Method and device for the inspection of a material by thermal imaging

• US 6,419,387 B1
• Filed: 01/31/2000
• Issued: 07/16/2002
• Est. Priority Date: 03/05/1997
• Status: Expired due to Term

• Current Assignee: Framatome Anp, Office National D'Etudes et de Recherches Aerospatiales
• Original Assignee: Framatome, Office National D'Etudes et de Recherches Aerospatiales
• Inventors: Legrandjacques, Laurent, Le Poutre, Francois, Krapez, Jean-Claude, Dehan, Christophe
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): VERBITSKY, GAIL KAPLAN
• Application Number:
  US09/380,547
• Time in Patent Office: 897 Days
• Field of Search: 374/5, 374/18, 374/22, 374/29, 374/30, 374/161, 374/57, 374/4, 374/45, 374/124, 374/137, 250/341.6, 250/332, 250/334
• US Class Current: 374/5
• CPC Class Codes: G01J 5/10 using electric radiation detectors
• CPC Class Codes: G01N 21/171 with calorimetric detection, e.g. with thermal lens detection
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

A heating zone (22) and a detection zone (23) at the surface (1a) of a part (1) are displaced in such a way as to carry out the scanning of the surface (1a) and a flux radiated in the detection zone (23) is detected by using a line of detectors (21) which is chosen from a matrix of detectors (20). The method makes is possible in particular to reduce the time for scanning the surface (1a) of the part and to be able to adjust the offset, in the direction of displacement (24), between the heating zone (22) and the detection (23), simply by choosing the line (21) of the matrix of detectors (20). The method and the device in accordance with the invention make it possible in particular to carry out thermographic inspections of parts made of any materials and in particular of metal parts which may have considerable dimensions and complex shapes.

Claims

1. Method for the photo-thermal inspection of a material, comprising:

heating a heating zone at a surface of a part made of the material, by using a heating means,

detecting a flux radiated by the surface of the part in a detection zone at a distance from the heating zone,

moving said heating means for displacing said heating zone at the surface of the part along a defined scanning path,

selecting at least one detector from a set of detectors arranged in relative spaced positions, to receive a flux radiated from the detection zone, said at least one selected detector being selected so as to optimize the photo-thermal inspection and to increase the speed of execution of this inspection;

processing an output signal of the at least one detector; and

adjusting the distance between the heating zone and the detection zone by selecting at least one detector in a set of detectors arranged in a line of detectors located in a detector matrix.

2. Method according to claim 1, comprising:

adjusting the value and the sense of the distance displacement between the heating zone and the detection zone by selecting the detector or row of detectors.

3. Method for the photo-thermal inspection of a material, comprising:

heating a heating zone at a surface of a part made of the material, by using a heating means,

detecting a flux radiated by the surface of the part in a detection zone at a distance from the heating zone,

moving said heating means for displacing said heating zone at the surface of the part along a defined scanning path,

selecting at least one detector from a set of detectors arranged in relative spaced positions, to receive a flux radiated from the detection zone, said at least one selected detector being selected so as to optimize the photo-thermal inspection and to increase the speed of execution of this inspection;

processing an output signal of the at least one detector; and

adjusting a length of the detection zone, by choosing a number of detectors of a row of detectors selected in the set of detectors.

4. Method for the photo-thermal inspection of a material, comprising:

heating a heating zone at a surface of a part made of the material, by using a heating means,

detecting a flux radiated by the surface of the part in a detection zone at some distance from the heating zone,

moving said heating means for displacing the heating zone at the surface of the part successively in a first direction and then in a second direction opposite to the first direction, along a defined scanning line, and

selecting, from a set of detectors arranged in relative spaced positions to receive a flux radiated from the detection zone, at least one first detector while moving said heating means in the first direction and at least one second detector while moving said heating means in the second direction.

5. Method according to claim 4, comprising modifying the value and the sign of the distance between said heating zone and said detection zone by selecting the at least one second detector between a first displacement of the heating means along the scanning line in the first direction and a second displacement of the heating means along the scanning line in the second direction.

6. Method according to claim 4, comprising selecting the at least one second detector of the set of detectors in such a way that the distance between the heating zone and the detection zone is directed along a line making an angle between 0 and 360°

.

7. Method for the photo-thermal inspection of a material, comprising:

heating a heating zone at a surface of a part made of the material, by using a heating means,

detecting a flux radiated by the surface of the part in a detection zone at a distance from the heating zone,

moving said heating means for displacing said heating zone at the surface of the part along a defined scanning path,

selecting at least one detector from a set of detectors arranged in relative spaced positions, to receive a flux radiated from the detection zone, said at least one selected detector being selected so as to optimize the photo-thermal inspection and to increase the speed of execution of this inspection;

processing an output signal of the at least one detector;

providing a set of detectors in the form of a matrix of detectors having the shape of a parallelogram array comprising relatively perpendicular lines and columns of detectors;

selecting a group of detectors of the set of detectors placed along at least one of a line of a matrix;

displacing the heating zone, during scanning, in a direction which is not parallel to lines of the set of detectors constituting a matrix and

selecting adjacent detectors of the matrix of detectors which are located along different lines of the matrix of detectors.

8. Method for the photo-thermal inspection of a material comprising:

heating a heating zone at a surface of a part made of the material with a laser beam,

detecting a flux radiated by the surface of the part in a detection zone at some distance of the heating zone, said flux being in the form of a detection beam, using optical detection means,

moving said laser beam for displacing said heating zone at the surface of the part along a defined scanning path,

measuring distances between said optical heating means and said optical detection means as well as between said heating zone and said detection zone, and

adjusting the focus of said heating laser beam and said detection beam from the measured distances.

9. Device for the photo-thermal inspection of material comprising a means of heating a heating zone of the surface of a part made of the material, means of detection of a flux radiated by the surface of the part in a detection zone, means of scanning for displacing the heating zone, and the detection zone over the entire surface of the part, and means for processing signals from the means of flux detection for constructing a thermographic image of the surface of the part, and electronic means for selecting at least one detector chosen from a set of detectors constituting a matrix of detectors, said at least one detector constituting the means of detection of the radiated flux;

and

the means of heating being a laser beam provided by a laser radiation source located in an optical path with optical means making it possible to focus the laser beam originating from the radiation source onto the surface of the part, and wherein the flux radiated by the detection zone of the surface of the part is an infrared radiation whose focusing is effected by focusing means, a meter for measuring the distance between the optical means for focusing the laser beam and the surface of the part, and for measuring the distance between the means of focusing the infrared radiation and the surface of the part, and means of real-time slaving of the optical focusing means to the distance measurements.

10. Device in accordance with claim 9, wherein the laser radiation source is linked to the optical focusing means by an optical fiber.

11. Device for the photo-thermal inspection of material comprising a means of heating a heating zone of the surface of a part made of the material, means of detection of a flux radiated by the surface of the part in a detection zone, means of scanning for displacing the heating zone, and the detection zone over the entire surface of the part, and means for processing signals from the means of flux detection for constructing a thermographic image of the surface of the part, and electronic means for selecting at least one detector chosen from a set of detectors constituting a matrix of detectors, said at least one detector constituting the means of detection of the radiated flux;

and

the means of heating the heating zone being a laser beam provided by a laser radiation source associated with optical means for focusing the laser beam originating from the laser radiation source onto the surface of the part, and wherein the flux radiated by the detection zone of the surface of the part is an infrared radiation focused by focusing means, a meter for measuring the distance between the optical means for focusing the laser beam and the surface of the part and for measuring the distance between the means for focusing the infrared radiation and the surface of the part, and means for storing in a memory the distances measured by the meter during scanning of the surface of the part and of controlling the means of focusing in non-real time on the basis of the distances stored in memory.

12. Device for the photo-thermal inspection of material comprising a means of heating a heating zone of the surface of a part made of the material, means of detection of a flux radiated by the surface of the part in a detection zone, means of scanning for displacing the heating zone, and the detection zone over the entire surface of the part, and means for processing signals from the means of flux detection for constructing a thermographic image of the surface of the part, and electronic means for selecting at least one detector chosen from a set of detectors constituting a matrix of detectors, said at least one detector constituting the means of detection of the radiated flux;

and

wherein the means of scanning comprise optical means and means for mechanically displacing the part.

13. Device for the photo-thermal inspection of material comprising a means of heating a heating zone of the surface of a part made of the material, means of detection of a flux radiated by the surface of the part in a detection zone, means of scanning for displacing the heating zone, and the detection zone over the entire surface of the part, and means for processing signals from the means of flux detection for constructing a thermographic image of the surface of the part, and electronic means for selecting at least one detector chosen from a set of detectors constituting a matrix of detectors, said at least one detector constituting the means of detection of the radiated flux;

and

wherein the means of scanning comprise optical means and also means for mechanically displacing a means for providing a laser beam for heating the surface of the part and for mechanically displacing reception of the flux radiated by the detection zone of the surface of the part.

14. Device for the photo-thermal inspection of material comprising a means of heating a heating zone of the surface of a part made of the material, means of detection of a flux radiated by the surface of the part in a detection zone, means of scanning for displacing the heating zone, and the detection zone over the entire surface of the part, and means for processing signals from the means of flux detection for constructing a thermographic image of the surface of the part, and electronic means for selecting at least one detector chosen from a set of detectors constituting a matrix of detectors, said at least one detector constituting the means of detection of the radiated flux;

and

a semi-reflecting plate for deflecting a heating beam towards the surface of the part and for transmitting the flux radiated by the detection zone of the surface of the part to the detection means.

15. Device for the photo-thermal inspection of material comprising a means of heating a heating zone of the surface of a part made of the material, means of detection of a flux radiated by the surface of the part in a detection zone, means of scanning for displacing the heating zone, and the detection zone over the entire surface of the part, and means for processing signals from the means of flux detection for constructing a thermographic image of the surface of the part, and electronic means for selecting at least one detector chosen from a set

of detectors constituting a matrix of detectors, said at least one detector constituting the means of detection of the radiated flux;

and

wherein the heating means is a radiation source associated with optical means of focusing, and wherein the optical means of focusing spread the radiation of the source selectively along a straight line or elongated ellipse of adjustable length and orientation.