Three-dimensional imaging super lens based on polarization multiplexing and three-dimensional imaging system

Abstract

The invention discloses a polarization multiplexing-based three-dimensional imaging super lens and a three-dimensional imaging system, the super lens is composed of nano structure units and a substrate, and each nano structure unit is periodically arranged on the substrate according to preset phase distribution; the three-dimensional imaging system comprises a polarization multiplexing super lens, a polarization camera and a rear-end calculation reconstruction module. When incoherent light enters the super lens, a light field modulated by the super lens encodes an object to be measured, a dual-channel polarization encoding image is obtained by the polarization camera, and finally three-dimensional information of the object is obtained through decoding and reconstruction of the computer. The polarization multiplexing super-lens three-dimensional imaging device provided by the invention can accurately obtain depth information and two-dimensional intensity distribution of an object within an extended depth-of-field range only through single measurement, and can be applied to a three-dimensional microscopic imaging integrated measurement and observation system.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging technology, and specifically relates to a three-dimensional imaging superlens and a three-dimensional imaging system based on polarization multiplexing. Background Technology

[0002] Three-dimensional microscopy has significant applications in optical microscopy analysis, biological tissue observation, and micro / nanostructure characterization. This technology enables the reconstruction of sample depth information and high-precision spatial positioning. However, traditional three-dimensional microscopy methods (such as confocal microscopy, two-photon microscopy, structured light illumination microscopy, and light-sheet microscopy) typically require mechanical axial scanning or multi-frame image acquisition to obtain information from different focal planes. While these methods achieve high imaging resolution, their complex system structures and large size hinder real-time imaging or high-throughput detection. Therefore, achieving the acquisition of three-dimensional information without mechanical scanning, relying solely on a single frame image, under lightweight and miniaturized hardware conditions, has become a critical problem that modern microscopy imaging technology urgently needs to solve.

[0003] Metasurface technology offers a novel approach to addressing these challenges. Composed of subwavelength-scale artificial structural units, metasurfaces enable precise control of the phase, amplitude, and polarization of light fields within ultrathin planar devices, significantly enhancing system integration. In point spread function (PSF) engineering, metasurfaces can introduce additional degrees of freedom such as polarization and wavelength, achieving multidimensional functions difficult to realize with traditional components. In recent years, metasurface-based double-helix PSF 3D imaging schemes have been used for depth sensing and multi-channel encoding, achieving axial positioning through the rotation angle of the PSF as its axial position changes. However, in imaging reconstruction based on power cepstral analysis, double-helix PSFs suffer from high-frequency component loss, leading to decreased reconstruction quality, excessive smoothing of image details, and difficulty in reliably distinguishing structural features. Furthermore, existing metasurface-based PSF engineering research primarily focuses on macroscopic scenes; under microscopic conditions, single-channel double-helix PSFs still face limitations in two-dimensional planar imaging quality and insufficient depth of field. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a three-dimensional imaging superlens and a three-dimensional imaging system based on polarization multiplexing.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a three-dimensional imaging superlens based on polarization multiplexing, wherein the three-dimensional imaging superlens includes a substrate and nanostructure units on its upper part. The nanostructure units are arranged on the substrate according to a specific phase distribution quasi-periodic or periodic arrangement. When a point light source passes through the three-dimensional imaging superlens, a pair of conjugate Airy point spread functions are generated, corresponding to two orthogonal polarization states respectively. When the point light source moves along the z-axis, this pair of decoupled point spread functions will generate a parabolic lateral displacement, i.e., parallax in stereo vision. By quantifying the relationship between the parallax of this pair of complementary point spread functions and its axial position, the depth information of the object is reconstructed. At the same time, the captured image is deconvolved to obtain two-dimensional intensity information, thereby realizing three-dimensional imaging.

[0006] Furthermore, the phase distribution of the nanostructure units must satisfy equations 1 and 2:

[0007] (1)

[0008] (2)

[0009] in: (3)

[0010] (4)

[0011] (5)

[0012] in: and These represent the total transmission phase delay for x- and y-linearly polarized light, respectively. and These are the wavefront encoding terms for x- and y-polarized light, respectively. The half-aperture of the metasurface, It is the cubic phase modulation coefficient. and These represent the coordinates on the metasurface plane. Where is the wavelength of the incident light. This is the focal length of the lens.

[0013] Furthermore, the substrate is made of a low-loss, low-refractive-index dielectric material, and the nanostructure units are made of a low-loss, high-refractive-index dielectric material or a semiconductor material.

[0014] Furthermore, the substrate is made of quartz glass, sapphire, calcium fluoride or barium fluoride, and the nanostructure units are made of titanium dioxide, hafnium dioxide, silicon nitride, gallium nitride, silicon or germanium.

[0015] Furthermore, the ratio of the dielectric constant of the substrate to that of the nanostructure unit is 1:(1.2 to 3.7).

[0016] Furthermore, the nanostructure units are arranged in a quasi-periodic or periodic manner on the substrate. The side length of each periodic unit is P, where P is 0.5λ to λ. All nanostructure units have the same height H, where H is 0.4λ to λ, and λ is the wavelength of the incident light wave.

[0017] Furthermore, the cross-sectional shape of the nanostructure unit is rectangular, square, elliptical, or circular.

[0018] Furthermore, when the cross-section of the nanostructure unit is rectangular, square, or elliptical, the size range of its major and minor axes is 0.2P to 0.8P, the angle between the major axis of the nanostructure unit and the x-axis is 0 to 180°, and P is the period of the nanostructure unit.

[0019] Furthermore, when the cross-sectional shape of the nanostructure unit is circular, its radius ranges from 0.1P to 0.4P, where P is the period of the nanostructure unit.

[0020] A three-dimensional imaging system based on polarization multiplexing includes the aforementioned three-dimensional imaging superlens, polarization camera, and back-end computing module;

[0021] The three-dimensional imaging superlens is located between the imaging object and the polarization camera. The polarization camera is used to capture the encoded image modulated by the superlens, and the back-end computing module is used to decode and reconstruct the encoded image.

[0022] To address the shortcomings of existing technologies, this invention proposes a single-frame 3D microscopic imaging scheme based on a polarization multiplexing superlens. This scheme generates a pair of complementary Airy PSFs through the superlens. Airy beams possess self-accelerating and nearly diffraction-free propagation characteristics, resulting in a deterministic lateral shift upon axial defocusing, thus forming natural dual-channel parallax information in a single-frame exposure. Utilizing this parallax information, high-quality extended depth-of-field imaging and high-precision, wide-range depth measurement can be achieved. Combined with corresponding computational decoding algorithms, high-precision 3D topography reconstruction can be maintained even over a wide defocus range. This invention provides a novel 3D microscopic imaging scheme that enables single-frame imaging, eliminates the need for mechanical scanning, and is easily integrated, showing broad application prospects in biological imaging, semiconductor defect detection, and other volumetric imaging applications.

[0023] This invention provides a polarization-multiplexed superlens three-dimensional imaging device and system. The system has advantages such as high-precision three-dimensional imaging, extended depth of field, single-frame acquisition, compact structure and low power consumption, and has broad application prospects in fields such as biological microscopy imaging and industrial three-dimensional metrology.

[0024] Therefore, compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The polarization-multiplexed superlens three-dimensional imaging device designed in this invention has an ultra-thin thickness (subwavelength nanometer level), which is beneficial for realizing the miniaturization and high integration of the system.

[0026] 2. This invention uses a low-loss, low-refractive-index medium material as the substrate, and the metasurface nanostructure units are made of a low-loss, high-refractive-index medium or semiconductor material, thereby enabling the polarization multiplexing superlens to have high optical control efficiency and significantly improve the three-dimensional information reconstruction capability.

[0027] 3. The polarization-multiplexed superlens 3D imaging system designed in this invention does not rely on traditional bulk lens components, can significantly shorten the optical path length and improve the system integration, and has the advantages of compact structure, low power consumption, and single-frame measurement. At the same time, it can achieve fast and stable 3D reconstruction.

[0028] 4. The polarization-multiplexed superlens 3D imaging device designed in this invention can maintain high imaging quality over a large depth of field, achieving high-efficiency extended depth-of-field 3D imaging. It provides a new solution for single-frame, mechanically scan-free, and easily integrated 3D microscopy imaging, and has broad potential applications in fields such as biological microscopy and semiconductor defect detection. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the framework for achieving single-frame three-dimensional imaging based on a polarization multiplexing superlens in an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the nanostructure unit used in the embodiments of the present invention, which includes an amorphous silicon dielectric nanopillar and a silicon dioxide substrate, with a height H=400 nm, and Lx and Ly being the major axis and minor axis of the rectangular structure, respectively.

[0031] Figure 3 In this embodiment of the invention, under the condition of incident linearly polarized light with an incident wavelength of λ=633 nm and a polarization direction along the x-axis, the phase delay distribution and transmittance distribution of rectangular nanostructure units of different sizes are shown.

[0032] Figure 4 This is an optical microscope image of the polarization multiplexing metalens prepared in the embodiments of the present invention.

[0033] Figure 5 These are scanning electron microscope images of the polarization multiplexing metalens device prepared in the embodiments of the present invention.

[0034] Figure 6 This is a schematic diagram of the optical path of a single-frame three-dimensional imaging system in an embodiment of the present invention.

[0035] Figure 7This is a comparison of numerical simulation and experimental measurement results of the intensity distribution of conjugate Airy PSF pairs as a function of Δz under x and y linearly polarized incident light conditions in an embodiment of the present invention.

[0036] Figure 8 This is a three-dimensional imaging result of a USAF 1951 resolution target in an embodiment of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0038] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0039] Example

[0040] This invention proposes a single-frame 3D imaging scheme based on a polarization multiplexing superlens, the working principle and overall framework of which are as follows: Figure 1 As shown, when a point light source passes through a polarization multiplexing superlens with cubic phase encoding, a pair of conjugate Airy PSFs can be generated in two orthogonal polarization states. This pair of decoupled PSFs undergoes a parabolic lateral displacement during propagation along the z-axis, behaving similarly to the parallax effect in stereoscopic vision. By quantizing the functional relationship between the parallax of this PSF pair and its axial position, the depth information of the object can be accurately reconstructed. Pollen grains distributed at different depths, after being modulated by the superlens, form a pair of coded images containing parallax information in the two orthogonal polarization channels of a polarization camera. By combining the captured coded images with a pre-acquired and calibrated PSF dataset, high-precision depth estimation of pollen grains can be obtained within an extended depth-of-field range through computational reconstruction.

[0041] This embodiment uses silicon dioxide as a substrate and amorphous silicon nanopillars with rectangular cross-sections as the basic structural unit of the superlens. The designed superlens nanostructure units are arranged quasi-periodicly or periodically on the substrate, with each period corresponding to one microstructure unit. Each microstructure metasurface unit consists of two parts: the amorphous silicon nanopillar and the silicon dioxide substrate. The height of the nanostructure unit is H, and its characteristic dimensions are Lx and Ly, as shown below. Figure 2 As shown.

[0042] In this embodiment, the polarization and phase of the light wave are jointly controlled, and the operating wavelength of the device is set to λ = 633 nm. When linearly polarized incident light with the polarization direction along the x-axis irradiates the superlens nanostructure unit, a parameter library of the nanostructure unit is established using the finite element method to obtain the phase delay and transmittance of a series of nanostructure units with different sizes. To provide phase coverage of 0-2π, this embodiment selects the period of the nanostructure unit as a subwavelength scale, P = 250 nm, and the structural height H = 400 nm. The feature size is scanned within the range of 50-200 nm for the length and width of the nanopillars. The calculated phase delay and transmittance are as follows: Figure 3 As shown. When selecting specific nanostructure units, the first priority should be to ensure that the corresponding phase delay is as close as possible to the target phase value. Secondly, structural parameters with higher transmittance should be selected to ensure that the device has high and uniformly distributed transmission efficiency.

[0043] Optical microscope images of the actual fabricated polarization multiplexing superlens are as follows: Figure 4 As shown, the size of the half-aperture =1mm, focal length f=15mm. Figure 5 This shows an image of the metalens device under a scanning electron microscope. Figure 6 This is a schematic diagram of the optical path of a single-frame 3D imaging system. The object being imaged is illuminated by an LED light source, modulated by a superlens, and then imaged onto a polarization camera. The photosensitive element captures two images with parallax information in two polarization channels, and the back-end computing module reconstructs the images to obtain the object's depth information and two-dimensional intensity distribution.

[0044] To obtain the PSF dataset for this superlens, the PSF of the fabricated superlens was measured and calibrated under illumination from a λ = 633 nm light source. A 20 μm diameter aperture was used as a point light source and placed at different axial positions. Subsequently, the polarization-decoupled complementary Airy PSF pairs generated by the metasurface were experimentally measured, and the results are as follows: Figure 7 As shown, the experimentally measured results show good agreement with the PSF obtained from numerical simulation based on the angular spectrum method. The PSF data obtained in the experiment can provide an accurate reference for the subsequent depth reconstruction process.

[0045] To evaluate the 3D reconstruction capability of the superlens across its entire depth-of-field measurement range, a 1951 USAF resolution target was placed in the transmission optical path shown in Figure 6, and the area marked by the box in the figure was analyzed in detail. The sample was sequentially moved axially to eight different positions using a precision displacement stage. Figure 8 The original coded image pairs acquired at the first defocus position are presented, along with a comparison of the reconstructed depth with the true depth. Within a depth range of 240–2920 μm, the average error of the reconstruction relative to the true depth is 3.75 μm; this corresponds to an error of approximately 0.14% across the full range of 2680 μm.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-dimensional imaging superlens based on polarization multiplexing, characterized in that: The three-dimensional imaging superlens includes a substrate and nanostructure units on top of it. The nanostructure units are arranged on the substrate according to a specific phase distribution quasi-periodic or periodic arrangement. When a point light source passes through the three-dimensional imaging superlens, a pair of conjugate Airy point spread functions are generated, corresponding to two orthogonal polarization states. When the point light source moves along the z-axis, this pair of decoupled point spread functions will produce a parabolic lateral displacement, i.e., parallax in stereo vision. By quantifying the relationship between the parallax of this pair of complementary point spread functions and its axial position, the depth information of the object is reconstructed. At the same time, the captured image is deconvolved to obtain two-dimensional intensity information, thus realizing three-dimensional imaging.

2. The three-dimensional imaging superlens based on polarization multiplexing according to claim 1, characterized in that: The phase distribution of the nanostructure unit must satisfy formulas 1 and 2: （1） （2） in: (3) （4） （5） in: and These represent the total transmission phase delay for x- and y-linearly polarized light, respectively. and These are the wavefront encoding terms for x- and y-polarized light, respectively. The half-aperture of the metasurface, It is the cubic phase modulation coefficient. and These represent the coordinates on the metasurface plane. Where is the wavelength of the incident light. This is the focal length of the lens.

3. The three-dimensional imaging superlens based on polarization multiplexing according to claim 1, characterized in that: The substrate is made of a low-loss, low-refractive-index dielectric material, and the nanostructure units are made of a low-loss, high-refractive-index dielectric material or a semiconductor material.

4. The three-dimensional imaging superlens based on polarization multiplexing according to claim 3, characterized in that: The substrate is made of quartz glass, sapphire, calcium fluoride or barium fluoride, and the nanostructure units are made of titanium dioxide, hafnium dioxide, silicon nitride, gallium nitride, silicon or germanium.

5. The three-dimensional imaging superlens based on polarization multiplexing according to claim 3, characterized in that: The ratio of the dielectric constant of the substrate to that of the nanostructure unit is 1:(1.2 to 3.7).

6. The three-dimensional imaging superlens based on polarization multiplexing according to claim 1, characterized in that: The nanostructure units are arranged in a quasi-periodic or periodic manner on the substrate. The side length of each periodic unit is P, where P is 0.5λ to λ. All nanostructure units have the same height H, where H is 0.4λ to λ, and λ is the wavelength of the incident light wave.

7. The three-dimensional imaging superlens based on polarization multiplexing according to claim 1, characterized in that: The cross-sectional shape of the nanostructure unit is rectangular, square, elliptical, or circular.

8. The three-dimensional imaging superlens based on polarization multiplexing according to claim 7, characterized in that: When the cross-section of the nanostructure unit is rectangular, square, or elliptical, the size range of its major and minor axes is 0.2P to 0.8P, the angle between the major axis of the nanostructure unit and the x-axis is 0 to 180°, and P is the period of the nanostructure unit.

9. The three-dimensional imaging superlens based on polarization multiplexing according to claim 7, characterized in that: When the cross-section of the nanostructure unit is circular, its radius ranges from 0.1P to 0.4P, where P is the period of the nanostructure unit.

10. A three-dimensional imaging system based on polarization multiplexing, characterized in that... include: The three-dimensional imaging superlens, polarization camera, and back-end computing module as described in any one of claims 1 to 9; The three-dimensional imaging superlens is located between the imaging object and the polarization camera. The polarization camera is used to capture the encoded image modulated by the superlens, and the back-end computing module is used to decode and reconstruct the encoded image.

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