Laser processing apparatus and method for complex microstructures

Abstract

The application discloses a kind of laser processing device and method of complex microstructure, solve the processing technology of existing complex microstructure Processing flexibility is poor, processing quality is low, processing precision is low, and the problem of low processing efficiency.The application is provided with numerical aperture conversion unit, and driving unit is also provided for focusing unit, can be flexibly adjusted according to the structure size required by the structure to be processed Focal spot size of processing laser, can also be processed layer by layer to processing position, improve the flexibility and processing precision of processing, and the overall structure is simple, can realize three-dimensional processing of complex microstructure without relying on multi-axis motion platform, avoid complex trajectory programming process.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser processing device and method, in particular to a laser processing device and method for complex microstructure. BACKGROUND

[0002] Complex microstructure plays a vital role in basic research, and has unique advantages in improving the optical, mechanical and biological properties of solid surfaces. For example, in nature, organisms that have evolved over millions of years exhibit unique abilities, such as the unique complex microstructure of butterfly, bird, insect, mosquito compound eye, lotus leaf, beetle, gecko, and pitcher plant, which exhibits excellent structural color, antifogging, adhesion, detachment, super-slip and other functions. Moreover, by complex design of microstructure, it can achieve the combined function of light trapping and self-cleaning. At the same time, by preparing complex microstructure inside the transparent medium, it has great potential in the preparation of various microfluidic chips and three-dimensional optical waveguide arrays.

[0003] Complex microstructure exhibits various characteristics by controlling the morphology and arrangement of micro-nano structures on the surface of macroscopic materials, and has gradually become a research hotspot in many fields at home and abroad. It has shown great potential in new energy, aerospace, microelectronic devices and flexible photonic devices, micro-optical devices, micro robots, etc. For example, the micro-nano structure of semiconductor detectors can effectively improve the photon coupling efficiency and equivalent optical path, break through the absorption limit of traditional bulk materials, improve the quantum efficiency of optoelectronic devices and reduce the dark current of the devices, and provide a new technical means for the research of high-performance infrared detectors. For another example, the manufacturing quality of complex microstructure on the surface of aircraft rudder / wing and aircraft engine inlet casing support plate determines its anti-icing function, which is crucial to maintaining its aerodynamic shape, maneuverability and stability. It can be seen that micro-nano structure manufacturing, as the basis for the application of micro-nano technology, is considered one of the focuses of international competition in advanced manufacturing technology.

[0004] The processing methods of complex microstructure include:

[0005] 1) Photolithography: refers to the use of ultraviolet light, photoresist and mask for selective exposure, transferring the mask pattern to the substrate material, then removing the unexposed area photoresist through development process, leaving the photoresist as an etching resist in the etching process, and then using etching reagent for etching to obtain the desired structure on the material surface. However, this method has high preparation cost and is difficult to achieve depth and large size lithography.

[0006] 2) Chemical etching: refers to removing the protective film of the etching area after exposure and development, and contacting the chemical solution during etching to achieve the effect of dissolution and corrosion, forming a concave-convex or hollow effect, but the etching precision is poor.

[0007] 3) Micro-machining technology: refers to the use of ultra-precision machining equipment to realize the preparation of complex microstructure, mainly applied to the preparation of microstructure on the surface of metal, ceramic and other materials, but the preparation ability in the material is insufficient.

[0008] 4) Electron beam lithography: refers to that under the control of computer, according to the required pattern, the focused electron beam is used to expose the resist on the substrate, and the areas with different solubility are generated in the resist. According to the solubility characteristics of different areas, the developer with selectivity is used for development, and the part of the resist with strong solubility is removed, and the part with poor solubility or insolubility is retained, so that the required resist pattern can be obtained. However, the manufacturing efficiency of this technology is low, and the preparation time is long.

[0009] 5) Ion beam etching: refers to that argon is decomposed into argon ions under the action of glow discharge principle, and the argon ions are physically bombarded on the sample surface through the acceleration of anode electric field to achieve etching. Focused ion beam and focused electron beam are both charged particles that are focused to a fine beam on the sample surface through electromagnetic field to complete processing, and the difference between the two is the quality of the processing particle source. Ion beam processing has high quality, but has high requirements for mask (mask manufacturing precision, long preparation period), and has insufficient curved surface preparation capability.

[0010] 6) Nanoimprint: refers to the photosensitive chemical action of high polymer material, which changes the solubility of high polymer material in a specific developing solution, so that the exposed part and the unexposed part are dissolved to form a surface micro-nano structure. This technology has problems of insufficient preparation width and curved surface processing capability.

[0011] 7) Femtosecond laser direct writing: femtosecond laser has extremely high energy density (up to about 1022W / cm2), extremely small action space (about 10-10m), and extremely short action time (about 10-15s), which makes its physical effect and action mechanism completely different from traditional manufacturing methods. It can precisely control the shape and property of the material through the transient nonlinear and non-equilibrium process, and can process any solid material with high quality and high precision. However, femtosecond laser currently only relies on one-dimensional motion platform, and can only realize the preparation of simple shapes such as cone and groove, and has insufficient preparation capability for complex microstructure three-dimensional structure. SUMMARY

[0012] In order to solve the technical problems of poor processing flexibility, low processing quality, low processing precision and low processing efficiency of the existing complex microstructure processing technology, the application provides a laser processing device and method for complex microstructure.

[0013] In order to achieve the above purpose, the application adopts the following technical scheme:

[0014] A laser processing device for complex microstructures, characterized in that:

[0015] The laser processing device comprises a laser source, a numerical aperture conversion unit and a focusing unit arranged in sequence, and a driving unit;

[0016] The laser source is used for emitting processing laser;

[0017] The numerical aperture conversion unit is used for adjusting the numerical aperture of the processing laser;

[0018] The focusing unit is used for focusing the processing laser with adjusted numerical aperture on a component to be processed;

[0019] The driving unit is connected with the focusing unit and is used for driving the focusing unit to move along the z-axis direction, wherein the z-axis is perpendicular to the surface of the position to be processed on the component to be processed.

[0020] Further, the numerical aperture conversion unit comprises a collimating zoom lens group, a first variable diaphragm and a reflecting mirror arranged in sequence along the light path of the processing laser;

[0021] The collimating zoom lens group is used for adjusting and collimating the beam diameter of the processing laser;

[0022] The first variable diaphragm is arranged at the exit end of the collimating zoom lens group and is used for filtering stray light of the adjusted processing laser;

[0023] The reflecting mirror is used for reflecting the processing laser with filtered stray light to the focusing unit.

[0024] Further, the numerical aperture conversion unit comprises a spatial light modulator, a second variable diaphragm, a 4f system and a filter arranged in sequence along the light path of the processing laser;

[0025] The spatial light modulator is used for adjusting the beam diameter of the processing laser by loading different holograms, or loading different diaphragm phase patterns and grating patterns, or loading different Fresnel lens phase patterns and grating patterns;

[0026] The second variable diaphragm is arranged at the exit end of the spatial light modulator and is used for filtering stray light of the adjusted processing laser;

[0027] The 4f system is used for spatially filtering the processing laser with filtered stray light and reflecting it to the focusing unit;

[0028] The filter is used for adjusting the energy of the reflected processing laser.

[0029] Further, the filter is a liquid crystal filter.

[0030] Furthermore, the focusing unit is a 20x microscope objective with a maximum incident pupil diameter D of 5mm, a maximum numerical aperture NAmax of 0.45, a focal length of 10mm, and a depth of focus of 1.56μm.

[0031] A laser processing method for complex microstructures, employing the aforementioned laser processing apparatus for complex microstructures, is characterized by comprising the following steps:

[0032] Step 1: Based on the driving accuracy of the driving unit along the z-axis, slice the workpiece at the position to be processed along the direction perpendicular to the z-axis at equal intervals, and obtain the position height h of each slice along the z-axis and the diameter d of each slice along the direction perpendicular to the z-axis.

[0033] Step 2: Based on the diameter d of each slice, obtain the required processing focal spot diameter φ for each slice;

[0034] Step 3: Calculate the numerical aperture NA and corresponding depth of focus DOF ​​of the processing laser for each slice based on the required processing focal spot diameter φ for each slice.

[0035] Step 4: Compare the calculated depth of focus (DOF) for each slice with the driving accuracy of the drive unit along the z-axis.

[0036] If the focal depth (DOF) corresponding to the i-th slice is i If the driving accuracy of the driving unit along the z-axis is less than or equal to the driving accuracy of the driving unit, then the position height h of the i-th layer slice is obtained from the position height h of each layer slice calculated in step 1. i And record it;

[0037] If the focal depth (DOF) corresponding to the i-th slice is i If the driving accuracy of the driving unit along the z-axis is greater than the driving accuracy of the i-th slice, then the depth of focus (DOF) is calculated according to the i-th slice. i Retrieve the position and height h of the i-th slice i 'and record;

[0038] Step 5: Start the laser source. The laser source emits a processing laser, and the processing laser emitted from the focusing unit is aligned with the position to be processed on the component.

[0039] Step 6: The driving unit drives the focusing unit to move based on the height of each position recorded in Step 4, so that the focusing unit can focus the processing laser to the corresponding slice position on the component to be processed.

[0040] Step 7: The numerical aperture transformation unit adjusts the numerical aperture of the processing laser to the numerical aperture NA calculated in Step 3 that corresponds to the corresponding layer slice.

[0041] Step 8, the corresponding layer slice position of the to-be-processed component is processed by the processing laser with the adjusted numerical aperture until the processing is completed at all slice layering positions corresponding to the position heights recorded in step 4.

[0042] Further, step 7 is specifically:

[0043] The collimating and zooming lens group adjusts the numerical aperture of the processing laser to the numerical aperture NA corresponding to the first layer slice calculated in step 3 and collimates;

[0044] The first variable diaphragm filters out stray light of the adjusted processing laser;

[0045] The mirror reflects the processing laser after filtering out the stray light to the focusing unit.

[0046] Further, step 7 is specifically:

[0047] According to the numerical aperture NA corresponding to the first layer slice calculated in step 3, the corresponding hologram is loaded to the spatial light modulator, or the corresponding diaphragm phase pattern and grating pattern are loaded, or the corresponding Fresnel lens phase pattern and grating pattern are loaded, so that the spatial light modulator adjusts the beam diameter of the processing laser accordingly;

[0048] The second variable diaphragm filters out stray light of the adjusted processing laser;

[0049] 4f system performs spatial filtering on the processing laser after filtering out the stray light to improve the beam quality and reflects it to the focusing unit;

[0050] The filter adjusts the energy of the reflected processing laser.

[0051] The beneficial effects of the present application are:

[0052] 1. The laser processing device and method for complex microstructure provided by the present application set a numerical aperture variable unit, and also set a driving unit for the focusing unit, which can flexibly adjust the focal spot size of the processing laser according to the required structure size of the to-be-processed structure, and can also process the processing position layer by layer, improve the flexibility and processing precision of the processing, and the overall structure is simple, which can realize three-dimensional processing of complex microstructure without relying on multi-axis motion platform, avoiding the complex trajectory programming process.

[0053] 2. The laser processing device and method for complex microstructure provided by the application improves the processing quality, and for the previous variable-diameter materials, such as elliptical or beam-waist structure, the processing laser needs to repeatedly track in space for processing, and cannot be formed at one time, especially the processing of the internal structure of the material, the same position of the material needs to be irradiated for multiple times, resulting in serious laser heat influence. The application only needs to be processed once, greatly inhibits the thermal effect (recasting, cracking, recrystallization, etc.) of the surface of the material, reduces the roughness of the surface of the material, and greatly improves the manufacturing quality.

[0054] 3. When the traditional laser processing device processes the internal part of the component to be processed with different thicknesses in three dimensions, at least a three-dimensional motion platform is used to change the focal point position, then a variable error of the theoretical position of the focal point in the material and the actual position of the focal point is introduced, and an error of the final processing appearance is caused; the laser processing device and method for complex microstructure provided by the application only have one-dimensional motion of the driving unit y along the Z-axis direction, the complex appearance material preparation is completed by changing the focal spot size, the error source is less, and the precision is high.

[0055] 4. The laser processing device and method for complex microstructure provided by the application can form the variable-diameter structure at one time, does not need to repeatedly track multiple times for manufacturing, greatly reduces the processing time, and improves the processing efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 Fig. 1 is a structure schematic diagram of the laser processing device for complex microstructure according to the first embodiment of the application;

[0057] Figure 2 Fig. 2 is a slice layering diagram of the component to be processed in the embodiment of the application, (a) is an equal-interval slice layering diagram obtained in step 1, and (b) is a slice layering diagram to be processed recorded in step 4,

[0058] Figure 3 Fig. 3 is a structure schematic diagram of the laser processing device for complex microstructure according to the second embodiment of the application;

[0059] Figure 4 Fig. 4 is a structure schematic diagram of the laser processing device for complex microstructure according to the third embodiment of the application.

[0060] REFERENCE NUMERALS:

[0061] 1-laser source, 211-collimating and variable magnification lens group, 212-first variable diaphragm, 213-reflection mirror, 221-space light modulator, 222-second variable diaphragm, 223-4f system, 224-filter, 3-focusing unit, 4-component to be processed. DETAILED DESCRIPTION

[0062] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0063] Embodiment one

[0064] The laser processing device for complex microstructure provided by the embodiment of the present application comprises a laser source 1, a numerical aperture conversion unit and a focusing unit 3 arranged in sequence, and a driving unit. Figure 1 The laser source 1 is used for emitting processing laser.

[0065] The laser source 1 is used for emitting processing laser.

[0066] The numerical aperture conversion unit comprises a collimating zoom lens group 211, a first variable diaphragm 212 and a reflecting mirror 213 arranged in sequence on the light path thereof along the processing laser exit direction; the collimating zoom lens group 211 is used for adjusting and collimating the beam diameter of the processing laser; the first variable diaphragm 212 is arranged at the exit end of the collimating zoom lens group 211 and is used for filtering stray light of the adjusted processing laser; and the reflecting mirror 213 is used for reflecting the processing laser after filtering stray light to the focusing unit 3.

[0067] The focusing unit 3 is used for focusing the processing laser after numerical aperture adjustment on a member to be processed 4. In this embodiment, the focusing unit 3 is preferably a 20 times microscopic objective lens, the maximum entrance pupil diameter D thereof is 5 mm, the numerical aperture NA thereof is 0.45, the focal length thereof is 10 mm, and the focal depth thereof is 1.56 μm.

[0068] The driving unit is connected with the focusing unit 3 and is used for driving the focusing unit 3 to move along the z-axis direction, the z-axis being the direction perpendicular to the surface of the position to be processed on the member to be processed 4.

[0069] The processing laser incident to the collimating zoom lens group 211 and the first variable diaphragm 212 can change the beam entrance aperture Dn of the focusing unit, so that the aperture Dn of the beam can be flexibly adjusted, but the maximum value thereof should be less than the pupil diameter or entrance pupil of the focusing unit (microscopic objective lens or focusing lens group), at this time, the numerical aperture of the focusing unit changes to NA=Dn / 2f, wherein f is the focal length of the focusing unit, wherein the maximum NA=D / 2f, D is the maximum pupil distance of the microscopic objective lens, and D is a fixed value after the focusing unit is selected, and NA=D / 8f. max min

[0070] ​​When the numerical aperture NA changes, the diameter of the focused spot is φ = 1.22λ / NA, where λ is the laser wavelength; it can be seen that the size of the focused spot increases with the decrease of the numerical aperture, and thus φ = 1.22λ / NA, the laser spot can be switched at will in the range of [φ, φ] min = 1.22λ / NA max , φ max = 1.22λ / NA min , the laser spot can be switched at will in the range of [φ, φ] min , φ max ]. When the numerical aperture changes, the focal depth DOF = (2nλNA 2 ) / (n 2 -NA 2 )c can be seen that the laser focal depth decreases with the increase of the numerical aperture; n is the refractive index of the objective lens, λ is the laser wavelength, NA is the numerical aperture, and c is the speed of light in vacuum. Therefore, any complex microstructure can be layered according to the focal depth DOF n , as shown in Figure 2 (b), and thus the layering interval is not equal interval, and is varied at will in the range of [DOF min , DOF max ].

[0071] The above device is used for laser processing, and the specific steps are as follows:

[0072] Step 1, according to the driving precision of the driving unit along the z-axis direction, as shown in Figure 2 (a), the to-be-processed position on the to-be-processed member 4 is equally spaced layered and sliced along the direction perpendicular to the z-axis, and the position height h of each slice along the z-axis direction and the diameter d of each slice along the direction perpendicular to the z-axis are obtained;

[0073] Step 2, according to the diameter d of each slice, the processing focal spot diameter φ required by each slice is obtained;

[0074] Step 3, according to the processing focal spot diameter φ required by each slice, the processing laser numerical aperture NA corresponding to each slice and the corresponding focal depth DOF are calculated;

[0075] Step 4, compare the focal depth DOF corresponding to each slice calculated with the driving precision of the driving unit along the z-axis direction;

[0076] If the focal depth DOF i corresponding to the i-th slice is less than or equal to the driving precision of the driving unit along the z-axis direction, the position height h i of the i-th slice is obtained from the position height h of each slice calculated in step 1 and recorded;

[0077] If the focal depth DOF igreater than the driving precision of the driving unit along the z-axis direction, then the focus depth DOF corresponding to the i-th layer slice is calculated according to the driving precision of the driving unit along the z-axis direction i reacquire the position height h of the i-th layer slice i recorded; obtain the slice layering to be processed as shown in Figure 2 (b).

[0078] Step 5, start the laser source 1, the laser source 1 emits processing laser, and the processing laser emitted by the focusing unit 3 is aligned with the to-be-processed position on the to-be-processed component 4;

[0079] Step 6, the driving unit drives the focusing unit 3 to move based on the position height of each position recorded in step 4, so that the focusing unit 3 can focus the processing laser to the corresponding layer slice position on the to-be-processed component 4;

[0080] Step 7, the collimating and variable magnification lens group 211 adjusts the numerical aperture of the processing laser to the numerical aperture NA corresponding to the first layer slice calculated in step 3 and collimates it; the first variable diaphragm 212 filters the stray light of the adjusted processing laser; the reflecting mirror 213 reflects the processing laser after filtering the stray light to the focusing unit 3.

[0081] Step 8, the corresponding layer slice position on the to-be-processed component 4 is processed by the processing laser after the numerical aperture adjustment, until all the slice layering positions corresponding to the position heights recorded in step 4 are processed.

[0082] As shown in Figure 4 , after the processing of one of the to-be-processed positions on the to-be-processed component 4 is completed according to the above steps, the entire device is shifted, the processing laser is aligned with the next to-be-processed position, and the processing is performed again.

[0083] Example Two

[0084] A laser processing device for complex microstructure, used for processing the complex flow channel inside the quartz optical fiber glass (to-be-processed component), as shown in Figure 3 , the laser processing device comprises a laser source 1, a numerical aperture variable unit and a focusing unit 3 arranged in sequence, and a driving unit.

[0085] The laser source 1 is used for emitting processing laser.

[0086] The numerical aperture variable unit comprises, in sequence along the direction of the machining laser exiting, a spatial light modulator 221, a second variable diaphragm 222, a 4f system 223, and a filter 224; the spatial light modulator 221 is used for adjusting the beam diameter of the machining laser by loading different holograms, or loading corresponding diaphragm phase patterns and grating patterns, or loading different Fresnel lens phase patterns and grating patterns; the second variable diaphragm 222 is arranged at the exit end of the spatial light modulator 221 and is used for filtering stray light of the adjusted machining laser; the 4f system 223 is used for spatially filtering the machining laser after the stray light is filtered and reflecting it to the focusing unit 3; and the filter 224 is used for adjusting the energy of the reflected machining laser. The filter 224 is a liquid crystal filter.

[0087] When the spatial light modulator 221 loads the diaphragm phase pattern and the grating pattern, the center circular phase of the diaphragm phase pattern is black 0 and gray 15, so that the center 0-order light beam directly passes through, the grating phase diffracts the ±1-order gratings to other angles and is intercepted by the subsequent fixed second variable diaphragm 222, and then the 4f system 223 ensures that the light beam is projected to the pupil of the microscope objective. When the aperture is large, the transmittance of the liquid crystal filter is reduced. When the aperture is small, the incident energy is increased through the liquid crystal filter.

[0088] The spatial light modulator 221 can also load the Fresnel lens phase pattern and the grating pattern, change the focal length of the lens by different annular intervals to relatively converge the light beams into different beam apertures, add grating phase information, flexibly adjust the diffraction efficiency of the light beam, and thus achieve the purpose of online regulating and controlling the energy. It is worth noting that this way changes the beam divergence angle, and when the numerical aperture is changed, the position of the spatial focus is changed, which is compensated by a one-dimensional motion platform.

[0089] The focusing unit 3 is used for focusing the machining laser after the numerical aperture is adjusted to the member to be machined 4. In this embodiment, the focusing unit 3 is preferably a 20 times microscope objective, the maximum incident pupil diameter D of which is 5 mm, the numerical aperture NA is 0.45, the focal length is 10 mm, and the focal depth is 1.56 μm. The beam aperture of the machining laser incident to the microscope objective varies in the interval [3 mm, 9 mm]. The minimum numerical aperture NA min = 0.15.

[0090] When the numerical aperture changes, the diameter of the focused spot is φ = 1.22λ / NA, where λ is the wavelength of the incident laser; it can be seen that the focused spot of the focused spot increases with the decrease of the numerical aperture, where φ min = 1.22λ / 0.45 = 2.88 μm, φ max = 1.22λ / NA min = 8.6 μm, and the laser spot can be switched at will in the interval [2.88 μm, 8.6 μm].

[0091] When the numerical aperture changes, the focal depth DOF = (2nλNA 2 ) / (n 2 -NA 2 ), it can be seen that the laser focal depth changes in the interval [0.17μm, 1.56μm].

[0092] The driving unit is connected with the focusing unit 3, and is used to drive the focusing unit 3 to move along the z-axis direction, and the z-axis is perpendicular to the surface of the to-be-processed position on the to-be-processed component 4.

[0093] The specific steps of laser processing by using the above device are as follows:

[0094] Step 1, according to the driving precision of the driving unit along the z-axis direction, the to-be-processed position on the to-be-processed component 4 is equally spaced sliced along the direction perpendicular to the z-axis, and the position height h of each slice along the z-axis direction and the diameter d of each slice along the direction perpendicular to the z-axis are obtained;

[0095] Step 2, based on the previous orthogonal process experiment, the required processing focal spot diameter φ of each slice is obtained according to the diameter d of each slice;

[0096] Step 3, based on the focal spot and focal depth calculation formula, the processing laser numerical aperture NA corresponding to each slice and the corresponding focal depth DOF are calculated according to the required processing focal spot diameter φ of each slice;

[0097] Step 4, the focal depth DOF corresponding to each slice calculated in step 1 is compared with the driving precision of the driving unit along the z-axis direction;

[0098] If the focal depth DOF i of the i-th slice is less than or equal to the driving precision of the driving unit along the z-axis direction, the position height h of the i-th slice is obtained from the position height h of each slice calculated in step 1 i and recorded;

[0099] If the focal depth DOF i of the i-th slice is greater than the driving precision of the driving unit along the z-axis direction, the position height h of the i-th slice is reacquired according to the focal depth DOF i of the i-th slice i ’ and recorded;

[0100] Step 5, the laser source 1 is started, the laser source 1 emits processing laser, and the processing laser emitted by the focusing unit 3 is aligned with the to-be-processed position on the to-be-processed component 4;

[0101] Step 6, the driving unit drives the focusing unit 3 to move based on the position height recorded in step 4, so that the focusing unit 3 can focus the machining laser to the corresponding layer slice position on the component 4 to be machined;

[0102] Step 7, according to the numerical aperture NA corresponding to the first layer slice calculated in step 3, a corresponding hologram is loaded to the spatial light modulator 221, or a corresponding diaphragm phase pattern and grating pattern is loaded, or a corresponding Fresnel lens phase pattern and grating pattern is loaded, so that the spatial light modulator 221 adjusts the beam diameter of the machining laser accordingly; the second variable diaphragm 222 filters the stray light of the adjusted machining laser; the 4f system 223 spatially filters the machining laser filtered of stray light to improve the beam quality and reflects it to the focusing unit 3; the filter 224 adjusts the energy of the reflected machining laser, for example, when the NA value becomes larger, the filter increases the light energy transmittance, and when the NA value becomes smaller, the filter reduces the light energy transmittance.

[0103] The aperture pattern hologram is composed of a binary grating and a geometric mask pattern. The binary grating is composed of two different gray scale values for generating a π phase shift, and the two gray scale values are set as G1=0 and G2=128; the geometric mask pattern is a target pattern with a gray scale value of 0 (including circular, triangular, rectangular and other patterns), which is used to generate a 0 phase shift, change the size and shape of the laser beam diameter, and has a function similar to a mirror, as shown in Figure 3 .

[0104] The Fresnel lens + two-dimensional grating hologram is composed of two different gray scale values, and the two gray scale values are set as G1=0 and G2=128. By adjusting the annular interval of the Fresnel lens to change the focal length of the lens and thus form different beam diameters, the numerical aperture of the beam is changed. On this basis, a superimposed grating hologram can also be selected to change the fringe interval of the grating to flexibly adjust the diffraction efficiency of the beam to achieve the purpose of online energy control. It is worth noting that the biggest difference between this method and the aperture diaphragm hologram is that the beam divergence angle before entering the focusing microscope is changed, so the focal point position in the Z-axis direction is changed, which can be compensated by a one-dimensional motion platform.

[0105] Step 8, the machining laser with the adjusted numerical aperture is used to machine the corresponding layer slice position of the component 4 to be machined until the slice layering positions corresponding to the position heights recorded in step 4 are all machined.

[0106] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1.A laser processing method for complex microstructures, comprising the following steps: Step 0, preparing a laser processing device for complex microstructures, comprising a laser source (1), a numerical aperture conversion unit, a focusing unit (3) and a driving unit arranged in sequence, wherein the laser source (1) is used for emitting processing laser; the numerical aperture conversion unit is used for adjusting the numerical aperture of the processing laser; the focusing unit (3) is used for focusing the processing laser with adjusted numerical aperture on a workpiece (4) to be processed; the driving unit is connected with the focusing unit (3) and used for driving the focusing unit (3) to move along the z-axis direction, wherein the z-axis is perpendicular to the surface of the position to be processed on the workpiece (4); and the numerical aperture conversion unit comprises a spatial light modulator (221); Step 1, according to the driving accuracy of the driving unit along the z-axis direction, equally spacing slicing the position to be processed on the workpiece (4) along the direction perpendicular to the z-axis direction, and obtaining the position height h of each slice along the z-axis direction and the diameter d of each slice along the direction perpendicular to the z-axis direction; Step 2, obtaining the processing focal spot diameter φ required by each slice according to the diameter d of each slice; Step 3, calculating the processing laser numerical aperture NA corresponding to each slice and the corresponding focal depth DOF according to the processing focal spot diameter φ required by each slice; Step 4, comparing the focal depth DOF corresponding to each slice with the driving accuracy of the driving unit along the z-axis direction; If the focal depth (DOF) corresponding to the i-th slice is i If the driving accuracy of the driving unit along the z-axis is less than or equal to the driving accuracy of the driving unit, then the position height h of the i-th layer slice is obtained from the position height h of each layer slice calculated in step 1. i And record it; If the focal depth (DOF) corresponding to the i-th slice is i If the driving accuracy of the driving unit along the z-axis is greater than the driving accuracy of the i-th slice, then the depth of focus (DOF) is calculated according to the i-th slice. i Retrieve the position and height h of the i-th slice i 'and record; Step 5, starting the laser source (1), and emitting processing laser by the laser source (1) so that the processing laser emitted by the focusing unit (3) is aligned with the position to be processed on the workpiece (4); Step 6, driving the focusing unit (3) to move based on the position height recorded in step 4 by the driving unit, so that the focusing unit (3) can focus the processing laser on the corresponding slice position on the workpiece (4); Step 7, loading the corresponding hologram into the spatial light modulator (221), or loading the corresponding diaphragm phase diagram and grating diagram, or loading the corresponding Fresnel lens phase diagram and grating diagram according to the numerical aperture NA corresponding to the first slice calculated in step 3, so that the spatial light modulator (221) adjusts the numerical aperture of the processing laser correspondingly; Step 8, processing the corresponding slice position on the workpiece (4) by the processing laser with adjusted numerical aperture until the slice layer positions corresponding to each position height recorded in step 4 are all processed. 2.The laser processing method for complex microstructures according to claim 1, characterized in that: in step 0, the numerical aperture conversion unit further comprises a second variable diaphragm (222), a 4f system (223) and a filter (224); step 7 further comprises filtering the stray light of the adjusted processing laser by the second variable diaphragm (222), spatial filtering the processing laser with filtered stray light by the 4f system (223) to improve the beam quality, and reflecting the processing laser to the focusing unit (3), and adjusting the energy of the reflected processing laser by the filter (224).

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