A multimode fiber mechanical sensing system and method based on wavefront shaping technology

Abstract

The application relates to the technical field of mechanical sensing, and provides a multimode optical fiber mechanical sensing system and method based on wavefront shaping technology. In the system, a first focal point image is formed at the distal end of a step-index fiber by using the wavefront shaping technology, the stress condition of the step-index fiber is determined by analyzing the first focal point image, and finally a mechanical sensing system with high sensitivity, a large range and no limitations is obtained. The system comprises a light splitting unit, a signal light processing unit, a combined light beam unit, a camera and a main processing unit. The main processing unit is used for singular value decomposition of the first focal point image to obtain a plurality of first singular values; a first left singular vector corresponding to the maximum first singular value is extracted; a first deviation value of the first left singular vector and a preset initial vector is calculated; the first deviation value is input into a preset external force change fitting curve formula to output a stress value, and the stress value is determined as a current stress value of the step-index fiber.

Description

Technical Field

[0001] This application relates to the field of mechanical sensing technology, and in particular to a multimode fiber mechanical sensing system and method based on wavefront shaping technology. Background Technology

[0002] Multimode fiber (MMF) has been widely used in the field of sensing. Unlike single-mode fiber, the mode aliasing and mode dispersion phenomena in the optical field transmission of multimode fiber, although considered a thorny obstacle in optical communication and optical imaging, can help in sensing.

[0003] In related technologies, many sensing systems based on multi-mode interference (MMI) support the measurement of various parameters, such as temperature, contact force, bending, refractive index, and displacement. Although these MMI-based sensing systems have different structures, they can be divided into two types in terms of the objects of analysis: speckle analysis and spectral analysis. The former mainly relies on speckle pattern correlation analysis and deep learning algorithms, while the latter relies on the drift of peaks or critical wavelengths in the transmission spectrum. However, spectral analysis methods typically require more complex experimental systems and more stringent detection methods, and speckle analysis has certain limitations. Summary of the Invention

[0004] In view of this, embodiments of this application provide a multimode fiber optic mechanical sensing system and method based on wavefront shaping technology. In this system, wavefront shaping technology is used to form a first focal point image at the far end of a step-index fiber. By analyzing the first focal point image, the stress condition of the step-index fiber is determined, and finally a mechanical sensing system with high sensitivity, large range, and no limitations is obtained.

[0005] According to one aspect of this application, a multimode fiber optic mechanical sensing system based on wavefront shaping technology is provided, comprising a beam splitting unit, a signal light processing unit, a reference light processing unit, a beam merging unit, a camera, and a main processing unit; wherein, the beam splitting unit is used to generate signal light and reference light; the signal light is input to the signal light processing unit, and the reference light is input to the reference light processing unit;

[0006] The signal light processing unit includes an optical shaping unit, a coupling optimization unit, a step-index fiber, and a collimation unit connected in sequence.

[0007] A beam merging unit is used to merge the processed reference light output by the reference light processing unit and the processed signal light output by the signal light processing unit.

[0008] A camera is used to generate a first focal point image based on the first combined processed beam output by the combined beam unit after the step-index fiber is subjected to force in an actual measurement scenario.

[0009] The main processing unit is configured to receive a first focal point image generated by the camera; perform singular value decomposition on the first focal point image to obtain multiple first singular values; extract the first left singular vector corresponding to the largest first singular value; calculate a first deviation value between the first left singular vector and a preset initial vector; input the first deviation value into a preset external force variation fitting curve formula to output a force value, and determine the force value as the current force value of the step-index fiber; wherein the preset initial vector and the preset external force variation fitting curve formula are determined based on the second focal point images generated by the camera under experimental test scenarios when no force is applied to the step-index fiber and when different forces are applied.

[0010] In some embodiments, the beam splitting unit includes a laser, an isolator, a first lens, a first reflector, a second lens, a second reflector, a first half-wave plate, a third lens, and a beam splitter;

[0011] The laser beam output from the laser is fed into the isolator; the first lens expands the beam output from the isolator; the first mirror adjusts the coupling position and direction of the beam output from the first lens; the second lens expands the beam output from the first mirror; the second mirror adjusts the coupling position and direction of the beam output from the second lens; the beam output from the second mirror is fed into the first half-wave plate; the third lens expands the beam output from the first half-wave plate; the beam output from the third lens is fed into the beam splitter, which splits the beam output from the third lens into a signal beam and a reference beam.

[0012] In some embodiments, the optical shaping unit includes a first variable optical attenuator, a first polarization-maintaining fiber, a fourth lens, and a second half-wave plate;

[0013] The signal light is fed into the first variable optical attenuator; the beam output from the first variable optical attenuator is fed into the first polarization-maintaining fiber; the fourth lens collimates the beam output from the first polarization-maintaining fiber; and the beam output from the fourth lens is polarized and controlled by the second half-wave plate before being irradiated onto the coupling optimization unit.

[0014] In some embodiments, the coupling optimization unit includes a spatial light modulator, a first polarizer, a third half-wave plate, a fifth lens, a beam deflector, a sixth lens, a seventh lens, a quarter-wave plate, and a first microscope objective.

[0015] The spatial light modulator receives the beam after its polarization state is controlled by the second half-wave plate; the first polarizer filters the beam output by the spatial light modulator; the third half-wave plate controls the polarization state of the beam output by the first polarizer; the beam output by the third half-wave plate passes sequentially through the fifth lens, the beam deflector, the sixth lens, the seventh lens, the quarter-wave plate, and the first microscope objective, and the beam output by the first microscope objective is transmitted into the step-index optical fiber.

[0016] In some embodiments, the collimation unit includes a second microscope objective and an eighth lens;

[0017] The light beam output from the step-index fiber is fed into the second microscope objective, and the light beam output from the second microscope objective is fed into the beam merging unit through the eighth lens.

[0018] In some embodiments, the reference light processing unit includes a second variable optical attenuator, a second polarization-maintaining fiber, a ninth lens, and a fourth half-wave plate;

[0019] The reference light is fed into the second variable optical attenuator; the beam output from the second variable optical attenuator is fed into the second polarization-maintaining fiber; the ninth lens collimates the beam output from the second polarization-maintaining fiber; and the beam output from the ninth lens is fed into the beam merging unit after passing through the fourth half-wave plate.

[0020] In some embodiments, the beam combining unit includes a beam combiner and a tenth lens;

[0021] The beams output from the ninth lens and the fourth half-wave plate are both fed into the beam combiner and merged to obtain a combined beam; the combined beam is then fed into the tenth lens and fed into the camera.

[0022] According to another aspect of this application, a multimode fiber optic mechanical sensing method based on wavefront shaping technology is provided, applied to the main processing unit of the system, the method comprising:

[0023] Receive the first focal point image generated by the camera;

[0024] The first focal point image is processed to obtain a first left singular vector; the first deviation value between the first left singular vector and the preset initial vector is calculated; the first deviation value is input into the preset external force variation fitting curve formula to output the force value, and the force value is determined as the current force value of the step-index fiber; wherein, the preset initial vector and the preset external force variation fitting curve formula are determined based on the second focal point image generated by the camera under the experimental test scenario when no force is applied to the step-index fiber and when different forces are applied.

[0025] In some embodiments, the method further includes determining a preset initial vector and a preset formula for fitting the external force variation curve; wherein, the step of determining the preset initial vector and the preset formula for fitting the external force variation curve includes:

[0026] In the experimental test scenario, the second focal point image generated by the camera when no force is applied to the step-index fiber and when different forces are applied are subjected to singular value decomposition to obtain multiple second singular values; the second left singular vector corresponding to the largest second singular value is extracted, and the second left singular vector determined when no force is applied to the step-index fiber is determined as the preset initial vector.

[0027] Calculate the second left singular vector determined when different forces are applied to the step-index fiber and the second deviation value of the preset initial vector, respectively;

[0028] A preset formula for the fitting curve of external force variation is obtained by linearly fitting the second deviation value corresponding to different applied forces.

[0029] In some embodiments, before the camera generates the second focal point image, the method further includes:

[0030] Receive the third focal point image generated by the camera;

[0031] The second merged beam used to generate the third focal point image is used as input data, and the third focal point image is used as output data.

[0032] Based on the input data and the output data, a transmission matrix for a step-index fiber is constructed.

[0033] The spatial light modulator is controlled based on the transmission matrix to ensure that the third focal point image has a focal point.

[0034] According to another aspect of this application, a computer device is provided, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, wherein the processor executes the multimode fiber optic mechanical sensing method based on wavefront shaping technology.

[0035] According to another aspect of this application, a storage medium is provided that stores a computer program thereon, which, when executed by a processor, implements the above-described multimode fiber optic mechanical sensing based on wavefront shaping technology.

[0036] By means of the above technical solution, this application provides a multimode fiber optic mechanical sensing system and method based on wavefront shaping technology. In this system, wavefront shaping technology is used to form a first focal point image at the far end of a step-index fiber. By analyzing the first focal point image, the stress condition of the step-index fiber is determined, and finally a mechanical sensing system with high sensitivity, large range and no limitations is obtained.

[0037] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0038] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0039] Figure 1 An exemplary schematic diagram of a multimode fiber optic mechanical sensing system based on wavefront shaping technology is shown according to some embodiments;

[0040] Figure 2 The contribution distribution curves of the first 10 principal components of the focal point image in the initial state;

[0041] Figures 3-10 The contribution distribution curves of the first 10 principal components of different speckle patterns obtained at different coupling angles in the initial state are shown.

[0042] Figures 11-12 Exemplary illustrations show schematic diagrams of different preset external force variation fitting curves according to some embodiments;

[0043] Figure 13 These are images of the focal point under different stress conditions on the optical fiber;

[0044] Figure 14 An exemplary flowchart is shown of a multimode fiber optic mechanical sensing method based on wavefront shaping technology according to some embodiments.

[0045] Wherein, 1-laser; 2-isolator; 3-first lens; 4-first reflector; 5-second lens; 6-second reflector; 7-first half-wave plate; 8-third lens; 9-beam splitter; 10-first variable optical attenuator; 11-first polarization-maintaining fiber; 12-fourth lens; 13-second half-wave plate; 14-spatial light modulator; 15-first polarizer; 16-third half-wave plate; 17-fifth lens; 18-beam deflector; 19-sixth lens; 20-seventh lens; 21-quarter-wave plate; 22-first microscope objective; 23-step-index fiber; 24-weight; 25-second variable optical attenuator; 26-second polarization-maintaining fiber; 27-ninth lens; 28-fourth half-wave plate; 29-second microscope objective; 30-eighth lens; 31-beam combiner; 32-tenth lens; 33-camera. Detailed Implementation

[0046] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0047] In related technologies, many MMI-based sensing systems support the measurement of various parameters, such as temperature, contact force, bending, refractive index, and displacement. Although these MMI-based sensing systems have different structures, they can be divided into two types in terms of the objects of analysis: speckle analysis and spectral analysis. The former mainly relies on speckle pattern correlation analysis and deep learning algorithms, while the latter relies on the drift of peaks or critical wavelengths in the transmission spectrum. However, spectral analysis methods typically require more complex experimental systems and more stringent detection methods, and speckle analysis has certain limitations.

[0048] Specifically, spectroscopic analysis relies on detecting the shift of peaks or critical wavelengths in the transmission spectrum when external parameters change. One related technology is a high-sensitivity surface plasmon resonance (SPR) sensor based on a multimode fiber (MMF)-tapered hollow-core fiber (THCF)-MMF structure for refractive index (RI) sensing, proposing a novel sensing method: as RI increases, the MMI peak undergoes a blue shift, opposite in direction to the SPR peak. By monitoring the difference between the two resonance peaks, a high-sensitivity RI sensor can be obtained. For an MMF-THCF-MMF probe with a normal hollow-core fiber (HCF) core diameter of 30 μm and a taper ratio of 3.3, by monitoring the wavelength difference, a sensitivity of 7592.25 nm / RIU can be achieved at an RI of 1.40, higher than the sensitivity of monitoring only the SPR peak. However, such spectroscopic analysis methods typically require complex experimental systems and more stringent detection methods.

[0049] Speckle analysis primarily relies on correlation analysis of speckle patterns or the use of deep learning algorithms. When the optical field propagates through a multimode fiber, it changes due to modal dispersion and mode aliasing, resulting in randomly distributed, irregular speckles at the fiber's distal end. These speckle images contain multiple modes and are highly sensitive to changes in the external environment. By analyzing these speckle variations, various physical parameters can be measured. One related technique uses a single MMF structure and, based on the quantization of intensity and modal phase deviation, calculates the normalized inner product of intensity (NIPC) on the fiber speckle pattern to measure the magnitude or location of applied forces on a 30×30 mm² array. Although this system provides a reliable response to single-point excitation, other techniques are needed to evaluate the magnitude and location of multiple forces. Another related technique proposes a novel structure for ultrashort multimode fiber for fiber speckle sensing and demonstrates its application in multi-bend sensing. This speckle pattern-based sensing method offers advantages such as system simplicity, low cost, and high sensitivity; however, the limitations of speckle pattern sensors are mainly related to the use of digital cameras to capture and analyze speckle patterns. Generally, a larger field of view (FOV) is better for collecting more information about the specks. However, this conflicts with the requirement that every speckle in the field of view should be digitally resolved, especially when camera bandwidth and data transmission are limited.

[0050] To address the aforementioned technical problems, this application proposes a multimode fiber optic mechanical sensing system and method based on wavefront shaping technology. In this system, wavefront shaping technology is used to form a first focal point image at the far end of a step-index fiber. By analyzing the first focal point image, the stress condition of the step-index fiber is determined, ultimately resulting in a mechanical sensing system with high sensitivity, large range, and no limitations.

[0051] The wavefront shaping (WFS) technique mentioned in this application embodiment is used to compensate for optical scattering in order to achieve deep diffraction-limited optical focusing in complex media. In this application embodiment, the changes in the physical environment of the optical fiber are tracked by analyzing the changes in the main characteristics of the focal point.

[0052] Specifically, this application provides a multimode fiber optic mechanical sensing system based on wavefront shaping technology. The system includes: a beam splitting unit, a signal light processing unit, a reference light processing unit, a beam merging unit, a camera, and a main processing unit.

[0053] The beam splitting unit is used to generate signal light and reference light; the signal light is input to the signal light processing unit, and the reference light is input to the reference light processing unit.

[0054] In some embodiments, Figure 1An exemplary schematic diagram of a multimode fiber optic mechanical sensing system based on wavefront shaping technology is shown according to some embodiments. The beam splitting unit includes a laser 1, an isolator 2, a first lens 3, a first reflector 4, a second lens 5, a second reflector 6, a first half-wave plate 7, a third lens 8, and a beam splitter 9.

[0055] The beam output from the laser 1 is transmitted into the isolator 2.

[0056] In this embodiment, laser 1 is configured to provide a light source for the system. Isolator 2 can prevent reflected light from the system from returning to laser 1.

[0057] The first lens 3 expands the beam output from the isolator 2; the first reflector 4 adjusts the coupling position and direction of the beam output from the first lens 3; the second lens 5 expands the beam output from the first reflector 4; the second reflector 6 adjusts the coupling position and direction of the beam output from the second lens 5; the beam output from the second reflector 6 is transmitted into the first half-wave plate 7.

[0058] In this embodiment, the first half-wave plate 7 can adjust the splitting ratio coupled into the beam splitter 9.

[0059] The third lens 8 expands the beam output from the first half-wave plate 7; the beam output from the third lens 8 is fed into the beam splitter 9, which splits the beam output from the third lens 8 into a signal beam and a reference beam. In one example, the splitting ratio of the signal beam is 98%, and the splitting ratio of the reference beam is 2%.

[0060] The signal light processing unit includes an optical shaping unit, a coupling optimization unit, a step-index fiber, and a collimation unit connected in sequence.

[0061] In some embodiments, the optical shaping unit includes a first variable optical attenuator 10, a first polarization-maintaining fiber 11, a fourth lens 12, and a second half-wave plate 13. The signal light is transmitted through the first variable optical attenuator 10. In this embodiment, the first variable optical attenuator 10 can control the intensity of the signal light.

[0062] The beam output from the first variable optical attenuator 10 is fed into the first polarization-maintaining fiber 11, and the fourth lens 12 collimates the beam output from the first polarization-maintaining fiber 11; the beam output from the fourth lens 12 is then irradiated onto the coupling optimization unit after being polarized by the second half-wave plate 13.

[0063] In this embodiment, the light beam output from the second half-wave plate illuminates the spatial light modulator 14 in the coupling optimization unit.

[0064] In some embodiments, the coupling optimization unit includes a spatial light modulator 14, a first polarizer 15, a third half-wave plate 16, a fifth lens 17, a beam deflector 18, a sixth lens 19, a seventh lens 20, a quarter-wave plate 21, and a first microscope objective 22.

[0065] The spatial light modulator 14 receives the beam after its polarization state is controlled by the second half-wave plate 13; the first polarizer 15 filters the beam output by the spatial light modulator 14; the third half-wave plate 16 controls the polarization state of the beam output by the first polarizer 15; the beam output by the third half-wave plate 16 passes sequentially through the fifth lens 17, the beam deflector 18, the sixth lens 19, the seventh lens 20, the quarter-wave plate 21, and the first microscope objective 22.

[0066] In this embodiment, the beam passes through a fifth lens 17, a beam deflector 18, a sixth lens 19, a seventh lens 20, and a quarter-wave plate 21 in sequence to change its polarization state.

[0067] The light beam output from the first microscope objective is fed into the step-index fiber. In this embodiment, the step-index fiber is a multimode fiber.

[0068] In some embodiments, the collimation unit includes a second microscope objective 29 and an eighth lens 30.

[0069] The light beam output from the step-index fiber is transmitted to the second microscope objective 29, and the light beam output from the second microscope objective 29 is transmitted to the beam merging unit through the eighth lens 30.

[0070] In this embodiment, the beam output from the step-index fiber is expanded by the second microscope objective 29 and the eighth lens 30 and then transmitted to the beam combiner 31 in the beam combining unit.

[0071] In some embodiments, the reference light processing unit includes a second variable optical attenuator 25, a second polarization-maintaining fiber 26, a ninth lens 27, and a fourth half-wave plate 28. The reference light is fed into the second variable optical attenuator 25. In this embodiment, the second variable optical attenuator 25 can control the intensity of the reference light. The beam output from the second variable optical attenuator 25 is fed into the second polarization-maintaining fiber 26, and the ninth lens 27 collimates the beam output from the second polarization-maintaining fiber 26; the beam output from the ninth lens 27 is then fed into the beam merging unit after passing through the fourth half-wave plate 28.

[0072] In this embodiment, the beam output from the fourth half-wave plate 28 is input into the beam combiner 31 in the beam combining unit.

[0073] The beam merging unit is used to merge the processed reference light output by the reference light processing unit and the processed signal light output by the signal light processing unit.

[0074] In some embodiments, the beam combining unit includes a beam combiner 31 and a tenth lens 32.

[0075] The beams output from the ninth lens 27 and the fourth half-wave plate 28 are both fed into the beam combiner 31 and merged to obtain a merged beam; the merged beam is fed into the tenth lens 32 and then into the camera 33.

[0076] Camera 33 is used to generate a first focal point image based on the first combined processed beam output by the combined beam unit after the step-index fiber 23 is subjected to force in an actual measurement scenario.

[0077] In this embodiment, under actual testing conditions, after the step-index fiber is subjected to force, the camera generates a first focal point image based on the first combined processed beam output by the beam merging unit. Specifically, after receiving the merged beam, the tenth lens in the beam merging unit outputs the first combined processed beam, and the camera generates the first focal point image after receiving the first combined processed beam.

[0078] In one example, the actual measurement scenario could be measuring the gravity of an object. The corresponding way to apply force to a step-index fiber is to place an object on the fiber, and the final force value output by the main processing unit is the gravity of the object.

[0079] The main processing unit is configured to receive a first focal point image generated by the camera; perform singular value decomposition (SVD) on the first focal point image to obtain multiple first singular values; extract the first left singular vector corresponding to the largest first singular value; calculate a first deviation value between the first left singular vector and a preset initial vector; input the first deviation value into a preset external force variation fitting curve formula to output a force value, and determine the force value as the current force value of the step-index fiber; wherein the preset initial vector and the preset external force variation fitting curve formula are determined based on the second focal point images generated by the camera under experimental test scenarios when no force is applied to the step-index fiber and when different forces are applied.

[0080] In this embodiment of the application, the first left singular vector corresponding to the largest first singular value in the first focal point image is extracted by singular value decomposition, specifically according to the following formulas (1)-(3):

[0081] (1)

[0082] (2)

[0083] (3)

[0084] in, Represented as the first focal point image; U, V and V are the left singular vector matrix, singular value matrix, and right singular vector matrix obtained after performing singular value decomposition on the first focal point image, respectively. The singular value matrix includes multiple first singular values, and the left singular vector matrix includes multiple first left singular vectors corresponding to the first singular values. It is the first singular value, which is related to the eigenvalue. There is a quadratic relationship; First singular value ( The first left singular vector corresponding to ) is r=min(a,b), where a represents the number of horizontal pixels in the first focal point image and b represents the number of vertical pixels in the first focal point image.

[0085] The first singular value reflects how the energy or information in the first focal point image is distributed in different directions. The largest first singular value indicates that the corresponding direction contains more information or change (i.e., higher energy), and its corresponding eigenvalue is often associated with the main features or patterns of the first focal point image, and best reflects the influence of external factors on the focal point.

[0086] In some embodiments, the method further includes: determining a preset initial vector and a preset external force variation fitting curve formula; wherein, the step of determining the preset initial vector and the preset external force variation fitting curve formula includes: in an experimental test scenario, performing singular value decomposition on the second focal point image generated by the camera when no force is applied to the step-index fiber and when different forces are applied to obtain multiple second singular values; extracting the second left singular vector corresponding to the largest second singular value, and determining the second left singular vector determined when no force is applied to the step-index fiber as the preset initial vector; calculating the second deviation values ​​of the second left singular vector determined when different forces are applied to the step-index fiber and the preset initial vector respectively; and performing linear fitting on the second deviation values ​​corresponding to the different forces to obtain the preset external force variation fitting curve formula.

[0087] In one example, different forces can be applied by placing weights 24 of varying weights on the step-index fiber. In another example, different forces can be applied by using a press on the step-index fiber.

[0088] In this embodiment of the application, before testing the stress condition of the step-index fiber in the actual test scenario, a second focal point image is generated in the experimental test scenario. The process of generating the second focal point image is the same as the process of generating the first focal point image in the actual test scenario. Both involve first emitting a laser beam, then generating a focal point image using the structure of the system, and then using the second focal point image generated in the experimental test scenario to determine the preset initial vector and the preset external force change fitting curve formula.

[0089] In this embodiment, SVD processing is performed on each second focal point image under different stress conditions, and the second left singular vector corresponding to the largest second singular value representing the most important feature of the second focal point image is extracted as an important parameter reflecting the change in the physical state of the optical fiber. In this embodiment, the formula used to calculate the second left singular vector using the second focal point image is the same as the formula used to calculate the first left singular vector using the first focal point image mentioned above. The second left singular vector determined when no force is applied to the step-index fiber is determined as a preset initial vector.

[0090] In this embodiment of the application, the second deviation value between the second left singular vector and the preset initial vector determined when different forces are applied to the step-index fiber is calculated. Specifically, the second deviation value between the second left singular vector and the preset initial vector can be calculated using the Euclidean distance method, and can be obtained using formula (4):

[0091] (4)

[0092] in, Let i be the i-th element in the preset initial vector. Let be the i-th element in the second left singular vector of the second focal point image under different forces. The value of D increases as the difference between the second left singular vector and the preset initial vector increases. n is the length of the second left singular vector, that is, the total number of elements contained in the second left singular vector.

[0093] In this embodiment, a preset external force variation fitting curve formula is obtained by linearly fitting the second deviation value corresponding to different applied forces. The specific linear fitting method can be MATLAB linear fitting. The horizontal axis of the preset external force variation fitting curve can be the applied external force, and the vertical axis can be the second deviation value.

[0094] In this embodiment, a focal point is formed at the far end of a step-index fiber using wavefront shaping technology, and a preset formula for fitting the external force variation curve is established by analyzing the changes in the focal point image under stress on the step-index fiber.

[0095] The above steps can be used to determine the preset initial vector and the preset formula for fitting the external force change curve.

[0096] In this embodiment of the application, the calculation of the first deviation value between the first left singular vector and the preset initial vector can be the same as the calculation of the second deviation value between the second left singular vector and the preset initial vector. Since it has been described in detail above, it will not be repeated here.

[0097] In this embodiment, a first deviation value can be input into a preset external force change fitting formula to obtain the corresponding force value, which is then used as the current force value of the step-index fiber. If the scenario involves testing the gravity of an object placed on the step-index fiber, the calculated current force value is the object's gravity.

[0098] In some embodiments, before the camera generates a second focal point image, the method further includes: receiving a third focal point image generated by the camera; using a second merged processed beam for generating the third focal point image as input data and the third focal point image as output data; constructing a transmission matrix for a step-index fiber based on the input data and the output data; and controlling a spatial light modulator based on the transmission matrix to ensure that the third focal point image has a focal point.

[0099] In this embodiment, the process of generating the third focal point image is the same as that of the first focal point image. First, a laser beam is emitted, and then the focal point image is generated using the structure of the system.

[0100] In this embodiment, the spatial light modulator can adjust the amplitude, phase, and polarization state of the light beam entering the step-index fiber. Before determining the preset initial vector and the preset external force variation fitting curve formula, the spatial light modulator needs to be controlled. Specifically, the optical field correspondence between the input and output of the step-index fiber is established, and the transmission matrix of the step-index fiber is constructed based on this. The spatial light modulator is precisely controlled using the transmission matrix to make the amplitude and phase of the output light of the step-index fiber generate a clear focal point at the output end of the step-index fiber.

[0101] In this embodiment, a transmission matrix for a step-index fiber is constructed based on input and output data using holographic interferometric projection.

[0102] In this embodiment, the feasibility of the system is verified through experiments. Specifically, principal component analysis is used to analyze the differences in feature distribution between the focal point image and the speckle image. Here, the principal component can be understood as the direction that captures image information; the higher the contribution rate of the principal component, the more information is distributed along this direction. When the contribution rate of a very small number of principal components in an image is much higher than that of other principal components, it indicates that most of the information in this image is concentrated in a very small number of directions; conversely, it indicates that the information in the image is relatively dispersed. To increase the completeness of the analysis, speckle images obtained at different coupling angles are also selected for comparison with the focal point image. Figure 2 The contribution distribution curves of the first 10 principal components of the focal point image in the initial state (without force applied to the step-index fiber). Figures 3-10 The figure shows the contribution distribution curves of the top 10 principal components of different speckle patterns obtained at different coupling angles in the initial state. It is clear from the figure that the maximum principal component contribution rate of the focal point image is as high as 0.99 or higher, with most of the image information concentrated in the direction corresponding to the maximum principal component. In contrast, the maximum principal component contribution rate of the speckle image is between 0.2 and 0.6, and the image information is more dispersed compared to the focal point image. Therefore, it can be concluded that the focal point image obtained using wavefront shaping technology has concentrated information and distinct features, and it holds promise for obtaining external information by tracking the feature changes of the focal point image.

[0103] The technical effects of the method in the embodiments of this application are as follows: Figure 11 and 12 As shown. Figure 11 The experimental results of this system are presented, with a force measurement range from 0.5N to 5N. The blue line represents the linear fitting curve between the second deviation value and the external force applied to the optical fiber, with a fitting R0. 2 The value is 0.9948, and the corresponding predetermined formula for the fitting curve of the external force change is y1=0.00567x+0.00120, where x is the external force and y is the second deviation value. Figure 12 This further demonstrates the system's resolution capability, with a minimum resolution of 0.05 N and a fitted R-value. 2 The value is 0.977, and the corresponding predetermined formula for the fitting curve of the external force change is y1=0.00532x+0.00110, where x is the external force and y is the second deviation value. Figure 13 The images shown here depict the focal point under different stress conditions on the optical fiber. All images have been logarithmically and normally processed. It can be seen that as the external force on the optical fiber increases, the noise around the focal point increases, but the center still appears as a bright circle. These results all indicate that the wavefront shaping technique used in this embodiment establishes a large-range, high-sensitivity system.

[0104] By applying the technical solutions of the above embodiments, a multimode fiber optic mechanical sensing system based on wavefront shaping technology is provided. In this system, a first focal point image is formed at the far end of a step-index fiber using wavefront shaping technology. The force condition of the step-index fiber is determined by analyzing the first focal point image. Finally, a mechanical sensing system with high sensitivity, large range, and no limitations is obtained, with a force measurement range of 0-0.5N and a minimum resolution of 0.05N.

[0105] In some embodiments, as a specific implementation of the multimode fiber optic mechanical sensing system based on wavefront shaping technology described in the above embodiments, some embodiments of this application also provide a multimode fiber optic mechanical sensing method based on wavefront shaping technology, applied to the main processing unit of the system.

[0106] Figure 14 An exemplary flowchart of a multimode fiber mechanics sensing method based on wavefront shaping technology is shown according to some embodiments. The method includes steps S100-S300. S100: Receiving a first focal point image generated by a camera; S200: Processing the first focal point image to obtain a first left singular vector; calculating a first deviation value between the first left singular vector and a preset initial vector; S300: Inputting the first deviation value into a preset external force variation fitting curve formula to output a force value, and determining the force value as the current force value of the step-index fiber; wherein the preset initial vector and the preset external force variation fitting curve formula are determined based on second focal point images generated by the camera under experimental testing scenarios when no force is applied to the step-index fiber and when different forces are applied.

[0107] It should be noted that the corresponding descriptions of the steps involved in the multimode fiber optic mechanical sensing method based on wavefront shaping technology provided in the embodiments of this application can be referred to the corresponding descriptions in the multimode fiber optic mechanical sensing system based on wavefront shaping technology provided in the above embodiments, and will not be repeated here.

[0108] This application also provides a computer device, specifically a personal computer, server, network device, etc. The computer device includes a bus, processor, memory, and communication interface, and may also include input / output interfaces and a display device. The processor of the computer device provides computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database of the computer device stores location information. The network interface of the computer device is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements the steps in the various method embodiments.

[0109] Those skilled in the art will understand that the structure of the computer device described above is only a partial structure related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. A specific computer device may include more or fewer components, or combine certain components, or have different component arrangements.

[0110] In one embodiment, a computer-readable storage medium is also provided, which may be non-volatile or volatile, having stored thereon a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0111] In one embodiment, a computer program product is also provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0112] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0113] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A multimode fiber optic mechanical sensing system based on wavefront shaping technology, characterized in that, include: The system comprises a beam splitting unit, a signal light processing unit, a reference light processing unit, a beam merging unit, a camera, and a main processing unit; wherein, the beam splitting unit is used to generate signal light and reference light; the signal light is input to the signal light processing unit, and the reference light is input to the reference light processing unit; The signal light processing unit includes an optical shaping unit, a coupling optimization unit, a step-index fiber, and a collimation unit connected in sequence. A beam merging unit is used to merge the processed reference light output by the reference light processing unit and the processed signal light output by the signal light processing unit. A camera is used to generate a first focal point image based on the first combined processed beam output by the combined beam unit after the step-index fiber is subjected to force in an actual measurement scenario. The main processing unit is configured to receive a first focal point image generated by the camera; perform singular value decomposition on the first focal point image to obtain multiple first singular values; extract the first left singular vector corresponding to the largest first singular value; calculate a first deviation value between the first left singular vector and a preset initial vector; input the first deviation value into a preset external force variation fitting curve formula to output a force value, and determine the force value as the current force value of the step-index fiber; wherein the preset initial vector and the preset external force variation fitting curve formula are determined based on the second focal point images generated by the camera under experimental test scenarios when no force is applied to the step-index fiber and when different forces are applied.

2. The system according to claim 1, characterized in that, The beam splitting unit includes a laser, an isolator, a first lens, a first reflector, a second lens, a second reflector, a first half-wave plate, a third lens, and a beam splitter; The laser beam output from the laser is fed into the isolator; the first lens expands the beam output from the isolator; the first mirror adjusts the coupling position and direction of the beam output from the first lens; the second lens expands the beam output from the first mirror; the second mirror adjusts the coupling position and direction of the beam output from the second lens; the beam output from the second mirror is fed into the first half-wave plate; the third lens expands the beam output from the first half-wave plate; the beam output from the third lens is fed into the beam splitter, which splits the beam output from the third lens into a signal beam and a reference beam.

3. The system according to claim 1, characterized in that, The optical shaping unit includes a first variable optical attenuator, a first polarization-maintaining fiber, a fourth lens, and a second half-wave plate. The signal light is fed into the first variable optical attenuator; the beam output from the first variable optical attenuator is fed into the first polarization-maintaining fiber; the fourth lens collimates the beam output from the first polarization-maintaining fiber; and the beam output from the fourth lens is polarized and controlled by the second half-wave plate before being irradiated onto the coupling optimization unit.

4. The system according to claim 3, characterized in that, The coupling optimization unit includes a spatial light modulator, a first polarizer, a third half-wave plate, a fifth lens, a beam deflector, a sixth lens, a seventh lens, a quarter-wave plate, and a first microscope objective. The spatial light modulator receives the beam after its polarization state is controlled by the second half-wave plate; the first polarizer filters the beam output by the spatial light modulator; the third half-wave plate controls the polarization state of the beam output by the first polarizer; the beam output by the third half-wave plate passes sequentially through the fifth lens, the beam deflector, the sixth lens, the seventh lens, the quarter-wave plate, and the first microscope objective, and the beam output by the first microscope objective is transmitted into the step-index optical fiber.

5. The system according to claim 4, characterized in that, The collimation unit includes a second microscope objective and an eighth lens; The light beam output from the step-index fiber is fed into the second microscope objective, and the light beam output from the second microscope objective is fed into the beam merging unit through the eighth lens.

6. The system according to claim 5, characterized in that, The reference light processing unit includes a second variable optical attenuator, a second polarization-maintaining fiber, a ninth lens, and a fourth half-wave plate; The reference light is fed into the second variable optical attenuator; the beam output from the second variable optical attenuator is fed into the second polarization-maintaining fiber; the ninth lens collimates the beam output from the second polarization-maintaining fiber; and the beam output from the ninth lens is fed into the beam merging unit after passing through the fourth half-wave plate.

7. The system according to claim 6, characterized in that, The beam combining unit includes a beam combiner and a tenth lens; The beams output from the ninth lens and the fourth half-wave plate are both fed into the beam combiner and merged to obtain a combined beam; the combined beam is then fed into the tenth lens and fed into the camera.

8. A multimode fiber optic mechanical sensing method based on wavefront shaping technology, applied to the main processing unit of the system described in any one of claims 1-7, characterized in that, The method includes: Receive the first focal point image generated by the camera; The first focal point image is processed to obtain a first left singular vector; the first deviation value between the first left singular vector and the preset initial vector is calculated; the first deviation value is input into the preset external force variation fitting curve formula to output the force value, and the force value is determined as the current force value of the step-index fiber; wherein, the preset initial vector and the preset external force variation fitting curve formula are determined based on the second focal point image generated by the camera under the experimental test scenario when no force is applied to the step-index fiber and when different forces are applied.

9. The method according to claim 8, characterized in that, It also includes determining a preset initial vector and a preset formula for fitting the external force variation curve; wherein, the step of determining the preset initial vector and the preset formula for fitting the external force variation curve includes: In the experimental test scenario, the second focal point image generated by the camera when no force is applied to the step-index fiber and when different forces are applied are subjected to singular value decomposition to obtain multiple second singular values; the second left singular vector corresponding to the largest second singular value is extracted, and the second left singular vector determined when no force is applied to the step-index fiber is determined as the preset initial vector. Calculate the second left singular vector determined when different forces are applied to the step-index fiber and the second deviation value of the preset initial vector, respectively; A preset formula for the fitting curve of external force variation is obtained by linearly fitting the second deviation value corresponding to different applied forces.

10. The method according to claim 9, characterized in that, Before the camera generates the second focal point image, the following is also included: Receive the third focal point image generated by the camera; The second merged beam used to generate the third focal point image is used as input data, and the third focal point image is used as output data. Based on the input data and the output data, a transmission matrix for a step-index fiber is constructed. The spatial light modulator is controlled based on the transmission matrix to ensure that the third focal point image has a focal point.

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