Method and device for evaluation of jointing regions on workpieces

• US 20050041852A1
• Filed: 11/14/2002
• Published: 02/24/2005
• Est. Priority Date: 11/15/2001
• Status: Active Grant

• Current Assignee: Precitec Vision GmbH & Co. KG
• Original Assignee: Precitec Vision GmbH & Co. KG
• Inventors: Schwarz, Joachim, Halschka, Martin
• Granted Patent: US 7,577,285 B2
• Time in Patent Office: Days
• US Class Current: 382/152
• CPC Class Codes: B23K 2101/185 Tailored blanks
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/044 Seam tracking
• CPC Class Codes: B23K 9/0956 using sensing means, e.g. optical
• CPC Class Codes: B23K 9/1274 Using non-contact, optical means, e.g. laser means
• CPC Class Codes: G01B 11/303 using photoelectric detection means

Abstract

A method and apparatus for detecting a joint between workpieces is provided. At least one light line is recorded by the light section method to detect the three-dimensional course of the joint and a grey-level image of the joint is also recorded. The grey-level image is evaluated to assess the quality of the joint.

Claims

1. Method for detecting a joint between workpieces wherein at least one light line is recorded by the light section method to detect the three-dimensional course of the joint and a grey-level image of the joint is also recorded, characterized in that the grey-level image is evaluated to assess the quality of the joint.

2. Method according to claim 1, characterized in that the at least one light line of the light section method and the grey-level image are recorded together as one image.

3. Method according to claim 1, characterized in that the recording containing at least one light line of the light section method is made by means of a non-linear, in particular logarithmic, sensor characteristic, and in that the grey-level image is recorded by a sensor with a substantially linear characteristic.

4. Method according to claim 3, characterized in that the substantially linear characteristic lies in the range of illumination intensity below that of the non-linear characteristic.

5. Method according to claim 3, characterized in that a single sensor is provided, which has both a linear and a non-linear characteristic segment.

6. Method according to claim 1, characterized in that under conditions of relative motion between workpiece and recording device, the exposure time for the at least one light line is made sufficiently long for the diffuse light of the light line to be reflected by a region of the seam that is wider than the light line.

7. Method according to claim 1, characterized in that under conditions of relative motion between workpiece and recording device, the time of exposure by means of a flash illumination device for the grey-level image is made sufficiently short to keep the motion-blur less than one pixel.

8. Method according to claim 1, characterized in that a colour image is recorded instead of, or in addition to, the grey-level image.

9. Use of the method according to claim 1 for assessing edge defects in the welding of tailored blanks.

12. Use according to claim 1 for assessing spot welds or adhesive beads.

10. Use of the method according to 1 for assessing weld seam quality in the welding of tailored blanks.

11. Use of the method according to claim 10, characterized in that the contours of the structures of the weld seam are highlighted and examined.

13. Apparatus for detecting a joint between workpieces, with a light line projection unit and a recording unit for recording the light line and a grey-level image, and with an image evaluation unit for the light line and the grey-level image, characterized in that the image evaluation unit is configured to detect quality features of the joint from the grey-level image.

14. Apparatus according to claim 13, characterized in that the recording unit is configured to record an image in which the light line and grey-level image are recorded together.

15. Apparatus according to claim 13, characterized in that the recording unit has a non-linear, in particular logarithmic sensor characteristic for the light line and a substantially linear characteristic for the grey-level image.

16. Apparatus according to claim 13, characterized in that the recording unit has a CMOS sensor, which has a substantially linear characteristic segment and a non-linear characteristic segment, with the substantially linear characteristic segment lying in the low illumination sensitivity range of the sensor.

17. Apparatus according to claim 13, characterized in that a flash illumination unit is provided for the recording of the grey-level image.

18. Apparatus according to claim 13, characterized in that the image evaluation unit is configured for the highlighting and evaluation of the contours of the joint region in the grey-level image.

19. Apparatus according to claim 13, characterized in that the recording unit is configured to record a colour image in addition to, or instead of, the grey-level image.

20. Method, for detecting a joint between workpieces before they are joined, in order to control a welding beam making the joint, wherein at least one light line is recorded by a light section method to detect a three-dimensional course of the joint and a grey-level image of the joint is also recorded, characterized in that the recording of the at least one light line of the light section method is made by means of a non-linear sensor characteristic, and in that the grey-level image is recorded by a sensor with a substantially linear characteristic.

21. Method according to claim 20, characterized in that the substantially linear characteristic lies in the range of illumination intensity below that of the non-linear characteristic.

22. Method according to claim 20, characterized in that a single CMOS sensor is provided which has both a linear and a non-linear characteristic segment.

23. Apparatus for detecting a joint between workpieces with a light line projection unit and a recording unit for recording the light line and a grey-level image, and with an image evaluation unit for the light line and the grey-level image, characterized in that the recording unit has a non-linear sensor characteristic for the light line, and a substantially linear characteristic for the grey-level image.

24. Apparatus according to claim 23, characterized in that the recording unit has a single CMOS sensor which has a substantially linear characteristic segment and a non-linear characteristic segment, with the substantially linear characteristic segment lying in the low illumination sensitivity range of the sensor.

25. Apparatus according to claim 23, characterized in that a flash illumination unit is provided for the recording of the grey-level image.

26. A method for detecting a joint between workpieces before the workpieces are joined, comprising the steps of:

recording at least one light line by a light section method to detect a three-dimensional course of the joint, wherein the recording of the light line is made by means of a non-linear sensor characteristic; and

recording a grey-level image of the joint, wherein the recording of the grey-level image is made by a sensor with a substantially linear characteristic.

27. An apparatus for detecting a joint between workpieces, comprising:

a light line projection unit;

a recording unit for recording the light line and a grey-level image, wherein the recording unit has a non-linear sensor characteristic for the light line, and a substantially linear characteristic for the grey-level image; and

an image evaluation unit for the light line and the grey-level image.