Ultrafast laser manufacturing method of electromagnetic shielding and infrared anti-reflection curved window

Abstract

The invention provides an ultrafast laser manufacturing method for an electromagnetic shielding and infrared anti-reflection curved window. The ultrafast laser manufacturing method comprises the following steps that S1, the curved window is subjected to ultrasonic cleaning, drying and protection glue spraying and then fixed through a self-centering clamp; s2, shaping the light beam into a Bessel light beam, focusing the Bessel light beam, and enabling the curved window and a laser focus to be coaxial; s3, focusing a laser focus 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, processing an infrared anti-reflection microstructure on the lower surface of the curved window according to an Archimedes equidistant spiral line; and S5, a mesh groove is machined in the upper surface of the curved window according to cross arch scanning, and then the curved window with the electromagnetic shielding and infrared anti-reflection composite function is obtained through vacuum coating, cleaning and photoresist removing. By means of the method, high-quality, high-efficiency and high-reliability manufacturing of the curved window with the electromagnetic shielding and infrared anti-reflection composite function can be achieved, and the electromagnetic shielding and infrared detection requirements in the fields of aerospace and the like are met.

Description

Technical Field

[0001] The invention relates to the field of infrared window processing and application technology, and in particular to an ultrafast laser manufacturing method for an electromagnetic shielding and infrared anti-reflection curved window. Background Art

[0002] In modern warfare scenarios, infrared detection technology has become one of the most critical detection methods due to its high resolution, high sensitivity and high information update rate. Nowadays, with the widespread application of electromagnetic interference and infrared stealth technology, infrared windows must have both high infrared transmittance and microwave electromagnetic shielding performance. However, there are many problems with conventional infrared windows. Due to the Fresnel reflection loss on its surface, the transmission of infrared signals will be weakened, and the electromagnetic shielding ability is generally lacking, which leads to external interference electromagnetic waves, especially electromagnetic waves generated by microwave weapons, which can easily enter the detection system and cause serious interference to electronic instruments and communication systems. This interference will not only have an adverse effect on the extraction and processing of infrared signals, but may even cause the infrared imaging equipment to fail or be damaged, greatly reducing the safety and reliability of the entire system. At the same time, considering the need to reduce wind resistance under actual working conditions, infrared windows are usually designed in the form of curved spherical covers. Therefore, the development of electromagnetic shielding and infrared anti-reflection curved windows with excellent optical / electrical performance and high physical stability is of great significance for enhancing the anti-interference ability of infrared detection weapons and equipment and improving their battlefield survivability.

[0003] Traditional micro-nano processing technologies, such as 3D printing, nanoimprinting, and photolithography, face huge challenges in the high-quality, high-efficiency, and high-reliability manufacturing of curved window surface microstructures, especially when electromagnetic shielding, infrared anti-reflection, and reliability need to be guaranteed at the same time. 3D printing technology is limited by printing accuracy and it is difficult to print metal grids with a width of microns. Although metal grids that are too wide can meet the shielding performance requirements, they will sacrifice the infrared transmittance of the window. In addition, the 3D-printed metal grid is not embedded in the window surface, resulting in a lack of wear resistance. Nanoimprinting technology faces challenges in processing hard and brittle window materials, and the mechanical properties of the processed microstructures are significantly reduced. Photolithography technology is limited by the mask. Windows of different sizes require different masks, and it cannot adapt to the large-area processing requirements of curved window microstructures.

[0004] In order to solve the problem that the existing technology cannot achieve high-performance manufacturing of electromagnetic shielding and infrared anti-reflection curved windows, this method uses ultrafast laser beam shaping technology and multi-axis linkage processing technology to achieve high-quality and high-efficiency manufacturing of functional microstructures on the surface of curved windows. By precisely controlling the shape and size of the beam, high-precision and high-quality processing of the microstructure can be achieved. Multi-axis linkage processing technology ensures precise positioning and motion trajectory during the processing process, thereby achieving large-area processing of curved window microstructures. At the same time, the infrared anti-reflection microstructure on the window substrate and the metal grid 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.), ensuring its long-term reliable performance. Summary of the invention

[0005] In view of the above problems, the present invention proposes an ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved window, the purpose of which is to achieve high-quality, high-efficiency and high-reliability manufacturing of electromagnetic shielding and infrared anti-reflection curved window.

[0006] The object of the present invention is achieved through the following technical solutions:

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

[0008] A control system, wherein the control system can simultaneously control an ultrafast laser and a high-precision motion platform;

[0009] An ultrafast laser, wherein the ultrafast laser can output a Gaussian beam with a pulse wavelength of 1030 nm and a pulse width ranging from 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 beam to adjust the spot diameter;

[0011] A beam reflection module, the beam reflection module comprising a first reflector, a second reflector, a third reflector and a fourth reflector, wherein the reflectivity of the first reflector and the second reflector to a 1030nm laser is higher than 99%, the third reflector is a dichroic mirror, the reflectivity to the 1030nm laser is greater than 98%, and the transmittance to white light is greater than 90%, and the fourth reflector is a half-reflecting mirror, the reflectivity and transmittance to white light are both 50%;

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

[0013] A high-precision motion platform, the 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;

[0014] A self-centering fixture, which is coaxially fixed to the curved window on the rotating motion A axis to ensure accurate positioning and stable clamping of the curved window during processing;

[0015] A coaxial observation system, comprising a CCD camera and a white light source, for observation and auxiliary positioning during the processing;

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

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

[0018] S2. Use a beam expansion module, a beam reflection module, and a beam spatial shaping module to expand, shape, and focus the Gaussian beam output by the ultrafast laser to form a Bessel beam focus with more concentrated energy and longer focal depth, and control the movement of the linear motion X-axis and the linear motion Y-axis to make the rotational motion A-axis, the curved window, and the laser focus coaxial;

[0019] S3, the second reflector, the third reflector, the fourth reflector, the beam space shaping module and the coaxial observation system are driven to move synchronously through the linear motion Z axis, thereby driving the laser focus to move; with the assistance of the coaxial observation system, the linear motion Y axis uniformly selects m sampling points n according to the distance to the central axis of the curved window i , controlled at each sampling point n i The laser focus is just focused on the sample surface, and the coordinates of the sampling point are recorded. Then, the contour of the surface window is fitted according to the polynomial, and the three-dimensional space coordinates of the surface window are calculated.

[0020] S4, moving the linear motion Z axis to focus the laser on the central axis of the lower surface of the curved window, and controlling the focus to always be focused on the lower surface of the curved window by rotating the A axis and linking the linear motion X axis and the linear motion Z axis, and moving from the inside to the outside according to the Archimedean equidistant spiral to obtain a periodic infrared anti-reflection microstructure;

[0021] S5. Move the linear motion Z axis to focus the laser 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, control the focus to always be focused on the upper surface of the curved window, and move in a cross-bow scanning manner to obtain periodic grid grooves. Then, take out the processed curved window, and use a vacuum coating process to plate metal in the grid grooves of the curved window. Then, place the coated curved window in a degumming solvent for cleaning, remove the protective glue and retain the metal grid, and finally obtain an electromagnetic shielding and infrared anti-reflection curved window.

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

[0023] Furthermore, the curved window is a circular window with a small curvature, a window diameter of 20 to 200 mm, and a window thickness of 1 to 3 mm.

[0024] Furthermore, the sampling point n i The number m>10.

[0025] Furthermore, the period of the infrared anti-reflection microstructure is 1 to 4 μm.

[0026] Furthermore, the period of the grid grooves is 100-500 μm.

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

[0028] In general, the above technical solution conceived by the present invention has the following advantages compared with the prior art:

[0029] (1) The present invention utilizes the coordinated work of optomechanical systems such as a beam expansion module, a beam reflection module, a beam spatial shaping module, and a high-precision motion platform to achieve high-quality processing of the laser focus on the surface of a curved window. Specifically, by shaping the Gaussian beam output by an ultrafast laser into a Bessel beam with a more concentrated energy distribution, and compressing the beam spot to the micron level, higher-quality microstructure molding and manufacturing can be achieved; at the same time, the long focal depth characteristic of the Bessel beam, that is, its energy distribution length can reach hundreds of microns, effectively reduces the influence of laser focus jitter or uneven curved window surface on processing accuracy, thereby significantly improving processing accuracy.

[0030] (2) The present invention can realize laser precise focusing, positioning, surface contour fitting and processing path planning of curved windows of different sizes through multi-axis linkage processing, Archimedean equidistant spiral scanning, cross-bow scanning, coaxial auxiliary observation and other technologies, thereby realizing large-area, high-efficiency and precise processing of curved window microstructures.

[0031] (3) The present invention uses ultrafast laser processing technology to manufacture electromagnetic shielding and infrared anti-reflection composite functional microstructures on the surface of the curved window, which has higher reliability in complex application environments: the electromagnetic shielding grid embedded in the surface of the curved window has excellent electromagnetic shielding performance, transmittance and friction resistance; the infrared anti-reflection microstructure processed on the surface can achieve a high efficiency improvement in infrared transmittance, and effectively solves the problem of failure of traditional anti-reflection films due to thermal expansion, and has higher reliability.

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

[0033] Figure 1 is a schematic diagram of an electromagnetic shielding and infrared anti-reflection curved window according to an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of an ultrafast laser manufacturing device for an electromagnetic shielding and infrared anti-reflection curved window according to an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of a self-centering fixture coaxially clamping a curved window according to an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of the laser focus fitting curved window profile according to an embodiment of the present invention;

[0037] Figure 5 Schematic diagram of an infrared anti-reflection microstructure processed on the lower surface of a laser focusing curved window according to an embodiment of the present invention;

[0038] Figure 6 It is a schematic diagram of processing grid grooves on the upper surface of the laser focusing curved window according to an embodiment of the present invention.

[0039] Explanation of the accompanying drawings: 1-control system; 2-ultrafast laser; 3-beam expansion module: 31-concave lens, 32-convex lens; 4-beam reflection module: 41-first reflector, 42-second reflector, 43-third reflector, 44-fourth reflector; 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-rotational motion A-axis, 65-marble base; 7-self-centering fixture; 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 to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0041] In view of the existing problems, the present invention provides an electromagnetic shielding and infrared anti-reflection curved window, such as Figure 1 The manufacturing method of the electromagnetic shielding and infrared anti-reflection curved window is as shown in Figures 2 to 6 Specifically, an ultrafast laser manufacturing device for electromagnetic shielding and infrared anti-reflection curved window was used, such as Figure 2 As shown. The device specifically includes: a control system, which can simultaneously control an ultrafast laser and a high-precision motion platform; an ultrafast laser, which can output a Gaussian beam with a pulse wavelength of 1030nm and a pulse width of 900fs; a beam expansion module, which includes a -50mm concave lens and a 200mm convex lens, and is used to expand the Gaussian beam to adjust the spot diameter; a beam reflection module, which includes a first reflector, a second reflector, a third reflector and a fourth reflector, wherein the reflectivity of the first reflector and the second reflector to the 1030nm laser is higher than 99%, and the third reflector is a dichroic mirror, and the reflectivity of the 1030nm laser is greater than 98%, and the reflectivity of the third reflector to the 1030nm laser is greater than 98%. White light transmittance>90%, the fourth reflector is a half-reflector, and the reflectance and transmittance of white light are both 50%; a beam space shaping module, the beam space shaping module includes a conical lens with a cone vertex angle of 175° and a 4F focusing system, the 4F focusing system consists of a 150mm convex lens and a 20x objective lens, which can shape and focus the beam into a Bessel beam with energy concentration and longer focal depth; a high-precision motion platform, the high-precision motion platform includes a linear motion X-axis, a linear motion Y-axis, a linear motion Z-axis, a rotational motion A-axis and a marble base; a self-centering fixture, the self-centering fixture is coaxially fixed to the rotational motion A-axis with the curved window to ensure accurate positioning and stable clamping of the curved window during processing, such as Figure 3 As shown; a coaxial observation system, the coaxial observation system includes a CCD camera and a white light source, which is used for observation and auxiliary positioning during the processing;

[0042] In the embodiment of the present invention, an ultrafast laser manufacturing method for an electromagnetic shielding and infrared anti-reflection curved window is provided. A V-shaped groove infrared anti-reflection 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 a diameter of 50 mm and a thickness of 2 mm, and a copper 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 anti-reflection curved window includes the following steps:

[0043] Step 1. Place the curved window in an ultrasonic cleaning machine and clean it with anhydrous ethanol and distilled water respectively for 20 minutes. After cleaning, transfer the curved window to a vacuum oven for drying, the temperature is set to 75°C, and the drying time is 50 minutes. Then, use a precision sprayer 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 2μm. 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 and the rotating motion A-axis coaxially with a coaxiality deviation better than ±0.015mm. During the fixing process, a high-precision coaxiality measuring instrument is used for real-time monitoring and adjustment to ensure the accuracy of the fixation.

[0044] Step 2: Use the beam expansion module, beam reflection module, and beam spatial shaping module to expand, shape, and focus the Gaussian beam output by the ultrafast laser. Among them, the beam expansion module uses a -50mm concave lens and a 200mm convex lens to expand the spot diameter by 4 times; the beam spatial shaping module uses a 150mm concave lens and a 20x objective lens for focusing, compressing the laser spot diameter to less than 2μm. 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. Subsequently, the linear motion X-axis and the linear motion Y-axis are controlled to move so that the rotational motion A-axis, the curved window, and the laser focus are coaxial.

[0045] Step 3: The second reflector, the third reflector, the fourth reflector, the beam space shaping module and the coaxial observation system are driven to move synchronously through the linear motion Z axis, thereby driving the laser focus to move; with 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 central axis of the curved window, controls the laser focus at each sampling point ni to just focus on the sample surface, and records the coordinates of the sampling point, and then fits the contour of the curved window according to the polynomial to calculate the three-dimensional spatial coordinates of the curved window, such as Figure 4 shown.

[0046] Step 4: Move the linear motion Z axis to focus the laser on the central axis of the lower surface of the curved window, and set the laser processing parameters of the infrared anti-reflection microstructure and the motion parameters of the high-precision motion platform. By rotating the A axis and linking the linear motion X axis and the linear motion Z axis, the focus is always controlled to focus on the lower surface of the curved window, and moves from the inside to the outside according to the Archimedean equidistant spiral with a period of 3.6μm, such as Figure 5 As shown. Thus, a V-shaped groove infrared anti-reflection microstructure with a period of 3.6 μm, a width of 2 μm, and a depth of 2 μm was obtained.

[0047] Step 5: Move the linear motion Z axis to focus the laser on the upper surface of the curved window, and set the laser processing parameters of the mesh groove and the motion parameters of the high-precision motion platform. Through the linkage of the linear motion X axis, the linear motion Y axis, and the linear motion Z axis, the focus is always controlled to focus on the upper surface of the curved window, and the movement is carried out in a cross-bow scanning manner with a period of 100μm, and a mesh groove with a period of 100μm, a width of 3μm, and a depth of 3μm is obtained. Figure 6 Then, the processed curved window is taken out, and a copper film with a thickness of 3 μm is plated in the mesh groove of the curved window by a magnetron sputtering coating process, and then the coated curved window is placed in a degumming solvent for cleaning, and the metal mesh 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 for an electromagnetic shielding and infrared anti-reflection curved window described in the present invention is not only suitable for a zinc sulfide curved window with a diameter of 50 mm and a thickness of 3 mm, but also suitable for high-quality, high-efficiency and high-reliability manufacturing of electromagnetic shielding and infrared anti-reflection functional microstructures on the surface of infrared window materials such as zinc sulfide, zinc selenide, sapphire, magnesium fluoride or barium fluoride of other sizes.

[0049] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An ultrafast laser manufacturing method for electromagnetic shielding and infrared anti-reflection curved window, using an ultrafast laser manufacturing device for electromagnetic shielding and infrared anti-reflection curved window, characterized in that: The device includes: A control system, wherein the control system can simultaneously control an ultrafast laser and a high-precision motion platform; An ultrafast laser, wherein the ultrafast laser 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 expansion module, comprising a concave lens of -50 to -100 mm and a convex lens of 100 to 400 mm, for expanding the Gaussian beam to adjust the spot diameter; A beam reflection module, the beam reflection module comprising a first reflector, a second reflector, a third reflector and a fourth reflector, wherein the reflectivity of the first reflector and the second reflector to a 1030nm laser is higher than 99%, the third reflector is a dichroic mirror, the reflectivity to the 1030nm laser is greater than 98%, and the transmittance to white light is greater than 90%, and the fourth reflector is a half-reflecting mirror, the reflectivity and transmittance to white light are both 50%; A beam spatial shaping module, the beam spatial shaping module includes a conical lens with a cone vertex angle of 175° to 178° and a 4F focusing system, the 4F focusing system consists of a 50-200mm convex lens and a 20-50x objective lens, which can shape and focus the beam into a Bessel beam with concentrated energy and longer focal depth; A high-precision motion platform, the 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; A self-centering fixture, which is coaxially fixed to the curved window on the rotating motion A axis to ensure accurate positioning and stable clamping of the curved window during processing; A coaxial observation system, comprising a CCD camera and a white light source, for observation and auxiliary positioning during the processing; The ultrafast laser manufacturing method of the electromagnetic shielding and infrared anti-reflection curved window comprises the following steps: S1. Ultrasonic cleaning and drying of the curved window to be processed, spraying a protective glue with a thickness of 1 to 5 μm on the upper surface of the curved window, and using a self-centering fixture to fix the curved window coaxially with the rotating motion axis A; S2. Use a beam expansion module, a beam reflection module, and a beam spatial shaping module to expand, shape, and focus the Gaussian beam output by the ultrafast laser to form a Bessel beam focus with more concentrated energy and longer focal depth, and control the movement of the linear motion X-axis and the linear motion Y-axis to make the rotational motion A-axis, the curved window, and the laser focus coaxial; S3, the second reflector, the third reflector, the fourth reflector, the beam space shaping module and the coaxial observation system are driven to move synchronously through the linear motion Z axis, thereby driving the laser focus to move; with the assistance of the coaxial observation system, the linear motion Y axis uniformly selects m sampling points n according to the distance to the central axis of the curved window i , controlled at each sampling point n i The laser focus is just focused on the sample surface, and the coordinates of the sampling point are recorded. Then, the contour of the surface window is fitted according to the polynomial, and the three-dimensional space coordinates of the surface window are calculated. S4, moving the linear motion Z axis to focus the laser on the central axis of the lower surface of the curved window, and controlling the focus to always be focused on the lower surface of the curved window by rotating the A axis and linking the linear motion X axis and the linear motion Z axis, and moving from the inside to the outside according to the Archimedean equidistant spiral to obtain a periodic infrared anti-reflection microstructure; S5. Move the linear motion Z axis to focus the laser 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, control the focus to always be focused on the upper surface of the curved window, and move in a cross-bow scanning manner to obtain periodic grid grooves. Then, take out the processed curved window, and use a vacuum coating process to plate metal in the grid grooves of the curved window. Then, place the coated curved window in a degumming solvent for cleaning, remove the protective glue and retain the metal grid, and finally obtain an electromagnetic shielding and infrared anti-reflection curved window.

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

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

4. The ultrafast laser manufacturing method of the 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 m>10.

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

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

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