CN113375800A - Adjustable optical filter based on optical super-surface and spectral imaging system - Google Patents
Adjustable optical filter based on optical super-surface and spectral imaging system Download PDFInfo
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- G—PHYSICS
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
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- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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Abstract
The invention discloses an adjustable optical filter based on an optical super surface and a spectral imaging system. The adjustable optical filter comprises a polaroid, a liquid crystal device and an optical super-surface device from top to bottom; the liquid crystal device comprises a liquid crystal substrate, a transparent conducting layer, an orientation layer and an internal liquid crystal molecular layer; the optical super-surface device comprises a micro-nano structure unit and an optical super-surface device substrate from top to bottom; the micro-nano structure unit has an anisotropic shape or period and is sensitive to polarization. The spectral imaging system comprises an adjustable optical filter, an imaging lens, a CCD (charge coupled device), a driving power supply, a synchronous signal trigger and a data acquisition card, wherein the adjustable optical filter, the imaging lens, the CCD and the data acquisition card are sequentially connected, the driving power supply is connected with the CCD through the synchronous signal trigger, and the data acquisition card is connected with the driving power supply. The tunable filter has the characteristics of large tuning range, high transmittance, low cost and the like. The system has the advantages of high-speed staring imaging, large wavelength detection range, high transmittance, compact structure and the like.
Description
Technical Field
The invention relates to an adjustable optical filter based on an optical super surface and a spectral imaging system, which can be applied to the fields of remote sensing, environment/resource and health monitoring and the like.
Background
The spectral imaging technology is used as a novel imaging means of 'spectrum integration', and can simultaneously acquire space and spectral information of an object, so that information which cannot be detected by a plurality of traditional imaging technologies can be acquired, and the spectral imaging technology plays an increasingly important role in the fields of resource detection, environment monitoring, quality detection, bioengineering and the like. The traditional spectral imaging technology mainly utilizes a mechanical scanning component to carry out spectral detection, has large volume and low stability, and cannot adapt to the development trend of miniaturization and compactness of devices. The gaze-type spectral imaging system based on the adjustable optical filter is expected to solve the problems of the traditional mechanical device. The currently mainstream tunable optical filter is a liquid crystal tunable optical filter. However, there are two problems with this device. On one hand, the transmittance of the device is very low, generally less than 10%, which makes the signal-to-noise ratio of a spectral imaging system based on the device not high, thereby limiting the use of the device in dark light, low reflectivity and other occasions; on the other hand, the price of the device is very expensive, taking a liquid crystal tunable filter of a visible light wave band of Thorlabs company as an example, the price of the device is as high as 6 million yuan RMB, and the high price limits the application range of the device to only a few fields of military, scientific research and the like. The development of the optical filter with low cost and high transmittance has important practical significance.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide an adjustable filter based on an optical super surface and a spectral imaging system. The adjustable optical filter based on the optical super-surface has the characteristics of large tuning range, high transmittance, low cost and the like.
An adjustable optical filter based on an optical super-surface comprises a polaroid, a liquid crystal device and an optical super-surface device from top to bottom; the liquid crystal device comprises a liquid crystal substrate, a transparent conducting layer, an orientation layer and an internal liquid crystal molecular layer, wherein the orientation layer, the transparent conducting layer and the liquid crystal substrate are vertically and symmetrically arranged in sequence by taking the liquid crystal molecular layer as a center;
the optical super surface device comprises a micro-nano structure unit and an optical super surface device substrate from top to bottom; the micro-nano structure unit has anisotropic shape or period and is sensitive to polarization.
And the change of the period, the size, the duty ratio or the thickness of the micro-nano structure unit is used for adjusting the transmission/reflection spectrum of the adjustable optical filter.
The micro-nano structure unit is a rectangular, oval or grating anisotropic unit array nano column or hole; or an isotropic round or square structure; the material is metal, including gold, silver or aluminum, or high-refractive-index semiconductor, dielectric material, including silicon, silicon nitride or titanium dioxide.
The spectral imaging system adopting the adjustable optical filter comprises the adjustable optical filter, an imaging lens, a CCD (charge coupled device), a driving power supply, a synchronous signal trigger and a data acquisition card, wherein the adjustable optical filter, the imaging lens, the CCD and the data acquisition card are sequentially connected, the driving power supply is connected with the CCD through the synchronous signal trigger, and the data acquisition card is connected with the driving power supply.
The spectral imaging system calibrates the spectral response of the adjustable optical filter under different driving signals in advance.
The spectrum imaging system synchronously triggers the adjustable optical filter and the CCD by utilizing the synchronous signal trigger, so that the spectral response of the adjustable optical filter under different driving signals corresponds to the intensity of the CCD one by one.
The spectral imaging system recovers spectral information of a single pixel from intensity information of each pixel of the CCD by using a linear regression or compressed sensing method.
The invention has the beneficial effects that:
1. the invention combines the optical super-surface device with the liquid crystal device, realizes the liquid crystal adjustable optical filter with polarization sensitivity, has high light flux, large tuning range, fast response speed, compact structure and low price, and is easy for large-scale production.
2. The invention adopts a staring type spectral imaging system, and can recover the target original spectrum from the light intensity signal through algorithms such as linear regression or compressed sensing. The system can reduce the volume of the existing spectral imaging system and improve the resolution of spectral imaging.
3. The invention adopts the liquid crystal device for regulation and control, can carry out spectrum tuning through electric signals, and abandons mechanical moving parts in the traditional staring type spectrum imaging system.
Drawings
FIG. 1 is a schematic diagram of a spectral imaging system based on an optical super-surface liquid crystal tunable filter.
FIG. 2 is a side view of an optical super-surface liquid crystal tunable filter.
FIG. 3(a) is a schematic diagram of a tunable filter structure of a silicon grating;
FIG. 3(b) transmission spectra of two orthogonal polarizations of the tunable filter.
FIG. 4(a) is a schematic diagram of a silver grating tunable filter structure;
FIG. 4(b) is the transmission spectrum of the tunable filter for two orthogonal polarizations.
FIG. 5(a) is a schematic diagram of a tunable filter structure with silicon nano-pillars;
FIG. 5(b) is a top view of an optical super-surface device.
FIG. 6(a) is a schematic diagram of a tunable filter with metal holes;
FIG. 6(b) is a top view of an optical super-surface device;
FIG. 6(c) is the transmission spectrum of the tunable filter for two orthogonal polarizations.
FIG. 7(a) is a schematic diagram of a tunable filter structure with a metal resonant cavity;
FIG. 7(b) is the transmission spectrum of the tunable filter for two orthogonal polarizations.
Description of reference numerals: the device comprises an adjustable optical filter 1, an imaging lens 2, a CCD 3, a driving power supply 4, a synchronous signal trigger 5, a data acquisition card 6, a polarizing plate 7, a liquid crystal device 8, an optical super-surface device 9, a liquid crystal substrate 10, a transparent conducting layer 11, an orientation layer 12, a liquid crystal molecular layer 13, an optical super-surface device substrate 14, a silicon grating 15, a silver grating 16, a silicon nano-pillar 17, a metal hole 18, a first reflecting layer 19, a dielectric layer 20 and a second reflecting layer 21.
Detailed Description
The invention is further illustrated below with reference to the figures and examples.
As shown in fig. 1, a spectral imaging system includes an adjustable optical filter 1 based on an optical super surface, an imaging lens 2, a CCD 3, a driving power source 4, a synchronous signal trigger 5, a data acquisition card 6, and other elements; wherein the tunable filter 1 is used for spectral separation; the imaging lens 2 is used to image an object on the CCD 3; the driving power supply 4 is used for controlling the filtering characteristic of the adjustable filter 1 so as to carry out spectrum scanning on the object in a target waveband; the CCD 3 synchronously acquires black and white images under the control of a synchronous signal trigger and acquires target intensity information in different filter states; the data acquisition card 6 is used for acquiring signals and processing the signals to finally obtain the image and the spectral information of the target object.
The core device of the system is an adjustable optical filter 1 based on an optical super surface, and the system has the advantages of large adjustment range, high transmittance, compact structure, high response speed, low price and the like. As shown in fig. 1 and 2, the tunable optical filter based on an optical super surface is composed of a polarizing plate 7, a liquid crystal device 8, and an optical super surface device 9. The liquid crystal device 8 is composed of a liquid crystal substrate 10, a transparent conductive layer 11, an alignment layer 12, and an inner liquid crystal molecular layer 13. The alignment layer 12 is subjected to an alignment treatment for aligning the liquid crystal molecule layer 13. The orientation of the liquid crystal molecule layer 13 can be in various ways such as parallel, vertical, mixed, twisted and the like; incident light enters the liquid crystal element 8 after passing through the polarizing plate 7, and a certain electric signal is applied to the transparent conductive layer 11, so that the phase retardation and the optical rotation characteristic of the liquid crystal element 8 can be changed, and the polarization state of light emitted from the liquid crystal element can be regulated.
The optical super-surface device 9 is composed of periodic and anisotropic structural units, the reflection/transmission spectrum of the optical super-surface device is sensitive to the polarization of incident light, and the polarization state of the incident light to the optical super-surface device 9 can be changed by applying an electric signal to the liquid crystal device 8, so that the emergent spectrum is regulated and controlled. The optical super-surface device 9 comprises an optical super-surface device substrate 14 and a micro-nano structure unit array on the optical super-surface device substrate, and a reflection/transmission spectrum is regulated and controlled by utilizing the resonance effect of the unit array, and the principle of the optical super-surface device comprises but is not limited to a Mie scattering resonator, a surface plasma resonator, a guided mode resonance resonator, a gap plasma resonator and the like. The structural unit has an anisotropic shape or period, so that the structural unit has polarization sensitive characteristics, and can generate different phase shifts and absorption for different incident lights. In addition, the transmission/reflection spectrum of the device can be adjusted by changing the period, the size, the duty ratio, the thickness and the like of the micro-nano structure unit.
In a further specific implementation, the unit arrays constituting the optical super-surface device 9 may have the same period in different directions, and the basic units thereof are anisotropic unit array nano-columns or holes such as rectangles, ellipses, gratings and the like; isotropic circle, square, etc. structures may also be used, but with varying directional periods. The essence of the device is that the device has anisotropic response through an artificial nano structure, and different phase delays and absorption are generated for incident light with different polarizations. The material can be metal such as gold, silver, aluminum, etc., or high refractive index semiconductor or dielectric material such as silicon, silicon nitride, titanium dioxide, etc.
In a further specific implementation, the micro-nano structure can be manufactured from the bottom to top by electron beam exposure, ultraviolet exposure, nano imprinting, two-beam interference exposure and the like, and can also be manufactured by self-assembly of nano particles, DNA molecules and organic polymers.
The optical signal reflected or transmitted by the object enters the adjustable optical filter 1, is imaged on the CCD 3 through the imaging lens 2, the drive power supply 4 applies a specific electric signal on the adjustable optical filter 1, the CCD 3 synchronously acquires intensity information, and transmits the corresponding electric signal to the data acquisition card 6 for data processing.
The CCD 3 may be a single-channel black-and-white CCD or a multi-channel color CCD, and the original spectrum of each point of the object can be restored by obtaining the intensity distribution information of each point recorded by the CCD under different voltages (different transmission or reflection spectra). The relationship between the output signal of the CCD and the spectrum value is as shown in formula 1:
wherein
Representing the output signals of the CCD 3 pixels at different voltages,
which represents the different driving voltages, the driving voltages,
which represent the different wavelengths of the light beam,
is the spectrum of the light source and,
representing the spectral response of the tunable filter 1,
is the spectral response of the pixel of the CCD 3,
representing the reflection or transmission spectrum of the object to be measured. Wherein
、
、
All can be obtained by pre-calibration, then equation 1 can be simplified to equation 2:
formula 2 is one
System of equations, matrix
The larger the rank of (D), the desired spectrum
The higher the precision of the method is, the equation can be quickly solved by utilizing algorithms such as linear regression or compressed sensing, and the like, so that the transmission/reflection spectrum of the object can be obtained.
In a further embodiment, the liquid crystal layer 13 in the liquid crystal device 8 may be a common positive liquid crystal or a negative liquid crystal, and the liquid crystal device 8 may be driven vertically by an electrical signal applied to the upper and lower substrates or planarly by an electrical signal applied to a single substrate.
In a further embodiment, the polarizer 7, the liquid crystal device 8 and the optical super-surface device 9 may be integrated by a transparent medium such as silicon dioxide, polymer, etc., or may be packaged and fixed by a mechanical structure.
In a further embodiment, the solution can be extended to the infrared band by using liquid crystals and other optical elements suitable for the infrared band.
Embodiment 1 spectral imaging system based on silicon grating tunable filter
As shown in fig. 3(a), the silicon grating tunable filter includes a polarizer 7, a liquid crystal device 8 (a liquid crystal substrate 10, a transparent conductive layer 11, an alignment layer 12, a liquid crystal molecular layer 13), and an optical super-surface device 9 (an optical super-surface device substrate 14, a silicon grating 15).
The optical signal passes through the polarizing plate 7 and enters the liquid crystal device 8, and the liquid crystal molecular layer 13 in the liquid crystal device 8 forms a parallel arrangement mode through the orientation layers 12 on both sides. Electrodes are provided on the transparent conductive layer 11, and by applying electric signals to the upper and lower electrodes, the liquid crystal molecular layer 13 is deflected by an applied electric field, thereby causing a change in birefringence Δ n, and thus a change in polarization state of incident light. And applying different voltages to obtain emergent light with different polarization states.
The light emitted from the liquid crystal device 8 enters and is incident on the optical super-surface device 9, as shown in fig. 3(a), the structure of the optical super-surface device is shown as a basic structure, the basic structure is a silicon grating 15, the whole structure is manufactured on the substrate 14 of the optical super-surface device, and the grating period is smaller than the working wavelength. Due to the structural anisotropy, the optical super-surface device 9 is sensitive to the polarization of incident light, and the intensity and phase change of the transmission/reflection spectrum of the incident light are different when the incident light is incident with different polarizations. The outgoing spectrum can be adjusted by changing the phase delay of the liquid crystal device 8 by electrification and adjusting the polarization state of the incident light to the optical super-surface device 9. Fig. 3(b) shows the transmittance of the device in different polarizations obtained by simulation.
And finally, applying different signals to the adjustable optical filter 1 to regulate and control the emergent spectrum, acquiring intensity information under different spectral responses by using the CCD 3, and restoring the original spectrum by adopting algorithms such as linear regression or compressive sensing.
Embodiment 2 spectral imaging system based on metal grating type dielectric filter
As shown in fig. 4(a), the metal grating type tunable filter includes a polarizing plate 7, a liquid crystal device 8 (a liquid crystal substrate 10, a transparent conductive layer 11, an alignment layer 12, a liquid crystal layer 13), and an optical super surface device 9 (an optical super surface device substrate 14, a silver grating structure 16).
The optical signal passes through the polarizing plate 7 and enters the liquid crystal device 8, and the liquid crystal layer 13 in the liquid crystal device 8 forms a vertical alignment by passing through the alignment layers 12 on both sides. Electrodes are arranged on the transparent conductive layers 11, and by applying an electric signal to the upper and lower transparent conductive layers 11, the liquid crystal molecule layer 13 is deflected with an external electric field, so that the birefringence Δ n is changed, and the polarization state of incident light is changed. And applying different voltages to obtain emergent light with different polarization states.
The light emitted from the liquid crystal device 8 enters and is incident on the optical super-surface device 9, as shown in fig. 4(a), the structure of the optical super-surface device is shown as a silver grating structure 16, the whole structure is manufactured on the optical super-surface device substrate 14, and the grating period is smaller than the working wavelength. Due to the structural anisotropy, the optical super-surface device 9 is sensitive to the polarization of incident light, and the intensity and phase change of the transmission/reflection spectrum of the incident light are different when the incident light is incident with different polarizations. The outgoing spectrum can be regulated by changing the phase delay of the liquid crystal device 8 by electrification and regulating the polarization state of the incident light to the optical super-surface device 9. Fig. 4(b) shows the transmittance of the device in different polarizations obtained by simulation.
And finally, applying different signals to the adjustable optical filter 1 to regulate and control the emergent spectrum, acquiring intensity information under different spectral responses by using the CCD 3, and restoring the original spectrum by adopting algorithms such as linear regression or compressive sensing.
Embodiment 3 spectral imaging system based on silicon nanorod adjustable optical filter
As shown in fig. 5(a), the silicon nanorod tunable filter includes a polarizer 7, a liquid crystal device 8 (a liquid crystal substrate 10, a transparent conductive layer 11, an alignment layer 12, a liquid crystal molecule layer 13), and an optical super-surface device 9 (an optical super-surface device substrate 14, a silicon nanorod structure 17).
The optical signal passes through the polarizer 7 and enters the liquid crystal device 8, and the liquid crystal molecular layer 13 in the liquid crystal device 8 forms a twisted arrangement mode through the orientation layers 12 on both sides. Electrodes are provided on the transparent conductive layer 11, and by applying electric signals to the upper and lower electrodes, the liquid crystal molecule layer 13 is deflected by an applied electric field, resulting in a change in birefringence Δ n, and thus a change in polarization state of incident light. And applying different voltages to obtain emergent light with different polarization states.
The light emitted from the liquid crystal device 8 enters and is incident on the optical super surface device 9, as shown in fig. 5(a), the structure of the optical super surface device is the basic structure of the silicon nano-pillar 17, and the whole structure is manufactured on the optical super surface device substrate 14. The silicon nano-pillar 17 array has the same period in different directions, the period is smaller than the wavelength of a detection wave band, and the basic unit adopts an anisotropic structure such as a rectangle, an ellipse and the like; due to the structural anisotropy, the optical super-surface device 9 is sensitive to the polarization of incident light, and the intensity and phase change of the transmission/reflection spectrum of the incident light are different when the incident light is incident with different polarizations. The outgoing spectrum can be regulated by changing the phase delay of the liquid crystal device 8 by electrification and regulating the polarization state of the incident light to the optical super-surface device 9. Fig. 5(b) shows the transmittance of the device in different polarizations obtained by simulation.
And finally, applying different electric signals to the adjustable optical filter 1 to regulate and control an emergent spectrum, obtaining intensity information under different spectral responses by using the CCD 3, and restoring the original spectrum by adopting algorithms such as linear regression or compressive sensing.
Embodiment 4 spectral imaging system based on adjustable filter with metal holes
As shown in fig. 6(a), the metal aperture tunable filter includes a polarizer 7, a liquid crystal device 8 (a liquid crystal substrate 10, a transparent conductive layer 11, an alignment layer 12, a liquid crystal molecular layer 13), and an optical super-surface device 9 (an optical super-surface device substrate 14, a metal aperture structure 18).
The optical signal passes through the polarizer 7 and enters the liquid crystal device 8, and a liquid crystal molecular layer 13 in the liquid crystal device forms a twisted arrangement mode through the orientation layers 12 on two sides. Electrodes are arranged on the transparent conductive layers 11, and by applying an electric signal to the upper and lower transparent conductive layers 11, the liquid crystal molecule layer 13 is deflected with an external electric field, so that the birefringence Δ n is changed, and the polarization state of incident light is changed. And applying different voltages to obtain emergent light with different polarization states.
The light exiting from the liquid crystal device 8 enters and impinges on the optical super-surface device 9, which is shown in fig. 6(a) as an optical super-surface device structure, the basic structure of which is a metal hole 18, and the whole structure is fabricated on the optical super-surface device substrate 14. The metal hole 19 array has the same period in different directions, the period is smaller than the wavelength of a detection wave band, and the basic unit adopts an anisotropic structure such as a rectangle, an ellipse and the like; due to the structural anisotropy, the optical super-surface device 9 is sensitive to the polarization of incident light, and the intensity and phase change of the transmission/reflection spectrum of the incident light are different when the incident light is incident with different polarizations. The outgoing spectrum can be regulated by changing the phase delay of the liquid crystal device 8 by electrification and regulating the polarization state of the incident light to the optical super-surface device 9. Fig. 6(b) shows the transmittance of the device in different polarizations obtained by simulation.
And finally, applying different electric signals to the adjustable optical filter 1 to regulate and control an emergent spectrum, obtaining intensity information under different spectral responses by using the CCD 3, and restoring the original spectrum by adopting algorithms such as linear regression or compressive sensing.
Embodiment 5 spectral imaging system based on tunable filter of metal resonant cavity
As shown in fig. 7(a), the metal resonator tunable filter includes a polarizer 7, a liquid crystal device 8 (a liquid crystal substrate 10, a transparent conductive layer 11, an alignment layer 12, a liquid crystal molecular layer 13), and an optical super-surface device 9 (an optical super-surface device substrate 14, a first reflective layer 19, a dielectric layer 20, and a second reflective layer 21).
The optical signal passes through the polarizer 7 and enters the liquid crystal device 8, and the liquid crystal layer 13 in the liquid crystal device 8 passes through the alignment layers 12 on both sides to form a hybrid alignment. Electrodes are provided on the transparent conductive layer 11, and by applying electric signals to the upper and lower electrodes, the liquid crystal molecule layer 13 is deflected by an applied electric field, resulting in a change in birefringence Δ n, and thus a change in polarization state of incident light. And applying different voltages to obtain emergent light with different polarization states.
The light emitted from the liquid crystal device 8 enters and is incident on the optical super surface device 9, as shown in fig. 7(a), the structure of the optical super surface device is composed of a first reflecting layer 19, a second reflecting layer 21 and an intermediate medium layer 20, and the whole structure is manufactured on the optical super surface device substrate 14. The first reflecting layer 19 is composed of periodic micro-nano structure units, the period of the periodic micro-nano structure units is smaller than the wavelength of a detection waveband, and the basic units are in anisotropic structures such as rectangles, ellipses and the like. Due to the structural anisotropy, the optical super-surface device 9 is sensitive to the polarization of incident light, and the intensity and phase change of the transmission/reflection spectrum of the incident light are different when the incident light is incident with different polarizations. The outgoing spectrum can be regulated by changing the phase delay of the liquid crystal device 8 by electrification and regulating the polarization state of the incident light to the optical super-surface device 9. Fig. 7(b) shows the transmittance of the device in different polarizations obtained by simulation.
And finally, applying different electric signals to the adjustable optical filter 1 to regulate and control an emergent spectrum, obtaining intensity information under different spectral responses by using the CCD 3, and restoring the original spectrum by adopting algorithms such as linear regression or compressive sensing.
The embodiments in the above description can be further combined or replaced, and the embodiments are only described as preferred examples of the present invention, and do not limit the concept and scope of the present invention, and various changes and modifications made to the technical solution of the present invention by those skilled in the art without departing from the design concept of the present invention belong to the protection scope of the present invention. The scope of the invention is given by the appended claims and any equivalents thereof.
Claims (7)
1. An adjustable optical filter based on an optical super-surface, characterized in that: the liquid crystal display comprises a polaroid, a liquid crystal device and an optical super-surface device from top to bottom; the liquid crystal device comprises a liquid crystal substrate, a transparent conducting layer, an orientation layer and an internal liquid crystal molecular layer, wherein the orientation layer, the transparent conducting layer and the liquid crystal substrate are vertically and symmetrically arranged in sequence by taking the liquid crystal molecular layer as a center; the optical super surface device comprises a micro-nano structure unit and an optical super surface device substrate from top to bottom; the micro-nano structure unit has anisotropic shape or period and is sensitive to polarization.
2. The tunable filter of claim 1, wherein: and the change of the period, the size, the duty ratio or the thickness of the micro-nano structure unit is used for adjusting the transmission/reflection spectrum of the adjustable optical filter.
3. The tunable filter of claim 1, wherein: the micro-nano structure unit is a rectangular, oval or grating anisotropic unit array nano column or hole; or an isotropic round or square structure; the material is metal, including gold, silver or aluminum, or high-refractive-index semiconductor, dielectric material, including silicon, silicon nitride or titanium dioxide.
4. A spectral imaging system employing the tunable filter of claim 1, wherein: the device comprises an adjustable optical filter, an imaging lens, a CCD, a driving power supply, a synchronous signal trigger and a data acquisition card, wherein the adjustable optical filter, the imaging lens, the CCD and the data acquisition card are sequentially connected, the driving power supply is connected with the CCD through the synchronous signal trigger, and the data acquisition card is connected with the driving power supply.
5. The spectral imaging system of claim 1, wherein: the spectral response of the adjustable optical filter under different driving signals is calibrated in advance.
6. The spectral imaging system of claim 1, wherein: and synchronously triggering the adjustable optical filter and the CCD by using a synchronous signal trigger, so that the spectral response of the adjustable optical filter under different driving signals corresponds to the intensity of the CCD one by one.
7. The spectral imaging system of claim 1, wherein: spectral information of a single pixel is recovered from intensity information of each pixel of the CCD by using a linear regression or compressed sensing method.
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