A method and system for detecting three-dimensional wavefront of atmospheric turbulence

Abstract

The present invention relates to the field of wavefront detection technology of adaptive optics, and in particular to a method and system for detecting three-dimensional wavefront of atmospheric turbulence, the method comprising the following steps: establishing a microsecond laser pulse return light model; using a wavefront sensor to perform atmospheric turbulence stratification measurement based on the microsecond laser pulse return light model; constructing an atmospheric turbulence three-dimensional reconstruction algorithm according to the results of the atmospheric turbulence stratification measurement; and using the atmospheric turbulence three-dimensional reconstruction algorithm to obtain three-dimensional wavefront distortion information of atmospheric turbulence. The present invention uses a three-dimensional wavefront stratification reconstruction algorithm to realize three-dimensional wavefront detection of atmospheric turbulence, avoiding the problems that traditional atmospheric turbulence three-dimensional detection technology is limited by the singular values ​​of the reconstruction matrix under integral detection and the high calculation delay, which is conducive to improving the accuracy and speed of the MCAO system in detecting three-dimensional atmospheric disturbances, and laying a solid foundation for large-aperture telescopes to achieve large-field high-resolution imaging.

Description

Technical Field

[0001] The present invention relates to the field of adaptive optical wavefront detection technology, and in particular to a method and system for detecting three-dimensional wavefront of atmospheric turbulence. Background Art

[0002] In the problem of "two dark, one black and three origins", precise observation of the dust disk of the star system is an important research method for the origin and evolution of the planetary system. The Hale Telescope, Keck Telescope and other telescopes have conducted preliminary imaging of a large number of dust disks, and statistically found that the size of the dust disks is between 0.4 arc seconds and 60 arc seconds. Therefore, the observation of dust disks requires ground-based large-aperture telescopes to have the performance of large-field and high-resolution observation.

[0003] In order to overcome the influence of random atmospheric disturbances on imaging quality, the use of adaptive optical systems to detect distorted wavefronts and compensate for them in real time has become an indispensable key part of current ground-based large-aperture telescopes. Laser guide star MCAO has become an essential key technology for ground-based large-aperture telescopes to achieve large-field high-resolution observations. Among them, the three-dimensional wavefront detection technology of atmospheric turbulence is the key and prerequisite for the MCAO system to achieve large-field high-resolution imaging. At present, the research results of MCAO on three-dimensional wavefront detection of atmospheric turbulence mainly include: using atmospheric tomography algorithms to restore the turbulence information of different altitude layers from the accumulated turbulence information in different line of sight directions; proposing a new type of wavefront sensor to reduce the complexity of the system; theoretically deriving the influence of calculation delay error and tomography error on the performance of the MCAO system.

[0004] However, in the prior art, what the wavefront sensor detects is the wavefront aberration accumulated by the turbulence on the entire path, and it is necessary to perform tomographic reconstruction of the atmospheric turbulence. However, there is no analytical expression when calculating the mode projection matrix, and the currently commonly used integral method has a slow calculation speed; moreover, due to its less coverage of the turbulent layer, its mode projection matrix generally has some very small singular values ​​and its condition number is very large, which leads to the "ill-conditioned" problem of the projection equation, affecting the accuracy of the wavefront reconstruction. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method and system for detecting three-dimensional wavefronts of atmospheric turbulence.

[0006] In order to achieve the above-mentioned purpose, in the first aspect, the present invention provides a method for detecting three-dimensional wavefront of atmospheric turbulence, the method comprising the following steps: establishing a microsecond laser pulse return light model; using a time-gated wavefront sensor to perform atmospheric turbulence stratification measurement based on the microsecond laser pulse return light model; constructing an atmospheric turbulence three-dimensional reconstruction algorithm according to the results of the atmospheric turbulence stratification measurement; and using the atmospheric turbulence three-dimensional reconstruction algorithm to obtain three-dimensional wavefront distortion information of atmospheric turbulence. The present invention uses a three-dimensional wavefront stratification reconstruction algorithm to realize three-dimensional wavefront detection of atmospheric turbulence, avoiding the problems that the traditional three-dimensional detection technology of atmospheric turbulence is limited by the singular values ​​of the reconstruction matrix under integral detection and the high calculation delay, which is conducive to improving the accuracy and speed of the MCAO system in detecting three-dimensional disturbances in the atmosphere, and laying a solid foundation for large-aperture telescopes to achieve large-field-of-view high-resolution imaging.

[0007] Optionally, the establishing of the microsecond laser pulse return light model comprises the following steps:

[0008] Constructing an atmospheric turbulence stratification model, wherein the atmospheric turbulence stratification model includes a low layer and a high layer;

[0009] The microsecond laser pulse return light model is established according to the atmospheric turbulence stratification model.

[0010] Optionally, the microsecond laser pulse light return model includes a laser pulse emission model and a laser pulse light return model;

[0011] The step of establishing the microsecond laser pulse return light model according to the atmospheric turbulence stratification model comprises the following steps:

[0012] Determine the pulse laser period, and then set a plurality of pulses within the pulse laser period according to the atmospheric turbulence stratification model to obtain the laser pulse emission model;

[0013] The laser pulse return model is obtained according to the atmospheric turbulence stratification model and the laser pulse emission model.

[0014] Optionally, the laser pulse emission model includes low-level pulses and high-level pulses. When the laser pulse emission model is used, the low-level pulses are emitted first and then the high-level pulses are emitted within one pulse laser cycle.

[0015] Optionally, the laser pulse echo model includes two echo signals, namely a low-layer echo signal and a high-layer echo signal. Taking the laser pulse emission time as the timing origin, within one pulse laser cycle, the echo time period of the low-layer echo signal and the echo time period of the high-layer echo signal respectively satisfy the following relationship:

[0016]

[0017]

[0018] Wherein, T1 is the retroreflection time period of the low-layer echo signal, T2 is the retroreflection time period of the high-layer echo signal, a < b and 2d / c + t1 + t2 + t3 < T, a is the thickness of the low layer, b is the distance between the lower boundary of the high layer and the ground, c is the speed of light, d is the distance between the upper boundary of the high layer and the ground, t1 is the pulse width of the low layer, t2 is the time interval between the low-layer pulse and the high-layer pulse, t3 is the pulse width of the high layer, and T is the pulse laser period.

[0019] Optionally, the atmospheric turbulence stratification measurement using the time-gated wavefront sensor based on the microsecond laser pulse retroreflection model includes the following steps:

[0020] 发射激光脉冲产生低层引星与高层引星,并产生所述低层回波信号和所述高层回波信号;

[0021] Use the time-gated wavefront sensor to sample the echo signal, and then obtain the wavefront information of different turbulence layers.

[0022] Optionally, the step of using the time-gated wavefront sensor to sample the echo signal and then obtain the wavefront information of different turbulence layers includes the following steps:

[0023] Use the time-gated wavefront sensor to sample the echo signal in the Shack-Hartmann sampling mode to obtain a low-layer echo sampling signal and a high-layer echo sampling signal;

[0024] Obtain the low-layer wavefront aberration information using the low-layer echo sampling signal, and at the same time obtain the combined wavefront aberration information using the high-layer echo sampling signal.

[0025] Optionally, the step of constructing an atmospheric turbulence three-dimensional reconstruction algorithm according to the results of the atmospheric turbulence stratification measurement includes the following steps:

[0026] Share the low-layer guide star and the high-layer guide star in the same atmospheric turbulence stratification model, and divide the atmosphere into a first region and a second region;

[0027] Use the low-layer guide star to detect the low-layer wavefront aberration of the first region and the second region, and use the high-layer guide star to detect the combined wavefront aberration of the first region and the second region;

[0028] Establish a wavefront aberration equation set, and substitute the low-layer wavefront aberration and the combined wavefront aberration into the wavefront aberration equation set to calculate the high-layer wavefront aberration of the first region and the second region.

[0029] Optionally, the wavefront aberration equation set satisfies the following relationship:

[0030]

[0031] Wherein, Ψ1 is the combined wavefront distortion of the first region, Ψ2 is the combined wavefront distortion of the second region, a1 and b1 are calculation coefficients, Ψ 11 is the high-level wavefront distortion of the first region, Ψ 21 is the low-level wavefront distortion of the first region, Ψ 12 is the high-level wavefront distortion of the second region, Ψ 22 is the low-level wavefront distortion of the second region.

[0032] In summary, the method provided by the present invention is based on the atmospheric turbulence layering measurement of microsecond pulsed laser, and the technology is combined with adaptive optical wavefront detection to realize the disturbance detection of atmospheric turbulence at various heights. At the same time, the method provided by the present invention also performs three-dimensional reconstruction of atmospheric turbulence based on the atmospheric turbulence layering measurement, so as to break through the problems that the traditional atmospheric turbulence three-dimensional detection technology is limited by the singular values ​​of the reconstruction matrix under integral detection and the high calculation delay, which is conducive to improving the accuracy and speed of the MCAO system in detecting atmospheric three-dimensional disturbances, and laying a solid foundation for large-aperture telescopes to achieve large-field high-resolution imaging.

[0033] In a second aspect, the present invention provides an atmospheric turbulence three-dimensional wavefront detection system, the system uses an atmospheric turbulence three-dimensional wavefront detection method provided by the present invention, the system includes: a light echo model construction device, the light echo model construction device is used to establish a microsecond laser pulse light echo model; a turbulence stratification measurement device, the turbulence stratification measurement device is used to perform atmospheric turbulence stratification measurement based on the microsecond laser pulse light echo model using a wavefront sensor; a three-dimensional wavefront detection device, the three-dimensional wavefront detection device is used to construct an atmospheric turbulence three-dimensional reconstruction algorithm based on the results of the atmospheric turbulence stratification measurement; and the three-dimensional wavefront distortion information of the atmospheric turbulence is obtained using the atmospheric turbulence three-dimensional reconstruction algorithm.

[0034] Furthermore, the system provided by the present invention not only has the same advantages as the present invention, but also can improve the efficiency of three-dimensional wavefront detection of atmospheric turbulence, laying a solid foundation for large-aperture telescopes to achieve large-field-of-view and high-resolution imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A schematic diagram of a flow chart of a method for detecting three-dimensional wavefront of atmospheric turbulence according to an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of a microsecond laser pulse return light model according to an embodiment of the present invention;

[0038] Figure 3 This is a timing diagram of atmospheric turbulence stratification measurement based on microsecond laser pulses according to an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of atmospheric region division according to an embodiment of the present invention;

[0040] Figure 5 A schematic diagram of the framework of an atmospheric turbulence three-dimensional wavefront detection system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not need to be adopted to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, software or methods are not specifically described.

[0042] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale.

[0043] It should be noted in advance that, in an optional embodiment, except for independent explanations, the same symbols or letters appearing in all formulas have the same meanings and values.

[0044] In an alternative embodiment, see Figure 1 The present invention provides a method for detecting three-dimensional wavefront of atmospheric turbulence, the method comprising the following steps:

[0045] S1. Establish a microsecond laser pulse return model.

[0046] Among them, S1 specifically includes the following steps:

[0047] S11. Constructing an atmospheric turbulence stratification model, wherein the atmospheric turbulence stratification model includes a low layer and a high layer.

[0048] Specifically, in this embodiment, the lower layer in the atmospheric turbulence stratification model is a layer close to the ground between two adjacent turbulence layers, and the higher layer is a layer far from the ground between two adjacent turbulence layers.

[0049] More specifically, for ease of explanation and understanding, the atmospheric turbulence stratification model used in this embodiment is a double-layer turbulence model, the lower layer is the Rayleigh layer, and the upper layer is the sodium layer, wherein the lower boundary of the Rayleigh layer is the ground, and the upper boundary of the Rayleigh layer is also the lower boundary of the sodium layer.

[0050] Furthermore, in other optional embodiments, the atmospheric turbulence may be divided into more layers, for example, the Rayleigh layer may be divided more finely.

[0051] S12. Establishing the microsecond laser pulse return light model according to the atmospheric turbulence stratification model.

[0052] The microsecond laser pulse return light model includes a laser pulse emission model and a laser pulse return light model, and S12 specifically includes the following steps:

[0053] S121, determining a pulse laser period, and then setting a plurality of pulses within the pulse laser period according to the atmospheric turbulence stratification model to obtain the laser pulse emission model.

[0054] Specifically, in this embodiment, the laser pulse emission model includes two pulses, a low-layer pulse and a high-layer pulse. When the laser pulse emission model is used, the low-layer pulse is first emitted in one pulse laser cycle to detect the low layer, and then the high-layer pulse is emitted to detect the high layer. Therefore, in one pulse laser cycle of the laser pulse emission model, the low-layer pulse is located before the high-layer pulse.

[0055] For more details, see Figure 2 In (a), the first pulse from left to right is the low-level pulse, and the second pulse is the high-level pulse.

[0056] Furthermore, in other optional embodiments, depending on the pulse laser cycle, one pulse laser cycle may include multiple low-layer pulses and high-layer pulses, but the number of low-layer pulses and the number of high-layer pulses in one pulse laser cycle must be the same.

[0057] S122. Acquire the laser pulse return model according to the atmospheric turbulence stratification model and the laser pulse emission model.

[0058] Specifically, in this embodiment, the laser pulse retroreflection model includes two echo signals, namely, a low-layer echo signal and a high-layer echo signal. Please refer to Figure 2 Figure (b) in

[0059]

[0060]

[0061] where T1 is the retroreflection time period of the low-layer echo signal, T2 is the retroreflection time period of the high-layer echo signal, a < b and 2d / c + t1 + t2 + t3 < T, a is the thickness of the low layer, b is the distance between the lower boundary of the high layer and the ground, c is the speed of light, d is the distance between the upper boundary of the high layer and the ground, t1 is the pulse width of the low layer, t2 is the time interval between the low-layer pulse and the high-layer pulse, t3 is the pulse width of the high layer, and T is the pulse laser period.

[0062] Furthermore, the retroreflection time period of the low-layer echo signal represents the pulse width of the low-layer echo signal, and the retroreflection time period of the high-layer echo signal represents the pulse width of the high-layer echo signal.

[0063] S2. Use a time-gated wavefront sensor to measure the atmospheric turbulence stratification based on the microsecond laser pulse retroreflection model.

[0064] Specifically, S2 includes the following steps:

[0065] S21.发射激光脉冲产生低层引星与高层引星,并产生所述低层回波信号和所述高层回波信号。 According to the laser pulse emission model, emit laser pulses into the atmosphere to generate a low-layer guide star and a high-layer guide star, and generate the low-layer echo signal and the high-layer echo signal.

[0066] Specifically, in this embodiment, please refer to Figure 3 Figure (a) in

[0067] It should be noted that in the translation of item , the original Chinese text seems to be incomplete or inaccurate. The translation is based on the best understanding of the context, but it may need to be adjusted according to the correct and complete Chinese content.Furthermore, since the upper layer is higher than the lower layer relative to the surface, and there is a time interval between two adjacent microsecond laser pulses, there will also be a time interval between the lower layer echo signal and the upper layer echo signal, that is, the lower layer echo signal will be received before the upper layer echo signal, so the time-gated wavefront sensor can be used to receive the lower layer echo signal and the upper layer echo signal in sequence. At the same time, the microsecond laser pulse width is wide enough and its peak power is not very high, which can avoid the laser pulse exciting the upper layer atoms to cause oversaturation and affect the brightness of the upper layer guide star, thereby improving the accuracy of atmospheric turbulence three-dimensional wavefront detection.

[0068] For further information, see Figure 3 In (b), (c) and (d), they show the return light sequence of the low-level echo signal and the high-level echo signal and the corresponding CCD exposure sequence and CCD readout sequence respectively. Figure 3 The three pulses from left to right in (b) are the low-layer echo signal, the high-layer echo signal, and the low-layer echo signal. Considering that the thickness of the low layer is 30km, 0-250μs is the return time period of the low-layer echo signal, and the return time period of the high-layer echo signal is 600μs-700μs. The pulse laser transmitter used to emit pulsed laser triggers the CCD to delay exposure for 150μs, and the exposure time is 100μs; since there is no echo signal in the 250μs-600μs time period, the CCD readout time is set to 350μs, so the next frame of CCD exposure just detects the high-layer echo signal, and the exposure time is also 100μs. After reading out 350μs, the CCD is locked and waits for the next external trigger signal to arrive; when the pulse laser transmitter continuously emits microsecond laser pulses of a specified frequency, the time-gated wavefront sensor can realize the alternating detection of low-layer echo signals and high-layer echo signals.

[0069] S22. Use the time-gated wavefront sensor to sample the echo signal, thereby acquiring wavefront information of different turbulent layers.

[0070] Among them, S22 specifically includes the following steps:

[0071] S221. Use the time-gated wavefront sensor to sample the echo signal using a Shack-Hartmann sampling method to obtain a low-level echo sampling signal and a high-level echo sampling signal.

[0072] S222. Use the low-layer echo sampling signal to obtain low-layer wavefront distortion information, and use the high-layer echo sampling signal to obtain combined wavefront distortion information.

[0073] Specifically, in this embodiment, the time-gated wavefront sensor is a Shack-Hartmann wavefront sensor, and the combined wavefront distortion information includes low-layer wavefront distortion information and high-layer wavefront distortion information. The high-layer wavefront distortion information is an unknown quantity and is also a quantity that needs to be calculated in subsequent steps.

[0074] Furthermore, steps S221 and S222 are both prior art and thus will not be described in detail herein.

[0075] S3. Construct an atmospheric turbulence three-dimensional reconstruction algorithm based on the results of atmospheric turbulence stratification measurements.

[0076] Among them, S3 specifically includes the following steps:

[0077] S31. Using the same atmospheric turbulence stratification model, the low-level guide star and the high-level guide star are used together to divide the atmosphere into a first region and a second region.

[0078] Specifically, in this embodiment, see Figure 4 , Figure 4 The three parallel lines shown in the figure represent the upper boundary of the high layer, the upper boundary of the low layer and the lower boundary of the low layer from top to bottom respectively. The line segment og represents sub-aperture 1, the line segment ow represents sub-aperture 2, and the vertex h of Δhgw represents the low-layer star guide and the high-layer star guide, that is, the low-layer star guide and the high-layer star guide are in a shared state at this time. The left side of the line segment oh is the first area, and the right side is the second area.

[0079] S32. Utilize the low-level star guide to detect the low-level wavefront distortion of the first region and the second region, and utilize the high-level star guide to detect the combined wavefront distortion of the first region and the second region.

[0080] Specifically, in this embodiment, the low-level wavefront distortion of the first region and the second region is the wavefront distortion of the low-level echo signal of the first region and the wavefront distortion of the low-level echo signal of the second region, and the combined wavefront distortion of the first region and the second region is the wavefront distortion of the high-level echo signal of the first region and the wavefront distortion of the high-level echo signal of the second region. In two adjacent layers of atmospheric turbulence in the same region, the wavefront distortion caused by the high-level atmospheric turbulence includes the wavefront distortion caused by the low-level atmospheric turbulence, the low-level wavefront distortion is the wavefront distortion caused only by the low-level, and the high-level wavefront distortion is the wavefront distortion caused only by the high-level. That is to say, in the same region, the combined wavefront distortion using high-level star detection is the wavefront distortion caused by both the low-level and high-level, and the combined wavefront distortion using high-level star detection includes the low-level wavefront distortion using low-level star detection.

[0081] Furthermore, this step is conducive to realizing the tomographic detection of the entire atmospheric disturbance and improving the accuracy and speed of detecting the three-dimensional atmospheric disturbance. It also provides a theoretical basis for the subsequent establishment of a group of wavefront distortion equations to calculate the high-level wavefront distortion.

[0082] S33, establishing a group of wavefront distortion equations, and bringing the low-level wavefront distortion and the combined wavefront distortion into the group of wavefront distortion equations to calculate the high-level wavefront distortion of the first region and the second region.

[0083] Specifically, in this embodiment, the wavefront distortion equations satisfy the following relationship:

[0084]

[0085] Where Ψ1 is the combined wavefront distortion of the first region, Ψ2 is the combined wavefront distortion of the second region, a1 and b1 are calculation coefficients, Ψ 11 is the high-level wavefront distortion of the first region, Ψ 21 is the low-level wavefront distortion of the first region, Ψ 12 is the high-level wavefront distortion of the second region, Ψ 22 is the low-level wavefront distortion of the second region.

[0086] More specifically, wg is the subaperture diameter, h0 is the star-introduction height, that is, Figure 4 The distance between the midpoint h and the ground, k1 and k2 are proportional coefficients, and the values ​​of k1 and k2 need to be determined according to the actual conditions of the low-level and high-level positions. In this embodiment, the values ​​of k1 and k2 are 1. Since in the same area, the high-level wavefront distortion includes the low-level wavefront distortion, and the low-level wavefront distortion and the combined wavefront distortion can be directly detected by using the low-level and high-level star guides, that is, Ψ1, Ψ2, Ψ 21 and 22 It is known that Ψ can be obtained accurately and quickly through the wavefront distortion equations. 11 and 12 , which can improve the accuracy and speed of detecting three-dimensional atmospheric disturbances.

[0087] Furthermore, in the traditional three-dimensional restoration algorithm, the two equations of the wavefront distortion equation group are related to four unknowns. In order to obtain a unique solution, it is necessary to establish a new equation, which requires signals from other directions, that is, more guide stars are needed. However, even if there are more guide stars, new unknowns will be introduced when establishing the new equation. Some equations in the given equation group are linearly related, and the entire equation is a singular group, resulting in a "morbid" problem in the projection equation, which seriously affects the accuracy of wavefront reconstruction. The atmospheric turbulence three-dimensional reconstruction algorithm provided by the present invention does not have these problems. Even if the atmospheric turbulence is divided into n layers (n>2), the wavefront distortion caused by each layer of atmospheric turbulence can be easily deduced from the low layer to the high layer according to the relationship provided in this step.

[0088] S4. Using the atmospheric turbulence three-dimensional reconstruction algorithm to obtain three-dimensional wavefront distortion information of atmospheric turbulence.

[0089] Specifically, in this embodiment, according to steps S31, S32 and S33, the low-level wavefront distortion of the first area and the second area, the combined wavefront distortion of the first area and the second area, and the high-level wavefront distortion of the first area and the second area can be obtained, that is, the three-dimensional wavefront distortion information of atmospheric turbulence.

[0090] It should be noted that, in some cases, the actions described in the specification can be performed in a different order and still achieve the desired results. In this embodiment, the order of steps given is only to make the embodiment appear clearer and easier to explain, rather than to limit it.

[0091] In an alternative embodiment, see Figure 5 The present invention also provides an atmospheric turbulence three-dimensional wavefront detection system, which uses an atmospheric turbulence three-dimensional wavefront detection method provided by the present invention. The system includes a light return model construction device A1, a turbulence stratification measurement device A2 and a three-dimensional wavefront detection device A3.

[0092] The light return model building device A1 is used to build a microsecond laser pulse light return model.

[0093] Specifically, in this embodiment, the light return model building device A1 specifically executes the content described in step S1, which will not be described in detail here.

[0094] The turbulence stratification measurement device A2 is used to perform atmospheric turbulence stratification measurement using a wavefront sensor based on the microsecond laser pulse return light model.

[0095] Specifically, in this embodiment, the turbulence stratification measuring device A2 includes a Shack-Hartmann wavefront sensor, and the turbulence stratification measuring device A2 is connected to the return light model building device A1 via a data line, and the turbulence stratification measuring device A2 specifically performs the content described in step S2.

[0096] The three-dimensional wavefront detection device A3 is used to construct an atmospheric turbulence three-dimensional reconstruction algorithm based on the results of atmospheric turbulence stratification measurement; and to obtain three-dimensional wavefront distortion information of atmospheric turbulence using the atmospheric turbulence three-dimensional reconstruction algorithm.

[0097] Specifically, in this embodiment, the three-dimensional wavefront detection device A3 is connected to the turbulence stratification measurement device A2 via a data line, and the three-dimensional wavefront detection device A3 specifically performs the contents described in steps S3 and S4.

[0098] In summary, the method provided by the present invention is based on the measurement of atmospheric turbulence stratification by microsecond pulsed laser, and the technology is combined with adaptive optical wavefront detection to realize the disturbance detection of atmospheric turbulence at various heights. At the same time, the method provided by the present invention also performs three-dimensional reconstruction of atmospheric turbulence based on the measurement of atmospheric turbulence stratification, so as to break through the problems that the traditional three-dimensional detection technology of atmospheric turbulence is limited by the singular values ​​of the reconstruction matrix under integral detection and the high calculation delay, which is conducive to improving the accuracy and speed of the MCAO system in detecting three-dimensional disturbances of the atmosphere, and lays a solid foundation for large-aperture telescopes to achieve large-field high-resolution imaging. In addition, the system provided by the present invention not only has the same advantages as the present invention, but also can improve the efficiency of three-dimensional wavefront detection of atmospheric turbulence, and lays a solid foundation for large-aperture telescopes to achieve large-field high-resolution imaging.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for detecting three-dimensional wavefront of atmospheric turbulence, characterized in that: The steps include: Constructing an atmospheric turbulence stratification model, wherein the atmospheric turbulence stratification model includes a low layer and a high layer; Determine the pulse laser period, and then set a plurality of pulses within the pulse laser period according to the atmospheric turbulence stratification model to obtain a laser pulse emission model; The laser pulse emission model includes a low-level pulse and a high-level pulse. When the laser pulse emission model is used, the low-level pulse is emitted first and then the high-level pulse is emitted in one pulse laser cycle. Acquire the laser pulse return model according to the atmospheric turbulence stratification model and the laser pulse emission model; The laser pulse echo model includes two echo signals, a low-layer echo signal and a high-layer echo signal. The laser pulse emission time is used as the timing origin. Within one pulse laser cycle, the echo time period of the low-layer echo signal and the echo time period of the high-layer echo signal respectively satisfy the following relationship: in, is the return light time period of the low-level echo signal, is the light return time period of the high-level echo signal, and , is the thickness of the lower layer, b is the distance between the lower boundary of the higher layer and the ground, c is the speed of light, d is the distance between the upper boundary of the higher layer and the ground, is the low-level pulse width, is the time interval between the low-level pulse and the high-level pulse, is the high-level pulse width, T is the pulse laser period; Measuring atmospheric turbulence stratification using a time-gated wavefront sensor based on a microsecond laser pulse echo model; The microsecond laser pulse light return model includes the laser pulse emission model and the laser pulse light return model; The atmosphere is divided into a first region and a second region by sharing the low-level guide star and the high-level guide star in the same atmospheric turbulence stratification model; Using the low-level star guide to detect low-level wavefront distortions in the first region and the second region, and using the high-level star guide to detect combined wavefront distortions in the first region and the second region; A wavefront distortion equation group is established, and the low-level wavefront distortion and the combined wavefront distortion are brought into the wavefront distortion equation group to calculate the high-level wavefront distortion of the first region and the second region, wherein the wavefront distortion equation group satisfies the following relationship: in, is the combined wavefront distortion of the first region, is the combined wavefront distortion of the second region, is the subaperture diameter, is the star-guiding altitude, and is the proportionality coefficient, is the wavefront distortion of the high-rise in the first region, b is the distance between the lower boundary of the high-rise and the ground, d is the distance between the upper boundary of the high-rise and the ground, is the low-level wavefront distortion of the first region, is the high-level wavefront distortion of the second region, is the low-level wavefront distortion of the second region; The three-dimensional wavefront distortion information of atmospheric turbulence is obtained by using the atmospheric turbulence three-dimensional reconstruction algorithm.

2. The atmospheric turbulence three-dimensional wavefront detection method according to claim 1, characterized in that: The method of measuring atmospheric turbulence stratification using a time-gated wavefront sensor based on a microsecond laser pulse return model comprises the following steps: According to the laser pulse emission model, laser pulses are emitted into the atmosphere to generate low-level star guides and high-level star guides, and the low-level echo signals and the high-level echo signals are generated; The time-gated wavefront sensor is used to sample the echo signal, thereby acquiring wavefront information of different turbulent layers.

3. The atmospheric turbulence three-dimensional wavefront detection method according to claim 2, characterized in that: The sampling of the echo signal using the time-gated wavefront sensor to obtain the wavefront information of different turbulence layers comprises the following steps: The time-gated wavefront sensor is used to sample the echo signal using a Shack-Hartmann sampling method to obtain a low-level echo sampling signal and a high-level echo sampling signal; The low-layer echo sampling signal is used to obtain low-layer wavefront distortion information, and the high-layer echo sampling signal is used to obtain combined wavefront distortion information.

4. A three-dimensional wavefront detection system for atmospheric turbulence, the system using a three-dimensional wavefront detection method for atmospheric turbulence according to any one of claims 1 to 3, characterized in that: include: A light return model construction device, wherein the light return model construction device is used to construct an atmospheric turbulence stratification model, wherein the atmospheric turbulence stratification model includes a low layer and a high layer; Determine the pulse laser period, and then set a plurality of pulses within the pulse laser period according to the atmospheric turbulence stratification model to obtain a laser pulse emission model; The laser pulse emission model includes a low-level pulse and a high-level pulse. When the laser pulse emission model is used, the low-level pulse is emitted first and then the high-level pulse is emitted in one pulse laser cycle. Acquire the laser pulse return model according to the atmospheric turbulence stratification model and the laser pulse emission model; The laser pulse echo model includes two echo signals, a low-layer echo signal and a high-layer echo signal. The laser pulse emission time is used as the timing origin. Within one pulse laser cycle, the echo time period of the low-layer echo signal and the echo time period of the high-layer echo signal respectively satisfy the following relationship: in, is the return light time period of the low-level echo signal, is the light return time period of the high-level echo signal, and , is the thickness of the lower layer, b is the distance between the lower boundary of the higher layer and the ground, c is the speed of light, d is the distance between the upper boundary of the higher layer and the ground, is the low-level pulse width, is the time interval between the low-level pulse and the high-level pulse, is the high-level pulse width, T is the pulse laser period; A turbulence stratification measuring device, wherein the turbulence stratification measuring device is used to measure atmospheric turbulence stratification using a wavefront sensor based on the microsecond laser pulse return light model; The microsecond laser pulse light return model includes the laser pulse emission model and the laser pulse light return model; A three-dimensional wavefront detection device, wherein the three-dimensional wavefront detection device is used to share a low-level guide star and a high-level guide star in the same atmospheric turbulence stratification model to divide the atmosphere into a first region and a second region; Using the low-level star guide to detect low-level wavefront distortions in the first region and the second region, and using the high-level star guide to detect combined wavefront distortions in the first region and the second region; A wavefront distortion equation group is established, and the low-level wavefront distortion and the combined wavefront distortion are brought into the wavefront distortion equation group to calculate the high-level wavefront distortion of the first region and the second region, wherein the wavefront distortion equation group satisfies the following relationship: in, is the combined wavefront distortion of the first region, is the combined wavefront distortion of the second region, is the subaperture diameter, is the star-guiding altitude, and is the proportionality coefficient, is the wavefront distortion of the high-rise in the first region, b is the distance between the lower boundary of the high-rise and the ground, d is the distance between the upper boundary of the high-rise and the ground, is the low-level wavefront distortion of the first region, is the high-level wavefront distortion of the second region, is the low-level wavefront distortion of the second region; The three-dimensional wavefront distortion information of atmospheric turbulence is obtained by using the atmospheric turbulence three-dimensional reconstruction algorithm.

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