An ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures

Abstract

This invention provides an ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures. The device includes: a control system, an ultrafast laser, a beam expander module, a beam reflection module, a beam spatial shaping module, a high-precision motion platform, a self-centering fixture, a curved surface window, and a coaxial observation system. The control system controls the ultrafast laser to output a Gaussian beam. After passing through the beam expander module, beam reflection module, and beam spatial shaping module sequentially, the high-precision motion platform, controlled by the control system, focuses the laser beam onto the surface of the curved window. Through contour fitting and processing path planning, embedded electromagnetic shielding grids and surface infrared anti-reflection microstructures are then processed. This ultrafast laser processing device can achieve high-quality, high-efficiency, and high-reliability manufacturing of electromagnetic shielding and infrared anti-reflection curved surface microstructures, meeting the electromagnetic shielding and infrared detection requirements of aerospace and other fields.

Description

Technical Field

[0001] This invention relates to the field of infrared window processing and application technology, and in particular to an ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures. Background Technology

[0002] In modern warfare, infrared detection technology, with its high resolution, high sensitivity, and high information update rate, has become a crucial detection method. Today, with the widespread application of electromagnetic interference and infrared stealth technologies, infrared windows must simultaneously possess high infrared transmittance and microwave electromagnetic shielding performance. However, conventional infrared windows suffer from several problems. Their surface loss due to Fresnel reflection weakens infrared signal transmission, and they generally lack electromagnetic shielding capabilities. This allows external electromagnetic interference waves, especially those generated by microwave weapons, to easily penetrate the detection system, causing severe interference to electronic instruments and communication systems. This interference not only adversely affects the extraction and processing of infrared signals but may even cause infrared imaging equipment to malfunction or be damaged, significantly reducing the safety and reliability of the entire system. Meanwhile, considering the need to reduce wind resistance under actual operating conditions, infrared windows are typically designed as curved domes. Therefore, developing an integrated curved window for infrared anti-reflection and electromagnetic shielding with superior optical / electrical performance and high physical stability is of paramount importance for enhancing the anti-interference capabilities of infrared detection weapons and improving their battlefield survivability.

[0003] Traditional micro-nano fabrication technologies, such as 3D printing, nanoimprinting, and photolithography, face significant challenges in achieving high-quality, high-efficiency, and high-reliability manufacturing of microstructures on curved window surfaces, especially when electromagnetic shielding, infrared transmittance enhancement, and reliability must be simultaneously guaranteed. 3D printing technology is limited by printing precision, making it difficult to print metal meshes with micrometer-level widths. While excessively wide metal meshes can meet shielding requirements, they sacrifice the window's infrared transmittance. Furthermore, 3D-printed metal meshes are not embedded in the window surface, resulting in a lack of wear resistance. Nanoimprinting technology struggles to process hard and brittle window materials, and the mechanical properties of the resulting microstructures are significantly reduced. Photolithography is limited by photomasks; different window sizes require different photomasks, and it cannot meet the large-area processing needs of curved window microstructures.

[0004] Therefore, there is still a contradiction between high quality, high efficiency and high reliability in the manufacturing of electromagnetic shielding and infrared anti-reflection curved surface microstructures. Existing processing technologies cannot meet these requirements at the same time, and there is an urgent need to develop an ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures. Summary of the Invention

[0005] To address the above problems, this invention proposes an ultrafast laser processing device for curved surface microstructures with electromagnetic shielding and infrared anti-reflection capabilities. The purpose is to achieve high-quality, high-efficiency, and high-reliability manufacturing of microstructures with electromagnetic shielding and infrared anti-reflection composite functions on curved infrared window surfaces.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] An ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures includes: a control system, an ultrafast laser, a beam expander module, a beam reflection module, a beam spatial shaping module, a high-precision motion platform, a self-centering fixture, a curved surface window, and a coaxial observation system. The ultrafast laser outputs a Gaussian beam, which passes sequentially through the beam expander module, the beam reflection module, and the beam spatial shaping module. The beam expander module is used to increase the beam spot diameter, the beam reflection module is used to change the beam propagation direction, and the beam spatial shaping module is used to shape the Gaussian beam into a Bessel beam with a longer processing distance and focus it. With the assistance of the coaxial observation system, the control system controls the high-precision motion platform to focus the laser focus on the surface of the curved surface window to sample points and fit its curved surface contour. The control system generates a processing path based on the fitted curved surface contour. The control system controls the high-precision motion platform to drive the laser focus along the predetermined processing path to perform equidistant spiral scanning to process the infrared anti-reflection microstructure on the lower surface of the curved surface window and cross-bow-shaped scanning to process the grid groove on the upper surface of the curved surface window.

[0008] Furthermore, the ultrafast laser outputs a Gaussian beam pulse with a wavelength of 1030 nm and a pulse width ranging from 100 fs to 10 ps.

[0009] Furthermore, the beam expander module consists of a concave lens of -50 to -100 mm and a convex lens of 100 to 400 mm, which expands the beam diameter by 2 to 8 times.

[0010] Furthermore, the beam reflection module includes a first reflector, a second reflector, a third reflector, and a fourth reflector. The angle between the reflectors and the horizontal plane is 45°. The first and second reflectors are used to reflect 1030nm laser light. The third reflector is a dichroic mirror with a reflectivity of >98% for 1030nm laser light and a transmittance of >90% for white light. The fourth reflector is a semi-reflective mirror with a reflectivity and transmittance of 50% for both white light.

[0011] Furthermore, the beam spatial shaping module includes a conical lens with a cone apex angle of 175° to 178° and a 4F focusing system. The 4F focusing system consists of a 50 to 200 mm convex lens and a 20 to 50x objective lens. The expanded Gaussian beam is shaped into a Bessel beam I by the conical lens, and the Bessel beam I is then compressed into a Bessel beam II with a spot diameter of less than 2 μm by the 4F focusing system.

[0012] Furthermore, the high-precision motion platform includes a linear motion X-axis, a linear motion Y-axis, a linear motion Z-axis, a rotary motion A-axis, and a marble base, with each axis moving in tandem to achieve precise control of the processing position.

[0013] Furthermore, the self-centering clamp is coaxially fixed on the rotational motion A-axis, and has four grippers that can move synchronously toward the center to achieve self-centering clamping of the curved window.

[0014] Furthermore, the coaxial observation system includes a CCD camera and a white light source, with the CCD camera used for imaging and the white light source used for illuminating the curved window surface.

[0015] Furthermore, the centers of the ultrafast laser, the beam expander module, and the first reflector are on the same horizontal line; the centers of the first reflector and the second reflector are on the same vertical line; the centers of the second reflector, the conical lens, and the third reflector are on the same horizontal line; the centers of the white light source and the fourth reflector are on the same horizontal line; and the centers of the CCD camera, the fourth reflector, the third reflector, and the 4F focusing system are on the same vertical line.

[0016] Furthermore, the second, third, and fourth reflectors, the beam space shaping module, and the coaxial observation system are packaged and connected as a whole, and move up and down synchronously with the linear Z-axis to adapt to the processing requirements of different heights of the curved surface.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) This invention utilizes the coordinated operation of an opto-electro-mechanical system, including a beam expander module, a beam reflector module, a beam spatial shaping module, and a high-precision motion platform, to achieve high-quality machining of curved window surfaces using laser focal points. Specifically, by shaping the Gaussian beam output from an ultrafast laser into a Bessel beam with a more concentrated energy distribution and compressing the beam spot to the micrometer level, higher-quality microstructures can be manufactured. At the same time, the long depth of focus characteristic of the Bessel beam, i.e., its energy distribution length can reach hundreds of micrometers, effectively reduces the impact of laser focal point jitter or unevenness of the curved window surface on machining accuracy, thereby significantly improving machining accuracy.

[0019] (2) This invention uses ultrafast laser processing technology to manufacture a composite microstructure with electromagnetic shielding and infrared anti-reflection on the surface of a 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 performance and abrasion resistance performance; the infrared anti-reflection microstructure processed on the surface can achieve a high efficiency improvement in infrared transmittance and effectively solve the problem of failure of traditional anti-reflection films due to thermal expansion, thus having higher reliability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of a self-centering fixture coaxially clamping a curved surface window according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the contour of the laser focus fitting surface window according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the infrared anti-reflection microstructure processed on the lower surface of the laser focusing curved window according to an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the processing of a grid groove on the upper surface of the laser focusing curved window according to an embodiment of the present invention.

[0025] Figure labeling: 1-Control system; 2-Ultrafast laser; 3-Beam expander module: 31-Concave lens, 32-Convex lens; 4-Beam reflection module: 41-First reflecting mirror, 42-Second reflecting mirror, 43-Third reflecting mirror, 44-Fourth reflecting 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 fixture; 8-Curved window; 9-Coaxial observation system: 91-CCD camera, 92-White light source. Detailed Implementation

[0026] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0027] To address the existing problems, this invention provides an ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures, such as... Figure 1As shown, the device includes: a control system, an ultrafast laser, a beam expander module, a beam reflection module, a beam spatial shaping module, a high-precision motion platform, a self-centering fixture, a curved window, and a coaxial observation system. The ultrafast laser outputs a Gaussian beam, which passes sequentially through the beam expander module, the beam reflection module, and the beam spatial shaping module. The beam expander module is used to increase the beam spot diameter, the beam reflection module is used to change the beam propagation direction, and the beam spatial shaping module is used to shape the Gaussian beam into a Bessel beam with a longer processing distance and focus it. With the assistance of the coaxial observation system, the control system controls the high-precision motion platform to focus the laser focus on the surface of the curved window to sample points and fit its curved contour. The control system generates a processing path based on the fitted curved contour. The control system controls the high-precision motion platform to drive the laser focus along the predetermined processing path to perform equidistant spiral scanning to process infrared anti-reflection microstructures on the lower surface of the curved window and cross-bow scanning to process grid grooves on the upper surface of the curved window.

[0028] The ultrafast laser outputs a Gaussian beam pulse with a wavelength of 1030 nm and a pulse width of 900 fs. The beam expander module consists of a -50 mm concave lens and a 200 mm convex lens, which expands the beam spot diameter by a factor of four. The beam reflection module includes a first, second, third, and fourth reflecting mirror. The angle between the reflecting mirrors and the horizontal plane is 45°. The first and second reflecting mirrors are used to reflect the 1030 nm laser. The third reflecting mirror is a dichroic mirror with a reflectivity of >98% for 1030 nm laser light and a transmittance of >90% for white light. The fourth reflecting mirror is a semi-reflective mirror with both a reflectivity and transmittance of 50% for white light. The beam shaping module includes a conical lens with a 175° apex angle and a 4F focusing system. The 4F focusing system consists of a 150mm convex lens and a 20x objective lens. The expanded Gaussian beam is shaped into a Bessel beam I by the conical lens, and then compressed into a Bessel beam II with a spot diameter of less than 2μm by the 4F focusing system. The high-precision motion platform includes 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 coordinated movement of these axes achieves precise control of the processing position. The self-centering fixture is coaxially fixed on the rotary motion A-axis and has four grippers that can move synchronously towards the center for self-centering clamping of curved windows, such as... Figure 2As shown. The coaxial observation system includes a CCD camera and a white light source. The CCD camera is used for imaging, and the white light source is used to illuminate the surface of the curved window. The centers of the ultrafast laser, the beam expander module, and the first mirror are on the same horizontal line. The centers of the first mirror and the second mirror are on the same vertical line. The centers of the second mirror, the cone lens, and the third mirror are on the same horizontal line. The center of the white light source and the fourth mirror are on the same horizontal line. The centers of the CCD camera, the fourth mirror, the third mirror, and the 4F focusing system are on the same vertical line. The second mirror, the third mirror, the fourth mirror, the beam spatial shaping module, and the coaxial observation system are encapsulated and connected into one body, and move up and down synchronously with the linear motion Z-axis to meet the processing requirements of different heights of the curved surface.

[0029] Figures 3-5 The specific process of processing the electromagnetic shielding and infrared antireflection composite functional microstructures by the ultrafast laser processing device for electromagnetic shielding and infrared antireflection curved surface microstructures is given. First, with the assistance of the coaxial observation system, control the high-precision motion platform to drive the laser focus to sample the outer surface of the curved window coated with 3μm thick photoresist, record the coordinate parameters when 30 laser foci just touch the surface of the curved window, and fit its curved surface contour. Subsequently, the control system respectively plans the processing paths for machining the electromagnetic shielding and infrared antireflection composite functional microstructures on the upper and lower surfaces of the curved window. Then, focus the laser focus on the lower surface of the curved window, set the laser processing parameters and the platform motion parameters, and through the linkage of the rotational motion A-axis, the linear motion X-axis, and the linear motion Z-axis, control the focus to always be focused on the lower surface of the curved window, and move from the inside to the outside in an Archimedean equidistant spiral with a period of 3.6μm to obtain a V-groove infrared antireflection microstructure with a period of 3.6μm, a width of 2μm, and a depth of 2μm. Then, focus the laser focus on the upper surface of the curved window, set the laser processing parameters and the platform motion parameters, and 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 with a period of 100μm to obtain a grid groove with a period of 100μm, a width of 3μm, and a depth of 3μm. Finally, take out the processed curved window, deposit a 3μm thick copper film in the grid grooves of the curved window through the magnetron sputtering coating process, and then place the coated curved window in a degumming solvent for cleaning. After removing the protective glue, the embedded metal grid is retained, thus obtaining the electromagnetic shielding and infrared antireflection curved surface microstructures.

[0030] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures, characterized in that, include: Control system, ultrafast laser, beam expander module, beam reflection module, beam spatial shaping module, high-precision motion platform, self-centering fixture, curved window and coaxial observation system; The ultrafast laser outputs a Gaussian beam, which passes sequentially through the beam expanding module, the beam reflecting module, and the beam spatial shaping module. The beam expanding module is used to expand the beam spot diameter, the beam reflecting module is used to change the beam propagation direction, and the beam spatial shaping module is used to shape the Gaussian beam into a Bessel beam that can be processed over a longer distance and focus it. With the assistance of the coaxial observation system, the control system controls the high-precision motion platform to focus the laser on the surface of the curved window to collect points and fit its curved contour. The control system generates a processing path based on the fitted curved contour. The control system controls a high-precision motion platform to drive the laser focus to perform equidistant spiral scanning to process infrared anti-reflection microstructures on the lower surface of the curved window according to a predetermined processing path, and to perform cross-bow-shaped scanning to process the grid grooves on the upper surface of the curved window.

2. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The ultrafast laser outputs a Gaussian beam pulse with a wavelength of 1030 nm and a pulse width ranging from 100 fs to 10 ps.

3. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The beam expander module consists of a concave lens of -50 to -100 mm and a convex lens of 100 to 400 mm. After beam expansion, the beam spot diameter is increased by 2 to 8 times.

4. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The beam reflection module includes a first reflector, a second reflector, a third reflector, and a fourth reflector. The angle between the reflectors and the horizontal plane is 45°. The first and second reflectors are used to reflect 1030nm laser light. The third reflector is a dichroic mirror with a reflectivity of >98% for 1030nm laser light and a transmittance of >90% for white light. The fourth reflector is a semi-reflective mirror with a reflectivity and transmittance of 50% for white light.

5. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The beam spatial shaping module includes a conical lens with a cone apex angle of 175° to 178° and a 4F focusing system. The 4F focusing system consists of a 50 to 200 mm convex lens and a 20 to 50x objective lens. The expanded Gaussian beam is shaped into a Bessel beam I by the conical lens, and the Bessel beam I is then compressed into a Bessel beam II with a spot diameter of less than 2 μm by the 4F focusing system.

6. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The high-precision motion platform includes 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 coordinated motion of each axis enables precise control of the processing position.

7. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The self-centering clamp is coaxially fixed on the rotational motion A-axis and has four grippers that can move synchronously toward the center to achieve self-centering clamping of curved windows.

8. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The coaxial observation system includes a CCD camera and a white light source. The CCD camera is used for imaging, and the white light source is used to illuminate the surface of the curved window.

9. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 1, characterized in that, The centers of the ultrafast laser, the beam expander module, and the first reflector are on the same horizontal line; the centers of the first reflector and the second reflector are on the same vertical line; the centers of the second reflector, the conical lens, and the third reflector are on the same horizontal line; the centers of the white light source and the fourth reflector are on the same horizontal line; and the centers of the CCD camera, the fourth reflector, the third reflector, and the 4F focusing system are on the same vertical line.

10. The ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures according to claim 4, characterized in that, The second, third, and fourth reflectors, the beam shaping module, and the coaxial observation system are packaged and connected as a whole, and move up and down synchronously with the linear Z-axis to adapt to the processing requirements of different heights of the curved surface.

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