A method and apparatus for automatically obtaining moire fringe wrapped phase

Abstract

The application discloses a method and device for automatically obtaining a wrapped phase of a moire fringe, obtains a moire fringe image of a flow field to be measured, selects a calculation region of the moire fringe image, and designs the calculation region as a matrix A of M*N; Fourier analysis is performed on the matrix A to obtain a matrix B; an average value of all elements in the i-th row of the matrix B is calculated as x i ; a maximum value corresponding to a row number of x i is obtained, x o =0 is set, a row number where a maximum value of remaining rows of the matrix B is located is set as h, h is in {i|o-k h i h =0 is set; in the matrix B where x o =0 and x h =0, a row number h' where a maximum value of an average value in a row is obtained; data in the h' row of the matrix B is placed in a center of a matrix D of M*N; inverse Fourier transform is performed on the matrix D to obtain a matrix E; and a wrapped phase distribution ψ of the moire fringe is calculated by using an inverse tangent function according to the matrix E. The method and device for automatically obtaining the wrapped phase of the moire fringe not only save time for data processing, but also provide a more accurate and reliable basis for phase unwrapping in a later period.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of automatically obtaining moire fringe wrapped phase method and device, belong to optical measurement technical field. BACKGROUND

[0002] Moire tomography is an important high-temperature complex flow field detection method, which provides effective methods and data in flow field diagnosis and other fields. In the application of moire tomography, first, the moire fringe of the flow field to be measured is obtained by experiment; then, the fringe is preprocessed and the phase information is extracted; finally, the refractive index distribution of the flow field to be measured is reconstructed, and the key parameter distribution of the flow field to be measured is inverted.

[0003] As can be seen, in the above process, the accurate extraction of phase information plays a crucial role in the subsequent results. It is worth noting that the extraction of the first-order spectrum of moire fringe has always been a key step in calculating the wrapped phase. The first-order spectrum contains the required phase information, and its accurate and fast extraction is also related to the accuracy and calculation efficiency of the subsequent wrapped phase.

[0004] In the existing process of extracting moire fringe wrapped phase using Fourier analysis method, after the fringe image is subjected to Fourier transform, the first-order spectrum of the fringe needs to be manually determined and extracted, which is relatively cumbersome and time-consuming, and the error caused by the naked eye is also lack of objectivity. In addition, if the sidelobe is not selected properly, it will also affect the subsequent acquisition of wrapped phase.

[0005] Therefore, how to better acquire moire fringe wrapped phase is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0006] Objective: In order to overcome the deficiencies in the prior art, the present application provides a method and device for automatically obtaining moire fringe wrapped phase, which uses the data characteristics corresponding to the first-order spectrum of moire fringe to automatically select and translate the sidelobe, can save the calculation time of moire fringe wrapped phase, and improve the extraction accuracy. In short, the related research will have important significance for the information extraction of moire fringe.

[0007] Technical solution: In order to solve the above technical problems, the technical scheme adopted by the present application is:

[0008] In a first aspect, a method for automatically obtaining moire fringe wrapped phase includes the following steps:

[0009] Step 1: Obtain the moire fringe image of the flow field to be measured, select the calculation region of the moire fringe image, and design the calculation region as a matrix A of MxN. Matrix A represents a pixel value matrix, M represents the number of row pixel points, and N represents the number of column pixel points.

[0010] Step 2: Fourier analysis is performed on the matrix A to obtain a matrix B.

[0011] Step 3: Calculate the average value of all elements in the i-th row of matrix B as x i .

[0012] Step 4: Obtain the maximum value of x i , and let x o = 0.

[0013] Step 5: Let the row number of the maximum value in the remaining rows of matrix B be h, and h has the following value range:

[0014] h∈{i|o-k<i<o+k},k=1,2,3,…,c

[0015] Where:

[0016]

[0017] c is the minimum value that satisfies the condition o-i in the brackets.

[0018] Step 6: Take k from 1 to c in turn, if x h is the maximum value in o-k<i<o+k, then let x h = 0.

[0019] Step 7: In the matrix B where x o = 0, x h = 0, obtain the row number h' corresponding to the maximum value of the average value in the row.

[0020] Step 8: Place the data of h' rows in matrix B into the positive center of the M×N matrix D.

[0021] Step 9: Perform inverse Fourier transform on matrix D to obtain matrix E.

[0022] Step 10: Calculate the wrapped phase distribution ψ of the Moiré fringe using the inverse tangent function based on matrix E.

[0023] The second embodiment is an apparatus for automatically obtaining the wrapped phase of a Moiré fringe, comprising the following modules:

[0024] A calculation region acquisition module is used to acquire the Moiré fringe image of the flow field to be measured, select a calculation region of the Moiré fringe image, and design the calculation region as a M×N matrix A. Matrix A represents a pixel value matrix, M represents the number of row pixel points, and N represents the number of column pixel points.

[0025] A matrix B acquisition module is used to perform Fourier analysis on matrix A to obtain matrix B.

[0026] An average value calculation module is used to calculate the average value of all elements in the i-th row of matrix B as xi .

[0027] First zero clearing module: used for obtaining x i The row number corresponding to the maximum value is o, and x o = 0.

[0028] Value range setting module: used for setting the row number of the maximum value in the remaining rows of matrix B as h, and the value range of h is as follows:

[0029] h∈{i|i-o-k<i<o+k},k=1,2,3,…,c, (1)

[0030] Wherein:

[0031]

[0032] c is the minimum value satisfying the condition o-i in the bracket.

[0033] Second zero clearing module: used for taking k from 1 to c in turn, if x h is the maximum value in o-k<i<o+k, then x h = 0.

[0034] Primary spectrum acquisition module: used for obtaining the row number h' corresponding to the maximum average value in the rows of matrix B in which x o = 0 and x h = 0.

[0035] Spectrum translation module: used for placing the data of h' rows in matrix B into the positive center of the matrix D of M×N.

[0036] Matrix E acquisition module: used for performing inverse Fourier transform on matrix D to obtain matrix E.

[0037] Wrapped phase calculation module: used for calculating the wrapped phase distribution ψ of the moire fringe according to matrix E by using the inverse tangent function.

[0038] As a preferred scheme, the calculation formula of matrix B is as follows:

[0039]

[0040] Wherein, is the Fourier transform.

[0041] As a preferred scheme, the calculation formula of x i is as follows:

[0042]

[0043] Wherein, N is the column number of matrix B, and B ij is the value of the i-th row and the j-th column.

[0044] As a preferred solution, h' is calculated as follows:

[0045]

[0046] As a preferred solution, E is calculated as follows:

[0047]

[0048] wherein, is the Fourier transform.

[0049] As a preferred solution, ψ is calculated as follows:

[0050]

[0051] wherein, Im[E] is the imaginary part of the matrix E, and Re[E] is the real part of the matrix E.

[0052] Beneficial effects: the method and device for automatically obtaining the wrapped phase of the moire fringe provided by the present application are used to overcome the cumbersome of manually extracting the first-order spectrum of the moire fringe. Not only the time of data processing is saved, but also a more accurate and reliable basis is provided for the later phase unwrapping. The advantages are as follows:

[0053] 1. The present application can automatically find the first-order spectrum of the moire fringe, save time and improve efficiency.

[0054] 2. The present application can provide a more reliable basis for extracting the wrapped phase of the moire fringe. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 is the flowchart of the method of the present application.

[0056] Figure 2 is the schematic diagram of the moire fringe image of the experimental flow field to be measured.

[0057] Figure 3 is the schematic diagram of the calculation area of the intercepted moire fringe image.

[0058] Figure 4 The left side is the result of the Fourier transform of the calculation area, and the right side is the numerical value of the first-order spectrum after the Fourier transform.

[0059] Figure 5 The left side is the result of the first-order spectrum after the translation, and the right side is the numerical value corresponding to the result after the translation.

[0060] Figure 6 is the schematic diagram of the calculation result of the wrapped phase of the first-order spectrum filtering. DETAILED DESCRIPTION

[0061] The application will be further described in connection with specific embodiments.

[0062] As shown in the first embodiment of the application, a method for automatically obtaining a Moiré fringe wrapped phase includes the following steps: Figure 1

[0063] Step 1: Obtain a Moiré fringe image of a flow field to be measured, select a calculation region of the Moiré fringe image, and design the calculation region as a matrix A of M×N.

[0064] The matrix A represents a pixel value matrix, M represents the number of row pixel points, and N represents the number of column pixel points.

[0065] Step 2: Perform Fourier analysis on the matrix A to obtain a matrix B.

[0066] The calculation formula of the matrix B is as follows:

[0067]

[0068] wherein, B is a Fourier transform.

[0069] Step 3: Calculate the average value of all elements in the ith row of the matrix B as x i .

[0070] x i The calculation formula is as follows:

[0071]

[0072] wherein, N is the number of columns of the matrix B, and B ij is the value in the ith row and the jth column.

[0073] Step 4: Obtain the row number corresponding to the maximum value of x i , and let x o = 0.

[0074] Step 5: Let the row number of the maximum value in the remaining rows of the matrix B be h, and the value range of h is as follows:

[0075] h∈{i|o-k<i<o+k},k=1,2,3,…,c (4)

[0076] wherein:

[0077]

[0078] c is the minimum value satisfying the condition o-i in the bracket.

[0079] Step 6: Take k from 1 to c in turn, and if x h is the maximum value in o-k<i<o+k, let x h = 0.​

[0080] Step 7: In the matrix B of x o = 0, x h = 0, the row number corresponding to the maximum average value in the row is h'.

[0081]

[0082] Step 8: Place the data of the h' rows in the matrix B in the positive center of the MxN matrix D.

[0083] Step 9: Perform inverse Fourier transform on the matrix D to obtain the matrix E.

[0084]

[0085] wherein, is the Fourier transform.

[0086] Step 10: Calculate the wrapped phase distribution ψ of the Moiré fringe from the matrix E using the inverse tangent function.

[0087]

[0088] wherein, Im[E] is the imaginary part of the matrix E, and Re[E] is the real part of the matrix E.

[0089] The second embodiment is an apparatus for automatically obtaining the wrapped phase of a Moiré fringe, comprising the following modules:

[0090] A module for obtaining the Moiré fringe image of the flow field to be measured, selecting the calculation region of the Moiré fringe image, and designing the calculation region as a MxN matrix A.

[0091] The matrix A represents a pixel value matrix, M represents the number of row pixel points, and N represents the number of column pixel points.

[0092] A module for obtaining the matrix B by performing Fourier analysis on the matrix A.

[0093] The calculation formula of the matrix B is as follows:

[0094]

[0095] wherein, is the Fourier transform.

[0096] A module for calculating the average value of all elements in the i-th row of the matrix B as x i .

[0097] x i The calculation formula is as follows:

[0098]

[0099] wherein N is the number of columns of matrix B, B ij is the value of the i-th row and j-th column.

[0100] First zeroing module: for obtaining x i The row number corresponding to the maximum value is o, and x o = 0.

[0101] Value range setting module: for setting the row number of the maximum value in the remaining rows of matrix B as h, and the value range of h is as follows:

[0102] h∈{i|i-o-k<i<o+k},k=1,2,3,…,c, (7)

[0103] wherein:

[0104]

[0105] c is the minimum value satisfying the condition o-i in the bracket.

[0106] Second zeroing module: for taking k from 1 to c in turn, if x h is the maximum value in o-k<i<o+k, then x h = 0.

[0107] Primary spectrum obtaining module: for obtaining the row number h' corresponding to the maximum average value in the rows of matrix B in which x o = 0 and x h = 0.

[0108]

[0109] Spectrum shifting module: for placing the data of h' rows in matrix B into the positive center of the matrix D of M×N.

[0110] Matrix E obtaining module: for performing inverse Fourier transform on matrix D to obtain matrix E.

[0111]

[0112] wherein, is the Fourier transform.

[0113] Wrapped phase calculation module: for calculating the wrapped phase distribution ψ of the Moire fringe according to matrix E using the inverse tangent function.

[0114]

[0115] wherein Im[E] is the imaginary part of matrix E, and Re[E] is the real part of matrix E.

[0116] Example 1:

[0117] like Figure 2 As shown, the moiré fringe image of the flow field under test was obtained based on a propane combustion field experiment. Figure 3 As shown, the computational region of the moiré fringe image is obtained. Figure 4 The left side shows a schematic diagram of the Fourier transform of the computational region of the moiré fringe image, as shown below. Figure 4 The right side shows the numerical value of matrix B corresponding to the computational region of the moiré fringe image. From the figure, it can be concluded that the zero-order spectrum corresponds to the average value vector x. i The maximum value of the spectrum is 1, but due to noise, the first-order spectrum may not be the second maximum value in matrix B.

[0118] like Figure 5 As shown, the method of the present invention is used to obtain the row data of matrix B with the number of rows h′, and then shifted to the center of the spectrum to obtain matrix D.

[0119] Import the moiré fringes into the computer to automatically acquire the phase of the moiré fringe wrapping. The distribution of the moiré fringe wrapping phase is shown below. Figure 6 As shown. The entire calculation time was 0.1281s, and the operating environment was a 16-inch 2019 MacBook Pro with an Intel Core i7-9750H CPU (six cores, frequency of 2.6GHz) and 16GB of memory (2667MHz, DDR4).

[0120] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0121] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0122] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0123] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0124] The above description is only preferred embodiments of the present application, it should be pointed out that for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for automatically acquiring the phase wrapped by moiré fringes, characterized in that: Includes the following steps: Step 1: Obtain the moiré fringe image of the flow field to be measured, select the calculation region of the moiré fringe image, and design the calculation region as follows. matrix ;matrix Represents a matrix of pixel values. Indicates the number of pixels in a row. Indicates the number of pixels in a column; Step 2: For the matrix Perform Fourier analysis to obtain matrix B; Step 3: Calculate the matrix The The average of all elements in the row is ; Step 4: Obtain The number of rows corresponding to the maximum value is ,make ; Step 5: Set up the matrix The row number containing the maximum value in the remaining rows is , The range of values ​​is as follows: ； in: ； c is the minimum value of oi that satisfies the condition in parentheses; Step 6: Change k from 1 to k in sequence. ,like for If the maximum value is found, then let ; Step 7: In , matrix In the example, the number of rows corresponding to the maximum average value among rows is... ; Step 8: Convert the matrix middle Data of rows put matrix The very center; Step 9: For the matrix Perform an inverse Fourier transform to obtain the matrix. ; Step 10: Based on the matrix The enclosing phase distribution of moiré fringes was calculated using the arctangent function. ; The formula for calculating matrix B is as follows: ； in, Fourier transform; The calculation formula is as follows: ； in, For matrix The number of columns, For the first Line 1 The values ​​in the column; The calculation formula is as follows: ； The calculation formula is as follows: ； in, This is the inverse Fourier transform; The calculation formula is as follows: ； in, For matrix The imaginary part, For matrix The real part.

2. A device for automatically acquiring the phase of moiré fringes, characterized in that: Includes the following modules: The computational region acquisition module is used to acquire the moiré fringe image of the flow field under test, select the computational region of the moiré fringe image, and design the computational region as follows. matrix ;matrix Represents a matrix of pixel values. Indicates the number of pixels in a row. Indicates the number of pixels in a column; The module for obtaining matrix B is used to process matrices. Perform Fourier analysis to obtain matrix B; The average value calculation module is used to calculate matrices. The The average of all elements in the row is ; First reset module: used to obtain The number of rows corresponding to the maximum value is ,make ; Value range setting module: used to set the matrix The row number containing the maximum value in the remaining rows is , The range of values ​​is as follows: ； in: ； c is the minimum value of oi that satisfies the condition in parentheses; The second reset module is used to sequentially change k from 1 to... ,like for If the maximum value is found, then let ; Level 1 spectrum acquisition module: used for... , matrix In the example, the number of rows corresponding to the maximum average value among rows is... ; Spectrum shifting module: used to shift the matrix middle Data of rows put matrix The very center; matrix Acquisition module: used for matrix... Perform an inverse Fourier transform to obtain the matrix. ; Wrap phase calculation module: used to calculate phase based on matrix The enclosing phase distribution of moiré fringes was calculated using the arctangent function. .

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