Patent ID: 8179521
Filing Date: 2012-05-15
Classification: G01F,G01P,G01S

Abstract:
1. 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: