Device and method for determining the focal position with consideration of process gas

Beam analysis device (10) according to any one of the preceding claims, wherein the evaluation device (80) comprises an input unit (83) for the cutting gas signal (63), an input unit (84) for the detector signal (64), a memory unit (81), and a calculation unit (86).

Beam analysis device (10) according to any one of the preceding claims, wherein the evaluation device (80) is configured to carry out the determination of the correction value taking into consideration calibration data which are stored in the memory unit (81), wherein the calibration data describe a change in the geometry parameter as a function of the cutting gas signal (63).

Beam analysis device (10) according to one of the preceding claims, wherein the evaluation device (80)

• is configured to receive a lens position signal (65) representing the axial position of an axially positionable lens or lens group of the laser processing optics (100), and
• is configured to determine the axial position of the focus (76) of the energy beam (77), taking into consideration the geometry parameter, the correction value and the lens position signal (65).

Beam analysis device (10) according to any one of the preceding claims, wherein the evaluation device (80) is

• is configured to calculate a focus tracking signal (67) from the determined axial position of the focus (76) of the energy beam (77), which is a focus actual position, and from a focus target position, and
• is configured to output the focus tracking signal (67), which is transferred directly or via a higher-level control device to a positioning device (105), by means of which a position of an axially positionable lens of the laser processing optics (100) can be adjusted.

Beam analysis device (10) according to any one of the preceding claims, wherein the beam shaping device (12) comprises an imaging device (50) with at least one optical lens (51).

Beam analysis device (10) according to any one of the preceding claims, wherein

• the beam shaping device (12) is configured to image the sample beam (70) onto the detector (40) and to form the intensity distribution (79) on the detector (40) with a beam spot (91) having a diameter Ø, and wherein
• the determination of the geometry parameter by the evaluation device (80) comprises a determination of the diameter Ø of the beam spot (91) on the detector (40).

Beam analysis device (10) according to any one of the preceding claims, wherein the evaluation device (80) is further configured to determine a lateral position of the overall intensity distribution (79) on the detector (40) and is configured to calculate a lateral position of the focus (76) of the energy beam (77) from the lateral position of the overall intensity distribution (79) and/or to calculate a change in the lateral position of the focus (76) of the energy beam (77) from a change in the lateral position of the overall intensity distribution (79).

System comprising a beam analysis device (10) according to any one of the preceding claims and laser processing optics (100) for guiding and focusing the energy beam (77), wherein the processing optics (100) comprises a beam decoupler (115) for decoupling the sample beam (70), and wherein the beam analysis device (10) is connectable to the processing optics (100) for receiving the decoupled sample beam (70).

(146) in the cavity (141) of the cutting gas device (141).