An infrared transparent window with diffuse reflection and reciprocity protection transmission

Abstract

The application relates to an infrared transparent window with diffuse reflection and reciprocal protection transmission, and relates to an infrared transparent window. The application aims at solving the problem that the symmetric characteristics of existing reflection and transmission hinder further improvement of infrared stealth. The infrared transparent window with diffuse reflection and reciprocal protection transmission is composed of 2 or more than 2 different structural units arranged in N columns and M rows in a non-periodic mode; the different structural units are sequentially composed of a lower substrate, a phase adjusting film layer and an upper substrate from bottom to top; the distance from the center of the phase adjusting film layer of the different structural units to the upper surface of the upper substrate is k, and the k of the different structural units are all different. The application is used for the infrared transparent window with diffuse reflection and reciprocal protection transmission.

Description

Technical Field

[0001] This invention relates to an infrared transparent window. Background Technology

[0002] Infrared transparent windows are special optical windows that allow infrared light to pass through, and they have important applications in infrared detectors, infrared imaging, infrared camouflage, and defense equipment. To achieve infrared camouflage, the outer surface of an infrared transparent window is often coated with an infrared transparent conductive film, achieving high infrared reflectivity and low emissivity. However, this method reflects infrared light in a specific direction, meaning that infrared reflection is stronger in certain directions, causing infrared stealth to fail at specific angles.

[0003] Scattering infrared light is another effective strategy for camouflaging infrared detection. For example, the scattering of infrared light by a rough surface causes the reflected infrared light to propagate in all directions, effectively reducing the energy received by the infrared detector in a specific direction. However, light passing through a rough surface is also scattered. This means that when a similar rough surface is applied to an infrared-transparent window, the infrared sensor image inside the window becomes blurred, similar to the effect of looking through frosted glass. Therefore, diffuse reflection mechanisms are difficult to apply to infrared-transparent windows, hindering the improvement of their camouflage characteristics.

[0004] It can be seen that traditional flat glass achieves clear imaging while reflecting and transmitting simultaneously, while frosted glass achieves diffuse reflection while reflecting and transmitting simultaneously. However, the symmetrical characteristics of reflection and transmission hinder further improvement of infrared stealth. Summary of the Invention

[0005] This invention aims to address the problem that the symmetrical characteristics of existing reflection and transmission hinder further improvement of infrared stealth, and proposes an infrared transparent window with diffuse reflection and reciprocal protection transmission.

[0006] An infrared transparent window with diffuse reflection and reciprocal protection transmission is provided. The infrared transparent window with diffuse reflection and reciprocal protection transmission is composed of two or more different structural units arranged non-periodically in N columns × M rows, where N≥5 and M≥5. The different structural units are arranged from bottom to top as a lower substrate, a phase adjustment film layer and an upper substrate. Let k be the distance from the center of the phase adjustment film layer of different structural units to the upper surface of the upper substrate. Then k = 0μm to 2μm, and k is different for different structural units.

[0007] The beneficial effects of this invention are:

[0008] Traditional flat glass can achieve clear imaging through both reflection and transmission, while frosted glass can achieve diffuse reflection through both reflection and transmission. However, the symmetrical nature of reflection and transmission hinders further infrared stealth. This invention proposes an infrared transparent window based on reciprocal protected transmission, achieving both diffuse reflection and clear imaging transmission, and remaining effective even under large-angle incident conditions. This design further enhances the stealth performance of the infrared window. Furthermore, due to the use of phase change materials, this design can achieve a transition from a diffuse reflection state to a clear imaging state, further expanding its application scenarios.

[0009] This invention relates to an infrared transparent window with diffuse reflection and reciprocal protection transmission. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structural unit in Embodiment 1, where k is the distance from the center of the phase adjustment film layer to the upper surface of the upper substrate;

[0011] Figure 2 The depth of the crystalline GST film of the four structural units in Example 1, and the changes in the reflection and transmission phases caused by different depths when infrared light with wavelengths of 5μm and 10μm is incident perpendicularly. A is the first structural unit, B is the second structural unit, C is the third structural unit, and D is the fourth structural unit.

[0012] Figure 3 This is a schematic diagram showing the number and position of the first, second, third, and fourth structural units after the optimal coding sequence is determined in Example 1. A represents the first structural unit, B represents the second structural unit, C represents the third structural unit, and D represents the fourth structural unit.

[0013] Figure 4 In Example 1, when the GST film in the infrared transparent window with diffuse reflection and reciprocity protection transmission is in a crystalline state, the scattering field distribution of infrared light with wavelengths of 5μm and 10μm along the plane wave normal and obliquely incident is shown.

[0014] Figure 5 The depth of the amorphous GST film of the four structural units in Example 1, and the changes in the reflection and transmission phases caused by different depths when infrared light with wavelengths of 5μm and 10μm is incident perpendicularly. A is the first structural unit, B is the second structural unit, C is the third structural unit, and D is the fourth structural unit.

[0015] Figure 6 In Example 1, when the GST film in the infrared transparent window with diffuse reflection and reciprocal protection transmission is in an amorphous state, the scattering field distribution of infrared light with wavelengths of 5μm and 10μm along the plane wave normal and obliquely incident is shown. Detailed Implementation

[0016] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0017] Specific Implementation Method 1: This implementation method provides an infrared transparent window with diffuse reflection and reciprocal protection transmission. The infrared transparent window with diffuse reflection and reciprocal protection transmission is composed of two or more different structural units arranged non-periodically in N columns × M rows, where N≥5 and M≥5. The different structural units are arranged from bottom to top as a lower substrate, a phase adjustment film layer, and an upper substrate. Let k be the distance from the center of the phase adjustment film layer of different structural units to the upper surface of the upper substrate. Then k = 0μm~2μm, and k is different for different structural units.

[0018] According to matrix theory, the complex reflection coefficient and complex transmission coefficient of a structure can be obtained, thereby yielding the amplitude and phase. For multilayer structural materials and interfaces, the wave transmission matrix M can be used. N The total matrix M represents... total It can be obtained by multiplying the wave transmission matrices. Therefore, for a typical multilayer material I, its total wave transmission matrix is ​​M. + =M N… M2M1, while for the inverted structure II of multilayer material I, its total wave transmission matrix M - =M 1… M N-1 M N .

[0019]

[0020]

[0021] Among them, A + B + C + D + For a matrix element of multi-layer structure I, A - B - C - D - These are the matrix elements of the flipped structure II. These matrix elements are determined by the material's refractive index, thickness, and arrangement. Since the wave transmission matrices in both the interface and the medium are symmetric matrices, we have M... N＝ M N T Where T represents the transpose of the matrix. Also, according to the arithmetic law (AB)... T =B T A T M can be further derived. + With M - The relationship between them:

[0022] M + =MN ...M2M1=M N T ...M2 T M1 T =(M1...M N-1 M N-1 ) T =M - T (3)

[0023] Furthermore, the reflection and transmission coefficients of the structures are obtained through the total wave transmission matrix M of the two structures. For the multilayer structure material I and its inverted structure II, their forward transmission coefficients can be expressed as:

[0024]

[0025] The forward reflection coefficients of the two structures can be expressed as:

[0026]

[0027]

[0028] Therefore, the transmission amplitude and phase of the multilayer structure material I and its flip structure II are kept consistent due to reciprocity protection, but the reflection amplitude and phase will differ because they are not reciprocally protected.

[0029] Based on this principle, this embodiment designs a structure that achieves infrared camouflage using diffuse reflection infrared waves while simultaneously providing clear infrared imaging. Furthermore, the influence of the depth of phase-adjusting films in different phase states within a ZnO substrate on the reflection and transmission phases was simulated.

[0030] The beneficial effects of this embodiment are:

[0031] Traditional flat glass can achieve clear imaging through both reflection and transmission, while frosted glass can achieve diffuse reflection through both reflection and transmission. However, the symmetrical nature of reflection and transmission hinders further infrared stealth. This embodiment proposes an infrared transparent window based on reciprocal protected transmission, achieving both diffuse reflection and clear imaging transmission, and remaining effective even under large-angle incident conditions. This design further enhances the stealth performance of the infrared window. Furthermore, due to the use of phase change materials, this design can achieve a transition from a diffuse reflection state to a clear imaging state, further expanding its application scenarios.

[0032] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that all structural units are square. Everything else is the same as in Specific Implementation Method One.

[0033] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the side lengths of the different structural units are all between 1 μm and 50 μm. Everything else is the same as in Specific Implementation Method One or Two.

[0034] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the materials of both the lower and upper substrates are ZnS, Al2O3, Y2O3, ZrO2, MgF2, or spinel. Everything else is the same as in Specific Implementation Methods One to Three.

[0035] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the phase adjustment film is made of GST, VO2, ITO, Ag, silver nanowires, or graphene. Everything else is the same as in Specific Implementation Methods One to Four.

[0036] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the total thickness of the lower substrate, phase adjustment film layer, and upper substrate is 1 μm to 3 cm. Everything else is the same as in Specific Implementation Methods One to Five.

[0037] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the thickness of the phase adjustment film layer is 0.01 μm to 3 μm. Everything else is the same as in Specific Implementation Methods One to Six.

[0038] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the number and position of the different structural units are determined by an optimal coding sequence. Everything else is the same as Specific Implementation Methods One to Seven.

[0039] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that it uses four different structural units arranged non-periodically in 14 columns × 14 rows, with the k values ​​of the four different structural units being 0.68 μm, 1.24 μm, 1.58 μm, and 1.95 μm, respectively. Everything else is the same as Specific Implementation Methods One through Eight.

[0040] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the material of both the lower and upper substrates is ZnS; and the material of the phase adjustment film layer is GST. Everything else is the same as in Specific Implementation Methods One to Nine.

[0041] The beneficial effects of the present invention are verified using the following embodiments:

[0042] Example 1, combined with Figure 1 Detailed explanation:

[0043] An infrared transparent window with diffuse reflection and reciprocal protection transmission is disclosed. The window is composed of four different structural units arranged aperiodically in 14 columns × 14 rows. The four different structural units are a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit. The first structural unit, the second structural unit, the third structural unit, and the fourth structural unit are, from bottom to top, a lower substrate, a GST film layer, and an upper substrate. Let the distances from the center of the GST film layer of the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit to the upper surface of the upper substrate be k1, k1, k3, and k4, respectively. Then k1 = 0.68 μm, k1 = 1.24 μm, k3 = 1.58 μm, and k4 = 1.95 μm.

[0044] The first, second, third, and fourth structural units are all squares with a side length of 3 μm.

[0045] Both the lower and upper substrates are made of ZnS.

[0046] The total thickness of the lower substrate, GST film layer and upper substrate is 2 μm.

[0047] The thickness of the GST film is 0.1 μm.

[0048] The number and position of the first, second, third, and fourth structural units are determined by the optimal coding sequence.

[0049] The GST film is divided into GST-a (amorphous state) and GST-a (amorphous state).

[0050] The calculations in Example 1 involved determining the reflection and transmission phases of mid- and far-infrared waves at different depths for the GST film layer, which was GST-c (crystalline). Figure 2 As shown, Figure 2The figure shows the depth of the crystalline GST film in the four structural units of Example 1, and the changes in reflection and transmission phases caused by different depths when infrared light with wavelengths of 5 μm and 10 μm is incident perpendicularly. A represents the first structural unit, B the second structural unit, C the third structural unit, and D the fourth structural unit. As shown in the figure, when the depth of the GST-c film changes, the reflection phase changes drastically, while the transmission phase changes little. With the same total thickness and GST film thickness, the different k values ​​in the four structural units correspond to the multilayer structure material I and its flipped structure II (after flipping, the distance from the center of the film to the upper surface of the substrate changes). Therefore, consistent with previous theoretical analysis, the transmission of the multilayer structure material I and its flipped structure II is reciprocally protected, but the reflection amplitude and phase will differ due to the lack of reciprocal protection. Furthermore, in the mid-infrared and long-infrared bands with wavelengths of 5 μm and 10 μm, the reflection phases of the four designed structures differ by approximately 90 degrees, thus satisfying the modulation requirements of the reflected light direction. The transmission phase changes of the four structures are small, thus ensuring clear transmission imaging.

[0051] In this embodiment, the number and position of the first, second, third, and fourth structural units are determined through an optimal coding sequence. The arrangement of the 14×14 structural unit matrix is ​​optimized. By employing an optimization algorithm, the ratio of the maximum to the average value of the upper half-space scattered field is minimized, thereby introducing a diffuse reflection mechanism. Figure 3 As shown, Figure 3 This is a schematic diagram showing the number and position of the first, second, third, and fourth structural units after the optimal coding sequence is determined in Example 1. A represents the first structural unit, B represents the second structural unit, C represents the third structural unit, and D represents the fourth structural unit.

[0052] Figure 4 In Example 1, when the GST film in the infrared transparent window with diffuse reflection and reciprocity protected transmission is in a crystalline state, the scattering field distribution of infrared light with wavelengths of 5 μm and 10 μm along the plane wave normal and at an oblique incidence is shown. The upper part of the structure in the figure shows the reflection pattern, and the lower part shows the transmission pattern. Observing the far-field distribution reveals that the incident infrared light is effectively scattered in all directions, thereby reducing the power in each direction and avoiding infrared detection. Furthermore, this effect remains unchanged even with an oblique 45-degree incidence.

[0053] The calculations in Example 1 involved determining the reflection and transmission phases of mid- and far-infrared waves at different depths for the GST film layer, which was GST-a (amorphous state). Figure 5 As shown, Figure 5The diagram illustrates the depth of the amorphous GST film in the four structural units of Example 1, and the changes in reflection and transmission phases caused by different depths when infrared light with wavelengths of 5 μm and 10 μm is incident perpendicularly. Unit A is the first structural unit, unit B is the second structural unit, unit C is the third structural unit, and unit D is the fourth structural unit. When the GST is converted to the amorphous state, i.e., the GST-a state, the structure will exhibit a planar glassy state, meaning that both reflection and transmission can produce clear images. Figure 5 As shown, the reflection phase of the four elements does not change much under incident conditions of 5μm and 10μm, which facilitates clear imaging of the combined array.

[0054] Figure 6 This diagram illustrates the scattering field distribution of 5μm and 10μm infrared light along the plane wave normal and oblique incidence in the infrared transparent window of Example 1, where the GST film is in an amorphous state. The upper part of the diagram shows the reflection pattern, and the lower part shows the transmission pattern. Under normal and oblique incidence conditions, the structure exhibits a main lobe in only specific directions during reflection and transmission, ensuring the clarity of both reflection and transmission imaging. Side lobes are only present when a 10μm electromagnetic wave is incident at a 45-degree angle. Overall, the structure demonstrates good angular stability.

Claims

1. An infrared transparent window with diffuse reflection and reciprocal protection transmission, characterized in that... The infrared transparent window with diffuse reflection and reciprocity protection transmission is composed of two or more different structural units arranged non-periodically in N columns × M rows, where N≥5 and M≥5; and the different structural units are arranged from bottom to top as a lower substrate, a phase adjustment film layer and an upper substrate. Let k be the distance from the center of the phase adjustment film layer of different structural units to the upper surface of the upper substrate, then k=0μm~2μm, and k is different for different structural units. The materials of the lower and upper substrates are ZnS, Al2O3, Y2O3, ZrO2, MgF2 or spinel; The phase adjustment film is made of GST.

2. The infrared transparent window with diffuse reflection and reciprocal protection transmission according to claim 1, characterized in that... All of the different structural units are square.

3. The infrared transparent window with diffuse reflection and reciprocal protection transmission according to claim 2, characterized in that... The side lengths of the different structural units are all between 1 μm and 50 μm.

4. The infrared transparent window with diffuse reflection and reciprocal protection transmission according to claim 1, characterized in that... The total thickness of the lower substrate, phase adjustment film layer and upper substrate is 1μm~3cm.

5. An infrared transparent window with diffuse reflection and reciprocal protection transmission according to claim 1, characterized in that... The thickness of the phase adjustment film is 0.01μm~3μm.

6. An infrared transparent window with diffuse reflection and reciprocal protection transmission according to claim 1, characterized in that... The number and position of the different structural units are determined by the optimal coding sequence.

7. An infrared transparent window with diffuse reflection and reciprocal protection transmission according to claim 1, characterized in that... Four different structural units are arranged aperiodically in 14 columns × 14 rows. The k values ​​of the four different structural units are 0.68 μm, 1.24 μm, 1.58 μm and 1.95 μm, respectively.

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