Machining head for a laser machining device

The invention relates to a machining head for a laser machining device, which is equipped for machining a workpiece (24) using laser radiation (30). The laser machining head comprises an adjustable focusing optical unit (34), which focuses the laser radiation (30) in a focal spot (22). The distance between the focal spot (22) and a machining head can be modified by modifying the focal length of the focusing optical unit (34). A scanning apparatus (44) deflects the laser radiation (30) in different directions. An optical coherence tomography device (48) measures a distance between the treatment head and the workpiece (24). Here, measuring light (52), which was generated by a measuring light source (50) and reflected by the workpiece (24), interferes in the coherence tomography device (48) with measuring light, which traveled an optical path length in a reference arm (60). A path-length modulator (74) is disposed in the reference arm (60) and it updates the optical path length in the reference arm (60) synchronously with, and dependent on, a change in the focal length of the focusing optical unit (34).