CN114705317A - Atmospheric temperature fluctuation measuring method - Google Patents

Atmospheric temperature fluctuation measuring method Download PDF

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CN114705317A
CN114705317A CN202111657837.XA CN202111657837A CN114705317A CN 114705317 A CN114705317 A CN 114705317A CN 202111657837 A CN202111657837 A CN 202111657837A CN 114705317 A CN114705317 A CN 114705317A
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moire fringes
moire
fluctuation
calculating
frame
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陈云云
徐梦
陈雅宜
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Nanjing University of Information Science and Technology
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Nanjing University of Information Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • 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
    • 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

Abstract

The invention discloses an atmospheric temperature fluctuation measuring method, which utilizes a laser of a Moire chromatography device to emit collimated light beams to obtain Moire fringes; continuously collecting moire fringes according to frames in measurement time, and intercepting local moire fringes at the same position of each frame; 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 distance of the moire fringes; and finally calculating the fluctuation of the atmospheric refractive index through the deflection angle of the emergent ray, and calculating the fluctuation of the atmospheric temperature according to the fluctuation of the atmospheric refractive index. The invention introduces the Moire chromatographic technique into the measurement of the fluctuation of the atmospheric temperature, and provides a certain reference for researching the self law of the atmospheric turbulence and the influence of the atmosphere on the aspects of detection, communication and the like.

Description

Atmospheric temperature fluctuation measuring method
Technical Field
The invention discloses an atmospheric temperature fluctuation measurement method, and relates to the technical field of optical detection.
Background
The atmospheric turbulence is a random air motion condition, and in the field of atmospheric optics, the 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 atmosphere with uneven refractive index distribution and random variation, phenomena such as deflection and phase shift can occur, which have non-negligible influence on aspects such as atmosphere detection and aircraft optical imaging detection, and can cause images received by the detector to generate deviation, jitter, blur 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 these by atmospheric turbulence are mainly caused by temperature fluctuations, and it is therefore of vital importance 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: an atmospheric temperature fluctuation measuring method comprising the steps of:
the method comprises the following steps: emitting a collimated light beam by using a laser of a moire tomography device, and obtaining moire fringes on a light screen of the moire tomography device;
step two: in the measuring time, continuously collecting moire fringes on an optical screen according to frames, intercepting local moire fringes at the same position of each frame, and acquiring a displacement value of the local moire fringes on the time;
step three: 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 distance of the moire fringes;
step four: and calculating the fluctuation of the atmospheric refractive index through the deflection angle of the emergent ray, and calculating the fluctuation of the atmospheric temperature according to the fluctuation of the atmospheric refractive index.
Further, in the first step, the moire chromatography device comprises: the laser device, the beam expanding and collimating system, the two gratings, the first imaging lens, the filter, the second imaging lens and the light screen are sequentially arranged from left to right along the laser incidence direction, and the beam expanding and collimating system comprises a first lens and a second lens which are sequentially arranged along the laser incidence direction; moire fringes are obtained on the light screen by emitting a collimated beam of light with a laser.
Further, in step three, the calculating of the deviation angle of the emergent ray includes the following steps:
processing a coordinate system of each frame of intercepted local moire fringes, and recording the coordinate position of the local moire fringes;
calculate the average position of the local moir e fringes for all frames:
Figure BDA0003446479180000021
e[i]the average position of the ith frame stripe is shown, and N is the total frame number;
calculating the displacement value of the local moire fringes of the ith frame in time:
Figure BDA0003446479180000022
calculating the deflection angle of the emergent ray corresponding to the local moire fringe of the ith frame:
Figure BDA0003446479180000023
z denotes the spacing of two gratings, d denotes the grating period, dmRepresenting the moire fringe spacing, the variation in spacing between adjacent moire fringes of different frame numbers is negligible.
Further, in the fourth step, the calculating the atmospheric refractive index fluctuation according to the deflection angle of the emergent ray, and the calculating the atmospheric temperature fluctuation according to the atmospheric refractive index fluctuation specifically includes the following steps:
step 1: calculating a structural constant representing the intensity of the random nonuniformity of the atmospheric refractive index through the deflection angle of the emergent ray:
Figure BDA0003446479180000024
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,
Figure BDA0003446479180000025
is the variance of the angle of the deflection,
Figure BDA0003446479180000026
Figure BDA0003446479180000027
refractive index structure function Dn(t) describes the fluctuation of the refractive index of the atmosphere, the refractive index structure function Dn(t) and refractive index structure constant
Figure BDA0003446479180000028
Can be expressed as:
Figure BDA0003446479180000029
wherein: n (t) represents the refractive index of the atmosphere at the t-th time, n (t- Δ t) represents the refractive index of the atmosphere at the (t- Δ t) th time,
step 2: calculating an atmospheric refractive index fluctuation term:
Figure BDA0003446479180000031
Figure BDA0003446479180000032
Figure BDA0003446479180000033
1≤i≤N
Figure BDA0003446479180000034
1≤i≤N
wherein, Δ t represents the time interval of moire fringes of two adjacent frames, v is the average wind speed in the measurement time, and < > represents the time average of the inner parameters;
and 3, step 3: calculating a temperature fluctuation term:
Figure BDA0003446479180000035
Figure BDA0003446479180000036
1≤i≤N
wherein: l represents the Lohimede constant, L is 2.687 × 1019cm-3Where κ is Boltzmann constant, λ is the wavelength of the probe light, A and B are constants related to the neutral particle species in the atmospheric flow field, A and B are parameters related to air, and A is 2.871 × 10-4，B＝1.628×10-6，
Figure BDA0003446479180000037
Is the average pressure in the area under test,
Figure BDA0003446479180000038
is the average temperature of the area under test.
Furthermore, local moire fringes at the same position of each frame are intercepted, the pixel size of the intercepted area is Q, and Q is a positive integer.
Further, the coordinate system processing of each frame of moire fringes comprises the following steps: binarization, thinning, lighting stripes, selecting an original point position by coordinates, processing by matlab, converting a stripe image into a gray image by adopting an rgb2gray function, binarizing by adopting an im2bw function, thinning by adopting a bwmorph function, taking the upper left corner of a screenshot as the original point, recording the position horizontal coordinates of points on a curve every other pixel of the intercepted moire stripes, and averaging.
Has the advantages that: the invention provides an atmospheric temperature fluctuation measuring method, which is characterized in that a relation model between temperature fluctuation and a deflection angle is obtained by establishing a relation between atmospheric refractive index fluctuation and the deflection angle and combining a relation expression between air temperature and refractive index, and the method is feasible for measuring atmospheric temperature fluctuation by utilizing a Moire chromatography technology; compared with the existing temperature fluctuation measurement method, the method provided by the invention is convenient to operate, has high precision, and can be used for large-scale, long-term and systematic measurement.
Drawings
FIG. 1 is a schematic structural view 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 the 3600 th frame in the present embodiment;
FIG. 3(c) is a moire pattern of the 5400 th frame of the present embodiment;
FIG. 3(d) is a moire pattern of the 7200 th frame 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 th frame in this embodiment;
FIG. 4(c) is a partial moire map of the 5400 th frame of the present embodiment;
FIG. 4(d) is a partial moire map of the 7200 th frame of the present embodiment;
FIG. 5(a) is a detailed view of local moire at frame 1800 of the present embodiment;
FIG. 5(b) is a detailed view of local moire at 3600 th frame in this embodiment;
FIG. 5(c) is a detailed view of local moire at 5400 frame of the present embodiment;
FIG. 5(d) is a detailed view of local moire at the 7200 th frame in the present embodiment;
FIG. 6 is a schematic view of deflection angle data according to the present embodiment;
FIG. 7 is a schematic diagram of temperature fluctuation in this embodiment.
Detailed Description
The following describes the embodiments in further detail with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The embodiment shown in fig. 1: this embodiment first builds up a moire tomography device as shown in fig. 1, which comprises: the laser, the beam expanding and collimating system, the two Langqi gratings, the first imaging lens, the filter, the second imaging lens and the light screen are sequentially arranged from left to right along the laser incidence direction, and the beam expanding and collimating system comprises the first lens and the second lens which are sequentially arranged along the laser incidence direction; utilizing the interference of the two Langqi gratings on the light beam to obtain moire fringes on the light screen, and using a CCD to collect the moire fringes on the light screen and store the moire fringes in a computer;
the laser wavelength used in the experiment is 532nm (model of the laser is LSR532NL-400), the distance between the lens 3 and the second langqi grating 6 is 85cm (E ═ 85cm), the focal length of the first and second imaging lenses is 30cm, the period of the two langqi gratings is d ═ 1/20mm, and the distance between the two langqi gratings is Z ═ 0.3 m; setting a CCD (charge coupled device) to collect moire fringes on a light screen at a rate of 1 frame/second (namely, the delta t is equal to 1s) and storing the moire fringes in a computer, wherein the model of the CCD is MER-125-30UC, and finally, collecting N is equal to 7200 frames of moire fringes (for 2 hours);
in one embodiment, shown in fig. 2, a method for measuring atmospheric temperature fluctuations includes the steps of:
the method comprises the following steps: emitting a collimated light beam by using a laser of a moire tomography device as shown in FIG. 1, and obtaining moire fringes on a light screen of the moire tomography device;
step two: in the measuring time, continuously collecting moire fringes on an optical screen according to frames, intercepting local moire fringes at the same position of each frame, and acquiring a displacement value of the local moire fringes on the time;
step three: 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 distance of the moire fringes;
step four: and calculating the fluctuation of the atmospheric refractive index according to the deflection angle of the emergent ray, and calculating the fluctuation of the atmospheric temperature according to the fluctuation of the atmospheric refractive index.
In the third step, the calculation of the deviation angle of the emergent ray comprises the following steps:
as shown in fig. 3(a), (b), (c), and (d), the moire fringe patterns of the 1800 th frame, 3600 th frame, 5400 th frame, and 7200 th frame are selected for processing; and cutting the area with the pixel size of 320 × 320 from the dot position downwards and to the right respectively to form screenshots of 1800 th frame, 3600 th frame, 5400 th frame and 7200 th frame of each group as shown in fig. 4(a), (b), (c) and (d); and binarizing and thinning the intercepted partial moire fringe image, and recording the position of a bright fringe, wherein the thinned fringe is shown in figures 5(a), (b), (c) and (d);
processing a coordinate system of each frame of intercepted local moire fringes, and recording the coordinate position of the local moire fringes;
in this example, 7200 bright stripes are processed as follows to obtain 7200 deflection angle data.
Calculate the average position of the local moir e fringes for all frames:
Figure BDA0003446479180000061
e[i]the position of local moire fringes of the ith frame is shown, and N is the total frame number;
calculating the displacement value of the local moire fringes of the ith frame in time:
Figure BDA0003446479180000062
calculating the deflection angle of the emergent ray corresponding to the local moire fringe of the ith frame:
Figure BDA0003446479180000063
z denotes the spacing of two gratings, d denotes the grating period, dmIndicating the moire pitch.
In the fourth step, the calculating the atmospheric refractive index fluctuation according to the deflection angle of the emergent ray, and the calculating the atmospheric temperature fluctuation according to the atmospheric refractive index fluctuation specifically comprises the following steps:
step 1: calculating a structural constant representing the intensity of the random nonuniformity of the atmospheric refractive index through the deflection angle of the emergent ray:
Figure BDA0003446479180000064
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,
Figure BDA0003446479180000065
is the variance of the angle of the deflection,
Figure BDA0003446479180000066
Figure BDA0003446479180000067
refractive index structure function Dn(t) describes the fluctuation of the refractive index of the atmosphere, the refractive index structure function Dn(t) and refractive index structure constant
Figure BDA0003446479180000068
Can be expressed as:
Figure BDA0003446479180000069
wherein: n (t) represents the atmospheric refractive index at the t-th time, n (t- Δ t) represents the atmospheric refractive index at the (t- Δ t) th time,
step 2: calculating an atmospheric refractive index fluctuation term:
Figure BDA0003446479180000071
Figure BDA0003446479180000072
Figure BDA0003446479180000073
1≤i≤N
Figure BDA0003446479180000074
1≤i≤N
wherein, Δ t represents the time interval of two adjacent frames of moire fringes, v is the average wind speed in the measurement time, and < > represents the time average of the inner parameters;
and step 3: calculating a temperature fluctuation term:
Figure BDA0003446479180000075
Figure BDA0003446479180000076
1≤i≤N
wherein: l represents the Lohimede constant, L is 2.687 × 1019cm-3κ is Boltzmann constant, λ is the wavelength of the probe light, A and B are constants related to the neutral particle species in the atmospheric flow field, A and B are parameters related to air, A ═ 2.871 × 10-4，B＝1.628×10-6，
Figure BDA0003446479180000077
Is the average pressure in the area under test,
Figure BDA0003446479180000078
is the average temperature of the area under test.
The deflection angle results of the selected 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 in this embodiment are shown in fig. 6 (corresponding to a total time of 2 hours); the hollow dots in the figure indicate the deflection angle data for frames 900, 1800, 2700, 3600, 4500, 5400, 6300 and 7200.
The pressure in this embodiment is one atmosphere of pressure,
Figure BDA0003446479180000079
the anemoscope synchronously measures the wind speed, the Mohr chromatography device synchronously measures the temperature, and 7200 groups of data are also recorded; the average temperature and the average wind speed in the measurement period are respectively
Figure BDA0003446479180000081
And<v>the diameter of the beam on the first grating is 0.05 m/s, 0.29 m/s. Theoretical basis formula finally deduced based on us
Figure BDA0003446479180000082
I is more than or equal to 1 and less than or equal to N, and then the calculation is carried outThe fluctuation distribution of the temperature in the above-mentioned time,
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 indicated by open dots in the figure, and the solid dots indicate the results of the temperature fluctuations measured by the anemometer at the corresponding time.
The temperature fluctuation in 2 hours (h) is shown in fig. 7, and it can be seen that the temperature fluctuation measured by the moire tomography is matched with the result measured by the anemometer. Relevant theoretical and experimental results indicate that it is feasible to introduce moire tomography techniques into the measurement of atmospheric temperature fluctuations.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (6)

1. An atmospheric temperature fluctuation measuring method characterized by comprising the steps of:
emitting collimated light beams by using a laser of a Moire chromatography device to obtain Moire fringes;
continuously collecting moire fringes according to frames in measurement time, and intercepting local moire fringes at the same position of each frame;
calculating the deflection angle of emergent rays of collimated light beams after the collimated light beams enter the atmosphere according to the displacement value of the local moire fringes in time and the distance of the moire fringes;
and calculating the fluctuation of the atmospheric refractive index through the deflection angle of the emergent ray, and calculating the fluctuation of the atmospheric temperature according to the fluctuation of the atmospheric refractive index.
2. A method for measuring temperature fluctuation according to claim 1, wherein in step one, the moire tomography device comprises: the laser device, the beam expanding and collimating system, the two gratings, the first imaging lens, the filter, the second imaging lens and the light screen are sequentially arranged from left to right along the laser incidence direction, and the beam expanding and collimating system comprises a first lens and a second lens which are sequentially arranged along the laser incidence direction; moire fringes are obtained on the light screen by emitting a collimated beam of light with a laser.
3. A method for measuring temperature fluctuation according to claim 2, wherein in step three, the calculation of the deviation angle of the outgoing ray comprises the following steps:
processing a coordinate system of each frame of intercepted local moire fringes, and recording the coordinate position of the local moire fringes;
calculate the average position of the local moir e fringes for all frames:
Figure FDA0003446479170000011
e[i]the average position of local moire fringes of the ith frame is shown, and N is the total frame number;
calculating the displacement value of the local moire fringes of the ith frame in time:
Figure FDA0003446479170000012
calculating the deflection angle of the emergent ray corresponding to the local moire fringe of the ith frame:
Figure FDA0003446479170000013
z denotes the spacing of two gratings, d denotes the grating period, dmIndicating the moire pitch.
4. The method for measuring temperature fluctuation according to claim 3, wherein in the fourth step, the calculating the atmospheric refractive index fluctuation from the deflection angle of the outgoing light ray includes the following steps:
step 1: calculating a structural constant representing the intensity of the random nonuniformity of the atmospheric refractive index through the deflection angle of the emergent ray:
Figure FDA0003446479170000021
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,
Figure FDA0003446479170000022
is the variance of the angle of the deflection,
Figure FDA0003446479170000023
Figure FDA0003446479170000024
step 2: calculating an atmospheric refractive index fluctuation term:
Figure FDA0003446479170000025
where Δ t represents the time interval of two adjacent frames of moire fringes, and v is the average wind speed in the measurement time;
and step 3: calculating a temperature fluctuation term:
Figure FDA0003446479170000026
wherein: l represents the Lohimede constant, L is 2.687 × 1019cm-3κ is boltzmann constant, λ is wavelength of collimated light beam, a is 2.871 × 10-4，B＝1.628×10-6，
Figure FDA0003446479170000027
Is the average pressure in the area under test,
Figure FDA0003446479170000028
is the average temperature of the area under test.
5. A method according to claim 3, wherein in step one, local moire fringes are captured at the same position in each frame, and the pixel size of the captured region is Q x Q, where Q is a positive integer.
6. A method as claimed in claim 3, wherein said coordinate system processing comprises: and (3) carrying out binarization and thinning processing on the intercepted moire fringes, recording the abscissa positions of points on the bright fringes every other pixel, and averaging all the recorded abscissa positions, wherein the average value is represented by e [ i ].
CN202111657837.XA 2021-12-30 2021-12-30 Atmospheric temperature fluctuation measuring method Pending CN114705317A (en)

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