Large-depth-of-field astigmatism correction type implantable contact lens based on photoetching technology and preparation method

Abstract

The invention relates to a large-depth-of-field astigmatism correction type implantable contact lens based on a photoetching technology and a preparation method, and belongs to the technical field of ophthalmology implantation instruments. The optical area of the contact lens comprises a central functional area and a peripheral adaptive area; the diameter of the central functional area is 1.2 mm, and a 32-order continuous curvature gradient structure is formed by processing through a deep ultraviolet curved surface photoetching technology; the curvature change range is 7.0 mm to 7.8 mm. Smooth transition without optical abrupt change is achieved between the 32-order curvature transition area of the central functional area and the peripheral adaptive area through a 0.2 mm wide transition curvature section. A sub-wavelength polarization regulation grating is arranged in the peripheral adaptation area, the grating is formed through the photoetching-ion beam etching technology and is of a rectangular tooth-shaped structure, the grating period is 300-500 nm, the depth is 0.12 m + / -0.02 m, and the included angle between the grating line direction and the optical center axis is 45 degrees. According to the invention, the night glare rate can be greatly reduced, the detail resolution under the medium-high spatial frequency is improved by more than 30% compared with the existing product, and the processing technology can greatly improve the yield.

Description

Technical Field

[0001] This invention belongs to the field of ophthalmic implantable device technology, and relates to an implantable contact lens with large depth of field astigmatism correction based on photolithography technology and its preparation method. Background Technology

[0002] The core technological bottleneck of implantable contact lenses lies in the overall optimization of astigmatism correction, depth of field extension, night vision quality, and detail resolution. Existing technologies suffer from four major shortcomings:

[0003] The high-order curvature gradient technology is insufficient: the highest order of the existing continuous curvature ICL is 12, and there are slight abrupt changes in curvature transition. The contrast sensitivity loss at mid-to-high frequency spatial frequencies is >8%, and the detail resolution is insufficient. Moreover, the processing relies on traditional mechanical polishing, and the accuracy is limited to ±0.005mm, which cannot meet the smooth transition requirements of high-order curvatures such as 32nd order.

[0004] The polarization control structure design is crude: existing polarization control ICLs mostly use simple strip gratings without optimizing the tooth structure and grating direction. The polarization filtering efficiency is less than 70%, and it is not designed in conjunction with curvature gradient, so it cannot take into account the depth of field extension function.

[0005] Poor matching between structural dimensions and optical parameters: The cross-sectional dimensions of existing ICLs do not take into account the distribution of refractive power and the physiological space inside the eye, which can easily lead to abnormal arch height; the refractive index of the substrate is mostly around 1.43, which is not optically matched with the aqueous humor (refractive index 1.336) inside the eye, causing additional spherical aberration.

[0006] Lack of synergy in processing technology: Traditional processes use "curvature processing + grating processing" in steps, with cumulative overlay error >0.003mm. Furthermore, multi-beam laser step-by-step exposure is not used, resulting in insufficient accuracy in the connection between curvature steps and leading to the risk of optical abrupt changes.

[0007] Therefore, there is an urgent need for an implantable contact lens that can provide a better clinical visual experience. Summary of the Invention

[0008] In view of this, and in view of the shortcomings of existing ICLs such as insufficient order, low polarization control efficiency, poor detail resolution, and lack of process synergy, the purpose of this invention is to provide a large depth-of-field astigmatism correction implantable contact lens and its fabrication method based on photolithography technology. By optimizing the 32nd order curvature gradient structure, designing a rectangular toothed subwavelength grating, matching the refractive index and cross-sectional size of the substrate, and developing a multi-beam laser step-by-step exposure process, the invention achieves four functions in synergy: "precise astigmatism correction + full-range depth of field + nighttime polarization optimization + mid-to-high frequency detail enhancement".

[0009] To achieve the above objectives, the present invention provides the following technical solution: An implantable contact lens with large depth of field for astigmatism correction based on photolithography technology is disclosed. The optical area of ​​the contact lens includes a central functional area and a peripheral adapter area. The central functional area has a diameter of 1.2 mm and is formed into a 32-step continuous curvature gradient structure using deep ultraviolet curved surface photolithography. The curvature variation range is 7.0 mm to 7.8 mm. A smooth transition without optical abruptness is achieved between the 32-step curvature gradient area of ​​the central functional area and the peripheral adapter area through a 0.2 mm wide transition curvature segment (7.8 mm to 7.5 mm). The peripheral adapter area is equipped with a subwavelength polarization control grating. The grating is formed by photolithography-ion beam etching process and adopts a rectangular tooth structure (tooth width: tooth pitch = 1:1). The grating period is 300-500 nm, the depth is 0.12 µm ± 0.02 µm, and the direction of the grating lines is at a 45° angle to the optical central axis.

[0010] Furthermore, the single-order change of the 32nd order curvature is 0.025mm ± 0.005mm, the deviation between the principal direction of the curvature change and the patient's astigmatic axis is ≤0.5°, and the astigmatism correction accuracy is ≤0.8D.

[0011] Furthermore, the subwavelength polarization modulation grating has a filtering efficiency of ≥80% for disordered unpolarized light; the substrate of the contact lens is a HEmA-PEG copolymer with a refractive index of 1.47±0.02, a light transmittance of >92%, a water content of 28%-32%, and a maximum thickness difference of ≤0.02mm in the central functional area.

[0012] Furthermore, the deep ultraviolet curved surface lithography technology adopts a "flexible curved surface stage + laser step-by-step exposure" mode, with an exposure resolution ≤0.5µm and an overlay accuracy of ±0.001mm.

[0013] Furthermore, the refractive power formed by the 32-step curvature gradient of the central functional area covers -6.5D to -1.2D, corresponding to visual requirements at distances of 5m, intermediate distances of 0.8m, and near distances of 25cm; the Z-axis cross-sectional dimensions of the contact lens are a total length of 12.6mm, an optical zone diameter of 5.2mm, a central hole of 0.36mm, an edge thickness of ≤0.2mm, and an intraocular arch height that is stable within a safe range of 0.3-0.6mm.

[0014] Furthermore, in the mid-to-high frequency band with a spatial frequency of 10-50 cycles / degree, the contrast sensitivity value of the contact lens is ≥0.6, which is more than 30% higher than that of the existing conventional multifocal ICL with a maximum curvature of 12th order, and the contrast sensitivity loss is ≤5%.

[0015] The present invention also provides a method for preparing the contact lens, comprising the following steps: S1: Substrate pretreatment: HEmA-PEG copolymer is made into a meniscus-shaped contact lens blank, using vacuum adsorption + elasticity... The blank is fixed to a flexible curved platform using a combined pressing and fixing method. The curvature of the platform matches the surface of the blank with a degree of greater than 99.9%, and the displacement error is less than 0.001 mm. S2: Deep ultraviolet curved surface lithography, using a step-by-step exposure mode with 32 independent laser light sources to form a 32-order curvature lithography pattern in the center area of ​​the blank. Each laser beam corresponds to 1 order of curvature, with an exposure energy of 85-95mJ / cm² and an exposure time of 10-15s / order. The exposure sequence is symmetrically advanced from the central axis to the periphery. Real-time correction is achieved through a laser interferometric positioning system. An error calibration is performed after every 5 exposures. The cumulative overlay error of 32 exposures is ≤0.003mm. A compensation scheme of 5% exposure energy attenuation is adopted for adjacent laser overlap areas. S3: Ion beam etching. An ion beam etching machine (etching gas Ar+, ion beam energy 500eV) is used to perform anisotropic etching on the photolithographic pattern at an etching rate of 5nm / min. Simultaneously, a subwavelength polarization modulation grating is processed in the peripheral area to ensure that the perpendicularity of the grating tooth wall is >89.5%, the curvature depth error is <±0.005mm, and the grating depth error is <±0.005µm. S4: Post-processing, the optical surface is polished using a magnetorheological polishing machine, and the surface roughness after polishing is <1nm.

[0016] The beneficial effects of this invention are as follows: This invention achieves astigmatism correction accuracy ≤0.8D, full visual range depth coverage (25cm-5m), and significantly reduced nighttime glare rate through a design of "32-order curvature gradient + subwavelength polarization grating + integrated photolithography processing". Furthermore, it improves detail resolution by more than 30% compared to existing 12-order curvature multifocal contact lenses at mid-to-high frequency spatial frequencies (10-50 cycles / degree). The processing technology, through flexible stage adsorption, step-by-step laser exposure, and simultaneous etching, significantly improves yield. This design is suitable for patients with moderate to high astigmatism (-2.0D to -6.0D) accompanied by decreased accommodative power (accommodative amplitude <2D).

[0017] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a three-dimensional front view of the overall structure of the ICL of the present invention; Figure 2A magnified schematic diagram of a subwavelength polarization modulation grating in the optical region; Figure 3 This is a schematic diagram of a 32-order curvature gradient depth of field coverage. Figure 4 This is a comparison chart of simulated optical performance; Figure 5 Schematic diagram of ICL Z-axis section cutting; Figure 6 This is a flowchart of the integrated ICL (Integrated Cladding) manufacturing process. Detailed Implementation

[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0020] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0021] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0022] The technical solution of this invention consists of three parts: core structure design, optical performance optimization, and integrated processing technology, which are described in detail below with reference to the accompanying drawings: (I) Core Structure Design 1. Overall structure and cross-sectional dimensions This invention provides an implantable collamer lens (ICL) with 32-order curvature gradient astigmatism correction and extended depth of field based on deep ultraviolet lithography technology. Figure 1 This is a three-dimensional front view of the overall structure of the ICL of the present invention. Figure 1 Notes: Optical zone diameter 5.2mm; 32-order curvature gradient zone 1.2mm; peripheral adapter zone includes subwavelength polarization grating; support haptic for intraocular fixation; transition curvature section (0.2mm wide). Figure 5 Note: The total length of the Z-axis section is 12.6 mm (distance between the endpoints of the support haptics), the central hole diameter is 0.36 mm, and the edge thickness is 0.2 mm. The curvature gradient zone is a continuous stepped shape along the Z-axis section, with the thickness change corresponding to each curvature step ≤0.003 mm, ensuring that the intraocular arch height remains stable within the safe range of 0.3-0.6 mm. The section dimensions are optimized based on the physiological space of the posterior chamber of the human eye. The 12.6 mm support haptic length is adapted to the ciliary sulcus diameter, and the 5.2 mm optical zone is adapted to the pupil diameter, avoiding light leakage.

[0023] 2.32nd order curvature gradient center functional area Curvature parameters: 32 curvatures are distributed in an equal gradient, with an initial curvature of 7.0 mm (center) and a final curvature of 7.8 mm (periphery). The single-order change is 0.025 mm ± 0.005 mm. Simulation using Zemax optical design software verified that this curvature gradient has no spherical aberration or coma accumulation, meeting the requirement for a smooth transition of refractive power across the entire viewing distance. The central functional area and the peripheral adaptation area are connected by a 0.2 mm wide transition segment, with the curvature linearly transitioning from 7.8 mm to 7.5 mm, effectively reducing edge aberrations and effectively controlling contrast sensitivity.

[0024] 3. Subwavelength polarization modulation grating Figure 2 Note: The grating period is 300-500nm (matching the visible light wavelength of 400-760nm), the grating depth is 0.12µm±0.02µm, and the grating line direction is at a 45° angle to the optical central axis; the substrate refractive index is 1.47±0.02, which forms an optimal optical match with the aqueous humor refractive index (1.336) to reduce interface reflection loss. Figure 3 Note: The grating uses a rectangular tooth structure with a tooth width to tooth pitch ratio of 1:1 and a tooth wall perpendicularity > 89.5°. The rectangular tooth structure can form a "polarization-selective channel," allowing only light rays aligned with the polarization-sensitive direction of the retinal photoreceptor cells to pass through, thus suppressing polarization state disorder caused by corneal astigmatism.

[0025] (ii) Optimization of optical performance 1. Full field of view depth coverage Figure 3Note: The 32-step curvature gradient forms the "extended focal segment", which corresponds to the visual needs at far distance (5m), medium distance (0.8m), and near distance (25cm). The far focal point corresponds to a curvature of 7.0mm (refractive power -6.5D), the medium focal point corresponds to a curvature of 7.4mm (refractive power -4.2D), and the near focal point corresponds to a curvature of 7.8mm (refractive power -1.2D).

[0026] 2. Improved resolution of details in mid-to-high frequencies Figure 4 Note: The horizontal axis represents spatial frequency (period / degree), and the vertical axis represents the contrast sensitivity value; Curve A is the traditional multifocal ICL, Curve B is the 12th-order ICL, and Curve C is the ICL of this patent; In the mid-to-high frequency band of 10-50 periods / degree, the contrast sensitivity value of the ICL of this patent is ≥0.72, which is more than 30% higher than that of the traditional ICL (≤0.45).

[0027] The 32-step continuous curvature gradient reduces the dispersion of light energy caused by abrupt changes in refractive power, and increases the concentration of light intensity in the mid-to-high frequency band by 40%, making it clearer for patients to recognize small text and complex patterns, especially suitable for people who perform fine work.

[0028] (III) Integrated processing technology Figure 6 Note: The process steps are performed in the order of "S1 Substrate Preparation → S2 Deep Ultraviolet Curved Surface Lithography → S3 Ion Beam Etching → S4 Post-Processing". The key parameters for each step are as follows: S1: The crescent-shaped blank is injection molded with a dimensional accuracy of ±0.002mm. It is fixed on a flexible curved platform using a combination of vacuum adsorption and elastic edge pressing. The platform is made of titanium alloy and silicone pad to ensure that the blank does not deform during processing.

[0029] S2: Employs 32 independent laser light sources, with exposure performed in a "center → periphery" sequence. The exposure energy of each laser beam is independently adjustable, with an exposure time of 10-15 seconds per step. Real-time correction is achieved through a laser interferometric positioning system, resulting in a cumulative overlay error of ≤0.003mm for the 32 exposures. The spot size of the 32 laser beams is 0.0375mm (1.2mm central area / 32 steps), with an overlap rate of 5% between adjacent laser beams. The exposure sequence progresses symmetrically outward from the central axis.

[0030] S3: The ion beam etching adopts the "dual-region synchronous processing" mode. The central region is etched with 32nd order curvature, and the outer region is synchronously etched with subwavelength grating. Ar+ is selected as the etching gas, the ion beam energy is 500eV, and the etching rate is 5nm / min, ensuring that the curvature depth error is <±0.005mm and the grating depth error is <±0.005µm.

[0031] S4: Magnetorheological polishing uses a flexible polishing head with a polishing pressure of 0.1 mPa and a cerium oxide suspension (particle size 0.5 µm) as the polishing fluid. The surface roughness after polishing is <1 nm. Ultrasonic cleaning is carried out in three steps (removal of adhesive → degreasing → rinsing). Finally, it is sterilized with ethylene oxide, with a residual amount of <10 μg / piece.

[0032] In summary, this invention employs a 32-order curvature gradient + rectangular toothed polarizing grating collaborative design, achieving astigmatism correction accuracy ≤0.8D; full-range depth of field coverage of 5m-25cm; and improved mid-to-high frequency detail resolution by over 30%. The Z-axis profile dimensions (12.6mm × 5.2mm × 0.36mm) precisely match the posterior chamber structure of the human eye, with an arch height anomaly rate <3%; the substrate refractive index of 1.47±0.02 forms an optimal optical match with the aqueous humor. A 32-beam laser step-by-step exposure + synchronous etching process achieves an overlay accuracy of ±0.001mm and a surface roughness <1nm.

[0033] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Focusing on the implementation of the core optical functions of the patent, with "precise realization of 32-order curvature gradient, subwavelength polarization grating optical matching, full-range depth-of-field coverage, and improved mid-to-high frequency detail resolution" as the core, while taking into account the water flow in the central aperture and the synergy of optical performance, it ensures that key optical indicators such as astigmatism correction accuracy, depth-of-field range, and night vision quality meet the design requirements. The processing technology is only used as an auxiliary means for the implementation of optical design, focusing on clarifying its guarantee boundary for optical performance, without emphasizing process details.

[0034] I. Preliminary Implementation Preparations The core substrate is made of HEmA-PEG copolymer, which must meet the following requirements: refractive index of 1.47±0.02 in the visible light band (400-760nm), with a detection error controlled within ±0.005; average visible light transmittance >92%, with no local absorption peaks; and water content maintained at 28%-32%, balancing optical stability and biocompatibility. The substrate must possess excellent optical homogeneity, with refractive index distribution non-uniformity ≤1×10⁻⁶. -4 This avoids light scattering or aberration accumulation caused by internal refractive index fluctuations, while ensuring uniformity of refractive power by keeping the maximum thickness difference in the central functional area ≤0.02mm.

[0035] Among the auxiliary optical materials, the deep ultraviolet photoresist needs to be compatible with the 200-280nm wavelength band, have excellent optical stability after exposure, and have a refractive index change of ≤±0.001 before and after exposure to avoid residual photoresist layer affecting the optical performance of the finished product; the polishing slurry uses cerium oxide suspension with a particle size of 0.5µm±0.05µm to ensure that there are no optical defects such as scratches and bubbles on the substrate surface after polishing, and to avoid introducing additional spherical aberration or stray light.

[0036] The auxiliary equipment used for processing is a deep ultraviolet lithography machine and an ion beam etching machine. The former must meet the requirements of exposure resolution ≤0.5µm and overlay accuracy ±0.001mm, while the latter must control the etching depth error ±0.005µm to ensure the forming accuracy of the optical structure.

[0037] II. Core Optical Design Implementation Steps (I) Optical Design and Implementation of the 32nd Order Curvature Gradient Center Functional Region The diameter of the 32-order curvature gradient central functional area is set at 1.2mm, designed with an equal gradient distribution. The central curvature is 7.0mm (corresponding to a distance of 5m and a refractive power of -6.5D), and the peripheral curvature is 7.8mm (corresponding to a near distance of 25cm and a refractive power of -1.2D). The single-order curvature variation is controlled within 0.025mm ± 0.005mm. To ensure optical continuity, a 0.2mm wide transition section is set between the central functional area and the peripheral adaptation area, with the curvature linearly transitioning from 7.8mm to 7.5mm, effectively reducing edge aberrations and controlling the contrast sensitivity loss to ≤5%.

[0038] The auxiliary processing stage adopts a combination of "deep ultraviolet curved surface lithography + ion beam etching". It uses 32 independent lasers for step-by-step exposure, with each laser beam corresponding to the first order of curvature. The exposure energy is controlled at 85-95mJ / cm², and the cumulative overlay error is ≤0.003mm, avoiding optical abrupt changes caused by inter-order connection deviation. During the etching process, the curvature depth is monitored in real time to ensure that the single-order curvature depth error is <±0.005mm, and the overall range of 32 order curvatures is strictly controlled within 7.0mm-7.8mm.

[0039] During testing and verification, a laser interferometer is used to scan the central functional area. The actual value of each curvature must deviate from the design value by ≤±0.002mm, and the overall curvature gradient must meet the requirement of equal gradient distribution. Astigmatism of different degrees from -2.0D to -6.0D is applied through a simulated eye system, and the principal direction of the curvature gradient is adjusted to align with the astigmatism axis to ensure that the axis deviation is ≤0.5° and the astigmatism correction accuracy is ≤0.8D. At the same time, the optical continuity of the transition section is tested to ensure that the contrast sensitivity value of the mid-to-high frequency (30 cycles / degree) is ≥0.72.

[0040] (II) Optical Design and Matching of Subwavelength Polarization Modulation Gratings The subwavelength polarization modulation grating adopts a rectangular tooth structure with a tooth width-to-tooth pitch ratio of 1:1, a period set at 300-500nm, and a depth controlled at 0.12µm±0.02µm. The grating orientation is designed to be at a 45° angle to the optical central axis, ensuring a filtering efficiency of ≥80% for disordered unpolarized light and maximizing the light transmittance in the polarization-sensitive direction of retinal photoreceptor cells.

[0041] In terms of optical matching, the interface between the grating and the substrate is optimized by combining the refractive index of the substrate (1.47±0.02) and the refractive index of the aqueous humor in the eye (1.336), so that the interface reflection loss is ≤3% and the overall light transmission efficiency is improved. At the same time, the perpendicularity of the grating tooth wall is strictly controlled to be >89.5% to avoid polarization direction shift caused by tooth wall tilting and ensure polarization filtering stability.

[0042] (III) Coordinated optimization of central aperture and overall optical parameters The central aperture diameter is set at 0.36 mm to balance aqueous humor flow and optical integrity. At this diameter, light leakage is controlled to ≤1%, ensuring no impact on the imaging quality of the core optical area. The distance between the central axis of the central aperture and the optical axis of the lens area must be <0.02 mm to avoid light refraction or increased aberrations caused by aperture misalignment. The edge thickness of the central aperture is controlled within the range of 0.01-0.2 mm, gradually decreasing along the connecting accessory towards the central aperture to reduce light scattering and reflection at the aperture edge.

[0043] In the overall optical dimension design, the optical zone diameter is 5.2mm (adapting to the maximum diameter of the human pupil to avoid light leakage), the total Z-axis length is 12.6mm (adapting to the ciliary sulcus diameter to ensure intraocular fixation stability), and the intraocular arch height is strictly controlled within a safe range of 0.3-0.6mm, within which optical aberrations are minimized and corneal endothelial cells are not compressed. Simultaneously, the maximum thickness difference in the detection center functional area is ≤0.02mm to avoid refractive power fluctuations caused by uneven thickness and to ensure accuracy in detail recognition.

[0044] III. Implementation Precautions The processing stage must prioritize optical performance. If issues such as exposure energy drift or etching depth deviation occur, processing parameters must be adjusted first to ensure that curvature gradient accuracy and grating parameters meet optical design requirements. This solution is based on a patented design concept, and all parameters are derived from the patent documentation. In actual implementation, reasonable fine-tuning can be made according to equipment performance and material characteristics.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A large depth of focus astigmatism correction type implantable contact lens based on a photolithography technique, characterized by, The optical region of this contact lens includes a central functional area and a peripheral adapter area. The central functional area has a diameter of 1.2 mm and is formed into a 32-step continuous curvature gradient structure using deep ultraviolet curved surface lithography. The curvature range is 7.0 mm to 7.8 mm. The 32-step curvature gradient area of ​​the central functional area and the peripheral adapter area are smoothly transitioned without optical abrupt changes through a 0.2 mm wide transition curvature segment. The peripheral adapter area is equipped with a subwavelength polarization control grating. The grating is formed by photolithography-ion beam etching process, adopts a rectangular tooth structure, has a grating period of 300-500 nm, a depth of 0.12 µm ± 0.02 µm, and the grating lines are at a 45° angle to the optical central axis.

2. The implantable contact lens with large depth of field astigmatism correction based on photolithography technology according to claim 1, characterized in that, The single-order change of the 32nd order curvature is 0.025mm ± 0.005mm, the deviation between the principal direction of the curvature gradient and the patient's astigmatic axis is ≤0.5°, and the astigmatism correction accuracy is ≤0.8D.

3. The implantable contact lens with large depth of field astigmatism correction based on photolithography technology according to claim 2, characterized in that, The subwavelength polarization modulation grating has a filtering efficiency of ≥80% for disordered unpolarized light; the substrate of the contact lens is HEmA-PEG copolymer with a refractive index of 1.47±0.02, a light transmittance of >92%, a water content of 28%-32%, and a maximum thickness difference of ≤0.02mm in the central functional area.

4. The implantable contact lens with large depth of field astigmatism correction based on photolithography technology according to claim 3, characterized in that, The deep ultraviolet curved surface lithography technology adopts the "flexible curved stage + laser step-by-step exposure" mode, with an exposure resolution ≤0.5µm and an overlay accuracy of ±0.001mm.

5. The implantable contact lens with large depth of field astigmatism correction based on photolithography technology according to claim 4, characterized in that, The 32-step curvature gradient of the central functional area provides a refractive power range of -6.5D to -1.2D, corresponding to visual requirements at distances of 5m, intermediate distances of 0.8m, and near distances of 25cm. The Z-axis cross-sectional dimensions of the contact lens are: total length 12.6mm, optical zone diameter 5.2mm, central hole 0.36mm, edge thickness ≤0.2mm, and intraocular arch height stable within a safe range of 0.3-0.6mm.

6. The implantable contact lens with large depth of field astigmatism correction based on photolithography technology according to claim 5, characterized in that, In the mid-to-high frequency band of 10-50 cycles / degree, the contrast sensitivity value of the contact lens is ≥0.6, which is more than 30% higher than that of the existing conventional multifocal ICL with a maximum curvature of 12th order, and the contrast sensitivity loss is ≤5%.

7. A method for preparing a contact lens according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Substrate pretreatment: HEmA-PEG copolymer is made into a meniscus-shaped contact lens blank, using vacuum adsorption + elasticity... The blank is fixed to a flexible curved platform using a combined pressing and fixing method. The curvature of the platform matches the surface of the blank with a degree of greater than 99.9%, and the displacement error is less than 0.001 mm. S2: Deep ultraviolet curved surface lithography, using a step-by-step exposure mode with 32 independent laser light sources to form a 32-order curvature lithography pattern in the center area of ​​the blank. Each laser beam corresponds to 1 order of curvature, with an exposure energy of 85-95mJ / cm² and an exposure time of 10-15s / order. The exposure sequence is symmetrically advanced from the central axis to the periphery. Real-time correction is achieved through a laser interferometric positioning system. An error calibration is performed after every 5 exposures. The cumulative overlay error of 32 exposures is ≤0.003mm. A compensation scheme of 5% exposure energy attenuation is adopted for adjacent laser overlap areas. S3: Ion beam etching. An ion beam etching machine is used to perform anisotropic etching on the photolithographic pattern at an etching rate of 5nm / min. Simultaneously, a subwavelength polarization modulation grating is processed in the peripheral area to ensure that the perpendicularity of the grating tooth wall is >89.5%, the curvature depth error is <±0.005mm, and the grating depth error is <±0.005µm. S4: Post-processing, the optical surface is polished using a magnetorheological polishing machine, and the surface roughness after polishing is <1nm.

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