A birefringent crystal wind imaging interferometer for eliminating temperature difference

Abstract

The present invention discloses a birefringent crystal wind imaging interferometer for eliminating temperature difference, which relates to the technical field of atmospheric detection instruments. It includes: a first birefringent crystal, a second birefringent crystal, a half-wave plate, a first birefringent crystal and a second birefringent crystal arranged in sequence, and the optical axes of the first birefringent crystal and the second birefringent crystal form an angle of 45° with the positive direction of the x-axis, and the optical axes of the second birefringent crystal and the second birefringent crystal form an angle of 135° with the positive direction of the x-axis; wherein, the positive direction of the x-axis is the transverse direction perpendicular to the optical axis; the directions of change of the thickness and refractive index of the first birefringent crystal with temperature are opposite to those of the second birefringent crystal with temperature. By the principle of complementary change amounts of optical path differences generated by two birefringent crystals, the present invention effectively improves the temperature difference elimination effect of the birefringent crystal wind imaging interferometer and enhances the stability of the birefringent interferometer in different temperature environments.

Description

Technical Field

[0001] The present invention relates to the technical field of atmospheric detection instruments, and particularly relates to a birefringent crystal wind imaging interferometer for eliminating temperature difference. Background Art

[0002] The upper atmosphere wind field is an important atmospheric dynamics parameter. High-precision and continuous detection of the atmospheric wind field can provide rich analysis data for the study of local or global atmospheric wave conditions, the coupling process between different atmospheric layers, and the characteristics of material and energy transport on a global scale. The atmospheric motion in the mesosphere and lower thermosphere regions is dominated by large-scale tides, planetary waves, and large-scale and small-scale gravity waves. Space-based observation data shows that these waves play an important driving role in the large-scale circulation of the middle atmosphere. However, the coupling, energy dissipation, and interaction mechanisms among them are still controversial. Therefore, it is necessary to perform high spatio-temporal resolution imaging detection on the middle and upper atmospheric dynamics processes, and finely depict the atmospheric disturbance images to improve and develop the atmospheric dynamics theoretical model. The passive wind imaging interference technology uses the airglow radiation naturally generated in the atmosphere as a light source to detect the atmospheric motion state (wind field). The particles that generate airglow radiation (such as O2, O, and OH, etc.) will move along with the atmosphere, and the spectral lines of the airglow radiation generated by them will have Doppler frequency shifts due to the motion relative to the observer. Measuring this Doppler frequency shift can obtain the motion speed of the target atmosphere along the line of sight, thereby inversely inferring the characteristics of atmospheric waves.

[0003] In the prior art, the birefringent crystal module of the birefringent crystal wind field interferometer consists of two birefringent crystals and a half-wave plate. The two birefringent crystals are respectively located in front of and behind the half-wave plate, and the included angles between their optical axes and the positive direction of the x-axis differ by 90°, so as to achieve a wide-field effect.

[0004] However, since the two birefringent crystals use the same crystal material, when the ambient temperature changes, the change trends of the two crystals are the same, resulting in a larger change in the reference optical path difference and reducing the stability of the birefringent wind imaging interferometer. Therefore, to give full play to the advantages of the birefringent wind imaging interferometer and improve its stability is a problem to be solved. Summary of the Invention

[0005] Based on this, it is necessary to provide a birefringent crystal wind imaging interferometer for eliminating temperature difference in view of the above technical problems.

[0006] The present invention adopts the following technical solutions:

[0007] A birefringent crystal wind imaging interferometer, comprising:

[0008] The first birefringent crystal, the second birefringent crystal, the half-wave plate, the first birefringent crystal and the second birefringent crystal in the arrangement setting; the included angle between the optical axes of the first birefringent crystal and the second birefringent crystal in front of the half-wave plate and the positive direction of the x-axis is set to 45°, and the included angle between the optical axes of the first birefringent crystal and the second birefringent crystal behind the half-wave plate and the positive direction of the x-axis is set to 135°; wherein, the positive direction of the x-axis is the transverse direction perpendicular to the optical axis;

[0009] The changing directions of the thickness and refractive index of the first birefringent crystal with temperature are opposite to those of the second birefringent crystal, so that the change amounts of the reference optical path differences generated by the first birefringent crystal and the second birefringent crystal are opposite, and the change amount of the total optical path difference generated by the first birefringent crystal and the second birefringent crystal with temperature is close to 0.

[0010] A method for eliminating temperature difference of a birefringent crystal wind imaging interferometer, comprising:

[0011] Select materials for the first birefringent crystal and the second birefringent crystal, so that the changing directions of the thickness and refractive index of the first birefringent crystal with temperature are opposite to those of the second birefringent crystal;

[0012] According to the material selection results of the first birefringent crystal and the second birefringent crystal, pair the first birefringent crystal and the second birefringent crystal, so that the change amount of the total optical path difference generated by the first birefringent crystal and the second birefringent crystal with temperature is close to 0, so as to improve the temperature difference elimination effect of the birefringent crystal wind imaging interferometer.

[0013] Preferably, the material selection for the first birefringent crystal and the second birefringent crystal specifically includes:

[0014] Construct a birefringent crystal library and enter the parameters of each birefringent crystal; wherein, the birefringent crystal includes the first birefringent crystal and the second birefringent crystal;

[0015] Arbitrarily combine the first birefringent crystal and the second birefringent crystal in the birefringent crystal library to obtain birefringent crystal combinations and obtain the crystal parameters of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combinations;

[0016] According to the preset reference optical path difference and the crystal parameters of the first birefringent crystal and the second birefringent crystal in each group of birefringent crystal combinations, obtain the crystal thicknesses of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combinations.

[0017] Preferably, the pairing of the first birefringent crystal and the second birefringent crystal specifically includes:

[0018] Calculate the total optical path difference change between the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination according to the crystal thicknesses of the two crystals.

[0019] Select the birefringent crystal combination with the total optical path difference change closest to 0 under different temperature and different field angle conditions as the paired combination of the optimal first birefringent crystal and the second birefringent crystal.

[0020] Preferably, the birefringent crystals include: calcite, lithium niobate, yttrium vanadate, titanium dioxide, and tellurium dioxide.

[0021] Preferably, the parameters of each birefringent crystal include: unit thickness d0, change in unit thickness Δd, temperature change ΔT, unit refractive index n0, change in unit refractive index Δn, thermal expansion coefficient α, and thermo-optic coefficient β;

[0022] The thermal expansion coefficient is the ratio of the change in unit thickness to the temperature change when the birefringent crystal undergoes a temperature change, that is

[0023] The thermo-optic coefficient is the ratio of the change in unit refractive index to the temperature change when the birefringent crystal undergoes a temperature change, that is

[0024] Preferably, obtaining the crystal thicknesses of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination specifically includes:

[0025] Substitute the parameters of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination into the calculation formula according to the preset reference optical path difference to obtain the crystal thicknesses of the first birefringent crystal and the second birefringent crystal. The calculation formula is as follows:

[0026]

[0027] In the formula, d1 and d2 are the thicknesses of the first birefringent crystal and the second birefringent crystal, Δ0 is the preset reference optical path difference, n o1 and n o2 are the ordinary light refractive indices of the first birefringent crystal and the second birefringent crystal, n e1 and n e2 are the extraordinary light refractive indices of the first birefringent crystal and the second birefringent crystal, α1 and α2 are the thermal expansion coefficients of the first birefringent crystal and the second birefringent crystal, and β1 and β2 are the thermo-optic coefficients of the first birefringent crystal and the second birefringent crystal.

[0028] Preferably, the calculation formula for the crystal thickness is simplified to x = A -1 B;

[0029] Among them, x is the thickness matrix of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination A represents the crystal parameter matrix B represents the optical path difference matrix

[0030] Preferably, the calculation formula for the change in the total optical path difference is:

[0031]

[0032] In the formula, is the change in the optical path difference generated by the first birefringent crystal, is the change in the optical path difference generated by the second birefringent crystal, d1 and d2 are the thicknesses of the first birefringent crystal and the second birefringent crystal respectively, n1 and n2 are the refractive indices of the first birefringent crystal and the second birefringent crystal respectively, α1 and α2 are the thermal expansion coefficients of the first birefringent crystal and the second birefringent crystal respectively, β1 and β2 are the thermo-optic coefficients of the first birefringent crystal and the second birefringent crystal respectively, and Δ is the change in the total optical path difference.

[0033] The above at least one technical solution adopted by the present invention can achieve the following beneficial effects:

[0034] By improving the double-crystal module in the existing birefringent crystal wind imaging interferometer, that is, adding another birefringent crystal on the basis of the original double-crystal module, the present invention makes the directions of the changes in the crystal thickness and refractive index of the two birefringent crystals opposite to the temperature change direction, and further makes the directions of the changes in the reference optical path differences generated by the two birefringent crystals opposite, and finally makes the change in the total optical path difference generated by the two crystals close to 0, thereby improving the stability of the birefringent interferometer in different temperature environments.

[0035] In addition, the angles between the optical axes of the first birefringent crystal and the second birefringent crystal in front of the half-wave plate and the positive direction of the x-axis are set to 45°, and the angles between the optical axes of the first birefringent crystal and the second birefringent crystal behind the half-wave plate and the positive direction of the x-axis are set to 135°, so that the interferometer maintains a good wide-field effect in different temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0037] Figure 1 is a schematic structural diagram of the birefringent crystal module of a birefringent crystal wind imaging interferometer for eliminating temperature difference provided by the present invention;

[0038] Figure 2Schematic flow chart of the selection method for the new birefringent crystal material and the original birefringent crystal material of a birefringent crystal wind imaging interferometer for eliminating temperature difference provided by the present invention;

[0039] Figure 3 Effect diagram of field of view broadening of a birefringent crystal wind imaging interferometer for eliminating temperature difference provided by the present invention;

[0040] Figure 4 Comparison diagram of temperature difference elimination effects of a birefringent crystal wind imaging interferometer for eliminating temperature difference provided by the present invention;

[0041] Figure 5 Comparison diagram of temperature difference elimination effects of using the pairing of CaCO3 and TiO2 and other pairing combinations in a birefringent crystal wind imaging interferometer for eliminating temperature difference provided by the present invention.

[0042] Figure 6 Comparison diagram of the temperature difference elimination method of a birefringent crystal wind imaging interferometer and the temperature difference elimination effect without compensation provided by the present invention;

[0043] Figure 7 Comparison diagram of the temperature difference elimination method of a birefringent crystal wind imaging interferometer and the field of view broadening effect without compensation provided by the present invention.

[0044] Reference numerals:

[0045] 1 - First birefringent crystal; 2 - Second birefringent crystal; 3 - Half-wave plate; 4 - First birefringent crystal; 5 - Second birefringent crystal. Detailed implementation manners

[0046] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0047] The following will detail the technical solutions provided by each embodiment of the present invention with reference to the drawings.

[0048] Such as Figure 1As shown in the figure, a birefringent crystal wind imaging interferometer includes: a first birefringent crystal, a second birefringent crystal, a half-wave plate, a first birefringent crystal, and a second birefringent crystal arranged in sequence; the included angles between the optical axes of the first birefringent crystal and the second birefringent crystal in front of the half-wave plate and the positive x-axis direction are set to 45°, and the included angles between the optical axes of the first birefringent crystal and the second birefringent crystal behind the half-wave plate and the positive x-axis direction are set to 135°; wherein, the positive x-axis direction is the transverse direction perpendicular to the optical axis.

[0049] The directions of the thickness and refractive index of the first birefringent crystal changing with temperature are opposite to those of the second birefringent crystal, so that the change amounts of the reference optical path differences generated by the first birefringent crystal and the second birefringent crystal are opposite, and the change amount of the total optical path difference generated by the first birefringent crystal and the second birefringent crystal with temperature is close to 0.

[0050] A method for eliminating temperature difference of a birefringent crystal wind imaging interferometer includes:

[0051] Select materials for the first birefringent crystal and the second birefringent crystal so that the directions of the thickness and refractive index of the first birefringent crystal changing with temperature are opposite to those of the second birefringent crystal;

[0052] According to the material selection results of the first birefringent crystal and the second birefringent crystal, pair the first birefringent crystal and the second birefringent crystal so that the change amount of the total optical path difference generated by the first birefringent crystal and the second birefringent crystal with temperature is close to 0, so as to improve the temperature difference elimination effect of the birefringent crystal wind imaging interferometer.

[0053] In addition, the calculation formula for the change amount of the total optical path difference is:

[0054]

[0055] In the formula, is the change amount of the optical path difference generated by the first birefringent crystal, is the change amount of the optical path difference generated by the second birefringent crystal, d1 and d2 are the thicknesses of the first birefringent crystal and the second birefringent crystal respectively, n1 and n2 are the refractive indices of the first birefringent crystal and the second birefringent crystal respectively, α1 and α2 are the thermal expansion coefficients of the first birefringent crystal and the second birefringent crystal respectively, β1 and β2 are the thermo-optic coefficients of the first birefringent crystal and the second birefringent crystal respectively, and Δ is the change amount of the total optical path difference.

[0056] In addition, the flow schematic diagram of selecting materials for the first birefringent crystal and the second birefringent crystal is as Figure 2 shown, and includes the following steps:

[0057] S101: Construct a library of birefringent crystals and record the parameters of each birefringent crystal.

[0058] Among them, the library of birefringent crystals includes: calcite, lithium niobate, yttrium vanadate, titanium dioxide, tellurium dioxide.

[0059] Among them, the parameters of each birefringent crystal include: unit thickness d0, change in unit thickness Δd, temperature change ΔT, unit refractive index n0, change in unit refractive index Δn, coefficient of thermal expansion α, and thermo-optic coefficient β.

[0060] The coefficient of thermal expansion is the ratio of the change in unit thickness to the temperature change when the temperature of the birefringent crystal changes, that is

[0061] The thermo-optic coefficient is the ratio of the change in unit refractive index to the temperature change when the temperature of the birefringent crystal changes, that is

[0062] S102: By arbitrarily combining the birefringent crystals in the library of birefringent crystals in pairs, obtain a combination of birefringent crystals and acquire the crystal parameters of the first birefringent crystal and the second birefringent crystal in the combination of birefringent crystals.

[0063] S103: According to the preset reference optical path difference and the parameters of each group of birefringent crystal combinations, obtain the crystal thicknesses of the first birefringent crystal and the second birefringent crystal in the combination of birefringent crystals.

[0064] According to the preset reference optical path difference, substitute the parameters of the first birefringent crystal and the second birefringent crystal in the combination of birefringent crystals into the calculation formula to obtain the crystal thicknesses of the first birefringent crystal and the second birefringent crystal. The calculation formula is as follows:

[0065]

[0066] In the formula, d1 and d2 are the thicknesses of the first birefringent crystal and the second birefringent crystal, Δ0 is the preset reference optical path difference, n o1 and n o2 are the ordinary light refractive indices of the first birefringent crystal and the second birefringent crystal, n e1 and n e2 are the extraordinary light refractive indices of the first birefringent crystal and the second birefringent crystal, α1 and α2 are the coefficients of thermal expansion of the first birefringent crystal and the second birefringent crystal, and β1 and β2 are the thermo-optic coefficients of the first birefringent crystal and the second birefringent crystal.

[0067] In addition, the calculation formula for the crystal thickness is simplified to x = A -1 B.

[0068] Among them, x is the thickness matrix of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination A represents the crystal parameter matrix B represents the optical path difference matrix

[0069] S104: Calculate the change in the reference optical path difference of the first birefringent crystal and the second birefringent crystal according to the crystal thicknesses of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination

[0070] S105: Select the newly added birefringent crystal combination with the change in the reference optical path difference closest to 0 under different temperature and different field angle conditions as the optimal newly added birefringent crystal pairing combination

[0071] Among them, the acquisition of the pairing combination of the optimal first birefringent crystal and the second birefringent crystal specifically includes: the birefringent crystal combination with the change in the optical path difference closest to 0 under different temperature and different field angle conditions is the pairing combination of the optimal first birefringent crystal and the second birefringent crystal

[0072] This embodiment is designed for the spectral line of 557 nm. The preset value of the reference optical path difference of the birefringent crystal wind imaging interferometer is 0.67 cm. Through the above steps, the optimal birefringent crystal pairing combination is obtained, specifically including: the material of the first birefringent crystal is CaCO3, and the material of the second birefringent crystal is TiO2. The thickness of the first birefringent crystal is 70.14 mm, and the thickness of the second birefringent crystal is 177.54 mm

[0073] Computer test analysis of the performance of the method for eliminating temperature difference by pairing two birefringent crystals of the present invention finds that it can achieve ideal field of view broadening and temperature difference elimination effects. The field of view broadening effect is as Figure 3 shown, the change in the optical path difference varies little with the field angle, and the temperature difference elimination effect is as Figure 3 shown, which well meets the requirements of wide field and temperature compensation

[0074] As Figure 4 shown, for pairing other birefringent crystals in the birefringent crystal library and comparing the temperature difference elimination effects of CaCO3 and TiO2, it can be seen that when using CaCO3 and TiO2 for pairing, the change in the reference optical path difference with temperature is less than that of other crystal pairings, and it can better meet the requirements of temperature compensation

[0075] As Figure 5As shown, when the ambient temperature changes, the crystal thickness will change accordingly, and the reference optical path difference will also change, so additional temperature drift correction is required. The method for eliminating temperature difference in the present invention reduces the change amount of the reference optical path difference with temperature by one order of magnitude. The entire interferometer system is not easily affected by external temperature changes and has lower temperature sensitivity.

[0076] On the other hand, the method for eliminating temperature difference proposed in the present invention has a better field of view broadening effect. As Figure 6 shown, the absolute value of the change rate of the reference optical path difference of the method for eliminating temperature difference with the field of view angle is only 2.298×10 -3 , while the absolute value of the change rate of the reference optical path difference of the traditional compensation scheme with an air gap reaches 3.138×10 -2 . The difference between the two is one order of magnitude. The method for eliminating temperature difference in the present invention is less sensitive to temperature than the uncompensated scheme and has a better wide-field effect. Using the design of the new method for eliminating temperature difference will greatly improve the environmental stability of the birefringent crystal wind imaging interferometer.

[0077] In summary, through the verification of this embodiment, it shows that the present invention improves the double-crystal module in the birefringent crystal wind imaging interferometer, adds another birefringent crystal on the basis of the original double-crystal module, provides a birefringent crystal wind imaging interferometer for eliminating temperature difference, and adopts the method of combining different birefringent crystals to improve the temperature difference elimination effect of the birefringent interferometer and maintain a good wide-field effect, thereby improving the stability of the birefringent interferometer in different temperature environments. The present invention provides a new birefringent crystal wind imaging interferometer for the problem that the existing birefringent crystal wind imaging interferometer cannot maintain its good temperature difference elimination effect and good stability in different temperature environments, and effectively solves the problems existing in the existing birefringent wind imaging interferometer.

[0078] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A birefringent crystal wind imaging interferometer, characterized in that, Including: The first birefringent crystal, the second birefringent crystal, the half-wave plate, the first birefringent crystal and the second birefringent crystal arranged and set; the included angle between the optical axes of the first birefringent crystal and the second birefringent crystal in front of the half-wave plate and the positive direction of the x-axis is set to 45°, and the included angle between the optical axes of the first birefringent crystal and the second birefringent crystal behind the half-wave plate and the positive direction of the x-axis is set to 135°; wherein, the positive direction of the x-axis is the transverse direction perpendicular to the optical axis. The variation directions of the thickness and refractive index of the first birefringent crystal with temperature are opposite to those of the second birefringent crystal, so that the change amounts of the reference optical path differences generated by the first birefringent crystal and the second birefringent crystal are opposite, and the change amount of the total optical path difference generated by the first birefringent crystal and the second birefringent crystal with temperature is close to 0.

2. A method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 1, characterized in that, Including: Select materials for the first birefringent crystal and the second birefringent crystal, so that the variation directions of the thickness and refractive index of the first birefringent crystal with temperature are opposite to those of the second birefringent crystal. According to the material selection results of the first birefringent crystal and the second birefringent crystal, pair the first birefringent crystal and the second birefringent crystal, so that the change amount of the total optical path difference generated by the first birefringent crystal and the second birefringent crystal with temperature is close to 0, so as to improve the temperature difference elimination effect of the birefringent crystal wind imaging interferometer.

3. The method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 2, characterized in that, The material selection for the first birefringent crystal and the second birefringent crystal specifically includes: Construct a birefringent crystal library and input the parameters of each birefringent crystal; wherein, the birefringent crystal includes the first birefringent crystal and the second birefringent crystal. Arbitrarily combine the first birefringent crystal and the second birefringent crystal in the birefringent crystal library in pairs to obtain birefringent crystal combinations and obtain the crystal parameters of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combinations. According to the preset reference optical path difference and the crystal parameters of the first birefringent crystal and the second birefringent crystal in each birefringent crystal combination, obtain the crystal thicknesses of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination.

4. The method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 2, wherein, The pairing of the first birefringent crystal and the second birefringent crystal specifically includes: Calculate the change amount of the total optical path difference between the first birefringent crystal and the second birefringent crystal according to the crystal thicknesses of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination. Select the birefringent crystal combination with the change amount of the total optical path difference closest to 0 under different temperatures and different field angles as the pairing combination of the optimal first birefringent crystal and the second birefringent crystal.

5. The method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 3, wherein, The birefringent crystal includes: calcite, lithium niobate, yttrium vanadate, titanium dioxide and tellurium dioxide.

6. The method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 3, characterized in that, The parameters of each birefringent crystal include: unit thickness d0, change amount of unit thickness Δd, temperature change amount ΔT, unit refractive index n0, change amount of unit refractive index Δn, thermal expansion coefficient α and thermo-optic coefficient β. The coefficient of thermal expansion is the ratio of the change in thickness per unit thickness to the change in temperature when the temperature of the birefringent crystal changes, that is The thermo-optic coefficient is the ratio of the change in the refractive index per unit temperature change to the temperature change when the temperature of the birefringent crystal changes, that is 7. The method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 3, characterized in that, The obtaining of the crystal thicknesses of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination specifically includes: According to the preset reference optical path difference, substitute the parameters of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination into the calculation formula to obtain the crystal thicknesses of the first birefringent crystal and the second birefringent crystal. The calculation formula is as follows: Wherein, d1 and d2 are the thicknesses of the first birefringent crystal and the second birefringent crystal, Δ0 is a preset reference optical path difference, n o1 and n o2 are the ordinary light refractive indices of the first birefringent crystal and the second birefringent crystal, n e1 and n e2 are the extraordinary light refractive indices of the first birefringent crystal and the second birefringent crystal, α1 and α2 are the thermal expansion coefficients of the first birefringent crystal and the second birefringent crystal, and β1 and β2 are the thermo-optic coefficients of the first birefringent crystal and the second birefringent crystal.

8. The method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 7, characterized in that, The calculation formula for the crystal thickness is simplified to x = A -1 B; where x is the thickness matrix of the first birefringent crystal and the second birefringent crystal in the birefringent crystal combination A represents the crystal parameter matrix B represents the optical path difference matrix 9. The method for eliminating temperature difference of a birefringent crystal wind imaging interferometer according to claim 4, characterized in that The calculation formula for the total optical path difference change amount is: In the formula, is the change in optical path difference generated by the first birefringent crystal, is the change in optical path difference generated by the second birefringent crystal, d1 and d2 are the thicknesses of the first birefringent crystal and the second birefringent crystal respectively, n1 and n2 are the refractive indices of the first birefringent crystal and the second birefringent crystal respectively, α1 and α2 are the thermal expansion coefficients of the first birefringent crystal and the second birefringent crystal respectively, β1 and β2 are the thermo-optic coefficients of the first birefringent crystal and the second birefringent crystal respectively, and Δ is the total change in optical path difference.

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