Shaft measuring method, device, medium and equipment

Abstract

The application provides a shaft part measurement method, device, medium and equipment, relates to the technical field of optical measurement, and comprises the following steps: placing a shaft part to be measured on an electric turntable; in the process that the electric turntable drives the shaft part to be measured to rotate, every time a preset rotation angle interval is reached, an image of the shaft part to be measured is collected by a camera until the electric turntable drives the shaft part to be measured to rotate by 360 degrees, then the collection is stopped, and a plurality of images of the shaft part to be measured are obtained; if the center of the rotating shaft of the electric turntable does not coincide with the image center of the image of the shaft part to be measured, the image of the shaft part to be measured is expanded and the gray information is translated according to the corresponding rotation angle, the image length, the distance of each pixel and the image length of the preset extended image of each image of the shaft part to be measured, so as to obtain the three-dimensional point cloud profile of the shaft part to be measured; and the size information of the shaft part to be measured is calculated. The application can quickly and universally realize the measurement of the three-dimensional profile and the wall thickness of a small shaft part.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical measurement, and particularly relates to a shaft part measurement method and device, medium and equipment. BACKGROUND

[0002] Small shaft parts, such as thin-walled hemispherical, cylindrical, conical shells made of glass or plastic, are widely used in aerospace, precision physics, national defense science and technology, optical engineering and other fields. For example, the hemispherical shaft part is a typical small shaft part, and the dustproof cover of some sensors. Since the key dimensions of the small shaft part often affect the precise constraint of the pose of other devices and the modulation effect on the light field, the detection of the three-dimensional profile and thickness of the small shaft part becomes the best basis for evaluating the application effect. In addition, the processing process of such devices, such as injection molding and blow molding process, has high uncertainty, so the shape consistency of the devices produced in batches is poor, and the devices also need to be quickly detected in shape to screen out defective products.

[0003] Small shaft parts usually have the characteristics of high transmittance, complex shape and small wall thickness. Optical detection technology is the most common high-precision non-destructive detection technology at present, and optical detection technology generally belongs to a reflective measurement method, that is, the information contained in the reflected light of the shaft part to be measured is needed. However, high transmittance makes it difficult to measure with optical detection technology, because most of the incident light is refracted rather than reflected into the sensor. At present, the optical three-dimensional profile measurement of transparent devices is mainly achieved by enhancing the reflection process, such as covering the surface with a Lambertian reflective coating to improve the reflectivity, such as talcum powder or matte paint, or immersing the measured device in a liquid, but it is easy to damage the surface and the process is complicated. Another solution is to collect data at multiple angles on the measured shaft part and reconstruct the parts that can reflect at each angle and achieve three-dimensional reconstruction by splicing. For example, some studies use motion weaving to identify and calculate the three-dimensional profile of transparent objects. This method takes multiple photos of the object by moving the camera, and then manually or by deep learning marks the feature points for calculation. Due to the blindness of this method, it will reduce the accuracy and increase the time consumption. In addition, the reflectivity is enhanced by using ultraviolet light source. Some scholars have proposed using the fluorescence generated on the surface of the object under ultraviolet laser irradiation to measure transparent devices. The line structured light form combined with ultraviolet multispectral and optical triangulation method can measure the three-dimensional profile of the high-transmittance outer surface, but it cannot measure the inner profile and wall thickness. Some studies use transmission method, which irradiates the device from the back and takes a photo of the projected profile from the other side, which can reconstruct the two-dimensional profile. However, the projection of the profile will cause aliasing and affect the measurement, and this method cannot measure the three-dimensional profile. Spectral confocal measurement technology can measure the wall thickness of transparent devices, but it is limited by the range and angle characteristics, and often needs to measure the surface along the local direction vector with multiple degrees of freedom, which is complex and requires local direction vector as a prerequisite for path planning. In the transmission type optical detection technology, the Computed Tomography (CT) measurement method based on X-ray can measure the profile and wall thickness of transparent devices, but the resolution is relatively low and has radioactivity, which limits the popularity of this method. In summary of the above analysis, there is currently a lack of a fast and universal method that can measure the three-dimensional profile and wall thickness of small shaft parts. SUMMARY

[0004] In view of the above technical problems, the present application provides a shaft part measurement method, device, medium and equipment, which at least partially solves the problems existing in the prior art.

[0005] In the first aspect of the present application, a shaft part measurement method is provided, applied to a shaft part measurement system, the shaft part measurement system comprising a visible light source, a motorized turntable and a camera; the method comprising:

[0006] placing the shaft to be measured on the motorized turntable; wherein the placement position of the shaft to be measured on the motorized turntable is such that the shaft to be measured does not exceed the field of view of the camera during rotation;

[0007] During the rotation of the shaft to be measured driven by the motorized turntable, an image of the shaft to be measured is collected by the camera every time a preset rotation angle interval is reached, until the shaft to be measured is rotated 360 degrees by the motorized turntable, and then the rotation is stopped, so as to obtain a plurality of images of the shaft to be measured; wherein the visible light source continuously irradiates the shaft to be measured during the rotation of the shaft to be measured driven by the motorized turntable;

[0008] If the center of the rotation shaft of the motorized turntable does not coincide with the image center of the image of the shaft to be measured, the image of the shaft to be measured is expanded and the gray scale information is translated according to the corresponding rotation angle, the image length, the distance of each pixel and the image length of the preset expanded image of each image of the shaft to be measured, so as to obtain the three-dimensional point cloud profile of the shaft to be measured; wherein the distance of each pixel is obtained according to the eccentric distance and the rotation angle;

[0009] The size information of the shaft to be measured is calculated according to the three-dimensional point cloud profile.

[0010] In the second aspect of the present application, a shaft measuring device is provided, which is applied to a shaft measuring system, and the shaft measuring system comprises a visible light source, a motorized turntable and a camera; the device comprises:

[0011] a placing unit, configured to place the shaft to be measured on the motorized turntable; wherein the placement position of the shaft to be measured on the motorized turntable is such that the shaft to be measured does not exceed the field of view of the camera during rotation;

[0012] an image acquisition unit, configured to collect an image of the shaft to be measured by the camera every time a preset rotation angle interval is reached during the rotation of the shaft to be measured driven by the motorized turntable, until the shaft to be measured is rotated 360 degrees by the motorized turntable, and then the rotation is stopped, so as to obtain a plurality of images of the shaft to be measured; wherein the visible light source continuously irradiates the shaft to be measured during the rotation of the shaft to be measured driven by the motorized turntable;

[0013] a point cloud acquisition unit, configured to expand the image of the shaft to be measured and translate the gray scale information according to the corresponding rotation angle, the image length, the distance of each pixel and the image length of the preset expanded image of each image of the shaft to be measured, if the center of the rotation shaft of the motorized turntable does not coincide with the image center of the image of the shaft to be measured, so as to obtain the three-dimensional point cloud profile of the shaft to be measured; wherein the distance of each pixel is obtained according to the eccentric distance and the rotation angle;

[0014] a size acquisition unit, configured to calculate the size information of the shaft to be measured according to the three-dimensional point cloud profile.

[0015] In a third aspect of the present application, a non-transitory computer readable storage medium is provided, the storage medium storing at least one instruction or at least one program, the at least one instruction or at least one program being loaded and executed by a processor to implement the aforementioned shaft part measurement method.

[0016] In a fourth aspect of the present application, an electronic device is provided, comprising a processor and the aforementioned non-transitory computer readable storage medium.

[0017] The present application has at least the following beneficial effects:

[0018] The shaft part measurement method provided by the present application places the shaft part to be measured on the motorized turntable and ensures that the shaft part does not exceed the field of view of the camera during rotation, ensuring that the camera can completely collect images; subsequently, under the condition that the motorized turntable drives the workpiece to rotate and visible light continuously irradiates, images are collected at preset angle intervals, providing a multi-view data basis for subsequent three-dimensional reconstruction; when there is a deviation between the center of the motorized turntable shaft and the center of the image, the image is expanded and the gray scale information is translated to correct the turntable error by means of the image expansion algorithm, without the need to adjust the position of the camera, the deviation between the center of the image obtained by the camera and the center of the motorized turntable shaft caused by the deviation of the camera position can be solved, and then a three-dimensional point cloud profile is obtained according to the corrected image, so that the obtained three-dimensional point cloud profile is more accurate; finally, the size information is calculated based on the three-dimensional point cloud profile, without the need to enhance the reflection by covering a reflective coating, immersing in a liquid or other methods that may damage the workpiece or are cumbersome as in the traditional method, and also avoiding the defects of low precision and limited applicability of methods such as multi-angle data acquisition splicing or relying on a specific light source (such as an ultraviolet light source), so that the measurement of the three-dimensional profile and wall thickness of small shaft parts can be quickly and universally realized, effectively meeting the needs of rapid detection and screening of such devices with high transmittance, complex shape, small wall thickness and poor processing consistency. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any inventive labor.

[0020] Figure 1 The flowchart of the shaft part measurement method provided by the embodiments of the present application is shown in Figure 1.

[0021] Figure 2 The structure diagram of the shaft part measurement system is shown in Figure 2.

[0022] Figure 3 The simulation effect diagram of inverse Radon transform reconstruction is shown in Figure 3; wherein, Figure 3 (a) is the original image before Radon transform; and Figure 3(b) is the gray information graph after Radon transform; Figure 3 (c) is the reconstructed image after inverse Radon transform;

[0023] Figure 4 is the algorithm principle diagram of image expansion method;

[0024] Figure 5 is the non-transparent sphere three-dimensional reconstruction process diagram based on filtered back-projection method; wherein, Figure 5 (a) is the simulation standard sphere contour graph; Figure 5 (b) is the back-projection effect graph at single height; Figure 5 (c) is the three-dimensional contour reconstruction result graph;

[0025] Figure 6 is the non-transparent sphere three-dimensional reconstruction graph when the axis is misaligned; wherein, Figure 6 (a) is the rotation axis misalignment error graph; Figure 6 (b) is the simulation standard sphere contour graph; Figure 6 (c) is the back-projection effect graph at single height; Figure 6 (d) is the three-dimensional contour reconstruction result graph;

[0026] Figure 7 is the non-transparent standard sphere measurement result graph; wherein, Figure 7 (a) is the measured standard sphere; Figure 7 (b) is the collected contour image; Figure 7 (c) is the back-projection effect at single height; Figure 7 (d) is the three-dimensional contour reconstruction result;

[0027] Figure 8 is the transparent sphere shell measurement result; Figure 8 (a) is the measured sphere shell; Figure 8 (b) is the collected contour image; Figure 8 (c) is the back-projection effect at single height; Figure 8 (d) is the three-dimensional contour reconstruction result;

[0028] Figure 9 is the structural block diagram of the shaft part measuring device provided by the embodiment of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application and the above-described accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular sequential or chronological order. It should be understood that the data thus used can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, device, product, or server including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0031] It should be noted that various aspects of the embodiments described below are within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms and that any specific structure and / or function described herein is merely illustrative. Based on the teachings provided herein one skilled in the art should appreciate that an aspect described herein can be implemented independently of any other aspects and that an aspect can be implemented both as any number of software and / or hardware configurations and that the aspects can be implemented at least in part as any number of virtual components. For example, one or more aspects can be implemented at least in part as a machine, computer, computer-implemented or computer-executable instructions, a computer- implemented or computer-executable component, or a computer-readable medium.

[0032] Reference is made to Figure 1 and Figure 2 Embodiments of the present application provide a shaft part measurement method, applied to a shaft part measurement system, as shown in Figure 2 The shaft part measurement system includes a visible light source, a motorized turntable, and a camera. The motorized turntable is used to place and drive the measured component (i.e. the shaft part to be measured) to rotate. Above the rotating table, there is a real light source to provide illumination for measurement. In front of the rotating table, a real camera is arranged to capture images of the measured component. In addition, on the left and right sides of the system, there are virtual cameras and virtual light sources, which may be used to simulate or assist the measurement process, cooperating with the real camera and light source from different angles to achieve more comprehensive and accurate measurement of the measured component.

[0033] The method includes:

[0034] S100, placing the shaft part to be measured on the motorized turntable; wherein the placement position of the shaft part to be measured on the motorized turntable is such that the shaft part to be measured does not exceed the field of view of the camera during rotation.

[0035] Specifically, the to-be-measured shaft part has the characteristics of high transmittance, complex shape, and small wall thickness, such as a glass or plastic thin-walled hemisphere, cylinder, cone, or other shell.

[0036] The industrial camera is calibrated by a chessboard, and the positioning accuracy of the turntable is calibrated by an interferometer. According to the analysis of the solution and the error, the to-be-measured part does not need to be placed in the center of the electric turntable in principle, and only needs to ensure that it does not deviate from the field of view of the camera during rotation.

[0037] S200, during the rotation of the to-be-measured shaft part driven by the electric turntable, an image of the to-be-measured shaft part is collected according to the camera every preset rotation angle interval, until the to-be-measured shaft part is rotated by 360 degrees driven by the electric turntable, and then stopped, to obtain a plurality of to-be-measured shaft part images; wherein the visible light source continuously irradiates the to-be-measured shaft part during the rotation of the to-be-measured shaft part driven by the electric turntable.

[0038] Specifically, as an example: the preset rotation angle interval can be 2°, then after the electric turntable drives the to-be-measured shaft part to rotate 360 degrees, 180 photos with a resolution of 1024x1280 are obtained.

[0039] The transmission gray scale information of the light emitted by the visible light source after passing through the to-be-measured shaft part will be collected by the camera. The rotation of the to-be-measured shaft part controlled by the turntable can be regarded as the continuous rotation of the camera and the light source relative to the to-be-measured shaft part, thereby realizing the image collection of the to-be-measured shaft part at different angles. The transparent thin-walled material will absorb and reflect the transmitted light, making the gray scale of the transmitted light darker. Without considering the refraction angle, this process is similar to the Radon transform process. In addition to the to-be-measured shaft part (small shaft part), the system can also measure the outer contour of some non-transparent devices.

[0040] The essence of the Radon transform process is to superimpose the elements of the matrix along each angle. The Radon transform of the image is the projection sum of the pixel gray scale values. With the decrease of the angle interval, the Radon transform result can contain more numerical and positional information of the matrix elements.

[0041] As shown in formula (1), the projection intensity information of Radon transform at angle a is R(S, a), which can be represented as matrix element f(x, y) and impulse function In real space R 2 The double integral of x and y is shown in formula (3), where s is the serial number of the intensity array; the impulse function Only when formula (2) is satisfied, the impulse function is 1, otherwise it is 0, which represents that R(S, a) is only summed along a single line. Formulas (1) and (2) are as follows:

[0042] (1)

[0043] (2)

[0044] Here, f(x, y) is the profile information of the axis class part to be measured in a certain cross section XOY along the z direction, where x and y are the horizontal and vertical indices of the matrix, which correspond to the actual x and y coordinate positions in the measurement coordinate system.

[0045] And the inverse Radon transform is obtained by doing two-dimensional inverse Fourier transform on R(S, a), and the derivation process is as follows:

[0046] As shown in formula (3), the Fourier transform of R(S, a) is done with respect to s, and because the impact function is only valid on the straight line , so after substituting this constraint, the expression on the right side of the formula is obtained.

[0047] (3)

[0048] Let k x =kcosα, k y =ksinα, formula (4) can be obtained, which is exactly the two-dimensional Fourier transform of f(x, y). Therefore, the Radon transform in the frequency domain is essentially the two-dimensional Fourier transform of f(x, y) along each angle, and then the inverse Radon transform result R(S, a) is obtained by performing two-dimensional inverse Fourier transform along and summing in the frequency domain.

[0049] (4)

[0050] Directly using the inverse Fourier transform method to realize the inverse Radon transform requires performing a Fourier transform and a two-dimensional inverse Fourier transform in sequence, which is time-consuming but has high precision. In practice, direct back projection method and filtered back projection method are usually used. The direct back projection method is to add the same R(S, a) to each element along the projection line direction, which is fast but has the lowest precision and is prone to produce some additional noise. The filtered back projection method adds a filtering step based on the direct back projection method to filter out some low frequencies, which can make the edges more sharpened. Since the filtered back projection method has high efficiency and high signal-to-noise ratio.

[0051] Through simulation, Radon transform and inverse Radon transform are reproduced, and a square image (see Figure 3 (a)) is simulated to pass through the reconstruction process of Radon transform and inverse Radon transform (see Figure 3 (b)). The gray scale information R(S, a) obtained after Radon transform is represented in column form, which is collectively plotted in Figure 3 (c), showing a periodic fluctuation shape similar to a sine curve. The length of the reconstructed square is the same as that of the original square.

[0052] S300, if the rotation axis center of the electric turntable does not coincide with the image center of the image of the shaft component to be tested, then the image of the shaft component to be tested is expanded and the grayscale information is translated according to the rotation angle, image length, pixel distance and the image length of the preset extended image corresponding to each image of the shaft component to be tested, so as to obtain the three-dimensional point cloud contour of the shaft component to be tested; wherein, the pixel distance is obtained according to the eccentric distance and rotation angle.

[0053] Specifically, such as Figure 4 The image expansion algorithm principle shown is as follows: if the rotation center of the motorized turntable does not coincide with the image center of the image of the shaft to be tested, this deviation is due to the fact that the straight line containing the camera's optical axis (the angle bisector of the field of view) does not pass through the rotation center of the motorized turntable, meaning there is a deviation in the camera's position. The result reflected in the image is that the rotation center of the motorized turntable does not coincide with the image center of the image of the shaft to be tested. In this case, the image of the shaft to be tested is expanded and its grayscale information is translated according to the rotation angle, image length, pixel distance, and the preset image length of the expanded image corresponding to each image of the shaft to be tested, to obtain the 3D point cloud contour of the shaft to be tested. Specifically, this includes:

[0054] S310, if the rotation center of the electric turntable does not coincide with the image center of the image of the shaft component to be tested, then obtain the eccentricity distance corresponding to each image of the shaft component to be tested; wherein, the eccentricity distance is the distance between the image center of the corresponding image of the shaft component to be tested and the rotation center of the electric turntable.

[0055] S320, based on the eccentricity distance and rotation angle corresponding to each shaft component image to be tested, the pixel distance between the image center of each shaft component image to be tested and the image center of the preset extended image is obtained; wherein, the image length of the preset extended image is greater than the image length of the shaft component image to be tested;

[0056] S330, based on the rotation angle, image length, pixel distance, and image length of the preset extended image corresponding to each shaft component image to be tested, the pixel grayscale information of each shaft component image to be tested is translated to the corresponding position of the preset extended image to obtain the shaft component extended image corresponding to each shaft component image to be tested; wherein, each shaft component extended image to be tested contains all the grayscale information of the corresponding shaft component image to be tested;

[0057] S340: Based on the extended image of the shaft component to be tested corresponding to each image of the shaft component to be tested, obtain the three-dimensional point cloud contour of the shaft component to be tested.

[0058] Here, as an example: obtain the eccentricity distance d corresponding to any image of the shaft-type component under test, which can be determined based on the motion trajectory of the component in the image. Since the trajectory is symmetrical about the turntable axis, the pixel index corresponding to the axis can be determined by taking the centroid of the projected contour of the component and calculating the rotation center, and then the eccentricity distance d corresponding to the image of the shaft-type component under test can be calculated.

[0059] The measurement area M is determined by mapping the image with the largest eccentricity at 0° or 90° of the shaft component under test onto the plane containing the shaft axis using a pinhole imaging model. First, the acquired image is expanded to a sufficient length (usually twice the length of the original image) to include all the grayscale information from the original image. For this purpose, the image center P of the shaft component under test needs to be calculated. c And the expanded image of the shaft-type component to be tested The pixel distance L between them. Let the rotation angle be θ, then the movement distance can be obtained by formula (5). When θ varies from 0° to 180°, L is positive, representing the pixel distance P in the image. c exist On the left, this bias is negative when θ is between 180° and 360°, representing P. c exist Right side.

[0060] (5)

[0061] Expand the pixel grayscale of the image Compared to the pixel grayscale of the original image The relationship is: (6)

[0062] Here, n i '=n i-Lcosθ This indicates the corresponding position of the pixel grayscale value in the image of the shaft component under test in the expanded image of the shaft component under test; n i =0 indicates the position of the black fill in the expanded image of the shaft component to be tested.

[0063] According to the above correction process, the image center of the expanded image of the shaft component under test coincides with the actual shaft center.

[0064] Therefore, this application expands the original image of each shaft component under test, ensuring that the image center of the expanded image coincides with the actual rotation center. This eliminates the need to move and reset the camera, thus achieving camera positioning correction. This saves time and resources and improves processing efficiency.

[0065] Further, obtaining the three-dimensional point cloud contour of the shaft-like component to be tested includes:

[0066] S360, each to-be-measured shaft part extended image is layered by row, and a filter back projection is independently performed on each layer to obtain projection data corresponding to each layer of each to-be-measured shaft part extended image.

[0067] S370, after the filter processing of the projection data of each layer of each to-be-measured shaft part extended image, a layer-by-layer reconstruction is performed to obtain a three-dimensional point cloud profile of the to-be-measured shaft part; wherein the pixel distance is obtained according to the eccentric distance and the rotation angle.

[0068] Here, a non-transparent sphere is rotated by 360°, and a measurement process of taking pictures at intervals of 2° obtains a total of 180 pictures with a resolution of 1024*1280. A standard sphere profile at 0° is shown in Figure 5 (a). The reconstruction process based on the inverse pull transformation is gradually solved by layering along the Z direction, and the picture row is used for layering. The solving resolution in the Z direction depends on the number of CCD row pixels of the camera. A profile of a certain layer reconstructed in the pixel coordinate system based on the filter back projection method is shown in Figure 5 (b). Since the single-direction back projection process will affect the matrix elements through each projection line, it is extremely easy to produce star-shaped false noise. This problem is particularly serious in the case of using the direct back projection method, while the filter back projection method can suppress this problem to a certain extent. For the false noise outside the sphere profile, threshold segmentation can be used to remove it well, and the removal effect increases with the increase of the angle sampling interval. In the pixel coordinate system, the three-dimensional reconstruction result of the sphere is shown in Figure 5 (c), and the spherical profile is well recovered. Since the camera focuses on the plane passing through the axis of the turntable, the mapping relationship between the pixel and the actual space distance can be calculated through the chessboard calibration.

[0069] If the center of the rotating shaft of the motorized turntable does not coincide with the image center of the to-be-measured shaft part image and no correction is performed, the back projection process needs to construct the mapping relationship between the gray information R(S, a) and the corresponding matrix elements along the projection line at an angle a. Therefore, the position error of the rotating shaft during image acquisition will directly affect the position of the projection line on the matrix, thereby causing an error in the mapping relationship. Because the turntable platform and the camera CCD can be leveled by the high-precision bubble level on the motorized turntable (the leveling accuracy is better than 0.02 mm / m), as shown in Figure 6 (a), the position error of the motorized turntable is usually only manifested as the offset distance between the turntable axis and the CCD meridian plane. Figure 6 (b)-(d) are the reconstruction results of the non-transparent sphere under the action of the error. Because the sphere profile will be misaligned when back projection is performed at the center of the picture matrix, the reconstruction result has obvious ghost point clouds.

[0070] After the correction based on the above method, simulation is performed for the correction strategy. In an embodiment, the original image size is set to 1024x1280, and the measurement area is 1024x1024. It is assumed that d is 40. A series of simulation images are generated at a sampling interval of 10°. When solving, the size of the expanded measurement area is 2048x2048. After using the correction strategy, the rectangular reconstruction effect is good except for the artifacts, and the size is consistent with the original size. In contrast, the reconstruction result without using the shaft correction shows obvious ghosting and poor contrast of the reconstructed profile.

[0071] S400, size information of the shaft to be measured is calculated according to the three-dimensional point cloud profile.

[0072] Specifically, step S400 further includes:

[0073] S410, polynomial fitting is performed on the inner and outer profiles to calculate the three-dimensional profile information of the shaft to be measured.

[0074] S420, local thickness information is obtained by extracting an arbitrary cross section for local thickness evaluation.

[0075] Specifically, step S410 can be obtained by the following steps:

[0076] From the three-dimensional point cloud data, the inner and outer boundary point sets of the shaft to be measured are separated. For the shaft, the inner and outer profiles of each layer can be extracted by projecting onto the XOY plane and performing edge detection. Data preprocessing: remove outliers (Outlier Removal), for example, use statistical filtering or radius filtering. And sort the profile points, so that they are arranged in circumferential order, which is convenient for subsequent fitting. Polynomial fitting: least squares polynomial fitting is performed on the inner and outer profile point sets of each layer. Common fitting functions are: circle fitting: suitable for ideal shafts, fitting the center coordinates (x0, y0) and radius r. Ellipse fitting: suitable for cases with slight deformation or measurement tilt. High-order polynomial: suitable for complex cross-sectional profiles. Finally, size calculation: diameter: obtained by multiplying the fitted circle radius by 2. Ovality: the difference between the major and minor axes of the ellipse. Coaxiality: the offset of the center of different layers in the axial (Z-axis) direction. Length: the range covered by the profile along the Z-axis direction.

[0077] Step S420 can be obtained by the following steps: first, select the profile position that needs to be evaluated, for example: the cross section of the axial fixed position (perpendicular to the Z axis). Oblique section of any inclination angle. In the three-dimensional point cloud, the point set of the section is intercepted. Then, the inner and outer contour point sets of the section are aligned in coordinates to ensure that the measurement results are at the same radial position. Then, the least square alignment or barycenter alignment method is realized. Finally, the calculation process: for the corresponding points on the inner and outer contours, the Euclidean distance is calculated, which is the local thickness of the point. The following methods can also be used to improve accuracy: sampling in multiple angular directions, calculating the average thickness. Smooth filtering of thickness data to reduce the influence of measurement noise. Finally, the local thickness distribution curve or heat map can be generated, and the maximum / minimum thickness, thickness deviation, uniformity index, etc. can be calculated.

[0078] In an exemplary embodiment of the present application, after step S300, the method further comprises:

[0079] S500, removing noise points in the three-dimensional point cloud profile according to the KD tree nearest neighbor filtering algorithm.

[0080] Specifically, the KD tree nearest neighbor filtering algorithm is used to remove noise points in the three-dimensional point cloud profile.

[0081] In an exemplary embodiment of the present application, after step S200, the method further comprises:

[0082] S600, binarizing each image of the shaft to be measured and extracting the contour edge.

[0083] Specifically, in order to reduce the influence of ambient light, each image of the shaft to be measured is binarized and the contour edge is extracted. Then, reconstruction is performed.

[0084] The method provided by the present application will be described below through specific embodiments. Embodiment 1

[0085] The industrial camera is calibrated by a chessboard, and the positioning accuracy of the turntable is calibrated by an interferometer. According to the analysis of the solution and the error, the part to be measured does not need to be placed in the center of the electric turntable in principle, only to ensure that it does not deviate from the field of view during rotation. The key hardware parameters are shown in Table 1.

[0086] Table 1 Key parameters of hardware devices

[0087] Device Key parameters Values Camera CCD resolution 1920×1440 Lens focal length 16 mm Turntable Angular positioning accuracy 0.01° Angular interval 2° Light source Brightness 1000 cd

[0088] A non-transparent standard ball with a nominal radius of 12.703 mm as shown in Figure 7 (a) was measured, and the collected image is shown in Figure 7 (b). In order to reduce the influence of ambient light, the image is binarized and the contour is extracted. The reconstructed standard ball is as followsFigure 7 (c)-(d) show, the fitting radius is 12.7043mm, and the RMS of the surface shape deviation is 0.0235mm. Although a certain amount of noise points are generated when the inverse Radon transform is performed for 3D reconstruction, the noise is uniform, so the impact on the size fitting evaluation such as radius fitting is relatively small. Example 2

[0089] The measurement process of a hemispherical shell is shown in Figure 8 (a)-(d). Since the spherical shell is a low-precision industrial part, a large number of noise points appear in the reconstruction result. After calculation by using the 3D point cloud filtering algorithm based on the nearest neighbor constraint of KD tree, Figure 8 the internal structure features can be better reflected in the two-dimensional cross-sectional profile of (d).

[0090] Referring to Figure 9 , the embodiment of the application provides a shaft part measuring device 100, which comprises:

[0091] a placing unit 110, configured to place a shaft part to be measured on a motorized turntable; wherein the placement position of the shaft part to be measured on the motorized turntable is such that the shaft part to be measured does not exceed the field of view of the camera during rotation;

[0092] an image acquisition unit 120, configured to, during the rotation of the motorized turntable with the shaft part to be measured, acquire an image of the shaft part to be measured according to the camera at every preset rotation angle interval until the motorized turntable rotates 360 degrees with the shaft part to be measured, and then stop, so as to obtain a plurality of images of the shaft part to be measured; wherein the visible light source continuously irradiates the shaft part to be measured during the rotation of the motorized turntable with the shaft part to be measured;

[0093] a point cloud acquisition unit 130, configured to, if the center of the rotation shaft of the motorized turntable does not coincide with the image center of the image of the shaft part to be measured, perform image expansion and gray information translation on the image of the shaft part to be measured according to the rotation angle corresponding to each image of the shaft part to be measured, the image length, the pixel distance and the image length of the preset expanded image, so as to obtain a three-dimensional point cloud profile of the shaft part to be measured; wherein the pixel distance is obtained according to the eccentric distance and the rotation angle;

[0094] a size acquisition unit 140, configured to calculate the size information of the shaft part to be measured according to the three-dimensional point cloud profile.

[0095] Those skilled in the art can understand that each aspect of the application can be implemented as an apparatus, a method or a program product. Therefore, each aspect of the application can be embodied as a complete hardware embodiment, a complete software embodiment (including firmware, microcode, etc.), or an embodiment combining hardware and software aspects, which can be collectively referred to as "circuitry", "module" or "apparatus" here.

[0096] An electronic device according to this embodiment of the present application. The electronic device is merely an example and should not bring any limitation to the function and usage range of the embodiments of the present application.

[0097] The electronic device is in the form of a general purpose computing device. The components of the electronic device can include, but are not limited to, the at least one processor described above, the at least one storage described above, a bus that connects the different device components, including the storage and the processor.

[0098] The storage stores program codes that can be executed by the processor, so that the processor performs the steps described in the above "Exemplary Method" section according to various exemplary embodiments of the present application.

[0099] The storage can include a readable medium in the form of a volatile storage, such as a random access memory (RAM) and / or a cache storage, and can further include a read only memory (ROM).

[0100] The storage can further include programs / utilities having a set of (at least one) program modules that include, but are not limited to: an operating system, one or more application programs, other program modules, and program data, each of which can include implementation of a network environment, or some combination thereof.

[0101] The bus can be one or more of several types of bus structures, including, but not limited to, a storage bus or bus controller, a peripheral bus, a graphics acceleration port, a processor or a local bus using any of a variety of bus structures.

[0102] The electronic device can also communicate with one or more external devices (such as a keyboard or a pointing device, a Bluetooth device, etc.) that can allow a user to interact with the electronic device, and / or one or more devices that enable the electronic device to communicate with one or more other computing devices. Such communication can occur via an input / output (I / O) interface. Still yet, the electronic device can communicate with one or more networks (such as a local area network (LAN), a wide area network (WAN), and / or the public network, such as the Internet) through a network adapter. As depicted, the network adapter is communicatively coupled to the other components of the electronic device through a bus. It should be appreciated that although not shown, other hardware and / or software components could be used in conjunction with the electronic device. These include, but are not limited to, microcode, device drivers, redundant processing units, external disk drive arrays, RAID devices, tape drives, and data archival storage devices, etc.

[0103] Those skilled in the art can clearly understand, through the description of the above embodiments, that the example embodiments described herein can be implemented by software, or by software in combination with necessary hardware. Therefore, the technical solutions according to the embodiments of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a U disk, a mobile hard disk, etc.) or a network, and includes a plurality of instructions to enable a computing device (which can be a personal computer, a server, a terminal device, or a network device, etc.) to perform the method according to the embodiments of the present application.

[0104] In the example embodiments of the present application, a computer readable storage medium is also provided, which stores a program product capable of implementing the method described above. In some possible embodiments, various aspects of the present application can also be implemented in the form of a program product, which includes program code for causing a terminal device to perform the steps according to various example embodiments of the present application described in the "example method" section of the present specification when the program product is run on the terminal device.

[0105] The program product can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium may, for example, be but is not limited to an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor device, device or means, or any combination of the above. More specific examples (non-exhaustive list) of readable storage media include an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0106] The computer readable signal medium can include a data signal propagated in a baseband or as a part of a carrier wave, in which readable program code is borne. Such a propagated data signal can take on multiple forms, including but not limited to an electromagnetic signal, an optical signal, or any suitable combination of the above. The readable signal medium can also be any readable medium other than the readable storage medium, which can send, propagate or transmit the program for use by or in connection with an instruction execution device, device or means.

[0107] The program code contained on the readable medium can be transmitted by any suitable medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0108] The program code may be executed by one or more programmable processing devices to perform the operations described herein. The processing devices may include processors, microprocessors, microcontrollers, programmable logic devices, field programmable gate arrays (FPGAs), or other processing devices. The processing devices may be configured to execute program code stored in memory. The memory may include one or more types of memory such as volatile memory (e.g., random access memory (RAM), dynamic random access memory (DRAM), or static random access memory (SRAM)), non-volatile memory (e.g., read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory, or other non-volatile memory), or other types of memory.

[0109] In addition, the above-described flowcharts are merely illustrative of the processes included in the method according to the exemplary embodiments of the present application, and are not intended to limit the purpose. It is easily understood that the processes shown in the above-described flowcharts do not indicate or limit the time sequence of the processes. In addition, it is also easily understood that the processes can be executed synchronously or asynchronously, for example, in a plurality of modules.

[0110] It should be noted that, although several modules or units of the device for action execution are mentioned in the above detailed description, such a division is not mandatory. Indeed, according to the embodiments of the present application, the features and functionalities of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functionalities of one module or unit described above can be further divided into embodied by a plurality of modules or units.

[0111] The above merely describes specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of measuring a shaft, characterized by, The application is applied to a shaft measuring system, the shaft measuring system comprises a visible light source, a motorized turntable and a camera; the method comprises: placing a shaft to be measured on the motorized turntable; wherein the placement position of the shaft to be measured on the motorized turntable is such that the shaft to be measured does not exceed the field of view of the camera during rotation; during the rotation of the shaft to be measured driven by the motorized turntable, an image of the shaft to be measured is collected by the camera every time a preset rotation angle interval is reached, until the shaft to be measured is rotated by 360 degrees driven by the motorized turntable, and then the rotation is stopped, so as to obtain a plurality of images of the shaft to be measured; wherein the visible light source continuously irradiates the shaft to be measured during the rotation of the shaft to be measured driven by the motorized turntable; if the center of the rotation shaft of the motorized turntable and the image center of the image of the shaft to be measured do not coincide, the image of the shaft to be measured is expanded and the gray information is translated according to the rotation angle, the image length, the distance of each pixel and the image length of the preset expanded image corresponding to each image of the shaft to be measured, so as to obtain the three-dimensional point cloud profile of the shaft to be measured; wherein the distance of each pixel is obtained according to the eccentric distance and the rotation angle; the size information of the shaft to be measured is calculated according to the three-dimensional point cloud profile.

2. The shaft member measurement method according to claim 1, wherein if the center of the rotation shaft of the motorized turntable and the image center of the image of the shaft to be measured do not coincide, the image of the shaft to be measured is expanded and the gray information is translated according to the rotation angle, the image length, the distance of each pixel and the image length of the preset expanded image corresponding to each image of the shaft to be measured, so as to obtain the three-dimensional point cloud profile of the shaft to be measured, comprising: if the center of the rotation shaft of the motorized turntable and the image center of the image of the shaft to be measured do not coincide, the eccentric distance corresponding to each image of the shaft to be measured is obtained; wherein the eccentric distance is the distance between the image center of the corresponding image of the shaft to be measured and the center of the rotation shaft of the motorized turntable; the pixel distance between the image center of each image of the shaft to be measured and the image center of the preset expanded image is obtained according to the eccentric distance and the rotation angle corresponding to each image of the shaft to be measured; wherein the image length of the preset expanded image is greater than the image length of the image of the shaft to be measured; the pixel gray information of each image of the shaft to be measured is translated to the corresponding position of the corresponding preset expanded image according to the rotation angle, the image length, the distance of each pixel and the image length of the preset expanded image corresponding to each image of the shaft to be measured, so as to obtain the expanded image of the shaft to be measured corresponding to each image of the shaft to be measured; wherein each expanded image of the shaft to be measured contains all the gray information of the corresponding image of the shaft to be measured; the three-dimensional point cloud profile of the shaft to be measured is obtained according to the expanded image of the shaft to be measured corresponding to each image of the shaft to be measured.

3. The shaft member measurement method according to claim 2, wherein the image length of the preset expanded image is twice the image length of the image of the shaft to be measured.

4. The shaft member measurement method according to claim 2, wherein the three-dimensional point cloud profile of the shaft to be measured is obtained according to the expanded image of the shaft to be measured corresponding to each image of the shaft to be measured, comprising: each expanded image of the shaft to be measured is layered by row, and each layer is independently filtered back projection to obtain the projection data corresponding to each layer of each expanded image of the shaft to be measured; The projection data of each layer of each to-be-measured shaft part expanded image is filtered and reconstructed layer by layer to obtain a three-dimensional point cloud profile of the to-be-measured shaft part; wherein the pixel distance is obtained according to the eccentric distance and the rotation angle.

5. The shaft member measurement method according to claim 1, wherein If the center of the rotation shaft of the motorized turntable does not coincide with the image center of the to-be-measured shaft part image, the to-be-measured shaft part image is expanded and gray information is translated according to the corresponding rotation angle, image length, each pixel distance and the image length of the preset expanded image of each to-be-measured shaft part image to obtain a three-dimensional point cloud profile of the to-be-measured shaft part; wherein the pixel distance is obtained according to the eccentric distance and the rotation angle. The noise points in the three-dimensional point cloud profile are removed according to the KD tree nearest neighbor filtering algorithm.

6. The shaft member measurement method according to claim 1, wherein The size information of the to-be-measured shaft part is calculated according to the three-dimensional point cloud profile, including: The inner and outer profiles are polynomial fitted to calculate the three-dimensional profile information of the to-be-measured shaft part; The local thickness information is obtained by extracting any section for local thickness evaluation.

7. The shaft member measurement method according to claim 1, wherein During the rotation of the to-be-measured shaft part driven by the motorized turntable, a to-be-measured shaft part image is collected by the camera every interval of a preset rotation angle interval until the to-be-measured shaft part is rotated by 360 degrees driven by the motorized turntable, and then the rotation is stopped to obtain a plurality of to-be-measured shaft part images. Each to-be-measured shaft part image is binarized to extract the profile edge.

8. A shaft member measuring device characterized by comprising: The device is applied to a shaft part measurement system, and the shaft part measurement system comprises a visible light source, a motorized turntable and a camera. The device comprises: A placing unit is configured to place a to-be-measured shaft part on the motorized turntable; wherein the placement position of the to-be-measured shaft part on the motorized turntable is such that the to-be-measured shaft part does not exceed the field of view of the camera during the rotation process; An image acquisition unit is configured to collect a to-be-measured shaft part image by the camera every interval of a preset rotation angle interval during the rotation of the to-be-measured shaft part driven by the motorized turntable until the to-be-measured shaft part is rotated by 360 degrees driven by the motorized turntable, and then the rotation is stopped to obtain a plurality of to-be-measured shaft part images; wherein the visible light source continuously irradiates the to-be-measured shaft part during the rotation of the to-be-measured shaft part driven by the motorized turntable; A point cloud acquisition unit is configured to, if the center of the rotation shaft of the motorized turntable does not coincide with the image center of the to-be-measured shaft part image, expand and translate the gray information of the to-be-measured shaft part image according to the corresponding rotation angle, image length, each pixel distance and the image length of the preset expanded image of each to-be-measured shaft part image to obtain a three-dimensional point cloud profile of the to-be-measured shaft part; wherein the pixel distance is obtained according to the eccentric distance and the rotation angle.

9. A non-transitory computer-readable storage medium, comprising: A size acquisition unit is configured to calculate the size information of the to-be-measured shaft part according to the three-dimensional point cloud profile.

10. An electronic device, comprising: The storage medium stores at least one instruction or at least one program, which is loaded and executed by the processor to realize the method of any one of claims 1-7. The device comprises a processor and the non-transitory computer readable storage medium of claim 9. The device comprises a processor and the non-transitory computer readable storage medium of claim 9.

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