Calibrating a scanner device

1. A method for calibrating a laser scanner for positioning a laser beam in a processing field, the method comprising:

arranging a retroreflector in or above the processing field of the laser scanner and also between a processing sample in the processing field and the laser scanner, wherein the processing field is formed in a powder layer processing chamber;

detecting laser radiation that is reflected back into the laser scanner from the retroreflector as the laser beam passes over the retroreflector;

determining an actual position of the laser beam in the processing field based on the detected laser radiation;

calibrating the laser scanner by correcting a target position of the laser beam specified for the laser scanner in the processing field based on the determined actual position of the laser beam in the processing field;

directing an additional laser beam at an additional processing field formed in the powder layer processing chamber;

detecting additional laser radiation that is reflected back into an additional laser scanner as the additional laser beam passes over the retroreflector;

determining an actual position of the additional laser beam in the additional processing field based on the additional laser radiation detected; and

calibrating the additional laser scanner by correcting a target position specified for the additional laser scanner based on the actual position of the additional laser beam in the additional processing field.

2. The method of claim 1 , wherein the retroreflector is arranged directly above the processing field of the laser scanner in an automated manner.

3. The method of claim 2 , wherein the retroreflector is attached to a movable arm that is configured to deposit powder layers in the processing field of the laser scanner.

4. The method of claim 1 , wherein the retroreflector is a ball transparent to a wavelength of the laser beam, and determining the actual position of the laser beam in the processing field is based on an intensity distribution of the detected laser radiation.

5. The method of claim 1 , wherein the retroreflector is in the form of a retroreflective surface region of a foil.

6. The method of claim 5 , wherein the foil comprises at least one non-retroreflective surface region that adjoins the retroreflective surface region.

7. The method of claim 6 , wherein determining the actual position of the laser beam in the processing field is based on a difference in an intensity of the detected laser radiation between the retroreflective surface region and the non-retroreflective surface region.

8. The method of claim 1 , wherein the laser beam comprises a pilot laser beam, wherein the pilot laser beam is provided at a lower power than a processing laser beam used to irradiate powder layers in the powder layer processing chamber.

9. The method of claim 1 , wherein the actual position of the laser beam and the actual position of the additional laser beam are determined simultaneously.

10. The method of claim 1 , wherein the laser radiation is detected upstream of a focusing device that is arranged upstream of the laser scanner, and wherein the additional laser radiation is detected upstream of an additional focusing device that is arranged upstream of the additional laser scanner.

11. A machining device for producing three-dimensional components by irradiating powder layers, the machining device comprising:

an irradiation device comprising a laser source and a laser scanner configured to direct a laser beam from the laser source toward a processing field;

a processing chamber in which the processing field is located wherein the processing chamber comprises a powder layer support surface on which the powder layers are applied and wherein the processing chamber comprises a retroreflector arranged in or above the processing field of the laser scanner and also between a processing sample in the processing field and the laser scanner;

a photodetector arranged to detect laser radiation reflected back into the laser scanner from the retroreflector as the laser beam passes over the retroreflector;

a computer coupled with non-transitory computer-readable medium encoding instructions that cause the computer to perform operations comprising

determining an actual position of the laser beam in the processing field based on the detected laser radiation,

specifying a target position of the laser beam in the processing field, and

correcting the specified target position based on the determined actual position;

an additional laser scanner configured to direct an additional laser beam in an additional processing field of the processing chamber; and

an additional photodetector arranged to detect additional laser radiation reflected back into the additional laser scanner by the retroreflector as the additional laser beam passes over the retroreflector, wherein the operations further comprise

determining an actual position of the additional laser beam in the additional processing field based on the additional laser radiation detected,

specifying a target position of the additional laser beam in the additional processing field, and

correcting the specified target position based on the determined actual position of the additional laser beam.

12. The machining device of claim 11 , further comprising: an arm configured to move the retroreflector into the processing field of the laser scanner.

13. The machining device of claim 12 , wherein the arm also is configured to deposit powder layers in the processing chamber.

14. The machining device of claim 11 , wherein the retroreflector is a transparent ball or is a retroreflective surface region of a foil.

15. The machining device of claim 11 , wherein the photodetector is a diode.

16. The device of claim 11 , comprising:

a focusing device arranged upstream of the laser scanner; and

an additional focusing device arranged upstream of the additional laser scanner, wherein the photodetector is upstream of the focusing device, and wherein the additional photodetector is upstream of the additional focusing device.

17. The device of claim 11 , wherein the laser beam is a pilot laser beam, and wherein both the laser source and the laser scanner are further configured to direct a processing laser beam from the laser source toward the processing filed to irradiate powder layers in the powder layer processing chamber, wherein the pilot laser beam is a lower power laser beam than the processing laser beam.