A visual measurement device for internal thread parameters based on spherical reflection imaging

Abstract

The application discloses a kind of based on spherical reflection imaging internal thread parameter visual measurement method and device, belong to thread parameter measurement technical field.The application utilizes spherical reflection principle, and builds non-contact detection device.Steel ball is fixed on moving platform, camera and telecentric lens are fixed above steel ball, camera is connected to host computer, and data communication is carried out;Low-angle ring light source is used for illumination, and for the detection of to-be-measured through-hole nut, nut is placed horizontally on fixed support, and steel ball is partially inserted into through-hole nut;For the detection of to-be-measured blind hole nut, steel ball is placed in blind hole nut.By collecting complete internal thread image, the thread detection of nut in four directions of up, down, left and right is realized on the basis of ensuring measurement speed.Compared with the thread comprehensive measuring machine based on metrological grating ruler, the detection speed of two important parameters of internal thread pitch and small diameter is improved, and it is suitable for fast non-contact measurement of ordinary nut, precision nut, blind hole nut and other workpieces.

Description

Technical Field

[0001] This invention relates to the field of thread parameter measurement technology, and in particular to a visual measurement device for internal thread parameters based on spherical reflection imaging. Background Technology

[0002] Threaded connections are widely used in industrial production and equipment manufacturing, serving to fasten equipment and tightly connect various parts. Commonly used threaded fasteners include nuts, studs, screws, and set screws, most of which are standard parts. Threads are divided into external threads and internal threads. External threads are exposed and located on the rotating side of the rotating fastener; internal threads are not exposed and located on the rotated side of the rotating fastener. The quality of the thread is crucial to the normal operation of equipment, and in severe cases, can even lead to loss of life and property. Therefore, the quality of the thread and the testing of its key parameters are of great significance.

[0003] Internal threads, due to their non-exposed threads and characteristics such as small diameter, complex internal structure, and large length-to-diameter ratio, present certain difficulties in measuring thread parameters. During manufacturing, external forces and the inherent material properties of the threaded connection itself can lead to defects such as indentations and scratches on the produced threads. However, compared to these defects, the more significant impact on threaded connection performance is the failure of internal thread dimensions to meet accuracy requirements. (Combined with...) Figure 1 The main parameters related to the crest 7 and root 8 of the internal thread include: thread inner diameter (major diameter D, pitch diameter D2, minor diameter D1), pitch (P), thread angle, etc. These parameters directly determine the effect of its mating with the bolt.

[0004] Currently, domestic and international methods for measuring thread parameters can be broadly categorized into two types: contact measurement and non-contact measurement. Contact methods, such as manual inspection of thread parameters by operators using plug gauges, are more common in industrial testing environments, but suffer from drawbacks such as low efficiency, slow speed, and high labor costs. With the introduction of thread comprehensive measuring machines, contact thread inspection technology has revolutionized traditional methods. Contact measurement utilizes a scanning probe to scan the axial profile of the thread surface. The measurement system obtains the morphology of the thread's axial profile and directly analyzes and calculates according to the relevant definitions of thread parameters to obtain the thread's comprehensive geometric parameters. The measurement and calculation follow the definitions of thread parameters, and its database can automatically determine the thread's conformity. The entire measurement takes approximately 2 minutes, and a single measurement can automatically obtain parameters such as the effective pitch diameter, single pitch diameter, pitch diameter, major diameter, minor diameter, pitch, thread angle, thread half-angle, thread flank straightness, thread helix angle, and taper of cylindrical and tapered threads, making it ideal for inspecting threads of all grades. However, a thread measuring machine is expensive and uses a contact measurement method. During the measurement process, the testing tool comes into direct contact with the threaded hole of the precision device, which may cause secondary damage to the thread. At the same time, the measurement speed is too slow, making it unsuitable for real-time rapid testing in production.

[0005] With the upgrading of my country's manufacturing industry, intelligent online real-time inspection methods are more in line with the strategic requirements of intelligent manufacturing, and non-contact inspection is gradually being preferred by many enterprises. Chen Sihan et al., in their paper "Automatic Internal Thread Inspection System Based on Machine Vision," proposed using a probe equipped with a 45° reflector to insert into the nut or pipe to be tested, reflecting the image of the workpiece's inner wall to detect defects. This method has two drawbacks: 1) Because the probe needs to be inserted and removed each time, and the method requires the probe to rotate into the workpiece, achieving the required inspection efficiency places very high demands on the imaging equipment's shooting speed; 2) The inspection method described in the paper mainly detects scratch defects on the inner wall of the thread, without mentioning the measurement of thread parameters.

[0006] In their paper "Detection of Threads in a 3D Density Field by Computed Tomography," Kosarevsky S et al. proposed using X-ray to perform tomographic scanning of the workpiece and reconstruct its 3D features. This method can detect various features of the workpiece, but its drawbacks are also obvious: extremely high cost and low efficiency. Wang Yunzhe et al. from Changchun University of Technology, in their paper "Machine Vision Inspection System for Internal Threads," proposed using an endoscope to acquire images of internal threads, and then applying erosion and dilation algorithms to process the images to obtain the image skeleton, thus completing the detection of the thread pitch. However, each endoscope image requires entry into the workpiece, which is time-consuming; and the diameter of the workpiece cannot be too small, making it unsuitable for detecting small-diameter nuts. Summary of the Invention

[0007] 1. The technical problem that the invention aims to solve

[0008] Given that existing contact-based internal thread measurement methods are inefficient, prone to wear, and expensive, while vision-based internal thread parameter measurement offers advantages such as non-contact, high precision, high efficiency, and low cost, this invention provides a visual measurement method and apparatus for internal thread parameters based on spherical reflection imaging. This invention establishes a machine vision inspection system based on spherical reflection imaging for non-contact measurement of internal threads; compared to thread measurement machines based on measuring grating rulers, it improves the detection speed of two important parameters: internal thread pitch and minor diameter.

[0009] 2. Technical Solution

[0010] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0011] The present invention discloses a visual measurement device for internal thread parameters based on spherical reflection imaging, comprising an image acquisition device, an illumination device, and a moving platform. The device is characterized in that it further comprises a spherical reflector disposed on the moving platform, with the image acquisition device and the illumination device disposed on one side of the spherical reflector. The test piece cooperates with the spherical reflector, enabling the image acquisition device to acquire a complete image of the internal thread of the test piece.

[0012] Furthermore, the spherical reflector is made of steel spheres.

[0013] Furthermore, the test piece is a through-hole nut, a fixed bracket is set on the moving platform, the through-hole nut is placed on the fixed bracket, and the spherical reflector part extends into the through-hole nut.

[0014] Furthermore, the test piece is a blind hole nut, and the spherical reflector is placed inside the blind hole nut.

[0015] Furthermore, the image acquisition device includes a camera and a telecentric lens, with the telecentric lens positioned between the camera and the spherical reflector, and the camera connected to a host computer; the lighting device uses a low-angle ring light source.

[0016] This invention provides a visual measurement method for internal thread parameters based on spherical reflection imaging, which calibrates the camera to obtain accurate lens magnification. γ The test piece is used in conjunction with a spherical reflector to acquire a complete image of the internal thread. Using an image processing algorithm, the thread image of the nut reflected by the spherical reflector is segmented. Then, using the theory of spherical mirror reflection and the gray value relationship of pixels in the image, the boundary points of the thread in the thread image are found. Finally, the pitch P and minor diameter D1 of the nut's internal thread are calculated.

[0017] Furthermore, the measurement process for the minor diameter D1 of the nut's internal thread is as follows:

[0018] Select a suitable rectangular region of interest (ROI) from the internal thread image and perform initial cropping. Preprocess the cropped image by performing grayscale transformation, thresholding, and median filtering. Then, use an iterative algorithm to find the circle representing the smallest internal thread reflected from the steel ball, segmenting the image into a circular ROI region with a radius denoted as . radius The minor diameter of the nut is D1 = radius ×Camera pixel size / γ .

[0019] Furthermore, the measurement process for the pitch P of the nut's internal thread is as follows:

[0020] (1) When measuring the small diameter, perform grayscale transformation, median filtering, bilateral filtering, and morphological closing operation on the segmented circular ROI region;

[0021] (2) Find a suitable thread boundary and calculate its distance to the center of the circle;

[0022] (3) Convert the pixel distance to the actual distance and select a suitable distance to perform an average calculation to obtain the internal thread pitch P.

[0023] Furthermore, step (2) is as follows: the preprocessed image is divided into four directions: top, bottom, left, and right, and the boundary points of the threads are found sequentially; for the left direction, the pixels in the row from the left boundary of the circle to the center are traversed, and the gray values ​​are calculated column by column; if the gray value of pixel i minus the gray value of pixel i-4 is greater than 20, the pixel is considered to be a thread boundary point, the coordinates of pixel i are recorded, and an array is obtained. ;right Subtract the x / y coordinates of adjacent elements in the middle, if If the found pixels are too close, then it is considered that the pixels are duplicated and the pixels that are too close are discarded; four thread boundary points are found in each direction; finally, the obtained... , Subtracting each from the x-coordinate of the circle's center, we get... Next, repeat the above operation three times, sequentially traversing the pixels from the right boundary of the circle to the center row, the top boundary of the circle to the center column, and the bottom boundary of the circle to the center column, to obtain the pixels in four directions. .

[0024] Furthermore, step (3) involves calculating the distance between two boundary points of two adjacent threads in the same vertical direction on the test piece in each direction. ; 3 in each direction , recorded as For all directions Subtract each value from the standard pitch of the nut and calculate the absolute value; if the absolute value is greater than 0.1, then determine the absolute value and compare it. The difference from the standard pitch, and The difference from the standard pitch is discarded, and the remaining two adjacent pitches are used. Repeat step (2); finally, all the results obtained after the initial screening will be processed. Subtract the standard pitch of the nut to be tested and calculate its absolute value; if the absolute value is greater than or equal to 0.5, the boundary point of the thread is considered to be incorrect, and this point is discarded. ; the remaining The average value is calculated to obtain the pitch value of the nut being tested. P .

[0025] 3. Beneficial effects

[0026] Compared with existing known technologies, the technical solution provided by this invention has the following significant advantages:

[0027] (1) Traditional methods based on endoscopes and reflecting prisms usually require multiple imaging and image stitching to obtain a complete image of the internal thread. This invention builds a machine vision inspection system based on spherical reflection imaging to perform non-contact measurement of the internal thread. Based on spherical reflection imaging, a complete image of the internal thread can be obtained at once, which improves the detection speed of the two important parameters of the internal thread pitch and minor diameter.

[0028] (2) The visual measurement device for internal thread parameters based on spherical reflection imaging of the present invention has the advantages of fast detection speed, simple device, and ability to measure nuts of various specifications compared with the traditional thread measurement machine that uses a measuring grating ruler as the length standard. The detection speed reaches 0.62 seconds / nut. The system's repeatability error is within 0.03mm, and the detection accuracy is high.

[0029] (3) The present invention provides a visual measurement method for internal thread parameters based on spherical reflection imaging, which is suitable for rapid non-contact measurement of the pitch and minor diameter of internal thread workpieces such as ordinary nuts, precision nuts, and blind hole nuts. It can accurately measure the minor diameter and pitch of internal threads and classify them according to the size specifications of the internal thread pitch. It can be used for the inspection of standard parts such as nuts, as well as for the parameter inspection of internal threads on workpieces. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the main parameters of the internal thread. The present invention mainly measures the pitch (P) and minor diameter (D1).

[0031] Figure 2 This is a schematic diagram of the through-hole nut measuring device, where: 1: Daheng camera MER-500-7UM; 2: telecentric lens GCO-232105; 3: low-angle ring light source; 4: nut to be measured; 5: steel ball (material: 100CR6, grade: G3); 6: host computer.

[0032] Figure 3 This is a schematic diagram of a blind hole nut measuring device, in which: 1: Daheng camera MER-500-7UM; 2: telecentric lens GCO-232105; 3: low-angle ring light source; 4: nut to be measured; 5: steel ball (material: 100CR6, grade: G3); 6: host computer.

[0033] Figure 4 This is a diagram illustrating the principle of image size to real size conversion. Formulas (1)-(5) are... Figure 4 The mathematical relationship between the parameters. Figure 4 In the diagram, (a) shows the coordinate relationship between the image plane and N, where N is the thread boundary point reflected from the steel ball. Let O be the distance from the center of the circle to point N. Figure 4 (b) in the diagram shows the relationship between the object point and the imaging point. , The two boundary points of two adjacent threads on the workpiece to be measured are in the same vertical direction; the marked point R is the vertical distance from the center of the circle to the inner wall of the workpiece to be measured. β is the perpendicular distance between the vertical axis passing through the center of the circle and the thread boundary point N; β is the angle between the thread boundary point N and the vertical axis; r is the radius of the steel ball; for and The distance.

[0034] Figure 5 Image processing flowchart for measuring the minor diameter of internal threads.

[0035] Figure 6 This is a flowchart of image processing for measuring the pitch of internal threads.

[0036] Figure 7 This is an actual image of a standard through-hole nut (specification: M20×1.5P).

[0037] Figure 8 This is the original image of a standard through-hole nut (size: M20×1.5P).

[0038] Figure 9 The image shown is the detection image obtained after image processing of the original image. The white dots in the image represent the found thread boundary points.

[0039] Figure 10-13 This is a magnified view of the thread boundary points found in the left, right, up, and down directions of the nut.

[0040] Figure 14 The same nut (specification: M20×1.5P) was placed on the device and rotated ten times. The pitch value was measured once after each rotation. It can be seen that the repeatability error of the system is within 0.03mm.

[0041] Figure 15 The same nut (specification: M20×1.5P) was placed on the device and rotated ten times. The minor diameter was measured once after each rotation. It can be seen that the repeatability error of the system is within 0.03mm.

[0042] Figure 16 This is an actual image of a blind hole nut (specification: M14×1.5P).

[0043] Figure 17 This is the original image of a blind hole nut (size: M14×1.5P).

[0044] Figure 18 This is a test result diagram of a blind hole nut. The upper direction was discarded because a suitable thread boundary point could not be found and the accurate pitch could not be measured. The pitch was measured using the thread boundary points in the right, left and lower directions.

[0045] Figure 19 The same blind hole nut (specification: M14×1.5P) was placed on the device and rotated ten times. The pitch value was measured once after each rotation. It can be seen that the repeatability error of the system is within 0.03mm.

[0046] Figure 20 The same blind hole nut (specification: M14×1.5P) was placed on the device and rotated ten times. The minor diameter was measured once after each rotation. It can be seen that the repeatability error of the system is within 0.03mm. Detailed Implementation

[0047] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0048] Example 1

[0049] Combination Figure 4 This embodiment utilizes the principle of spherical reflection to construct a non-contact detection device. A steel ball 5 is fixed on a moving platform, and a camera 1 and a telecentric lens 2 are fixed directly above the steel ball 5. The camera 1 is connected to a host computer 6 for data communication. A low-angle ring light source 3 is used for illumination. For the detection of the nut 4 (through-hole nut), the nut is placed horizontally on a fixed support, and part of the steel ball 5 extends into the through-hole nut (e.g., ...). Figure 2 As shown); for the testing of the blind hole nut, steel ball 5 is placed inside the blind hole nut (as shown). Figure 3 (As shown).

[0050] This embodiment achieves thread detection in four directions (up, down, left, and right) of the nut by acquiring a complete image of the internal thread, while ensuring measurement speed.

[0051] The measurement process using this device is as follows: First, the camera is calibrated to obtain the precise lens magnification; second, using image processing algorithms, the thread image corresponding to the nut reflected by the steel ball is segmented; then, using the theory of spherical mirror reflection and the gray value relationship of pixels in the image, the boundary points of the thread in the image are found; finally, the pitch and minor diameter of the nut are calculated.

[0052] Example 2

[0053] This embodiment presents a visual measurement method for internal thread parameters based on spherical reflection imaging. The test objects are: ordinary through-hole nuts (specification: M20×1.5P) and ordinary blind-hole nuts (specification: M14×1.5P). The relevant parameters of the tested nuts are shown in Table 1.1. As shown in Table 1.1, the manufacturer only provides the tolerance range for the thread pitch diameter and minor diameter. However, the internal thread minor diameter and pitch measurement method designed in this embodiment uses all of the above parameters as test objects.

[0054] Table 1.1 Test Nut Relevant Parameters

[0055]

[0056]

[0057] Measurement steps:

[0058] (1) Set up the testing device. Fix a steel ball of known radius on the device platform. Fix the camera and telecentric lens directly above the steel ball. Place the nut to be tested horizontally on the support (e.g., Figure 2 As shown); for the inspection of blind hole nuts, a steel ball is placed inside the through hole nut (as shown). Figure 3(As shown).

[0059] (2) Camera calibration: The system is calibrated using Zhang's calibration method to obtain the true magnification γ of the telecentric lens.

[0060] (3) Capturing the image of the nut: Set the camera exposure time to 35000μs, adjust the lens aperture and object distance to focus the camera, and capture a clear and complete image of the internal thread (e.g., Figure 8 (As shown).

[0061] (4) Image processing:

[0062] 1) Measurement of minor diameter of internal thread:

[0063] First, define a suitable rectangular Region of Interest (ROI) for initial image cropping. Then, perform grayscale transformation, thresholding, and median filtering on the cropped image. Next, use an iterative algorithm to find the circle representing the smallest internal thread area reflected from the steel ball, thus segmenting the circular ROI region. This is the image of the nut's internal thread reflected from the steel ball (e.g., ...). Figure 9 (As shown). The minor diameter of the nut, D1, is calculated as: radius × camera pixel size / γ.

[0064] 2) Measurement of internal thread pitch:

[0065] 2.1) Image Preprocessing

[0066] When measuring the minor diameter, the segmented circular ROI region is subjected to grayscale transformation to improve image quality and simplify information; median filtering makes the surrounding pixel values ​​closer to the real situation and eliminates isolated noise; bilateral filtering protects the thread boundary information on the image; morphological closing operation further smooths the thread contour.

[0067] 2.2) Find a suitable thread boundary and calculate its distance from the center of the circle.

[0068] The preprocessed image is divided into four directions: top, bottom, left, and right. The boundary points of the threads are then located sequentially. The first direction is the row of pixels from the left boundary of the circle to the center. The grayscale value of each column is calculated. If the grayscale value of pixel i minus the grayscale value of pixel i-4 is greater than 20, that pixel is considered a thread boundary, and the coordinates of pixel i are recorded, resulting in an array. ;right Subtract the x and y coordinates of adjacent elements. If the pixel is too close to the other pixel, it is considered a duplicate and should be discarded to avoid false positives. Four thread boundary points are found in each direction (e.g., ...). Figure 9 (As shown by the points marked in the middle). Finally, the obtained... ( Subtracting each from the x-coordinate of the circle's center, we get... Next, repeat the above operation three times, sequentially traversing the pixels from the right boundary of the circle to the center row, the top boundary of the circle to the center column, and the bottom boundary of the circle to the center column. This yields the pixels in four directions. .

[0069] 2.3) Convert pixel distance to actual distance, and select suitable distances for averaging to obtain the measured pitch.

[0070] Calculate each direction according to formula (1-5) The size. Three should be obtained in each direction. , recorded as For all directions Subtract each value from the standard pitch of the nut (e.g., the standard pitch of an M20×1.5P nut is 1.5mm) and calculate the absolute value. If the absolute value is greater than 0.1, then the absolute value is judged and compared. The difference from the standard pitch and The difference from the standard pitch is discarded, and the remaining two adjacent pitches are used. Repeat step (2.2). This initial screening removes thread boundary points with significant errors, improving the accuracy of pitch calculation. Finally, all the threads obtained after the initial screening... Subtract the standard pitch of the nut to be tested and calculate its absolute value. If the absolute value is greater than or equal to 0.5, the boundary point of the thread is considered incorrect, and this value is discarded. The remaining Calculate the average (Formula 6) to obtain P This is the measured pitch value of the nut to be tested.

[0071]

[0072] In the formula, N represents the number of distances remaining between two boundary points of two adjacent threads in the same vertical direction on the test part in each direction after removing erroneous pitches. Let O be the distance from the center of the circle to point N. , The two boundary points of two adjacent threads on the workpiece to be measured are in the same vertical direction; the marked point R is the vertical distance from the center of the circle to the inner wall of the workpiece to be measured. β is the perpendicular distance between the vertical axis passing through the center of the circle and the thread boundary point N; β is the angle between the thread boundary point N and the vertical axis; r is the radius of the steel ball; for and The distance.

[0073] Combination Figure 14 , Figure 15 , Figure 19 and Figure 20The visual measurement method for internal thread parameters in this embodiment has a repeatability error within 0.03mm, exhibiting high detection accuracy. It is suitable for rapid, non-contact measurement of the pitch and minor diameter of internal thread workpieces such as ordinary nuts, precision nuts, and blind hole nuts. It can accurately measure the minor diameter and pitch of internal threads and classify them according to their pitch specifications. It can be used for the inspection of standard nuts as well as for the parameter detection of internal threads on workpieces.

[0074] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A visual measurement device for internal thread parameters based on spherical reflection imaging, comprising an image acquisition device, an illumination device, and a moving platform, characterized in that: It also includes a spherical reflector, which is mounted on a moving platform. An image acquisition device and an illumination device are mounted on one side of the spherical reflector. The test piece cooperates with the spherical reflector so that the image acquisition device can acquire a complete image of the internal thread of the test piece. The spherical reflector is made of steel spheres; The visual measurement process for the internal thread parameters of this device is as follows: The camera (1) was calibrated to obtain the accurate lens magnification. γ The test piece is used in conjunction with a spherical reflector to acquire a complete image of the internal thread. Using image processing algorithms, the thread image of the nut reflected by the spherical reflector is segmented. Then, using the theory of spherical mirror reflection and the gray value relationship of pixels in the image, the boundary points of the thread in the thread image are found. Finally, the pitch P and minor diameter D1 of the nut's internal thread are calculated. The measurement process for the minor diameter D1 of the nut's internal thread is as follows: Select a suitable rectangular region of interest (ROI) from the internal thread image and perform initial cropping. Preprocess the cropped image by performing grayscale transformation, thresholding, and median filtering. Then, use an iterative algorithm to find the circle representing the smallest internal thread reflected from the steel ball, segmenting the image into a circular ROI region with a radius denoted as . radius The minor diameter of the nut is D1 = radius ×Camera pixel size / γ ; The measurement process for the pitch P of the internal thread of the nut is as follows: (1) When measuring the small diameter, perform grayscale transformation, median filtering, bilateral filtering, and morphological closing operation on the segmented circular ROI region; (2) Find a suitable thread boundary and calculate its distance to the center of the circle; The process is as follows: Divide the preprocessed image into four directions: top, bottom, left, and right, and sequentially find the boundary points of the threads. For the left direction, traverse the pixels in the row from the left boundary of the circle to the center, and calculate the gray value column by column. If the gray value of pixel i minus the gray value of pixel i-4 is greater than 20, the pixel is considered a thread boundary point, and the coordinates of pixel i are recorded to obtain an array. ;right Subtract the x / y coordinates of adjacent elements in the middle, if If the found pixels are too close, then it is considered that the pixels are duplicated and the pixels that are too close are discarded; four thread boundary points are found in each direction; finally, the obtained... , Subtracting each from the x-coordinate of the circle's center, we get... Next, repeat the above operation three times, sequentially traversing the pixels from the right boundary of the circle to the center row, the top boundary of the circle to the center column, and the bottom boundary of the circle to the center column, to obtain the pixels in four directions. ; (3) Convert the pixel distance to the actual distance, and select a suitable distance to perform an average calculation to obtain the internal thread pitch P; the process is as follows: Calculate the distance between two boundary points of two adjacent threads in the same vertical direction on the test piece in each direction. ; 3 in each direction , recorded as For all directions Subtract each value from the standard pitch of the nut and calculate the absolute value; if the absolute value is greater than 0.1, then determine the absolute value and compare it. The difference from the standard pitch, and The difference from the standard pitch is discarded, and the remaining two adjacent pitches are used. Repeat step (2); finally, all the results obtained after the initial screening will be processed. Subtract the standard pitch of the nut to be tested and calculate its absolute value; If the absolute value is greater than or equal to 0.5, then the boundary point of the thread is considered incorrect, and this point is discarded. ; the remaining The average value is calculated to obtain the pitch value of the nut being tested. P .

2. The visual measurement device for internal thread parameters based on spherical reflection imaging according to claim 1, characterized in that: The test piece is a through-hole nut. A fixed bracket is set on the moving platform, the through-hole nut is placed on the fixed bracket, and the spherical reflector part extends into the through-hole nut.

3. The visual measurement device for internal thread parameters based on spherical reflection imaging according to claim 1, characterized in that: The test piece is a blind hole nut, and the spherical reflector is placed inside the blind hole nut.

4. The visual measurement device for internal thread parameters based on spherical reflection imaging according to claim 1, characterized in that: The image acquisition device includes a camera (1) and a telecentric lens (2). The telecentric lens (2) is positioned between the camera (1) and the spherical reflector. The camera (1) is connected to a host computer (6). The lighting device uses a low-angle ring light source.

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