Thales

Ecole Normale Superieure De Lyon

Patrick Feneyrou

Grégoire Pillet

Jean-Claude Lehureau

Jean-Pierre Schlotterbeck

Jean Minet

Daniel Dolfi

Philippe Rondeau

Jérôme Bourderionnet

Olivier Maury

Nicolas Bastien

Hervé Barny

Gerard Berginc

Pierre-Antoine Bouit

Marie-Chantal Andraud

Aude Martin

A method for processing a signal from a coherent lidar comprising a periodically frequency-modulated coherent source (L), the method includes the following steps: A decomposing each modulation period indexed j into a plurality of intervals indexed i, and determining, for each interval Iij, an elementary power spectral density DSP(i,j) of the beat signal over the interval, B determining an average power spectral density over j DSP(i), C determining a lower frequency bound of the average power density DSP(i) and an upper frequency bound, D determining a distance dk(i) and a velocity of the fluid vk(i) from the lower and upper bounds.

Frequency-modulated coherent lidar

A method for processing a signal from a coherent lidar includes a coherent source, the method comprising steps consisting of: generating a first beat signal and a second beat signal, using respectively a first detection assembly and a second detection assembly for a plurality of n time intervals, determining n respective values of spectral density using a transform in the frequency domain of the cross-correlation between the first and second beat signals, determining a mean value of the spectral density using said n values of spectral density, determining a piece of location information on the target using the mean value of said spectral density.

Method for processing a signal from a coherent lidar in order to reduce noise and related lidar system

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 (&#x3b1;i), 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 (&#x3b1;i) 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 (&#x3bd;) determining information on the velocity and information on the distance of the target on the basis of said n characteristic frequencies (&#x3bd;).

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

A method for reducing the peak factor of a signal transmitted in a frequency band comprising several channels, the signal using a plurality of channels in the band comprises: a step of clipping the signal, a step of subtracting the clipped signal from the signal, so as to obtain a peak signal, a step of filtering the peak signal with the aid of a multichannel filter configured to comply with a predetermined spectral mask for each of the channels used by the signal, and a step of subtracting the filtered peak signal from the signal. A device for emitting a multichannel signal implementing the method for reducing the peak factor is also provided.

Method for measuring the frequency modulation of a laser source

The general field of the invention is that of optical lidars comprising an optical porthole and operating at a first wavelength. The optical porthole of the lidar according to the invention comprises a layer or a sheet made of an optical material. The lidar comprises means for illuminating said layer or said sheet at a second wavelength different from the first wavelength, said material being transparent at the first wavelength and absorbent at the second wavelength, said second wavelength being located in the visible spectrum.

Lidar comprising optical means for deicing or preventing icing

A method for generating M demodulation signals is disclosed. In one aspect, the method includes: providing M input signals, injecting each input signal into at least one first interferometer, and detecting M demodulation signals. The method also includes choosing M positive integers that are not all equal to zero and computing M demodulation signals. The idemodulation signal being the product of R+1 functions, Rbeing the chosen integer that corresponds to the first delay of the ifirst interferometer, and the pfunction being equal to S(t)=S(t=p&#x3c4;), where p is an integer between 0 and R, &#x3c4;is the first delay introduced by the delay line of the ifirst interferometer, and S is a transform of the signal at the output of the ifirst interferometer.

Method for generating M demodulation signals using at least one primary interferometer

The general field of the invention is that of optical devices designed for measuring anemometer parameters such as speed and temperature, the device being mounted on an aircraft and comprising an optical emission module illuminating the outside air, an optical reception module capable of receiving the light scattered by the air molecules, optical means forming a reference path and computing means connected to the reception module. The optical reception module comprises optical mixing means for mixing a portion of the beam originating from the reference path and a portion of the scattered light beam. The optical emission and reception means are arranged so that the reception device collects the light originating from the Brillouin-Mandel'shtam scattering.

Optical device for measuring anemometer parameters

The invention relates to a passive optical limiter having a nonlinear material capable of switching in a predetermined optical band from a transparent state to an opaque state as a function of the power of an incident laser beam. The nonlinear material is an organic dye which comprises molecules derived from 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene into which a nitrogen atom is inserted at the meso position, referred to as aza-bodipy molecules, and which have conjugated &#x3c0; chains functionalized so as to exhibit absorption for two photons around an incident beam wavelength lying between 1.45 &#x3bc;m and 1.6 &#x3bc;m.

Passive optical limiter having nonlinear material

The invention relates to a method of protecting aircraft in flight against clear air turbulence (CAT). Consider an aircraft occupying a position P and moving horizontally at a speed V, a plane Pbeing the horizontal plane passing through P. According to the invention, the method includes performing at least one pair of evaluations of air temperature T, Tat two points B, C which have positions that are symmetrical relative to the plane P. At least one pair of horizontal air speed evaluations are performed VH, VHat the two points B, C; An air temperature gradient is determined; A horizontal air speed gradient is determined; An index signifying a presence of CAT is determined; The preceding steps are repeated; A trend is analyzed over time of the index.

Growing community of inventors

Igny, France

Patrick Feneyrou