Method for processing a signal arising from coherent lidar and associated lidar system

Abstract

A method for processing a signal arising from coherent lidar includes a coherent source that is periodically frequency-modulated; a beat signal being generated by photodetector on the basis of the interference between an optical signal that is referred to as the local oscillator having a local oscillator frequency (f(t)) and an optical signal that is backscattered by a target illuminated by the lidar, said beat signal being digitized; the local oscillator frequency (f(t)) being made up of the sum of a mean value (f0) and of a modulation frequency (f(t)) arising from the modulation of the source, the modulation frequency being periodic according to a modulation period (T), each period comprising n linear portions having n frequency slopes (αi), respectively, where n is greater than or equal to 2, the method comprising the steps consisting in: complexly modulating the beat signal; complexly demodulating the modulated signal (S) by n demodulation frequencies (f(i)) each having a single slope that is equal to the respective frequency slope (αi) of the modulation frequency (f), in order to obtain n demodulated signals (S(i)); determining n spectral densities (SP(i)) of the n demodulated signals (SO)); determining n characteristic frequencies (ν) determining information on the velocity and information on the distance of the target on the basis of said n characteristic frequencies (ν).