Photon integrated interferometric imaging reconstruction method based on spatial zero-filling

Abstract

The present invention relates to the field of photon integrated interference imaging technology, and in particular to a photon integrated interference imaging reconstruction method based on spatial domain zero filling, comprising: S1: calculating the frequency sampling points of each paired baseline; S2: calculating the size of the reconstructed image; S3: generating a frequency domain mask; S4: updating the spectrum using the frequency domain mask; S5: inverse Fourier transforming the spectrum into a spatial domain image; S6: using the spatial domain mask to perform zero filling constraints on the spatial domain image to obtain a spatial domain image; S7: Fourier transforming the spatial domain image into a spectrum O; S8: repeating steps S4-S7 until the spectrum O converges to obtain a final spatial domain image; S9: cropping the zero filling area of ​​the final spatial domain image according to the size of the reconstructed image to obtain a reconstructed image. The present invention can supplement the frequency value of the unsampled area in a zero area constraint manner in the spatial domain zero filling area, and reduce artifacts in the reconstructed image.

Description

Technical Field

[0001] The present invention relates to the technical field of photon integrated interference imaging, and in particular to a photon integrated interference imaging reconstruction method based on spatial domain zero filling. Background Art

[0002] In the field of astronomical observation and remote sensing imaging, in order to improve the imaging resolution, it is usually chosen to increase the aperture of the optical system. However, as the aperture of the optical system increases, its manufacturing cost increases exponentially. Photon integrated interferometric imaging technology provides a new technical approach to replace traditional large-aperture optical telescopes. The use of photon integrated chips (PICs) to realize the beam synthesis of the interference array can significantly improve the system's real-time, sensitivity, scalability and other capabilities, and effectively enhance the system's stability and reliability. The processing and manufacturing are simple, the process is stable, and the manufacturing cost is effectively reduced. However, unlike the imaging mode in the traditional Cartesian coordinate system, the frequency sampling method in the current photon integrated interferometric imaging is polar coordinate discrete sampling. Discrete sampling will cause a large number of frequency loss, resulting in a large number of artifacts in the reconstructed image, resulting in a decrease in the quality of the reconstructed image. The discrete Fourier transform in the traditional Cartesian coordinate system requires that all frequency points are distributed as integer frequency distributions, while the frequency distribution in the polar coordinate system is relatively sparse and not integer distribution. Therefore, using discrete Fourier to transform the sampling frequency points in the polar coordinate system will result in approximation errors, resulting in a decrease in the quality of the reconstructed image. Summary of the invention

[0003] In order to solve the problem that the prior art uses discrete Fourier to transform sampling frequency points in polar coordinates, which will lead to approximate errors and cause the quality of reconstructed images to decrease, the present invention provides a photon integrated interferometric imaging reconstruction method based on spatial zero-filling, which can supplement the frequency values ​​of unsampled areas in a zero-area constraint manner in the spatial zero-filling area and reduce artifacts in the reconstructed image, and can effectively deal with the problems caused by sparse sampling and non-uniform sampling in polar coordinates.

[0004] The photon integrated interferometric imaging reconstruction method based on spatial zero filling proposed in the present invention specifically comprises the following steps:

[0005] S1: According to the baseline configuration and baseline pairing method of the photon integrated interferometric imaging system, the frequency sampling point coordinates of the photon integrated interferometric imaging system are calculated by the following formula:

[0006] (1);

[0007] Among them, B p is the paired baseline of group p, is the jth imaging wavelength of the photon integrated interferometric imaging system, z is the imaging distance of the photon integrated interferometric imaging system, is the frequency sampling point of the photon integrated interferometric imaging system, and there are n groups of frequency sampling points in total, ( x , y ) is the spatial coordinate;

[0008] S2: Combined with formula (1), the size of the reconstructed image is calculated by the following formula :

[0009] (2);

[0010] (3);

[0011] (4);

[0012] (5);

[0013] Among them, R is the number rounded up, is the ratio of the maximum frequency to the fundamental frequency of the photon integrated interferometric imaging system, is the maximum frequency of the photon integrated interferometric imaging system, is the fundamental frequency of the photon integrated interferometric imaging system, N is the zero-filling ratio, B min is the shortest paired baseline, B max is the longest paired baseline, is the minimum imaging wavelength of the photon integrated interferometric imaging system, is the maximum imaging wavelength of the photon integrated interferometric imaging system;

[0014] S3: Generate a frequency domain mask according to the coordinates of all frequency sampling points obtained in step S1 by the following formula:

[0015] (6);

[0016] (7);

[0017] (8);

[0018] Among them, N is the frequency sampling point expanded N times, P is the frequency domain mask, To expand the horizontal coordinate of the nth group of frequency sampling points by N times, The ordinate of the nth group of frequency sampling points expanded N times;

[0019] S4: Update the spectrum using the frequency domain mask:

[0020] (9);

[0021] (10);

[0022] (11);

[0023] in, is the spectrum, S is the initialization spectrum, is the complex visibility of the nth group of frequency sampling points, is the phase of the complex visibility of the nth frequency sampling point, is the modulus of the complex visibility of the nth group of frequency sampling points;

[0024] S5: The spectrum is inversely transformed into a spatial domain image by the following formula :

[0025] (12);

[0026] Where IFT is the inverse Fourier transform, For the spatial domain image The coordinates of

[0027] S6: Construct a spatial mask and use it to modify the spatial image Perform zero-filling constraints to obtain the filtered spatial domain image :

[0028] (13);

[0029] (14);

[0030] Among them, M is the spatial mask, is the dot product;

[0031] S7: The spatial domain image is transformed into The Fourier transform is the spectrum O:

[0032] (15);

[0033] Where FT is Fourier transform;

[0034] S8: Repeat steps S4-S7 until the spectrum O converges to obtain the final spatial domain image ;

[0035] S9: The final spatial domain image is reconstructed according to the size of the image The zero-filled area is cropped to obtain the reconstructed image.

[0036] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0037] The photon integrated interferometric imaging reconstruction method based on spatial zero-filling proposed in the present invention can effectively overcome the coordinate approximation error caused by sparse sampling and the artifact problem caused by sparse sampling by amplifying the coordinate values ​​of the frequency sampling points and using the zero-domain constraint of the zero-filling area, and can improve the signal-to-noise ratio of the reconstructed image. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic flow chart of a photon integrated interferometric imaging reconstruction method based on spatial zero-filling provided in accordance with an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of the distribution of frequency sampling point coordinates provided according to an embodiment of the present invention;

[0040] Figure 3 is a schematic diagram of a spatial domain mask provided according to an embodiment of the present invention;

[0041] Figure 4 is a simulated high-resolution image provided according to an embodiment of the present invention;

[0042] Figure 5 It is a reconstructed image obtained by using a conventional photon integrated interference imaging technique according to an embodiment of the present invention;

[0043] Figure 6 It is a reconstructed image obtained by adopting a photon integrated interference imaging reconstruction method based on spatial zero filling provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present 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 present invention and do not constitute a limitation of the present invention.

[0046] The photon integrated interferometric imaging reconstruction method based on spatial zero-filling proposed in the embodiment of the present invention can overcome the problem of a large number of artifacts in the spatial domain image caused by non-uniform sparse sampling, effectively reduce image artifacts, and improve the signal-to-noise ratio of the reconstructed image by virtue of the 0-domain constraint of the zero-filling area.

[0047] Figure 1 The process of the photon integrated interference imaging reconstruction method based on spatial zero filling provided by an embodiment of the present invention is shown; Figure 2shows the distribution of frequency sampling point coordinates provided according to an embodiment of the present invention; Figure 3 A spatial domain mask provided according to an embodiment of the present invention is shown.

[0048] like Figure 1-Figure 3 As shown, the photon integrated interferometric imaging reconstruction method based on spatial zero filling proposed in an embodiment of the present invention specifically includes the following steps:

[0049] S1: According to the baseline configuration and baseline pairing method of the photon integrated interferometric imaging system, the frequency sampling point coordinates of the photon integrated interferometric imaging system are calculated by the following formula:

[0050] (1);

[0051] Among them, B p is the paired baseline of group p, is the jth imaging wavelength of the photon integrated interferometric imaging system, z is the imaging distance of the photon integrated interferometric imaging system, is the frequency sampling point of the photon integrated interferometric imaging system, and there are n groups of frequency sampling points in total, ( x , y ) is the spatial coordinate;

[0052] S2: Combined with formula (1), the size of the reconstructed image is calculated by the following formula :

[0053] (2);

[0054] (3);

[0055] (4);

[0056] (5);

[0057] Among them, R is the number rounded up, is the ratio of the maximum frequency to the fundamental frequency of the photon integrated interferometric imaging system, is the maximum frequency of the photon integrated interferometric imaging system, is the fundamental frequency of the photon integrated interferometric imaging system, N is the zero-filling ratio, B min is the shortest paired baseline, B max is the longest paired baseline, is the minimum imaging wavelength of the photon integrated interferometric imaging system, is the maximum imaging wavelength of the photon integrated interferometric imaging system;

[0058] S3: Generate a frequency domain mask according to the coordinates of all frequency sampling points obtained in step S1 by the following formula:

[0059] (6);

[0060] (7);

[0061] (8);

[0062] Among them, N is the frequency sampling point expanded N times, which is equivalent to the zero padding operation around the original image, and P is the frequency domain mask. To expand the horizontal coordinate of the nth group of frequency sampling points by N times, The ordinate of the nth group of frequency sampling points expanded N times;

[0063] S4: Update the spectrum using the frequency domain mask:

[0064] (9);

[0065] (10);

[0066] (11);

[0067] in, is the spectrum, S is the initialization spectrum, is the complex visibility of the nth group of frequency sampling points, is the phase of the complex visibility of the nth frequency sampling point, is the modulus of the complex visibility of the nth group of frequency sampling points;

[0068] S5: The spectrum is inversely transformed into a spatial domain image by the following formula :

[0069] (12);

[0070] Where IFT is the inverse Fourier transform, For the spatial domain image The coordinates of

[0071] S6: Construct a spatial mask and use it to modify the spatial image Perform zero-filling constraints to obtain the filtered spatial domain image :

[0072] (13);

[0073] (14);

[0074] Among them, M is the spatial mask, is the dot product;

[0075] S7: The spatial domain image is transformed into The Fourier transform is the spectrum O:

[0076] (15);

[0077] Where FT is Fourier transform;

[0078] S8: Repeat steps S4-S7 until the spectrum O converges to obtain the final spatial domain image ;

[0079] S9: The final spatial domain image is reconstructed according to the size of the image The zero-filled area is cropped to obtain the reconstructed image.

[0080] Figure 4 shows a simulated high-resolution image provided according to an embodiment of the present invention, Figure 5 The figure shows a reconstructed image obtained by using a conventional photon integrated interference imaging technique provided by an embodiment of the present invention; Figure 6 A reconstructed image obtained by using a photon integrated interference imaging reconstruction method based on spatial zero-filling provided in an embodiment of the present invention is shown.

[0081] like Figure 4-Figure 6 As shown, by comparing the reconstructed image obtained by processing the simulated high-resolution image using the traditional photon integrated interference imaging technology and the reconstructed image obtained by processing the simulated high-resolution image using the photon integrated interference imaging reconstruction method based on spatial zero filling, it can be seen that the photon integrated interference imaging reconstruction method based on spatial zero filling provided by the embodiment of the present invention has better reconstruction effect than the traditional photon integrated interference imaging technology.

[0082] 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 the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0083] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A photon integrated interferometric imaging reconstruction method based on spatial zero filling, characterized in that: The specific steps include: S1: According to the baseline configuration and baseline pairing method of the photon integrated interferometric imaging system, the frequency sampling point coordinates of the photon integrated interferometric imaging system are calculated by the following formula: （1）； Among them, B p is the paired baseline of group p, is the jth imaging wavelength of the photon integrated interference imaging system, z is the imaging distance of the photon integrated interference imaging system, is the frequency sampling point of the photon integrated interference imaging system, and there are n groups of frequency sampling points in total, ( x , y ) is the spatial coordinate; S2: Combined with formula (1), the size of the reconstructed image is calculated by the following formula : （2）； （3）； （4）； （5）； Among them, R is the number rounded up, is the ratio of the maximum frequency to the fundamental frequency of the photon integrated interference imaging system, is the maximum frequency of the photon integrated interferometric imaging system, is the fundamental frequency of the photon integrated interference imaging system, N is the zero filling ratio, B min is the shortest paired baseline, B max is the longest paired baseline, is the minimum imaging wavelength of the photon integrated interferometric imaging system, is the maximum imaging wavelength of the photon integrated interference imaging system; S3: Generate a frequency domain mask according to the coordinates of all frequency sampling points obtained in step S1 by the following formula: （6）； （7）； （8）； Wherein, N is the frequency sampling point expanded N times, P is the frequency domain mask, To expand the horizontal coordinate of the nth group of frequency sampling points by N times, The ordinate of the nth group of frequency sampling points expanded N times; S4: Update the spectrum using the frequency domain mask: （9）； （10）； （11）； in, is the spectrum, S is the initialization spectrum, is the complex visibility of the nth group of frequency sampling points, is the phase of the complex visibility of the nth frequency sampling point, is the modulus of the complex visibility of the nth group of frequency sampling points; S5: The spectrum is inversely Fourier transformed into a spatial domain image by the following formula : （12）； Where IFT is the inverse Fourier transform, is the spatial domain image The coordinates of S6: construct a spatial domain mask, and use the spatial domain mask to Perform zero-filling constraints to obtain the filtered spatial domain image : （13）； （14）； Among them, M is the spatial mask, is the dot product; S7: The spatial domain image is transformed into The Fourier transform is the spectrum O: （15）； Where FT is Fourier transform; S8: Repeat steps S4-S7 until the spectrum O converges to obtain the final spatial domain image ; S9: The final spatial domain image is reconstructed according to the size of the image The zero-filled area is cropped to obtain the reconstructed image.

Images