CN106997051B - Laser vector wind measurement method and wind measurement radar based on polarization effect and self-mixing effect - Google Patents
Laser vector wind measurement method and wind measurement radar based on polarization effect and self-mixing effect Download PDFInfo
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Abstract
The invention relates to the technical field of wind direction testing, in particular to a laser vector wind measuring method based on polarization effect and self-mixing effect, which has the following principle: (1) Based on the laser polarization effect, measuring the wind speed components in different vector directions by utilizing lasers in different polarization states; (2) Simultaneously, measuring the wind speed component in each vector direction by utilizing the laser in each polarization state based on the self-mixing effect of the laser; (3) And finally, synthesizing the wind speed components measured in the two vector directions based on a vector measurement method to obtain the actual wind speed and wind direction information. The method is used for measuring the wind speed, not only can obtain wind speed and wind direction data, but also only needs a single light path for measurement, the complexity and the cost of a measuring system are reduced, the measuring system can adopt all-optical elements, the stability, the reliability and the robustness of the wind measuring system are improved, the requirement on the light source width of the laser in the measuring process is low, and high-precision measurement can be realized for different types of laser light sources.
Description
Technical Field
The invention relates to the technical field of wind direction testing, in particular to a laser vector wind measurement method and a wind measurement radar based on a polarization effect and a self-mixing effect.
Background
Wind energy is taken as a clean renewable energy source, is gradually paid attention by all countries in the world, and the rapid development of the installed capacity of wind power generation is promoted. However, wind power generation is adversely affected by random changes of wind speed and wind direction, including problems of fan yaw caused by changes of wind direction and power fluctuation caused by changes of wind speed, so that how to measure wind direction in real time is a key to achieve high-efficiency and high-safety wind power generation.
At present, wind measuring equipment is mainly divided into two types: traditional cup vane formula anemorumbometer and novel laser anemometry radar. Compared with the traditional wind cup vane type anemorumbometer, the novel laser wind measuring radar has the advantages of being high in testing accuracy and high in response speed, non-contact remote measurement of wind speed and wind direction can be achieved, interference of fan blades can be avoided conveniently, the wavelength of the laser wind measuring radar is short, detection light can be reflected by particles such as dust and aerosol in the air, the novel laser wind measuring radar is more suitable for high-accuracy real-time wind speed and wind direction measurement under a clear air condition, and therefore the novel laser wind measuring radar is widely applied.
The existing laser wind-finding radar can be divided into pulse type and continuous wave type according to the working mechanism. Compared with pulse type laser wind measuring radar, the continuous wave laser wind measuring radar has the advantages of high testing precision, small testing blind area, low cost, good stability and the like, so that the continuous wave laser wind measuring radar becomes a main technical means for detecting the wind speed and the wind direction in front of the wind driven generator in real time at present.
However, the current continuous light laser radar has the following problems:
1. the system has a complex structure, generally needs to be realized by adopting an optical heterodyne interference mode, the light path at least needs a reference light path and a detection light path, and if the wind speed vector needs to be further measured in multiple directions, the light path is more complex and the cost is higher.
2. Optical path components are numerous, and even if a coating process, wedge angle design or inclined installation and the like are adopted, extra loss cannot be avoided.
3. Laser light sources are a major source of cost for anemometry systems. Because the extraction precision of the wind measurement system on Doppler frequency shift is closely related to the line width of scattered light, a laser light source with narrow line width is generally needed, and the related cost is greatly increased.
4. Because the wind field has a mechanism of non-fixed point measurement, a large number of mechanical motion (scanning) elements are required, and the system reliability is poor.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a continuous wave laser vector wind measurement method and a wind measurement radar based on the method, wherein the continuous wave laser vector wind measurement method is used for detecting by utilizing a polarization beam splitting simultaneous detection mode or a polarization time-sharing detection mode based on a laser self-mixing effect formed by feeding back external feedback light into a laser resonant cavity.
In order to achieve the technical purpose, one technical scheme of the invention is as follows:
a laser vector wind measurement method based on polarization effect and self-mixing effect comprises the following specific steps:
A. laser emitted by the laser forms linearly polarized light through the polarizing plate;
B. the linearly polarized light forms two beams of linearly polarized light with mutually orthogonal polarization directions through a polarization beam splitter, and the included angles between the polarization directions of the two beams of linearly polarized light and the polarization direction of the linearly polarized light are both 45 degrees;
C. two linearly polarized light beams respectively pass through two output light paths and are projected into the same uniform wind field to be measured at the same time and then return, and the included angle between the projection directions of the two linearly polarized light beams is smaller than 90 degrees;
D. two returned linearly polarized light beams carrying wind speed information in two vector directions are combined and fed back to a laser resonant cavity to form a laser self-mixing signal, wherein the laser self-mixing signal comprises laser self-mixing signal components formed in different polarization directions;
E. and detecting the laser self-mixing signal, analyzing and processing the laser self-mixing signal to obtain wind speed information in two vector directions, and synthesizing the wind speed information in the two vector directions to obtain actual wind speed information and wind direction information.
And C, as an improvement, a beam expanding telescope system is arranged on each of the two output light paths in the step C.
The wind measuring radar based on the wind measuring method comprises a laser, a polarizing film, a polarization beam splitter, a first beam splitter, a second beam splitter, a first detector, a second detector and a data processing unit, wherein the laser emits laser, the laser forms initial linearly polarized light through the polarizing film, the initial linearly polarized light is divided into first linearly polarized light and second linearly polarized light through the polarization beam splitter, the polarization direction of the first linearly polarized light and the polarization direction of the second linearly polarized light are orthogonal to each other, the included angle between the polarization direction of the first linearly polarized light and the polarization direction of the second linearly polarized light is 45 degrees, the first linearly polarized light and the second linearly polarized light are projected into a uniform wind field to be measured and then return, the included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is smaller than 90 degrees, the returned first linearly polarized light and the second linearly polarized light are fed back to a laser self-mixing signal cavity along the original path to form a laser self-mixing signal, the laser self-mixing signal component of the first linearly polarized signal and the second linearly polarized signal component of the second linearly polarized signal are fed back to the laser self-mixing signal component, the first linearly polarized signal component and the second linearly polarized signal are respectively processed by the first polarization beam splitter and the first polarization beam detector, and the second polarization beam polarization detector, and the first polarization direction and the second polarization beam polarization direction is respectively, and the first polarization self-mixing signal is processed to obtain two sets of the laser self-mixing signal, and the second polarization information which are respectively, and then the second polarization information is processed to obtain two laser self-mixing signal, and the two laser self-mixing signal which are respectively, and the second polarization information which are respectively output to the second polarization information which is output to the second polarization detector, and the second polarization information which is processed to the two sets of the second polarization detector, and the two laser self-mixing signal which is processed to the electric signal, and the electric signal.
And as an improvement, the first linearly polarized light and the second linearly polarized light are projected to a uniform wind field to be measured through a first beam expanding telescope system and a second beam expanding telescope system respectively.
Preferably, the first beam expanding telescope system and the second beam expanding telescope system are both a reflective beam expanding telescope system or a transmissive beam expanding telescope system.
Preferably, the polarization beam splitter adopts a Brewster window plate or a Wollaston prism.
Preferably, the laser is a semiconductor laser, a fiber laser, a solid laser, or a gas laser.
In order to achieve the technical purpose, the other technical scheme of the invention is as follows:
a laser vector wind measurement method based on polarization effect and self-mixing effect comprises the following specific steps:
A. laser emitted by the laser forms initial linearly polarized light through the polaroid;
B. the initial linearly polarized light enters the time delay device, and the polarization direction of the linearly polarized light alternately generates 0-degree deflection or 90-degree deflection by controlling the time delay amount of the time delay device;
C. linearly polarized light with the polarization direction changed alternately is divided into linearly polarized light with the polarization direction deflected by 0 degree and linearly polarized light with the polarization direction deflected by 90 degrees through a polarization beam splitter, two beams of linearly polarized light respectively pass through two output light paths and return after being projected into the same uniform wind field to be measured simultaneously, and the included angle between the projection directions of the two beams of linearly polarized light is smaller than 90 degrees;
D. two returned linearly polarized light beams carrying wind speed information in two vector directions are fed back to a laser resonant cavity after being combined to form a laser self-mixing signal, wherein the laser self-mixing signal comprises laser self-mixing signal components formed in different polarization directions;
E. and detecting the laser self-mixing signal, analyzing and processing the laser self-mixing signal to obtain wind speed information in two vector directions, and synthesizing the wind speed information in the two vector directions to obtain actual wind speed information and wind direction information.
And C, as an improvement, a beam expanding telescope system is arranged on each of the two output light paths in the step C.
The wind measuring radar based on the wind measuring method comprises a laser, a polarizing film, an electric control delayer, a polarization beam splitter, a detector and a data processing unit, wherein the laser emits laser, the laser forms initial linear polarized light through the polarizing film, the initial linear polarized light forms deflection linear polarized light with 0-degree deflection and 90-degree deflection in a time-sharing mode in the polarization direction through the electric control delayer, the deflection linear polarized light is divided into first linear polarized light with 0-degree deflection in the polarization direction and second linear polarized light with 90-degree deflection in the polarization direction through the polarization beam splitter, the first linear polarized light and the second linear polarized light return after being projected into a uniform wind field to be measured, an included angle between the projection direction of the first linear polarized light and the projection direction of the second linear polarized light is smaller than 90 degrees, the returned first linear polarized light and second linear polarized light are fed back to a laser self-mixing signal cavity along an original path to form a laser self-mixing signal, the laser self-mixing signal comprises a laser self-mixing signal component in the first linear polarized direction and a laser self-mixing signal component in the second linear polarized direction, the two signal components appear in a time-sharing mode, the detector receives the laser self-mixing signal and converts the laser self-mixing signal into an electric signal, the wind speed data processing unit processes two electric signal to obtain the vector information, and then synthesizes the wind speed information, and the actual wind speed information.
And as an improvement, the first linearly polarized light and the second linearly polarized light are projected to a uniform wind field to be measured through a first beam expanding telescope system and a second beam expanding telescope system respectively.
Preferably, the first beam expanding telescope system and the second beam expanding telescope system are both a reflective beam expanding telescope system or a transmissive beam expanding telescope system.
Preferably, the polarization beam splitter adopts a Brewster window plate or a Wollaston prism.
Preferably, the laser is a semiconductor laser, a fiber laser, a solid laser, or a gas laser.
As can be seen from the above description, the present invention has the following advantages:
1. the wind measuring radar only needs a single light path, so that the volume, complexity and cost of the whole system are greatly simplified, and the collecting light efficiency of the system is improved.
2. The wind measuring radar adopts all-optical elements and does not have any mechanical motion element, so that the stability, reliability and robustness of a wind measuring system are greatly improved.
3. When the feedback light returns to the cavity of the laser, the steady state condition of the laser can be changed, the line width of the laser can be further compressed, and meanwhile, the related distance of the laser self-mixing effect is not influenced by the line width of the laser theoretically, so that the requirement of the polarization feedback laser self-mixing wind measurement system on the line width of the laser is greatly reduced, and high-precision wind measurement can be realized for different types of laser light sources.
Drawings
FIG. 1 is a schematic view of the vector measurement principle of the present invention;
FIG. 2 is a schematic diagram of a theoretical model of a three mirror cavity;
FIG. 3 is a schematic view of the wind speed synthesis;
FIG. 4 is a schematic structural view of embodiment 1 of the present invention;
fig. 5 is a schematic view of the laser light transmission direction and the laser light polarization direction of embodiment 1 of the present invention;
FIG. 6 is a schematic configuration diagram of embodiment 2 of the present invention;
fig. 7 is a schematic view of the laser light transmission direction and the laser light polarization direction in embodiment 2 of the present invention.
Detailed Description
The invention is based on the laser Doppler velocity measurement principle, but because the laser Doppler signals can only measure the velocity of the light beam direction, the laser Doppler signals can only measure the wind speed of the light beam direction when being applied to the occasion of measuring the wind speed, and the wind direction data can not be directly obtained. Therefore, the present invention intends to measure wind speed and wind direction by using a vector measurement method, which is described below with reference to fig. 1.
Fig. 1 is a schematic diagram of the synthesis of wind speed based on the vector measurement method. The vector measurement method comprises the steps of firstly detecting wind speed components in two vector directions, and then synthesizing the two detected components, so as to obtain the actual wind speed and wind direction.
Based on the vector measurement method, the wind direction is measured by combining the laser polarization effect and the laser self-mixing effect, and the specific measurement principle is as follows:
(1) Based on the laser polarization effect, measuring the wind speed components in different vector directions by utilizing lasers in different polarization states;
(2) The method for measuring the wind speed component in each vector direction by utilizing the laser based on the self-mixing effect of the laser comprises the following steps: projecting laser into a wind field to be measured, forming backward scattering by the laser projected onto aerosol particles in the wind field to be measured and returning, feeding back the laser to a laser resonant cavity to form a laser self-mixing signal, performing power analysis on the laser self-mixing signal to obtain backward scattering information of the aerosol particles so as to obtain movement information of the aerosol particles, and analyzing wind speed information by the movement information of the aerosol particles;
(3) And finally, synthesizing the wind speed components measured in the two vector directions based on a vector measurement method to obtain the actual wind speed and wind direction information.
Based on the measurement principle, a theoretical model is established for theoretical derivation so as to demonstrate the feasibility of the method. The specific derivation process is as follows:
as shown in FIG. 2, in the three-mirror-cavity theoretical model, the interior of the laser is equivalent to a three-mirror-cavity theoretical model consisting of a front end surface M and a rear end surface M 1 、M 2 The cavity structure of which has reflection coefficients of r 1 、r 2 The output laser is back scattered into the laser cavity by the external atmospheric aerosol particles, wherein the atmospheric aerosol is equivalent to an external reflecting surface M 3 Since the absorption and scattering of laser light by the atmosphere can cause attenuation of laser energy, the final high power of the signal returned to the laser can be expressed as:
P＝P 0 η o η T [T(R)] 2 (cβ/2)(A r /R 2 ) Formula (1)
In formula (1), P 0 Is the initial output power of the laser, eta o Is the transmission efficiency, eta, of the optical system (including beam expanding, collimating, etc.) T For the loss of truncation (insertion loss) of the laser beam through the optical system,
A r ＝πD 2 the/4 is a receiving section of the beam expanding telescoping system, and the D is the beam expanding telescoping system; beta is qiThe backscattering coefficient of the sol; t (R) is the atmospheric transmission rate at a transmission distance R.
Under the condition of a uniform atmosphere, the atmospheric transmittance follows the beer-lambert law and can be expressed as:
in the formula (2), α (r) is an atmospheric extinction coefficient at an arbitrary distance r, and includes both effects of atmospheric molecules and aerosols. External reflectivity R in the three mirror cavity theory 3 
Can be equivalent to:
R 3 ＝η o η T [T(R)] 2 (cβ/2)(A r /R 2 ) Formula (3)
Depending on the laser steady state conditions, the phase φ (v) offset Δ φ (v) should therefore have a value equal to 0, i.e.:
where α is the line width broadening factor of the laser, v 0 V is the laser frequency of the laser with and without feedback light, xi represents the coupling coefficient of the feedback light to the laser cavity, and
the time delays of the inner cavity and the outer cavity are tau respectively d (＝2n 0 d/c)(n 0 Internal refractive index of laser) and τ R (＝2R/c)。
The laser output power can be expressed according to the relationship between the laser output power and the gain and frequency of the laser as follows:
P＝P 0 [1+m×cos(φ ext )]formula (5)
Wherein phi ext (= 4 π vR/c) is a shuttle cavity mirror M 2 -M 3 M is a modulation factor.
In practical measurements, the speed is related to the self-mixing signal frequency shift Δ f by the following equation:
in the system, the wind speeds in two different directions are respectively measured by p light and s light (the p light and the s light are laser components which are orthogonal and have different polarization directions)
As shown in fig. 3, the actual wind speed can then be expressed as:
and theta is the included angle between the p light and the s light. The geometric relationship can be used to obtain the vcos alpha-v p cosθ＝v s Then, the angle α between the actual wind direction and the s-ray can be expressed as:
because the polarization state control method of the same laser beam can adopt two modes of simultaneous different polarization state control or time-sharing different polarization state control, the following two wind measuring methods can be formed based on the theoretical basis.
The first wind measuring method comprises the following steps:
a laser vector wind measurement method based on polarization effect and self-mixing effect comprises the following specific steps:
A. laser emitted by the laser forms linearly polarized light through the polarizing plate;
B. the linearly polarized light forms two beams of linearly polarized light with mutually orthogonal polarization directions through a polarization beam splitter, and the included angles between the polarization directions of the two beams of linearly polarized light and the polarization direction of the linearly polarized light are both 45 degrees;
C. two linearly polarized light beams respectively pass through two output light paths and are projected into the same uniform wind field to be measured at the same time and then return, and the included angle between the projection directions of the two linearly polarized light beams is smaller than 90 degrees;
D. two returned linearly polarized light beams carrying wind speed information in two vector directions are combined and fed back to a laser resonant cavity to form a laser self-mixing signal, wherein the laser self-mixing signal comprises laser self-mixing signal components formed in different polarization directions;
E. and detecting the laser self-mixing signal, analyzing and processing the laser self-mixing signal to obtain wind speed information in two vector directions, and synthesizing the wind speed information in the two vector directions to obtain actual wind speed information and wind direction information.
And C, a beam expanding telescope system can be additionally arranged on the two output light paths in the step C, so that linearly polarized light is expanded before being projected to a wind field, the coverage angle of the light beam is increased, and sufficient backscattering information of aerosol particles is obtained.
In the method, the linearly polarized light is divided into two linearly polarized light with different polarization states by using the polarization beam splitter within the same time period, and the linearly polarized light with the two different polarization states is output along different output light paths, so that the wind speeds in two vector directions are measured.
The second wind measuring method comprises the following steps:
a laser vector wind measurement method based on polarization effect and self-mixing effect comprises the following specific steps:
A. laser emitted by the laser forms initial linearly polarized light through the polaroid;
B. the initial linearly polarized light enters the time delay device, and the polarization direction of the linearly polarized light alternately generates 0-degree deflection or 90-degree deflection by controlling the time delay amount of the time delay device;
C. linearly polarized light with the alternately changed polarization directions is divided into linearly polarized light with the polarization direction of 0 degree deflection and linearly polarized light with the polarization direction of 90 degrees deflection by a polarization beam splitter, two beams of linearly polarized light are respectively projected into the same uniform wind field to be measured simultaneously through two output light paths and then return, and the included angle between the projection directions of the two beams of linearly polarized light is smaller than 90 degrees;
D. two returned linearly polarized light beams carrying wind speed information in two vector directions are combined and fed back to a laser resonant cavity to form a laser self-mixing signal, wherein the laser self-mixing signal comprises laser self-mixing signal components formed in different polarization directions;
E. and detecting the laser self-mixing signal, analyzing and processing the laser self-mixing signal to obtain wind speed information in two vector directions, and synthesizing the wind speed information in the two vector directions to obtain actual wind speed information and wind direction information.
And C, a beam expanding telescope system can be additionally arranged on the two output light paths in the step C, so that linearly polarized light is expanded before being projected to a wind field, the coverage angle of the light beam is increased, and sufficient backscattering information of aerosol particles is obtained.
The method utilizes the time delay device to enable the linearly polarized light to generate linearly polarized light with time-sharing change of polarization states when the polarization directions of the linearly polarized light are different in different time periods, and after the linearly polarized light with time-sharing change of polarization states passes through the polarization beam splitter, the linearly polarized light with different polarization states are respectively output through different output light paths, so that the wind speeds in two vector directions are measured.
The following describes example 1 of the present invention in detail with reference to fig. 4 and 5, but the present invention is not limited to the claims.
As shown in fig. 4, a laser vector wind radar based on polarization effect and self-mixing effect includes a laser, a polarizer, a polarization beam splitter, a first beam splitter, a second beam splitter, a first detector, a second detector, and a data processing unit;
laser emitted by a laser forms initial linearly polarized light through a polarizing plate, the initial linearly polarized light is divided into first linearly polarized light and second linearly polarized light through a polarizing beam splitter, the polarization direction of the first linearly polarized light and the polarization direction of the second linearly polarized light are orthogonal to each other, the included angle between the polarization direction of the first linearly polarized light and the polarization direction of the second linearly polarized light is 45 degrees, the first linearly polarized light and the second linearly polarized light return after being projected into a uniform wind field to be measured, the included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is smaller than 90 degrees, the returned first linearly polarized light and the second linearly polarized light which respectively carry two vector direction wind speed signals are fed back to a laser resonant cavity along the original path to form laser self-mixing signals, the laser self-mixing signal at the moment comprises a laser self-mixing signal component in the first linear polarization light polarization direction and a laser self-mixing signal component in the second linear polarization light polarization direction, the laser self-mixing signal component in the first linear polarization light polarization direction and the laser self-mixing signal component in the second linear polarization light polarization direction are respectively fed back to a first detector and a second detector through a first beam splitter and a second beam splitter, the first detector and the second detector respectively convert the laser self-mixing signal component received by the first detector and the second detector into electric signals and then output the electric signals, a data processing unit respectively processes and analyzes the two groups of output electric signals to obtain wind speed information in two vector directions, and then the wind speed information in the two vector directions is synthesized to obtain actual wind speed and wind direction information;
further, in order to improve the light beam coverage angle (i.e. improve the measurement coverage angle) projected into the wind field, it is preferable to respectively provide a first beam expanding telescope system and a second beam expanding telescope system on the output light path of the first linearly polarized light and the second linearly polarized light, and to expand the beams of the first linearly polarized light and the second linearly polarized light by using the first beam expanding telescope system and the second beam expanding telescope system, at this time, it is preferable to respectively provide a first beam splitter and a second beam splitter on two light paths formed by the polarization beam splitter and the first beam expanding telescope system and the second beam expanding telescope system.
In this embodiment:
(1) The included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is smaller than 90 degrees, and the first linearly polarized light projection optical path and the second linearly polarized light projection optical path can be arranged. For example: a. as shown in fig. 4, an included angle between a projection optical path of the first linearly polarized light (an optical path of the polarization beam splitter — the first beam expanding telescopic system) and a projection optical path of the second linearly polarized light (an optical path of the polarization beam splitter — the second beam expanding telescopic system) may be set to be smaller than 90 degrees; b. an included angle between a projection light path of the first linearly polarized light (a light path of the polarization beam splitter, the first beam splitter and the first beam expanding telescope system) and a projection light path of the second linearly polarized light (a light path of the polarization beam splitter, the second beam splitter and the second beam expanding telescope system) can be set to be larger than 90 degrees, then reflectors are respectively arranged on subsequent light paths of the first beam expanding telescope system and the second beam expanding telescope system, and the two beams of linearly polarized light are reflected to a wind field through the two reflectors, so that the included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is ensured to be smaller than 90 degrees.
(2) The polarization beam splitter can adopt a Brewster window plate or a Wollaston prism, and can also adopt a polarization beam splitter or a calcite beam shifter, and the two polarization beam splitters are combined with a reflection light path for use.
(3) Both the first beam expanding telescopic system and the second beam expanding telescopic system can adopt a reflection type beam expanding telescopic system (such as a newton type telescopic system, a griigy type telescopic system, a cassegrain type telescopic system, and the like) or a transmission type beam expanding telescopic system (such as a kepler type telescopic system, a galilean type telescopic system, and the like), and both the first beam expanding telescopic system and the second beam expanding telescopic system in fig. 2 adopt a galilean type telescopic system.
(4) The laser light source can adopt various lasers such as a semiconductor laser, a fiber laser, a solid laser or a gas laser.
(5) The data processing unit at least comprises a data acquisition part (acquiring electrical signals converted from optical signals in two vector directions, namely two electrical signals) and a data processing part (synthesizing analysis results according to a vector principle after respectively processing and analyzing the two electrical signals).
As shown in fig. 5, which is a schematic diagram of the laser light transmission direction and the laser light polarization direction of example 1, the arrows on the optical paths in the figure represent the laser light transmission direction, the solid lines represent the transmission direction of the outgoing light, the broken lines represent the transmission direction of the returning light, and the arrows inside the circles represent the light polarization directions on the respective optical paths.
The following describes embodiment 2 of the present invention in detail with reference to fig. 6 and 7, but the present invention is not limited to the claims.
As shown in fig. 6, a laser vector wind measuring radar based on polarization effect and self-mixing effect includes a laser, a polarizer, an electronic control delayer, a polarization beam splitter, a detector and a data processing unit, wherein the laser emits laser, the laser forms an initial linearly polarized light through the polarizer, the initial linearly polarized light forms a polarized linearly polarized light with polarization direction time sharing of 0 degree deflection and 90 degree deflection through the electronic control delayer, the polarized linearly polarized light is divided into a first linearly polarized light with polarization direction of 0 degree deflection and a second linearly polarized light with polarization direction of 90 degree deflection through the polarization beam splitter, the first linearly polarized light and the second linearly polarized light are projected into a uniform wind field to be measured and then return, an included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is smaller than 90 degrees, the returned first linearly polarized light and the second linearly polarized light are fed back to a laser self-mixing signal along an original path to form a laser self-mixing signal in a laser resonant cavity, the laser self-mixing signal comprises a laser self-mixing signal component in the first linearly polarized direction and a laser self-mixing signal component in the second linearly polarized direction, the two laser self-mixing signal components appear in time sharing manner, the laser self-mixing signal is received and converted into two laser vector processing units, and the two laser-mixing wind speed information processing units, and then the two laser vector information of the two laser vector re-mixing signals are obtained.
Furthermore, in order to improve the light beam coverage angle (i.e. improve the measurement coverage angle) projected to the wind field, a first beam expanding telescope system and a second beam expanding telescope system are respectively arranged on the output light paths of the first linearly polarized light and the second linearly polarized light, and the first beam expanding telescope system and the second beam expanding telescope system are used for expanding the beams of the first linearly polarized light and the second linearly polarized light.
In this embodiment:
(1) The polarization state of initial linearly polarized light can be changed by setting the delay amount of the electric control retarder, namely the delay amount of the retarder is controlled to be switched between 0 and half wavelength in an electric control mode, so that the deflection direction of the linearly polarized light output by the retarder generates 0-degree deflection and 90-degree deflection, and the 0-degree deflection and the 90-degree deflection of the linearly polarized light occur in a time-sharing mode due to the fact that the delay amount of the retarder is switched between 0 and half wavelength, namely the polarization directions of the linearly polarized light in different time intervals are different. When linearly polarized light with the deflection direction changed in a time-sharing manner passes through the polarization beam splitter, the linearly polarized light with different polarization directions can be output along different output light paths, so that the wind field can be measured from two vector directions.
(2) The included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is smaller than 90 degrees, and the first linearly polarized light projection optical path and the second linearly polarized light projection optical path can be arranged. For example: a. as shown in fig. 6, an included angle between a projection optical path of the first linearly polarized light (a light path of the first beam expanding and telescopic system, which is a polarization beam splitter) and a projection optical path of the second linearly polarized light (a light path formed by the polarization beam splitter, which is a second beam expanding and telescopic system) may be set to be smaller than 90 degrees; b. an included angle between a projection light path of the first linearly polarized light (a polarization beam splitter-a light path of the first beam expanding telescope system) and a projection light path of the second linearly polarized light (a polarization beam splitter-a light path of the second beam expanding telescope system) can be set to be larger than 90 degrees, then a reflector is respectively arranged on the subsequent light paths of the first beam expanding telescope system and the second beam expanding telescope system, and two beams of linearly polarized light are reflected to a wind field through the two reflectors, so that the included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is ensured to be smaller than 90 degrees.
(3) The polarization beam splitter can adopt a Brewster window plate or a Wollaston prism, and can also adopt a polarization beam splitter or a calcite beam shifter, and the two polarization beam splitters are combined with a reflection light path for use.
(4) Both the first beam expanding telescoping system and the second beam expanding telescoping system can adopt a reflection type beam expanding telescoping system (such as a newton type telescoping system, a griigy type telescoping system, a cassegrain type telescoping system, etc.) or a transmission type beam expanding telescoping system (such as a kepler type telescoping system, a galilean type telescoping system, etc.), and both the first beam expanding telescoping system and the second beam expanding telescoping system in fig. 4 adopt a galilean type telescoping system.
(5) The laser can be semiconductor laser, fiber laser, solid laser or gas laser. When a semiconductor laser is used, the semiconductor laser can also function as a detector.
(6) The data processing unit at least comprises a data acquisition part (acquiring electric signals converted from optical signals in two vector directions, namely two paths of electric signals) and a data processing part (synthesizing analysis results according to a vector principle after respectively processing and analyzing the two paths of electric signals).
As shown in fig. 7, a schematic diagram of the laser light transmission direction and the laser light polarization direction of example 2 is shown, in which an arrow on an optical path indicates the laser light transmission direction, a solid line indicates the transmission direction of outgoing light, a broken line indicates the transmission direction of returning light, and an arrow inside a circle indicates the light polarization direction on the corresponding optical path.
In summary, the invention has the following advantages:
1. the wind-measuring radar only needs a single light path, so that the volume, complexity and cost of the whole system are greatly simplified, and the collection light efficiency of the system is improved.
2. The wind measuring radar of the invention adopts all-optical elements and has no mechanical motion elements, thereby greatly improving the stability, reliability and robustness of the wind measuring system.
3. Because the steady state condition of the laser can be changed when the feedback light returns to the resonant cavity of the laser, the line width of the laser can be further compressed, and meanwhile, the related distance of the laser self-mixing effect is not influenced by the line width of the laser theoretically, the requirement of the polarization feedback laser self-mixing wind measurement system on the line width of the laser is greatly reduced, and high-precision wind measurement can be realized for different types of laser light sources.
It should be understood that the detailed description of the invention is only for illustrating the invention and is not limited to the technical solutions described in the embodiments of the invention. It will be understood by those skilled in the art that the present invention may be modified and equivalents substituted for elements thereof to achieve the same technical result; as long as the use requirements are met, the method is within the protection scope of the invention.
Claims (10)
1. A laser vector wind measurement method based on polarization effect and self-mixing effect comprises the following specific steps:
A. the emergent laser forms linearly polarized light through a polarizing plate;
B. the linearly polarized light forms two beams of linearly polarized light with mutually orthogonal polarization directions through a polarization beam splitter, and the included angles between the polarization directions of the two beams of linearly polarized light and the polarization direction of the linearly polarized light are both 45 degrees;
C. two linearly polarized light beams respectively pass through two output light paths and are projected into the same uniform wind field to be measured at the same time and then return, and the included angle between the projection directions of the two linearly polarized light beams is smaller than 90 degrees;
D. two returned linearly polarized light beams carrying wind speed information in two vector directions are combined and fed back to a laser resonant cavity to form a laser self-mixing signal, wherein the laser self-mixing signal comprises laser self-mixing signal components formed in different polarization directions;
E. and detecting the laser self-mixing signal, analyzing and processing the laser self-mixing signal to obtain wind speed information in two vector directions, and synthesizing the wind speed information in the two vector directions to obtain actual wind speed information and wind direction information.
2. The laser vector anemometry method based on polarization effect and self-mixing effect according to claim 1, characterized in that: and D, in the step C, two output light paths are respectively provided with a beam expanding telescope system.
3. Wind-measuring radar based on the laser vector wind-measuring method based on polarization effect and self-mixing effect of claim 1, characterized in that: the wind speed sensor comprises a laser, a polarizing film, a polarization beam splitter, a first beam splitter, a second beam splitter, a first detector, a second detector and a data processing unit, wherein the laser emits laser, the laser forms initial linearly polarized light through the polarizing film, the initial linearly polarized light is divided into first linearly polarized light and second linearly polarized light through the polarization beam splitter, the polarization direction of the first linearly polarized light and the polarization direction of the second linearly polarized light are orthogonal to each other, the included angle between the first linearly polarized light and the polarization direction of the initial linearly polarized light is 45 degrees, the first linearly polarized light and the second linearly polarized light are projected into a uniform wind field to be detected and then return, the included angle between the projection direction of the first linearly polarized light and the projection direction of the second linearly polarized light is smaller than 90 degrees, the returned first linearly polarized light and the second linearly polarized light are fed back to a laser resonant cavity along an original path to form a laser self-mixing signal, the laser self-mixing signal component of the first linearly polarized light and the laser self-mixing signal component of the second linearly polarized light are respectively fed back to the first beam splitter and the second linearly polarized light self-mixing signal component, the laser self-mixing signal component of the first linearly polarized light and the second linear polarized light polarization direction are respectively processed by the first beam splitter and the second beam splitter, and then two sets of laser self-mixing wind speed information are respectively output to the two laser self-mixing signal processing units, and the two sets of the wind speed sensor, and the two sets of laser self-mixing signal are respectively, and the wind speed sensor, and the two sets of laser self-mixing signal are respectively output electric signals, and the wind speed sensor, and then the two sets of the wind speed sensor.
4. A laser vector wind measurement method based on polarization effect and self-mixing effect comprises the following specific steps:
A. laser emitted by the laser forms linearly polarized light through the polarizing plate;
B. linearly polarized light enters a time delay device, and the polarization direction of the linearly polarized light alternately generates 0-degree deflection or 90-degree deflection by controlling the time delay amount of the time delay device;
C. linearly polarized light with the alternately changed polarization directions is divided into linearly polarized light with the polarization direction of 0 degree deflection and linearly polarized light with the polarization direction of 90 degrees deflection by a polarization beam splitter, two beams of linearly polarized light are respectively projected into the same uniform wind field to be measured simultaneously through two output light paths and then return, and the included angle between the projection directions of the two beams of linearly polarized light is smaller than 90 degrees;
D. two returned linearly polarized light beams carrying wind speed information in two vector directions are fed back to a laser resonant cavity after being combined to form a laser self-mixing signal, wherein the laser self-mixing signal comprises laser self-mixing signal components formed in different polarization directions;
E. and detecting the laser self-mixing signal, analyzing and processing the laser self-mixing signal to obtain wind speed information in two vector directions, and synthesizing the wind speed information in the two vector directions to obtain actual wind speed information and wind direction information.
5. The laser vector anemometry method based on polarization effect and self-mixing effect according to claim 4, characterized in that: and D, in the step C, two output light paths are respectively provided with a beam expanding telescope system.
6. Wind-measuring radar based on the method for laser vector wind measurement based on polarization effect and self-mixing effect according to claim 4, characterized in that: the wind speed sensor comprises a laser, a polarizing film, an electric control delayer, a polarization beam splitter, a detector and a data processing unit, wherein the laser emits laser, the laser forms initial linear polarized light through the polarizing film, the initial linear polarized light forms deflection linear polarized light with 0-degree deflection and 90-degree deflection in a time-sharing manner in the polarization direction through the electric control delayer, the deflection linear polarized light is divided into first linear polarized light with 0-degree deflection in the polarization direction and second linear polarized light with 90-degree deflection in the polarization direction through the polarization beam splitter, the first linear polarized light and the second linear polarized light return after being projected into a uniform wind field to be detected, an included angle between the projection direction of the first linear polarized light and the projection direction of the second linear polarized light is smaller than 90 degrees, the returned first linear polarized light and second linear polarized light are fed back to a laser resonant cavity along original paths to form a laser self-mixing signal, the laser self-mixing signal comprises a laser self-mixing signal component in the first linear polarized signal direction and a laser self-mixing signal component in the second linear polarized signal direction, the two signal components appear in a time-sharing manner, the detector receives the laser self-mixing signal and converts the laser self-mixing signal into an electric signal output, the data processing unit processes and analyzes the wind speed information of the output electric signal to obtain wind speed information, and synthesizes the actual wind speed information of the two vector information.
7. The wind radar according to claim 3 or 6, wherein: and the first linear polarized light and the second linear polarized light are projected to a uniform wind field to be measured through the first beam expanding telescope system and the second beam expanding telescope system respectively.
8. The wind radar according to claim 7, wherein: the first beam expanding telescopic system and the second beam expanding telescopic system are both a reflection type beam expanding telescopic system or a transmission type beam expanding telescopic system.
9. The wind radar according to claim 3 or 6, wherein: the polarization beam splitter adopts a Brewster window plate or a Wollaston prism.
10. The wind radar according to claim 3 or 6, wherein: the laser is a semiconductor laser, a fiber laser, a solid laser or a gas laser.
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| CN108614278B (en) * | 2018-05-04 | 2020-03-03 | 南京航空航天大学 | Atmospheric laser remote sensing method based on polarization modulation and polarization laser radar |
| CN110823517B (en) * | 2018-05-31 | 2021-06-08 | 安徽大学 | Method for measuring feedback factor C in laser feedback system |
| CN108646047B (en) * | 2018-07-02 | 2024-03-26 | 哈工科讯(沈阳)工业技术研究院有限公司 | Speed measuring sensor based on Doppler effect band correction structure and calibration and measurement method |
| CN108469531B (en) * | 2018-07-02 | 2023-11-10 | 北方民族大学 | Doppler effect-based double-correction type speed measurement sensor and calibration and measurement method |
| CN108594258B (en) * | 2018-07-02 | 2023-09-15 | 北方民族大学 | Doppler effect-based correction type speed measurement sensor and calibration and measurement method thereof |
| CN109724648B (en) * | 2019-01-21 | 2020-09-25 | 安徽大学 | Device and method for synchronously measuring temperature and strain based on orthogonal polarization dual-wavelength laser multi-longitudinal-mode self-mixing effect |
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