US 12,214,441 B2
Method and system for determining the local position of at least one optical element in a machine for laser processing of a material, using low-coherence optical interferometry techniques
Simone Donadello, Rodigo (IT); Barbara Previtali, Milan (IT); and Daniele Colombo, Renate (IT)
Assigned to ADIGE S.P.A., Levico Terme (IT)
Appl. No. 17/781,594
Filed by ADIGE S.P.A., Levico Terme (IT)
PCT Filed Dec. 4, 2020, PCT No. PCT/IB2020/061507
§ 371(c)(1), (2) Date Jun. 1, 2022,
PCT Pub. No. WO2021/111393, PCT Pub. Date Jun. 10, 2021.
Claims priority of application No. 102019000023214 (IT), filed on Dec. 6, 2019.
Prior Publication US 2022/0410309 A1, Dec. 29, 2022
Int. Cl. B23K 26/046 (2014.01); G01B 9/02055 (2022.01); G01B 9/0209 (2022.01)
CPC B23K 26/046 (2013.01) [G01B 9/02072 (2013.04); G01B 9/0209 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A method for determining a local position of at least one optical element associated with an optical transport path for a laser beam in a working head of a machine for laser processing of a material, the method comprising:
generating a respective measurement beam of low coherence optical radiation, leading said measurement beam towards said at least one optical element, and leading the measurement beam reflected or diffused by at least one back-reflective surface of said at least one optical element, on which said measurement beam impinges with at least a partial back-reflection, towards an optical interferometric sensor arrangement, wherein the measurement beam travels a measurement optical path from a respective source to said optical interferometric sensor arrangement including a first section between said source and said at least one back-reflective surface of said at least one optical element and a second section between said at least one back-reflective surface of said at least one optical element and the interferometric sensor arrangement, having a respective predetermined nominal geometric length when said at least one optical element is in a predetermined nominal position corresponding to a predetermined operating condition,
generating a respective reference beam of said low coherence optical radiation, and leading said reference beam towards said optical interferometric sensor arrangement, wherein the reference beam travels a reference optical path having an optical length equivalent to the optical length of the measurement optical path in a nominal operating condition in which a position of said at least one optical element is the predetermined nominal position;
superimposing the measurement beam and the reference beam on a common region of incidence of said optical interferometric sensor arrangement, along a predetermined illumination axis;
detecting a position of a pattern of interference fringes between the measurement beam and the reference beam along said predetermined illumination axis on said common region of incidence, wherein an extension of said pattern of interference fringes along the predetermined illumination axis corresponds to a coherence length of said low coherence optical radiation, or detecting a frequency of a pattern of interference fringes in a wavelength spectrum, obtained by an interference between the measurement beam and the reference beam by wavelength dispersion of said measurement and reference beams, whose extension in a frequency domain is determined by the coherence length of said low coherence optical radiation; and
determining a difference in optical length between the measurement optical path and the reference optical path, indicative of a difference between (a) a current local position of said at least one optical element and (b) a predetermined nominal local position of said at least one optical element along an axis of the measurement beam, as a function respectively of the position of said pattern of interference fringes along said predetermined illumination axis of said common region of incidence, or of the frequency of said pattern of interference fringes in the frequency domain.