Patent ID: 7430484

Claim:
A method of real-time processing of position measurements made by oscillations of probing sensors and/or beams scanning undulating surfaces, including gratings and diffraction patterns generated thereby, that comprises, generating a synthesized signal having many multiple integer harmonic frequencies of a sinusoidal phase modulated signal output of said sensor or beam produced during said oscillation scanning; basing said synthesized signal on estimated phase modulation amplitude of said oscillations and upon momentarily estimated phase information under said sinusoidal phase modulation; multiplying said signal output and the multiple harmonic frequencies of the synthesized signal; comparing the resulting product of the multiplication with reference signals with integer multiples of said sinusoidal phase modulation signal on a continual basis; and readjusting said estimated phase information until the difference between the actual and the estimated phase information becomes zero, wherein the synthesized signal has the form of a sine function within a sine/cosine function and, wherein the generated synchronized multifrequency signal q is given by q=sin({circumflex over (r)}ω sin ωt−ω{circumflex over (X)} o ) where {circumflex over (r)} and {circumflex over (X)} o represent the estimated probe or beam oscillation radius and the estimated probe or beam position respectively, and ω is the oscillation frequency and t represents time.