Method and device for measuring three-dimensional refractive index tensor

Abstract

A method and apparatus for measuring a three-dimensional refractive index tensor are provided. The method of one embodiment includes: controlling incident plane wave light at at least one angle and polarization; and measuring two-dimensional diffracted light of a specimen relative to the incident light at at least one angle and polarization in a polarization-dependent manner. This method can measure the birefringence value and the three-dimensional structure of the molecular arrangement direction in the specimen, including birefringence.

Description

Technical Field

[0001] The following various embodiments relate to a method and apparatus for measuring a three-dimensional refractive index tensor, and more particularly, to a method and apparatus for measuring a three-dimensional refractive index tensor for achieving three-dimensional birefringence restoration. Background Art

[0002] Optical Diffraction Tomography (ODT) can quantitatively restore the three-dimensional refractive index (RI) distribution of a specimen in a non-invasive manner. Therefore, it is not only used in biological research on bacteria, cells, and tissues, but also in various fields such as confirming defects in plastic lenses and precisely measuring three-dimensional temperature distribution (Non-Patent Literature 1-3).

[0003] However, existing optical diffraction tomography (ODT) technology requires the assumption of a scalar wave, that is, all wavefronts along the electric field vibration direction of light are the same. Therefore, the existing technology is limited in its application to birefringent specimens with different refractive indices depending on the direction.

[0004] Non-patent documents 4-6, as current research, demonstrate the ability to measure a two-dimensional phase retardation image for each polarization of a specimen using two-dimensional quantitative phase imaging technology. Korean Patent No. 10-1461235 describes a polarization sensitivity-interference image acquisition probe and a polarization sensitivity-interference image detection probe for examining these biological tissues, as well as a method for driving a polarization sensitivity-interference image system for examining biological tissues.

[0005] There is a technology that can measure a two-dimensional optical field image for each polarization of a specimen that exhibits birefringence depending on the polarization of incident light (Non-Patent Documents 4-6) or a two-dimensional optical field image for each polarization depending on depth (Korean Patent No. 10-1461235), but there is no known theory or method for measuring the three-dimensional refractive index tensor, which is a basic physical quantity of a specimen that produces this birefringence phenomenon.

[0006] Non-patent literature 1: Kim, K., et al. (2016). "Optical diffractiontomography techniques for the study of cell pathophysiology." arXiv preprintarXiv: 1603.00592.

[0007] Non-patent literature 2: Wolf, E. (1969). "Three-dimensional structure determination of semi-transparent objects from holographic data." Optics Communications 1(4): 153-156.

[0008] Non-patent document 3: Park, Y. (2018). "Quantitative phase imaging in biomedicine." Nature Photonics 12(10): 578-589.

[0009] Non-patent document 4: Colomb, T., Dahlgren, P., Beghuin, D., Cuche, E., Marquet, P., & Depeursinge, C. (2002). Polarization imaging by use of digital holography. Appliedoptics, 41(1), 27-37.

[0010] Non-patent literature 5: Wang, Z., Millet, LJ, Gillette, MU, & Popescu, G. (2008). Jonesphase microscopy of transparent and anisotropic samples. Optics letters, 33(11), 1270-1272.

[0011] Non-patent literature 6: Kim, Y., Jeong, J., Jang, J., Kim, MW, & Park, Y. (2012). Polarization holographic microscopy for extracting spatio-temporallyresolvedJones matrix. Optics Express, 20(9), 9948-9955. Summary of the Invention

[0012] Technical issues

[0013] Various embodiments describe a method and apparatus for measuring a three-dimensional refractive index tensor, and more specifically, provide a technique for accurately measuring birefringence values ​​and the three-dimensional orientations of multiple molecules in a specimen containing birefringence.

[0014] Various embodiments provide a method and apparatus for measuring a three-dimensional refractive index tensor, which can not only accurately measure the three-dimensional birefringence distribution of a specimen containing a birefringent substance, but also obtain information related to the three-dimensional arrangement direction of multiple molecules.

[0015] Furthermore, various embodiments provide a method and apparatus for measuring a three-dimensional refractive index tensor, which can directly optically measure the interaction between molecules in a closed space by observing the three-dimensional molecular arrangement direction of liquid crystal droplets, and can selectively observe the bone and muscle fiber structures in biological cells or tissue specimens in three dimensions without additional labeling.

[0016] Solutions to the Problem

[0017] A method for measuring a three-dimensional refractive index tensor in one embodiment includes: a step of controlling incident light of a plane wave at at least one angle and polarization; and a step of measuring two-dimensional diffracted light of a test piece relative to the incident light incident at at least one angle and polarization in a polarization-dependent manner. The method for measuring a three-dimensional refractive index tensor can measure the birefringence value and the three-dimensional structure of the arrangement direction of multiple molecules in the test piece including birefringence.

[0018] The step of controlling the incident light of the plane wave at at least one angle and polarization may include the step of controlling the angle of the incident light.

[0019] The step of controlling the angle of the incident light can be achieved by using a motor to control and move the position of a dual mirror, or by using at least one of a dual mirror, a galvanometric mirror, a deformable mirror, a digital micromirror device, a liquid-crystal spatial light modulator, and a two-dimensional micro electromechanical system mirror (MEMS mirror) to control the angle of the incident light.

[0020] The step of controlling the incident light of the plane wave at at least one angle and polarization may include the step of controlling the polarization of the incident light.

[0021] In the step of controlling the polarization of the incident light, the polarization of the incident light may be controlled by utilizing at least one of a polarization beam splitter, an optical fiber polarization controller, a rotating polarization plate, a liquid-crystal retarder, and a metasurface.

[0022] The step of measuring the two-dimensional diffracted light of the sample relative to the incident light in a polarization-dependent manner can utilize the following methods: using temporal and spatial intensity modulation interferometry, including at least one of Mach-Zehnder interferometry, phase-shifting interferometry, and quantitative phase imaging units, or using at least one of the transport of intensity equations and Fourier ptychography to measure the two-dimensional diffracted light. Furthermore, the two-dimensional diffracted light can be measured in a polarization-dependent manner using a rotating polarizer, a liquid-crystal retarder, a metasurface, or the like.

[0023] The measured refractive index tensor can be diagonalized using the tensor properties of the birefringence caused by the spatial rotation of the birefringence specimen, thereby performing three-dimensional tomographic reconstruction of the birefringence value and the arrangement direction of multiple molecules in the birefringence specimen.

[0024] Another embodiment of a three-dimensional refractive index tensor measurement device includes: an incident light control unit for controlling incident light of a plane wave at at least one angle and polarization; and a diffracted light measurement unit for measuring two-dimensional diffracted light of a test piece relative to the incident light incident at at least one angle and polarization in a polarization-dependent manner. The three-dimensional refractive index tensor measurement device can measure the birefringence value in the test piece including birefringence and the three-dimensional structure of the arrangement direction of multiple molecules.

[0025] The incident light control unit may include: an angle control unit for controlling the angle of the incident light; and a polarization control unit for controlling the polarization of the incident light.

[0026] The measured refractive index tensor can be diagonalized using the tensor properties of the birefringence caused by the spatial rotation of the birefringence specimen, thereby performing three-dimensional tomographic reconstruction of the birefringence value and the arrangement direction of multiple molecules in the birefringence specimen.

[0027] Effects of the Invention

[0028] According to various embodiments, a method and apparatus for measuring a three-dimensional refractive index tensor can be provided, which can not only accurately measure the three-dimensional birefringence distribution of a specimen containing a birefringent substance, but also obtain information related to the three-dimensional arrangement direction of multiple molecules.

[0029] Furthermore, according to various embodiments, a method and apparatus for measuring a three-dimensional refractive index tensor can be provided, which can directly optically measure the interaction results between molecules in a closed space by observing the three-dimensional molecular arrangement direction of liquid crystal droplets, and can selectively observe the bone and muscle fiber structures in biological cells or tissue specimens in three dimensions without additional labeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. 1 is a block diagram briefly showing a device for measuring a three-dimensional refractive index tensor according to an embodiment.

[0031] Figure 2 FIG. 4 is a block diagram showing a device for measuring a three-dimensional refractive index tensor according to an embodiment.

[0032] Figure 3 FIG. 1 is a flow chart illustrating a method for measuring a three-dimensional refractive index tensor according to an embodiment.

[0033] Figure 4 FIG. 1 is a flow chart illustrating a method for controlling incident light of a plane wave according to an embodiment in terms of angle and polarization.

[0034] Figure 5 The measurement results of the three-dimensional refractive index tensor according to one embodiment are shown. DETAILED DESCRIPTION

[0035] Various embodiments will be described below with reference to the accompanying drawings. However, the various embodiments described can be modified in various other forms, and the scope of the present invention is not limited to the various embodiments described below. Furthermore, the various embodiments are provided to more fully describe the present invention to those skilled in the art. The shapes and sizes of elements in the drawings may be exaggerated for clarity.

[0036] The following embodiments relate to a method and apparatus for measuring a three-dimensional refractive index tensor. These methods aim to restore the three-dimensional birefringence of birefringent specimens by extending the theory of existing optical diffraction tomography (ODT) technology. Ultimately, these embodiments can more accurately measure the birefringence values ​​and the three-dimensional orientations of multiple molecules in birefringent specimens.

[0037] Various embodiments relate to techniques for achieving three-dimensional birefringence restoration. To this end, developing a theory that overcomes the limitations of existing theories and a measurement device for practical implementation of the theory are key.

[0038] Below, we first describe the development of a theory that overcomes the limitations of existing theories.

[0039] The key to developing the theory is to solve the vector wave equation based on vector waves and the refractive index tensor, thereby breaking away from the scalar wave assumption that is a limitation of existing theories.

[0040] By assuming a weakly scattering sample, the following vector wave equation can be derived from the interior of the material.

[0041] Mathematical formula 1

[0042]

[0043] Where k is the size of the wave vector, is the refractive index tensor, is the electric field vector.

[0044] If the above wave equation is expressed in the form of an inhomogeneous Helmholtz equation, it can be expressed as the following equation.

[0045] Mathematical formula 2

[0046]

[0047] in, is the scattering potential tensor.

[0048] The Rytov approximation can be used to find an analytical solution to Equation 2. In the Rytov method, the wavefront is represented as an exponential function, and the weak diffraction wavefront can be significantly approximated to the first order in the exponential series expression, which can be expressed as the following equation.

[0049] Mathematical formula 3

[0050]

[0051] Among them, ψ x =|nE x .

[0052] The solution of Mathematical Formula 2 obtained by using the Rytov approximation of Mathematical Formula 3 can be expressed as the following formula.

[0053] Mathematical formula 4

[0054]

[0055] in, is the polarization vector of the incident plane wave, δ is the Dirac delta function, and the subscript 0 indicates the characteristics of the incident light.

[0056] It is known that the refractive index tensor must be a symmetric matrix based on energy conservation. Therefore, in this embodiment, the refractive index tensor can also be assumed to be a symmetric matrix having 6 components to be measured.

[0057] Since two perpendicular polarization vectors can be defined for each incident light angle, the diffraction wavefront can be represented as six vector components. However, one component of the two perpendicular polarization vectors always depends on the other, resulting in an underdetermined system with five independent equations and six refractive index tensor variables.

[0058] A slight tilt method can be provided to solve this problem. Since the position of the scattering potential that affects the diffraction wave surface is Therefore, if the incident angle is changed, the scattering potential signal is measured at different locations, so the system remains underdetermined. However, if the incident angle is changed very slightly, the diffraction wavefront can be represented by the scattering potential before the slight angle change and its derivative, and a vector component can be created that is also perpendicular to the polarization vector of the incident light. This can be expressed as the following equation.

[0059] Mathematical formula 5

[0060]

[0061] In the expression of Mathematical Formula 5, if the Fourier transform characteristics of the differential function are utilized, it can be expressed as the following formula.

[0062] Mathematical formula 6

[0063]

[0064] in,

[0065] That is, additional information required for an underdetermined system can be input from the vector wavefront measured by slightly tilting the incident angle.

[0066] Finally, the tensor properties of the birefringence caused by the spatial rotation of the birefringent material can be used to diagonalize the measured refractive index tensor, thereby performing three-dimensional tomographic reconstruction of the birefringence value and the arrangement direction of multiple molecules.

[0067] Next, the development of a measuring device for practical implementation of the developed theory is described.

[0068] Figure 1 FIG. 1 is a block diagram briefly showing a device for measuring a three-dimensional refractive index tensor according to an embodiment.

[0069] Reference Figure 1 The key to practical implementation of this technology is to control the plane wave incident light at various angles and polarizations and measure the scattered optical field in a polarization dependent manner.

[0070] Existing optical diffraction tomography (ODT) technology controls the angle of incident light and measures the corresponding scattered wavefront, but the technology of this embodiment differs in controlling the polarization of incident light and measuring the polarization-dependent wavefront.

[0071] In one embodiment, a three-dimensional refractive index tensor measurement device 100 may include: an incident light control unit 110 for controlling incident light of a plane wave at at least one angle and polarization; and a diffracted light measurement unit 120 for measuring two-dimensional diffracted light of a test piece relative to incident light incident at at least one angle and polarization in a polarization-dependent manner, thereby measuring the birefringence value and the three-dimensional structure of the arrangement direction of multiple molecules in the test piece including birefringence.

[0072] The three-dimensional refractive index tensor measuring apparatus 100 will be described in more detail below.

[0073] Figure 2 FIG. 4 is a block diagram showing a device for measuring a three-dimensional refractive index tensor according to an embodiment.

[0074] Reference Figure 2In one embodiment, a three-dimensional refractive index tensor measurement apparatus 100 may include an incident light control unit 110 and a diffracted light measurement unit 120. Incident light control unit 110 may include an angle control unit 111 and a polarization control unit 112, and diffracted light measurement unit 120 may include a wavefront measurement unit 122. Furthermore, depending on the embodiment, diffracted light measurement unit 120 may further include a test piece 121.

[0075] The incident light control unit 110 can control incident light of a plane wave at least at an angle and polarization.

[0076] The incident light control unit 110 may include an angle control unit 111 , and the angle control unit 111 may control the angle of the incident light.

[0077] Devices that can quickly and stably control the angle of incident light include two-way mirrors, galvanometric mirrors, deformable mirrors, digital micromirror devices, liquid-crystal spatial light modulators, and two-dimensional microelectromechanical system (MEMS) mirrors. For example, the angle of incident light can be quickly and stably controlled by using a motor to control and move the position of a two-way mirror.

[0078] Furthermore, the incident light control unit 110 may further include a polarization control unit 112 , and the polarization control unit 112 may control the polarization of the incident light.

[0079] Methods for controlling the polarization of incident light include methods using a polarization beam splitter, an optical fiber polarization controller, a rotating polarization plate, a liquid-crystal retarder, a metasurface, and the like.

[0080] The diffracted light measuring unit 120 can measure two-dimensional diffracted light (diffracted optical field) of the test piece 121 with respect to incident light incident at at least one angle and polarization in a polarization-dependent manner.

[0081] The two-dimensional diffraction optical field can be measured using the following methods: temporal and spatial intensity modulation interferometry, including Mach-Zehnder interferometry, phase shifting interferometry, and quantitative phase imaging units, or using the transport of intensity equation and Fourier ptychography. Furthermore, two-dimensional diffracted light can be measured in a polarization-dependent manner using rotating polarizers, liquid-crystal retarders, and metasurfaces.

[0082] In addition to the aforementioned two-dimensional diffraction optical field measurement methods, polarization-dependent optical fields can also be measured using a rotating polarization plate, liquid crystal retarder, or metasurface in front of a camera, as described above for controlling the polarization of incident light. Furthermore, simultaneous measurements can be performed using a polarization camera with a polarization plate mounted in front of the camera's image sensor, or using polarization plates or polarization beam splitters with different orientations and two cameras.

[0083] Using these methods, the two-dimensional diffraction optical field of the test piece 121 relative to a plane wave incident at various angles and polarization states is measured in a polarization-dependent manner. Then, using a theory that overcomes the limitations of the above-mentioned existing theories, the birefringence index of the birefringent test piece 121 and the three-dimensional structure of the arrangement direction of multiple molecules can be analyzed.

[0084] Figure 3 FIG. 1 is a flow chart illustrating a method for measuring a three-dimensional refractive index tensor according to an embodiment of the present invention. Figure 4 FIG. 1 is a flow chart illustrating a method for controlling incident light of a plane wave according to an embodiment in terms of angle and polarization.

[0085] Reference Figure 3 In one embodiment, a method for measuring a three-dimensional refractive index tensor may include: step S110 of controlling incident plane wave light at at least one angle and polarization; and step S120 of measuring two-dimensional diffracted light from the test piece 121 relative to the incident light at the at least one angle and polarization in a polarization-dependent manner. This allows measurement of the three-dimensional structure of the birefringence of the test piece 121, including the birefringence value and the alignment direction of multiple molecules.

[0086] Reference Figure 4The step S110 of controlling the incident light of the plane wave at at least one angle and polarization may include: a step S111 of controlling the angle of the incident light; and a step S112 of controlling the polarization of the incident light.

[0087] According to various embodiments, three-dimensional quantitative imaging can be performed on birefringence structures that cannot be measured by conventional techniques, and label-free molecular specific 3D imaging can be achieved using the measured refractive index values ​​and ratios.

[0088] The following describes in more detail the various steps of the method for measuring the three-dimensional refractive index tensor according to an embodiment.

[0089] The method for measuring the three-dimensional refractive index tensor of an embodiment can be Figure 1 and Figure 2 The three-dimensional refractive index tensor measurement apparatus 100 according to one embodiment described in

[15] is described as an example. As described above, the three-dimensional refractive index tensor measurement apparatus 100 according to one embodiment may include an incident light control section 110 and a diffracted light measurement section 120. Incident light control section 110 may include an angle control section 111 and a polarization control section 112, and diffracted light measurement section 120 may include a wavefront measurement section 122.

[0090] In step S120 , the incident light control unit 110 may control incident plane wave light at at least one angle and polarization.

[0091] The incident light control unit 110 can control the angle of the incident light. To this end, the incident light control unit 110 can control the angle of the incident light by using at least one of a two-way mirror, a galvanometric mirror, a deformable mirror, a digital micromirror device, a liquid-crystal spatial light modulator, and a two-dimensional micro electro mechanical system mirror (MEMS mirror).

[0092] Furthermore, the incident light control unit 110 can control the polarization of the incident light by using at least one of a polarization beam splitter, an optical fiber polarization controller, a rotating polarization plate, a liquid-crystal retarder, and a metasurface.

[0093] In step S120 , the diffracted light measuring unit 120 can measure two-dimensional diffracted light of the test piece 121 with respect to incident light incident at at least one angle and polarization in a polarization-dependent manner.

[0094] In order to measure the two-dimensional diffracted light of the test piece 121 with respect to the incident light in a polarization-dependent manner, the diffracted light measurement unit 120 can use the following methods: using temporal and spatial intensity modulation interferometry including at least one of Mach-Zehnder interferometry, phase shifting interferometry, and quantitative phase imaging unit, or using at least one of the transport of intensity equation and Fourier ptychography to measure the two-dimensional diffracted light.

[0095] This allows for measurement of the birefringence values ​​and the three-dimensional structure of the alignment directions of the molecules in the birefringent sample 121. By utilizing the tensor properties of the birefringence resulting from the spatial rotation of the birefringent sample 121, the measured refractive index tensor can be diagonalized, thereby enabling three-dimensional tomographic reconstruction of the birefringence values ​​and the alignment directions of the molecules in the birefringent sample 121.

[0096] Figure 5 The measurement results of the three-dimensional refractive index tensor of one embodiment are shown, wherein the measured specimens are biological cells (A549 cells; lung cancer cells).

[0097] According to various embodiments, not only can the three-dimensional refractive index distribution of a test piece containing a birefringent substance be measured more accurately, but information related to the three-dimensional arrangement directions of multiple molecules can also be obtained.

[0098] Applying various embodiments, it is possible to observe the three-dimensional molecular alignment of liquid crystal droplets, which is impossible to directly measure using existing technologies, thereby directly optically measuring the interactions between molecules within a closed space. Bones and muscle fibers in biological cells or tissue specimens exhibit greater polarization than their surroundings, making it possible to selectively observe these structures in three dimensions without additional labeling. Furthermore, since stresses caused by warping, stretching, and other factors in manufactured plastic products can induce optical polarization properties, this method is expected to be more effectively applied to the production defect detection of small plastic lenses.

[0099] The above-mentioned devices can be implemented as hardware components, software components and / or a combination of hardware components and software components. For example, the devices and components described in the embodiments can be implemented using one or more general-purpose computers or special-purpose computers such as a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor (DSP), a microcomputer, a field programmable gate array (FPGA), a programmable logic unit (PLU), a microprocessor, or any other device that can execute and respond to instructions. The processing device can execute an operating system (OS) and one or more software applications running on the above-mentioned operating system. In addition, the processing device can also access, store, operate, process and generate data in response to the execution of the software. For ease of understanding, the processing device can be described as using a single element, but a person skilled in the art of the present invention will understand that the processing device includes multiple processing elements and / or various types of processing elements. For example, the processing device can include multiple processors or include a processor and a controller. In addition, other processing configurations such as parallel processors are also feasible.

[0100] Software may include a computer program, code, instruction, or a combination of more than one of these, and may configure a processing device to operate as needed, or to command the processing device independently or collectively. Software and / or data may be embodied as any type of machine, component, physical device, virtual device, computer storage medium, or device for interpreting instructions or data by or providing instructions or data to a processing device. Software may be distributed across networked computer systems and stored or executed in a distributed manner. Software and data may be stored in one or more computer-readable recording media.

[0101] The method according to various embodiments can be implemented in the form of program instructions that can be executed by various computer devices, and recorded in a computer-readable medium. The above-mentioned computer-readable medium may include single or multiple program instructions, data files, data structures, etc. The program instructions recorded on the medium may be specially designed and configured for the present embodiment, or may be known and available to those skilled in the art of computer software. The example of a computer-readable medium includes magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices such as ROMs, RAMs, flash memories, etc. that are specifically used to store and execute program instructions. The example of program instructions includes not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

[0102] As described above, although the description is based on limited embodiments and figures, those skilled in the art may make various modifications and improvements based on the above description. For example, the components of the systems, structures, devices, circuits, etc. may be performed in a different order than the method described, and / or combined or combined in a different manner than the method described, or replaced or substituted with other components or equivalent technical solutions to achieve appropriate results.

[0103] Therefore, other implementation methods, other examples and technical solutions equivalent to the scope of protection claimed in the invention also fall within the scope of protection claimed in the invention described later.

Claims

1. A method for measuring a three-dimensional refractive index tensor, characterized in that: include: The step of controlling incident light as a plane wave at at least one angle and polarization; and a step of measuring, in a polarization-dependent manner, two-dimensional diffracted light of the test piece relative to the incident light incident at at least one angle and polarization, The three-dimensional refractive index tensor measurement method measures the three-dimensional structure of the birefringence value and the arrangement direction of multiple molecules in the test piece including birefringence. The step of measuring the two-dimensional diffracted light of the sample relative to the incident light in a polarization-dependent manner utilizes the following method: using a temporal and spatial intensity modulation interferometer including at least one of a Mach-Zehnder interferometer, a phase-shifting interferometer, and a quantitative phase imaging unit, or using at least one of an intensity transfer equation and Fourier stack imaging to measure the two-dimensional diffracted light, The measured refractive index tensor is diagonalized using the tensor property of the birefringence caused by the spatial rotation of the birefringence specimen, thereby performing three-dimensional tomographic reconstruction of the birefringence value and the arrangement direction of multiple molecules in the birefringence specimen.

2. The method for measuring the three-dimensional refractive index tensor according to claim 1, wherein: The step of controlling the incident light of the plane wave at at least one angle and polarization includes the step of controlling the angle of the incident light.

3. The method for measuring the three-dimensional refractive index tensor according to claim 2, wherein: In the step of controlling the angle of the incident light, the angle of the incident light is controlled by using at least one of a bidirectional mirror, a galvanometer mirror, a deformable mirror, a digital micromirror device, a liquid crystal spatial light modulator, and a two-dimensional micro-electromechanical system mirror.

4. The method for measuring the three-dimensional refractive index tensor according to claim 1, wherein: The step of controlling the incident light of a plane wave at at least one angle and polarization includes the step of controlling the polarization of the incident light.

5. The method for measuring the three-dimensional refractive index tensor according to claim 4, wherein: In the step of controlling the polarization of the incident light, the polarization of the incident light is controlled by utilizing at least one of a polarization beam splitter, a fiber polarization controller, a rotating polarization plate, a liquid crystal retarder, and a metasurface.

6. A device for measuring a three-dimensional refractive index tensor, characterized in that: include: an incident light control unit for controlling incident light of a plane wave at at least one angle and polarization; and a diffracted light measuring unit for measuring, in a polarization-dependent manner, two-dimensional diffracted light of the test piece relative to the incident light incident at at least one angle and polarization; The three-dimensional refractive index tensor measurement method measures the three-dimensional structure of the birefringence value and the arrangement direction of multiple molecules in the test piece including birefringence. The diffracted light measuring unit uses the following method: using a temporal and spatial intensity modulation interferometer including at least one of a Mach-Zehnder interferometer, a phase-shifting interferometer, and a quantitative phase imaging unit, or using at least one of an intensity transfer equation and Fourier stack imaging to measure two-dimensional diffracted light, The measured refractive index tensor is diagonalized using the tensor property of the birefringence caused by the spatial rotation of the birefringence specimen, thereby performing three-dimensional tomographic reconstruction of the birefringence value and the arrangement direction of multiple molecules in the birefringence specimen.

7. The device for measuring the three-dimensional refractive index tensor according to claim 6, wherein: The incident light control unit includes: an angle control unit, configured to control the angle of the incident light; and The polarization control unit is used to control the polarization of the incident light.

8. The device for measuring the three-dimensional refractive index tensor according to claim 6, wherein: The measured refractive index tensor is diagonalized using the tensor property of the birefringence caused by the spatial rotation of the birefringence specimen, thereby performing three-dimensional tomographic reconstruction of the birefringence value and the arrangement direction of multiple molecules in the birefringence specimen.

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