The full dielectric film system structure is visible near-infrared low transmission simulation vegetation, mid-infrared high reflection, and microwave high transmission

Abstract

This invention provides an all-dielectric film structure that simulates vegetation with low transmittance in the visible and near-infrared range, high reflectance in the mid-infrared range, and high transmittance in the microwave range. From top to bottom, the invention comprises: a visible and near-infrared vegetation simulation layer, composed of first to fourth dielectric layers, configured to simulate the reflectance spectral characteristics of vegetation in the 380-2500 nm band and exhibiting low transmittance; a mid-infrared high reflectance layer, composed of alternating stacks of the first and third dielectric layers, configured to form high reflectance in the 3-14 μm band; and a substrate layer; the overall film thickness is much smaller than the microwave wavelength, enabling the film system to maintain high transmittance in the microwave band. By introducing amorphous InSb material with high loss characteristics in the visible and near-infrared range, this invention achieves high-precision simulation of vegetation reflectance spectra while reducing the average transmittance in the 1500-2500 nm range to 0.095, thereby simulating low transmittance of vegetation in this band.

Description

Technical Field

[0001] This invention belongs to the field of hyperspectral camouflage technology, specifically relating to a full-dielectric film structure that simulates vegetation with low transmission in the visible and near-infrared range, high reflectivity in the mid-infrared range, and high transmission in the microwave range. Background Technology

[0002] With the rapid development of modern detection technology, stealth methods targeting only a single wavelength band are no longer sufficient to meet practical needs. In addition to common infrared and microwave detection, hyperspectral imaging technology with a spectral resolution of 5-10 nm also poses a significant challenge to traditional camouflage. As the primary background for ground targets, green vegetation has several significant spectral features that are easily identified by hyperspectral detection, thus exposing camouflaged targets. The main reflectance features of vegetation in the visible-near-infrared band include: (1) a green peak near 550 nm; (2) a red edge at 680–780 nm; (3) a near-infrared plateau at 800–1300 nm; and (4) water absorption peaks at 1450 nm and 1950 nm. Therefore, it is increasingly urgent to achieve accurate simulation of the vegetation spectrum in this band.

[0003] Several studies have focused on hyperspectral camouflage films in the visible-near-infrared band, such as the "Visible-Laser-Infrared Compatible Camouflage Film Simulating Natural Vegetation" described in Chinese Patent CN119717096A, the "Thermal Infrared Low-Emissivity Green Leaf Simulated Multilayer Film and Its Preparation Method" in Chinese Patent CN119758501A, and the "Multilayer Film for Hyperspectral-Laser Stealth" in Chinese Patent CN114690278A. While these film systems can simulate the typical spectral characteristics of vegetation, they still have significant shortcomings: the aforementioned film systems only simulate the reflectivity of vegetation, exhibiting high transmittance in the 1500-2500 nm band, which does not match the low transmittance of real vegetation in this band. For example, the CN119717096A film system has an average transmittance of 83.4% in this band. Because these film systems do not simulate the low transmittance of vegetation in the 1500-2500 nm band, if applied to highly reflective substrates such as metal armor, the superposition of substrate reflection and the reflection of the upper film layer will disrupt the simulated spectral curve.

[0004] Furthermore, to reduce detectability in the mid-infrared band, the film system needs to have high reflectivity in the two atmospheric windows of 3-5 µm and 8-14 µm to achieve low emissivity. At the same time, to avoid affecting the communication and detection functions of the equipment itself, the film system also needs to maintain good microwave transmission performance.

[0005] Therefore, there is an urgent need to develop a novel composite membrane structure that can accurately simulate vegetation spectra in the visible-near infrared range, while exhibiting high reflectivity in the mid-infrared and high transmittance in the microwave band. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes an all-dielectric film structure that can simulate vegetation spectra with low transmission in the visible-near infrared band, while possessing high reflectivity in the mid-infrared and high transmission in the microwave.

[0007] The present invention comprises, from top to bottom, the following:

[0008] The visible and near-infrared simulated vegetation layer, composed of the first to fourth dielectric layers, is configured to simulate the reflectance spectral characteristics of vegetation in the 380-2500 nm band and has low transmission characteristics.

[0009] A mid-infrared high-reflectivity layer, composed of alternating stacked first and third dielectric layers, is configured to generate high reflectivity in the 3-14 μm wavelength band; and

[0010] Substrate layer;

[0011] The overall film thickness is much smaller than the microwave wavelength, which allows the film system to maintain high transmittance in the microwave band.

[0012] Furthermore, the first dielectric layer is selected from ZnS or HfO2; the second dielectric layer is YbF3; the third dielectric layer is selected from Ge or Si; and the fourth dielectric layer is selected from amorphous InSb or crystalline Ge2Sb2Se4Te1.

[0013] Furthermore, the first dielectric layer is ZnS; the second dielectric layer is YbF3; the third dielectric layer is Ge; and the fourth dielectric layer is amorphous InSb.

[0014] Furthermore, the thickness of the first dielectric layer is 10-550 nm; the thickness of the second dielectric layer is 30-100 nm; the thickness of the third dielectric layer is 4-600 nm; and the thickness of the fourth dielectric layer is 500-1000 nm.

[0015] Furthermore, the visible and near-infrared simulated vegetation layer comprises, from top to bottom: a ZnS layer with a thickness of 10 nm, a YbF3 layer with a thickness of 44 nm, a Ge layer with a thickness of 4 nm, a ZnS layer with a thickness of 75 nm, a YbF3 layer with a thickness of 87 nm, a ZnS layer with a thickness of 52 nm, a Ge layer with a thickness of 532 nm, a ZnS layer with a thickness of 125 nm, a Ge layer with a thickness of 48 nm, a YbF3 layer with a thickness of 36 nm, an amorphous InSb layer with a thickness of 995 nm, a Ge layer with a thickness of 7 nm, and an amorphous InSb layer with a thickness of 990 nm.

[0016] Furthermore, the mid-infrared high reflectivity layer is composed of alternating stacks of a first dielectric layer and a third dielectric layer, with the third dielectric layer being the layer closest to the substrate. From top to bottom, the third dielectric layer comprises:

[0017] A Ge layer with a thickness of 518 nm, a ZnS layer with a thickness of 393 nm, a Ge layer with a thickness of 30 nm, a ZnS layer with a thickness of 562 nm, a Ge layer with a thickness of 590 nm, a ZnS layer with a thickness of 473 nm, a Ge layer with a thickness of 220 nm, a ZnS layer with a thickness of 497 nm, a Ge layer with a thickness of 271 nm, a ZnS layer with a thickness of 534 nm, a Ge layer with a thickness of 516 nm, a ZnS layer with a thickness of 452 nm, a Ge layer with a thickness of 39 nm, a ZnS layer with a thickness of 507 nm, and a Ge layer with a thickness of 517 nm.

[0018] Furthermore, the overall thickness of the membrane system is 8-10 μm.

[0019] Furthermore, the reflectance spectrum of the membrane system in the 380-2500 nm band has a consistency of more than 90% with the reflectance spectrum of standard vegetation, and the spectral channels meet the requirements of standard vegetation spectral characteristics, and the average transmittance in the 1500-2500 nm band is less than 0.1.

[0020] Furthermore, the average reflectance of the film system is not less than 0.75 in the 3-5 μm band and not less than 0.6 in the 8-14 μm band.

[0021] Furthermore, the transmittance of the membrane system in the 5-40 GHz microwave band is not less than 99%.

[0022] In summary, the all-dielectric film structure provided by this invention, which simulates vegetation with low transmission in the visible-near infrared band, high reflectivity in the mid-infrared band, and high microwave transmission, can accurately simulate the vegetation spectrum in the visible to near-infrared band, achieve high reflectivity stealth in the infrared atmospheric window, and maintain excellent microwave transmission performance. It is particularly suitable for various devices that simultaneously have the requirements of hyperspectral camouflage, mid-infrared stealth, and microwave communication.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. Achieved simulation of visible and near-infrared vegetation under low transmission conditions: By introducing amorphous InSb material with high loss characteristics in the visible and near-infrared, while achieving high-precision simulation of vegetation reflectance spectrum, the average transmittance of 1500-2500 nm was reduced to 0.095, thereby realizing the simulation of low transmittance of vegetation in this band, solving the problem that high-transmittance film systems cannot be directly used on high-reflectance substrates such as metals.

[0025] 2. It also has mid-infrared high reflectivity stealth performance: The average reflectivity of the film system is 0.7855 and 0.6181 in the two atmospheric windows of 3-5µm and 8-14µm, respectively, which effectively reduces the detectability in the mid-infrared band.

[0026] 3. Excellent hyperspectral simulation performance: In the visible-near infrared band, the reflectance spectrum of the film system is in high agreement with the reference spectrum of green vegetation, and more than 90% of the reflectance channels meet the requirements of standard vegetation spectral characteristics.

[0027] 4. Strong structural feasibility and easy preparation: The all-dielectric membrane system structure of the present invention uses mature thin film materials, has a relatively simple structure, and the number of layers is within an acceptable range, which makes large-scale preparation possible. Attached Figure Description

[0028] Figure 1 This is a diagram showing the distribution of functional layers in the membrane system.

[0029] Figure 2 This is a simulated vegetation layer structure diagram in visible and near-infrared spectroscopy.

[0030] Figure 3 This is a diagram of the mid-infrared high reflectivity layer structure.

[0031] Figure 4 The visible and near-infrared reflectance and transmission spectra of the membrane structure in this embodiment of the invention are shown.

[0032] Figure 5 This is the mid-infrared reflectance spectrum of the membrane structure in an embodiment of the present invention;

[0033] Figure 6 This is a microwave transmission spectrum of the membrane structure in an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] To address the issues of high transmittance in the 1500-2500 nm wavelength band of existing thin films, making them unsuitable for direct use on high-reflectivity substrates, this application introduces functional dielectric materials such as amorphous InSb, achieving the following comprehensive performance: high-precision simulation of vegetation reflectance spectra in the 380-2500 nm band, and simulation of low vegetation transmittance in the 1500-2500 nm band, thus making it suitable for high-reflectivity substrates such as metal armor; high reflectance in the two mid-infrared atmospheric windows of 3-5 μm and 8-14 μm, meeting infrared stealth requirements; and high transmittance in the microwave band, ensuring unaffected communication and detection functions.

[0036] The membrane structure consists of, from top to bottom, a visible and near-infrared simulated vegetation layer, a mid-infrared high-reflectivity layer, and a substrate layer.

[0037] The visible and near-infrared simulated vegetation layer consists of four dielectric layers, whose optical parameters have been optimized to ensure a high degree of match between the film's reflectance spectrum and the typical spectrum of vegetation. The fourth dielectric layer, made of amorphous InSb material, exhibits certain losses in the 380-2500 nm range, giving it low transmission characteristics. This significantly reduces the interference of the underlying mid-infrared high-reflectance layer on the visible and near-infrared spectrum, allowing the two layers to be designed relatively independently.

[0038] The mid-infrared high-reflectivity layer is composed of alternating stacked first and third dielectric layers, with the third dielectric layer being the layer closest to the substrate. Based on the low-loss characteristics of the selected dielectric material in the infrared band, this stacked structure can achieve high reflectivity in the 3-5 μm and 8-14 μm bands, realizing effective thermal infrared stealth.

[0039] All of the above dielectric layers use low-conductivity dielectric materials, and the overall film thickness is much smaller than the microwave wavelength, so there is almost no attenuation of the microwave signal, ensuring the high microwave transmission performance of the film system as a whole.

[0040] Preferably, the first dielectric layer is selected from a material with a refractive index of 2 to 3;

[0041] The second dielectric layer is selected from a material with a refractive index of 1 to 2;

[0042] The third dielectric layer is selected from a material with a refractive index of 3 to 5;

[0043] The fourth dielectric layer is selected from a visible and near-infrared high-loss material with a refractive index of 3 to 5.

[0044] As a further preferred option, the first dielectric layer is ZnS or HfO2;

[0045] The second dielectric layer is YbF3;

[0046] The third dielectric layer is Ge or Si;

[0047] The fourth dielectric layer is either InSb (amorphous) or Ge2Sb2Se4Te1 (crystalline).

[0048] As a further preferred option, the first dielectric layer is ZnS;

[0049] The second dielectric layer is YbF3;

[0050] The third dielectric layer is Ge;

[0051] The fourth dielectric layer is InSb (amorphous).

[0052] Preferably, the thickness of the first dielectric layer is 10~550 nm;

[0053] The thickness of the second dielectric layer is 30~100nm;

[0054] The thickness of the third dielectric layer is 4~600nm;

[0055] The thickness of the fourth dielectric layer is 500~1000nm.

[0056] As a specific preferred embodiment, the all-dielectric film system structure simulating low-transmittance vegetation in the visible and near-infrared, high reflectance in the mid-infrared, and high transmittance in the microwave is ZnS (10 nm) / YbF3 (44 nm) / Ge (4 nm) / ZnS (75 nm) / YbF3 (87 nm) / ZnS (52 nm) / Ge (532 nm) / ZnS (125 nm) / Ge (48 nm) / YbF3 (36 nm) / InSb (995 nm) / Ge (7 nm) / InSb (990 nm) / Ge (518 nm) / ZnS (393 nm) / Ge (30 nm) / ZnS (562 nm) / Ge (590 nm) / ZnS (473 nm) / Ge (220 nm) / ZnS (497 nm) / Ge (271 nm) / ZnS (534 nm) / Ge (516 nm) / ZnS (452 ​​nm) / YbF3 (44 nm) / Ge (4 nm) / ZnS (452 ​​nm) / YbF3 (44 nm) / Ge (4 nm) / ZnS (452 ​​nm) / YbF3 (48 nm) / Ge (4 nm) / ZnS (452 ​​nm) / YbF3 (48 nm) / YbF3 (48 nm) / InSb (995 nm) / Ge (7 nm) / InSb (990 nm) / Ge (518 nm) / ZnS (393 nm) / Ge (30 nm) / ZnS (562 nm) / Ge (590 nm) / ZnS (473 nm) / Ge (220 nm) / ZnS (497 nm) / Ge (271 nm) / ZnS (534 nm) / Ge (516 nm) / ZnS (452 ​​nm) / YbF3 ( nm) / Ge (39 nm) / ZnS (507 nm) / Ge (517 nm) / Si.

[0057] For the visible and near-infrared simulated vegetation layer: This invention utilizes a combination of multiple media and achieves simulation of the characteristic reflectance spectrum of vegetation in the 380-2500 nm band through thin film interference and refractive index gradient matching. Due to the high loss characteristics of amorphous InSb, this layer has extremely low transmittance in the visible and near-infrared band.

[0058] Regarding the infrared high reflectivity portion in the embodiments: This invention utilizes a photonic crystal structure constructed by combining a high refractive index material film layer (third dielectric layer) and a low refractive index material film layer (first dielectric layer). By optimizing the thickness of each layer, high reflectivity is achieved in two atmospheric windows, 3-5µm and 8-14µm, thereby realizing the stealth effect in the mid-infrared band.

[0059] Since all the dielectric layers mentioned above use dielectric materials with low conductivity, and the overall film thickness is much smaller than the microwave wavelength, there is almost no attenuation of the microwave signal, thus ensuring the high microwave transmission performance of the film system as a whole.

[0060] Example:

[0061] like Figure 1 As shown, in one embodiment, a fully dielectric film structure with visible and near-infrared low-transmission simulated vegetation, mid-infrared high reflectivity and microwave high transmittance consists of, from top to bottom: visible and near-infrared simulated vegetation layer 1, mid-infrared high reflectivity layer 2, and substrate layer 3.

[0062] like Figure 2 As shown, in one embodiment, the visible-near-infrared simulated vegetation layer comprises, from top to bottom, a first dielectric layer, a second dielectric layer, a third dielectric layer, and a fourth dielectric layer. The materials of the first, second, third, and fourth dielectric layers are preferably ZnS, YbF3, Ge, and InSb, respectively. The specific thickness of the structure is: ZnS (10 nm) / YbF3 (44 nm) / Ge (4 nm) / ZnS (75 nm) / YbF3 (87 nm) / ZnS (52 nm) / Ge (532 nm) / ZnS (125 nm) / Ge (48 nm) / YbF3 (36 nm) / InSb (995 nm) / Ge (7 nm) / InSb (990 nm), and the total thickness of the structure is 3.005 µm.

[0063] like Figure 3 As shown, in one embodiment, the mid-infrared high reflectivity layer is composed of alternating stacked first and third dielectric layers to satisfy the Bragg reflection condition. The specific thickness of the structure is: Ge (518 nm) / ZnS (393 nm) / Ge (30 nm) / ZnS (562 nm) / Ge (590 nm) / ZnS (473 nm) / Ge (220 nm) / ZnS (497 nm) / Ge (271 nm) / ZnS (534 nm) / Ge (516 nm) / ZnS (452 ​​nm) / Ge (39 nm) / ZnS (507 nm) / Ge (517 nm), and the total thickness of the structure is 6.119 µm.

[0064] The designed membrane structure has a total thickness of 9.124µm, which is negligible compared to microwave wavelengths, and the materials are all low-conductivity dielectrics, thus exhibiting high transmittance in the microwave band.

[0065] The designed all-dielectric film structure, featuring low visible and near-infrared transmission simulating vegetation, high mid-infrared reflectance, and high microwave transmission, was simulated and obtained as follows: Figure 4 The visible-near-infrared reflectance spectrum is shown. (From...) Figure 4It can be seen that the reflectance spectrum of this film structure in the entire visible-near infrared band (380-2500 nm) is highly similar to that of standard vegetation. Simulation calculations show that over 90% of the reflectance meets the reference standard spectral channels for green vegetation, and it has good simulation effects on key characteristics of vegetation in the visible-near infrared band, such as the green peak, red edge, near-infrared plateau, and multiple water absorption peaks. Due to the strong absorption of amorphous InSb in the visible-near infrared region, the all-dielectric film structure exhibits low transmission characteristics throughout the 380-2500 nm range.

[0066] The infrared reflectance spectra of the above all-dielectric film structures are as follows: Figure 5 As shown, by optimizing the thickness of the first and third dielectric layers, the average reflectivity is 0.7855 and 0.6181 in the two atmospheric windows of 3-5µm and 8-14µm, respectively, indicating that the device has low emissivity in the mid-infrared and achieves mid-infrared stealth.

[0067] The microwave transmittance of the above-mentioned all-dielectric film structure is as follows: Figure 6 As shown, within the 5-40GHz range, the device exhibits almost no attenuation of microwave signals, and its transmittance remains consistently above 99.9%, demonstrating excellent microwave transmission capability.

[0068] In this embodiment, by optimizing the thickness combination of ZnS, YbF3, Ge, and InSb layers, the overall film structure not only achieves low-transmittance vegetation simulation in the visible and near-infrared range, but also maintains high reflectivity in the mid-infrared range and high transmittance in the microwave band. This multi-scale, multi-functional synergistic design enables the film to possess excellent visible-near-infrared vegetation simulation performance, making it suitable for ground platforms such as vehicles and buildings that require low visibility-near-infrared detectability against a vegetation background and compatibility with microwave communication.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. The present invention is not limited to the examples described above. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A fully dielectric film structure exhibiting low transmittance in the visible and near-infrared regions to simulate vegetation, high reflectance in the mid-infrared region, and high transmittance in the microwave region, characterized in that... From top to bottom, they include: The visible and near-infrared simulated vegetation layer, composed of the first to fourth dielectric layers, is configured to simulate the reflectance spectral characteristics of vegetation in the 380-2500 nm band and has low transmission characteristics. A mid-infrared high-reflectivity layer, composed of alternating stacked first and third dielectric layers, is configured to generate high reflectivity in the 3-14 μm wavelength band; and Substrate layer; The overall film thickness is much smaller than the microwave wavelength, which allows the film system to maintain high transmittance in the microwave band. The first dielectric layer is ZnS; the second dielectric layer is YbF3; the third dielectric layer is Ge; and the fourth dielectric layer is amorphous InSb. The visible and near-infrared simulated vegetation layer comprises, from top to bottom: a ZnS layer with a thickness of 10 nm, a YbF3 layer with a thickness of 44 nm, a Ge layer with a thickness of 4 nm, a ZnS layer with a thickness of 75 nm, a YbF3 layer with a thickness of 87 nm, a ZnS layer with a thickness of 52 nm, a Ge layer with a thickness of 532 nm, a ZnS layer with a thickness of 125 nm, a Ge layer with a thickness of 48 nm, a YbF3 layer with a thickness of 36 nm, an amorphous InSb layer with a thickness of 995 nm, a Ge layer with a thickness of 7 nm, and an amorphous InSb layer with a thickness of 990 nm.

2. The all-dielectric film system structure according to claim 1, characterized in that, The mid-infrared high reflectivity layer is composed of alternating stacks of a first dielectric layer and a third dielectric layer, with the third dielectric layer being the layer closest to the substrate. From top to bottom, the third dielectric layer comprises: A Ge layer with a thickness of 518 nm, a ZnS layer with a thickness of 393 nm, a Ge layer with a thickness of 30 nm, a ZnS layer with a thickness of 562 nm, a Ge layer with a thickness of 590 nm, a ZnS layer with a thickness of 473 nm, a Ge layer with a thickness of 220 nm, a ZnS layer with a thickness of 497 nm, a Ge layer with a thickness of 271 nm, a ZnS layer with a thickness of 534 nm, a Ge layer with a thickness of 516 nm, a ZnS layer with a thickness of 452 nm, a Ge layer with a thickness of 39 nm, a ZnS layer with a thickness of 507 nm, and a Ge layer with a thickness of 517 nm.

3. The all-dielectric film system structure according to claim 1 or 2, characterized in that, The overall thickness of the membrane system is 8-10 μm.

4. The all-dielectric film stack structure of claim 3, wherein, The reflectance spectrum of the membrane system in the 380-2500 nm band has a consistency of more than 90% with the reflectance spectrum of standard vegetation, and the spectral channels meet the requirements of standard vegetation spectral characteristics. Furthermore, the average transmittance in the 1500-2500 nm band is less than 0.

1.

5. The all-dielectric film stack structure of claim 3, wherein, The average reflectance of the film system is not less than 0.75 in the 3-5 μm band and not less than 0.6 in the 8-14 μm band.

6. The all-dielectric film system structure according to claim 3, characterized in that, The transmittance of the membrane system in the 5-40 GHz microwave band is not less than 99%.

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