Patent ID: 8878096

Claim:
A method for detecting and adjusting the focus (F) of a laser beam in the laser machining of workpieces having the following steps: a) delivery and focusing of a laser beam of a machining laser ( 1 ) emitted from a machining head ( 48 ) into a machining point ( 26 ) on or with respect to the surface ( 49 ) of a workpiece to be machined, where the focusing takes place by means of an optical focusing element ( 2 ), b) delivery and focusing of the radiation ( 28 , 31 ) emitted by at least one first adjusting light source ( 22 ) and a second adjusting light source ( 23 ) onto the surface ( 49 ) of the workpiece to be machined, where the wavelengths of the radiation admitted by the adjusting light sources ( 22 , 23 ) are different, c) uncoupling the electromagnetic radiation arising around the machining point ( 26 ) due to scattering and/or reflection of the laser beam ( 1 ) of the machining laser at the surface ( 49 ) of the workpiece to be machined, by means of an optical system ( 2 , 4 ) having chromatic aberration and detecting their intensity by means of a first detector ( 5 ), d) uncoupling the radiation ( 34 , 36 ) of the adjusting light sources ( 22 , 23 ) back-reflected from the surface of the workpiece to be machined by means of the optical system ( 2 , 4 ) having chromatic aberration and separate detection of the intensities of the reflected radiation ( 34 , 36 ) of the adjusting light sources ( 22 , 23 ) by means of at least one second detector ( 20 ), e) determining the position of the focus (F) of the laser beam ( 1 ) of the machining laser using the intensities detected in steps (c) and (d), f) adjusting the focus (F) of the laser beam ( 1 ) of the machining laser onto a desired machining point ( 26 ) with respect to the surface ( 49 ) of the workpiece to be machined.