CN114705317B - A method for measuring atmospheric temperature fluctuations - Google Patents
A method for measuring atmospheric temperature fluctuations Download PDFInfo
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- G—PHYSICS
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/006—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using measurement of the effect of a material on microwaves or longer electromagnetic waves, e.g. measuring temperature via microwaves emitted by the object
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K13/00—Thermometers specially adapted for specific purposes
- G01K13/02—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow
- G01K13/024—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow of moving gases
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K3/00—Thermometers giving results other than momentary value of temperature
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Abstract
The invention discloses an atmospheric temperature fluctuation measuring method, which utilizes a laser of a Moire chromatographic device to emit a collimated light beam to obtain Moire fringes, continuously collects the Moire fringes according to frames in measuring time, intercepts local Moire fringes at the same position of each frame, calculates an emergent ray deflection angle of the collimated light beam after entering the atmosphere according to a displacement value of the local Moire fringes in time and the distance between the Moire fringes, and finally calculates atmospheric refractive index fluctuation according to the emergent ray deflection angle. The invention introduces the Moire chromatography technology into the atmospheric temperature fluctuation measurement, and provides a certain reference for researching the self-rule of the atmospheric turbulence and the influence of the atmosphere on the aspects of detection, communication and the like.
Description
Technical Field
The invention discloses an atmospheric temperature fluctuation measuring method, and relates to the technical field of optical detection.
Background
Atmospheric turbulence is a random air movement condition, and in the field of atmospheric optics, turbulence mainly refers to random changes of refractive index caused by random changes of local temperature and pressure in the atmosphere. When light passes through the atmosphere with uneven refractive index distribution and random change, phenomena such as deflection, phase shift and the like can occur, and the phenomena have non-negligible influence on the aspects of atmosphere detection, aircraft optical imaging detection and the like, so that images received by the detector can be offset, dithered, blurred and the like. In addition, in atmospheric laser communication, the influence of atmospheric turbulence on laser transmission sometimes seriously affects the performance of a communication system, and even causes interruption of communication. The effects of atmospheric turbulence are mainly caused by temperature fluctuations, so it is important to accurately measure the atmospheric temperature fluctuations.
Disclosure of Invention
Aiming at the defects in the background technology, the invention provides an atmospheric temperature fluctuation measuring method which is simple and accurate.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows, and the atmospheric temperature fluctuation measuring method comprises the following steps:
utilizing a laser of a Moire chromatographic device to emit a collimated light beam, and obtaining Moire fringes on a light screen of the Moire chromatographic device;
Continuously collecting moire fringes on a light screen according to frames in measurement time, and intercepting local moire fringes at the same position of each frame to obtain a displacement value of the local moire fringes in time;
Calculating the deflection angle of emergent light after the collimated light beam enters the atmosphere according to the displacement value of the local moire fringes in time and the interval of the moire fringes;
and step four, calculating the atmospheric refractive index fluctuation through the deflection angle of the emergent light, and calculating the atmospheric temperature fluctuation according to the atmospheric refractive index fluctuation.
In the step one, the moire chromatographic device comprises a laser, a beam expanding and collimating system, two gratings, a first imaging lens, a filter, a second imaging lens and a light screen which are sequentially arranged from left to right along the incidence direction of laser, wherein the beam expanding and collimating system comprises a first lens and a second lens which are sequentially arranged along the incidence direction of the laser, and the laser is used for emitting collimated light beams to obtain moire fringes on the light screen.
Further, in the third step, the calculation of the deflection angle of the outgoing light ray includes the following steps:
Processing the intercepted local moire fringes of each frame by a coordinate system, and recording the coordinate positions of the local moire fringes;
Calculating the average position of the local moire fringes of all frames: e i is the average position of the ith frame stripe, N is the total frame number;
calculating the displacement value of the local moire fringes of the ith frame in time:
calculating the deflection angle of emergent light corresponding to the local moire fringes of the ith frame:
z represents the pitch of two gratings, d represents the grating period, d m represents the moire pitch, and the pitch variation between adjacent moire patterns of different frames is negligible.
In the fourth step, the calculating the atmospheric refractive index fluctuation through the deflection angle of the outgoing light, and calculating the atmospheric temperature fluctuation according to the atmospheric refractive index fluctuation specifically includes the following steps:
Step 1, calculating a structural constant representing intensity of random non-uniformity of the refractive index of the atmosphere through a deflection angle of emergent light:
where D is the diameter of the collimated beam on the first grating, E is the transmission distance of the collimated beam in the atmosphere, Is the variance of the angle of the deflection,
Refractive index Structure function D n (t) describes the fluctuation of the atmospheric refractive index, refractive index Structure function D n (t) and refractive index Structure constantCan be expressed as:
Wherein n (t) represents the atmospheric refractive index at t, n (t- Δt) represents the atmospheric refractive index at (t- Δt),
Step 2, calculating an atmospheric refractive index fluctuation term:
1≤i≤N
1≤i≤N
wherein, deltat represents the time interval of two adjacent frames of moire fringes, v is the average wind speed in the measurement time, and the time average of the internal parameters is represented;
step 3, calculating a temperature fluctuation term:
1≤i≤N
wherein L represents a Loxidechucking constant, L=2.687X 19cm-3, kappa represents a Boltzmann constant, lambda represents a wavelength of probe light, A and B are constants related to a kind of neutral particles in an atmospheric flow field, A and B take relevant parameters of air, A= 2.871 × -4,B＝1.628×10-6, Is the average pressure of the region under test,Is the average temperature of the region being measured.
Further, intercepting local moire fringes at the same position of each frame, wherein the pixel size of an intercepting region is Q, and Q is a positive integer.
Further, the coordinate system processing of each frame of moire fringes comprises the following steps of binarization, refinement, bright fringe, coordinate selection of an origin position, specifically, the steps of processing through matlab, converting a fringe pattern into a gray image by adopting an rgb2gray function, binarizing by adopting an im2bw function, refining by adopting a bwmorph function, taking the left upper corner of a screenshot as the origin, recording the bit transverse coordinates of points on a curve for every other pixel of the intercepted moire fringes, and averaging.
The atmospheric temperature fluctuation measuring method has the beneficial effects that the relation between the atmospheric refractive index fluctuation and the deflection angle is established, and the relation between the atmospheric refractive index fluctuation and the deflection angle is combined with the relation between the air temperature and the refractive index to obtain the relation model, so that the atmospheric temperature fluctuation measuring method is provided for measuring the atmospheric temperature fluctuation by using the Moire chromatography technology, and the atmospheric temperature fluctuation measuring method is convenient to operate, high in precision and capable of carrying out large-scale, long-term and systematic measurement.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic flow chart of the present invention;
FIG. 3 (a) is a moire pattern of the 1800 th frame of the present embodiment;
fig. 3 (b) is a moire pattern of 3600 frame of the present embodiment;
FIG. 3 (c) is a moire pattern of 5400 th frame of this embodiment;
FIG. 3 (d) is a moire pattern of 7200 frames of the present embodiment;
FIG. 4 (a) is a partial moire map of the 1800 th frame of the present embodiment;
FIG. 4 (b) is a partial moire map of the 3600 frame of the present embodiment;
FIG. 4 (c) is a partial moire map of 5400 th frame of this embodiment;
FIG. 4 (d) is a partial moire map of 7200 frames of the present embodiment;
FIG. 5 (a) is a partial moire refinement of the 1800 th frame of the present embodiment;
FIG. 5 (b) is a partial moire refinement of the 3600 frame of the present embodiment;
FIG. 5 (c) is a partial moire refinement of 5400 frames of this embodiment;
FIG. 5 (d) is a partial moire refinement of 7200 frames of the present embodiment;
FIG. 6 is a diagram showing the deflection angle data of the present embodiment;
Fig. 7 is a schematic diagram of temperature fluctuation in the present embodiment.
Detailed Description
The implementation of the technical solution is described in further detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.
The embodiment shown in figure 1 is that the moire chromatographic device shown in figure 1 is firstly built, the moire chromatographic device comprises a laser, a beam expanding and collimating system, two Lang Ji gratings, a first imaging lens, a filter, a second imaging lens and a light screen, wherein the laser, the beam expanding and collimating system, the two Lang Ji gratings, the first imaging lens, the filter, the second imaging lens and the light screen are sequentially arranged from left to right along the incidence direction of laser, the beam expanding and collimating system comprises the first lens and the second lens which are sequentially arranged along the incidence direction of laser;
The wavelength of the laser used in the experiment is 532nm (the model of the laser is LSR532 NL-400), the distance between the lens 3 and the second Lang Ji grating 6 is 85cm (E=85 cm), the focal length of the first imaging lens and the second imaging lens is 30cm, the period of the two Lang Ji gratings is d=1/20 mm, the distance is Z=0.3 m, the CCD is set to collect moire fringes on the light screen at the rate of 1 frame/second (namely Δt=1s) and store the moire fringes in a computer, the model of the CCD is MER-125-30UC, and the total collection of N=7200 frames of moire fringes is finally carried out (total 2 hours);
In one embodiment as shown in fig. 2, an atmospheric temperature fluctuation measuring method includes the steps of:
Step one, utilizing a laser of a Moire chromatography device shown in figure 1 to emit collimated light beams, and obtaining moire fringes on a light screen of the Moire chromatography device;
Continuously collecting moire fringes on a light screen according to frames in measurement time, and intercepting local moire fringes at the same position of each frame to obtain a displacement value of the local moire fringes in time;
Calculating the deflection angle of emergent light after the collimated light beam enters the atmosphere according to the displacement value of the local moire fringes in time and the interval of the moire fringes;
and step four, calculating the atmospheric refractive index fluctuation through the deflection angle of the emergent light, and calculating the atmospheric temperature fluctuation according to the atmospheric refractive index fluctuation.
In the third step, the calculation of the deflection angle of the emergent light rays comprises the following steps:
Selecting 1800 th frames, 3600 frames, 5400 frames and 7200 frames moire patterns for processing and illustration as shown in fig. 3 (a), (b), (c) and (d), intercepting areas with pixel sizes of 320 x 320 downwards and rightwards respectively from dot positions to form screenshots of 1800 th frames, 3600 frames, 5400 frames and 7200 frames of each group as shown in fig. 4 (a), (b), (c) and (d), binarizing and refining intercepted partial moire patterns, recording bright fringe positions, and refining fringes as shown in fig. 5 (a), (b), (c) and (d);
Processing the intercepted local moire fringes of each frame by a coordinate system, and recording the coordinate positions of the local moire fringes;
In this example, 7200 pieces of deflection angle data are obtained by performing the following processing on the position data of 7200 bright stripes.
Calculating the average position of the local moire fringes of all frames: e i is the position of local moire fringe of the ith frame, N is the total frame number;
calculating the displacement value of the local moire fringes of the ith frame in time:
calculating the deflection angle of emergent light corresponding to the local moire fringes of the ith frame:
Z represents the pitch of the two gratings, d represents the grating period, and d m represents the moire pitch.
In the fourth step, the calculating the atmospheric refractive index fluctuation through the deflection angle of the emergent light, and calculating the atmospheric temperature fluctuation according to the atmospheric refractive index fluctuation specifically comprises the following steps:
Step 1, calculating a structural constant representing intensity of random non-uniformity of the refractive index of the atmosphere through a deflection angle of emergent light:
where D is the diameter of the collimated beam on the first grating, E is the transmission distance of the collimated beam in the atmosphere, Is the variance of the angle of the deflection,
Refractive index Structure function D n (t) describes the fluctuation of the atmospheric refractive index, refractive index Structure function D n (t) and refractive index Structure constantCan be expressed as:
Wherein n (t) represents the atmospheric refractive index at t, n (t- Δt) represents the atmospheric refractive index at (t- Δt),
Step 2, calculating an atmospheric refractive index fluctuation term:
1≤i≤N
1≤i≤N
wherein, deltat represents the time interval of two adjacent frames of moire fringes, v is the average wind speed in the measurement time, and the time average of the internal parameters is represented;
step 3, calculating a temperature fluctuation term:
1≤i≤N
wherein L represents a Loxidechucking constant, L=2.687X 19cm-3, kappa represents a Boltzmann constant, lambda represents a wavelength of probe light, A and B are constants related to a kind of neutral particles in an atmospheric flow field, A and B take relevant parameters of air, A= 2.871 × -4,B＝1.628×10-6, Is the average pressure of the region under test,Is the average temperature of the region being measured.
In this embodiment, the deflection angle results of 900 th, 1800 th, 2700 th, 3600 th, 4500 th, 5400 th, 6300 th and 7200 th frames are shown in fig. 6 (corresponding to a total time of 2 hours), and the deflection angle data of 900 th, 1800 th, 2700 th, 3600 th, 4500 th, 5400 th, 6300 th and 7200 th frames are marked by open dots.
The pressure in this embodiment is one atmosphere,The anemometer synchronously measures wind speed, the Moire chromatography device synchronously measures temperature, 7200 groups of data are recorded, and the average temperature and the average wind speed in the measuring time period are respectivelyAnd < v > = 0.29m/s, the beam diameter on the first grating is d=0.05 m. Based on theoretical basis formula finally deduced by usI is more than or equal to 1 and less than or equal to N, the fluctuation distribution of the temperature in the time can be calculated,
As shown in fig. 7, similarly, the temperature fluctuations corresponding to the 900 th frame, 1800 th frame, 2700 th frame, 3600 th frame, 4500 th frame, 5400 th frame, 6300 th frame, and 7200 th frame are marked with open dots in the figure, and the open dots mark the results of the temperature fluctuations measured by the anemometer at the corresponding times.
From the temperature fluctuations within 2 hours (h) given in fig. 7, it can be seen that the temperature fluctuations measured by moire chromatography are comparable to the results measured by anemometer. Related theory and experimental results indicate that it is feasible to introduce moire techniques into the atmospheric temperature fluctuation measurements.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.
Claims (4)
1. An atmospheric temperature fluctuation measuring method, characterized by comprising the steps of:
utilizing a laser of a Moire chromatographic device to emit a collimated light beam to obtain Moire fringes;
In the measurement time, continuously collecting moire fringes according to frames, and intercepting local moire fringes at the same position of each frame;
calculating the deflection angle of the emergent light after the collimated light beam enters the atmosphere according to the displacement value of the local moire fringes in time and the interval of the moire fringes;
calculating the atmospheric refractive index fluctuation through the deflection angle of the emergent light, and calculating the atmospheric temperature fluctuation according to the atmospheric refractive index fluctuation;
the moire chromatographic device comprises a laser, a beam expanding and collimating system, two gratings, a first imaging lens, a filter, a second imaging lens and a light screen which are sequentially arranged from left to right along the incidence direction of laser, wherein the beam expanding and collimating system comprises a first lens and a second lens which are sequentially arranged along the incidence direction of the laser;
the calculation of the deflection angle of the emergent ray comprises the following steps:
Processing the intercepted local moire fringes of each frame by a coordinate system, and recording the coordinate positions of the local moire fringes;
Calculating the average position of the local moire fringes of all frames: e i is the average position of local moire fringe of the ith frame, N is the total frame number;
calculating the displacement value of the local moire fringes of the ith frame in time:
calculating the deflection angle of emergent light corresponding to the local moire fringes of the ith frame:
Z represents the pitch of the two gratings, d represents the grating period, and d m represents the moire pitch.
2. An atmospheric temperature fluctuation measuring method according to claim 1, wherein the calculating of the atmospheric refractive index fluctuation from the deflection angle of the outgoing light ray specifically comprises the steps of:
Step 1, calculating a structural constant representing intensity of random non-uniformity of the refractive index of the atmosphere through a deflection angle of emergent light:
where D is the diameter of the collimated beam on the first grating, E is the transmission distance of the collimated beam in the atmosphere, Is the variance of the angle of the deflection,
Step 2, calculating an atmospheric refractive index fluctuation term:
wherein deltat represents the time interval of two adjacent frames of moire fringes, and v is the average wind speed in the measurement time;
step 3, calculating a temperature fluctuation term:
Where L denotes the lorentz shedding constant, l=2.687×10 19cm-3, κ is the boltzmann constant, λ is the wavelength of the collimated beam, a= 2.871 ×10 -4,B＝1.628×10-6, Is the average pressure of the region under test,Is the average temperature of the region being measured.
3. An atmospheric temperature fluctuation measuring method according to claim 1, wherein local moire fringes at the same position of each frame are intercepted, the pixel size of the intercepted area is Q x Q, and Q is a positive integer.
4. An atmospheric temperature fluctuation measuring method according to claim 1, wherein the coordinate system processing includes binarizing and thinning the truncated moire fringes, recording the abscissa position of the point on the bright fringe every other pixel, and averaging all the recorded abscissa positions, denoted by ej.
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