CN113670205B - System and method for three-dimensional detection of geometric parameters of film hole of aero-engine blade based on zoom microscopy - Google Patents
System and method for three-dimensional detection of geometric parameters of film hole of aero-engine blade based on zoom microscopy Download PDFInfo
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- CN113670205B CN113670205B CN202111025062.4A CN202111025062A CN113670205B CN 113670205 B CN113670205 B CN 113670205B CN 202111025062 A CN202111025062 A CN 202111025062A CN 113670205 B CN113670205 B CN 113670205B
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- 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
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- 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
- G01B11/08—Measuring arrangements characterised by the use of optical techniques for measuring diameters
- G01B11/12—Measuring arrangements characterised by the use of optical techniques for measuring diameters internal diameters
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- G—PHYSICS
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- 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
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- G—PHYSICS
- 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
- G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
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Abstract
The invention discloses a three-dimensional detection system and a three-dimensional detection method for geometrical parameters of an aero-engine blade air film hole based on a zoom microscopic technology, wherein the detection system comprises a CCD camera, a lens cone, a computer, an XYZ three-dimensional electric translation table, an objective table and a blade clamp; adjusting the position of the blade air film hole to be detected to the imaging area of the CCD camera during detection, acquiring an image sequence of the blade air film hole of the aircraft engine, calculating a focusing function evaluation function value of each pixel point of the image sequence by using a focusing evaluation function to obtain final three-dimensional data of the blade air film hole, and calculating the three-dimensional data of the inner surface of the hole to obtain the roughness S of the inner surface of the holeaAnd various geometric parameters can be obtained in one-time measurement, so that the efficiency is high, the measurement repeatability is high, and the uncertainty is low.
Description
Technical Field
The invention belongs to the field of aviation industry, relates to an aviation engine blade detection technology, and particularly relates to a system and a method for three-dimensionally detecting geometric parameters of an air film hole of an aviation engine blade based on a zoom microscopy technology.
Background
With the continuous development of the aviation industry, the new generation of aircraft engine has the advantages that the thrust is larger, the thrust-weight ratio is higher, and the oil consumption rate is lower by increasing the gas temperature in front of the turbine, so that the reliability and the maneuverability of the aircraft are improved. The air film hole is a necessary structure for improving the temperature bearing capacity of the blade and ensuring the reliable service of the blade. According to the cooling principle, the geometric parameters of the film hole directly influence the mechanical performance and the cooling effect of the blade, and mainly comprise the aperture, the spatial position, the roughness of the inner surface of the hole and the like of the film hole. Therefore, in order to ensure that the film holes meet the design requirements of the blade, the geometric parameters of the film holes must be detected with high precision.
At present, the method for measuring the geometric parameters of the film hole of the blade of the aero-engine is mainly a contact type or non-contact type detection technology, wherein the contact type measurement needs to be made by a micro probe to extend into the hole for detection, but the method has the defects of low measurement speed, low efficiency, incapability of simultaneously obtaining a plurality of parameters and the like. The non-contact measurement is mainly based on various optical measurement modes, for example, a measurement method of an optical interference spectrum analysis technology can obtain good repeatability, but the detection requirement of the gas film holes in batches cannot be met due to low efficiency. The zooming microscopic measurement method is an optical morphology measurement method, has the characteristics of high efficiency, no damage, good repeatability, low uncertainty and the like, and is suitable for three-dimensional measurement and geometric parameter extraction of the air film hole.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a system and a method for three-dimensional detection of geometric parameters of an aero-engine blade air film hole based on a zoom microscopy technology, which can effectively obtain three-dimensional data of the aero-engine blade air film hole, can obtain various geometric parameters in one-time measurement and can realize batch detection of the air film hole.
In order to achieve the purpose, the invention adopts the following technical scheme:
a three-dimensional detection system for geometrical parameters of an aero-engine blade air film hole based on a zoom microscopic technology comprises a CCD camera, a lens cone, a computer, an XYZ three-dimensional electric translation table, an object stage and a blade clamp;
the first lens, the beam splitter prism, the third lens and the objective lens are sequentially arranged from near to far along the path of an incident light of the CCD camera from one side close to the CCD camera, the objective table is arranged behind the objective lens, and the blade clamp is arranged on the objective table; the beam splitter prism is obliquely arranged, the coaxial light source and the second lens are sequentially arranged in an incident light path of the beam splitter prism from bottom to top, an emergent light path of the beam splitter prism is coaxial with the third lens and the objective lens, the first lens, the beam splitter prism, the second lens and the third lens are packaged in the lens barrel, the objective lens is connected to the lens barrel, and the annular light source is clamped on the outer side of the objective lens;
the lens cone is installed on an XYZ three-dimensional electric translation table, and the CCD camera and the XYZ three-dimensional electric translation table are respectively connected with a computer to realize linkage triggering.
Further, the blade anchor clamps are including being used for fixing rotatory concave station on the objective table, offer the through-hole that is used for inserting the locking bolt on the rotatory concave station, rotatory boss of assembly on the rotatory concave station, rotatory boss can 360 degrees rotations and its upper symmetry is provided with first jack catch and the second jack catch that is used for cliping the blade, offer on first jack catch and the second jack catch and be used for inserting the locking bolt through-hole.
Further, the lens cone is installed on an XYZ three-dimensional electric translation table through a right-angle type connecting plate.
The three-dimensional detection system and method for the geometric parameters of the film hole of the blade of the aero-engine based on the zoom microscopic technology comprises the following steps:
1) fixing the blade on an objective table through a blade clamp, and adjusting the gas film hole part of the blade to be measured to the imaging area of the CCD camera by adjusting an XYZ three-dimensional electric translation table and the objective table;
2) controlling a CCD camera to acquire images through a computer, and acquiring an image sequence of an aeroengine blade air film hole;
3) performing image preprocessing, traversing all pixel points of the air film hole image sequence, and calculating a focusing function evaluation function value of each pixel point of the image sequence by using a focusing evaluation function;
4) threshold screening is carried out on the focusing evaluation function values, different sample points are removed, then the positions of the maximum values of the focusing evaluation functions of all pixel points are obtained by using a fast Gaussian fitting method, and final three-dimensional data of the blade air film holes are obtained;
5) performing least square plane fitting on the three-dimensional data at the edge of the hole profile, extracting the hole profile from the three-dimensional data, fitting an arc to obtain fitting circle data, obtaining the center and radius R of the fitting circle from the fitting circle data, namely the three-dimensional coordinate of the hole center and the size of the hole diameter, and calculating the three-dimensional data on the inner surface of the hole to obtain the holeRoughness S of inner surfacea。
Further, the step 2) specifically comprises the following steps:
(2.1) scanning the air film holes on the blades by a computer-driven XYZ three-dimensional electric translation table according to a specified step pitch along the x-axis direction, simultaneously controlling a CCD (charge coupled device) camera to acquire images by the computer, and obtaining air film hole image sequences with different focusing degrees by using different light intensities of a coaxial light source and a ring light source;
and (2.2) after the acquisition is finished, positioning the XYZ three-dimensional electric translation table at a starting point, and repeating the step (2.1) to acquire an image sequence of the next air film hole.
Further, the image preprocessing in step 3) is to perform gaussian filtering on all images, and then perform a high contrast highlighting algorithm on each image, and the following formula is adopted:
IN(x，y)＝I0(x，y)+r×(I0(x，y)-IB(x，y))
in the formula IN(x, y) is the processed image, I0(x, y) is a Gaussian filtered image, r is a coefficient, IB(x, y) is a fully blurred background image.
Further, the step 3) of calculating the focus function evaluation function value of each pixel point of the image sequence by using the focus evaluation function adopts the following formula:
in the formula, p (x, y) is a focus evaluation function value at the pixel (x, y), f (x +2, y) is a gray value at the pixel (x +2, y), and f (x, y) is a gray value at the pixel (x, y).
Further, the step 4) of performing threshold value screening on the focus evaluation function value includes the specific process of removing the different sampling points:
firstly, searching an image sequence index x corresponding to the maximum value F (x) of the focus evaluation function value of each pixel point, and normalizing the focus value F (x +1) at the x +1 position and the focus value F (x-1) at the x-1 position to obtain N1 and N2 respectively;
secondly, setting a threshold value T, if N1> T and N2> T, storing x and F (x), otherwise, making F (x) equal to (F (x +1) + F (x-1))/2, and repeatedly circulating the processes; if x is 1 or x is n and n is the total number of the image sequences, finding the minimum value f (x) of the focus evaluation function values, making f (x), and repeating the process until all the focus evaluation function values are screened.
Further, the position of the maximum value of the focus evaluation function of each pixel obtained by using the fast gaussian fitting method in the step 4) is an image sequence index x corresponding to the maximum value f (x) of the focus evaluation function value of each pixel, a fitted image index interval [ x-n, x + n ] is set, and double gaussian fitting is performed on the focus function evaluation value corresponding to each image index integer in the interval to obtain the maximum value of the focus evaluation function.
Further, the step 5) calculates the roughness S of the inner surface of the holeaFirstly, processing noise points by adopting a bilateral filtering algorithm, and secondly, carrying out surface roughness S in the hole by utilizing a tangent plane methodaAnd (4) calculating.
The detection system disclosed by the invention is characterized in that a monochromatic light source is emitted from outside to inside through a collimating lens, and an XYZ three-dimensional electric translation table and a CCD camera are respectively connected with a computer to realize linkage triggering; the annular light source is clamped outside the objective lens, aperture data and surface roughness in the aperture in the contour can be effectively obtained through the system, various geometric parameters can be obtained in one-time measurement, and the system has the characteristics of high efficiency, no damage, good repeatability, low uncertainty and the like.
The method has the advantages that the method highlights an area with high image contrast, facilitates detection of a focus evaluation function, reduces noise point influence, better performs edge detection, and can more accurately detect a focus point compared with the method which directly uses the focus function for evaluation, and better completes three blade parametersRecovering the dimensional appearance; threshold value screening is carried out on the function value before interpolation fitting, so that different sampling points can be removed, and the influence of a coarse error on a result is reduced; the maximum value of the focusing evaluation function value is more accurately and rapidly searched by using a rapid Gaussian fitting algorithm, and the roughness S of the surface in the hole is carried out by using a tangent plane methodaCalculating (1); the three-dimensional detection system and the method can obtain various geometric parameters in one measurement, and have the advantages of high efficiency, high measurement repeatability and low uncertainty.
Drawings
FIG. 1 is a schematic diagram of the detection system of the present invention;
FIG. 2 is a schematic view of a blade clamp according to the present invention;
FIG. 3 is a top view of FIG. 2;
FIG. 4 is a flow chart of a zoom measurement method of the present invention for extracting three-dimensional data;
FIG. 5 is a flow chart of the geometric parameter extraction of the three-dimensional data of the gas film hole of the present invention;
FIG. 6 is a graph of a zoom measurement method of the present invention after focus evaluation;
FIG. 7 is a diagram illustrating the effect of threshold screening on the evaluation value of the focusing function according to the present invention;
the notation in the figure is: the device comprises a CCD camera, 2-a first lens, 3-a coaxial light source, 4-a second lens, 5-a beam splitter prism, 6-a third lens, 7-an objective lens, 8-a ring light source, 9-a lens cone, 10-a computer, 11-an XYZ three-dimensional electric translation table, 12-a right-angle connecting plate, 13-an objective table, 14-a blade clamp, 15-a rotary concave table, 16-a rotary convex table, 17-a first clamping jaw and 18-a second clamping jaw.
Detailed Description
The present invention will be explained in further detail with reference to examples.
As shown in FIG. 1, the three-dimensional detection system for geometrical parameters of an aero-engine blade air film hole based on the zoom microscopy technology comprises a CCD camera 1, a first lens 2, a coaxial light source 3, a second lens 4, a beam splitter prism 5, a third lens 6, an objective lens 7, an annular light source 8, a lens barrel 9, a computer 10, an XYZ three-dimensional electric translation stage 11, a right-angle connecting plate 12, an objective table 13 and a blade clamp 14.
CCD camera 1 sets up at the leftmost side, sets gradually first lens 2, beam splitter prism 5, third lens 6 and objective 7 along CCD camera 1 incident light path from left to right, and objective table 13 sets up on objective 7 right side, and blade anchor clamps 14 are installed on objective table 13. The light splitting prism 5 is obliquely arranged, the coaxial light source 3 and the second lens 4 are sequentially arranged in an incident light path of the light splitting prism 5 from bottom to top, an emergent light path of the light splitting prism 5 is coaxial with the third lens 6 and the objective lens 7, the first lens 2, the light splitting prism 5, the second lens 4 and the third lens 6 are all packaged in the lens barrel 9, and the objective lens 7 is connected to the lens barrel 9 and clamps the annular light source 8 on the outer side.
The lens cone 9 is installed on an XYZ three-dimensional electric translation table 11 through a right-angle type connecting plate 12, and the CCD camera 1 and the XYZ three-dimensional electric translation table 11 are respectively connected with the computer 10 to realize linkage triggering.
As shown in fig. 2 and 3, when measuring the aerial engine blade film hole image, the blade is fixed on the object stage 13 by a blade clamp 14; blade anchor clamps 14 is including being used for fixing rotatory concave station 15 on objective table 13, there is the through-hole on rotatory concave station 15, can insert the stop bolt, rotatory boss 16 of assembly on the rotatory concave station 15, rotatory boss 16 can rotate 360 degrees and the symmetry is provided with first jack catch 17 and the second jack catch 18 that is used for cliping the blade, first jack catch 17 with there is the through-hole on the second jack catch 18, can insert the stop bolt.
As shown in fig. 4 and 5, the three-dimensional detection method for the geometric parameters of the film hole of the blade of the aero-engine based on the zoom microscopy comprises the following steps:
1) adjusting the gas film hole part of the blade to be detected to the imaging area of the CCD camera;
the method specifically comprises the following steps:
and (1.1) fixing the blade on the blade clamp, and turning on the coaxial light source and the annular light source.
(1.2) driving an XYZ three-dimensional electric translation table and manually adjusting the pose of a blade clamp through a computer, observing light spots, and aligning the gas film hole part to be detected with an objective lens 7;
(1.3) observing a CCD camera imaging interface on a computer, wherein a hole-type image is positioned in the center of the interface;
2) acquiring an image sequence of an aeroengine blade air film hole;
(2.1) scanning the gas film holes in the blades along the x-axis direction by a specified step pitch through a XYZ three-dimensional electric translation table driven by a computer, and simultaneously controlling a CCD (charge coupled device) camera to acquire images by the computer to obtain gas film hole image sequences with different focusing degrees;
(2.2) after the acquisition is finished, the XYZ three-dimensional electric translation table is placed at the starting position, and the steps (1.2), (1.3) and (2.1) are repeated to acquire an image sequence of the next air film hole;
3) performing image preprocessing, traversing all pixel points of the air film hole image sequence, calculating a focusing function evaluation function value of each pixel point of the image sequence by using a focusing evaluation function, wherein,
the image preprocessing is to perform Gaussian filtering on all images and then perform a high contrast highlighting algorithm on each image, and the adopted formula is as follows:
IN(x，y)＝I0(x，y)+r×(I0(x，y)-IB(x，y))
in the formula IN(x, y) is the processed image, I0(x, y) is a Gaussian filtered image, r is a coefficient, IB(x, y) is a fully blurred background image.
The method for calculating the focus function evaluation function value of each pixel point of the image sequence by using the focus evaluation function adopts the following formula:
in the formula, P (x, y) is a focus evaluation function value at the pixel (x, y), f (x +2, y) is a gray value at the pixel (x +2, y), and f (x, y) is a gray value at the pixel (x, y).
As shown in fig. 6, the normalized focusing function evaluation value of a certain pixel point in the pore photograph evaluated by using the focusing function after image preprocessing, and the total number of image sequences 141, it can be seen from the figure that after the image preprocessing method is used, the image has a single peak and is basically free of other noise effects.
4) Threshold value screening is carried out on the focusing evaluation function value, the different sampling points are removed, then the position of the maximum value of the focusing evaluation function of all pixel points is obtained by using a fast Gaussian fitting method, and the final three-dimensional data of the blade air film hole is obtained;
the specific process of removing the different sampling points comprises the following steps:
firstly, searching an image sequence index x corresponding to the maximum value F (x) of the focus evaluation function value of each pixel point, and normalizing the focus value F (x +1) at the x +1 position and the focus value F (x-1) at the x-1 position to obtain N1 and N2 respectively;
setting a threshold value T, if N1> T and N2> T, saving x and F (x), otherwise, making F (x) equal to (F (x +1) + F (x-1))/2, and repeating the process;
if x is 1 or x is n and n is the total number of the image sequences, finding the minimum value f (x) of the focus evaluation function value, making f (x), and repeating the above process.
As shown in fig. 7, the three-dimensional topography of the film hole structure of the aviation blade of the embodiment is obtained by performing three-dimensional reconstruction by using two methods, i.e., no threshold value screening and threshold value screening, and it can be seen from comparison that the threshold value screening can remove the different sampling points and reduce the influence of gross errors.
The specific process of obtaining the position of the maximum value of the focusing evaluation function of each pixel point by using the fast Gaussian fitting method comprises the following steps:
firstly, searching an image sequence index x corresponding to the maximum value of a focusing evaluation function value of each pixel point, and setting a fitting image index interval [ x-n, x + n ]; and then, carrying out double-Gaussian fitting on the focusing function evaluation value corresponding to each image index integer in the interval to obtain the maximum value of the focusing evaluation function.
5) Performing least square plane fitting on the three-dimensional data of the hole profile edge, extracting the hole profile from the three-dimensional data, fitting the circular arc to obtain fitting circle data, and obtaining fitting circle data from the fitting circle dataThe center and the circle radius R are three-dimensional coordinates of the center of the hole and the aperture size, and the three-dimensional data of the inner surface of the hole is calculated to obtain the roughness S of the inner surface of the holea；
The calculation yields the roughness S of the inner surface of the holeaFirstly, processing noise points by adopting a bilateral filtering algorithm, and secondly, carrying out surface roughness S in the hole by utilizing a tangent plane methodaCalculating (1);
the tangent plane method is that point cloud data of the inner wall of a hole to be measured is C1, a curved surface of the hole wall to be fitted is C2, the distance from a certain point P1 on C1 to a curved surface C2 is L1, other two points on the C1 area, which are not in the same straight line with the point P1, are selected to construct a temporary curved surface, a tangent plane SP1 of the point C1 at the point is obtained, any point P2 is found on the curved surface C2 and is used as a tangent plane SP2, the point P1 is used for leading to SP1, the point P2 is used for leading a perpendicular line to SP2, and the vertical feet P1_0 and P2_0 are obtained. According to the search step length, next iteration points P11 and P21 can be taken out from the line segment P1P1_0 and the line segment P2P2_0, the distance between the point pair is continuously reduced until the accuracy is allowed, finally a near point pair of C1 and C2 is obtained, and the distance between the two is obtained, namely the distance between the point P1 in the point set C1 and the curved surface is obtained. It is assumed here that the curved surfaces to which the curved surfaces C2 and C1 arbitrary points and their neighborhood points are fitted are all convex, where the point P1 and the convex curved surface C2 on the point cloud data C1 satisfy the following condition: the presence of a point P2 on the patch C2, such that the point P1 and the convex curve C2 are located on either side of the SP2, ensures that the closest point to the point P1 can be searched for on the patch C1. Calculating the shortest distance from all points in all C1 to the curved surface C2 as D, the contour calculation number average deviation Sa can be calculated by the following formula:
Claims (9)
1. three-dimensional detecting system of aeroengine blade air film hole geometric parameters based on zoom microtechnology, its characterized in that: the device comprises a CCD camera (1), a lens cone (9), a computer (10), an XYZ three-dimensional electric translation table (11), an object stage (13) and a blade clamp (14);
the device is characterized in that a first lens (2), a beam splitter prism (5), a third lens (6) and an objective lens (7) are sequentially arranged from near to far along the incident light path of the CCD camera (1) from one side close to the CCD camera (1), the objective table (13) is arranged behind the objective lens (7), and the blade clamp (14) is arranged on the objective table (13); the light splitting prism (5) is obliquely arranged, the coaxial light source (3) and the second lens (4) are sequentially arranged in an incident light path of the light splitting prism (5) from bottom to top, an emergent light path of the light splitting prism (5) is coaxial with the third lens (6) and the objective lens (7), the first lens (2), the light splitting prism (5), the second lens (4) and the third lens (6) are packaged in the lens barrel (9), and the objective lens (7) is connected to the lens barrel (9) and clamps the annular light source (8) at the outer side;
the lens cone (9) is installed on an XYZ three-dimensional electric translation table (11), and the CCD camera (1) and the XYZ three-dimensional electric translation table (11) are respectively connected with a computer (10) to realize linkage triggering;
blade anchor clamps (14) are including being used for fixing rotatory concave station (15) on objective table (13), offer the through-hole that is used for inserting the locking bolt on rotatory concave station (15), rotatory concave station (15) are gone up and are assembled rotatory boss (16), rotatory boss (16) can 360 degrees rotations and its symmetry is provided with first jack catch (17) and second jack catch (18) that are used for cliping the blade, offer on first jack catch (17) and second jack catch (18) and be used for inserting the locking bolt through-hole.
2. The three-dimensional detection system for geometrical parameters of an aero-engine blade film hole based on the zoom microscopy technology as claimed in claim 1, wherein: the lens cone (9) is installed on an XYZ three-dimensional electric translation table (11) through a right-angle connecting plate (12).
3. A three-dimensional detection method for the geometrical parameters of the aero-engine blade film hole based on the zoom microscopy technology and used for the detection system of claim 1 is characterized by comprising the following steps:
1) fixing the blade on an objective table (13) through a blade clamp (14), and adjusting the air film hole part of the blade to be measured to the imaging area of the CCD camera by adjusting an XYZ three-dimensional electric translation table (11) and the objective table (13);
2) controlling a CCD camera to acquire images through a computer, and acquiring an image sequence of an aeroengine blade air film hole;
3) performing image preprocessing, traversing all pixel points of the air film hole image sequence, and calculating a focusing function evaluation function value of each pixel point of the image sequence by using a focusing evaluation function;
4) threshold screening is carried out on the focusing evaluation function values, different sample points are removed, then the positions of the maximum values of the focusing evaluation functions of all pixel points are obtained by using a fast Gaussian fitting method, and final three-dimensional data of the blade air film holes are obtained;
5) performing least square plane fitting on the three-dimensional data at the edge of the hole profile, extracting the hole profile from the three-dimensional data, fitting an arc to obtain fitting circle data, obtaining the center and radius R of the fitting circle from the fitting circle data, namely the three-dimensional coordinate of the hole center and the size of the hole diameter, and calculating the three-dimensional data of the inner surface of the hole to obtain the roughness S of the inner surface of the holea。
4. The three-dimensional detection method for the geometric parameters of the film hole of the aero-engine blade based on the zoom microscopy technology as claimed in claim 3, wherein the step 2) specifically comprises the following steps:
(2.1) scanning the air film holes on the blades by a computer-driven XYZ three-dimensional electric translation table according to a specified step pitch along the x-axis direction, simultaneously controlling a CCD (charge coupled device) camera to acquire images by the computer, and obtaining air film hole image sequences with different focusing degrees by using different light intensities of a coaxial light source and a ring light source;
and (2.2) after the acquisition is finished, positioning the XYZ three-dimensional electric translation table at a starting point, and repeating the step (2.1) to acquire an image sequence of the next air film hole.
5. The three-dimensional detection method for the geometric parameters of the film hole of the aero-engine blade based on the zoom microscopy technology as claimed in claim 3, wherein the method comprises the following steps: the image preprocessing in the step 3) is to perform gaussian filtering on all images and then perform a high contrast highlighting algorithm on each image, and the formula is as follows:
IN(x，y)＝I0(x，y)+r×(I0(x，y)-IB(x，y))
in the formula IN(x, y) is the processed image, I0(x, y) is a Gaussian filtered image, r is a coefficient, IB(x, y) is a fully blurred background image.
6. The three-dimensional detection method for the geometric parameters of the film hole of the aero-engine blade based on the zoom microscopy technology as claimed in claim 3, wherein the method comprises the following steps: the step 3) of calculating the focus function evaluation function value of each pixel point of the image sequence by using the focus evaluation function adopts the following formula:
in the formula, P (x, y) is a focus evaluation function value at the pixel (x, y), f (x +2, y) is a gray value at the pixel (x +2, y), and f (x, y) is a gray value at the pixel (x, y).
7. The three-dimensional detection method for the geometric parameters of the film hole of the aero-engine blade based on the zoom microscopy technology as claimed in claim 3, wherein the method comprises the following steps: the step 4) of performing threshold screening on the focus evaluation function value comprises the following specific processes of:
firstly, searching an image sequence index x corresponding to the maximum value F (x) of the focus evaluation function value of each pixel point, and normalizing the focus value F (x +1) at the x +1 position and the focus value F (x-1) at the x-1 position to obtain N1 and N2 respectively;
secondly, setting a threshold value T, if N1 is greater than T and N2 is greater than T, storing x and F (x), otherwise, making F (x) equal to (F (x +1) + F (x-1))/2, and repeating the process; if x is 1 or x is n and n is the total number of the image sequences, finding the minimum value f (x) of the focus evaluation function values, making f (x), and repeating the process until all the focus evaluation function values are screened.
8. The three-dimensional detection method for the geometric parameters of the film hole of the aero-engine blade based on the zoom microscopy technology as claimed in claim 7, wherein the three-dimensional detection method comprises the following steps: the position of the maximum value of the focusing evaluation function of all the pixel points obtained by using the fast Gaussian fitting method in the step 4) is an image sequence index x corresponding to the maximum value F (x) of the focusing evaluation function value of each pixel point, a fitting image index interval [ x-n, x + n ] is set, double Gaussian fitting is performed on the focusing function evaluation value corresponding to each image index integer in the interval, and the maximum value of the focusing evaluation function is solved.
9. The three-dimensional detection method for the geometric parameters of the film hole of the aero-engine blade based on the zoom microscopy technology as claimed in claim 3, wherein the method comprises the following steps: the step 5) of calculating the roughness S of the inner surface of the holeaFirstly, processing noise points by adopting a bilateral filtering algorithm, and secondly, carrying out surface roughness S in the hole by utilizing a tangent plane methodaAnd (4) calculating.
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