US 5,850,068 A · Focus control of lasers in material processing operations

Abstract

When a laser beam interacts with a workpiece to be welded by the beam, a plume of optical radiation is generated. An apparatus and method is disclosed in which radiation from the plume is received back through a beam delivery path comprising optical elements (L1,L2) having chromatic aberration. This alters the focus of different spectral bands of the plume radiation and a discriminating aperture is formed by a face of an optical fibre (3). After passing through the fibre, the plume radiation is separated from any laser radiation and the respective powers of the different spectral bands are measured (5). By subtraction, an error signal is obtained which is used to control the focus of the laser beam.

Claims18

Dependent claims

Apparatus for monitoring the focus of a laser beam comprising beam delivery apparatus forming a beam delivery path for delivering a laser beam to a workpiece, the beam delivery apparatus including an optical assembly having chromatic aberration and being arranged so that at least a portion of optical radiation generated at the workpiece by virtue of interaction between the workpiece and the laser beam is transmitted back through the optical assembly;

an intensity discriminating aperture;
means for separating the received optical radiation, after passing through the aperture, into at least two spectral bands;
means for detecting the respective powers of the received radiation of the at least two spectral bands and generating electrical signals representative of said powers, and means for generating, from the electrical signals, an error signal representative of the separation of the focus of the laser beam from the workpiece.

Dependencies are inferred from the claim text.

Focus control of lasers in material processing operations

Life of this patent

Focus control of lasers in material processing operations

Life of this patent

Abstract

Claims18