Inverted dynamic focusing laser direct writing device and method for microlens array

Abstract

The application belongs to the technical field of laser micro-processing, and particularly relates to a micro-lens array inverted dynamic focusing laser direct writing processing device and method. The processing device comprises: a fixed platform; a three-dimensional motion platform subsystem fixedly installed on the fixed platform; a workpiece clamping and chip removal subsystem fixedly installed on a motion end of the three-dimensional motion platform subsystem; a laser light path and dynamic focusing subsystem arranged on the fixed platform; and a scanning galvanometer subsystem fixedly installed on the fixed platform, the scanning galvanometer subsystem being arranged at a laser emission end of the laser light path and dynamic focusing subsystem. Through reconstruction of a processing space posture, high-precision three-dimensional laser beam control is realized by combining a dynamic focusing module, a two-dimensional scanning galvanometer and a telecentric field lens, efficient discharge of large-particle chips in processing production and vacuum non-shielding clamping are realized by combining gravity assistance, and the problems of chip retention, oxide layer generation, poor processing consistency, limited processing depth and clamping shielding in traditional normal processing are solved.

Description

Technical Field

[0001] This invention belongs to the field of laser micromachining technology, and particularly relates to an inverted dynamic focusing laser direct writing processing device and method for microlens arrays. Background Technology

[0002] Microlens arrays are core components of micro-optics, widely used in beam homogenization, imaging, and sensing. As systems evolve towards larger fields of view and higher resolutions, the demand for fabricating large-aperture, high-duty-ratio spherical microlens arrays is urgent, placing higher demands on microfabrication precision and process adaptability. Laser direct writing technology, with its advantages of non-contact and high precision, has become an important fabrication method; however, its layered processing strategy has inherent limitations: discretized layering easily produces a staircase effect, requiring layer thickness to be compressed to the sub-micrometer level, necessitating extremely high Z-axis positioning accuracy; the large inertia and slow response of mechanical motion axes easily lead to depth positioning deviations; the Gaussian energy distribution of the laser causes ablation pits to have a Gaussian morphology, and regional stitching errors during large-scale processing can reduce the consistency of array morphology. Therefore, a voice coil motor-driven dynamic focusing lens group (positioning accuracy ≥0.1μm, frequency 20Hz) can be used to achieve precise Z-axis adjustment, combined with a two-dimensional galvanometer and a telecentric field mirror to complete continuous global scanning in the plane. The synergy of these three components is the core to ensure processing accuracy.

[0003] However, when processing microlens arrays with high-power pulsed lasers, large debris tends to accumulate in dead corners such as microlens grooves, and traditional air-blowing cleaning methods are ineffective. Residual debris, after laser irradiation, forms a dense oxide layer, which not only degrades surface quality but also hinders energy transfer due to differences in absorption coefficients and ablation thresholds, severely limiting processing efficiency. While inverting the workpiece allows for gravity-based chip removal, a balanced tilt angle is necessary—too small an angle results in insufficient chip removal, while too large an angle contaminates the galvanometer. Existing systems struggle to balance chip removal and processing consistency. Furthermore, traditional front-mounted clamping methods obstruct the processing area, and commercial equipment lacks dynamic focusing capabilities and targeted chip removal designs, making it difficult to support high-quality fabrication of large-diameter, high-duty-cycle arrays. In summary, current laser processing technologies face bottlenecks in precision, chip removal, optical path configuration, and equipment adaptability that urgently require breakthroughs.

[0004] Therefore, it is necessary to design an inverted dynamic focusing laser direct writing processing device and method for microlens arrays to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an inverted dynamic focusing laser direct writing processing device and method for microlens arrays. By reconstructing the processing space posture, high-precision three-dimensional laser beam control is achieved by combining a dynamic focusing module, a two-dimensional scanning galvanometer, and a telecentric field mirror. Combined with gravity assistance, efficient removal of large particles and vacuum unobstructed clamping are achieved, solving the problems of debris retention, oxide layer formation, poor processing consistency, limited processing depth, and clamping obstruction in traditional upright processing.

[0006] To achieve the above objectives, the present invention provides the following solution: an inverted dynamic focusing laser direct writing processing device for a microlens array, comprising: Fixed platform; The three-dimensional motion platform subsystem is fixedly installed on the fixed platform; The workpiece clamping and chip removal subsystem is fixedly installed at the moving end of the three-dimensional motion platform subsystem. The workpiece clamping and chip removal subsystem is used to clamp the workpiece to be processed in an inclined downward manner. The three-dimensional motion platform subsystem is used to drive the workpiece clamping and chip removal subsystem and the workpiece to be processed to move in three-dimensional space. A laser optical path and dynamic focusing subsystem are mounted on the fixed platform. The laser optical path and dynamic focusing subsystem are used to emit laser light and adjust the focal point of the laser light. A scanning galvanometer system is fixedly installed on the fixed platform. The scanning galvanometer system is located at the laser emitting end of the laser optical path and the dynamic focusing subsystem. The scanning galvanometer system is used to adjust the laser to the surface of the workpiece to be processed in an upward tilting manner.

[0007] Preferably, the laser optical path and dynamic focusing subsystem includes a laser, the emitting end of the laser is provided with a reflector group, the emitting end of the reflector group is provided with a dynamic focusing lens group, and the scanning galvanometer system is located on the side of the dynamic focusing lens group away from the reflector group.

[0008] Preferably, the dynamic focusing lens group includes a plano-concave lens and a plano-convex lens, the plano-concave lens and the plano-convex lens are coaxially arranged, the plano-concave lens is close to the exit end of the reflecting mirror group, the plano-concave lens is fixedly connected to the mover of the voice coil motor module, the voice coil motor module is fixedly connected to the fixed platform, and the plano-convex lens is fixedly connected to the scanning galvanometer system.

[0009] Preferably, the scanning galvanometer system includes a galvanometer mounting bracket, which is fixedly connected to the fixed platform. The plano-convex lens is fixedly connected in the light-transmitting hole of the galvanometer mounting bracket. A two-dimensional scanning galvanometer lens is fixedly connected to the side of the galvanometer mounting bracket away from the dynamic focusing lens group, and a telecentric field lens is fixedly connected to the two-dimensional scanning galvanometer lens.

[0010] Preferably, the galvanometer mounting bracket has multiple mounting holes arranged in a ring, with an angular interval of 15° between two adjacent mounting holes. The tilt angle of the mounting holes can be adjusted from 0° to 90°. The two-dimensional scanning galvanometer head is fixedly connected to the galvanometer mounting bracket through the mounting holes.

[0011] Preferably, the mounting angle of the two-dimensional scanning lens is 60°.

[0012] Preferably, the three-dimensional motion platform subsystem includes an XY two-dimensional linear micro-motion platform, which is fixedly connected to the fixed platform. An optical breadboard is fixedly connected to the moving end of the XY two-dimensional linear micro-motion platform. The optical breadboard is vertically arranged. An adjustable angle platform is fixedly connected to the side wall of the optical breadboard near the scanning galvanometer system. A Z-axis micro-motion platform is fixedly connected to the adjustable angle platform. The workpiece clamping and chip removal subsystem is fixedly connected to the moving end of the Z-axis micro-motion platform.

[0013] Preferably, the workpiece clamping and chip removal subsystem includes a workpiece fixture, which is fixedly connected to the moving end of the Z-axis micro-motion platform. The workpiece fixture is provided with auxiliary air blowing ports and auxiliary air suction and chip collection ports on opposite sides. The workpiece fixture is provided with bolt auxiliary positioning modules and vacuum adsorption pipes on the other opposite sides. The vacuum adsorption pipes are connected to a vacuum flow channel opened inside the workpiece fixture.

[0014] A method for inverted dynamic focusing laser direct writing of a microlens array, and an inverted dynamic focusing laser direct writing apparatus based on a microlens array, includes the following steps: Device assembly and angle calibration: Adjust the tilt angle of the scanning galvanometer system and the three-dimensional motion platform subsystem so that the clamping surface of the workpiece clamping and chip removal subsystem is perpendicular to the light output axis of the scanning galvanometer system; build the laser optical path and adjust the laser optical path and the dynamic focusing subsystem so that the laser beam is perpendicularly incident on the entrance pupil of the scanning galvanometer system to complete the optical path collimation; Workpiece clamping and positioning: Place the workpiece on the clamping surface of the workpiece clamping and chip removal subsystem, start the vacuum generator to create negative pressure inside the workpiece clamping and chip removal subsystem, and fix the workpiece by adsorption; adjust the workpiece clamping and chip removal subsystem to perform lateral positioning and auxiliary clamping of the workpiece. Focusing and trajectory planning: The three-dimensional motion platform subsystem is driven to complete the coarse positioning of the workpiece, and the laser optical path and dynamic focusing subsystem are used in conjunction with low-power laser to complete the fine focus calibration; the three-dimensional model of the convex microlens array is imported into the host computer software, and layer slicing is performed. The contour coordinates of each layer are converted into two-dimensional deflection signals of the scanning galvanometer, and the depth coordinates of each layer are converted into displacement signals of the laser optical path and dynamic focusing subsystem to generate the machining trajectory. Inverted processing: The laser optical path and dynamic focusing subsystem are activated, and the workpiece clamping and chip removal subsystem is simultaneously turned on to introduce gas; the scanning galvanometer completes the scanning processing of the single-layer microstructure contour. After each layer is processed, the laser optical path and dynamic focusing subsystem move the laser focus down along the normal direction by one slice processing layer thickness, and the next layer is processed. This process is repeated layer by layer until the entire convex microlens array is completed. During the processing, the debris is detached from the workpiece surface and collected under the combined action of gravity and directional airflow. After processing is complete, turn off the laser and gas circuit, release the vacuum adsorption and lateral clamping, and remove the workpiece.

[0015] Preferably, in focusing and trajectory planning, the thickness of a single layer of the slice is 0.5μm-3μm; in inverted machining, the gas introduced into the workpiece clamping and chip removal subsystem is dry compressed air or other inert gas.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: 1. Improved chip removal and inhibition of oxide layer formation. This invention employs an inclined and inverted processing configuration, allowing large particles of debris generated during processing to naturally slide off the workpiece surface under the dominant force of gravity. This fundamentally alters the trajectory of the debris, significantly reducing its residence time and probability in the processing area. Combined with the airflow field formed by directional blowing and suction, the debris can be efficiently peeled off and collected, effectively preventing the formation of a dense oxide layer due to repeated processing by subsequent laser pulses. This ensures the morphological quality of the processed surface and eliminates the obstruction of the oxide layer to deep processing, enabling sustainable processing of large-depth microlens arrays.

[0017] 2. Unobstructed clamping across the entire area, suitable for large-diameter array processing. This invention adopts a back-side vacuum adsorption clamping method, eliminating the need for fixing structures such as pressure blocks and cover plates on the front of the workpiece. The entire surface of the workpiece to be processed is completely exposed, enabling unobstructed processing across the entire area. It is particularly suitable for the batch production of large-diameter, high-duty-ratio microlens arrays, improving material utilization and processing efficiency.

[0018] 3. High-precision 3D machining capability ensures the accuracy of structure fabrication. This invention combines the macroscopic positioning of a high-precision micro-motion platform, the two-dimensional rapid scanning of a high-speed scanning galvanometer, and the high-precision depth control of voice coil-driven dynamic focusing, enabling the machining of complex 3D structures with micron-level precision. Combined with a telecentric field mirror, it ensures the consistency of the incident angle and size of the light spot across the entire field of view, guarantees the uniformity of machining at various positions on the tilted surface, and improves the surface uniformity and optical performance of the microlens array.

[0019] 4. High system integration and strong adaptability. This invention organically integrates modules such as motion planning and control, optical path transmission, workpiece clamping, and chip management, resulting in a compact structure. Each module adopts a modular design, facilitating optical path calibration, equipment maintenance, and function upgrades. The galvanometer tilt angle and workpiece tilt angle are adjustable, adapting to the processing needs of different materials and depths, and making it suitable for a wide range of scenarios. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall device of the present invention; Figure 2 This is a schematic diagram of the laser optical path and dynamic focusing subsystem of the present invention; Figure 3 This is a schematic diagram of the laser direct writing processing trajectory of the microlens array in the processing method of the present invention; Figure 4 This is a schematic diagram of the workpiece clamping and chip removal subsystem of the present invention; Figure 5 This is a schematic diagram of the galvanometer mounting bracket of the present invention; Figure 6 The processing apparatus and method of the present invention provide a large-aperture, high-duty-ratio convex microlens array structure containing 157 microlens pixels, with a microlens pixel diameter D=3.9mm, depth h=1.69mm, center distance W=4mm, and array size 56mm×56mm.

[0022] The components include: 1. Two-dimensional scanning galvanometer lens; 2. Telecentric field lens; 3. Workpiece fixture; 4. Z-axis micro-motion platform; 5. Adjustable angle platform; 6. Optical breadboard; 7. XY two-dimensional linear micro-motion platform; 8. Dynamic focusing lens group; 9. Voice coil motor module; 10. Galvanometer mounting bracket; 11. Fixed platform; 12. Laser; 13. Reflector group; 3-1. Auxiliary air blowing port; 3-2. Bolt auxiliary positioning module; 3-3. Auxiliary air suction and debris collection port; 3-4. Vacuum adsorption pipe; 8-1. Plano-concave lens; 8-2. Plano-convex lens; 10-1. Mounting holes. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Reference Figures 1 to 6 As shown, the present invention provides an inverted dynamic focusing laser direct writing processing device for microlens arrays, comprising: Fixed platform 11; The three-dimensional motion platform subsystem is fixedly installed on the fixed platform 11; The workpiece clamping and chip removal subsystem is fixedly installed at the moving end of the three-dimensional motion platform subsystem. The workpiece clamping and chip removal subsystem is used to clamp the workpiece to be processed in an inclined downward manner. The three-dimensional motion platform subsystem is used to drive the workpiece clamping and chip removal subsystem and the workpiece to be processed to move in three-dimensional space. The laser optical path and dynamic focusing subsystem is set on the fixed platform 11. The laser optical path and dynamic focusing subsystem is used to emit laser and adjust the focusing point of the laser. The scanning galvanometer system is fixedly installed on the fixed platform 11. The scanning galvanometer system is located at the laser emitting end of the laser optical path and the dynamic focusing subsystem. The scanning galvanometer system is used to adjust the laser to the surface of the workpiece to be processed in an upward tilting manner.

[0026] Further optimization of the scheme: the laser optical path and dynamic focusing subsystem includes a laser 12, a reflector group 13 is provided at the emitting end of the laser 12, a dynamic focusing mirror group 8 is provided at the emitting end of the reflector group 13, and the scanning galvanometer system is located on the side of the dynamic focusing mirror group 8 away from the reflector group 13.

[0027] Laser 12 is a femtosecond pulsed laser.

[0028] Further optimization of the scheme: the dynamic focusing lens group 8 includes a plano-concave lens 8-1 and a plano-convex lens 8-2. The plano-concave lens 8-1 and the plano-convex lens 8-2 are coaxially arranged. The plano-concave lens 8-1 is close to the exit end of the reflecting mirror group 13. The plano-concave lens 8-1 is fixedly connected to the mover of the voice coil motor module 9. The voice coil motor module 9 is fixedly connected to the fixed platform 11. The plano-convex lens 8-2 is fixedly connected to the scanning galvanometer system.

[0029] The voice coil motor module 9 drives the plano-concave lens 8-1 to move along the optical axis, changing the relative distance between the plano-concave lens 8-1 and the plano-convex lens 8-2, and modulating the laser beam divergence angle in real time, so that the focal point can be continuously displaced along the normal direction of the workpiece with micron-level precision.

[0030] The scheme is further optimized. The scanning galvanometer system includes a galvanometer mounting bracket 10, which is fixedly connected to a fixed platform 11. A plano-convex lens 8-2 is fixedly connected in the light-transmitting hole of the galvanometer mounting bracket 10. A two-dimensional scanning galvanometer lens 1 is fixedly connected to the side of the galvanometer mounting bracket 10 away from the dynamic focusing lens group 8. A telecentric field lens 2 is fixedly connected to the two-dimensional scanning galvanometer lens 1.

[0031] The telecentric field lens 2 is an object-side telecentric field lens, coaxially mounted on the light-emitting end of the two-dimensional scanning galvanometer lens 1; within the full scanning field of view, the main ray of the focused spot is perpendicular to the workpiece processing surface, and the spot size remains consistent.

[0032] The laser beam output by the laser 12 is deflected by the mirror group 13 and then passes through the dynamic focusing mirror group 8 and is perpendicularly incident on the entrance pupil of the two-dimensional scanning galvanometer head 1. After being deflected by the galvanometer, it is focused on the processing surface of the workpiece by the telecentric field mirror 2. The dynamic focusing mirror group 8 is driven by the voice coil motor module 9 and is used to adjust the divergence angle of the laser beam so that the focal point is continuously displaced along the normal direction of the workpiece surface.

[0033] The scheme is further optimized by providing multiple mounting holes 10-1 on the galvanometer mounting bracket 10. The multiple mounting holes 10-1 are arranged in a ring, and the angle interval between two adjacent mounting holes 10-1 is 15°. The tilt angle adjustment range of the mounting holes 10-1 is 0°-90°. The two-dimensional scanning galvanometer head 1 is fixedly connected to the galvanometer mounting bracket 10 through the mounting holes 10-1.

[0034] The design was further optimized so that the installation tilt angle of the two-dimensional scanning lens 1 was 60°.

[0035] The two-dimensional scanning lens 1 is fixed in an upward tilted position through the mounting hole 10-1, and its light output axis forms an acute angle with the vertical direction.

[0036] Further optimization of the scheme: the three-dimensional motion platform subsystem includes an XY two-dimensional linear micro-motion platform 7, which is fixedly connected to a fixed platform 11. An optical breadboard 6 is fixedly connected to the moving end of the XY two-dimensional linear micro-motion platform 7. The optical breadboard 6 is vertically set. An adjustable angle platform 5 is fixedly connected to the side wall of the optical breadboard 6 near the scanning galvanometer system. A Z-axis micro-motion platform 4 is fixedly connected to the adjustable angle platform 5. The workpiece clamping and chip removal subsystem is fixedly connected to the moving end of the Z-axis micro-motion platform 4.

[0037] The adjustable angle platform 5 is a hinged angle adjustment platform. The adjusted tilt angle is fixed by a locking structure and is used to adjust the clamping surface angle of the workpiece fixture 3 to ensure that it is perpendicular to the light output axis of the two-dimensional scanning diaphragm head 1.

[0038] Further optimization of the scheme: the workpiece clamping and chip removal subsystem includes a workpiece fixture 3, which is fixedly connected to the moving end of the Z-axis micro-motion platform 4. On the opposite two sides of the workpiece fixture 3, there are auxiliary air blowing ports 3-1 and auxiliary air suction and chip collection ports 3-3. On the other two opposite sides of the workpiece fixture 3, there are bolt auxiliary positioning modules 3-2 and vacuum adsorption pipes 3-4. The vacuum adsorption pipes 3-4 are connected to the vacuum flow channel opened inside the workpiece fixture 3.

[0039] The workpiece fixture 3 is mounted on the moving parts of the Z-axis micro-motion platform 4. Its clamping surface is inclined downward and perpendicular to the light output axis of the two-dimensional scanning diaphragm head 1. The workpiece fixture 3 has a through vacuum channel inside. The vacuum channel is connected to a vacuum generator through the vacuum adsorption pipe 3-4 to form a vacuum suction cup structure to adsorb and fix the workpiece with negative pressure. The bolt auxiliary positioning module 3-2 is set on the side of the workpiece fixture 3 for lateral positioning and auxiliary clamping of the workpiece. The auxiliary air blowing port 3-1 and the auxiliary air suction and chip collection port 3-3 are respectively arranged on the upper and lower parts of the workpiece fixture 3 to form a directional airflow to assist in the discharge of processing chips.

[0040] The bolt auxiliary positioning module 3-2 consists of multiple sets of adjustable pressure bolt push rods distributed on both sides of the vacuum suction cup structure. The ends of the bolt push rods abut against the side wall of the workpiece, providing lateral clamping force to enhance clamping reliability.

[0041] The air blowing direction of the auxiliary air blowing port 3-1 is inclined downward along the workpiece surface. The auxiliary air suction and debris collection port 3-3 is connected to an external dust collection device. The two work together to form a directional airflow field from top to bottom along the workpiece surface to capture and remove dust and debris generated during processing.

[0042] A method for inverted dynamic focusing laser direct writing of a microlens array, and an inverted dynamic focusing laser direct writing apparatus based on a microlens array, includes the following steps: Device assembly and angle calibration: The two-dimensional scanning galvanometer head 1 is fixed at a set angle upward by the galvanometer mounting bracket 10. The tilt angle of the adjustable angle platform 5 is adjusted so that the clamping surface of the workpiece fixture 3 is perpendicular to the light output axis of the two-dimensional scanning galvanometer head 1. The laser optical path is built, and the reflector group 13 is adjusted so that the laser beam is perpendicularly incident on the entrance pupil of the two-dimensional scanning galvanometer head 1, thus completing the optical path collimation. Workpiece clamping and positioning: Place the workpiece on the clamping surface of the workpiece fixture 3, start the vacuum generator, and create negative pressure inside the fixture through the vacuum adsorption pipe 3-4 to adsorb and fix the workpiece; adjust the bolt auxiliary positioning module 3-2 to perform lateral positioning and auxiliary clamping of the workpiece; Focusing and trajectory planning: The XY two-dimensional linear micro-motion displacement platform 7 and the Z-axis micro-motion displacement platform 4 are driven to complete the coarse positioning of the workpiece, and the low-power laser and dynamic focusing lens group 8 are used to complete the fine focus calibration; the three-dimensional model of the microlens array is imported into the host computer software, and layer slicing is performed. The contour coordinates of each layer are converted into the deflection signal of the two-dimensional scanning diaphragm head 1, and the depth coordinates of each layer are converted into the displacement signal of the voice coil motor module 9 to generate the machining trajectory; Inverted processing: Start the laser 12 and simultaneously open the auxiliary air blowing port 3-1 and the auxiliary air suction and debris collection port 3-3; complete the scanning processing of the single-layer microstructure contour through the two-dimensional scanning galvanometer 1. After each layer is processed, the focal point is moved down along the normal direction by one slice processing layer thickness through the dynamic focusing lens group 8, and the next layer is processed. Process layer by layer until the entire microlens array is completed; during the processing, the debris is removed from the workpiece surface and collected under the combined action of gravity and directional airflow. After processing is complete, turn off the laser and gas circuit, release the vacuum adsorption and lateral clamping, and remove the workpiece.

[0043] Further optimization of the scheme: In focusing and trajectory planning, based on laser parameters, the single-layer thickness of the layered slice is adjustable from 0.5 to 3 μm, and the axial positioning accuracy of the dynamic focusing lens group 8 is not less than 0.1 μm; In the inverted processing, the gas introduced into the auxiliary air blowing port 3-1 is dry compressed air or other inert gas, and the blowing pressure is adjustable from 0.2 to 0.5 MPa; The negative pressure of the auxiliary air suction and debris collection port 3-3 is adjustable from -0.03 to -0.08 MPa.

[0044] Example 1 This embodiment provides an inverted dynamic focusing laser direct writing processing device for microlens arrays. The overall structure adopts an inverted configuration of "light output from tilted upwards and workpiece clamping from tilted downwards". Specifically, it includes a three-dimensional motion platform subsystem, a scanning galvanometer system, a workpiece clamping and chip removal subsystem, and a laser optical path and dynamic focusing subsystem.

[0045] The three-dimensional motion platform subsystem serves as the device's support and macroscopic positioning module, comprising an XY two-dimensional linear micro-motion platform 7, an optical breadboard 6, an adjustable angle platform 5, and a Z-axis micro-motion platform 4. The XY two-dimensional linear micro-motion platform 7 is horizontally fixed on a fixed platform 11, consisting of two sets of mutually perpendicular linear micro-motion platforms stacked together along the X and Y axes. Its positioning accuracy is 1mm, used to achieve two-dimensional translational positioning of the workpiece in the horizontal plane. The optical breadboard 6 is vertically mounted on the mover of the XY two-dimensional linear micro-motion platform 7 via a support structure, its surface perpendicular to the horizontal plane, and moves synchronously with the XY platform. The adjustable angle platform 5 is a hinged angle adjustment platform; its fixed end is mounted on the surface of the optical breadboard 6, allowing it to rotate around a horizontal axis with an adjustment range of 0°-90°, and the adjusted angle is fixed by locking bolts. The Z-axis micro-motion platform 4 is fixedly mounted on the support surface of the adjustable angle platform 5, its direction of movement perpendicular to the support surface, used to achieve axial focusing and fine-tuning of the workpiece's position.

[0046] The scanning galvanometer system is used to achieve high-speed two-dimensional deflection of the light beam, including a two-dimensional scanning galvanometer head 1 and a galvanometer mounting bracket 10. The galvanometer mounting bracket 10 is a rigid metal bracket, fixedly mounted on the fixed platform 11, located to the side of the optical breadboard 6. The mounting surface of the galvanometer mounting bracket 10 has multiple sets of mounting holes 10-1, each set of mounting holes 10-1 corresponding to different mounting angles, with the angle range covering 0°-90°, and the angle interval between adjacent holes is 15°. The two-dimensional scanning galvanometer head 1 is fixed to the mounting hole 10-1 with the corresponding angle by bolts, and the whole is tilted upward with the light output posture, and its light output axis forms an acute angle with the vertical direction. In this embodiment, a 60° tilt angle mounting hole is selected to balance chip removal effect and optical path layout convenience. A telecentric field lens 2 is coaxially mounted at the light output end of the two-dimensional scanning galvanometer head 1. Within its full scanning field of view, the principal ray of the focused spot is always perpendicular to the focal plane, and the spot size deviation does not exceed 5%, ensuring the uniformity of the processing effect at each position on the tilted processing surface.

[0047] The workpiece clamping and chip removal subsystem is used for workpiece fixation and chip management, including a workpiece fixture 3, an auxiliary air blowing port 3-1, a bolt auxiliary positioning module 3-2, an auxiliary air suction and chip collection port 3-3, and a vacuum adsorption pipe 3-4. The workpiece fixture 3 is a flat plate structure, fixedly mounted on the mover of the Z-axis micro-motion platform 4, with its clamping surface facing downwards. By adjusting the tilt angle of the adjustable angle platform 5, the clamping surface can be made strictly perpendicular to the light output axis of the two-dimensional scanning galvanometer head 1, ensuring consistent optical characteristics of the focused light spot on the machining surface. Multiple sets of through holes are distributed on the clamping surface of the workpiece fixture 3. These holes are connected to the vacuum flow channel inside the fixture. The vacuum flow channel is connected to an external vacuum generator via the vacuum adsorption pipe 3-4, forming a vacuum suction cup structure. During operation, the vacuum generator generates a negative pressure of -0.03 to -0.08 MPa, applying adsorption force from the back of the workpiece to firmly fix it on the inclined clamping surface, eliminating the need for front-side clamping and avoiding obstruction of the machining area.

[0048] Bolt auxiliary positioning modules 3-2 are set on the left and right sides of workpiece fixture 3. Each group contains two adjustable stroke bolt push rods. The ends of the push rods are made of flexible material. Tightening the bolts can make the push rods abut against the side wall of the workpiece, providing lateral positioning and auxiliary clamping force, preventing the workpiece from shifting during high-power processing, and improving the reliability of tilt clamping.

[0049] The auxiliary air blowing port 3-1 is located at the upper end of the workpiece fixture 3, with the air blowing direction inclined downwards along the workpiece surface. Dry compressed air or other inert gases can be introduced, and the blowing pressure is adjustable from 0.2 to 0.5 MPa. The auxiliary suction and debris collection port 3-3 is located at the lower end of the workpiece fixture 3, connected to an external industrial dust collection device, providing a negative pressure of -0.03 to -0.08 MPa. The two work together to form a directional airflow field from top to bottom along the workpiece surface. On the one hand, this accelerates the removal of debris from the workpiece surface, and on the other hand, it captures the dispersed dust and fine debris, preventing them from contaminating optical components or spreading into the processing environment.

[0050] The laser optical path and dynamic focusing subsystem adopt a spatial optical path design, including a laser 12, a mirror group 13, a dynamic focusing mirror group 8, a two-dimensional scanning galvanometer head 1, and a telecentric field mirror 2. In this embodiment, the laser 12 is a femtosecond pulsed laser with an output wavelength of 1030nm, an adjustable pulse width of 300fs, and an adjustable repetition frequency of 2kHz-1MHz, suitable for low-thermal-affect precision machining of brittle optical materials. The laser 12 is fixed on a vibration-isolated optical platform, and the output parallel laser beam is refracted multiple times by the mirror group 13 (containing multiple planar mirrors) before being incident on the dynamic focusing mirror group 8.

[0051] The dynamic focusing lens group 8 includes a plano-concave lens 8-1 and a plano-convex lens 8-2 arranged sequentially along the optical axis. The plano-concave lens 8-1 is fixedly connected to the mover of the voice coil motor module 9, and the plano-convex lens 8-2 is fixedly mounted on the optical path base near the galvanometer. The voice coil motor module 9 can drive the plano-concave lens 8-1 to reciprocate at high speed along the optical axis, with a maximum frequency of 20 Hz, a stroke of 10 mm, and a positioning accuracy of not less than 0.1 μm. By changing the relative distance between the plano-concave lens 8-1 and the plano-convex lens 8-2, the divergence angle of the laser beam can be modulated in real time, thereby causing the focal point after being focused by the telecentric field lens 2 to continuously shift along the normal direction of the workpiece, achieving dynamic adjustment in the depth direction. The laser beam modulated by the dynamic focusing lens group is perpendicularly incident on the center of the entrance pupil of the two-dimensional scanning galvanometer head 1. After being deflected at high speed by the internal X and Y axis galvanometers, it is focused onto the machined surface of the workpiece by the telecentric field lens 2. The scanning galvanometer and the dynamic focusing lens group work together to achieve high-speed and high-precision movement of the focused spot in three-dimensional space, meeting the processing needs of complex three-dimensional microstructures.

[0052] This embodiment provides a method for inverted dynamic focusing laser direct writing of microlens arrays, the specific steps of which are as follows: 1. Device assembly and optical path calibration The XY two-dimensional linear micro-motion platform 7 is horizontally fixed on the fixed platform 11. The optical breadboard 6, the adjustable angle platform 5, and the Z-axis micro-motion platform 4 are installed in sequence. According to the processing requirements, the mounting hole 10-1 with a 60° tilt angle on the galvanometer mounting bracket 10 is selected. The two-dimensional scanning galvanometer head 1 and the telecentric field lens 2 are assembled and fixed at an upward tilt. The tilt angle of the adjustable angle platform 5 is adjusted and locked. The angle calibrator is used to calibrate the workpiece clamping surface 3 to ensure that it is strictly perpendicular to the light output axis of the two-dimensional scanning galvanometer head 1.

[0053] Arrange the laser 12 and the reflector group 13, and connect the dynamic focusing lens group 8 into the optical path; adjust the angle and position of each reflector one by one, and use a spot detector to monitor, so that the laser beam passes through the center of the plano-concave lens 8-1 and the plano-convex lens 8-2 in sequence, and is perpendicularly incident on the center of the entrance pupil of the two-dimensional scanning galvanometer 1, thus completing the optical path collimation.

[0054] 2. Workpiece clamping and positioning A square monocrystalline silicon plate is selected as the workpiece to be processed and placed on the clamping surface of the workpiece fixture 3. The vacuum generator is started and the vacuum level is adjusted to -0.05MPa to ensure that the workpiece is firmly adsorbed. The bolts on both sides of the auxiliary positioning module 3-2 are tightened to make the push rod evenly abut against the side wall of the workpiece, completing the lateral positioning and auxiliary clamping, and ensuring that the workpiece does not move when tilted.

[0055] 3. Focusing and processing trajectory generation Drive the XY two-dimensional linear micro-motion platform 7 and the Z-axis micro-motion platform 4, turn on the low-power indicator light, and roughly move the focused spot to the center position of the workpiece surface. Then, through the offset function of the scanning galvanometer and the axial adjustment of the dynamic focusing lens group 8, combined with the beam quality analyzer, perform fine focus calibration to determine the zero-position reference of the workpiece surface.

[0056] Import the 3D model of the microlens array to be processed. This array contains 157 microlens pixels, with a pixel radius of 3.9 mm, a pixel depth of 1.69 mm, a pixel center distance of 4 mm, and an overall array size of 56 mm × 56 mm. A layer-by-layer slicing algorithm with equal layer thickness is used to discretize the 3D model, setting the single-layer processing thickness to 1 μm. The 2D contour coordinates of a single planar processing layer are converted into deflection control values ​​for the scanning galvanometer. After focusing by the telecentric field lens, global array processing in the planar direction is achieved. The depth coordinates of each layer are converted into displacement values ​​for the voice coil motor module 9, generating a complete layered processing trajectory file.

[0057] 4. Inverted laser processing Set the processing parameters: laser power 5W, repetition frequency 200kHz, scanning speed 100mm / s. Start the laser 12, and simultaneously open the auxiliary air blowing port 3-1 and the auxiliary air suction and debris collection port 3-3. Set the air blowing pressure to 0.3MPa and the suction negative pressure to -0.05MPa. Use dry air as the blowing gas to further accelerate the removal of material from the microlens surface.

[0058] During the processing, the scanning galvanometer drives the laser beam to scan and fill along a single-layer planar trajectory, which is then focused by the telecentric field mirror 2 to continuously remove the material from the planar layer of the global array structure. After each layer is processed, the voice coil motor module 9 drives the plano-concave lens 8-1 to move a corresponding distance, shifting the laser focus point 1μm down along the workpiece normal direction, and continuing to scan and process the next layer. This process is repeated layer by layer until the entire 56mm×56mm area of ​​the convex microlens array is processed.

[0059] During the processing, the material debris generated by laser ablation slides down the inclined workpiece surface under the action of gravity. At the same time, the airflow from top to bottom further accelerates the debris peeling and prevents the debris from rebounding. Finally, the debris and dust are captured by the air intake below and collected in the dust collection equipment, with no obvious debris retention in the processing area.

[0060] 5. Processing completed After all processing is completed, turn off the pulsed laser, delay for 5 seconds and then turn off the auxiliary gas path. Then turn off the vacuum generator, loosen the bolts of the auxiliary positioning module 3-2, and remove the processed workpiece.

[0061] The processed convex microlens array was inspected, and the results showed that the microlens had clear outlines, no obvious oxidation discoloration or debris adhesion on the surface, and the morphology of each unit in the array was consistent. Compared with the traditional upright processing method, which cannot achieve the processing of microlens arrays at this depth, this method effectively solves the problems of large particle debris retention and oxide layer hindering deep processing, and significantly improves the surface accuracy and consistency of the prepared microlens array.

[0062] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0063] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A microlens array inverted dynamic focusing laser direct writing processing device, characterized in that, include: Fixed platform (11); The three-dimensional motion platform subsystem is fixedly installed on the fixed platform (11); The workpiece clamping and chip removal subsystem is fixedly installed at the moving end of the three-dimensional motion platform subsystem. The workpiece clamping and chip removal subsystem is used to clamp the workpiece to be processed in an inclined downward manner. The three-dimensional motion platform subsystem is used to drive the workpiece clamping and chip removal subsystem and the workpiece to be processed to move in three-dimensional space. A laser optical path and dynamic focusing subsystem is set on the fixed platform (11). The laser optical path and dynamic focusing subsystem is used to emit laser and adjust the focusing point of the laser. The scanning galvanometer system is fixedly installed on the fixed platform (11). The scanning galvanometer system is located at the laser emitting end of the laser optical path and the dynamic focusing subsystem. The scanning galvanometer system is used to adjust the laser to the surface of the workpiece to be processed in an upward tilting manner.

2. The inverted dynamic focusing laser direct writing processing device for a microlens array according to claim 1, characterized in that, The laser optical path and dynamic focusing subsystem includes a laser (12), the emitting end of the laser (12) is provided with a reflector group (13), the emitting end of the reflector group (13) is provided with a dynamic focusing lens group (8), and the scanning galvanometer system is located on the side of the dynamic focusing lens group (8) away from the reflector group (13).

3. The inverted dynamic focusing laser direct writing processing device for a microlens array according to claim 2, characterized in that, The dynamic focusing lens group (8) includes a plano-concave lens (8-1) and a plano-convex lens (8-2). The plano-concave lens (8-1) and the plano-convex lens (8-2) are coaxially arranged. The plano-concave lens (8-1) is close to the exit end of the reflecting mirror group (13). The plano-concave lens (8-1) is fixedly connected to the mover of the voice coil motor module (9). The voice coil motor module (9) is fixedly connected to the fixed platform (11). The plano-convex lens (8-2) is fixedly connected to the scanning galvanometer system.

4. The inverted dynamic focusing laser direct writing processing device for a microlens array according to claim 3, characterized in that, The scanning galvanometer system includes a galvanometer mounting bracket (10), which is fixedly connected to the fixed platform (11). The plano-convex lens (8-2) is fixedly connected in the light-transmitting hole of the galvanometer mounting bracket (10). A two-dimensional scanning galvanometer lens (1) is fixedly connected to the side of the galvanometer mounting bracket (10) away from the dynamic focusing lens group (8). A telecentric field lens (2) is fixedly connected to the two-dimensional scanning galvanometer lens (1).

5. The inverted dynamic focusing laser direct writing processing device for a microlens array according to claim 4, characterized in that, The galvanometer mounting bracket (10) has multiple mounting holes (10-1) arranged in a ring. The angle interval between two adjacent mounting holes (10-1) is 15°. The tilt angle adjustment range of the mounting holes (10-1) is 0°-90°. The two-dimensional scanning galvanometer head (1) is fixedly connected to the galvanometer mounting bracket (10) through the mounting holes (10-1).

6. The inverted dynamic focusing laser direct writing processing device for a microlens array according to claim 5, characterized in that, The mounting angle of the two-dimensional scanning lens (1) is 60°.

7. The inverted dynamic focusing laser direct writing processing device for a microlens array according to claim 1, characterized in that, The three-dimensional motion platform subsystem includes an XY two-dimensional linear micro-motion platform (7), which is fixedly connected to the fixed platform (11). An optical breadboard (6) is fixedly connected to the moving end of the XY two-dimensional linear micro-motion platform (7). The optical breadboard (6) is vertically arranged. An adjustable angle platform (5) is fixedly connected to the side wall of the optical breadboard (6) near the scanning galvanometer system. A Z-axis micro-motion platform (4) is fixedly connected to the adjustable angle platform (5). The workpiece clamping and chip removal subsystem is fixedly connected to the moving end of the Z-axis micro-motion platform (4).

8. The inverted dynamic focusing laser direct writing processing device for a microlens array according to claim 7, characterized in that, The workpiece clamping and chip removal subsystem includes a workpiece clamp (3), which is fixedly connected to the moving end of the Z-axis micro-motion platform (4). On the opposite sides of the workpiece clamp (3), there are auxiliary air blowing ports (3-1) and auxiliary air suction and chip collection ports (3-3). On the other two opposite sides of the workpiece clamp (3), there are bolt auxiliary positioning modules (3-2) and vacuum adsorption pipes (3-4). The vacuum adsorption pipes (3-4) are connected to the vacuum flow channel opened inside the workpiece clamp (3).

9. A method for inverted dynamic focusing laser direct writing of a microlens array, based on the inverted dynamic focusing laser direct writing apparatus for a microlens array according to any one of claims 1-8, characterized in that, Includes the following steps: Device assembly and angle calibration: Adjust the tilt angle of the scanning galvanometer system and the three-dimensional motion platform subsystem so that the clamping surface of the workpiece clamping and chip removal subsystem is perpendicular to the light output axis of the scanning galvanometer system; build the laser optical path and adjust the laser optical path and the dynamic focusing subsystem so that the laser beam is perpendicularly incident on the entrance pupil of the scanning galvanometer system to complete the optical path collimation; Workpiece clamping and positioning: Place the workpiece on the clamping surface of the workpiece clamping and chip removal subsystem, start the vacuum generator to create negative pressure inside the workpiece clamping and chip removal subsystem, and fix the workpiece by adsorption; adjust the workpiece clamping and chip removal subsystem to perform lateral positioning and auxiliary clamping of the workpiece. Focusing and trajectory planning: The three-dimensional motion platform subsystem is driven to complete the coarse positioning of the workpiece, and the laser optical path and dynamic focusing subsystem are used in conjunction with low-power laser to complete the fine focus calibration; the three-dimensional model of the convex microlens array is imported into the host computer software, and layer slicing is performed. The contour coordinates of each layer are converted into two-dimensional deflection signals of the scanning galvanometer, and the depth coordinates of each layer are converted into displacement signals of the laser optical path and dynamic focusing subsystem to generate the machining trajectory. Inverted processing: The laser optical path and dynamic focusing subsystem are activated, and the workpiece clamping and chip removal subsystem is simultaneously turned on to introduce gas; the scanning galvanometer completes the scanning processing of the single-layer microstructure contour. After each layer is processed, the laser optical path and dynamic focusing subsystem move the laser focus down along the normal direction by one slice processing layer thickness, and the next layer is processed. This process is repeated layer by layer until the entire convex microlens array is completed. During the processing, the debris is detached from the workpiece surface and collected under the combined action of gravity and directional airflow. After processing is complete, turn off the laser and gas circuit, release the vacuum adsorption and lateral clamping, and remove the workpiece.

10. The method for inverted dynamic focusing laser direct writing of a microlens array according to claim 9, characterized in that, In focusing and trajectory planning, the thickness of a single layer of the slice is 0.5μm-3μm; in inverted machining, the gas introduced into the workpiece clamping and chip removal subsystem is dry compressed air or other inert gas.

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