Compact Michelson wind imaging interferometer based on lens array

Abstract

The invention discloses a compact Michelson wind imaging interferometer based on a lens array, which relates to the technical field of atmospheric remote sensing instruments and comprises a beam splitter, second compensation glass, first compensation glass and a compensation prism. The reflected light is propagated along the thickness direction of the second compensation glass, is reflected by the four reflecting surfaces, passes through the second compensation glass again and is emitted from the beam splitter; the transmission light sequentially penetrates through the first compensation glass and the compensation prism after passing through the transmission film of the first compensation glass, the compensation prism reflects the transmission light to the reflection film of the first compensation glass, and the transmission light is reflected by the single reflection surface, returns along the original path and then is emitted; the transmission light and the reflection light emitted from the beam splitter pass through the lens array and then converge on the CCD detector arranged below the lens array for interference. A complex cube-corner prism alignment system is omitted, linear light paths of two arms of a traditional Michelson interferometer are folded into a compact layout, and the size and the weight of the whole system are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atmospheric remote sensing instruments, in particular to a compact Michelson wind imaging interferometer based on a lens array. BACKGROUND

[0002] Accurate detection of planetary atmospheric dynamic parameters is an important basis for studying atmospheric physical processes. Wind speed and temperature, as core parameters representing the dynamics of the atmospheres of planets such as Earth and Mars, directly affect the processes of atmospheric energy transfer and material transport. High-precision detection of atmospheric wind speed and temperature is crucial for studying planetary atmospheres, building climate models, and ensuring the safety of spacecraft.

[0003] Interferometric detection technology uses the atomic or molecular airglow widely existing in the atmosphere as the target light source, and inverses the atmospheric wind speed and temperature by detecting the Doppler shift and line width of the airglow spectral line. It has the advantages of high throughput, high sensitivity, and simultaneous detection of multiple parameters, and can sensitively extract weak airglow spectral line shift and broadening information, becoming 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, lightweight, and detection accuracy are constantly increasing, and existing interferometric measurement technology still faces the bottleneck problem of urgent breakthrough.

[0004] Existing Michelson wind imaging interferometers include dynamic mirror scanning wind imaging interferometers and static wind imaging interferometers. Dynamic mirror scanning wind imaging interferometers need to move the mirror to obtain four-phase interferograms at different times, and the time nonsynchronization of observation data leads to an increase in wind speed measurement error. Static wind imaging interferometers use fixed optical path difference design, but generally rely on complex light splitting devices such as four-sided corner cube prisms, and the supporting optical system needs to realize accurate registration of the light splitting surface and the detector pixels, significantly increasing the complexity of the optical-mechanical structure.

[0005] The closest existing static Michelson interferometer technical solution related paper is as follows: Static wind imaging Michelson interferometer for the measurement of stratospheric wind fields, 2023, Optic Express. Its technical solution is as follows: Figure 5As shown, the technical scheme adopts a four-sided corner prism for light splitting, finally realizes static acquisition of four interference patterns, and solves the problem of increased wind speed measurement error caused by time non-synchronization of observation data of a traditional wind imaging interferometer. However, the use of the four-sided corner prism needs to increase a relay optical system, and the four-part mirror is conjugated with the four-sided corner prism, which increases the volume and weight of the system, and the layout of the two-arm light paths has problems of low space utilization and large volume, which restricts the lightweight development of a spaceborne instrument and is not conducive to the miniaturization design of the spaceborne instrument. SUMMARY

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

[0007] The present application adopts the following technical scheme: The present application provides a compact Michelson wind imaging interferometer based on a lens array, comprising the following steps: A collimation system is used for collimating target gas glow to obtain parallel light along the horizontal direction; A beam splitter is arranged on the output side of the collimation system and is used 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 compensation glass is arranged on the top of the beam splitter, and four reflection surfaces are formed on the top end of the second compensation glass by coating a four-part reflection film on the top end of the second compensation glass; the reflected light propagates along the thickness direction of the second compensation glass, is reflected by the four reflection surfaces after passing through the second compensation glass, and then passes through the second compensation glass again and is emitted from the beam splitter; A first compensation glass is arranged on the side of the beam splitter and the second compensation glass away from the collimation system, and a single reflection surface is formed by coating a transmission film on the part of the first compensation glass abutting the beam splitter and coating a reflection film on the part of the first compensation glass abutting the second compensation glass; A compensation prism is arranged 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 in sequence, and then passes through the first compensation glass and the compensation prism; the compensation prism reflects the transmitted light to the reflection film of the first compensation glass, and the transmitted light is reflected by the single reflection surface along the original path, and is emitted after re-passing through the compensation prism, the first compensation glass, and the beam splitter; A lens array is arranged below the beam splitter, is composed of four identical sub-lenses, and the four sub-lenses correspond to the four reflection surfaces one by one; the transmitted light and the reflected light emitted from the beam splitter converge on a CCD detector arranged below the lens array after passing through the lens array to interfere, and four interference patterns with different phases are formed.

[0008] Preferably, the collimation system comprises: a telescope for converging light of a target gas glow and forming an image of the target gas glow at a back focal plane of the telescope; a field stop arranged at the image plane of the telescope for limiting the field of view of the instrument; a collimator arranged at a conjugate plane of the focal plane of the telescope for collimating the light of the target gas glow to obtain parallel light; wherein the focal length of the telescope is greater than the focal length of the collimator.

[0009] Preferably, the beam splitter is a right cube beam splitter, which is composed of two triangular prisms, and the hypotenuse bonding surfaces of the two triangular prisms are coated with a half-transmission half-reflection film.

[0010] Preferably, the compensating prism is a right-angle prism, both of whose right-angle surfaces are coated with a reflection film, and the hypotenuse surface is coated with a transmission film and is bonded to the first compensating glass.

[0011] Preferably, the four-part reflection film has different phases, which are 0, π / 2, π and 3π / 2, respectively.

[0012] Preferably, the instrument further comprises: a filter for filtering incident light to obtain the light of the target gas glow.

[0013] 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. The optical path difference of the interferometer is as follows: ; wherein, is the optical path difference.

[0014] Preferably, the interferometer needs to satisfy the field widening condition, which is as follows: .

[0015] Preferably, the interferometer needs to satisfy the temperature compensation condition, which is as follows: ; wherein, is the temperature, , and are the thermal expansion coefficients of the first compensating glass, the compensating prism and the second compensating glass, respectively, , and are the refractive index temperature coefficients of the first compensating glass, the compensating prism and the second compensating glass, respectively.

[0016] Compared with the prior art, the at least one technical scheme adopted by the present application can achieve the following beneficial effects: The present application firstly splits the parallel light by the beam splitter to obtain transmitted light along the horizontal direction and reflected light along the vertical direction. A second compensation glass is arranged on the top of the beam splitter, the top end of which is coated with a four-partition reflection film to form four reflection surfaces. Four sub-lenses are arranged below the beam splitter, and the four sub-lenses correspond to the four reflection surfaces one by one. The present application integrates the spatial light splitting and synchronous imaging of the four-phase interference pattern into the partition-coated reflection surface of the second compensation prism by coating the top end of the second compensation prism with a partition film, and replaces the traditional four-sided corner prism with a lens array, which directly images to different regions of the detector in combination with the lens array, completely eliminates the timing error of the moving mirror scanning, and eliminates the complex corner prism alignment system, so that the wind speed measurement error is greatly reduced. In addition, the straight light path of the two arms of the existing interferometer is folded into a compact layout by the second compensation glass and the compensation prism, which reduces the volume and weight of the entire system, making it more compact, small and lightweight. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0018] Figure 1 The present application is a schematic diagram of the optical path of a compact Michelson wind imaging interferometer based on a lens array. Figure 2 The present application is a left view of the compensation glass in the xy plane. Figure 3 The present application is a schematic diagram of the end of the compensation glass in the xz plane. Figure 4 The present application is a schematic diagram of the distribution of the lens array in the xy plane. Figure 5 The present application is a schematic diagram of the distribution of the lens array in the xy plane.

[0019] In the figure: 1-filter, 2-telescope, 3-field stop, 4-collimator, 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 DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0021] The present application solves the problem of increased wind speed measurement error caused by time non-synchronization of traditional interferometer observation data, the problem of increased volume and weight caused by using four-cornered corner prisms in existing static interferometers, and the problem of insufficient compactness of glass layout of two arms of the interferometer, and realizes miniaturization and compactness design of the interferometer, which is used for global remote sensing detection of key parameters such as planetary atmospheric wind field and temperature field.

[0022] The present application provides a compact Michelson wind imaging interferometer based on a lens array, which comprises 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 arranged in sequence along the main optical axis direction.

[0023] After the incident light (all airglow light) is filtered by the filter 1, the incident target airglow light is obtained. After the pre-telescope system, the parallel light is obtained, and after the beam splitter 5, the parallel light is divided into two mutually perpendicular beams: transmitted light and reflected light. The transmitted light propagates along the direction of the parallel light, and the reflected light propagates along the vertical upward direction. The reflected light is reflected by the four-quadrant reflection film coated on the end face of the second compensation glass 8, and then passes through the second compensation glass 8 again and is emitted from the 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 reflection surface at the end of the upper half, and returns to the original route, and is emitted after passing through the compensation prism 7, the lower half of the first compensation glass 6 and the beam splitter 5. The two beams of light converge on the CCD detector 10 after passing through the lens array 9 to interfere. The four reflection surfaces formed by the four-quadrant reflection film correspond one-to-one to the four sub-lenses of the lens array, and finally four interference patterns with different phases are formed on the CCD detector, from which the wind speed and temperature of the planetary atmosphere are inversely calculated.

[0024] Further, a rectangular coordinate system xyz is established with the main optical axis as the positive direction of the z-axis, and the coordinate system satisfies the right-hand rule.

[0025] The telescope 2, the field stop 3 and the collimator 4 form a front telescope system, and the field stop 3 is located at the primary image plane of the telescope 2, which can most directly and most effectively limit the field angle of the object space without vignetting. The focal length of the telescope 2 is greater than the focal length of the collimator 4, so the magnification of the front telescope system is greater than 1. The magnification is equal to the focal length of the telescope divided by the focal length of the collimator. The magnification greater than 1 is beneficial to improve the light energy collection efficiency.

[0026] The beam splitter 5 is a right cube beam splitter, which is composed of two triangular prisms, and the hypotenuse bonding surfaces of the two triangular prisms are coated with a semi-transparent and semi-reflective film.

[0027] In the rectangular coordinate system, Figure 1 The upper left side of the first compensation glass 6 is coated with a reflective film with a reflectivity of up to 99.5%. The left schematic view in the xy plane is shown in Figure 2 The lower half 61 is coated with a high-transmission film (projection film) allowing light to pass through with high transmittance. The upper half 62 is coated with a high-reflective film (reflective film) with a reflectivity of up to 99.5%.

[0028] The compensation prism 7 is a right-angle prism, which not only folds the optical path, but also participates in the temperature, optical path difference and field compensation of the interferometer. Both of its right-angle surfaces are coated with a high-reflective film with a reflectivity of up to 99.5%.

[0029] The top end (the end away from the beam splitter 5) of the second compensation glass 8 is coated with a four-part high-reflective film, as shown in Figure 3 The first sub-region 81, the second sub-region 82, the third sub-region 83 and the fourth sub-region 84 are made as follows: first, the first sub-region 81 of the second compensation glass 8 is shielded, and a layer of fused quartz material is coated 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, and then a multi-layer high-reflective film is coated on the first sub-region 81, the second sub-region 82, the third sub-region 83 and the fourth sub-region 84. The reflectivity is up to 99.5%.

[0030] The lens array 9 is composed of four identical sub-lenses, which correspond one-to-one to the four sub-regions of the second compensation glass 8, and the spatial distribution is shown in Figure 4 , including the first sub-lens 91, the second sub-lens 92, the third sub-lens 93 and the fourth sub-lens 94.

[0031] In addition, the interferometer needs to compensate the refractive index n and thickness d of the glass to meet the large optical path difference, field of view expansion condition and temperature compensation condition required for atmospheric wind field detection. n1, n2 and n3 represent the refractive indices of the first compensation glass 6, the compensation prism 7 and the second compensation glass 8 respectively, and d1, d2 and d3 represent the thicknesses of the first compensation glass 6, the compensation prism 7 and the second compensation glass 8 respectively along the z-axis or the physical width in the direction of light advancement. The thickness d2 of the compensation prism refers to the height width of the hypotenuse of the right-angle prism.

[0032] As Figure 1 , the structural dimensions of the beam splitter 5, the first compensation glass 6, the compensation prism 7 and the second compensation glass 8 are related to each other, so that the entire interferometer system is particularly compact. The size limitation analysis is as follows: assuming that the edge length (thickness) of the positive cubic beam splitter 5 is d0, the three-dimensional size thereof is d0×d0×d0. The size of the first compensation glass 6 is d1×(d0+d3)×d0. The hypotenuse of the compensation prism 7 is d0+d3, and the thickness, i.e. the height of the hypotenuse, is d2. The size of the second compensation glass 8 is d3×d0×d0.

[0033] The optical path difference of the interferometer of the present application can be represented as: (1); In the formula, Further, the field of view expansion condition needs to be met and is represented as: (2); Further, the temperature compensation condition needs to be met and is represented as: (3); wherein, is the temperature, is the refractive index of the first compensation glass, is the thickness of the first compensation glass or prism, is the thermal expansion coefficient of the first compensation glass, is the refractive index temperature coefficient of the first compensation glass. In the present design, three compensation glasses or prisms are used, so .

[0034] Further, the compensation glasses are selected according to the formulas (1)-(3) and meet the size limitation, and the glass pairs that meet the above conditions are selected from the glass library to design and manufacture the interferometer.

[0035] Synchronization detection precision improvement and system simplification: through four sub-zone coated reflecting surfaces (coated area phase difference accurate control is π / 2), the spatial light splitting of four-phase interference images and synchronous imaging are integrated in the sub-zone coated reflecting surface, combined with the lens array (replacing the traditional four-cornered prism) to directly image to the different regions of the detector, which completely eliminates the timing error of the moving mirror scanning, and at the same time, the complex light splitting prism alignment system is omitted, so that the wind speed measurement error is greatly reduced.

[0036] Compact structure and lightweight design: the folding reflective light path (double reflective arm re-compact layout) is adopted, the straight light path of the two arms of the traditional Michelson interferometer is folded into a compact layout, so that the volume of the instrument is reduced, the weight is reduced, and the strict requirements of spaceborne load on space and weight are met.

[0037] Optical efficiency and signal-to-noise ratio optimization: the sub-zone coating realizes >99.5% reflectivity in the air glow spectral line band, combined with the aberration correction function of the lens array, so that the system light energy utilization rate is greatly improved, and the system signal-to-noise ratio is improved.

[0038] Assembly process and cost control: after the four-cornered prism is cancelled, the modular assembly of the four reflecting surfaces and the lens array (based on the rapid alignment technology of laser interference) greatly shortens the assembly and adjustment time, and reduces the production cost.

[0039] The present application takes the air glow generated by the spontaneous radiation of oxygen atoms, oxygen molecules and other gas molecules in the atmosphere of the planet as the detection target, designs a compact wind imaging interferometer, obtains four interference images with a phase difference of π / 2 synchronously, combines the inversion algorithm of spectral line Doppler frequency shift and modulation degree, and realizes high-precision synchronous measurement of atmospheric wind speed and temperature. The use of the edge observation geometry effectively improves the vertical resolution, and the combination of the spaceborne platform can realize continuous monitoring of atmospheric dynamics parameters in the global range. Compared with the traditional moving mirror scanning interferometer, the static detection system avoids the wind speed inversion error introduced by the timing observation, and at the same time, the instrument integration is significantly improved through the innovative design of the optical system.

[0040] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0041] Obviously, those skilled in the art can make various modifications and changes to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and changes of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and changes.

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) in sequence, 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, 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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