A standard device for geometric measurement and calibration

Abstract

The present invention relates to the field of dimension measurement technology, and specifically to a standard device for geometric measurement and calibration, comprising: a base and at least one standard ball, wherein the base comprises a first fixing plate, a second fixing plate, a third fixing plate and a fourth fixing plate, wherein the first fixing plate, the second fixing plate, the third fixing plate and the fourth fixing plate form a trapezoidal structure, wherein a hollow space is arranged inside the trapezoidal structure; wherein the first fixing plate, the second fixing plate and the third fixing plate are each provided with at least one boss, wherein the boss corresponds to the standard ball one by one, wherein each boss is provided with a blind hole, wherein the standard ball is arranged in the blind hole; wherein the present invention can adopt a hollow trapezoidal structure, wherein the first fixing plate, the second fixing plate and the third fixing plate form spatial staggering and height differences, thereby improving the imaging effect and the calibration stability of the calibration device, and statistically analyzing the measurement errors of geometric quantities of different sizes, and having wide applicability.

Description

Technical Field

[0001] The invention relates to the technical field of dimension measurement, in particular to a standard device for geometric measurement and calibration. Background Art

[0002] In recent years, industrial CT has relied on computer tomography technology to combine the most advanced X-ray scanning technology and CT technology, and with advanced measurement and analysis software, it can clearly, accurately and intuitively display the internal structure, material composition and defect status of the inspected object in the form of two-dimensional tomographic images or three-dimensional stereo images without destroying the structure of the inspected object. It has demonstrated excellent accuracy, versatility and professionalism in non-destructive testing technology and dimensional measurement technology, and has become an effective means to solve complex and difficult quality problems. It is suitable for most material and dimensional testing tasks, seamlessly connecting with the testing needs of advanced manufacturing fields such as plastic engineering, aerospace, automobiles, electronics, precision machining and nano-industry, and solving industry application problems such as dimensional and geometric tolerance measurement, porosity analysis, wall thickness analysis, composite material analysis, assembly inspection, mold modification, reverse engineering, and industrial metrology in products that are difficult to reach and hidden.

[0003] Industrial CT can accurately reproduce the three-dimensional structure inside an object and can quantitatively provide physical and mechanical properties inside the object, such as the location and size of defects, density changes and levels, the shape and precise size of special-shaped structures, impurities and distribution inside the object, etc. Using a micro-focus ray source, it can achieve a resolution of microns or even nanometers, which is suitable for high-precision and subtle defect detection and can be applied to high-precision nano-size detection needs.

[0004] However, due to the special imaging principle and complex error sources of industrial CT (such as X-ray source, detector, image reconstruction algorithm, etc.), the lack of standard instruments, especially high-precision nano-size standard instruments, makes traceability calibration relatively difficult. my country has conducted some research on independently developed standard instruments, and some national or international standards on the application of industrial CT in the field of geometric measurement are being drafted or have been released. At present, there is no unanimously recognized method for the calibration of geometric measurement errors of industrial CT at home and abroad.

[0005] The above problems are problems that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of the above-mentioned problems in the prior art, the purpose of the present invention is to provide a calibration device for geometric quantity measurement, which can adopt a hollow trapezoidal structure to form a spatial staggered and height difference between the first fixed plate and the left third fixed plate, thereby improving the imaging effect and the calibration stability of the calibration device, and statistically analyzing the measurement errors of geometric quantities of different sizes, and has wide applicability.

[0007] In order to solve the above problems, the present invention provides a calibration device for geometric measurement, comprising a base and at least one standard ball, wherein the base comprises a first fixing plate, a second fixing plate, a third fixing plate and a fourth fixing plate, wherein the first fixing plate, the second fixing plate, the third fixing plate and the fourth fixing plate form a trapezoidal structure, wherein a hollow space is provided inside the trapezoidal structure;

[0008] The first fixing plate, the second fixing plate and the third fixing plate are each provided with at least one boss, the bosses correspond to the standard balls one by one, each of the bosses is provided with a blind hole, and the standard ball is arranged in the blind hole.

[0009] Furthermore, the base is made of carbon fiber.

[0010] Furthermore, the trapezoidal structure is an isosceles trapezoid.

[0011] Furthermore, the second fixing plate and the third fixing plate both form a certain angle with the first fixing plate, and the angle is 135° or 150°.

[0012] Furthermore, the thickness of the first fixing plate, the second fixing plate, the third fixing plate and the fourth fixing plate are all 5-10 mm.

[0013] Furthermore, a boss is provided at the center of the first fixing plate and is set as a center boss. The standard ball arranged on the center boss is a center standard ball. The standard balls arranged on other bosses form a circular structure around the center standard ball.

[0014] Furthermore, the angle between the center lines of the plurality of standard balls arranged on the second fixing plate is one of 30°, 60°, 90° or 120°.

[0015] Furthermore, the angle between the center lines of the plurality of standard balls arranged on the third fixing plate is one of 30°, 60°, 90° or 120°.

[0016] Furthermore, the standard ball is fixed in the blind hole by an adhesive.

[0017] Furthermore, the diameter of the standard ball is 2-10 mm.

[0018] Due to the above technical solution, the present invention has the following beneficial effects:

[0019] 1) A standard device for geometric measurement and calibration of the present invention adopts a hollow trapezoidal structure to prevent the base plate from being too thick, which causes the X-rays of the low-power CT to be unable to penetrate the sample normally, affecting the imaging effect;

[0020] 2) A standard device for geometric measurement and calibration of the present invention fixes a standard ball in a blind hole of a boss, so that the standard ball is not subjected to any destructive processing, thereby avoiding damage to the standard ball caused by processing that leads to a decrease in the accuracy of the measurement result, thereby improving the accuracy of the measurement result;

[0021] 3) A standard device for geometric measurement and calibration of the present invention adopts a hollow trapezoidal structure, so that the first fixing plate, the second fixing plate, and the third fixing plate are staggered in space and have a height difference, thereby avoiding the use of a support rod to fix the standard ball. The longer the support rod, the greater the bending or deformation, which leads to a decrease in measurement accuracy, thereby improving the stability of the calibration device;

[0022] 4) The standard device for geometric measurement and calibration of the present invention has a simple structure and wide applicability and can adapt to measurement and analysis of different sizes and angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments or prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 1 is a schematic diagram of the structure of a standard device for geometric measurement and calibration provided by an embodiment of the present invention;

[0025] Figure 2 is a top view of a standard device for geometric measurement and calibration provided by an embodiment of the present invention;

[0026] In the figure, 1-base, 11-first fixing plate, 12-second fixing plate, 13-third fixing plate, 14-fourth fixing plate, 2-standard ball. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0029] Embodiment 1

[0030] This embodiment provides a standard device for geometric measurement and calibration, such as Figure 1 As shown, the device includes: a base 1 and at least one standard ball 2, the base 1 includes a first fixing plate 11, a second fixing plate 12, a third fixing plate 13 and a fourth fixing plate 14, the first fixing plate 11, the second fixing plate 12, the third fixing plate 13 and the fourth fixing plate 14 form a trapezoidal structure, and a hollow space is provided inside the trapezoidal structure. The hollow structure is adopted to avoid that the base plate is too thick, resulting in the X-rays of the low-power CT being unable to penetrate the sample normally, affecting the imaging effect;

[0031] The first fixing plate 11, the second fixing plate 12 and the third fixing plate 13 are each provided with at least one boss, and the bosses correspond to the standard balls 2 one by one. Each of the bosses is provided with a blind hole, and the standard ball 2 is arranged in the blind hole.

[0032] Specifically, the base 1 is made of carbon fiber, which has many excellent properties, including high axial strength and modulus, low density, no creep, small thermal expansion coefficient, anisotropy, corrosion resistance, and good X-ray transmittance. In addition, the X-ray attenuation coefficient of the carbon fiber material is significantly smaller than that of the standard sphere 2, ensuring that the carbon fiber base and the standard sphere 2 are successfully segmented by setting a threshold during image processing without affecting subsequent measurements and calculations.

[0033] Furthermore, the base 1 is integrally formed.

[0034] Further, the trapezoidal structure is an isosceles trapezoid, which can cause the first fixing plate 11, the second fixing plate 12 and the third fixing plate 13 to form a spatial stagger and height difference, avoiding the use of a support rod to fix the standard ball. The longer the support rod is, the greater the bending or deformation amount is, resulting in a reduction in measurement accuracy, and improving the stability of the standard device.

[0035] Further, both the second fixing plate 12 and the third fixing plate 13 form a certain angle with the first fixing plate 11, and the angle of the angle is 135° or 150°.

[0036] Preferably, the angle of the angle is 135°.

[0037] Further, the thicknesses of the first fixing plate 11, the second fixing plate 12, the third fixing plate 13 and the fourth fixing plate 14 are all 5 - 10 mm.

[0038] Preferably, the thicknesses of the first fixing plate 11, the second fixing plate 12, the third fixing plate 13 and the fourth fixing plate 14 are all 8 mm.

[0039] Further, the fourth fixing plate 14 is provided with a through hole, and the through hole has an internal thread for fixing on brackets at different heights.

[0040] Specifically, a boss is provided at the center of the first fixing plate 11, which is set as the center boss, and the standard ball 2 provided on the center boss is the center standard ball. The standard balls 2 provided on other bosses form a circular structure around the center standard ball, showing a "rice" shape.

[0041] In some embodiments, the distribution of the bosses on the second fixing plate 12 and the third fixing plate 13 is the same as the distribution of the bosses on the first fixing plate 11.

[0042] Further, the axial centers of several blind holes provided on the first fixing plate 11 are at the same distance from the center of the first fixing plate 11.

[0043] Further, the connection line between the centers of the standard balls 2 surrounding the center standard ball and the center of the center standard ball is the center connection line, and the included angle between adjacent center connection lines is one of 30°, 45°, 60°, 90° or 120°.

[0044] Preferably, the included angle between adjacent center connection lines is 45°.

[0045] Specifically, the included angle between the center connection lines of multiple standard balls provided on the second fixing plate is one of 30°, 60°, 90° or 120°.

[0046] Specifically, the angle between the center lines of the plurality of standard balls arranged on the third fixing plate is one of 30°, 60°, 90° or 120°.

[0047] Furthermore, the standard ball 2 is fixed in the blind hole by an adhesive, so that the standard ball is not subjected to any destructive processing, thereby avoiding the reduction in the accuracy of the measurement result caused by the damage of the standard ball due to processing, and improving the accuracy of the measurement result.

[0048] Furthermore, the material of the standard ball 2 is artificial corundum. The ruby ​​standard ball made of artificial corundum has a moderate mass attenuation coefficient, a relatively low thermal expansion coefficient, and has the characteristics of corrosion resistance, wear resistance, and good light transmission performance.

[0049] Furthermore, the diameter of the standard ball 2 is 2-10 mm.

[0050] Preferably, the standard ball 2 has a diameter of 4 mm.

[0051] Specifically, according to the principle that the measurement error of two points at different positions in the measurement space is the size measurement error, it is first necessary to determine the calibration value, which is the fixed length value of the distance between any two centers of the standard balls 2. The coordinates of the centers of the standard balls 2 are calibrated by a calibrated coordinate measuring machine.

[0052] Furthermore, the distance between the centers of any two standard spheres is determined and used for calibrating the measurement error of the length geometric quantity of the sphere center distance of industrial CT.

[0053] Specifically, it is then necessary to establish a ball model, measure and record 25 points on the surface of the standard ball 2, set the 25 points in a dispersed manner, calculate the least squares fitting method to obtain the ball center, and establish the ball model based on the ball center.

[0054] Furthermore, the centers of two different standard balls 2 are determined as endpoints for size measurement.

[0055] In some embodiments, it is necessary to form a dual coordinate system with a common origin, in which the center of the standard sphere 2 set on the second fixed plate 12 and the third fixed plate 13 and the center of the standard sphere at the center of the circle form an isosceles triangle, and the vertex angle of the isosceles triangle is 45°. The center of the standard sphere at the center of the circle of the first fixed plate 11 is defined as the origin, and the line connecting the centers of the standard sphere 2 set on the second fixed plate 12 and the third fixed plate 13 is defined as the coordinate axis.

[0056] Specifically, the geometric length measurement of industrial CT is finally calibrated at 7 different positions or directions according to the ISO 10360-2 standard.

[0057] Specifically, the calibrated industrial CT geometric dimensions are used for measurement. During the industrial CT geometric dimension measurement process, the test sample is rotated 360° and the angle error is measured to improve the accuracy of each angle. An image is obtained for each rotation of a set angle. Using three-dimensional tomography theory and three-dimensional reconstruction software, the two-dimensional plane image is reconstructed to obtain three-dimensional stereo information, so that a three-dimensional model with small error and accurate calibration can be established.

[0058] The first embodiment of the present invention provides a calibration device for geometric measurement. Due to its simple structure and wide applicability, it can adapt to the measurement and analysis of different sizes and angles. The geometric dimensions of the calibrated industrial CT are measured with small errors and high precision, and the three-dimensional model is accurately constructed.

[0059] The above description has fully disclosed the specific embodiments of the present invention. It should be pointed out that any changes made by those skilled in the art to the specific embodiments of the present invention do not deviate from the scope of the claims of the present invention. Accordingly, the scope of the claims of the present invention is not limited to the above specific embodiments.

Claims

1. A standard device for geometric measurement and calibration, characterized in that: include: A base (1) and at least one standard ball (2), wherein the base (1) comprises a first fixing plate (11), a second fixing plate (12), a third fixing plate (13) and a fourth fixing plate (14), wherein the first fixing plate (11), the second fixing plate (12), the third fixing plate (13) and the fourth fixing plate (14) form a trapezoidal structure, wherein a hollow space is provided inside the trapezoidal structure; The first fixing plate (11), the second fixing plate (12) and the third fixing plate (13) are each provided with at least one boss, the bosses corresponding one to one with the standard balls (2), each boss being provided with a blind hole, the standard balls (2) being arranged in the blind hole.

2. A standard device for geometric measurement and calibration according to claim 1, characterized in that: The base (1) is made of carbon fiber.

3. A standard device for geometric measurement and calibration according to claim 1, characterized in that: The trapezoidal structure is an isosceles trapezoid.

4. A standard device for geometric measurement and calibration according to claim 3, characterized in that: The second fixing plate (12) and the third fixing plate (13) both form a certain angle with the first fixing plate (11), and the angle is 135° or 150°.

5. A standard device for geometric measurement and calibration according to claim 1, characterized in that: The thickness of the first fixing plate (11), the second fixing plate (12), the third fixing plate (13) and the fourth fixing plate (14) are all 5-10 mm.

6. A standard device for geometric measurement and calibration according to claim 1, characterized in that: A boss is provided at the center of the first fixing plate (11), which is set as a center boss. The standard ball (2) arranged on the center boss is a center standard ball. The standard balls (2) arranged on other bosses form a circular structure around the center standard ball.

7. A standard device for geometric measurement and calibration according to claim 1, characterized in that: The connecting lines between the centers of the plurality of standard balls (2) arranged on the second fixing plate (12) form a certain angle, and the angle at least includes angles of 30°, 60°, 90° and 120°.

8. A standard device for geometric measurement and calibration according to claim 1, characterized in that: The connecting lines between the centers of the plurality of standard balls (2) arranged on the third fixing plate (13) form a certain angle, and the angle at least includes angles of 30°, 60°, 90° and 120°.

9. A standard device for geometric measurement and calibration according to claim 1, characterized in that: The standard ball (2) is fixed in the blind hole by means of an adhesive.

10. A standard device for geometric measurement and calibration according to claim 1, characterized in that: The diameter of the standard ball (2) is 2-10 mm.

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