Method for evaluating adaptive optics correction ability of atmospheric turbulence layering on ground layer

Abstract

The application discloses a method for evaluating self-adaptive optical ground layer GLAO layer correction ability of atmospheric turbulence. The method comprises the following steps: obtaining wavefront phase statistical information after GLAO system correction according to GLAO correction requirement of atmospheric turbulence; obtaining wavefront distortion phase statistical information without adaptive optical system correction from a telescope system; and obtaining GLAO layer correction efficiency through the change of wavefront phase statistical information before and after correction. By using the application, the GLAO layer correction ability of atmospheric turbulence can be evaluated, the effective correction height range of the GLAO system can be determined, and the correction performance of the large field of view GLAO system can be optimized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of adaptive optics, and particularly relates to a method for evaluating the atmospheric turbulence layering correction capability of ground-layer adaptive optics. BACKGROUND

[0002] Ground-layer adaptive optics (GLAO) has now become an important technology for ground-based large-aperture telescopes to achieve high-resolution imaging in a large field of view. GLAO detects the wavefront aberration caused by ground-layer atmospheric turbulence through multi-guide-star detection, and controls a single deformable mirror conjugated to the vicinity of the pupil to compensate and correct the ground-layer turbulence wavefront aberration, thereby achieving high-resolution imaging of a large-aperture telescope in a large field of view in the angular component. Because the atmospheric turbulence that GLAO needs to correct has a continuous distribution, the correction capability of GLAO for atmospheric turbulence at different heights is also a continuous change process. Evaluating the atmospheric turbulence layering correction capability of GLAO can help us analyze the effective degree of GLAO correction for turbulence at different heights, determine the effective correction height range of the GLAO system itself, and optimize and improve the performance of the GLAO system.

[0003] At present, the evaluation method of the atmospheric turbulence correction capability of GLAO includes the method given by Rigaut, which is to calculate the height range of the atmospheric turbulence that the GLAO system can effectively correct. RIGAUT. Ground Conjugate Wide Field Adaptive Optics for the ELTs;proceedings of the Beyond Conventional Adaptive Optics, Venice, F, 2001 [C].), and Tokovinin divided the height range of atmospheric turbulence corrected by GLAO system (TOKOVININ A. Seeing improvement with ground-layer adaptive optics [J]. Publications of the Astronomical Society of the Pacific, 2004, 116(824): 941-51.). The first method roughly gives the height that can be corrected by GLAO system, but its determination of the effective height range of GLAO system depends on the atmospheric turbulence intensity. The second method divides the atmospheric turbulence corrected by GLAO into regions, but its determination of the effective height range of GLAO system depends on the atmospheric turbulence intensity and the imaging wavelength. Moreover, the above two methods cannot evaluate the GLAO correction ability of atmospheric turbulence layering. According to the above background, the current evaluation method of GLAO correction ability of atmospheric turbulence cannot give the effective height range of GLAO system itself, and cannot evaluate the GLAO correction ability of atmospheric turbulence layering. SUMMARY

[0004] In order to evaluate the GLAO correction ability of atmospheric turbulence layering and determine the effective height range of GLAO system itself, the present application provides an evaluation method of GLAO correction ability of atmospheric turbulence layering.

[0005] The technical scheme adopted by the present application is as follows: an evaluation method of ground layer adaptive optics (GLAO) correction ability of atmospheric turbulence layering, which evaluates the GLAO correction ability of atmospheric turbulence layering by defining the GLAO correction efficiency of different height atmospheric turbulence, and comprises the following steps:

[0006] Step (1): According to the GLAO correction requirement of atmospheric turbulence, obtain the wavefront phase statistical information corrected by the GLAO system.

[0007] Step (2): Obtain the wavefront distortion phase statistical information not corrected by the adaptive optics system from the telescope system.

[0008] Step (3): Obtain the GLAO layer correction efficiency by the change of wavefront phase statistical information before and after correction.

[0009] Further, in step (1), the wavefront phase statistical information after the GLAO system correction can be derived from: the wavefront phase information after correction in the actual GLAO system, the wavefront phase information after correction obtained by numerical simulation, and the wavefront phase information after correction calculated in theoretical analysis. The wavefront phase statistical information forms include but are not limited to: the root mean square of the wavefront phase, the structure function of the wavefront phase.

[0010] In step (2), the wavefront distortion phase statistical information obtained from the telescope system without adaptive optical system correction can be derived from: the wavefront phase information without adaptive optical system correction in the telescope system, the wavefront phase information without correction obtained by numerical simulation, and the wavefront phase information without correction calculated in theoretical analysis. The wavefront distortion phase statistical information forms include but are not limited to: the root mean square of the wavefront phase, the structure function of the wavefront phase.

[0011] In step (3), the GLAO layer correction efficiency is as follows:

[0012]

[0013] Wherein, Φ ∈ is the wavefront phase statistical information of a specific turbulence layer after GLAO system correction, is the wavefront distortion phase statistical information of a specific turbulence layer without adaptive optical system correction. The GLAO layer correction efficiency is not affected by the imaging wavelength and the turbulence intensity and distribution, and depends on the correction ability of the GLAO system itself to the specific layer turbulence.

[0014] The present application is expected to achieve the beneficial effects:

[0015] (1) The GLAO layer correction ability of the present application can be evaluated;

[0016] (2) The effective correction height range of the GLAO system itself can be determined by the present application, which will not be affected by the wavelength and the turbulence intensity and distribution, and depends on the system itself;

[0017] (3) The GLAO system correction performance can be further optimized by using the present application;

[0018] The present application does not need complex hardware conditions. The present application can be realized by numerical simulation on a computer. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a flow chart of the present application, a method for evaluating the adaptive optical layer of the ground layer to the atmospheric turbulence layer correction ability.

[0020] Figure 2This is a framework diagram of a specific implementation example of the evaluation method for the ability of surface layer adaptive optics to correct atmospheric turbulence stratification according to the present invention.

[0021] Figure 3 The results were used to calculate the GLAO layer correction efficiency at 16 different heights after averaging across the entire field of view and pupil plane. Detailed Implementation

[0022] The invention will be further explained below with reference to the illustrative figures and specific implementations.

[0023] like Figure 1 The flowchart shown is a method for evaluating the ability of surface layer adaptive optics to correct atmospheric turbulence stratification according to the present invention. The method quantifies the ability of GLAO to correct atmospheric turbulence at different layer heights by defining GLAO layer correction efficiency. The method includes the following steps:

[0024] Step (1): Based on the GLAO's requirement for atmospheric turbulence correction, obtain the wavefront phase statistics after correction by the GLAO system.

[0025] Step (2): Obtain wavefront distortion phase statistics from the telescope system without adaptive optics correction.

[0026] Step (3): Obtain the GLAO layer correction efficiency by measuring the changes in wavefront phase statistics before and after correction.

[0027] Specific implementation examples: such as Figure 2 The diagram shown is a framework example of a specific implementation of the method for evaluating the ability of surface layer adaptive optics to correct atmospheric turbulence stratification according to the present invention. The parameters of a 1-meter telescope's GLAO system are used as simulation input parameters, as shown in Table 1.

[0028] Table 1 Parameters of a 1-meter telescope GLAO system

[0029]

[0030] The process of substituting the GLAO system parameters into the GLAO linear system spatial frequency filtering model in steps (1) and (2) to obtain the structure function of the telescope pupil phase is as follows:

[0031] The relationship between the uncorrected and corrected power spectral densities is established by G(f), where f represents the spatial frequency, as shown below:

[0032] W ∈ (f)=W Φ (f)|G(f)| 2 (3)

[0033] Where, |G(f)| 2The function W ∈ (f) represents the residual power spectral density, W Φ (f) represents the atmospheric power spectral density. The structure function of the telescope pupil phase is derived from the Wiener-Khintchine theorem:

[0034] D ∈ (r) = ∫{1 - cos[2π(f · r)]}W ∈ (f) df (4)

[0035] where W ∈ (f) and W Φ (f) are given by the superposition of several turbulent layers, i turbulent layers with the von Karman phase power spectrum, as follows:

[0036]

[0037] where r 0,i is the Fried constant of each layer, where is the integral of each turbulent layer, λ is the imaging wavelength, and L0is the outer scale of turbulence.

[0038] Combining the previous equations with the ETF, the final residual structure function of the telescope pupil phase D ∈ is obtained as follows:

[0039]

[0040] where D i (r) is called the standard structure function:

[0041]

[0042] The corresponding ETF for K guide stars is as follows:

[0043]

[0044] where a is the angular coordinate of the target with respect to the guide stars, a k is the angular coordinate of the guide star position. γ represents the relationship between the diameter of the sampling area of the guide star at height H and the pupil sampling area at height h turbulent layer, γ = 1 in the case of natural guiding star. R(f) here describes the smoothing produced by the DM, if f ≤ 2 / d, then R(f) = 1. Otherwise R(f) = 0. w k is the normalized correction weight of the guide star.

[0045] In step (3), the change of the structure function of the telescope pupil phase before and after the correction is used to measure the change of the correction degree of GLAO to a certain layer of the turbulence layer, so as to define the GLAO layer correction efficiency. The defined GLAO layer correction efficiency is in the following form:

[0046] At a certain height h i , the correction efficiency of the atmospheric turbulence of the layer at the position r is in the following form:

[0047]

[0048] The formula (3), (4), (6) is substituted into (7) to obtain the following formula:

[0049]

[0050] Wherein, |G i (f)| 2 represents the ETF of GLAO of the atmospheric turbulence of the i layer.

[0051] Sampling points are taken at each 200m height in the height range of 0-3000m starting from 0m, and there are 16 sampling points, that is, 16 different layer height atmospheric turbulences. Then, the GLAO layer correction efficiencies of 16 different heights after the full field of view and full pupil average are calculated, and the results are shown in Figure 3 . It can be seen that the GLAO layer correction efficiency reflects the effective degree of correction of GLAO system to atmospheric turbulence at different heights, and clearly evaluates the layer correction ability of GLAO to atmospheric turbulence. With the layer correction efficiencies of GLAO at different heights, the effective correction height range of GLAO system itself can be determined. Through the form of formula (10), it can be seen that the GLAO layer correction efficiency is not affected by the imaging wavelength and the turbulence intensity and distribution.

[0052] The above is only a specific embodiment of the present application, and the parts not described in detail are the known technology in the art. However, the protection scope of the present application is not limited to this, any person skilled in the art can understand the replacement or reduction within the technical range disclosed by the present application, which should be covered in the inclusive scope of the present application, therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for evaluating the adaptive optical correction ability of the ground layer to atmospheric turbulence stratification, characterized in that, The method realizes evaluation of the GLAO layer correction ability by defining the correction efficiency of GLAO to different atmospheric turbulence layer height, and comprises the following steps: Step (1): obtaining wavefront phase statistical information after correction by GLAO according to the correction requirement of GLAO to atmospheric turbulence; Step (2): obtaining wavefront distortion phase statistical information without correction by adaptive optical system from a telescope system; Step (3): obtaining GLAO layer correction efficiency through the change of wavefront phase statistical information before and after correction; The GLAO layer correction efficiency is in the following form: （1） wherein, is the statistical information of the wavefront phase of the specific turbulent layer after the GLAO system correction, is the statistical information of the wavefront distortion phase of the specific turbulent layer without the adaptive optical system correction, the GLAO layer correction efficiency is not affected by the imaging wavelength and the turbulence intensity and distribution, and depends on the correction ability of the GLAO system itself to the specific layer turbulence.

2. The method according to claim 1, wherein, In step (1), the wavefront phase statistical information after correction by GLAO is from: actual GLAO system wavefront phase information after correction, numerical simulation obtained wavefront phase information after correction, and theoretical analysis calculated wavefront phase information after correction; the wavefront phase statistical information form includes wavefront phase root mean square and wavefront phase structure function.

3. The method of claim 1, wherein the method is characterized by: In step (2), the wavefront distortion phase statistical information without correction by adaptive optical system from a telescope system is from: telescope system wavefront phase information without correction by adaptive optical system, numerical simulation obtained wavefront phase information without correction, and theoretical analysis calculated wavefront phase information without correction; the wavefront distortion phase statistical information form includes: wavefront phase root mean square and wavefront phase structure function.

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