A method for controlling the polished surface profile of a multimodal adaptive aspherical lens

Abstract

This application relates to a multimodal adaptive aspherical lens polishing surface control method, aiming to solve the problems of over-polishing and under-polishing caused by the inability of existing technologies to adapt stiffness and vibration parameters according to the curvature zones of the lens. First, the surface curvature distribution data of the lens to be polished is obtained to identify the locations of high and low curvature regions. A polishing disk rotating around an axis is provided, with Ni-Ti based shape memory alloy wires embedded in an array within its elastic matrix, and several piezoelectric ceramic ultrasonic vibrators are embedded within it. Differential currents are applied to the alloy wires in different regions according to the curvature data, and the stiffness of the corresponding regions of the polishing disk is adjusted through a martensitic-austenitic phase transformation, with low stiffness adapted to high curvature regions and high stiffness adapted to low curvature regions. During polishing, the ultrasonic vibrators are synchronously controlled to output vibration parameters matching the curvature regions, achieving multimodal coupled polishing. This method effectively avoids over-polishing and under-polishing defects, balancing processing accuracy and efficiency, and meeting the requirements of high-end fields for nanometer-level surface accuracy of aspherical lenses.

Description

Technical Field

[0001] This application relates to the technical field of polishing processes, and in particular to a method for controlling the polishing surface profile of a multimodal adaptive aspherical lens. Background Technology

[0002] Aspherical lenses, with their superior optical properties such as reduced aberrations, improved light-gathering efficiency, and simplified optical system structure, have been widely used in high-end fields such as precision optical imaging, laser processing, and aerospace exploration. Surface accuracy is the core indicator determining the optical performance of aspherical lenses, and polishing, as the final key process in aspherical lens manufacturing, aims to remove residual errors from previous processes while avoiding the introduction of new surface defects, ultimately achieving nanometer-level surface accuracy control.

[0003] Currently, the mainstream aspherical lens polishing technologies mainly include three categories: fixed-stiffness polishing disc polishing, single-mode adaptive polishing, and preliminary multi-mode polishing. Fixed-stiffness polishing disc polishing technology uses resin, metal, or a single-hardness elastomer as the polishing disc substrate. The contact stiffness remains constant during polishing, and processing conditions are adjusted based on preset parameters or operator experience. This is suitable for low-precision aspherical lens processing. Single-mode adaptive polishing technology can be further divided into two categories: variable stiffness adaptation only and ultrasonic vibration assistance only. The former adjusts the polishing disc stiffness through materials with adjustable elastic modulus or mechanical drive mechanisms, but it cannot achieve precise zoned control based on lens curvature distribution, and its response speed is slow. The latter refines the abrasive cutting trajectory and improves removal efficiency by integrating ultrasonic vibration units, but it does not consider the differentiated contact pressure requirements of different curvature regions. Preliminary multi-mode polishing technology attempts to combine stiffness adjustment and ultrasonic vibration, but it has not established a linkage logic between the two modes and the lens curvature distribution. It only uses uniform parameters for full-area polishing, failing to achieve adaptation of curvature, stiffness, and vibration.

[0004] However, existing technologies still have many shortcomings in addressing the complex curvature distribution characteristics of aspherical lenses. First, existing fixed stiffness or single variable stiffness technologies cannot adaptively adjust the contact stiffness of the polishing disc according to the lens curvature distribution. In high curvature areas, due to the large surface curvature, the contact area between the polishing disc and the lens is small and the pressure is concentrated, which easily leads to local over-polishing. In low curvature areas, due to the large contact area and dispersed cutting force, under-polishing is prone to occur. Ultimately, the overall surface accuracy of the lens cannot meet the stringent requirements of high-end fields.

[0005] In summary, existing aspherical lens polishing technologies lack key design features such as zoned adaptive stiffness adjustment based on curvature distribution and a synergistic coupling mechanism between stiffness and ultrasonic vibration. As a result, they struggle to balance processing accuracy and efficiency, failing to meet the demands of high-end fields for nanometer-level surface accuracy of aspherical lenses. Therefore, there is an urgent need for a multimodal adaptive polishing surface control method that can achieve adaptation of curvature, stiffness, and vibration. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to provide a multimodal adaptive aspherical lens polishing surface control method. This method can achieve precise adaptation and coordinated control of the contact stiffness of the polishing disc and the ultrasonic vibration parameters based on the surface curvature distribution of the aspherical lens, effectively avoiding the defects of over-polishing in high curvature areas and under-polishing in low curvature areas, balancing processing accuracy and processing efficiency, and meeting the requirements of high-end fields for the nanometer-level surface accuracy of aspherical lenses.

[0007] The above-mentioned objective of this application is achieved through the following technical solution:

[0008] A method for controlling the polishing surface profile of a multimodal adaptive aspherical lens, characterized by the following steps: Step 1, acquiring surface curvature distribution data of the lens to be polished, and determining the positions of the high curvature region and the low curvature region of the lens; Step 2, providing a polishing disk that rotates around an axis, wherein Ni-Ti based shape memory alloy wires with a diameter of 0.3mm~0.7mm are arrayed and embedded in the elastic matrix of the polishing disk, the shape memory alloy wires are electrically connected to a micro current controller, and several piezoelectric ceramic ultrasonic vibrators are embedded in the elastic matrix of the polishing disk; Step 3, based on the curvature distribution data obtained in Step 1, controlling the surface profile of the aspherical lens in different regions through the micro current controller. Differential currents are passed through the shape memory alloy wires, and the current heating triggers the martensitic-austenitic phase transformation of the shape memory alloy wires, thereby adjusting the contact stiffness of the corresponding area of ​​the polishing disk. Specifically, for the high curvature area of ​​the lens, the shape memory alloy wires in the corresponding area of ​​the polishing disk are controlled to be in the martensitic phase to reduce the contact stiffness; for the low curvature area of ​​the lens, the shape memory alloy wires in the corresponding area of ​​the polishing disk are controlled to be in the austenitic phase to increase the contact stiffness. In step 4, during the polishing operation, several piezoelectric ceramic ultrasonic vibrators are simultaneously controlled to output vibration parameters that match the curvature area of ​​the lens, and multi-mode coupled polishing is performed on the lens to complete the surface accuracy correction.

[0009] As a preferred embodiment of the present invention, the phase transformation temperature of the base shape memory alloy wire is 60℃~80℃. In step 3, the current supplied to the shape memory alloy wire corresponding to the high curvature region is 0.4A~0.6A, so that the temperature of the shape memory alloy wire is maintained below 60℃ and in the martensitic phase, and the contact stiffness of the polishing disk in the corresponding region is 1500N / m~2000N / m; the current supplied to the shape memory alloy wire corresponding to the low curvature region is 1.0A~1.3A, so that the temperature of the alloy wire is raised to 70℃~80℃ and transforms into the austenitic phase, and the contact stiffness of the polishing disk in the corresponding region is 4000N / m~4500N / m.

[0010] As a preferred embodiment of the present invention, the piezoelectric ceramic ultrasonic vibrator is embedded in a radial section along the polishing disk. In step 4, the piezoelectric ceramic ultrasonic vibrator controls the corresponding section vibrator to output a high-frequency, low-amplitude vibration of 70kHz~80kHz with an amplitude of 0.5μm~1μm for the high curvature region of the lens, and controls the corresponding section vibrator to output a low-frequency, high-amplitude vibration of 20kHz~30kHz with an amplitude of 3μm~5μm for the low curvature region of the lens.

[0011] As a preferred embodiment of the present invention, the shape memory alloy wire and the micro current controller are electrically connected through multiple independent conductive slip rings. The stationary ring of the conductive slip ring is connected to the micro current controller, and the moving ring is connected to the shape memory alloy wire in each region through a radially partitioned current collector plate inside the polishing disk. The number of channels of the conductive slip ring is consistent with the number of partitions of the shape memory alloy wire.

[0012] As a preferred embodiment of the present invention, a laser pretreatment step is further included between step 1 and step 2, wherein a pulsed laser generator is used to perform photothermal softening treatment on the polished area according to the curvature distribution of the lens.

[0013] As a preferred embodiment of the present invention, during photothermal softening treatment, the pulsed laser generator uses a laser energy density of 5 J / cm² to 8 J / cm² and a scanning frequency of 500 Hz for the high curvature region, and a laser energy density of 10 J / cm² to 12 J / cm² and a scanning frequency of 200 Hz for the low curvature region.

[0014] As a preferred embodiment of the present invention, during photothermal softening treatment, the laser parameters are fed back and corrected in real time by a hardness sensor to ensure the degree of softening.

[0015] As a preferred embodiment of the present invention, in step 1, the curvature distribution data of the lens surface is acquired by a three-dimensional laser scanner.

[0016] As a preferred embodiment of the present invention, after step 4 is completed, a laser-induced phase transition strengthening step is also included, in which the pulsed laser generator is switched to a low energy density mode, and the lens polishing surface is scanned in its entirety at an energy density of 3J / cm²~5J / cm² and a scanning frequency of 100Hz. The microstructure phase transition of the surface is achieved through photothermal induction, thereby improving the wear resistance of the lens surface.

[0017] As a preferred embodiment of the present invention, during the polishing process in step 4, a surface interferometer is also used to collect the surface error data of the lens in real time. If a local surface error is detected to exceed the set value, the current amplitude of the shape memory alloy wire in the corresponding area is adjusted to correct the contact stiffness, and the frequency of the piezoelectric ceramic ultrasonic vibrator is adjusted until the surface error is reduced to within the set range, thereby achieving the correction of the surface accuracy.

[0018] In summary, the beneficial technical effects of this application are as follows:

[0019] This application acquires surface curvature distribution data of the lens to be polished by setting up a three-dimensional laser scanner. Combined with Ni-Ti based shape memory alloy wires embedded in the elastic matrix of the polishing pad and a micro current controller, differentiated currents are applied to the alloy wires in different areas to trigger the martensitic-austenitic phase transformation. This achieves zoned adaptive adjustment of the contact stiffness of the corresponding areas of the polishing pad. It specifically solves the core problem of existing technologies that cannot accurately adapt stiffness according to the curvature distribution of the lens, resulting in over-polishing in high curvature areas and under-polishing in low curvature areas. It effectively balances the contact pressure in different curvature areas, significantly improves the overall surface accuracy of the lens, and meets the requirements of high-end fields for nanometer-level surface accuracy.

[0020] This application embeds several piezoelectric ceramic ultrasonic vibrators arranged radially in the elastic matrix of the polishing disc. During polishing, the output vibration parameters are synchronously controlled to match the curvature region of the lens, forming a multimodal coupling control mechanism with the partition stiffness adjustment. This solves the defects of the prior art where stiffness adjustment and ultrasonic vibration are independently controlled, and the processing accuracy and efficiency cannot be balanced. The high-frequency low-amplitude vibration in the high curvature region can refine the abrasive cutting trajectory and protect the microscopic surface, while the low-frequency high-amplitude vibration in the low curvature region can improve the material removal efficiency, thus achieving synergistic optimization of accuracy and efficiency.

[0021] This application adopts an array-type embedded design of Ni-Ti based shape memory alloy wires, and achieves stiffness adjustment by triggering phase change through current heating. Compared with existing mechanical drive or elastic material adjustment methods, it has a faster response speed and can achieve independent control of multiple radial regions. It solves the problems of insufficient zoning accuracy and slow response of existing variable stiffness technology, and can dynamically adapt to the contact requirements of different curvature regions of the lens during the rotation of the polishing disc, thereby improving the adaptability and stability of the polishing process. Attached Figure Description

[0022] Figure 1 A simplified flowchart of a multimodal adaptive aspherical lens polishing surface profile control method. Detailed Implementation

[0023] The present application will be further described in detail below with reference to the accompanying drawings.

[0024] like Figure 1As shown, before polishing an aspherical lens, it is necessary to first obtain the surface curvature distribution data of the lens to be polished, based on which subsequent precise adaptation and adjustment can be achieved. Specifically, a mature 3D laser scanner can be used to complete the data acquisition. This device scans the lens surface by emitting a laser beam, and calculates the spatial coordinates of each point using the phase difference or time of flight of the laser reflection signal, thereby fitting complete surface curvature distribution data. After acquisition, the data is denoised and smoothed using conventional image processing algorithms. Then, based on the size of the curvature radius, the lens is divided into high curvature and low curvature regions. Generally, regions with smaller curvature radii and steeper surface arcs are high curvature regions, while regions with larger curvature radii and relatively flat surfaces are low curvature regions. Clarifying the specific location and range of these two types of regions provides data support for the subsequent adjustment of polishing parameters.

[0025] Next, a polishing disc rotating around its axis is prepared for the polishing operation. The main body of the polishing disc includes an elastic matrix, which can be made of materials commonly used in existing technologies, such as silicone rubber or polyurethane elastomers. These materials have a suitable elastic modulus, which not only provides a basis for subsequent stiffness adjustment but also ensures good adhesion to the lens surface during polishing. Ni-Ti based shape memory alloy wires are embedded in the elastic matrix in an array. The diameter of these alloy wires is selected from 0.3mm to 0.7mm. This size range ensures both the structural strength and phase transition response sensitivity of the alloy wires while avoiding the impact of excessively large diameters on the overall elasticity of the elastic matrix. Ni-Ti based shape memory alloy wires are a type of functional material with martensitic-austenitic phase transformation properties. Their core characteristic is that they undergo a crystal structure transformation upon temperature change, leading to significant differences in elastic modulus. The array-type embedding method employs a concentric array along the radial direction of the polishing disk. Specifically, within the elastic matrix, Ni-Ti based shape memory alloy wires are embedded in a concentric array along the radial direction of the polishing disk. Each shape memory alloy wire is processed into a ring structure, and all the ring shape memory alloy wires have different dimensions; that is, the inner and outer diameters of each ring alloy wire increase sequentially, forming a set of ring components with a diameter gradient distribution. These ring shape memory alloy wires of different sizes are sequentially nested along the radial direction of the polishing disk, maintaining a uniform spacing between adjacent ring alloy wires, ensuring that the central axis of all ring alloy wires coincides with the rotation axis of the polishing disk, ultimately forming several concentrically distributed ring stiffness adjustment layers within the elastic matrix.

[0026] The core advantage of this concentric ring array design lies in its ability to divide the polishing disk radially into multiple independent stiffness-adjustable regions. Each ring-shaped shape memory alloy wire corresponds to a radial partition. When a differentiated current is applied to the ring alloy wires in different radial partitions via a micro current controller, the ring alloy wires at different positions will undergo martensitic-austenitic phase transformations, thereby changing the overall stiffness of the elastic matrix of the corresponding radial partition. The small-diameter ring alloy wire located on the inner side of the polishing disk corresponds to the high curvature region of the lens. By applying a small-amplitude current, it is kept in the martensitic phase, reducing the contact stiffness of the radial partition. The large-diameter ring alloy wire located on the outer side of the polishing disk corresponds to the low curvature region of the lens. By applying a large-amplitude current, it is transformed into the austenitic phase, increasing the contact stiffness of the radial partition. Through this structural design, the polishing disc can form a stiffness distribution that gradually increases radially from the inside to the outside. The inner side of the polishing disc corresponds to the high curvature area of ​​the matching lens, and the outer side of the polishing disc corresponds to the low curvature area of ​​the matching lens, thereby achieving differentiated requirements and ensuring the precise matching of contact pressure in each area during the polishing process. Structurally, this ensures the feasibility and accuracy of zoned stiffness adjustment.

[0027] In practical implementation, the number of annular shape memory alloy wires can be reasonably set according to the complexity of the lens curvature distribution of the polishing disk diameter. For example, for a polishing disk with a diameter of 80mm, 3 to 5 annular alloy wires can be set to cover the inner, middle, and outer radial zones respectively. The material of the annular alloy wires is a conventional Ni-Ti binary alloy or Ni-Ti-Cu ternary alloy. Its annular structure can be prepared by existing processing technology such as die forging and laser cutting to ensure the roundness and dimensional accuracy of the annular structure and avoid the uniformity of stiffness adjustment due to structural deviations.

[0028] Simultaneously, a Ni-Ti-based shape memory alloy wire is electrically connected to a micro current controller. This micro current controller can be a constant current source module based on an MCU (microcontroller unit) from existing technologies. It has multi-channel independent output function, can accurately adjust the amplitude of each output current, and has a fast response speed, which can meet the dynamic control requirements during the polishing process. In addition, several piezoelectric ceramic ultrasonic vibrators are embedded in the elastic matrix of the polishing disc. These vibrators are mature components in the existing ultrasonic processing field. Their working principle is to apply an alternating voltage through an ultrasonic drive power supply to make the piezoelectric ceramic sheet generate high-frequency mechanical vibration. The vibration frequency is usually adjustable in the range of 20kHz to 100kHz. The piezoelectric ceramic ultrasonic vibrators can be embedded by bonding or embedding to ensure that they are firmly connected to the elastic matrix and that the vibration energy can be effectively transferred to the surface of the polishing disc. The distribution of the vibrators must be adapted to the subsequent zone control logic to ensure that each area corresponding to the curvature receives a matching vibration effect.

[0029] After completing the preliminary preparations, the core parameter control and polishing operation stage begins. Based on the previously acquired lens curvature distribution data, differentiated currents are applied to Ni-Ti based shape memory alloy wires in different regions through a micro current controller. These different regions correspond one-to-one with the high curvature and low curvature regions of the lens to the radial partitions of the polishing disk. The shape memory alloy wires within the same partition can be connected in parallel through a pre-set radial partition current collector inside the polishing disk. This current collector is an existing metal conductive plate, and its function is to aggregate the alloy wire lines in the same region, facilitating connection with an external control unit. When an electric current passes through the alloy wire, it generates Joule heating. This heat is used to trigger the martensitic-austenitic phase transformation of the shape memory alloy wire. For the high curvature region of the lens, a small current is passed through the alloy wire in the corresponding polishing pad section to keep the wire's temperature below its phase transformation temperature. At this time, the alloy wire is in the martensitic phase, with a low elastic modulus, which reduces the contact stiffness of the polishing pad in that region, thus avoiding over-polishing caused by the small contact area and concentrated pressure in the high curvature region. For the low curvature region of the lens, a larger current is passed through the alloy wire in the corresponding polishing pad section to raise the wire's temperature above its phase transformation temperature, causing it to transform from the martensitic phase to the austenitic phase. At this time, the elastic modulus of the alloy wire increases significantly, and the contact stiffness of the polishing pad in that region increases accordingly, meeting the cutting force requirements of the low curvature region and avoiding under-polishing. It should be noted that the phase transition temperature of Ni-Ti based shape memory alloy wire is an inherent characteristic. By selecting Ni-Ti alloys with different composition ratios, the desired phase transition temperature range can be obtained. With the adjustment of the current amplitude, the phase transition of the alloy wire can be precisely controlled, thereby achieving quantitative adjustment of the contact stiffness.

[0030] Furthermore, based on the high curvature and low curvature regions of the lens and referencing the hardness variations in different areas of the polishing pad, the contact pressure between the polishing pad and the lens is dynamically adjusted, enabling grinding of different intensities to be achieved for different areas of the lens.

[0031] During the polishing process, the polishing disc rotates around its own axis under the drive of the motor, maintaining a certain polishing pressure on the lens surface. Simultaneously, several piezoelectric ceramic ultrasonic vibrators are controlled to operate, outputting vibration parameters that match the lens's curvature region. Specifically, for the high curvature region of the lens, the corresponding piezoelectric ceramic ultrasonic vibrators output high-frequency, low-amplitude vibrations. These vibrations, with their higher frequency and smaller amplitude, refine the cutting trajectory of the abrasive grains, reducing the amount of material removed per unit time and preventing over-polishing while ensuring processing accuracy. For the low curvature region of the lens, the corresponding piezoelectric ceramic ultrasonic vibrators output low-frequency, high-amplitude vibrations. These vibrations, with their lower frequency and larger amplitude, enhance the impact cutting effect of the abrasive grains on the material, improving material removal efficiency and ensuring processing progress in the low curvature region. The synergistic effect of stiffness adjustment and ultrasonic vibration constitutes multimodal coupled polishing. Through the linkage of these two control methods, the problem of mismatched contact pressure in different curvature regions is solved, and the cutting effect is optimized, ultimately achieving the surface accuracy correction of the lens and realizing nanometer-level surface control.

[0032] It should be further explained that the electrical connection during the rotation of the polishing disc can be achieved through multiple independent conductive slip rings in the existing technology. The stationary ring of the conductive slip ring is fixedly connected to the micro current controller, and the moving ring rotates synchronously with the rotation axis of the polishing disc. The moving ring is connected to the radially partitioned current collector plate inside the polishing disc through a flexible wire. The number of rings of the conductive slip ring is consistent with the number of partitions of the shape memory alloy wire, ensuring that each differentiated current can be transmitted stably, avoiding problems such as wire entanglement and poor contact during rotation, and ensuring the reliability of control.

[0033] When implementing the above stiffness adjustment process, the selected Ni-Ti based shape memory alloy wire has a clear phase transformation temperature range. Its martensite-austenite phase transformation temperature is set to 60℃~80℃. This phase transformation temperature range has been specifically selected to avoid the interference of the polishing environment temperature on the alloy phase state, and to achieve phase state switching quickly through current heating, thus taking into account both control reliability and response efficiency.

[0034] For the radial partitions of the polishing pad corresponding to the high curvature region of the lens, a current with an amplitude of 0.4A~0.6A is applied to the annular shape memory alloy wire in this region via a micro current controller. According to Joule's law, the heat generated by the current passing through the alloy wire is positively correlated with the square of the current, the resistance, and the energizing time. Combined with the inherent resistance characteristics of the selected Ni-Ti based shape memory alloy wire, this current amplitude can precisely maintain the temperature of the alloy wire below 60℃, i.e., below its phase transformation temperature lower limit, at which point the alloy wire remains in the martensitic phase. Since the martensitic phase of the Ni-Ti based shape memory alloy has a low elastic modulus, the contact stiffness of the corresponding polishing pad partition is reduced to 1500N / m~2000N / m. This stiffness level is suitable for the characteristics of the high curvature region and the small contact area with the polishing pad, where pressure is easily concentrated, effectively avoiding excessive local material removal.

[0035] For the radial sections of the polishing pad corresponding to the low curvature region of the lens, a current with an amplitude of 1.0A~1.3A is supplied to the annular shape memory alloy wire in this region via a micro current controller. The larger current amplitude generates more Joule heat, causing the alloy wire temperature to rise rapidly to 70℃~80℃. This temperature range falls within the phase transformation temperature range of the alloy, prompting the alloy wire to completely transform from the martensitic phase to the austenitic phase. The elastic modulus of the austenitic Ni-Ti-based shape memory alloy is significantly higher than that of the martensitic phase, thereby increasing the contact stiffness of the corresponding polishing pad section to 4000N / m~4500N / m. This stiffness level meets the requirements of a large contact area between the low curvature region and the polishing pad, necessitating sufficient cutting force to ensure adequate material removal and avoid under-polishing.

[0036] It should be noted that by adjusting the current amplitude, the temperature of the alloy wire can be precisely controlled, thereby stabilizing and regulating the phase state, and ultimately achieving quantitative adjustment of the contact stiffness. This ensures a dynamic balance between polishing pressure and material removal efficiency in different curvature regions, providing parameter assurance for nanoscale surface precision control. Furthermore, this parameter range has good compatibility; it can be fine-tuned by ±0.1A based on the specific composition of the selected Ni-Ti based shape memory alloy wire, such as Ni-Ti binary alloy or Ni-Ti-Cu ternary alloy, as well as the material and thickness of the polishing disc's elastic matrix, to adapt to different processing scenarios.

[0037] The piezoelectric ceramic ultrasonic vibrator is precisely matched with the radial stiffness partition of the polishing disk. It is arranged by embedding the vibrator in the radial partition of the polishing disk. That is, the number of partitions and the radial coverage of the vibrator are completely consistent with the stiffness control partition of the ring shape memory alloy wire mentioned above. At least one piezoelectric ceramic ultrasonic vibrator is embedded in each radial partition, and the vibrators in the same partition are connected in parallel through the circuit and controlled by an independent ultrasonic drive module to ensure that the vibration parameters of each partition can be adjusted individually.

[0038] In the multimodal coupling stage of the polishing operation, the output parameters of the piezoelectric ceramic ultrasonic vibrator for the corresponding zone are precisely matched and controlled according to the differentiated processing requirements of the high and low curvature regions of the lens. For the high curvature region of the lens, its surface curvature is steep, the contact area with the polishing pad is small, and the corresponding polishing pad zone has been kept at low stiffness by shape memory alloy wire control. At this time, the piezoelectric ceramic ultrasonic vibrator in this zone is controlled to output high-frequency vibration of 70kHz~80kHz and low-amplitude vibration of 0.5μm~1μm. High-frequency vibration can significantly refine the cutting trajectory of abrasive grains on the polishing interface, reduce the impact force of a single abrasive grain on the lens surface, and avoid microscopic surface damage caused by concentrated cutting force under low stiffness adaptation; low-amplitude vibration can control the material removal rate to be within a mild range, and together with the pressure buffering effect of low stiffness, the risk of over-polishing in the high curvature region is doubly avoided from both the aspects of cutting strength and contact pressure, while improving the surface processing quality.

[0039] For the low curvature region of the lens, where the surface is relatively flat and the contact area with the polishing pad is large, the corresponding polishing pad section has been controlled by shape memory alloy wire to maintain high rigidity to ensure cutting force. At this time, the piezoelectric ceramic ultrasonic vibrator in this section outputs low-frequency vibration of 20kHz~30kHz and high-amplitude vibration of 3μm~5μm. The low-frequency vibration can enhance the impact cutting effect of the abrasive grains on the material surface. Combined with the stable contact pressure brought by the high rigidity, it can significantly improve the material removal efficiency per unit time and solve the problem of cutting force dispersion and under-polishing risk caused by the large contact area in the low curvature region. The high-amplitude vibration can optimize the contact state between the abrasive grains and the material surface, avoid the abrasive grains from failing due to excessive contact area, and ensure that the processing efficiency and surface correction progress are promoted in sync.

[0040] The aforementioned vibration parameter range not only conforms to the conventional working characteristics of piezoelectric ceramic ultrasonic vibrators (20kHz~100kHz is a commonly used frequency range for ultrasonic processing, and the micron-level amplitude can be precisely controlled by the drive power supply), but also achieves optimal synergy with the stiffness parameters of the corresponding zones. The high curvature region forms a combination of low stiffness and high-frequency, low-amplitude vibration, focusing on surface accuracy and surface quality; the low curvature region forms a combination of high stiffness and low-frequency, high-amplitude vibration, balancing processing efficiency and removal uniformity. Ultimately, through this precise vibration control of the zones, a multimodal coupling effect is formed with stiffness adjustment, comprehensively ensuring the overall surface accuracy correction effect of the aspherical lens.

[0041] To achieve precise supply of differentiated current to shape memory alloy wires in different radial zones while the polishing disc is rotating, and to avoid problems such as wire tangling and poor contact, a stable electrical connection is established between the shape memory alloy wires and the micro current controller through multiple independent conductive slip rings. This connection structure is the key to ensuring the reliability of zone stiffness adjustment.

[0042] The conductive slip ring adopts a mature multi-channel independent loop structure, which consists of two core parts: a stationary ring and a moving ring. The stationary ring is a fixed component that is directly connected to the multi-channel output terminals of the micro current controller via wires, ensuring stable input of control signals and current. The moving ring is a rotating component that is fixed coaxially with the rotation axis of the polishing disk and can rotate synchronously with the polishing disk around the axis. The moving ring is electrically connected to the pre-set radial partition current collector plate inside the polishing disk through several flexible conductive wires. The toroidal shape memory alloy wires of each radial partition mentioned above are all connected to the corresponding radial partition current collector plate through internal leads. That is, all toroidal shape memory alloy wires in the same radial partition are connected in parallel to the current collector plate of that partition, and then the current collector plate is uniformly connected to the corresponding terminal of the moving ring.

[0043] Crucially, the number of independent channels in the conductive slip rings perfectly matches the number of radial sections in the shape memory alloy wire. For example, if the polishing disk is divided into three stiffness adjustment sections radially, the corresponding conductive slip rings are configured with three independent channels. Each channel corresponds to the current transmission of one radial section, ensuring that the different amplitude currents output by the micro current controller can be accurately transmitted to the corresponding shape memory alloy wire sections through their respective independent channels, without crosstalk or interference between different sections. This ensures the independence and precision of stiffness adjustment in each radial section from the circuit connection perspective, enabling the polishing disk to achieve stable stiffness adaptation to the lens curvature distribution, providing reliable circuit support for multimodal coupling polishing.

[0044] In addition, the radial partition current collector can be made of existing high-conductivity metal plates such as copper foil and aluminum substrate, and is fixed inside the elastic matrix of the polishing pad by bonding or embedding. Its shape is adapted to the radial partition contour of the polishing pad, and the surface is insulated to avoid short circuits between different partition current collectors. The flexible conductive wire is made of wear-resistant and bend-resistant silver-plated copper wire or alloy wire to ensure that the wire is not easy to break during the long-term rotation of the polishing pad, further improving the service life and stability of the electrical connection.

[0045] After obtaining the surface curvature distribution data of the lens to be polished and identifying the locations of high and low curvature regions using a 3D laser scanner, this method adds a laser pretreatment step before preparing the polishing pad to further optimize the cutting effect of subsequent polishing operations and reduce the differences in processing difficulty caused by uneven material hardness in different curvature regions. This step uses a pulsed laser generator to perform targeted photothermal softening treatment on the lens polishing area, laying a uniform and easily machinable material foundation for subsequent multimodal coupling polishing.

[0046] The pulsed laser generator used is a mature nanosecond-level pulsed laser in existing technology. Its core working principle is to utilize the photothermal effect of pulsed lasers to concentrate laser energy onto a thin layer of the lens surface, causing the surface temperature of the material to rise rapidly to the softening point, but not to the melting temperature, thereby reducing the material's hardness and cutting resistance while avoiding damage to the lens's internal structure. In the specific photothermal softening process, the pulsed laser generator uses differentiated laser parameters for high-curvature and low-curvature regions based on the lens curvature distribution data determined earlier. For the high-curvature region of the lens, where the surface arc is steep and contact pressure is easily concentrated during subsequent polishing, excessive softening may lead to surface collapse. Therefore, a combination of a low energy density of 5J / cm²~8J / cm² and a high scanning frequency of 500Hz is used. The low energy density controls the softening depth, typically 1μm~3μm, avoiding changes in the properties of deeper materials, while the high scanning frequency ensures that the laser energy is within the specified range. The high-curvature region has a uniform surface distribution, achieving gentle and uniform softening. For the low-curvature region of the lens, the surface is relatively flat, the contact area is large during subsequent polishing, and the cutting force is dispersed, requiring more thorough softening to improve cutting efficiency. Therefore, a combination of a high energy density of 10J / cm²~12J / cm² and a low scanning frequency of 200Hz is used. The high energy density can enhance the softening effect and reduce the material's cutting resistance, while the low scanning frequency can extend the laser's action time per unit area, ensuring that the softening degree meets the standard and providing suitable material conditions for the subsequent high-rigidity, low-frequency, high-amplitude vibration polishing mode.

[0047] To precisely control the softening degree of each region and avoid insufficient or excessive softening, this method introduces a real-time feedback adjustment mechanism during the photothermal softening process. A hardness sensor is used to detect the softened hardness of the lens surface in real time. This hardness sensor is a microhardness sensor with an accuracy of HV0.01, which is currently available in the technology. Its detection probe moves synchronously with the laser scanning trajectory, collecting surface hardness data of high and low curvature regions in real time and transmitting the data to the main control system. The control system presets a target softening hardness range adapted to the subsequent polishing process. When the hardness of a certain region is detected to be higher than the target range (i.e., insufficient softening), the laser energy density of that region is automatically increased by 0.5 J / cm² each time, or the scanning frequency is decreased by 50 Hz each time. When the hardness of a certain region is detected to be lower than the target range (i.e., excessive softening), the laser energy density is automatically decreased or the scanning frequency is increased. Through this dynamic correction mechanism, it is ensured that the softening degree of both high and low curvature regions of the lens accurately matches the cutting requirements of subsequent polishing, providing a prerequisite for achieving nanometer-level surface accuracy control.

[0048] In step 1, the acquisition of the curvature distribution data of the lens surface is completed using a mature 3D laser scanner. With its non-contact measurement characteristics, this device can avoid scratching or contaminating the surface of the lens to be processed, and can achieve micron-level measurement accuracy, which fully meets the data accuracy requirements of subsequent zonal adaptation and control.

[0049] During the data acquisition process, the lens to be polished is first fixed to the measurement platform using vacuum adsorption or a flexible clamp, ensuring that the lens center coincides with the measurement reference axis of the 3D laser scanner to avoid data distortion caused by clamping deviations. The 3D laser scanner can be a triangulation or time-of-flight type device. Its working principle is to emit a continuous laser beam to scan the entire surface of the lens. After the laser beam hits the lens surface, it is reflected. The scanner's built-in photodetector captures the reflected signal, and by combining the time difference or phase difference between laser emission and reception, the 3D spatial coordinates of each scan point are calculated. To ensure the integrity of data coverage, the scanning path can be set to a spiral or grid pattern. The scanning resolution is set according to the lens size and accuracy requirements to ensure no measurement blind spots.

[0050] After scanning, the scanner's built-in data analysis software processes the massive amount of collected 3D coordinate points. First, it uses filtering algorithms to remove outliers caused by environmental interference or equipment noise. Then, it employs surface fitting algorithms such as the least squares method to fit the discrete coordinate points into a complete 3D model of the lens surface. Next, the curvature calculation module calculates the curvature value at each point on the model, ultimately generating a global surface curvature distribution map. Based on the curvature values, the high-curvature and low-curvature regions of the lens can be clearly defined. Typically, a preset curvature radius threshold is used as the boundary. Regions with a curvature radius smaller than this threshold and a steeper surface are identified as high-curvature regions, while regions with a curvature radius larger than this threshold and a relatively flat surface are identified as low-curvature regions. The specific location coordinates and coverage of both types of regions are recorded, providing precise data support for subsequent laser preprocessing, polishing disc stiffness adjustment, and ultrasonic vibration parameter matching.

[0051] After completing the multimodal coupling polishing and surface accuracy correction in step 4, to further optimize the mechanical properties of the polished lens surface and extend its service life under complex working conditions, this method adds an additional laser-induced phase transition strengthening step. This step shares the same pulsed laser generator as the laser pretreatment step described above, and the function can be switched simply by changing the working mode of the overall control system. No additional dedicated equipment is required, simplifying the overall process layout and reducing equipment investment costs.

[0052] During the specific enhancement process, the pulsed laser generator was switched to a low-energy-density operating mode, employing an energy density of 3J / cm²~5J / cm² combined with a scanning frequency of 100Hz to perform a uniform scan across the entire polished surface of the lens. This parameter combination was specifically optimized. The low-energy-density design avoids damage to the corrected nanoscale surface profile caused by excessive energy, while precisely raising the temperature of the thin layer on the lens surface to near the phase transition critical temperature, triggering microstructural transformation. The 100Hz scanning frequency ensures uniform distribution of laser energy on the surface, avoiding performance inconsistencies caused by localized energy concentration, while balancing enhancement efficiency and processing effect.

[0053] Its core working principle is to utilize the precise photothermal effect of pulsed lasers to induce a microscopic phase transition in the lens surface material. When laser energy acts on a thin surface layer, the material atoms gain energy and rearrange themselves. The disordered grain structure that may exist after polishing is transformed into a dense, uniform fine-grained or amorphous structure. This optimization of the microstructure can significantly improve the surface hardness and wear resistance of the material. It should be noted that this strengthening process only acts on an extremely thin area of ​​the lens surface and will not affect the internal optical performance or overall structural stability of the lens. Moreover, the entire process is non-contact, avoiding damage to the precision of the already formed surface shape.

[0054] Through this laser-induced phase transition strengthening step, the wear resistance of the polished lens surface can be greatly improved, effectively resisting slight friction or particle impact that may occur during subsequent assembly and use, ensuring long-term stability of its optical performance, and further expanding the application scenarios of lenses in high-end fields such as aerospace and laser processing where surface wear resistance is required.

[0055] In the multimodal coupling polishing process in step 4, in order to monitor the changes in surface accuracy in real time and correct the processing errors in a timely manner, this method simultaneously introduces a surface interferometer for real-time detection and closed-loop control. Through the dynamic cycle of detection, judgment and adjustment, it is ensured that the final surface accuracy of the lens stably reaches the preset standard.

[0056] The surface profile interferometer used is a mature, high-precision optical inspection device in existing technology. Fizeau or Michelson interferometers can be selected, with inspection accuracy reaching the nanometer level, perfectly matching the surface profile accuracy requirements of high-end aspherical lenses. This interferometer generates surface profile interference fringes by emitting monochromatic parallel light to illuminate the polished surface of the lens, utilizing the principle of light interference. An image sensor then acquires the interference fringe images, and a built-in algorithm analyzes and calculates the deviation values ​​of each point on the lens surface from the ideal surface profile, i.e., the surface profile error data. During the inspection process, the inspection field of view of the surface profile interferometer corresponds in real time to the polishing area of ​​the polishing disk, and can move synchronously with the rotation and feed of the polishing disk, achieving real-time monitoring of the entire lens polishing process without blind spots. The acquired surface profile error data is transmitted to the central control system in real time through a data interface, providing a basis for control decisions.

[0057] The overall control system presets a permissible range of surface shape error to match the lens's usage requirements. This setting is typically set to within λ / 20 based on the requirements of high-end applications. The control system compares the collected local surface shape error data with the preset setting in real time. When it detects that the surface shape error in a certain area exceeds the setting value, such as over-polishing in a high-curvature area leading to excessive error, or under-polishing in a low-curvature area leading to excessive error, it immediately activates a collaborative adjustment mechanism. On one hand, it sends instructions to the micro current controller for the radial partition of the polishing pad corresponding to that area, fine-tuning the current amplitude of the shape memory alloy wire. By changing the phase ratio of the alloy wire, it corrects the contact stiffness. In over-polished areas, the current is lowered to reduce stiffness, and in under-polished areas, the current is raised to increase stiffness. On the other hand, it simultaneously sends instructions to the ultrasonic drive module to adjust the frequency of the piezoelectric ceramic ultrasonic vibrator in the corresponding partition, optimizing the abrasive cutting intensity. In over-polished areas, the frequency is raised to refine the cutting, and in under-polished areas, the frequency is lowered to enhance the cutting.

[0058] After adjustment, the surface interferometer continues to monitor the area in real time. If the surface error still has not been reduced to within the set range, the control system will repeat the above adjustment process until the error meets the requirements. This closed-loop mechanism of real-time detection and dynamic coordinated adjustment can promptly compensate for surface deviations caused by material property fluctuations and slight parameter drifts during the polishing process, avoid error accumulation, and ensure that the surface accuracy of each area of ​​the lens can be stably met, ultimately achieving the goal of high-precision and high-stability surface accuracy correction.

[0059] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A multi-modal adaptive aspherical lens polishing surface shape control method, characterized by, Includes the following steps: Step 1: Obtain the surface curvature distribution data of the lens to be polished, and determine the positions of the high curvature region and the low curvature region of the lens; Step 2: Provide a polishing disk that rotates around an axis. Ni-Ti based shape memory alloy wires with a diameter of 0.3mm to 0.7mm are embedded in an array within the elastic matrix of the polishing disk. The shape memory alloy wires are electrically connected to a micro current controller. Several piezoelectric ceramic ultrasonic vibrators are embedded within the elastic matrix of the polishing disk. Step 3: Based on the curvature distribution data obtained in Step 1, differentiated currents are applied to the shape memory alloy wires in different regions through the micro current controller. The current heating triggers the martensitic-austenitic phase transformation of the shape memory alloy wires, thereby adjusting the contact stiffness of the corresponding region of the polishing disk. Specifically, for the high curvature region of the lens, the shape memory alloy wire in the corresponding region of the polishing disk is controlled to be in the martensitic phase to reduce contact stiffness; for the low curvature region of the lens, the shape memory alloy wire in the corresponding region of the polishing disk is controlled to be in the austenitic phase to increase contact stiffness. Step 4: During the polishing process, several piezoelectric ceramic ultrasonic vibrators are simultaneously controlled to output vibration parameters that match the curvature region of the lens, and multi-mode coupling polishing is performed on the lens to complete the surface accuracy correction. The phase transformation temperature of the base shape memory alloy wire is 60℃~80℃. In step 3, the current flowing through the shape memory alloy wire corresponding to the high curvature region is 0.4A~0.6A, so that the temperature of the shape memory alloy wire is maintained below 60℃ and in the martensitic phase, and the contact stiffness of the polishing disk in the corresponding region is 1500N / m~2000N / m; the current flowing through the shape memory alloy wire corresponding to the low curvature region is 1.0A~1.3A, so that the temperature of the alloy wire rises to 70℃~80℃ and transforms into the austenitic phase, and the contact stiffness of the polishing disk in the corresponding region is 4000N / m~4500N / m. The piezoelectric ceramic ultrasonic vibrator is embedded in the radial section along the polishing disk. In step 4, the piezoelectric ceramic ultrasonic vibrator controls the corresponding section vibrator to output high-frequency low-amplitude vibration of 70kHz~80kHz and amplitude of 0.5μm~1μm for the high curvature region of the lens, and controls the corresponding section vibrator to output low-frequency high-amplitude vibration of 20kHz~30kHz and amplitude of 3μm~5μm for the low curvature region of the lens.

2. The multi-modal adaptive aspherical lens polishing surface shape control method of claim 1, wherein, The shape memory alloy wire and the micro current controller are electrically connected through multiple independent conductive slip rings. The stationary ring of the conductive slip ring is connected to the micro current controller, and the moving ring is connected to the shape memory alloy wire in each region through the radial partition current collector plate inside the polishing disk. The number of channels of the conductive slip ring is consistent with the number of partitions of the shape memory alloy wire.

3. The multi-modal adaptive aspherical lens polishing surface shape control method of claim 1, wherein, Between step 1 and step 2, there is also a laser pretreatment step, in which a pulsed laser generator is used to perform photothermal softening treatment on the polished area according to the curvature distribution of the lens.

4. The multi-modal adaptive aspherical lens polishing surface shape control method of claim 3, wherein, During photothermal softening, the pulsed laser generator uses a laser energy density of 5 J / cm²~8 J / cm² and a scanning frequency of 500 Hz for the high curvature region, and a laser energy density of 10 J / cm²~12 J / cm² and a scanning frequency of 200 Hz for the low curvature region.

5. The method for controlling the polished surface profile of a multimodal adaptive aspherical lens according to claim 4, characterized in that, During photothermal softening, the laser parameters are adjusted in real time using a hardness sensor to ensure the degree of softening.

6. The method for controlling the polished surface profile of a multimodal adaptive aspherical lens according to claim 1, characterized in that, In step 1, the curvature distribution data of the lens surface is acquired using a 3D laser scanner.

7. The method for controlling the polished surface profile of a multimodal adaptive aspherical lens according to claim 1, characterized in that, After step 4 is completed, a laser-induced phase transition strengthening step is also included. The pulsed laser generator is switched to a low energy density mode and the lens polishing surface is scanned in its entirety at an energy density of 3J / cm²~5J / cm² and a scanning frequency of 100Hz. The microstructure phase transition of the surface is achieved through photothermal induction to improve the wear resistance of the lens surface.

8. The method for controlling the polished surface shape of a multimodal adaptive aspherical lens according to claim 1, characterized in that, During the polishing process in step 4, a surface interferometer is used to collect the surface error data of the lens in real time. If a local surface error is detected to exceed the set value, the current amplitude of the shape memory alloy wire in the corresponding area is adjusted to correct the contact stiffness. At the same time, the frequency of the piezoelectric ceramic ultrasonic vibrator is adjusted until the surface error is reduced to within the set range, thereby achieving the correction of the surface accuracy.

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