Ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructure

Abstract

The invention provides an ultrafast laser processing device for an electromagnetic shielding and infrared anti-reflection curved surface microstructure. The device comprises a control system, an ultrafast laser, a light beam expanding module, a light beam reflecting module, a light beam space shaping module, a high-precision motion platform, a self-centering clamp, a curved surface window and a coaxial observation system. The control system controls the ultrafast laser to output a Gaussian beam, the Gaussian beam sequentially passes through the beam expanding module, the beam reflecting module and the beam space shaping module, then the control system controls the high-precision motion platform to focus a laser focus on the surface of the curved window under the assistance of the coaxial observation system, and the surface of the curved window is machined through contour fitting and machining path planning. And an embedded electromagnetic shielding mesh and a surface infrared anti-reflection microstructure are processed. According to the ultrafast laser processing device, high-quality, efficient and high-reliability manufacturing of the electromagnetic shielding and infrared anti-reflection curved surface microstructure 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 processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructure. 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. Today, 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 Fresnel reflection loss on its surface, the transmission of infrared signals will be weakened, and they generally lack electromagnetic shielding capabilities, 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 an integrated curved window with infrared anti-reflection and electromagnetic shielding that has excellent optical / electrical performance and high physical stability is of great significance for enhancing the anti-interference capability 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 is difficult to process 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] Therefore, there is still a contradiction between the high-quality, high-efficiency and high-reliability manufacturing of electromagnetic shielding and infrared anti-reflection curved surface microstructures. The existing processing technology cannot meet these requirements at the same time. It is urgent to develop an ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructures. Summary of the invention

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

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

[0007] An ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved microstructures comprises: a control system, an ultrafast laser, a beam expansion 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 control system controls the ultrafast laser to output a Gaussian beam, and after the Gaussian beam passes through the beam expansion module, the beam reflection module and the beam spatial shaping module in sequence, the control system controls the high-precision motion platform to focus the laser on the curved window surface with the assistance of the coaxial observation system, and then processes the embedded electromagnetic shielding grid and the infrared anti-reflection microstructure through contour fitting and processing path planning; wherein the beam expansion module is used to expand 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.

[0008] Furthermore, the Gaussian beam pulse wavelength output by the ultrafast laser is 1030 nm, and the pulse width ranges from 100 fs to 10 ps.

[0009] Furthermore, the beam expansion module is composed of a concave lens of -50 to -100 mm and a convex lens of 100 to 400 mm, and the spot diameter is expanded by 2 to 8 times after beam expansion.

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

[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, wherein the 4F focusing system is composed of a 50 to 200 mm convex lens and a 20 to 50 times objective lens. The expanded Gaussian beam is shaped into a Bessel beam I by the conical lens, and the Bessel beam I is compressed into a Bessel beam II with a spot diameter 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 rotational motion A-axis and a marble base, and the axes move in coordination to achieve precise control of the processing position.

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

[0014] Furthermore, 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 for illuminating the surface of the curved window.

[0015] Furthermore, the centers of the ultrafast laser, the beam expansion 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 reflector, the third reflector, the fourth reflector, the beam spatial shaping module and the coaxial observation system are packaged and connected as a whole, and move up and down synchronously with the linear motion Z axis to meet the processing requirements of different heights of the curved surface.

[0017] The beneficial effects of the present invention are:

[0018] (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.

[0019] (2) 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0022] Figure 3 Schematic diagram of the laser focus fitting curved window profile according to an embodiment of the present invention;

[0023] Figure 4 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;

[0024] Figure 5 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.

[0025] 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

[0026] 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.

[0027] In view of the existing problems, the present invention provides an ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructure, such as Figure 1 As shown. The device includes: a control system, an ultrafast laser, a beam expansion module, a beam reflection module, a beam space shaping module, a high-precision motion platform, a self-centering fixture, a curved window and a coaxial observation system; the control system controls the ultrafast laser to output a Gaussian beam, and after the Gaussian beam passes through the beam expansion module, the beam reflection module and the beam space shaping module in sequence, the control system controls the high-precision motion platform to focus the laser on the curved window surface with the assistance of the coaxial observation system, and then processes the embedded electromagnetic shielding grid and the infrared anti-reflection microstructure through contour fitting and processing path planning; wherein, the beam expansion module is used to expand the beam spot diameter, the beam reflection module is used to change the beam propagation direction, and the beam space shaping module is used to shape the Gaussian beam into a Bessel beam with a longer processing distance and focus it.

[0028] The Gaussian beam pulse wavelength output by the ultrafast laser is 1030nm, and the pulse width is 900fs. The beam expansion module is composed of a -50mm concave lens and a 200mm convex lens, and the spot diameter is expanded by 4 times after beam expansion. The beam reflection module includes a first reflector, a second reflector, a third reflector and a fourth reflector, and the angle between the reflector and the horizontal plane is 45°. The first reflector and the second reflector are used to reflect the 1030nm laser, the third reflector is a dichroic mirror, and the reflectivity of the 1030nm laser is greater than 98%, and the transmittance of the white light is greater than 90%, and the fourth reflector is a half-reflector, and the reflectivity and transmittance of the white light are both 50%. The beam spatial shaping module includes a conical lens with a cone apex angle of 175° 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 the Bessel beam I is compressed into a Bessel beam II with a spot diameter 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 each axis realizes precise control of the processing position. The self-centering fixture is coaxially fixed on the rotary motion A-axis. It has 4 jaws that can move synchronously toward the center, which are used to realize self-centering clamping of curved windows, such as Figure 2 As 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 curved window surface. The centers of the ultrafast laser, the beam expansion 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. The second reflector, the third reflector, the fourth reflector, the beam spatial shaping module and the coaxial observation system are packaged and connected as a whole, and move up and down synchronously with the linear motion Z axis to meet the processing requirements of curved surfaces at different heights.

[0029] Figure 3 to Figure 5The specific process of processing electromagnetic shielding and infrared anti-reflection composite microstructures by ultrafast laser processing device for electromagnetic shielding and infrared anti-reflection curved microstructures is given. First, with the assistance of the coaxial observation system, the high-precision motion platform is controlled to drive the laser focus to sample the outer surface of the curved window coated with 3μm thick photoresist, and the coordinate parameters of 30 laser focuses when they just touch the surface of the curved window are recorded, and the surface contour is fitted. Subsequently, the control system plans the processing paths for processing electromagnetic shielding and infrared anti-reflection composite microstructures on the upper and lower surfaces of the curved window respectively. Next, the laser focus is focused on the lower surface of the curved window, the laser processing parameters and platform motion parameters are set, and the focus is always focused on the lower surface of the curved window through the linkage of the rotary motion A axis with the linear motion X axis and the linear motion Z axis. The focus is moved from the inside to the outside according to the Archimedean equidistant spiral with a period of 3.6μm, and a V-shaped groove infrared anti-reflection microstructure with a period of 3.6μm, a width of 2μm, and a depth of 2μm is processed. Then, the laser focus is focused on the upper surface of the curved window, and the laser processing parameters and platform motion parameters are set. Through the linkage of the linear motion X-axis, the linear motion Y-axis, and the linear motion Z-axis, the focus is always focused 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. Finally, the processed curved window is taken out, and a copper film with a thickness of 3μm is plated in the mesh groove of the curved window through a magnetron sputtering coating process, and then the coated curved window is placed in a degumming solvent for cleaning, and the embedded metal mesh is retained after removing the protective glue, thereby obtaining an electromagnetic shielding and infrared anti-reflection curved microstructure.

[0030] 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 processing device for electromagnetic shielding and infrared anti-reflection curved surface microstructure, characterized in that: include: A control system, an ultrafast laser, a beam expansion 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 control system controls the ultrafast laser to output a Gaussian beam, and after the Gaussian beam passes through the beam expansion module, the beam reflection module and the beam spatial shaping module in sequence, the control system controls the high-precision motion platform to focus the laser on the curved window surface with the assistance of the coaxial observation system, and then processes the embedded electromagnetic shielding grid and the infrared anti-reflection microstructure through contour fitting and processing path planning; wherein the beam expansion module is used to expand 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.

2. The electromagnetic shielding and infrared anti-reflection curved surface microstructure ultrafast laser processing device according to claim 1 is characterized in that: The Gaussian beam pulse wavelength output by the ultrafast laser is 1030nm, and the pulse width ranges from 100fs to 10ps.

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

4. The electromagnetic shielding and infrared anti-reflection curved surface microstructure ultrafast laser processing device 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 reflector and the horizontal plane is 45°, the first reflector and the second reflector are used to reflect 1030nm laser, the third reflector is a dichroic mirror, the reflectivity of 1030nm laser is greater than 98%, and the transmittance of white light is greater than 90%, and the fourth reflector is a semi-reflective mirror, and the reflectivity and transmittance of white light are both 50%.

5. The electromagnetic shielding and infrared anti-reflection curved surface microstructure ultrafast laser processing device according to claim 1, characterized in that: 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 is composed of a 50-200mm convex lens and a 20-50x objective lens. The expanded Gaussian beam is shaped into a Bessel beam I by the conical lens, and the Bessel beam I is compressed into a Bessel beam II with a spot diameter less than 2μm by the 4F focusing system.

6. The electromagnetic shielding and infrared anti-reflection curved surface microstructure ultrafast laser processing device 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, and the coordinated motion of each axis realizes precise control of the processing position.

7. The electromagnetic shielding and infrared anti-reflection curved surface microstructure ultrafast laser processing device according to claim 1, characterized in that: The self-centering clamp is coaxially fixed on the rotary motion A axis, and has four clamping jaws that can move synchronously toward the center, so as to realize the self-centering clamping of the curved window.

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

9. The electromagnetic shielding and infrared anti-reflection curved surface microstructure ultrafast laser processing device according to claim 1, characterized in that: The centers of the ultrafast laser, the beam expansion 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 aconic 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 electromagnetic shielding and infrared anti-reflection curved surface microstructure ultrafast laser processing device according to claim 1, characterized in that: The second reflector, the third reflector, the fourth reflector, 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 motion Z axis to meet the processing requirements of different heights of the curved surface.

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