CN114485464B - Large-range plane element white light interference rapid measurement method - Google Patents
Large-range plane element white light interference rapid measurement method Download PDFInfo
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- CN114485464B CN114485464B CN202210079883.4A CN202210079883A CN114485464B CN 114485464 B CN114485464 B CN 114485464B CN 202210079883 A CN202210079883 A CN 202210079883A CN 114485464 B CN114485464 B CN 114485464B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/70—Determining position or orientation of objects or cameras
Abstract
The invention discloses a method for quickly measuring white light interference of a large-range planar element, which comprises the following steps: s1, determining the focusing height of a white light interference sensor by utilizing a coarse focusing step; s2, selecting a picture-taking interval containing the focusing height; s3, acquiring initial fringe coordinates of at least four different positions on the planar element in the image acquisition interval according to the fine acquisition step; s4, fitting the pose of the to-be-measured plane element according to the initial fringe coordinate, and performing height compensation to obtain the measurement pose of the to-be-measured plane element; and S5, determining an actual image acquisition interval according to the measurement pose of the to-be-measured plane element. The method adopts the coarse focusing step and the fine acquisition step to quickly determine the initial fringe coordinate, determines the overall pose of the to-be-detected planar element by adopting the plane pose calibration, can quickly and accurately determine the actual image acquisition interval according to the overall pose of the to-be-detected planar element, and greatly improves the measurement accuracy and the measurement efficiency aiming at the large-range planar element with large measurement area.
Description
Technical Field
The invention relates to the technical field of precision measurement, in particular to a method for quickly measuring a large-range plane element by white light interference.
Background
With the rapid development of the fields of intelligent manufacturing, aerospace, national defense science and technology, communication transmission and the like, the requirement of large-range planar elements with micro-nano structures is increasing, for example, micro circuits, MEMS devices, micro optical elements and the like. Most electronic, smart and measurement devices are currently manufactured from such precision components, and any minor errors in the manufacturing process and specifications of such precision components may further cause the devices to malfunction. Therefore, microstructure measurements on precision components are essential to ensure proper and orderly operation of the device. However, the production and manufacturing of the precision element have the characteristics of nanoscale, microscopic surface effect, large range of micro-structure to be measured, interference of dust or foreign matters on the measurement result, large influence of optical diffraction and the like, and most conventional detection means cannot meet the measurement requirement at present. Therefore, a high-efficiency and high-precision micro-structure measuring method is needed to be found, the production qualification rate of the precision element is improved, the micro-structure measuring efficiency is improved, and the requirements of the micro-nano manufacturing industry are met.
At present, the measuring method of the large-range planar element with the micro-nano structure can be divided into contact measurement and non-contact measurement according to whether the large-range planar element is in contact with a piece to be measured or not. The contact type contourgraph and the step profiler are the most traditional contact type measuring methods, have the advantages of stability, large dynamic range and strong reliability, but for a coating surface layer and a soft measured material, the surface layer of a measured sample is easy to be damaged by contact type detection. In addition, the contact measurement speed is slow due to the influence of the stylus diameter, shape, load and dynamic characteristics. The non-contact measurement method comprises scanning microscopic measurement methods based on SEM, STM and AFM, a laser triangulation method, a fringe projection method, a white light interferometry and the like, the scanning microscopic measurement method is expensive, has high requirements on operating environment and low measurement speed, and is mainly used for structural analysis of atomic-scale or nano-scale materials and biological surfaces. The laser triangulation method is strong in universality and high in measurement efficiency, but a light path is easily shielded and generates a measurement blind area, and the fringe projection method is complex in calibration and low in measurement precision and is not suitable for measuring the shape of the microstructure. In contrast, white light interference determines the height of the to-be-detected piece through an accurate zero optical path difference position so as to detect the morphology of the microstructure, and therefore, the method is more suitable for microstructure detection.
The measurement method based on white light interference adopts a non-contact measurement mode, and has the advantages of high measurement precision, high measurement efficiency and the like, so that researchers can be widely applied to microstructure measurement. The method mainly calculates the height information of points on the inner wall of the corresponding part through the accurate zero optical path difference position on the interference image, so that the microstructure appearance of the to-be-measured piece can be measured with high precision, and therefore, the method is essential for collecting the image with stripes. The existing white light interference measuring instrument has high measuring precision, but is expensive and small in view field, when the microstructure is measured, multi-region continuous image acquisition and identification of each view field fringe interval are required, a large-stroke horizontal moving shaft system is required to be matched for measuring a large-range planar element, the cost of a measuring system is increased, a large amount of measuring time is required for identification of all the measured view field fringe intervals, and the industrial requirement for rapid production of the microstructure is not met.
Disclosure of Invention
The invention aims to provide a method for quickly measuring white light interference of a large-range plane element, which adopts a rough focusing step and a fine acquisition step to quickly determine an initial fringe coordinate, and adopts plane pose calibration to determine the overall pose of the plane element to be measured, so that an actual image acquisition interval can be quickly and accurately determined according to the overall pose of the plane element to be measured, and the measurement accuracy and the measurement efficiency of the large-range plane element with a large measurement area are greatly improved.
In order to achieve the purpose, the invention provides the following technical scheme: a white light interference quick measuring method for a large-range plane element comprises the following steps:
s1, determining the focusing height of a white light interference sensor by using a coarse focusing step;
s2, selecting a drawing collecting interval containing the focusing height;
s3, acquiring initial fringe coordinates of at least four different positions on the planar element to be detected in the image acquisition interval according to the fine acquisition step;
s4, fitting the pose of the to-be-measured planar element according to the initial fringe coordinate, and performing height compensation to obtain the measurement pose of the to-be-measured planar element;
s5, determining an actual image acquisition interval according to the measurement pose of the to-be-measured planar element;
and S6, acquiring the image in different areas of the to-be-detected planar element by using the actual image acquisition intervals, and obtaining the integral surface micro-topography of the to-be-detected planar element by using a topography calculation algorithm and a splicing algorithm.
Preferably, the step of coarse focusing in S1 includes:
s101, continuously collecting a plurality of images above a planar element to be detected by a white light interference sensor in a first step amount;
s102, processing and judging the images, and determining the focusing height of the white light interference sensor.
Preferably, the S102 includes determining a position where the interference fringe is most apparent as a focal height of the white light interference sensor according to a distribution of gray values of the image.
Preferably, the step of fine acquisition in S3 includes:
s301, sequentially collecting a plurality of images at least four different positions on the planar element by second step amount in the image collecting interval, wherein the second step amount is smaller than the first step amount.
Preferably, the S3 further includes:
and S302, processing the image acquired in the S301 to obtain corresponding initial fringe coordinates.
Preferably, the processing of the image acquired in S301 in S302 includes performing filtering processing on the image to remove noise influence, and removing background influence through single-image multi-scale information calculation and processing.
Preferably, the filtering process uses the following image filtering formula:
wherein g (x, y) represents the processed image, n is the size of the template, I (x, y) is the gray value of the pixel point of the image, x, y are coordinate values, and S is a gray value set;
the single-image multi-scale information calculation and processing formula is as follows:
wherein, L (x, y, sigma) and L (x, y, alpha) represent different scale spaces of the image, sigma and alpha are scale coordinates, I (x, y) represents the gray value of the pixel point of the image, G (x, y, sigma) and G (x, y, alpha) are scale variable Gaussian functions,
the multiscale change is denoted as L' (x, y) = L (x, y, σ) × L (x, y, α), where α =1/σ, and the processed single image is denoted as: i '(x, y) = I (x, y) × L' (x, y), where x, y are coordinate values.
Preferably, the processing of the image obtained in step S1 in step S2 is the same as the image filtering processing and the single-image multi-scale information calculation processing method in step S302.
Preferably, the obtaining of the initial fringe coordinates in S302 includes identifying a gray value change of the processed image, generating a gray value change distribution curve, and determining an initial position of the interference fringes according to the gray value change distribution curve; the formula is as follows:
x＝g(t)＝k*t+b
F(x)＝a(n)*x n +a(n-1)*x (n-1) +...+a(1)*x+a(0)
wherein t is the position of the image, k and b are the internal function optimal coefficients of the composite function, x and g (t) are the results obtained by the internal function in the composite function, F (x) is the gray value flag bit, n is the highest fitting times of the composite function, and a (n) is the result obtained by curve fitting of the composite function.
Preferably, the S6 includes fitting the pose of the planar element to be measured by using a least square method, and the formula is as follows:
Ax+By+Cz+D＝0
in the formula, x, y and z are three-dimensional point coordinates of angular points, and A, B, C and D are plane parameters obtained by fitting.
Compared with the prior art, the invention has the beneficial effects that:
the invention adopts a coarse focusing step to quickly determine a focusing position, selects an image acquisition interval in a certain range from the upper part to the lower part of the focusing position to carry out a fine acquisition step so as to quickly determine initial fringe coordinates of at least four angular points, fits the pose of a planar element to be detected according to the initial fringe coordinates, determines an actual image acquisition interval according to the measurement pose of the planar element to be detected, and carries out image acquisition according to the actual image acquisition interval, thereby greatly improving the measurement accuracy and the measurement efficiency aiming at the large-range planar element with large measurement area.
Drawings
FIG. 1 is a block diagram of a process of a method for fast measurement of a large-scale planar element by white light interference according to the present invention;
FIG. 2 is a schematic diagram of rough focusing in a large-scale planar device white light interference fast measurement method according to the present invention;
FIG. 3 is a schematic diagram of fine acquisition in a large-scale planar device white light interferometry rapid measurement method according to the present invention;
FIG. 4 is a schematic diagram of image gray value distribution during coarse focusing in the method for fast measurement of large-scale planar element by white light interference according to the present invention;
FIG. 5 is a schematic diagram showing the gray scale value flag bit variation in the process of determining the initial position of the measurement fringe in the method for fast measurement of white light interference of a large-scale planar element according to the present invention;
fig. 6 is a schematic structural diagram of a motion axis system provided in a method for fast measurement of a large-scale planar element by white light interference according to the present invention.
In the figure: 1. a white light interference sensor; 2. a Z-axis adjustment mechanism; 3. a marble gantry; 4. a horizontal X-axis adjustment mechanism; 5. a horizontal Y-axis adjustment mechanism; 6. a marble base; 7. a planar element to be tested; 8. a corner point.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the present invention provides an embodiment of a method for fast white light interferometry measurement of a large-area planar element, where the method includes the following steps:
s1, determining the focusing height of a white light interference sensor by utilizing a coarse focusing step;
s2, selecting a picture-taking interval containing the focusing height;
s3, acquiring initial fringe coordinates of at least four different positions on the planar element in the image acquisition interval according to the fine acquisition step;
s4, fitting the pose of the to-be-measured planar element according to the initial fringe coordinate, and performing height compensation to obtain the measurement pose of the to-be-measured planar element;
s5, determining an actual image acquisition interval according to the measurement pose of the to-be-measured planar element;
and S6, acquiring the image in different areas of the to-be-detected planar element by using the actual image acquisition intervals, and obtaining the integral surface micro-topography of the to-be-detected planar element by using a topography calculation algorithm and a splicing algorithm.
In the embodiment, the initial fringe coordinate is quickly determined by adopting the coarse focusing step and the fine acquisition step, the overall pose of the to-be-measured planar element is determined by adopting the plane pose calibration, the actual image acquisition interval can be quickly and accurately determined according to the overall pose of the to-be-measured planar element, and the measurement accuracy and the measurement efficiency of the large-range planar element with a large measurement area are greatly improved.
As shown in fig. 2 and 4, specifically, the step of coarse focusing in S1 includes:
s101, continuously acquiring a plurality of images by a white light interference sensor in a first step amount above a planar element to be detected (in a given larger image acquisition interval, a group of images are rapidly acquired by the white light interference sensor from defocusing to focusing and then defocusing);
s102, processing and judging the plurality of images (filtering the images collected by the white light interference sensor under the condition of keeping image fringe characteristics, inhibiting noise of a target image, removing image highlight areas of the filtered images in an image processing mode, and avoiding influence of highlight backgrounds on interference fringes), and determining the focusing height of the white light interference sensor (judging the height of the white light interference sensor when the interference fringes are most obvious according to the gray value distribution condition of the images after image processing, namely determining the coarse focusing position of the white light interference sensor).
The step S102 includes determining a position where the interference fringes are most significant as a focusing height of the white light interference sensor according to a distribution of gray values of the image (in fig. 4, an abscissa is an image height, and an ordinate is a fringe significance degree of the preprocessed image).
As shown in fig. 3 and 5, the fine acquisition step in S3 includes:
s301, sequentially collecting a plurality of images at least four different positions on the planar element by using second step amount in the image collecting interval, wherein the second step amount is smaller than the first step amount (after the focusing position is determined through the steps, certain ranges are respectively taken along the upper part and the lower part of the focusing position to serve as the image collecting interval for accurately identifying the interference fringes, and a series of images are collected by using the step amount smaller than the first step amount in the image collecting interval in the small range of the last step).
And S302, processing the image collected in S301 (including image processing modes such as filtering the collected image, reducing the influence of the image background on the interference fringes and improving the contrast ratio of the interference fringes and the background), and obtaining corresponding initial fringe coordinates (determining the gray value change trend according to the gray value change condition after image processing to obtain a series of gray value change distribution curves, representing the gray value change trend by adopting a complex function curve fitting mode, and determining the accurate position of the image when the interference fringes appear according to the result obtained by fitting, so as to determine the height of the white light interference sensor at the moment).
Preferably, the processing of the image acquired in S301 in S302 includes performing filtering processing on the image to remove noise influence, and removing background influence through single-image multi-scale information calculation and processing.
Preferably, the filtering process uses the following image filtering formula:
wherein g (x, y) represents the processed image, n is the size of the template, I (x, y) is the gray value of the image pixel point, x, y are coordinate values, and S is a gray value set;
the single-image multi-scale information calculation and processing formula is as follows:
wherein, L (x, y, sigma) and L (x, y, alpha) represent different scale spaces of the image, sigma and alpha are scale coordinates, I (x, y) represents the gray value of the pixel point of the image, G (x, y, sigma) and G (x, y, alpha) are scale variable Gaussian functions,
the multiscale change is denoted as L' (x, y) = L (x, y, σ) × L (x, y, α), where α =1/σ, and the processed single image is denoted as: i '(x, y) = I (x, y) × L' (x, y), where x, y are coordinate values.
Preferably, the processing of the image obtained in step S1 in step S2 is the same as the image filtering processing and the single-image multi-scale information calculation processing method in step S302.
As shown in fig. 4 and 5, in this embodiment, the fringe features are highlighted through image processing, a certain range of gray values are taken as flag bits, and the focusing position can be directly determined according to the distribution of the gray value flag bits, because the interference fringes at the focusing position are very obvious and are often easy to identify, the identification efficiency is higher by adopting an identification mode of gray change; and the initial position of the stripe is accurately identified by utilizing the gray value change, so that the time when the stripe just begins to appear can be accurately identified. By adopting the image processing process, the influence of interference signals such as noise on the image on the interference fringes is avoided, and the identification efficiency and accuracy are improved.
Preferably, the obtaining of the initial fringe coordinates in S302 includes identifying a gray value change of the processed image, generating a gray value change distribution curve, and determining an initial position of the interference fringes according to the gray value change distribution curve; the formula is as follows:
x＝g(t)＝k*t+b
F(x)＝a(n)*x n +a(n-1)*x (n-1) +...+a(1)*x+a(0)
in the formula, t is the position of the image, k and b are the inner function optimal coefficients of the composite function, x and g (t) are the results obtained by the inner function in the composite function, F (x) is a gray value flag bit, n is the highest fitting time of the composite function, and a (n) is the result obtained by curve fitting of the composite function.
Preferably, the S6 includes fitting the pose of the planar element to be measured by using a least square method, and the formula is as follows:
Ax+By+Cz+D＝0
in the formula, x, y and z are three-dimensional point coordinates of angular points, and A, B, C and D are plane parameters obtained by fitting.
And after the fitting error is obtained, respectively providing different height compensations for points at different positions on the plane, and adding the fitting value of each point and the error value to obtain the actual height of all the points on the plane so as to finish the pose calibration of the wafer plane. And reconstructing and splicing the acquired images to obtain the appearance of the full-field wafer.
As shown in fig. 6, according to the schematic structural diagram of the motion axis system provided by the present invention, the measurement structure is integrally disposed on the marble base 6, the marble gantry 3 is mounted on the marble base 6, the white light interference sensor 1 is mounted on the marble gantry 3 through the Z-axis adjusting mechanism 2, the planar element 7 to be measured is mounted on the marble base 6 through the horizontal X-axis adjusting mechanism 4 and the horizontal Y-axis adjusting mechanism 5, and by using the motion axis system measurement structure, the overall measurement steps include:
(1) The white light interference sensor 1 is moved to a certain position above a planar element 7 to be measured through a horizontal X-axis adjusting mechanism 4, a horizontal Y-axis adjusting mechanism 5 and a Z-axis adjusting mechanism 2, and a series of images are acquired in a larger step amount in a larger image acquisition interval.
(2) The image collected by the white light interference sensor 1 is filtered under the condition of keeping the image fringe characteristics, and the noise of the target image is suppressed.
(3) And removing the image highlight area of the filtered image in an image processing mode, and avoiding the influence of the highlight background on the interference fringes.
(4) And judging the height of the white light interference sensor 1 when the interference fringes are most obvious according to the gray value distribution condition of the image after the image processing, namely the coarse focusing position of the white light interference sensor 1.
(5) After the focusing position is determined through the steps, certain ranges are respectively taken up and down along the focusing position to serve as image acquisition intervals for accurately identifying the interference fringes.
(6) In the small-range image acquisition interval of the last step, a series of images are acquired in a smaller step amount relative to step (1).
(7) And image processing modes such as filtering and the like are carried out on the acquired image, the influence of the image background on the interference fringes is weakened, and the contrast ratio of the interference fringes and the background is improved.
(8) And selecting the gray value which changes most obviously on the image as a marker bit, and obtaining a series of gray distribution curves according to the number of the gray value marker bits after the image is processed, thereby determining the gray value change trend of the image.
(9) And (3) representing the gray value change trend by adopting a composite function curve fitting mode, and determining the accurate position of the image when the stripes appear according to the result obtained by fitting, thereby determining the height of the measuring head at the moment.
(10) Setting the positions of four angular points 8 of a planar element 7 to be detected, and automatically moving the planar element to the four angular points 8 of the plane through the horizontal X-axis adjusting mechanism 4, the horizontal Y-axis adjusting mechanism 5 and the Z-axis adjusting mechanism 2 to acquire images.
(11) And (3) respectively determining the initial positions of the interference fringes of the four angular points 8 view fields of the plane by using the coarse focusing and accurate interference fringe identification method in the step 1.
(12) And fitting the overall pose of the to-be-measured planar element 7 by using a least square method by combining the horizontal and vertical coordinates of the four angular points 8 and the initial positions of the stripes.
(13) Calculating the deviation between the height of the angular point 8 of the plane element to be measured obtained by fitting and the position where the actual stripe appears, and performing height compensation on points at different positions away from the angular point 8 according to a certain rule to determine the actual pose of the plane.
(14) And driving the white light interference sensor 1 to other positions except for the angular point 8 by using the horizontal X-axis adjusting mechanism 4 and the horizontal Y-axis adjusting mechanism 5, and judging the rationality of compensation according to the initial height value of the fringes after height compensation.
(15) And obtaining the initial position of the stripe appearing in different view fields according to the obtained pose of the planar element to be detected 7, thereby obtaining the actual image acquisition interval.
(16) And (4) acquiring images in the predicted image acquisition intervals in different areas of the planar element 7 to be detected, and acquiring the overall surface micro-topography of the large-range planar element by adopting a proper topography calculation algorithm and a splicing algorithm.
The working principle is as follows: the invention firstly highlights the stripe characteristics by image processing and other methods, and then determines the position of a measuring head of the white light interference sensor 1 when the stripe appears by the gray value influence brought by the stripe characteristics to the collected image, thereby determining the plane pose according to the position of the measuring head at the angular point 8, removing the noise influence of the image by image processing methods such as image filtering and the like when identifying the initial position of the stripe, removing the background influence of the image by the methods such as single-image multi-scale information calculation and processing and the like, and highlighting the characteristics of the stripe. According to the method, the focusing position is determined according to the gray value distribution condition of the image when the focusing position is determined roughly and the stripe initial position is identified accurately, the focusing position is determined according to the gray value distribution condition of different images, polynomial fitting is carried out on gray value change curves of different images to determine the stripe initial position, and the stripe initial position is identified accurately by adopting the gray value change trend of a complex function curve fitting mode and threshold setting. The invention is suitable for fast pose calibration and measurement of the planar element 7 to be measured with large range of microstructures such as wafers, etc., has more precise measurement, high measurement precision requirement and large measurement area, can be suitable for pose identification of the large range microstructure with the size of 15 inches (the diameter of 38 centimeters), can control the identification speed within 30 seconds, and greatly improves the measurement accuracy and the measurement efficiency of the large range planar element with large measurement area.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Claims (10)
1. A white light interference quick measuring method for a large-range plane element is characterized by comprising the following steps:
s1, determining the focusing height of a white light interference sensor by utilizing a coarse focusing step;
s2, selecting a picture-taking interval containing the focusing height;
s3, acquiring initial fringe coordinates of at least four different positions on the to-be-detected planar element in the image acquisition interval according to the fine acquisition step;
s4, fitting the pose of the to-be-measured plane element according to the initial fringe coordinate, and performing height compensation to obtain the measurement pose of the to-be-measured plane element;
s5, determining an actual image acquisition interval according to the measurement pose of the to-be-measured planar element;
s6, acquiring the image in different areas of the to-be-detected planar element in actual image acquisition intervals, and obtaining the overall surface micro-topography of the to-be-detected planar element through a topography calculation algorithm and a splicing algorithm.
2. The large-scale planar element white light interferometric fast measurement method according to claim 1, characterized in that the coarse focusing step in S1 comprises:
s101, continuously collecting a plurality of images above a planar element to be detected by a white light interference sensor in a first step amount;
s102, processing and judging the images, and determining the focusing height of the white light interference sensor.
3. The method for white light interference fast measurement of the large-range planar element according to claim 2, wherein the step S102 includes determining a position where the interference fringe is most obvious as a focusing height of the white light interference sensor according to a distribution of image gray values.
4. The wide-area planar element white light interferometric fast measurement method according to claim 3, characterized in that the fine acquisition step in S3 comprises:
s301, sequentially collecting a plurality of images at least four different positions on the planar element by second step amount in the image collecting interval, wherein the second step amount is smaller than the first step amount.
5. The large-scale planar element white light interferometric fast measurement method according to claim 4, characterized in that said S3 further comprises:
and S302, processing the image acquired in the S301 to obtain corresponding initial fringe coordinates.
6. The large-scale planar element white light interference rapid measurement method according to claim 5, wherein the processing of the image acquired in S301 in S302 includes filtering the image to remove noise influence, and removing background influence through single-image multi-scale information calculation and processing.
7. The method for fast white light interferometry for wide area planar elements according to claim 6, wherein the filtering process uses the following image filtering formula:
wherein g (x, y) represents the processed image, n is the size of the template, I (x, y) is the gray value of the pixel point of the image, x, y are coordinate values, and S is a gray value set;
the single-image multi-scale information calculation and processing formula is as follows:
wherein, L (x, y, sigma) and L (x, y, alpha) represent different scale spaces of the image, sigma and alpha are scale coordinates, I (x, y) represents the gray value of the pixel point of the image, G (x, y, sigma) and G (x, y, alpha) are scale variable Gaussian functions,
the multiscale change is denoted as L' (x, y) = L (x, y, σ) × L (x, y, α), where α =1/σ, and the processed single image is denoted as: i '(x, y) = I (x, y) × L' (x, y), where x, y are coordinate values.
8. The method for fast white light interferometry according to the large-range planar element of claim 7, wherein the processing of the image obtained in step S1 in S2 is the same as the image filtering processing and the single-image multi-scale information calculation processing method in step S302.
9. The method for rapid white light interference measurement of large-scale planar elements according to any one of claims 5 to 8, wherein the obtaining of the initial fringe coordinates in S302 includes identifying gray value changes of the processed image, generating a gray value change distribution curve, and determining an initial position of the interference fringe according to the gray value change distribution curve; the formula is as follows:
x＝g(t)＝k*t+b
F(x)＝a(n)*x n +a(n-1)*x (n-1) +...+a(1)*x+a(0)
wherein t is the position of the image, k and b are the internal function optimal coefficients of the composite function, x and g (t) are the results obtained by the internal function in the composite function, F (x) is the gray value flag bit, n is the highest fitting times of the composite function, and a (n) is the result obtained by curve fitting of the composite function.
10. The method for fast white light interferometry for measuring the wide-range planar element according to claim 9, wherein S6 comprises fitting the pose of the planar element to be measured by using the least square method, wherein the formula is as follows:
Ax+By+Cz+D＝0
in the formula, x, y and z are three-dimensional point coordinates of angular points, and A, B, C and D are plane parameters obtained by fitting.
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