Patent ID: 8179521

Claim:
Process for measuring a speed or vibration characteristic which uses a LIDAR device with heterodyne detection, wherein an optical wave emission signal is emitted from an optical head of said device in the direction of a target volume, and a backscattered signal is collected by said optical head then is detected by heterodyne detection so as to produce a heterodyne detection signal, said process comprising the following steps for a measurement cycle: /1/ producing a modulation of a phase characteristic of the optical wave in the emission signal, /2/ demodulating the heterodyne detection signal relative to the modulation of the phase characteristic, with compensating for a propagation delay of the emission signal and backscattered signal between the optical head of the device and the target volume, /3/ combining a spectral analysis of the demodulated heterodyne detection signal with an accumulation over successive analysis time windows, so as to isolate a contribution to the heterodyne detection signal coming from the target volume, and /4/ obtaining a result for the speed or vibration characteristic measurement, from a Doppler analysis of the contribution isolated in step /3/, and wherein: the modulation is obtained by shifting the phase characteristic of the optical wave during successive modulation time slots, by a fixed increment which is multiplied by factors q respectively assigned to said modulation time slots, the factors q are determined according to one of the two following methods /i/ or /ii/, with only one of said methods used during the entire measurement cycle: /i/ the scale factors q are equal to b+a p [n], where for said method method /i/: n is an integer greater than or equal to four, and is constant during the measurement cycle, a and b are two other integers, which are also constant during the measurement cycle, p is an exponent integer which is positive or zero and is strictly less than Φ(n), where Φ is a Euler's totient function, and p has varying values which are respectively assigned to the modulation time slots, b+a p [n] indicates the b+a p modulo n reduction, and a is selected such that a[n] is not zero or one, /ii/ the factors q are equal to d+c·(p+1)·p/2 [n], where for said method /ii/: n is an integer greater than or equal to four, and is constant during the measurement cycle, d and c are two integers, which are also constant during the measurement cycle, p is an integer factor of variation which is positive or zero, strictly less than n, and with varying values respectively assigned to the modulation time slots, d+c·(p+1)·p/2 [n] designates the d+c·(p+1)·p/2 modulo n reduction, and c is selected such that c[n] is not zero.