Invisible film system structure and color tuning method and device based on femtosecond laser direct writing

Abstract

The invention provides a stealth film system structure and a color tuning method and device based on femtosecond laser direct writing, and the stealth film system structure comprises a substrate, a reflecting layer and a medium matching layer. The reflecting layer is made of metal, and the medium matching layer is made of antimony trisulfide; a Fabry-Perot resonant cavity is formed according to the reflecting layer and the medium matching layer, so that a visible light wave band function is realized; a high-reflection structure is formed according to the reflection layer and the medium matching layer with the low extinction coefficient, and the infrared light band function is achieved. According to the invention, the longitudinal laminated film system and the transverse micro-nano structure are designed and optimized, and the two-layer film structure comprising the antimony trisulfide film and the metal film is adopted, so that the structure is simple, the preparation is easy, and the low radiation of the visible light band for optical stealth color and the medium-wave infrared and long-wave infrared bands is realized.

Description

Technical Field

[0001] The present invention relates to the field of multi-band stealth technology, and in particular to a stealth film structure and a color tuning method and device based on femtosecond laser direct writing. Background Art

[0002] With the continuous development of diversified detection technology and its widespread use on the battlefield, stealth technology has become an important means to ensure the safety of weapons, facilities, and personnel and improve survivability in modern battlefields. Stealth technology refers to the use of various means to hide the characteristics of the target so that the target blends into the background environment, thereby avoiding being discovered by the local detection system or minimizing the possibility of being discovered. According to the detection technology of different bands, stealth technology can be divided into visible light stealth, infrared stealth, radar stealth, etc. Among them, since visible light and infrared bands are the main working bands of the human eye and commonly used detection equipment, visible light stealth and infrared stealth occupy an important position in the research of stealth technology.

[0003] Traditional stealth technology has the problem of single working band and fixed functions, which makes it unable to adapt to the modern battlefield environment. On the one hand, diversified detection equipment based on different working bands and different working principles are generally used in combination, such as cameras in the visible light band that detect natural light reflected by the target, infrared cameras that detect based on the target's own thermal radiation, etc., which makes it difficult for stealth technology with a single working band to play a role; on the other hand, the actual battlefield environment is complex and changeable, such as oceans, forests, deserts, mountains, etc., which makes it difficult for stealth technology with fixed functions to play a role. It can be seen that the existing stealth technology can no longer meet the needs of the current battlefield, and it is urgent to develop a new generation of stealth technology with visible light-infrared compatible dynamic stealth capabilities.

[0004] Visible light-infrared compatible dynamic stealth refers to hiding the characteristics of the target in the visible light, infrared bands and complex and changeable actual environments so that the target blends into the background environment, thereby achieving a stealth effect. Among them, in the visible light band, the detection signal mainly comes from the reflection of natural light. Stealth requires the target surface to have a specific color to match the background environment. The corresponding means include camouflage based on the principle of characteristic reflectivity, transparent materials based on the principle of reducing reflectivity, and highly absorbent materials; in the infrared band, the medium-wave infrared and long-wave infrared bands are two commonly used detection bands as atmospheric windows. The detection signal mainly comes from the target's own thermal radiation. Stealth requires suppressing the target's thermal radiation to match the background environment. The corresponding means include low-emissivity materials based on the principle of reducing emissivity and transformation thermodynamics based on the principle of reducing temperature. It can be seen that the characteristics that need to be hidden by stealth are mainly manifested in spectral characteristics such as reflectivity and emissivity. Therefore, regulating the spectral characteristics of different bands of the target is the key to visible light-infrared compatible dynamic stealth.

[0005] Film structures can be designed to have specific spectral characteristics in different bands, and have become the main way to achieve visible light-infrared compatible stealth. The design mechanisms of film structures are mainly longitudinal laminated film systems and transverse micro-nano structures. The spectral characteristics of longitudinal laminated film systems mainly depend on the overall configuration and material properties. By designing parameters such as material refractive index, film layer combination order, and film layer thickness, optical phenomena such as Fabry-Perot resonance, metal-insulator-metal structure, and photonic crystal can be formed, thereby realizing the reflection, transmission or absorption of electromagnetic waves in different bands; the spectral characteristics of transverse micro-nano structures mainly depend on geometric configurations and characteristic sizes. By designing the period, shape, and size of micro-nano units, optical phenomena such as grating dispersion, chessboard configuration scattering of incident waves, plasmon resonance, and Mie resonance can be formed, thereby realizing the reflection, transmission, or absorption of electromagnetic waves in different bands. However, specific materials and characteristic sizes often correspond to specific optical response bands, which limits the working band of the film structure and thus affects the stealth performance. The existing visible light-infrared stealth technology still has the following limitations when meeting the requirements of multi-band compatible stealth such as visible light, medium-wave infrared, and long-wave infrared: (1) The film system structure has many layers and a complex structure, which leads to low manufacturing efficiency and high cost; (2) Compared with single-band stealth technology, the stealth performance of each working band needs to be improved; (3) It is difficult to achieve dynamic tuning of the color of the visible light band while ensuring that the infrared stealth performance is not affected.

[0006] After the film structure is manufactured, its function is fixed and cannot meet the demand for dynamic tuning of spectral characteristics. It is urgent to develop a dynamically tunable film structure. The introduction of active materials is the main means to achieve dynamic tuning of film structures. Among them, active materials such as semiconductors, liquid crystals, and graphene are volatile and unstable, and require a constant energy supply to maintain the changed state. For non-volatile dynamic tuning, phase change materials can achieve rapid and stable color changes between amorphous and crystalline states because the phase change on the sub-nanosecond time scale causes a significant change in its optical constants. However, most phase change materials, including the widely used Ge2Sb2Te5 (GST), only exhibit a small refractive index change when switching between states, and correspondingly present a small spectral shift of ~35nm in the visible spectrum.

[0007] In summary, there is an urgent need to develop a stealth structure and method that is easy to prepare and has excellent stealth performance in the visible light, mid-wave infrared, and long-wave infrared bands, and at the same time has a wide color tuning range. Summary of the invention

[0008] Based on this, it is necessary to provide a stealth film structure and a color tuning method and device based on femtosecond laser direct writing to address the above technical problems.

[0009] A stealth film structure comprises: a substrate, a reflection layer and a dielectric matching layer; the reflection layer is made of metal, and the dielectric matching layer is made of antimony trisulfide; a Fabry-Perot resonant cavity is formed according to the reflection layer and the dielectric matching layer to realize the visible light band function; a high reflection structure is formed according to the reflection layer and the dielectric matching layer with a low extinction coefficient to realize the infrared light band function.

[0010] In one embodiment, the reflective layer is 100 nm aluminum, and the dielectric matching layer is 80 nm antimony trisulfide.

[0011] A color tuning method based on femtosecond laser direct writing is used to perform color tuning on a stealth film structure as described above, comprising the following steps: obtaining a pattern to be processed of a sample, partitioning the pattern according to the color of the pattern to be processed, and obtaining multiple patterns of processing areas corresponding to multiple colors, wherein the sample is a stealth film structure; adjusting the laser repetition frequency and the laser pulse energy, setting the origin, the direct writing spacing and the scanning speed, processing the sample by femtosecond laser direct writing, obtaining color one and corresponding pattern one, and returning to the origin; adjusting one or two of the laser pulse energy and the scanning speed, keeping the other parameters unchanged, processing the sample by femtosecond laser direct writing, obtaining color two and corresponding pattern two, returning to the origin, and processing multiple times to obtain a multi-order laser-induced surface periodic structure. Color pattern; adjust the wave plate angle, convert the laser from linear polarization to circular polarization, adjust one or two of the laser pulse energy and scanning speed, keep the other parameters unchanged, process the sample by femtosecond laser direct writing, obtain color three and corresponding pattern three, return to the origin, process multiple times, obtain a multi-order color pattern without laser-induced surface periodic structure, and form a nested color pattern with two surface micro-nano structures; adjust one or more of the laser pulse energy, scanning speed, and wave plate angle, keep the other parameters unchanged, tune the color of pattern one by secondary direct writing pattern one, process multiple times, and realize continuous multi-order modulation of the color of pattern one; set the annealing temperature, annealing time, heating and cooling speeds, and ambient atmosphere, and perform continuous multi-order modulation of the sample color by annealing heat treatment.

[0012] In one of the embodiments, the annealing temperature is 300° C., the annealing time is 5-60 min, the heating and cooling rates are 10° C. / min, and the ambient atmosphere is an argon atmosphere.

[0013] In one embodiment, the laser pulse energy is adjusted in a range of 6-65 nJ, and the scanning speed is adjusted in a range of 0.1-2 mm / s.

[0014] In one of the embodiments, the wave plate is a quarter wave plate, which is not used when the laser-induced surface periodic structure is generated, and is set to 45° when the laser-induced surface periodic structure is not generated.

[0015] A color tuning device based on femtosecond laser direct writing is used to use the color tuning method based on femtosecond laser direct writing as described above to perform color tuning on the stealth film system structure as described above, comprising: a femtosecond laser, an optical shutter, a first reflector group, an aperture group, an attenuation plate, a wave plate group, a second reflector group, a beam splitter, a dichroic mirror, a focusing objective lens, a three-dimensional mobile platform, an illumination light source and an imaging CCD; the wave plate group comprises a half wave plate and a quarter wave plate for adjusting a polarization mode; the attenuation plate is used to adjust laser energy; the femtosecond laser emits a light beam, which passes through the optical shutter, the first reflector group, the aperture group, the attenuation plate, the wave plate group, the second reflector group, the dichroic mirror and the focusing objective lens in sequence, and the light beam is focused onto a sample surface; the sample is fixed on the three-dimensional mobile platform, the illumination light source passes through the beam splitter and the dichroic mirror, is reflected by the beam splitter and is incident on the imaging CCD, and the sample is a stealth film system structure.

[0016] In one embodiment, the focusing objective lens is a 10x objective lens with a numerical aperture of 0.30, the central wavelength of the femtosecond laser is 1030 nm, the pulse width is 290 fs, and the repetition frequency is 1000 Hz.

[0017] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: a visible light-infrared compatible stealth film system structure comprises a substrate, a reflective layer and a dielectric matching layer, the material of the reflective layer is metal, the material of the dielectric matching layer is antimony trisulfide, a Fabry-Perot resonant cavity is formed based on the reflective layer and the dielectric matching layer, and the color of the visible light band for optical stealth is realized, a high reflective structure is formed based on the reflective layer and the dielectric matching layer with a low extinction coefficient, and low radiation in the medium-wave infrared and long-wave infrared bands is realized, thereby realizing visible light-medium-wave infrared-long-wave infrared compatible stealth; by designing and optimizing the longitudinal stacked film system and the transverse micro-nano structure, a two-layer film structure of antimony trisulfide and metal two-layer films is adopted, the structure is simple and easy to prepare, and the color of the visible light band for optical stealth and low radiation in the medium-wave infrared and long-wave infrared bands are realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a stealth film structure and a color tuning method based on femtosecond laser direct writing in one embodiment.

[0019] Figure 2 The figure is a flow chart of a color tuning method based on femtosecond laser direct writing in one embodiment.

[0020] Figure 3 Schematic diagram of the structure of a color tuning device based on femtosecond laser direct writing in one embodiment.

[0021] Figure 4The coordinates of the visible light color presented by the stealth film structure under different laser parameter processing and modulation in the CIE1931 chromaticity diagram in an embodiment, and the infrared absorption spectrum under different laser energy processing.

[0022] Figure 5 This is an experimental verification diagram of color pattern processing and modulation in one embodiment.

[0023] Figure 6 This is an experimental verification diagram of visible light-infrared compatible stealth in an embodiment. DETAILED DESCRIPTION

[0024] Before describing the specific embodiments of the present invention, the overall concept of the present invention is described as follows:

[0025] The present invention is mainly developed based on the visible light-infrared compatible stealth process. At present, the film system structure has many layers and complex structure, resulting in low manufacturing efficiency and high cost, and the multi-band stealth performance is low. It is difficult to achieve dynamic tuning of the color in the visible light band while ensuring that the infrared stealth performance is not affected.

[0026] Therefore, the present invention proposes a stealth film system structure, including a substrate, a reflective layer and a dielectric matching layer. The material of the reflective layer is metal, and the material of the dielectric matching layer is antimony trisulfide. A Fabry-Perot resonant cavity is formed based on the reflective layer and the dielectric matching layer, and the color of the visible light band for optical stealth is realized. A high-reflection structure is formed based on the reflective layer and the dielectric matching layer with a low extinction coefficient, and low radiation in the medium-wave infrared and long-wave infrared bands is realized, thereby realizing visible light-medium-wave infrared-long-wave infrared compatible stealth. By designing and optimizing the longitudinal stacked film system and the transverse micro-nano structure, a two-layer film structure of antimony trisulfide and metal two-layer films is adopted, which has a simple structure and is easy to prepare, and the color of the visible light band for optical stealth and low radiation in the medium-wave infrared and long-wave infrared bands are realized.

[0027] After introducing the overall concept of the present invention, in order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail by specific implementation methods in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] In one embodiment, Figure 1 As shown, a stealth film structure is provided, including: a substrate, a reflective layer and a dielectric matching layer; the material of the reflective layer is metal, and the material of the dielectric matching layer is antimony trisulfide; the Fabry-Perot resonant cavity composed of the reflective layer and the dielectric matching layer realizes the visible light band function, and the high reflection structure composed of the reflective layer and the dielectric matching layer with a low extinction coefficient realizes the infrared light band function.

[0029] In this embodiment, the visible light-infrared compatible stealth film system structure includes a substrate, a reflective layer and a dielectric matching layer. The material of the reflective layer is metal, and the material of the dielectric matching layer is antimony trisulfide. A Fabry-Perot resonant cavity is formed based on the reflective layer and the dielectric matching layer, and the color of the visible light band for optical stealth is realized. The high reflection structure is formed based on the reflective layer and the dielectric matching layer with a low extinction coefficient, and the low radiation in the medium-wave infrared and long-wave infrared bands is realized, thereby realizing the visible light-medium-wave infrared-long-wave infrared compatible stealth. By designing and optimizing the longitudinal stacked film system and the transverse micro-nano structure, a two-layer film structure of antimony trisulfide and metal two-layer film is adopted, which has a simple structure and is easy to prepare, and the color of the visible light band for optical stealth and the low radiation in the medium-wave infrared and long-wave infrared bands are realized.

[0030] Specifically, this embodiment uses antimony trisulfide as a wide bandgap phase change material, which has the characteristics of low absorption, high refractive index and refractive index change of up to 1 in the visible spectrum, and is an ideal choice for dynamic color tuning. The dynamic tuning of Sb2S3 can be achieved through a variety of excitation methods such as femtosecond laser, thermal annealing, and electric pulses. Among them, based on the unique advantages of ultrafast and ultra-strong, ultrafast lasers can achieve faster color switching, with high tuning accuracy and good flexibility. Based on the precise control of micro-nano structures and material properties, while controlling the phase change of Sb2S3, inducing the physical morphology changes of the micro-nano structures on the surface of Sb2S3, it is possible to introduce richer electromagnetic responses, thereby significantly broadening the color tuning range.

[0031] Specifically, this embodiment combines the longitudinal stacked film system and the transverse micro-nano structure to design the film system structure, breaking through the limitations of material properties and characteristic dimensions, making the design more flexible and facilitating the realization of visible light-infrared compatible stealth.

[0032] In one embodiment, the reflective layer material may be one of metals such as aluminum, gold, and silver, and the dielectric matching layer material may be antimony trisulfide phase change material.

[0033] The reflective layer is 100nm aluminum and the dielectric matching layer is 80nm antimony trisulfide.

[0034] In one embodiment, the visible light-infrared compatible stealth film structure meets the following requirements: it has a characteristic reflectivity in the 380-780nm band, and a color tuning range of 106.7% sRGB; it has an emissivity of less than 0.05 in the 3-5μm band; and it has an emissivity of less than 0.05 in the 8-14μm band.

[0035] In one embodiment, Figure 1 and 2 As shown, a color tuning method based on femtosecond laser direct writing is provided, which is used to perform color tuning on a stealth film structure as described above, comprising the following steps:

[0036] Step S101, obtaining a pattern to be processed of a sample, partitioning the pattern according to the color of the pattern to be processed, and obtaining multiple patterns of processing areas corresponding to multiple colors, wherein the sample is a stealth film structure.

[0037] Specifically, a sample is fixed on a processing device. The sample is a stealth film structure. The pattern to be processed corresponding to the sample is obtained. The pattern is partitioned according to the color of the pattern to be processed. The pattern is divided into multiple areas to obtain multiple patterns of processing areas corresponding to multiple colors. Different parameters need to be set for the processing of different color areas to facilitate partitioned processing.

[0038] Step S102, adjust the laser repetition frequency and laser pulse energy, set the origin, direct writing spacing and scanning speed, process the sample by femtosecond laser direct writing, obtain color one and corresponding pattern one, and return to the origin.

[0039] Specifically, a femtosecond laser direct writing processing system is used to adjust the laser repetition frequency and laser pulse energy, set the origin, set the direct writing spacing and scanning speed, and process the sample by femtosecond laser direct writing to obtain color one and pattern one consisting of the corresponding processing area, and then return to the origin.

[0040] Step S103, adjust one or both of the laser pulse energy and the scanning speed, keep the other parameters unchanged, process the sample by femtosecond laser direct writing, obtain color two and corresponding pattern two, return to the origin, and process multiple times to obtain a multi-order color pattern with a laser-induced surface periodic structure.

[0041] Specifically, one or two of the laser pulse energy and the scanning speed are adjusted, and the other parameters (such as direct spacing and scanning speed) are kept unchanged. The sample is processed by femtosecond laser direct writing to obtain color two and pattern two consisting of the corresponding processing area, and then the sample returns to the origin. After multiple processing with similar steps, a multi-order color pattern with a laser-induced surface periodic structure is obtained.

[0042] Step S104, adjust the wave plate angle, convert the laser from linear polarization to circular polarization, adjust one or two of the laser pulse energy and scanning speed, keep the other parameters unchanged, process the sample by femtosecond laser direct writing, obtain color three and corresponding pattern three, return to the origin, and process multiple times to obtain a multi-order color pattern without laser-induced surface periodic structure, forming a nested color pattern with two surface micro-nano structures.

[0043] Specifically, a quarter wave plate is used as the wave plate, the angle of the quarter wave plate is adjusted, the femtosecond laser is converted from linear polarization to circular polarization, one or two of the laser pulse energy and the scanning speed are adjusted, and the other parameters (such as laser repetition frequency, direct writing spacing) are kept unchanged. The sample is processed by femtosecond laser direct writing to obtain color three and pattern three consisting of the corresponding processing area, and then the sample returns to the origin. After multiple processing with similar steps, a multi-order color pattern without laser-induced surface periodic structure is obtained, and finally a nested color pattern with two surface micro-nano structures is obtained.

[0044] Step S105, adjust one or more of the laser pulse energy, scanning speed, and wave plate angle, keep the other parameters unchanged, perform color tuning of pattern one by direct writing pattern one twice, and perform multiple processing to achieve continuous multi-order modulation of the color of pattern one.

[0045] Specifically, one or more of the laser pulse energy, scanning speed, and quarter-wave plate angle are adjusted, while the other parameters (such as laser repetition frequency and direct writing spacing) are kept unchanged. The purpose of pattern-color tuning is achieved through secondary direct writing of pattern-one. After multiple processings of similar steps, continuous multi-order modulation of pattern-color is achieved. Similarly, continuous multi-order modulation of the sample color is achieved.

[0046] The adjustment range of the laser pulse energy is 6-65nJ, and the adjustment range of the scanning speed is 0.1-2mm / s.

[0047] Among them, the wave plate is a quarter wave plate, which is not used when the laser-induced surface periodic structure is generated, and is set to 45° when the laser-induced surface periodic structure is not generated.

[0048] Specifically, the laser pulse energy range for color patterning processing and modulation is: 6-65nJ, the scanning speed range is 0.1-2mm / s, and different processing parameters within this range correspond to specific colors; the angle of the quarter-wave plate used is selected as: 45° when no laser-induced surface periodic structure is generated, and not used when a laser-induced surface periodic structure is generated.

[0049] Step S106, setting the annealing temperature, annealing time, heating and cooling speeds and ambient atmosphere, and performing continuous multi-level modulation of the sample color through annealing heat treatment.

[0050] Specifically, a tubular furnace is used, and the annealing temperature, annealing time, heating and cooling rates, and environmental atmosphere are set, and continuous multi-stage modulation of the sample color is achieved through annealing heat treatment.

[0051] The annealing temperature is 300°C, the annealing time is 5-60min, the heating and cooling rates are 10°C / min, and the ambient atmosphere is argon atmosphere.

[0052] Specifically, the annealing temperature for phase change and even color modulation of antimony trisulfide is 300° C., the annealing time is 5-60 min, the heating and cooling rates are 10° C. / min, and the ambient atmosphere is an argon atmosphere.

[0053] In this embodiment, by obtaining the pattern to be processed of the stealth film structure sample, the pattern is partitioned according to the color of the pattern to be processed, and multiple patterns of processing areas corresponding to multiple colors are obtained. By adjusting the laser repetition frequency and the laser pulse energy, the origin, the direct writing spacing and the scanning speed are set, and the sample is processed by femtosecond laser direct writing to obtain color one and the corresponding pattern one, and then return to the origin; by adjusting at least one of the laser pulse energy and the scanning speed, color two and pattern two are processed, and then return to the origin, and the processing is repeated to obtain a multi-order color pattern with a laser-induced surface periodic structure; the wave plate angle is adjusted, and the laser is deflected from the line to the surface. The laser pulse energy and scanning speed are adjusted to convert the laser pulse energy into circular polarization, and at least one of the laser pulse energy and scanning speed is adjusted to process the color three and pattern three, return to the origin, and process multiple times to obtain a multi-order color pattern without laser-induced surface periodic structure, and obtain a nested color pattern with two surface micro-nano structures; adjust one or more of the laser pulse energy, scanning speed, and wave plate angle, and directly write pattern one for the second time to tune the color of pattern one, and process multiple times to achieve continuous multi-order modulation of the color of pattern one; after the direct writing is completed, set the annealing temperature, annealing time, heating and cooling speed, and environmental atmosphere, and perform continuous multi-order modulation of the sample color through annealing heat treatment. In the above steps, the film is accurately removed by femtosecond lasers with different energy and scanning speed parameters to achieve rich colors, and the film is processed with two surface micro-nano structures by femtosecond lasers with different polarization parameters to achieve natural light and strong light observation modes and further expand the color tuning range. The film is continuously modulated by femtosecond lasers with different parameters and thermal annealing to achieve multi-order tuning of the color, and the infrared stealth performance is not affected during the color tuning process.

[0054] In one embodiment, the above steps S102-S105 can be configured accordingly according to the sample pattern, such as adjusting the order of the steps, deleting or adding the steps, etc., so as to process different sample patterns.

[0055] like Figure 3As shown, a color tuning device based on femtosecond laser direct writing is provided, which is used to use the color tuning method based on femtosecond laser direct writing as described above to perform color tuning on the above-mentioned stealth film structure, including: a femtosecond laser 1, an optical shutter 2, a first reflector group, an aperture group, an attenuation plate 8, a wave plate group, a second reflector group, a beam splitter 18, a dichroic mirror 13, a focusing objective lens 14, a three-dimensional moving platform 16, an illumination light source 17 and an imaging CCD 19; the wave plate group includes a half wave plate 9 and a four-wave plate The one-fifth wave plate 10 is used to adjust the polarization mode; the attenuation plate 8 is used to adjust the laser energy; the femtosecond laser 1 emits a light beam, which passes through the optical shutter 2, the first reflector group, the aperture group, the attenuation plate 8, the wave plate group, the second reflector group, the dichroic mirror 13 and the focusing objective lens 14 in sequence, and the light beam is focused onto the sample surface; the sample is fixed on the three-dimensional moving platform 16, and the illumination light source 17 passes through the beam splitter 18 and the dichroic mirror 13, and is reflected by the beam splitter 18 to be incident on the imaging CCD 19, and the sample is a stealth film structure.

[0056] In this embodiment, a femtosecond laser 1 generates a laser pulse, which passes through an optical shutter 2, a reflector 3, a reflector 4 and a reflector 5 in a first reflector group, an aperture 6 and an aperture 7 in an aperture group, an attenuation plate 8, a half wave plate 9 and a quarter wave plate 10 in a wave plate group, and a reflector 11 and a reflector 12 in a second reflector group in sequence, and then is reflected by a dichroic mirror 13 and focused by a focusing lens 14 to a surface of a processed sample 15. The processed sample 15 is a stealth film structure, and the processed sample 15 is fixed on a three-dimensional moving platform 16. At the same time, an illumination light source 17 passes through a beam splitter 1 8. The dichroic mirror 13 is reflected by the beam splitter 18 and incident into the imaging CCD 19. The thin film of the processed sample 15 is precisely removed by setting femtosecond lasers with different energy and scanning speed parameters to achieve rich color tuning. The processed sample 15 is processed with two surface micro-nano structures by using femtosecond lasers with different polarization parameters to achieve natural light and strong light observation modes and further expand the color tuning range. The thin film is continuously modulated in multiple stages by using femtosecond lasers with different parameters and thermal annealing to achieve multi-stage color tuning and ensure that the infrared stealth performance is not affected during the color tuning process.

[0057] Specifically, the femtosecond laser 1, the optical shutter, the first reflector group, the aperture group, the attenuation plate 8, the wave plate group, the second reflector group, the dichroic mirror 13 and the focusing objective lens 14 are optically connected, and the illumination light source 17, the beam splitter 18, the dichroic mirror 13 and the imaging CCD 19 are optically connected.

[0058] Specifically, the above-mentioned device uses femtosecond laser direct writing to accurately remove the thickness of the antimony trisulfide film to manufacture a multi-order Fabry-Perot cavity, producing a wide range of colors, and introduces a grating dispersion response through a laser-induced surface periodic structure. After manufacturing is completed, the antimony trisulfide medium matching layer can still be controlled by femtosecond laser direct writing and thermal annealing to achieve multi-order color modulation.

[0059] In one embodiment, the focusing objective lens is a 10-matrix objective lens with a numerical aperture of 0.30, the central wavelength of the femtosecond laser is 1030 nm, the pulse width is 290 fs, and the repetition frequency is 1000 Hz.

[0060] In one embodiment, Figure 4 As shown, the coordinates of the visible light colors presented under different laser parameter processing and modulation in the CIE1931 chromaticity diagram, as well as the infrared absorption spectra under different laser energy processing, are shown. The multi-order Fabry-Perot resonant cavity is manufactured by precisely removing the Sb2S3 film with a femtosecond laser, achieving a wide range of color tuning of 71.4% sRGB. The color tuning range is further expanded to 106.7% sRGB by introducing a grating dispersion response through a laser-induced surface periodic structure. Based on the low infrared absorption characteristics of antimony trisulfide and aluminum, the device has a low emissivity of less than 0.05 in the 3-5μm and 8-14μm bands, and laser processing basically does not affect the infrared performance.

[0061] like Figure 5 As shown in the figure, it is an experimental verification of color patterning and modulation. By adjusting one or more of the laser energy, scanning speed, and quarter-wave plate angle, a "cartoon dragon" color pattern is manufactured. Among them, the "Year of the Dragon Good Luck" text part is manufactured by a linearly polarized femtosecond laser, which has a laser-induced periodic surface structure, and the other parts are manufactured by a circularly polarized femtosecond laser. By adjusting the laser parameters to manufacture antimony trisulfide films of different thicknesses, various colors, including blue, purple, red, orange, etc., are manufactured at different positions of the "cartoon dragon". By matching the colors manufactured by the two polarization modes, the text part is hidden in the circularly polarized manufacturing area with similar colors around. Therefore, the text part is visible as a diffraction image only at a specific observation angle. Next, the antimony trisulfide film is further removed on the manufactured "cartoon dragon" pattern using a femtosecond laser, so that the color of each position changes, such as from purple to red. Finally, the antimony trisulfide film is transformed from an amorphous state to a crystalline state by thermal annealing, and the color of each position changes greatly, such as from red to blue.

[0062] like Figure 6As shown in the figure, it is an experimental verification of the visible light-infrared compatible stealth simulation structure. A 2×2cm camouflage pattern is manufactured using different laser parameters. The camouflage pattern consists of four colors and is suitable for marine environments. After manufacturing, active color tuning can be performed according to environmental changes, such as from the ocean (blue), mountain (gray) to the desert (khaki); an 8-14μm infrared camera is used to capture infrared images of the camouflage pattern and the black layer in the temperature range of 30-250℃. The camouflage pattern and the black layer are heated by a heating table, and the camouflage pattern is almost unrecognizable at a temperature of up to 250℃. In addition, since the phase transition temperature of antimony trisulfide is 270℃, the color of the camouflage pattern will not be affected during the heating process. In contrast, the black layer is completely exposed in the detection of the infrared camera. Obviously, the stealth model structure of the present invention has excellent stealth performance, and can achieve dynamic tuning of the color in the visible light band while ensuring that the infrared stealth performance is not affected.

[0063] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0064] Obviously, those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a computer storage medium (ROM / RAM, magnetic disk, optical disk) and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than that here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Therefore, the present invention is not limited to any specific combination of hardware and software.

[0065] The above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A stealth film structure, characterized in that: include: Substrate, reflective layer and dielectric matching layer; The material of the reflective layer is metal, and the material of the dielectric matching layer is antimony trisulfide; A Fabry-Perot resonant cavity is formed according to the reflection layer and the dielectric matching layer to realize the visible light band function; The reflective layer and the medium matching layer with a low extinction coefficient form a high reflective structure to achieve infrared light band function.

2. The stealth film structure according to claim 1, characterized in that: The reflective layer is 100 nm aluminum, and the dielectric matching layer is 80 nm antimony trisulfide.

3. A color tuning method based on femtosecond laser direct writing, characterized in that: The method is used to perform color tuning on a stealth film structure according to any one of claims 1 to 2, comprising the following steps: Obtaining a pattern to be processed of a sample, partitioning the pattern according to the color of the pattern to be processed, and obtaining a plurality of patterns corresponding to processing areas with a plurality of colors, wherein the sample is a stealth film structure; Adjust the laser repetition frequency and laser pulse energy, set the origin, direct writing spacing and scanning speed, process the sample by femtosecond laser direct writing, obtain color one and corresponding pattern one, and return to the origin; Adjust one or two of the laser pulse energy and the scanning speed, keep the other parameters unchanged, process the sample by femtosecond laser direct writing, obtain color 2 and corresponding pattern 2, return to the origin, and process multiple times to obtain a multi-order color pattern with a laser-induced surface periodic structure; Adjust the wave plate angle, convert the laser from linear polarization to circular polarization, adjust one or two of the laser pulse energy and scanning speed, keep the other parameters unchanged, process the sample by femtosecond laser direct writing, obtain color three and corresponding pattern three, return to the origin, and process multiple times to obtain a multi-order color pattern without laser-induced surface periodic structure, forming a nested color pattern with two surface micro-nano structures; Adjust one or more of the laser pulse energy, scanning speed, and wave plate angle, keep the other parameters unchanged, perform color tuning of pattern one by direct writing pattern one twice, perform multiple processing, and realize continuous multi-order modulation of the color of pattern one; The annealing temperature, annealing time, heating and cooling speeds and environmental atmosphere are set, and the sample color is modulated in multiple stages continuously through annealing heat treatment.

4. The color tuning method based on femtosecond laser direct writing according to claim 3 is characterized in that: The annealing temperature is 300° C., the annealing time is 5-60 min, the heating and cooling speeds are 10° C. / min, and the ambient atmosphere is an argon atmosphere.

5. The color tuning method based on femtosecond laser direct writing according to claim 3, characterized in that: The adjustment range of the laser pulse energy is 6-65nJ, and the adjustment range of the scanning speed is 0.1-2mm / s.

6. The color tuning method based on femtosecond laser direct writing according to claim 3, characterized in that: The wave plate is a quarter wave plate, which is not used when the laser-induced surface periodic structure is generated, and is set to 45° when the laser-induced surface periodic structure is not generated.

7. A color tuning device based on femtosecond laser direct writing, characterized in that: The method is used to perform color tuning on a stealth film structure according to any one of claims 1 to 2 by using a color tuning method based on femtosecond laser direct writing according to any one of claims 3 to 6, comprising: Femtosecond laser, optical shutter, first reflector group, aperture group, attenuation plate, wave plate group, second reflector group, beam splitter, dichroic mirror, focusing objective lens, three-dimensional moving platform, illumination light source and imaging CCD; The wave plate set includes a half wave plate and a quarter wave plate, which are used to adjust the polarization mode; The attenuation sheet is used to adjust the laser energy; The femtosecond laser emits a light beam, which sequentially passes through the optical shutter, the first reflector group, the aperture group, the attenuation plate, the wave plate group, the second reflector group, the dichroic mirror and the focusing objective lens, and the light beam is focused onto the sample surface; The sample is fixed on the three-dimensional moving platform, and the illumination light source passes through the beam splitter and the dichroic mirror, is reflected by the beam splitter and incident into the imaging CCD, and the sample is a stealth film structure.

8. The color tuning device based on femtosecond laser direct writing according to claim 7, characterized in that: The focusing objective lens is a 10-fold objective lens with a numerical aperture of 0.30, the central wavelength of the femtosecond laser is 1030 nm, the pulse width is 290 fs, and the repetition frequency is 1000 Hz.

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