An ultrafast laser manufacturing method of electromagnetic shielding and infrared antireflection curved surface window

Abstract

The application provides an ultrafast laser manufacturing method of a curved electromagnetic shielding and infrared antireflection window, comprising the following steps: S1, ultrasonic cleaning, drying, and spraying protective glue on the curved window, and then fixing the curved window by using a self-centering clamp; S2, beam shaping into a Bessel beam and focusing, and coaxially arranging the curved window and the laser focal point; S3, focusing the laser focal point on the surface of the curved window, uniformly sampling according to the distance to the central axis, fitting a curved window contour model, and planning a scanning path; S4, machining infrared antireflection microstructures on the lower surface of the curved window according to Archimedes equidistant spirals; S5, machining a mesh groove on the upper surface of the curved window according to cross-arch scanning, and then performing vacuum coating, cleaning, and degumming to obtain the curved electromagnetic shielding and infrared antireflection composite function window. The method can realize high-quality, high-efficiency, and high-reliability manufacturing of the curved electromagnetic shielding and infrared antireflection composite function window, and meets the electromagnetic shielding and infrared detection requirements in the fields of aviation and aerospace.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of infrared window processing and application, and particularly relates to an ultrafast laser manufacturing method of an electromagnetic shielding and infrared antireflection curved window. BACKGROUND

[0002] In the modern war scenario, infrared detection technology has become one of the most critical detection means due to its high resolution, high sensitivity and high information update rate. Nowadays, with the wide application of electromagnetic interference and infrared stealth technology, the infrared window must have high infrared transmittance and microwave electromagnetic shielding performance. However, the conventional infrared window has many problems. Due to Fresnel reflection loss, the surface of the infrared window will weaken the transmission of the infrared signal, and generally lacks electromagnetic shielding capability. This results in that the interference electromagnetic waves from the outside, especially the electromagnetic waves generated by microwave weapons, can easily enter the inside of the detection system, causing serious interference to electronic instruments and communication systems. Such interference not only has an adverse effect on the extraction and processing of infrared signals, but also may cause the infrared imaging device to fail or be damaged, greatly reducing the safety and reliability of the entire system. At the same time, considering the demand for reducing wind resistance under actual working conditions, the infrared window is usually designed in the form of a curved dome. Therefore, the development of an electromagnetic shielding and infrared antireflection curved window with excellent optical / electrical performance and high physical stability is of great significance to enhance the anti-interference ability of infrared detection weapon equipment and improve its battlefield survivability.

[0003] Traditional micro-nano processing technologies, such as 3D printing, nano-imprinting and photolithography, face great challenges in the high-quality, high-efficiency and high-reliability manufacturing of microstructures on the surface of curved windows, especially when electromagnetic shielding, infrared antireflection and reliability need to be ensured at the same time. The 3D printing technology is limited by printing accuracy and is difficult to print metal mesh with a micron-level width. Although the metal mesh with a wider width can meet the shielding performance, it will sacrifice the infrared transmittance of the window. In addition, the metal mesh printed by 3D printing is not embedded on the surface of the window, resulting in that it does not have wear resistance. The nano-imprinting technology faces challenges when processing hard and brittle window materials, and the mechanical properties of the microstructure after processing are significantly reduced. The photolithography technology is limited by the mask, different mask is needed for different size of window, and it cannot meet the large-area processing demand of microstructure on the curved window.

[0004] In order to solve the problem that high-performance manufacturing of electromagnetic shielding and infrared anti-reflection curved window cannot be realized in the prior art, the method realizes high-quality and high-efficiency manufacturing of the functional microstructure on the surface of the curved window by using ultrafast laser beam shaping technology and multi-axis linkage machining technology. By accurately controlling the shape and size of the light beam, high-precision and high-quality machining of the microstructure can be realized. The multi-axis linkage machining technology ensures accurate positioning and motion trajectory during the machining process, thereby realizing large-area machining of the microstructure of the curved window. At the same time, the infrared anti-reflection microstructure on the window substrate and the metal mesh embedded in the groove also ensure the service stability of the curved window in extremely complex environments (such as high temperature, high pressure, wind and sand, etc.), and ensure its long-term reliable performance. SUMMARY

[0005] In view of the above problems, the present application provides an ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved window, which aims to realize high-quality, high-efficiency and high-reliability manufacturing of electromagnetic shielding and infrared anti-reflection curved window.

[0006] The object of the present application is achieved by the following technical solutions:

[0007] An ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved window uses an ultrafast laser manufacturing device for electromagnetic shielding and infrared anti-reflection curved window, characterized in that the device comprises:

[0008] A control system that can simultaneously control the ultrafast laser and the high-precision motion platform;

[0009] An ultrafast laser that can output a Gaussian light beam with a pulse wavelength of 1030 nm and a pulse width range of 100 fs to 10 ps;

[0010] A beam expansion module comprising a concave lens of-50 to-100 mm and a convex lens of 100 to 400 mm, for expanding the Gaussian light beam to adjust the spot diameter;

[0011] A beam reflection module comprising a first mirror, a second mirror, a third mirror and a fourth mirror, wherein the first mirror and the second mirror have a reflectivity of more than 99% for 1030 nm laser, the third mirror is a dichroic mirror with a reflectivity of more than 98% for 1030 nm laser and a transmittance of more than 90% for white light, and the fourth mirror is a half mirror with a reflectivity and transmittance of 50% for white light;

[0012] A light beam spatial shaping module, which comprises a conical lens with a cone top angle of 175-178° and a 4F focusing system composed of a 50-200 mm convex lens and a 20-50 times objective, can shape and focus the light beam into a Bessel beam with concentrated energy and longer focal depth;

[0013] A high-precision motion platform, which comprises a linear motion X-axis, a linear motion Y-axis, a linear motion Z-axis, a rotary motion A-axis and a marble base;

[0014] A self-centering clamp, which is coaxially fixed to the rotary motion A-axis with the curved window, ensures accurate positioning and stable clamping of the curved window during processing;

[0015] A coaxial observation system, which comprises a CCD camera and a white light source, is used for observation and auxiliary positioning during processing;

[0016] The ultrafast laser manufacturing method of the electromagnetic shielding and infrared antireflection curved window comprises the following steps:

[0017] S1, ultrasonic cleaning and drying the curved window to be processed, spraying a protective glue with a thickness of 1-5 μm on the upper surface of the curved window, and using a self-centering clamp to coaxially fix the curved window with the rotary motion axis A;

[0018] S2, using a light beam expansion module, a light beam reflection module and a light beam spatial shaping module to expand, shape and focus the Gaussian beam output by the ultrafast laser into a Bessel beam focus with more concentrated energy and longer focal depth, and controlling the linear motion X-axis and the linear motion Y-axis to move, so that the rotary motion A-axis, the curved window and the laser focus are coaxial;

[0019] S3, by driving the second mirror, the third mirror, the fourth mirror, the light beam spatial shaping module and the coaxial observation system to move synchronously through the linear motion Z-axis, thereby driving the laser focus to move; under the assistance of the coaxial observation system, the linear motion Y-axis uniformly selects m sampling points n i at the distance from the center axis of the curved window, controls the laser focus to be in focus with the sample surface at each sampling point n i , records the coordinates of the sampling points, and then fits the profile of the curved window according to a polynomial to calculate the three-dimensional spatial coordinates of the curved window;

[0020] S4, moving the linear motion Z-axis to focus the laser focus on the center axis of the lower surface of the curved window, and through the linkage of the rotary motion A-axis with the linear motion X-axis and the linear motion Z-axis, controlling the focus to be always focused on the lower surface of the curved window and moving according to the Archimedean equidistant spiral from inside to outside, to process the periodic infrared antireflection microstructure;

[0021] S5, the moving linear motion Z axis focuses the laser focal point on the upper surface of the curved window, through the linkage of the linear motion X axis, the linear motion Y axis and the linear motion Z axis, the focal point is always focused on the upper surface of the curved window, and moves in the form of cross-arched scanning, and a periodic grid groove is processed; then, the processed curved window is taken out, a vacuum coating process is used to coat metal in the grid groove of the curved window, the coated curved window is placed in a degumming solvent for cleaning, the metal grid is retained after the protective glue is removed, and finally an electromagnetic shielding and infrared anti-reflection curved window is obtained.

[0022] Further, the curved window is zinc sulfide, zinc selenide, sapphire, magnesium fluoride or barium fluoride.

[0023] Further, the curved window is a small curvature circular window, the window aperture is 20-200mm, and the window thickness is 1-3mm.

[0024] Further, the number m of the sampling points n i is greater than 10.

[0025] Further, the period of the infrared anti-reflection microstructure is 1-4pm.

[0026] Further, the period of the grid groove is 100-500pm.

[0027] Further, the metal material is one or more of copper, silver, gold, nickel or chromium.

[0028] Overall, compared with the prior art, the above technical scheme conceived by the present application mainly has the following advantages:

[0029] (1) The present application utilizes the collaborative work of the optical, mechanical and electrical system such as the beam expansion module, the beam reflection module, the beam spatial shaping module and the high-precision motion platform, to realize high-quality processing of the laser focal point on the curved window surface. Specifically, by shaping the Gaussian beam output by the ultrafast laser into a Bessel beam with more concentrated energy distribution, and compressing the beam spot to microns, higher-quality microstructure forming and manufacturing are realized; at the same time, the long focal depth characteristic of the Bessel beam, i.e. its energy distribution length can reach hundreds of microns, effectively reduces the influence of laser focal point jitter or curved window surface unevenness on the processing precision, thereby significantly improving the processing precision.

[0030] (2) The present application can realize laser precise focusing, positioning, surface contour fitting and processing path planning of curved windows of different sizes through multi-axis linkage processing, Archimedes equidistant spiral scanning, cross-arched scanning, coaxial auxiliary observation and other technologies, so as to realize large-area high-efficiency precise processing of curved window microstructure

[0031] (3) The application manufactures electromagnetic shielding and infrared anti-reflection composite functional microstructure on the surface of the curved window through ultrafast laser processing technology, which has higher reliability in complex application environment: the electromagnetic shielding grid embedded in the surface of the curved window has excellent electromagnetic shielding performance, transmission performance and friction resistance; the infrared anti-reflection microstructure processed on the surface can efficiently improve the infrared transmittance and effectively solve the problem of failure of traditional anti-reflection film due to thermal expansion, and has higher reliability.

[0032] Therefore, the application has significant advantages in manufacturing electromagnetic shielding and infrared anti-reflection curved window with high quality, high efficiency and high reliability. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic diagram of the electromagnetic shielding and infrared anti-reflection curved window of the embodiment of the application;

[0034] Figure 2 is a schematic diagram of the ultrafast laser manufacturing device of the electromagnetic shielding and infrared anti-reflection curved window of the embodiment of the application;

[0035] Figure 3 is a schematic diagram of the self-centering clamp coaxially clamping the curved window of the embodiment of the application;

[0036] Figure 4 is a schematic diagram of the laser focal point fitting the profile of the curved window of the embodiment of the application;

[0037] Figure 5 is a schematic diagram of the laser focusing on the lower surface of the curved window to process the infrared anti-reflection microstructure of the embodiment of the application;

[0038] Figure 6 is a schematic diagram of the laser focusing on the upper surface of the curved window to process the grid groove of the embodiment of the application.

[0039] BRIEF DESCRIPTION OF DRAWINGS: 1 - control system; 2 - ultrafast laser; 3 - beam expansion module: 31 - concave lens, 32 - convex lens; 4 - beam reflection module: 41 - first mirror, 42 - second mirror, 43 - third mirror, 44 - fourth mirror; 5 - beam spatial shaping module: 51 - conical lens, 52 - convex lens, 53 - objective lens; 6 - high-precision motion platform: 61 - linear motion X-axis, 62 - linear motion Y-axis, 63 - linear motion Z-axis, 64 - rotary motion A-axis, 65 - marble base; 7 - self-centering clamp; 8 - curved window; 9 - coaxial observation system: 91 - CCD camera, 92 - white light source. DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and advantages of the application more clear, the following will be described in detail in combination with the drawings and specific embodiments.

[0041] To solve the above problems, the present application provides an electromagnetic shielding and infrared antireflection curved window, as shown in Figure 1 The manufacturing method of the electromagnetic shielding and infrared antireflection curved window is shown in Figures 2 to 6 Specifically, an ultrafast laser manufacturing device for the electromagnetic shielding and infrared antireflection curved window is used, as shown in Figure 2 The device specifically comprises a control system, which can simultaneously control an ultrafast laser and a high-precision motion platform; an ultrafast laser, which can output a Gaussian light beam with a pulse wavelength of 1030 nm and a pulse width of 900 fs; a light beam expansion module, which comprises a concave lens with a focal length of-50 mm and a convex lens with a focal length of 200 mm, and is used to expand the Gaussian light beam to adjust the spot diameter; a light beam reflection module, which comprises a first mirror, a second mirror, a third mirror and a fourth mirror, wherein the first mirror and the second mirror have a reflectivity of more than 99% for 1030 nm laser, the third mirror is a dichroic mirror with a reflectivity of more than 98% for 1030 nm laser and a transmittance of more than 90% for white light, and the fourth mirror is a half mirror with a reflectivity and a transmittance of 50% for white light; a light beam spatial shaping module, which comprises a conical lens with a conical top angle of 175° and a 4F focusing system composed of a convex lens with a focal length of 150 mm and a 20x objective, and can shape and focus the light beam into a Bessel light beam with energy concentration and longer focal depth; a high-precision motion platform, which comprises a linear motion X axis, a linear motion Y axis, a linear motion Z axis, a rotary motion A axis and a marble base; a self-centering clamp, which is coaxially fixed to the rotary motion A axis with the curved window, and ensures accurate positioning and stable clamping of the curved window during the machining process, as shown in Figure 3 A coaxial observation system, which comprises a CCD camera and a white light source, is used for observation and auxiliary positioning during the machining process;

[0042] In the embodiment of the present application, an ultrafast laser manufacturing method for the electromagnetic shielding and infrared antireflection curved window is provided, in which a V-shaped groove infrared antireflection microstructure with a period of 3.6 μm, a width of 2 μm and a depth of 2 μm is manufactured on the lower surface of a zinc sulfide curved window with an aperture of 50 mm and a thickness of 2 mm, and a copper mesh grid with a period of 100 μm, a width of 3 μm and a thickness of 3 μm is manufactured on the upper surface. The manufacturing of the electromagnetic shielding and infrared antireflection curved window comprises the following steps:

[0043] Step one, put the curved window into the ultrasonic cleaning machine, and clean it with anhydrous ethanol and distilled water respectively, the cleaning time is 20 minutes. After cleaning, transfer the curved window to the vacuum oven for drying, the temperature is set to 75°C, and the drying time is 50 minutes. Then, use a precision spray instrument to spray a layer of photoresist with uniform thickness on the upper surface of the curved window to form a protective glue with a thickness of 2 μm. After spraying, carefully place the curved window on the self-centering fixture, and use the automatic centering function of the fixture to fix the curved window coaxially with the rotating motion A shaft with coaxiality deviation better than ±0.015mm. During the fixing process, use a high-precision coaxiality measuring instrument for real-time monitoring and adjustment to ensure the accuracy of the fixing.

[0044] Step two, use the light beam expansion module, light beam reflection module and light beam spatial shaping module to expand, shape and focus the Gaussian beam output by the ultrafast laser. Among them, the light beam expansion module selects a-50mm concave lens and a 200mm convex lens to expand the spot diameter by 4 times; the light beam spatial shaping module selects a 150mm concave lens and a 20x objective lens for focusing, which compresses the laser spot diameter to below 2 μm. Therefore, after the Gaussian beam passes through the above three modules, a Bessel beam focus with more concentrated energy and longer focal depth is formed. Then, control the linear motion X axis and the linear motion Y axis to move, so that the rotating motion A shaft, the curved window and the laser focus are coaxial.

[0045] Step three, drive the second mirror, third mirror, fourth mirror, light beam spatial shaping module and coaxial observation system to move synchronously by the linear motion Z axis, so as to drive the laser focus to move; under the assistance of the coaxial observation system, the linear motion Y axis uniformly selects m=30 sampling points ni according to the distance to the center axis of the curved window, controls the laser focus to focus on the sample surface at each sampling point ni, and records the coordinates of the sampling point, and then fits the profile of the curved window according to the polynomial to calculate the three-dimensional spatial coordinates of the curved window, as shown in Figure 4 .

[0046] Step four, move the linear motion Z axis to focus the laser focus on the center axis of the lower surface of the curved window, and set the laser processing parameters of the infrared antireflection microstructure and the motion parameters of the high-precision motion platform. By linkage of the rotating motion A shaft and the linear motion X axis and the linear motion Z axis, control the focus to always focus on the lower surface of the curved window, and move according to the Archimedean equidistant spiral with a period of 3.6 μm from inside to outside, as shown in Figure 5 . Thus, the V-shaped groove infrared antireflection microstructure with a period of 3.6 μm, a width of 2 μm and a depth of 2 μm is obtained.

[0047] Step five, the linear motion Z axis focuses the laser focal point on the upper surface of the curved window, and sets the laser processing parameters of the grating groove and the high-precision motion platform motion parameters. By the linkage of the linear motion X axis, the linear motion Y axis and the linear motion Z axis, the focal point is always focused on the upper surface of the curved window, and moves in the form of a periodic 100μm cross-arched scan, and a grating groove with a period of 100μm, a width of 3μm and a depth of 3μm is processed, as shown in Figure 6 Then, the processed curved window is taken out, a 3μm thick copper film is plated in the grating groove of the curved window by using a magnetron sputtering film plating process, the curved window after plating is placed in a degumming solvent for cleaning, the metal grating is retained after removing the protective glue, and finally an electromagnetic shielding and infrared anti-reflection curved window is obtained.

[0048] The ultrafast laser manufacturing method of the electromagnetic shielding and infrared anti-reflection curved window provided by the application is not only suitable for a zinc sulfide curved window with an aperture of 50mm and a thickness of 3mm, but also suitable for high-quality, high-efficiency and high-reliability manufacturing of electromagnetic shielding and infrared anti-reflection functional microstructures on surfaces of other sizes of zinc sulfide, zinc selenide, sapphire, magnesium fluoride or barium fluoride infrared window materials.

[0049] The above is the preferred embodiment of the application, and it should be pointed out that for ordinary skilled persons in the art, some improvements and refinements can be made without departing from the principles of the application, and these improvements and refinements should also be regarded as the protection scope of the application.

Claims

1. A method for manufacturing an ultrafast laser-based electromagnetically shielded and infrared-anti-reflective curved window, comprising an ultrafast laser manufacturing apparatus for an electromagnetically shielded and infrared-anti-reflective curved window, characterized in that, The device includes: A control system that can simultaneously control an ultrafast laser and a high-precision motion platform; An ultrafast laser that can output a Gaussian beam with a pulse wavelength of 1030 nm and a pulse width ranging from 100 fs to 10 ps; A beam expander module, comprising a concave lens of -50 to -100 mm and a convex lens of 100 to 400 mm, is used to expand a Gaussian beam to adjust the beam spot diameter. The beam reflection module includes a first reflector, a second reflector, a third reflector, and a fourth reflector. The first and second reflectors have a reflectivity of over 99% for 1030nm laser light. The third reflector is a dichroic mirror with a reflectivity of over 98% for 1030nm laser light and a transmittance of over 90% for white light. The fourth reflector is a semi-reflective mirror with a reflectivity and transmittance of 50% for both white light. A beam shaping module, comprising a conical lens with a cone apex angle of 175° to 178° and a 4F focusing system, wherein the 4F focusing system consists of a 50 to 200 mm convex lens and a 20 to 50x objective lens, which can shape and focus the beam into a Bessel beam with concentrated energy and a longer depth of focus. A high-precision motion platform, comprising a linear motion X-axis, a linear motion Y-axis, a linear motion Z-axis, a rotary motion A-axis, and a marble base; The self-centering fixture is coaxially fixed to the curved window on the rotational A-axis to ensure the precise positioning and stable clamping of the curved window during the processing. A coaxial observation system, comprising a CCD camera and a white light source, is used for observation and auxiliary positioning during the processing. The ultrafast laser manufacturing method for the electromagnetic shielding and infrared anti-reflection curved window includes the following steps: S1. Ultrasonically clean and dry the curved window to be processed. Spray a 1-5 μm thick protective adhesive on the upper surface of the curved window. Use a self-centering clamp to fix the curved window coaxially with the rotary motion axis A. S2. The beam expansion module, beam reflection module, and beam spatial shaping module are used to expand, shape, and focus the Gaussian beam output by the ultrafast laser to form a Bessel beam focus with more concentrated energy and a longer depth of focus. The linear motion X-axis and linear motion Y-axis are controlled to make the rotational motion A-axis, the curved window, and the laser focus coaxial. S3. The linear motion along the Z-axis drives the second, third, and fourth reflecting mirrors, the beam shaping module, and the coaxial observation system to move synchronously, thereby moving the laser focus. With the assistance of the coaxial observation system, the linear motion along the Y-axis uniformly selects m sampling points n according to the distance to the center axis of the curved window. i Control at each sampling point n i The laser focus is precisely aligned with the sample surface, and the coordinates of the sampling point are recorded. Then, the contour of the curved window is fitted according to a polynomial to calculate the three-dimensional spatial coordinates of the curved window. S4. The linear motion Z-axis focuses the laser focus on the central axis of the lower surface of the curved window. By linking the rotational motion A-axis with the linear motion X-axis and Z-axis, the focus is controlled to always be focused on the lower surface of the curved window. The laser moves from the inside to the outside along an Archimedes equidistant spiral to process a periodic infrared anti-reflection microstructure. S5. The linear motion Z-axis focuses the laser focus on the upper surface of the curved window. Through the linkage of the linear motion X-axis, linear motion Y-axis, and linear motion Z-axis, the focus is always focused on the upper surface of the curved window. The movement is carried out in a cross-bow scanning manner to process periodic grid grooves. Then, the processed curved window is taken out, and metal is deposited in the grid grooves of the curved window using a vacuum coating process. The coated curved window is then placed in a descaling solvent for cleaning. After removing the protective adhesive, the metal grid is retained, and finally, an electromagnetic shielding and infrared anti-reflection curved window is obtained.

2. The ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved surface windows according to claim 1, characterized in that, In step S1, the curved window is zinc sulfide, zinc selenide, sapphire, magnesium fluoride, or barium fluoride.

3. The ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved surface windows according to claim 1, characterized in that, In step S1, the curved window is a small curvature circular window with a window diameter of 20-200mm and a window thickness of 1-3mm.

4. The ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved window according to claim 1, characterized in that, In step S3, the sampling point n i The number of elements m > 10.

5. The ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved surface windows according to claim 1, characterized in that, In step S4, the period of the infrared anti-reflection microstructure is 1 to 4 μm.

6. The ultrafast laser manufacturing method for the electromagnetic shielding and infrared anti-reflection curved window according to claim 1, characterized in that, In step S5, the period of the grid groove is 100-500 μm.

7. The ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved windows according to claim 1, characterized in that, In step S5, the metal material is one or more of copper, silver, gold, nickel, or chromium.

Images