Abstract: An airborne compact anemometric lidar system includes a laser that can emit a laser beam, an optical system suitable for forming the laser beam emitted by the laser, an optical window that is transparent to the laser radiation emitted by the laser, wherein the lidar system comprises a first prism and a second prism, the first prism being fixed and configured to deflect the laser beam formed by the optical system, the second prism being mounted on a rotation device configured to perform a rotation about the axis of propagation of the laser beam transmitted by the first prism, so that a laser beam deflected by the second prism passes through the optical window by forming, with the normal {right arrow over (n)} to the optical window, a non-zero angle, the angle between the optical axis of the optical system and the normal {right arrow over (n)} being less than 10°, the rotation device being driven by a circuit that makes it possible to orient the second prism so as to select the angle with which the laser beam p

Abstract: The invention relates to the measurement of the speed of an aircraft by Doppler laser anemometry, the aircraft being equipped with a LiDAR using coherent detection.

Abstract: A method for determining the speed vector ({right arrow over (Vd)}), with respect to the surrounding air, of a rotary wing aircraft (HL) equipped with a beam scanning Doppler laser anemometry device for measuring (Step1) a set of projections (Vm) of said speed vector ({right arrow over (Vd)}) in at least four non-coplanar directions, comprising the following steps: detecting (Step2) any anomaly of at least one element from the set of measured projections (Vm), from a comparison with respect to a first threshold (S1), of a deviation between the measurements (Vm) and the measurements (Vp) predicted from a predetermined model depending on values of beam scanning parameters of the anemometry device; and reducing (Step3) the effect of a detected anomaly by invalidating measurements corresponding to said anomaly and computing the components of the speed vector from valid measurements.

Abstract: The general field of the invention is that of Doppler lidars intended to measure the speed of a target. The lidar according to the invention comprises: First means for modulating the optical frequency of the transmission signal, said frequency being the sum of a constant frequency and of a variable frequency of determined amplitude modulated by a periodic temporal function; Second means for computing the spectrum of the measured heterodyne signal and for creating two measurement spectra obtained by shifting the spectrum of the heterodyne signal by a positive and negative frequency value, said realignment frequency equal to the difference between the instantaneous frequency of the transmission signal and the frequency of a signal transmitted at a time shifted by the round-trip travel time between the lidar and the target; Third means for comparing the two measurement spectra, the difference in amplitude between the two spectra at the Doppler frequency determining the direction of the speed of the target.

Abstract: An anemometry system comprising a laser source supplying an incident beam that is backscattered by passing through the incident beam mixing means for mixing the backscattered beam and a reference beam, creating an interferometry wave conversion means, converting the interferometry wave into an electrical signal proportional to the power of said wave first determination means, for determining a time-frequency diagram of said electrical signal. The system also comprises second determination means for determining spots of said diagram, each spot being a set of connected points of said diagram, having exceeded a detection threshold computation means for computing an average of the frequency, a duration and a slope characterizing the trend of the frequency as a function of time in the time-frequency diagram, and determination means 107 for determining the air speed from all or part of said averages of the frequency, said durations and said slopes.

Abstract: The general field of the invention is that of Doppler lidars intended to measure the speed of a target. The lidar according to the invention comprises: First means for modulating the optical frequency of the transmission signal, said frequency being the sum of a constant frequency and of a variable frequency of determined amplitude modulated by a periodic temporal function; Second means for computing the spectrum of the measured heterodyne signal and for creating two measurement spectra obtained by shifting the spectrum of the heterodyne signal by a positive and negative frequency value, said realignment frequency equal to the difference between the instantaneous frequency of the transmission signal and the frequency of a signal transmitted at a time shifted by the round-trip travel time between the lidar and the target; Third means for comparing the two measurement spectra, the difference in amplitude between the two spectra at the Doppler frequency determining the direction of the speed of the target.

Abstract: A method for determining the speed vector ({right arrow over (Vd)}), with respect to the surrounding air, of a rotary wing aircraft (HL) equipped with a beam scanning Doppler laser anemometry device for measuring (Step1) a set of projections (Vm) of said speed vector ({right arrow over (Vd)}) in at least four non-coplanar directions, comprising the following steps: detecting (Step2) any anomaly of at least one element from the set of measured projections (Vm), from a comparison with respect to a first threshold (S1), of a deviation between the measurements (Vm) and the measurements (Vp) predicted from a predetermined model depending on values of beam scanning parameters of the anemometry device; and reducing (Step3) the effect of a detected anomaly by invalidating measurements corresponding to said anomaly and computing the components of the speed vector from valid measurements.

Abstract: A device for determining the presence of damage or dirt on a Doppler laser anemometry probe (2) porthole (1) comprising means (6) for implementing a continuous angular scan of the laser beam, means (7) for determining a current spectral component of the output signal of the probe (2) corresponding to a parasitic signal due to parasitic reflections on the path common to the emitted wave and the wave backscattered by the medium during spectral analysis of the anemometric signal, and means (8) for comparing said current spectral component of the current parasitic signal with a reference spectral component of the reference parasitic signal.

Abstract: The laser anemometry probe (LAP) system with continuous coherent detection, with single-particle mode, comprises means (AN) for analyzing the measurement signals of the said probe (LAP) and means (MES_T) for measuring the temperature (T). The system comprises, furthermore, means (DET_CG) for determining icing conditions when means (DET_GEL) for detecting the presence of a liquid water drop detect the presence of a liquid water drop, and when the said temperature (T) is below the said third threshold (S3).

Abstract: A method for estimating the transverse component Vtrans of the velocity of the air comprises the following steps: emitting a focused laser beam; acquiring an electrical signal resulting from the transit of a particle across the beam at a point of transit; analyzing the signal so as to obtain a spectrogram revealing an elongate mark representative of the transit; estimating the duration of traversal of the laser beam by the particle and the slope of the mark; deducing from the duration and from the slope the distance between the point of traversal of the beam and the focusing point; determining the radius of the beam at the point of transit; deducing the transverse component from the radius and from the duration.

Abstract: The invention relates to the measurement of the speed of an aircraft by Doppler laser anemometry, the aircraft being equipped with a LiDAR using coherent detection.

Abstract: A method for estimating the transverse component Vtrans of the velocity of the air comprises the following steps: emitting a focused laser beam; acquiring an electrical signal resulting from the transit of a particle across the beam at a point of transit; analysing the signal so as to obtain a spectrogram revealing an elongate mark representative of the transit; estimating the duration of traversal of the laser beam by the particle and the slope of the mark; deducing from the duration and from the slope the distance between the point of traversal of the beam and the focusing point; determining the radius of the beam at the point of transit; deducing the transverse component from the radius and from the duration.

Abstract: Method of measuring the velocity of an aircraft at a given instant, by laser Doppler anemometry, by performing the steps of acquiring a backscattered signal on at least three oriented line-of-sight axes, and calculating the spectrum of the backscattered signal on each of the line-of-sight axes. Further, acquiring an additional backscattered signal on at least one additional line-of-sight axis (X4) not coincident with one of the three first line-of-sight axes (X1, X2, X3), and calculating the spectrum of the backscattered signal on the additional line-of-sight axis (X4). Several candidate velocity vectors ({right arrow over (V)}c) and of the projections of the candidate vectors on at least one line-of-sight axis (X1, X2, X3, X4) are calculated. The consistency of the candidate vectors ({right arrow over (V)}c) is calculated as a function of their projections and as a function of each spectrum of the corresponding backscattered signal on the respective calculation axis (X1, X2, X3, X4).

Abstract: The present invention concerns a single-particle LIDAR anemometry method and system comprising the continuous emission of one or more light beams through a gas containing particles, said beam being focused onto a measurement volume, a step of detecting a signal backscattered by particles passing through said volume, the method being characterized in that it comprises at least the following phases: determining in a time period ?t the frequency of each of the pulses included in the backscattered signal; distinguishing pulses based on duration and/or intensity and/or frequency-modulation criteria; and estimating the displacement velocity of said beam relative to the gas from several of the frequencies determined over the time period ?t excluding those corresponding to the pulses distinguished during the preceding step A notable application of the invention is for the measurement of the airspeed of an aircraft.

Abstract: The present invention concerns a single-particle LIDAR anemometry method and system comprising the continuous emission of one or more light beams through a gas containing particles, said beam being focused onto a measurement volume, a step of detecting a signal backscattered by particles passing through said volume, the method being characterized in that it comprises at least the following phases: determining in a time period ?t the frequency of each of the pulses included in the backscattered signal; distinguishing pulses based on duration and/or intensity and/or frequency-modulation criteria; and estimating the displacement velocity of said beam relative to the gas from several of the frequencies determined over the time period ?t excluding those corresponding to the pulses distinguished during the preceding step A notable application of the invention is for the measurement of the airspeed of an aircraft

Abstract: Bistatic anemometric optical probes include an emitting first optical head that illuminates a measurement region and a receiving second optical head.

Abstract: Method of measuring the velocity of an aircraft at a given instant, by laser Doppler anemometry, by performing the steps of acquiring a backscattered signal on at least three oriented line-of-sight axes, and calculating the spectrum of the backscattered signal on each of the line-of-sight axes. Further, acquiring an additional backscattered signal on at least one additional line-of-sight axis (X4) not coincident with one of the three first line-of-sight axes (X1, X2, X3), and calculating the spectrum of the backscattered signal on the additional line-of-sight axis (X4). Several candidate velocity vectors ({right arrow over (V)}c) and of the projections of the candidate vectors on at least one line-of-sight axis (X1, X2, X3, X4) are calculated. The consistency of the candidate vectors ({right arrow over (V)}c) is calculated as a function of their projections and as a function of each spectrum of the corresponding backscattered signal on the respective calculation axis (X1, X2, X3, X4).

Abstract: The invention relates to an optical measurement device intended for determining a relative velocity vector {right arrow over (v)} of a carrier, such as an aircraft, with respect to a reference medium MILREF. The device includes an optical signal system EMIREC, delivering an optical signal Sinc that follows a direction called the line of sight LDV and is concentrated in a focusing zone ZOF, and means for displacing the focusing zone ZOF in the reference medium MILREF.

Abstract: The invention relates to a device for measuring a Doppler frequency shift, including an optical signal channel delivering a signal light beam illuminating a reference medium; and a reference channel delivering a reference light beam for detecting the Doppler frequency shift. The frequency shift is determined from the difference in frequency between the light signal illuminating the reference medium and the light beam returned by the reference medium. The device includes at least two light radiation sources, preferably lasers, with one light radiating source generating the light beam for the signal channel and the other source generating the light beam for the reference channel.

Abstract: The invention relates to an optical measurement device intended for determining a relative velocity vector {right arrow over (v)} of a carrier, such as an aircraft, with respect to a reference medium MILREF. The device includes an optical signal system EMIREC, delivering an optical signal Sinc that follows a direction called the line of sight LDV and is concentrated in a focusing zone ZOF, and means for displacing the focusing zone ZOF in the reference medium MILREF.