A high-contrast imaging wavefront detection and correction method and system

Abstract

The application discloses a kind of high contrast imaging wave front detection and correction method and system, this method uses FPGA and CPU hybrid programming architecture to realize high-precision high contrast imaging wave front detection and correction, locking is realized to high contrast imaging dark area in closed-loop correction, wherein, high-precision wave front slope calculation is completed in FPGA, sub-aperture image division and wave front recovery calculation are realized in CPU, and voltage control deformable mirror correction wave front aberration is output.The application uses hybrid programming architecture to carry out high contrast imaging wave front detection and correction, realizes high-precision wave front detection and correction, solves the problem of insufficient performance of CPU for aerospace, and then realizes the locking of high contrast imaging dark area of space coronagraph, for direct imaging detection of exoplanet.After wave front detection and correction, the energy stability of high contrast imaging dark area can be guaranteed, and dark area locking is completed.

Description

Technical Field

[0001] This invention belongs to the field of high-contrast imaging, specifically relating to a high-contrast imaging wavefront detection and correction method and system based on a hybrid programming architecture. Background Technology

[0002] Exoplanet detection is a key focus of contemporary astronomical research. With the continuous development of astronomical technology, humanity's ability to observe exoplanets has significantly improved, enabling us to obtain more information about their mass, size, and composition. In particular, the introduction of direct imaging methods has made spectroscopic analysis of exoplanets possible. The key to direct imaging of exoplanets lies in achieving high contrast. To detect Earth-like planets orbiting within the habitable zone of Sun-like spectral stars in the visible light spectrum, an imaging contrast of 10⁻⁶ is required. -10 To achieve this high contrast, a coronagraph is needed to effectively suppress the diffraction of the primary star in order to obtain an ultra-high contrast imaging region. Wavefront detection and correction technology is the key to achieving high contrast imaging.

[0003] Ground-based adaptive optics typically employs mature and stable algorithms designed using pure CPU computation, enabling high-performance wavefront processing. However, limited by the performance of aerospace CPUs, space wavefront detection algorithms require FPGAs as the primary computational unit for wavefront detection. Therefore, a high-contrast imaging wavefront detection and correction method based on a hybrid FPGA and CPU programming architecture is needed. Summary of the Invention

[0004] Technical problem solved: To address the above-mentioned technical problems, this invention provides a high-contrast imaging wavefront detection and correction method and system, which can realize high-contrast imaging wavefront detection and correction for space coronagraphs, solve the problem of insufficient CPU performance in aerospace applications, and thus achieve the locking of dark areas in high-contrast imaging for direct imaging detection of exoplanets.

[0005] Technical solution:

[0006] A high-contrast imaging wavefront detection and correction method is proposed. This method uses a hybrid programming architecture of FPGA and CPU to achieve high-precision high-contrast imaging wavefront detection and correction. The method locks the dark area of ​​high-contrast imaging in the closed-loop correction. The wavefront slope is calculated with high precision in the FPGA, and the sub-aperture image segmentation and wavefront restoration calculation are performed in the CPU. The output voltage controls the deformable mirror to correct the wavefront aberration.

[0007] Furthermore, the high-contrast imaging wavefront detection and correction method includes the following steps:

[0008] The first step involves the wavefront sensor acting as a data source during wavefront processing, sending images to a computer for wavefront calibration.

[0009] The second step is to obtain the reference sub-aperture coordinates, centroid data, and wavefront restoration matrix based on the wavefront calibration results.

[0010] The third step is to use a wavefront sensor to acquire real-time wavefront images;

[0011] The fourth step involves dividing the sub-aperture image in the CPU based on the sub-aperture coordinates obtained from wavefront calibration. The CPU and FPGA exchange data and transmit the divided wavefront image data.

[0012] The fifth step is to calculate the current sub-aperture centroid in real time in the FPGA, read the reference sub-aperture centroid data that has been stored in the memory during the initialization process, calculate the wavefront slope, and send the wavefront slope calculation result back to the CPU.

[0013] The sixth step is to perform wavefront restoration calculation, which involves multiplying the wavefront slope obtained in the fifth step and the wavefront restoration matrix obtained in the second step in the CPU to obtain the wavefront correction voltage data.

[0014] The seventh step is to package the driving voltage control quantity and connect it to the deformable mirror control box, send the voltage data to the deformable mirror, drive the actuator of the deformable mirror to correct the wavefront error, and complete one iteration of the adaptive optics system correction.

[0015] Step 8: Determine whether it is necessary to continue locking and observing the dark areas of high-contrast imaging based on the observation requirements. If it is necessary to continue observation, repeat steps 3 to 7 to continuously correct wavefront aberrations until the observation ends.

[0016] Furthermore, the wavefront slope calculation is expressed as follows:

[0017]

[0018]

[0019] In the formula: I i,j The internal coordinates of the aperture are (x i ,y j The pixel grayscale value at (x) spot ,y spot (x) represents the actual centroid coordinates before wavefront aberration correction. ref ,y ref The actual wavefront centroid coordinates are the coordinates of the ideal wavefront centroid; the two-dimensional wavefront slope information (Δx) is obtained from the deviation between the actual and ideal wavefront centroid coordinates. i ,Δy j ).

[0020] Furthermore, the wavefront reconstruction calculation is expressed as follows:

[0021]

[0022] This formula can be simplified to:

[0023] E=D·G#

[0024] Where: D is the wavefront restoration matrix, G is the slope vector, E is the restoration voltage vector, n is the number of effective sub-apertures in the adaptive optics system, and m is the number of driving units for the deformable mirror.

[0025] Furthermore, the high precision is determined by the fractional step size of the fixed-point number during FPGA centroid calculation.

[0026] A high-contrast imaging wavefront detection and correction system includes a laser source, a first collimating mirror, a TTM mirror, a deformable mirror, and a beam splitter arranged sequentially. The light beam is transmitted through the beam splitter into the scientific imaging optical path, and the light beam is reflected by the beam splitter into the wavefront detection optical path. The wavefront detection optical path is used to complete the high-contrast imaging wavefront detection and correction method.

[0027] Furthermore, the wavefront detection optical path includes a second imaging lens, a third imaging lens, a microlens array, and a wavefront sensor arranged sequentially.

[0028] Furthermore, the scientific imaging optical path includes, in sequence, a pupil transmittance modulator, a fourth imaging lens, a focal plane mask, a fifth imaging lens, and an imaging camera.

[0029] Beneficial Effects: This invention employs a hybrid programming architecture for high-contrast imaging wavefront detection and correction, achieving high-precision wavefront detection and correction and solving the problem of insufficient CPU performance in aerospace applications. This enables the locking of dark areas in high-contrast imaging using a space coronagraph, facilitating direct imaging and detection of exoplanets. After wavefront detection and correction, energy stability in the dark areas of the high-contrast imaging is ensured, thus completing dark area locking. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the optical principle of the present invention;

[0031] Figure 2 This is a flowchart of wavefront detection and correction.

[0032] Figure 3 This is the data flow design diagram for the wavefront computation unit;

[0033] Figure 4 This is a dark area locked image when the centroid calculation precision is single-precision floating point;

[0034] Figure 5It is a dark area locked image with centroid calculation accuracy of 5 fixed-point digital length;

[0035] Figure 6 It is a dark area locked image with centroid calculation accuracy of 6 fixed-point digital length;

[0036] Figure 7 It is a dark area locked image with centroid calculation accuracy of 7 fixed-point digital length;

[0037] Figure 8 These are the phase errors corresponding to different calculation accuracies.

[0038] The diagram is labeled as follows: 1-Laser source, 2-First collimating lens, 3-TTM lens, 4-Deformable lens, 5-Beam splitter, 6-Second imaging lens, 7-Third imaging lens, 8-Microlens array, 9-Wavefront sensor, 10-Pupil transmittance modulator, 11-Fourth imaging lens, 12-Focal plane mask, 13-Fifth imaging lens, 14-Imaging camera, 15-Wavefront detection optical path. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] like Figure 1 As shown, this embodiment provides a high-contrast imaging wavefront detection and correction system, including a laser source 1, a first collimating lens 2, a TTM mirror 3, a deformable mirror 4, a beam splitter 5, a scientific imaging optical path, and a wavefront detection optical path 15, arranged in sequence. The light beam is transmitted through the beam splitter 5 into the scientific imaging optical path, and the light beam is reflected by the beam splitter 5 into the wavefront detection optical path 15. The wavefront detection optical path 15 includes a second imaging lens 6, a third imaging lens 7, a microlens array 8, and a wavefront sensor 9, arranged in sequence. The scientific imaging optical path includes a pupil transmittance modulator 10, a fourth imaging lens 11, a focal plane mask 12, a fifth imaging lens 13, and an imaging camera 14 (e.g., a CCD), arranged in sequence. Light emitted from a single-mode fiber SF1@632.8nm is collimated by the first collimating lens 2, reflected by the TTM mirror 3 and the deformable mirror 4, and then transmitted by the beam splitter 5 into the scientific imaging optical path and reflected into the wavefront detection optical path. The wavefront detection optical path 15 is used to detect wavefront aberrations introduced by the telescope in real time and correct them through closed-loop control of the deformable mirror 4. The beam of the scientific imaging path is modulated by the pupil transmittance modulator 10, then passes through the focal plane mask 12 to block the starlight, and is directly imaged on the scientific imaging camera (CCD) after passing through the fifth imaging lens 13.

[0042] The wavefront detection and correction system of this invention allows for the selection of optical components according to actual needs. The system optical schematic diagram provided in this embodiment is as follows: Figure 1 As shown, it is mainly used for wavefront detection and correction in high-contrast spatial imaging.

[0043] Example 2

[0044] like Figure 2 and Figure 3 As shown, the present invention provides a high-contrast imaging wavefront detection and correction method based on a hybrid programming architecture, comprising the following steps:

[0045] The first step involves the wavefront sensor serving as the data source during wavefront processing. It transmits images with a resolution of 256*256 and a pixel depth of 16 bits to the computer unit via the Camera Link cable for wavefront calibration.

[0046] The second step is to obtain the reference sub-aperture coordinates, centroid data, and wavefront restoration matrix based on the wavefront calibration results.

[0047] The third step is to use a wavefront sensor to acquire real-time wavefront images;

[0048] The fourth step is to divide the sub-aperture image in the CPU according to the sub-aperture coordinates obtained by wavefront calibration. The CPU exchanges data with the FPGA through the PCI-E bus and uses DMA FIFO to communicate and transmit the divided wavefront image data.

[0049] The fifth step is to calculate the current sub-aperture centroid in real time in the FPGA, read the 577*2 reference sub-aperture centroid data that were stored in the memory during the initialization process, and calculate the wavefront slope. The wavefront slope calculation result is transmitted back to the CPU memory in the same way.

[0050] The wavefront slope is calculated as follows:

[0051]

[0052]

[0053] In the formula: I i,j The internal coordinates of the aperture are (x i ,y j The pixel grayscale value at (x) spot ,y spot (x) represents the actual centroid coordinates before wavefront aberration correction. ref ,y ref The coordinates of the centroid of the ideal wavefront are Δx and Δy. The two-dimensional wavefront slope information (Δx) can be obtained from the deviation between the actual and ideal centroid positions. i ,Δy j ).

[0054] The sixth step is to multiply the obtained wavefront slope and the wavefront restoration matrix obtained in the calibration step in the CPU to obtain the wavefront corrected voltage data.

[0055] The wavefront recovery calculation is as follows:

[0056]

[0057] This formula can be simplified to:

[0058] E=D·G#

[0059] Where: D is the wavefront restoration matrix, G is the slope vector, E is the restoration voltage vector, n is the number of effective sub-apertures in the adaptive optics system, and m is the number of driving units for the deformable mirror.

[0060] The seventh step is to package the driving voltage control quantity and send the voltage data to the deformable mirror via fiber optic connection to the deformable mirror control box, thereby driving the deformable mirror actuator to correct the wavefront error and completing one iteration of the adaptive optics system correction.

[0061] Step 8: Determine whether it is necessary to continue locking the dark area of ​​the high-contrast imaging based on the observation requirements. If it is necessary to continue observation, repeat steps 3 to 7 to continuously correct the wavefront aberration until the observation ends.

[0062] The results are as follows Figures 4-8 As shown: Figure 4 This is a dark area locked image when the centroid calculation precision is single-precision floating point. Figures 5-7 These are dark area locked images with centroid calculation accuracy of 3 integer digits at fixed points and 5-7 digits, i.e., fractional step sizes of 0.25, 0.125, and 0.0625, respectively. Figure 8 The RMS values ​​of voltage changes were calculated under different centroid calculation accuracies. It can be clearly seen that the dark area locking effect is significant. A fixed-point digital length of 7 (i.e., a decimal step size of 0.25) cannot meet the system design requirements, while fixed-point digital lengths with decimal steps smaller than this value can meet the system design requirements.

[0063] The method in this embodiment achieves high-precision, high-contrast imaging wavefront detection and correction using a hybrid FPGA and CPU programming architecture, enabling the locking of dark areas in high-contrast imaging during closed-loop correction. Specifically, high-precision wavefront slope calculation is performed in the FPGA, while sub-aperture image segmentation and wavefront restoration calculations are implemented in the CPU, with output voltage controlling the deformable mirror to correct wavefront aberrations. The high precision is determined by the fractional step size of the fixed-point calculation during FPGA centroid calculation.

[0064] In summary, the high-contrast imaging wavefront detection and correction method of the present invention includes the following steps: a wavefront sensor detects wavefront information; a CPU calculates and calibrates the reference sub-aperture coordinates and centroid data based on the wavefront information; the wavefront sensor sends the real-time wavefront information to the CPU to divide the sub-aperture image, and sends the divided image data to the FPGA for centroid offset calculation; the CPU reads the data and performs wavefront restoration calculation; the wavefront correction voltage is sent to the deformable mirror controller to drive the deformable mirror to correct wavefront aberrations. This invention can achieve high-precision wavefront detection and correction, solve the problem of insufficient CPU performance in aerospace applications, and thus achieve the locking of high-contrast imaging dark areas in space coronagraphs for direct detection of exoplanets.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for high-contrast imaging wavefront detection and correction, characterized in that, A high-precision, high-contrast imaging wavefront detection and correction is achieved using a hybrid FPGA and CPU programming architecture. The closed-loop correction process locks in the dark areas of the high-contrast imaging. Specifically, high-precision wavefront slope calculation is performed in the FPGA, while sub-aperture image segmentation and wavefront restoration calculations are implemented in the CPU. The output voltage controls a deformable mirror to correct wavefront aberrations. The method includes the following steps: The first step involves the wavefront sensor acting as a data source during wavefront processing, sending images to a computer for wavefront calibration. The second step is to obtain the reference sub-aperture coordinates, centroid data, and wavefront restoration matrix based on the wavefront calibration results. The third step is to use a wavefront sensor to acquire real-time wavefront images; The fourth step involves dividing the sub-aperture image in the CPU based on the sub-aperture coordinates obtained from wavefront calibration. The CPU and FPGA exchange data and transmit the divided wavefront image data. The fifth step is to calculate the current sub-aperture centroid in real time in the FPGA, read the reference sub-aperture centroid data that has been stored in the memory during the initialization process, calculate the wavefront slope, and send the wavefront slope calculation result back to the CPU. The sixth step is to perform wavefront restoration calculation, which involves multiplying the wavefront slope obtained in the fifth step and the wavefront restoration matrix obtained in the second step in the CPU to obtain the wavefront correction voltage data. The seventh step is to package the driving voltage control quantity and connect it to the deformable mirror control box, send the voltage data to the deformable mirror, drive the actuator of the deformable mirror to correct the wavefront error, and complete one iteration of the adaptive optics system correction. Step 8: Determine whether it is necessary to continue locking and observing the dark areas of high-contrast imaging based on the observation requirements. If it is necessary to continue observation, repeat steps 3 to 7 to continuously correct wavefront aberrations until the observation ends.

2. The high-contrast imaging wavefront detection and correction method according to claim 1, characterized in that, The wavefront slope calculation is expressed as follows: ， ， In the formula: The internal coordinates of the aperture are ( The pixel grayscale value at () These are the actual centroid coordinates before wavefront aberration correction. The coordinates of the actual wavefront centroid are the ideal coordinates; the two-dimensional wavefront slope information is obtained from the deviation between the actual and ideal wavefront centroid coordinates. .

3. The high-contrast imaging wavefront detection and correction method according to claim 2, characterized in that, The wavefront restoration calculation is expressed as follows: ， This formula can be simplified to: ， Where: D is the wavefront restoration matrix, G is the slope vector, E is the restoration voltage vector, n is the number of effective sub-apertures in the adaptive optics system, and m is the number of driving units for the deformable mirror.

4. The high-contrast imaging wavefront detection and correction method according to claim 1, characterized in that, The high precision is determined by the fractional step size of the fixed-point number during FPGA centroid calculation.

5. A high-contrast imaging wavefront detection and correction system, characterized in that, The system includes a laser source, a first collimating mirror, a TTM mirror, a deformable mirror, a beam splitter, a scientific imaging optical path, and a wavefront detection optical path, arranged sequentially. The light beam is transmitted through the beam splitter into the scientific imaging optical path, and the light beam is reflected by the beam splitter into the wavefront detection optical path. The wavefront detection optical path is used to complete the high-contrast imaging wavefront detection and correction method described in claim 1.

6. The high-contrast imaging wavefront detection and correction system according to claim 5, characterized in that, The wavefront detection optical path includes a second imaging lens, a third imaging lens, a microlens array, and a wavefront sensor arranged in sequence.

7. The high-contrast imaging wavefront detection and correction system according to claim 5, characterized in that, The scientific imaging optical path includes, in sequence, a pupil transmittance modulator, a fourth imaging lens, a focal plane mask, a fifth imaging lens, and an imaging camera.

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