Patent DE-102010015023-A1 (DE)
Title: Laser processing e.g. laser welding of workpieces, by locally heating workpiece in thermal active zone by laser beam emerging from processing head, and determining spatially resolved temperature of active zone for process control
IPC: B23K26/03
Filed: 2010-04-14
Abstract: The method comprises locally heating a workpiece in a thermal active zone by a laser beam emerging from a processing head (1), and determining a spatially resolved temperature profile of the active zone for process control by a non-contact temperature measuring device, which detects the temperature of the workpiece or the workpiece temperature that is proportional to several parameters within the detected active zone in spaced apart measuring points (4). A measured distance to a surface (11) and the emissivity of the surface of the workpiece in the active zone is simultaneously determined. The method comprises locally heating a workpiece in a thermal active zone by a laser beam emerging from a processing head (1), and determining a spatially resolved temperature profile of the active zone for process control by a non-contact temperature measuring device, which detects the temperature of the workpiece or the workpiece temperature that is proportional to several parameters within the detected active zone in spaced apart measuring points (4). A measured distance to a surface (11) and the emissivity of the surface of the workpiece in the active zone is simultaneously determined using a non-contact measuring device and the value of the measured distance and emissivity is used for the calculation and/or correction of the measurement at each measurement point. A fiber bundle (5) with a first optical fiber and a second optical fiber is associated with each measuring point. The free fiber ends of the fiber bundles are arranged in each of its associated measurement point in a measuring distance to the surface of the workpiece and the light is emitted from each measuring point thermal radiation in the optical fiber of the associated fiber bundle coupled to the optical fiber and temperature measuring device. The emitted thermal radiation from each measuring point without an imaging lens is coupled to the optical fiber of the associated fiber bundle. The fiber bundle comprises a third optical fiber that is coupled with a light source present at the end of the second and third optical fibers, each of which emerges at the free fiber end and in the active zone impinges on the surface of the workpiece. The light source present in the second and third optical fibers exhibits lights having different wavelength. The respective fiber bundles measuring point emitted thermal radiation is coupled in the free end of the first optical fiber in the fiber bundle and is de-coupled at the other end of the optical fiber using a band-pass filter spectrally filtered and directed to a radiation sensitive detector of the temperature measuring device. The light emitted at the surface of the workpiece is reflected in the free end of the second and third optical fibers of each fiber bundle, where the reflected light is coupled into the free end of another fiber of the same fiber bundle and at the other end of each of the other optical fiber, and is spectrally filtered by a filter. A detector is present to determine the measurement distance of the respective fiber bundles associated with measuring point. The distance measuring device measures the distance determined through a confocal distance non-contact measurement with a back reflection method. An independent claim is included for a device for laser processing of workpieces.