Method and apparatus for controllably laser processing a surface

摘要

Laser treatment of an e.g. metallic surface (1) such as welding or cutting, is carried out by impinging a process beam (2) of laser radiation on the surface (1). A monitoring laser beam (4) of the same wavelength but lower intensity is impinged on the surface prior to the process beam impingement. The change in temperature of the surface (1) resulting from the monitoring beam impingement is measured by means (12) to determine the effective absorption coefficient dependent upon the condition, composition and/or microstructure of the surface (1). At least one operating characteristic of the process beam (2) is varied in dependence upon the measured effective absorption coefficient in order to deliver a constant heat input to the surface along the line of the cut or weld. The beam intensity or the speed of traverse may be varied.