Method and system for improving reconstructed image quality of digital holographic image

Abstract

The invention discloses a digital holographic interference image reconstruction image quality improvement method and system. The method comprises the following steps: calculating initial frequency distribution information of an original holographic interference fringe image; iteratively calculating gradient gradual change factors of the initial frequency distribution information in different directions by taking self-adaptive consistent decrease of discrete gradient thresholds as a principle; a gradient gradual change factor is obtained based on iterative calculation, and spectrum epitaxial growth observation values in the directions are calculated at the same time; based on initial frequency distribution information of the original holographic interference fringe image and epitaxial growth observation values in all directions, complete frequency spectrum information for constructing a holographic reconstruction image is calculated; and performing frequency domain-to-time domain conversion on the complete frequency spectrum information of the reconstructed image by using fast Fourier inverse transform to obtain a reconstructed image of the holographic interference fringe image. According to the method, the image quality of the digital holographic reconstructed image can be effectively improved, the obtained digital holographic reconstructed image has comprehensive detail information, and the reconstructed digital holographic image can improve the visual effect of an observer.

Description

Technical Field

[0001] The invention relates to a method and system for improving the image quality of digital holographic interference image reconstruction, and belongs to the technical field of image processing and image measurement. Background Art

[0002] Compared with ordinary image processing technology, the biggest advantage of digital holography is that it can provide observers with the three-dimensional surface features of the target to be observed, thereby obtaining a clearer and more intuitive visual experience of the target to be measured. Therefore, digital holography has important applications in the fields of three-dimensional measurement and three-dimensional modeling.

[0003] However, there are some unfavorable factors in the application process of existing digital holographic technology that need to be solved urgently. First of all, digital holographic technology mostly adopts lensless image acquisition technology. Its principle is to use optical interference method to form light and dark optical interference fringes on the surface of image receiving devices such as CCD or CMOS. The fringes record the reflected light intensity information of the object to be measured and the phase difference information formed by the height difference information of different spatial positions to complete the recording of the morphology and spatial depth information of the object to be measured. Therefore, there is a common phenomenon in digital holographic technology that the details of the object to be measured are clear and the morphology is blurred when reconstructing the image due to the low resolution of the fringes recorded by interference. In severe cases, it will affect the precise observation of the object.

[0004] Generally, in order to effectively improve the image quality of the reconstructed image of the digital holographic interference image, it can be achieved by improving the precision of the optical path and the acquisition system to increase the resolution of the stripes themselves. However, this method is too expensive and is not conducive to large-scale practical application and promotion. As for the image quality improvement algorithm of the reconstructed image, the existing algorithm is affected by the excessive diffraction energy brought by the zero-order diffraction stripes in the digital holographic imaging and the speckle noise introduced in the reconstruction process, making it difficult to obtain an intuitive improvement in the reconstructed image. Speckle noise and the detail information in the reconstructed image to be enhanced belong to the high-frequency information of the image. Therefore, simply enhancing the high-frequency details will inevitably enhance the noise and affect the final visual effect. However, due to the complex design of optical lenses and lasers and the cumbersome mechanical operation, the ordinary noise reduction method is complicated and cannot effectively improve the quality of the reconstructed image. The existing image quality improvement method cannot be used in practice, and the detailed information of the digital holographic image cannot be fully obtained. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art. The present invention provides a method and system for improving the image quality of digital holographic interference image reconstruction, which reconstructs the original holographic interference fringe image and obtains a digital holographic reconstructed image with comprehensive detail information.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a method for improving the image quality of digital holographic image reconstruction, comprising the following steps: Step 1, initial acquisition: obtaining the initial frequency distribution information of the original holographic interference fringe image.

[0007] Step 2, first iterative calculation: based on the principle of adaptive and consistent decrease of discrete gradient threshold, iteratively calculate the gradient change factor of each direction of the initial frequency distribution information.

[0008] Step 3: Calculation of spectrum epitaxial growth observation values: Based on iterative calculation, the gradient gradient factor is obtained, and the spectrum epitaxial growth observation values ​​are calculated from each direction at the same time.

[0009] Step 4: Calculation of complete spectrum information: Based on the initial frequency distribution information of the original holographic interference fringe image and the epitaxial growth observation value, calculate the complete spectrum information of the holographic reconstructed image, and then determine whether the complete spectrum information of the holographic reconstructed image satisfies the adaptive consistent descent.

[0010] Step 5, second iterative calculation: use inverse fast Fourier transform to transform the complete spectrum information of the reconstructed image from the frequency domain to the time domain to obtain a reconstructed image of the holographic interference fringe image.

[0011] Preferably, the initial frequency distribution information of the original holographic interference fringe image is obtained, and the specific acquisition process is as follows: S11, obtaining a digital interference fringe image.

[0012] S12. Preprocess the digital interference fringe image using fast Fourier transform to obtain an original holographic interference fringe image.

[0013] S13. Use fast Fourier transform to process the original holographic interference fringe image to obtain initial frequency distribution information of the original holographic interference fringe image.

[0014] Preferably, the iterative calculation of the gradient change factor of each direction of the initial frequency distribution information is specifically calculated as follows: construct a plane rectangular coordinate system at a preset position of the original holographic interference fringe image, and substitute it into the iterative calculation formula In the formula, the gradient gradient factors of each direction at the coordinate position (x, y) in the original holographic interference fringe image are obtained, where k represents the number of iterations, k ≥ 1, It represents the gradient factor in the horizontal direction at the coordinate position (x, y) at the kth iteration. Indicates the gradient factor in the vertical direction at the coordinate position (x, y) at the kth iteration; α (k-1) Indicates the preset gradient threshold for the k-1th iteration, G h Represents the preset horizontal gradient operator, G h+1represents the preset vertical gradient operator, G represents the preset gradient operator, ω (k-1) Represents the holographic interference fringe image corresponding to the k-1th iteration.

[0015] Preferably, the spectrum epitaxial growth observation value is calculated from each direction, and the specific calculation process is as follows: by calculating formula The observed value of the spectrum epitaxial growth at the kth iteration is obtained as ζ(ω k ), where the symbol * indicates conjugate calculation, ζ(I) k-1 represents the iterative solution at the k-1th iteration, β k-1 represents the gradient threshold contribution parameter at the k-1th iteration, It represents the gradient factor in the horizontal direction at the coordinate position (x, y) at the kth iteration. Indicates the gradient factor in the vertical direction at the coordinate position (x, y) at the kth iteration, G h Represents the preset horizontal gradient operator, G h+1 represents the preset vertical gradient operator, ω represents the original holographic interference fringe image, k represents the number of iterations, k≥1.

[0016] Preferably, the complete spectrum information of the CGH reconstructed image is specifically calculated as follows: ζ(I k )=ζ(T) * ζ(I0)+γ k-1 ζ(ω k ), where ζ(I0) represents the complete spectrum information of the original holographic interference fringe image, ζ(I k ) represents the complete spectrum information of the holographic interference fringe image at the kth iteration, γ represents the synthetic contribution parameter, ζ(ω k ) represents the observed value of the spectrum epitaxial growth at the kth iteration, ζ(T) represents the modified transfer function of the frequency transfer system, k represents the number of iterations, and k≥1.

[0017] Preferably, the process of judging whether the complete spectrum information of the holographic reconstructed image satisfies the adaptive consistent decline is as follows: S41: If Then it is determined that the complete spectrum information of the holographic reconstruction image satisfies the adaptive consistent decline, and then the iteration is stopped and step 5 is executed, where represents the L1 norm, represents the complete spectrum information ζ(I k ) and the complete spectrum information ζ(I k-1 ), and ε is the preset convergence constant.

[0018] S42, It is determined that the complete spectrum information of the holographic reconstructed image does not satisfy the adaptive consistent descent, and the iteration parameters are reinitialized and return to step two.

[0019] In a second aspect, the present invention provides a digital holographic image reconstruction image quality improvement system, comprising the following modules: an initial acquisition module: used to obtain the initial frequency distribution information of the original holographic interference fringe image.

[0020] The first iterative calculation module is used to iteratively calculate the gradient change factor of each direction of the initial frequency distribution information based on the principle of adaptive and consistent decrease of discrete gradient threshold.

[0021] Spectrum epitaxial growth observation value calculation module: used to obtain the gradient gradient factor based on iterative calculation, and calculate the spectrum epitaxial growth observation value from each direction at the same time.

[0022] Complete spectrum information calculation module: used to calculate the complete spectrum information of the holographic reconstructed image based on the initial frequency distribution information of the original holographic interference fringe image and the epitaxial growth observation value, and then determine whether the complete spectrum information of the holographic reconstructed image satisfies the adaptive consistent descent.

[0023] The second iterative calculation module is used to transform the complete spectrum information of the reconstructed image from the frequency domain to the time domain using the inverse fast Fourier transform to obtain the reconstructed image of the holographic interference fringe image.

[0024] The beneficial effects of the present invention are as follows: 1. The present invention obtains the initial frequency distribution information of the original holographic interference fringe image; based on the principle of adaptive consistent descent of discrete gradient thresholds, the gradient gradient factors in different directions of the initial frequency distribution information are iteratively calculated; based on the gradient gradient factors obtained by iterative calculation, the spectrum epitaxial growth observation values ​​are simultaneously calculated from the horizontal and vertical directions, which can reduce the noise of the original holographic interference fringe image and extract the high-frequency information of the original holographic interference fringe image.

[0025] 2. The present invention calculates the complete spectrum information of the holographic image based on the initial frequency distribution information of the original holographic interference fringe image and the spectrum epitaxial growth observation value; in response to the convergence of the complete spectrum information, the complete spectrum information of the holographic image is processed by inverse Fourier transform to obtain a reconstructed image of the holographic image; the present invention adds the spectrum epitaxial growth observation value back to the initial frequency distribution information of the original holographic interference fringe image, reconstructs the low-quality original holographic interference fringe image, and the obtained digital holographic image has comprehensive detail information.

[0026] 3. The original holographic interference fringe image of the present invention is screened by an adaptive Gaussian filter, which can ensure that the frequency of the initial reconstruction of the civil engineering entering the iterative calculation is kept in the low frequency area, and can ensure the convergence of the iterative steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a flow chart of a method for improving image quality of digital holographic interference image reconstruction according to the present invention.

[0029] Figure 2 It is a schematic diagram of the construction of a digital holographic imaging optical path for a method for improving the image quality of digital holographic interference image reconstruction provided in the second embodiment of the present invention.

[0030] Figure 3 It is a reconstruction effect diagram of a method for improving the image quality of digital holographic interference image reconstruction provided by embodiments 1 and 2 of the present invention; Figure 3 (a) is the original holographic interference fringe pattern; Figure 3 (b) Normal reconstructed image quality; Figure 3 (c) The image quality of the reconstructed image of the present invention.

[0031] Figure 4 This is a schematic diagram of module connections of a digital holographic interference image reconstruction and image quality improvement system of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1 As shown, in the first aspect, the present invention provides a method for improving the image quality of digital holographic interference image reconstruction, comprising the following steps: Step 1, initial acquisition: obtaining the initial frequency distribution information of the original holographic interference fringe image.

[0034] In a specific embodiment, the initial frequency distribution information of the original holographic interference fringe image is obtained, and the specific acquisition process is as follows: S11, obtaining a digital interference fringe image.

[0035] See also Figure 2As shown in the above, the original holographic interference fringe image is obtained, and the specific acquisition process is as follows: a helium-neon laser is used to emit laser to a semi-transparent and semi-reflective mirror, and then the laser beam reflected on the semi-transparent and semi-reflective mirror passes through a convex lens to illuminate the object, and then reflects on the semi-transparent and semi-reflective mirror; at the same time, the laser beam on the semi-transparent and semi-reflective mirror is expanded by a beam expander, and then reflected by a reflector to reach the semi-transparent and semi-reflective mirror; and then a CCD camera is used to capture the digital interference fringe image through the semi-transparent and semi-reflective mirror.

[0036] S12. Preprocess the digital interference fringe image using fast Fourier transform to obtain an original holographic interference fringe image.

[0037] It should be noted that, first, the digital interference fringe image is loaded into the computer. If the image is in color, it is converted into a grayscale image. The grayscale image is processed using fast Fourier transform, the image is converted from the time domain to the frequency domain, and filtering is performed in the frequency domain to enhance or weaken the components of a specific frequency. The processed frequency domain image is subjected to inverse fast Fourier transform to convert it back to the time domain to generate the original holographic interference fringe image.

[0038] The original holographic interference fringe image of the present invention is screened by an adaptive Gaussian filter, which can ensure that the frequency of the initial reconstruction of the iterative calculation is kept in the low frequency region, and can ensure the convergence of the iterative steps.

[0039] S13. Use fast Fourier transform to process the original holographic interference fringe image to obtain initial frequency distribution information of the original holographic interference fringe image.

[0040] It should be noted that the original holographic interference fringe image is subjected to fast Fourier transform to generate the spectrum of the original holographic interference fringe image, and the initial frequency distribution information is extracted from the spectrum.

[0041] It should also be noted that the original holographic interference fringe image needs to be screened by an adaptive Gaussian filter. The spectrum of the original holographic interference fringe image is subjected to a large-step discrete convolution to extract the high-frequency information and low-frequency information in the original holographic interference fringe image. The high-frequency information is the detail information of the image, usually manifested as edges, details, etc. The low-frequency information is the energy information, manifested as the brightness and morphology of the image. The sum of the high-frequency information and the low-frequency information constitutes the original holographic interference fringe image.

[0042] Step 2, first iterative calculation: based on the principle of adaptive and consistent decrease of discrete gradient threshold, iteratively calculate the gradient change factor of each direction of the initial frequency distribution information.

[0043] In a specific embodiment, the iterative calculation of the gradient change factor of each direction of the initial frequency distribution information is as follows: construct a plane rectangular coordinate system at a preset position of the original holographic interference fringe image, and substitute it into the iterative calculation formula In the formula, the gradient gradient factors of each direction at the coordinate position (x, y) in the original holographic interference fringe image are obtained, where k represents the number of iterations, k ≥ 1, It represents the gradient factor in the horizontal direction at the coordinate position (x, y) at the kth iteration. Indicates the gradient factor in the vertical direction at the coordinate position (x, y) at the kth iteration; α (k-1) Indicates the preset gradient threshold for the k-1th iteration, G h Represents the preset horizontal gradient operator, G h+1 represents the preset vertical gradient operator, G represents the preset gradient operator, ω (k-1) Represents the holographic interference fringe image corresponding to the k-1th iteration.

[0044] It should be noted that G h , G h+1 and G satisfy the following relationship:

[0045] In the formula, M and N represent the number of pixels in the row direction and the number of pixels in the column direction of the original holographic interference fringe image, and ω represents the original holographic interference fringe image. G is Gω i,j The overall expression of G h It's G h ω i,j The overall expression of G h+1 It's G h+1 ω i,j overall expression of .

[0046] It should also be noted that ω i+1,j represents the original holographic interference fringe image at the coordinate position (x+1,y), ω i,j represents the original holographic interference fringe image at the coordinate position (x, y), ω i,j+1 Represents the original holographic interference fringe image at the coordinate position (x, y+1).

[0047] Step 3: Calculation of spectrum epitaxial growth observation values: Based on iterative calculation, the gradient gradient factor is obtained, and the spectrum epitaxial growth observation values ​​are calculated from each direction at the same time.

[0048] In a specific embodiment, the spectrum epitaxial growth observation value is calculated from each direction, and the specific calculation process is as follows:

[0049] The observed value of the spectrum epitaxial growth at the kth iteration is obtained as ζ(ω k ), where the symbol * indicates conjugate calculation, ζ(I) k-1 represents the iterative solution at the k-1th iteration, β k-1 represents the gradient threshold contribution parameter at the k-1th iteration, It represents the gradient factor in the horizontal direction at the coordinate position (x, y) at the kth iteration. Indicates the gradient factor in the vertical direction at the coordinate position (x, y) at the kth iteration, G h Represents the preset horizontal gradient operator, G h+1 represents the preset vertical gradient operator, and ω represents the original holographic interference fringe image.

[0050] It should be noted that the iterative solution at the k-1th iteration and the gradient threshold contribution parameter at the k-1th iteration are extracted from the digital holographic interference image reconstruction image quality improvement system.

[0051] The present invention obtains the initial frequency distribution information of the original holographic interference fringe image of the original image; based on the principle of adaptive consistent descent of discrete gradient thresholds, iteratively calculates the gradient gradual change factors of the initial frequency distribution information in different directions; based on the gradient gradual change factors obtained by iterative calculation, the spectrum epitaxial growth observation values ​​are calculated simultaneously from the horizontal and vertical directions, which can reduce the noise of the original holographic interference fringe image and extract the high-frequency information of the original holographic interference fringe image.

[0052] Step 4: Calculation of complete spectrum information: Based on the initial frequency distribution information of the original holographic interference fringe image and the epitaxial growth observation value, calculate the complete spectrum information of the holographic reconstructed image, and then determine whether the complete spectrum information of the holographic reconstructed image satisfies the adaptive consistent descent.

[0053] In a specific embodiment, the complete spectrum information of the CGH reconstructed image is specifically calculated as follows: ζ(I k )=ζ(T) * ζ(I0)+γ k-1 ζ(ω k ), where ζ(I0) represents the complete spectrum information of the original holographic interference fringe image, ζ(I k ) represents the complete spectrum information of the holographic interference fringe image at the kth iteration, γ represents the synthetic contribution parameter, ζ(ω k ) represents the observed value of the spectrum epitaxial growth at the kth iteration, ζ(T) represents the modified transfer function of the frequency transfer system, k represents the number of iterations, and k≥1.

[0054] It should be noted that the calculation formula of the modified transfer function ζ(T) of the frequency transfer system is: In the formula, p represents the pixel pitch of the analog fringe image acquisition sensor array, δ and Both represent the frequency coordinate of the modified transfer function of the frequency transfer system, π represents pi, and e represents a natural constant.

[0055] It should also be noted that the pixel spacing of the analog fringe image acquisition sensor array, the frequency coordinates of the corrected transfer function of the frequency transfer system, and the synthetic contribution parameters are extracted from the digital holographic interference image reconstruction image quality improvement system; and the complete spectrum information is obtained from the holographic interference fringe image at the kth iteration.

[0056] In another specific embodiment, the process of judging whether the complete spectrum information of the holographic reconstructed image satisfies the adaptive uniform decrease is as follows: S41: If Then it is determined that the complete spectrum information of the holographic reconstruction image satisfies the adaptive consistent decline, and then the iteration is stopped and step 5 is executed, where represents the L1 norm, represents the complete spectrum information ζ(I k ) and the complete spectrum information ζ(I k-1 ), and ε is the preset convergence constant.

[0057] S42, It is determined that the complete spectrum information of the holographic reconstructed image does not satisfy the adaptive consistent descent, and the iteration parameters are reinitialized and return to step two.

[0058] It should be noted that ε is selected between 0.001 and 0.0001.

[0059] like Figure 3 As shown, step five, second iterative calculation: use the inverse fast Fourier transform to transform the complete spectrum information of the reconstructed image from the frequency domain to the time domain to obtain a reconstructed image of the holographic interference fringe image.

[0060] The present invention calculates the complete spectrum information of a holographic image based on the initial frequency distribution information of the original holographic interference fringe image and the spectrum epitaxial growth observation value; in response to the convergence of the complete spectrum information, the complete spectrum information of the holographic image is processed by inverse Fourier transform to obtain a reconstructed image of the holographic image; the present invention adds the spectrum epitaxial growth observation value back to the initial frequency distribution information of the original holographic interference fringe image, reconstructs the low-quality original holographic interference fringe image, and the obtained digital holographic image has comprehensive detail information.

[0061] See also Figure 4As shown, in the second aspect, the present invention provides a digital holographic image reconstruction image quality improvement system, including the following modules: an initial acquisition module, a first iterative calculation module, a spectrum epitaxial growth observation value calculation module, a complete spectrum information calculation module and a second iterative calculation module.

[0062] Initial acquisition module: used to obtain the initial frequency distribution information of the original holographic interference fringe image.

[0063] The first iterative calculation module is used to iteratively calculate the gradient change factor of each direction of the initial frequency distribution information based on the principle of adaptive and consistent decrease of discrete gradient threshold.

[0064] Spectrum epitaxial growth observation value calculation module: used to obtain the gradient gradient factor based on iterative calculation, and calculate the spectrum epitaxial growth observation value from each direction at the same time.

[0065] Complete spectrum information calculation module: used to calculate the complete spectrum information of the holographic reconstructed image based on the initial frequency distribution information of the original holographic interference fringe image and the epitaxial growth observation value, and then determine whether the complete spectrum information of the holographic reconstructed image meets the adaptive consistent descent;

[0066] The second iterative calculation module is used to transform the complete spectrum information of the reconstructed image from the frequency domain to the time domain using the inverse fast Fourier transform to obtain the reconstructed image of the holographic interference fringe image.

[0067] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined in this specification, they shall all fall within the protection scope of the present invention.

Claims

1. A method for improving the image quality of digital holographic image reconstruction, characterized in that: The steps include: Step 1: Initial acquisition: obtaining the initial frequency distribution information of the original holographic interference fringe image; Step 2, first iterative calculation: based on the principle of adaptive and consistent decrease of discrete gradient threshold, iteratively calculate the gradient change factor of each direction of the initial frequency distribution information; Step 3: Calculation of spectrum epitaxial growth observation value: Obtain the gradient gradient factor based on iterative calculation, and calculate the spectrum epitaxial growth observation value from each direction at the same time; Step 4: Calculate the complete spectrum information: Based on the initial frequency distribution information of the original holographic interference fringe image and the epitaxial growth observation value, calculate the complete spectrum information of the holographic reconstructed image, and then determine whether the complete spectrum information of the holographic reconstructed image meets the adaptive consistent descent; Step 5, second iterative calculation: use inverse fast Fourier transform to transform the complete spectrum information of the reconstructed image from the frequency domain to the time domain to obtain a reconstructed image of the holographic interference fringe image.

2. The method for improving the image quality of digital holographic image reconstruction according to claim 1, characterized in that: The initial frequency distribution information of the original holographic interference fringe image is obtained, and the specific acquisition process is as follows: S11, acquiring a digital interference fringe image; S12, preprocessing the digital interference fringe image by using fast Fourier transform to obtain an original holographic interference fringe image; S13. Use fast Fourier transform to process the original holographic interference fringe image to obtain initial frequency distribution information of the original holographic interference fringe image.

3. The method for improving the image quality of digital holographic image reconstruction according to claim 1, characterized in that: The iterative calculation of the gradient change factor of each direction of the initial frequency distribution information is specifically calculated as follows: Construct a plane rectangular coordinate system at the preset position of the original holographic interference fringe image, and substitute it into the iterative calculation formula In the formula, the gradient gradient factors of each direction at the coordinate position (x, y) in the original holographic interference fringe image are obtained, where k represents the number of iterations, k ≥ 1, It represents the gradient factor in the horizontal direction at the coordinate position (x, y) at the kth iteration. Indicates the vertical gradient factor at the coordinate position (x, y) at the kth iteration; α( k-1 ) represents the preset gradient threshold for the k-1th iteration, G h Represents the preset horizontal gradient operator, G h+1 represents the preset vertical gradient operator, G represents the preset gradient operator, ω( k-1 ) represents the holographic interference fringe image corresponding to the k-1th iteration.

4. The method for improving the image quality of digital holographic image reconstruction according to claim 1, characterized in that: The spectrum epitaxial growth observation values ​​are calculated from each direction, and the specific calculation process is as follows: By calculating the formula The observed value of the spectrum epitaxial growth at the kth iteration is obtained as follows: k ), where the symbol * indicates conjugate calculation, ζ(I) k-1 represents the iterative solution at the k-1th iteration, β k-1 represents the gradient threshold contribution parameter at the k-1th iteration, It represents the gradient factor in the horizontal direction at the coordinate position (x, y) at the kth iteration. Indicates the gradient factor in the vertical direction at the coordinate position (x, y) at the kth iteration, G h Represents the preset horizontal gradient operator, G h+1 represents the preset vertical gradient operator, ω represents the original holographic interference fringe image, k represents the number of iterations, k≥1.

5. The method for improving the image quality of digital holographic image reconstruction according to claim 1, characterized in that: The complete spectrum information of the CGH reconstructed image is calculated in the following specific process: Calculated by the following formula: k )=ζ(T) * ζ(I0)+γ k-1 ζ(ω k ) where ζ(I0) represents the complete spectrum information of the original holographic interference fringe image, ζ(I k ) represents the complete spectrum information of the holographic interference fringe image at the kth iteration, γ represents the synthetic contribution parameter, ζ(ω k ) represents the observed value of the spectrum epitaxial growth at the kth iteration, ζ(T) represents the modified transfer function of the frequency transfer system, k represents the number of iterations, and k≥1.

6. The method for improving the image quality of digital holographic image reconstruction according to claim 1, characterized in that: The specific process of judging whether the complete spectrum information of the holographic reconstructed image satisfies the adaptive consistent decrease is as follows: S41, if Then it is determined that the complete spectrum information of the holographic reconstructed image satisfies the adaptive consistent decline, and then the iteration is stopped and step 5 is executed, where represents the L1 norm, represents the complete spectrum information ζ(I k ) and the complete spectrum information ζ(I k-1 ), ε is the preset convergence constant; S42, It is determined that the complete spectrum information of the holographic reconstructed image does not satisfy the adaptive consistent descent, and the iteration parameters are reinitialized and return to step two.

7. A digital holographic image reconstruction image quality improvement system using the digital holographic image reconstruction image quality improvement method according to any one of claims 1 to 6, characterized in that: Includes the following modules: Initial acquisition module: used to obtain the initial frequency distribution information of the original holographic interference fringe image; The first iterative calculation module is used to iteratively calculate the gradient change factor of each direction of the initial frequency distribution information based on the principle of adaptive and consistent decrease of discrete gradient threshold; Spectrum epitaxial growth observation value calculation module: used to obtain the gradient gradient factor based on iterative calculation, and calculate the spectrum epitaxial growth observation value from each direction at the same time; Complete spectrum information calculation module: used to calculate the complete spectrum information of the holographic reconstructed image based on the initial frequency distribution information of the original holographic interference fringe image and the epitaxial growth observation value, and then determine whether the complete spectrum information of the holographic reconstructed image meets the adaptive consistent descent; The second iterative calculation module is used to transform the complete spectrum information of the reconstructed image from the frequency domain to the time domain using the inverse fast Fourier transform to obtain the reconstructed image of the holographic interference fringe image.

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