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1. (WO2017153100) METHOD FOR DETERMINING THE POSITION OF THE FOCUS OF A LASER BEAM ARRANGEMENT AND METHOD FOR PROCESSING A WORKPIECE WITH A LASER BEAM

Pub. No.:    WO/2017/153100    International Application No.:    PCT/EP2017/052503
Publication Date: Fri Sep 15 01:59:59 CEST 2017 International Filing Date: Tue Feb 07 00:59:59 CET 2017
IPC: B23K 26/046
B23K 26/04
Applicants: TECHNISCHE UNIVERSITÄT MÜNCHEN
Inventors: GANSER, Andreas
FAGERER, Peter
Title: METHOD FOR DETERMINING THE POSITION OF THE FOCUS OF A LASER BEAM ARRANGEMENT AND METHOD FOR PROCESSING A WORKPIECE WITH A LASER BEAM
Abstract:
The invention relates to a method for determining the position of the focus (19) of a laser beam arrangement (10) in relation to a reference surface (55), comprising the steps (A) directing a laser beam (14) onto the reference surface (55) by means of the laser beam (10), (B) measuring the intensity of direct and/or diffuse reflected light (16, 17) produced by the reference surface (55) due to the laser beam (14), wherein (C) the steps (A) and (B) are repeated for a plurality of different, respectively fixed effective distances (15-1) between the reference surface (55) and the laser beam arrangement (10), and (D) the effective distance (15-1) between the reference surface (55) and the laser beam arrangement (10) is determined as a focal distance (15) which is representative of the position of the focus (19) and for which the measured or an interpolated intensity of the reflected light (16, 17) is extremal, if (E) during each run through steps (A) and (B) the laser beam arrangement (10) and the reference surface (55) are moved relative to one another in such a way that the laser beam (14) travels completely over a surface region (56) of the reference surface (55) with higher direct reflection and lower diffuse reflection and with a structure (57) formed in the interior thereof and having a higher diffuse reflection and lower direct reflection.