Method and device for determining the position of an optical boundary surface along a first direction

A method for determining the position of an optical boundary surface along a first direction includes a) imaging a pattern in a plane transverse to the first direction, and recording a two-dimensional image of the pattern imaged in the plane; b) repeating step a) for different positions in the first direction, wherein the different positions cover an area in the first direction in which the optical boundary surface lies; c) averaging each image from step a) along a direction transverse to the second direction such that in each case a one-dimensional data set is produced; d) transforming each data set from step c) into a frequency domain; e) determining the frequency of the greatest amplitude of all data sets transformed in step d); and f) determining the position along the first direction by evaluating the data sets transformed in step d) at the frequency determined in step e).