Image reconstruction and screening method and device based on phase shift distribution convergence criterion

Abstract

The present application discloses an image reconstruction and screening method and device based on the phase shift distribution convergence criterion. By acquiring multiple groups of interference images, each frame of each group of interference images is mapped to a predefined phase shift target value set to obtain a mapping function, and then a phase shift convergence strategy is used to perform primary, secondary, tertiary, quaternary and multi-level screening, and gradually optimize to screen out the most accurate combination of phase shift distribution. During the screening process, the MAD index is calculated to evaluate the phase shift accuracy of the pixel points, and the overall phase shift data concentration of the multi-level screening results is evaluated according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements. The image reconstruction and screening method and device based on the phase shift distribution convergence criterion provided by the present application not only improves the accuracy of phase measurement, but also reduces the computational cost by reducing the reliance on complex algorithms; in addition, the adaptive screening mechanism of the method enables it to maintain high efficiency in a variable measurement environment.

Description

Technical Field

[0001] The present application relates to the technical field of optical interference measurement, and in particular to an image reconstruction and screening method and device based on a phase shift distribution convergence criterion. Background Art

[0002] In the field of modern optics and precision engineering, phase-shifting interferometry has attracted widespread attention due to its excellent performance in phase measurement and object morphology analysis. Phase-shifting interferometry obtains the phase information of an object by analyzing the interference pattern of two or more light waves, thereby achieving accurate measurement of the surface or internal structure of the object. However, due to environmental factors (such as temperature fluctuations), mechanical vibrations, and imperfections in the optical system, the actual interference pattern often contains noise and systematic errors, which seriously affect the accuracy and reliability of the measurement results.

[0003] In traditional phase-shifting interferometry, a variety of methods are used to process and optimize the interferogram in order to improve the measurement accuracy. For example, the interferogram is filtered and noise is suppressed by digital signal processing technology, or the phase information is unwrapped using complex algorithms. Although these methods improve the measurement quality to a certain extent, they usually require complex calculation processes and have limited effectiveness in the face of strong noise interference.

[0004] In addition, existing phase-shift interferometry techniques often rely on fixed phase-shift intervals when processing multi-frame interferograms, which limits their application in complex measurement environments. In practical applications, due to slight changes in the optical system or deformation of the sample, the ideal phase-shift interval may be difficult to maintain, resulting in deviations in the measurement results. Summary of the invention

[0005] To this end, the present application provides an image reconstruction and screening method and device based on the phase shift distribution convergence criterion to solve the problems of complex calculations of existing phase shift interference technology, poor results when facing strong noise interference, and inaccurate measurement results.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] In a first aspect, an image reconstruction and screening method based on a phase shift distribution convergence criterion comprises:

[0008] Step 1: Acquire multiple sets of interference images under different environmental conditions, map each frame of each set of interference images to a predefined set of phase shift target values, and obtain a mapping function;

[0009] Step 2: Select four elements from the mapping function as initial screening elements according to the phase shift solution formula;

[0010] Step 3: Traverse all the image permutations and combinations of the initial screening elements, and calculate the phase shift amount of each image permutation and combination according to the phase shift amount solution formula;

[0011] Step 4: Calculate the MAD index according to the phase shift amount and the target phase shift amount, and select the image combination with the smallest phase shift deviation as the screening result according to the MAD index;

[0012] Step 5: Fix one or more elements in the screening results, use one or more elements as new screening elements, and select new elements from the mapping function to ensure that the new screening elements are four elements;

[0013] Step 6: Repeat steps 2 to 5 until all elements in the mapping function are filtered and a multi-level screening result is obtained;

[0014] Step 7: Evaluate the overall phase shift data concentration of the multi-stage screening results according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements.

[0015] Preferably, in step 1, the interference image is obtained by a phase-shifting laser interferometer.

[0016] Preferably, in step 2 and step 3, the phase shift solution formula is:

[0017]

[0018] in, represents the phase shift of the i-th row and j-th column, arccos represents the inverse cosine, Represents the grayscale value of the pixel in the i-th row and j-th column of the k-th frame.

[0019] Preferably, in step 4, the MAD indicator calculation formula is:

[0020]

[0021] in, represents the phase shift of the i-th row and j-th column, represents the target phase shift amount, and M represents the total number of pixels.

[0022] Preferably, in step 4, the target phase shift is set to 90°.

[0023] Preferably, in step 7, the discrete coefficient calculation formula is:

[0024]

[0025] Where CV represents the coefficient of dispersion, The phase shift amount of the combination with the minimum phase shift deviation in multi-level screening is accumulated and averaged. express The phase shift data that appears most frequently in the data, express The average value in the data.

[0026] In a second aspect, an image reconstruction and screening device based on a phase shift distribution convergence criterion comprises:

[0027] A mapping module is used to obtain multiple groups of interference images under different environmental conditions, and map each frame of each group of interference images to a predefined phase shift target value set to obtain a mapping function;

[0028] A screening element determination module is used to screen out four elements as initial screening elements from the mapping function according to a phase shift amount solution formula;

[0029] A phase shift calculation module is used to traverse all image combinations of the initial screening elements and calculate the phase shift of each image combination according to the phase shift solution formula;

[0030] A screening result determination module is used to calculate the MAD index according to the phase shift amount and the target phase shift amount, and select the image arrangement combination with the smallest phase shift deviation as the screening result according to the MAD index;

[0031] A screening element supplementing module is used to fix one or more elements in the screening result, use the one or more elements as new screening elements, and select new elements from the mapping function to ensure that the new screening elements are four elements;

[0032] Iteration module, used to filter all elements in the mapping function and obtain multi-level filtering results;

[0033] The phase shift data concentration evaluation module is used to evaluate the overall phase shift data concentration of the multi-stage screening results according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements.

[0034] In a third aspect, a computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of an image reconstruction and screening method based on a phase shift distribution convergence criterion when executing the computer program.

[0035] In a fourth aspect, an image reconstruction and screening system based on the phase shift distribution convergence criterion includes the computer device, a control box, a PZT and a laser interference system, wherein the laser interference system includes a CMOS, a first collimating objective lens, a beam splitter, a laser, a second collimating objective lens, a standard mirror and a measured mirror, wherein the standard mirror is fixed on the PZT, the CMOS, the first collimating objective lens, the beam splitter, the second collimating objective lens, the standard mirror and the measured mirror are arranged in sequence from left to right, and the optical axes are located in the same straight line, and the laser is arranged above the beam splitter and perpendicular to the beam splitter; the CMOS and the control box are electrically connected to the computer device, and the control box is electrically connected to the PZT.

[0036] Compared with the prior art, this application has at least the following beneficial effects:

[0037] The present application provides an image reconstruction and screening method and device based on the phase shift distribution convergence criterion, which obtains multiple groups of interference images under different environmental conditions, maps each frame of each group of interference images to a predefined phase shift target value set, and obtains a mapping function; selects four elements from the mapping function as initial screening elements according to the phase shift solution formula; traverses all image combinations of the initial screening elements, and calculates the phase shift of each image combination according to the phase shift solution formula; calculates the MAD index according to the phase shift and the target phase shift, and selects the image combination with the smallest phase shift deviation as the screening result according to the MAD index; fixes one or more elements in the screening result, uses one or more elements as new screening elements, and selects new elements from the mapping function to ensure that the new screening elements are four elements; repeats the iteration until all elements in the mapping function are screened and a multi-level screening result is obtained, and the overall phase shift data concentration of the multi-level screening result is evaluated according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements. The present application provides an image reconstruction and screening method and device based on the phase shift distribution convergence criterion, which not only improves the accuracy of phase measurement, but also reduces the computational cost by reducing the reliance on complex algorithms; in addition, the method's adaptive screening mechanism enables it to maintain high efficiency in a changing measurement environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more intuitively illustrate the prior art and the present application, exemplary drawings are given below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing the present application; for example, those skilled in the art are capable of easily making conventional adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components) based on the technical concepts and exemplary drawings disclosed in the present application.

[0039] Figure 1A basic flow chart of an image reconstruction and screening method based on a phase shift distribution convergence criterion provided in the first embodiment of the present application;

[0040] Figure 2 A judgment flow chart of an image reconstruction and screening method based on a phase shift distribution convergence criterion provided in the first embodiment of the present application;

[0041] Figure 3 A schematic diagram of the structure of an image reconstruction and screening system based on a phase shift distribution convergence criterion provided in Embodiment 4 of the present application.

[0042] Description of reference numerals:

[0043] 1. CMOS; 2. First collimating lens; 3. Beam splitter; 4. Laser; 5. Second collimating lens; 6. PZT; 7. Standard lens; 8. Mirror to be measured; 9. Computer equipment; 10. Control box. DETAILED DESCRIPTION

[0044] The present application is further described below in detail through specific embodiments in conjunction with the accompanying drawings.

[0045] In the description of this application: unless otherwise specified, "plurality" means two or more. The terms "first", "second", "third", etc. in this application are intended to distinguish the objects referred to, and do not have special meanings in terms of technical connotations (for example, they should not be understood as emphasizing the importance or order, etc.). Expressions such as "including", "comprising", "having", etc. also mean "not limited to" (certain units, components, materials, steps, etc.).

[0046] The terms such as "upper", "lower", "left", "right", "middle", etc. cited in this application are usually used to indicate the general relative position relationship for the purpose of intuitive understanding by referring to the drawings, and are not absolute limitations on the position relationship in the actual product.

[0047] Embodiment 1

[0048] See also Figure 1 and Figure 2 This embodiment provides an image reconstruction and screening method based on a phase shift distribution convergence criterion, including:

[0049] S1: Acquire multiple sets of interference images under different environmental conditions, map each frame of each set of interference images to a predefined set of phase shift target values, and obtain a mapping function;

[0050] For example: This embodiment uses a phase-shifting laser interferometer to obtain 10 groups of interference images under different environmental conditions, each group contains 9 frames of images, and the phase shift distribution is 0°, 90°, 180°, 270°, 0°, 90°, 180°, 270°, and 0°.

[0051] Then each frame image (where i∈{1, 2, …, 10}, j∈{0, 1, …, 8}) is mapped to a predefined set of phase shift target values ​​to obtain a mapping function f, i.e., f:{0, 1, 2, …, 8}→{0, 90, 180, 270, 0, 90, 180, 270, 0}.

[0052] S2: Select four elements from the mapping function as initial screening elements according to the phase shift solution formula;

[0053] Specifically, the phase shift solution formula is:

[0054]

[0055] in, represents the phase shift of the i-th row and j-th column, arccos represents the inverse cosine, Represents the grayscale value of the pixel in the i-th row and j-th column of the k-th frame.

[0056] For example: From the phase shift solution formula, we can see that the four selected elements are , , and , so for the mapping function f, the four elements of the primary screening are (f(0), f(1), f(3), f(4)).

[0057] S3: traverse all the image permutations and combinations of the initial screening elements, and calculate the phase shift amount of each image permutation and combination according to the phase shift amount solution formula;

[0058] S4: calculating the MAD index according to the phase shift amount and the target phase shift amount, and selecting the image arrangement combination with the smallest phase shift deviation as the screening result according to the MAD index;

[0059] Specifically, the MAD indicator calculation formula is:

[0060]

[0061] in, represents the phase shift of the i-th row and j-th column, represents the target phase shift amount, and M represents the total number of pixels; the interference pattern group selected in this embodiment has a phase shift interval of 90°, so Set to 90°, the MAD metric provides an assessment of the accuracy of the phase shift at each pixel in the interferogram combination.

[0062] S5: fix one or more elements in the screening result, use the one or more elements as new screening elements, and select new elements from the mapping function to ensure that the new screening elements are four elements;

[0063] For example, taking the mapping function f as an example, in the secondary screening, the images f(1) and f(4) determined in the primary screening are fixed, and f(1) is taken as the standard. , , and The other two elements are f(2) and f(5), thus obtaining four elements for the secondary screening.

[0064] S6: Repeat iterating S2 to S5 until all elements in the mapping function are screened and a multi-level screening result is obtained;

[0065] For example, taking the mapping function f as an example, there are 9 elements in the mapping function f, so it needs to be iterated four times:

[0066] Primary screening: Screen four elements: (f(0), f(1), f(3), f(4)), traverse all the image combinations of the initial screening elements, and calculate the phase shift of each image combination according to the phase shift solution formula, calculate the MAD index according to the phase shift and the target phase shift, and select the image combination with the smallest phase shift deviation as the initial screening result according to the MAD index;

[0067] Secondary screening: fix the images f(1) and f(4) determined in the primary screening, and traverse the images of f(2) and f(5). For each new combination, recalculate the phase shift distribution and MAD index, and select the combination with the smallest phase shift deviation as the secondary screening result;

[0068] Third-level screening: Keep the images f(3) and f(4) determined in the first two stages unchanged, traverse the images of (6) and f(7), calculate the phase shift distribution and MAD index of each new combination, and select the combination with the smallest phase shift deviation as the third-level screening result;

[0069] Four-level screening: keep the images f(4), f(5) and f(7) determined in the first three stages unchanged, traverse the image of f(8), calculate the phase shift distribution and MAD index of each new combination, and select the combination with the smallest phase shift deviation as the four-level screening result.

[0070] S7: Evaluate the overall phase shift data concentration of the multi-stage screening results according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements.

[0071] Specifically, the calculation formula of the dispersion coefficient is:

[0072]

[0073] Where CV represents the coefficient of dispersion, The phase shift amount of the combination with the minimum phase shift deviation in multi-level screening is accumulated and averaged. express The phase shift data that appears most frequently in the data, express The average value in the data; the coefficient of variation CV indicator can provide an assessment of the concentration of the overall phase shift data of the interferogram combination.

[0074] The present embodiment provides an image reconstruction and screening method based on the phase shift distribution convergence criterion. First, a phase-shifting laser interferometer is used to obtain multiple groups of interference images. Then, the images are mapped to a predetermined set of phase shift target values ​​through a defined mapping function. Then, a phase shift convergence strategy (i.e., S2 to S6) is adopted to implement multi-level screening including primary, secondary, tertiary, and quaternary levels, and the interference image combination is gradually optimized to screen out the combination with the most accurate phase shift distribution. During the screening process, the MAD index is calculated to evaluate the phase shift accuracy of the pixel points. Finally, the discrete coefficient CV is calculated to evaluate the overall phase shift data concentration of the final combination, thereby determining the interference pattern combination that meets the preset accuracy requirements. The method provided in the present embodiment can screen out high-quality interference pattern combinations from the interference pattern set and improve the accuracy of phase measurement.

[0075] The present embodiment provides an image reconstruction and screening method based on the phase shift distribution convergence criterion, which realizes all-round matching of the interference pattern set through multi-level screening, while avoiding redundant calculations and reducing calculation time; the four elements selected in each level of screening are determined according to the phase shift solution formula, which helps to improve the accuracy and reliability of phase measurement; in addition, the application of MAD index and CV index is used to evaluate the phase shift accuracy of a single pixel point and the concentration of the overall phase shift data, respectively, providing an effective quantitative basis for optimizing the interference pattern combination.

[0076] The image reconstruction and screening method based on the phase shift distribution convergence criterion provided in this embodiment not only improves the accuracy of phase measurement, but also reduces the computational cost by reducing the reliance on complex algorithms. In addition, the adaptive screening mechanism of the method enables it to maintain high efficiency in a variable measurement environment, providing a new technical solution for the field of optical testing and precision measurement. Through this method, the optimization of interference patterns can be achieved, thereby promoting the development of high-precision measurement technology in multiple fields such as optical imaging, optical detection, materials science, and biomedical engineering.

[0077] Embodiment 2

[0078] This embodiment provides an image reconstruction and screening device based on a phase shift distribution convergence criterion, comprising:

[0079] A mapping module is used to obtain multiple groups of interference images under different environmental conditions, and map each frame of each group of interference images to a predefined phase shift target value set to obtain a mapping function;

[0080] A screening element determination module is used to screen out four elements as initial screening elements from the mapping function according to a phase shift amount solution formula;

[0081] A phase shift calculation module is used to traverse all image combinations of the initial screening elements and calculate the phase shift of each image combination according to the phase shift solution formula;

[0082] A screening result determination module is used to calculate the MAD index according to the phase shift amount and the target phase shift amount, and select the image arrangement combination with the smallest phase shift deviation as the screening result according to the MAD index;

[0083] A screening element supplementing module is used to fix one or more elements in the screening result, use the one or more elements as new screening elements, and select new elements from the mapping function to ensure that the new screening elements are four elements;

[0084] Iteration module, used to filter all elements in the mapping function and obtain multi-level filtering results;

[0085] The phase shift data concentration evaluation module is used to evaluate the overall phase shift data concentration of the multi-stage screening results according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements.

[0086] The specific implementation contents of each module in the image reconstruction and screening device based on the phase shift distribution convergence criterion can be found in the above definition of the image reconstruction and screening method based on the phase shift distribution convergence criterion, which will not be repeated here.

[0087] Embodiment 3

[0088] This embodiment provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the image reconstruction and screening method based on the phase shift distribution convergence criterion are implemented.

[0089] Embodiment 4

[0090] See also Figure 3The present embodiment provides an image reconstruction and screening system based on the phase shift distribution convergence criterion, comprising a computer device 9, a control box 10, a PZT 6 and a laser interference system, wherein the laser interference system comprises a CMOS 1, a first collimating lens 2, a beam splitter 3, a laser 4, a second collimating lens 5, a standard lens 7 and a measured lens 8, wherein the standard lens 7 is fixed on the PZT 6, the CMOS 1, the first collimating lens 2, the beam splitter 3, the second collimating lens 5, the standard lens 7 and the measured lens 8 are arranged in sequence from left to right, and the optical axes are located in the same straight line, and the laser 4 is arranged above the beam splitter 3 and perpendicular to the beam splitter 3; the CMOS 1 and the control box 10 are electrically connected to the computer device 9, and the control box 10 is electrically connected to the PZT 6.

[0091] Its working principle is:

[0092] The laser 4 emits a monochromatic light beam through the second collimating lens 5 to the standard mirror 7. A part of the light returns directly from the reference surface of the standard mirror 7. This part of the light is called the reference beam. During the return process, it is reflected at the beam splitter 3 and then incident on the CMOS 1, which is received and processed by the CMOS 1. Another part of the light passes through the standard mirror 7 and is incident on the measured mirror 8. This part of the light is called the test beam. During the return process, it is also reflected at the beam splitter 3 and then incident on the CMOS 1 through the first collimating lens 2. The test beam has an additional distance between the standard surface and the measured surface compared to the reference beam. Other beam distances are the same. The standard surface and the measured surface need to be adjusted to a suitable distance to ensure that the light reflected from the two planes is coherent. There is a small angle between the inner and outer surfaces of the reference standard mirror 7, that is, the inner surface (reference plane) is a slightly inclined surface, which can ensure that the two beams form interference fringes after interference, and then analyze them in combination with the fringes image received by the CMOS 1.

[0093] The technical features of the above embodiments may be arbitrarily combined (as long as there is no contradiction in the combination of these technical features). To make the description concise, not all possible combinations of the technical features in the above embodiments are described; these embodiments that are not explicitly written should also be considered to be within the scope of this specification.

Claims

1. An image reconstruction and screening system based on phase shift distribution convergence criterion, characterized in that: The invention comprises a computer device, a control box, a PZT and a laser interference system, wherein the laser interference system comprises a CMOS, a first collimating objective lens, a beam splitter, a laser, a second collimating objective lens, a standard mirror and a measured mirror, wherein the standard mirror is fixed on the PZT, the CMOS, the first collimating objective lens, the beam splitter, the second collimating objective lens, the standard mirror and the measured mirror are arranged in sequence from left to right, and the optical axes are located in the same straight line, and the laser is arranged above the beam splitter and perpendicular to the beam splitter; the CMOS and the control box are electrically connected to the computer device, and the control box is electrically connected to the PZT; The computer device includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, an image reconstruction and screening method based on a phase shift distribution convergence criterion is implemented, wherein the image reconstruction and screening method based on a phase shift distribution convergence criterion includes: Step 1: Acquire multiple sets of interference images under different environmental conditions, map each frame of each set of interference images to a predefined set of phase shift target values, and obtain a mapping function; Step 2: Select four elements from the mapping function as initial screening elements according to the phase shift solution formula; Step 3: Traverse all the image permutations and combinations of the initial screening elements, and calculate the phase shift amount of each image permutation and combination according to the phase shift amount solution formula; Step 4: Calculate the MAD index according to the phase shift amount and the target phase shift amount, and select the image combination with the smallest phase shift deviation as the screening result according to the MAD index; Step 5: Fix one or more elements in the screening results, use one or more elements as new screening elements, and select new elements from the mapping function to ensure that the new screening elements are four elements; Step 6: Repeat steps 2 to 5 until all elements in the mapping function are filtered and a multi-level screening result is obtained; Step 7: Evaluate the overall phase shift data concentration of the multi-stage screening results according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements.

2. The image reconstruction and screening system based on the phase shift distribution convergence criterion according to claim 1, characterized in that: In step 1, the interference image is obtained by a phase-shifting laser interferometer.

3. The image reconstruction and screening system based on the phase shift distribution convergence criterion according to claim 1, characterized in that: In step 2 and step 3, the phase shift solution formula is: ， in, Indicates i OK j The phase shift of the column, arccos represents the inverse cosine, Shidi k Frame No. i Line j The pixel grayscale value of the column.

4. The image reconstruction and screening system based on the phase shift distribution convergence criterion according to claim 1, characterized in that: In step 4, the MAD indicator calculation formula is: ， in, Indicates i OK j The phase shift of the column, represents the target phase shift amount, M Indicates the total number of pixels.

5. The image reconstruction and screening system based on the phase shift distribution convergence criterion according to claim 1, characterized in that: In step 4, the target phase shift is set to 90°.

6. The image reconstruction and screening system based on the phase shift distribution convergence criterion according to claim 1, characterized in that: In step 7, the discrete coefficient calculation formula is: ， in, CV represents the coefficient of dispersion, The phase shift amount of the combination with the minimum phase shift deviation in multi-level screening is accumulated and averaged. express The phase shift data that appears most frequently in the data, express The average value in the data.

7. An image reconstruction and screening device based on the phase shift distribution convergence criterion, characterized in that: include: A mapping module is used to obtain multiple groups of interference images under different environmental conditions, and map each frame of each group of interference images to a predefined phase shift target value set to obtain a mapping function; A screening element determination module is used to screen out four elements as initial screening elements from the mapping function according to a phase shift amount solution formula; A phase shift calculation module is used to traverse all image combinations of the initial screening elements and calculate the phase shift of each image combination according to the phase shift solution formula; A screening result determination module is used to calculate the MAD index according to the phase shift amount and the target phase shift amount, and select the image arrangement combination with the smallest phase shift deviation as the screening result according to the MAD index; A screening element supplementing module is used to fix one or more elements in the screening result, use the one or more elements as new screening elements, and select new elements from the mapping function to ensure that the new screening elements are four elements; Iteration module, used to filter all elements in the mapping function and obtain multi-level filtering results; The phase shift data concentration evaluation module is used to evaluate the overall phase shift data concentration of the multi-stage screening results according to the discrete coefficient, so as to determine the interference pattern combination that meets the preset accuracy requirements.

Images