Method and computer program product for OCT measurement beam adjustment

A method for determining translational or rotational deviations between a measurement coordinate system of a measurement mirror scanner being tiltable about two axes and deflecting a measurement beam two-dimensionally, and a processing coordinate system of a processing mirror scanner being tiltable about two axes and deflecting both the measurement beam deflected by the measurement mirror scanner and a processing beam two-dimensionally onto a workpiece, the method comprising:

• returning the measurement beam reflected at the workpiece on a path of the incident measurement beam and capturing the returned measurement beam by a spatially resolving measurement sensor to ascertain spatially resolving information of the workpiece, and in a zero position of the measurement mirror scanner, imaging the reflected measurement beam in a sensor image of the measurement sensor, onto a previously known image position;
• ascertaining an x-y focal position deviation of the processing beam relative to a pinhole diaphragm center of a pinhole diaphragm detector disposed on a workpiece support plane by scanning the pinhole diaphragm with the processing beam deflected by the processing mirror scanner in an x-y grid and by evaluating a laser power detected at each of grid points, and by fixing the processing mirror scanner in a scan position having been corrected based on the ascertained x-y focal position deviation, the focal position of the processing beam in the scan position being situated in a predetermined position;
• capturing spatially resolving height information of the pinhole diaphragm, with the processing mirror scanner fixed in a corrected scan position, by using the measurement sensor to scan the pinhole diaphragm with the measurement beam deflected by the measurement mirror scanner;
• and
• determining the translational deviation between the processing and measurement coordinate systems based on a deviation between the previously known image position corresponding to the focal position of the processing beam and the pinhole diaphragm center captured from the height information, being present in the sensor image of the measurement sensor.