A handheld laser scanner calibration device

Abstract

This utility model relates to the technical field of calibration devices for large-size measuring instruments, and discloses a handheld laser scanner calibration device, including a first reference unit. The first reference unit includes a base, a support column fixedly connected to the base, and four connecting arms arranged in a cross shape on the support column. The inner ends of the four connecting arms are fixedly connected to the top of the support column, and the outer ends of two opposite connecting arms are fixedly connected to spherical targets, while the outer ends of the other two opposite connecting arms are connected to planar targets. This utility model further expands the calibration dimension, making it possible to evaluate planar and angular errors in different poses in three-dimensional space, and realistically reproduces the actual use scenario of a handheld laser scanner.

Description

Technical Field

[0001] This utility model relates to the technical field of calibration devices for large-size measuring instruments, and in particular to a handheld laser scanner calibration device. Background Technology

[0002] Handheld laser scanners mainly consist of a laser emitter, optical sensor, positioning and tracking system, software system, and accessories. They are portable measuring instruments that utilize laser technology to quickly and non-contactly acquire the three-dimensional geometry of the surface of the object being measured, generating high-precision point cloud data or mesh models. Primarily used in manufacturing and industry, automotive and transportation, cultural heritage and art, and medical and rehabilitation fields, they have become key instruments in Industry 4.0, digital twins, and the metaverse, with their application scenarios still rapidly expanding, especially in the fields of automated inspection and AI-driven analysis. To ensure the accuracy and reliability of handheld laser scanners, according to the National Metrological Technical Specification of the People's Republic of China JJF1951-2021 "Calibration Specification for Optical Three-Dimensional Measurement Systems Based on Structured Light Scanning," periodic calibration of handheld laser scanners is required within the recalibration interval.

[0003] In existing technologies, the calibration of distance measurement indication errors for handheld laser scanners typically only evaluates the standard fixed distance between the centers of two spheres in a two-dimensional plane. This results in drawbacks such as limited geometric feature elements, unadjustable standard distance, and a single spatial dimension. Similarly, the calibration of geometric shape detection errors typically only evaluates spherical shape detection errors, planar shape detection errors, and sphere size detection errors. This also results in limited geometric feature elements and an inability to reproduce the actual usage conditions of the handheld laser scanner.

[0004] Patent CN118857104A discloses a mobile 3D laser scanner calibration device, including an instrument mounting platform and a heavy-duty support. The instrument mounting platform has a mounting bracket on top, from which a testing instrument is mounted. This mobile 3D laser scanner calibration device and method, by adjusting structures such as the balance bar, electric telescopic bar, crossbar, and support plate while keeping the calibration platform in place, allows for rapid movement of the testing target assembly to multiple different coordinate positions within a small area around the calibration platform. The heavy-duty support can be moved over a wide range using lifting casters, facilitating the setup of multiple calibration devices. However, because it calibrates the 3D laser scanner using only a pair of target balls, its spatial dimension and geometric features are limited, and it differs significantly from the actual usage of a handheld laser scanner. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a handheld laser scanner calibration device to overcome the shortcomings of current handheld laser scanner calibration, which has the disadvantage of having only one geometric feature element and being unable to reproduce the actual use state of the handheld laser scanner.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0007] A handheld laser scanner calibration device includes a first reference unit. The first reference unit includes a base, a support column fixedly connected to the base, and four connecting arms arranged in a cross shape on the support column. The inner ends of the four connecting arms are fixedly connected to the top of the support column, and the outer ends of two opposite connecting arms are fixedly connected to spherical targets, while the outer ends of the other two opposite connecting arms are connected to planar targets.

[0008] Furthermore, the connecting arm is telescopic, and the planar targets are omnidirectionally connected to the corresponding connecting arms.

[0009] Furthermore, the support column includes a column whose bottom end is fixedly connected to the base and an installation section that is universally connected to the top of the column, with the inner ends of the four connecting arms respectively fixedly connected to the installation section.

[0010] Furthermore, it also includes a second reference unit located next to the first reference unit. The second reference unit includes a bracket and at least one of a standard planar body, a polyhedron, or a variable angle reference mechanism that is universally connected to the top of the bracket.

[0011] Furthermore, the variable angle reference mechanism includes a mounting plate and two standard planar bodies hinged together in a U-shape. The mounting plate is universally connected to the top of the bracket. Both standard planar bodies are perpendicular to the mounting plate. One standard planar body is fixedly connected to the mounting plate, and the other standard planar body has a lug fixedly connected to it. The mounting plate has an arc-shaped sliding groove. The hinge axis of the two standard planar bodies passes through the center of the sliding groove. A screw is inserted through the lug and passes through the sliding groove. The lug has a hole for the screw to pass through. A wing nut is screwed onto the screw. After tightening the wing nut, the included angle between the two standard planar bodies is locked.

[0012] Furthermore, it also includes a fixed slide rail and a slide table slidably connected to the top of the slide rail. The first reference unit is located on one side of the slide rail, and a robotic arm is mounted on the slide table. The handheld laser scanner to be calibrated is gripped by the hand of the robotic arm.

[0013] Furthermore, it also includes a third reference unit located next to the first reference unit, wherein the third reference unit is at least one of a cube standard block, a cuboid standard block, a cylinder standard block, a hemispherical standard block, a right-angled standard block, a grooved standard block, and a stepped high standard block.

[0014] The positive effects of this utility model are:

[0015] This invention integrates various geometric features such as cubes, cuboids, cylinders, hemispheres, right angles, groove depths, and step heights through a multi-parameter geometric layout, overcoming the limitations of existing technologies that can only calibrate standard spheres and standard planes, and achieving a more comprehensive evaluation of geometric shape detection errors. The first reference unit and the variable angle reference mechanism further expand the calibration dimension, making it possible to evaluate planar and angular errors in different poses within three-dimensional space, realistically replicating the actual usage scenario of a handheld laser scanner. The multi-parameter spatial distance standard device, through the cooperation of a universal ball head, a retractable connecting arm, and a retractable column, can freely adjust the center-to-center distance between spherical targets, the plane distance between planar targets, and the distance between spherical and planar targets in three-dimensional space, achieving customized calibration of standard distances. The slide rail 11 uses high-precision grade 0 marble, combined with a center-to-center distance error of ±0.0006mm between spherical targets and a flatness error of ≤0.012mm for planar targets, ensuring the accuracy of calibration. The movements of the robotic arm and the slide table simulate the movements of a human arm, automating the calibration process and significantly improving calibration efficiency. This invention provides a one-stop solution to the shortcomings of traditional calibration devices, such as single geometric features, fixed standard distances, and limited spatial dimensions. It features easy operation, wide applicability, high accuracy, and a high degree of automation. It improves the traceability chain of handheld laser scanners, enhances the accuracy of traceability, increases the efficiency of calibration work, reduces the workload of calibration personnel, and provides a more scientific and comprehensive calibration solution for handheld laser scanners. Attached Figure Description

[0016] Figure 1 This is the front view of the first standard unit;

[0017] Figure 2 yes Figure 1 Top view;

[0018] Figure 3 This is a diagram illustrating the use of this utility model;

[0019] Figure 4 This is a top view of the variable angle reference mechanism;

[0020] Figure 5 This is a schematic diagram of the third reference unit;

[0021] In the picture:

[0022] 1. Bracket; 2. Standard planar block; 3. Universal ball head; 4. Polyhedron; 5. Spherical target; 6. Planar target; 7. Connecting arm; 8. Handheld laser scanner; 9. Robotic arm; 10. Slide table; 11. Slide rail; 12. Column; 13. Base; 14. Mounting plate; 15. Slide groove; 16. Wing nut; 17. Lug; 18. Cube standard block; 19. Cuboid standard block; 20. Cylinder standard block; 21. Hemispherical standard block; 22. Groove standard block; 23. Stepped standard block; 24. Right-angled standard block; 25. Mounting section; 26. Support column. Detailed Implementation

[0023] Example 1

[0024] like Figures 1 to 3 As shown, a handheld laser scanner calibration device includes a first reference unit. The first reference unit includes a base 13, a vertical support column 26 fixedly connected to the base 13, and four connecting arms 7 arranged in a cross shape on the support column 26. The inner ends of the four connecting arms 7 are fixedly connected to the top of the support column 26, and the outer ends of two opposite connecting arms 7 are fixedly connected to spherical targets 5. The two spherical targets 5 are symmetrically arranged on both sides of the support column 26. The outer ends of the other two opposite connecting arms 7 are connected to planar targets 6. The two planar targets 6 are symmetrically arranged on both sides of the connecting arms 7.

[0025] The connecting arm 7 is a telescopic rod, and the planar target 6 is connected to the corresponding connecting arm 7 via a universal ball head 3.

[0026] The support column 26 includes a column 12 whose bottom end is fixedly connected to the base 13, and a rectangular mounting section 25 that is omnidirectionally connected to the top of the column 12 via an omnidirectional ball head 3. The inner ends of the four connecting arms 7 are fixedly connected to the mounting section 25 respectively. The column 12 is an electrically telescopic rod used to adjust the height of the spherical target 5 and the planar target 6.

[0027] The base 13 is supported on the ground by three screws arranged in an equilateral triangle through its bottom. A slide rail 11 fixed to the ground and a slide platform 10 slidably connected to the top of the slide rail 11 are provided beside the column 12. The slide platform 10 is an air-bearing slide platform, and the slide rail 11 is made of grade 0 marble. The first reference unit is located beside the robotic arm 9, and the robotic arm 9 is mounted on the slide platform 10. The handheld laser scanner 8 to be calibrated is gripped by the hand of the robotic arm 9.

[0028] The working process of this utility model is as follows:

[0029] 1. Adjust the position and orientation of the two spherical targets 5 and the two planar targets 6;

[0030] 2. Using the laser tracker standard, measure each spherical target 5 and planar target 6 in sequence to obtain the standard value of the distance between the centers of the two spherical targets 5, the standard value of the distance between the center of the spherical target 5 and the planar target 6, and the standard value of the distance between the two planar targets 6 (the two planar targets 6 are parallel). The use and measurement method of the laser tracker standard are existing technologies and will not be described in detail here.

[0031] 3. The slide table 10 moves longitudinally on the slide rail 11, and the robotic arm 9 drives the handheld laser scanner 8 to scan the spherical target 5 and the planar target 6 to obtain the measured distance between the centers of the two spherical targets 5, the measured distance between the center of the spherical target 5 and the planar target 6, and the measured distance between the two planar targets 6 (the two planar targets 6 are parallel).

[0032] 4. Based on the above measured distance and standard value, the error value is calculated, and the handheld laser scanner 8 is calibrated accordingly. The specific calculation methods are all existing technologies and will not be elaborated here.

[0033] The robotic arm 9 can simulate human arm movements to drive the handheld laser scanner 8, thus better matching the on-site usage conditions of the handheld laser scanner 8. By changing the extension length of the connecting arm 7, the distance between the two spherical targets 5 and the distance between the two planar targets 6 can be changed. The angle of the planar target 6 can be changed by the universal ball head 3 between the connecting arm 7 and the planar target 6. The angle of the mounting section 25 can be changed by the universal ball head 3. The position of the handheld laser scanner 8 under test can be changed by the moving slide 10. This allows for rapid adjustment of the coordinate positions of the spherical targets 5 and the planar targets 6, followed by measurement of the error value changes under different coordinates. Multiple sets of data can be compared and analyzed, making the calibration of the handheld laser scanner 8 more accurate.

[0034] Example 2

[0035] Combination Figure 4 As shown, the difference between this embodiment and Embodiment 1 is that:

[0036] This utility model also includes a second reference unit, which includes three supports 1 placed sequentially beside the slide rail 11, and a standard planar body 2, a polyhedron 4, and a variable angle reference mechanism that are omnidirectionally connected to the top of the three supports 1 by an omnidirectional ball head 3.

[0037] The variable angle reference mechanism includes a fan-shaped mounting plate 14 and two standard plane bodies 2 hinged together in a Λ shape. The bottom of the mounting plate 14 is omnidirectionally connected to the top of the bracket 1 via a universal ball head 3. Both standard plane bodies 2 are perpendicular to the mounting plate 14. The left standard plane body 2 is fixedly connected to the mounting plate 14, and the right standard plane body 2 has a lug 17 fixedly connected to its inner side. The mounting plate 14 has an arc-shaped groove 15 at a position corresponding to the lug 17. The hinge axis of the two standard plane bodies 2 passes through the center of the groove 15. A screw is inserted through the lug 17 and passes through the groove 15. The lug 17 has a hole for the screw to pass through. A wing nut 16 is screwed onto the screw. After tightening the wing nut 16, the lug 17 is pressed against the mounting plate 14, thereby locking the included angle between the two standard plane bodies 2.

[0038] The standard planar body 2 and polyhedron 4 in the second reference unit can be arbitrarily combined with the spherical target 5 and planar target 6 in the first reference unit, thereby better conforming to the actual use state of the handheld laser scanner 8 and making the calibration of the handheld laser scanner 8 more accurate.

[0039] Example 3

[0040] Combination Figure 5 As shown, the present invention also includes a third reference unit placed next to the slide rail 11. The third reference unit includes a cube standard block 18, a cuboid standard block 19, a cylinder standard block 20, a hemispherical standard block 21, a right-angled standard block 24, a grooved standard block 22, and a stepped height standard block 23.

[0041] For the calibration of geometric shape detection error, the slide table 10 moves to drive the handheld laser scanner 8 and collect spatial point cloud information of different geometric feature elements in the third reference unit in the two-dimensional plane. The cube, cuboid, cylinder, hemisphere, right-angled prism, groove depth, and step height are reconstructed in reverse order, and their geometric shape detection error is evaluated.

[0042] Taking the sphere shape detection error as an example (such as detecting a standard hemispherical block 21), the point cloud at each measurement position is calculated to obtain the fitted sphere. The difference between the maximum and minimum distances from all points to the center of the fitted sphere is the sphere shape detection error PFi at that position.

[0043] Next, the handheld laser scanner 8 to be inspected is moved to the second reference unit. The two planar targets 6 of the first reference unit generate standard planes under different spatial poses. The two standard plane bodies 2 of the variable angle reference mechanism of the second reference unit generate different angles under different spatial poses. The handheld laser scanner 8 collects spatial point cloud information of different geometric feature elements in three-dimensional space, and reversely reconstructs the standard planes and standard angles, and evaluates its geometric shape detection error.

[0044] Taking planar shape detection error as an example, the planar target 6 generates at least 6 different poses in the scanning space, and the point cloud data of the standard planar working surface is obtained by scanning. The best fitting plane is calculated for each scanning direction. The algebraic sum of the maximum distances from the points distributed on both sides of the fitting plane to one side of the fitting plane is used as the planar shape detection error Fi, where i is the sequence number of the scanning position. The maximum value among all positions is taken as the measurement result of the planar shape detection error F.

[0045] For the calibration of spatial distance indication error, the handheld laser scanner 8 is moved by the slide table 10, and the standard center distance between two spherical targets 5 and the standard plane distance between two planar targets 6 can be generated by the extension and retraction of the column 12 and the universal ball head 3 on it.

[0046] Simultaneously, the standard length of the distance between the centers of the two spherical targets 5 and the plane distance between the two planar targets 6 can be adjusted by utilizing the telescopic changes of the connecting arm 7. Furthermore, by adjusting the gimbal 3 at the planar target 6 to be perpendicular to the spherical target 6, the standard distance between the center of the sphere and the plane (i.e., the distance from the center of the spherical target 6 to the planar target 6) can be generated. A handheld laser scanner 8 acquires spatial point cloud information of the spherical target 6 and the planar target 6 in different poses within three-dimensional space, reconstructs the standard sphere and standard plane in reverse, and evaluates the measurement errors of the distance between the centers of the two spherical targets 6, the distance between the center of the spherical target 6 and the planar target 6, and the distance between the two planar targets 6.

[0047] Taking the center-to-center distance measurement error as an example, the center-to-center distance between the two spherical targets 6 will generate at least 7 different positions in the scanning space. For all measurement positions, the fixed radius fitting method is used to fit all the center positions, and the center-to-center distance between the two spherical targets 6 at each position is calculated. The center-to-center distance measurement error SDi is the difference between the measured value Lai and the calibrated value Lr of the measured length. The one with the largest absolute value among all positions is taken as the measurement result of the center-to-center distance measurement error SD, where i is the sequence number of the scanning position.

[0048] The above-described embodiments are detailed and specific, illustrating preferred embodiments of the present utility model. They are only used to illustrate the technical ideas and features of the present utility model, with the aim of enabling those skilled in the art to understand the content of the present utility model and implement it accordingly. However, they are not limited to the present utility model, and the patent scope of the present utility model cannot be limited by this embodiment alone. That is, any equivalent changes or modifications made to the spirit disclosed in the present utility model, without departing from the structure of the present utility model, such as local improvements within the system and modifications or transformations between subsystems, are still within the patent scope of the present utility model.

Claims

1. A handheld laser scanner calibration device, characterized in that, The first reference unit includes a base (13), a support column (26) fixedly connected to the base (13), and four connecting arms (7) arranged in a cross shape on the support column (26). The inner ends of the four connecting arms (7) are fixedly connected to the top of the support column (26), and the outer ends of two opposite connecting arms (7) are fixedly connected to spherical targets (5), and the outer ends of the other two opposite connecting arms (7) are connected to planar targets (6).

2. The handheld laser scanner calibration device according to claim 1, characterized in that, The connecting arm (7) is telescopic, and the planar target (6) is omnidirectionally connected to the corresponding connecting arm (7).

3. The handheld laser scanner calibration device according to claim 1, characterized in that, The support column (26) includes a column (12) whose bottom end is fixedly connected to the base (13) and an installation section (25) which is universally connected to the top of the column (12). The inner ends of the four connecting arms (7) are fixedly connected to the installation section (25) respectively.

4. The handheld laser scanner calibration device according to claim 1, characterized in that, It also includes a second reference unit located next to the first reference unit. The second reference unit includes a bracket (1) and at least one of a standard planar body (2), a polyhedron (4), and a variable angle reference mechanism that are universally connected to the top of the bracket (1).

5. The handheld laser scanner calibration device according to claim 4, characterized in that, The variable angle reference mechanism includes a mounting plate (14) and two standard plane bodies (2) hinged to each other in a Λ shape. The mounting plate (14) is universally connected to the top of the bracket (1). Both standard plane bodies (2) are perpendicular to the mounting plate (14). One of the standard plane bodies (2) is fixedly connected to the mounting plate (14), and the other standard plane body (2) is fixedly connected to a lug (17). The mounting plate (14) is provided with an arc-shaped slide groove (15). The hinge axis of the two standard plane bodies (2) passes through the center of the slide groove (15). A screw is provided through the lug (17) and passes through the slide groove (15). The lug (17) is provided with a hole for the screw to pass through. A wing nut (16) is screwed onto the screw. After tightening the wing nut (16), the included angle between the two standard plane bodies (2) is locked.

6. The handheld laser scanner calibration device according to claim 1, characterized in that, It also includes a fixed slide rail (11) and a slide table (10) slidably connected to the top of the slide rail (11). The first reference unit is located on one side of the slide rail (11). A robotic arm (9) is mounted on the slide table (10). The handheld laser scanner (8) to be calibrated is gripped by the hand of the robotic arm (9).

7. The handheld laser scanner calibration device according to claim 1, characterized in that, It also includes a third reference unit located next to the first reference unit, the third reference unit being at least one of the following: a cube standard block (18), a cuboid standard block (19), a cylinder standard block (20), a hemispherical standard block (21), a right-angled standard block (24), a grooved standard block (22), and a stepped high standard block (23).

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