Static Doppler imaging interferometer

Abstract

The two arms of the static Doppler imaging interferometer comprise two pieces of compensation glass, the two pieces of compensation glass are connected to the emergent face of reflected light and the emergent face of projected light of a beam splitting film of a beam splitter respectively, and the two pieces of compensation glass are the first compensation glass and the second compensation glass respectively. The first compensation glass is connected to the incident plane of reflected light of the beam splitting film of the beam splitter, the second compensation glass is connected to the emergent plane of the reflected light of the beam splitting film of the beam splitter, the total reflection mirror and the four-partition reflection mirror are plated at the tail end of the first compensation glass and the tail end of the second compensation glass respectively, and the two pieces of compensation glass are bonded through photosensitive glue. Therefore, the air gap between the two arms of the static Doppler imaging interferometer is eliminated, the stability reduction of the Doppler imaging interferometer caused by the existence of the air gap is effectively avoided, the influence of low air pressure and air flow can be reduced under different environmental conditions, the situation that interference fringes are unstable is avoided, and the stability of the Doppler imaging interferometer is improved. Therefore, the instrument calibration precision and the wind speed detection accuracy are improved.

Description

Technical Field

[0001] The invention relates to the technical field of atmosphere detection instruments, in particular to a static Doppler imaging interferometer. Background Art

[0002] Atmospheric motion in the mesosphere and lower thermosphere is dominated by large-scale tides, planetary waves, and large-scale and small-scale gravity waves. Space-based observation data show that these fluctuations have an important driving effect on large-scale circulation in the middle atmosphere. However, the coupling, energy dissipation and interaction mechanisms are still unclear, so it is necessary to detect the dynamic processes of the middle atmosphere with high temporal and spatial resolution and high precision.

[0003] Passive wind imaging interferometry uses the naturally occurring airglow radiation in the atmosphere as a light source to detect the atmospheric motion state (wind field). Particles that produce airglow radiation (such as O2, O, and OH) move with the atmosphere, and the airglow radiation spectrum they produce produces a Doppler frequency shift due to their movement relative to the observer. By measuring this Doppler frequency shift, the speed of the target atmosphere along the line of sight can be determined, thereby inverting the atmospheric wave characteristics. Passive wind imaging interferometry does not require a light source emission device, has a long detection distance and a wide range, and has great advantages.

[0004] The reflector of one arm of the traditional moving mirror Doppler imaging interferometer obtains four interference intensities through precise reciprocating motion. Therefore, a certain gap needs to be left between the moving mirror and the compensation glass to ensure the movement space of the moving mirror. The static Doppler imaging interferometer obtains four interference intensities through fixed four-partition step phase reflection, and the reflector does not need to move. However, due to the influence of the compensation design of the traditional moving mirror Doppler imaging interferometer, the compensation design of the existing static Doppler imaging interferometer still retains the air gap, and the existence of the air gap will reduce the stability of the Doppler imaging interferometer. Summary of the invention

[0005] The purpose of the present invention is to provide a static Doppler imaging interferometer, which can give full play to the advantages of the static Doppler imaging interferometer and improve its stability in a complex aerospace environment.

[0006] The technical solution of the present invention is:

[0007] A static Doppler imaging interferometer comprises a beam splitter, a first compensation glass and a second compensation glass, the two compensation glasses respectively corresponding to the two arms of the static Doppler imaging interferometer, the first compensation glass is connected to the incident surface of the reflected light of the beam splitter film, the second compensation glass is connected to the exit surface of the reflected light of the beam splitter film, and a total reflection mirror and a four-partition reflection mirror are respectively plated on the ends of the first compensation glass and the second compensation glass to eliminate the air gaps in the two arms of the static Doppler imaging interferometer.

[0008] Furthermore, the method for selecting and pairing the materials and thickness parameters of the two compensation glasses includes the following steps:

[0009] S1. Pair the glasses in the glass library in pairs and extract two glass parameters of each group: refractive index n1, n2, linear expansion coefficient of glass α1, α2, coefficient of change of glass refractive index with temperature β1, β2;

[0010] S2, respectively set the reference optical path difference weight coefficient w1, the field of view widening weight coefficient w2, and the temperature difference elimination weight coefficient w3;

[0011] S3 Plug-in

[0012]

[0013] Where d1 and d2 are the two glass thicknesses, Δ0 is the preset reference optical path difference, represented by w Indicated by A Represented by x Indicated by B Rewrite the above formula in the form of wAx=B, and the glass pairing thickness is solved by the following formula:

[0014] x=(A T w T wA) -1 A T w T B

[0015] S4. Use the calculated total thickness of each group of two glasses as the horizontal axis and the absolute value of the difference in thickness between the two glasses as the vertical axis to draw a scatter plot of all glass combinations, and select the group closest to the lower left corner as the optimal pairing combination.

[0016] Furthermore, the two compensation glasses are bonded together by photosensitive adhesive.

[0017] Furthermore, the bonding method of the two compensation glasses includes the following steps: applying photosensitive adhesive on the bonding end faces, splicing the two compensation glasses on the beam splitter, using a laser parallel beam to incident the beam splitter, using a white screen at the exit to receive the outgoing light, observing the generated interference fringes, and finely adjusting the bonding position and angle of the two compensation glasses. When equal-inclined interference fringes appear on the four-partition reflector, stop adjusting, and place the whole in a UV light box for curing. The compensation system is assembled.

[0018] Furthermore, it also includes: a metal shell, and the interference system composed of the beam splitter and the two compensation glasses is placed in the metal shell.

[0019] Furthermore, the interference system and the metal shell are connected by filling with soft glue.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The static Doppler imaging interferometer of the present invention has better aerospace stability, especially its sensitivity to ambient temperature and air pressure is better than that of the traditional Doppler imaging interferometer with air gap. It effectively avoids the reduction of stability of the Doppler imaging interferometer caused by the existence of air gap, and after eliminating the air gap, the present invention can reduce the influence of air pressure and air flow under different environmental conditions (such as space-based detection and ground-based detection), avoid the occurrence of unstable interference fringes, thereby improving the calibration accuracy of the instrument and the accuracy of wind speed detection;

[0022] In the static Doppler imaging interferometer of the present invention, two pieces of compensation glass are respectively bonded to the beam splitter, which avoids the need for the existing compensation glass to be supported and fixed by a mechanical structure of other materials (such as aluminum, cast iron, etc.), resulting in a decrease in the overall temperature stability and rigidity of the instrument. When the all-solid-state compensation glass combination is affected by the external environment (such as temperature, humidity, and pressure), the environmental factors are compensated according to the theoretical design, thereby ensuring the stability of the interferometer. In addition, through a weighted pairing algorithm when selecting the thickness parameters of the two pieces of compensation glass, the field of view widening effect and the temperature difference elimination effect can be guaranteed when the glass thickness parameters are calculated. The two effect requirements are determined by the setting of the weight coefficient, so that the interferometer without air gap of the present invention does not need to calculate the field of view widening effect and the temperature difference elimination effect pair by pair after the glass thickness parameters are calculated. On the premise of ensuring the accuracy and stability of the interferometer, the efficiency of the compensation design is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the interferometer structure using the all-solid-state compensation method of the present invention.

[0024] Figure 2 This is the field-of-view widening effect of the interferometer using the all-solid-state compensation method of the present invention.

[0025] Figure 3 This is the temperature difference elimination effect of the interferometer using the all-solid-state compensation method of the present invention.

[0026] Figure 4 The temperature difference elimination effect of the interferometer using the all-solid-state compensation method of the present invention is compared with that of the interferometer using the traditional compensation method.

[0027] Figure 5 The comparison of the pressure resistance of the interferometer using the all-solid-state compensation method of the present invention and the interferometer using the traditional compensation method is shown.

[0028] Among them, 1. total reflection mirror, 2. beam splitter, 3. first compensation glass, 4. second compensation glass, 5. four-partition reflection mirror. DETAILED DESCRIPTION

[0029] Combine the following Figures 1 to 5 , the specific embodiments of the present invention are described in detail. In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0030] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0031] Example

[0032] The existing interferometer four-partition reflector and the second compensation glass supported and fixed by a mechanical structure are separated, with air in the middle and an air gap. Therefore, the connection between the two parts can only be supported by a metal frame, which is greatly affected by the environment. First, the air gap is easily affected by air pressure and air flow under different environmental conditions (such as space-based detection and ground-based detection), resulting in unstable interference fringes, affecting the calibration accuracy of the instrument and the accuracy of wind speed detection; secondly, since one of the arm reflectors is not directly connected to the compensation glass, it needs to be supported and fixed by a mechanical structure of other materials (such as aluminum, cast iron, etc.), resulting in a decrease in the overall temperature stability and rigidity of the instrument.

[0033] In the all-solid-state compensation method of this specific implementation, the three strong lines and three weak lines in the near-infrared 1.27μm band are designed. The central wavelengths of the two sets of spectral lines are 1264.277nm and 1278.408nm respectively. The wavelength difference is small, so the influence of chromatic aberration can be ignored. The wide field and temperature compensation are mainly considered. The design value of the reference optical path difference of the near-infrared static four-partition coated wind imaging interferometer is 10cm. The static Doppler imaging interferometer using the all-solid-state compensation method includes a beam splitter, a first compensation glass 3 and a second compensation glass 4. The two compensation glasses correspond to the two arms of the static Doppler imaging interferometer respectively. There is no requirement for the order, such as Figure 1As shown, in this embodiment, the first compensation glass 3 is connected to the incident surface of the reflected light of the beam splitter film of the beam splitter 2, and the second compensation glass 4 is connected to the exit surface of the reflected light of the beam splitter film of the beam splitter. The total reflection mirror 1 and the four-partition reflection mirror 5 are respectively plated on the ends of the first compensation glass 3 and the second compensation glass 4. The two compensation glasses are bonded by photosensitive adhesive to eliminate the air gap in the two arms of the static Doppler imaging interferometer.

[0034] like Figure 1 As shown, on the beam splitter 2, the left side adjacent to the bonding surface of the beam splitter 2 and the first compensation glass 3 is the incident surface, and the side surface adjacent to the incident surface is the exit surface.

[0035] Preferably, the bonding method of two compensating glasses comprises the following steps:

[0036] Apply photosensitive adhesive on the bonding end surface, assemble the two compensation glasses on the beam splitter 2, use a laser parallel beam to incident on the beam splitter 2, use a white screen to receive the outgoing light on the exit surface at the exit, observe the generated interference fringes, and finely adjust the bonding position and angle of the two compensation glasses. When equal-inclined interference fringes appear on the four-partition reflector 5, no further adjustments are made, and the whole is placed in a UV light box for curing. The compensation system is assembled.

[0037] In some embodiments, it also includes: an L-shaped metal housing, and an interference system consisting of a beam splitter 2 and two compensation glasses is placed in the L-shaped metal housing.

[0038] In order to avoid the influence of thermal expansion and contraction of metal, the interference system and the L-shaped metal shell are connected by filling with soft glue. At this time, the metal shell can protect and fix the interference system. At the same time, the metal shell and the interference system will not affect each other due to environmental changes.

[0039] The material and thickness parameters of the two compensation glasses are obtained by the following algorithm flow:

[0040] S1. Pair the glasses in the glass library in pairs and extract two glass parameters of each group: refractive index n1, n2, linear expansion coefficient of glass α1, α2, coefficient of change of glass refractive index with temperature β1, β2;

[0041] S2, respectively set the reference optical path difference weight coefficient w1, the field of view widening weight coefficient w2, and the temperature difference elimination weight coefficient w3;

[0042] S3 Plug-in

[0043]

[0044] Where d1 and d2 are the two glass thicknesses, Δ0 is the preset reference optical path difference, represented by w Indicated by A Use x to represent Indicated by B Rewrite the above formula in the form of wAx=B, and the glass pairing thickness is solved by the following formula:

[0045] x=A T w T wxya -1 A T w T B

[0046] S4. Use the calculated total thickness of each group of two glasses as the horizontal axis and the absolute value of the difference in thickness between the two glasses as the vertical axis to draw a scatter plot of all glass combinations, and select the group closest to the lower left corner as the optimal pairing combination.

[0047] In S4, in addition to selecting the optimal combination based on the minimum thickness and minimum thickness difference of the two compensation glasses, the prices of different glasses can also be taken into account, and the use of high-refractive-index glass and uncommon special glass can be avoided as much as possible. The optimal choice is comprehensively considered in terms of the volume and cost of the interference system.

[0048] like Figure 1 As shown, the material of the first compensation glass 3 is Chengdu Guangming Glass H-ZLaF2A, and the material of the second compensation glass 4 is Chengdu Guangming Glass H-K8. The thickness of the first compensation glass 3 is 99.19 mm, and the thickness of the second compensation glass 4 is 84.15 mm.

[0049] The performance of the two-glass all-solid-state compensation method in this embodiment was tested and analyzed by computer, and it was found that it can achieve the ideal field of view widening and temperature difference elimination effect. Figure 2 As shown, there is no more than one fringe within a 4° field of view, and the temperature difference elimination effect is as follows Figure 3 As shown, the thermal drift of the static Doppler imaging interferometer can be controlled below 0.01 fringe per degree Celsius, which well meets the requirements of wide field and temperature compensation.

[0050] like Figure 4 As shown in the figure, affected by the thermal expansion of the aluminum bracket, the absolute value of the rate of change of the reference optical path difference of the traditional compensation scheme with an air gap with temperature reaches 0.52fringes / ℃. It can be observed in the experiment that the obvious change of the four-zone interference intensity with temperature requires additional temperature drift correction. The absolute value of the rate of change of the reference optical path difference with temperature of the all-solid-state compensation method of this embodiment is 0.01fringes / ℃. The entire interferometer system is self-contained and is not easily affected by the temperature changes of other external structures, and has lower temperature sensitivity. At the same time, the all-solid-state solution has better system rigidity, compact structure, stronger vibration resistance, and is more suitable for aerospace satellite exploration missions.

[0051] On the other hand, the all-solid-state compensation scheme is much less affected by pressure changes than the compensation scheme with air gaps. Figure 5 As shown in Figure 2, the absolute value of the rate of change of the reference optical path difference of the all-solid-state compensation method with atmospheric pressure is only 8.19×10 - 5 fringes / kPa, the absolute value of the change rate of the reference optical path difference of the traditional compensation scheme with air gap with atmospheric pressure reaches 6.28×10 -2 fringes / kPa. The difference between the two is 3 orders of magnitude. The sensitivity of the all-solid compensation method in this embodiment to temperature and atmospheric pressure is lower than that of the traditional compensation scheme with air gap. The use of a new all-solid compensation scheme design will greatly improve the environmental stability of the static Doppler imaging interferometer and obtain higher accuracy in the detection of atmospheric dynamic parameters.

[0052] The above disclosures are only several preferred specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A static Doppler imaging interferometer, characterized in that: The invention comprises a beam splitter, a first compensation glass (3) and a second compensation glass (4), wherein the two compensation glasses correspond to two arms of a static Doppler imaging interferometer respectively, the first compensation glass (3) is connected to the incident surface of the reflected light of the beam splitter film, and the second compensation glass (4) is connected to the exit surface of the reflected light of the beam splitter film. A total reflection mirror (1) and a four-partition reflection mirror (5) are respectively plated on the ends of the first compensation glass (3) and the second compensation glass (4) to eliminate the air gaps in the two arms of the static Doppler imaging interferometer.

2. A static Doppler imaging interferometer according to claim 1, characterized in that: The method for selecting and pairing the materials and thickness parameters of the two compensation glasses comprises the following steps: S1. Pair the glasses in the glass library in pairs and extract two glass parameters of each group: refractive index n1, n2, linear expansion coefficient of glass α1, α2, coefficient of change of glass refractive index with temperature β1, β2; S2, respectively set the reference optical path difference weight coefficient w1, the field of view widening weight coefficient w2, and the temperature difference elimination weight coefficient w3; S3 Plug-in Where d1 and d2 are the two glass thicknesses, Δ0 is the preset reference optical path difference, represented by w Indicated by A Represented by x Indicated by B Rewrite the above formula in the form of wAx=B, and the glass pairing thickness is solved by the following formula: x=(A T w T wA) -1 A T w T B S4. Use the calculated total thickness of each group of two glasses as the horizontal axis and the absolute value of the difference in thickness between the two glasses as the vertical axis to draw a scatter plot of all glass combinations, and select the group closest to the lower left corner as the optimal pairing combination.

3. A static Doppler imaging interferometer according to claim 1, characterized in that: The two compensation glasses are bonded together by photosensitive adhesive.

4. A static Doppler imaging interferometer according to claim 1, characterized in that: The bonding method of two compensating glasses comprises the following steps: Apply photosensitive adhesive to the bonding end surface, assemble the two compensation glasses on the beam splitter (2), use a laser parallel beam to enter the beam splitter (2), use a white screen to receive the outgoing light at the exit, observe the generated interference fringes, and finely adjust the bonding position and angle of the two compensation glasses. When the four-partition reflector (5) has equal-inclination interference fringes, stop adjusting, solidify the whole, and the compensation system is assembled.

5. A static Doppler imaging interferometer according to claim 1, characterized in that: Also includes: A metal shell, wherein the interference system composed of the beam splitter (2) and the two compensating glasses is placed inside the metal shell.

6. A static Doppler imaging interferometer according to claim 5, characterized in that: The interference system and the metal shell are connected by filling with soft glue.

7. A static Doppler imaging interferometer according to claim 1, characterized in that: The material of the first compensation glass (3) is Chengdu Guangming Glass H-ZLaF2A, and the material of the second compensation glass (4) is Chengdu Guangming Glass H-K8. The thickness of the first compensation glass (3) is 99.19 mm, and the thickness of the second compensation glass (4) is 84.15 mm.

Images