A method of inspecting a metal surface and associated device
The present invention relates to a method of inspecting a one piece metal surface.

FR 3020678 describes a process photothermal inspection of a room.

According to this method, the surface is scanned by two similar scanning devices each comprising a heat input element. To do this, each device comprises a laser source arranged to emit a laser beam and a gonomiètre adapted to reflect the laser beam toward the surface.

This allows for non-destructive testing of a metal surface of a workpiece.

Typically, this process employs laser beams having a wavelength substantially equal to 1064 nm, which is commonly used for applications requiring high power heating.

However, such a laser beam presents risks for a possible manipulator. Specifically, the laser beam is likely to deteriorate irreversibly eye of a manipulator that is not equipped to fit.

Thus, wearing protective equipment is strictly asked all manipulator and a protection device is usually set up for the duration of the inspection.

This complicates the implementation of the inspection process and can represent an obstacle to its implementation, including a production site, so a regular inspection of the relevant parts.

An object of the invention is therefore to provide a method of inspecting a metal surface of a workpiece whose implementation is facilitated.

To this end, the invention relates to a the aforementioned type inspection method, comprising the steps of:

- providing a first laser source arranged to generate a first laser beam having a first wavelength between 1000 nm and 1100 nm and a power greater than 1 W;

- obtain one second laser source arranged to generate a second laser beam having a second wavelength between 1500 nm and 1800 nm and a power greater than 1 W;

- obtain an optical device comprising an input for a laser beam, and a device arranged to project the laser beam on the metal surface to scan the metal surface with the laser beam;

- activate one of the first and second laser sources and transmitting the first or the second laser beam to the entrance of the optical;

- scan the metal surface with the first or second laser beam projected by the optics;

- acquiring at least one image of the infrared radiation emitted by the metal surface.

The presence of two laser sources is used to select one that is most suitable for the desired use. Wavelengths between 1500 nm and 1800 nm do not penetrate into the eye, thus making it possible to simplify the protective elements in place during the inspection process.

An inspection method according to the invention may comprise one or more of the following characteristics, taken alone or in any technically possible combinations:

- during scanning, the metal surface is heated by the laser beam projected by the optical system;

- optics comprises optical elements, the optical elements having the same absorption and transmission properties at the first wavelength and the second wavelength;

- the method comprises a processing step of an optical surface of at least one of the optical elements, so that said optical element has the same absorption and transmission properties at the first wavelength and second wavelength;

- the method is provided for inspecting new parts on a manufacturing site, the first laser source being turned on and the first laser beam being transmitted to the input optics,

- the method is provided for the inspection of parts already in operation, the second laser source being turned on and the second laser beam being transmitted to the input of the optical; and or

- the infrared radiation image is acquired by the same sensor for the first laser source and the second laser source.

The invention further relates to an inspection device of a metal surface of a workpiece, the apparatus comprising:

- a first laser source arranged to generate a first laser beam having a first wavelength between 1000 and 1100 nm and a power greater than 1 W;

- one second laser source arranged to generate a second laser beam having a second wavelength included between 1500 and 1800 nm and a power greater than 1 W;

- an optical device comprising an input for a laser beam and a device arranged to project the laser beam on the metal surface to scan the metal surface with the laser beam;

- a sensor capable of acquiring at least one image of the infrared radiation emitted by the metal surface

the first and second laser beams being adapted to be transmitted one or the other to the input of the optics.

An inspection device according to the invention may comprise one or more of the following characteristics, taken alone or in any technically possible combinations:

- optics comprises optical elements, the optical elements having the same absorption and transmission properties at the first wavelength and the second wavelength; and or

- at least one of the optical elements has an optical surface treated, so that said optical element has the same absorption and transmission properties at the first wavelength and the second wavelength.

The invention will be better understood from reading the description which follows, given by way of example and with reference to the attached figures:

- Figure 1 is a schematic representation of an inspection device according to an embodiment of the invention, and

- Figure 2 is a schematic representation of an inspection method according to an embodiment of the invention.

The method described is a method of examination type active photothermal. The process is said to be active because the piece to be characterized is subjected to heating. The process is said photothermal because it relies on the acquisition of infrared images of the heated room.

This method is particularly suitable for the detection of through or non-through defects in industrial components. It is particularly suitable for metal parts, including metal components for nuclear power.

The inspection method is for performing the inspection mechanized, automated or robotic such parts, manufacturing or maintenance.

1 shows an inspection device 10 according to one embodiment of the invention.

The device 10 is provided for inspecting a metallic surface 12 of a workpiece

13.

The device 10 comprises a first laser source 14, a second laser source

16, an optic 18 and a sensor 20.

The first laser source 14 is arranged to generate a first laser beam 15 having a first wavelength between 1000 and 1100 nm, in particular equal to 1064 nm, and greater than 1 W power

Advantageously, the first laser source 14 is adapted to control and change the power of the first laser beam in a given interval.

The first laser source 14 has an activated state, wherein the source generates the first laser beam and an off state, wherein the source does not generate a laser beam.

The first laser beam 15 is, for example, oriented in a longitudinal direction X.

The second laser source 16 is arranged to generate a second laser beam 17 having a second wavelength included between 1500 and 1800 nm and a power sufficient to create a temperature difference in the event of presence of at least one defect. The power is generally higher than 1 W, and more preferably greater than 10 W.

The second laser beam has a particular geometry. It is, for example, diverge.

Advantageously, the second laser source 16 is adapted to control and change the power of the second laser beam in a given interval.

The second laser source 16 has an activated state, wherein the source generates the second laser beam, and an off state, wherein the source does not generate a laser beam.

The second laser beam 17 is, for example, oriented in a transverse direction Y, perpendicular to the longitudinal direction X.

The first laser beam 15 and second laser beam 17 are oriented such that, if they were switched on simultaneously, they would intersect at a cross point.

In the cross point, an optical element 21 is provided for directing at least partially the first laser beam 15 and second laser beam 17 to the optic.

The optical element 21 is, for example, a half mirror.

The first laser beam 15 passes through at least partly semi-reflecting mirror without being deflected, optics 18 being substantially aligned with the first laser source 14 in the longitudinal direction X.

The second laser beam 17 is at least partially reflected by the half mirror according to an angle substantially equal to 45 °.

After the intersection point, the optical paths of the first laser beam 15 and second laser beam 17 are combined here according to the longitudinal direction X.

The optic 18 includes an input 22 for a laser beam 26 and a device 24 arranged to project the laser beam 26 on the metal surface 12 and to scan the metal surface 12 with the laser beam 26.

The first and second laser beams 15, 17 are adapted to be transmitted one or the other until the inlet 22 of the optic 18, in particular through the optical element 21 at the point of overlap.

The optics 18 includes optical elements.

The optics 18 includes a scanning device 28 of the laser beam comprising at least one of optical elements, for example, a mirror or a goniometer whose orientation relative to the surface 12 is variable. Thus, the scanning device 28 is adapted to scan the laser beam 26 on the metal surface.

The laser beam transmitted to the input 22 of the optic 18 has an optical path in the optical 18 defined by the optical elements.

The optical elements have the same absorption and transmission properties at the first wavelength and the second wavelength.

At least one of the optical elements has an optical surface treated, so that said optical element has the same absorption and transmission properties at the first wavelength and the second wavelength.

Processing said optical surface is, for example, in the deposition of a layer or a substrate made of borosilicate glass or borosilicate crown, for example, marketed under the designation N-BK7 BK7 or (registered trademarks). Alternatively or additionally, at least one of the optical elements has the same kind of absorption and transmission properties at the first wavelength and the second wavelength.

Thus, the first laser beam and the second laser beam have a similar optical path in the optical 18.

An example of optical elements is shown in Figure 1, and the associated optical path.

The optics 18 includes, for example, in the order of the optical path of a laser beam, the following optical elements:

- generation of a laser optical sheet 32,

- a reflecting mirror 34,

- a dichroic plate 36, and

- the scanning device 28, here a goniometer.

The optical generation of a particular sheet 32 ​​serves laser generating a laser beam having a geometry as a line along a cutting plane perpendicular to the beam from a laser beam having a geometry as point in a plane cut perpendicular to the beam. The beam then forms a three-dimensional sheet.

The generation of a laser optical sheet includes, for example, a cylindrical lens.

The mirror 34 reflects the beam.

The dichroic plate 36 reflects all beam having a wavelength between 1000 nm and 1100 nm or 1500 nm and 1800 nm.

The dichroic plate further transmits wavelengths within a given spectrum, for example corresponding to the operation of the spectrum sensor 20.

The mirror 34 and the dichroic plate 36 form an angle substantially equal to 45 ° with the optical path of the laser beam. Thus, the mirror 34 and the dichroic plate 36 reflect the laser beam at a right angle.

The scanning device 28 forms an angle of between 45 ° minus a scan angle and 45 ° over the scan angle. The full opening of the scanning device is between -45 ° and + 45 °.

Other embodiments in nature and arrangement of the optical elements are possible.

The laser beam 26 is directed by the scanning device 28 to the surface 12 and creates a heat input 30 of the surface 12.

The sensor 20 is adapted to acquire at least one image of the infrared radiation emitted by the metal surface 12.

The sensor 20 detects the wavelengths of operation for the spectrum between 2000 nm and 0.1 mm, more particularly between 3 and 5 μηι μηι or between 8 and 12 μηι μηι.

The sensor 20 is, for example, a digital infrared camera having an optical axis O.

A part of the infrared radiation emitted by the metal surface 12 is transmitted to the optic at the output, is reflected by the scanning device 28 and is transmitted by the dichroic plate 36. The sensor 20 is, for example, placed such that said portion of radiation is sensed by the sensor 20 after transmission through the dichroic plate. Its optical axis O makes the angle of 45 ° with the dichroic plate.

The laser beam 26 output from the optical 18 is collimated with the optical axis O of the sensor 20, that is to say that the laser beam 26 is parallel to the optical axis O.

The dichroic plate serves in particular to protect the back of a laser sensor. Indeed, sometimes the laser beam is partially reflected or generates a secondary beam interacting with the surface and forms a return. If this return reaches the sensor, it is likely to damage it. The dichroic plate does not transmit the first and second wavelengths, thus avoiding a potential return laser beam reaches the sensor 20.

The sensor 20 is adapted to acquire a plurality of images at a plurality of instants. In one embodiment, the sensor 20 is provided for acquiring images, each of the entire surface 12 to be inspected.

Alternatively, the sensor 20 is capable of acquiring an image of a region of the surface, the sensor 20 is provided to scan the area on the entire surface to be inspected. The area comprises or is close to the heat input on the surface 12 by the laser beam 26.

A method of inspecting a metal surface of a workpiece will now be described with reference to Figure 2.

The method is, for example, implemented by the inspection device described above.

The method comprises the steps of:

- providing a first laser source 100;

- obtain a second laser source 102;

- obtain an optical 104;

- activate one of the first and second laser sources and transmitting the first or the second laser beam to the entrance of the optical 106;

- 108 scan the metal surface with the first or second laser beam projected by the optics;

- January 10 acquire at least one image of the infrared radiation emitted by the metal surface.

Optics, the first laser source and the second laser source are similar to what has been described above.

In addition, the method optionally includes a step of treatment of an optical surface of at least one of the optical elements of the optics, so that said optical element has the same absorption and transmission properties in the first wavelength and the second wavelength.

A single laser source between the first laser source and the second laser source is activated, so as to transmit a single laser beam from the first laser beam and the second laser beam, as described above, until the inlet 22 of optics 18.

The transmitted laser beam 26 is thus input 22 is a wavelength between 1000 nm and 1100 nm and a power greater than 1 W, a wavelength between 1 500 nm and 1 800 nm and a power greater than 1 W, preferably greater than 10 W.

The beam transmitted to the input 22 of the optic 18 is particularly suitable for implementation of the method.

In one embodiment, the method is provided for inspecting new parts on a manufacturing site. In this case, the first laser source is activated and the first laser beam is transmitted to the entrance optics.

The first laser beam has a wavelength between 1000 nm and 1100 nm and a power greater than 1 W.

Alternatively, the method is intended for inspection of parts already in operation.

Then, the second laser source is activated and the second laser beam is transmitted to the entrance optics.

The workpiece is, for example, a pelton wheel or a turbine disc.

The second laser beam has a wavelength between 1 500 nm and 1 800 nm and a power greater than 1 W, preferably greater than 10 W.

The method does not require an important inspection device that when a laser beam having a wavelength between 1000 nm and 1100 nm. Thus, the implementation of the inspection in an operating site is facilitated.

The laser beam 26 is projected and scanned by the optics 18 on the surface 12.

The scanning is, for example, carried out in a plurality of lines substantially parallel to a first direction D1.

During scanning, the laser beam 26 projected by the optical system 18 generates a heat input 30 of the surface 12.

The heat input of 30 has any kind of form.

Heat input is, for example, a segment lying along directions perpendicular to the first direction D1, the elongated segment being generated by the laser generating optical sheet 32. The segment has a length between 10 mm and 30 mm and a thickness of between 1 mm and 3 mm on the surface 12.

Alternatively, the heat supply 30 is a point moving at high speed perpendicularly to the first direction D1 to be a segment. This is, for example, performed using the laser beam scanned on the one hand at a first speed in a direction perpendicular to the first direction D1 and the other at a second speed in the first direction D1 within the scan 108, optics 18 does not then having generation of laser optical sheet 32. the first speed is greater than the second speed.

The heat supply 30 may also have the shape of a circle, ellipse, rectangle, or any other suitable shape.

Scanning 108 is made with an overlap of the heat supply, so that each point on the surface undergoes during the process heat input due to the transmitted laser beam 26.

At least one image of the infrared radiation emitted by the surface 12 is acquired by the sensor 20.

The image of the infrared radiation is acquired by the same sensor 20 that the transmitted laser beam is the first laser beam or the second laser beam.

In one embodiment, the sensor 20 acquires an image of the entire infrared radiation emitted by the surface 12 at each acquisition. A plurality of images of the infrared radiation from the surface 12 is acquired during the scan 108.

Alternatively, the sensor 20 acquires an image of the infrared radiation emitted by an area of ​​the surface at each acquisition. The area is scanned with overlapping on the whole surface to be inspected simultaneously the transmitted laser beam 26. The scan of the area is, for example, carried out in a plurality of lines substantially parallel to the first direction D1.

The area comprises or is close to the heat input on the surface 12 by the laser beam 26. The sensor 20 acquires a plurality of images of the infrared radiation during its scan and the scanning 108 of the metal surface by laser beam.

Then the acquired images are processed so as to detect defects in the part. Methods for processed images thus acquired are known in the art, for example, the document FR 3,020,678.

The presence of two laser sources with different characteristics allows to choose the most suitable laser beam for the intended use. In a production site, for example, it can be complicated to set up the set of security measures normally employed for a laser having a wavelength between 1000 nm and 1100 nm without interfering excessively exploitation. Thus, the use of a laser beam having a wavelength between 1500 nm and 1800 nm is more appropriate, such a laser beam limiting risks and thus the necessary equipment. The power greater than 1 W, preferably greater than 10 W, also makes it possible to penetrate the surface 12.

WE CLAIMS

1. - A method of inspecting a metal surface (12) of a workpiece (13), the method comprising the steps of:

- providing a first laser source (14) arranged to generate a first laser beam having a first wavelength between 1000 nm and 1100 nm and a power greater than 1 W;

- obtain a second laser source (16) arranged to generate a second laser beam having a second wavelength between 1500 nm and 1800 nm and a power greater than 1 W;

- obtain an optical system (18) comprising an inlet (22) for a laser beam, and a device arranged to project the laser beam on the metal surface to scan the metal surface (12) with the laser beam (26);

- activate one of the first and second laser sources and transmitting the first or the second laser beam to the entrance of the optical;

- scan the metal surface (12) with the first or the second laser beam projected by the optics;

- acquiring at least one image of the infrared radiation emitted by the metal surface (12).

2. - A method of inspecting according to claim 1, characterized in that, during scanning, the metal surface (12) is heated by the laser beam (26) projected by the optical system (18).

3.- A method of inspecting according to claim 1 or 2, characterized in that the optic (18) comprises optical elements, the optical elements having the same absorption and transmission properties at the first wavelength and at the second wavelength.

4.- A method of inspecting according to claim 3, comprising a step of treatment of an optical surface of at least one of the optical elements, so that said optical element has the same absorption and transmission properties in the first wavelength and the second wavelength.

5. An inspection method according to any one of claims 1 to 4, provided for the inspection of new parts on a manufacturing site, the first laser source (14) being activated and the first laser beam being transmitted until to the inlet (22) of the optic (18).

6. - A method of inspection according to any one of claims 1 to 4, provided to the parts inspection already in operation, the second laser source (16) being activated and the second laser beam being transmitted to the input (22) of the optic (18).

7. - A method of inspection according to any one of claims 1 to 6, characterized in that the infrared radiation image is acquired by the same sensor (20) for the first laser source and the second laser source.

8. - A device for inspecting a metal surface of a workpiece, the apparatus comprising:

- a first laser source (14) arranged to generate a first laser beam having a first wavelength between 1000 and 1100 nm and a power greater than 1 W;

- a second laser source (16) arranged to generate a second laser beam having a second wavelength included between 1500 and 1800 nm and a power greater than 1 W;

- an optical system (18) comprising an inlet (22) for a laser beam and a device arranged to project the laser beam on the metal surface to scan the metal surface with the laser beam;

- a sensor capable of acquiring at least one image of the infrared radiation emitted by the metal surface

the first and second laser beams being adapted to be transmitted one or the other to the inlet (22) of the optic (18).

9. - An inspection apparatus according to claim 8, characterized in that the optic (18) comprises optical elements, the optical elements having the same absorption and transmission properties at the first wavelength and second wavelength.

10. - An inspection apparatus according to claim 9, characterized in that at least one of the optical elements has an optical surface treated, so that said optical element has the same absorption and transmission properties in the first wavelength and the second wavelength.