A large-aperture telescope wavefront curvature sensing method, electronic equipment and computer readable storage medium

Abstract

The application discloses a large-aperture telescope wavefront curvature sensing method, comprising the following steps: obtaining a defocus star point image of single exposure through a sensor defocus; obtaining a phase distribution of the defocus star point image of single exposure; applying defocus to the defocus star point image of single exposure in a reverse direction to obtain a reverse defocus star point image; and obtaining wavefront curvature reconstruction through the phase distribution of the defocus star point image of single exposure and the reverse defocus star point image, so as to realize single-exposure curvature sensing. The application also provides corresponding electronic equipment and a computer readable storage medium.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to a large aperture telescope wavefront curvature sensing method and a computer readable storage medium. BACKGROUND

[0002] The "black hole, dark matter and dark energy, origin of the universe, origin of celestial bodies, origin of cosmic life" is a hot spot in the field of astronomy in recent years. In order to better explore dark matter and dark energy, scientists have put forward higher resolution and imaging quality requirements for the next generation of large aperture and wide field of view telescopes. The increase of the aperture of the telescope can not only effectively improve the resolution of the nearby target, but also increase the light collecting ability of the telescope in a square rule, which can effectively improve the signal-to-noise ratio of the imaging of dark targets and expand the limit of the detection ability, and finally realize the exploration of the more distant universe. Therefore, the large aperture and wide field of view telescope is the key to verify the latest theory of cosmology and increase the academic discourse power in the field of time domain astronomy in the future.

[0003] The curvature sensor was proposed by Roddier in 1988, and its basic principle is to estimate the wavefront curvature change by the light intensity distribution of the pre-focal and post-focal images, and to solve the wavefront information. Since it can meet the specific needs of the large aperture survey active optical photographic survey telescope, it can be used with the same device as the scientific camera, which is convenient for image acquisition and post-maintenance, has the advantages of non-interference, simple structure, good environmental adaptability, stable solution, small aperture obstruction influence and other unique advantages, and has been widely used in the active optical wavefront sensing system of large aperture photographic survey telescope.

[0004] Therefore, the wavefront phase of the large field of view survey telescope system can be solved based on the curvature sensing. As a focal plane wavefront sensing strategy, the other advantage of the curvature sensing is that it can detect the extended target to enhance the imaging characteristics of the system. However, in order to obtain a larger dynamic range and error sensitivity, the existing curvature sensing selects a larger defocus amount, which may affect the correction ability of the closed loop curvature sensing. SUMMARY

[0005] The present application aims to overcome the defects of the prior art, and adopts the following technical solutions:

[0006] On the one hand, the present application provides a large aperture telescope wavefront curvature sensing method. The large aperture telescope wavefront curvature sensing method comprises the steps of:

[0007] S1, obtaining a single exposure defocus star point image by defocusing the sensor;

[0008] S2, obtaining the phase distribution of the single exposure defocus star point image;

[0009] S3, applying defocus to the defocus star image of the single exposure in the opposite direction to obtain an opposite direction defocus star image;

[0010] S4, obtaining the reconstruction of wavefront curvature through the phase distribution of the defocus star image of the single exposure and the opposite direction defocus star image, realizing the curvature sensing of the single exposure.

[0011] In some embodiments, the phase distribution of the defocus star image of the single exposure is obtained through a calculation method of phase recovery.

[0012] In some embodiments, after obtaining the defocus star image of the single exposure through sensor defocus in step S1, the method further comprises the following step:

[0013] S11, judging the defocus star image obtained by the single exposure, if there is no light intensity overlap, then performing step S2.

[0014] In some embodiments, after judging the defocus star image obtained by the single exposure in step S11, if there is light intensity overlap, the method further comprises step S12, selecting the light intensity overlap part, only calculating the non-overlapping part by changing the aperture function aperture, and then performing step S2.

[0015] In some embodiments, after selecting the light intensity overlap part and only calculating the non-overlapping part in step S12, the method further comprises: removing the overlapping part.

[0016] In some embodiments, after obtaining the wavefront parameter, the light intensity distribution of the defocus spot is predicted by using the Fourier optical principle, and compared with the existing light intensity distribution, and iterative correction is performed, and when the residual error is less than a preset value, the iteration is stopped.

[0017] In some embodiments, the defocus star image of the single exposure is obtained by using an internal misalignment type curvature sensor.

[0018] In some embodiments, the internal misalignment type curvature sensor uses two detectors respectively located before and after the focal plane to simultaneously collect defocus images.

[0019] In a second aspect, the present application provides an electronic device comprising a processor and a memory. When the processor executes the computer program stored in the memory, the large aperture telescope wavefront curvature sensing method as described above is realized.

[0020] In a third aspect, the present application provides a computer readable storage medium for storing a computer program, wherein when the computer program is executed by a processor, the large aperture telescope wavefront curvature sensing method as described above is realized.

[0021] From the above technical solutions can be seen, the present application provides a kind of large aperture telescope wavefront curvature sensing method, comprising: by sensor defocus obtains single exposure defocus star point image;Obtain the phase distribution of the single exposure defocus star point image;The single exposure defocus star point image is applied to the defocus in reverse direction, to obtain reverse direction defocus star point image;By the phase distribution of the single exposure defocus star point image and the reverse direction defocus star point image obtains wavefront curvature reconstruction, realizes single exposure curvature sensing.By the implementation of the above steps, since it is not necessary to move sensor, with the characteristics of high efficiency.The large aperture telescope wavefront curvature sensing method provided by the present application can improve the correction ability of curvature sensing, so that the result obtained finally is more accurate, reduces the correction time of entire active optical system, and further improves the observation accuracy of telescope on deep space field, satisfies actual demand.In addition, the present application also provides corresponding electronic equipment and computer readable storage medium for large aperture telescope wavefront curvature sensing method, further makes the above method more practical, and the electronic equipment and computer readable storage medium have corresponding advantages. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 The principle diagram of curvature sensing provided for the embodiments of the present application;

[0024] Figure 2 The flowchart of wavefront curvature reconstruction provided for the embodiments of the present application;

[0025] Figure 3 The flowchart of large aperture telescope wavefront curvature sensing method according to one embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute limitation to the present application.

[0027] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, technologies, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0028] It is to be understood that the terminology "includes", "has", "holds", "contains" and / or similar words in the present application and the appended claims are used inclusively and that one or more of other features, integers, steps, operations, elements, and / or groups thereof can be added and / or deleted.

[0029] It is also to be understood that the terminology "and / or" in the present application and the appended claims, when used in a list of two or more items, covers all possible combinations of the items, including a single one of the items.

[0030] As used in the present application and the appended claims, the terminology "if" can be interpreted as meaning "when" or "upon" or "in response to a determination" or "in response to a detection" depending on the context. Similarly, the phrase "if determined" or "if detected [the described condition or event]" can be interpreted as meaning "upon a determination" or "in response to a determination" or "upon a detection [of the described condition or event]" or "in response to a detection [of the described condition or event]" depending on the context.

[0031] In addition, the terms "first", "second", "third", etc. in the description of the present application and the appended claims are used only to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0032] Reference in the specification to "one embodiment" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "in some embodiments" in various places in the specification are not necessarily all referring to the same embodiment, although it can. The terms "including", "containing", "having" and variations thereof in the specification are meant to encompass the terms "including but not limited to", unless otherwise expressly specified or limited by context.

[0033] The present application aims to overcome the drawbacks of the prior art, with reference to Figure 2 and 3As shown, the present application provides a large aperture telescope wavefront curvature sensing method, comprising the steps of:

[0034] S1, obtaining a defocus star point image of single exposure through sensor defocus;

[0035] S2, obtaining a phase distribution of the defocus star point image of single exposure;

[0036] S3, applying defocus in the opposite direction to the defocus star point image of single exposure to obtain a defocus star point image in the opposite direction;

[0037] S4, obtaining wavefront curvature reconstruction through the phase distribution of the defocus star point image of single exposure and the defocus star point image in the opposite direction, to realize single exposure curvature sensing.

[0038] In some embodiments, the phase distribution of the defocus star point image of single exposure is obtained through a phase recovery calculation method.

[0039] In some embodiments, after obtaining the defocus star point image of single exposure through sensor defocus in step S1, the method further comprises the steps of:

[0040] S11, judging the defocus star point image obtained by single exposure, if there is no light intensity overlap, then performing step S2.

[0041] In some embodiments, after judging the defocus star point image obtained by single exposure in step S11, if there is light intensity overlap, the method further comprises step S12, selecting the light intensity overlap part, only calculating the non-overlapping part by changing the aperture function aperture, and then performing step S2.

[0042] In some embodiments, in step S12, after selecting the light intensity overlap part and only calculating the non-overlapping part, the method further comprises: removing the overlapping part.

[0043] In some embodiments, after obtaining the wavefront parameter, the light intensity distribution of the defocus spot is predicted using the Fourier optical principle, and compared with the existing light intensity distribution, and iterative correction is performed, and when the residual error is less than a preset value, the iteration is stopped.

[0044] In some embodiments, the defocus star point image of single exposure is obtained through an embedded misalignment type curvature sensor.

[0045] In some embodiments, the embedded misalignment type curvature sensor uses two detectors respectively located before and after the focal plane to simultaneously collect defocus images.

[0046] Taking a large-aperture, wide-field-of-view survey telescope with a prime focus as an example, after coarse alignment of the large-aperture prime focus assembly, the wavefront sensor can achieve imaging. Considering the compact optical system, multi-spectral observation, and compact focal plane space of the large-aperture, wide-field-of-view survey telescope, a misaligned curvature sensor is selected as the wavefront sensor. This involves using two misaligned sensors to simultaneously obtain the front-focus and back-focus images of targets in adjacent fields of view by dividing the field of view, which becomes the most feasible option. The prime focus assembly includes a scientific terminal, and the misaligned curvature sensor can be placed inside the scientific terminal. Assuming the illumination intensity is unsaturated, when the prime focus assembly defocuses, the misaligned sensor can estimate the wavefront curvature based on the difference in light intensity distribution on both sides of the defocused area.

[0047] The large-aperture telescope wavefront curvature sensing method provided in the embodiments of the present invention includes: firstly, coarsely aligning the large-aperture principal focus assembly, and then imaging using two misaligned sensors located on both sides of the focal plane; and obtaining a defocused star image from a single exposure by defocusing the sensors.

[0048] After obtaining the out-of-focus star image, its phase distribution is acquired using calculation methods such as phase retrieval. However, due to the effects of large aberrations such as second-order blurring and aperture function, the phase distribution is presented as noise and lacks sensing capability. Therefore, defocusing is applied in the opposite direction to obtain the out-of-focus star image in the opposite direction. Wavefront curvature is reconstructed using the phase distribution of the out-of-focus star image from the single exposure and the out-of-focus star image in the opposite direction, achieving curvature sensing for a single exposure. This method is highly efficient as it does not require moving the sensor.

[0049] In practice, optionally, the out-of-focus star image obtained from a single exposure can be used for calculation. (Reference) Figure 2 and Figure 3 As shown, the specific steps can be as follows:

[0050] S1, obtains a defocused star image from a single exposure by defocusing the sensor;

[0051] S11, judge the out-of-focus star image obtained by the single exposure. If there is no light intensity overlap, proceed to step S2.

[0052] If there is light intensity overlap, step S12 is also included, where the overlapping part of light intensity is selected, and only the non-overlapping part is calculated by changing the aperture function aperture, and then step S2 is performed.

[0053] S2, Obtain the phase distribution of the out-of-focus star image from the single exposure;

[0054] S3, applying defocus to the defocus star point image of the single exposure in the opposite direction to obtain an opposite direction defocus star point image;

[0055] S4, obtaining the reconstruction of the wavefront curvature through the phase distribution of the defocus star point image of the single exposure and the opposite direction defocus star point image, realizing the curvature sensing of the single exposure.

[0056] After the wavefront parameter is obtained, the intensity distribution of the defocus spot can be predicted by using the Fourier optical principle, and compared with the existing intensity distribution, and when the residual error is less than a preset value, the iteration is stopped.

[0057] For the case of overlap, only the non-overlapping part is calculated, and the calculation accuracy of the system is increased by changing the aperture function aperture.

[0058] For the case of intensity overlap, the overlapping part can be removed to realize the iterative calculation of the new aperture function.

[0059] When overlap occurs, the intensity distribution diagrams of two defocus star point images are obtained; then the intensity distribution diagrams of the two defocus star point images are taken as the basis for judgment, the overlapping part is removed, the phase distribution of the selected part is obtained, and the reconstruction of the wavefront information is obtained. Through this method, the correction ability of the curvature sensing can be improved, the result of the wavefront sensing obtained finally is more accurate, the correction time of the whole active optical system is reduced, and the observation accuracy of the telescope on the deep space field is improved, and the actual demand is met.

[0060] Correspondingly, the embodiment of the present application also discloses an electronic device, and the present application provides an electronic device which comprises a processor and a memory. Wherein, the processor realizes the large aperture telescope wavefront curvature sensing method as described above when executing the computer program stored in the memory.

[0061] The more specific process of the above method can refer to the corresponding contents disclosed in the foregoing embodiments, and will not be repeated here.

[0062] Further, the present application provides a computer readable storage medium for storing a computer program, wherein the computer program is executed by a processor to realize the large aperture telescope wavefront curvature sensing method as described above.

[0063] The more specific process of the above method can refer to the corresponding contents disclosed in the foregoing embodiments, and will not be repeated here.

[0064] As for the devices, equipment, storage media disclosed in each embodiment in the specification, since they correspond to the method disclosed in the embodiment, the description is relatively simple, and the related part can be referred to the method part.

[0065] To make the present solution easier to understand, the principle of curvature sensing is described below through specific examples.

[0066] Wavefront curvature sensing is a technology for measuring wavefront based on curvature sensors. The principle on which the measurement is based is as follows: the change in curvature of the wavefront will cause the light intensity distribution of the in-focus image and the out-of-focus image to change correspondingly, and according to this change, the wavefront can be estimated radially, that is, the difference of light intensity along the optical axis is used to establish the estimation of the wavefront curvature, and the wavefront phase information is extracted from the curvature signal by using a corresponding solving method. The principle of measurement is shown in Figure 1 which the part indicated by 2 represents an optical system, and the part indicated by 1 represents an image plane, wherein z represents the optical axis direction, l represents the focal length, and Δz represents the defocus amount. The arrow is the optical axis direction.

[0067] Taking a large-aperture survey telescope in the form of a main focal point as an example, in the camera terminal of the main focal point assembly, a misaligned curvature sensor (which uses two detectors located in front of and behind the focal plane to simultaneously collect out-of-focus images) is built in, the illumination intensity of the light source is unsaturated, the main focal point assembly adjusts the focus, the misaligned curvature sensor is located on one side of the focal plane, and during the process of opening the dome for observation, the defocus amount is gradually adjusted while reducing the level of aberration. According to the transmission equation of the near-field electromagnetic wave, the wavefront information can be solved, as shown in equation (1):

[0068]

[0069] wherein is the intensity, is the phase, is the gradient operator, and the result obtained is the slope, is the Laplace operator, and the result obtained is the curvature. is the coordinate inside the pupil, and δ is the Dirac operator. It can be seen that the result is related to both the slope and the curvature.

[0070] Here, equation (1) is deformed, and the light intensity difference along the optical axis is used instead of the differential , and at the same time, the influence of the edge pixels is ignored to obtain:

[0071]

[0072] The solution of the Poisson equation for equation (2) can be obtained, and then the method of Fourier transform can be used to solve equation (2). Using this theory, the defocus amount z can be analyzed with a certain deviation, and the high-order statistical moments of the out-of-focus image can be analyzed. On the basis of the quantitative analysis of the donut algorithm, the relationship between the high-order statistical moments of the out-of-focus image and the wavefront aberration is tried to be established.

[0073]

[0074]

[0075]

[0076]

[0077] The defocus face positioning problem will affect the wavefront sensing quality, and the current solution is to lock the distance of the defocus amount, that is, to determine the total defocus amount, which is divided into two categories: using diffraction elements and physically locking the distance.

[0078]

[0079]

[0080] In the case of considering the defocus error, the wavefront curvature can be obtained as

[0081]

[0082] It can be seen that the influence caused by inaccurate defocus is δz + +δz - =0

[0083]

[0084]

[0085] The large-aperture telescope wavefront curvature sensing method provided by the application comprises the following steps: obtaining a single-exposure defocus star point image through defocus of a sensor; obtaining a phase distribution of the single-exposure defocus star point image; applying defocus in the opposite direction to the single-exposure defocus star point image to obtain an opposite-direction defocus star point image; and obtaining wavefront curvature reconstruction through the phase distribution of the single-exposure defocus star point image and the opposite-direction defocus star point image to realize single-exposure curvature sensing. Through the above steps, the sensor does not need to be moved, and the method has the characteristics of high efficiency. The large-aperture telescope wavefront curvature sensing method provided by the application can improve the correction ability of curvature sensing, make the finally obtained wavefront sensing result more accurate, reduce the correction time of the whole active optical system, and further improve the observation accuracy of the telescope on the deep space field, thereby meeting the actual demand. In addition, the application also provides corresponding electronic equipment and computer readable storage medium for the large-aperture telescope wavefront curvature sensing method, which further makes the above method more practical, and the electronic equipment and computer readable storage medium have corresponding advantages.

[0086] The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM, flash memory, ROM, electrically programmable ROM (EPROM or EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC.

[0087] In the description of the present application, it is to be understood that the symbols such as numerals, variables, program names and the like mentioned in the embodiments of the present application can be replaced by any other symbols not causing confusion.

[0088] In the description of the present application, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0089] In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include at least one of the features.

[0090] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixed connection, or it can be detachable connection, or it can be integrated; it can be mechanical connection, or it can be electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0091] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature is "over", "above" and "on top of" a second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. A first feature is "under", "below" and "underneath" a second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0092] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and integrated by those skilled in the art without contradiction, under the condition that they do not contradict each other.

[0093] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

[0094] The above-described specific embodiments of the present application do not constitute a limitation on the protection scope of the present application. Any various other corresponding changes and modifications made according to the technical concept of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A method for sensing wavefront curvature in a large aperture telescope, comprising: The method comprises the steps of: S1, obtaining a defocus star point image of a single exposure by sensor defocus; S2, obtaining a phase distribution of the defocus star point image of the single exposure; S3, applying defocus in the opposite direction to the defocus star point image of the single exposure to obtain an opposite direction defocus star point image; S4, obtaining a wavefront curvature reconstruction by the phase distribution of the defocus star point image of the single exposure and the opposite direction defocus star point image to realize single exposure curvature sensing.

2. The large aperture telescope wavefront curvature sensing method according to claim 1, wherein the phase distribution of the defocus star point image of the single exposure is obtained by a phase recovery calculation method.

3. The large aperture telescope wavefront curvature sensing method according to claim 1, wherein after the step S1 of obtaining the defocus star point image of the single exposure by sensor defocus, the method further comprises the step of: S11, judging the defocus star point image obtained by the single exposure, and if there is no light intensity overlap, performing the step S2.

4. The large aperture telescope wavefront curvature sensing method according to claim 3, wherein if there is light intensity overlap in the judgment of the defocus star point image obtained by the single exposure, the method further comprises the step S12 of selecting the light intensity overlap part, calculating only the non-overlapping part by changing the aperture function aperture, and then performing the step S2.

5. The large aperture telescope wavefront curvature sensing method according to claim 4, wherein in the step S12, after selecting the light intensity overlap part and calculating only the non-overlapping part, the method further comprises the step of removing the overlapping part.

6. The large aperture telescope wavefront curvature sensing method according to claim 4, wherein after obtaining the wavefront parameters, the light intensity distribution of the defocus spot is predicted by using the Fourier optical principle, and compared with the existing light intensity distribution, and iterative correction is performed, and the iteration is stopped when the residual error is less than a preset value.

7. The large aperture telescope wavefront curvature sensing method according to claim 1, wherein the defocus star point image of the single exposure is obtained by an internal misplacement type curvature sensor.

8. The large aperture telescope wavefront curvature sensing method according to claim 7, wherein the internal misplacement type curvature sensor uses two detectors located before and after the focal plane to simultaneously collect defocus images. A device comprising a processor and a memory, wherein the processor implements the large aperture telescope wavefront curvature sensing method according to any one of claims 1 to 8 when executing a computer program stored in the memory. A computer program for storing, wherein the computer program is executed by a processor to implement the large aperture telescope wavefront curvature sensing method according to any one of claims 1 to 8. ​ ​ ​ ​ ​ 9. An electronic device, comprising: ​ 10. A computer-readable storage medium, characterized in that, ​

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