Patent DE-102010039633-A1 (DE)
Title: Device for determining focal position of focused laser beam in beam propagation direction, comprises selection unit with selection element for selecting partial laser beam, detection unit, evaluation device, and further selection unit
Inventor: RITTER ULRICH
IPC: B23K26/04
Filed: 2010-08-23
Abstract: The device comprises a selection unit (4) having a selection element (5a) arranged at a distance to a laser beam axis (2) for selecting a partial beam of a focused laser beam (1) extending at an angle to the laser beam axis, a detection unit arranged in the beam path after the selection unit and comprising a sensor element (9a) arranged at the distance to the laser beam axis for detecting the intensity of the selected partial beam, an evaluation device for determining a focus position of the laser beam using the detected intensity, a further selection unit, and a further selection element. The device comprises a selection unit (4) having a selection element (5a) arranged at a distance to a laser beam axis (2) for selecting a partial beam of a focused laser beam (1) extending at an angle to the laser beam axis, a detection unit arranged in the beam path after the selection unit and comprising a sensor element (9a) arranged at the distance to the laser beam axis for detecting the intensity of the selected partial beam, an evaluation device for determining a focus position of the laser beam using the detected intensity, a further selection unit, a further selection element, and a deflection device. The device is designed to detect a maximum intensity of the selected partial beam when the focus position of the laser beam coincides with a reference focus position of the device, which is defined by an intersection of the laser beam axis with a line-of-sight on which the selection element and the sensor element are located. The evaluation device is adapted to identify a distribution of the intensity of the laser beam to be incorporated and a maximum intensity of the laser beam at the reference focus position when changing the focal position of the laser beam relative to the device along the laser beam axis. The detection unit comprises a further sensor element, which lies on a further line-of-sight with the selection element or a further selection element of the selection unit, where the first line-of-sight intersects at the reference focus position. The selection unit is a planar or cylindrical diaphragm, and the selection element forms a partially transmissive region of a diaphragm opening or a reflective region of the diaphragm and a further diaphragm. The further selection element is arranged at the distance to the laser beam axis, where the line-of-sight, the selection element and the sensor element are located on the further selection element. The further selection element forms a diaphragm opening, whose dimensions are smaller than the dimensions of the sensor element. The sensor element is adapted for the spatially resolved detection of the intensity of incident laser beam. The sensor element, the selection element and/or the further selection element are parallelly or perpendicularly displaceable with each other. The deflection device is: adapted for deflecting the focused laser beam; arranged in the beam path in front of the selection unit; and formed as a beam splitter, and a scraper mirror. An independent claim is included for a method of determining a focal position of a focused laser beam on a laser beam axis.