Laser processing device and method for complex fine structure

Abstract

The invention discloses a laser machining device and method for a complex fine structure. The problems that an existing machining technology for the complex fine structure is poor in machining flexibility, low in machining quality, low in machining precision and low in machining efficiency are solved. The numerical aperture conversion unit is arranged, the driving unit is further arranged for the focusing unit, the size of a focus light spot of machining laser can be flexibly adjusted according to the required structure size of a to-be-machined structure, the machining position can be machined layer by layer, the machining flexibility and machining precision are improved, the overall structure is simple, and the machining cost is low. Three-dimensional machining of a complex fine structure can be achieved without depending on a multi-axis motion platform, and the complex track programming process is avoided.

Description

Technical Field

[0001] The invention relates to a laser processing device and method, and in particular to a laser processing device and method for complex microstructures. Background Art

[0002] Complex microstructures play a vital role in basic research, and they have unique advantages in improving the optical properties, mechanical properties and biomimetic properties of solid surfaces. For example, in nature, organisms that have evolved over tens of millions of years have shown unique abilities, such as butterflies, birds, insects, mosquito compound eyes, lotus leaves, beetles, geckos, pitcher plants, etc., which have excellent structural color, anti-reflection, anti-fog, adhesion, desorption, super-slippery and many other functions due to their unique complex microstructures on the surface. In addition, through the complex design of microstructures, they can achieve the composite functions of light trapping and self-cleaning. At the same time, by preparing complex microstructures inside transparent media, it also has great potential in the preparation of various microfluidic chips and three-dimensional optical waveguide arrays.

[0003] Complex microstructures have gradually become a research hotspot in many fields at home and abroad, by controlling the morphology and arrangement of micro-nanostructures on the surface of macroscopic materials to make them exhibit various characteristics. They have demonstrated promising capabilities in new energy, aerospace, microelectronic devices and flexible photonic devices, micro-optical devices, micro-robots, etc. For example: the micro-nanostructure 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 devices, and provide a new technical means for the research of high-performance infrared detectors. For another example, the manufacturing quality of complex microstructures on the surface of aircraft rudders / wings and aircraft engine intake casing support plates determines their anti-icing function, which is crucial to maintaining their aerodynamic shape, maneuverability and stability. It can be seen that micro-nanostructure manufacturing, as the basis for supporting the application of micro-nanotechnology, is considered to be one of the focuses of international competition in advanced manufacturing technology.

[0004] Processing methods for complex microstructures 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, and then removing the photoresist in the unexposed area through the development process. The remaining photoresist is used as the anti-etching layer in the etching process, and then etching is performed using an etching agent to obtain the desired structure on the material surface. However, this method has a high preparation cost and is difficult to achieve deep and large-size lithography.

[0006] 2) Chemical etching: refers to the removal of the protective film of the area to be etched after exposure and development. During etching, the area is exposed to chemical solutions to achieve the effect of dissolution and corrosion, forming a concave-convex or hollow-out effect, but its etching accuracy is poor.

[0007] 3) Micromachining technology: refers to the use of ultra-precision machining equipment to achieve the preparation of complex microstructures. It is mainly used in the preparation of surface microstructures of materials such as metals and ceramics, but the preparation capabilities inside the materials are insufficient.

[0008] 4) Electron beam etching: refers to the process of exposing the resist on the substrate with a focused electron beam under computer control according to the required graphics, producing areas with different solubility properties in the resist, and using a selective developer to develop the resist according to the solubility characteristics of different areas. The highly soluble parts of the resist are removed, and the poorly soluble or insoluble parts are retained, so that the required resist graphics 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 the decomposition of argon gas into argon ions under the action of the glow discharge principle. The argon ions are accelerated by the anode electric field and physically bombard the sample surface to achieve the etching effect. Both the focused ion beam and the focused electron beam are charged particles that are focused by the electromagnetic field to form a thin beam to the sample surface to complete the processing. The difference between the two lies in the quality of the processing particle source. The ion beam processing quality is higher, but the requirements for the mask are extremely high (the manufacturing accuracy of the mask and the preparation cycle are long), and the surface preparation capability is insufficient.

[0010] 6) Nanoimprinting: refers to the process based on the photosensitive chemical action of polymer materials, which changes the solubility of polymer materials in a specific developer, so that the exposed and unexposed parts are dissolved to form surface micro-nano structures. This technology has the problem of insufficient preparation format and curved surface processing capabilities.

[0011] 7) Femtosecond laser direct writing: The energy density of femtosecond laser is extremely high (up to about 1022W / cm2), the action space is extremely small (about 10-10m), and the action time is extremely short (about 10-15s). This makes its physical effect and action mechanism in the manufacturing process completely different from the traditional manufacturing method. It achieves the purpose of precise shape-controllable manufacturing through transient nonlinear and non-equilibrium processes with the material, and can process any solid material with high quality and high precision. However, at present, femtosecond laser only relies on one-dimensional motion platform, and can only realize the preparation of simple morphologies such as cone holes and grooves, and the preparation ability of three-dimensional structures with complex and fine morphologies is insufficient. Summary of the invention

[0012] In order to solve the technical problems of poor processing flexibility, low processing quality, low processing accuracy and low processing efficiency in the existing processing technology of complex and fine structures, the present invention provides a laser processing device and method for complex and fine structures.

[0013] In order to achieve the above object, the present invention adopts the following technical solution:

[0014] A laser processing device for complex microstructures, which is special in that:

[0015] It includes a laser source, a numerical aperture conversion unit and a focusing unit, and a driving unit which are arranged in sequence;

[0016] The laser source is used to emit processing laser;

[0017] The numerical aperture conversion unit is used to adjust the numerical aperture of the processing laser;

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

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

[0020] Furthermore, the numerical aperture conversion unit comprises a collimating zoom lens group, a first variable aperture and a reflector which are sequentially arranged on the optical path thereof along the emitting direction of the processing laser;

[0021] The collimating zoom lens group is used to adjust and collimate the beam diameter of the processing laser;

[0022] The first variable iris is arranged at the exit end of the collimating zoom lens group, and is used to filter out stray light of the adjusted processing laser;

[0023] The reflector is used to reflect the processing laser after the stray light is filtered out to the focusing unit.

[0024] Furthermore, the numerical aperture conversion unit includes a spatial light modulator, a second variable aperture, a 4f system and a filter which are sequentially arranged on the optical path thereof along the emitting direction of the processing laser;

[0025] The spatial light modulator is used to adjust the beam diameter of the processing laser by loading different holograms, or loading different aperture phase images and grating images, or loading different Fresnel lens phase images and grating images;

[0026] The second variable iris is arranged at the output end of the spatial light modulator, and is used to filter out stray light of the adjusted processing laser;

[0027] The 4f system is used to spatially filter the processing laser after filtering out stray light, and reflect it to the focusing unit;

[0028] The filter is used to adjust the energy of the reflected processing laser.

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

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

[0031] A laser processing method for complex microstructures, using the above-mentioned laser processing device for complex microstructures, is characterized in that it includes the following steps:

[0032] Step 1: According to the driving accuracy of the driving unit along the z-axis direction, the position to be processed on the component to be processed is sliced ​​in layers at equal intervals 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;

[0033] Step 2, according to the diameter d of each slice layer, obtain the processing focus spot diameter φ required for each slice layer;

[0034] Step 3, calculating the processing laser numerical aperture NA and the corresponding focal depth DOF corresponding to each slice layer according to the processing focus spot diameter φ required for each slice layer;

[0035] Step 4, comparing the calculated focal depth DOF corresponding to each slice with the driving accuracy of the driving unit along the z-axis direction;

[0036] If the focal depth DOF corresponding to the i-th slice 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 along the z-axis, 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 record;

[0037] If the focal depth DOF corresponding to the i-th slice i If the driving accuracy of the driving unit along the z-axis is greater than the driving accuracy of the driving unit along the z-axis, then the focal depth DOF corresponding to the i-th slice is i Re-obtain the position height h of the i-th layer slice i 'And record;

[0038] Step 5, start the laser source, the laser source emits a processing laser, and the processing laser emitted by the focusing unit is aligned with the position to be processed on the component to be processed;

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

[0040] Step 7, the numerical aperture conversion unit adjusts the numerical aperture of the processing laser to the numerical aperture NA corresponding to the corresponding layer slice calculated in step 3;

[0041] Step 8: Process the corresponding layer slicing positions of the component to be processed by the processing laser with the numerical aperture adjusted, until all the slice layering positions corresponding to the heights of the positions recorded in step 4 are processed.

[0042] Furthermore, step 7 is specifically as follows:

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

[0044] The first variable aperture filters out stray light from the adjusted processing laser;

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

[0046] Furthermore, step 7 is specifically as follows:

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

[0048] The second variable aperture filters out stray light from the adjusted processing laser;

[0049] The 4f system spatially filters the processing laser 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] Beneficial effects of the present invention:

[0052] 1. The present invention provides a laser processing device and method for complex microstructures, which is equipped with a numerical aperture conversion unit and a driving unit for the focusing unit. The focal spot size of the processing laser can be flexibly adjusted according to the required structural size of the structure to be processed, and the processing position can be processed layer by layer, thereby improving the processing flexibility and processing accuracy. Moreover, the overall structure is simple, and three-dimensional processing of complex microstructures can be achieved without relying on a multi-axis motion platform, thus avoiding a complex trajectory programming process.

[0053] 2. The laser processing device and method of complex microstructures provided by the present invention improve the processing quality. For the previous variable-caliber materials, such as elliptical or waisted structures, the processing laser needs to repeatedly move the trajectory in space for processing, and cannot be formed in one time. Especially for the processing of the internal structure of the material, the same position of the material needs to be irradiated multiple times, resulting in serious laser thermal effects. The present invention only needs to be processed once, which greatly suppresses the thermal effects (recasting, cracks, recrystallization, etc.) on the surface of the material, reduces the roughness of the surface of the material, and greatly improves the manufacturing quality.

[0054] 3. When traditional laser processing devices perform three-dimensional processing on the interior of components to be processed of different thicknesses, at least a three-dimensional motion platform is used to change the focal position, which will introduce a variation error between the theoretical focal position and the actual focal position inside the material, resulting in an error in the final processed morphology. The present invention provides a laser processing device and method for complex microstructures, in which only the driving unit y moves in one dimension along the Z-axis direction, and the preparation of complex morphology materials is completed by changing the focal spot size, with fewer error sources and higher precision.

[0055] 4. The laser processing device and method for complex microstructures provided by the present invention can form variable-aperture structures in one step without the need for repeated manufacturing of multiple trajectories, which greatly reduces processing time and improves processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a structural schematic diagram of a first embodiment of a laser processing device for complex microstructures of the present invention;

[0057] Figure 2 : is a slice layer diagram of the component to be processed method in an embodiment of the present invention; (a) is the equally spaced slice layer diagram obtained in step 1, (b) is the slice layer diagram to be processed recorded in step 4,

[0058] Figure 3 It is a structural schematic diagram of a second embodiment of a laser processing device for complex microstructures of the present invention;

[0059] Figure 4 It is a schematic diagram of the structure of shifting to other positions to be processed after processing one position in the present invention.

[0060] Figure Number:

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

[0062] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] Embodiment 1

[0064] The embodiment of the present invention provides a laser processing device for complex microstructures, such as Figure 1 As shown, the laser processing device includes a laser source 1, a numerical aperture conversion unit and a focusing unit 3, and a driving unit which are arranged in sequence;

[0065] The laser source 1 is used to emit processing laser.

[0066] The numerical aperture conversion unit includes a collimating zoom lens group 211, a first variable iris 212 and a reflector 213 which are sequentially arranged on the optical path of the processing laser along the emission direction of the processing laser; the collimating zoom lens group 211 is used to adjust and collimate the beam diameter of the processing laser; the first variable iris 212 is arranged at the emission end of the collimating zoom lens group 211, and is used to filter out stray light of the adjusted processing laser; the reflector 213 is used to reflect the processing laser after the stray light is filtered out to the focusing unit 3.

[0067] The focusing unit 3 is used to focus the processing laser with adjusted numerical aperture onto the to-be-processed component 4. In this embodiment, the focusing unit 3 is preferably a 20x microscope objective lens, with a maximum entrance pupil diameter D of 5 mm, a numerical aperture NA of 0.45, a focal length of 10 mm, and a focal depth of 1.56 μm.

[0068] The driving unit is connected to the focusing unit 3 and is used to drive the focusing unit 3 to move along the z-axis direction, where the z-axis is a direction perpendicular to the surface of the to-be-processed position on the to-be-processed component 4 .

[0069] The processing laser is incident on the collimating zoom lens group 211, and the first variable aperture 212 can change the beam diameter Dn of the beam incident on the focusing unit, so that the beam diameter Dn can be flexibly adjusted, but its maximum value should be smaller than the pupil diameter or the entrance pupil of the focusing unit (microscope objective or focusing lens group). At this time, the numerical aperture entering the focusing unit is changed to: NA = Dn / 2f, where f is the focal length of the focusing unit, and the maximum NA max =D / 2f, D is the maximum pupil distance of the microscope objective lens. Generally, D is a fixed value after the focusing unit is selected. min =D / 8f.

[0070] When the numerical aperture NA changes, the diameter of the focused light spot φ=1.22λ / NA, where λ is the laser wavelength. It can be seen that the size of the focused light spot increases with the decrease of the numerical aperture, so, φ min =1.22λ / NA max ,φ max =1.22λ / NA min , the laser spot can be in [φ min ,φ max ] can be switched arbitrarily. When the numerical aperture changes, the depth of focus DOF ​​= (2nλNA 2 ) / (n 2 -NA 2 )c shows that the focal depth of the laser 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 a vacuum. Therefore, any complex microstructure can be constructed according to the focal depth DOF n To stratify, such as Figure 2 (b) As shown, the layer spacing is unequal, in [DOF min , DOF max ] can be changed arbitrarily.

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

[0072] Step 1: According to the driving accuracy of the driving unit along the z-axis direction, Figure 2 As shown in (a), the position to be processed on the component 4 to be processed is sliced ​​in equal intervals 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 layer, obtain the processing focus spot diameter φ required for each slice layer;

[0074] Step 3, calculating the processing laser numerical aperture NA and the corresponding focal depth DOF corresponding to each slice layer according to the processing focus spot diameter φ required for each slice layer;

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

[0076] If the focal depth DOF corresponding to the i-th slice 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 along the z-axis, 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 record;

[0077] If the focal depth DOF corresponding to the i-th slice iIf the driving accuracy of the driving unit along the z-axis is greater than the driving accuracy of the driving unit along the z-axis, then the focal depth DOF corresponding to the i-th slice is i Re-obtain the position height h of the i-th layer slice i 'And record; get Figure 2 (b) The slices to be processed are layered.

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

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

[0080] Step 7, the collimating zoom 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 aperture 212 filters out stray light of the adjusted processing laser; the reflector 213 reflects the processing laser after the stray light is filtered out to the focusing unit 3.

[0081] Step 8: Process the corresponding layer slicing positions of the component 4 to be processed by the processing laser with the numerical aperture adjusted, until all the slicing layering positions corresponding to the heights of the positions recorded in step 4 are processed.

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

[0083] Embodiment 2

[0084] A laser processing device for complex microstructures is used to process complex flow channels inside quartz optical fiber glass (components to be processed), such as Figure 3 As shown, the laser processing device includes a laser source 1, a numerical aperture conversion unit and a focusing unit 3, which are arranged in sequence, and a driving unit.

[0085] The laser source 1 is used to emit processing laser.

[0086] The numerical aperture conversion unit includes a spatial light modulator 221, a second variable aperture 222, a 4f system 223 and a filter 224 which are sequentially arranged on the optical path of the processing laser along the direction of the processing laser emission; the spatial light modulator 221 is used to adjust the beam diameter of the processing laser by loading different holograms, or loading corresponding aperture phase diagrams and grating diagrams, or loading different Fresnel lens phase diagrams and grating diagrams; the second variable aperture 222 is arranged at the emission end of the spatial light modulator 221, and is used to filter the stray light of the adjusted processing laser; the 4f system 223 is used to spatially filter the processing laser after filtering the stray light, and reflect it to the focusing unit 3; the filter 224 is used to adjust the energy of the reflected processing laser. The filter 224 is a liquid crystal filter.

[0087] When the spatial light modulator 221 is loaded with the aperture phase diagram and the grating diagram, the central circular phase of the aperture phase diagram is black 0 and gray 15, so that the central 0-order light beam passes directly, and the grating phase diffracts the ±1-order grating to other angles and is intercepted by the subsequent fixed second variable aperture 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 energy transmittance is reduced by the liquid crystal filter. When the aperture is small, the incident energy is increased by the liquid crystal filter.

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

[0089] The focusing unit 3 is used to focus the processing laser after the numerical aperture is adjusted onto the component to be processed 4. In this embodiment, the focusing unit 3 is preferably a 20x microscope objective lens, whose maximum entrance pupil diameter D is 5mm, the numerical aperture NA is 0.45, the focal length is 10mm, and the focal depth is 1.56μm. The processing laser beam aperture incident on the microscope objective lens varies in the range of [3mm, 9mm]. 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 light spot increases with the decrease of the numerical aperture, where φ min =1.22λ / 0.45=2.88μm,φ max =1.22λ / NA min =8.6μm, the laser spot can be switched arbitrarily between [2.88μm, 8.6μm].

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

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

[0093] The above device is used for laser processing, and the specific steps are as follows:

[0094] Step 1: According to the driving accuracy of the driving unit along the z-axis direction, the position to be processed on the component 4 to be processed is sliced ​​in layers at equal intervals 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 processing focus spot diameter φ required for each layer of slices is obtained according to the diameter d of each layer of slices;

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

[0097] Step 4, comparing the calculated focal depth DOF corresponding to each slice with the driving accuracy of the driving unit along the z-axis direction;

[0098] If the focal depth DOF corresponding to the i-th slice 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 along the z-axis, 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 record;

[0099] If the focal depth DOF corresponding to the i-th slice i If the driving accuracy of the driving unit along the z-axis is greater than the driving accuracy of the driving unit along the z-axis, then the focal depth DOF corresponding to the i-th slice is i Re-obtain the position height h of the i-th layer slice i 'And record;

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

[0101] Step 6: The driving unit drives the focusing unit 3 to move based on the heights of each position recorded in step 4, so that the focusing unit 3 can focus the processing laser to the corresponding layer slicing position on the component to be processed 4;

[0102] Step 7, according to the numerical aperture NA corresponding to the first slice calculated in step 3, the corresponding hologram is loaded into the spatial light modulator 221, or the corresponding aperture phase image and grating image is loaded, or the corresponding Fresnel lens phase image and grating image is loaded, so that the spatial light modulator 221 adjusts the beam diameter of the processing laser accordingly; the second variable aperture 222 filters the stray light of the adjusted processing laser; the 4f system 223 performs spatial filtering on the processing laser with the stray light filtered out to improve the beam quality, and reflects it to the focusing unit 3; the filter 224 adjusts the energy of the reflected processing 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 consists of a binary grating and a geometric mask pattern. The binary grating consists of two different grayscale values, which are used to produce a π phase shift. The two grayscale values ​​are set to G1=0 and G2=128; the geometric mask pattern is a target pattern with a grayscale value of 0 (including patterns such as circles, triangles, rectangles, etc.), which is used to produce 0 phase shift and change the diameter and shape of the laser beam, similar to the function of a reflector. Figure 3 shown.

[0104] Fresnel lens + two-dimensional grating hologram, the hologram is composed of two different grayscale values, the two grayscale values ​​are set to G1 = 0, G2 = 128, and the lens focal length is changed by adjusting the annular interval of the Fresnel lens to form different beam diameters, thereby changing the numerical aperture of the beam. On this basis, you can also choose to superimpose a grating hologram, change the grating stripe interval to flexibly adjust the diffraction efficiency of the beam, so as to achieve the purpose of online energy regulation. It is worth noting that the biggest difference between this method and the aperture stop hologram is that the beam divergence angle of the light beam before entering the focusing microscope objective is changed, thereby changing the focal position in the Z-axis direction, which can be compensated by a one-dimensional motion platform.

[0105] Step 8: Process the corresponding layer slicing positions of the component 4 to be processed by the processing laser with the numerical aperture adjusted, until all the slicing layering positions corresponding to the heights of the positions recorded in step 4 are processed.

[0106] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A laser processing device for complex microstructures, characterized in that: It comprises a laser source (1), a numerical aperture conversion unit and a focusing unit (3) which are arranged in sequence, and a driving unit; The laser source (1) is used to emit processing laser; The numerical aperture conversion unit is used to adjust the numerical aperture of the processing laser; The focusing unit (3) is used to focus the processing laser with the numerical aperture adjusted onto the component to be processed (4); The driving unit is connected to the focusing unit (3) and is used to drive the focusing unit (3) to move along the z-axis direction, wherein the z-axis is a direction perpendicular to the surface of the position to be processed on the component to be processed (4).

2. The laser processing device for complex microstructures according to claim 1, characterized in that: The numerical aperture conversion unit comprises a collimating variable magnification lens group (211), a first variable diaphragm (212) and a reflector (213) which are sequentially arranged on the optical path thereof along the emitting direction of the machining laser; The collimating variable magnification lens group (211) is used to adjust and collimate the beam diameter of the processing laser; The first variable diaphragm (212) is arranged at the output end of the collimating zoom lens group (211) and is used to filter out stray light from the adjusted processing laser; The reflector (213) is used to reflect the processing laser after the stray light is filtered out to the focusing unit (3).

3. The laser processing device for complex microstructures according to claim 1, characterized in that: The numerical aperture conversion unit comprises a spatial light modulator (221), a second variable diaphragm (222), a 4f system (223) and a filter (224) which are sequentially arranged on the optical path thereof along the emitting direction of the machining laser; The spatial light modulator (221) is used to adjust the beam diameter of the processing laser by loading different holograms, or loading different aperture phase images and grating images, or loading different Fresnel lens phase images and grating images; The second variable iris (222) is arranged at the output end of the spatial light modulator (221) and is used to filter out stray light from the adjusted processing laser. The 4f system (223) is used to spatially filter the processing laser after filtering out stray light, and reflect it to the focusing unit (3); The filter (224) is used to adjust the energy of the reflected processing laser.

4. The laser processing device for complex microstructures according to claim 3, characterized in that: The filter (224) is a liquid crystal filter.

5. The laser processing device for complex microstructures according to any one of claims 1 to 4, characterized in that: The focusing unit (3) is a 20x microscope objective lens, with a maximum entrance pupil diameter D of 5 mm and a maximum numerical aperture NA max is 0.45, the focal length is 10mm, and the depth of focus is 1.56μm.

6. A method for laser processing of a complex microstructure, using the laser processing device for a complex microstructure according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: According to the driving accuracy of the driving unit along the z-axis direction, the position to be processed on the component to be processed (4) is sliced ​​in layers at equal intervals 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; Step 2, according to the diameter d of each slice layer, obtain the processing focus spot diameter φ required for each slice layer; Step 3, calculating the processing laser numerical aperture NA and the corresponding focal depth DOF corresponding to each slice layer according to the processing focus spot diameter φ required for each slice layer; Step 4, comparing the calculated 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 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 along the z-axis, 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 record; If the focal depth DOF corresponding to the i-th slice i If the driving accuracy of the driving unit along the z-axis is greater than the driving accuracy of the driving unit along the z-axis, then the focal depth DOF corresponding to the i-th slice is i Re-obtain the position height h of the i-th slice i 'And record; Step 5, starting the laser source (1), the laser source (1) emits a processing laser, and the processing laser emitted by the focusing unit (3) is aligned with a position to be processed on the component to be processed (4); Step 6: The driving unit drives the focusing unit (3) to move based on the heights of the various positions recorded in step 4, so that the focusing unit (3) can focus the processing laser to the corresponding layer slicing position on the component to be processed (4); Step 7, the numerical aperture conversion unit adjusts the numerical aperture of the processing laser to the numerical aperture NA corresponding to the corresponding layer slice calculated in step 3; Step 8, processing the corresponding layer slicing positions of the component to be processed (4) by using the processing laser with the numerical aperture adjusted, until all the slicing layering positions corresponding to the heights of the positions recorded in step 4 are processed.

7. The laser processing method for complex microstructures according to claim 6, characterized in that: Step 7 is as follows: The collimating variable magnification lens group (211) adjusts the numerical aperture of the processing laser to the numerical aperture NA corresponding to the first slice calculated in step 3 and collimates the laser; The first variable iris (212) filters out stray light from the adjusted processing laser; The reflector (213) reflects the processing laser light after the stray light is filtered out to the focusing unit (3).

8. The laser processing method for complex microstructures according to claim 6, characterized in that: Step 7 is as follows: According to the numerical aperture NA corresponding to the first slice calculated in step 3, a corresponding hologram is loaded into the spatial light modulator (221), or a corresponding aperture phase image and grating image is loaded, or a corresponding Fresnel lens phase image and grating image is loaded, so that the spatial light modulator (221) adjusts the beam diameter of the processing laser accordingly; The second variable iris (222) filters out stray light from the adjusted processing laser; The 4f system (223) performs spatial filtering on the processing laser light after filtering out stray light to improve the beam quality, and reflects it to the focusing unit (3); The filter (224) adjusts the energy of the reflected processing laser.

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