sub.s)} of the selected column n.sub.s.

[0057] The step 15 of constructing a local two-dimensional column image Y.sub.i,j for the point O(i, j) in question comprises determining, from the corresponding temporal column image SC.sub.i,j(n.sub.s, t), a reflected wave amplitude at various points of a plane P.sub.j(n.sub.s) passing through the elements E(m, n.sub.s) of the selected column n.sub.s. The plane P.sub.j(n.sub.s) is perpendicular to the rows of the matrix sensor 1. According to a particular embodiment, the local two-dimensional column image Y.sub.i,j is constructed by a total focusing method (TFM).

[0058] The step 12 of acquiring a temporal row image SL.sub.i,j and the step 14 of acquiring a temporal column image SC.sub.i,j for a given measurement point O(i, j) are implemented successively so as to avoid interference between the waves emitted by the elements of the selected row and those emitted by the elements of the selected column. The order of these steps may of course be reversed.

[0059] Moreover, it has been considered, in each step of acquiring a temporal row or column image, that an incident wave is emitted successively by each of the elements of the row or of the column selected. Nevertheless, each step 12 of acquiring a temporal row image SL.sub.i,j may comprise the successive emission of a plurality of incident waves by a plurality of elements of the selected row m.sub.s, each incident wave being emitted with a predetermined angle of incidence θ.sub.k, and the generation of a temporal signal SL.sub.i,j(m.sub.s, n.sub.r, θ.sub.k, t) for each element E(m.sub.s, n.sub.r) of the selected row and for each incident wave. The incident waves may in particular be emitted with angles of incidence different from each other. The temporal row image for the measurement point O(i,j), also denoted SL.sub.i,j(m.sub.s,t) and abbreviated to SL.sub.i,j, is then formed by all the temporal signals SL.sub.i,j(m.sub.s, n.sub.r, θ.sub.k, t) generated for the various pairs of elements E(m.sub.s, n.sub.r) of the selected row and of incident wave. The step 13 of constructing a local two-dimensional row image X.sub.i,j for the point O(i,j) is constructed from the corresponding temporal row image SL.sub.i,j(m.sub.s, t). In a similar manner, each step 14 of acquiring a temporal column image SC.sub.i,j may comprise the successive emission of a plurality of incident waves by a plurality of elements of the selected column n.sub.s, each incident wave being emitted with a predetermined angle of incidence θ.sub.k, and the generation of a temporal signal SC.sub.i,j(m.sub.r, n.sub.s, θ.sub.k, t) for each element E(m.sub.r, n.sub.s) of the selected column and for each incident wave. The incident waves may in particular be emitted with angles of incidence different from each other. The temporal column image for the measurement point O(i,j), also denoted SC.sub.i,j(n.sub.s, t) and abbreviated to SC.sub.i,j, is then formed by all the temporal signals SC.sub.i,j(m.sub.r, n.sub.s, θ.sub.k, t) generated for the various pairs of elements E(m.sub.r, n.sub.s) of the selected column and of incident wave. The step 15 of constructing a local two-dimensional column image Y.sub.i,j for the point O(i,j) in question is constructed from the corresponding temporal column image SC.sub.i,j(n.sub.s, t).

[0060] The step 16 of checking the completeness of the scanning consists of checking that the matrix sensor has been moved at each measurement point O(i,j) and that a local two-dimensional row image X.sub.i,j and a local two-dimensional column image Y.sub.i,j have been constructed at each of these points.

[0061] The step 17 of constructing two-dimensional row images X.sub.i comprises, for each scanning line L.sub.i, a concatenation of all the local two-dimensional images X.sub.i,j of the scanning line L.sub.i in question. Each two-dimensional row image X.sub.i then represents a reflected wave amplitude at various points of the plane P.sub.i(m.sub.s) passing through the elements E(m.sub.s, n) of the selected row m.sub.s. The concatenation is for example implemented by adding the reflected wave amplitude at the various points of the plane P.sub.i(m.sub.s).

[0062] In a similar manner, the step 18 of constructing two-dimensional column images Y.sub.j comprises, for each increment line L.sub.j, a concatenation of all the local two-dimensional images X.sub.i,j of the increment line L.sub.i in question. Each two-dimensional column image Y then represents a reflected wave amplitude at various points of the plane P.sub.j(n.sub.s) passing through the elements E(m, n.sub.s) of the selected column n.sub.s. The concatenation is for example implemented by adding the reflected wave amplitude at the various points of the plane P.sub.j(n.sub.s).

[0063] FIG. 4 illustrates schematically the formation of the two-dimensional row X.sub.i and column Y.sub.j images after scanning of the matrix sensor 1 following the various scanning lines L.sub.i and increment lines L.sub.j. The two-dimensional row images X.sub.i represent the amplitude of the reflection of the incident waves in the planes P.sub.i(m.sub.s), which constitute planes substantially perpendicular locally to the surface of the part. The two-dimensional column images Y.sub.j represent the amplitude of the reflection of the incident waves in the planes P.sub.j(n.sub.s), which constitute planes substantially perpendicular locally to the surface of the part and to the planes P.sub.i(m.sub.s).

[0064] FIGS. 5A and 5B show two examples of two-dimensional row images X.sub.i obtained for the three-dimensional surface 3 shown in FIG. 3B and forming a portion of a torus. These images are obtained by the steps 11 to 18 of the method described above with the use of a total focusing method. FIG. 5A shows a two-dimensional row image X.sub.i for a scanning line L.sub.i not passing through the locally deformed zone 4 and FIG. 5B shows a two-dimensional row image X.sub.i for a scanning line L.sub.i passing through the locally deformed zone 4.

[0065] FIGS. 6A and 6B show two examples of two-dimensional column images Y.sub.j obtained for the three-dimensional surface 3. These images are obtained by the steps 11 to 18 of the method described above with the use of a total focusing method. FIG. 6A shows a two-dimensional column image Y.sub.j for an increment line L.sub.j not passing through the locally deformed zone 4 and FIG. 6B shows a two-dimensional column image Y.sub.j for an increment line L.sub.j passing through the locally deformed zone 4.

[0066] The step 19 of constructing a three-dimensional image comprises determining, from all the two-dimensional row images X.sub.i and from all the two-dimensional column images Y.sub.j a reflected wave amplitude at various points of a volume encompassing the various planes P.sub.i(m.sub.s) and P.sub.j(n.sub.s) of these two-dimensional images. In this case, the volume is delimited by the first and last planes P.sub.i(m.sub.s) and by the first and last planes P.sub.j(n.sub.s). The three-dimensional image is formed by these reflected wave amplitudes at the various points of the volume. In practice, constructing the three-dimensional image consists for example in merging the two-dimensional row images X.sub.i and column images Y.sub.j.

[0067] FIG. 7 shows an example of a three-dimensional image obtained for the three-dimensional surface 3 shown in FIG. 3B. It can be observed in this figure that the two-dimensional row images X.sub.i and the two-dimensional column images Y.sub.j provide complementary data for constructing the three-dimensional image, more specifically at the locally deformed zone 4, for which an absence of reflected wave can be observed for all the elements of a row of the matrix sensor because of an inclination of the three-dimensional surface 3 located under the matrix sensor 1 in a plane not perpendicular to the plane P.sub.i(m.sub.s) passing through this row.

[0068] The reconstruction method according to the invention may also include, following the step 19 of constructing the three-dimensional image, a step of extrapolating this three-dimensional image, wherein reflected wave amplitudes are determined for various complementary points of the volume situated between the points of the volume for which a wave amplitude has been determined. FIG. 8 shows an example of an extrapolated three-dimensional image obtained from the three-dimensional image in FIG. 7.