Evaluation method of reconstructed image quality in photon integrated interferometric imaging system

Abstract

The present invention belongs to the field of photon integrated interference imaging technology, and in particular, relates to a method for evaluating the reconstructed image quality of a photon integrated interference imaging system. The method comprises: S1: calculating the discrete modulation transfer function of the photon integrated interference imaging system according to the parameters of the photon integrated interference imaging system; S2: acquiring the original image using the photon integrated interference imaging system to obtain a reconstructed image; S3: performing multi-resolution decomposition of the original image and the reconstructed image in turn using a Gaussian pyramid to obtain an original image group and a reconstructed image group; S4: calculating the mutual information of the images with the same resolution contained in the original image group and the reconstructed image group; S5: evaluating the image quality of the photon integrated interference imaging system according to the calculation results of step S1 and step S4. The present invention objectively evaluates the reconstructed image quality of the photon integrated interference imaging system based on two measurements, spatial domain and frequency domain, to make up for the lack of evaluation in a single dimension.

Description

Technical Field

[0001] The present invention belongs to the technical field of photon integrated interference imaging, and in particular relates to a method for evaluating reconstructed image quality of a photon integrated interference imaging system. Background Art

[0002] Photon integrated interferometric imaging is a new imaging system developed in recent years, which is expected to replace the traditional optical imaging system and realize large-scale high-resolution imaging needs. In the actual evaluation process of image quality reconstruction of optical systems, traditional evaluation indicators such as MTF (modulation transfer function), MSE (mean square error), PSNR (peak signal-to-noise ratio) have always occupied a dominant position. In the face of the new imaging system of photon integrated interferometric imaging, the role of traditional optical evaluation indicators is limited. In recent years, scholars have begun to introduce SSIM (structural similarity), maximum entropy and other information-theoretic evaluation indicators to meet new needs. Since photon integrated interferometry imaging technology is a type of indirect imaging, different from traditional direct imaging, its sampling of the target spectrum is sparse and discontinuous. Traditional optical system evaluation indicators such as MTF and PSF can only partially reflect the characteristics of the photon integrated interferometry imaging system itself. However, for the photon integrated interferometry imaging system, even if the system's own evaluation indicators such as MTF are very high, the discontinuity and sparsity of its sampling may cause the loss of the main frequency points, resulting in unsatisfactory imaging effects. Therefore, it is not objective and comprehensive to evaluate the reconstructed image quality from the performance of the photon integrated interferometry imaging system itself. Therefore, although the traditional optical evaluation indicators have played a role in the objective evaluation of the reconstructed image quality of the photon integrated interferometry imaging system to a certain extent, they cannot comprehensively and accurately analyze and evaluate the reconstructed image quality of the photon integrated interferometry imaging system. Summary of the invention

[0003] In view of this, the present invention aims to provide a method for evaluating the reconstructed image quality of a photon integrated interferometric imaging system, so as to solve the problem that the prior art is unable to comprehensively and accurately analyze and evaluate the reconstructed image quality of a photon integrated interferometric imaging system. The present invention objectively evaluates the reconstructed image quality of a photon integrated interferometric imaging system based on two measurements, namely, spatial domain and frequency domain, thus making up for the lack of evaluation in a single dimension.

[0004] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0005] A method for evaluating the reconstructed image quality of a photon integrated interference imaging system comprises the following steps:

[0006] S1: Calculate the discrete modulation transfer function of the photon integrated interferometric imaging system according to the parameters of the photon integrated interferometric imaging system;

[0007] S2: using a photon integrated interference imaging system to collect the original image and obtain a reconstructed image;

[0008] S3: Use the Gaussian pyramid to perform multi-resolution decomposition on the original image and the reconstructed image in turn to obtain an original image group and a reconstructed image group;

[0009] S4: calculating mutual information of images with the same resolution contained in the original image group and the reconstructed image group;

[0010] S5: Implement image quality evaluation of the photon integrated interference imaging system according to the calculation results of step S1 and step S4.

[0011] Furthermore, in step S1, the calculation formula of the discretized modulation transfer function of the photon integrated interference imaging system is:

[0012] ;

[0013] ;

[0014] in, is the modulation transfer function, is the pupil function, The value is 0 or 1. is the transfer function of the photon integrated interferometric imaging system, is the position coordinate of pixel point f, is the wavelength of the photon integrated interferometric imaging system, is the normalized unit modulus value, is the displacement of the i-th staggered pupil.

[0015] Furthermore, in step S3, the original image group and the reconstructed image group each contain the same number of images, and the resolutions correspond one to one.

[0016] Furthermore, in step S4, the mutual information calculation formula is:

[0017] I(A,B)=H(A)+H(B)−H(A,B);

[0018] Wherein, I(A,B) is the mutual information of the images with the same resolution contained in the original image group and the reconstructed image group, H(A) and H(B) are the entropies of the images with the same resolution contained in the original image group and the reconstructed image group, respectively, and H(A,B) is the joint entropy of the images with the same resolution contained in the original image group and the reconstructed image group.

[0019] Compared with the prior art, the invention can achieve the following beneficial effects:

[0020] (1) The present invention creates a method for evaluating the reconstructed image quality of the photon integrated interferometric imaging system. First, the MTF of the intrinsic detection capability of the system is evaluated to determine a measurement standard. Then, the reconstructed image and the original image are subjected to pyramid decomposition to solve the image mutual information at different scales. The reconstructed image quality is evaluated from two measurements (the two measurements refer to the intrinsic performance measurement of the system and the image quality measurement after the imaging is calculated, which can also be understood as two measurements in the spatial domain and the frequency domain). The present invention can comprehensively and objectively evaluate the imaging capability of the optical imaging system. In addition, the direct connection between the two measurements is that the reconstructed image is obtained by inverse Fourier transform of the sampling characteristics of the system itself. The imaging quality of the optical imaging system is supplemented by the mutual information between the reconstructed image and the original target image, making the evaluation result more comprehensive and objective.

[0021] (2) The present invention creates a method for evaluating the reconstructed image quality of the photon integrated interference imaging system, which uses discrete modulation transfer function and multi-resolution mutual information as performance measures, respectively, and analyzes the discrete modulation transfer function of different photon integrated interference imaging systems with the same equivalent aperture and the multi-resolution mutual information of the reconstructed image based on relevant physical relationships, wherein the multi-resolution decomposition of the reconstructed image is decomposed using a Gaussian pyramid. The present invention realizes an objective evaluation of the reconstructed image quality of the photon integrated interference imaging system based on two measures, the spatial domain and the frequency domain, that is, the present invention realizes an objective evaluation of the reconstructed image quality of the photon integrated interference imaging system from the two aspects of optical transfer characteristics and information acquisition capabilities, and the evaluation results are accurate and comprehensive, which is of great significance for evaluating the imaging quality of the photon integrated interference imaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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:

[0023] Figure 1 A schematic flow chart of a method for evaluating the reconstructed image quality of a photon integrated interference imaging system according to an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of the structure of the Gaussian pyramid described in the embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the array structure of IDEAL described in an embodiment of the present invention;

[0026] Figure 4 A schematic diagram of the SPIDER array structure described in an embodiment of the present invention;

[0027] Figure 5A schematic diagram of the HMSLA array structure described in an embodiment of the present invention;

[0028] Figure 6 A schematic diagram of the array structure of the ESPIA described in the embodiment of the present invention;

[0029] Figure 7 Schematic diagram of discrete MTF curves of four arrays described in the embodiments of the present invention;

[0030] Figure 8 A schematic diagram of mutual information curves of four arrays described in an embodiment of the present invention;

[0031] Fig. 9 The original image corresponding to the IDEAL array described in the embodiment of the present invention;

[0032] Fig.10 A reconstructed image corresponding to the SPIDER array described in the embodiment of the present invention;

[0033] Fig.11 A reconstructed image corresponding to the HMSLA array described in the embodiment of the present invention;

[0034] Fig.12 This is the reconstructed image corresponding to the ESPIA array described in the embodiment of the present invention.

[0035] 1. Original reconstructed image; 2. First layer image after decomposition; 3. Second layer image after decomposition; 4. Third layer image after decomposition; 5. Fourth layer image after decomposition. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the invention more clear, 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 here are only used to explain the invention and do not constitute a limitation of the invention.

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present 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 present 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. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0039] 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.

[0040] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0041] like Figure 1 As shown, the reconstructed image quality evaluation method of the photon integrated interference imaging system proposed in the present invention specifically includes the following steps:

[0042] S1: Calculate the discrete modulation transfer function of the photon integrated interferometric imaging system according to the parameters of the photon integrated interferometric imaging system;

[0043] The calculation formula of the discrete modulation transfer function of the photon integrated interferometric imaging system is:

[0044] ;

[0045] ;

[0046] in, is the modulation transfer function, is the pupil function, The value is 0 or 1. is the transfer function of the photon integrated interferometric imaging system, is the position coordinate of pixel point f, is the wavelength of the photon integrated interferometric imaging system, is the normalized unit modulus value, is the displacement of the i-th staggered pupil.

[0047] S2: using a photon integrated interference imaging system to collect the original image and obtain a reconstructed image;

[0048] S3: Use the Gaussian pyramid to perform multi-resolution decomposition on the original image and the reconstructed image in turn to obtain an original image group and a reconstructed image group;

[0049] The original image group and the reconstructed image group each contain the same number of images, and the resolutions thereof correspond one to one.

[0050] S4: calculating mutual information of images with the same resolution contained in the original image group and the reconstructed image group;

[0051] In step S4, the mutual information calculation formula is:

[0052] I(A,B)=H(A)+H(B)−H(A,B);

[0053] Wherein, I(A,B) is the mutual information of the images with the same resolution contained in the original image group and the reconstructed image group, H(A) and H(B) are the entropies of the images with the same resolution contained in the original image group and the reconstructed image group, respectively, and H(A,B) is the joint entropy of the images with the same resolution contained in the original image group and the reconstructed image group.

[0054] Mutual information is a key concept in information theory that measures the statistical correlation between two random variables. Mutual information is widely used in image processing fields such as image registration and reconstruction. Mutual information in the image field is usually based on the probability distribution entropy of the grayscale values ​​in the image.

[0055] S5: Implement image quality evaluation of the photon integrated interference imaging system according to the calculation results of step S1 and step S4.

[0056] The closer the discretized modulation transfer function value and the mutual information value are to 1, the better the reconstructed image quality of the current photon integrated interferometric imaging system is.

[0057] The image pyramid can be viewed as a series of permutations of images of different resolutions, where the bottom image is the original image, and the image resolution of each layer of the pyramid decreases successively, and the top low-resolution image may even have only one pixel. There are many ways to obtain low-resolution images, such as using a Gaussian low-pass filter to generate a Gaussian pyramid, using neighborhood averaging to generate an average pyramid, or not filtering and directly downsampling to generate a sub-sampling pyramid.

[0058] like Figure 2 As shown in the figure, we use a Gaussian low-pass filter to perform multi-resolution decomposition on the reconstructed image, including the original reconstructed image 1, the decomposed first layer image 2, the decomposed second layer image 3, the decomposed third layer image 4 and the decomposed fourth layer image 5. That is, a multi-resolution histogram is generated using a Gaussian pyramid to facilitate the comparison of the information acquisition capabilities of the reconstructed images of each array at different resolutions.

[0059] like Figure 3-Figure 6 As shown, the relevant parameters of the four arrays are shown in Table 1. The parameter information of the four arrays is used as a simulation basis to verify the universality and effectiveness of the evaluation method of the present invention.

[0060] Table 1

[0061]

[0062] like Figure 7 and Figure 8 As shown in the figure, the four arrays correspond to four different parameters of the photon integrated interferometric imaging system. The image corresponding to the IDEAL array is taken as the original image, and the other three arrays are calculated. The discretized modulation transfer function value and mutual information value of the ESPIA array tend to 1, and Figure 9-12 As shown, the numerical results of the present invention correspond to the image quality effects of the actual reconstructed images, which verifies the universality and effectiveness of the evaluation method of the present invention.

[0063] 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.

[0064] 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 method for evaluating the reconstructed image quality of a photon integrated interferometric imaging system, characterized in that: The specific steps include: S1: Calculate the discrete modulation transfer function of the photon integrated interferometric imaging system according to the parameters of the photon integrated interferometric imaging system; The calculation formula of the discrete modulation transfer function of the photon integrated interferometric imaging system is: ； ； in, is the modulation transfer function, is the pupil function, The value is 0 or 1. is the transfer function of the photon integrated interferometric imaging system, is the position coordinate of pixel point f, is the wavelength of the photon integrated interferometric imaging system, is the normalized unit modulus value, is the displacement of the i-th staggered pupil; S2: using a photon integrated interference imaging system to collect the original image and obtain a reconstructed image; S3: Use the Gaussian pyramid to perform multi-resolution decomposition on the original image and the reconstructed image in turn to obtain an original image group and a reconstructed image group; S4: performing mutual information calculation on the images with the same resolution respectively included in the original image group and the reconstructed image group; S5: evaluating the image quality of the photon integrated interference imaging system according to the calculation results of step S1 and step S4; The closer the discretized modulation transfer function value and the mutual information value are to 1, the better the reconstructed image quality of the current photon integrated interferometric imaging system.

2. The reconstructed image quality evaluation method of the photon integrated interference imaging system according to claim 1, characterized in that: In step S3, the original image group and the reconstructed image group each contain the same number of images, and the resolutions correspond one to one.

3. The reconstructed image quality evaluation method of the photon integrated interference imaging system according to claim 1, characterized in that: In step S4, the mutual information calculation formula is: I(A,B)=H(A)+H(B)−H(A,B); Wherein, I(A,B) is the mutual information of the images with the same resolution contained in the original image group and the reconstructed image group, H(A) and H(B) are the entropies of the images with the same resolution contained in the original image group and the reconstructed image group, respectively, and H(A,B) is the joint entropy of the images with the same resolution contained in the original image group and the reconstructed image group.

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