Thermography method

• US 20040081221A1
• Filed: 12/22/2003
• Published: 04/29/2004
• Est. Priority Date: 01/26/2001
• Status: Active Grant

• Current Assignee: Rolf Sandvoss
• Original Assignee: Rolf Sandvoss
• Inventors: Sandvoss, Rolf
• Granted Patent: US 7,044,634 B2
• Time in Patent Office: Days
• US Class Current: 374/130
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

The invention relates to a method and to a device (1) for testing materials by determining and displaying as an image temperature differences above a threshold value on the surface of test objects (8). In a first step, a camera for determining and displaying as an image the temperature differences above a threshold value is used to determine the temperatures of object elements (22) within a test area (14) of the test object (8) facing the camera. The test area (14) is then provided with heat by means of a laser beam (4) in such a manner that the temperature of the surface of the test object (8) rises in the test area (14) by at least the amount of the threshold value. The object elements (22) are displayed as image elements in such a manner that the temperature differences above the threshold value between the object elements (22) are visible. The cool-down of the test area (14) is indicated by means of the image elements (20).

Claims

1. A method for testing materials wherein by means of a camera, which determines temperature differences above a definite threshold value, temperature differences on surfaces of test objects (8) are determined and displayed as an image so that:

a) the individual temperatures of object elements (22) within a test area of the surface of said test object (8) facing the camera are determined and displayed, and

b) the temperature of said object elements (22) is, precisely within a test area (14) to be defined in any shape, actively changed by means of a focussed light beam, especially a laser beam (4), in such a manner that the temperature of the surface of the test object positioned in the test area changes by at least the amount of the threshold value, and

c) the object elements (22) the temperature of which has been changed are displayed as image elements (20) in such a manner that their individual temperature behaviour becomes discernible due to the temperature change, and

d) preferably the further temperature change of the test area is displayed by means of the image elements (20).

3. A method or device according to claim 1 or 2, characterised in that said laser beam (4) is emitted from a diode laser device and guided via a scan head (6).

4. A method or device according to any of claims 1 to 3, characterised in that a focal spot (16) of said laser beam (4) is guided meandrically at a speed from 1 to 10,000 mm per second across the surface of said test object (8).

5. A method or device according to any of claims 1 to 4, characterised in that said test area (14) is sequentially heated several times during one testing process.

6. A method or device according to any of claims 1 to 5, characterised in that the heating of the individual object elements is performed for less than one second, preferably less than a tenth of a second.

7. A method or device according to any of claims 1 to 6, characterised in that the amount of heat absorbed by the surface is technically measured and recorded immediately following the supply of heat.

8. A method or device according to claim 7, characterised in that the temperatures of said object elements (22) are determined by means of said thermographic camera immediately following the supply of heat, while during another subsequent supply of heat the determined differing heat absorption capabilities of individual or several object elements (22) are equalised by heat supply of correspondingly differing intensities in such a manner that a homogeneous heat supply into the depth of said test object (8) is accomplished.

9. A method or device according to claim 7, characterised in that a reflected image is determined by a CCD camera, while during another subsequent supply of heat the determined differing reflection capabilities of individual or several object elements (22) are equalised by heat supply of correspondingly differing intensities in such a manner that a homogeneous heat supply into the depth of said test object (8) is accomplished.

10. A method or device according to any of claims 1 to 9, characterised in that the temperature change of said test area is displayed on a monitor screen in real time using said image elements (20).

2. A device for testing materials comprising a camera for determining and displaying temperature differences above a threshold value and a laser device (2) which emits a laser beam (4) for changing the temperature of a test area (14( facing said camera (10) of a test object (8) by at least the amount of said threshold value.