A compact Michelson wind imaging interferometer based on a lens array

Abstract

This invention discloses a compact Michelson wind imaging interferometer based on a lens array, relating to the field of atmospheric remote sensing instrument technology. It includes a beam splitter, a second compensation glass, a first compensation glass, and a compensation prism. Reflected light propagates along the thickness direction of the second compensation glass, is reflected by four reflective surfaces, passes through the second compensation glass again, and exits from the beam splitter. Transmitted light passes through the transmission film of the first compensation glass and then sequentially through the first compensation glass and the compensation prism. The compensation prism reflects the transmitted light back to the reflective film of the first compensation glass, and the transmitted light is reflected back along its original path by a single reflective surface before exiting. The transmitted and reflected light exiting the beam splitter converge on a CCD detector positioned below the lens array for interference. This invention eliminates the complex cornerstone prism alignment system, folding the straight optical paths of the two arms of a traditional Michelson interferometer into a compact layout, reducing the overall system size and weight.

Description

Technical Field

[0001] This invention relates to the field of atmospheric remote sensing instrument technology, and in particular to a compact Michelson wind imaging interferometer based on a lens array. Background Technology

[0002] Precise detection of planetary atmospheric dynamics parameters is a crucial foundation for studying atmospheric physics processes. Among these, wind speed and temperature, as core parameters characterizing the atmospheric dynamics of planets such as Earth and Mars, directly influence atmospheric energy transfer and mass transport processes due to their spatiotemporal distribution characteristics. High-precision detection of atmospheric wind speed and temperature is key to studying planetary atmospheres, constructing climate models, and ensuring spacecraft safety.

[0003] Interferometric detection technology uses the airglow of atoms or molecules widely present in the atmosphere as the target light source. By detecting the Doppler shift and linewidth of the airglow spectral lines, it inverts atmospheric wind speed and temperature. It has advantages such as high throughput, high sensitivity, and simultaneous detection of multiple parameters, and can sensitively extract information on the frequency shift and broadening of weak airglow spectral lines, making it a core remote sensing method for obtaining global-scale atmospheric wind and temperature fields. However, with the rapid development of space exploration missions, the requirements for instrument miniaturization, lightweighting, and detection accuracy are constantly increasing, and existing interferometric measurement technology still faces bottlenecks that urgently need to be overcome.

[0004] Existing Michelson wind imaging interferometers include moving mirror scanning interferometers and static wind imaging interferometers. Moving mirror scanning interferometers require time-division multiplexing of four-phase interferograms by moving mirrors, and the time asynchrony of the observation data leads to increased wind speed measurement errors. Although static wind imaging interferometers adopt a fixed optical path difference design, they generally rely on complex beam-splitting devices such as tetrahedral prisms, and the supporting optical system needs to achieve precise registration between the beam-splitting surface and the detector pixels, which significantly increases the complexity of the optomechanical structure.

[0005] The closest existing technical solution for a static Michelson interferometer is presented in the following paper: Static windimaging Michelson interferometer for the measurement of stratospheric windfields, 2023, Optic Express. Its technical solution is as follows: Figure 5As shown, this technical solution uses a tetrahedral pyramidal prism for beam splitting, ultimately achieving static acquisition of four interferograms, thus solving the problem of increased wind speed measurement errors caused by the time asynchrony of observation data in traditional wind imaging interferometers. However, the use of a tetrahedral pyramidal prism requires the addition of a relay optical system, conjugating the four-segment reflector with the tetrahedral pyramidal prism. This increases the system's size and weight, and the layout of the two-arm optical paths suffers from low space utilization and large size, hindering the lightweight development of spaceborne instruments and impeding their miniaturization design. Summary of the Invention

[0006] In view of the defects of the prior art, the present invention provides a compact Michelson wind imaging interferometer based on a lens array, which solves the existing problems.

[0007] The present invention adopts the following technical solution:

[0008] This invention provides a compact Michelson wind imaging interferometer based on a lens array, comprising the following steps:

[0009] A collimation system is used to collimate the gas glow of a target to obtain parallel light along the horizontal direction.

[0010] A beam splitter, located on the output side of the collimation system, is used to split parallel light into transmitted light that propagates in the same direction as the parallel light and reflected light that propagates vertically upward.

[0011] The second compensation glass is set on the top of the beam splitter. A four-segment reflective film is coated on its top to form four reflective surfaces. The reflected light propagates along the thickness direction of the second compensation glass, is reflected by the four reflective surfaces after passing through the second compensation glass, passes through the second compensation glass again, and exits from the beam splitter.

[0012] The first compensating glass is located on the side of the beam splitter and the second compensating glass away from the collimation system. The part of the first compensating glass that is in contact with the beam splitter is coated with a transmission film, and the part that is in contact with the second compensating glass is coated with a reflection film, forming a single reflective surface.

[0013] A compensation prism is positioned on the side of the first compensation glass away from the beam splitter. The transmitted light propagates along the thickness direction of the first compensation glass, passes through the transmission film of the first compensation glass, and then passes through the first compensation glass and the compensation prism in sequence. The compensation prism reflects the transmitted light to the reflection film of the first compensation glass. The transmitted light is reflected by a single reflective surface and returns along the original path, passing through the compensation prism, the first compensation glass, and the beam splitter again before exiting.

[0014] The lens array, located below the beam splitter, consists of four identical sub-lenses, each corresponding to one of the four reflecting surfaces. The transmitted and reflected light emitted from the beam splitter converges on the CCD detector located below the lens array after passing through the lens array, resulting in interference and forming four interference patterns with different phases.

[0015] Preferably, the collimation system includes:

[0016] A telescope is used to focus the gas glow of a target and form a primary image of the target gas glow at its rear focal plane.

[0017] A field stop is placed at the primary image plane of a telescope to limit the instrument's field of view.

[0018] A collimating lens, located at the conjugate plane of the telescope's focal plane, is used to collimate the gas glow of the target to obtain parallel light.

[0019] The focal length of the telescope is greater than that of the collimating lens.

[0020] Preferably, the beam splitter is a cubic beam splitter, consisting of two triangular prisms, with the inclined bonding surfaces of the two triangular prisms coated with a semi-transparent, semi-reflective film.

[0021] Preferably, the compensation prism is a right-angle prism, with both right-angle faces coated with a reflective film and the inclined face coated with a transmissive film, the inclined face being in contact with the first compensation glass.

[0022] Preferably, the four-zone reflective film has different phases, namely 0, π / 2, π and 3π / 2.

[0023] Preferred options also include:

[0024] A filter is used to filter incident light to obtain the target gas glow.

[0025] Preferably, n1, n2, and n3 represent the refractive indices of the first compensating glass, the compensating prism, and the second compensating glass, respectively, and d0, d1, d2, and d3 represent the thicknesses of the beam splitter, the first compensating glass, the compensating prism, and the second compensating glass, respectively.

[0026] The optical path difference of the interferometer is shown below:

[0027] ;

[0028] In the formula, This is the optical path difference.

[0029] Preferably, the interferometer needs to meet the field-of-view widening condition, as shown below:

[0030] .

[0031] Preferably, the interferometer needs to meet temperature compensation conditions, as detailed below:

[0032] ;

[0033] In the formula, For temperature, , and The coefficients of thermal expansion of the first compensating glass, the compensating prism, and the second compensating glass are respectively. , and The refractive index temperature coefficients of the first compensation glass, the compensation prism, and the second compensation glass are given.

[0034] Compared with the prior art, the above-mentioned at least one technical solution adopted by the present invention can achieve the following beneficial effects:

[0035] This invention first splits parallel light using a beam splitter to obtain transmitted light in the horizontal direction and reflected light in the vertical direction. A second compensation glass is placed at the top of the beam splitter, with a four-section reflective film coated on its top, forming four reflective surfaces. Four sub-lenses are placed below the beam splitter, with each sub-lens corresponding to one of the four reflective surfaces. This invention integrates spatial beam splitting and synchronous imaging of the four-phase interferogram into the partitioned coated reflective surface by partitioning the top of the second compensation prism. Simultaneously, a lens array replaces the traditional tetrahedral pyramidal prism, directly imaging different areas of the detector, completely eliminating timing errors from moving mirror scanning. It also eliminates the need for a complex pyramidal prism alignment system, significantly reducing wind speed measurement errors. Furthermore, by folding the transmitted light path using the second compensation glass and compensation prism, the straight light paths of the existing interferometer arms are folded into a compact layout, reducing the overall system size and weight, making it more compact, smaller, and lighter. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the optical path of a compact Michelson wind imaging interferometer based on a lens array according to the present invention;

[0038] Figure 2 This is a left view of the compensating glass of the present invention in the xy plane;

[0039] Figure 3 The end of the compensation glass of the present invention is shown in a schematic xz plane view;

[0040] Figure 4 This is a schematic diagram of the lens array of the present invention distributed in the xy plane;

[0041] Figure 5 This is the existing optical path diagram.

[0042] In the diagram: 1-Filter, 2-Telescope, 3-Field stop, 4-Collimating lens, 5-Beam splitter, 6-First compensation glass, 61-Lower half of the first compensation glass, 62-Upper half of the first compensation glass, 7-Compensation prism, 8-Second compensation glass, 81-First sub-region, 82-Second sub-region, 83-Third sub-region, 84-Fourth sub-region, 9-Lens array, 91-First sub-lens, 92-Second sub-lens, 93-Third sub-lens, 94-Fourth sub-lens, 10-CCD detector. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] This invention addresses the problems of increased wind speed measurement errors caused by the time asynchrony of observation data in traditional interferometers, the increased size and weight of existing static interferometers due to the use of tetrahedral pyramidal prisms, and the insufficient compactness of the glass layout in the two arms of the interferometer. It achieves a miniaturized and compact design of the interferometer for global remote sensing detection of key parameters such as atmospheric wind fields and temperature fields of planetary systems.

[0045] This invention proposes a compact Michelson wind imaging interferometer based on a lens array, comprising, in sequence along the principal optical axis, a filter 1, a collimation system, a beam splitter 5, a first compensation glass 6, a compensation prism 7, a second compensation glass 8, a lens array 9, and a CCD detector 10. The collimation system (front telescope system) comprises, in sequence, a telescope 2, a field stop 3, and a collimating lens 4.

[0046] The incident light (all gas glow) is filtered by filter 1 to obtain the incident target gas glow. After passing through the pre-telescope system, it becomes parallel light and is split into two mutually perpendicular beams by beam splitter 5: transmitted light and reflected light. The transmitted light propagates in the direction of parallel light, and the reflected light propagates vertically upward. The reflected light is reflected by the four-segment reflective film coated on the end face of the second compensation glass 8, and then passes through the second compensation glass 8 again and exits from beam splitter 5. The reflected light passes through the lower half of the first compensation glass 6, the compensation prism 7, and the upper half of the first compensation glass 6, and is reflected by the reflective surface at the end of the upper half, returning along the same path, and exiting again after passing through the compensation prism 7, the lower half of the first compensation glass 6, and beam splitter 5. The two beams are converged by lens array 9 and interfere on CCD detector 10. The four reflective surfaces formed by the four-segment reflective film correspond one-to-one with the four sub-lenses of the lens array, ultimately forming four interferograms with different phases on the CCD detector, from which the wind speed and temperature of the planet's atmosphere can be deduced.

[0047] Furthermore, a rectangular coordinate system xyz is established with the principal optical axis as the positive z-axis, and the coordinate system satisfies the right-hand rule.

[0048] The front-mounted telescope system comprises telescope 2, field stop 3, and collimating lens 4. Field stop 3 is located at the primary image plane of telescope 2, allowing it to directly, effectively, and without vignetting restrict the field of view in the object space. Furthermore, the focal length of telescope 2 is greater than that of collimating lens 4, resulting in a magnification greater than 1 for the front-mounted telescope system. Magnification is equal to the focal length of the telescope divided by the focal length of the collimating lens. A magnification greater than 1 improves light energy collection efficiency.

[0049] Beam splitter 5 is a cubic beam splitter, consisting of two triangular prisms, with the inclined bonding surfaces of the two triangular prisms coated with a semi-transparent, semi-reflective film.

[0050] In a rectangular coordinate system Figure 1 The upper left side of the first compensating glass 6 is coated with a reflective film, achieving a reflectivity of up to 99.5%. Its schematic diagram in the xy-plane is shown below. Figure 2 As shown. The lower half 61 is coated with a high-transmittance film (projection film), allowing light to pass through with high transmittance. The upper half 62 is coated with a high-reflectance film (reflection film), with a reflectivity of up to 99.5%.

[0051] The compensating prism 7 is a right-angle prism that not only folds the optical path but also participates in the interferometer's temperature, optical path difference, and field-of-view compensation. Both of its right-angled faces are coated with a high-reflectivity film, achieving a reflectivity of up to 99.5%.

[0052] The top of the second compensation glass 8 (the end face furthest from the beam splitter 5) is coated with a four-segment high-reflectivity film, such as... Figure 3As shown in the diagram. The fabrication process of the first sub-region 81, the second sub-region 82, the third sub-region 83, and the fourth sub-region 84 is as follows: First, the first sub-region 81 of the second compensating glass 8 is blocked. A layer of fused silica material is deposited on the second sub-region 82, the third sub-region 83, and the fourth sub-region 84, with thicknesses of 1 / 8 wavelength, 1 / 4 wavelength, and 3 / 8 wavelength, respectively. Then, a multi-layer high-reflectivity film is deposited on the entire first sub-region 81, the second sub-region 82, the third sub-region 83, and the fourth sub-region 84. The reflectivity reaches as high as 99.5%.

[0053] Lens array 9 consists of four identical sub-lenses, which correspond one-to-one with the four sub-sections of the second compensating glass 8, and their spatial distribution is as follows: Figure 4 As shown, it includes a first sub-lens 91, a second sub-lens 92, a third sub-lens 93, and a fourth sub-lens 94.

[0054] Furthermore, the refractive index *n* and thickness *d* of the interferometer's compensating glass must meet the requirements for large optical path difference, widened field of view, and temperature compensation necessary for atmospheric wind field detection. Let *n1*, *n2*, and *n3* represent the refractive indices of the first compensating glass 6, the compensating prism 7, and the second compensating glass 8, respectively, and their thicknesses, i.e., the physical width along the z-axis or the direction of light propagation, be represented by *d1*, *d2*, and *d3*, respectively. The thickness *d2* of the compensating prism refers to the height of the hypotenuse of the right-angle prism.

[0055] like Figure 1 The structural dimensions of beam splitter 5, first compensating glass 6, compensating prism 7, and second compensating glass 8 are related, making the entire interferometer system particularly compact. The dimensional constraints are analyzed as follows: Let the side length (thickness) of the cubic beam splitter 5 be d0, then its three-dimensional dimensions are d0×d0×d0. The dimensions of the first compensating glass 6 are d1×(d0+d3)×d0. The hypotenuse of the compensating prism 7 is d0+d3, and its thickness, i.e., the height of the hypotenuse, is d2. The dimensions of the second compensating glass 8 are d3×d0×d0.

[0056] The optical path difference of the interferometer of the present invention can be expressed as:

[0057] (1);

[0058] In the formula,

[0059] Furthermore, the field of view widening condition needs to be met, expressed as:

[0060] (2);

[0061] Furthermore, temperature compensation conditions need to be met, expressed as:

[0062] (3);

[0063] in, For temperature, For the first Compensating for the refractive index of the glass, For the first The thickness of the compensating glass or prism. For the first The coefficient of thermal expansion of the compensating glass. For the first The temperature coefficient of refractive index of the compensating glass. In this design, three types of compensating glass or prisms are used, therefore... .

[0064] Furthermore, the selection of compensation glass is based on formulas (1) to (3) and meets its size restrictions. Glass pairs that meet the above conditions are selected from the glass library, and the interferometer is designed and manufactured.

[0065] Improved synchronous detection accuracy and system simplification: By using four partitioned coated reflective surfaces (with the phase difference of the coated areas precisely controlled to π / 2), the spatial beam splitting and synchronous imaging of the four-phase interferogram are integrated into the partitioned coated reflective surfaces. Combined with a lens array (replacing the traditional tetrahedral pyramidal prism), the image is directly imaged to different areas of the detector, completely eliminating the timing error of the moving mirror scanning. At the same time, the complex beam splitting prism alignment system is eliminated, greatly reducing the wind speed measurement error.

[0066] Compact structure and lightweight design: The folded reflective optical path (double reflective arms are re-compressed) is adopted, and the straight optical path of the two arms of the traditional Michelson interferometer is folded into a compact layout, which reduces the size and weight of the instrument and meets the stringent space and weight requirements of spaceborne payloads.

[0067] Optical efficiency and signal-to-noise ratio optimization: The partitioned coating achieves a reflection efficiency of >99.5% in the gas glow spectral band. Combined with the aberration correction function of the lens array, the system's light energy utilization is greatly improved, thus enhancing the system's signal-to-noise ratio.

[0068] Assembly and adjustment process and cost control: After eliminating the tetrahedral pyramidal prism, the modular assembly of the four reflecting surfaces and the lens array (based on laser interference rapid alignment technology) greatly shortens the assembly and adjustment time and reduces mass production costs.

[0069] This invention uses the gas glow generated by the spontaneous emission of oxygen atoms, oxygen molecules, and other gas molecules in a planetary atmosphere as the detection target. A compact wind imaging interferometer is designed to simultaneously acquire four interferometric images with a phase difference of π / 2. Combined with an inversion algorithm based on spectral Doppler shift and modulation, high-precision synchronous measurement of atmospheric wind speed and temperature is achieved. Employing limb observation geometry effectively improves vertical resolution, and combined with a spaceborne platform, continuous monitoring of atmospheric dynamic parameters can be achieved globally. Compared to traditional moving mirror scanning interferometers, this static detection system avoids wind speed inversion errors introduced by time-series observations, while innovative optical system design significantly improves instrument integration.

[0070] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0071] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A compact Michelson wind imaging interferometer based on lens array, characterized in that, The application relates to a device for detecting target gas emission, which comprises: a collimating system for collimating target gas emission light to obtain parallel light along a horizontal direction; a beam splitter (5) arranged at the output side of the collimating system for splitting the parallel light to obtain transmitted light propagating along the same direction of the parallel light and reflected light propagating vertically upward; a second compensating glass (8) arranged at the top of the beam splitter (5), the top end of which is coated with a four-part reflective film to form four reflective surfaces; the reflected light propagates along the thickness direction of the second compensating glass (8), is reflected by the four reflective surfaces after passing through the second compensating glass (8), and then passes through the second compensating glass (8) again and is emitted from the beam splitter (5); a first compensating glass (6) arranged at the side of the beam splitter (5) and the second compensating glass (8) away from the collimating system, the part of which adhering to the beam splitter (5) is coated with a transmission film, and the part of which adhering to the second compensating glass (8) is coated with a reflective film to form a single reflective surface; a compensating prism (7) arranged at the side of the first compensating glass (6) away from the beam splitter (5); the transmitted light propagates along the thickness direction of the first compensating glass (6), passes through the transmission film of the first compensating glass (6) in sequence, and then passes through the first compensating glass (6) and the compensating prism (7), the compensating prism (7) reflects the transmitted light to the reflective film of the first compensating glass (6), the transmitted light is reflected by the single reflective surface along the original path, and is emitted after passing through the compensating prism (7), the first compensating glass (6) and the beam splitter (5) again; a lens array (9) arranged below the beam splitter (5) and composed of four identical sub-lenses, the four sub-lenses corresponding to the four reflective surfaces one by one; the transmitted light and the reflected light emitted from the beam splitter converge on a CCD detector (10) arranged below the lens array (9) to interfere and form four interference patterns with different phases.

2. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 1, wherein, The collimating system comprises: a telescope (2) for converging target gas emission light and forming a primary image of the target gas emission at the back focal plane of the telescope (2); a field stop (3) arranged at the primary image plane of the telescope (2) for limiting the field of view of the instrument; a collimating mirror (4) arranged at the conjugate plane of the focal plane of the telescope (2) for collimating the target gas emission light to obtain parallel light; wherein the focal length of the telescope (2) is greater than the focal length of the collimating mirror (4).

3. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 1, wherein, The beam splitter (5) is a positive cubic beam splitter composed of two triangular prisms, the hypotenuse bonding surfaces of the two triangular prisms being coated with a semi-transparent and semi-reflective film.

4. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 1, wherein, The compensating prism (7) is a right-angle prism, the two right-angle surfaces of which are coated with reflective films, and the hypotenuse surface is coated with a transmission film, the hypotenuse surface adhering to the first compensating glass (6).

5. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 1, wherein, The four-part reflective film has different phases, which are 0, pi / 2, pi and 3pi / 2 respectively.

6. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 1, wherein, The device further comprises: a filter (1) for filtering incident light to obtain target gas emission light.

7. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 1, wherein, n1, n2 and n3 represent the refractive indexes of the first compensating glass (6), the compensating prism (7) and the second compensating glass (8) respectively, and d0, d1, d2 and d3 represent the thicknesses of the beam splitter (5), the first compensating glass (6), the compensating prism (7) and the second compensating glass (8) respectively. The optical path difference of the interferometer is as follows: ； In the formula, is the optical path difference.

8. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 7, wherein, The interferometer needs to satisfy a field of view widening condition, and the specific condition is as follows: 。 9. A compact Michelson wind imaging interferometer based on lens array as claimed in claim 7, wherein, The interferometer needs to satisfy a temperature compensation condition, and the specific condition is as follows: ； wherein T is the temperature, , and are the coefficients of thermal expansion of the first compensation glass (6), the compensation prism (7) and the second compensation glass (8), respectively, , and are the temperature coefficients of the refractive index of the first compensation glass (6), the compensation prism (7) and the second compensation glass (8).

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