Method and device for calibrating a workpiece laser-processing machine

• US 6,615,099 B1
• Filed: 01/11/2001
• Issued: 09/02/2003
• Est. Priority Date: 07/13/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi VIA Mechanics Limited (Hitachi, Ltd.)
• Original Assignee: Siemens AG
• Inventors: Roth, Friedbert, Polgar, Mladen, Van Biesen, Mark, Müller, Lothar, De Steur, Hubert
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): SWINDELL, WALTER R
• Application Number:
  US09/743,585
• Time in Patent Office: 964 Days
• Field of Search: 700/95, 700/166, 219/121.11, 219/121--12, 372/31
• US Class Current: 700/166
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/043 along the beam path, i.e. alignment of laser beam axis relative to laser beam apparatus

Abstract

A method and arrangement for calibrating a laser processing machine for processing workpieces. The present invention ensures a fast and reproducible method and arrangement for calibrating a laser processing machine by measuring a position of a predetermined test pattern on a test plate while taking into account any imaging errors caused by the deflection unit.

Claims

1. A method for calibrating a laser processing machine for processing workpieces, comprising:

positioning a calibration plate in front of an objective;

recording an image of the calibration plate, which is generated by the objective and a deflection unit, by moving the objective and a field of view of a camera over the calibration plate under control of the deflection unit;

determining imaging errors caused by the deflection unit and by the objective from said image in a control unit, the control unit being connected downstream of the camera;

storing said imaging errors;

positioning a test plate in front of the objective;

writing a test pattern onto the test plate by a laser beam from a laser source with a predetermined drive of the deflection unit;

measuring a position of the test pattern;

determining an optical offset of the laser source based on a measured position of the test pattern taking said imaging errors into account;

storing the optical offset; and

compensating for the stored optical offset and the stored imaging errors during the processing of workpieces.

2. A method according to claim 1, further comprising the steps of:

moving the field view of the camera over the test plate by the deflection unit; and

measuring the position of the test pattern.

3. A method according to claim 1, further comprising the step of:

diverting the image of the calibration plate into the camera by a mirror, said mirror being placed in a beam path of the laser beam between a device for shaping the laser beam and the deflection unit, said mirror being transparent to a laser light from the laser source, said mirror being reflective to a light with which the camera records the image of the calibration plate.

4. A method according to claim 1, further comprising the steps of:

recording via the camera reference points that are arranged on one of the workpieces to be processed,

determining in the control unit a workpiece'"'"'s influence on an imaging, said influence on the imagine based on said recording while taking into account the imaging errors and the optical offset;

storing the workpiece'"'"'s influence on the imaging; and

taking into account the workpiece'"'"'s influence during subsequent processing of the workpiece.

5. A method according to claim 4, for providing data for structuring non-planar areas of workpieces, further comprising the step of:

altering an optical path of the laser beam by a device for modulating the optical path, said device being controlled by said control unit such that a focal point of the imaging is adapted by the objective in accordance with a geometrical shape of the workpiece.

6. An arrangement for calibrating a laser processing machine for processing of workpieces comprising:

a laser source;

a device for shaping a laser beam, said laser beam being emitted from said laser source;

a deflection device for the laser beam;

a camera for visually observing a workpiece;

a control device for the deflection device and the camera and the device for shaping the laser beam, said control device connected downstream of the camera for imaging error determination;

an objective for focusing a deflected laser beam on the workpiece;

a partially transparent mirror located in a path of the laser beam;

a calibration plate, said calibration plate initially placed in front of the objective, an image of the calibration plate is recorded by movement of a field of view of the camera under control of the deflection device, based on said image the control device determines imaging errors generated by the deflection device and the objective; and

a test plate, said test plate being placed in front of the objective subsequent to removal of the calibration plate from a front of the objective, said laser beam writes a test pattern on the test plate by a predetermined drive of the deflection unit, said position of the test pattern being measured and with said imaging errors, being utilized for determination of an optical offset of said laser source.

7. An arrangement according to claim 6, wherein:

the device for shaping the laser beam further comprises a device that expands the laser beam and a device that modulates an optical path of the laser beam.

8. An arrangement according to claim 6, wherein:

the partially transparent mirror deflects the laser beam in a direction of the workpiece, said partially transparent mirror deflects a light from the workpiece in a direction of the camera, said partially transparent mirror being placed between the device for shaping the laser beam and the deflection device.

9. An apparatus for compensating during processing of workpieces, comprising:

first means for recording an image of a calibration plate positioned in front of an objective, the image being generated by the objective and deflection unit, by moving the objective and a field of view over the calibration plate under control of the defection unit;

second means for determining imaging errors caused by the deflection unit and by the objective from said image;

third means for storing said determined imaging errors; and

laser means for writing a test pattern onto a test plate positioned in front of the objective, with a predetermined drive of the deflection unit, wherein a position of the test pattern is measured, the second means further determining an optical offset of the laser means based on the measured position of the test pattern, taking said determined imaging errors into account;

said third means storing the optical offset, wherein, during the processing of workpieces, the stored optical offset and imaging errors are compensated for.

10. An apparatus according to claim 9, further comprising:

a mirror for diverting the image of the calibration plate into the first means, said mirror being placed in a beam path of the laser means between a device for shaping the laser beam and the deflection unit, said mirror being transparent to a laser light from the laser means, said mirror being transparent to a laser light from the laser means, and said mirror being reflective to a light with which the first means records the image of the calibration plate.

11. An apparatus according to claim 9, wherein

the first means is further for recording reference points that are arranged on one of the workpieces to be processed,

the second means is further for determining a workpiece'"'"'s influence on an imaging, said influence on the imaging based on said recording while taking into account the imaging errors and the optical offset;

the third means is further for storing the workpiece'"'"'s influence on the imaging and wherein the workpiece'"'"'s influence is taken into account during subsequent processing of the workpiece.