White light interferometric phase unwrapping method, device, equipment and medium

Abstract

The invention discloses a white light interference phase unwrapping method, device and equipment and a medium, and relates to the technical field of interference light measurement. The method comprises the following steps: acquiring a plurality of white light interference images of a white light interference vertical measurement method; calculating light intensity difference images of the adjacent white light interference images, and calculating a plurality of difference images by adopting a centroid method to obtain a rough contour surface of the sample piece; calculating the original light intensity data by adopting a spatial frequency domain method to obtain ununwrapped phase data; obtaining a phase jump position based on the ununwrapped phase data, and segmenting the difference data of the rough contour surface and the ununwrapped phase data according to the jump position; and the phase is corrected by comparing adjacent segments, so that phase unwrapping is realized. The phase unwrapping method for correcting the phase jump region of the phase data on the basis of the rough contour surface has the advantages of being simple in algorithm implementation, high in precision, high in processing speed and good in robustness.

Description

Technical Field

[0001] The present invention relates to the field of interference light measurement technology, and in particular to a white light interference phase unwrapping method, device, equipment and medium. Background Art

[0002] Phase unwrapping is the process of restoring the wrapped phase modulated with a modulus of 2π obtained by phase shifting, spatial carrier and other technologies to the unmodulated phase. It is widely used in aerospace, mechanics research, and optical measurement technology.

[0003] In the field of interference light measurement technology, monochromatic light cannot avoid errors in phase unwrapping due to its long coherence length, nor can it estimate the number of cycles contained in the phase difference. Therefore, it can only be assumed that the height change of adjacent data points is less than a quarter wavelength, and there is a phase ambiguity problem. Monochromatic light interferometry is only suitable for measuring samples with relatively flat and smooth surfaces. The spectrum of white light is wider, and the coherence wavelength is shorter than that of monochromatic light. White light interference fringes only appear in a smaller area, thus avoiding the phase ambiguity problem of monochromatic light. White light interferometry is applicable to a wider range of samples.

[0004] White light interference is the mutual superposition of interference of countless "laser pairs" of different bands, and the width of interference fringes in different bands is different. As the optical path difference increases, the interference light intensity is uniformized and the light intensity contrast is zero. Only when the optical path difference between the reference light and the test light is zero, the peaks of countless laser interferences coincide at the same place, where the light intensity is the strongest. The corresponding height value can be obtained by calculation.

[0005] The commonly used methods for calculating height are the centroid method and the frequency domain correlation algorithm. The conventional centroid method is affected by environmental noise and background light intensity, so the calculation accuracy is poor and the displacement accuracy of the equipment is high. The frequency domain correlation algorithm gets rid of the dependence of white light interferometry on the contrast of interference light intensity, and only obtains the height value through the slope of the relationship between phase and spatial angular frequency. The calculation accuracy is high, but there will be a 2π periodic phase jump, which needs to be unwrapped.

[0006] However, the existing unwrapping methods have problems such as poor robustness, slow calculation speed, low accuracy and complex implementation methods. For example, the patent document with publication number CN114791271A (named "A quality-guided branch tangent phase unwrapping method") uses the second-order differential of the wrapped phase to determine whether the residual point is effectively optimized, and then sets the branch tangent for phase unwrapping. Although it is more efficient than the conventional branch cutting method, the implementation method is complex and the calculation speed is slow; the patent document with publication number CN118709744A (named "Phase unwrapping method based on deep learning semantic segmentation network") performs phase unwrapping through model training. Although the running speed is relatively fast when deployed, the accuracy is affected by the previous test data, and the model design is relatively complex, which is difficult to implement.

[0007] Therefore, how to achieve high-precision, fast and robust phase unwrapping of white light interferometry is a problem that needs to be solved urgently. Summary of the invention

[0008] The present invention provides a white light interference phase unwrapping method, device, equipment and medium to solve the problems of low precision, slow calculation speed and complex implementation of the unwrapping method of the existing related algorithm.

[0009] The present invention is achieved through the following technical solutions:

[0010] A first aspect of the present invention provides a white light interference phase unwrapping method, comprising:

[0011] Acquire multiple white light interference images collected from the sample in the vertical direction according to a fixed step value;

[0012] Performing differential calculation on the light intensity data of two adjacent white light interference images to obtain a plurality of differential images, and using a centroid method to calculate the plurality of differential images to obtain a rough contour surface of the sample;

[0013] The spatial frequency domain method is used to calculate the raw light intensity data to obtain the unwrapped phase data;

[0014] Obtaining a phase jump position based on the unwrapped phase data, and segmenting the difference data between the rough contour surface and the unwrapped phase data according to the jump position;

[0015] The mean data of adjacent segments are compared with multiples of half wavelength, and the phase is corrected based on the comparison result to obtain the unwrapped phase data.

[0016] The unwrapping method of the present invention combines the advantages of simple calculation of the centroid method and high calculation accuracy of the frequency algorithm. The centroid method is first used to obtain a rough contour surface, and then the unwrapped phase data is obtained by the frequency domain algorithm. The phase jump area of ​​the phase data is corrected based on the rough contour surface, thereby realizing phase unwrapping. This method partially uses simple judgment calculation logic to make the calculation amount of phase unwrapping small and high in accuracy. The influence of background light intensity and environment is eliminated by differential calculation. Compared with the branch cutting method and the method related to deep learning, this method has a simpler algorithm implementation, high accuracy, fast processing speed and good robustness.

[0017] Furthermore, the method of using the centroid method to calculate the plurality of differential images to obtain the rough contour surface of the sample includes:

[0018] The height value of each pixel is calculated by the improved centroid method. The calculation formula is:

[0019]

[0020] Among them, Z (i,j) Represents the height of the pixel (i, j), i and j represent the row and column of the pixel in the image respectively. d (n) represents the light intensity value of the nth differential image. The pixel point (i, j) is taken for calculation, n∈[1,k-1], k is the total number of white light interference images, is the mean light intensity of k-1 differential images;

[0021] According to the height values ​​of all pixel points, the rough contour surface of the sample is obtained.

[0022] Furthermore, the use of the spatial frequency domain method to calculate the original light intensity data to obtain the unwrapped phase data includes:

[0023] Perform Fourier transform on the original light intensity data to obtain frequency domain data;

[0024] Extracting the positive frequency part of the frequency domain data to obtain positive frequency data;

[0025] Calculate the phase of each pixel point according to the positive frequency data, and find the phase corresponding to the central wave number through the central wave number of the white light source;

[0026] The unwrapped phase data of the actual height are obtained according to the phase calculation of the corresponding central wave number.

[0027] Furthermore, the phase of each pixel is calculated according to the positive frequency data, and the formula is:

[0028] φ i =tan -1 (Im(P j) / Re(P j ))

[0029] Among them, φ i Represents the i-th frequency domain data P i The corresponding phase value, P j Indicates positive frequency data, Im(P j ) indicates P j The imaginary part value, Re(P j ) indicates P j The real value of .

[0030] Furthermore, the unwrapped phase data of the actual height is obtained by calculating the phase corresponding to the central wave number, and the formula is:

[0031]

[0032] λ0=2*ScanStep*k / k0

[0033] Among them, Z h represents the height value, φ represents the phase value corresponding to the central wave number k0, λ0 represents the central wavelength, ScanStep represents the step value, and k represents the total number of white light interference images.

[0034] Further, obtaining a phase jump position based on the unwrapped phase data includes:

[0035] Performing differential calculation on the unwrapped phase data row by row to obtain differential phase row data of each row;

[0036] The differential phase line data is compared with a set threshold value, and if the set threshold value is exceeded, the pixel position corresponding to the differential phase line data is determined as the phase jump position.

[0037] Further, comparing the mean data of adjacent segments with multiples of half wavelengths, and correcting the phase based on the comparison result to obtain the unwrapped phase data, includes:

[0038] S5-1, correct the phase of the initial segment, the calculation formula is as follows:

[0039] H d (N(1):N(2))=H d (N(1):N(2)).+preIntegerλ0 / 2

[0040] Among them, H d (N(1):N(2)) represents all the data indexed in the transition region N(1) to N(2) of the differential phase line data, .+ represents the same operation for each data, and preInteger represents the result after rounding off the half-wavelength multiple of the initial segment;

[0041] S5-2, calculate the approximate error errorDelta between the half-wavelength multiples of two adjacent segments, the calculation formula is:

[0042] errorDelta=round(Z g (i+1)-preDiff)

[0043] Where preDiff represents the half-wavelength multiple of the previous segment in the adjacent segment, and its initial value is the half-wavelength multiple of the initial segment, denoted by Z g (1), Z g (i+1) represents the half-wavelength multiple of the current calculation segment, i=1,2…m-1, m is the total length of the jump position;

[0044] S5-3, determine whether the approximate error errorDelta is 0, if not 0, execute S5-4, otherwise execute S5-5;

[0045] S5-4, calculate the jump integer Integer = preInteger + errorDelta, and at the same time Z g (i+1) is assigned to preDiff;

[0046] S5-5, calculate the jump integer Integer = preInteger;

[0047] S5-6, correct the phase of the current calculation segment according to the jump integer Integer, and the correction formula is:

[0048] H d (N(i)+1:N(i+1))=H d (N(i)+1:N(i+1)).+Integer*λ0 / 2

[0049] Wherein, i=2,…m-1, and m is the total length of the jump positions.

[0050] S5-7, repeat the correction process from S5-2 to S5-5, correct all segments in sequence, and obtain unwrapped phase data.

[0051] A second aspect of the present invention provides a white light interference phase unwrapping device, comprising:

[0052] A data acquisition module, used to acquire multiple white light interference images collected from the sample in the vertical direction according to a fixed step value;

[0053] A differential calculation module is used to perform differential calculation on the light intensity data of two adjacent white light interference images to obtain multiple differential images;

[0054] A first height calculation module, used for calculating the plurality of differential images by using a centroid method to obtain pixel point heights, and obtaining a rough contour surface of the sample based on the heights of the respective pixel points;

[0055] A second height calculation module is used to calculate the plurality of white light interference images using a spatial frequency domain method to obtain unwrapped phase data of actual height;

[0056] A jump positioning module, used for performing differential calculation on the unwrapped phase data row by row to obtain phase differential data, and obtaining a jump position based on the differential data;

[0057] A segmented extraction module, used for subtracting the rough contour surface and the unwrapped phase data row by row, segmenting the difference data obtained by the subtraction according to the jump position, and calculating the mean value of each segment and the multiple of the half wavelength;

[0058] The phase correction module is used to compare the mean values ​​of adjacent segments with multiples of half wavelength, correct the phase based on the comparison result, and obtain the unwrapped phase data of the actual height.

[0059] According to a third aspect of the present invention, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the white-light interference phase unwrapping method described in any one of the first aspects of the present invention is implemented.

[0060] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the white-light interferometry phase unwrapping method described in any one of the first aspects of the present invention.

[0061] Compared with the prior art, the present invention has the following advantages and beneficial effects: a rough contour surface is obtained by an optimized centroid method, and then the unwrapped high-precision phase data is obtained by a frequency domain algorithm, and the phase jump area of ​​the phase data is corrected based on the rough contour surface to achieve phase unwrapping. The specific algorithm of this method is simple to implement, has high precision, fast processing speed, and good robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0063] Figure 1 is a flow chart of a white light interferometric phase unwrapping method according to an embodiment of the present invention;

[0064] Figure 2 is a schematic diagram of a rough profile surface type according to an embodiment of the present invention;

[0065] Figure 3 is a schematic diagram of an unwrapped phase according to an embodiment of the present invention;

[0066] Figure 4 is a schematic diagram of an unwrapped phase according to an embodiment of the present invention;

[0067] Figure 5 is a schematic diagram of the correspondence between rough profile surface row data and subtracted row data of unwrapped phase row data according to an embodiment of the present invention;

[0068] Figure 6 is a flow chart of a phase correction method according to an embodiment of the present invention;

[0069] Figure 7 It is a schematic diagram of an unwrapping phase according to an embodiment of the present invention. DETAILED DESCRIPTION

[0070] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0071] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to or inherent to other steps or units of the device.

[0072] The terms used in various embodiments of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present invention.

[0073] Embodiments of the present invention provide a white light interferometric phase unwrapping method, device, equipment and medium, which are suitable for white light vertical interferometric measurement application scenarios, and are beneficial to improving measurement accuracy, and improving the computational speed and robustness of white light interferometric phase unwrapping.

[0074] like Figure 1 The flowchart of a white light interferometric phase unwrapping method of an embodiment of the present invention is shown. First, the influence of background light intensity is eliminated by differentiating the light intensity data, and then the rough contour surface is calculated by the centroid method after deducting the light intensity mean; then the un-unwrapped phase data is calculated by the spatial frequency domain method, and then the phase data is differentiated line by line to obtain differential data, and then the differential data is threshold-determined to find the phase jump position; finally, the rough contour surface obtained by the centroid method is deducted from the phase data in the corresponding jump area, and the adjacent jump area is numerically determined, so that the phase data is unwrapped to obtain the real contour surface. Specifically, the following steps are included.

[0075] S1, obtaining multiple white light interference images collected from the sample in the vertical direction according to a fixed step value.

[0076] White light vertical interferometry is an interferometric measurement technique that uses white light with a certain spectral width instead of monochromatic light as the interference light source for measurement. The white light interferometer collects images of the sample in the vertical direction at a fixed step value to obtain multiple white light interference images. The step value is usually in the range of 50nm to 150nm, generally 100nm, and the light intensity data corresponding to each pixel point of the group of images can be obtained along the vertical direction.

[0077] S2, performing differential calculation on the light intensity data of two adjacent white light interference images to obtain a plurality of differential images; and using the centroid method to calculate the plurality of differential images to obtain the rough contour surface of the sample.

[0078] First, the background light intensity is eliminated by differential calculation. The specific calculation formula can be expressed as:

[0079]

[0080] Wherein, n∈[1,k-1], k is the total number of white-light interference images, n is the index value of the white-light interference image, and the index value is set according to the order of image acquisition, that is, the n+1th white-light interference image is the next image acquired after the nth white-light interference image; (i,j) represents the pixel index, that is, the pixel point located in the i-th row and j-th column in the white-light interference image, I (i,j) (n+1) represents the pixel point in the i-th row and j-th column in the n+1-th white light interference image; I (i,j) (n) represents the pixel point in the i-th row and j-th column in the n-th white light interference image, which corresponds to the same sampling position on the sample. Represents the difference in light intensity between the pixel at the i-th row and j-th column of the n+1-th white-light interference image and the n-th white-light interference image.

[0081] Calculate for all pixels That is, a differential image is obtained. By calculating the difference between all pixels of two adjacent white light interference images, a total of k-1 differential images can be obtained. Then, the height value of each pixel can be calculated by the centroid method, and the rough contour surface of the sample can be obtained based on the height of all pixels.

[0082] In one embodiment, the improved centroid method is used to calculate the plurality of differential images to obtain the rough contour surface of the sample, which specifically includes the following steps:

[0083] S2-1, calculate the height value of each pixel using the improved centroid method, the calculation formula is:

[0084]

[0085] Among them, Z (i,j) Represents the height of the pixel (i, j), i and j represent the row and column of the pixel in the image respectively. d (n) represents the light intensity value of the nth differential image. The pixel point (i, j) is taken for calculation, n∈[1,k-1], k is the total number of white light interference images, is the mean light intensity of k-1 differential images, that is,

[0086] S2-2, according to the height value of each pixel point, obtain the rough contour surface of the sample, that is, the contour surface composed of the height values ​​corresponding to the positions of all pixel points. Figure 2 Shown is a schematic diagram of a rough contour surface.

[0087] The improvement of the centroid method is to use differential calculation to eliminate the influence of background light intensity and environment, and then deduct the mean value. The environmental influence is further eliminated, so that the rough contour surface extracted by the centroid method also improves the accuracy.

[0088] S3, the original light intensity data is calculated using the spatial frequency domain method to obtain the unwrapped phase data.

[0089] The spatial frequency domain unwrapping performs Fourier transform on the interference image intensity data, extracts the phase of each pixel, and then obtains the pixel height value according to the phase and height calculation formula. The specific steps are as follows.

[0090] S3-1, performing Fourier transform on the original light intensity data to obtain frequency domain data;

[0091] S3-2, extracting the positive frequency part of the frequency domain data to obtain the positive frequency data;

[0092] S3-3, calculating the phase of each pixel point according to the positive frequency data, and finding the phase corresponding to the central wave number of the white light source;

[0093] S3-4, obtain the unwrapped phase data of the actual height according to the phase calculation of the corresponding central wave number.

[0094] The original light intensity data is obtained based on the multiple white light interference images collected in S1. For each white light interference image, the original light intensity data is subjected to discrete Fourier transform. The formula can be expressed as: P = DFT(I), where DFT(·) is the discrete Fourier transform formula, I represents the original light intensity data, P is the transformed frequency domain data, and the i-th frequency domain data P i It can be expressed as:

[0095] P i =|P i |exp(iφ i )

[0096] Among them, φ i Represents the i-th frequency domain data P i The corresponding phase value.

[0097] Take the positive frequency part to calculate the phase value, the calculation formula is:

[0098] φ i =tan -1 (Im(P j ) / Re(P j ))

[0099] Among them, P j represents the jth positive frequency data, the value range of j is [1, round(k / 2)+1], k is the number of collected white light interference images, Im(P j ) indicates P j The imaginary part value, Re(P j ) indicates P j The real value of .

[0100] After obtaining the phase value of each pixel point according to the positive frequency data, find the phase φ corresponding to the central wave number among these phases according to the central wave number of the white light source. The central wave number is an integer, representing the index position of the phase. Assuming that the central wave number is k0, find the phase φ i The phase φ corresponding to the central wave number is obtained by taking the k0th value in the equation.

[0101] Among them, the calculation formula of the central wave number k0 is:

[0102] k0=round(2ScanStep*k / λ)

[0103] Among them, ScanStep represents the fixed step value in S1, λ is the wavelength (as long as the device light source is determined, there will be a theoretical fixed value λ), k represents the total number of white light interference images, k0 is the approximate value of the calculation result, and round(*) represents the rounding function.

[0104] Finally, the phase value corresponding to the central wave number is substituted into the phase and height calculation formula to calculate the height value of the corresponding central wave number k0 of each pixel point, and the unwrapped phase data of the actual height is obtained. Figure 3 Shown is a schematic diagram of the unwrapped phase.

[0105] The calculation formula of phase and height value is:

[0106]

[0107] Among them, h represents the height value, φ represents the phase value corresponding to the central wave number k0, λ0 represents the central wavelength, ScanStep represents the step value, and the two adjacent collected images are separated by a fixed distance in nm.

[0108] The calculation formula of λ0 is:

[0109] λ0=2*ScanStep* / k0

[0110] Among them, ScanStep represents the fixed step value in S1, k represents the total number of white light interference images, and λ0 is not rounded off at this time.

[0111] S4, obtaining a phase jump position based on the unwrapped phase data, segmenting the difference data between the rough contour surface obtained in step S2 and the unwrapped phase data obtained in step S3 according to the jump position to obtain segmented data.

[0112] This step facilitates comparison of adjacent jump regions, thereby correcting the phase and obtaining unwrapped phase data of the actual height.

[0113] In one implementation, the phase jump position is obtained by the following method:

[0114] Perform differential calculation on the unwrapped phase data row by row to obtain differential phase row data of each row;

[0115] The differential phase line data is compared with a set threshold value, and if it exceeds the set threshold value, the corresponding pixel position is determined as the phase jump position.

[0116] The threshold determination formula is expressed as:

[0117]

[0118] Among them, Npart is the calculated phase jump position index, threshold is the judgment threshold, Indicates the nth differential phase row data of the i-th row. When the judgment is effective, The corresponding position is added to the phase jump position index, and then the start and end positions are added to the head and tail of Npart to obtain the final jump position N={1,Npart,k}.

[0119] like Figure 4 d is a schematic diagram of an unwrapped phase, d represents a row of original data in the unwrapped phase data, and e represents differential phase data after row-by-row differential calculation of the row.

[0120] The segment mean data is expressed as:

[0121]

[0122] in, Represents the nth subtracted row data of the i-th row data of the rough profile surface and the i-th row data of the corresponding unwrapped phase, Z i Represents the i-th row of data on the rough contour surface, represents the i-th row of data in the unwrapped phase, and n represents the subtracted row of data Corresponding to the index position, the value range of n is N(i)+1,…N(i+1); i=1,2…m-1, m is the total length of the jump position N, that is, the total number of jump positions in Npart plus the start and end positions, N(i) represents the value corresponding to the i-th jump position; Z f Represents the mean value of the subtracted row data in each segment at the jump position.

[0123] like Figure 5 The figure shows the correspondence between the rough profile surface row data and the subtracted row data of the un-unwrapped phase row data, where a represents the rough surface row data, b represents the un-unwrapped phase row data, and c represents the subtracted row data.

[0124] S5, comparing the mean data of adjacent segments with the multiple of half wavelength, and correcting the phase based on the comparison result to obtain unwrapped phase data.

[0125] First, calculate the mean of each segment and the multiple of half wavelength, the formula is as follows:

[0126] Z g =Z f / (λ0 / 2)

[0127] Among them, Z grepresents the calculated multiple of half wavelength, and λ0 represents the center wavelength.

[0128] like Figure 6 Shown is a flow chart of a phase correction method, comprising the following steps:

[0129] S5-1, correct the phase of the initial segment, the calculation formula is as follows:

[0130] H d (N(1):N(2))=H d (N(1):N(2)).+preIntegerλ0 / 2

[0131] Among them, H d (N(1):N(2)) represents all the data indexed by the phase line data in the jump area N(1) to N(2), .+ represents the same operation for each data, preInteger represents the result after rounding to half wavelength multiples of the initial segment, which is calculated as preInteger=round(Z g (1)), Z g (1) represents the half-wavelength multiple of the initial segment.

[0132] S5-2, calculate the half-wavelength multiple Z of two adjacent segments g The approximate error errorDelta between them is calculated as follows:

[0133] errorDelta=round(Z g (i+1)-preDiff)

[0134] Where preDiff represents the half-wavelength multiple of the previous segment in the adjacent segment, and its initial value is Z g (1), Z g (i+1) represents the half-wavelength multiple of the current calculation segment.

[0135] S5-3, determine whether the approximate error errorDelta is 0, if not 0, execute S5-4, otherwise execute S5-5.

[0136] S5-4, calculate the jump integer Integer = preInteger + errorDelta, and at the same time Z g (i+1) is assigned to preDiff.

[0137] S5-5, calculate the jump integer Integer = preInteger;

[0138] S5-6, correct the phase of the current calculation segment according to the jump integer Integer, and the correction formula is:

[0139] H d (N(i)+1:N(i+1))=N(N(i)+1:N(i+1)).+Integer*λ0 / 2

[0140] Among them, i = 2, ... m-1, m is the segment mean data Z f Length.

[0141] S5-7, repeat the correction process from S5-2 to S5-5, correct all the segments in turn, and obtain the unwrapped phase data. Figure 7 Shown is a schematic diagram of the unwrapping phase.

[0142] A second aspect of the present invention provides a white light interference phase unwrapping device, comprising:

[0143] An acquisition module, used for acquiring a plurality of white light interference images collected from a sample in a vertical direction according to a fixed step value;

[0144] A first calculation module is used to perform differential calculation on the light intensity data of two adjacent white light interference images to obtain a plurality of differential images, and to calculate the plurality of differential images using a centroid method to obtain a rough contour surface of the sample;

[0145] The second calculation module is used to calculate the original light intensity data using a spatial frequency domain method to obtain unwrapped phase data;

[0146] A jump calculation module, used for obtaining a phase jump position based on the unwrapped phase data, and segmenting the difference data between the rough contour surface and the unwrapped phase data according to the jump position;

[0147] The phase correction module is used to compare the mean data of adjacent segments with multiples of half wavelength, and correct the phase based on the comparison result to obtain unwrapped phase data.

[0148] Furthermore, in the first calculation module, the light intensity data of two adjacent white light interference images are differentially calculated to obtain multiple differential images, and the calculation formula is:

[0149]

[0150] Wherein, n∈[1,k-1], k is the total number of white-light interference images, n is the index value of the white-light interference image, and the index value is set according to the order of image acquisition, that is, the n+1th white-light interference image is the next image acquired after the nth white-light interference image; (i,j) represents the pixel index, that is, the pixel point located in the i-th row and j-th column in the white-light interference image, I (i,j) (n+1) represents the pixel point in the i-th row and j-th column in the n+1-th white light interference image; I (i,j)(n) represents the pixel point in the i-th row and j-th column in the n-th white light interference image, which corresponds to the same sampling position on the sample. Represents the difference in light intensity between the pixel at the i-th row and j-th column of the n+1-th white-light interference image and the n-th white-light interference image.

[0151] Furthermore, the first calculation module includes a height calculation module and a contour surface extraction module. The height calculation module calculates the height value of each pixel point by a centroid method. The calculation formula is:

[0152]

[0153] Among them, Z (i,j) Represents the height of the pixel (i, j), i and j represent the row and column of the pixel in the image respectively. d (n) represents the light intensity value of the nth differential image. The pixel point (i, j) is taken for calculation, n∈[1,k-1], k is the total number of white light interference images, is the mean light intensity of k-1 differential images;

[0154] The contour surface extraction module obtains the rough contour surface of the sample according to the height values ​​of all pixel points.

[0155] Furthermore, the second calculation module includes a Fourier transform module, a positive frequency extraction module, a phase calculation module and a height calculation module.

[0156] The Fourier transform module is used to perform Fourier transform on the original light intensity data to obtain frequency domain data;

[0157] The positive frequency extraction module is used to extract the positive frequency part of the frequency domain data to obtain the positive frequency data;

[0158] The phase calculation module is used to calculate the phase of each pixel point according to the positive frequency data, and find the phase of the corresponding central wave number through the central wave number of the white light source;

[0159] The height calculation module is used to obtain the unwrapped phase data of the actual height according to the phase calculation of the corresponding central wave number. Furthermore, the jump calculation module includes a jump positioning module and a segmentation calculation module. The jump positioning module is used to obtain the phase jump position based on the unwrapped phase data, and the segmentation calculation module segments the difference data between the rough contour surface and the unwrapped phase data according to the jump position. The jump positioning module specifically performs:

[0160] Performing differential calculation on the unwrapped phase data row by row to obtain differential phase row data;

[0161] The differential phase line data is compared with a set threshold value, and if it exceeds the set threshold value, the pixel position corresponding to the differential phase line data is determined as the phase jump position.

[0162] The segmented calculation module calculates the segmented mean data:

[0163]

[0164] in, represents the nth subtracted row data of the i-th row data of the rough profile surface and the i-th row data of the corresponding unwrapped phase, Z i Represents the i-th row of data on the rough contour surface, represents the i-th row of data in the unwrapped phase, and n represents the subtracted row of data Corresponding to the index position, the value range of n is N(i)+1,…N(i+1); i=1,2…m-1, m is the total length of the jump position N, N(i) represents the value corresponding to the i-th jump position; Z f Represents the mean value of the subtracted row data in each segment at the jump position.

[0165] Furthermore, the correction module specifically performs the following phase correction process:

[0166] S5-1, correct the phase of the initial segment, the calculation formula is as follows:

[0167] H d (N(1):N(2))=H d (N(1):N(2)).+preInteger*λ0 / 2

[0168] Among them, H d (N(1):N(2)) represents all the data indexed by the phase line data in the jump area N(1) to N(2), .+ represents the same operation for each data, preInteger represents the result after rounding to half wavelength multiples of the initial segment, which is calculated as preInteger=round(Z g (1)).

[0169] S5-2, calculate the half-wavelength multiple Z of two adjacent segments g The approximate error errorDelta between them is calculated as follows:

[0170] errorDelta=round(Z g (i+1)-preDiff)

[0171] Where preDiff represents the half-wavelength multiple of the previous segment, and its initial value is Z g (1), Zg (i+1) represents the half-wavelength multiple of the current calculation segment.

[0172] S5-3, determine whether the approximate error errorDelta is 0, if not 0, execute S5-4, otherwise execute S5-5.

[0173] S5-4, calculate the jump integer Integer = preInteger + errorDelta, and at the same time Z g (i+1) is assigned to preDiff.

[0174] S5-5, calculate the jump integer Integer = preInteger;

[0175] S5-6, correct the phase of the current calculation segment according to the jump integer Integer, and the correction formula is:

[0176] H d (N(i)+1:N(i+1))=H d (N(i)+1:N(i+1)).+Integer*λ0 / 2

[0177] Among them, i = 2, ... m-1, m is the segment mean data Z f Length.

[0178] S5-7, repeat the correction process from S5-2 to S5-5, correct all segments in sequence, and obtain unwrapped phase data.

[0179] An embodiment of the present invention further provides an electronic device, which includes a processor and a memory, and the number of processors may be one or more. The memory, as a computer-readable storage medium, can be used to store software programs, computer executable programs, and modules. The processor executes various functional applications and data processing of the electronic device by running the software programs, instructions, and modules stored in the memory, so as to implement the white light interferometric phase unwrapping method of any of the above embodiments of the present invention.

[0180] The memory may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required for at least one function; the data storage area may store data created according to the use of the terminal, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some instances, the memory may further include a memory remotely arranged relative to the processor, and these remote memories may be connected to the electronic device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0181] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the white-light interferometric phase unwrapping method of any embodiment of the present invention.

[0182] The computer storage medium of the embodiment of the present invention can adopt any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples (non-exhaustive list) of computer-readable storage media include: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present invention, a computer-readable storage medium can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it.

[0183] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, which carry computer-readable program code. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. Computer-readable signal media may also be any computer-readable medium other than a computer-readable storage medium, which may send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0184] An embodiment of the present invention further provides a computer program product. When the computer program product is run on a computer, the computer is enabled to execute the white-light interference phase unwrapping method of any of the above embodiments of the present invention.

[0185] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A white light interference phase unwrapping method, characterized in that: include: Acquire multiple white light interference images collected from the sample in the vertical direction according to a fixed step value; Performing differential calculation on the light intensity data of two adjacent white light interference images to obtain a plurality of differential images, and using a centroid method to calculate the plurality of differential images to obtain a rough contour surface of the sample; The spatial frequency domain method is used to calculate the raw light intensity data to obtain the unwrapped phase data; Obtaining a phase jump position based on the unwrapped phase data, and segmenting the difference data between the rough contour surface and the unwrapped phase data according to the jump position; The mean data of adjacent segments are compared with multiples of half wavelength, and the phase is corrected based on the comparison result to obtain the unwrapped phase data.

2. The white light interference phase unwrapping method according to claim 1, characterized in that: The method of using the centroid method to calculate the plurality of differential images to obtain the rough contour surface of the sample includes: The height value of each pixel is calculated by the improved centroid method. The calculation formula is: Among them, Z (i,j) Represents the height of the pixel (i, j), i and j represent the row and column of the pixel in the image respectively. d (n) represents the light intensity value of the nth differential image. The pixel point (i, j) is taken for calculation, n∈[1,k-1], k is the total number of white light interference images, is the mean light intensity of k-1 differential images; According to the height values ​​of all pixel points, the rough contour surface of the sample is obtained.

3. The white light interference phase unwrapping method according to claim 1, characterized in that: The method of using the spatial frequency domain method to calculate the original light intensity data to obtain the unwrapped phase data includes: Perform Fourier transform on the original light intensity data to obtain frequency domain data; Extracting the positive frequency part of the frequency domain data to obtain positive frequency data; Calculate the phase of each pixel point according to the positive frequency data, and find the phase corresponding to the central wave number through the central wave number of the white light source; The unwrapped phase data of the actual height are obtained according to the phase calculation of the corresponding central wave number.

4. The white light interference phase unwrapping method according to claim 3, characterized in that: The phase of each pixel is calculated according to the positive frequency data, and the formula is: φ i <tan -1 (And(P j ) / Re(P j )) Among them, φ i Represents the i-th frequency domain data P i The corresponding phase value, P j Indicates positive frequency data, Im(P j ) indicates P j The imaginary part value, Re(P j ) indicates P j The real value of .

5. The white light interference phase unwrapping method according to claim 3, characterized in that: The unwrapped phase data of the actual height is obtained by calculating the phase corresponding to the central wave number, and the formula is: λ0=2*ScanStep* / k0 Among them, Z h represents the height value, φ represents the phase value corresponding to the central wave number k0, λ0 represents the central wavelength, ScanStep represents the step value, and k represents the total number of white light interference images.

6. The white light interference phase unwrapping method according to claim 1, characterized in that: Obtaining a phase jump position based on the unwrapped phase data includes: Performing differential calculation on the unwrapped phase data row by row to obtain differential phase row data of each row; The differential phase line data is compared with a set threshold value, and if the set threshold value is exceeded, the pixel position corresponding to the differential phase line data is determined as the phase jump position.

7. The white light interference phase unwrapping method according to claim 6, characterized in that: The step of comparing the mean data of adjacent segments with multiples of half wavelength, and correcting the phase based on the comparison result to obtain the unwrapped phase data includes: S5-1, correct the phase of the initial segment, the calculation formula is as follows: H d (N(1):N(2))=H d (N(1):N(2)).+preIntegerλ0 / 2 Among them, H d (N(1):N(2)) represents all the data indexed in the transition region N(1) to N(2) of the differential phase line data, .+ represents the same operation for each data, and preInteger represents the result after rounding off the half-wavelength multiple of the initial segment; S5-2, calculate the approximate error errorDelta between the half-wavelength multiples of two adjacent segments, the calculation formula is: errorDelta=round(Z g (i+1)-preDiff) Where preDiff represents the half-wavelength multiple of the previous segment in the adjacent segment, and its initial value is the half-wavelength multiple of the initial segment, denoted by Z g (1), Z g (i+1) represents the half-wavelength multiple of the current calculation segment, i=1,2…m-1, m is the total length of the jump position; S5-3, determine whether the approximate error errorDelta is 0, if not 0, execute S5-4, otherwise execute S5-5; S5-4, calculate the jump integer Integer = preInteger + errorDelta, and at the same time Z g (i+1) is assigned to preDiff; S5-5, calculate the jump integer Integer = preInteger; S5-6, correct the phase of the current calculation segment according to the jump integer Integer, and the correction formula is: H d (N(i)+1:N(i+1))=H d (N(i)+1:N(i+1)).+Integer*λ0 / 2 Wherein, i=2,…m-1, and m is the total length of the jump positions. S5-7, repeat the correction process from S5-2 to S5-5, correct all segments in sequence, and obtain unwrapped phase data.

8. A white light interference phase unwrapping device, characterized in that: include: An acquisition module, used for acquiring a plurality of white light interference images collected from a sample in a vertical direction according to a fixed step value; A first calculation module is used to perform differential calculation on the light intensity data of two adjacent white light interference images to obtain a plurality of differential images, and to calculate the plurality of differential images using a centroid method to obtain a rough contour surface of the sample; The second calculation module is used to calculate the original light intensity data using a spatial frequency domain method to obtain unwrapped phase data; A jump calculation module, used for obtaining a phase jump position based on the unwrapped phase data, and segmenting the difference data between the rough contour surface and the unwrapped phase data according to the jump position; The phase correction module is used to compare the mean data of adjacent segments with multiples of half wavelength, and correct the phase based on the comparison result to obtain unwrapped phase data.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the white light interference phase unwrapping method described in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the white light interference phase unwrapping method according to any one of claims 1 to 7 is implemented.

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