Coherent tomographic wavefront measurement device and method based on fiber interconnection and point diffraction

Abstract

The present application belongs to the field of optical measurement and detection, and particularly relates to a coherent tomographic wavefront measurement device and method based on optical fiber interconnection and point diffraction. The measurement device separates the fundamental mode and high-order modes of test light through a few-mode optical fiber. The fundamental mode generates a reference spherical wave through point diffraction, serving as reference light, and the high-order mode serves as test light. After the test light and the reference light are coupled and interfered through an optical fiber, an interference pattern is obtained by a detector, and then wavefront error measurement and optimization are realized through wavefront solving and correction. The present application has high precision and high stability, and can realize fast closed-loop feedback correction.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement and detection technology, and particularly relates to a coherent tomography wavefront measurement device and method based on optical fiber interconnection and point diffraction. Background Technology

[0002] Traditional point diffraction interferometers (PDIs), as a high-precision, reference-mirror-free wavefront measurement method, are of significant value in fields such as optical surface shape inspection. Their basic principle is to use a micrometer-sized pinhole to diffract light waves, generating a near-ideal spherical wave as a reference wavefront. This reference wavefront interferes with the test wavefront passing through the system under test, thereby extracting the wavefront error. However, this classic architecture has inherent limitations: First, its single-wavelength operating mode cannot separate the phase contributions at different depths of the test piece, limiting its application in characterizing multilayer structures or gradient refractive index materials; second, the alignment of the free-space pinhole is extremely sensitive, resulting in poor system stability, and environmental vibrations and airflow can easily cause interference fringes to become unstable; third, the quality of the reference wavefront heavily depends on the size and shape processing accuracy of the pinhole, leading to high manufacturing costs and susceptibility to damage; fourth, traditional PDIs are only open-loop measurement tools, requiring external correction mechanisms (such as deformable mirrors) for error compensation, resulting in a complex system with a slow response speed.

[0003] To overcome the limitations of single-wavelength operation, extended techniques based on wavelength scanning or white-light interferometry have emerged. However, these techniques typically suffer from slow scanning speeds, complex data stitching, or short coherence lengths. In adaptive optics, while Shaker-Hartmann wavefront sensors can achieve real-time detection and correction, their spatial resolution is limited by the number of microlens arrays, and there is a trade-off between dynamic range and accuracy. Furthermore, existing technologies are insufficient in handling phase transitions at the edges of interferograms, often employing path-tracking unwrapping algorithms. These algorithms are prone to error propagation in low signal-to-noise ratio or complex phase distribution regions, affecting the reliability of full-aperture measurements.

[0004] Therefore, there is an urgent need in this field for a new wavefront measurement and control system that combines high precision, high stability, multi-dimensional information acquisition capabilities, and the ability to achieve rapid closed-loop feedback correction. Summary of the Invention

[0005] In view of this, the present invention aims to provide a novel wavefront measurement and control system that combines high precision, high stability, multi-dimensional information acquisition capabilities, and rapid closed-loop feedback correction.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A coherent tomography wavefront measurement device based on optical fiber interconnection and point diffraction includes: a first few-mode fiber, a second few-mode fiber, a third few-mode fiber, a first single-mode fiber, a second single-mode fiber, a third single-mode fiber, a fourth single-mode fiber, a mode splitter, a first fiber coupler, a second fiber coupler, a third fiber coupler, a fourth fiber coupler, a first photodetector, a second photodetector, a wavefront calculation module, a wavefront corrector, and an image acquisition and optimization module; The first few-mode fiber is used to couple the test light carrying wavefront error received by the telescope system, and simultaneously excite the fundamental mode and higher-order modes. The mode separator is used to separate the fundamental mode from the higher-order modes, so that the fundamental mode enters the second few-mode fiber and the higher-order modes enter the third few-mode fiber; The first fiber coupler is used to split the fundamental mode transmitted by the second few-mode fiber into two beams, which enter the first single-mode fiber and the second single-mode fiber respectively. The exit end face of the first single-mode fiber and the exit end face of the second single-mode fiber serve as point diffraction apertures. The two fundamental modes are diffracted by the exit end face of the first single-mode fiber and the exit end face of the second single-mode fiber respectively to generate reference spherical waves, which serve as reference light. The second fiber coupler is used to split the high-order modes transmitted in the third few-mode fiber into two beams, which are then fed into the third single-mode fiber and the fourth single-mode fiber, respectively, as test beams. The two test beams have different mode components. The third fiber coupler is used to couple the reference light transmitted through the first single-mode fiber and the test light transmitted through the third single-mode fiber, so that the two coupled beams interfere with each other. The fourth fiber coupler is used to couple the reference light transmitted through the second single-mode fiber and the test light transmitted through the fourth single-mode fiber, so that the two coupled beams interfere with each other. The first photodetector is used to receive the interference light output from the third fiber coupler and form an interference pattern; The second photodetector is used to receive the interference light output from the fourth fiber coupler and form an interference pattern; The wavefront resolution module is used to demodulate the test wavefront of the test light from the two interference patterns respectively using the Fourier transform method; A wavefront corrector is used for preliminary correction of the test wavefront; The image acquisition and optimization module is used to acquire images after preliminary correction, calculate the image sharpness evaluation function value, and update the control signal of the wavefront corrector through an iterative optimization algorithm to perform fine correction on the test wavefront.

[0007] Furthermore, the wavefront corrector can be a spatial light modulator, a deformable mirror, or an array of fiber phase modulators driven by piezoelectric ceramics.

[0008] Furthermore, pinholes are respectively provided in front of the output ends of the first single-mode fiber and the second single-mode fiber for spatial filtering.

[0009] Furthermore, the pinhole is circular or elliptical in shape, and the light enters the pinhole either orally or obliquely.

[0010] A method for coherent tomography wavefront measurement based on fiber optic interconnection and point diffraction, implemented using the aforementioned coherent tomography wavefront measurement device based on fiber optic interconnection and point diffraction, includes the following steps: S1: The test light carrying wavefront error received by the telescope system is coupled into the first few-mode fiber; S2: The test light is separated into fundamental mode and higher-order modes by a mode splitter. The fundamental mode enters the second few-mode fiber and is then split into two beams by the first fiber coupler, which enter the first single-mode fiber and the second single-mode fiber, respectively. The exit end faces of the first and second single-mode fibers serve as point diffraction apertures. The two fundamental mode beams are diffracted by the exit end faces of the first and second single-mode fibers, respectively, to generate reference spherical waves, which serve as reference light. The higher-order modes are split into two beams by the second fiber coupler, which enter the third and fourth single-mode fibers, respectively, as test light. The two test light beams have different mode components. S3: The reference light transmitted through the first single-mode fiber and the test light transmitted through the third single-mode fiber are coupled and interfered in the third fiber coupler, and the interference pattern is collected by the first photodetector; the reference light transmitted through the second single-mode fiber and the test light transmitted through the fourth single-mode fiber are coupled and interfered in the fourth fiber coupler, and the interference pattern is collected by the second photodetector. S4: The test wavefront of the test light is demodulated from the two interferograms using the wavefront solution module based on the Fourier transform method; among them, the phase jump in the edge region of the interferogram is handled by the overall boundary phase difference matrix construction and solution algorithm to avoid point-by-point error propagation. S5: Drive the wavefront corrector to perform preliminary correction on the test wavefront; S6: Acquire the output image of the telescope system after preliminary correction through the image acquisition and optimization module, and calculate its sharpness evaluation function value; S7: With the goal of maximizing the sharpness evaluation function value, the control signal of the wavefront corrector is updated through an iterative optimization algorithm to perform fine correction on the test wavefront.

[0011] Furthermore, the image sharpness evaluation function can be any of the following:

[0012] in, I Represents the image plane ( x , y Light intensity at point ( );dx and dy Represents the integral variable in the xy coordinate system of the image plane; M The shape of the aperture is indicated, and it takes a non-zero value only within the circular aperture region; m and n represent the relative positions of the aperture. x and y The order of the partial derivatives; The mixed partial derivative represents the image intensity; n represents the power. r ln() represents the distance from a point on the image plane to the origin; ln() represents the natural logarithm. I 0 represents the reference light intensity.

[0013] Furthermore, during the iteration process, eight image sharpness evaluation functions are computed in parallel, and the one that is most sensitive to changes in the test wavefront and has the best convergence is selected for subsequent optimization.

[0014] Furthermore, the algorithm for constructing and solving the global boundary phase difference matrix includes: extracting the phase difference values ​​at all boundaries in the interferogram, constructing a global linear equation system, and solving it all at once to obtain a globally continuous phase distribution, thus avoiding point-by-point error propagation.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. High-precision and high-stability point diffraction interferometry measurement was achieved. By employing a single-mode fiber endface as a natural, integrated point diffraction source, the traditional free-space pinhole is replaced. The fiber endface size is comparable to the wavelength, naturally generating high-quality spherical waves. Furthermore, this structure eliminates the need for precise alignment, exhibits strong resistance to vibration and airflow interference, significantly improves the system's long-term stability and environmental adaptability, and reduces assembly difficulty and cost.

[0016] 2. It incorporates intelligent closed-loop feedback correction capability. This system creatively combines the optimization of image sharpness evaluation functions (such as S1, S3, S7, etc.) with interferometry. The system actively introduces tentative perturbations through wavefront correction actuators (such as spatial light modulators) and calculates the sharpness value of the interferogram in real time. With the goal of maximizing sharpness, it quickly determines and applies the optimal correction amount. This transforms the system from a passive measurement device into an adaptive optics system with active optimization capabilities, enabling real-time aberration compensation and direct optimization of the final image quality or beam performance.

[0017] 3. Improved robustness and accuracy of complex wavefront solutions. To address the challenge of phase calculation in the edge region of interferograms, an algorithm for constructing and solving the global boundary phase difference matrix is ​​proposed. This method constructs the phase difference constraints of all pixels at the edge into a global matrix and solves it all at once, avoiding the point-to-point error propagation defect in traditional path tracing algorithms. This significantly improves the accuracy and reliability of full-aperture wavefront reconstruction, especially when measuring large-aperture or complex-aperture optical elements. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of the structure of the coherent tomography wavefront measurement device based on fiber interconnection and point diffraction as described in the embodiment of the present invention; Figure 2 This is a schematic flowchart of the coherent tomography wavefront measurement method based on fiber interconnection and point diffraction described in an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: First few-mode fiber 1, second few-mode fiber 2, third few-mode fiber 3, first single-mode fiber 4, second single-mode fiber 5, third single-mode fiber 6, fourth single-mode fiber 7, mode splitter 8, first fiber coupler 9, second fiber coupler 10, third fiber coupler 11, first photodetector 12, fourth fiber coupler 13, second photodetector 14, telescope system 15. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "assembly," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, an embodiment of the present invention provides a coherent tomography wavefront measurement device based on optical fiber interconnection and point diffraction, comprising: a first few-mode fiber 1, a second few-mode fiber 2, a third few-mode fiber 3, a first single-mode fiber 4, a second single-mode fiber 5, a third single-mode fiber 6, a fourth single-mode fiber 7, a mode separator 8, a first fiber coupler 9, a second fiber coupler 10, a third fiber coupler 11, a first photodetector 12, a fourth fiber coupler 13, a second photodetector 14, a wavefront calculation module, a wavefront corrector, and an image acquisition and optimization module.

[0026] The first few-mode fiber 1 is used to couple the test light carrying wavefront error received by the telescope system, and simultaneously excite the fundamental mode and higher-order modes.

[0027] The mode separator 8 is used to separate the fundamental mode from the higher-order modes, so that the fundamental mode enters the second few-mode fiber 2 and the higher-order modes enter the third few-mode fiber 3.

[0028] The first fiber coupler 9 is used to split the fundamental mode transmitted by the second few-mode fiber 2 into two beams, which enter the first single-mode fiber 4 and the second single-mode fiber 5 respectively. The exit end face of the first single-mode fiber 4 and the exit end face of the second single-mode fiber 5 serve as point diffraction apertures. The two fundamental modes are diffracted by the exit end face of the first single-mode fiber 4 and the exit end face of the second single-mode fiber 5 respectively to generate reference spherical waves, which serve as reference light.

[0029] The second fiber coupler 10 is used to split the high-order modes transmitted in the third few-mode fiber 3 into two beams, which are respectively fed into the third single-mode fiber 6 and the fourth single-mode fiber 7 as test beams. The two test beams have different mode components.

[0030] The third fiber coupler 11 is used to couple the reference light transmitted through the first single-mode fiber 4 and the test light transmitted through the third single-mode fiber 6, so that the two coupled beams interfere with each other.

[0031] The fourth fiber coupler 13 is used to couple the reference light transmitted through the second single-mode fiber 5 and the test light transmitted through the fourth single-mode fiber 7, so that the two coupled beams interfere with each other.

[0032] The first photodetector 12 is used to receive the interference light output from the third fiber coupler 11 to form an interference pattern.

[0033] The second photodetector 14 is used to receive the interference light output from the fourth fiber coupler 13 to form an interference pattern.

[0034] The wavefront demodulation module is used to demodulate the test wavefront of the test light from the two interference patterns respectively using the Fourier transform method.

[0035] A wavefront corrector is used to perform preliminary correction on the test wavefront.

[0036] The image acquisition and optimization module is used to acquire images after preliminary correction, calculate the image sharpness evaluation function value, and update the control signal of the wavefront corrector through an iterative optimization algorithm to perform fine correction on the test wavefront.

[0037] Furthermore, the wavefront corrector can be a spatial light modulator, a deformable mirror, or an array of fiber phase modulators driven by piezoelectric ceramics.

[0038] Furthermore, pinholes are respectively provided in front of the output ends of the first single-mode fiber and the second single-mode fiber for spatial filtering.

[0039] Furthermore, the pinhole is circular or elliptical in shape, and the light enters the pinhole either orally or obliquely.

[0040] In one specific embodiment of the present invention, the wavefront corrector is a spatial light modulator, a deformable mirror, or a piezoelectric ceramic-driven fiber optic phase modulator array. The beam splitter module 2 can be an optical fiber coupler.

[0041] A pinhole is positioned at the output end of the single-mode fiber for spatial filtering. The pinhole is circular or elliptical in shape, and the light enters the pinhole either normally or obliquely. The elliptical / circular pinhole and normal / oblique incidence designs provide users with flexible means to optimize the reference wavefront characteristics for different application scenarios (such as high numerical aperture systems and off-axis measurements).

[0042] like Figure 2 As shown in the figure, an embodiment of the present invention also provides a coherent tomography wavefront measurement method based on fiber optic interconnection and point diffraction, which is implemented using the aforementioned coherent tomography wavefront measurement device based on fiber optic interconnection and point diffraction, and includes the following steps: S1: The test light carrying wavefront error received by the telescope system is coupled into the first few-mode fiber.

[0043] S2: The test light is separated into fundamental mode and higher-order modes by a mode splitter. The fundamental mode enters the second few-mode fiber and is then split into two beams by the first fiber coupler, which enter the first single-mode fiber and the second single-mode fiber, respectively. The exit end faces of the first and second single-mode fibers serve as point diffraction apertures. The two fundamental mode beams are diffracted by the exit end faces of the first and second single-mode fibers, respectively, to generate reference spherical waves, which serve as reference light. The higher-order modes are split into two beams by the second fiber coupler, which enter the third and fourth single-mode fibers, respectively, as test light. The two test light beams have different mode components.

[0044] S3: The reference light transmitted through the first single-mode fiber and the test light transmitted through the third single-mode fiber are coupled and interfered in the third fiber coupler, and the interference pattern is collected by the first photodetector; the reference light transmitted through the second single-mode fiber and the test light transmitted through the fourth single-mode fiber are coupled and interfered in the fourth fiber coupler, and the interference pattern is collected by the second photodetector.

[0045] S4: The test wavefront of the test light is demodulated from the two interferograms using the wavefront solution module based on the Fourier transform method. For the phase jump in the edge region of the interferogram, the overall boundary phase difference matrix construction and solution algorithm is used to avoid point-by-point error propagation.

[0046] The demodulation algorithm for the test wavefront is the traditional Fourier transform method, specifically: Step 1: Obtain the light intensity distribution of the interference pattern.

[0047] The intensity distribution of the interference pattern can be represented as: ; Where a(x,y) represents the background light intensity (low-frequency component); b(x,y) represents the modulation intensity (stripe contrast); f0x and f0y represent the spatial carrier frequencies (generated by a small angle of tilt artificially introduced between the two beams, making the stripes present a regular sinusoidal distribution); (x,y) represents the wavefront phase to be determined (including aberration information of the optical system).

[0048] Step 2: Perform a two-dimensional Fourier transform on the interferogram.

[0049] ; Where A represents the zero-order spectrum (background light intensity); C represents the positive first-order spectrum (containing phase information); This represents the negative first-order spectrum (conjugate).

[0050] Step 3: Frequency domain filtering to extract the first-level spectrum.

[0051] Design a suitable bandpass filter (such as a Gaussian filter or a rectangular window) to isolate the positive first-order spectrum.

[0052] Step 4: Obtain the complex amplitude using inverse Fourier transform.

[0053] Performing an inverse Fourier transform on the filtered first-order spectrum yields a complex amplitude distribution containing phase information: .

[0054] Step 5: Calculate the package phase.

[0055] Extracting the phase angle (principal phase) from the complex amplitude: ; This phase is enclosed in [ , Within the interval, it exhibits a jagged, discontinuous pattern.

[0056] Step 6: Calculate the package phase.

[0057] Using phase unfolding algorithms (such as least squares, mass-oriented methods, or the multi-region boundary global solution strategy you mentioned), the wrapped phase is restored to a continuous phase: .

[0058] Step 7: Calculate the package phase.

[0059] Subtract the linear carrier frequency phase introduced by the tilt from the expanded phase: ; Convert phase to wavefront error: ; Where λ is the operating wavelength.

[0060] To address phase jumps in the edge regions of the interferogram, an algorithm for constructing and solving the global boundary phase difference matrix is ​​employed to avoid point-to-point error propagation. Specifically, the algorithm includes: extracting the phase difference values ​​at all boundaries in the interferogram, constructing a global linear equation system, and solving it all at once to obtain a globally continuous phase distribution, thus avoiding point-to-point error propagation.

[0061] S5: Drive the wavefront corrector to perform preliminary correction on the test wavefront; S6: Acquire the output image of the telescope system after preliminary correction through the image acquisition and optimization module, and calculate its sharpness evaluation function value.

[0062] The image sharpness evaluation function can be any of the following:

[0063] in, I Represents the image plane ( x , y Light intensity at point ( ); dx and dy Represents the integral variable in the xy coordinate system of the image plane; M The shape of the aperture is indicated, and it takes a non-zero value only within the circular aperture region; m and n represent the relative positions of the aperture. x and y The order of the partial derivatives; The mixed partial derivative represents the image intensity; n represents the power. r ln() represents the distance from a point on the image plane to the origin; ln() represents the natural logarithm. I 0 represents the reference light intensity.

[0064] During the iteration process, eight image sharpness evaluation functions are computed in parallel, and the one that is most sensitive to changes in the test wavefront and has the best convergence is selected for subsequent optimization.

[0065] S7: With the goal of maximizing the sharpness evaluation function value, the control signal of the wavefront corrector is updated through an iterative optimization algorithm to perform fine correction on the test wavefront.

[0066] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0067] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A coherent tomographic wavefront measurement device based on fiber optic interconnection and point diffraction, characterized in that, It includes a first few-mode fiber, a second few-mode fiber, a third few-mode fiber, a first single-mode fiber, a second single-mode fiber, a third single-mode fiber, a fourth single-mode fiber, a mode splitter, a first fiber coupler, a second fiber coupler, a third fiber coupler, a fourth fiber coupler, a first photodetector, a second photodetector, a wavefront calculation module, a wavefront corrector, and an image acquisition and optimization module; The first few-mode fiber is used to couple the test light carrying wavefront error received by the telescope system, and simultaneously excite the fundamental mode and higher-order modes. The mode separator is used to separate the fundamental mode from the higher-order modes, so that the fundamental mode enters the second few-mode fiber and the higher-order modes enter the third few-mode fiber; The first fiber coupler is used to split the fundamental mode transmitted by the second few-mode fiber into two beams, which enter the first single-mode fiber and the second single-mode fiber respectively. The exit end face of the first single-mode fiber and the exit end face of the second single-mode fiber serve as point diffraction apertures. The two fundamental modes are diffracted by the exit end face of the first single-mode fiber and the exit end face of the second single-mode fiber respectively to generate reference spherical waves, which serve as reference light. The second fiber coupler is used to split the high-order modes transmitted in the third few-mode fiber into two beams, which are then fed into the third single-mode fiber and the fourth single-mode fiber, respectively, as test beams. The two test beams have different mode components. The third fiber coupler is used to couple the reference light transmitted through the first single-mode fiber and the test light transmitted through the third single-mode fiber, so that the two coupled beams interfere with each other. The fourth fiber coupler is used to couple the reference light transmitted through the second single-mode fiber and the test light transmitted through the fourth single-mode fiber, so that the two coupled beams interfere with each other. The first photodetector is used to receive the interference light output from the third fiber coupler and form an interference pattern; The second photodetector is used to receive the interference light output from the fourth fiber coupler and form an interference pattern; The wavefront resolution module is used to demodulate the test wavefront of the test light from the two interference patterns respectively using the Fourier transform method; A wavefront corrector is used for preliminary correction of the test wavefront; The image acquisition and optimization module is used to acquire images after preliminary correction, calculate the image sharpness evaluation function value, and update the control signal of the wavefront corrector through an iterative optimization algorithm to perform fine correction on the test wavefront.

2. The coherent tomography wavefront measurement device based on fiber optic interconnection and point diffraction according to claim 1, characterized in that, The wavefront corrector is a spatial light modulator, a deformable mirror, or a piezoelectric ceramic driven fiber phase modulator array.

3. The coherent tomography wavefront measurement device based on fiber optic interconnection and point diffraction according to claim 1, characterized in that, Pinholes are respectively provided in front of the output ends of the first single-mode fiber and the second single-mode fiber for spatial filtering.

4. The coherent tomography wavefront measurement device based on fiber optic interconnection and point diffraction according to claim 3, characterized in that, The pinhole is round or elliptical in shape, and the light enters the pinhole either directly or obliquely.

5. A method for coherent tomography wavefront measurement based on fiber optic interconnection and point diffraction, implemented using the coherent tomography wavefront measurement device based on fiber optic interconnection and point diffraction as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: The test light carrying wavefront error received by the telescope system is coupled into the first few-mode fiber; S2: The test light is separated into fundamental mode and higher-order modes by a mode splitter. The fundamental mode enters the second few-mode fiber and is then split into two beams by the first fiber coupler, which enter the first single-mode fiber and the second single-mode fiber, respectively. The exit end faces of the first and second single-mode fibers serve as point diffraction apertures. The two fundamental mode beams are diffracted by the exit end faces of the first and second single-mode fibers, respectively, to generate reference spherical waves, which serve as reference light. The higher-order modes are split into two beams by the second fiber coupler, which enter the third and fourth single-mode fibers, respectively, as test light. The two test light beams have different mode components. S3: The reference light transmitted through the first single-mode fiber and the test light transmitted through the third single-mode fiber are coupled and interfered in the third fiber coupler, and the interference pattern is collected by the first photodetector. The reference light transmitted through the second single-mode fiber and the test light transmitted through the fourth single-mode fiber are coupled and interfered in the fourth fiber coupler, and the interference pattern is collected by the second photodetector. S4: The test wavefront of the test light is demodulated from the two interferograms using the wavefront solution module based on the Fourier transform method; among them, the phase jump in the edge region of the interferogram is handled by the overall boundary phase difference matrix construction and solution algorithm to avoid point-by-point error propagation. S5: Drive the wavefront corrector to perform preliminary correction on the test wavefront; S6: Acquire the output image of the telescope system after preliminary correction through the image acquisition and optimization module, and calculate its sharpness evaluation function value; S7: With the goal of maximizing the sharpness evaluation function value, the control signal of the wavefront corrector is updated through an iterative optimization algorithm to perform fine correction on the test wavefront.

6. The method for coherent tomography wavefront measurement based on fiber optic interconnection and point diffraction according to claim 5, characterized in that, The image sharpness evaluation function can be any of the following: in, I Represents the image plane ( x , y Light intensity at point ( ); dx and dy Represents the integral variable in the xy coordinate system of the image plane; M The shape of the aperture is indicated, and it takes a non-zero value only within the circular aperture region; m and n represent the relative positions of the aperture. x and y The order of the partial derivatives; The mixed partial derivative represents the image intensity; n represents the power. r ln() represents the distance from a point on the image plane to the origin; ln() represents the natural logarithm. I 0 represents the reference light intensity.

7. The coherent tomographic wavefront measurement method based on fiber optic interconnection and point diffraction according to claim 6, characterized in that, During the iteration process, eight image sharpness evaluation functions are computed in parallel, and the one that is most sensitive to changes in the test wavefront and has the best convergence is selected for subsequent optimization.

8. The method for coherent tomography wavefront measurement based on fiber optic interconnection and point diffraction according to claim 5, characterized in that, The algorithm for constructing and solving the global boundary phase difference matrix includes: extracting the phase difference values ​​at all boundaries in the interferogram, constructing a global linear equation system, and solving it all at once to obtain a global continuous phase distribution, thus avoiding point-by-point error propagation.

Images