Patent ID: 8576410

Claim:
A method for determining a height of a number of spatial positions on a sample, defining a height map of a surface of said sample, the method comprising: irradiating the surface of the sample with light comprising a spatial periodic pattern which is periodic in a direction perpendicular to an optical axis and moves in a direction parallel to a direction in which the periodic pattern is periodic; scanning the surface in the direction of the optical axis and for each position of the surface; detecting light reflected by the sample by a detector during the scanning and converting the light reflected by the sample into signals; and determining, for each spatial position of the detector, an amplitude of the signal detected during the scanning and determining a scanning location where the amplitude is maximal, wherein in any scanning position only a single image is taken; the scanning speed has a predetermined relation to a phase of the periodic pattern; and the light reflected by the sample travels over partially the same path as the light irradiating of the sample.