Tension sensor based on diffraction pattern of helical structure and tension detection method

Abstract

The application discloses a tension sensor based on a spiral structure diffraction pattern and a tension detection method, the tension sensor comprises a laser, a lens group, a light shield with adjustable light transmittance, a spring and a light screen arranged along an optical path; the laser, the lens group and the light screen are concentrically arranged, and the lens group is used for focusing; one end of the spring is fixed, and the other end is provided with a tension device; the spring is a cylindrical spring; a diffraction image is acquired based on the tension sensor; after binaryzation processing of the acquired diffraction image, each equal division area center is calculated through equal division, and an approximate straight line is obtained through fitting; the straight line is equally divided and fitted again, and the included angle of the two fitted straight lines is calculated; according to the corrected camera tilt angle, the included angle between the two straight lines is corrected; the force borne by the spring is calculated by using the corrected included angle and the parameters of the spring itself; through selection of a spring with a suitable diameter and a light source with a suitable wavelength, the measurement and identification of the optical quantity can effectively reduce experimental errors, and higher precision than that of an existing spring dynamometer can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a tensile sensor and tensile force detection method based on a helical structure diffraction pattern. Background Technology

[0002] Existing force sensors used in physics education convert force values ​​into electrical signals, but they cannot demonstrate the conversion process and are susceptible to environmental changes such as temperature. Furthermore, the materials and structures of these force sensors age or deteriorate over time and with use, leading to inaccurate or unstable force measurement results. In addition, there are currently no dedicated teaching instruments for demonstrating Franklin's DNA X-ray diffraction experiment in physics education. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a tensile sensor and tensile detection method based on a helical structure diffraction pattern. This force sensor is based on optical signals, which differs from the mechanism of traditional force sensors that convert mechanical signals into electrical signals through material strain characteristics.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a tension sensor based on a helical diffraction pattern, comprising a laser, a lens group, a light shield with adjustable transmittance, a cylindrical spring, and a screen arranged along the optical path; the laser, lens group, and screen are arranged concentrically, and the lens group is used for focusing; one end of the cylindrical spring is fixed, and the other end is provided with a tension device.

[0005] Furthermore, the lens group includes a first lens and a second lens arranged concentrically along the optical path, wherein the diameter of the first lens is smaller than the diameter of the second lens, and the focal length of the first lens is smaller than the focal length of the second lens.

[0006] Furthermore, a through hole is opened in the center of the light screen.

[0007] Furthermore, it also includes a base, on which the laser, lens group, adjustable light transmittance light shield and light screen are all mounted. The base can be a perforated plate platform, a sliding rail platform or an integrated base.

[0008] Furthermore, a spring bracket is fitted on the outer side of the cylindrical spring.

[0009] Furthermore, the tensioning device is a weight or a tensioning machine. When the tensioning device uses a weight, the cylindrical spring is arranged vertically and is installed through a spring bracket. When the tensioning device uses a tensioning machine, the cylindrical spring is arranged vertically or horizontally.

[0010] Furthermore, the laser is a semiconductor laser with a center wavelength of 650±10nm and a power of 20mW.

[0011] Based on the diffraction image acquired by the aforementioned tension sensor, this invention provides a tension detection method using a tension sensor with a helical diffraction pattern, comprising the following steps: binarizing the acquired diffraction image to obtain a binarized image: Divide the binarized image horizontally into equal parts, and then divide the binarized image vertically into upper and lower parts from the middle to obtain several equally divided regions. Calculate the geometric center of each region. The geometric centers of all regions are fitted with straight lines using the least squares method, and the fitted lines basically coincide with the lines in the diffraction image. For the two fitted straight lines, detect 0 and 1 in the binarized image along their paths, and use this as the basis for resegmentation. After resegmentation, each segment contains a bright spot. Calculate the geometric center of each segment after all resegments; The least squares method is used to fit two straight lines to the geometric center of each segment after re-segmentation, and the angle between the two lines is obtained by the slope of the fitted two lines. The angle between the light path and the camera direction is the camera tilt angle. The angle between the two lines is corrected using the following formula:

[0012] in The angle between the two lines obtained by the final fitting. The camera tilt angle; The force on the cylindrical spring is calculated using the following formula.

[0013] In the formula, F, n, k, d, Φ These are the force, number of coils, spring constant, mean diameter, and wire diameter of the cylindrical spring. θ The angle between the two lines after correction.

[0014] Furthermore, the binarization process for the diffraction image includes: setting the HSV threshold from (0, 40, 80) to (160, 255, 255) for all pixels in the diffraction image, filtering out the points in the diffraction pattern that meet the threshold, and the selected points are the bright spots. The corresponding pixels are set to 1 in the binarized image, corresponding to white spots; the remaining pixels that do not meet the threshold are considered not to belong to the bright spots of the diffraction image, and are set to 0 in the binarized image, corresponding to black spots.

[0015] Furthermore, for the horizontally 600px diffraction image, the left region is divided into smaller regions ranging from 100px to 160px, and the right region ranges from 330px to 390px, with each region being divided into smaller regions every 12px.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: This invention combines Hooke's law for cylindrical springs in mechanics with the principle of grating diffraction in optics. It uses non-contact optical measurement to measure the deformation of cylindrical springs and thus the force on them. By selecting a cylindrical spring with a suitable wire diameter and a light source with a suitable wavelength, the measurement and identification of optical quantities can effectively reduce experimental errors and achieve higher accuracy than existing cylindrical spring force gauges. Non-contact acquisition of cylindrical spring structural information has potential applications in industry; the device described in this invention can also serve as a measuring instrument for the spring constant of cylindrical springs, filling a gap in existing cylindrical spring constant measuring instruments; all experimental instruments are observable and adjustable, allowing for an understanding of the overall optical path structure from the appearance, the specific location of diffraction, and the corresponding light propagation path; it can be used as a teaching instrument to demonstrate the principle of diffraction to students, providing an intuitive teaching effect, and simultaneously involving the understanding and application of knowledge from multiple perspectives such as single-wire diffraction, grating diffraction, and Hooke's law; this invention fills the gap in physics teaching regarding teaching instruments for demonstrating Franklin's DNA X-ray diffraction experiment, obtaining rich helical structure information through the analysis of X-ray diffraction patterns, presenting the process, principles, and creative scientific inquiry methods of DNA structure discovery, and showcasing the exploratory spirit of scientists in the last century. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the tensile sensor principle described in this invention.

[0018] Figure 2 This is a schematic diagram of an implementable device structure according to the present invention.

[0019] Figure 3 This is a schematic diagram of a light screen according to the present invention.

[0020] Figure 4 This is a schematic diagram of the spring support structure provided on the outside of the cylindrical spring according to the present invention, where a is a front view, b is a side view, and c is a top view.

[0021] Figure 5 This is a schematic diagram of the human-machine interface for testing tensile force using the apparatus and method described in this invention.

[0022] Figure 6 The diffraction pattern is obtained based on the device.

[0023] Figure 7 To Figure 6 The image obtained after binarization.

[0024] In the attached diagram, 1-laser, 2-lens group, 3-adjustable light-transmitting light shield, 4-spring bracket, 5-light screen, 6-CCD camera, 7-base. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0028] Principle reference of tension sensor based on helical structure diffraction pattern Figure 1 , Figure 2 earrings Figure 3 In this system, the semiconductor laser 1, adjustable light shield 3, lens group 2, and screen 5 are kept in a straight line to ensure that the laser passes through the center of the adjustable light shield 3, lens group 2, and screen 5 in sequence. A tilt angle exists between the CCD camera 6 and the screen. The CCD camera 6 receives the diffraction pattern and measures the deformation of the cylindrical spring using the optical diffraction pattern.

[0029] As an optional embodiment, laser 1 is a semiconductor laser with a center wavelength of 650±10nm and a power of 20mW, used for emitting laser light; refer to Figure 4The lens group 2 includes two concentric convex lenses for focusing and reducing the beam; the first lens is Φ23.9mm with a focal length of 25mm, and the second lens is Φ25.1mm with a focal length of 50mm; the adjustable transmittance light shield 3 is used to reduce the light intensity of the laser; the spring bracket 4 is equipped with a replaceable cylindrical spring; the screen 5 is used to receive the diffraction pattern of the laser emitted by the laser after passing through the cylindrical spring; the CCD camera 6 captures the diffraction pattern received on the screen, and performs data analysis and calculation based on the diffraction pattern.

[0030] As an optional embodiment, the device described in this invention is automated and operated through a human-machine interface. During operation, it includes the following steps: Step 1: Turn on the laser power, connect the CCD camera 6 to the computer, hang the cylindrical spring on the spring bracket 4, and hang weights under the cylindrical spring.

[0031] Step 2: Open the software and set the spring parameters and the tilt angle of the CCD camera 6 to the screen in the UI interface.

[0032] Step 3: The program controls the CCD camera 6 to acquire the diffraction pattern of the cylindrical spring, and directly measures the diffraction information and load-bearing capacity of the cylindrical spring.

[0033] When the cylindrical spring needs to be replaced, it can be replaced directly on the instrument. Click "Reset" in the UI interface, and re-enter the parameters of the cylindrical spring and the tilt angle of the CCD camera 6 before proceeding with the next measurement.

[0034] Preferably, regarding the selection of the screen 5, if an unprocessed complete screen is used, a large amount of laser light that has not undergone diffraction will hit the center of the image, scattering and generating a large amount of stray light, partially obscuring the diffraction pattern. Therefore, in this invention, a through hole is opened in the center of the screen so that the central laser beam passes through the screen without scattering, achieving central extinction and improving image quality.

[0035] Optionally, the position of the convex lens group can be controlled to focus the parallel beam emitted by the laser onto the screen, and the optical path is as follows: Figure 4 As shown, this makes the diffraction pattern on the screen the clearest; Optionally, the CCD camera 6 is driven by a computer to process the diffraction images it captures, using an algorithm program interface. Figure 5 The calculation process is visualized as shown. The diffraction pattern is as follows. Figure 6 As shown.

[0036] When processing the diffraction image, two straight lines in the diffraction pattern are fitted, and then the force on the cylindrical spring is calculated by the angle between the two straight lines.

[0037] The method of fitting straight lines: For each small bright spot on the two straight lines in the diffraction pattern, find the geometric center of each bright spot, connect them, and the two straight lines can be obtained. Specifically, this includes: 1. Image Binarization: For all pixels in the diffraction image, set the HSV threshold (H color, S grayscale, V brightness) to (0, 40, 80) to (160, 255, 255), and filter out the points in the diffraction pattern that meet the threshold. The selected points are bright spots, and the corresponding pixels are set to 1 (white points) in the binarized image; the remaining pixels that do not meet the threshold are considered not to belong to the bright spots of the diffraction image and are set to 0 (black points) in the binarized image. The binarized image is as follows. Figure 7 As shown.

[0038] 2. Segmentation and Geometric Center Calculation: The image captured by the CCD camera is 600px horizontally. After binarizing the image, it is divided horizontally and vertically. First, horizontally, the left region is divided from 100px to 160px; the right region from 330px to 390px, with each region further divided into smaller regions every 12px, resulting in 10 horizontally segmented regions. Then, vertically, it is divided into upper and lower parts from the middle, resulting in 20 smaller regions. These regions all contain a portion of the bright spot and avoid the influence of central stray light. As an example, the geometric center of each of these 20 smaller regions is calculated. Treating each small white dot in the region as having the same mass, calculating the geometric center is equivalent to calculating the centroid of all the small white dots and the average of their x and y coordinates.

[0039] 3. First fitting: Use the least squares method to fit a straight line to the geometric center of all small blocks. At this time, the fitted line and the line in the diffraction image basically coincide.

[0040] 4. Re-segmentation: Because the division of small blocks is not based on bright spots, each calculated geometric center is not the geometric center of a single bright spot, but rather the geometric center of a portion of several bright spots. Therefore, a second fitting is performed to reduce the error. For the two fitted lines from the first fitting, 0 and 1 values ​​in the binarized image are detected along their paths. This serves as the basis for re-segmentation, resulting in each small block containing a bright spot after re-segmentation.

[0041] 5. Recalculate the geometric center: Recalculate the geometric center of each small block after all resegments.

[0042] 6. Second fitting: Use the least squares method to fit a straight line to the geometric center of each small block after resegmentation. The resulting straight line can fit the diffraction pattern more accurately. The angle between the two fitted straight lines is obtained by the slope of the two fitted straight lines.

[0043] 7. Camera Tilt Angle Correction: CCD cameras can only receive images from the side; otherwise, they would block the light path. Therefore, there is a tilt angle when shooting onto the screen, which affects image recognition. The angle between the light path and the camera direction is defined as the camera tilt angle, and it is calculated according to...

[0044] The angle between the two lines is obtained by correcting the fit, where To help the program identify the angle between two lines, The camera tilt angle; 8. Calculate the force on the cylindrical spring: Calculate the force on the cylindrical spring based on the angle-force formula derived from physics.

[0045]

[0046] In the formula, F, n, k, d, Φ These are the force, number of coils, spring constant, mean diameter, and wire diameter of the cylindrical spring. θ The angle between the two straight lines in the diffraction pattern is denoted as α.

[0047] Optionally, the swaying of the cylindrical spring is limited by the spring bracket 4 for ease of use, and the spring bracket 4 is matched with the outer side of the cylindrical spring.

[0048] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A tensile sensor based on a helical diffraction pattern, characterized in that, It includes a laser (1), a lens group (2), a light shield with adjustable transmittance (3), a cylindrical spring, and a screen (5) arranged along the optical path; the laser (1), the lens group (2), and the screen (5) are arranged concentrically, and the lens group (2) is used for focusing; one end of the cylindrical spring is fixed, and the other end is equipped with a tension device; The lens group (2) includes a first lens and a second lens arranged concentrically along the optical path. The diameter of the first lens is smaller than that of the second lens, and the focal length of the first lens is smaller than that of the second lens. A through hole is opened in the center of the screen (5). It also includes a base, and the laser (1), lens group (2), adjustable light transmittance light shield (3) and light screen (5) are all installed on the base (7). The base (7) adopts a perforated plate platform, slide rail platform or integrated base; a spring bracket (4) is sleeved on the outside of the cylindrical spring; the tension device is a weight or a tension machine. When the tension device adopts a weight, the cylindrical spring is arranged vertically and the cylindrical spring is installed through the spring bracket (4); when the tension device adopts a tension machine, the cylindrical spring is arranged vertically or horizontally.

2. The tensile sensor based on a helical diffraction pattern according to claim 1, characterized in that, The laser (1) is a semiconductor laser with a center wavelength of 650±10nm and a power of 20mW.

3. A tensile force detection method based on a tensile force sensor with a helical diffraction pattern, characterized in that, The method for acquiring a diffraction image based on the tension sensor described in claim 1 or 2 includes the following steps: binarizing the acquired diffraction image to obtain a binary image: Divide the binarized image horizontally into equal parts, and then divide the binarized image vertically into upper and lower parts from the middle to obtain several equally divided regions. Calculate the geometric center of each region. The geometric centers of all regions are fitted with straight lines using the least squares method, and the fitted lines basically coincide with the lines in the diffraction image. For the two fitted straight lines, detect 0 and 1 in the binarized image along their paths, and use this as the basis for resegmentation. After resegmentation, each segment contains a bright spot. Calculate the geometric center of each segment after all resegments; The least squares method is used to fit two straight lines to the geometric center of each segment after re-segmentation, and the angle between the two lines is obtained by the slope of the fitted two lines. The angle between the light path and the camera direction is the camera tilt angle. The angle between the two lines is corrected using the following formula: in The angle between the two lines obtained by the final fitting. The camera tilt angle; The force on the cylindrical spring is calculated using the following formula. In the formula, F, n, k, d, Φ These are the force, number of coils, spring constant, mean diameter, and wire diameter of the cylindrical spring. θ The angle between the two lines after correction.

4. The tensile force detection method based on a helical structure diffraction pattern tensile sensor according to claim 3, characterized in that, The binarization process for the diffraction image includes: setting the HSV threshold from (0, 40, 80) to (160, 255, 255) for all pixels in the diffraction image, filtering out the points in the diffraction pattern that meet the threshold, and the selected points are the bright spots. The corresponding pixels are set to 1 in the binarized image, corresponding to white spots; the remaining pixels that do not meet the threshold are considered not to belong to the bright spots of the diffraction image, and are set to 0 in the binarized image, corresponding to black spots.

5. The tensile force detection method based on a helical structure diffraction pattern tensile sensor according to claim 3, characterized in that, For a diffraction image with a horizontal length of 600px, the image is divided into smaller regions every 12px, with the left region ranging from 100px to 160px and the right region ranging from 330px to 390px.

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