Device with an optical head arrangement

摘要

A device with an optical head arrangement has a drive device (48) for an objective lens (82). An objective lens (82) for movement along a beam path is supported in the optics head (52) aligned with the vertical axis of the optics head (52). Furthermore, the objective lens (82) can be moved with respect to the optics head (52) along the optical axis by means of a coil (84) and a permanent magnet (80). A laser beam is guided via the optics head (52) onto a test surface (50) and reflected from there and detected by a detector (46). A difference amplifier (92) generates a signal with a level corresponding to the distance between the objective lens (82) and the test surface (50), and the optics head (52) is moved in the system (48) until this signal reaches a predetermined value. When the signal has reached a predetermined level, the drive device (48) is switched off, while the objective lens (82) is moved by the coil (84). In this way, the distance between the objective lens (82) and the test surface (50) is set so that it corresponds in focal length to the objective lens (82). <IMAGE>