Hyperspectral imaging chip, device and system based on adjustable and reconfigurable metasurface

Abstract

The invention discloses a hyper-spectral imaging chip, device and system based on an adjustable and reconfigurable metasurface, the chip comprises a metasurface unit array, a metasurface reconstruction module, a metasurface adjustment module, a CMOS image sensor and a spectrum reconstruction and identification module, the metasurface unit array comprises a plurality of metasurface units arranged on a silicon layer; the metasurface reconstruction module is used for adjusting the number of metasurface units included in the reconfigurable metasurface unit array; the metasurface adjusting module is used for being connected with the silicon layer of the metasurface unit array through a wire and changing the spectral response of the metasurface unit by adjusting the voltage of the wire; the CMOS image sensor is used for detecting optical signals modulated by the reconfigurable metasurface unit array; and the spectrum reconstruction and identification module is used for performing hyper-spectrum reconstruction and imaging according to the optical signal detected by the CMOS image sensor. The system is adjustable in spectral response, and has ultrahigh spectral resolution, real-time dynamic monitoring capability and adaptive imaging capability.

Description

Technical Field

[0001] The present invention relates to a hyperspectral imaging chip, and in particular to a hyperspectral imaging chip, device and system based on an adjustable and reconfigurable hypersurface. Background Art

[0002] Spectral imaging technology is a key means of obtaining spatial and spectral information. This technology analyzes the composition and state of matter by capturing the spectral information of each point in the field of view. Therefore, it has important application prospects in many research fields, especially in real-time monitoring of complex processes. However, current spectral imaging technology has two main limitations: first, most technologies can only continuously collect data within a limited wavelength range and cannot fully reflect the spectral changes of a wide bandwidth; second, traditional spectral imaging equipment relies on spatial or temporal scanning and cannot meet the requirements of high temporal, spatial and spectral resolution. This poses a huge challenge to the study of rapidly changing activities, especially real-time spectral imaging.

[0003] In recent years, spectral devices based on micro-nano filters have been widely used to improve the level of integration and miniaturization, especially in the development of on-chip integrated spectral devices. There are two main types of such devices: resonant filters and broadband filters. Resonant filters, such as microring resonators, optical microcavities, and resonant metasurface structures, can separate light of different wavelengths for spectral analysis and have high spectral resolution. However, it is difficult for resonant filters to achieve detection over a wide spectral range while maintaining high spectral resolution. Broadband filters, such as quantum dot arrays, photonic crystal plate arrays, metasurface unit arrays, disordered scattering structures, and bandgap-adjustable nanowires, encode the spectral information of the incident light at different detector positions and combine computational spectral reconstruction algorithms to restore the incident spectrum. This makes the development of micro-spectrometers possible.

[0004] Although extensive progress has been made in the field of integrated micro-spectrometers, existing technologies still face the following problems: the refractive index of the metasurface unit is fixed after preparation, and the spectral response mode is fixed. If other modes of spectral response need to be achieved, the metasurface unit needs to be re-prepared, and the spectral response mode cannot be adjusted. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a hyperspectral imaging chip, device and system with adjustable spectral response based on an adjustable and reconfigurable metasurface.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A hyperspectral imaging chip based on an adjustable and reconfigurable metasurface, comprising:

[0008] A metasurface unit array, used for modulating incident light, comprising a plurality of metasurface units arranged in an array and having different spectral responses, each of which is disposed on a silicon layer;

[0009] A metasurface reconstruction module, used to adjust the number of metasurface units included in the reconfigurable metasurface unit array according to the fidelity, spectral resolution and spatial resolution requirements of the reconstructed spectrum;

[0010] A metasurface adjustment module is connected to the silicon layer of the metasurface unit array through a wire, and is used to apply an electric field to the corresponding metasurface unit by adjusting the voltage of the wire, thereby changing the refractive index of the corresponding metasurface unit, and then changing the spectral response of the metasurface unit;

[0011] A CMOS image sensor for detecting modulated optical signals from the reconfigurable metasurface unit array;

[0012] The spectrum reconstruction and recognition module is used to perform hyperspectral reconstruction and imaging based on the optical signal detected by the CMOS image sensor.

[0013] Furthermore, the metasurface reconstruction module is specifically used to adjust the number of metasurface units included in the reconfigurable metasurface unit array according to the following rules:

[0014] Obtaining a reference number of metasurface units of the reconstructed spectrum at a reference fidelity, a reference spectral resolution, and a reference spatial resolution;

[0015] If the spectral resolution required for the reconstructed spectrum increases compared to the reference spectral resolution, the number of hypersurface units is reduced based on the reference number of hypersurface units; if the spectral resolution required for the reconstructed spectrum decreases compared to the reference spectral resolution, the number of hypersurface units is increased based on the reference number of hypersurface units;

[0016] If the spatial resolution required for reconstructing the spectrum increases compared to the reference spatial resolution, the number of hypersurface units is increased based on the reference number of hypersurface units; if the spatial resolution required for reconstructing the spectrum decreases compared to the reference spatial resolution, the number of hypersurface units is reduced based on the reference number of hypersurface units;

[0017] If the fidelity required for reconstructing the spectrum increases compared to the reference fidelity, the number of hypersurface units is increased based on the reference number of hypersurface units; if the fidelity required for reconstructing the spectrum decreases compared to the reference fidelity, the number of hypersurface units is reduced based on the reference number of hypersurface units.

[0018] Furthermore, the metasurface adjustment module is specifically used to adjust the refractive index of the metasurface unit according to the following rules:

[0019] Obtaining the refractive index of the metasurface unit at a reference voltage;

[0020] If the refractive index of the metasurface unit needs to be increased, the absolute value of the wire voltage is increased within the range of -5.2V to 5.2V;

[0021] If the refractive index of the metasurface unit needs to be reduced, the absolute value of the wire voltage is adjusted to a smaller value within the range of -5.2V to 5.2V.

[0022] An optical imaging device is provided with the above chip.

[0023] An optical imaging system comprises the above optical imaging device.

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

[0025] 1. The present invention can adjust the refractive index of the metasurface unit by adjusting the wire voltage of the silicon layer, thereby changing the spectral response of the metasurface unit and achieving multiple spectral responses;

[0026] 2. The present invention adopts a reconfigurable metasurface design, which can reconstruct the metasurface unit array according to the image scene, realizing seamless switching of image and spectral information;

[0027] 3. The present invention can achieve an optimal balance between high temporal, spatial and spectral resolution, achieving a central wavelength accuracy of 0.04nm and a spectral resolution of 0.8nm, which is better than most existing on-chip spectrometers;

[0028] 4. The chip adopts standard CMOS-compatible manufacturing process, has the characteristics of low cost and easy integration, and can be seamlessly combined with existing optical imaging systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a module schematic diagram of a hyperspectral imaging chip based on an adjustable and reconfigurable metasurface provided by the present invention;

[0030] Figure 2 Schematic diagram of the structure of five metasurface unit arrays with C4 symmetry provided by the present invention;

[0031] Figure 3 A spectrum data diagram of monochromatic light reconstruction implemented by the present invention;

[0032] Figure 4 This is a spectrum data diagram of complex light reconstruction achieved by the present invention. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0034] The embodiment of the present invention provides a hyperspectral imaging chip based on an adjustable and reconfigurable metasurface, which realizes real-time imaging with high temporal, spatial and spectral resolution by constructing multiple micro-spectrometers on a CMOS image sensor. Figure 1 The chip includes a metasurface unit array, a metasurface reconstruction module, a metasurface adjustment module, a CMOS image sensor, and a spectrum reconstruction and recognition module.

[0035] The metasurface unit array includes a plurality of metasurface units with different spectral responses arranged in an array, each of which is arranged on a silicon layer, and each of which constitutes a micro-spectrometer. Each metasurface unit is modulated by a specific micro-nano pattern, and can respond to light of different wavelengths and generate a spectral response signal. The metasurface unit array has a C4 symmetric structure, such as Figure 2 As shown, it helps to improve the uniformity of spectral response and spectral resolution.

[0036] In this embodiment, the metasurface unit is micro-nano processed on a 220nm thick silicon-on-insulator (SOI) wafer by electron beam lithography. First, the pattern is formed by electron beam lithography, and then the pattern is transferred to the silicon layer by inductively coupled plasma (ICP) etching. Finally, the middle silicon oxide layer is removed by wet etching to form a suspended metasurface structure. The metasurface structure is transferred to the CMOS image sensor using the PDMS (polydimethylsiloxane) transfer process, achieving seamless integration with the sensor.

[0037] The metasurface reconstruction module is used to adjust the number of metasurface units included in the reconfigurable metasurface unit array according to the fidelity, spectral resolution and spatial resolution requirements of the reconstructed spectrum according to the following rules:

[0038] Obtaining the reference number of metasurface units for reconstructing the spectrum at a reference fidelity, a reference spectral resolution, and a reference spatial resolution; the specific number can be obtained through experiments;

[0039] If the spectral resolution required for the reconstructed spectrum increases compared to the reference spectral resolution, the number of hypersurface units is reduced based on the reference number of hypersurface units; if the spectral resolution required for the reconstructed spectrum decreases compared to the reference spectral resolution, the number of hypersurface units is increased based on the reference number of hypersurface units;

[0040] If the spatial resolution required for reconstructing the spectrum increases compared to the reference spatial resolution, the number of hypersurface units is increased based on the reference number of hypersurface units; if the spatial resolution required for reconstructing the spectrum decreases compared to the reference spatial resolution, the number of hypersurface units is reduced based on the reference number of hypersurface units;

[0041] If the fidelity required for reconstructing the spectrum increases compared to the reference fidelity, the number of hypersurface units is increased based on the reference number of hypersurface units; if the fidelity required for reconstructing the spectrum decreases compared to the reference fidelity, the number of hypersurface units is reduced based on the reference number of hypersurface units.

[0042] For example, when 25 metasurface units are selected, the fidelity of the transmission spectrum reconstructed by the 25 metasurface units is about 96.2%, and the spectral resolution is about 1.4nm; when the number of metasurface units is increased to 220, the fidelity of the reconstructed spectrum can be increased to 99.2%, and the spectral resolution is about 0.8nm; according to different requirements for the fidelity of the reconstructed spectrum, adjustments can be made within the range of 25 to 200 metasurface units to achieve dynamic adjustment of the reconstructed spectrum resolution; different micro-spectrometers can share some metasurface units to optimize the capture of spectral information within a certain spatial range without significantly sacrificing spatial resolution. For scenes with rich spatial and spectral information, the shape of the micro-spectrometer can be a regular rectangle or an irregular shape dynamically adjusted according to the imaging scene. The algorithm avoids the spectrometer from crossing the significant boundaries of the image by identifying the edges or high-frequency areas in the image, thereby maximizing the accuracy of spectral reconstruction.

[0043] The metasurface adjustment module connects the silicon layer of the metasurface unit array through wires, adjusts the voltage of the wires in the range of -5.2V to 5.2V, applies an electric field to the corresponding metasurface unit, changes the refractive index of the corresponding metasurface unit, and thus changes the spectral response of the metasurface unit. The change in refractive index utilizes the Kerr photoelectric effect of silicon. By changing the refractive index of silicon, the transmission spectrum of the metasurface unit at a wavelength of 400nm to 1000nm is changed, thereby changing the spectral response of the metasurface unit, and forming an image-adaptive micro-spectrometer through dynamic multiplexing.

[0044] Specifically, the relationship between the change in the refractive index of the metasurface unit and the applied electric field is:

[0045]

[0046] In the formula, Δn represents the change in the refractive index of the metasurface unit, e is the electron charge, n is the refractive index of single crystal silicon for light with a vacuum wavelength of λ, and m *is the effective mass of the electron, ω0 is the resonant frequency of the resonance model, x is the average displacement of the silicon atom, E is the applied electric field strength, and because E is proportional to the absolute value of the voltage, Δn is proportional to the square of the voltage. Therefore, the metasurface adjustment module adjusts the refractive index of the metasurface unit according to the following rules: first, the refractive index of the metasurface unit at the reference voltage is obtained; if the refractive index of the metasurface unit needs to be increased, the absolute value of the wire voltage is increased within the range of -5.2V to 5.2V; if the refractive index of the metasurface unit needs to be reduced, the absolute value of the wire voltage is reduced within the range of -5.2V to 5.2V.

[0047] The CMOS image sensor is used to detect the modulated optical signal from the reconfigurable metasurface unit array. The hyperspectral imaging chip of the present invention is integrated in an area not exceeding 0.5 cm 2 The CMOS image sensor contains up to 1 adaptive micro-spectrometer, each of which can be dynamically reconstructed according to the requirements of spectral resolution and spatial resolution of imaging.

[0048] The spectral reconstruction and recognition module is used to perform hyperspectral reconstruction and imaging based on the optical signals detected by the CMOS image sensor (CIS). Each metasurface unit has a specific spectral transfer function under a certain silicon layer voltage. The CIS sensor records the spectral signals from each metasurface unit, and then performs spectral reconstruction through a compressed sensing algorithm to obtain a complete spectral image. In this way, real-time high-spectral resolution imaging can be achieved without relying on traditional scanning methods.

[0049] The hyperspectral imaging chip in this embodiment modulates the incident light through the metasurface unit array to capture spectral information within a wide wavelength range. Each super unit is equivalent to a miniature spectrometer. By dynamically combining these super units and adjusting the silicon layer voltage of the super unit, the chip can operate within the wavelength range of 400nm to 1000nm. The spectral reconstruction results are shown in Figure 2. Figure 3 , 4 As shown, the spectral resolution is up to 0.8nm and the central wavelength accuracy is 0.04nm.

[0050] The chip provided in the embodiment of the present invention can be applied to any optical imaging device to realize optical imaging, such as CMOS industrial camera, and the optical imaging device can also be applied to any optical imaging system, such as confocal microscope and Raman spectrometer, to expand its application in different scenarios. The present invention can also be combined with image recognition technology to realize seamless switching of image information and spectral information, thereby having a wider application prospect in the fields of medical imaging, environmental monitoring and military detection.

[0051] It should be understood that the above embodiments and descriptions only describe the principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A hyperspectral imaging chip based on an adjustable and reconfigurable metasurface, characterized in that: include: A metasurface unit array, used for modulating incident light, comprising a plurality of metasurface units arranged in an array and having different spectral responses, each of which is disposed on a silicon layer; A metasurface reconstruction module, used to adjust the number of metasurface units included in the reconfigurable metasurface unit array according to the fidelity, spectral resolution and spatial resolution requirements of the reconstructed spectrum; A metasurface adjustment module is connected to the silicon layer of the metasurface unit array through a wire, and is used to apply an electric field to the corresponding metasurface unit by adjusting the voltage of the wire, thereby changing the refractive index of the corresponding metasurface unit, and then changing the spectral response of the metasurface unit; A CMOS image sensor for detecting modulated optical signals from the reconfigurable metasurface unit array; The spectrum reconstruction and recognition module is used to perform hyperspectral reconstruction and imaging based on the optical signal detected by the CMOS image sensor.

2. The hyperspectral imaging chip based on the adjustable and reconfigurable metasurface according to claim 1, characterized in that: The metasurface reconstruction module is specifically used to adjust the number of metasurface units included in the reconfigurable metasurface unit array according to the following rules: Obtaining a reference number of metasurface units of the reconstructed spectrum at a reference fidelity, a reference spectral resolution, and a reference spatial resolution; If the spectral resolution required for the reconstructed spectrum increases compared to the reference spectral resolution, the number of hypersurface units is reduced based on the reference number of hypersurface units; if the spectral resolution required for the reconstructed spectrum decreases compared to the reference spectral resolution, the number of hypersurface units is increased based on the reference number of hypersurface units; If the spatial resolution required for reconstructing the spectrum increases compared to the reference spatial resolution, the number of hypersurface units is increased based on the reference number of hypersurface units; if the spatial resolution required for reconstructing the spectrum decreases compared to the reference spatial resolution, the number of hypersurface units is reduced based on the reference number of hypersurface units; If the fidelity required for reconstructing the spectrum increases compared to the reference fidelity, the number of metasurface units is increased based on the reference number of metasurface units; If the fidelity required for reconstructing the spectrum is reduced compared to the reference fidelity, the number of metasurface units is reduced based on the reference number of metasurface units.

3. The hyperspectral imaging chip based on the adjustable and reconfigurable metasurface according to claim 2, characterized in that: The number of the super surface units is adjusted within a range of 25 to 200 super surface units.

4. The hyperspectral imaging chip based on the adjustable and reconfigurable metasurface according to claim 1, characterized in that: The metasurface adjustment module is specifically used to adjust the refractive index of the metasurface unit according to the following rules: Obtaining the refractive index of the metasurface unit at a reference voltage; If the refractive index of the metasurface unit needs to be increased, the absolute value of the wire voltage is increased within the range of -5.2V to 5.2V; If the refractive index of the metasurface unit needs to be reduced, the absolute value of the wire voltage is adjusted to a smaller value within the range of -5.2V to 5.2V.

5. The hyperspectral imaging chip based on the adjustable and reconfigurable metasurface according to claim 1, characterized in that: The metasurface unit array adopts a C4 symmetric structure.

6. The hyperspectral imaging chip based on the adjustable and reconfigurable metasurface according to claim 1, characterized in that: The metasurface unit is formed by micro-nano manufacturing processes, including electron beam lithography, inductively coupled plasma etching and wet etching.

7. The hyperspectral imaging chip based on the adjustable and reconfigurable metasurface according to claim 1, characterized in that: The chip operates in the wavelength range of 400nm to 1000nm.

8. The hyperspectral imaging chip based on the adjustable and reconfigurable metasurface according to claim 1, characterized in that: The spectrum reconstruction and recognition module uses a compressed sensing algorithm to perform spectrum reconstruction on the collected light signal.

9. An optical imaging device, characterized in that: The device is equipped with a chip according to any one of claims 1 to 8.

10. An optical imaging system, characterized in that: The system comprises the optical imaging device according to claim 9.

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