Three-dimensional topography analysis method and system for femtosecond laser processing of irregular surfaces

Abstract

A three-dimensional topography analysis method and system for femtosecond laser processing of irregular curved surfaces, belonging to the field of non-silicon micro-nano manufacturing technology. The present invention includes a femtosecond laser cooperative five-axis linkage precision translation stage system, a CCD imaging system, a three-dimensional topography microscopic imaging system, and a complex curved surface contour analysis system. The rotation center of the turntable of the five-axis machining platform, the center of the specially made clamped workpiece, and the center of the incident laser beam are on the same straight line. The present invention analyzes the component information of the sample to be processed; uses time-domain shaping, spatial-domain shaping, and frequency-domain shaping to cooperate for beam control, and directly acts the high-quality light spot after femtosecond laser shaping on the object surface, significantly improving the positioning accuracy, processing accuracy, and finished product rate of the sample. The present invention can not only perform a complete surface three-dimensional topography analysis on the processing area of the actual sample, but also feed back to the model reconstruction and code optimization before laser processing, further improving the precision of femtosecond laser processing.

Description

Technical Field

[0001] The present invention relates to a three-dimensional topography analysis method and system for femtosecond laser processing of irregular surfaces, belonging to the field of non-silicon micro-nano manufacturing technology. Background Art

[0002] Advanced manufacturing technologies for difficult-to-machine materials are the key to the leapfrog improvement of the performance of national defense weapons, medical implants, electronic devices, etc. Inertial devices play an irreplaceable role in all-region, all-time, and all-weather autonomous navigation. Among them, the accuracy of three-axis floated gyroscopes directly affects the navigation / strike accuracy and strategic deterrence of strategic missiles, and the processing technology of the irregular surface of the hydrodynamic spiral groove determines the gyro accuracy and stability, thus affecting the advancement and practicality of strategic weaponry.

[0003] Currently, the processing of complex surfaces of hydrodynamic spiral grooves is usually carried out by ion beam etching and laser ablation methods, but there are still many problems: the processing accuracy of a single groove is very low, the consistency of multiple grooves is poor, the qualified rate of finished products is low, etc. The key to restricting these problems lies in the fact that in the actual processing process, the selection of experimental parameters cannot be accurately controlled, and the analysis of the three-dimensional topography of the sample after the completion of the complex irregular surface processing process cannot be fed back and optimized to the experimental processing steps. Therefore, there is an urgent need for a complete system of three-dimensional topography analysis methods for femtosecond laser processing of irregular surfaces to improve the accuracy and yield of actual processed samples. Summary of the Invention

[0004] The main purpose of the present invention is to provide a three-dimensional topography analysis method and system for femtosecond laser processing of irregular surfaces, which can not only perform a complete surface three-dimensional topography analysis on the processing area of the actual sample, but also be fed back to the model reconstruction and code optimization before laser processing, thereby significantly improving the accuracy of femtosecond laser processing of irregular surfaces and reducing the defective rate.

[0005] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0006] A three-dimensional topography analysis method for femtosecond laser processing of irregular surfaces disclosed by the present invention includes the following steps:

[0007] Step 1: According to the actual size and component information of the sample to be processed, fabricate a suitable clamping workpiece to ensure the normal operation of the high-precision five-axis machining platform.

[0008] Step 2: Detect the sensitivity of the charge-coupled device (CCD camera) and the five-axis displacement stage during the actual processing, and confirm the influence brought by instrument response and accidental errors. The charge-coupled device is a CCD camera.

[0009] Step 3. Calculate the femtosecond laser ablation threshold of the materials used and adjust the position of the laser focus: Locate the focus and mark the signal to make the imaging plane basically coincide with the focal plane, and record the real-time spot size and power for extracting and analyzing subsequent changes in laser parameters.

[0010] Step 4. Ensure the "three centers in one": Align the rotation center of the turntable of the five-axis machining platform, the center of the specially designed workpiece clamping, and the center of the incident laser beam on the same straight line to reduce machining errors.

[0011] Step 5. Import G-code that conforms to the actual machining conditions into the data reading module of the five-axis platform: It is necessary to use software to generate the theoretical model of the sample and determine the defocus distance of the laser focus, and then compensate the G-code. Under different working conditions of femtosecond laser rapid scanning, realize real-time tracking of the laser focus on complex three-dimensional surfaces.

[0012] Step 6. Three-dimensional topography analysis: Analysis of the surface topography composition, specific element distribution, depth and roughness of the machining area, and overall roundness and line profile.

[0013] Step 7. Three-dimensional model reconstruction: According to the specific information of the machining area obtained from the three-dimensional topography analysis, reconstruct the theoretical model of the irregular surface sample and repeatedly modify the G-code.

[0014] Step 8. Feedback and optimize the machining process: According to the modified model and code, change the positions of the two rotating axes B and C and the three displacement planes X, Y, and Z. After the machining is completed, return to Step 6 and Step 7 for iterative optimization until the three-dimensional topography analysis of femtosecond laser machining of irregular surfaces is achieved.

[0015] The present invention also discloses a three-dimensional topography analysis system for femtosecond laser machining of irregular surfaces, which is used to implement the three-dimensional topography analysis method for femtosecond laser machining of irregular surfaces.

[0016] The three-dimensional topography analysis system for femtosecond laser machining of irregular surfaces includes: ① a femtosecond laser collaborative five-axis linkage precision translation stage system, ② a CCD imaging system for irregular surfaces, ③ a three-dimensional topography microscopic imaging system, and ④ a complex surface contour analysis system.

[0017] The femtosecond laser collaborative five-axis linkage precision translation stage system is composed of a titanium sapphire femtosecond laser light source, a high-precision five-degree-of-freedom machining translation stage, and various basic optical elements. The femtosecond laser collaborative five-axis linkage precision translation stage system is used to achieve three-dimensional profiling of irregular surfaces. The five degrees of freedom include the X-axis, Y-axis, Z-axis, B-axis, and C-axis. The base of the platform includes an air-bearing vibration isolation platform and a marble support frame, and the laser machining error caused by environmental vibration is reduced through the platform base.

[0018] The CCD imaging system for irregular surfaces mainly consists of a white light illumination system and an industrial integrated camera system. The CCD imaging system includes a beam splitter, a reflector, a plano-convex lens, an optical element base, a long and narrow lens barrel, and a CCD camera. Among them, femtosecond laser is focused on the sample surface through reflectors, beam splitters, plano-convex lenses, etc. and generates reflected light. The reflected light is collected by the CCD camera after passing through the beam splitter, and real-time imaging observation is displayed on the image software to ensure the focus position and the processing situation during processing.

[0019] The three-dimensional morphology microscopic imaging system mainly consists of a laser confocal microscope, a coordinate measuring machine, a profilometer, a scanning electron microscope, a TOF-SIMS time-of-flight secondary ion mass spectrometer, and a white light interferometer. The laser confocal microscope is used to provide feedback on the processing results of planar samples of the same material. The coordinate measuring machine and the scanning electron microscope mainly reflect the basic morphological information of complex curved surface profiling. Data such as roundness and line profile of the surface of the processed sample are extracted through the profilometer and the white light interferometer, and the extracted data are used for fitting analysis and then optimization.

[0020] The complex curved surface contour analysis system is used for specific model reconstruction and code optimization compensation of different complex curved surface samples to optimize subsequent processing parameters.

[0021] Advantageous effects:

[0022] 1. A three-dimensional morphology analysis method and system for femtosecond laser processing of irregular surfaces disclosed by the present invention are not limited to the surface morphology analysis of the curved surface profiling of hemispherical hydrodynamic spiral grooves, and can also process and analyze various relatively complex irregular surfaces and heterogeneous surfaces of composite laminates, having universality and practicability.

[0023] 2. A three-dimensional morphology analysis method and system for femtosecond laser processing of irregular surfaces disclosed by the present invention, through the coordinated manner of time-domain shaping (regulating the pulse delay of femtosecond laser), spatial-domain shaping (flattening the beam to homogenize the electron distribution), and frequency-domain shaping (regulating the ablation threshold of surface materials), directly acts on the object surface with the high-quality light spot after femtosecond laser shaping, breaking through the efficiency limitation of traditional processing technologies and significantly improving the positioning accuracy, processing accuracy, and yield rate of the sample.

[0024] 3. A three-dimensional morphology analysis method and system for femtosecond laser processing of irregular surfaces disclosed by the present invention, jointly uses various algorithms to assist the process of model reconstruction, enables the processing results to form a closed-loop feedback with the selection of processing parameters, and significantly improves the accuracy and convenience of users in configuring experimental conditions. Description of the Drawings

[0025] The present invention will be further described below in conjunction with the drawings and embodiments:

[0026] Figure 1 It is a schematic structural diagram of an overall processing system provided by an embodiment of the present application, which can assist the femtosecond laser "optical knife" in processing irregular surfaces.

[0027] Figure 2 It is a schematic flowchart of a three-dimensional topography analysis method for femtosecond laser processing of irregular surfaces provided by an embodiment of the present application.

[0028] As Figure 3 shown, it is a roundness and line profile analysis of femtosecond laser processing of irregular surfaces provided by an embodiment of the present application.

[0029] As Figure 4 shown, it is a curve extraction analysis of the three-dimensional topography cross-section of femtosecond laser processing of irregular surfaces provided by an embodiment of the present application.

[0030] As Figure 5 shown, it is the variation law of the element distribution in the femtosecond laser processing irregular surface area with the thickness direction provided by an embodiment of the present application. Specific Embodiments

[0031] Embodiment 1

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] As Figure 1 shown, a three-dimensional topography analysis system for femtosecond laser processing of irregular surfaces disclosed in this embodiment includes: ① a femtosecond laser cooperative five-axis linkage precision translation stage system, ② a CCD imaging system for irregular surfaces, ③ a three-dimensional topography microscopic imaging system, and ④ a complex surface contour analysis system.

[0034] In the above system, the femtosecond laser cooperative five-axis linkage precision translation stage system is composed of a titanium-sapphire femtosecond laser light source, a high-precision five-degree-of-freedom processing translation stage, and various basic optical elements. It can realize the three-dimensional profiling technology for irregular surfaces. The five degrees of freedom include the X-axis, Y-axis, Z-axis, B-axis, and C-axis. The base of the platform is an air-bearing vibration isolation platform and a marble support frame, which can effectively reduce the laser processing error caused by environmental vibration.

[0035] The CCD imaging system for irregular surfaces is composed of a white light illumination system and an industrial-grade integrated camera system. The specific components include a beam splitter, a mirror, a plano-convex lens, an optical element base, a long barrel, a CCD camera, etc. Among them, the femtosecond laser is focused on the sample surface through a mirror, a beam splitter, a plano-convex lens, etc. and generates reflected light. The reflected light is collected by the CCD camera after passing through the beam splitter, and real-time imaging observation is displayed on the image software to ensure the focus position and the progress of processing during processing.

[0036] The three-dimensional topography microscopic imaging system is composed of a laser confocal microscope, a coordinate measuring machine, a profiler, a scanning electron microscope, a TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometer), and a white light interferometer. Among them, the laser confocal microscope can provide feedback on the processing results of planar samples of the same material. The coordinate measuring machine and the scanning electron microscope mainly reflect the basic topography information of complex curved surface profiling. The combined use of the profiler and the white light interferometer can extract data on the roundness and line profile of the surface of the machined sample, which is conducive to the subsequent fitting analysis and optimization process.

[0037] The complex curved surface contour analysis system mainly uses various model software and algorithms to finally achieve the specific model reconstruction of different complex curved surface samples and the optimization compensation of the code, facilitating the optimization of subsequent processing parameters.

[0038] As Figure 2 shown, this embodiment discloses a three-dimensional topography analysis method for femtosecond laser processing of irregular curved surfaces, which is implemented based on the three-dimensional topography analysis system for femtosecond laser processing of irregular curved surfaces. The specific steps are as follows:

[0039] S101. Confirm the basic information of the hemispherical sample as Figure 3 shown: basic components of the material, height, radius, line profile, and other information. This step is important for analyzing the model of the sample to be processed in the initial stage.

[0040] S102. Clamp the sample on a special workpiece, use a micrometer to take readings and observe. Ensure that the center of the sphere of the hemispherical sample coincides with the rotation center of the turntable with a small error.

[0041] S103. Locate the laser focus position on a common silicon wafer substrate and mark it on the image to make the imaging plane coincide with the laser focus plane, facilitating subsequent operations to find the focus on the complex curved surface.

[0042] S104. After adjusting the five-axis translation stage, move the focus position so that the center of the sphere of the hemispherical sample, the rotation center of the turntable, and the incident center of the laser are on a straight line, and record the coordinate values at this time for modification and compensation in the post-processing constructor.

[0043] S105. Use Inventor software to precisely construct the model of the sample to be profiled and use UG_NX software to export the actual area to be processed.

[0044] S106. Start the high-precision five-axis machining translation stage, import the original G code representing the actual machining area, and after preliminary debugging of the stage, prepare to start profiling the complex curved surface.

[0045] S107. Select the single-step operation experimental platform and repeat the enabling to determine the defocusing distance h from the lower end to the upper end of the sample during laser processing.

[0046] S108. Perform non-linear multiple compensations on the G code according to the ablation threshold F of the actual sample th and the defocusing distance h to ensure that there is basically no defocus phenomenon for the femtosecond laser during the processing.

[0047] S109. After the complex surface profiling is completed, remove the hemispherical sample and perform multiple ultrasonic cleanings with anhydrous ethanol and distilled water, and use a vernier caliper and a coordinate measuring machine to record the basic dimension information.

[0048] S110. Use an optical microscope and a scanning electron microscope to observe the three-dimensional morphology of the surface profiling, pay attention to the ablation area at the junction of the processed area and the original surface, and record the differences in accuracy under different processing parameters.

[0049] S111. Use the EDS Mapping mode to analyze the element distribution on the surface of the three-dimensional morphology, exclude the interference of impurity elements, and guide and optimize the selection of the processing technology.

[0050] S112. TOF-SIMS time-of-flight secondary ion mass spectrometry analysis: Confirm the changes in the thickness and basic composition of each laminated film after processing, and can also confirm the element distribution along the thickness direction.

[0051] S112. As Figure 4 shown, use a roundness instrument and a white light interferometer to perform surface profile analysis on the hemispherical sample, and export the test curve; use origin software and matlab software to analyze the error between the actual test curve and the model construction curve, and perform repeated compensation on the G code.

[0052] S113. TOF-SIMS time-of-flight secondary ion mass spectrometry analysis: Confirm the changes in the thickness and basic composition of each laminated film after processing, and can also confirm the element distribution along the thickness direction, and obtain the variation law of the element distribution in the irregular surface area processed by the femtosecond laser along the thickness direction as Figure 5 shown.

[0053] It should be understood that the sequence numbers of the steps in the above embodiments do not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0054] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A three-dimensional topography analysis method for femtosecond laser processing of irregular curved surfaces, characterized in that: comprising the following steps, Step 1: Fabricate a clamping workpiece adapted to the workpiece to be processed according to the actual size and component information of the workpiece to be processed, ensuring the normal operation of the high-precision five-axis machining platform; Step 2: Detect the sensitivity of the charge-coupled device and the five-axis displacement stage during the actual machining process, and confirm the influence brought by instrument response and accidental errors; the charge-coupled device is a CCD camera; Step 3: Calculate the femtosecond laser ablation threshold of the material used and debug the position of the laser focus: find the focus and mark the signal, make the imaging plane basically coincide with the focus plane, and record the real-time spot size and power for extracting and analyzing subsequent changes in laser parameters; Step 4: Ensure "the three centers coincide": make the rotation center of the rotary table of the five-axis machining platform, the center of the clamping workpiece, and the center of the incident laser beam be on the same straight line to reduce machining errors; Step 5: Import the G code that conforms to the actual machining conditions into the data reading module of the five-axis platform: it is necessary to use software to generate the theoretical model of the sample, determine the defocus distance of the laser focus, and then compensate the G code; under different working conditions of femtosecond laser rapid scanning, realize real-time tracking of the laser focus on complex three-dimensional surfaces; Step 6: Three-dimensional topography analysis: analysis of the surface topography composition, specific element distribution, depth and roughness of the machining area, overall roundness and line profile; Step 7: Three-dimensional model reconstruction: According to the specific information of the machining area obtained from the three-dimensional topography analysis, reconstruct the theoretical model of the irregular surface sample and modify the G code repeatedly; Step 8: Feedback and optimize the machining process: According to the modified model and code, change the positions of the two rotating axes of the B axis and C axis and the three displacement planes of the X axis, Y axis, and Z axis. After the machining is completed, return to Step 6 and Step 7 until the three-dimensional topography analysis of the femtosecond laser machining of the irregular surface is realized.

2. A three-dimensional topography analysis system for femtosecond laser processing of irregular surfaces, which is used to implement the three-dimensional topography analysis method for femtosecond laser processing of irregular surfaces as described in claim 1, and is characterized in that: including: ① A femtosecond laser cooperative five-axis linkage precision translation stage system, ② A CCD imaging system for irregular surfaces, ③ A three-dimensional topography microscopic imaging system, ④ A complex surface contour analysis system; The femtosecond laser cooperative five-axis linkage precision translation stage system is composed of a titanium sapphire femtosecond laser light source, a high-precision five-degree-of-freedom machining translation stage, and various basic optical elements; the femtosecond laser cooperative five-axis linkage precision translation stage system is used to realize three-dimensional profiling of irregular surfaces. The five degrees of freedom include the X axis, Y axis, Z axis, B axis, and C axis. The base of the platform includes an air-floating shock-absorbing platform and a marble support frame, and the laser machining error caused by environmental vibration is reduced through the platform base; The CCD imaging system for irregular surfaces is mainly composed of a white light illumination system and an industrial-grade integrated camera system; the CCD imaging system includes a beam splitter, a reflector, a plano-convex lens, an optical element base, a long and narrow lens barrel, and a CCD camera; among them, the femtosecond laser is focused on the sample surface through reflectors, beam splitters, plano-convex lenses, etc. and generates reflected light. The reflected light is collected by the CCD camera after passing through the beam splitter, and real-time imaging observation is displayed on the image software to ensure the focus position and the machining progress during machining; The three-dimensional topography microscopic imaging system mainly consists of a laser confocal microscope, a coordinate measuring machine, a profilometer, a scanning electron microscope, a TOF-SIMS time-of-flight secondary ion mass spectrometer, and a white light interferometer. The laser confocal microscope is used to provide feedback on the processing results of planar samples of the same material. The coordinate measuring machine and the scanning electron microscope mainly reflect the basic topography information of complex curved surface engraving. The roundness and line profile of the surface of the processed sample are extracted through the profilometer and the white light interferometer, and the extracted data is used for fitting analysis and further optimization.

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