Device for determining a focus position in a laser machining system, laser machining system comprising same, and method for determining a focus position in a laser machining system

A laser machining system comprising:

• a laser device for providing a laser beam;
• a focusing optics for focusing the laser beam on a workpiece;
• and
• a device for determining a focus position of the laser beam in the laser machining system, comprising:
• at least two surfaces of at least one optical element, each configured to reflect a portion of the laser beam for outcoupling a sub-beam such that at least two sub-beams are outcoupled, the at least two sub-beams including a first sub-beam and a second sub-beam being superimposed coaxially;
• a spatially-resolving sensor for detecting an intensity distribution of the coaxially superimposed sub-beams on the spatially-resolving sensor;
• an evaluation unit configured to determine the focus position of the laser beam based on the intensity distribution of the coaxially superimposed sub-beams detected by the spatially-resolving sensor;
• and
• a beam splitter configured to transmit the laser beam to a workpiece and to reflect the coaxially superimposed sub-beams to the spatially-resolving sensor,
• wherein the evaluation unit is configured to determine diameters of the sub-beams based on the intensity distribution of the coaxially superimposed sub-beams detected by the spatially-resolving sensor and to determine the focus position of the laser beam from the diameters of the coaxially superimposed sub-beams.

A method for determining a focus position of a laser beam in a laser machining system, comprising:

• outcoupling at least a first sub-beam and a second sub-beam from at least one optical element arranged in a beam path of the laser beam, wherein the first sub-beam and the second sub-beam are coaxially superimposed, wherein the coaxially superimposed sub-beams are reflected to a spatially-resolving sensor by a beam splitter;
• detecting, by the spatially-resolving sensor, a spatially-resolved intensity distribution of the coaxially superimposed sub-beams on the spatially-resolving sensor;
• determining diameters of the coaxially superimposed sub-beams based on the intensity distribution of the coaxially superimposed sub-beams;
• and
• determining the focus position of the laser beam based on the determined diameters of the coaxially superimposed sub-beams.