Patent ID: 8711337

Claim:
A method for determining a linear speed (Δv) of an object, comprising the steps of: a) sampling a series of light intensity courses I(t) over time t, each light intensity courses I(t) covering a different azimuthal direction, each different azimuthal direction defining a detection length (λ i ; i=1, . . . , k) of a series of detection lengths (λ i ) as seen in a direction of the linear speed (Δv) to be determined; b) transforming the series of detection lengths (λ i ) for the azimuthal directions into a series of linear spatial frequencies (SF i ); c) defining for each azimuthal direction a band pass or a high pass filter, relating for each detection length (λ i ) characteristic filter frequencies to respective linear spatial frequencies (SF i ); d) filtering sampled light intensity for each azimuthal direction with the respective band pass or high pass filter to obtain a set of filtered light intensities; e) calculating the linear speed by dividing the characteristic filter frequencies through the linear spatial frequencies (SF i ) for at least one of azimuthal directions for which the filtered light intensity exceeds a predefined threshold; and f) determining the linear speed by correlating the calculated linear speeds for those azimuthal directions for which the filtered light intensity exceeds a predefined threshold.