Lidar system for measuring the velocity of fluids
AssigneeOffice National d'Etudes et de Recherches Aerospatiales
InventorsDavid Tomline MICHEL, Laurent LOMBARD, Matthieu VALLA
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Abstract
A pulsed LIDAR system that is capable of varying a radiation modulation frequency inside each pulse, such that a component of a detection signal which is of use for measuring a velocity of a target is spectrally shifted according to its distance from the target. Such a LIDAR system makes it possible to spectrally separate the useful component of the detection signal from a narcissus signal which is caused by an output optic being shared by a emission channel and a detection channel of the LIDAR system. The LIDAR can used to measure indicated airspeeds.
Claims14
1-13. (canceled)
A LIDAR system adapted to measure a velocity of at least one target, and comprising:
- a emission channel, adapted to emit radiation pulses towards the target through an output optic of the LIDAR system;
- a detection channel, comprising a photodetector, and adapted to collect, also through the output optic, and direct onto the photodetector, a portion of the pulses that has been retroreflected or backscattered by the target, so as to produce a detection signal;
- and
- a signal processing unit, configured to output a target-related speed measurement result from the detection signal,
- the LIDAR system being characterized in that:
- the emission channel is further adapted to vary a modulation frequency of the radiation within each pulse, so that a component of the detection signal that is useful for measuring velocity, referred to as the useful component, is spectrally shifted as a function of a distance of the target from the LIDAR system;
- and
- the signal processing unit is further configured to extract the useful component from a spectrum of the detection signal, so as to isolate said useful component from at least one other component of the detection signal which results from partial retroreflection or backscattering of the emitted pulses occurring in the output optic (18) of the LIDAR system, and to obtain the result of the velocity measurement from the extracted useful component.
A method of measuring a velocity of at least one target using a LIDAR system, comprising the following steps:
- /1/emitting radiation pulses in the direction of the target through an output optic (18);
- /2/using the output optic, collecting a portion of the pulses that have been retroreflected or backscattered by the target;
- /3/detecting the retroreflected or backscattered portion of the pulses, using a photodetector which produces a detection signal;
- and
- /4/from the detection signal, outputting a speed measurement result relative to the target,
- the method being characterized in that:
- a modulation frequency of the radiation is varied within each pulse during step/1/, so that a component of the detection signal used in step/4/for velocity measurement, referred to as the useful component, is spectrally shifted as a function of a distance of the target from the LIDAR system;
- and
- the useful component is extracted from a spectrum of the detection signal in step/4/, so as to isolate said useful component from at least one other component of the detection signal which results from a partial retroreflection or backscattering of the emitted pulses occurring in the output optic, then the result of the velocity measurement is obtained from the extracted useful component.
Dependencies are inferred from the claim text.