Abstract: An apparatus for observing and controlling a laser machining process. A working laser beam is focused in an interaction zone on a workpiece by means of a focusing mirror. The apparatus includes a radiation-sensitive receiver arrangement, and an observation mirror which deflects radiation coming from a region of the interaction zone and couples the radiation out of a working beam path onto the receiver arrangement. The observation mirror has substantially the same imaging properties as the focusing mirror. In addition, an evaluation circuit is provided to which output signals from the receiver arrangement of the observation apparatus are supplied, which processes the output signals received from the receiver arrangement and which supplies output signals for an open-loop and closed-loop control circuit, which in turn controls the laser beam and/or the laser machining process as a function of the output signals from the evaluation circuit.

Abstract: The invention relates to a sensor device for detecting radiation from the region of a zone of interaction (16) between a laser beam and a workpiece (17) for monitoring a laser machining operation and a workpiece, in particular a laser welding operation, and a device for monitoring the laser machining operation, in particular the laser welding operation, and a laser machining head having such a sensor device. The sensor device possesses a radiation-sensitive receiver arrangement and an imaging device which images a region to be observed in the region of a zone of interaction (16) onto the receiver arrangement. In order to achieve a compact and space-saving structure it is provided that the imaging device comprises a focusing mirror arranged in the working beam pathway of the laser beam which diverts radiation from the region to be observed out of the working beam pathway and focuses it onto the receiver arrangement.