# US 9,435,890 B2 · Laser anemometry system and method

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- Number: US 9,435,890 B2
- Document ID: US9435890B2
- Status: Granted
- Kind: B2
- Application number: 13/852,744
- Filed: 2013-03-28
- Published: 2016-08-11
- Granted: 2016-09-06
- Earliest claimed: 2012-03-29
- Assignees: Thales
- Applicants: Thales
- Inventors: Xavier Lacondemine; Nicolas Martin; Jean-Pierre Schlotterbeck; Gregory Baral-Baron
- Web page: https://patentgrep.com/patent/US9435890B2

## CPC

- G01S 17/58: Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01F 1/663: by measuring Doppler frequency shift
- G01P 5/26: by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
- G01F 1/661: using light
- G01S 17/95: for meteorological use
- Y02A 90/10: Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## 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.

## Claims

### Claim 1

Laser anemometry system comprising: a set of at least one coherent laser source supplying an incident beam, said beam being backscattered by a set of particles passing through said incident beam;
mixing means, respectively associated with a laser source, for mixing said backscattered beam and a reference beam, said reference beam being the duplication of said incident beam, creating an interferometry wave;
conversion means, respectively associated with a laser source, converting said wave into an electrical signal, the instantaneous intensity of which is proportional to the instantaneous power of said wave;
first determination means, respectively associated with a laser source, for determining a time-frequency diagram of said electrical signal;
characterized in that it also comprises
second determination means, respectively associated with a laser source, for determining spots of said diagram, each spot being a set of connected points of said diagram, having exceeded a detection threshold;
computation means, respectively associated with a laser source, 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, respectively associated with a spot third determination means for determining the air speed from all or part of said averages of the frequency, of said durations and of said slopes, said third determination means also being suitable for computing a Doppler frequency, said Doppler frequency being the average of all or part of said averages of the frequency respectively associated with spots for which one of the following conditions is met;
said duration is less than a first duration threshold;
the multiplication of said duration by said slope is less than a second threshold; and
said multiplication of said slope by the square of said duration is less than a third threshold.

### Claim 2 (depends on 1)

The laser anemometry system of claim 1, in which the third determination means for determining the air speed are suitable for determining parameters of a theoretical curve, such that the points of a graph, of which the first axis represents a frequency and the second axis represents either a slope or a frequency variation, and containing a set of points, each point being respectively associated with one of said spots and each point having as coordinates, according to the first and the second axis respectively, the average of the frequency and the slope or the frequency variation of said spot, converge the most with said curve and the determination of a Doppler frequency, said Doppler frequency corresponding to a singularity on said theoretical curve.

### Claim 3 (depends on 2)

The laser anemometry system of claim 2, in which the third determination means for determining the air speed are suitable for determining said parameters through the use of a linear regression from said graph.

### Claim 4 (depends on 3)

The laser anemometry system of claim 3, in which said computation means are suitable for using the following relationships:
P
b
⁡
(
f
,
t
)
=
P
u
⁡
(
f
,
t
)
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
t
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
σ
t
2
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
2
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
2
ρ
t
,
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
⁢
m
f
slope
⁢
=
⁢
ρ
t
,
f
σ
t
2
duration
⁢
=
4
⁢
2
⁢
σ
t
in which spot is the set of points of one of said spots, Pu(f,t) is the value of the time-frequency graph for the frequency f and the time t, mf is the average of the frequency of said spot, slope is the slope of said spot and duration is the duration of said spot.

### Claim 5 (depends on 3)

The laser anemometry system of claim 3, in which said computation means are suitable for determining the slope of one of said spots by using a linear regression on said spot.

### Claim 6 (depends on 2)

The laser anemometry system of claim 2, in which the third determination means for determining the air speed are suitable for determining said parameters through the use of a correlation between said theoretical curve and said graph.

### Claim 7 (depends on 6)

The laser anemometry system of claim 6, in which said computation means are suitable for determining the slope of one of said spots by using a linear regression on said spot.

### Claim 8 (depends on 2)

The laser anemometry system of claim 2, in which said computation means are suitable for using the following relationships:
P
b
⁡
(
f
,
t
)
=
P
u
⁡
(
f
,
t
)
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
t
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
σ
t
2
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
2
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
2
ρ
t
,
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
⁢
m
f
slope
⁢
=
⁢
ρ
t
,
f
σ
t
2
duration
⁢
=
4
⁢
2
⁢
σ
t
in which spot is the set of points of one of said spots, Pu(f,t) is the value of the time-frequency graph for the frequency f and the time t, mf is the average of the frequency of said spot, slope is the slope of said spot and duration is the duration of said spot.

### Claim 9 (depends on 2)

The laser anemometry system of claim 2, in which said computation means are suitable for using the following relationships:
P
b
⁡
(
f
,
t
)
=
P
u
⁡
(
f
,
t
)
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
t
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
σ
t
2
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
2
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
2
ρ
t
,
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
⁢
m
f
slope
⁢
=
⁢
ρ
t
,
f
σ
t
2
duration
⁢
=
4
⁢
2
⁢
σ
t
in which spot is the set of points of one of said spots, Pu(f,t) is the value of the time-frequency graph for the frequency f and the time t, mf is the average of the frequency of said spot, slope is the slope of said spot and duration is the duration of said spot.

### Claim 10 (depends on 2)

The laser anemometry system of claim 2, in which said computation means are suitable for determining the slope of one of said spots by using a linear regression on said spot.

### Claim 11 (depends on 1)

The laser anemometry system of claim 1, in which said computation means are suitable for using the following relationships:
P
b
⁡
(
f
,
t
)
=
P
u
⁡
(
f
,
t
)
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
t
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
m
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
σ
t
2
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
2
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
2
ρ
t
,
f
=
∫
∫
spot
⁢
P
u
⁡
(
f
,
t
)
⁢
⁢
t
⁢
⁢
f
⁢
⁢
ⅆ
f
⁢
⁢
ⅆ
t
-
m
t
⁢
m
f
slope
⁢
=
⁢
ρ
t
,
f
σ
t
2
duration
⁢
=
4
⁢
2
⁢
σ
t
in which spot is the set of points of one of said spots, Pu(f,t) is the value of the time-frequency graph for the frequency f and the time t, mf is the average of the frequency of said spot, slope is the slope of said spot and duration is the duration of said spot.

### Claim 12 (depends on 11)

The laser anemometry system of claim 11, in which said computation means are suitable for determining the slope of one of said spots by using a linear regression on said spot.

### Claim 13 (depends on 1)

The laser anemometry system of claim 1, in which said computation means are suitable for determining the slope of one of said spots by using a linear regression on said spot.

### Claim 14

Laser anemometry method comprising the following steps:
a step of transmission of an incident beam by at least one coherent laser source, said beam being backscattered by a set of particles passing through said incident beam;
a mixing step, respectively associated with a laser source, for mixing said backscattered beam and a reference beam, said reference beam being the duplication of said incident beam, creating an interferometry wave;
a conversion step, respectively associated with a laser source, converting said wave into an electrical signal, the instantaneous intensity of which is proportional to the instantaneous power of said wave;
a first determination step, respectively associated with a laser source, for determining a time-frequency diagram of said electrical signal;
characterized in that it also comprises:
a second determination step, respectively associated with a laser source, for determining spots of said diagram, each spot being a set of connected points of said diagram, that have exceeded a detection threshold;
a computation step, respectively associated with a laser source, 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, respectively associated with a spot;
a third determination step for determining the air speed from all or part of said averages of the frequency, of said durations and of said slopes, said third determination step also being suitable for computing a Doppler frequency, said Doppler frequency being the average of all or part of said averages of the frequency respectively associated with spots for which one of the following conditions is met:
said slope is less than a first slope threshold;
the multiplication of said duration by said slope is less than a second threshold; or
said multiplication of said slope by the square of said duration is less than a third threshold.