A polarization michelson wind measurement interferometer based on lcvr and a measurement method thereof

Abstract

The application belongs to a polarization Michelson wind measurement interferometer, and aims at the technical problems of resolution reduction, instrument volume and weight increase caused by internal movement components or aperture division of the existing wind imaging interferometer, and provides a polarization Michelson wind measurement interferometer based on LCVR and a measurement method thereof. Incident light is sequentially divided into transmitted light and reflected light after passing through a front telescope system, a first linear polarizer and a polarization beam splitter. The transmitted light forms first linearly polarized light by passing through a first compensation glass, a second compensation glass and a first achromatic quarter-wave plate. The reflected light forms second linearly polarized light by passing through a third compensation glass and a back surface of a second achromatic quarter-wave plate. The first linearly polarized light and the second linearly polarized light have an optical path difference and orthogonal polarization directions. The first linearly polarized light and the second linearly polarized light are sequentially imaged on a surface array CCD after passing through a first imaging lens, an aperture diaphragm, a second imaging lens, an LCVR and a second linear polarizer.

Description

Technical Field

[0001] This application relates to a polarization Michelson anemometer, specifically a polarization Michelson anemometer based on LCVR and its measurement method. Background Technology

[0002] Wind field (including wind speed and temperature) is a key parameter in atmospheric dynamics. Measuring wind field is crucial for understanding various atmospheric wave behaviors, studying the thermodynamic properties and composition of the atmosphere, and ensuring spacecraft flight safety. Passive optical remote sensing is a highly effective method for measuring wind fields in the middle and upper atmosphere of Earth or Mars. It uses airglow radiation, which is widely present in the atmosphere, as the observation source and employs interferometry to measure the Doppler shift and spectral broadening of the airglow radiation to retrieve wind speed and temperature.

[0003] Currently, wide-field Michelson interferometers have seen significant development due to their large field of view, high throughput, and ability to perform two-dimensional imaging of wind fields. A representative instrument successfully applied to atmospheric wind field measurement is WINDII (Wind Interferometer Imaging), jointly developed by Canada and France and launched in 1991. It is a wide-field Michelson wind imaging interferometer. Its key technology lies in a mirror driven by a high-precision micro-displacement platform, which generates a quarter-wavelength optical path difference with each step. Through multiple steps, it scans the wind field interferogram, and then uses multiple interferograms (usually four) to invert temperature and wind speed. Its disadvantages include poor stability, high power consumption, and complex and frequent calibration processes due to the presence of moving parts, making it suitable as a spaceborne instrument. Subsequently, based on the WINDII instrument concept, various advanced wind imaging interferometers were gradually developed, the most representative being WAMI (Waves Michelson Interferometer) and MIMI (Mesospheric Imaging Michelson Interferometer). Both share the characteristic of eliminating the moving mirror present in WINDII, instead employing a segmented aperture approach, dividing a mirror into four sections, each coated with a reflective film of different phase steps. For imaging, a tetrahedral prism is used to assist in projecting four interferograms onto different positions on the CCD, enabling static sampling of wind field interferograms. WAMI and MIMI perform well in single-wavelength operation; however, in multi-wavelength operation, due to the wavelength selectivity of the coating, it is impossible to guarantee consistent phase steps at each wavelength, and the coating cannot be changed once applied. If more interferograms are needed, a motion device is introduced. Furthermore, the installation and debugging of aperture-splitting systems are quite difficult. The addition of components such as tetrahedral pyramidal prisms increases the system's size and weight, hindering the miniaturization and weight reduction of spaceborne payloads. Aperture splitting also leads to a decrease in the instrument's spatial resolution. Domestic and international scholars have proposed the Polarizing Michelson Interferometer (PAMI), based on polarization interference; however, it also requires rotating polarizers to achieve phase stepping. In addition, to expand the field of view and meet the requirements of long optical path length, achromatic aberration, and temperature difference compensation, the aforementioned wind imaging interferometers require the use of three or more media as compensation media, often including air gaps, which reduces the interferometer's stability. Summary of the Invention

[0004] This application addresses the technical problem of existing wind imaging interferometers, which suffer from reduced resolution and increased instrument size and weight due to the presence of moving parts or aperture divisions. It provides a polarization Michelson wind measurement interferometer based on LCVR and its measurement method.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] In a first aspect, this application proposes a polarization Michelson wind interferometer based on LCVR, comprising: a first compensation glass, a second compensation glass, a first achromatic quarter-wave plate, a third compensation glass, a second achromatic quarter-wave plate, a first imaging lens, an aperture stop, a second imaging lens, an LCVR, a second linear polarizer and a CCD array, and a front-mounted telescope system, a first linear polarizer and a polarization beam splitter arranged sequentially along the principal optical axis of the incident light;

[0007] In a rectangular coordinate system of xyz space that satisfies the right-hand rule, the direction of the principal optical axis of the incident light is the positive z-axis.

[0008] The back surfaces of both the first and second achromatic quarter-wave plates are coated with reflective films;

[0009] The incident light is sequentially split into a transmitted light and a reflected light after passing through a pre-telescope system, a first linear polarizer, and a polarizing beam splitter. The transmitted light passes through a first compensation glass, a second compensation glass, and a first achromatic quarter-wave plate, and is reflected by a reflective film on the back of the first achromatic quarter-wave plate. It then passes through a second compensation glass, a first compensation glass, and a polarizing beam splitter to form first linearly polarized light with a polarization angle of 90° to the x-axis. The reflected light passes through a third compensation glass, is reflected by a reflective film on the back of the second achromatic quarter-wave plate, and then passes through a third compensation glass and a polarizing beam splitter to form second linearly polarized light with a polarization angle of 0° to the x-axis. There is an optical path difference between the first linearly polarized light and the second linearly polarized light.

[0010] The first and second linearly polarized light rays pass sequentially through the first imaging lens, the aperture stop, the second imaging lens, the LCVR, and the second linear polarizer before being imaged on the area array CCD.

[0011] Preferably, the magnification of the front-view telescope system is greater than 1;

[0012] The forward telescope system includes a telescope, a field stop, and a collimating lens arranged sequentially along the principal optical axis of the incident light.

[0013] Preferably, the polarization direction of the first linear polarizer and the polarization direction of the second linear polarizer both form a 45° angle with the positive x-axis direction;

[0014] The fast axis direction of both the first and second achromatic quarter-wave plates forms a 45° angle with the positive x-axis.

[0015] Preferably, the fast axis direction of the LCVR forms a 45° angle with the positive x-axis direction.

[0016] Preferably, the reflective films on the back of the first and second achromatic quarter-wave plates both have a reflectivity greater than or equal to 99.5%.

[0017] Preferably, the optical path difference Δ0 of the polarization Michelson anemometer is:

[0018] Δ0=2n1d1+2n2d2-2n3d3 (50mm≤Δ0≤150mm).

[0019] Wherein, n1 is the refractive index of the first compensating glass (6), n2 is the refractive index of the second compensating glass (7), n3 is the refractive index of the third compensating glass (9), d1 is the thickness of the first compensating glass (6), d2 is the thickness of the second compensating glass (7), and d3 is the thickness of the third compensating glass (9).

[0020] Preferably, the refractive index of the first compensating glass, the refractive index of the second compensating glass, the refractive index of the third compensating glass, the thickness of the first compensating glass, the thickness of the second compensating glass, and the thickness of the third compensating glass satisfy the following relationship:

[0021]

[0022] Preferably, the temperature compensation condition of the polarization Michelson anemometer satisfies the following relationship:

[0023]

[0024] Where T is temperature, n j For the refractive index of the j-th compensating glass, d j For the thickness of the j-th compensating glass, α j Let β be the coefficient of thermal expansion of the j-th compensating glass. j Let be the temperature coefficient of refractive index of the j-th compensating glass, where j = 1, 2, 3.

[0025] Preferably, the aperture stop is located on the front focal plane of the second imaging lens.

[0026] Secondly, this application proposes a measurement method for the aforementioned LCVR-based polarization Michelson anemometer interferometer, comprising:

[0027] After the incident light enters the front telescope system, by changing the voltage of the LCVR, wind field interferograms with phase steps of 0°, 45°, 90° and 135° are acquired on the area array CCD16.

[0028] Atmospheric temperature and wind speed are obtained by inverting the modulation and phase of the wind field interferogram using the four-intensity method.

[0029] Compared with the prior art, this application has the following beneficial effects:

[0030] This application proposes a polarization Michelson wind interferometer based on LCVR. By using a first, second, and third compensation glass, the interferometer is constructed as a fully solid entity, improving its vibration resistance and other performance characteristics. Furthermore, considering the practical application where interferometers operate in narrow wavelength bands, this application abandons the achromatic condition, achieving wide field, large optical path difference, and temperature compensation effects comparable to traditional three- or even four-layer compensation media, while also facilitating the selection of compensation glass. More importantly, the use of LCVR enables rapid modulation of the interferometer's phase step, improving modulation efficiency compared to traditional mechanical stepping and eliminating moving parts. Placing the LCVR in the image-side telecentric optical path ensures that light from each field of view enters the LCVR at a small angle, giving it high phase modulation accuracy and thus improving the accuracy of wind field inversion. In addition, compared to aperture-splitting wind field interferometers, this application eliminates the need for matching tetrahedral prisms and other optical systems, resulting in higher spatial resolution and smaller size and weight. Simultaneously, this application also provides some suppression of stray light present in the system. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of an embodiment of the polarization Michelson anemometer based on LCVR of this application;

[0033] Figure 2 The diagrams show a comparison of the LCVR and voltage applied in the embodiment of the polarization Michelson anemometer based on LCVR in this application; where (a) is a schematic diagram without voltage applied and (b) is a schematic diagram with voltage applied.

[0034] Among them: 1-Telescope, 2-Field stop, 3-Collimating lens, 4-First linear polarizer, 5-Polarizing beam splitter, 6-First compensation glass, 7-Second compensation glass, 8-First achromatic quarter-wave plate, 9-Third compensation glass, 10-Second achromatic quarter-wave plate, 11-Imaging lens, 12-Aperture stop, 13-Second imaging lens, 14-LCVR, 15-Second linear polarizer, 16-Area array CCD. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0037] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0038] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0040] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0041] In order to overcome the problems of reduced resolution and increased instrument size and weight of existing wind imaging interferometers due to the presence of moving parts or aperture divisions, it is imperative to develop a small, lightweight, high-performance atmospheric wind field detection device.

[0042] To address the aforementioned issues, this application proposes a polarization Michelson wind interferometer based on LCVR14 and its control method. The low-power LCVR14 (Liquid Crystal Variable Retarder) is used to adjust the phase step of the wind field interferogram. The relative amount, number of steps, and step time of the phase step can be set according to actual needs, and adjustments can be made at multiple wavelengths. It eliminates the need for aperture-splitting imaging devices and moving parts, constructing an all-solid-state interferometer using only three layers of glass (without air gaps), ensuring the interferometer's insensitivity to vibration. Furthermore, it fully utilizes the spatial resolution of the CCD16 array, enabling it to be used for wind field imaging over a wider area or at higher resolutions.

[0043] The present application will be further described in detail below with reference to the embodiments and accompanying drawings. For the convenience of the following description, in the xyz spatial rectangular coordinate system that satisfies the right-hand rule, the direction of the principal optical axis of the incident light is defined as the positive z-axis direction.

[0044] See Figure 1 This application discloses a polarization Michelson wind interferometer based on LCVR14, including a first compensation glass 6, a second compensation glass 7, a first achromatic quarter-wave plate 8, a third compensation glass 9, a second achromatic quarter-wave plate 10, a first imaging lens 11, an aperture stop 12, a second imaging lens 1311, LCVR14, a second linear polarizer 15, and a CCD array 16, as well as a front telescope system, a first linear polarizer 4, and a polarization beam splitter 5 arranged sequentially along the principal optical axis of the incident light.

[0045] The back of both the first achromatic quarter-wave plate 8 and the second achromatic quarter-wave plate 10 are coated with a reflective film.

[0046] It should be noted that an achromatic quarter-wave plate is a special type of waveplate, for example, made of quartz crystal and magnesium fluoride, where the fast axis of the quartz plate is aligned with the slow axis of the magnesium fluoride plate, allowing a retardation value of λ / 4 within the target wavelength range. Because it is coated with a reflective film, light reaching the achromatic quarter-wave plate can be reflected. Compensation glass refers to high-performance optical glass of a certain thickness. By combining different compensation glasses, the required optical path difference of the interferometer can be generated, and the wide field of view and temperature compensation conditions required for wind field detection can be met, thereby improving the signal-to-noise ratio and temperature stability of the interferometer system and ensuring high-precision wind field measurement. LCVR14 is a device that uses liquid crystal material to achieve optical phase retardation. Phase retardation of light is achieved by controlling the refractive index of the liquid crystal molecules through voltage. The basic structure of LCVR14 consists of liquid crystal material filled between two flat glass plates, with transparent electrodes and a calibration layer deposited on the glass plates. The gap between the glass plates is controlled by fine glass fibers at their edges. When a voltage is applied, the liquid crystal molecules rearrange, causing a change in refractive index, thereby achieving phase retardation of light.

[0047] The incident light becomes parallel light after passing through the front telescope system. This parallel light then passes through the first linear polarizer 4 and the polarizing beam splitter 5, splitting into two beams of linearly polarized light with perpendicular polarization directions: one is transmitted light, and the other is reflected light. The transmitted light, after being transmitted through the polarizing beam splitter 5, passes through the first compensation glass 6, the second compensation glass 7, and the first achromatic quarter-wave plate 8 with a reflective coating on its back. After being reflected by the first achromatic quarter-wave plate 8, it passes through the second compensation glass 7, the first compensation glass 6, and the polarizing beam splitter 5 again, becoming first linearly polarized light with a polarization direction at an angle of 90° to the x-axis. The other reflected light, after being reflected by the polarizing beam splitter 5, passes sequentially through the third compensation glass 9 and the second achromatic quarter-wave plate 10 with a reflective coating on its back. After being reflected by the second achromatic quarter-wave plate 10, it passes through the third compensation glass 9 and the polarizing beam splitter 5 again, becoming second linearly polarized light with a polarization direction at an angle of 0° to the x-axis. The first and second linearly polarized lights have a certain optical path difference. The first and second linearly polarized lights, which are orthogonally polarized, pass through the first imaging lens 11, the aperture stop 12, and the second imaging lens 13 in sequence, and their polarization directions remain unchanged. Then, after passing through the LCVR 14 and the second linear polarizer 15, they undergo polarization interference and are imaged on the area array CCD 16.

[0048] In practical applications, changing the voltage of LCVR14 can alter the phase delay of the interferogram, thereby achieving four-fold modulation of the interferogram phase. Finally, wind field interferograms with phase steps of 0°, 45°, 90°, and 135° can be obtained on the area array CCD16. Based on the "four-intensity method," the modulation degree and phase of the interferogram can be inverted, thus obtaining the atmospheric temperature and wind speed.

[0049] This application also discloses another polarization Michelson wind interferometer based on LCVR14, including a first compensation glass 6, a second compensation glass 7, a first achromatic quarter-wave plate 8, a third compensation glass 9, a second achromatic quarter-wave plate 10, a first imaging lens 11, an aperture stop 12, a second imaging lens 13, LCVR14, a second linear polarizer 15, and a CCD array 16, as well as a front telescope system, a first linear polarizer 4, and a polarization beam splitter 5 arranged sequentially along the principal optical axis of the incident light.

[0050] The front-view telescope system includes a telescope 1, a field stop 2, and a collimating lens 3. The magnification of the front-view telescope system is greater than 1, which helps to collect more light energy. The field stop 2 limits the instrument's field of view and reduces stray light. After the incident airglow radiation passes through the front-view telescope system (comprising telescope 1, field stop 2, and collimating lens 3, with a magnification greater than 1), the beam is reduced to a size acceptable to the interferometer and exits as parallel light.

[0051] The polarization directions of the first linear polarizer 4 and the second linear polarizer 15 are both at a 45° angle to the positive x-axis. Similarly, the fast axis directions of the first achromatic quarter-wave plate 8 and the second achromatic quarter-wave plate 10 are both at a 45° angle to the positive x-axis. Both the back surfaces of the first achromatic quarter-wave plate 8 and the second achromatic quarter-wave plate 10 are coated with a high-reflectivity film, which can achieve a reflectivity of 99.5% or higher. After passing through the first linear polarizer 4 (with a 45° angle between its polarization direction and the positive x-axis), the parallel beam becomes linearly polarized at a 45° angle. This light is then split into two linearly polarized beams with different polarization directions by the polarization beam splitter 5. The polarization direction of the reflected beam is at a 90° angle to the positive x-axis, while the polarization direction of the transmitted beam is at a 0° angle to the positive x-axis. The reflected light after passing through the polarizing beam splitter 5 passes through the first compensating glass 6 and the first achromatic quarter-wave plate 8 with a high-reflection coating on its back. After being reflected by the back of the first quarter-wave plate, it passes through the first achromatic quarter-wave plate 8 again and exits as linearly polarized light, but the angle between its polarization direction and the positive x-axis becomes 0°, allowing it to pass through the first compensating glass 6 and the polarizing beam splitter 5 without changing its polarization direction. Similarly, the linearly polarized light transmitted from the polarizing beam splitter 5 at an angle of 0° to the positive x-axis passes through the first compensating glass 6, the second compensating glass 7, and the second achromatic quarter-wave plate 10 with a high-reflection coating on its back. After being reflected by the back of the second quarter-wave plate, it passes through the second achromatic quarter-wave plate 10 again and exits as linearly polarized light, but this time the polarization direction changes to a 90° angle with the positive x-axis, allowing it to pass through the first compensating glass 6, the second compensating glass 7, and the polarizing beam splitter 5 without changing its polarization direction. Finally, both the reflected and transmitted linearly polarized beams exit from the polarization beam splitter 5 as linearly polarized light, but their polarization directions are orthogonal.

[0052] A compact, large-field-of-view, all-solid-state wind field imaging interferometer is constructed using three types of compensating glass (without air gaps). The first compensating glass 6, the second compensating glass 7, and the third compensating glass 9 work together to meet the wide field-of-view, large optical path difference, and temperature compensation conditions required for wind field detection. Therefore, the refractive index and thickness of the three glass components need to satisfy certain relationships, specifically, the following relationships (1) to (3) should be satisfied:

[0053] Large optical path difference condition: Δ0=2n1d1+2n2d2-2n3d3 (50mm≤Δ0≤150mm) (1)

[0054] Wide field conditions:

[0055] Temperature compensation conditions:

[0056] Where, n1 is the refractive index of the first compensating glass 6, n2 is the refractive index of the second compensating glass 7, n3 is the refractive index of the third compensating glass 9, d1 is the thickness of the first compensating glass 6, d2 is the thickness of the second compensating glass 7, d3 is the thickness of the third compensating glass 9, T is the temperature, and n j For the refractive index of the j-th compensating glass, d j For the thickness of the j-th compensating glass, α j Let β be the coefficient of thermal expansion of the j-th compensating glass. j Let be the temperature coefficient of refractive index of the j-th compensating glass, where j = 1, 2, 3.

[0057] In the entire wind measurement interferometer, the aperture stop 12 is located on the front focal plane of the second imaging lens 13, forming a telecentric system structure that allows both on-axis and off-axis beams to be incident almost perpendicularly on the LCVR 14 and the second linear polarizer 15, thereby ensuring the accuracy of phase step modulation of the interferogram.

[0058] The beam reflected by polarizing beam splitter 5 is linearly polarized when it exits from polarizing beam splitter 5, with its polarization direction making a 0° angle with the positive x-axis. Let the optical path length it travels in the interferometer be r1. Then the electric field vector E of this beam... rx It can be represented as:

[0059]

[0060] Where A represents amplitude, w represents angular frequency, k represents wave vector of incident light, t represents time, and i represents imaginary unit.

[0061] A beam of light transmitted through polarizing beam splitter 5 exits from polarizing beam splitter 5 as linearly polarized light, with its polarization direction making a 90° angle with the positive x-axis. Let the optical path length it traverses in the interferometer be r2. Then, the electric field vector E of this beam...ty It can be represented as:

[0062]

[0063] According to the principle of polarization interference, linearly polarized light with orthogonal polarization directions, as represented by equations (4) and (5), will experience phase delay after passing through LCVR14, where the fast axis direction makes an angle of 45° with the positive x-axis. The electric field component will also be projected onto the fast axis direction of LCVR14 and the direction perpendicular to it. Finally, after passing through the second linear polarizer 15, the polarization directions are unified and coherently superimposed, ultimately forming an interference pattern on the area array CCD16. Let the phase difference generated by LCVR14 be... According to the principle of polarized light interference, the electric vector E reaching the CCD16 array is... out It can be represented as:

[0064]

[0065] The interferogram on the CCD16 array, i.e., light intensity I out It can be represented as:

[0066]

[0067] Where I0 represents the total incident light intensity, Δ0 represents the optical path difference of the interferometer, which is generated by the compensation glass in this application and has a value range of 50mm to 150mm, and σ represents the wavenumber of the incident light, i.e., the reciprocal of the wavelength.

[0068] The fast axis of LCVR14 forms an angle of 45° with the positive x-axis. The phase delay can be adjusted by applying voltage across the liquid crystal. The phase delay of LCVR14 can be adjusted to 0°, 45°, 90° and 135° in sequence.

[0069] like Figure 2 The image shows a comparison of LCVR14 with and without applied voltage. The phase delay is adjusted by changing the voltage across LCVR14. By changing the phases sequentially at 0°, 45°, 90°, and 135°, four wind field interferograms with different phase steps are obtained, which are represented as follows:

[0070]

[0071]

[0072]

[0073]

[0074] Where I1, I2, I3, and I4 represent four wind field interferograms with different phase steps, U represents the instrument modulation of the interferometer, which is related to the instrument setup and ranges from 0 to 1, and V represents the spectral line modulation, which is related to the luminous particles of the airglow radiation and the atmospheric temperature in which they are located, V = exp(-QTΔ 2 Where, Q = 1.82 × 10⁻⁶ -12 (σ0 2 / M)(K -1 cm -2 ), where M represents the number of luminescent particles, T represents the atmospheric temperature, and Δ represents the optical path difference of the interferometer.

[0075] The value of Q varies depending on the gasglow radiation band. For example, for the O2 near-infrared 1.27 μm gasglow radiation band, Q = 3.526 × 10⁻⁶. -6 cm -2 K -1 Typically, V ranges from 0 to 1. ψ represents the total phase, which can be expressed as ψ = 2πσΔ0 + φ w .

[0076] Where, φ w Indicates wind speed phase, φ w =2πσ0Δv / c, where v represents atmospheric wind speed and σ0 represents the central wavenumber of the luminous particle.

[0077] The spectral modulation index V and wind speed phase φ were finally obtained using the "four-intensity method". w ,as follows:

[0078] I0=(I1+I3) / 2=(I2+I4) / 2 (12)

[0079] V = [(I1-I3)] 2 +(I4-I2) 2 ] 1 / 2 / 2UI0 (13)

[0080] φ w =arctan((I4-I2) / (I1-I3)) (14)

[0081] Then, the atmospheric wind speed v and atmospheric temperature T can be calculated, that is:

[0082]

[0083]

[0084] This application constructs an all-solid-state, wide-field-of-view Michelson wind polarization interferometer using three layers of compensating glass. An LCVR14 is placed within an image-side telecentric optical structure. By adjusting the voltage of the LCVR14 to change its phase retardation, the phase step of the wind field interferogram is quasi-statically adjusted. Four interferograms are acquired, allowing for wide-field-of-view, high-resolution, quasi-static detection of the atmospheric wind field using the traditional "four-intensity method." This application solves the problem of limited spatial resolution or field of view in existing wind field interferometers due to internal moving parts or the use of aperture division. It also avoids interference from reflected light from reflective liquid crystal phase retarders. Furthermore, it offers advantages such as simple instrument structure, low stray light, large field of view, quasi-static detection, good vibration resistance, and low cost.

[0085] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A polarization Michelson anemometer based on LCVR, characterized in that, include: The system comprises a first compensation glass (6), a second compensation glass (7), a first achromatic quarter-wave plate (8), a third compensation glass (9), a second achromatic quarter-wave plate (10), a first imaging lens (11), an aperture stop (12), a second imaging lens (13), an LCVR (14), a second linear polarizer (15), and a surface array CCD (16), as well as a front-mounted telescope system, a first linear polarizer (4), and a polarizing beam splitter (5) arranged sequentially along the principal optical axis of the incident light. In a rectangular coordinate system of xyz space that satisfies the right-hand rule, the direction of the principal optical axis of the incident light is the positive z-axis. The back surfaces of the first achromatic quarter-wave plate (8) and the second achromatic quarter-wave plate (10) are both coated with a reflective film; The incident light is split into a transmitted light and a reflected light after passing through the front telescope system, the first linear polarizer (4), and the polarization beam splitter (5). The transmitted light passes through the first compensation glass (6), the second compensation glass (7), and the first achromatic quarter-wave plate (8) in sequence. After being reflected by the reflective film on the back of the first achromatic quarter-wave plate (8), it passes through the second compensation glass (7), the first compensation glass (6), and the polarization beam splitter (5) in sequence to form a first linearly polarized light with a polarization direction at an angle of 90° to the x-axis. The reflected light passes through the third compensation glass (9), is reflected by the reflective film on the back of the second achromatic quarter-wave plate (10), and then passes through the third compensation glass (9) and the polarization beam splitter (5) in sequence to form a second linearly polarized light with a polarization direction at an angle of 0° to the x-axis. There is an optical path difference between the first linearly polarized light and the second linearly polarized light. The first linearly polarized light and the second linearly polarized light pass through the first imaging lens (11), the aperture stop (12), the second imaging lens (13), the LCVR (14), and the second linear polarizer (15) in sequence, and are then imaged on the area array CCD (16). Optical path difference of the polarization Michelson wind interferometer for: in, , n 1 represents the refractive index of the first compensating glass (6). n 2 represents the refractive index of the second compensating glass (7). n 3 represents the refractive index of the third compensating glass (9). d 1 represents the thickness of the first compensating glass (6). d 2 represents the thickness of the second compensating glass (7). d 3 represents the thickness of the third compensating glass (9); The refractive index of the first compensating glass (6), the refractive index of the second compensating glass (7), the refractive index of the third compensating glass (9), the thickness of the first compensating glass (6), the thickness of the second compensating glass (7), and the thickness of the third compensating glass (9) satisfy the following relationship: The temperature compensation condition of the polarization Michelson anemometer interferometer satisfies the following relationship: in, For temperature, For the first Compensating for the refractive index of the glass, For the first To compensate for the thickness of the glass, For the first Compensating for the coefficient of thermal expansion of the glass, For the first The temperature coefficient of refractive index of compensating glass. .

2. The polarization Michelson wind interferometer based on LCVR according to claim 1, characterized in that, The magnification of the front-view telescope system is greater than 1; The front telescope system includes a telescope (1), a field stop (2), and a collimating lens (3) arranged sequentially along the principal optical axis of the incident light.

3. The polarization Michelson wind interferometer based on LCVR according to claim 1, characterized in that, The polarization direction of the first linear polarizer (4) and the polarization direction of the second linear polarizer (15) both form an angle of 45° with the positive x-axis direction; The fast axis direction of the first achromatic quarter-wave plate (8) and the fast axis direction of the second achromatic quarter-wave plate (10) both form a 45° angle with the positive x-axis direction.

4. The polarization Michelson wind interferometer based on LCVR according to claim 1, characterized in that, The fast axis direction of the LCVR (14) forms a 45° angle with the positive x-axis direction.

5. The polarization Michelson wind interferometer based on LCVR according to claim 1, characterized in that, The reflective films on the back of the first achromatic quarter-wave plate (8) and the second achromatic quarter-wave plate (10) have a reflectivity greater than or equal to 99.5%.

6. The polarization Michelson wind interferometer based on LCVR according to claim 5, characterized in that, The aperture stop (12) is located on the front focal plane of the second imaging lens (13).

7. A measurement method for a polarization Michelson anemometer based on LCVR as described in any one of claims 1 to 6, characterized in that, include: After the incident light enters the front telescope system, by changing the voltage of the LCVR, wind field interferograms with phase steps of 0°, 45°, 90° and 135° are acquired on the area CCD (16). Atmospheric temperature and wind speed are obtained by inverting the modulation and phase of the wind field interferogram using the four-intensity method.

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