Patent ID: 7808647

Claim:
A measuring method for detecting a deviation Δz of a distance z of a plurality of surface points from an objective, comprising the steps of: providing first and second light sources for which the spectral centroids differ by the wavelength difference Δλ and which produce spectral components comprising a first signal frequency f o and of a second signal frequency f o +Δf, where Δf is sufficiently small that a beat frequency occurs in the inverse Fourier transformation, and wherein at least one of the light sources is short coherent; dividing the light from the first and second light sources into a measuring light beam and a reference light beam; simultaneously directing the measuring beam onto a two dimensional matrix of surface points and, following reflection by the matrix of surface points, combining the reference and measuring beams and directing the combined beam onto a photo receiver, whereby a length of a measuring light path traversed by the measuring light beam is changed relative to a length of a reference light path traversed by the reference light beam; from a time-variant measuring signal containing spectral components produced by the photo receiver, extracting the two spectral components comprising a first signal frequency f o and a second signal frequency f o +Δf for the matrix of points; determining the relative phase angles φ 1 and φ 2 of the first and second signal frequencies f o and f o +Δf, respectively for the matrix of points; and determining the deviation Δz from the difference between the respective phase angles φ 1 and φ 2 .