Imaging device and method for acquiring target spectral light field information based on a metasurface array

Abstract

The application discloses an imaging device and method for obtaining target spectral light field information based on a metasurface array, and the imaging device comprises, in sequence along an optical axis direction, a first imaging lens, an aperture, a second imaging lens, a polarizer, a double-layer metasurface array, an analyzer and a detector; the front focal plane of the second imaging lens and the aperture are coincident with the image plane position of the first imaging lens; the light transmission axis direction of the polarizer and the analyzer is 45 degrees with the positive direction of the Y axis; the double-layer metasurface array is a double-layer 3*3 unit structure, and comprises a first layer of super lens array and a second layer of super lens array arranged along the optical axis. The application realizes orthogonal polarization decomposition and convergent imaging through the super lens array, significantly reduces the volume of the system, and can synchronously obtain the spectral and light field depth information of a target scene through algorithm reconstruction.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging and detection technology, and in particular relates to an imaging device and method for acquiring target spectral light field information based on metasurface array. Background Technology

[0002] Existing multidimensional detection systems cannot meet the requirements of low structural complexity, high dynamics, and simultaneous spatiotemporal acquisition of multidimensional information. Traditional multidimensional systems with beam-splitting structures often employ two or more detectors through beam splitting, resulting in complex system structures with multiple detectors, high costs, and low optical efficiency. Such systems require a series of lens groups for aberration correction, leading to excessively large system sizes, which is not conducive to small-scale integrated detection applications.

[0003] Metasurfaces are typically composed of subwavelength metallic or dielectric nanoantenna arrays. Through the design and optimization of metasurface unit structures, the subwavelength resolution of metasurfaces allows for arbitrary manipulation of multiple physical quantities of emitted light, such as amplitude, phase, polarization state, orbital angular momentum, and frequency. The powerful wavefront manipulation capabilities of metasurfaces make them a promising alternative to traditional optical components. Metaoptics was named one of the top ten scientific advances of 2016 by Science magazine and one of the top ten emerging technologies of 2019 by Scientific American.

[0004] With the application and development of meta-components in optical imaging, meta-optical components have achieved breakthroughs in commercial and military applications in the past two years. In 2022, Metatalenz launched PolarEyes, a polarization sensor based on meta-components, which realizes polarization 3D imaging. Compared with traditional polarization cameras, it is 5,000 times smaller and includes full Stokes parameters. The technology is characterized by low cost, high sensitivity, and small size. It uses planar meta-optical components to collect polarization information lost by traditional polarization cameras and analyzes this information for use in professional scenarios.

[0005] In the same year, STMicroelectronics and Metalenz collaborated to launch a new generation of Time-of-Flight (ToF) ranging sensors. By embedding a monolithic meta-optical lens, this ranging sensor can provide more functions. This technology replaces multiple optical elements in traditional modules, enabling monolithic 3D imaging. Metalenz combined semiconductor processes and optical technologies, using integrated circuit chip wafer foundries to manufacture 5,000 to 10,000 meta-components on a single 12-inch wafer, achieving mass production. This marked the first appearance of metasurfaces in the commercial field, currently mainly used in consumer electronics devices.

[0006] In summary, metasurface-based multidimensional imaging systems eliminate the need for bulky mechanical scanning systems, offering advantages such as small size and light weight. This results in excellent integrability and high system stability, making them suitable for various scenarios and possessing significant application value. With the development of nanophotonics, combining nano-optical sensing systems, including metasurfaces, with multidimensional imaging systems to achieve miniaturization and integration has gradually become one of the main development directions in the field of multidimensional imaging. Summary of the Invention

[0007] The technical problem solved by the present invention is to overcome the shortcomings of the prior art and provide an imaging device and method for acquiring target spectral light field information based on metasurface array. Orthogonal polarization decomposition and convergence imaging are achieved through metalens array, which significantly reduces the size of the system. The spectral and light field depth information of the target scene can be obtained simultaneously through algorithm reconstruction.

[0008] To address the aforementioned technical problems, this invention discloses an imaging device for acquiring target spectral light field information based on a metasurface array, comprising: a first imaging lens, an aperture, a second imaging lens, a polarizer, a double-layer metasurface array, an analyzer, and a detector arranged sequentially along the optical axis.

[0009] The front focal plane of the second imaging lens and the aperture stop are aligned with the image plane of the first imaging lens.

[0010] The transmission axis of the polarizer and analyzer forms an angle of 45° with the positive Y-axis; wherein, the Y-axis is perpendicular to the optical axis;

[0011] The dual-layer metasurface array is a dual-layer 3×3 unit structure, comprising: a first-layer metalens array and a second-layer metalens array arranged along the optical axis.

[0012] In the imaging device for acquiring target spectral light field information based on the above-mentioned metasurface array, each sub-unit A in the first layer meta-lens array has the same structure. Each sub-unit A includes anisotropic nanopillars a. The anisotropic nanopillars a are distributed in a ring array and have a horizontal axis length and a vertical axis length. The horizontal axis length and vertical axis length are the same on the same radius ring with the center of each sub-unit A as the origin. The horizontal axis length and vertical axis length are different on rings with different radii.

[0013] In the imaging device for acquiring target spectral light field information based on the above-mentioned metasurface array, the first layer metalens array is a polarization-dependent beam splitting metalens array, and the substrate material of the first layer metalens array is silicon dioxide.

[0014] In the aforementioned imaging device for acquiring target spectral light field information based on metasurface arrays, the material of the anisotropic nanopillar a is gallium nitride, the structural shape of the anisotropic nanopillar a is cuboid a, and the length and width of the anisotropic nanopillar a are determined according to the lens phase required at different positions. The height and period of the anisotropic nanopillar a remain unchanged at different positions. When the length and width of the anisotropic nanopillar a are different, the anisotropic nanopillar a will produce different effective refractive indices for the orthogonal components of the incident ray polarized light of different wavelengths, resulting in different phases of the outgoing ray polarized light.

[0015] In the aforementioned imaging device for acquiring target spectral light field information based on metasurface arrays, when incident polarized light passes through the heterogeneous nanopillars a, the resonant phase generated by each heterogeneous nanopillar a... The following lens phase formula requirements must be met:

[0016]

[0017] Where λ represents the wavelength of the incident polarized light, x and y represent the position coordinates in the horizontal and vertical directions, respectively, and f represents the focal length of the lens.

[0018] In the imaging device for acquiring target spectral light field information based on the above-mentioned metasurface array, each sub-unit B in the second layer metalens array has the same structure. Each sub-unit B includes anisotropic nanopillars b. The anisotropic nanopillars b are distributed in a ring array and have a horizontal axis length, a vertical axis length, and a rotation angle. The horizontal axis length and vertical axis length are the same on the same radius ring with the center of each sub-unit B as the origin, but the rotation angle is different. The horizontal axis length, vertical axis length, and rotation angle are different on rings with different radii.

[0019] In the imaging device for acquiring target spectral light field information based on the above-mentioned metasurface array, the second metalens array is a polarization-dependent achromatic metalens array, and the substrate material of the second metalens array is silicon dioxide.

[0020] In the aforementioned imaging device for acquiring target spectral light field information based on metasurface arrays, the material of the anisotropic nanopillar b is gallium nitride, the structural shape of the anisotropic nanopillar b is cuboid, the length and width of the anisotropic nanopillar b are determined according to the lens phase required at different positions, the rotation angle of the anisotropic nanopillar b is determined according to the target phase, and the height and period of the anisotropic nanopillar b remain unchanged at different positions; wherein, when the length, width, and rotation angle of the anisotropic nanopillar b are different, the anisotropic nanopillar b will generate different optical path differences for linearly polarized light of different wavelengths and converge them onto the detector.

[0021] In the aforementioned imaging device for acquiring target spectral light field information based on metasurface arrays, when linearly polarized light of different wavelengths passes through the anisotropic nanopillars b, the phase generated by each anisotropic nanopillar b... The following lens phase formula requirements must be met:

[0022]

[0023] Where λ represents the wavelength of the incident polarized light, x and y represent the position coordinates in the horizontal and vertical directions, respectively, f represents the focal length of the lens, and θ represents the rotation angle of the anisotropic nanopillar b.

[0024] Accordingly, this invention also discloses an imaging method for acquiring target spectral light field information based on a metasurface array, comprising:

[0025] The incident light from the target is imaged onto the aperture by the first imaging lens, and then incident on the second imaging lens to form collimated light, which is then converted into linearly polarized light by the polarizer.

[0026] Linearly polarized light is decomposed into o-light and e-light with mutually orthogonal vibration directions by each sub-unit A in the first layer of meta-lens array; the o-light and e-light are converted into e-light and o-light and emitted by each sub-unit B in the second layer of meta-lens array. The e-light and o-light have an optical path difference, and the optical path difference of e-light and o-light is different for incident light of different wavelengths.

[0027] The e-beam and the o-beam are incident on the analyzer, forming a beam with the same polarization direction;

[0028] Beams with the same polarization direction converge on the detector to form a 3×3 array image and produce interference fringes;

[0029] Using an image deconstruction algorithm, the 3×3 array image and interference fringes are extracted from the original image, and the depth and spectrum of the target scene are reconstructed using the light field image information and interference fringes information, respectively.

[0030] The present invention has the following advantages:

[0031] (1) This invention discloses an imaging scheme for acquiring target spectral light field information based on metasurface array. A double-layer metasurface array is placed behind the imaging surface of the snapshot system. The double-layer metasurface array can simultaneously acquire spectral and light field depth information in a single exposure, replacing the birefringent prism and phase delay device in the traditional multidimensional detection system, and greatly reducing the size of the system.

[0032] (2) This invention discloses an imaging scheme for acquiring target spectral light field information based on a metasurface array. The two-layer metalens array has different functions. The first layer is a beam-splitting metalens array, which solves the beam splitting problem of orthogonally linearly polarized light by using the size and structure of the anisotropic nanopillars a. The second layer is an achromatic metalens array, which solves the achromatic imaging problem by using the size and structure of the anisotropic nanopillars b. This significantly improves the ability to simultaneously detect multidimensional information of the target. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of an imaging device for acquiring target spectral light field information based on a metasurface array according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of a first-layer metalens array according to an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the structure of a second-layer metalens array in an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments disclosed herein will be described in further detail below with reference to the accompanying drawings.

[0037] like Figure 1 In this embodiment, the imaging device for acquiring target spectral light field information based on a metasurface array includes: a first imaging lens 1, an aperture 2, a second imaging lens 3, a polarizer 4, a dual-layer metasurface array 5, an analyzer 6, and a detector 7 arranged sequentially along the optical axis. The front focal plane of the second imaging lens 3 and the aperture 2 coincide with the image plane of the first imaging lens 1; the transmission axis of the polarizer 4 and the analyzer 6 forms an angle of 45° with the positive Y-axis; the Y-axis is perpendicular to the optical axis. The dual-layer metasurface array 5 is a dual-layer 3×3 unit structure, including: a first-layer metasurface lens array 51 and a second-layer metasurface lens array 52 arranged along the optical axis.

[0038] In this embodiment, as Figure 2 In the first layer of meta-lens array 51, each sub-unit A has the same structure. Each sub-unit A includes anisotropic nanopillars a. The anisotropic nanopillars a are distributed in a ring array and have a horizontal axis length and a vertical axis length. The horizontal axis length and vertical axis length are the same on the same radius ring with the center of each sub-unit A as the origin. The horizontal axis length and vertical axis length are different on rings with different radii.

[0039] Preferably, the first layer metalens array 51 is a polarization-dependent beam-splitting metalens array, and the substrate material of the first layer metalens array 51 is silicon dioxide. The material of the anisotropic nanopillar a is gallium nitride, and the structural shape of the anisotropic nanopillar a is cuboid a. The length and width of the anisotropic nanopillar a are determined according to the lens phase required at different positions, and the height and period of the anisotropic nanopillar a remain unchanged at different positions. Among them, when the length and width of the anisotropic nanopillar a are different, the anisotropic nanopillar a will produce different effective refractive indices for the orthogonal components of the incident ray polarized light of different wavelengths, resulting in different phases of the outgoing ray polarized light.

[0040] Preferably, when incident polarized light passes through the anisotropic nanopillar a, the resonant phase generated by each anisotropic nanopillar a is... The following lens phase formula requirements must be met:

[0041]

[0042] Where λ represents the wavelength of the incident polarized light, x and y represent the position coordinates in the horizontal and vertical directions, respectively, and f represents the focal length of the lens.

[0043] In this embodiment, as Figure 3 In the second layer of meta-lens array 52, each sub-unit B has the same structure. Each sub-unit B includes anisotropic nanopillars b. The anisotropic nanopillars b are distributed in a ring array and have a horizontal axis length, a vertical axis length, and a rotation angle. The horizontal axis length and vertical axis length are the same on the same radius ring with the center of each sub-unit B as the origin, but the rotation angle is different. The horizontal axis length, vertical axis length, and rotation angle are different on rings with different radii.

[0044] Preferably, the second-layer metalens array 52 is a polarization-dependent achromatic metalens array, and the substrate material of the second-layer metalens array 52 is silicon dioxide. The material of the anisotropic nanopillar b is gallium nitride, and the structure of the anisotropic nanopillar b is cuboid. The length and width of the anisotropic nanopillar b are determined according to the lens phase required at different positions, and the rotation angle of the anisotropic nanopillar b is determined according to the target phase. The height and period of the anisotropic nanopillar b are constant at different positions. When the length, width, and rotation angle of the anisotropic nanopillar b are different, the anisotropic nanopillar b will generate different optical path differences for linearly polarized light of different wavelengths and converge them onto the detector 7.

[0045] Preferably, when linearly polarized light of different wavelengths passes through the anisotropic nanopillar b, the phase generated by each anisotropic nanopillar b is... The following lens phase formula requirements must be met:

[0046]

[0047] Where λ represents the wavelength of the incident polarized light, x and y represent the position coordinates in the horizontal and vertical directions, respectively, f represents the focal length of the lens, and θ represents the rotation angle of the anisotropic nanopillar b.

[0048] In this embodiment, an imaging method for acquiring target spectral light field information based on a metasurface array is also disclosed. This imaging method is implemented using the aforementioned imaging device and specifically includes the following steps:

[0049] Step 1: The incident light from the target is imaged onto the aperture 2 by the first imaging lens 1, and then incident onto the second imaging lens 3 to form collimated light, which is then converted into linearly polarized light by the polarizer 4.

[0050] Step 2: Linearly polarized light is decomposed into o-light and e-light with mutually orthogonal vibration directions by each sub-unit A in the first layer meta-lens array 51; o-light and e-light are transformed into e-light and o-light by each sub-unit B in the second layer meta-lens array 52 and emitted. The e-light and o-light have an optical path difference, and the optical path difference of e-light and o-light obtained by incident light of different wavelengths is different.

[0051] Step 3: The e-beam and o-beam are incident on the analyzer 6 to form a beam with the same polarization direction.

[0052] Step 4: Beams with the same polarization direction converge on detector 7 to form a 3×3 array image and generate interference fringes.

[0053] Step 5: Using an image deconstruction algorithm, the 3×3 array image and interference fringes are extracted from the original image, and the depth and spectrum of the target scene are reconstructed using the light field image information and interference fringes information, respectively.

[0054] In summary, this invention places a dual-layer metasurface array behind the imaging surface of a snapshot system. This dual-layer metasurface array allows for the simultaneous acquisition of spectral and optical field depth information in a single exposure. The two metasurface arrays possess different functionalities: the first layer is a beam-splitting metalens array, which solves the beam-splitting problem of orthogonally linearly polarized light through the size and structure of the anisotropic nanopillars a; the second layer is an achromatic metalens array, which solves the achromatic imaging problem through the size and structure of the anisotropic nanopillars b. This significantly improves the ability to simultaneously detect multidimensional information about the target.

[0055] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0056] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. An imaging device for acquiring target spectral light field information based on a metasurface array, characterized in that, include: A first imaging lens (1), an aperture (2), a second imaging lens (3), a polarizer (4), a double-layer metasurface array (5), an analyzer (6), and a detector (7) are arranged sequentially along the optical axis. The front focal plane of the second imaging lens (3) and the aperture (2) coincide with the image plane of the first imaging lens (1). The transmission axis of the polarizer (4) and the analyzer (6) forms a 45° angle with the positive Y-axis, and the Y-axis is perpendicular to the optical axis. The double-layer metasurface array (5) is a double-layer 3 The structure comprises a 3-unit structure, including a first-layer metalens array (51) and a second-layer metalens array (52) arranged along the optical axis; the first-layer metalens array (51) is a polarization-dependent beam-splitting metalens array, and the substrate material of the first-layer metalens array (51) is silicon dioxide; the second-layer metalens array (52) is a polarization-dependent achromatic metalens array, and the substrate material of the second-layer metalens array (52) is silicon dioxide; each subunit A in the first-layer metalens array (51) has the same structure, and each subunit A includes anisotropic nanopillars a, which are arranged in a ring array. The array is distributed in columns and has horizontal and vertical axis lengths. The horizontal and vertical axis lengths are the same on the same radius ring with the center of each subunit A as the origin. The horizontal and vertical axis lengths are different on different radius rings. The second layer of meta-lens array (52) has the same structure for each subunit B. Each subunit B includes anisotropic nanopillars b. The anisotropic nanopillars b are distributed in a ring array and have horizontal, vertical and rotation angles. The horizontal and vertical axis lengths are the same on the same radius ring with the center of each subunit B as the origin. The rotation angles are different on different radius rings.

2. The imaging device for acquiring target spectral light field information based on a metasurface array according to claim 1, characterized in that, The material of the anisotropic nanopillar a is gallium nitride, and the structure of the anisotropic nanopillar a is a cuboid. The length and width of the anisotropic nanopillar a are determined according to the lens phase required at different positions. The height and period of the anisotropic nanopillar a remain unchanged at different positions. When the length and width of the anisotropic nanopillar a are different, the anisotropic nanopillar a will produce different effective refractive indices for the orthogonal components of the incident ray polarized light of different wavelengths, resulting in different phases of the outgoing ray polarized light.

3. The imaging device for acquiring target spectral light field information based on a metasurface array according to claim 1, characterized in that, When incident polarized light passes through the heterogeneous nanopillars a, the resonant phase generated by each heterogeneous nanopillar a is... The following lens phase formula requirements must be met: in, Indicates the wavelength of the incident polarized light. and These represent the position coordinates along the horizontal and vertical axes, respectively. Indicates the focal length of the lens.

4. The imaging device for acquiring target spectral light field information based on a metasurface array according to claim 1, characterized in that, The material of the anisotropic nanopillar b is gallium nitride. The structure of the anisotropic nanopillar b is a cuboid. The length and width of the anisotropic nanopillar b are determined according to the lens phase required at different positions. The rotation angle of the anisotropic nanopillar b is determined according to the target phase. The height and period of the anisotropic nanopillar b are constant at different positions. When the length, width and rotation angle of the anisotropic nanopillar b are different, the anisotropic nanopillar b will generate different optical path differences for linearly polarized light of different wavelengths and converge onto the detector (7).

5. The imaging device for acquiring target spectral light field information based on a metasurface array according to claim 1, characterized in that, When linearly polarized light of different wavelengths passes through the anisotropic nanopillar b, the phase generated by each anisotropic nanopillar b... The following lens phase formula requirements must be met: in, Indicates the wavelength of the incident polarized light. and These represent the position coordinates along the horizontal and vertical axes, respectively. Indicates the focal length of the lens. The angle of rotation of the heterogeneous nanopillar b is indicated.

6. An imaging method based on the imaging device for acquiring target spectral light field information based on a metasurface array as described in claim 1, characterized in that, include: The incident light from the target is imaged onto the aperture (2) by the first imaging lens (1), and then incident onto the second imaging lens (3) to form collimated light, which is then converted into linearly polarized light by the polarizer (4). Linearly polarized light is decomposed into o-light and e-light with mutually orthogonal vibration directions by each subunit A in the first layer of meta-lens array (51); o-light and e-light are transformed into e-light and o-light by each subunit B in the second layer of meta-lens array (52) and emitted. e-light and o-light have an optical path difference. The optical path difference between e-light and o-light is different for incident light of different wavelengths. The e-beam and the o-beam are incident on the analyzer (6) to form a beam with the same polarization direction; Beams with the same polarization direction converge on detector (7) to form an image, creating a 3D image.

3. Array images and generate interference fringes; Using image deconstruction algorithms, 3 The array image and interference fringes were extracted from the original image, and the depth and spectrum of the target scene were reconstructed using the light field image information and interference fringes information, respectively.

Images