Detection method for measuring coaxiality, and system for detecting coaxiality

Abstract

The present disclosure describes a detection method for measuring coaxiality, which is a detection method for measuring coaxiality between an optical axis of a photographing module and a bearing surface of the photographing module, the coaxiality including perpendicularity of the optical axis to the bearing surface and a tilt direction of the optical axis, placing a measurement workpiece on the bearing surface, photographing the measurement workpiece by using the photographing module to obtain a photographed image of the measurement workpiece, and obtaining the coaxiality based on the photographed image. Thus, the coaxiality between the optical axis of the photographing module and the bearing surface of the photographing module can be detected. The present disclosure also describes a system for detecting coaxiality, which includes an optical component having an optical axis and a mechanical component having a bearing surface, and measures the coaxiality between the optical axis and the bearing surface by using the above detection method.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the intelligent manufacturing equipment industry, in particular to a detection method for measuring coaxiality and a system for detecting coaxiality. BACKGROUND

[0002] As a common precision instrument for measurement based on the principle of CCD imaging, the image measuring device generally includes a worktable and a measuring lens, and the worktable and the measuring lens are arranged to be perpendicular to each other. The image measuring device is used to take a picture of a to-be-measured object placed on the worktable through the measuring lens, and analyze the picture to obtain the specific size and parameters of the to-be-measured object. When the image measuring device is used to measure a measurement object with a certain height, if the extension direction of the central light line (optical axis) of the measuring lens is not perpendicular to the worktable, the picture taken by the measuring lens and the actual planar image of the to-be-measured object are prone to have a large deviation, especially when the distance between the imaging surface of the lens and the worktable is larger, the error of the taken picture will also be larger. When the taken picture has a large error, the actual size and parameters of the to-be-measured object obtained based on the analysis of the taken picture are also prone to have a large error. Therefore, it is often necessary to ensure the accuracy of the taken picture and the measurement accuracy of the image measuring device. Generally speaking, when the worktable and the lens are perpendicular to each other, the imaging lens can accurately obtain the picture.

[0003] In the prior art, a calibration table is generally arranged beside the Z-axis of the image measuring device, and the calibration table slides up and down when the guide rail of the image measuring device moves. Data is collected multiple times when the calibration table slides, and then the data is analyzed to determine the perpendicularity of the Z-axis on which the worktable and the lens move.

[0004] However, this method can only measure the mechanical perpendicularity between the worktable and the lens, and cannot measure the perpendicularity of the optical axis between the imaging optical axis of the imaging lens and the worktable (or the optical axis is inclined to which side), and thus cannot improve the accuracy of the taken picture of the imaging lens, and of course the measurement accuracy of the image measuring device will be reduced. Moreover, the operation process of this measurement method is relatively complicated, and thus the measurement efficiency is prone to be reduced. SUMMARY

[0005] The present disclosure is proposed in view of the above-mentioned prior art, and aims to provide a detection method for measuring coaxiality and a system for detecting coaxiality.

[0006] To this end, the present disclosure provides, in one aspect, a detection method for measuring coaxiality, which is a detection method for measuring coaxiality between an optical axis of a photographing module and a bearing surface of the photographing module, the coaxiality including perpendicularity of the optical axis to the bearing surface and a tilt direction of the optical axis, placing a measurement workpiece on the bearing surface, photographing the measurement workpiece using the photographing module to obtain a photographed image of the measurement workpiece, and obtaining the coaxiality based on the photographed image.

[0007] In the present disclosure, after obtaining a photographed image of a measurement workpiece by a photographing module, the coaxiality between the optical axis of the photographing module and the bearing surface can be determined based on the photographed image, and by analyzing the photographed image, the specific data of the coaxiality (e.g., the positional relationship between the optical axis and the bearing surface, and the tilt direction of the optical axis with respect to the bearing surface) can be detected. At this time, the position of the photographing module and the bearing surface can be adjusted based on the detected coaxiality to make the optical axis coaxial with the bearing surface, thereby improving the measurement accuracy of the image measurement device.

[0008] In addition, in the detection method according to the present disclosure, the measurement workpiece can be in a hollow cylindrical shape. In this case, especially in the ideal case where the optical axis of the photographing lens is coaxial with the bearing surface, the photographed image of the measurement workpiece by the photographing lens can obtain an ideal circular ring pattern, and thus the actual photographed image and the ideal circular ring pattern can be compared to determine the coaxiality between the optical axis of the photographing lens and the bearing surface.

[0009] In addition, in the detection method according to the present disclosure, a target image corresponding to the measurement workpiece can be obtained based on the photographed image, a target pattern can be obtained based on the target image, and the perpendicularity of the optical axis to the bearing surface can be obtained based on the distance between the contour of the target image and the geometric center of the target pattern.

[0010] In addition, in the detection method according to the present disclosure, the contour can include an outer contour and an inner contour, and the perpendicularity of the optical axis can be calculated based on the maximum distance between the geometric center of the target pattern and the outer contour, the minimum distance between the geometric center of the target pattern and the inner contour, and a predetermined length. Thus, the perpendicularity of the optical axis and the bearing surface can be accurately obtained.

[0011] In addition, in the detection method, a target ray is optionally drawn with the geometric center of the target pattern as an end point, a target pixel number of the target ray is obtained, the target pixel number is the number of pixel points on the target ray having a predetermined pixel value, the target ray is rotated around the geometric center of the target pattern to make the target ray have a plurality of different inclination angles, a target pixel number corresponding to each inclination angle is obtained, and an inclination direction of the optical axis is obtained based on the target pixel number corresponding to each inclination angle. In this case, the more the optical axis is inclined (or the more the stage is inclined), the more the sum of the number of target pixel numbers in the inclination direction. Thus, the inclination direction of the optical axis can be identified by observing the number of target pixels.

[0012] In addition, in the detection method, a target pixel number-inclination angle image is optionally obtained based on the target pixel number corresponding to each inclination angle, at least two peaks of the target pixel number-inclination angle image are obtained, and the inclination direction of the optical axis is obtained based on the inclination angle corresponding to the peaks. Thus, the inclination direction of the optical axis can be easily confirmed.

[0013] In addition, in the detection method, when the direction of the target ray is the same as the target direction, the inclination angle of the target ray is 0°, and the at least two peaks include a first peak with an inclination angle not greater than 90° and a second peak with an inclination angle greater than 90°. In this case, the inclination angle at which the peak of the target pixel number is obtained, and the inclination angle is processed, can reduce the error in determining the inclination direction. Thus, the detection accuracy of the inclination direction and the coaxiality can be improved.

[0014] In addition, in the detection method, the target image is obtained by performing a binaryzation process on the captured image, the pixel points of the target image are extracted and fitted to obtain the target pattern. In this case, the binaryzation process can better highlight the outline of the pattern in the captured image and reduce the calculation of irrelevant pixel points. The computational load of image analysis can be reduced.

[0015] In addition, in the detection method, the target pattern is a circle. In this case, compared with analyzing an irregular target pattern, analyzing a regular target pattern such as a circle can effectively reduce the complexity of data analysis. Thus, the detection efficiency of the detection method can be improved.

[0016] Another aspect of the present disclosure also provides a system for detecting coaxiality, comprising an optical component having an optical axis and a mechanical component having a bearing surface, and the coaxiality of the optical axis and the bearing surface is measured by the detection method of claims 1-9.

[0017] According to the present disclosure, a detection method and system for detecting the coaxiality of the optical axis of a shooting module and the bearing surface of the shooting module can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0018] The present disclosure will now be explained in further detail by way of example only with reference to the drawings wherein:

[0019] Figure 1 is a diagram showing the application scenario of the detection method related to the embodiments of the present disclosure.

[0020] Figure 2 is a flowchart showing the detection method related to the embodiments of the present disclosure.

[0021] Figure 3A is a diagram showing the shooting image of the measured workpiece when the optical axis and the bearing surface are coaxial.

[0022] Figure 3B is a diagram showing the shooting image of the measured workpiece when the optical axis and the bearing surface are not coaxial.

[0023] Figure 4 is a flowchart showing the measurement of the coaxiality related to the embodiments of the present disclosure.

[0024] Figure 5 is a diagram showing the measurement of the perpendicularity related to the embodiments of the present disclosure.

[0025] Figure 6 is a diagram showing the planar analysis of the perpendicularity related to the embodiments of the present disclosure.

[0026] Figure 7 is a diagram showing the target ray related to the embodiments of the present disclosure.

[0027] Figure 8 is a diagram showing the target pattern related to the embodiments of the present disclosure.

[0028] Figure 9 is a diagram showing the simulation of the target pixel number-tilt angle related to the embodiments of the present disclosure.

[0029] REFERENCE NUMERALS:

[0030] 1…image measurement device, 2…measured workpiece. DETAILED DESCRIPTION

[0031] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same components are given the same reference numerals, and overlapping description is omitted. In addition, the drawings are schematic diagrams, and the ratio of the sizes of the components to each other or the shape of the components, etc. can be different from the actual.

[0032] It should be noted that the terms "comprising" and "having" and any variations thereof, such as a process, method, system, product, or apparatus including or having a series of steps or units, are not necessarily limited to only those steps or units clearly listed, but can include or have other steps or units that are not clearly listed or inherent to such processes, methods, products, or apparatuses.

[0033] In addition, the subheadings and the like involved in the following description of the present disclosure are not intended to limit the content or scope of the present disclosure, but merely serve as a reading aid. Such subheadings cannot be understood as dividing the content of the article, nor should the content under the subheading be limited only within the scope of the subheading.

[0034] One aspect of the present disclosure relates to a detection method for measuring coaxiality, which can be used to measure the coaxiality between the optical axis of a photographing module and the bearing surface of the photographing module.

[0035] In some examples, the coaxiality can include the perpendicularity of the optical axis to the bearing surface and the tilt direction of the optical axis. The perpendicularity of the optical axis to the bearing surface represents the tilt angle of the optical axis deviating from the normal line of the bearing surface, and the tilt direction of the optical axis can represent the direction in which the optical axis tilts compared to the normal line of the bearing surface.

[0036] In some examples, a measurement workpiece can be placed on the bearing surface, and the measurement workpiece is photographed by using the photographing module to obtain a photographed image of the measurement workpiece, and the coaxiality is obtained based on the photographed image. In this case, when the optical axis and the bearing surface are not perpendicular, the image of the sleeve on the photographed image will produce a shadow. Thus, it can be determined whether the bearing surface and the lens are perpendicular during photographing based on the shadow condition of the photographed image. Thus, it is convenient to detect the coaxiality.

[0037] In the present disclosure, the detection method for measuring coaxiality can detect the coaxiality between the optical axis of the photographing module and the bearing surface of the photographing module. Thus, the optical axis and the bearing module can be adjusted based on the coaxiality, and the measurement accuracy of the image measuring instrument can be improved.

[0038] In the present disclosure, the detection method for measuring coaxiality is particularly suitable for detecting optical equipment with an optical image system. For example, the optical equipment can be an image measuring instrument.

[0039] In some examples, the detection method for measuring coaxiality can also be referred to as a detection method or an analysis method, and the system for detecting coaxiality can also be referred to as a detection device or a detection apparatus.

[0040] Hereinafter, the detection method related to the present disclosure will be described with reference to the image measurement device and the accompanying drawings.

[0041] Figure 1 FIG. 1 is a schematic diagram showing an application scenario of the detection method related to the embodiments of the present disclosure.

[0042] In some examples, the detection method can be used in an image measurement device 1, which can be used to detect the size of a to-be-measured object. In some examples, the image measurement device 1 can include a shooting module. In some examples, the shooting module can include a shooting lens, a light source, and a bearing platform. In some examples, the shooting lens can shoot the to-be-measured object, the light source can illuminate the to-be-measured object and the shooting lens, and the bearing platform can have a bearing surface and bear the to-be-measured object. In some examples, the bearing surface can bear the to-be-measured object, such as a measurement workpiece 2 (see FIG. 2). Figure 1

[0043] In some examples, the optical axis can represent the optical axis of the light source and the optical axis of the camera lens, and the coaxiality can represent the degree of coaxiality between the optical axis of the light source and the bearing surface. Specifically, when the light source is coaxial with the bearing surface, it can be represented that the optical axis of the light source is perpendicular to the plane where the bearing surface is located, and when the optical axis of the light source is not perpendicular to the bearing surface, the degree of coaxiality can be determined by the degree of perpendicularity between the optical axis of the light source and the bearing surface and the inclination direction between the light source and the bearing surface.

[0044] In some examples, the coaxiality can also represent the degree of coaxiality between the optical axis of the camera lens and the bearing surface. That is, the optical axis of the camera lens is perpendicular to the plane where the bearing surface is located. In this case, when the optical axis of the camera lens is perpendicular to the plane where the bearing surface is located, the direction of the optical axis of the camera lens can be perpendicular to the bearing surface, and the image captured by the camera lens is a planar image of the object on the bearing surface.

[0045] The following related description will be described taking the coaxiality between the optical axis of the camera lens and the bearing surface as an example, but it should also be deducible taking the coaxiality between the optical axis of the light source and the bearing surface as an example, and the same technical effects should be obtained. The related description of the related technical solutions should not be regarded as a specific limitation.

[0046] Figure 2 FIG. 1 is a schematic diagram showing an application scenario of the detection method related to the embodiments of the present disclosure.

[0047] ​In some examples, the flow of the detection method can include: placing the measurement workpiece 2 (S101), acquiring a photographed image of the measurement workpiece 2 (S102), and acquiring coaxiality (S103).

[0048] In some examples, in step S101, the measurement workpiece 2 can be placed on a bearing platform (i.e., a bearing surface) of the video measurement device 1. In some examples, the measurement workpiece 2 can be placed on the bearing surface manually. In other examples, the measurement workpiece 2 can also be automatically carried onto the bearing surface.

[0049] In some examples, the measurement workpiece 2 can be hollow and have a predetermined length. In some examples, the measurement workpiece 2 can be placed on the bearing surface at will, for example, the measurement workpiece 2 can be placed at any position (central region or surrounding region of the bearing surface) of the bearing surface at will. In some examples, preferably, when the measurement workpiece 2 is placed, the plane on which the bearing surface is located can be perpendicular to the length direction of the measurement workpiece 2.

[0050] In some examples, the measurement workpiece 2 can be any hollow workpiece with a predetermined height. And the cross section taken along the length direction perpendicular to the measurement workpiece 2 can be a hollow pattern. For example, it can be a circular ring, a hollow rectangle, a hollow gear shape, etc. In some examples, the contour of the outer edge of the hollow pattern can be enlarged by a certain proportion according to the contour of the inner edge. In other words, the inner and outer walls of the measurement workpiece 2 can be shapes with different sizes but the same contour.

[0051] In some examples, the measurement workpiece 2 can be a symmetrical and regular solid workpiece. In some examples, preferably, the measurement workpiece 2 can be a hollow cylinder. In this case, the cross section taken along the length direction perpendicular to the measurement workpiece 2 can be a circular ring. In the ideal state that the optical axis of the shooting lens is perpendicular to the stage, a photographed image of the measurement workpiece 2 taken by the shooting lens can obtain an ideal circular ring pattern. When the optical axis of the shooting lens is not perpendicular to the stage, compared with other irregular measurement workpieces 2, the analysis of the photographed image of the measurement workpiece 2 in the form of a hollow cylinder can reduce the difficulty of data analysis, and thus can improve the efficiency of the photographed image analysis processing. In the following, the detection method related to the present disclosure will be described taking the measurement workpiece 2 in the form of a hollow cylinder (which can be referred to as a cylindrical workpiece for short) as an example.

[0052] In some examples, the measurement workpiece 2 can be a thin-walled sleeve. In some examples, the measurement workpiece 2 can have a length of 5-50 mm, a thickness of 0.1-3 mm, and an inner diameter of 5-20 mm. In some examples, the measurement workpiece 2 can also be used as a standard or reference for actual comparison or reference. In some examples, in step S102, the measurement workpiece 2 can be photographed by a photographing lens. When the measurement workpiece 2 is placed on the bearing surface, the photographing lens is used to take a photograph to obtain a photograph image of the measurement workpiece 2. It can be understood that when the measurement workpiece 2 is vertically placed on the bearing surface, the photograph image can have a shape substantially the same as the shape of the cross section of the measurement workpiece 2 along the radial direction.

[0053] In some examples, in step S103, the photograph image can be analyzed. Specifically, the photograph image can be compared with a pattern in an ideal state, and the coaxiality of the photographing module can be obtained according to the comparison result (to be described later). In the present disclosure, the pattern in the ideal state refers to the pattern of the measurement workpiece 2 photographed by the photographing lens when the optical machine is coaxial (i.e., the optical axis of the camera lens is perpendicular to the plane on which the bearing surface is located).

[0054] Figure 3A FIG. 1 is a schematic view showing a photograph image of the measurement workpiece 2 when the optical machine is coaxial according to an embodiment of the present disclosure. Figure 3B FIG. 2 is a schematic view showing a photograph image of the measurement workpiece 2 when the optical machine is not coaxial according to an embodiment of the present disclosure.

[0055] In some examples, when the optical machine is coaxial (i.e., the optical axis of the photographing lens is perpendicular to the bearing surface), the schematic view of the measurement workpiece 2 under the photographing lens can be as shown in FIG. 1. At this time, the circular ring-shaped pattern on the image is consistent with the shape of the cross section of the measurement workpiece 2 along the length direction. Figure 3A

[0056] In other examples, when the optical machine is not coaxial (i.e., the optical axis of the photographing lens is not perpendicular to the bearing surface), the schematic view of the measurement workpiece 2 under the photographing lens can be as shown in FIG. 2. In some examples, as shown in FIG. 3 and FIG. 4, it can be found that when the optical machine is not coaxial, the shape of the cross section perpendicular to the length direction of the measurement workpiece 2 has a large difference, and the photograph image can show that there are shadows near the inner wall and the outer wall of the measurement workpiece 2. Figure 3B Figure 3A Figure 3B

[0057] (Calculation of the coaxiality)

[0058] Figure 4 FIG. 5 is a schematic view showing a flow of measuring the coaxiality according to an embodiment of the present disclosure. Figure 5 FIG. 6 is a schematic view showing the measurement of the perpendicularity according to an embodiment of the present disclosure.​​​​Figure 6 is a schematic diagram showing a planar analysis of perpendicularity involved in the embodiments of the present disclosure. Figure 7 is a schematic diagram showing a target ray involved in the embodiments of the present disclosure. Figure 8 is a schematic diagram showing a target pattern S involved in the embodiments of the present disclosure. Figure 6 may be as shown in Figure 5 is a planar schematic diagram when detecting coaxiality.

[0059] In some examples, the method of acquiring coaxiality can include: acquiring a target pattern S (S201), calculating perpendicularity (S202), acquiring the number of target pixels at different angles (S203), and acquiring a tilt direction (S204) (see Figure 4 ).

[0060] In some examples, in step S201, the target pattern S can be acquired based on a captured image. In some examples, the target pattern S and the measurement workpiece 2 can be matched. Specifically, when the measurement workpiece 2 is in the form of a hollow cylinder, the target pattern S can be circular. When the measurement workpiece 2 is in the form of a hollow prism, the target pattern S can have a shape matching the cross section of the prism along the length direction.

[0061] In some examples, after acquiring the captured image, a binarization process can be performed to obtain a target image. In this case, the captured image after binarization can better highlight the outline of the pattern, and the analysis difficulty of the corresponding pixel points of the binarized image can be reduced. Thus, the calculation difficulty of the captured image analysis can be reduced.

[0062] In some examples, the target image can have an inner contour and an outer contour. It should be understood that when the optical machine is coaxial, the patterns of the outer contour and the inner contour are both circular, and when the optical machine is de-coaxial, the shapes of the outer contour and the inner contour will have partial differences (not necessarily circular).

[0063] In some examples, after acquiring the target image, the target pattern S can be obtained based on the target image. Specifically, the pixel points of the target image can be extracted, and then the point set composed of each pixel point is fitted to obtain the target pattern S. In this case, the measurement and calculation of coaxiality can be performed based on the target pattern S.

[0064] In some examples, the target pattern S can be circular. In this case, compared to analyzing irregular patterns, analyzing regular patterns such as the target circular pattern S can effectively reduce the complexity of data analysis. Thus, the detection efficiency of the detection method can be improved.

[0065] In some examples, the point set of the pixel points can be fitted by a least square method to obtain a least square circle (i.e., the target figure S in a circular shape). In this way, the accuracy of fitting the target figure S can be improved, and the accuracy of the coaxiality calculation based on the target figure S in the subsequent step can be improved. In addition, the target figure S is displayed in the form of a formula, which is beneficial for the subsequent step of data analysis based on the target figure S, and the efficiency of the analysis can be improved.

[0066] In some examples, after obtaining the target figure S, the geometric center O of the target figure S can be extracted, and the maximum distance radius Rmax of the point set of the pixel points to the geometric center O and the minimum distance radius Rmin of the point set to the geometric center O can be obtained based on the geometric center O (see Figure 8 ).

[0067] In some examples, the maximum distance radius Rmax can be the maximum distance of the point set of the pixel points of the target image to the geometric center O (i.e., the maximum distance of the outer contour of the target image to the geometric center O), and the minimum distance radius Rmin can be the minimum distance of the point set of the pixel points of the target image to the geometric center O (i.e., the minimum distance of the inner contour of the target image to the geometric center O). In some examples, the difference between the maximum distance radius Rmax and the minimum distance radius Rmin can be d.

[0068] In some examples, in step S202, the perpendicularity of the optical axis can be calculated based on the above-mentioned d (i.e., the maximum distance radius Rmax and the minimum distance radius Rmin) and the predetermined length of the workpiece 2.

[0069] In some examples, when the workpiece 2 is placed on the support platform as shown in Figure 5 , the bottom of the shooting module emits a light beam, and part of the light passes through the camera lens in the shooting module for acquiring the shooting image. When the shooting module acquires the shooting image of the workpiece 2, an image with a shadow as shown in Figure 3B or Figure 6 is obtained. Since the optical axis and the normal of the support surface are not coaxial at this time, the angle between the optical axis of the shooting module and the normal of the support surface at this time can be set as α, and a plane analysis schematic diagram as shown in Figure 6 is established. In some examples, when the workpiece 2 is placed on the support surface, the height of the workpiece 2 can be set as H.

[0070] In some examples, as shown in Figure 6 , if the perpendicularity of the optical axis and the support surface at this time is α, in this case, by d (the difference between the maximum distance radius Rmax and the minimum distance radius Rmin) and the predetermined length of the workpiece 2, and by the relationship of the three sides of a right triangle, the perpendicularity of the optical axis and the support surface can be calculated.

[0071] In some examples, in order to facilitate calculation, when a is small enough, a can be considered as a ~ tan a, and a can be obtained by calculating a = d / H. As described above, H can be the height of the workpiece 2 when placed on the bearing surface, and it can be understood that the height H of the workpiece 2 can also be equivalent to measuring the predetermined length of the workpiece 2. Thus, the perpendicularity of the optical axis and the bearing surface can be obtained based on the maximum distance diameter Rmax, the minimum distance diameter Rmin, and the predetermined length of the workpiece 2.

[0072] In some examples, in step S203, a target ray with the geometric center O as an end point can be obtained, and the target ray can have different inclination angles. The number of pixel points located on the target ray with a predetermined pixel value is the target pixel number, and the inclination direction of the optical axis is obtained by the target pixel number corresponding to each inclination angle.

[0073] In some examples, the target ray can be a ray with the geometric center O as an end point, and rotating the target ray with the geometric center O as an end point can form a plurality of target rays. The angles of the target ray rotations can be different. In some examples, the maximum rotation angle of the target ray can be a circular angle of 360°. In some examples, the plurality of target rays can have different rotation angles, which can also be represented as the target rays having different inclination angles. In some examples, after rotating the target rays, target rays with inclination angles of 0° to 360° can be obtained (see Figure 7 , and for convenience, Figure 7 only a part of the target rays are illustrated).

[0074] In some examples, when the target rays are rotated, a target ray with an inclination angle of 0° can be selected as an initial target ray. In some examples, the initial target ray can be rotated along a first direction with the geometric center O of the target pattern S as an end point. The first direction can be a clockwise direction or a counterclockwise direction. When the initial target ray is rotated at a predetermined speed, the target rays with different rotation angles are extracted at a predetermined time, and the target rays at different positions can be obtained based on the target pattern S. In some examples, the rays at different positions can also represent target rays with different inclination angles.

[0075] In some examples, the target rays can be rotated around the geometric center O to have different inclination angles, and the target pixel numbers corresponding to different inclination angles can be obtained by taking the inclination angle as a variable. In this case, the target rays at different positions can be obtained by rotation, and the target rays at different positions around the geometric center O can be obtained more comprehensively.

[0076] In some examples, when each target ray is set to extend to the target image with the geometric center O as the end point, the target ray will intersect the inner contour and the outer contour to form intersection points, respectively, and one target ray will intersect the target image to form two intersection points. In some examples, the number of pixels can be obtained by analyzing the pixel points on the target ray between the two intersection points. In some examples, when the pixel value of a pixel point exceeds a predetermined value, the pixel point can be considered as a pixel point in the shadow in the captured image. In the present disclosure, the shadow can be understood as a position on the captured image where the pixel value exceeds a predetermined pixel value when the camera lens and the bearing surface are not coaxial.

[0077] It can be understood that, since the target rays at different orientations on the target graph S have different inclination angles, when each target ray intersects the inner contour and the outer contour of the target image, the target rays at different inclination angles will intersect the contours (the inner contour and the outer contour) of the target image to form different intersection points. By analyzing the pixel points between the two intersection points of the target ray at each inclination angle, the number of pixel points exceeding the predetermined pixel value between the contour of the target image and the target ray corresponding to the corresponding inclination angle can be obtained.

[0078] In some examples, the target pixel number can be obtained based on the number of pixels with the predetermined pixel value between the two intersection points. In some examples, the target pixel number can be the total number of pixel points exceeding the predetermined pixel value on each target ray. In some examples, the target pixel number at different target rays and the inclination angle of the position of the target ray can be corresponding. In other words, the target ray based on a specific inclination angle can obtain the target pixel number corresponding to the inclination angle.

[0079] In some examples, when the camera lens and the bearing surface are not coaxial, the direction of the optical axis is inclined (not perpendicular) relative to the plane of the bearing surface, and in the direction in which the optical axis is inclined, the part of the captured image where the shadows overlap is the most. In this case, by analyzing the target pixel number at each inclination angle, the inclination direction can be obtained. In other words, the higher the target pixel number, the closer the target ray at the inclination angle matching the target pixel number to the inclination direction of the optical axis.

[0080] Figure 9 FIG. 6 is a simulation diagram illustrating the target pixel number- inclination angle involved in the embodiment of the present disclosure.

[0081] In some examples, as described above, in step S204, the inclination direction can be obtained.

[0082] In some examples, in step S204, the target pixel number- inclination angle image can be obtained based on the target pixel number corresponding to each inclination angle. As Figure 8As shown in the target pixel number-tilt angle image, the Y axis is the target pixel number, and the X axis is the tilt angle.

[0083] In some examples, an initial target ray can be rotated at a fixed unit at the geometric center O of the target figure S to obtain target rays with different tilt angles, the target pixel number at each tilt angle can be calculated, and the data can be processed to obtain a target pixel number-tilt angle image. In some examples, the fixed unit can be a rotatable value that the initial target ray can reach, for example, the fixed unit can be 0.01°, 0.2°, 0.5°, 1°, etc. In some examples, a 360° rotation can be performed on any target ray at the geometric center O on the target figure S until target rays with different tilt angles are obtained between 0° and 360°. In some examples, the smaller the fixed unit, the more target rays obtained after rotating the initial target ray, and the more accurate the number of target pixel numbers at different tilt angles of the target ray is calculated. In some examples, after obtaining the target pixel number at different tilt angles, the relationship between the target pixel number and the tilt angle can be fitted to obtain a target pixel number-tilt angle image (see Figure 8 ).

[0084] In some examples, after obtaining the target pixel number-tilt angle image, the target pixel number peak can be obtained by analyzing the image. In some examples, the higher the target pixel number, the closer the target ray at the tilt angle matching the target pixel number to the tilt direction of the optical axis. When the target pixel number reaches the peak in the target pixel number-tilt angle image (the peak is the position with the most target pixel number), the tilt angle corresponding to the peak in the target pixel number-tilt angle image can be obtained based on the peak, and the target ray corresponding to the tilt angle can be obtained to obtain the tilt direction of the optical axis.

[0085] In some examples, at least two peaks of the target pixel number corresponding to each tilt angle can be obtained based on the target pixel number-tilt angle image, and the tilt direction of the optical axis can be obtained based on the tilt angle corresponding to the peak (i.e., when the workpiece 2 is placed on the bearing surface, the direction in which the workpiece 2 tilts relative to the optical axis is measured). In this case, the position of the tilt angle corresponding to the peak can be the position where the optical axis tilts most severely.

[0086] In some examples, when the direction of the target ray is the same as the target direction, the tilt angle of the target ray can be 0°, a first peak with a tilt angle not greater than 90° and a second peak with a tilt angle greater than 90° can be obtained. In some examples, the target direction can be the direction of the initial target ray. In other examples, the target direction can be the direction of the target ray with a tilt angle of 0° or a tilt angle of 360° (see Figure 7 ).

[0087] In some examples, the tilt angle corresponding to the first peak can be θ1, the tilt angle corresponding to the second peak can be θ2 (see Figure 4 ), and the tilt direction of the optical axis can be obtained based on θ1 and θ2. In some examples, the tilt direction of the optical axis can be denoted as β (described later). In some examples, β can be obtained by the formula β = (θ1 + θ2 - π) / 2.

[0088] In some examples, after β is obtained, the horizontal right direction on the target image can be taken as the initial direction (the direction of the initial target ray), and the direction of the target ray obtained by rotating the first direction by β can be the tilt direction of the optical axis. In this case, the calculation based on the tilt angle of the peak where the number of target pixels is located can reduce the error in the determination of the tilt direction.

[0089] In an ideal condition, due to the symmetry of the angle, θ2 = θ1 + π, so β = (θ1 + θ2 - π) / 2 = (θ1 + θ1 + π - π) / 2 = θ1. In other words, the tilt direction can be obtained by the formula β = θ1, but in actual measurement, θ2 and (θ1 + π) are not strictly equal, and the random error of the tilt direction obtained by this equal relationship is large, which reduces the accuracy of the detection of the tilt direction, thereby reducing the measurement accuracy of the coaxiality. In this case, θ1 and θ2 are obtained by analyzing the target pixel number-tilt angle image as shown in Figure 9 , and β is obtained by the calculation formula β = (θ1 + θ2 - π) / 2, which can effectively reduce the error in the analysis and calculation of the tilt direction. Thus, the detection accuracy of the tilt direction can be improved, and the detection accuracy of the coaxiality can be improved.

[0090] (Adjustment method)

[0091] In some examples, after the coaxiality (perpendicularity and tilt direction) is obtained, the image measurement device 1 can be adjusted based on the coaxiality to make the optical axis and the bearing surface coaxial. In some examples, the bearing platform can be adjusted to make the optical axis and the bearing surface coaxial. In other examples, the optical axis of the shooting lens can also be adjusted to make the optical axis and the bearing surface coaxial.

[0092] In some examples, the bearing platform and the shooting module can be repeatedly adjusted until the coaxiality (perpendicularity and tilt direction) is within a preset range. In some examples, during the adjustment, the images obtained by the shooting lens shooting the measurement workpiece 2 multiple times can be analyzed, and the coaxiality can be detected by the above detection method.

[0093] In some examples, the adjusting step can include: adjusting the bearing platform, taking a measurement workpiece 2 to obtain a shooting image to calculate the coaxiality; adjusting the optical axis of the shooting module, taking a measurement workpiece 2 to obtain a shooting image to calculate the coaxiality, and adjusting multiple times until the coaxiality is in the preset range. In some examples, when the coaxiality is in the preset range, it can be determined that the optical machine is coaxial.

[0094] In some examples, when adjusting, the optical axis of the shooting module can be adjusted first, and then the bearing platform can be adjusted. In some examples, after the adjustment of the bearing platform or the adjustment of the optical axis is completed, if the coaxiality is still not in the preset range, the above-mentioned adjustment step is repeated until the coaxiality is in the preset range.

[0095] The present disclosure also proposes a system for detecting the coaxiality of an optical machine, which measures the coaxiality of the optical axis and the bearing surface by the detection method described above.

[0096] In some examples, the detection system can include optical components and mechanical components (see Figure 1 ). In some examples, the optical components can include a light source and a shooting lens, and the mechanical components can include a bearing platform. In some examples, the bearing platform can have a bearing surface for placing a to-be-measured object, the light source can illuminate or light the to-be-measured object, and the light emitted by the light source can enter the shooting lens, thereby facilitating the brightness when the shooting lens is shooting. In some examples, the shooting lens can shoot the to-be-measured object placed on the bearing surface. Thus, the coaxiality can be detected by the detection system.

[0097] According to the present disclosure, a detection method for measuring the coaxiality and a system for detecting the coaxiality can be provided.

[0098] Although the present disclosure is specifically described above in combination with the drawings and examples, it should be understood that the above description does not limit the present disclosure in any form. Those skilled in the art can modify and change the present disclosure as needed without departing from the spirit and scope of the present disclosure, and these modifications and changes all fall within the scope of the present disclosure.

Claims

1. A method for measuring coaxiality, comprising measuring the coaxiality between the optical axis of an imaging module and the bearing surface of the imaging module, wherein the coaxiality includes the perpendicularity of the optical axis to the bearing surface and the tilt direction of the optical axis, characterized in that, The measurement workpiece is placed on the bearing surface, and the measurement workpiece is photographed by the shooting module to obtain a shooting image of the measurement workpiece, and the coaxiality is obtained based on the shooting image, the measurement workpiece is a hollow cylinder, the measurement workpiece has an inner wall, an outer wall and a predetermined height, and when the optical axis is not perpendicular to the bearing surface, there is a shadow on the shooting image close to the inner wall and the outer wall; A target image matched with the measurement workpiece is obtained based on the shooting image, a target pattern is obtained based on the target image, and the perpendicularity of the optical axis to the bearing surface is obtained based on the distance between the contour of the target image and the geometric center of the target pattern; A target ray with the geometric center of the target pattern as an end point is made, and a target pixel number of the target ray is obtained, the target pixel number is the number of pixel points with a predetermined pixel value on the target ray, the target ray is rotated around the geometric center of the target pattern to make the target ray have a plurality of different inclination angles, a target pixel number corresponding to each inclination angle is obtained, and the inclination direction of the optical axis is obtained based on the target pixel number corresponding to each inclination angle.

2. The detection method of claim 1, wherein: The contour includes an outer contour and an inner contour, and the perpendicularity of the optical axis is calculated based on the maximum distance between the geometric center of the target pattern and the outer contour, the minimum distance between the geometric center of the target pattern and the inner contour, and a predetermined length.

3. The detection method of claim 1, wherein: A target pixel number-inclination angle image is obtained based on the target pixel number corresponding to each inclination angle, at least two peaks of the target pixel number-inclination angle image are obtained, and the inclination direction of the optical axis is obtained based on the inclination angle corresponding to the peaks.

4. The detection method of claim 3, wherein: When the direction of the target ray is the same as a target direction, the inclination angle of the target ray is 0°, and the at least two peaks include a first peak with an inclination angle not greater than 90° and a second peak with an inclination angle greater than 90°.

5. The detection method of claim 1, wherein: The shooting image is binarized to obtain the target image, and pixel points of the target image are extracted and fitted to obtain the target pattern.

6. The detection method of claim 5, wherein: The target pattern is a circle.

7. A system for detecting coaxiality, characterized by The system includes an optical component having an optical axis and a mechanical component having a bearing surface, and the system measures the coaxiality of the optical axis to the bearing surface by the detection method of any one of claims 1-6.

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