Wavefront detection system for dark and weak target under strong sky background

Abstract

The invention relates to the technical field of adaptive optics, and particularly provides a wavefront detection system for a dark and weak target under a strong sky background, the wavefront detection system comprises a Shack-Hartmann wavefront sensor system and a wavefront detection processing unit, the Shack-Hartmann wavefront sensor system carries out wavefront detection on a short wave infrared band of 1.3-1.7 [mu] m, and the wavefront detection processing unit carries out wavefront detection on the short wave infrared band of 1.3-1.7 [mu] m. And the wavefront detection processing unit corrects a sub-aperture image obtained by detection through a weighted self-threshold local contrast algorithm, performs self-threshold operation on pixels in a center unit according to a gray scale ratio weight of the center unit and a background unit of the sub-aperture image, introduces an energy weight to eliminate PNHB noise, and reconstructs a centroid of the sub-aperture image. According to the invention, a Shack-Hartmann wavefront sensor system is applied to a short-wave infrared band, so that a sky background spectrum is effectively blocked, the target brightness is ensured, background light radiation photons received by a detector are reduced to the greatest extent, various noises and background interferences are inhibited by optimizing a threshold algorithm, and the wavefront detection precision is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of adaptive optics, and specifically provides a wavefront detection system for a dark target under a strong skylight background. Background Art

[0002] One of the main applications of ground-based large-aperture optical imaging telescopes is to obtain high-resolution images of space targets. Adaptive optics technology is the core technology of ground-based large-aperture imaging telescopes. It is used to compensate for imaging aberrations caused by atmospheric turbulence in real time. Its ability directly determines the imaging quality of optical telescopes. Limited by the influence of strong sky background during the day, adaptive optics systems can generally only work at night or in the early morning and dusk periods. Conventional ground-based photoelectric detection systems cannot work during the entire daytime period, which seriously affects the timeliness of space target detection.

[0003] The adaptive optics (AO) system of traditional ground-based optical telescopes only works under extremely weak background light conditions, that is, during the dawn and dusk periods. Compared with the dawn and dusk periods, the AO aberration correction technology during the daytime faces many challenges. On the one hand, due to the strong background radiation of the sky light, the photoelectric detection device is very easy to saturate, which limits the effective exposure time of the optical system and leads to an extremely low signal-to-noise ratio; on the other hand, the sky light background is unevenly distributed in time and space at different sub-apertures or even the same sub-aperture, and the fixed threshold algorithm fails. Therefore, a core strategy to improve the centroid extraction accuracy of the Shack-Hartman wavefront sensor (SHWS) is to improve the hardware design of the optical system and improve the signal-to-noise ratio of the system wavefront detection. For example, the spectral filtering combined with the polarization filtering method or the combination of the advantages of SHWS and other wavefront sensors, but while reducing the sky light background, it also leads to the attenuation of the target energy. Another method is to optimize the threshold setting strategy to accurately eliminate background interference, such as TmCOG, WCOG, The brightest pixel selection algorithm and other threshold methods, but when applied to daytime periods, the centroid extraction accuracy decreases.

[0004] In order to eliminate the interference of fluctuating strong skylight background, improve the signal-to-noise ratio of wavefront detection, realize adaptive closed-loop correction of dim targets in daytime scenes, and obtain high-resolution imaging in daytime, the existing solutions all use target signal modulation methods such as polarization and spectral filtering to enhance the signal-to-noise ratio, but while enhancing the signal-to-noise ratio, they will cause target energy loss to varying degrees. In addition, some people have proposed combining the Shack-Hartmann wavefront sensor with other wavefront sensors to compensate for large-scale wavefronts and perform high-sensitivity correction on small-scale wavefronts, but this method involves the combination of the Shack-Hartmann wavefront sensor with other wavefront sensors, which will lead to an overly complex optical structure, and the combination cannot meet the application requirements of adaptive correction of dim spatial targets under strong skylight background during the day. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a wavefront detection system for dim targets under strong skylight background, performs wavefront detection in the short-wave infrared band, and applies the Shack-Hartmann wavefront sensing technology of efficient transmission of space target spectrum and effective blocking of skylight background spectrum, which can minimize the background light radiation photons received by the detector while maintaining the target brightness, and can significantly improve the signal-to-noise ratio of space target detection. In addition, by improving the optical design and developing a new threshold algorithm, optimization is performed for the PNHB phenomenon that occurs in the uneven skylight background and short-wave infrared band. By utilizing the difference between the target and non-target features, the target is separated from the non-target, and the imaging resolution of dim targets under strong skylight background during the day is significantly improved.

[0006] To achieve the above object, the technical solution created by the present invention is implemented as follows: The wavefront detection system for dim targets under strong skylight background provided by the present invention comprises: a Shack-Hartmann wavefront sensor system and a wavefront detection processing unit; The Shack-Hartmann wavefront sensor system is provided with: a dichroic mirror, a beam reduction unit, a microlens array and a Hartmann detector in sequence along the incident light path, wherein the dichroic mirror is used to inject the short-wave infrared band into the Shack-Hartmann wavefront sensor system; the beam reduction unit includes a field diaphragm, which constrains the sub-aperture field of view through the field diaphragm, and obtains a sub-aperture image on the Hartmann detector through the microlens array; The wavefront detection processing unit is used to correct the sub-aperture image.

[0007] Preferably, the dichroic mirror reflects the short-wave infrared radiation in the range of 1.3 μm to 1.7 μm into the beam reduction unit.

[0008] Preferably, the beam reduction unit further comprises a first beam reduction mirror and a second beam reduction mirror, and a rear focus of the first beam reduction mirror coincides with a front focus of the second beam reduction mirror.

[0009] Preferably, the center of the field stop coincides with the rear focus of the first beam reducer and the front focus of the second beam reducer.

[0010] Preferably, the detection band of the Hartmann detector is 1.3 μm-1.7 μm.

[0011] Preferably, the wavefront detection processing unit corrects the sub-aperture image by a weighted self-threshold local contrast algorithm.

[0012] Preferably, the process of correcting the sub-aperture image by weighted self-threshold local contrast algorithm is: S1: Divide each sub-aperture image into nine-unit image blocks in the form of 3×3, the image block at the center is the center unit, and each image block outside the center unit is a background unit. Perform a self-threshold operation on the pixels in the center unit according to the grayscale ratio weight of the center unit and the background unit; S2: Introduce energy weight to remove PNHB noise in sub-aperture images; S3: Calculate the centroid of the sub-aperture image by the centroid method.

[0013] Preferably, in S1, the grayscale calculation method of the central unit is: The grayscale average of all pixels in the cross area centered on the central pixel of the central unit is taken as the grayscale of the central unit.

[0014] Preferably, in S1, the grayscale calculation method of each background unit is: Remove the pixel with the largest grayscale value in the background unit, and take the average grayscale value of the remaining pixels in the background unit as the grayscale of the background unit.

[0015] Preferably, the energy weight for: ; in, is the maximum grayscale value in the cross area, is the predicted value grayscale, which satisfies the linear distribution with the minimum grayscale value and the secondary maximum grayscale value in the cross area; According to the energy weight The weighted calculation of the pixels in the center unit is: ; in, is the pixel grayscale in the central unit obtained after introducing the energy weight, is the pixel grayscale within the center unit obtained after the threshold operation.

[0016] Compared with the prior art, the invention can achieve the following beneficial effects: The present invention specifically screens the incident light band through a dichroic mirror, and applies the Shack-Hartmann wavefront sensor system (SHWS) in the short-wave infrared band that can efficiently transmit the space target spectrum and effectively block the sky background spectrum. Compared with the traditional SHWS applied to the visible light band, the sky background radiation power in the short-wave infrared band is much lower than that in the visible light band, and the sky background has little effect on the detected target. Therefore, the present invention can ensure that the target has a high brightness while minimizing the background light radiation photons received by the detector, thereby significantly improving the signal-to-noise ratio of space target detection.

[0017] The present invention adds a field of view diaphragm in the beam reduction optical path and sets the position of the field of view diaphragm to suppress crosstalk between sub-apertures, constrain the field of view of each sub-aperture, greatly suppress the influence of strong daylight background on the Hartmann wavefront sensor, and improve the optical performance of the system.

[0018] In addition, the present invention designs a new threshold algorithm to target the phenomenon of pixel sized noises with high brightness (PNHB) in the uneven skylight background and the shortwave infrared band. It suppresses background noise and detector response deviation through local contrast self-threshold operation and energy weight judgment. It separates targets from non-targets by utilizing the differences in target and non-target features, eliminates various types of noise and background interference, realizes effective adaptive closed-loop correction of dark space targets, and improves the centroid extraction accuracy of sub-aperture images in the wavefront detection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 is a schematic diagram of the optical path of a wavefront detection system for a dim target under a strong skylight background provided by an embodiment of the present invention; Figure 2 is a correction flow chart of a sub-aperture image according to an embodiment of the present invention; Figure 3 is a schematic diagram of graphical division of a sub-aperture image provided by an embodiment of the present invention; Figure 4 is a schematic diagram of sub-aperture reconstruction provided according to an embodiment of the present invention.

[0020] Reference numerals include: Color dichroic mirror 1, first beam reducer 2, field stop 3, second beam reducer 4, microlens array 5, Hartmann detector 6. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the invention clearer, the invention is 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 invention and do not constitute a limitation to the invention. Similar components in different embodiments use associated similar component numbers. In the following embodiments, many detailed descriptions are to enable the invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other components, materials, and methods. In some cases, some operations related to the invention are not shown or described in the specification, in order to avoid the core part of the invention being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0022] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed.

[0023] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention. In addition, the terms "first", "second", 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 as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0024] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0025] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0026] See also Figure 1 In one embodiment of the present invention, a wavefront detection system for dim targets under a strong skylight background is provided to overcome the problem that the adaptive optical system of a traditional ground-based optical telescope can only work under extremely weak background light conditions. By performing wavefront detection for a specific band, improving the system structure, and optimizing the correction algorithm of the Hartmann image, an adaptive closed-loop correction of dim targets in daytime scenes is achieved, meeting the current detection needs under a strong skylight background during the day. Specifically, the wavefront detection system includes: a Shack-Hartmann wavefront sensor system and a wavefront detection processing unit, wherein the Shack-Hartmann wavefront sensor system includes: a dichroic mirror 1, a beam reduction unit, a microlens array 5, and a Hartmann detector 6 arranged along the incident light path. In the embodiment of the present invention, background light interference is suppressed, and Shack-Hartmann wavefront detection is performed only for a specific short-wave infrared band. By adding a dichroic mirror 1, the short-wave infrared band of 1.3μm-1.7μm is reflected into the beam reduction unit. Compared with the wavefront detection process of traditional detection systems, the sky light background radiation power in the short-wave infrared band is much lower than that in the visible light band, which can greatly reduce the impact of sky light background on target detection.

[0027] The beam reduction unit mainly includes a first beam reduction mirror 2, a field stop 3, and a second beam reduction mirror 4, wherein the short-wave infrared band reflected by the dichroic mirror 1 first enters the first beam reduction mirror 2, and is emitted to the second beam reduction mirror 4 after being processed by the first beam reduction mirror 2, the rear focus of the first beam reduction mirror 2 coincides with the front focus of the second beam reduction mirror 4, and the center of the field stop 3 is set at the focus coincidence position. It can be understood that the focal points of the two side directions close to the first beam reduction mirror 2 and the second beam reduction mirror 4 coincide, and this confocal configuration can ensure that the light is highly collimated when transmitted between the two beam reduction mirrors, and setting the field stop 3 at the confocal position can effectively control the field of view and aperture of the light beam, which helps to limit the diameter of the light beam entering the system, reduce stray light and background noise, and improve the beam quality and imaging resolution of the system. In addition, in the Shack-Hartmann wavefront sensor system, the design of the field of view aperture 3 helps to suppress crosstalk between sub-apertures. By precisely controlling the field of view of each sub-aperture, it can ensure that the short-wave infrared band light beam captured by each sub-aperture will not overlap with the light beams of other sub-apertures, thereby improving the signal-to-noise ratio and imaging quality of the system.

[0028] After being transmitted through the beam reduction unit, the short-wave infrared band light beam is transmitted through the microlens array 5 and forms an image on the target surface of the Hartmann detector 6. The microlens array 5 is an array composed of a plurality of small-sized lenses. The microlens array 5 divides the incident light wavefront into a plurality of sub-wavefronts, each of which forms a light spot on the focal plane, and each light spot is a sub-aperture image. The detection band of the Hartmann detector 6 is 1.3μm-1.7μm.

[0029] Since the sub-aperture image will be affected by the strong sky light background during the day and the PNHB phenomenon caused by the response deviation of the infrared detector and electronic noise, it is necessary to further correct the sub-aperture image through the wavefront detection processing unit to reconstruct the spot centroid of the sub-aperture image.

[0030] In the embodiment of the present invention, the wavefront detection processing unit mainly corrects the short-wave infrared Hartmann image of the weak target with strong sky light background detected on the target surface of the Hartmann detector 6 by using the weighted self-threshold local contrast algorithm. For details, please refer to Figure 2 , the image correction process includes the following steps: S1: For each sub-aperture image in the short-wave infrared Hartmann image with a weak target against a strong sky background, the following Figure 3 The 3×3 nine-unit image blocks shown in FIG. traverse each sub-aperture image pixel by pixel, that is, each sub-aperture image is divided into 3×3 nine-unit image blocks, where the image block T at the center is called the center unit, and the 8 image blocks outside the center unit T are called background units, that is, , , , , , , and By calculating the center unit T and the background unit separately , , , , , , and The grayscale ratio weight is used to perform a self-threshold operation on the pixels in the central unit to obtain the local feature saliency map of the sub-aperture image. The specific calculation process is: First, to ensure the integrity of the features of the central unit, a cross region centered on the central pixel of the central unit is defined. , that is, the center pixel is extended in both horizontal and vertical directions, and the grayscale average value of all pixels in the area represents the grayscale of the center unit T, which is used as the comparison object in the subsequent self-thresholding process. For the convenience of expression, the grayscale of the center pixel is used. represents the central pixel. The grayscale of the central unit T reflects the target grayscale, where the cross area It can be expressed as: ; in, Center pixel The coordinates of is the coordinate of the neighborhood pixel, that is, the cross area Inner center pixel Other pixels outside the cross area, k is the cross area In the embodiment of the present invention, the size of each image block is defined according to the theoretical size of the target spot, that is, the center unit T and the background unit , , , , , , and However, for the central unit T, we only take the central pixel and its four neighborhoods, so the value of k is 1.

[0031] Grayscale of the central unit T It can be expressed as: ; in, The cross area In the embodiment of the present invention, The value of is 5. Indicates the cross area The grayscale of any pixel within.

[0032] To avoid background cells , , , , , , and Interference with the central unit T, the grayscale of each background unit is defined as the grayscale average of other pixel areas after removing the maximum grayscale pixel in its image block. The calculation formula is: ; in, The values ​​of are 1, 2, 3, 4, 5, 6, 7 and 8, corresponding to the background unit , , , , , , and , The number of pixels after removing the maximum grayscale pixel for each background cell, The value of is the total number of pixels in the image block minus 1. Indicates the labels of other pixels in the background unit after removing the maximum grayscale pixel.

[0033] As a preferred embodiment, according to the interference degree of the background noise on the target, the number of pixels to be removed can be adaptively adjusted in the process of calculating the grayscale of the background unit according to actual needs.

[0034] Calculate the center unit T and background unit , , , , , , and After the grayscale of the image is obtained, the similarity weights representing the features of different regions of the sub-aperture image are calculated. , that is, calculate the center unit T and the background unit respectively , , , , , , and Ratio of: .

[0035] Based on the calculated similarity weight , for the center pixel Perform self-threshold operation and automatically determine the local threshold according to the local characteristics of the image. This local threshold is used to adjust the target grayscale and background grayscale to the same level or within a relatively consistent range. If the grayscale value of the central pixel is is higher than the local threshold, it represents part of the target and can be retained; if the gray value of the central pixel is If it is lower than the local threshold, it may belong to the background, so it needs to be suppressed. In this way, the contrast between the target and the background can be improved, making the target features more prominent. The specific self-threshold operation is: ; ; in, represents the pixel grayscale in the center unit T obtained after the threshold operation, Represents the discriminant function for the self-thresholding operation.

[0036] S2: Since the present invention performs wavefront detection in the short-wave infrared band, the nonlinear response and hysteresis effect of photons in the infrared detection process may cause noise or signal instability, namely PNHB noise. In order to eliminate the PNHB noise interference in the sub-aperture image, the embodiment of the present invention adjusts and optimizes the energy weight W by introducing the energy weight W. , in order to improve the accuracy and robustness of target detection. Sort the pixels in the part by grayscale and determine their minimum value , submaximum With the maximum value , whose coordinates are (1, )、(2, ) and (3, ). Then, we can use (1, ) and (2, )The linear model is constructed as follows: ; in: represents the slope and B represents the intercept. , .

[0037] According to the constructed linear model, when the value of x is 3, we get as follows: ; according to and Determining Energy Weights The expression is: ; According to the energy weight The pixels in the central unit T are weighted and calculated to obtain the corresponding value of the central pixel in the central unit T obtained by weighted calculation after introducing the energy weight. for: .

[0038] S3: For each sub-aperture image, the local contrast self-threshold operation and the energy weight are connected with each other using the product. After the above operation is completed, Figure 4 As shown in the figure, the maximum grayscale pixel in the sub-aperture image is selected as the center to construct an N×N pixel area template to reconstruct the new sub-aperture image. The center of mass of the spot of the sub-aperture image is calculated by the center of mass method (COG) algorithm, that is, the original sub-aperture image is processed and corrected, and the center of mass of the newly calculated sub-aperture image is:

[0039] in, represents the grayscale of the newly created sub-aperture image, and The centroid coordinates of the newly created sub-aperture image are shown in Table 1. The centroid calculation process of the newly created sub-aperture image belongs to the prior art and will not be described in detail here.

[0040] Furthermore, the difference between the centroid coordinates of the newly created sub-aperture image and the reference wavefront centroid coordinates of the adaptive optical system of the ground-based optical telescope where the wavefront detection system is located can be calculated, and the average slope of each sub-wavefront of the telescope can be calculated based on a simple geometric relationship, and then the control voltage of each actuator of the deformable mirror in the telescope system can be obtained according to the direct slope method to realize adaptive closed-loop correction.

[0041] In addition, the embodiment of the present invention is for the short-wave infrared band of 1.3 μm-1.7 μm, and the working bands of the dichroic mirror 1 and the Hartmann detector 6 can also be adjusted accordingly to apply them to other infrared bands. And the weighted self-threshold local contrast algorithm inside the wavefront detection processing unit can also be replaced with other local contrast algorithms, and accordingly, the form of dividing the sub-aperture image into image blocks can also be replaced and optimized.

[0042] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included in the protection scope of this specification.

[0043] The systems, devices, modules or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0044] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0045] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0046] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A wavefront detection system for dim targets under strong skylight background, characterized in that: include: Shack-Hartmann wavefront sensor system and wavefront detection processing unit; The Shack-Hartmann wavefront sensor system is provided with: a dichroic mirror, a beam reduction unit, a microlens array and a Hartmann detector in sequence along the incident light path, wherein the dichroic mirror is used to inject the short-wave infrared band into the Shack-Hartmann wavefront sensor system; the beam reduction unit includes a field diaphragm, through which the sub-aperture field of view is constrained, and a sub-aperture image is obtained on the Hartmann detector through the microlens array; The wavefront detection processing unit is used to correct the sub-aperture image.

2. The wavefront detection system for dim targets under strong skylight background as claimed in claim 1, characterized in that: The dichroic mirror reflects the short-wave infrared radiation in the range of 1.3 μm to 1.7 μm into the beam reduction unit.

3. The wavefront detection system for dim targets under strong skylight background as claimed in claim 1, characterized in that: The beam reduction unit further includes a first beam reduction mirror and a second beam reduction mirror, wherein a rear focus of the first beam reduction mirror coincides with a front focus of the second beam reduction mirror.

4. The wavefront detection system for dim targets under strong skylight background as claimed in claim 3, characterized in that: The center of the field stop coincides with the rear focus of the first beam reducer and the front focus of the second beam reducer.

5. The wavefront detection system for dim targets under strong skylight background as claimed in claim 1, characterized in that: The detection band of the Hartmann detector is 1.3 μm-1.7 μm.

6. The wavefront detection system for dim targets under strong skylight background as claimed in claim 1, characterized in that: The wavefront detection processing unit corrects the sub-aperture image by a weighted self-threshold local contrast algorithm.

7. The wavefront detection system for dim targets under strong skylight background as claimed in claim 6, characterized in that: The process of correcting the sub-aperture image by weighted self-threshold local contrast algorithm is: S1: Divide each sub-aperture image into nine-unit image blocks in the form of 3×3, wherein the image block at the center is a center unit, and each image block outside the center unit is a background unit, and perform a self-threshold operation on the pixels in the center unit according to the grayscale ratio weight of the center unit and the background unit; S2: introducing energy weight to remove PNHB noise in the sub-aperture image; S3: Calculate the centroid of the sub-aperture image by using a centroid method.

8. The wavefront detection system for dim targets under strong skylight background as claimed in claim 7, characterized in that: In S1, the grayscale calculation method of the central unit is: The grayscale average value of all pixels in a cross region centered on the central pixel of the central unit is taken as the grayscale of the central unit.

9. The wavefront detection system for dim targets under strong skylight background as claimed in claim 7, characterized in that: In S1, the grayscale calculation method of each background unit is: The pixel with the largest grayscale value in the background unit is removed, and the average grayscale value of the remaining pixels in the background unit is taken as the grayscale of the background unit.

10. The wavefront detection system for dim targets under strong skylight background as claimed in claim 7, characterized in that: The energy weight for: ； in, is the maximum grayscale value in the cross area, is the predicted value grayscale, which satisfies the linear distribution with the minimum grayscale value and the secondary maximum grayscale value in the cross area; According to the energy weight The weighted calculation of the pixels in the central unit is: ； in, is the pixel grayscale in the central unit obtained after introducing the energy weight, is the pixel grayscale within the central unit obtained after the threshold operation.

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