Laser processing head with integrated sensor device for focus position monitoring

摘要

The laser processing head (1) comprises an integrated sensor device for monitoring focal points, a focusing lens (4), a downstream protective glass (5) to focus a processing beam bundle that hits on the focusing lens as parallel beam bundle in a resulting focal point of the focusing lens with the downstream protective glass in which a workpiece is arranged, a beam splitter (3) arranged upstream to the focusing lens in a parallel beam path, and a sensor connected with an evaluation unit. The beam splitter transmits the processing beam bundle for a first portion of a laser beam bundle (8). The laser processing head (1) comprises an integrated sensor device for monitoring focal points, a focusing lens (4), a downstream protective glass (5) to focus a processing beam bundle that hits on the focusing lens as parallel beam bundle in a resulting focal point of the focusing lens with the downstream protective glass in which a workpiece is arranged, a beam splitter (3) arranged upstream to the focusing lens in a parallel beam path, and a sensor connected with an evaluation unit. The beam splitter transmits the processing beam bundle for a first portion of a laser beam bundle (8) coupled into the laser processing head and reflects a measurement-beam bundle for a second portion of the laser beam bundle. A focusing mirror is arranged to the beam splitter in reflection direction, so that it reflects the measurement-beam bundle at an angle (alpha ) to an optical axis of the focusing lens to represent an image point conjugated to the focal point on a receiving area of the sensor. A focal width of the mirror is coordinated to the resulting focal width of the focusing lens with the protective glass, so that the sensor is arranged outside of the processing beam bundle nearer to the protective glass. The beam splitter is a perforated mirror and is both-side mirrored plane-parallel plate, which causes a geometrical beam division of the laser beam bundle into the processing beam bundle and the measurement-beam bundle on one side and reflects a radiation coming from the workpiece with different wavelength for processing laser radiation on other side to guide it over an additional focusing lens to a downstream additional sensor for process control. The beam splitter is a plane-concave annular lens mirrored on both sides, so that the plane annular surface couples the measurement-beam bundle from the laser beam bundle and the concave annular surface reflects the radiation coming from the workpiece to guide it to the downstream additional sensor for process control.