WO2024255411A1 - 用于红外高光谱成像的调制结构、探测器及红外光谱仪 - Google Patents

用于红外高光谱成像的调制结构、探测器及红外光谱仪 Download PDF

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Publication number
WO2024255411A1
WO2024255411A1 PCT/CN2024/087004 CN2024087004W WO2024255411A1 WO 2024255411 A1 WO2024255411 A1 WO 2024255411A1 CN 2024087004 W CN2024087004 W CN 2024087004W WO 2024255411 A1 WO2024255411 A1 WO 2024255411A1
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modulation
infrared
units
microstructure
micro
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English (en)
French (fr)
Inventor
张佳豪
胡传真
马强
朱永浩
魏东
朱镇峰
蔡宏
毛慧
浦世亮
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Hangzhou Hikvision Digital Technology Co Ltd
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Hangzhou Hikvision Digital Technology Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/2823—Imaging spectrometer

Definitions

  • the present application relates to the technical field of infrared hyperspectral imaging, and in particular to a modulation structure, a detector and an infrared spectrometer for infrared hyperspectral imaging.
  • micro-nano modulation structures made of high refractive index materials can be used to modulate the spectral dimension of the incident light, and the spectral image can be obtained in a snapshot manner by combining computational optics methods.
  • the main purpose of this application is to provide a modulation structure, a detector and an infrared spectrometer for infrared hyperspectral imaging, aiming to solve the technical problem of low signal-to-noise ratio after hyperspectral imaging caused by the spectral modulation structure.
  • the present application proposes a modulation structure for infrared hyperspectral imaging, comprising: a detector window packaging layer; an infrared anti-reflection film, the infrared anti-reflection film is arranged on the side surface of the detector window packaging layer facing the pixel, and the refractive index of the material of the infrared anti-reflection film is smaller than the refractive index of the material of the detector window packaging layer; and a plurality of microstructure modulation units, the plurality of microstructure modulation units are arranged on the side surface of the infrared anti-reflection film facing away from the detector window packaging layer according to a preset arrangement rule, so that a partial area of the side surface of the infrared anti-reflection film facing away from the detector window packaging layer is left vacant to form at least one empty modulation unit.
  • the preset arrangement rules include at least one of the following: the microstructure modulation unit is adjacent to the at least one empty modulation unit; in the first direction or the second direction of the pixel array, there are at most two empty modulation units between two adjacent microstructure modulation units, and the first direction is perpendicular to the second direction; among all the microstructure modulation units adjacent to each empty modulation unit, the structures of any two microstructure modulation units are different from each other.
  • the microstructure modulation units and the empty modulation units are arranged alternately with each other, and in a second direction, the microstructure modulation units and the empty modulation units are arranged alternately with each other.
  • the infrared anti-reflection film includes at least two transparent film layers stacked in sequence, and the refractive index of the at least two transparent film layers gradually decreases in a direction away from the detector window packaging layer.
  • the material of the transparent film layer includes ZnS zinc sulfide, ZnSe zinc selenide, BaF2 barium fluoride, CaF2 calcium fluoride, YbF3 ytterbium fluoride, Ge germanium or Si silicon.
  • each of the microstructure modulation units includes a plurality of micro-nanostructure sub-units arranged in a rectangular array, and the plurality of micro-nanostructure sub-units are spaced apart from each other.
  • the multiple micro-nano structure sub-units are constructed as a columnar structure protruding from the sub-region, and the material of the columnar structure is an infrared high refractive index material; or an infrared high refractive index medium layer is provided on the surface of the infrared anti-reflection film on the side facing away from the detector window packaging layer, and the multiple micro-nano structure sub-units are constructed as a hole structure that penetrates the infrared high refractive index medium layer along the thickness direction of the detector window packaging layer.
  • the cross-sectional shape of the micro-nano structure subunit is configured as a rotationally symmetrical figure with a rotation angle of 90°.
  • the side length of a pixel in the pixel array is less than or equal to 17 ⁇ m
  • the number of micro-nanostructure sub-units in the third direction of the rectangular array is less than or equal to 10
  • the number of micro-nanostructure sub-units in the fourth direction of the rectangular array is less than or equal to 10; wherein the third direction is perpendicular to the fourth direction.
  • the height of the micro-nanostructure subunit is greater than 5 ⁇ m.
  • the present application further provides a detector, comprising: an image sensor, the image sensor comprising a pixel array; and a modulation structure for infrared hyperspectral imaging as in the first aspect, wherein a microstructure modulation unit and a pixel array of the modulation structure are arranged relative to each other.
  • the present application further provides an infrared spectrometer, comprising: a detector as provided in the second aspect; and an image signal processor, wherein the image signal processor is connected to the detector.
  • the technical solution of the present application is to add an infrared anti-reflection film to the detector window packaging layer, and arrange a plurality of microstructure modulation units on the infrared anti-reflection film according to a preset arrangement rule, so that part of the surface of the infrared anti-reflection film is left vacant to form at least one empty modulation unit.
  • the microstructure modulation unit and the empty modulation unit together form the spectral modulation structure of the detector.
  • the embodiment of the present application improves the transmittance reduction phenomenon caused by microstructure reflection through the anti-reflection ability provided by the infrared anti-reflection film on the one hand, and reduces the use area of the micro-nano structure in the detector window through the structureless empty modulation unit on the other hand, thereby jointly improving the signal-to-noise ratio after hyperspectral imaging.
  • FIG1 is a schematic diagram of a structure of an embodiment of a modulation structure for infrared hyperspectral imaging of the present application
  • FIG2 is a schematic diagram of the spectral modulation structure distribution of an embodiment of a modulation structure for infrared hyperspectral imaging of the present application
  • FIG3 is a schematic structural diagram of another embodiment of the modulation structure for infrared hyperspectral imaging of the present application, wherein the infrared antireflection film is a double-layer structure;
  • FIG4 is a schematic structural diagram of another embodiment of the modulation structure for infrared hyperspectral imaging of the present application, wherein the infrared antireflection film is a three-layer structure;
  • FIG5 is a schematic structural diagram of an embodiment of a modulation structure for infrared hyperspectral imaging of the present application, wherein the micro-nano structure subunit is a hole-shaped structure;
  • FIG6 is a schematic diagram of the antireflection effect of Example 1.
  • FIG. 7 is a comparison diagram of modulation curves of the five microstructure modulation units 21 and the four empty modulation units 22 of Example 1;
  • FIG8 is a comparison diagram of the average light transmittance of the spectrum modulation unit of Example 1 and the average light transmittance of the microstructure modulation unit (such as micro-nanohole) generally arranged on the Si window;
  • FIG9 is a graph showing nine spectrum modulation curves generated by nine spectrum modulation units of Example 1;
  • FIG10 is a schematic diagram showing the arrangement of the microstructure modulation unit and the empty modulation unit of Example 2 of the present application.
  • connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • fixation can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • Hyperspectral imaging can simultaneously obtain information about the spatial distribution of objects and high spectral resolution, and has wide applications in areas such as material identification, environmental monitoring, chemical industry, and food safety.
  • Traditional hyperspectral imaging solutions mostly use a single-point spectrometer with an external mechanical device for spatial scanning imaging, but such devices are often large in size and take a long time to obtain spectral images.
  • micro-nano modulation structures made of high-refractive index materials such as micro-nano circular hole structures formed by etching on silicon flat plates
  • the spectral image can be obtained in a snapshot manner using computational optics methods.
  • the area occupied by the micro-nano modulation structure is limited.
  • the space proportion of the micro-nano modulation structure can be increased.
  • increasing the space proportion of the micro-nano modulation structure will cause the micro-nano modulation structure to have the characteristics of high reflectivity and low light transmittance, which will lead to a low signal-to-noise ratio after imaging.
  • the spectral modulation of the micro-nano modulation structure needs to meet the conditions of large whole spectrum modulation amplitude, large number of modulation peaks and narrow peak width.
  • the micro-nano modulation structure needs to use high refractive index materials of the corresponding band.
  • the modulation transmittance of micro-nano modulation structures such as micro-nano circular hole structures etched on silicon flat plates is low (often less than 50%), resulting in poor signal-to-noise ratio.
  • the infrared detectors used are usually photothermal type, which has large noise.
  • the signal of the object to be measured is weak, and the signal-to-noise ratio is lower than that of the visible light band technology.
  • Materials such as Ge and Si have almost no light loss in the long-wave infrared band, but due to the small number of pixels in the infrared detector and the limited area occupied by the micro-nano modulation structure, in order to improve the modulation effect, the spatial proportion of the micro-nano modulation structure has to be increased, resulting in high reflection and low light transmittance of the micro-nano modulation structure of materials such as Ge and Si, which in turn leads to a low signal-to-noise ratio after imaging.
  • an embodiment of the present application provides a modulation structure for infrared hyperspectral imaging, which adds an infrared anti-reflection film to the packaging layer of the detector window, and arranges a plurality of microstructure modulation units on the infrared anti-reflection film according to a preset arrangement rule, so that a partial area of the surface of the infrared anti-reflection film is left vacant to form at least one empty modulation unit.
  • the microstructure modulation unit and the empty modulation unit together form the spectral modulation structure of the detector.
  • the embodiment of the present application reduces the use area of the micro-nano structure in the detector window through the anti-reflection ability provided by the infrared anti-reflection film, and on the other hand, reduces the transmittance drop caused by the microstructure reflection through the unstructured empty modulation unit, thereby jointly improving the signal-to-noise ratio after hyperspectral imaging.
  • the embodiment of the present application proposes a modulation structure for infrared hyperspectral imaging.
  • the spectral modulation structure 20 of the infrared hyperspectral imaging and the pixel array 30 on the image sensor are arranged relative to each other for spectrally modulating the incident light.
  • the pixel array 30 on the image sensor After receiving the modulated spectral signal, the pixel array 30 on the image sensor outputs a detection signal.
  • the modulation structure for infrared hyperspectral imaging includes a detector window packaging layer 10 , an infrared anti-reflection film 40 , and a plurality of microstructure modulation units 21 .
  • the infrared anti-reflection film 40 is arranged on the side surface of the detector window packaging layer 10 facing the pixel array 30, and the refractive index of the material of the infrared anti-reflection film 40 is smaller than the refractive index of the material of the detector window packaging layer 10; a plurality of microstructure modulation units 21 are arranged on the side surface of the infrared anti-reflection film 40 facing away from the detector window packaging layer 10 according to a preset arrangement rule, so that a partial area of the side surface of the infrared anti-reflection film 40 facing away from the detector window packaging layer 10 is left vacant to form at least one empty modulation unit 22.
  • the detector has a sealing cover plate, and the plate body of the sealing cover plate has an infrared window area that allows infrared light to pass through, that is, the detector window sealing layer 10 in this embodiment.
  • the detector window sealing layer 10 and the pixel array 30 are arranged relative to each other, so that the infrared light passing through the infrared window area is received by the pixel array 30.
  • the material of the detector window sealing layer 10 includes germanium Ge or silicon Si.
  • the detector window packaging layer 10 is provided with an infrared anti-reflection film 40 on one side of the surface facing the pixel array 30.
  • the infrared anti-reflection film 40 is divided into at least four sub-areas arranged in a rectangular array on the side facing away from the detector window packaging layer 10.
  • a rectangular array is generally constructed as a square array with equal number of rows and columns, so that each The sub-regions are all square.
  • the surface of the infrared anti-reflection film 40 is divided into 9 sub-regions arranged in a 3 ⁇ 3 pattern, or divided into 16 sub-regions arranged in a 4 ⁇ 4 pattern.
  • a plurality of spectral modulation structures 20 are arranged on the surface of the infrared anti-reflection film 40 on the side away from the detector window packaging layer 10, wherein the number of spectral modulation structures 20 is equal to the number of imaging pixels of the hyperspectral camera, and the spectral modulation structure 20 includes different spectral modulation units.
  • the surface of the infrared anti-reflection film 40 is divided into 9 spectral modulation units (including microstructure modulation units 21 and empty modulation units 22) arranged in 3 ⁇ 3, wherein each spectral modulation unit corresponds to a pixel one-to-one, so that the spectral modulation structure 20 and the pixel correspond one-to-one.
  • spectral modulation units including microstructure modulation units 21 and empty modulation units 22
  • the dotted box is a spectral modulation structure 20, which corresponds one-to-one to a pixel 30 below.
  • the spectral modulation structure 20 includes a microstructure modulation unit 21 and an empty modulation unit 22 formed by being vacant.
  • Each microstructure modulation unit 21 is protrudingly arranged on a sub-region, and its interior supports a waveguide mode for spectral modulation. For some sub-regions, there is no structure distributed in the space at the same height as the microstructure modulation unit 21, thereby forming an empty modulation unit 22 without a structure thereon.
  • the pixel 30 of the detector is relatively small, for example, the pixel 30 size of 17 ⁇ m only corresponds to 1-2 infrared band wavelengths, the number of microstructure modulation units 21 is limited, so that the edge scattering intensity of the microstructure modulation unit 21 is relatively large, so that under the scattering effect of the surrounding microstructure modulation units 21, the air modulation unit 22 also has spectral modulation capability.
  • the empty modulation unit 22 without structure in this embodiment reduces the use area of the micro-nano structure in the detector window, improves the transmittance reduction problem caused by the reflection of the micro-nano structure, and improves the luminous flux of the spectral modulation unit of the micro-nano structure, thereby improving the signal-to-noise ratio after hyperspectral imaging.
  • the refractive index of the material of the infrared anti-reflection film 40 is less than the refractive index of the material of the detector window packaging layer 10, thereby forming a gradient distribution of high refractive index material-low refractive index material-air in the direction from the detector window packaging layer 10 to the pixel 30. It can be understood that when light enters from one medium into another medium, if the difference in the refractive index of the two media decreases, the energy of the reflected light decreases and the energy of the transmitted light increases. Thus, in this embodiment, when infrared light penetrates the refractive index gradient distribution area, the transmittance can be improved.
  • this embodiment reduces the use area of the micro-nano structure in the detector window by combining the air-retaining control unit and the anti-reflection ability provided by the infrared anti-reflection film, thereby jointly improving the transmittance reduction problem caused by the reflection of the micro-nano structure and jointly improving the signal-to-noise ratio after hyperspectral imaging.
  • the transmittance of the infrared band is improved by the infrared anti-reflection film 40, and the passing amount of the spectral modulation structure 20 set on the surface of the infrared anti-reflection film 40 facing the pixel 30 is increased by setting the air-retaining modulation unit 22.
  • the spectral modulation structure 20 has more light passing, and the scattering effect of the microstructure modulation unit 21 is stronger, thereby also improving the spectral modulation ability of the air-retaining modulation unit 22, thereby not only improving the hyperspectral imaging
  • the signal-to-noise ratio can also be improved, and the accuracy of spectral reconstruction can be improved.
  • the preset arrangement rule includes at least one of the following:
  • the microstructure modulation unit 21 is adjacent to at least one empty modulation unit 22;
  • the pixel array 30 is arranged in a matrix, and the first direction may be the row direction of the pixel array 30, and the second direction may be the column direction of the pixel array 30. Alternatively, the first direction may be the column direction of the pixel array 30, and the second direction may be the row direction of the pixel array 30.
  • the microstructure modulation unit 21 is arranged according to the above-mentioned preset arrangement rule, so that the microstructure modulation unit 21 and the air-retention modulation unit 22 form a mosaic arrangement required for spectral reconstruction.
  • each microstructure modulation unit 21 is surrounded by at least one empty modulation unit 22.
  • the microstructure modulation unit 21 may have two empty modulation units 22 located on different sides, and in the second direction, the microstructure modulation unit 21 may also have two empty modulation units 22 located on different sides.
  • the spectral modulation capability of the air modulation unit 22 is provided by the microstructure modulation units 21 around it, there are at most two consecutive air modulation units 22 to avoid too many consecutive air modulation units 22 affecting the spectral modulation capability of the air modulation units 22 due to the absence of edge scattering of the microstructure modulation units 21.
  • the structures of any two microstructure modulation units 21 are different from each other, so that the modulation curves of the multiple spectral modulation structures 20 are different from each other and have a large difference, thereby ensuring that after the spectrum is reconstructed by the algorithm, it has a higher spectral reconstruction accuracy.
  • the microstructure modulation units 21 are arranged according to the above preset arrangement rules.
  • the microstructure modulation units 21 and the empty modulation units 22 are alternately arranged with each other, and in the second direction, the microstructure modulation units 21 and the empty modulation units 22 are alternately arranged with each other.
  • the microstructure modulation unit 21 and The empty modulation units 22 are arranged alternately with each other, and in any column of the rectangular array formed by at least four sub-areas, the microstructure modulation units 21 and the empty modulation units 22 are arranged alternately with each other.
  • microstructure modulation units 21 are set on the upper left corner sub-region, upper right corner sub-region, center sub-region, lower left corner sub-region and lower right corner sub-region, and the remaining sub-regions are empty modulation units 22.
  • the microstructure modulation units 21 and the air-retaining modulation units 22 are arranged alternately with each other, so that the microstructure modulation units 21 with edge scattering capability are relatively evenly distributed around the air-retaining modulation units 22, thereby enabling the air-retaining modulation units 22 to have spectral modulation capability.
  • the infrared anti-reflection film 40 includes at least two transparent film layers stacked in sequence, and the refractive index of the plurality of transparent film layers gradually decreases in a direction away from the detector window packaging layer 10 .
  • the infrared anti-reflection film 40 includes at least two transparent film layers which are stacked in sequence and whose refractive index gradually decreases in the direction away from the detector window packaging layer 10, thereby further reducing the refractive index difference between two adjacent transparent film layers in the propagation path of the infrared band after entering from the detector window, improving the transmittance between adjacent transparent film layers, and further improving the overall transmittance of the refractive index gradient distribution area.
  • each transparent film layer depends on the wavelength of the infrared band and the refractive index of the infrared band in each transparent film layer.
  • the material of the transparent film layer includes ZnS zinc sulfide, ZnSe zinc selenide, BaF2 barium fluoride, CaF2 calcium fluoride, YbF3 ytterbium fluoride, Ge germanium or Si silicon.
  • the refractive index of ZnS and ZnSe is between 2-3
  • the refractive index of BaF2 , CaF2 and YbF3 is between 1-2
  • the refractive index of Si is greater than 3
  • the refractive index of Ge is greater than 4.
  • the material of the detector window packaging layer 10 is silicon Si
  • the infrared anti-reflection film 40 adopts a double-layer transparent film design, including a ZnS transparent film layer 41 disposed on the detector window packaging layer 10, and a BaF2 transparent film layer 42 disposed on the side of the ZnS transparent film layer 41 away from the detector window packaging layer 10. Therefore, for the ZnS transparent film layer 41, its thickness is h1, where 0.5 ⁇ m ⁇ h1 ⁇ 1.5 ⁇ m; for the BaF2 transparent film layer 42, its thickness is h2, where 1 ⁇ m ⁇ h2 ⁇ 2 ⁇ m.
  • the material of the detector window packaging layer 10 is germanium Ge
  • the infrared anti-reflection film 40 adopts a three-layer anti-reflection film design, including a Si silicon transparent film layer 43 disposed on the detector window packaging layer 10, a ZnS transparent film layer 41 disposed on the side of the Si transparent film layer 43 away from the detector window packaging layer 10, and a BaF2 transparent film layer 42 disposed on the side of the ZnS transparent film layer 41 away from the Si transparent film layer 43.
  • the Si transparent film layer 43 its thickness is h3, where 0.1 ⁇ m ⁇ h3 ⁇ 1 ⁇ m; for the ZnS transparent film layer 41, its thickness is h1, where 0.1 ⁇ m ⁇ h3 ⁇ 1 ⁇ m; Wherein 0.5 ⁇ m ⁇ h1 ⁇ 1.5 ⁇ m; for the BaF 2 transparent film layer 42 , its thickness is h2, wherein 0.8 ⁇ m ⁇ h2 ⁇ 2 ⁇ m.
  • the microstructure modulation unit 21 includes a plurality of micro-nanostructure sub-units 211 arranged in a rectangular array, and the plurality of micro-nanostructure sub-units 211 are spaced apart from each other.
  • the structures of any two microstructure modulation units 21 are different from each other, and the structure of the microstructure modulation unit 21 includes at least one of the shape of the micro-nanostructure subunit 211, the arrangement period of the micro-nanostructure subunit 211, or the number of the micro-nanostructure subunit 211. If the structures of two microstructure modulation units 21 are different, at least one of the shape of the micro-nanostructure subunit 211, the arrangement period of the micro-nanostructure subunit 211, or the number of the micro-nanostructure subunit 211 of the two microstructure modulation units 21 is different.
  • any microstructure modulation unit 21 when at least one of the following parameters of the microstructure modulation unit 21 changes, the spectrum modulation capability of the microstructure modulation unit 21 will be affected:
  • the shape of the micro-nano structure subunit 211 includes but are not limited to the height dimension, cross-sectional shape or cross-sectional dimension of each micro-nano structure subunit 211.
  • the cross-sectional area of the micro-nano structure subunit 211 is the area obtained by cutting the micro-nano structure subunit 211 with a plane parallel to the plane where the detector window packaging layer 10 is located.
  • micro-nanostructure subunits 211 Arrangement period of micro-nanostructure subunits 211. It is understandable that multiple micro-nanostructure subunits 211 can be arranged in a rectangular array. In this case, the arrangement period of the micro-nanostructure subunits 211 is the distance between the axes of adjacent micro-nanostructure subunits 211 in the row and column directions of the rectangular array.
  • micro-nanostructure subunits 211 The number of micro-nanostructure subunits 211.
  • the number of micro-nanostructure subunits 211 determines the overall arrangement of the array of micro-nanostructure subunits 211.
  • micro-nanostructure subunits 211 of the same shape are arranged in 2 ⁇ 2 in one sub-region, but in 3 ⁇ 3 in another sub-region.
  • the shapes of the micro-nanostructure sub-units 211 of the microstructure modulation units 21 around each air-retaining modulation unit 22 are all different.
  • the micro-nano structure subunit 211 is constructed as a columnar structure protruding from the infrared anti-reflection film 40 , and the material of the columnar structure is an infrared high refractive index material.
  • the micro-nano structure subunit 211 can be constructed as a micro-nano dielectric column formed of an infrared high refractive index material, which extends in a direction away from the detector window packaging layer 10 to protrude from the infrared anti-reflection film 40.
  • Each micro-nano dielectric column supports a waveguide mode for spectral modulation.
  • an infrared high refractive index medium layer 212 formed of an infrared high refractive index material is disposed on the side of the sub-region corresponding to the microstructure modulation unit 21 away from the detector window packaging layer 10. At this time, the infrared high refractive index medium layer 212 is provided with a hole structure 213 penetrating the infrared high refractive index medium layer 212 along the thickness direction of the detector window packaging layer 10. It is worth mentioning that the infrared high refractive index material is Ge or Si.
  • the height of the micro-nano structure sub-unit 211 is H, where H>5 ⁇ m, so that each micro-nano structure sub-unit 211 can support multiple waveguide modes for spectral modulation.
  • the spectral modulation of the micro-nanostructure subunit 211 should be polarization-independent.
  • the cross-sectional shape of the micro-nanostructure subunit 211 is constructed as a rotationally symmetrical figure with a rotation angle of 90°, such as a square, a circle, etc.
  • the side length of the pixel is n
  • the number of the micro-nanostructure sub-units 211 is m1
  • the number of the micro-nanostructure sub-units 211 is m2
  • m1 and m2 satisfy: m1 ⁇ 10 and m2 ⁇ 10; wherein the third direction is perpendicular to the fourth direction.
  • the third direction may be the row extension direction of the rectangular array, and the fourth direction may be the column extension direction of the rectangular array.
  • the third direction may be the column extension direction of the rectangular array, and the fourth direction may be the row extension direction of the rectangular array.
  • the third direction may be parallel to the first direction, in which case the fourth direction may be parallel to the second direction.
  • the side length of the sub-region can be set to 17 ⁇ m.
  • the pixel size of 17 ⁇ m is relatively small.
  • the side length of a single pixel corresponds to only 1-2 infrared band wavelengths.
  • the number of micro-nanostructure sub-units 211 that can be arranged in the sub-region is limited.
  • the number of micro-nanostructure sub-units 211 in the sub-region is less than 10 ⁇ 10.
  • the spectrum modulation capability of the air modulation unit 22 can be comparable to the spectrum modulation capability of the microstructure modulation unit 21.
  • m pixels in the pixel array form a macro pixel, and each macro pixel corresponds to m spectral modulation structures 20.
  • the m spectral modulation structures 20 include n spectral channels in total, and the incident spectrum of the region is ⁇ .
  • the energy values I 1 , I 2 , ...I m received by the macro pixel satisfy the underdetermined equation.
  • M m is the high transmittance modulation curve of the mth spectral modulation structure 20.
  • the compressed sensing algorithm can be used to solve the above underdetermined equation to obtain the incident spectrum ⁇ at the macro-pixel position, and the entire infrared spectrum image can be obtained by solving each macro-pixel one by one.
  • the detector window packaging layer 10 is a Si window.
  • a double-layer anti-reflection film design is used on the Si window.
  • the first transparent film layer close to the Si window is a ZnS transparent film layer 41 with a thickness of 0.88 ⁇ m.
  • the second transparent film layer disposed on the ZnS transparent film layer 41 and away from the Si window is a BaF2 transparent film layer 42 with a thickness of 1.26 ⁇ m.
  • the BaF2 transparent film layer contains 3 ⁇ 3 spectral modulation structures 20, and the specifications of each sub-region are 17 ⁇ m ⁇ 17 ⁇ m.
  • a total of 5 sub-regions including the upper left corner sub-region, the upper right corner sub-region, the middle sub-region, the lower left corner sub-region and the lower right corner sub-region, are provided with microstructure modulation units 21, and the remaining 4 sub-regions are empty modulation units 22.
  • the micro-nano structure subunit 211 is a periodically arranged Ge cylinder, wherein the arrangement period of the Ge cylinder array in the five sub-regions is between 2.5 ⁇ m and 8 ⁇ m, the cylinder duty cycle is between 0.2 and 0.8, and the height is between 5 ⁇ m and 30 ⁇ m.
  • the arrangement period of Ge cylinders in the upper left sub-region is 3 ⁇ m, the cylinder duty cycle is 0.45, and the height is 20 ⁇ m;
  • the arrangement period of Ge cylinders in the upper right sub-region is 4 ⁇ m, the cylinder duty cycle is 0.45, and the height is 20 ⁇ m;
  • the arrangement period of Ge cylinders in the center sub-region is 5.5 ⁇ m, the cylinder duty cycle is 0.5, and the height is 20 ⁇ m;
  • the arrangement period of Ge cylinders in the lower left sub-region is 6.5 ⁇ m, the cylinder duty cycle is 0.55, and the height is 20 ⁇ m;
  • the arrangement period of Ge cylinders in the lower right sub-region is 7.5 ⁇ m, the cylinder duty cycle is 0.55, and the height is 20 ⁇ m.
  • the single-side transmittance of the Si window is about 70%, while the double-side transmittance drops to less than 50%, and the transmittance is seriously reduced.
  • the wavelength average of the single-side transmittance of the Si window can reach more than 98%, and the anti-reflection effect is obvious.
  • Figure 7 is a comparison diagram of the modulation curves of 5 microstructure modulation units 21 and 4 empty modulation units 22. Due to the edge scattering of the microstructure modulation unit 21, the modulation curve of the empty modulation unit 22 also has a stronger modulation intensity, a larger number of modulation peaks and a narrower peak width, which is similar to the modulation curve characteristics of the microstructure modulation unit 21.
  • FIG8 is a comparison chart of the average light transmittance of the spectral modulation unit in this example and the average light transmittance of the microstructure modulation unit (such as micro-nanohole) generally set on the Si window.
  • the light transmittance of this example is increased from an average of 48% to 82%, so the reconstructed spectral signal-to-noise ratio is expected to be improved by 71%.
  • FIG9 shows nine spectral modulation curves generated by the nine spectral modulation units of this example, and the results of spectral reconstruction of a series of Gaussian spectra with different bandwidths in the range of 8 ⁇ m-14 ⁇ m.
  • the solid line in the figure is the true value spectrum, and the dotted line is the reconstructed spectrum. From left to right, the bandwidths of the series of Gaussian spectra in the figure are 400nm, 300nm and 200nm, respectively. Among them, the reconstruction effect of the Gaussian spectrum with a bandwidth as narrow as 300nm (about 2.7% ⁇ ) is still good. It can be seen that the high-flux spectral modulation curve of this example can maintain a high reconstructed spectral resolution.
  • the detector window packaging layer 10 is a Ge window.
  • a three-layer anti-reflection film design is used on the Ge window.
  • the first transparent film layer close to the Ge window is a Si transparent film layer 43, with a thickness between 0.1 ⁇ m and 1 ⁇ m.
  • the second transparent film layer disposed on the Si transparent film layer away from the Ge window is a ZnS transparent film layer 41, with a thickness between 0.5 ⁇ m and 1.5 ⁇ m.
  • the third transparent film layer disposed on the ZnS transparent film layer 41 away from the Si transparent film layer 43 is a BaF2 transparent film layer 42, with a thickness between 0.8 ⁇ m and 2 ⁇ m.
  • the BaF2 transparent film layer 42 contains 4 ⁇ 4 spectrum modulation structures 30, and the size of each sub-region is 12 ⁇ m ⁇ 12 ⁇ m. From left to right, each spectrum modulation unit in the first column and the fourth column is a microstructure modulation unit 21, and each spectrum modulation unit in the second column and the third column is a space modulation unit 22.
  • the eight spectral modulation micro-nanostructure subunits 211 are periodically arranged Si square pillars, wherein the arrangement period of the Si square pillar array is between 3 ⁇ m and 10 ⁇ m, the square pillar duty cycle is between 0.2 and 0.8, and the height is between 5 and 30 ⁇ m.
  • the present application also provides a detector, including: an image sensor and a modulation structure for infrared hyperspectral imaging, wherein the image sensor includes a pixel array, and the microstructure modulation unit of the modulation structure is arranged relative to the pixel array.
  • the specific structure of the modulation structure for infrared hyperspectral imaging of this embodiment refers to the above-mentioned embodiment. Since this detector adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.
  • an embodiment of the present application further provides an infrared spectrometer, comprising: a detector and an image signal processor, wherein the image signal processor is connected to the detector.
  • the image signal processor is used to receive the spectral image of the detector and output the image after processing.

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Abstract

一种用于红外高光谱成像的调制结构（20）、探测器及红外光谱仪，调制结构（20）包括：探测器窗口封装层（10）；红外增透膜（40），红外增透膜（40）设置于探测器窗口封装层（10）朝向像元阵列（30）的一侧表面，且红外增透膜（40）的材料的折射率小于探测器窗口封装层（10）的材料的折射率；以及多个微结构调制单元（21），多个微结构调制单元（21）按照预设排布规则设置于红外增透膜（40）的背离探测器窗口封装层（10）的一侧表面，以使红外增透膜（40）的背离探测器窗口封装层（10）的一侧表面部分区域空置形成至少一个留空调制单元（22），通过红外增透膜（40）和留空设计，提升微结构调制单元（21）光通量，可以实现较高的信噪比。

Description

用于红外高光谱成像的调制结构、探测器及红外光谱仪 技术领域
本申请涉及红外高光谱成像技术领域，特别涉及一种用于红外高光谱成像的调制结构、探测器及红外光谱仪。
背景技术
在高光谱成像相关技术中，可利用采用高折射率材料制成的微纳调制结构(如在硅平板刻蚀形成的微纳圆孔结构等)对入射光进行光谱维度调制，结合计算光学方法快照式获取光谱图像。
发明内容
本申请的主要目的是提供一种用于红外高光谱成像的调制结构、探测器及红外光谱仪，旨在解决光谱调制结构导致高光谱成像后信噪比较低的技术问题。
为实现上述目的，本申请提出一种用于红外高光谱成像的调制结构，包括：探测器窗口封装层；红外增透膜，红外增透膜设置于探测器窗口封装层朝向像元的一侧表面，且红外增透膜的材料的折射率小于探测器窗口封装层的材料的折射率；以及多个微结构调制单元，多个微结构调制单元按照预设排布规则设置于红外增透膜的背离探测器窗口封装层的一侧表面，以使红外增透膜的背离探测器窗口封装层的一侧表面部分区域空置形成至少一个留空调制单元。
在本申请可能的一种实施例中，预设排布规则包括以下至少一项：所述微结构调制单元与所述至少一个留空调制单元相邻；在所述像元阵列的第一方向或第二方向上，相邻两个所述微结构调制单元之间具有至多两个留空调制单元，所述第一方向垂直于所述第二方向；每个所述留空调制单元相邻的所有微结构调制单元中，任意两个微结构调制单元的结构彼此不同。
在本申请可能的一种实施例中，在第一方向上，微结构调制单元和留空调制单元彼此交替设置，且在第二方向上，微结构调制单元和留空调制单元彼此交替设置。
在本申请可能的一种实施例中，红外增透膜包括至少两层依次层叠设置的透明膜层，且沿远离探测器窗口封装层的方向，所述至少两层透明膜层的折射率逐渐减小。
在本申请可能的一种实施例中，透明膜层的材质包括ZnS硫化锌、ZnSe硒化锌、BaF2氟化钡、CaF2氟化钙、YbF3氟化镱、Ge锗或者Si硅。
在本申请可能的一种实施例中，每个所述微结构调制单元包括多个呈矩形阵列排布的微纳结构子单元，且多个微纳结构子单元彼此间隔开。
在本申请可能的一种实施例中，所述多个微纳结构子单元构造为凸出设置于子区域的柱状结构，柱状结构的材质为红外高折射率材料；或红外增透膜的背离探测器窗口封装层的一侧表面设置有红外高折射率介质层，所述多个微纳结构子单元构造为沿探测器窗口封装层的厚度方向贯穿红外高折射率介质层的孔状结构。
在本申请可能的一种实施例中，微纳结构子单元的横截面形状构造为旋转角为90°的旋转对称图形。
在本申请可能的一种实施例中，像元阵列中像元的边长小于等于17μm，在矩形阵列的第三方向上，微纳结构子单元的数量小于等于10个，在矩形阵列的第四方向上微纳结构子单元的数量小于等于10个；其中，第三方向垂直于第四方向。
在本申请可能的一种实施例中，微纳结构子单元的高度大于5μm。
第二方面，本申请还提供了一种探测器，包括：图像传感器，图像传感器包括像元阵列；以及如第一方面的用于红外高光谱成像的调制结构，调制结构的微结构调制单元和像元阵列相对设置。
第三方面，本申请还提供了一种红外光谱仪，包括：如第二方面提供的探测器；以及图像信号处理器，图像信号处理器与探测器连接。
本申请技术方案通过在探测器窗口封装层上添加红外增透膜，并在红外增透膜上按照预设排布规则排布多个微结构调制单元，以使所述红外增透膜表面的部分区域空置形成至少一个留空调制单元。微结构调制单元和留空调制单元共同形成了探测器的光谱调制结构。如此，本申请实施例一方面通过红外增透膜提供的增透能力，另一方面通过无结构的留空调制单元减少探测器窗口内微纳结构的使用面积，改善了微结构反射带来的透过率下降现象，从而共同提高了高光谱成像后的信噪比。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于 本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图示出的结构获得其他的附图。
图1为本申请用于红外高光谱成像的调制结构一实施例的结构示意图；
图2为本申请用于红外高光谱成像的调制结构一实施例的光谱调制结构分布示意图；
图3为本申请用于红外高光谱成像的调制结构又一实施例的结构示意图，其中，红外增透膜为双层结构；
图4为本申请用于红外高光谱成像的调制结构再一实施例的结构示意图，其中，红外增透膜为三层结构；
图5为本申请用于红外高光谱成像的调制结构一实施例的结构示意图，其中，微纳结构子单元为孔状结构；
图6为示例1的增透效果示意图；
图7为示例1的5个微结构调制单元21和4个留空调制单元22的调制曲线对比图；
图8为示例1光谱调制单元的平均透光量和Si窗口上一般设置的微结构调制单元(如微纳孔)的平均透光量对比图；
图9为示例1的9个光谱调制单元产生的9条光谱调制曲线图；
图10为本申请示例2的微结构调制单元和留空调制单元排布示意图。
本申请目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请的一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
需要说明，本申请实施例中所有方向性指示(诸如上、下、左、右、前、后……)仅用于解释在某一特定姿态(如附图所示)下各部件之间的相对位置关系、运动情况等，如果该特定姿态发生改变时，则该方向性指示也相应地随之改变。
在本申请中，除非另有明确的规定和限定，术语“连接”、“固定”等应做广义理解，例如，“固定”可以是固定连接，也可以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系，除非另有明确的限定。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
另外，若本申请实施例中有涉及“第一”、“第二”等的描述，则该“第一”、“第二”等的描述仅用于描述目的，而不能理解为指示或暗示其相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。另外，全文中出现的“和/或”的含义，包括三个并列的方案，以“A和/或B”为例，包括A方案、或B方案、或A和B同时满足的方案。另外，各个实施例之间的技术方案可以相互结合，但是必须是以本领域普通技术人员能够实现为基础，当技术方案的结合出现相互矛盾或无法实现时应当认为这种技术方案的结合不存在，也不在本申请要求的保护范围之内。
高光谱成像可同时获取物体空间分布和较高的光谱分辨率信息，在物质鉴别、环境监测、化工和食品安全等领域具有广泛应用。传统的高光谱成像方案多采用单点光谱仪外加机械装置进行空间扫描成像，但该类器件往往体积大，且获取光谱图像耗时长。相关技术中，可利用采用高折射率材料制成的微纳调制结构(如在硅平板刻蚀形成的微纳圆孔结构等)对入射光进行光谱维度调制，结合计算光学方法快照式获取光谱图像。
在长波红外波段，由于红外探测器像元数量少，微纳调制结构所占面积有限，为了提升调制效果，可以加大微纳调制结构的空间占比。但是提高微纳调制结构的空间占比会导致微纳调制结构具有高反射率、低透光量的特性，进而导致成像后信噪比较低。
为获取高光谱分辨率图像，微纳调制结构的光谱调制需要满足整谱调制幅度大、调制峰数量多以及峰宽较窄等条件，为满足前述条件，需要微纳调制结构使用相应波段的高折射率材料。然而由于硅Si材料的可见光损耗和高反射特性，在硅平板刻蚀形成的微纳圆孔结构等微纳调制结构的调制通光量低(往往小于50％)，导致信噪比较差。
特别的，在波长8μm-14μm的长波红外波段，所用红外探测器通常为光热型，其噪声大，加之待测物体信号弱，信噪比相较于可见光波段技术更低。尽管锗Ge、Si 等材料在长波红外波段几乎无光损耗，但由于红外探测器像元数量少，微纳调制结构所占面积有限，为了提升调制效果，不得不加大微纳调制结构的空间占比，导致了Ge、Si等材料微纳调制结构的高反射、低透光量，进而导致成像后信噪比较低。
为此，本申请实施例提供一种用于红外高光谱成像的调制结构，该调制结构在探测器窗口(window)的封装层上添加红外增透膜，并在红外增透膜上按照预设排布规则排布多个微结构调制单元，以使所述红外增透膜表面的部分区域空置形成至少一个留空调制单元。微结构调制单元和留空调制单元共同形成了探测器的光谱调制结构。如此，本申请实施例一方面通过红外增透膜提供的增透能力，另一方面通过无结构的留空调制单元减少探测器窗口内微纳结构的使用面积，改善了微结构反射带来的透过率下降现象，从而共同提高了高光谱成像后的信噪比。
下面结合一些具体实施例具体阐述本申请实施例的发明构思。
本申请实施例提出一种用于红外高光谱成像的调制结构。
如图1所示，该红外高光谱成像的光谱调制结构20和图像传感器上的像元阵列30相对设置，用于对入射光进行光谱调制，图像传感器上的像元阵列30接受调制后的光谱信号后，输出检测信号。
请参阅图1及图2，本实施例中，用于红外高光谱成像的调制结构包括探测器窗口封装层10、红外增透膜40以及多个微结构调制单元21。
其中，红外增透膜40设置于探测器窗口封装层10朝向像元阵列30的一侧表面，且红外增透膜40的材料的折射率小于探测器窗口封装层10的材料的折射率；多个微结构调制单元21按照预设排布规则设置于红外增透膜40的背离探测器窗口封装层10的一侧表面，以使红外增透膜40的背离探测器窗口封装层10的一侧表面部分区域空置形成至少一个留空调制单元22。
具体而言，探测器具有封层盖板，封装盖板的板体具有可容红外光透过的红外窗口区，即本实施例中的探测器窗口封装层10。探测器窗口封装层10和像元阵列30相对设置，从而使得红外窗口区透过的红外光被像元阵列30接收。其中，探测器窗口封装层10的材料包括锗Ge或者硅Si。
探测器窗口封装层10朝向像元阵列30的一侧表面设置有红外增透膜40。红外增透膜40的背离探测器窗口封装层10的一侧表面分割成呈矩形阵列排布的至少4个子区域。当然，在成像领域中，矩形阵列一般构造为行数与列数相等的方阵，从而每个 子区域均为方形。如红外增透膜40的表面分割成呈3×3排布的9个子区域，或者，分割成4×4排布的16个子区域。
在本实施例中，在红外增透膜40的背离探测器窗口封装层10的一侧表面设置有多个光谱调制结构20，其中，光谱调制结构20的数量等于高光谱相机的成像像素个数，光谱调制结构20包括不同光谱调制单元。如红外增透膜40表面分割成呈3×3排布的9个光谱调制单元(包括微结构调制单元21和留空调制单元22)，其中每个光谱调制单元与像元一一对应，从而以使光谱调制结构20和像元一一对应，例如参考图1，虚线框中为一个光谱调制结构20，其与下方的一个像元30一一对应。特别注意的是，在本实施例中，光谱调制结构20包括微结构调制单元21以及空置而形成的留空调制单元22。每个微结构调制单元21凸出设置于一子区域上，其内部支持用于光谱调制的波导模式。而其中对于部分子区域，其上和微结构调制单元21位于相同高度的空间内没有结构分布，从而形成其上无结构的留空调制单元22。
可以理解的，由于探测器的像元30尺寸较小，例如17μm的像元30尺寸仅对应1-2个红外波段波长，微结构调制单元21的数量有限，从而微结构调制单元21的边缘散射强度较大，使得在周围微结构调制单元21的散射作用下，留空调制单元22也具有光谱调制能力。
相较于密布排列的微纳结构调制单元，本实施例无结构存在的留空调制单元22减少了探测器窗口内微纳结构的使用面积，改善了微纳结构反射带来的透过率下降问题，也即提升了微纳结构的光谱调制单元光通量，进而提高高光谱成像后的信噪比。
此外，红外增透膜40的材料的折射率小于探测器窗口封装层10的材料的折射率，从而在探测器窗口封装层10至像元30的方向上，形成了高折射率材料-低折射率材料-空气的渐变分布。可以理解的，当光从一种介质进入另一种介质时，如果两种介质的折射率相差减小，反射光的能量减小，透射光的能量增加。如此，本实施例中，红外光在穿透该折射率渐变分布区域时，可提高透过率，进而本实施例通过结合留空调制单元减少探测器窗口内微纳结构的使用面积，和红外增透膜提供的增透能力，共同改善了微纳结构反射带来的透过率下降问题，共同提高了高光谱成像后的信噪比。
此外，本实施例中，通过红外增透膜40提高了红外波段的透过率，通过设置留空调制单元22提高了红外波段在红外增透膜40朝向像元30的一侧表面设置的光谱调制结构20的通过量，如此，光谱调制结构20的通光量更多，微结构调制单元21的散射作用更强，从而也提高了留空调制单元22的光谱调制能力，进而不仅提高高光谱成像 后的信噪比，还可提高光谱重建精度。
在本申请可能的实施例中，预设排布规则包括以下至少一项：
(1)微结构调制单元21与至少一个留空调制单元22相邻；
(2)在像元阵列30的第一方向或第二方向上，相邻两个微结构调制单元21之间具有至多两个留空调制单元22，第一方向垂直于第二方向；
(3)与每个留空调制单元22相邻的所有微结构调制单元21中，任意两个微结构调制单元21的结构彼此不同。
其中，像元阵列30呈矩阵排布，此时第一方向可以是像元阵列30的行方向，第二方向可以是像元阵列30的列方向。或者，第一方向也可以是像元阵列30的列方向，第二方向可以是像元阵列30的行方向。本实施例中，微结构调制单元21按照上述预设排布规则排布，可使得微结构调制单元21和留空调制单元22形成光谱重建所需的马赛克排列。
在形成的马赛克排列中，每个微结构调制单元21周围具有至少一个留空调制单元22。如在第一方向上，微结构调制单元21可能具有位于相异侧的两个留空调制单元22，在第二方向，微结构调制单元21可能也具有位于相异侧的两个留空调制单元22。
在第一方向上或者第二方向上，由于留空调制单元22的光谱调制能力由其周围的微结构调制单元21提供，因此连续的留空调制单元22最多具有2个，以避免连续过多的留空调制单元22由于没有微结构调制单元21的边缘散射影响留空调制单元22的光谱调制能力。
此外，无结构存在的留空调制单元22相邻的所有微结构调制单元21中，任意两个微结构调制单元21的结构彼此不同，从而使得多个光谱调制结构20彼此之间的调制曲线不同，具有较大的差异，从而可保证通过算法重建光谱后，具有较高的光谱重建精度。
在一些实施例中，微结构调制单元21按照以上预设排布规则进行排布。
在本申请可能的一些实施例中，在第一方向上，微结构调制单元21和留空调制单元22彼此交替设置，且在第二方向上，微结构调制单元21和留空调制单元22彼此交替设置。
具体而言，在至少4个子区域形成的矩形阵列的任一行上，微结构调制单元21和 留空调制单元22彼此交替设置，且在至少4个子区域形成的矩形阵列的任一列上，微结构调制单元21和留空调制单元22彼此交替设置。
请参阅图2，对于一3×3排布的矩形阵列，其左上角子区域、右上角子区域、正中子区域、左下角子区域和右下角子区域上均设置有微结构调制单元21，剩余的子区域则为留空调制单元22。
本实施例中，采用该微结构调制单元21和留空调制单元22彼此交替布置的方式，可以确保留空调制单元22周围较为均匀地分布着具有边缘散射能力的微结构调制单元21，从而使得留空调制单元22具有光谱调制能力。
在本申请一实施例中，红外增透膜40包括至少两层依次层叠设置的透明膜层，且沿远离探测器窗口封装层10的方向，多个透明膜层的折射率逐渐减小。
本实施例中，红外增透膜40包括至少两层依次层叠设置，且沿远离探测器窗口封装层10的方向折射率逐渐减小的透明膜层，从而进一步减小红外波段在从探测器窗口进入后的传播路径上，相邻两个透明膜层之间的折射率差值，提高相邻透明膜层之间的透过率，进而提高该折射率渐变分布区域整体的透过率。
可以理解的，每层透明膜层的具体厚度取决于红外波段的波长和红外波段在每层透明膜层中的折射率。在本实施例中，透明膜层的材质包括ZnS硫化锌、ZnSe硒化锌、BaF2氟化钡、CaF2氟化钙、YbF3氟化镱、Ge锗或者Si硅。其中，ZnS和ZnSe的折射率在2-3之间，而BaF2、CaF2和YbF3的折射率在1-2之间，Si的折射率大于3，Ge的折射率大于4。
在一示例中，请参阅图3，探测器窗口封装层10的材质为硅Si，此时红外增透膜40采用双层透明膜层设计，包括设置于探测器窗口封装层10上的ZnS透明膜层41，和设置于ZnS透明膜层41的背离探测器窗口封装层10一侧的BaF2透明膜层42。因此，对于ZnS透明膜层41，其厚度为h1，其中0.5μm≤h1≤1.5μm；对于BaF2透明膜层42，其厚度为h2，其中1μm≤h2≤2μm。
如在另一示例中，请参阅图4，探测器窗口封装层10的材质为锗Ge，此时红外增透膜40采用三层增透膜设计，包括设置于探测器窗口封装层10上的Si硅透明膜层43、设置于Si透明膜层43的背离探测器窗口封装层10一侧的ZnS透明膜层41以及设置于ZnS透明膜层41的背离Si透明膜层43一侧的BaF2透明膜层42。对于Si透明膜层43，其厚度为h3，其中0.1μm≤h3≤1μm；对于ZnS透明膜层41，其厚度为h1， 其中0.5μm≤h1≤1.5μm；对于BaF2透明膜层42，其厚度为h2，其中0.8μm≤h2≤2μm。
在本申请可能的一实施例中，请参阅图2和图10，微结构调制单元21包括多个呈矩形阵列排布的微纳结构子单元211，且多个微纳结构子单元211彼此间隔开。
此时，与每个留空调制单元22相邻的所有微结构调制单元21中，任意两个微结构调制单元21的结构彼此不同中，微结构调制单元21的结构包括微纳结构子单元211的形状、微纳结构子单元211的排布周期或者微纳结构子单元211的数量中的至少一者。如果两个微结构调制单元21的结构不同，则这两个微结构调制单元21的微纳结构子单元211的形状、微纳结构子单元211的排布周期或者微纳结构子单元211的数量中的至少一者不同。
具体而言，对于任一微结构调制单元21而言，微结构调制单元21以下参数至少之一发生变化时会对微结构调制单元21的光谱调制能力产生影响：
1)微纳结构子单元211的形状。微纳结构子单元211的形状参数包括但不限于每个微纳结构子单元211的高度尺寸、横截面形状或者横截面尺寸。其中，微纳结构子单元211的横截面为利用与探测器窗口封装层10所在平面相平行的平面对微纳结构子单元211进行剖切得到的区域。
2)微纳结构子单元211的排布周期。可以理解的，多个微纳结构子单元211可以呈矩形阵列排布，此时，微纳结构子单元211的排布周期为在该矩形阵列的行方向和列方向上，相邻微纳结构子单元211的轴线之间的距离。
3)微纳结构子单元211的数量。微纳结构子单元211的数量决定了微纳结构子单元211阵列的整体排布。如相同形状的微纳结构子单元211，其在一子区域中呈2×2排布，但是在另一子区域中呈3×3排布。
当然，为了使得每个留空调制单元22周围的微结构调制单元21的光谱调制能力差异较大以利于后续的光谱重建，每个留空调制单元22周围的微结构调制单元21的微纳结构子单元211的形状、微纳结构子单元211的排布周期和微纳结构子单元211的数量均不同。
在本申请一实施例中，微纳结构子单元211构造为凸出设置于红外增透膜40的柱状结构，柱状结构的材质为红外高折射率材料。
在本申请一实施例中，例如参见图5，红外增透膜40的背离探测器窗口封装层10 的一侧表面设置有红外高折射率介质层212，微纳结构子单元211构造为沿探测器窗口封装层10的厚度方向贯穿红外高折射率介质层212的孔状结构213。
在本申请一实施例中，微纳结构子单元211可以构造为采用红外高折射率材料形成的微纳介质柱，微纳介质柱沿远离探测器窗口封装层10的方向上延伸以凸出于红外增透膜40。每个微纳介质柱内支持用于光谱调制的波导模式。
在本申请一实施例中，请参阅图5，采用红外高折射率材料形成的红外高折射率介质层212设置于微结构调制单元21对应的子区域的背离探测器窗口封装层10的一侧。此时，红外高折射率介质层212开设有沿探测器窗口封装层10的厚度方向贯穿红外高折射率介质层212的孔状结构213。值得一提的是，红外高折射率材料为Ge或Si。
微纳结构子单元211的高度为H，H＞5μm，以使得每个微纳结构子单元211内部可支持多个用于光谱调制的波导模式。
在本申请可能的一实施例中，为了保证微纳结构子单元211的高透过率，微纳结构子单元211的光谱调制应具有偏振无关性，此时，微纳结构子单元211的横截面形状构造为旋转角为90°的旋转对称图形，如正方形、圆形等。
在本申请可能的一实施例中，像元的边长为n，在微结构调制单元21的矩形阵列的第三方向上，微纳结构子单元211的数量为m1，在微结构调制单元21的矩形阵列的第四方向上微纳结构子单元211的数量为m2，m1和m2满足：m1≤10且m2≤10；其中，第三方向垂直于第四方向。
其中，第三方向可以是矩形阵列的行延伸方向，而第四方向可以是矩形阵列的列延伸方向。或者，第三方向可以是矩形阵列的列延伸方向，而第四方向可以是矩形阵列的行延伸方向。此外，第三方向可以和第一方向平行，此时，第四方向可以和第二方向平行。
具体而言，由于像元的尺寸一般为17μm或以下，因此可以设置子区域的边长也为17μm，17μm的像元尺寸较小，例如单个像元的边长对应仅1-2个红外波段波长，此时，子区域内可排布的微纳结构子单元211的数量有限，为了进一步提高微纳结构子单元211的边缘散射，从而确保留空调制单元22的光谱调制能力，子区域内微纳结构子单元211的的数量小于10×10个。
本实施例中，当子区域内微纳结构子单元211的数量小于10×10个时，留空调制单元22的光谱调制能力可与微结构调制单元21的光谱调制能力相当。
可以理解的，像元阵列中m个像元组成一宏像素，每个宏像素对应于m个光谱调制结构20。m个光谱调制结构20共包括n个光谱通道，且所处区域的入射光谱为φ。此时该宏像素接收到的能量值I1,I2,...Im满足欠定方程。
欠定方程为：
其中，Mm为第m个光谱调制结构20的高透过率调制曲线。当然，若所需光谱通道数较多，即n≥m，则可利用压缩感知算法，求解上述欠定方程得到该宏像素位置处的入射光谱φ，逐个宏像素求解即可获取整个红外光谱图像。
为使得本领域技术人员，更好地理解本申请权利要求的保护范围。以下通过具体的应用场景中的具体实施示例，对本申请权利要求记载的技术方案进行解释说明，可以理解的是，以下示例仅用于解释本申请，而不用于限定本申请权利要求的保护范围。
示例1：请参阅图1和图3，探测器窗口封装层10为Si窗口，Si窗口上采用双层增透膜设计，靠近Si窗口的第一层透明膜层为ZnS透明膜层41，厚度为0.88μm。设置于ZnS透明膜层41的背离Si窗口的第二层透明膜层为BaF2透明膜层42，厚度为1.26μm。BaF2透明膜层上含有3×3个光谱调制结构20，各子区域的规格为17μm×17μm。其左上角子区域、右上角子区域、正中子区域、左下角子区域和右下角子区域共5个子区域设置有微结构调制单元21，剩余的4个子区域则为留空调制单元22。
微纳结构子单元211为周期性排列的Ge圆柱。其中，5个子区域内的Ge圆柱阵列的排布周期在2.5μm-8μm之间，圆柱占空比在0.2-0.8之间，高度在5μm-30μm之间。其中，左上角子区域内Ge圆柱的排布周期为3μm，圆柱占空比为0.45，高度为20μm；右上角子区域内Ge圆柱的排布周期为4μm，圆柱占空比为0.45，高度为20μm；正中子区域内Ge圆柱的排布周期为5.5μm，圆柱占空比为0.5，高度为20μm；左下子区域内Ge圆柱的排布周期为6.5μm，圆柱占空比为0.55，高度为20μm；右下角子区域Ge圆柱的排布周期为7.5μm，圆柱占空比为0.55，高度为20μm。
如图6，以未添加增透膜时的Si窗口为对比为例，Si窗口单面透过率约为70％，双面透过率则降为小于50％，透过率严重下降。在本示例中添加增透膜后，Si窗口单面透过率波长平均值可达到98％以上，增透效果明显。
图7为5个微结构调制单元21和4个留空调制单元22的调制曲线对比图，由于微结构调制单元21的边缘散射，留空调制单元22的调制曲线同样具有较强的调制强度、较多的调制峰数量和较窄的峰宽，与微结构调制单元21的调制曲线特性相近。
图8是本示例光谱调制单元的平均透光量和Si窗口上一般设置的微结构调制单元(如微纳孔)的平均透光量对比图，本示例的透光量从平均48％提升至82％，因此重建光谱信噪比预期可提升71％。
图9是本示例的9个光谱调制单元产生的9条光谱调制曲线，对8μm-14μm范围内不同带宽的系列高斯光谱进行光谱重建结果。图中实线为真值光谱，虚线为重建光谱。从左至右图的系列高斯光谱带宽分别为400nm、300nm和200nm，其中带宽窄至300nm(约2.7％λ)的高斯光谱重建效果依然较好。可见，本示例的高光通量光谱调制曲线可以保持较高的重建光谱分辨率。
示例2：请参阅图4和图10，探测器窗口封装层10为Ge窗口，Ge窗口上采用三层增透膜设计，靠近Ge窗口的第一层透明膜层为Si透明膜层43，厚度在0.1μm-1μm之间。设置于Si透明膜层的背离Ge窗口的第二层透明膜层为ZnS透明膜层41，厚度在0.5μm-1.5μm之间。设置于ZnS透明膜层41的背离Si透明膜层43的第三层透明膜层为BaF2透明膜层42，厚度在0.8μm-2μm之间。
BaF2透明膜层42上含有4×4个光谱调制结构30，各子区域的规格为12μm×12μm。其中，从左至右，第一列和第四列中各个光谱调制单元均为微结构调制单元21，而第二列和第三列中各个光谱调制单元均为留空调制单元22。
8个光谱调制微纳结构子单元211为周期性排列的Si方柱。其中，Si方柱阵列的排布周期在3μm-10μm之间，方柱占空比在0.2-0.8之间，高度在5-30μm之间。
第二方面，本申请实施例还提供了一种探测器，包括：图像传感器和用于红外高光谱成像的调制结构。其中，图像传感器包括像元阵列，调制结构的微结构调制单元和像元阵列相对设置。
本实施例的用于红外高光谱成像的调制结构的具体结构参照上述实施例，由于本探测器采用了上述所有实施例的全部技术方案，因此至少具有上述实施例的技术方案所带来的所有有益效果，在此不再一一赘述。
第三方面，本申请实施例还提供了一种红外光谱仪，包括：探测器以及图像信号处理器，图像信号处理器与探测器连接。
其中，图像信号处理器用于接收探测器的光谱图像，以处理后输出图像。
本实施例的探测器的具体结构参照上述实施例，由于本红外光谱仪采用了上述所有实施例的全部技术方案，因此至少具有上述实施例的技术方案所带来的所有有益效果，在此不再一一赘述。
以上所述仅为本申请的一些实施例，并非因此限制本申请的保护范围，凡是在本申请的发明构思下，利用本申请说明书及附图内容所作的等效结构变换，或直接/间接运用在其他相关的技术领域均包括在本申请的保护范围内。

Claims (13)

  1. 一种用于红外高光谱成像的调制结构，包括：
    探测器窗口封装层；
    红外增透膜，所述红外增透膜设置于所述探测器窗口封装层朝向像元阵列的一侧表面，且所述红外增透膜的材料的折射率小于所述探测器窗口封装层的材料的折射率；以及
    多个微结构调制单元，多个所述微结构调制单元按照预设排布规则设置于所述红外增透膜的背离所述探测器窗口封装层的一侧表面，以使所述红外增透膜的背离所述探测器窗口封装层的一侧表面部分区域空置形成至少一个留空调制单元。
  2. 根据权利要求1所述的用于红外高光谱成像的调制结构，其中，所述预设排布规则包括以下至少一项：
    所述微结构调制单元与所述至少一个所述留空调制单元相邻；
    在所述像元阵列的第一方向或第二方向上，相邻两个所述微结构调制单元之间具有至多两个所述留空调制单元，所述第一方向垂直于所述第二方向；或
    每个所述留空调制单元相邻的所有所述微结构调制单元中，任意两个微结构调制单元的结构彼此不同。
  3. 根据权利要求2所述的用于红外高光谱成像的调制结构，其中，在所述第一方向上，所述微结构调制单元和所述留空调制单元彼此交替设置，且在所述第二方向上，所述微结构调制单元和所述留空调制单元彼此交替设置。
  4. 根据权利要求2所述的用于红外高光谱成像的调制结构，其中，所述红外增透膜包括至少两层依次层叠设置的透明膜层，且沿远离所述探测器窗口封装层的方向，所述至少两层透明膜层的折射率逐渐减小。
  5. 根据权利要求4所述的用于红外高光谱成像的调制结构，其中，所述透明膜层的材质包括ZnS硫化锌、ZnSe硒化锌、BaF2氟化钡、CaF2氟化钙、YbF3氟化镱、Ge锗或者Si硅。
  6. 根据权利要求1至5任一项所述的用于红外高光谱成像的调制结构，其中，每个所述微结构调制单元包括多个呈矩形阵列排布的微纳结构子单元，且多个所述微纳结构子单元彼此间隔开。
  7. 根据权利要求6所述的用于红外高光谱成像的调制结构，其中，所述多个微纳结构子单元构造为凸出设置于所述红外增透膜的柱状结构，所述柱状结构的材质为红外高折射率材料。
  8. 根据权利要求6所述的用于红外高光谱成像的调制结构，其中，所述红外增透膜的背离所述探测器窗口封装层的一侧表面设置有红外高折射率介质层，所述多个微纳结构子单元构造为沿所述探测器窗口封装层的厚度方向贯穿所述红外高折射率介质层的孔状结构。
  9. 根据权利要求7或8所述的用于红外高光谱成像的调制结构，其中，所述微纳结构子单元的横截面形状构造为旋转角为90°的旋转对称图形。
  10. 根据权利要求6所述的用于红外高光谱成像的调制结构，其中，所述像元阵列中像元的边长小于或等于17μm，在所述矩形阵列的第三方向上，所述微纳结构子单元的数量小于或等于10个，在所述矩形阵列的第四方向上所述微纳结构子单元的数量小于或等于10个；其中，所述第三方向垂直于所述第四方向。
  11. 根据权利要求6所述的用于红外高光谱成像的调制结构，其中，所述微纳结构子单元的高度大于5μm。
  12. 一种探测器，包括：
    图像传感器，所述图像传感器包括像元阵列；以及
    如权利要求1至11任一项所述的用于红外高光谱成像的调制结构，所述调制结构的微结构调制单元和所述像元阵列相对设置。
  13. 一种红外光谱仪，包括：
    如权利要求12所述的探测器；以及
    图像信号处理器，所述图像信号处理器与所述探测器连接。
PCT/CN2024/087004 2023-06-14 2024-04-10 用于红外高光谱成像的调制结构、探测器及红外光谱仪 Ceased WO2024255411A1 (zh)

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