Aperture synthesis method

Abstract

The present invention provides an aperture synthesis method, comprising the following steps: S1, using a polarization beam splitter to split incident light carrying information about an observed target into a reference beam and a probe beam; S2, performing phase detection on the incident light; S3, performing aperture synthesis using the phase information and light intensity information of each sub-aperture to holographically reconstruct the observed target; S2 and S3 can be performed simultaneously. This method effectively solves the problem of difficulty in obtaining phase information of the observed target during large-field-of-view, high-resolution astronomical imaging, achieves sub-aperture synthesis, and effectively improves phase detection accuracy, while also enhancing the signal-to-noise ratio and visibility of coherent detection.

Description

Technical Field

[0001] The present invention relates to the technical field of astronomical observation, and in particular provides an aperture synthesis method based on a coherent synthetic aperture telescope system. Background Art

[0002] As humanity's exploration of outer space continues to deepen, the habitability of exoplanets and the presence of life have become important research areas. Currently, one of the primary methods for achieving high-contrast direct detection of exoplanets is optical interferometry. Compared to ground-based observations, space-based interferometry offers advantages such as the ability to obtain high-resolution images unaffected by atmospheric interference and significantly broaden the wavelength band for exoplanet observations. Therefore, based on the scientific needs and technical challenges of direct detection of exoplanets, as well as the development of space-based interferometer technologies, spatially distributed synthetic aperture optical interferometry has become a highly promising method for direct detection of exoplanets.

[0003] However, traditional optical imaging platforms are limited by the size of the optical lens aperture, making it difficult to achieve the imaging resolution required for accurate detection of distant targets. Because single-aperture systems face numerous technical and economic challenges, multi-aperture systems have gained increasing attention in the last century to further enhance telescope observation capabilities. Synthetic apertures can effectively reduce telescope size and achieve super-resolution imaging. However, during the synthetic aperture process, phase information of the observed target is difficult to obtain, and the information obtained often has large errors, making it difficult to achieve holographic reconstruction of the observed target. Summary of the Invention

[0004] To solve the above problems, the present invention provides an aperture synthesis method, which mainly obtains phase information by performing spectroscopic processing on the light reflected from the observation target, and then performs aperture synthesis on the sub-apertures to achieve holographic reconstruction of the observation target.

[0005] The pore size synthesis method provided by the present invention comprises the following steps:

[0006] S1. Using a polarization beam splitter, the incident light carrying information of the observed target is split into a reference beam and a detection beam;

[0007] S2. performing phase detection on the incident light;

[0008] S3. Perform aperture synthesis using the phase information and light intensity information of each sub-aperture to holographically reconstruct the observed target:

[0009] The simultaneous execution of S2 and S3 does not affect the aperture synthesis.

[0010] Preferably, the polarization splitting element is a beam splitting prism.

[0011] Preferably, the reference beam is projected onto the first photodetector through a microlens array, and the reference wavefront is obtained by the first photodetector.

[0012] Preferably, the phase detection method adopts a physical detection process as follows: the detection beam is injected into a single-mode optical fiber, and then the detection beam and the reference beam are interfered to obtain interference fringes, and phase information is obtained through the interference fringes.

[0013] Preferably, the phase detection method adopts a digital detection process as follows: the detection beam is projected onto a stepped optical element to achieve regional defocusing, and the stepped optical element is used to perform field-of-view defocus modulation, and then reflected onto a second photodetector to obtain phase information and light intensity information.

[0014] Preferably, the aperture synthesis adopts a physical synthesis process as follows: the incident light of at least two coherent synthetic aperture telescopes is transmitted into a single-mode optical fiber for coupling, and then the coupled light beams are interfered, and the holographic reconstruction of the observed target is achieved through the obtained interference fringes, that is, the sub-apertures are synthesized.

[0015] Preferably, the aperture synthesis adopts a digital synthesis process as follows: the phase information and light intensity information of the incident light of at least two coherent synthetic aperture telescopes are directly used to holographically reconstruct the observed target, that is, the sub-apertures are aperture synthesized. The synthesized aperture is a circular aperture, and the light field parameters of the circular aperture are calculated as follows:

[0016] Amplitude transmittance t A (ξ,η):

[0017]

[0018] Wherein, N represents the number of subapertures, ξ and η represent the frequency coordinates of the incident light, circ represents the circular function, (ξ i ,η i ) represents the center coordinate of the i-th sub-aperture, φ i represents the phase offset of the i-th subaperture, D represents the aperture length of the subaperture, e represents the natural base which is a constant, j is the imaginary unit, and δ represents the pulse function;

[0019] Complex Amplitude Distribution I A :

[0020]

[0021] Wherein, λ represents the wavelength of the incident light, (ρ i ,δ i ) represents the polar coordinate position of the array formed by the sub-aperture, J1 represents the first-kind Bessel function, and θ represents the incident angle of the incident light.

[0022] Preferably, the stepped optical element is a stepped prism.

[0023] A synthetic aperture telescope system uses the aperture synthesis method.

[0024] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0025] 1. The present invention effectively solves the problem of difficulty in obtaining phase information of the observed target, realizes the synthesis of sub-apertures, realizes holographic reconstruction of the observed target and calculates the light field parameters of the circular aperture.

[0026] 2. The present invention effectively improves the phase detection accuracy and, at the same time, can also improve the signal-to-noise ratio and visibility of coherent detection.

[0027] 3. The present invention can also be used for holographic detection of dome seeing and mirror seeing, and tomographic detection of wavefront and mirror seeing of a coherent synthetic aperture telescope system can be achieved through integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flow chart of a synthetic aperture method provided according to an embodiment of the present invention;

[0029] Figure 2 This is a diagram of an aperture synthesis structure using a physical synthesis method provided in Example 1 of the present invention;

[0030] Figure 3 This is a diagram of an aperture synthesis structure using a physical synthesis method provided in Example 2 of the present invention;

[0031] Figure 4 This is an aperture synthesis structure diagram using a digital synthesis method provided in Example 3 of the present invention.

[0032] The reference numerals in the first embodiment include: polarization beam splitter 1, reference beam 2, detection beam 3, microlens array 4, first photodetector 5, cylindrical lens 6, prism 7, camera 8, piezoelectric ceramic 9;

[0033] The reference numerals in the second embodiment also include: coupler 10, spectrometer 11;

[0034] The reference numerals in the third embodiment also include: a detection beam 3 ′, a stepped optical element 12 , and a second photodetector 13 . DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, identical modules are denoted by identical reference numerals. In the case of identical reference numerals, their names and functions are also identical. Therefore, their detailed description will not be repeated.

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0037] Figure 1 A flow chart of a synthetic aperture method provided according to an embodiment of the present invention is shown.

[0038] Figure 2 The system structure of aperture synthesis using physical synthesis method provided in the first embodiment of the present invention is shown.

[0039] like Figure 1 、 Figure 2 As shown, the first embodiment adopts a physical detection method to obtain phase information, and then synthesizes the aperture through a physical method. The specific steps are as follows:

[0040] S1. Laser light is irradiated onto the surface of the observation target and reflected. The reflected light is converged and shrunk by a lens group and enters each coherent synthetic aperture telescope. The incident light carrying information about the observation target is split into a reference beam 2 and a detection beam 3 by a polarization beam splitter 1. The polarization beam splitter 1 uses a beam splitter prism. The reference beam 2 is projected onto a first photodetector 5 through a microlens array 4, and a reference wavefront is obtained by the first photodetector 5.

[0041] S2, the detection beam 3 is injected into the single-mode optical fiber, and then the detection beam 2 interferes with the reference wavefront to obtain interference fringes. Phase information is obtained through the interference fringes. Phase information can also be obtained through methods such as four-step shifting or shearing interference.

[0042] S3. Perform circular aperture synthesis on the detection beam 3 transmitted by each coherent synthetic aperture telescope through the single-mode optical fiber, that is, perform circular aperture synthesis on the phase information and light intensity information of the sub-aperture. The detection beam 3 is emitted from the single-mode optical fiber and pressed side by side. The detection beam 3 is injected into the cylindrical lens 6 for line convergence, and then is color-scattered by the prism 7 to the camera 8 to obtain the spectrum and the intensity and phase information of the incident light. Holographic reconstruction of the observed target is performed based on the light intensity and phase information.

[0043] It should be noted that: in the first embodiment, when the sub-apertures are synthesized, a piezoelectric ceramic 9 is provided on at least one single-mode optical fiber for transmitting the detection beam 3. The piezoelectric ceramic 9 is used for phase modulation to facilitate the acquisition of phase information of the incident light.

[0044] Figure 3 The structure of an aperture synthesis system using a physical synthesis method provided in accordance with the second embodiment of the present invention is shown.

[0045] like Figure 1 、 Figure 3 As shown, the second embodiment adopts a physical detection method to obtain phase information, using a coupler 10 and a spectrometer 11 to obtain a synthetic aperture through a physical method, and the specific steps are as follows:

[0046] S1 and S2 in the second embodiment are the same as S1 and S2 in the first embodiment, and are not described in detail here.

[0047] S3. In the second embodiment, the detection beam 3 transmitted by each coherent synthetic aperture telescope through the single-mode optical fiber is transmitted to the coupler 10 for coupling, and then the coupled beam is transmitted to the spectrometer 11. The spectrometer 11 is used to perform spectral analysis on the coupled beam to obtain information such as the intensity and phase of the incident light, thereby realizing holographic reconstruction of the observed target.

[0048] It should be noted that: in the second embodiment, when the sub-apertures are synthesized, a piezoelectric ceramic 9 is provided on at least one single-mode optical fiber for transmitting the detection beam 3. The piezoelectric ceramic 9 is used for phase modulation to facilitate the acquisition of phase information of the incident light.

[0049] Figure 4 The structure of an aperture synthesis system using a digital synthesis method provided in accordance with the third embodiment of the present invention is shown.

[0050] like Figure 4 As shown, the third embodiment adopts a digital detection method to obtain phase information, and then synthesizes the aperture by a digital method. The specific steps are as follows:

[0051] S1. Laser light is irradiated onto the surface of the observation target and reflected. The reflected light is converged and contracted by a lens group and enters each coherent synthetic aperture telescope. A polarization beam splitter 1 is used to split the incident light carrying information about the observation target into a reference beam 2 and a detection beam 3'. The detection beam 3' here is essentially the same as the detection beam 3 in Examples 1 and 2, except that the beams are directed to different elements. The polarization beam splitter 1 uses a beam splitter prism. The reference beam 2 passes through a microlens array 4 and is projected onto a first photodetector 5, where a reference wavefront is obtained.

[0052] S2. The detection beam 3' in each coherent synthetic aperture telescope is respectively incident on the surface of the stepped optical element 12. The stepped optical element 12 adopts a stepped prism to achieve regional defocusing. The stepped optical element 12 is used to perform field-of-view defocus modulation, and then reflected onto the second photodetector 13 to obtain phase information, and information such as light intensity can also be obtained.

[0053] S3. Based on the phase information and light intensity information obtained by each coherent synthetic aperture telescope, the holographic reconstruction of the observed target is directly performed by calculation, that is, the sub-apertures are aperture synthesized. The synthesized aperture is a circular aperture. The light field parameters of the circular aperture are calculated as follows:

[0054] Amplitude transmittance t A (ξ,η):

[0055]

[0056] Wherein, N represents the number of subapertures, ξ and η represent the frequency coordinates of the incident light, circ represents the circular function, (ξ i ,η i ) represents the center coordinate of the i-th sub-aperture, φ i represents the phase offset of the i-th subaperture, D represents the aperture length of the subaperture, e represents the natural base which is a constant, j is the imaginary unit, and δ represents the pulse function;

[0057] Complex Amplitude Distribution I A :

[0058]

[0059] Where λ represents the wavelength of the incident light, (ρ i ,δ i ) represents the polar coordinate position of the array formed by the sub-aperture, J1 represents the first-kind Bessel function, and θ represents the incident angle of the incident light.

[0060] It should be noted that the coherent synthetic aperture telescope system includes at least two coherent synthetic aperture telescopes, that is, at least two sub-apertures for aperture synthesis.

[0061] When there are enough coherent synthetic aperture telescopes, S2 and S3 in the aperture synthesis method of the present invention can be performed simultaneously.

[0062] The neutron aperture of this method can not only be synthesized into a circular aperture, but is also applicable to apertures of other shapes such as rectangles.

[0063] The present invention can also be used for holographic detection of dome seeing and mirror seeing, and can realize tomographic detection of wavefront and mirror seeing of a coherent synthetic aperture telescope system through integration.

[0064] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0065] The above specific embodiments of the present invention do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for pore synthesis, characterized in that: The following steps are involved: S1. Using a polarization beam splitter, the incident light carrying information about the observed target is split into a reference beam and a detection beam; the reference beam is projected onto a first photodetector through a microlens array, and a reference wavefront is obtained by the first photodetector; S2. performing phase detection on the incident light; S3, performing aperture synthesis based on the phase information and light intensity information of each sub-aperture to holographically reconstruct the observed target; The simultaneous execution of S2 and S3 does not affect the aperture synthesis.

2. The aperture synthesis method according to claim 1, wherein: The polarization beam splitting element adopts a beam splitting prism.

3. The aperture synthesis method according to claim 1, wherein: The phase detection method adopts the following physical detection process: the detection beam is injected into a single-mode optical fiber, and then the detection beam and the reference beam interfere to obtain interference fringes, and phase information is obtained through the interference fringes.

4. The aperture synthesis method according to claim 1, wherein: The phase detection method adopts a digital detection process as follows: the detection beam is projected onto a stepped optical element to achieve regional defocusing, the stepped optical element is used to perform field-of-view defocus modulation, and then reflected onto a second photodetector to obtain phase information and light intensity information.

5. The aperture synthesis method according to claim 3, wherein: The aperture synthesis adopts a physical synthesis process as follows: the incident light of at least two coherent synthetic aperture telescopes is transmitted into a single-mode optical fiber for coupling, and then the coupled light beams are interfered. The holographic reconstruction of the observed target is achieved through the obtained interference fringes, that is, the sub-apertures are synthesized.

6. The aperture synthesis method according to claim 4, wherein: The aperture synthesis adopts a digital synthesis process as follows: the phase information and light intensity information of the incident light of at least two coherent synthetic aperture telescopes are directly used to holographically reconstruct the observed target, that is, the sub-apertures are aperture synthesized. The synthesized aperture is a circular aperture. The light field parameters of the circular aperture are calculated as follows: Amplitude transmittance : ； Wherein, N represents the number of subapertures, and represents the frequency coordinate of the incident light, represents the circular domain function, represents the center coordinate of the i-th subaperture, represents the phase offset of the i-th subaperture, D represents the aperture length of the subaperture, e represents the natural base which is a constant, j is the imaginary unit, represents the impulse function; Complex Amplitude Distribution I A : ； Wherein, λ represents the wavelength of the incident light, represents the polar coordinate position of the array formed by the sub-aperture, J1 represents the first kind of Bessel function, and θ represents the incident angle of the incident light.

7. The aperture synthesis method according to claim 4, wherein: The stepped optical element is a stepped prism.

8. A synthetic aperture telescope system, characterized in that: Utilize the aperture synthesis method according to any one of claims 1 to 7.

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