Standard for optical three-dimensional measurement system and calibration method

Abstract

The invention provides an etalon for an optical three-dimensional measurement system and a calibration method. The etalon comprises a test sample block and a target ball group, the test sample block comprises a bottom plate, a square block and inclined blocks, the bottom surface of the square block is fixed on the bottom plate, the cross section of the square block is square, and the four inclined blocks are fixedly connected between the four side surfaces, perpendicular to the bottom plate, of the square block and the bottom plate respectively; the target ball group comprises five standard balls, the first standard ball is fixed in the center of the top of the square block, the second, third, fourth and fifth standard balls are fixed on the bottom plate and are respectively positioned in four directions of two diagonal lines of the bottom surface of the square block, and the distances between the second, third, fourth and fifth standard balls and the first standard ball are the same. The standard device integrating the standard ball and the standard flat plate is designed, and the technical problem that the angle of the standard device needs to be adjusted in the calibration process is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical three-dimensional measurement system calibration, and particularly relates to a standard device for an optical three-dimensional measurement system and a calibration method. BACKGROUND

[0002] Three-dimensional measurement, as the name implies, is a full-range measurement of a measured object to determine three-dimensional coordinate measurement data of the measured object. Compared with the calibration method in a normal temperature environment, the standard part needs to be placed in a high-temperature environment (a high-temperature furnace, a laser heating device, etc.) in a high-temperature environment, and the calibration can be carried out only after heating to a specified temperature. The existing standard device suitable for a normal temperature environment needs to use a standard ball, a ball rod and a plane for calibration at a normal temperature, and different angles need to be adjusted in the calibration process. However, this method is not suitable for a high-temperature environment, and it is not convenient to adjust the angle when the standard device cannot be replaced. Therefore, it is not suitable for a high-temperature calibration environment.

[0003] The existing standard part lacks a standard ball that can provide different spatial positions, a ball center distance in different directions and a plane shape in different directions, and cannot meet the calibration requirements of the optical three-dimensional measurement system without adjusting the direction. SUMMARY

[0004] The present application aims to solve one of the above technical problems, and provides a standard device for an optical three-dimensional measurement system and a calibration method. The standard device integrating a standard ball and a standard plate is designed to solve the technical problem of adjusting the angle of the standard device in the calibration process.

[0005] The technical solution adopted by the present application to solve the above technical problems is as follows:

[0006] The present application provides a standard device for an optical three-dimensional measurement system, which comprises a test sample block and a target ball group.

[0007] The test sample block comprises a bottom plate, a square block and an inclined block. The bottom surface of the square block is fixed on the bottom plate. The cross section of the square block is a square. Four inclined blocks are respectively fixed and connected between the four side surfaces of the square block perpendicular to the bottom plate and the bottom plate.

[0008] The target ball group comprises five standard balls. A first standard ball is fixed at the top center of the square block. A second, a third, a fourth and a fifth standard ball are fixed on the bottom plate and respectively located on the four direction extension lines of the bottom surface of the square block. The distances between the second, the third, the fourth and the fifth standard balls and the first standard ball are the same.

[0009] Further, the top plane of the square block is perpendicular to the measurement axis of the three-dimensional measurement system. The angle between the inclined surface of the inclined block and the bottom plate is 45°.

[0010] Further, the standard device further comprises a base, one side of the base is provided with a mounting groove, the test block bottom plate is fixedly connected with a mounting piece below, the test block is clamped in the base mounting groove through the mounting piece; the base and the mounting piece are provided with corresponding limiting holes, and the limiting structure passes through the limiting holes to limit the base and the mounting piece.

[0011] Further, the standard device is made of ceramic material and is an integral molding structure.

[0012] Further, mounting grooves are arranged on the bottom plate and the block, and the standard balls are fixed in the mounting grooves, respectively.

[0013] Further, the diameter of the standard ball is 1-150mm, and the roundness is 0.5-5 microns.

[0014] As another aspect of the present application, a calibration method of an optical three-dimensional measurement system is also provided, comprising the following steps

[0015] Adjusting the optical axis of the three-dimensional measurement system to be perpendicular to the top plane of the block of the standard device, adjusting the focal length of the three-dimensional measurement system to meet the imaging requirements;

[0016] Controlling the three-dimensional measurement system to perform topographic measurement;

[0017] Processing the point cloud data of the five standard balls obtained by measurement to obtain the spherical shape detection error, the spherical size detection error and the center distance measurement value error of the standard device;

[0018] Processing the point cloud data of the top plane of the block and the four inclined surfaces of the inclined blocks obtained by measurement to obtain the plane shape detection error of the standard device.

[0019] Further, the processing of the point cloud data of the five standard balls obtained by measurement to obtain the spherical shape detection error, the spherical size detection error and the center distance measurement value error of the standard device specifically comprises the following steps:

[0020] Calculating the fitting ball of the five standard balls according to the point cloud data;

[0021] Calculating the spherical shape detection error of each fitting ball:

[0022] P Fi =r maxi -r mini

[0023] Wherein, r maxi represents the maximum value of the distance from all points on the i-th fitting ball to the fitting ball center, r mini represents the minimum value of the distance from all points on the i-th fitting ball to the fitting ball center, i represents the serial number of each fitting ball, i=1, 2, …, 5;

[0024] The size detection error of each fitting sphere is calculated:

[0025] P Si = D ai -D r

[0026] wherein D ai represents the diameter of the ith fitting sphere, D r represents the standard sphere diameter reference value;

[0027] The center distance measurement indication error of two adjacent standard spheres is calculated:

[0028] SD j = L aj -L r

[0029] wherein L ai represents the center distance measurement value of the jth group of two adjacent standard spheres, L r is the measured length calibration value, and j represents the serial number of the center distance measurement combination formed by two adjacent standard spheres, j = 1, …, 8;

[0030] The sphere shape detection error is P F = max P Fi |;

[0031] The sphere size detection error is P S = max P Si |;

[0032] The center distance measurement indication error is SD = max SD j |.

[0033] Further, the point cloud data of the top plane of the square block and the four inclined surfaces of the inclined blocks obtained by the measurement is processed to obtain a standard device plane shape detection error, specifically including the following steps:

[0034] The fitting planes of the five planes are calculated according to the point cloud data;

[0035] The plane shape detection error of each fitting plane is calculated:

[0036] F w = L 1w + L 2w

[0037] wherein L 1w is the distance from the farthest point of the first side surface of the wth fitting plane, L 2w is the distance from the farthest point of the second side surface of the wth fitting plane, and w represents the serial number of the five plane measurement positions, w = 1, 2, …, 5;

[0038] The maximum value among the planar shape detection errors of each fitted plane is taken as the planar shape detection error of the standard.

[0039] The beneficial effects of this invention compared to the prior art are as follows:

[0040] I. This invention can provide standard spheres in different spatial positions, sphere center distances in different orientations, and planar shapes in different orientations, ensuring that the calibration requirements of the optical three-dimensional measurement system are met without orientation adjustment.

[0041] Second, the five standard spheres of this invention can form eight combinations. The first, second, third, fourth, and fifth standard spheres can be used independently for measuring the sphere shape detection error. In a plane perpendicular to the measurement axis, the second, third, fourth, and fifth standard spheres can provide combinations of 0 degrees, 90 degrees, and ±45 degrees. The first standard sphere and the other four standard spheres can provide a combination with an angle of 45 degrees to the measurement axis. According to calibration requirements, they can be used to measure the sphere shape size detection error. Attached Figure Description

[0042] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0043] Figure 1 A schematic diagram of the structure of the standard provided in a specific embodiment of the present invention;

[0044] Figure 2 A schematic diagram of the test sample structure provided in a specific embodiment of the present invention;

[0045] Figure 3 A schematic diagram of the connection structure between the test sample and the substrate provided in a specific embodiment of the present invention;

[0046] Figure 4 This is a schematic diagram of the installation structure of the target ball assembly provided in a specific embodiment of the present invention;

[0047] Figure 5 A schematic diagram of the planar shape detection error of the fitting plane provided for a specific embodiment of the present invention;

[0048] Figure 6 A schematic diagram of the structure of the calibration device for the optical three-dimensional measurement system provided in a specific embodiment of the present invention;

[0049] Figure 7This is a schematic diagram of the sphere shape detection error and size detection error test provided for a specific embodiment of the present invention.

[0050] The above figures include the following reference numerals:

[0051] 1. Cooling system; 2. Vacuum pump; 3. Mechanical pump; 4. Vacuum chamber; 5. Standard; 6. Fixing structure; 7. Electron probe system; 8. Electron beam; 9. Infrared thermometer; 10. Projection engine; 11. Filter; 12. Lens; 13. CCD camera; 14. Computer; 15. Lead wire chamber; 100. Substrate; 101. Mounting slot; 102. U-shaped limit bolt; 200. Test sample block; 201. Square block; 202. Inclined block; 203. Base plate; 204. Flat surface; 205. Inclined surface; 206. Mounting slot; 207. Mounting component; 300. Target ball group; 301. First standard ball; 302. Second standard ball; 303. Third standard ball; 304. Fourth standard ball; 305. Fifth standard ball. Detailed Implementation

[0052] Specific embodiments of the present invention will now be described in detail. In the following description, specific details are set forth for purposes of explanation and not limitation, in order to aid in a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced in other embodiments departing from these specific details.

[0053] It should be noted that, in order to avoid obscuring the invention with unnecessary details, only the device structure and / or processing steps closely related to the solution of the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0054] Example 1

[0055] like Figures 1-4As shown, this embodiment provides a standard for an optical three-dimensional measurement system. The standard includes a test block 200 and a target ball group 300. The test block 200 includes a base plate 203, a block 201, and inclined blocks 202. The bottom surface of the block 201 is fixed on the base plate 203. The cross-section of the block 201 is square. Four inclined blocks 202 are fixedly connected to the four sides of the block 201 perpendicular to the base plate 203. The target ball group 300 includes five standard balls. The first standard ball 301 is fixed at the top center of the block 201. The second standard ball 302, the third standard ball 303, the fourth standard ball 304, and the fifth standard ball 305 are fixed on the base plate 203 and are located in the four directions of the two diagonals of the bottom surface of the block 201, respectively. The second, third, fourth, and fifth standard balls are equidistant from the first standard ball 301. This standard is made of high-temperature resistant materials (such as high-temperature resistant ceramics), which can meet the requirements of high-temperature testing environments. At the same time, it can provide standard spheres in different spatial positions, sphere center distances in different orientations, and planar shapes in different orientations, ensuring that the calibration requirements of optical three-dimensional measurement systems are met without orientation adjustments.

[0056] like Figure 2 As shown, the test block 200 includes five planes, four of which are the inclined surfaces 205 of the inclined block 202, and one plane is the top flat surface 204 of the block, which is used to measure the detection error of the plane shape and size during the calibration process.

[0057] In one embodiment, preferably, the flat surface 204 is perpendicular to the measurement axis of the three-dimensional measurement system, and the angle between the inclined surface 205 and the base plate 203 is 45°. This configuration simplifies the algorithm for calculating the surface shape and size detection error. The five standard spheres of this invention can form eight combinations. The first, second, third, fourth, and fifth standard spheres can be used independently for measuring the sphere shape detection error. In a plane perpendicular to the measurement axis, the second, third, fourth, and fifth standard spheres can provide combinations of 0 degrees, 90 degrees, and ±45 degrees. The first standard sphere and the other four standard spheres can provide combinations with an angle of 45 degrees to the measurement axis. These can be used to measure the sphere shape and size detection error according to calibration requirements.

[0058] In one embodiment, to facilitate flexible installation of the test sample 200, the standard also includes a base 100. The base 100 is a flat plate structure with a mounting groove 101 integrally formed on one side. A mounting member 207 is fixedly connected to the side of the test sample 200 base plate 203 away from the block 201. The mounting member 207 engages inside the mounting groove 101 to achieve a fixed connection between the test sample 200 and the base 100. In this embodiment, the mounting groove 101 is an L-shaped groove extending inward along one side of the base 100, and the mounting member 207 is a connecting key with an L-shaped cross-section. This structure allows for quick installation of the mounting member 207 and the mounting groove 101. Preferably, two pairs of through holes are correspondingly provided on the base 100 and the mounting member 207. The two ends of the U-shaped limiting bolt 102 pass through the base 100 and then through the mounting member 207 to achieve limiting of both.

[0059] The first standard sphere 301, the second standard sphere 302, the third standard sphere 303, the fourth standard sphere 304, and the fifth standard sphere 305 are used to measure the error of sphere shape detection, the error of sphere shape size detection, and the error of sphere center distance measurement. They should be fixed in an appropriate way, such as integral molding or embedded fixing, to avoid measurement errors caused by instability.

[0060] In one embodiment, four integrally formed mounting grooves 206 are equidistantly provided on the base plate 203 between the adjacent faces of the four inclined blocks 202. An integrally formed mounting groove 206 is provided at the center of the flat surface 204 of the block 201. The first standard ball 301 is installed in the mounting groove on the flat surface 204. The second standard ball 302, the third standard ball 303, the fourth standard ball 304, and the fifth standard ball 305 are all installed in the mounting grooves 206 on the base plate. The five standard balls are embedded in the mounting grooves, stably connected, and prevent displacement. The first standard ball 301, the second standard ball 302, the third standard ball 303, the fourth standard ball 304, the fifth standard ball 305, and the test sample block 200 are all made of high-temperature resistant ceramic material.

[0061] In one embodiment, the standard is integrally molded from high-temperature resistant ceramic material to ensure structural stability.

[0062] In one embodiment, the diameters of the first, second, third, fourth, and fifth standard spheres are 1-150 mm; the roundness of the first, second, third, fourth, and fifth standard spheres is 0.5-5 micrometers; and the distance between the surface of the second, third, fourth, and fifth standard spheres and the edge of the test sample base plate is 5-25 mm when they are installed.

[0063] Example 2

[0064] The spherical shape detection error P of the three-dimensional measurement system was measured using the standard instrument in Example 1. FSize detection error P S The planar shape detection error F was tested by measuring the target sphere and the plane from different orientations. The point cloud data obtained from the measurements were analyzed and calculated to obtain the sphere shape detection error P of the measurement system. F Size detection error P S And the planar shape detection error F.

[0065] 1. Measure the standard sphere to obtain point cloud data on the surface of the standard sphere, and calculate the obtained point cloud data to obtain the fitted sphere.

[0066] 2. The difference between the maximum and minimum distances from all points to the fitted sphere center is the sphere shape detection error P at that location. Fi :

[0067] P Fi =r maxi -r mini

[0068] Where, r maxi r represents the maximum distance from all points on the fitted sphere at position i to the center of the fitted sphere. mini Let i represent the minimum distance from all points on the fitted sphere at position i to the center of the fitted sphere, where i = 1, 2, ..., 5, and i represents the index of each fitted sphere.

[0069] 3. The diameter D of the fitted sphere ai Compared with the reference value D of the measuring ball diameter r The difference between them is the size detection error P at that location. Si :

[0070] P Si =D ai -D r

[0071] Among them, D ai D represents the diameter of the fitted sphere at the i-th position. r This indicates the reference value for the diameter of a standard sphere.

[0072] 4. Take the largest shape detection error and the largest size detection error among all positions, and use them as the sphere shape detection error P. F and size detection error P S Measurement results:

[0073] P F =maxP Fi

[0074] P S =max(P Si |)

[0075] In the formula: i represents the sequence number of the fitted sphere at each measurement position, i = 1, 2, ..., 5.

[0076] 5. Error of SD in the measurement of the distance between the centers of the sphere j

[0077] The measurement error of the center distance between two adjacent standard spheres is calculated. For five standard spheres within the measurement range of the three-dimensional measurement system, the center positions are fitted using a fixed radius fitting method. Adjacent standard spheres are combined (two standard spheres at different positions can form eight combinations with different spatial orientations; in this embodiment, the first standard sphere forms four center distance combinations with the other four standard spheres, and the second, third, fourth, and fifth standard spheres form four center distance combinations). The measurement error SD of the center distance of any combination is calculated. j SD j =L aj -L r , where L aj L represents the measured distance between the centers of two adjacent standard spheres in the j-th group. r The measured length calibration value (specifically, the actual center distance between two adjacent standard spheres on the standard), j represents the sequence number of the measurement combination formed by the two adjacent standard spheres, j = 1, ..., 8.

[0078] Compare the SD values ​​of the ball center distance measurement for any combination. j The maximum value among them is taken as the measurement error SD of the ball center distance. The measurement error SD of the ball center distance is: SD = maxSD j |, among which, SD j This indicates the error in the measurement of the distance between the centers of the spheres for any combination.

[0079] 6. Planar shape detection error F

[0080] The optical axis of the three-dimensional measurement system is perpendicular to the flat surface 204. It measures the shape of the working surface at different positions on the standard, calculates the point cloud data obtained from each position, and obtains the fitting plane for each position (5 planes).

[0081] like Figure 5 As shown, for the w-th fitting plane, for points distributed on both sides of the fitting plane, the algebraic sum of the distances from the two points with the largest single distance to one side of the fitting plane is selected as the plane shape detection error F at that location. w =L 1w +L 2w L 1w L is the distance from the farthest point on the first side of the w-th fitted plane. 2w is the distance from the farthest point on the second side of the w-th fitted plane, where w represents the index of the five plane measurement positions, w = 1, 2, ..., 5;

[0082] Compare the planar shape detection errors at each location and take the maximum value as the measurement result of the planar shape detection error F; Planar shape detection error F: F = maxF w |, where F w This represents the detection error of the planar shape at any location.

[0083] The test data include the sphere shape detection error PF, the sphere shape size detection error PS, the sphere center distance measurement indication error, and the planar shape size detection error F.

[0084] Example 3

[0085] To meet the requirements of high-temperature testing environments, this embodiment provides a calibration device for an optical three-dimensional measurement system. In conjunction with the standard designed in this invention, it can provide a high-temperature testing environment, avoid the need for standard angle adjustment and replacement, and solve the calibration problem of optical three-dimensional measurement systems in high-temperature testing environments.

[0086] like Figure 6 As shown, the calibration device includes a vacuum chamber 4, a vacuum pump 2, an electron probe system 7, a fixing structure 6, a standard 5, and an infrared thermometer 9. The vacuum pump 2 is connected to the vacuum chamber 4 and is used to adjust the vacuum level of the vacuum chamber. The fixing structure 6 is set inside the vacuum chamber 4 and is used to fix the standard 5. The output end of the electron beam 8 of the electron probe system 7 extends into the vacuum chamber 4 to generate an electron beam, irradiate the standard, and control the surface temperature rise of the standard. The vacuum chamber 4 also includes a first window, a second window, and an opening and closing window for taking out and placing the standard. A camera 13 and a projection optical engine 10 of the three-dimensional measurement system to be calibrated are respectively set outside the first and second windows. The projection optical engine 10 is used to irradiate light onto the standard to enhance the imaging effect. The infrared thermometer is set outside the vacuum chamber and is used to collect the surface temperature of the standard.

[0087] In this embodiment, the electron beam 8 of the electron probe system 7 heats the standard 5 to provide the high-temperature test required for testing. The standard is made of high-temperature resistant material and has standard spheres in different spatial positions, sphere center distances in different orientations, and planar shapes in different orientations, which can effectively meet the high-temperature environment testing requirements of the optical three-dimensional measurement system.

[0088] Furthermore, the electron probe system 7 is mounted above the vacuum chamber 4, the standard 5 is located within the electron beam range, and the first and second windows are positioned on the sides of the vacuum chamber. This configuration ensures that the electron beam irradiation direction is perpendicular to the image acquisition direction of the three-dimensional measurement system, thereby enhancing the image acquisition effect.

[0089] Furthermore, the calibration device also includes a cooling system 1, the cooling channels of which are disposed on the wall of the vacuum chamber to control the wall temperature of the vacuum chamber and prevent the vacuum chamber structure from being damaged at high temperatures.

[0090] Furthermore, the calibration device also includes a mechanical pump 3, which is connected to the vacuum chamber and used to evacuate the vacuum chamber. With this configuration, the mechanical pump can be used to initially evacuate the vacuum chamber, and then the vacuum pump can be used to remove the residual gas to achieve the required vacuum level in the vacuum chamber, thereby improving the evacuation efficiency.

[0091] Furthermore, high-temperature resistant glass is installed in the first and second windows, and an infrared thermometer 9 is set outside the second window; the fixing structure is fixed in the vacuum chamber by a gripping arm, bracket and other structures.

[0092] Furthermore, the calibration device and the three-dimensional topography measurement system to be calibrated are placed in the lead wire chamber 15. The lead wire chamber is used to protect the entire calibration process environment to ensure safety and controllability, and to improve the image acquisition effect.

[0093] Furthermore, the three-dimensional topography measurement system also includes a filter 11 and a computer 14. The filter is set outside the lens of the CCD camera, and the computer receives the images acquired by the three-dimensional topography measurement system.

[0094] In this embodiment, the diameters of the first, second, third, fourth, and fifth standard spheres of the standard device 5 are 80 mm, the roundness of the first, second, third, fourth, and fifth standard spheres is 0.5 micrometers, and the distance between the surface of the second, third, fourth, and fifth standard spheres and the edge of the test sample base plate is 15 mm when they are installed.

[0095] When the optical three-dimensional measurement system calibration device in this embodiment is used, the following steps are included:

[0096] I. According to Figure 6 A calibration device for the optical three-dimensional measurement system (hereinafter referred to as the calibration device) is set up so that the three-dimensional measurement system (hereinafter referred to as the measurement system) faces the test window;

[0097] 2. Place the standard in the fixed structure position inside the device and adjust the orientation of the standard so that the front (flat side) of the standard faces the viewfinder.

[0098] 3. Turn on the power to the measurement system and fine-tune the orientation of the standard according to the imaging situation, ensuring that the front of the standard faces the measurement system. Figure 7 As shown, adjust the focus of the measurement system to ensure that the measurement system can produce clear and stable images;

[0099] 4. Close the calibration device window and power on the calibration device;

[0100] 5. Turn on the vacuum pump of the calibration device to evacuate the interior;

[0101] 6. Turn on the cooling system of the calibration device and turn on the electron beam heating function to heat the standard;

[0102] 7. Use an infrared thermometer to measure the standard. Once the surface temperature of the standard reaches 2000℃, start the three-dimensional morphology measurement test.

[0103] 8. The control and measurement system starts image acquisition, performs morphological measurement on standard spheres at different measurement positions, and simultaneously uses an infrared thermometer to measure the temperature field.

[0104] 9. Generate point clouds based on the measurement results, process the data according to the measurement methods for spherical shape detection error and size detection error, and record the results; process the point cloud data according to the test methods for planar shape detection error, and record the detection error of different orientation planes;

[0105] 10. Turn off the electron beam heating function. After the temperature of the standard returns to room temperature, turn off the vacuum pump to allow the calibration device to return to the atmospheric environment.

[0106] 11. After the test is completed, turn off the power to the calibration device and the measurement system.

[0107] The technical solution of this embodiment can greatly simplify the calibration process. After the standard is debugged, no angle adjustment is required. The temperature of the standard can be flexibly controlled as needed to meet the calibration requirements of various optical three-dimensional measurement systems.

[0108] The features described and / or illustrated above with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, and / or in combination with or in lieu of features in other embodiments.

[0109] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, components, or combinations thereof.

[0110] Many features and advantages of these embodiments are apparent from this detailed description, and therefore the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since many modifications and alterations will readily occur to those skilled in the art, the embodiments of the invention are not intended to be limited to the precise structures and operations illustrated and described, but rather to encompass all suitable modifications and equivalents falling within their scope.

[0111] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0112] The parts of this invention not described in detail are techniques known to those skilled in the art.

Claims

1. A standard for an optical three-dimensional measuring system, characterized in that The application relates to a standard device for calibrating a three-dimensional measurement system, which comprises a test block and a target ball group; the test block comprises a bottom plate, a square block and four inclined blocks; the bottom surface of the square block is fixed on the bottom plate; the cross section of the square block is a square; four inclined blocks are respectively fixed and connected between the four sides of the square block perpendicular to the bottom plate; the target ball group comprises five standard balls; a first standard ball is fixed on the top center of the square block; a second, a third, a fourth and a fifth standard ball are fixed on the bottom plate and are respectively located on the four direction extension lines of the two diagonal lines of the bottom surface of the square block; the distances between the second, the third, the fourth and the fifth standard balls and the first standard ball are the same.

2. The standard according to claim 1, characterized in that The top plane of the square block is perpendicular to the measurement axis of the three-dimensional measurement system; and the angle between the inclined surface of the inclined block and the bottom plate is 45 degrees.

3. The standard according to claim 1, characterized in that The standard device further comprises a base; one side of the base is provided with a mounting groove; a mounting piece is fixedly connected below the bottom plate of the test block; and the test block is clamped in the mounting groove of the base through the mounting piece.

4. A standard according to claim 3, characterised in that The base and the mounting piece are provided with corresponding limiting holes; and a limiting structure passes through the limiting holes to limit the base and the mounting piece.

5. The standard according to claim 1, characterized in that The standard device is made of ceramic material and is an integrally formed structure.

6. The standard according to claim 1, characterized in that Mounting grooves are arranged on the bottom plate and the square block; and the standard balls are respectively fixed in the mounting grooves.

7. The standard according to claim 1, characterized in that The diameter of the standard ball is 1-150 mm, and the roundness is 0.5-5 microns.

8. A method of calibrating an optical three-dimensional measuring system, characterized in that The calibration method comprises the following steps by using the standard device in any one of claims 1-7: The optical axis of the three-dimensional measurement system is adjusted to be perpendicular to the top plane of the square block of the standard device; the focal length of the three-dimensional measurement system is adjusted to meet the imaging requirement; The three-dimensional measurement system is controlled to perform topography measurement; Point cloud data of the five standard balls obtained through measurement are processed to obtain the spherical shape detection error, the spherical size detection error and the center distance measurement value error of the standard device; Point cloud data of the top plane of the square block and the inclined surfaces of the four inclined blocks obtained through measurement are processed to obtain the plane shape detection error of the standard device.

9. The method of calibration of claim 8, wherein, The point cloud data of the five standard balls obtained through measurement are processed to obtain the spherical shape detection error, the spherical size detection error and the center distance measurement value error of the standard device, and the specific steps include the following steps: A fitting sphere of the five standard balls is calculated according to the point cloud data; The spherical shape detection error of each fitting sphere is calculated: P Fi ＝r maxi -r mini wherein r maxi represents the maximum value of the distance from the center of the fitting sphere to all points on the ith fitting sphere, r mini represents the minimum value of the distance from the center of the fitting sphere to all points on the ith fitting sphere, i represents the serial number of each fitting sphere, i = 1, 2, …, 5; The size detection error of each fitting sphere is calculated: P Si = D ai - D r where D ai represents the diameter of the ith fitting sphere, D r represents the standard sphere diameter reference value; The center distance measurement value error of two adjacent standard balls is calculated: SD j = L aj - L r wherein, L ai represents the measured value of the center-to-center distance of the jth group of two adjacent standard spheres, L r is the calibration value of the measured length, and j represents the serial number of the center-to-center distance measurement combination formed by two adjacent standard spheres, j = 1, …, 8. The spherical shape detection error is P F = max P Fi |; The spherical shape size detection error is P S = max P Si |; The spherocenter distance measurement indication error is SD = maxSD j | 10. The method of calibration of claim 8, wherein, The point cloud data of the top plane of the square block and the inclined surfaces of the four inclined blocks obtained through measurement are processed to obtain the plane shape detection error of the standard device, and the specific steps include the following steps: A fitting plane of the five planes is calculated according to the point cloud data; The plane shape detection error of each fitting plane is calculated: F w = L 1w + L 2w wherein L 1w is the distance of the farthest point from the first side of the wth fitting plane, L 2w is the distance of the farthest point from the second side of the wth fitting plane, and w represents the serial number of the five plane measurement positions, w = 1, 2, …, 5. The maximum value in the plane shape detection errors of each fitting plane is taken as the plane shape detection error of the standard device.

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