An X-ray based nacre thickness measuring device and measuring method

Abstract

The present invention relates to an X-ray-based nacre thickness measuring device and a measuring method. The measuring device includes an X-ray source, a three-axis test box, and an X-ray detector arranged in sequence. Among them, the three-axis test box is a standard cube structure, with a sample accommodation cavity provided at its center, and hollow windows are opened on each surface of the standard cube. Compared with the prior art, the present invention has the advantages of high precision, comprehensive and fast measurement, etc.

Description

Technical Field

[0001] The present invention relates to a pearl quality detection technology, and in particular to an X-ray based device and method for measuring the thickness of a pearl layer. Background Art

[0002] With the rapid development of the technology of nucleated cultured pearls, many enterprises have higher requirements for strictly controlling the quality of pearls themselves, including the size, roundness, color, luster, smoothness, etc. of pearls. The most important thing is the thickness of the pearl layer, which is also the most important index for measuring the value of pearls. The thickness of the pearl layer is also the main determinant of the durability of pearls used as jewelry. Therefore, the detection of thickness is imperative. However, there is currently no mature technology in the market that can quickly and accurately detect the thickness of the pearl layer. The lack of effective detection means has led to a chaotic market situation, and the situation of passing off inferior goods as good ones occurs from time to time. This has caused obstacles to regulating the market order and enhancing the brand image of enterprises, and is a difficult problem that urgently needs to be overcome on the development path of the pearl industry.

[0003] For the thickness of the pearl layer, the currently mainly used detection technologies are X-ray radiography technology and optical coherence tomography technology. However, both of these technologies currently have some defects. Optical coherence tomography technology can detect the structural information of the shallow surface profile of an object through the backscattered and scattered signals from the object surface. But this technology generally can only measure the pearl layer with a thickness of less than 2 mm, and is helpless for the Edison pearls with a thickness of about 3 mm on the current market. This technology has a very fast measurement speed, but it can only measure the profile in one direction at a time. If you want to detect the thickness of the pearl in a full circle, the measurement time required will be relatively long. In addition, although this technology has a relatively high measurement precision, due to the fact that the accurate value of the refractive index of the substance to be measured must be used in the result calculation, there are systematic errors that are difficult to eliminate.

[0004] X-ray radiography technology uses X-rays to penetrate the object to be measured, and then uses an X-ray receiver to receive. It uses the difference in the penetration characteristics of X-rays for different substances to form an image. Since the image is formed by means of photography, the thickness of the pearl layer in a full circle of the pearl can be intuitively measured at the same time. However, the existing X-ray detection technology still has several important technical defects in pearl detection:

[0005] (1) Low precision: The detection area is much larger than the size of the pearl, while the resolution and precision cannot meet the detection requirements;

[0006] (2) Small detection range: It can only measure the photographic image in one direction, while the measurement of the pearl layer thickness generally requires photographic images in at least three directions of X, Y, and Z;

[0007] (3) Low image contrast or overexposure: The problem of low contrast is common in X-ray radiography. If contrast stretching is directly performed, overexposure will occur at the edges of the pearl image, which makes it impossible to accurately find the boundary of the pearl, thus affecting the measurement of the nacre thickness of the pearl. Summary of the Invention

[0008] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a nacre thickness measurement device and method based on X-rays with high precision, comprehensive and rapid measurement.

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] An X-ray-based nacre thickness measurement device includes an X-ray source, a three-axis test box, and an X-ray detector arranged in sequence. Among them,

[0011] The three-axis test box is of a standard cube structure, with a sample accommodation cavity in its center, and hollow windows are opened on each surface of the standard cube.

[0012] Further, the three-axis test box includes a sample box and a sample box cover connected by a rotating shaft.

[0013] Further, the contact surface between the sample box and the sample box cover is hexagonal, and this hexagon is composed of the midpoints of six edges that are not adjacent to the two diagonal vertices of the standard cube.

[0014] Further, the sample box is provided with a hook, and the sample box cover is provided with a slot corresponding to the hook.

[0015] Further, elastic films are arranged on the contact surfaces of the sample box and the sample box cover.

[0016] Further, the elastic film is fixed by a retaining ring.

[0017] Further, the three-axis test box is a plastic test box.

[0018] Further, the distance between the X-ray source and the X-ray detector satisfies the following formula:

[0019] N ≤ eL / (P + e)

[0020] Wherein, N is the distance between the center of the sample to be measured and the X-ray detector, L is the distance between the X-ray source and the X-ray detector, e is the pixel interval of the X-ray detector, and P is the size of the focus of the X-ray source.

[0021] The present invention also provides a nacre thickness measurement method using the above-mentioned X-ray-based nacre thickness measurement device, including the following steps:

[0022] 1) Place a certain side of the three-axis test box containing the pearl to be measured facing upwards;

[0023] 2) Adjust the tube voltage of the X-ray source to the first voltage, and this first voltage is less than the pearl penetration voltage;

[0024] 3) Collect the first image obtained by the X-ray detector, and extract the outer contour of the pearl from this first image;

[0025] 4) Adjust the tube voltage of the X-ray source to the second voltage, and this second voltage is greater than the pearl penetration voltage;

[0026] 5) Collect the second image obtained by the X-ray detector, and obtain the pearl nucleus fitting circle by fitting from this second image;

[0027] 6) Calculate the pearl layer thickness based on the outer contour of the pearl and the pearl nucleus fitting circle;

[0028] 7) Repeat steps 1)-6) to obtain the pearl layer thicknesses in the X, Y, and Z directions.

[0029] Furthermore, the specific steps for obtaining the pearl nucleus fitting circle are as follows:

[0030] Adjust the measurement time to make the pearl nucleus image the clearest, mark three points on the boundary of the pearl nucleus to form a triangle, and calculate the circumcircle of the triangle to fit and obtain the pearl nucleus fitting circle.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention designs a special three-axis test box for detection. While the three-axis test box fixes the pearl sample, it can completely avoid affecting the image, and solves the problem that general test boxes or jigs cannot meet the requirement of imaging the pearl in the X, Y, and Z directions simultaneously.

[0033] 2. The present invention first uses a common X-ray source and a small X-ray detector for dental use in combination, and calculates the best distance that can exert the full performance of the device through a formula, so that the detection image can obtain high intensity and clarity. After sacrificing the detection range, the obtained image exceeds the effects of most micro-focus X-ray sources and flat panel X-ray detectors, greatly reducing the device volume and cost.

[0034] 3. The secondary imaging method adopted by the present invention can accurately measure the outer contour of the pearl and the position of the pearl nucleus, and solves the problem of inaccurate measurement of the pearl layer thickness.

[0035] 4. The combination of the three-axis test box and the secondary imaging method of the present invention solves the problem of being unable to accurately measure the nacre thickness of pearls in multiple directions, making it possible to grade the nacre thickness of pearls.

[0036] 5. Each surface of the three-axis test box designed in the present invention is provided with through holes as large as possible, effectively avoiding the cut parts, leaving space for the placement of the pressure ring, and being relatively beautiful. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of the three-axis test box of the present invention;

[0038] Figure 2 is a front view of the three-axis test box of the present invention;

[0039] Figure 3 is an exploded view of the three-axis test box of the present invention;

[0040] Figure 4 is a schematic diagram of the opening of the sample box and the sample box cover of the three-axis test box of the present invention;

[0041] Figure 5 is a schematic diagram of an angle of the sample box of the present invention;

[0042] Figure 6 is a schematic diagram of another angle of the sample box of the present invention;

[0043] Figure 7 is a schematic diagram of an angle of the sample box cover of the present invention;

[0044] Figure 8 is a schematic diagram of another angle of the sample box cover of the present invention;

[0045] Figure 9 is a schematic diagram of the working state of the measuring device of the present invention;

[0046] Figure 10 is a schematic diagram of the X, Y, and Z directions of the three-axis test box during the measurement process of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0047] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0048] As Figure 9As shown in the figure, this embodiment provides an apparatus for measuring the nacre thickness based on X-rays, which includes an X-ray source 1, a three-axis test box 2, and an X-ray detector 3 arranged in sequence. The pearl to be measured is fixed in the three-axis test box 2. The X-ray source 1 emits X-rays that completely penetrate the three-axis test box 2 and irradiate on the pearl to be measured. Depending on the different transmittance of different parts of the pearl, they are respectively penetrated or absorbed, and finally projected onto the X-ray detector to form an X-ray radiograph. The imaging obtained by the X-ray detector 3 is collected, and the imaging is analyzed to obtain the nacre thickness of the pearl to be measured.

[0049] As Figure 1 shown in the figure, the three-axis test box 2 has a standard cube structure, and a sample accommodation cavity for placing the pearl to be measured is provided at its center. Hollow windows 25 are opened on each face of the standard cube, that is, through holes are provided to ensure that there are no obstacles during the process of X-rays penetrating the pearl, so as to avoid affecting the test results.

[0050] In this embodiment, the three-axis test box 2 is a plastic test box.

[0051] As Figures 2 - 4 shown in the figure, the three-axis test box 2 includes a sample box 21 and a sample box cover 22 connected by a rotating shaft. The contact surface between the sample box 21 and the sample box cover 22 (i.e., the cut surface of the standard cube) is hexagonal, and this hexagon is composed of the midpoints of six edges that are not adjacent to the two diagonal vertices of the standard cube. Only in this way can the linear projection interference at the joint of the test box be completely avoided on the X-ray image. This interference will not only affect the imaging effect but also cause image distortion, making the measured nacre thickness inaccurate. If cut in other ways, the interference in one or two directions among the X, Y, and Z directions can be avoided, but it is impossible to completely avoid the interference in all three directions. Elastic films 23 are provided on the contact surfaces of the sample box 21 and the sample box cover 22. The elastic films 23 are fixed by retaining rings 24. The elastic films 23 can be plastic elastic films. After the test box is closed, the plastic elastic films on the two cut surfaces clamp to play a role in fixing the pearl sample.

[0052] As Figure 1 shown in the figure, the hollow windows 25 opened on each face of the standard cube are also hexagonal, and this hexagon is a symmetric structure, having a pair of parallel sides parallel to the cut edges on the corresponding face, so that the through holes are as large as possible without affecting the test, and at the same time, it is ensured that the pearl to be measured can be stably placed in the sample accommodation cavity.

[0053] As Figures 5 - 8 shown in the figure, the sample box 21 is provided with a hook 211, and the sample box cover 22 is provided with a slot 221 corresponding to the hook 211.

[0054] As Figure 9As shown in the figure, to obtain the maximum detection intensity, the X-ray needs to exactly cover the entire detector. α is the scattering angle of the X-ray source, u and v are the length and width of the detector, and the distance from the detector to the X-ray source is L. Then, there is:

[0055]

[0056] The diameter of the focal spot is P, and the projected diameter on the detector after the focal spot passes through any point on the pearl boundary is Q. M is the distance from the X-ray source to the center of the pearl, and N is the distance from the center of the pearl to the detector. According to similar triangles, there is:

[0057] P / Q = M / N

[0058] The pixel pitch of the detector is e. To obtain the best resolution of the detector, it is necessary to ensure:

[0059] e ≥ Q = PN / M = PN / (L - N)

[0060] There is:

[0061] N ≤ eL / (P + e)

[0062] Under the condition of satisfying the maximum resolution of the detector, to make the image as clear as possible, a larger image magnification should be obtained as much as possible. The image magnification is C, and there is:

[0063] C = L / (L - N)

[0064] It can be seen from this that the larger N is, the larger the image magnification is and the clearer the image is.

[0065] Therefore, when:

[0066] N = eL / (P + e)

[0067] At this time, the entire system not only satisfies the best detector resolution, but also obtains the maximum image magnification, and obtains the clearest X-ray radiograph.

[0068] The specific steps for measuring the nacre thickness of pearls using the above X-ray-based nacre thickness measuring device include:

[0069] 1) Turn a certain side of the three-axis test box containing the pearl to be measured upwards;

[0070] 2) Adjust the tube voltage of the X-ray source to the first voltage, and this first voltage is less than the pearl penetration voltage;

[0071] 3) Collect the first image obtained by the X-ray detector, and extract the outer contour of the pearl from this first image;

[0072] 4) Adjust the tube voltage of the X-ray source to the second voltage, and this second voltage is greater than the pearl penetration voltage;

[0073] 5) Collect the second image obtained by the X-ray detector, and obtain the pearl nucleus fitting circle from the second image by fitting, specifically:

[0074] Adjust the measurement time to make the pearl nucleus image the clearest, mark three points on the pearl nucleus to form a triangle, and calculate the circumcircle of the triangle by fitting to obtain the pearl nucleus fitting circle;

[0075] 6) Calculate the pearl layer thickness based on the pearl outer contour and the pearl nucleus fitting circle;

[0076] 7) Repeat steps 1)-6) to obtain the pearl layer thicknesses in the X, Y, and Z directions, as Figure 10 shown.

[0077] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. An X-ray-based nacre thickness measuring device, characterized in that, It includes an X-ray source, a three-axis test box, and an X-ray detector arranged in sequence. Among them, the three-axis test box is of a standard cube structure, with a sample accommodation cavity provided at its center, and hollowed-out windows are opened on each face of the standard cube; the three-axis test box includes a sample box and a sample box cover connected by a rotating shaft; the contact surfaces of the sample box and the sample box cover are hexagonal, and this hexagon is composed of the midpoints of six edges that are not adjacent to the two diagonal vertices of the standard cube; the sample box is provided with a catch, and the sample box cover is provided with a card slot corresponding to the catch.

2. The X-ray based nacre thickness measuring device according to claim 1, characterized in that, Elastic films are arranged on the contact surfaces of the sample box and the sample box cover.

3. The X-ray-based nacre thickness measuring device according to claim 2, characterized in that, The elastic films are fixed by retaining rings.

4. The X-ray based nacre thickness measuring device according to claim 1, characterized in that, The three-axis test box is a plastic test box.

5. The X-ray-based nacre thickness measuring device according to claim 1, characterized in that, The distance between the X-ray source and the X-ray detector satisfies the following formula: N ≤ eL / (P + e) where N is the distance between the center of the pearl to be measured and the X-ray detector, L is the distance between the X-ray source and the X-ray detector, e is the pixel pitch of the X-ray detector, and P is the size of the focus of the X-ray source.

6. A method for measuring the nacre thickness using the X-ray-based nacre thickness measuring device as described in claim 1, characterized in that, It includes the following steps: 1) Turn a certain face of the three-axis test box containing the pearl to be measured upwards; 2) Adjust the tube voltage of the X-ray source to a first voltage, and this first voltage is less than the pearl penetration voltage; 3) Collect the first image obtained by the X-ray detector, and extract the outer contour of the pearl from this first image; 4) Adjust the tube voltage of the X-ray source to a second voltage, and this second voltage is greater than the pearl penetration voltage; 5) Collect the second image obtained by the X-ray detector, and obtain the pearl nucleus fitting circle by fitting from this second image; 6) Calculate the pearl layer thickness based on the pearl outer contour and the pearl nucleus fitting circle; 7) Repeat steps 1)-6) to obtain the pearl layer thicknesses in the X, Y, and Z directions.

7. The nacre thickness measurement method according to claim 6, wherein The specific steps for obtaining the pearl nucleus fitting circle are as follows: Adjust the measurement time to make the pearl nucleus image clear, mark three points on the boundary of the pearl nucleus to form a triangle, and calculate the circumcircle of the triangle to fit and obtain the pearl nucleus fitting circle.

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