Precise measurement platform

Abstract

The utility model belongs to the technical field of precision measurement, and discloses a precision measurement platform which comprises a machine table, an XY moving module, a target camera and a coordinate camera, the target camera is installed on the machine table, a calibration plate and a track transmission device are installed at the output end of the XY moving module, and the track transmission device is used for conveying workpieces. The XY moving module is used for driving the calibration plate and the track transmission device to move along the ab direction and the cd direction; the target camera is installed on the machine table, faces the workpiece and is used for obtaining parameter characteristics of the workpiece; the coordinate camera is installed on the machine table, faces the calibration plate and is used for obtaining the coordinate position of the calibration plate. The target camera is adopted to shoot the workpiece and the coordinate camera is adopted to shoot the calibration plate, thereby improving the measurement precision.

Description

Technical Field

[0001] The utility model relates to the technical field of precision measurement, in particular to a precision measurement platform. Background Art

[0002] XY motion platform systems are the foundation of CNC and electronic processing equipment, such as laser processing platforms, surface mount equipment, and 2D measurement equipment. They primarily consist of computers, motion controllers, stepper motors, servo motors, or linear motors, along with related control modules. XY motion platform systems are prone to errors during motion, resulting in a discrepancy between the actual and theoretical coordinate positions. This error is called absolute positioning error. Causes of absolute positioning error include: 1. Motor: Errors inherent in the motor, such as lost steps in stepper motors, which can lead to cumulative errors; 2. Screw: Dimensional errors in the screw; 3. Zeroing error: Errors that occur every time the worktable is zeroed; the theoretical zero position and actual zero position are always different; 4. Assembly error: Assembly errors between the various modules in the XY motion platform; 5. Errors due to geometric tolerances: Direct or indirect errors such as those caused by perpendicularity, straightness, parallelism, and flatness; and 6. Other errors: These include thermal expansion and contraction due to temperature or algorithm errors.

[0003] To address the absolute positioning error in XY motion platform systems, our company has filed a patent application, CN106537269B, titled "A Method, Apparatus, and System for Improving the Accuracy of an XY Motion Platform System." The system uses a preset calibration plate as a reference. While a controlled device on the XY motion platform is in motion, the system simultaneously captures an image of the plate. This image is analyzed to obtain the pixel coordinates of the calibration points within the image. The system then reads the actual coordinates of the calibration points from the plate and calculates the actual position coordinates of the controlled device on the XY motion platform from the actual coordinates and pixel coordinates. The system then adjusts the XY motion platform's motion control system based on the actual position coordinates, controlling the XY motion platform to perform corresponding motion compensation for the controlled device. The system uses the actual position coordinates of the controlled device as feedback information to adjust the XY motion platform's motion control system and compensate for the controlled device's motion. This method, apparatus, and system for improving the accuracy of an XY motion platform system primarily aims to compensate for the controlled device's motion.

[0004] However, the current XY motion platform is not suitable for precise measurement of workpiece parameter characteristics, and cannot decouple the measurement effects caused by the above errors, resulting in insufficient measurement accuracy. Utility Model Content

[0005] The purpose of the utility model is to provide a precision measuring platform, which adopts a target camera to shoot a workpiece and a coordinate camera to shoot a calibration plate, thereby improving measurement accuracy.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] Precision measurement platform, including:

[0008] Machine;

[0009] An XY moving module is installed on the machine platform. A calibration plate and a track transmission device are installed on the output end of the XY moving module. The track transmission device is used to transport the workpiece. The XY moving module is used to drive the calibration plate and the track transmission device to move along the ab direction and the cd direction;

[0010] A target camera is installed on the machine platform, the target camera faces the workpiece, and the target camera is used to obtain parameter characteristics of the workpiece;

[0011] A coordinate camera is installed on the machine platform, the coordinate camera faces the calibration plate, and the coordinate camera is used to obtain the coordinate position of the calibration plate.

[0012] As an optional technical solution, the track transmission device includes:

[0013] A Y-axis moving module is installed at the output end of the XY moving module;

[0014] The X-axis track module includes a first track assembly and a second track assembly arranged in parallel. The first track assembly is installed at the output end of the XY moving module, and the second track assembly is installed at the output end of the Y-axis moving module. The Y-axis moving module is used to drive the second track assembly to approach or move away from the first track assembly along the a′b′ direction. The second track assembly and the first track assembly are used to jointly clamp the workpiece and transport the workpiece along the c′d′ direction.

[0015] As an optional technical solution, a light source board is installed on the XY moving module, and the light source board covers the side of the calibration plate away from the coordinate camera. The target camera and the track transmission device are jointly located on the side of the light source board away from the calibration plate.

[0016] As an optional technical solution, the light source board and the calibration board are spaced apart.

[0017] As an optional technical solution, a fixed plate is installed on the XY moving module, and the edge of the calibration plate is embedded between the fixed plate and the XY moving module. A first buffer pad is provided between the side of the calibration plate facing the target camera and the fixed plate, and a second buffer pad is provided between the side of the calibration plate facing the coordinate camera and the XY moving module.

[0018] As an optional technical solution, the first buffer pad is made of silicone rubber material, and / or the second buffer pad is made of silicone rubber material.

[0019] As an optional technical solution, the fixed plate includes a fixing part and a limiting part. The fixing part is installed on the XY moving module and is located on the outside of the calibration plate. The limiting part is connected to the fixing part and extends to the side of the calibration plate facing the target camera. The first buffer pad is located between the limiting part and the calibration plate.

[0020] As an optional technical solution, a glue injection space is formed between the fixing part and the calibration plate, and the glue injection space is used to accommodate glue. A glue injection groove connected to the glue injection space is opened on the fixing plate, and the glue is injected into the glue injection space from the glue injection groove.

[0021] As an optional technical solution, a plurality of the glue injection grooves are provided on the fixing plate, and the plurality of the glue injection grooves are spaced apart along the length direction of the glue injection space.

[0022] As an optional technical solution, the XY moving module includes a supporting plate, the supporting plate is provided with an avoidance opening, the edge of the calibration plate is fixedly connected to the supporting plate, and the avoidance opening is located on the calibration plate facing the coordinate camera.

[0023] Beneficial effects of the utility model:

[0024] The precision measurement platform provided by the utility model includes a machine platform, an XY moving module, a target camera and a coordinate camera. The target camera is installed on the machine platform. A calibration plate and a track transmission device are installed on the output end of the XY moving module. The track transmission device is used to transport the workpiece. The XY moving module is used to drive the calibration plate and the track transmission device to move along the ab direction and the cd direction; the target camera is installed on the machine platform, the target camera faces the workpiece, and the target camera is used to obtain the parameter characteristics of the workpiece; the coordinate camera is installed on the machine platform, the coordinate camera faces the calibration plate, and the coordinate camera is used to obtain the coordinate position of the calibration plate.

[0025] When the precision measurement platform measures the workpiece, it uses the target camera to shoot the workpiece, obtains the parameter characteristics of the workpiece, calculates the feature center of the workpiece, uses the coordinate camera to shoot the calibration plate, obtains the coordinate position of the calibration plate, and performs algorithm calculations based on the image data obtained by the target camera and the coordinate camera to obtain the parameter characteristic deviation value of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of the precision measurement platform of the utility model from a first perspective;

[0027] Figure 2This is a top view of the precision measuring platform of the utility model;

[0028] Figure 3 yes Figure 2 Cross-sectional view of section AA;

[0029] Figure 4 yes Figure 3 A partial enlarged view of position B in the middle;

[0030] Figure 5 yes Figure 4 A partial enlarged view of the middle C position;

[0031] Figure 6 It is a structural schematic diagram of the load-bearing plate of the utility model;

[0032] Figure 7 It is a structural schematic diagram of the fixing plate of the present utility model.

[0033] In the picture:

[0034] 1. Machine;

[0035] 2. XY moving module; 21. Carrying plate; 211. Avoidance opening; 212. First step; 213. Second step;

[0036] 3. Calibration plate;

[0037] 4. Track transmission device; 41. Y-axis moving module; 42. X-axis track module; 421. First track assembly; 422. Second track assembly;

[0038] 51. Target camera; 52. Coordinate camera;

[0039] 6. Light source board;

[0040] 7. Fixed plate; 71. Fixed portion; 72. Limiting portion; 73. Glue injection groove;

[0041] 8. First cushion;

[0042] 9. Second cushion;

[0043] 10. Glue injection space. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all of its components.

[0045] In the description of this utility model, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0046] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0047] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0048] like Figures 1 to 7 As shown, this embodiment provides a precision measurement platform, which includes a machine 1, an XY moving module 2, a calibration plate 3, a track transmission device 4, a target camera 51 and a coordinate camera 52; the XY moving module 2 is installed on the machine 1, the calibration plate 3 and the track transmission device 4 are installed at the output end of the XY moving module 2, the track transmission device 4 is used to transport the workpiece, and the XY moving module 2 is used to drive the calibration plate 3 and the track transmission device 4 to move along the ab direction and the cd direction; the target camera 51 is installed on the machine 1, the target camera 51 faces the workpiece, and the target camera 51 is used to obtain the parameter characteristics of the workpiece; the coordinate camera 52 is installed on the machine 1, the coordinate camera 52 faces the calibration plate 3, and the coordinate camera 52 is used to obtain the coordinate position of the calibration plate 3.

[0049] The target camera 51 and the coordinate camera 52 are both electrically connected to the computer control system. When the precision measuring platform measures the workpiece, the coordinate camera 52 shoots the calibration plate 3 and sends the image information to the computer control system. The computer control system uses the actual coordinate position of the calibration plate 3 as the reference coordinate, thereby establishing an absolute coordinate system. The target camera 51 shoots the workpiece and sends the image information to the computer control system. The computer control system performs algorithm calculations based on the reference coordinates and the actual parameter characteristics of the workpiece photographed by the target camera 51, thereby obtaining the parameter characteristic deviation value of the workpiece, and can accurately measure the difference between the theoretical parameter characteristics of the workpiece and the actual parameter characteristics of the workpiece.

[0050] The calibration plate 3 and the track transmission device 4 are installed at the output end of the XY moving module 2, so that the calibration plate 3 and the track transmission device 4 can be moved and adjusted along the ab direction and the cd direction. It can be applied to measure workpieces of different shapes and sizes and has a wide range of applications.

[0051] The XY moving module 2 has an absolute positioning error. When the XY moving module 2 moves along the ab direction and the cd direction to adjust the position of the calibration plate 3, the actual coordinate position of the calibration plate 3 is affected by the absolute positioning error of the XY moving module 2. There is an error between the actual coordinate position of the calibration plate 3 and the theoretical coordinate position. However, the information fed back by the coordinate camera 52 to the computer control system is always the actual coordinate position of the calibration plate 3. The computer control system always uses the actual coordinate position of the calibration plate 3 as the reference coordinate. The absolute positioning error of the XY moving module 2 does not affect the computer control system's acquisition of the reference coordinate, and the absolute coordinate system is not affected.

[0052] Similarly, there is also an installation error of the coordinate camera 52 on the machine platform 1. However, the installation error of the coordinate camera 52 does not affect the acquisition of the reference coordinates by the computer control system, and does not affect the measurement accuracy after calibration.

[0053] The number of coordinate cameras 52 can be set according to actual needs, such as one group, two groups, or even more groups, to collect data from the calibration plate 3 and compensate for coordinate position errors.

[0054] The track transmission device 4 has an absolute positioning error. When the track transmission device 4 moves along the ab direction and the cd direction to adjust the position of the workpiece, the actual coordinate position of the workpiece is affected by the absolute positioning error of the track transmission device 4. There is an error between the actual coordinate position of the workpiece and the theoretical coordinate position. However, the information fed back by the target camera 51 to the computer control system is always the actual parameter characteristics of the workpiece. The computer control system always performs calculations based on the actual parameter characteristics of the workpiece. The absolute positioning error of the track transmission device 4 does not affect the computer control system's calculation of the actual parameter characteristics of the workpiece.

[0055] Similarly, there is also an installation error of the target camera 51 on the machine 1. However, the installation error of the target camera 51 does not affect the calculation of the actual parameter characteristics of the workpiece by the computer control system, and does not affect the measurement accuracy after calibration.

[0056] Optionally, the target camera 51 is a 2D industrial camera or a 3D industrial camera or other machine vision camera. Different types of cameras can achieve corresponding detection or measurement purposes.

[0057] Optionally, the track transmission device 4 includes a Y-axis moving module 41 and an X-axis track module 42. The Y-axis moving module 41 is installed at the output end of the XY moving module 2. The X-axis track module 42 includes a first track assembly 421 and a second track assembly 422 arranged in parallel. The first track assembly 421 is installed at the output end of the XY moving module 2, and the second track assembly 422 is installed at the output end of the Y-axis moving module 41. The Y-axis moving module 41 is used to drive the second track assembly 422 to approach or move away from the first track assembly 421 along the a′b′ direction. The second track assembly 422 and the first track assembly 421 are used to jointly clamp the workpiece and transport the workpiece along the c′d′ direction. The a′b′ direction tends to be parallel to the ab direction, and the c′d′ direction tends to be parallel to the cd direction.

[0058] The workpiece can be placed directly on the track transmission device 4, or the workpiece can be placed on a pallet and then the pallet is placed on the track transmission device 4. The track transmission device 4 clamps the pallet. Taking the optical lens as an example of the workpiece, the structural parameters of the optical lens need to be tested after assembly. Multiple optical lenses are placed on the pallet. Since different manufacturers have different production needs, the sizes of the pallets are different. When the number of optical lenses to be supported is large, the size of the pallet is larger. When the number of optical lenses to be supported is small, the size of the pallet is smaller. Therefore, this embodiment uses the Y-axis moving module 41 to adjust the second track component 422 to the first track component 421, so that the interval value between the second track component 422 and the first track component 421 meets the matching requirements with the size value of the pallet. After all the optical lenses on the pallet have been inspected, the second track component 422 and the first track component 421 jointly transport the pallet to the next workstation.

[0059] The workpiece may also be other products, such as a circuit board, etc. The circuit board may be directly placed on the track transmission device 4 , and the target camera 51 may be used to detect the structural parameters of the circuit board.

[0060] In some other embodiments, the track transmission device 4 is a clamping claw structure.

[0061] In this embodiment, the Y-axis moving module 41 and the first track assembly 421 are both mounted on the carrier plate 21 , and the second track assembly 422 is mounted on the ball screw of the Y-axis moving module 41 .

[0062] Optionally, a light source board 6 is installed on the XY moving module 2 , and the light source board 6 covers the side of the calibration plate 3 away from the coordinate camera 52 , and the target camera 51 and the track transmission device 4 are located together on the side of the light source board 6 away from the calibration plate 3 .

[0063] The light source board 6 covers the side of the calibration plate 3 facing away from the coordinate camera 52 to prevent the light source board 6 from blocking the coordinate camera 52 from photographing the calibration plate 3; the light source board 6 can increase the shooting brightness, so that the target camera 51 can clearly photograph the workpiece of the track transmission device 4 and the coordinate camera 52 can clearly photograph the calibration plate 3.

[0064] Optionally, the light source board 6 is spaced apart from the calibration board 3. The calibration board 3 is expensive and has a high level of protection. It is necessary to prevent the light source board 6 from touching the calibration board 3 and to prevent the heat of the light source board 6 from being directly transferred to the calibration board 3.

[0065] Optionally, a fixed plate 7 is installed on the XY moving module 2, and the edge of the calibration plate 3 is embedded between the fixed plate 7 and the XY moving module 2. A first buffer pad 8 is provided between the side of the calibration plate 3 facing the target camera 51 and the fixed plate 7, and a second buffer pad 9 is provided between the side of the calibration plate 3 facing the coordinate camera 52 and the XY moving module 2.

[0066] In this embodiment, a first buffer pad 8 and a second buffer pad 9 are respectively provided on both sides of the calibration plate 3 to prevent the calibration plate 3 from being crushed. The friction coefficient of the buffer pad is relatively high, and the calibration plate 3 is squeezed by the buffer pad, resulting in a large friction resistance, which can prevent the calibration plate 3 from slipping.

[0067] In this embodiment, a fixing plate 7 , a first buffer pad 8 and a second buffer pad 9 are provided around the periphery of the calibration plate 3 .

[0068] Optionally, the first buffer pad 8 is made of silicone rubber material, and / or the second buffer pad 9 is made of silicone rubber material.

[0069] Optionally, the fixing plate 7 includes a fixing portion 71 and a limiting portion 72. The fixing portion 71 is mounted on the XY movable module 2 and is located outside the calibration plate 3. The limiting portion 72 is connected to the fixing portion 71 and extends to the side of the calibration plate 3 facing the target camera 51. The first buffer pad 8 is located between the limiting portion 72 and the calibration plate 3. The limiting portion 72 limits the position of the first buffer pad 8 and the calibration plate 3. The fixing portion 71 is fixed to the supporting plate 21 using threaded fasteners.

[0070] Optionally, a glue injection space 10 is formed between the fixing portion 71 and the calibration plate 3 , and the glue injection space 10 is used to accommodate glue. A glue injection groove 73 connected to the glue injection space 10 is opened on the fixing plate 7 , and glue is injected into the glue injection space 10 from the glue injection groove 73 .

[0071] The glue solidifies in the glue injection space 10 to form an elastic body with a hardness of HRC60, which fixes and limits the calibration plate 3. When the ambient temperature changes, the calibration plate 3 expands and contracts, and the elastic body plays a buffering role.

[0072] Optionally, a plurality of glue injection grooves 73 are provided on the fixing plate 7, and the plurality of glue injection grooves 73 are spaced apart along the length direction of the glue injection space 10. Each glue injection groove 73 can be injected with glue, thereby increasing the glue injection speed and preventing the glue injection space 10 from being hollowed out at a certain position.

[0073] Optionally, the XY moving module 2 includes a supporting plate 21 , which is provided with an avoidance opening 211 , and the edge of the calibration plate 3 is fixedly connected to the supporting plate 21 . The avoidance opening 211 is located on the calibration plate 3 facing the coordinate camera 52 for heat dissipation.

[0074] Specifically, the avoidance opening 211 is set in the middle of the carrying plate 21, and the edge position of the avoidance opening 211 is set as a two-stage step structure. When installing the calibration plate 3, first place the second buffer pad 9 on the top surface of the first step 212, then place the calibration plate 3 on the second buffer pad 9, and then place the first buffer pad 8 on the top surface of the calibration plate 3, and then place the fixing plate 7 on the top surface of the first step 212. At this time, the fixing portion 71 is located on the outer layer of the calibration plate 3 and abuts against the first step 212. The top surface of the step 212, the limiting part 72 abuts against the top surface of the first buffer pad 8, and a threaded fastener is used to pass through the fixing part 71 and the first step 212 to lock the fixing part 71 to the top surface of the first step 212. At this time, the limiting part 72 presses the first buffer pad 8, the calibration plate 3 and the second buffer pad 9, and glue is injected into multiple glue injection grooves 73. The glue flows into the glue injection space 10, and then the light source board 6 is installed on the top surface of the secondary step 213. The light source board 6 does not contact the fixing plate 7.

[0075] Obviously, the above-described embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the manner in which the present invention is to be implemented. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. Precision measuring platform, characterized by: include: Machine (1); An XY moving module (2) is installed on the machine platform (1); a calibration plate (3) and a track transmission device (4) are installed on the output end of the XY moving module (2); the track transmission device (4) is used to transport workpieces; and the XY moving module (2) is used to drive the calibration plate (3) and the track transmission device (4) to move along the ab direction and the cd direction; A target camera (51) is installed on the machine platform (1), the target camera (51) faces the workpiece, and the target camera (51) is used to obtain parameter characteristics of the workpiece; A coordinate camera (52) is installed on the machine platform (1), the coordinate camera (52) faces the calibration plate (3), and the coordinate camera (52) is used to obtain the coordinate position of the calibration plate (3).

2. The precision measurement platform according to claim 1, characterized in that: The track transmission device (4) comprises: A Y-axis moving module (41) is installed at the output end of the XY moving module (2); The X-axis track module (42) comprises a first track component (421) and a second track component (422) arranged in parallel, wherein the first track component (421) is installed at the output end of the XY moving module (2), and the second track component (422) is installed at the output end of the Y-axis moving module (41), and the Y-axis moving module (41) is used to drive the second track component (422) to approach or move away from the first track component (421) along the a′b′ direction, and the second track component (422) and the first track component (421) are used to jointly clamp the workpiece and transport the workpiece along the c′d′ direction.

3. The precision measurement platform according to claim 1, characterized in that: A light source board (6) is installed on the XY moving module (2), and the light source board (6) covers the side of the calibration board (3) facing away from the coordinate camera (52), and the target camera (51) and the track transmission device (4) are located together on the side of the light source board (6) facing away from the calibration board (3).

4. The precision measurement platform according to claim 3, characterized in that: The light source plate (6) and the calibration plate (3) are spaced apart.

5. The precision measuring platform according to any one of claims 1 to 4, characterized in that: A fixed plate (7) is mounted on the XY moving module (2); an edge of the calibration plate (3) is embedded between the fixed plate (7) and the XY moving module (2); a first buffer pad (8) is provided between the side of the calibration plate (3) facing the target camera (51) and the fixed plate (7); and a second buffer pad (9) is provided between the side of the calibration plate (3) facing the coordinate camera (52) and the XY moving module (2).

6. The precision measurement platform according to claim 5, characterized in that: The material of the first buffer pad (8) is a silicone rubber material, and / or the material of the second buffer pad (9) is a silicone rubber material.

7. The precision measurement platform according to claim 5, characterized in that: The fixing plate (7) comprises a fixing portion (71) and a limiting portion (72), wherein the fixing portion (71) is mounted on the XY moving module (2) and is located outside the calibration plate (3), and the limiting portion (72) is connected to the fixing portion (71) and extends to a side of the calibration plate (3) facing the target camera (51), and the first buffer pad (8) is located between the limiting portion (72) and the calibration plate (3).

8. The precision measuring platform according to claim 7, characterized in that: A glue injection space (10) is formed between the fixing portion (71) and the calibration plate (3), and the glue injection space (10) is used to accommodate glue. A glue injection groove (73) communicating with the glue injection space (10) is provided on the fixing plate (7), and the glue is injected into the glue injection space (10) from the glue injection groove (73).

9. The precision measurement platform according to claim 8, characterized in that: The fixing plate (7) is provided with a plurality of the glue injection grooves (73), and the plurality of the glue injection grooves (73) are arranged at intervals along the length direction of the glue injection space (10).

10. The precision measuring platform according to any one of claims 1 to 4, characterized in that: The XY moving module (2) comprises a carrier plate (21), the carrier plate (21) is provided with an avoidance opening (211), the edge of the calibration plate (3) is fixedly connected to the carrier plate (21), and the avoidance opening (211) is located on the calibration plate (3) facing the coordinate camera (52).

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