Fractal geometry-based visible light band asymmetric transmittance control material and design method thereof

Abstract

The application provides a fractal geometry-based asymmetric transmittance control material in a visible light band and a design method thereof, and belongs to the technical field of optical functional materials, fractal geometry and visible light camouflage material design. The asymmetric transmittance control material is composed of periodic arrangement of three-dimensional unit cell structures in a plane, the unit cell structure is a three-dimensional fractal structure, is layered according to the similarity between structure heights, the transmittance of the innermost layer and the outermost layer of the unit cell structure is different in the visible light band, and the transmittance difference corresponds to the positive and negative transmittance difference of a camouflage target, and the transmittance of each layer of the unit cell structure is determined by an optical transmission impedance equation. The asymmetric transmittance control material can adapt to complex environmental light intensity distribution through parameterized design, and solves the limitation of symmetric transmission of traditional homogeneous materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical functional materials, fractal geometry and visible light camouflage materials, and particularly relates to a design method of a visible light band asymmetric transmittance regulation material based on fractal geometry, which is suitable for visible light camouflage scenes of ground facilities and mobile objects. BACKGROUND

[0002] The core of the visible light camouflage technology is to match the light reflection / transmission characteristics of the target and the background. Traditional camouflage materials (such as coating pigments and homogeneous optical films) are difficult to realize asymmetric transmittance regulation in a wide frequency visible light range due to the lack of multi-scale structure design. When the ambient light is incident from different angles, the transmittance distribution of the homogeneous material presents symmetry, and cannot simulate the asymmetric characteristics of the light field in the natural scene (such as the light intensity attenuation gradient of the leaf gap and the scattering non-uniformity of the rock surface). The fractal geometry theory provides a new idea for solving the multi-scale regulation problem of the light field. The self-similarity characteristic of the fractal geometry can make the structure present consistent optical response law at different scales, thereby realizing the asymmetric modulation of the wide frequency light field. Existing researches show that the geometric complexity (represented by the fractal dimension) of the fractal structure is related to the light scattering loss, but there is no fractal optical structure design system for visible light camouflage. On the one hand, there is no quantitative correlation model between the fractal geometry parameters (fractal dimension, duty cycle, etc.) and the optical performance parameters (refractive index, extinction coefficient); on the other hand, there is no transmission theory considering the interaction between the fractal structure and the light field, which makes it difficult to guide the engineering design of asymmetric transmittance regulation.

[0003] Therefore, it is urgent to develop a design method of optical regulation material based on fractal geometry to realize the precise control of the asymmetric transmittance in the visible light band. SUMMARY

[0004] In order to overcome the deficiencies in the prior art, the present application provides a visible light band asymmetric transmittance regulation material based on fractal geometry and a design method thereof, a unit cell structure with self-similar multi-scale characteristics is constructed to realize the asymmetric transmittance regulation in the 400-760nm visible light band, and the limitation of the symmetric transmission of the traditional homogeneous optical material in the complex ambient light field is solved, thereby providing a precise light field regulation scheme for the camouflage of photoelectric equipment.

[0005] The technical scheme provided by the present application is as follows:

[0006] In a first aspect, there is a visible light band asymmetric transmittance control material based on fractal geometry. The asymmetric transmittance control material is composed of a periodic arrangement of three-dimensional unit cell structures in a plane. The unit cell structure is a three-dimensional structure, layered according to structural similarity in the height direction. The innermost and outermost layers of the unit cell structure have different transmittance in the visible light band, and the transmittance difference corresponds to the forward and reverse transmittance difference of the camouflage target. The transmittance of each layer of the unit cell structure is determined by the optical transmission impedance equation.

[0007] Secondly, a design method for materials with asymmetric transmittance modulation in the visible light band based on fractal geometry includes:

[0008] An initial geometric configuration for an asymmetric transmittance modulating material is constructed, wherein the asymmetric transmittance modulating material is composed of a periodic arrangement of three-dimensional unit cell structures in a plane.

[0009] The unit cell structure is layered according to the structural similarity in the height direction, and a parameterized model of the unit cell structure is constructed based on the fractal dimension and layer structure parameters of the unit cell structure.

[0010] Based on the parameterized model of the unit cell structure, the optical transmission impedance equation of the unit cell structure is constructed to determine the transmittance of the innermost and outermost layers in the visible light band. The difference in transmittance between the innermost and outermost layers is used as the transmittance asymmetry in this band.

[0011] The configuration and parameterized model of the unit cell structure are optimized until the transmittance asymmetry of the unit cell structure in multiple visible light bands meets the control requirements, thus obtaining the optimized control material.

[0012] The third aspect involves a design device for asymmetric transmittance modulation materials in the visible light band based on fractal geometry, comprising:

[0013] One or more processors;

[0014] Storage device for storing one or more programs.

[0015] When the one or more programs are executed by the one or more processors, the one or more processors implement the design method for asymmetric transmittance modulated materials in the visible light band based on fractal geometry as described in the second aspect.

[0016] Fourthly, a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the design method for asymmetric transmittance modulated materials in the visible light band based on fractal geometry as described in the second aspect.

[0017] Fifthly, a computer program product comprising: a computer program (also referred to as code or instructions) that, when run, executes the design method for asymmetric transmittance control materials in the visible light band based on fractal geometry as described in the second aspect.

[0018] The present invention provides a material and design method for controlling asymmetric transmittance in the visible light band based on fractal geometry, which has the following advantages:

[0019] (1) This invention provides a material for controlling the asymmetric transmittance of visible light band based on fractal geometry and its design method. It proposes a fractal structure light transmission model based on Fresnel diffraction theory, introduces an optical resonance effect factor related to fractal dimension and duty cycle to correct the interface optical impedance gradient, and solves the matching loss problem of multi-band optical fields.

[0020] (2) This invention provides a material and its design method for asymmetric transmittance control in the visible light band based on fractal geometry. It establishes a mapping relationship between fractal geometric characteristics and optical transmission performance. By quantitatively controlling the multi-scale light field dissipation capability of the structure through fractal dimension, the material achieves transmittance asymmetry in the 400-760nm frequency band, covering the main visible light bands. For example, when the fractal dimension... D At a value of 2.96, the control material composed of a four-layer honeycomb single-cell structure can achieve a forward transmittance of 72% and a backward transmittance of 44% for 550nm green light, effectively simulating the asymmetry of light scattering in leaves.

[0021] (3) This invention provides a fractal geometry-based material for controlling asymmetric transmittance in the visible light band and its design method. It constructs a fractal material design process suitable for visible light camouflage, starting from ambient light spectrum analysis and forming a closed-loop design system of "configuration screening - parameter optimization - performance verification". The fractal optical material designed through this process can have its fractal structure parameters customized according to the light intensity distribution of the target scene (such as the spectral characteristics of deserts and jungles), ensuring the spectral matching accuracy of visible light camouflage. Attached Figure Description

[0022] Figure 1 A control material structure for honeycomb-configured single-cell structures;

[0023] Figure 2 It has a honeycomb-like single-cell structure;

[0024] Figure 3 This is a flowchart of the design method for asymmetric transmittance control materials in the visible light band based on fractal geometry, as described in this invention. Detailed Implementation

[0025] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0026] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0027] This invention provides an asymmetric transmittance control material for the visible light band based on fractal geometry, suitable for visible light camouflage scenarios of ground facilities and moving objects. The asymmetric transmittance control material is composed of a periodic arrangement of three-dimensional unit cell structures in a plane. These unit cell structures are three-dimensional structures, including but not limited to honeycomb configurations, stepped pyramidal configurations, or stacked wood configurations. Figure 1 The structure of the material that regulates the formation of the honeycomb-configured unit cell structure is presented. Figure 2 A honeycomb-shaped unit cell structure is given; layered according to structural similarity at different heights, the innermost and outermost layers of the unit cell structure have different transmittances in the visible light band (400~760nm), and the transmittance difference corresponds to the forward and reverse transmittance difference of the camouflage target. The transmittance of each layer of the unit cell structure is determined by the optical transmission impedance equation, which is:

[0028]

[0029] in, T ( k ) is the first k Layer transmittance, T ( k -1) is the first k -1 layer transmittance, G ( k ) is the first k Layer impedance gradient correction coefficient, T 0( k ) is the first k intrinsic transmittance of the layer β ( k ) is the first k Layer light attenuation coefficient, d ( k ) is the first k Layer upon layer, thick. T (0) is used as the input for the first iteration of the optical transmission impedance equation, and its value is 1.

[0030] No. k Layer impedance gradient correction factor G ( k )=1+ g ( k ), of which the optical resonance effect factor g ( k )=p ( k )·( D - D 0) n ; p ( k ) is the first k Layer duty cycle; D The fractal dimension of a unit cell structure; D 0 is the baseline fractal dimension, with values ​​ranging from 2.5 to 3; n The correction index ranges from 1 to 1.5.

[0031] fractal dimension of unit cell structure D The box dimension method of fractal geometry is used for calculation. The specific method is as follows: for a volume of V The single-cell structure uses a radius r The cubic mesh covers the three-dimensional configuration of the unit cell structure, and the number of meshes containing the unit cell structure is counted. N ( r ), using the least squares method to apply ln N ( r ) and ln(1 / r A linear fit is performed, and the absolute value of the slope of the line is the fractal dimension. D .

[0032] No. k Layer light attenuation coefficient , j It is a complex number. Lambda The incident light wavelength, n ( k ) is the first k The equivalent refractive index of the layer, c ( k ) is the first k The extinction coefficient of the layer, where , , n s The refractive index of the matrix material. n p It is the refractive index at the pores (or the equivalent refractive index of the matrix-free region). c s denoted as the extinction coefficient of the matrix material.

[0033] See Figure 3 The present invention also provides a design method for asymmetric transmittance modulating materials in the visible light band based on fractal geometry, comprising the following steps:

[0034] Step 1: Construct the initial geometric configuration of the asymmetric transmittance control material. The asymmetric transmittance control material is composed of a periodic arrangement of three-dimensional unit cell structures in a plane. Determine the fractal dimension of the unit cell structure under the initial geometric configuration.

[0035] Step 2: Layer the unit cell structure according to the structural similarity between heights, and construct a parameterized model of the unit cell structure based on the fractal dimension and layer structure parameters of the unit cell structure.

[0036] like Figure 2 As shown, based on the similarity between structural heights, the unit cell structure is divided into four layers.

[0037] The layer structure parameters of a unit cell include the number of layers. l Duty cycle of each floor p and the thickness of each layer d fractal dimension is selected D Number of floors l Duty cycle of each floor p Each layer thickness d The configuration of a single cell can be uniquely determined by using it as a core parameter.

[0038] Step 3: Construct the optical transmission impedance equation of the unit cell structure based on the parameterized model of the unit cell structure, determine the transmittance of the innermost and outermost layers in the visible light band, and use the difference in transmittance between the innermost and outermost layers as the transmittance asymmetry in this band.

[0039] The optical transmission impedance equation is:

[0040]

[0041] in, T ( k ) is the first k Layer transmittance, k =1,2,3,…, l , T ( k -1) is the first k -1 layer transmittance, G ( k ) is the first k Layer impedance gradient correction coefficient, T 0( k ) is the first k intrinsic transmittance of the layer β ( k ) is the first k Layer light attenuation coefficient, d ( k ) is the first k The thickness varies from layer to layer. The parameter determination method is the same as above, and will not be repeated here.

[0042] Transmittance asymmetry = T ( l )- T (1), where T ( lThe outermost layer transmittance is ). T (1) is the transmittance of the innermost layer.

[0043] Step 4: Optimize the configuration and parameterization model of the unit cell structure until the transmittance asymmetry of the unit cell structure in the visible light multi-band (400~760nm) meets the control requirements, and obtain the optimized control material.

[0044] The inventors have discovered that the higher the fractal dimension, the higher the geometric complexity of the unit cell structure and the better the asymmetry effect. In order to achieve rapid optimization of the unit cell structure and enable the material to achieve a transmittance asymmetry of ≥20% in the 400~760nm frequency band, the fractal dimension is preferably adjusted in the range of 2.5~3.0.

[0045] Furthermore, after optimizing the configuration and parameterized model of the unit cell structure using the above iterative method and completing the measurement of transmittance asymmetry, the asymmetric control effect is verified by simulation. If the simulation results determine that the transmittance asymmetry of the unit cell structure in the visible light multi-frequency band also meets the requirements, the optimization ends; otherwise, the iterative optimization steps continue until the data measurement results and simulation results simultaneously meet the requirements.

[0046] The following example illustrates the design process of asymmetric transmittance control materials in the visible light band based on fractal geometry.

[0047] Example 1

[0048] 1. Constructing the initial geometric configuration of the control material

[0049] The fractal dimension of a unit cell structure was calculated using the box-counting dimension method: For a polymethyl methacrylate (PMMA) based four-layer honeycomb structure, the fractal dimension was calculated using the side length... r A 3D configuration is covered by cubic meshes with dimensions of 5μm, 1μm, and 0.1μm. The number of meshes containing the structure is counted. N ( r ).by r Taking 5μm as an example, the measured N (5) = 12800, r =1μm N (1) = 1256000, by calculating ln N ( r ) and ln(1 / r The slope of the linear fit is used to obtain the fractal dimension. D =2.96. This fractal dimension characterizes the geometric complexity of the structure at the submicron scale and directly affects the scattering and dissipation efficiency of the light field.

[0050] 2. Establish a parameterized model of the unit cell structure.

[0051] fractal dimensionD =2.96 as the core, select duty cycle p (0.1-0.8) and layer thickness d (5-50 μm) were used as optimized parameters to fabricate fractal unit cell structure samples via micro / nano 3D printing. For example, a four-layer fractal unit cell structure was designed for camouflage in jungle environments: surface layer... p =0.3、 d =10μm, intermediate layer p =0.5、 d =15μm, transition layer p =0.7、 d =20μm, substrate bonding layer p =0.8、 d =15μm. This parameter combination can achieve a smooth transition of optical field impedance through the variation of the pore gradient of the fractal structure, thereby enhancing the asymmetric transmission effect.

[0052] 3. Calculate the transmittance asymmetry of visible light across multiple frequency bands.

[0053] Based on Fresnel diffraction theory, the first k Layer transmittance T ( k The calculation of the optical impedance needs to consider the optical impedance correction effect of the unit cell structure. Specifically, the optical impedance gradient correction coefficient... G ( k )=1+ p ( k )·( D -2.5) 1.2 This reflects the scattering loss of the light field due to fractal geometry. Equivalent refractive index. n ( k ) = 1.49·(1- p ( k ))+1.0· p ( k Extinction coefficient Substitute into the formula for optical attenuation coefficient This allows for the calculation of transmittance distribution at different wavelengths. For 550nm green light, the calculated values ​​are... T (1) = 72%, T (4) = 44%. The optical impedance gradient matching makes the forward transmittance 28% higher than the backward transmittance, which meets the asymmetric requirements of light scattering in the jungle environment.

[0054] Example 2: Visible Light Camouflage Application Case

[0055] Taking the visible light camouflage of a certain type of armored vehicle as an example, the target scene is a temperate jungle, and the main spectral peaks of the ambient light are 550nm (green light) and 650nm (red light). The fractal optical modulation material is designed according to the following process:

[0056] Spectrum analysis: The target wavelength band of 450-700nm was determined, with a focus on controlling the intensity distribution at 550nm and 650nm.

[0057] Configuration screening: Select D A stepped cone fractal structure with a fractal dimension of 2.85, whose multi-scale cone-shaped pores can match the wavelength characteristics of green and red light; with fractal dimension... D Number of floors l Duty cycle of each floor p and the thickness of each layer d Characterize the unit cell structure.

[0058] Parameter optimization: Optimized using a genetic algorithm. p =[0.25,0.65], d =A two-layer structure with [20μm, 18μm].

[0059] Performance simulation: The calculated forward transmittance at 550nm is 62%, the backward transmittance is 38%, and the transmittance asymmetry is 24%; the forward transmittance at 650nm is 58%, the backward transmittance is 32%, and the transmittance asymmetry is 26%.

[0060] Example 3: The Influence of Fractal Dimension on Light Transmission Asymmetry

[0061] Design three fractal unit cell structures: honeycomb type ( D =2.96), stepped cone type ( D =2.99), woodpile type ( D =2.88), all using PMMA matrix, honeycomb duty cycle p =[0.6388,0.2775,0.2203,0.1630], Stepped cone duty cycle p =[1,0.6400,0.4440,0.2840], Woodpile type duty cycle p =[0.7730,0.5230,0.1670,0.1800], with a single-layer thickness of 20 μm for each configuration. Simulation results show:

[0062] Stepped pyramidal structure ( D =2.99) has a forward transmittance of 68% and a backward transmittance of 34% at 550nm, with an asymmetry of 34%; honeycomb structure ( D =2.96) has a transmittance asymmetry of 30% in the same wavelength band; woodpile structure ( D =2.88) The transmittance asymmetry is 22% in the same band.

[0063] Data shows that when the fractal dimension DWhen the fractal dimension was increased from 2.88 to 2.99, the asymmetry of 550nm light increased from 22% to 34%, an increase of 55%. The higher the fractal dimension, the higher the geometric complexity of the structure, and the better the asymmetric control effect of visible light.

[0064] This invention also provides a design device for asymmetric transmittance modulation materials in the visible light band based on fractal geometry, comprising:

[0065] One or more processors;

[0066] Storage device for storing one or more programs.

[0067] When the one or more programs are executed by the one or more processors, the one or more processors implement the design method for asymmetric transmittance modulated materials in the visible light band based on fractal geometry described above.

[0068] The present invention also provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described design method for asymmetric transmittance modulated materials in the visible light band based on fractal geometry.

[0069] The readable storage media include, but are not limited to, USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0070] This invention also provides a computer program product, comprising: a computer program (also referred to as code or instructions), which, when run, executes the aforementioned design method for asymmetric transmittance control materials in the visible light band based on fractal geometry. The computer program product can pre-store unit cell structures of various typical configurations; by selecting a pre-stored unit cell structure, the initial geometric configuration of the asymmetric transmittance control material can be rapidly constructed.

[0071] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, microwave, etc.) means.

[0072] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0073] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and modules described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0074] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0075] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A material for controlling asymmetric transmittance in the visible light band based on fractal geometry, characterized in that, The asymmetric transmittance control material is composed of a periodic arrangement of three-dimensional unit cell structures in a plane. The unit cell structure is a three-dimensional structure, layered according to the structural similarity in the height direction. The innermost and outermost layers of the unit cell structure have different transmittance in the visible light band, and the transmittance difference corresponds to the forward and reverse transmittance difference of the camouflage target. The transmittance of each layer of the unit cell structure is determined by the optical transmission impedance equation. The optical transmission impedance equation is as follows: in, T ( k ) is the first k Layer transmittance, T ( k -1) is the first k -1 layer transmittance, G ( k ) is the first k Layer impedance gradient correction coefficient, T 0( k ) is the first k intrinsic transmittance of the layer β ( k ) is the first k Layer light attenuation coefficient, d ( k ) is the first k Layer upon layer, thick.

2. The visible light band asymmetric transmittance modulation material based on fractal geometry according to claim 1, characterized in that, The first k Layer impedance gradient correction factor G ( k )for: G ( k )=1+ g ( k ) in, g ( k ) is the optical resonance effect factor. g ( k )= p ( k )·( D - D 0) n ; p ( k ) is the first k Layer duty cycle; D The fractal dimension of a unit cell structure; D 0 is the baseline fractal dimension, with values ​​ranging from 2.5 to 3; n The correction index ranges from 1 to 1.

5.

3. The visible light band asymmetric transmittance modulation material based on fractal geometry according to claim 2, characterized in that, The first k Layer light attenuation coefficient β ( k )for: in, j It is a complex number. λ The incident light wavelength, n ( k ) is the first k The equivalent refractive index of the layer, c ( k ) is the first k The extinction coefficient of the layer, where , , n s The refractive index of the matrix material. n p The refractive index at the pores, c s The extinction coefficient of the matrix material.

4. A design method for a fractal geometry-based visible light band asymmetric transmittance control material as described in any one of claims 1 to 3, characterized in that, include: An initial geometric configuration for an asymmetric transmittance modulating material is constructed, wherein the asymmetric transmittance modulating material is composed of a periodic arrangement of three-dimensional unit cell structures in a plane. The unit cell structure is layered according to the structural similarity in the height direction, and a parameterized model of the unit cell structure is constructed based on the fractal dimension and layer structure parameters of the unit cell structure. Based on the parameterized model of the unit cell structure, the optical transmission impedance equation of the unit cell structure is constructed to determine the transmittance of the innermost and outermost layers in the visible light band. The difference in transmittance between the innermost and outermost layers is used as the transmittance asymmetry in this band. The configuration and parameterized model of the unit cell structure are optimized until the transmittance asymmetry of the unit cell structure in multiple visible light bands meets the control requirements, thus obtaining the optimized control material.

5. The design method for asymmetric transmittance control materials in the visible light band based on fractal geometry according to claim 4, characterized in that, The layer structure parameters of the unit cell structure include the number of layers, the duty cycle of each layer, and the thickness of each layer. The parameterized model of the unit cell structure is constructed using the fractal dimension, the number of layers, the duty cycle of each layer, and the thickness of each layer.

6. The design method for asymmetric transmittance control materials in the visible light band based on fractal geometry according to claim 4, characterized in that, When optimizing the configuration and parameterization model of the unit cell structure, the fractal dimension is adjusted within the range of 2.5 to 3.

0.

7. The design method for asymmetric transmittance control materials in the visible light band based on fractal geometry according to claim 4, characterized in that, The effect of asymmetric modulation is verified by simulation. If the simulation results show that the asymmetry of the transmittance of the unit cell structure in the visible light multi-band also meets the requirements, the optimization ends. Otherwise, the iterative optimization steps continue until the data measurement results and simulation results meet the requirements at the same time.

8. A design device for materials with asymmetric transmittance modulation in the visible light band based on fractal geometry, characterized in that, include: One or more processors; Storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the design method for visible light band asymmetric transmittance modulated materials based on fractal geometry as described in any one of claims 4 to 7.

9. A computer program product, characterized in that, The computer program product includes: a computer program that, when run, executes the design method for asymmetric transmittance control materials in the visible light band based on fractal geometry as described in any one of claims 4 to 7.

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