A three-dimensional magnetic field visualization method based on focused vector beam

Abstract

The application provides a three-dimensional magnetic field visualization method based on a focused vector light beam, and belongs to the technical field of optical sensing. The method comprises the following steps: step one, building an optical path, wherein the optical path is sequentially arranged with a sensing assembly, a filtering assembly and an imaging assembly along the propagation direction of a radial vector light beam; step two, placing the optical path built in step one in a three-dimensional magnetic field; and step three, making the radial vector light beam incident into the sensing assembly, so that a light beam image containing three-dimensional magnetic field information can be obtained through the imaging assembly. Through two lenses and a magnetic field crystal, three-dimensional magnetic field information in space can be transcribed into a focused vector light beam, and the focused vector light beam is output after collimation, and three-dimensional magnetic field information can be obtained by analyzing the polarization state, so that the visualization of the magnetic field is realized.

Description

Technical Field

[0001] This invention relates to a three-dimensional magnetic field visualization method based on a focused vector beam, belonging to the field of optical sensing technology. Background Technology

[0002] Magnetic fields are ubiquitous in nature and artificial environments, including the Earth, the Sun, planets, electromagnetic waves, and various industrial equipment and systems. Effective observation of three-dimensional magnetic fields has applications in numerous fields. For example, in space science, measuring the magnetic fields of the Earth and other celestial bodies allows for the analysis of their structure, evolution, interactions with the cosmic environment, and the prediction of solar storms. In geophysics, measuring three-dimensional magnetic fields helps in understanding the Earth's magnetic field structure, mantle convection, plate tectonics, and other phenomena. In industrial applications, three-dimensional magnetic field measurements facilitate the analysis and optimization of magnetic fields in power transmission, disk storage, and equipment monitoring. In the biological field, magnetic imaging is a key application of three-dimensional magnetic field measurement technology. Therefore, three-dimensional magnetic field measurement provides crucial support for human understanding of nature and technological advancement. However, one effective way to achieve three-dimensional magnetic field measurement is to first visualize the three-dimensional magnetic field. Therefore, how to visualize three-dimensional magnetic fields is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for visualizing three-dimensional magnetic fields based on a focused vector beam.

[0004] This invention is achieved through the following technical solution:

[0005] A method for visualizing a three-dimensional magnetic field based on a focused vector beam includes the following steps:

[0006] Step 1: Construct the optical path. Sensing components, filtering components, and imaging components are arranged sequentially along the radial vector beam propagation direction.

[0007] Step 2: Place the optical path established in Step 1 into a three-dimensional magnetic field;

[0008] Step 3: Inject the radial vector beam into the sensing component, and the imaging component can obtain a beam image containing three-dimensional magnetic field information.

[0009] The sensing element includes lens A, a magneto-optical crystal, and lens B arranged sequentially along the radial vector beam propagation direction, with lens A and lens B arranged coaxially. In use, the direction of the magnetic field at the location of the sensing element will change the direction of the stripes in the output image, and its magnitude will affect the number and position of the stripes in the output image, thus the image displays magnetic field information.

[0010] Lens A and lens B are high numerical aperture lenses with a numerical aperture greater than 1. A larger numerical aperture allows the beam to be deflected at a larger angle, which allows the beam to carry more three-dimensional magnetic field information.

[0011] The filtering component is a polarizer.

[0012] The imaging component is an infrared camera.

[0013] With the centroid of the magneto-optical crystal as the origin and the direction perpendicular to lens A as the positive Z-axis, a three-dimensional Cartesian coordinate system is established. When a beam of light is incident on lens A along the Z-axis, its momentum space k is represented as k = (0, 0, 1). After being focused, its momentum space is transformed into... Where θ is the angle between the line connecting the exit point of the beam on lens A to the focal point and the optical axis when focusing, θ = arctan(ρ / f), where f is the focal length, ρ is the distance of the beam to the center of lens A, and φ is the azimuth coordinate of the beam at lens A.

[0014] Assume the magnetic field vector is represented as B = (B x B y B z ), where the subscripts indicate the components of the magnetic field on that coordinate axis. Then, the Faraday rotations produced by the magnetic field on space beams with different momentum are:

[0015]

[0016] Where V is the Wilder constant, which can also be considered as the magneto-optical coefficient, k0 is the wavenumber, and L is the length of the magneto-optical crystal. During the focusing process, the momentum space of the radial vector beam undergoes a transformation. Beams at different positions enter the focal point in different directions. Under the influence of the magnetic field, beams at different positions are affected by different magneto-optical Faraday effects, thus changing the polarization state of the beam. In other words, after the radial vector beam is focused, its momentum space changes, and beams at different spatial coordinates propagate in different directions. When the magneto-optical Faraday effect acts on the beam, the magnetic field component along the beam propagation direction takes effect. Therefore, the electric field polarization of the output beam from the sensing component is different at different spatial positions. Thus, the polarization of the output beam from the sensing component carries magnetic field information.

[0017] When the incident light field is a radial vector light field, its electric field polarization state is represented by the Jones vector as follows:

[0018]

[0019] The polarization state of the emitted light carrying magnetic field information is then represented as:

[0020]

[0021] After filtering by a horizontal polarizer, the scalar expression of its electric field is:

[0022] E′=cos(φ+β)

[0023] Therefore, the camera will display an image containing magnetic field information.

[0024] The beneficial effects of this invention are as follows: by using two lenses and a magnetic field crystal, three-dimensional magnetic field information in space can be transcribed into a focused vector beam, collimated, and output. By analyzing its polarization state, three-dimensional magnetic field information can be obtained, thus realizing the visualization of the magnetic field. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the sensing component of the present invention.

[0026] Figure 2 This is a schematic diagram of the structure for establishing a three-dimensional Cartesian rectangular coordinate system according to the present invention.

[0027] Figure 3 It is a diagram showing the field distribution and polarization state of the incident beam.

[0028] Figure 4 This is the output light spot pattern without a magnetic field.

[0029] Figure 5 This is a light spot pattern when a magnetic field of 150mT is applied in the X direction.

[0030] Figure 6 This is a light spot pattern when a magnetic field of 150mT is applied in the Y direction.

[0031] Figure 7 It is a light spot diagram when a magnetic field of 150mT in the X direction and 150mT in the Y direction is applied.

[0032] Figure 8 It is a light spot pattern when a magnetic field of 50mT in the X direction and 150mT in the Y direction is applied.

[0033] Figure 9 It is a light spot pattern when a magnetic field of 50mT in the X direction and 50mT in the Y direction is applied.

[0034] Figure 10 This is a light spot pattern when a magnetic field of 150mT is applied in the Z direction.

[0035] Figure 11 It is a light spot pattern when a magnetic field of 150mT in the X direction, 150mT in the Y direction, and 0mT in the Z direction is applied.

[0036] Figure 12 It is a light spot diagram when a magnetic field of 150mT is applied in the X direction, 150mT in the Y direction, and 150mT in the Z direction.

[0037] In the diagram: 1-Lens A, 2-Magneto-optical crystal, 3-Lens B. Detailed Implementation

[0038] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0039] This invention provides a method for visualizing three-dimensional magnetic fields based on a focused vector beam, referring to... Figures 1 to 12 In the preferred embodiment, the following description is provided in conjunction with the accompanying drawings:

[0040] Example 1:

[0041] like Figure 1 and Figure 2 As shown, lens A1 focuses the light beam, lens B3 collimates the light beam, and the magneto-optical crystal 2 in the middle provides the medium for the magneto-optical effect. Figure 2 The coordinate system is marked in the figure. The incident light propagates along the z-axis, is focused by lens A1 and enters magneto-optical crystal 2. After passing through the Faraday effect, it is collimated by lens B3 and then emitted.

[0042] The field distribution and polarization of the incident vector beam are as follows Figure 3 As shown.

[0043] In this embodiment, numerical simulation is used to simulate the output light spot obtained by the beam under magnetic fields in different directions. The parameters used in this simulation experiment are as follows: the magneto-optical crystal is a YIG crystal, the Wilder constant is 1885 rad / (T·m), the incident light spot width is 5 mm, the lens NA=1.3 objective lens, the focal length is 1.8 mm, the YIG crystal thickness is 2 mm, and magnetic fields in different directions are applied to the sensing component.

[0044] In this embodiment, the beam output by the sensing element is horizontally polarized and filtered, and then the field distribution of its output is observed.

[0045] In this embodiment, the output light spot without a magnetic field is as follows: Figure 4 As shown.

[0046] In this embodiment, when a magnetic field of 150mT is applied in the X direction, the output light spot is as follows: Figure 5 As shown.

[0047] In this embodiment, when a magnetic field of 150mT is applied in the Y direction, the output light spot is as follows: Figure 6 As shown.

[0048] In this embodiment, when a magnetic field of 150mT is applied in the X direction and a magnetic field of 150mT in the Y direction, the output light spot is as follows: Figure 7 As shown.

[0049] In this embodiment, when a magnetic field of 50mT is applied in the X direction and a magnetic field of 150mT in the Y direction, the output light spot is as follows: Figure 8 As shown.

[0050] In this embodiment, when a magnetic field of 50mT is applied in the X direction and a magnetic field of 50mT in the Y direction, the output light spot is as follows: Figure 9 As shown.

[0051] As can be seen from the above results, a transverse magnetic field (magnetic field in the XY plane) will cause the direction of the light spot stripes to be consistent with the direction of the magnetic field, and the stronger the magnetic field, the denser the stripes.

[0052] In this embodiment, when a Z-direction magnetic field of 150mT is applied, the output light spot is as follows: Figure 10 As shown. With Figure 4 As can be seen from the comparison, when there is no transverse magnetic field, the magnetic field in the Z direction will cause the light spot to rotate.

[0053] In this embodiment, a magnetic field of 150 mT is applied in the X direction, a magnetic field of 150 mT is applied in the Y direction, and the Z direction is 0, as shown in the light spot. Figure 11 As shown. When a magnetic field of 150 mT is applied in the X direction, 150 mT in the Y direction, and 150 mT in the Z direction, the light spot is as follows. Figure 12 As shown, when a transverse magnetic field is present, a longitudinal magnetic field causes the stripes to shift.

[0054] This invention utilizes the momentum space transformation of a focused vector beam to enable the polarization of the output light field to carry three-dimensional magnetic field information. By analyzing its polarization, a visualized image of the three-dimensional magnetic field can be obtained. In the output light spot, the transverse magnetic field causes the fringe direction of the output light spot to align with the transverse magnetic field direction; the larger the magnetic field, the more fringe lines there are. The longitudinal magnetic field causes the fringe of the output light spot to shift. Since the fringe lies in the cosine function, when the Faraday effect exceeds 180°, it will return to its original position. Therefore, limited by this period, the amount of shift caused by the longitudinal magnetic field has an upper limit. This invention provides a three-dimensional magnetic field visualization method based on a focused vector beam, which allows the acquisition of three-dimensional magnetic field information by observing the light spot.

Claims

1. A method for three-dimensional magnetic field visualization based on focused vector beams, characterized in that: Includes the following steps: Step 1: Construct the optical path. Sensing components, filtering components, and imaging components are arranged sequentially along the radial vector beam propagation direction. Step 2: Place the optical path established in Step 1 into a three-dimensional magnetic field; Step 3: Inject the radial vector beam into the sensing component, and the imaging component can obtain a beam image containing three-dimensional magnetic field information. The sensing element includes a lens A (1), a magneto-optical crystal (2) and a lens B (3) arranged sequentially along the radial vector beam propagation direction, and the lens A (1) and the lens B (3) are arranged coaxially. With the center of mass of the magneto-optical crystal (2) as the origin and the direction perpendicular to lens A (1) as the positive Z-axis, a three-dimensional Cartesian coordinate system is established. When a beam of light is incident on lens A (1) along the Z-axis, its momentum space... Represented as After being focused, its momentum space is converted into ,in It is the angle between the line connecting the exit point of the beam on lens A (1) to the focal point and the optical axis when the beam is focused. ,in Focal length The distance from the beam to the center of lens A(1) is... Let be the azimuth coordinates of the beam at lens A(1); Assume the magnetic field vector is represented as The subscripts indicate the components of the magnetic field on that coordinate axis. Therefore, the Faraday rotations produced by the magnetic field on beams of different momentum spaces are: ， in It is the Wilder constant, which can also be considered as the magneto-optical coefficient. For wave number, The length of the magneto-optical crystal (2); When the incident light field is a radial vector light field, its electric field polarization state is represented by the Jones vector as follows: ， The polarization state of the emitted light carrying magnetic field information is then represented as: ， After filtering by the polarizer, the scalar expression of its electric field is: ， Therefore, the camera will display an image containing magnetic field information.

2. The three-dimensional magnetic field visualization method based on a focused vector beam as described in claim 1, characterized in that: Lens A (1) and lens B (3) are high numerical aperture lenses with a numerical aperture greater than 1.

3. The three-dimensional magnetic field visualization method based on a focused vector beam as described in claim 1, characterized in that: The filtering component is a polarizer.

4. The three-dimensional magnetic field visualization method based on a focused vector beam as described in claim 1, characterized in that: The imaging component is an infrared camera.

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