Calibration of laser light section sensors during simultaneous measurement

• US 20140029018A1
• Filed: 01/25/2012
• Published: 01/30/2014
• Est. Priority Date: 01/25/2011
• Status: Active Grant

• Current Assignee: Data M Sheet Metal Solutions GmbH
• Original Assignee: Data M Sheet Metal Solutions GmbH
• Inventors: Freitag, Stefan, Sedlmaier, Albert, Lang, Udo
• Granted Patent: US 9,127,936 B2
• Time in Patent Office: Days
• US Class Current: 356/601
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence
• CPC Class Codes: G01B 11/2504 Calibration devices
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object

Abstract

Method for measuring an extruded profile using a measuring apparatus, wherein the measuring apparatus is designed to produce and measure at least two laser light sections on a surface of the profile, which is being pulled through the measuring apparatus, by means of at least one laser light section sensor from a respective, different position around the profile, wherein the at least two laser light sections are situated essentially in one plane. By positioning at least two references and/or reference markers from the adjacent positions together with the extruded profile in a respective common measurement capture area, said references or reference markers are used for calibration of respective raw image of the at least one laser light section sensor. Thus, the calibrated raw image data are correctly mapped in a common coordinate system from the respective position

Claims

1. Method for measuring a sheet-metal or extruded profile with a measuring device which is adapted to generate and to measure at least two laser light sections on a surface of the extruded profile which is guided through the measuring device by means of at least one laser light section sensor which is arranged in a different respective position around the extruded profile, where the at least two laser light sections are generated such that they are located on one common plane or such that their respective laser light section planes are offset in parallel from each other just so far that they do not interfere with each other and so that they form a common measurement recording region, the method comprising the following steps:

a) measurement of the laser light sections on the extruded profile from the respective different position by means of the at least one laser light section sensor, thereby obtaining raw image data and forwarding to a computing unit, with the raw image data from a first position corresponding to a first laser light section being used as calibrated image data;

b) arrangement and measurement of at least two references or of at least two reference markers or of at least one reference and one reference marker in the common measurement recording region from the first position and from a second, adjacent position, the references being present in the extruded profile and the reference markers being arranged between the positions of the at least one laser light section sensor and the extruded profile;

c) determination, by means of the references and/or the reference markers, of a shifting and a rotation angle of the raw image data at the second, adjacent position with reference to the calibrated image data from the first position;

d) calculation of a transformation matrix from the shifting and from the rotation angle determined in step c), and application to the raw image data at the second, adjacent position in order to obtain calibrated image data at the second position, so that the recorded references and/or reference markers in the calibrated image data of the second position match the recorded references and/or reference markers in the calibrated image data of the first position in a common coordinate system; and

e) outputting and usage of all calibrated image data in the common coordinate system for determining the extruded profile.

2. Method according to claim 1, where the sequence of steps b) through e) is repeatedly performed for all other raw image data of the at least one laser light section sensor in other adjacent positions up to a last adjacent position, starting from the raw image data of the position adjacent to the position of the image data calibrated last, with these raw image data being calibrated each time with reference to the image data calibrated last.

3. Method according to claim 1, where the references are embodied as planar, round or curved surfaces or combinations thereof, which are recorded as straight lines, circles, segments of circles or combinations thereof in the extruded profile.

4. Method according to claim 1, where the reference markers are embodied as rods, metal sheets or combinations thereof, which are imaged in the laser light section as circles, straight lines, segments of circles.

5. Method according to claim 1, where at least one of the reference markers has an encoding which can be identified in the respective raw image data and in the calibrated image data, with the encoding being embodied, for instance, as an additional edge, rounding or as a different orientation of the reference marker.

6. Method according to claim 1, where in step c) the determination of the shifting and of the rotation angle of the raw image data in relation to the calibrated image data of the preceding, adjacent laser light section sensor takes place in such a way that the recorded and recognized references and reference markers which are recorded as straight lines or at least partially as straight lines are connected and/or extrapolated so that this results in at least two non-parallel straight lines which are respectively caused to overlap between the raw image data and the calibrated image data.

7. Method according to claim 1, where in step c) the determination of the shifting and of the rotation angle of the raw image data in relation to the calibrated image data of the adjacent laser light section sensor takes place in such a way that several recorded and recognized references and reference markers in the calibrated image data of the neighboring laser light section sensors are caused to overlap according to a method of an optimal matching, for instance according to a least mean square method.

8. Method according to claim 1, where in step c) for the determination of the shifting and of the rotation angle of the raw image data in relation to the calibrated image data of the adjacent laser light section sensor, the references and reference markers are identified and allocated by the mutual positions of the neighboring laser light section sensors being already known, for instance due to a first calibration with other, defined reference markers, allowing subsequently an unambiguous allocation of the reference markers in a specific location.

9. Method according to claim 1, where in step c) in addition to the detection of the shifting and of the rotation angle of the raw image data in relation to the calibrated image data of the adjacent laser light section sensor, a scaling correction of the raw image data or of the calibrated image data takes, respectively, place by the reference markers having known mutual spacings and/or known lengths or widths, respectively.

10. Method according to claim 1, where in step c) in addition to the detection of the shifting and of the rotation angle of the raw image data in relation to the calibrated image data of the adjacent laser light section sensor, the scaling correction of the raw image data or of the calibrated image data, respectively, takes place by the integration of one or more reference markers embodied as reference bodies with detectable widths, heights and depths into the common measurement recording region.

11. Method according to claim 1, where at least two of the laser section planes are generated by respective laser light section sensors and where at least two of the laser section planes are created by moving a laser light section sensor to the various positions so as to generate the raw image data from the respective measuring perspective and then, via the transformation matrix, the calibrated image data, with the laser light section sensor preferably being moved on a circular trajectory.

12. Method according to claim 1, where the at least two laser light section sensors are arranged on a circular or U-shaped device and each have a measurement recording region which is directed inwardly towards the extruded profile.

13. Method according to claim 1, where with nearly continuous measurement of the extruded profile, the calibration of the laser light section sensors takes place either with each measurement, at periodic intervals, in dependence on the device temperature, at the pressing of a button or in a combination thereof.

14. Method according to claim 1, where the at least one laser light section sensor is embodied as a 2D or 3D sensor.

15. Method according to claim 1, where the common plane or the planes offset in parallel extend perpendicularly to the extruded profile.

16. Measuring device for measuring an extruded profile according to the method according to claim 1, comprising:

at least two laser light section sensors which are arranged preferably on a circular device and oriented towards the extruded profile, each having a respective measurement recording region in common with an adjacent laser light section sensor, their laser light section planes being generated such that they are located in a common plane or such that they are mutually offset in parallel just so far that they do not mutually interfere, the laser light section sensors providing raw image data;

b) at least two references or at least two reference markers or at least one reference and one reference marker the references being present in the extruded profile and the reference markers being arranged between the at least two laser light section sensors and the extruded profile in the common measurement recording region; and

c) a computing unit for processing the raw image data and for determining calibrated image data of the at least two laser light section sensors.

17. Measuring device for measuring an extruded profile according to the method according to claim 1, comprising:

a) at least one laser light section sensor which is arranged movably on a preferably circular device and is oriented towards the extruded profile and assumes several positions in succession, wherein the respective measurement recording region of the at least one laser light section sensor at a specific position has a measurement recording region in common with the measurement recording region at an adjacent position, and wherein the at least one laser light section sensor provides raw image data,

b) at least two references or at least two reference markers or at least one reference and one reference marker the references being present in the extruded profile and the reference markers being arranged between the positions of the at least one laser light section sensor and the extruded profile in the common measurement recording region, and

c) a computing unit for processing the raw image data and for determining calibrated image data of the at least one laser light section sensor.

18. Measuring device for performing a method according to claim 16, the computing unit for transformation of the raw image data of the respective laser light section sensor into the corresponding calibrated image data being arranged either in the respective laser light section sensor or as a separate unit.

19. Measuring device for performing a method according to claim 17, the computing unit for transformation of the raw image data of the respective laser light section sensor into the corresponding calibrated image data being arranged either in the respective laser light section sensor or as a separate unit.