Five-degree-of-freedom microscopic depth of field measurement device and method

Abstract

A five-degree-of-freedom (DOF) microscopic depth-of-field measurement device and method are disclosed. In the device, a five-DOF motion platform is mounted on a support, possessing three translational degrees of freedom (X, Y, Z) and two rotational degrees of freedom (B, C) (or A, C). A clamping stage for the object to be measured is fixed to the motion platform. An optical measurement system is connected to the motion platform via a brittle clamp, and the optical measurement system includes an industrial camera, a lens barrel, an objective lens, and a light source connected in sequence. This invention first automates the acquisition of the displacement of each axis of the motion platform by converting the workpiece coordinates of the microstructure to be measured to the measurement coordinates, and guides the motion platform to a designated position based on the displacement of each axis. Then, it acquires image sequences of the microstructure at equal intervals along the same direction. By extracting the focal position of each pixel in the image, it achieves three-dimensional point cloud measurement or large depth-of-field image measurement of the object to be measured, featuring high measurement efficiency and anti-collision protection.

Description

Technical Field

[0001] This invention relates to the field of microscopic optical measurement technology, and in particular to a five-degree-of-freedom microscopic depth-of-field measurement device and method. Background Technology

[0002] Microscopic depth-of-field measurement is a method that first uses an optical microscope to acquire a sequence of two-dimensional images of the object under test, and then uses the positional information and focused area in the image sequence to achieve three-dimensional measurement or two-dimensional large depth-of-field measurement of the object's surface. This method is often used in microstructural microscopy, allowing not only three-dimensional measurement of microstructures but also two-dimensional image measurement of structures with large height differences using small depth-of-field objectives. Furthermore, by selecting optical microscopes with different magnifications, measurements of microstructures of different sizes can be achieved. In the process of microscopic depth-of-field measurement, accurately acquiring image sequences of microstructures at specified locations is crucial for improving the efficiency of depth-of-field measurement of complex curved surface microstructures.

[0003] Taking the tiny film-forming holes on turbine blades as an example, since a turbine blade is a complex curved surface, it is impractical to obtain the axial position of the film-forming holes and achieve depth-of-field measurement along its axis by only using a motion platform with three or fewer degrees of freedom (X, Y, Z). For some film-forming holes that are not on the same plane, manual assistance is required to adjust the position of the turbine blade. This not only makes it difficult to obtain the optimal measurement position of the microstructure, but also makes the detection efficiency of the film-forming holes on the turbine blade extremely low. It often takes more than ten hours to complete the measurement of hundreds of tiny film-forming holes on the turbine blade, which is extremely time-consuming and cannot meet the actual measurement needs.

[0004] Currently, most common microscopic measurement devices only use motion platforms with three degrees of freedom (X, Y, and Z) as the detection platform. They can only measure microstructures with simple spatial positions. When there are many microstructures to be measured, the adjustment of the measurement position takes a long time and is inefficient, making it difficult to meet the needs of scenarios with a large number of microstructures or automated measurement.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To address the shortcomings or defects of the existing technology, a five-degree-of-freedom microscopic depth-of-field measurement device and method are provided. These methods offer high measurement efficiency, automated measurement of microstructures on complex curved surfaces, and collision protection.

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] A five-degree-of-freedom microscopic depth-of-field measurement device includes,

[0009] Measuring device support;

[0010] A five-degree-of-freedom motion platform is mounted on the support. The five-degree-of-freedom motion platform has three translational degrees of freedom (X, Y, Z) and two rotational degrees of freedom (B, C), or two rotational degrees of freedom (A, C).

[0011] The object to be tested is mounted on the five-degree-of-freedom motion platform.

[0012] An optical measurement system is connected to the five-degree-of-freedom motion platform via a brittle material clamp. The optical measurement system includes an industrial camera, a microscope tube, an objective lens, and a light source connected in sequence.

[0013] The five-degree-of-freedom microscopic depth-of-field measurement device also includes a processor connected to the optical measurement system, which obtains the three-dimensional topographic point cloud of the object under test and synthesizes a large depth-of-field image based on the two-dimensional image acquired by the optical measurement system.

[0014] In the aforementioned five-degree-of-freedom microscopic depth-of-field measurement device, the light source includes a coaxial illumination source and a ring-shaped supplementary light source with zoned brightness control.

[0015] In the aforementioned five-degree-of-freedom microscopic depth-of-field measuring device, the base of the five-degree-of-freedom motion platform is made of marble and is connected to the measuring device support via an air-bearing vibration isolation component.

[0016] In the aforementioned five-degree-of-freedom microscopic depth-of-field measuring device, the brittle material clamp is made of ceramic, glass, or a highly brittle polymer, and its fracture strength is lower than the impact resistance of the optical measuring system.

[0017] A measurement method for the aforementioned five-degree-of-freedom microscopic depth-of-field measuring device includes,

[0018] Obtain the workpiece coordinates of the object to be measured;

[0019] Establish the relationship between the workpiece coordinate system and the detection coordinate system, and solve for the displacement of each axis of the five-degree-of-freedom motion platform;

[0020] The five-DOF microscopic depth-of-field measuring device is moved to the detection position according to the solved displacement of each axis. While keeping all positions except the Z-axis unchanged, it is displaced at equal intervals along the Z-axis to acquire multiple two-dimensional images with different focal areas.

[0021] Obtain the image location with the largest focus value for each pixel in a two-dimensional image, and combine this with the relationship between the pixel size and the actual spatial size to obtain spatial location information;

[0022] The spatial location information of the pixel with the maximum focal position is converted into a point cloud to obtain the three-dimensional shape point cloud of the object under test. The gray level of the pixel with the maximum focal position is extracted onto the same image to obtain a large depth-of-field image.

[0023] In the method described above, the detection position is determined by controlling the five-degree-of-freedom motion platform to move according to the displacement, so that the microstructure under test is located at the center of the objective lens field of view and its surface normal is parallel to the optical axis.

[0024] In the method described, after Gaussian filtering each two-dimensional image, a focus evaluation function is used to calculate the focus evaluation value of each pixel, an array of focus evaluation values ​​for each pixel in the image sequence is constructed, and the image number corresponding to the maximum value is located. Based on the image number, Z-axis step size interval and pixel-spatial size mapping relationship, the spatial three-dimensional coordinates corresponding to each pixel are calculated to generate a three-dimensional point cloud of the object under test; or the gray values ​​of each pixel in the best focused image are extracted to synthesize a large depth-of-field image.

[0025] In the method described, the focusing evaluation function is any one of the Sobel operator, Tenengrad operator, Laplacian operator, or Brenner operator.

[0026] In the method described, the relationship between the workpiece coordinate system and the detection coordinate system is established, and the displacement of each axis of the five-degree-of-freedom motion platform is calculated.

[0027] Establish a homogeneous transformation matrix model that includes five-axis motion;

[0028] The system is calibrated using standard calibration parts or known feature points to obtain the initial pose parameters of the optical measurement system end relative to the motion platform;

[0029] Substitute the workpiece coordinates and calibration parameters of the object under test into the homogeneous transformation matrix model, and solve the target displacement of each axis analytically through inverse kinematics.

[0030] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention combines depth-of-field measurement with a five-degree-of-freedom motion platform, and can transform the workpiece coordinates of the microstructure under test into measurement coordinates through coordinate transformation, enabling automated measurement of microstructures on complex curved surfaces; furthermore, it can stitch microstructures at different positions into the same point cloud based on the measurement coordinates, achieving a larger measurement range; compared with existing microscopic measurement schemes, it can greatly improve the efficiency and measurement range of microscopic measurement; this invention can achieve three-dimensional point cloud measurement or two-dimensional large depth-of-field measurement of microstructures according to the measurement content, meeting the measurement needs in different scenarios; this invention uses a fixture made of brittle material as the connecting part between the five-degree-of-freedom motion platform and the optical measurement system, which will brittlely break when the optical measurement system collides with the object under test or the machine tool itself, thus protecting the optical measurement system; this invention uses a coaxial light source and a ring light source with segmented supplementary lighting as the illumination scheme, allowing for different lighting combinations of the light source under different measurement conditions to meet the current measurement lighting requirements. This invention features high measurement efficiency, automated measurement of microstructures on complex curved surfaces, and collision protection.

[0031] The description provided is merely an overview of the technical solution of this invention. In order to make the technical means of this invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and to make the described and other objects, features and advantages of this invention more obvious and understandable, specific embodiments of this invention are described below. Attached Figure Description

[0032] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0033] In the attached diagram:

[0034] Figure 1 This is a schematic diagram of the structure of the present invention;

[0035] Figure 2 A schematic diagram of a specific image from an image sequence of images of film pores on a turbine blade;

[0036] Figure 3 This is a schematic diagram of the three-dimensional point cloud of the turbine blade film pores measured by the present invention;

[0037] Figure 4This is a schematic diagram of the large depth-of-field turbine blade film pore image obtained by the present invention;

[0038] The labels in the attached diagram are: 1-measuring device support, 2-five-degree-of-freedom motion platform, 3-object clamping stage, 4-objective lens, 5-industrial camera, 6-light source, 7-microscope tube, 8-brittle material clamp, 9-air-floating vibration isolation component.

[0039] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0040] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0041] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0042] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0043] To better understand, such as Figures 1 to 4 As shown, a five-degree-of-freedom microscopic depth-of-field measurement device includes,

[0044] Measuring device bracket 1;

[0045] The five-degree-of-freedom motion platform 2 is mounted on the bracket. The five-degree-of-freedom motion platform 2 has three translational degrees of freedom (X, Y, Z) and two rotational degrees of freedom (B, C), or two rotational degrees of freedom (A, C).

[0046] The object to be tested is mounted on the five-degree-of-freedom motion platform 2.

[0047] An optical measurement system is connected to the five-degree-of-freedom motion platform 2 via a brittle material clamp 8. The optical measurement system includes an industrial camera 5, a microscope tube 7, an objective lens 4, and a light source 6 connected in sequence.

[0048] In a preferred embodiment of the five-degree-of-freedom microscopic depth-of-field measurement device, a processor connected to the optical measurement system is further included, which obtains the three-dimensional topographic point cloud of the object under test and synthesizes a large depth-of-field image based on the two-dimensional image acquired by the optical measurement system.

[0049] In a preferred embodiment of the five-degree-of-freedom microscopic depth-of-field measurement device, the light source 6 includes a coaxial illumination source and a ring-shaped supplementary light source with zoned brightness control.

[0050] In a preferred embodiment of the five-degree-of-freedom microscopic depth-of-field measuring device, the base of the five-degree-of-freedom motion platform 2 is made of marble and is connected to the measuring device support 1 via an air-bearing vibration isolation component 9.

[0051] In a preferred embodiment of the five-degree-of-freedom microscopic depth-of-field measurement device, the brittle material clamp 8 is made of ceramic, glass, or a highly brittle polymer, and its fracture strength is lower than the impact resistance of the optical measurement system.

[0052] Taking the measurement of film pores on a certain type of turbine blade as an example, a measurement method for a five-degree-of-freedom microscopic depth-of-field measuring device includes:

[0053] Obtain the workpiece coordinates of the film cooling holes in the turbine blade to be tested;

[0054] Establish the relationship between the workpiece coordinate system and the detection coordinate system, and solve for the displacement of each axis of the five-degree-of-freedom motion platform;

[0055] The five-degree-of-freedom microscopic depth-of-field measuring device is moved to the detection position according to the solved displacement of each axis. While keeping all positions except the Z-axis unchanged, it is displaced at equal intervals along the Z-axis to acquire multiple two-dimensional images of the turbine blade film pores with different focusing areas.

[0056] The focus evaluation value of all pixels in each image is calculated by the focus evaluation operator. Then, the image position with the largest focus value of each pixel is obtained. After calibration by the calibration board, the conversion relationship between pixel size and actual size is determined. Finally, the spatial position information is obtained by combining the relationship between the pixel size and the actual spatial size of the pixel.

[0057] The spatial location information of the pixel at the maximum focal position is converted into a point cloud to obtain the three-dimensional topographic point cloud of the air film vent of the turbine blade. The grayscale of the pixel at the maximum focal position is extracted onto the same image to obtain a large depth-of-field image of the air film vent of the turbine blade.

[0058] In a preferred embodiment of the method, the detection position is to control the five-degree-of-freedom motion platform to move according to the displacement, so that the air film hole of the turbine blade under test is located at the center of the objective lens field of view and the normal of its hole surface is parallel to the optical axis.

[0059] In a preferred embodiment of the method, after Gaussian filtering each two-dimensional image, a focus evaluation function is used to calculate the focus evaluation value of each pixel, an array of focus evaluation values ​​for each pixel in the image sequence is constructed, and the image number corresponding to the maximum value is located. Based on the image number, Z-axis step size spacing and pixel-spatial size mapping relationship, the spatial three-dimensional coordinates corresponding to each pixel are calculated to generate a three-dimensional point cloud of the film vent of the turbine blade under test; or the gray values ​​of each pixel in the best focused image are extracted to synthesize a large depth-of-field image of the film vent of the turbine blade.

[0060] In a preferred embodiment of the method, the focusing evaluation function is any one of the Sobel operator, Tenengrad operator, Laplacian operator, or Brenner operator.

[0061] In a preferred embodiment of the method, the relationship between the workpiece coordinates of the turbine blade film-forming hole and the detection coordinate system is established, and the displacements of each axis of the five-degree-of-freedom motion platform are solved, including...

[0062] Establish a homogeneous transformation matrix model that includes five-axis motion;

[0063] The system is calibrated using standard calibration parts or known feature points to obtain the initial pose parameters of the optical measurement system end relative to the motion platform;

[0064] Substitute the workpiece coordinates and calibration parameters of the film gas hole of the turbine blade under test into the homogeneous transformation matrix model, and solve the target displacement of each axis analytically through inverse kinematics.

[0065] In one embodiment of turbine blade film venting measurement, when acquiring a sequence of two-dimensional turbine blade film venting images at equal intervals, the spacing information between the two images and the sequence number of each image are recorded. Based on the image sequence number of the current pixel, the spacing when the images were acquired, and the correspondence between the pixel size and the actual size, the spatial information at the maximum focal position of each pixel is obtained. The spatial information at the maximum position of each pixel is converted into point cloud information to obtain the three-dimensional morphology of the film venting. Alternatively, the grayscale of each pixel is obtained based on the image sequence number and pixel coordinates at the maximum focal position, and then the grayscale is extracted into an image according to the pixel coordinates to achieve the acquisition of a large depth-of-field image of the turbine blade film venting.

[0066] The coordinates of the workpiece are obtained by the measuring device through coordinate transformation, specifically including the following steps:

[0067] 2.1 Establish the transformation relationship between the workpiece coordinates and the detection coordinates of the turbine blade film-forming holes;

[0068] 2.2 Solve the transformation relationship between the workpiece coordinates and the detection coordinates of the turbine blade film-forming holes;

[0069] 2.3 Obtaining Unknown Parameters Through Calibration ,in It is the position of the focal point of the optical system in the world coordinate system. It refers to the orientation of the optical system's axis in the world coordinate system;

[0070] 2.4 Substitute the calibration data into the equations obtained in 2.2 and solve them again to obtain the displacement of each axis of the five-degree-of-freedom motion platform.

[0071] The image location with the highest focus value for each pixel is obtained through a focus evaluation function and a peak localization function, specifically including the following steps:

[0072] 5.1 Gaussian filtering is applied to each image in the turbine blade film pore image sequence to reduce the impact of noise on the subsequent focusing evaluation process;

[0073] 5.2 Focus evaluation is performed on each pixel I(x,y) of each image in the filtered turbine blade film pore image sequence to obtain the focus evaluation value f(x,y);

[0074] 5.3 Obtain an array of focus evaluation values ​​for each pixel I(x,y) across the entire image sequence. ;

[0075] 5.4 Obtaining the Array Maximum Focus Evaluation Value The corresponding image number m;

[0076] 5.5 Multiply the pixel position (x, y) by the correspondence between pixel size and spatial size. This allows us to obtain the planar position information (X, Y) of a pixel. Multiplying the pixel's image index m by the image spacing yields the pixel's height position information. By combining these three pieces of information, we can obtain the spatial information (X, Y, Z) of a pixel.

[0077] The obtained three-dimensional point cloud of the turbine blade film pores is stitched together into a larger point cloud using the measurement coordinates obtained during microstructure measurement, thus achieving large-scale measurement under a small field of view.

[0078] In one embodiment, a five-degree-of-freedom microscopic depth-of-field measuring device is configured as follows: Figure 1As shown, it includes a measuring device support 1, a five-degree-of-freedom motion platform 2, an optical measuring system and a clamping stage for the object to be measured 3 connected to the five-degree-of-freedom motion platform 2, and the optical measuring system and the five-degree-of-freedom motion platform are connected by a clamping fixture made of a specific brittle material 8.

[0079] The five-degree-of-freedom motion platform 2 has three basic degrees of freedom, X, Y, and Z, plus B and C degrees of freedom or A and C degrees of freedom. It can be manually moved or perform high-precision electric motion according to command coordinates in all five degrees of freedom.

[0080] An air-bearing vibration isolation assembly 9 connects the marble base and support frame of the five-degree-of-freedom motion platform. The optical measurement system includes an industrial camera 5, a microscope tube 7, an objective lens 4, and a light source 6 connected in sequence. The light source 6 is a coaxial light and a ring light that can provide supplementary lighting for different areas. The objective lens 4 can be selected with a magnification range of 1×-200×. The coaxial light and the objective lens are fixed to each other through a coaxial optical path with the microscope tube to achieve coaxial illumination. The ring light is coaxially fixed with the objective lens 4 and can provide supplementary lighting for different areas within the ring range as needed, and the light intensity can be adjusted.

[0081] The specific clamp 8 connecting the optical measurement system and the five-degree-of-freedom motion platform is a connector made of a brittle material, which is a material that is prone to fracture when subjected to force.

[0082] The measurement method of the five-degree-of-freedom microscopic depth-of-field measuring device includes the following steps:

[0083] Obtain the workpiece coordinates of the film cooling holes in the turbine blade to be tested;

[0084] Establish the relationship between the workpiece coordinates and the detection coordinate system of the turbine blade film hole, and solve for the displacement of each axis of the five-degree-of-freedom motion platform;

[0085] The five-degree-of-freedom microscopic depth-of-field measuring device is moved to the detection position according to the solved displacement of each axis;

[0086] Keeping all positions except the Z-axis unchanged, perform equidistant displacement along the Z-axis to acquire multiple images of the turbine blade film pores with different focusing areas, such as... Figure 2 As shown;

[0087] The image location with the largest focus value for each pixel in the turbine blade film vent image is obtained, and spatial location information is obtained by combining the relationship between the pixel size and the actual spatial size of that pixel.

[0088] By converting the spatial location information of the pixel's maximum focal point into a point cloud, the three-dimensional topographic point cloud of the turbine blade's film cooling vents can be obtained, such as... Figure 3As shown; by extracting the grayscale values ​​at the maximum focal point of each pixel and applying them to the same image, a large depth-of-field image of the turbine blade's film vents can be obtained, such as... Figure 4 As shown.

[0089] In measurement step 4, when acquiring the turbine blade film vent image sequence at equal intervals, the spacing information between two images and the sequence number information of each image are recorded. In step 5, the spatial information of the maximum focal position of each pixel is obtained based on the image sequence number of the current pixel, the spacing when the images were acquired, and the correspondence between the pixel size and the actual size. In step 6, the spatial information of the maximum position of each pixel is converted into point cloud information to obtain the three-dimensional morphology of the turbine blade film vent, or the gray level of each pixel is obtained based on the image sequence number and pixel coordinates of the maximum focal position, and then the gray level is extracted into an image according to the pixel coordinates to achieve the acquisition of a large depth-of-field image of the turbine blade film vent.

[0090] Step 2 establishes the relationship between the workpiece coordinate system and the detection coordinate system, and solves for the displacement of each axis of the five-degree-of-freedom motion platform. This specifically includes the following steps:

[0091] 2.1 Establish the transformation relationship between workpiece coordinates and inspection coordinates;

[0092] The workpiece coordinate system of the turbine blade film-forming hole will transform with the movement of the five-degree-of-freedom motion platform along the X, Y, B, and C axes, while the detection coordinate system will transform with the movement of the Z axis. Let... , , , , These represent the motion quantities along the X, Y, Z, B, and C axes of a five-degree-of-freedom motion platform, respectively. This represents the transformation matrix of the workpiece coordinate system relative to the world coordinate system as the five-degree-of-freedom motion platform moves. This represents the transformation matrix of the detection coordinate system relative to the world coordinate system as it moves with the five-DOF motion platform. Assume that the workpiece coordinate system coincides with the world coordinate system in the initial state, and the coordinates of the origin of the detection coordinate system relative to the world coordinate system are... ,but:

[0093]

[0094]

[0095] Let the machining point be in the workpiece coordinate system. The processing direction is The end of the detection system points to Then the following equation holds:

[0096]

[0097] 2.2 By solving for the transformation relationship between workpiece coordinates and inspection coordinates, we can obtain:

[0098]

[0099] 2.3 Obtaining Unknown Parameters Through Calibration ;

[0100] 2.4 Substitute the calibration data into equation 2.2 and solve for the displacements of each axis of the five-degree-of-freedom motion platform:

[0101]

[0102] In step 5, the image position with the largest focus value for each pixel is obtained through a focus evaluation function and a peak localization function, specifically including the following steps:

[0103] 5.1 Perform Gaussian filtering on each image in the turbine blade film pore image sequence, that is, apply Gaussian filter kernel g to each pixel value of the image. Convolution is performed to reduce the impact of noise on the subsequent focusing evaluation process;

[0104] Taking a 3×3 Gaussian filter kernel as an example:

[0105]

[0106] The filtered pixel value is I(x,y):

[0107]

[0108] 5.2 Focus evaluation is performed on each pixel I(x,y) of each image in the filtered turbine blade film vent image sequence to obtain the focus evaluation value f(x,y). There are many methods for focus evaluation. Taking the Sobel focus evaluation operator as an example, when using the Sobel operator, it is necessary to first differentiate the pixel I(x,y) in both the x and y directions, that is, to convolve the pixel I(x,y) with the kernels in the horizontal and vertical directions respectively. The results are denoted as f(x,y) and f(x,y) respectively. , :

[0109]

[0110]

[0111] The image pixel focus evaluation value f(x,y) can be used , Find:

[0112]

[0113] 5.3 Obtain an array of focus evaluation values ​​for each pixel I(x,y) across the entire image sequence. ;

[0114] 5.4 Obtaining the Array Maximum Focus Evaluation Value The corresponding image number m:

[0115]

[0116]

[0117] 5.5 Multiply the pixel position (x, y) by the correspondence between pixel size and spatial size. This allows us to obtain the planar position information (X, Y) of a pixel. Multiplying the pixel's image index m by the image spacing yields the pixel's height position information. By combining these three pieces of information, we can obtain the spatial information (X, Y, Z) of a pixel, that is:

[0118]

[0119]

[0120]

[0121] The three-dimensional point cloud of the turbine blade film vents obtained in step 6 can be stitched together into a larger point cloud by using the measurement coordinates during the measurement of the turbine blade film vents, after transforming the point clouds at different measurement positions according to the measurement position coordinates, thus achieving large-scale measurement under a small field of view.

[0122] The working principle of this invention is as follows: First, the workpiece coordinates of the air film aperture of the turbine blade to be measured are transformed into the measurement coordinates of a five-degree-of-freedom microscopic depth-of-field measuring device through coordinate transformation. Then, the workpiece and optical system are moved to the measurement position using a five-degree-of-freedom motion platform. After that, while keeping other axes stationary, images are acquired at equal intervals along the Z-axis at preset intervals. Then, the image sequence is focused and evaluated to obtain the spatial position corresponding to the maximum focus evaluation value of each pixel. By performing point cloud processing on the spatial position, a three-dimensional point cloud of the air film aperture of the turbine blade can be obtained, or the grayscale of the focus position can be extracted into an image to obtain a large depth-of-field image of the air film aperture of the turbine blade.

[0123] This invention not only enables depth-of-field measurement of micro-holes at arbitrary locations on objects with complex curved surfaces, but also allows for continuous depth-of-field measurement of multiple different microstructures on the same object, greatly improving the efficiency and automation of depth-of-field measurement. Furthermore, this invention can combine measurement position information during measurement to spatially stitch together the positions of multiple different microstructures on the same object, thereby expanding the applicability of depth-of-field measurement. The brittle material tooling used in this invention can achieve brittle fracture upon collision between the optical system and the workpiece, thus protecting the optical measurement system. The coaxial light and the ring light with regional supplementary lighting used in this invention can achieve brightness compensation under different ambient lighting conditions.

[0124] Furthermore, the introduction of the five-degree-of-freedom (X / Y / Z / B / C or A / C) motion platform in this invention fundamentally solves the problem of spatial attitude matching: For workpieces with free-form surfaces such as turbine blades, the normal directions of their surface microstructures (such as film pores) are arbitrarily distributed in space. Traditional platforms with only translational degrees of freedom cannot automatically align the objective lens optical axis with the microstructure axis, resulting in extremely low measurement efficiency. However, this invention, through precise control of two rotational degrees of freedom (B / C or A / C), can automatically adjust the area to be measured to the optimal imaging posture of the objective lens—that is, the surface normal of the microstructure is parallel to the optical axis, thereby ensuring that the subsequent Z-axis depth-of-field scanning is strictly performed along the local normal, significantly improving the efficiency of 3D reconstruction measurement. Secondly, the automatic pose calculation mechanism based on coordinate transformation and inverse kinematics realizes the leap from "manual trial and error" to "one-click positioning". The system pre-acquires the position and orientation of the microstructure in the workpiece coordinate system (e.g., from a CAD model or upstream 3D measurement data), combines this with the calibrated geometric parameters of the optical system's end effector relative to the motion platform, constructs a complete homogeneous transformation model, and analytically solves for the required displacement commands across the five axes. This process requires no manual intervention and can complete path planning and precise positioning of hundreds of film-forming holes within seconds, reducing the inspection time for a single blade from over ten hours to less than six hours, significantly improving the efficiency of automated measurement.

[0125] At the imaging and data processing level, Z-axis equidistant depth-of-field scanning combined with pixel-level focus evaluation algorithms constitutes the core of high-precision 3D topography reconstruction. By independently calculating focus evaluation values ​​(such as Sobel gradient, Laplacian variance, etc.) for each pixel in the image sequence and accurately locating the Z-position corresponding to its maximum response, the system can assign independent height information to each pixel, thereby generating a 3D point cloud with sub-micron resolution. Simultaneously, this mechanism naturally supports the synthesis of large depth-of-field 2D images—simply mapping the optimal focus grayscale values ​​of each pixel to a unified image plane yields a fully clear macroscopic view of microstructures, meeting the needs of various application scenarios.

[0126] Furthermore, this invention features innovative designs in terms of safety and environmental adaptability: it employs brittle material clamps to connect the optical system and the motion platform, which preferentially break in the event of an accidental collision, effectively protecting high-value precision optical components such as cameras and objectives; it is equipped with a composite illumination scheme of coaxial light and zoned ring light, which can eliminate glare from highly reflective surfaces using coaxial light, and dynamically compensate for uneven illumination caused by microstructure tilting or local occlusion by independently controlling the brightness of the four sectors of the ring light source, significantly improving image contrast and focus evaluation reliability; and the air-bearing vibration isolation component effectively isolates ground vibration and platform motion disturbances, ensuring imaging stability at the micrometer or even submicrometer scale.

[0127] Finally, the multi-field point cloud stitching capability based on measurement pose overcomes the inherent limitation of the small field of view in microscopic systems. The system simultaneously records the precise pose of the five-DOF platform during each local measurement, and uses this pose to uniformly transform each local point cloud into the global coordinate system, achieving seamless stitching and ultimately forming a large-scale, high-resolution three-dimensional topography model covering the entire complex surface. This capability makes the device suitable not only for single-point microstructure inspection but also for full-field micro-topography quality assessment of entire blades or molds.

[0128] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0129] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A five-degree-of-freedom microscopic depth-of-field measurement device, characterized in that, It includes, Measuring device support (1); A five-degree-of-freedom motion platform (2) is mounted on the support. The five-degree-of-freedom motion platform (2) has three translational degrees of freedom (X, Y, Z) and two rotational degrees of freedom (B, C), or two rotational degrees of freedom (A, C). The object to be tested is mounted on a clamping platform (3), which is fixed on the five-degree-of-freedom motion platform (2); An optical measurement system is connected to the five-degree-of-freedom motion platform (2) via a brittle material clamp (8). The optical measurement system includes an industrial camera (5), a microscope tube (7), an objective lens (4), and a light source (6) connected in sequence.

2. The five-degree-of-freedom microscopic depth-of-field measuring device as described in claim 1, characterized in that, Preferably, it also includes a processor connected to the optical measurement system, which obtains a three-dimensional topographic point cloud of the object under test and a synthetic large depth-of-field image based on the two-dimensional image acquired by the optical measurement system.

3. The five-degree-of-freedom microscopic depth-of-field measuring device as described in claim 1, characterized in that, The light source (6) includes a coaxial illumination source and a ring-shaped supplementary light source with zoned brightness control.

4. The five-degree-of-freedom microscopic depth-of-field measuring device as described in claim 1, characterized in that, The base of the five-degree-of-freedom motion platform (2) is made of marble and is connected to the measuring device bracket (1) through the air-bearing vibration isolation component (9).

5. The five-degree-of-freedom microscopic depth-of-field measuring device as described in claim 1, characterized in that, The brittle material clamp (8) is made of ceramic, glass or a highly brittle polymer, and its fracture strength is lower than the impact strength of the optical measurement system.

6. A measurement method for a five-degree-of-freedom microscopic depth-of-field measuring device as described in any one of claims 1-5, characterized in that, It includes, Obtain the workpiece coordinates of the object to be measured; Establish the relationship between the workpiece coordinate system and the detection coordinate system, and solve for the displacement of each axis of the five-degree-of-freedom motion platform; The five-DOF microscopic depth-of-field measuring device is moved to the detection position according to the solved displacement of each axis. While keeping all positions except the Z-axis unchanged, it is displaced at equal intervals along the Z-axis to acquire multiple two-dimensional images with different focal areas. Obtain the image location with the largest focus value for each pixel in a two-dimensional image, and combine this with the relationship between the pixel size and the actual spatial size to obtain spatial location information; The spatial location information of the pixel with the maximum focal position is converted into a point cloud to obtain the three-dimensional shape point cloud of the object under test. The gray level of the pixel with the maximum focal position is extracted onto the same image to obtain a large depth-of-field image.

7. The method as described in claim 6, characterized in that, The detection position is achieved by controlling the five-degree-of-freedom motion platform to move according to the displacement, so that the microstructure to be tested is located at the center of the objective lens field of view and its surface normal is parallel to the optical axis.

8. The method as described in claim 6, characterized in that, After Gaussian filtering each 2D image, a focus evaluation function is used to calculate the focus evaluation value of each pixel, constructing an array of focus evaluation values ​​for each pixel in the image sequence, and locating the image number corresponding to the maximum value. Based on the image number, Z-axis step size, and pixel-spatial size mapping relationship, the spatial 3D coordinates corresponding to each pixel are calculated to generate a 3D point cloud of the object under test; or the gray values ​​of each pixel in the best focused image are extracted to synthesize a large depth-of-field image.

9. The method as described in claim 6, characterized in that, The evaluation function is any one of the Sobel operator, Tenengrad operator, Laplacian operator, or Brenner operator.

10. The method as described in claim 6, characterized in that, Establish the relationship between the workpiece coordinate system and the inspection coordinate system, and solve for the displacements of each axis of the five-degree-of-freedom motion platform. Establish a homogeneous transformation matrix model that includes five-axis motion; The system is calibrated using standard calibration parts or known feature points to obtain the initial pose parameters of the optical measurement system end relative to the motion platform; Substitute the workpiece coordinates and calibration parameters of the object under test into the homogeneous transformation matrix model, and solve the target displacement of each axis analytically through inverse kinematics.

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