High-transmission low-aberration ultraviolet optical lens

Abstract

This application discloses a high-transmittance, low-aberration ultraviolet optical lens, relating to the field of optical lens technology. Addressing the problem that existing ultraviolet lenses struggle to balance high transmittance with low aberrations, as well as significant residual chromatic aberration and spherical aberration over a wide wavelength range, this application provides a solution. The lens, along its optical path, sequentially includes a protective lens, a front lens group, an aperture stop, a rear lens group, and an imaging plane. The front lens group consists of a calcium fluoride plano-concave negative lens and a fused silica biconvex positive lens; the rear lens group consists of a calcium fluoride meniscus positive lens, a fused silica biconvex negative lens, and a calcium fluoride plano-convex positive lens. Through specific material combinations and optical power allocation, chromatic aberration is corrected using the dispersion difference between calcium fluoride and fused silica, and spherical aberration and astigmatism are suppressed by optimizing the lens surface shape. This application achieves a balance between high transmittance and low aberrations over a wide wavelength range of 193nm to 400nm, significantly improving focusing energy density and imaging clarity, making it suitable for ultraviolet laser processing and precision inspection.

Description

Technical Field

[0001] This application relates to a high-transmission, low-aberration ultraviolet optical lens, belonging to the field of optical lens technology. Background Technology

[0002] In ultraviolet optics applications, such as ultraviolet laser processing, precision micro / nano manufacturing, and high-resolution imaging detection, optical lenses are core components whose performance directly determines the final processing accuracy and imaging quality of the system. Existing ultraviolet optical lens designs typically employ a combination of multiple lenses, utilizing optical materials with good transmittance in the ultraviolet band, such as fused silica or calcium fluoride (CaF2), and employing traditional optical power allocation principles to construct the imaging optical path. Mainstream designs often focus on optimizing single performance indicators, such as prioritizing transmittance at specific wavelengths or performing localized correction for certain aberrations, while using aperture adjustment to control the beam aperture to meet basic focusing or imaging requirements. These existing technologies can maintain basic optical functions in conventional ultraviolet applications, forming the foundational architecture of current ultraviolet optical systems.

[0003] However, as ultraviolet applications evolve towards shorter wavelengths, higher numerical apertures, and larger fields of view, the aforementioned existing technologies are gradually revealing their inherent limitations. Specifically, when processing wide-band ultraviolet light (such as 193nm to 400nm), traditional designs often struggle to achieve a balance between high transmittance and low aberrations simultaneously due to limitations in material dispersion characteristics and uneven distribution of lens power. This results in significant residual geometric aberrations such as axial chromatic aberration, spherical aberration, and astigmatism, severely impacting focal energy density and image sharpness. Furthermore, existing lens structures often suffer from wavefront distortion due to thermal effects or material absorption issues when dealing with high-power ultraviolet lasers. Some designs excessively increase the number of lenses or employ complex curved surfaces to correct aberrations, increasing assembly difficulty and system size, and introducing more reflection losses, leading to a decrease in overall transmittance. This fails to meet the stringent requirements of high-end ultraviolet applications for "high transmittance, low aberrations," miniaturization, and high stability. Summary of the Invention

[0004] According to one aspect of this application, a high-transmittance, low-aberration ultraviolet optical lens is provided, which aims to solve the technical problem that existing ultraviolet optical lenses are difficult to simultaneously achieve high transmittance and low aberration performance in wide-band (193nm to 400nm) applications.

[0005] Specifically, existing technologies often suffer from significant residual geometric aberrations such as axial chromatic aberration, spherical aberration, and astigmatism due to limitations in material dispersion characteristics and uneven distribution of optical power, which affect focal energy density and imaging clarity. At the same time, traditional designs tend to increase system complexity or introduce additional losses when pursuing aberration correction, failing to meet the stringent requirements of high-end ultraviolet laser processing and precision imaging for high luminous efficiency, high precision, and compact structure.

[0006] To achieve the above objectives, this application provides the following technical solution: This application provides a high-transmission, low-aberration ultraviolet optical lens, comprising a protective lens, a front lens group, an aperture stop, a rear lens group, and an imaging / focusing surface arranged coaxially along the incident light direction; The front lens group includes a first lens and a second lens arranged sequentially along the incident direction. The first lens is a plano-concave negative lens made of calcium fluoride material, and the second lens is a biconvex positive lens made of fused silica material. The rear lens group includes a third lens, a fourth lens, and a fifth lens arranged sequentially along the incident direction. The third lens is a meniscus positive lens made of calcium fluoride material, the fourth lens is a biconcave negative lens made of fused silica material, and the fifth lens is a plano-convex positive lens made of calcium fluoride material. The total optical power of the front lens group is as follows. The total optical power of the rear lens group and the total optical power of the lens Each satisfies a specific combination of optical power to correct chromatic aberration and spherical aberration in the ultraviolet band.

[0007] Furthermore, the total optical power of the front lens group Satisfying the formula: (1) in, The optical power of the first lens. The optical power of the second lens. The center distance between the first lens and the second lens; Furthermore, optical power With focal length The relationship satisfies the formula: (2) Furthermore, the total optical power of the rear lens group Satisfying the formula: (3) in, The optical power of the third lens. The optical power of the fourth lens. The optical power of the fifth lens. The center distance between the third and fourth lenses. The center distance between the fourth and fifth lenses. The center distance between the third and fifth lenses. Furthermore, the total optical power of the lens Satisfying the formula: (4) in, This is the center distance between the front lens group and the rear lens group.

[0008] Optionally, the aberration correction index of the lens satisfies: Axial color difference ≤0.01mm; Maximum ball difference ≤0.005mm; Like scattered ≤0.003mm; Relative distortion ≤0.03%.

[0009] Furthermore, the axial chromatic aberration of the lens Satisfying the formula: (5) in, For the lens in ultraviolet light Focal length in the band (486.1nm), For the lens in ultraviolet light Focal length in the band (656.3nm); Furthermore, the maximum spherical aberration of the lens Satisfying the formula: (6) in, Let be the image-side intercept of the edge ray. The image-side intercept of the paraxial ray; Furthermore, the camera needs to be like a bokeh effect. Satisfying the formula: (7) in, The intercept of the meridian image plane. The intercept of the sagittal image plane; Furthermore, the lens Satisfying the formula: (8) in, For actual image height, For the ideal image high Optionally, the center distance between the first lens and the second lens Satisfying 5mm≤ ≤8mm; The center distance between the third lens and the fourth lens Satisfying 3mm≤ ≤5mm; The center distance between the fourth lens and the fifth lens Satisfying 4mm≤ ≤6mm; The center distance between the front lens group and the rear lens group Satisfying 10mm≤ ≤15mm.

[0010] Optionally, the refractive index n of the calcium fluoride material at 355 nm wavelength satisfies 1.37≤n≤1.39, and the dispersion coefficient v satisfies 94≤v≤96; The refractive index n of the fused silica material at 355nm wavelength satisfies 1.46≤n≤1.47, and the dispersion coefficient v satisfies 67≤v≤68.

[0011] Optionally, the protective lens is a plano-convex lens made of fused silica material, with a center thickness of 1.5 mm to 2.5 mm, and a transmittance of greater than or equal to 90% in the 193 nm to 400 nm wavelength band; The center distance between the protective mirror and the front lens group Satisfying 2mm≤ ≤3mm.

[0012] Optionally, the aperture stop is disposed between the front lens group and the rear lens group, and is positioned close to the rear lens group, and the aperture D of the aperture stop satisfies 2mm≤D≤5mm.

[0013] Optionally, the lens operates in a wavelength range of 193nm to 400nm, with a focal length f of 100mm ≤ f ≤ 150mm, a numerical aperture NA of 0.8 ≤ NA ≤ 1.0, an entrance pupil diameter Din of 8mm ≤ Din ≤ 12mm, and an optical total length TTL of 180mm ≤ TTL ≤ 220mm.

[0014] Optionally, it also includes an integrated lens barrel, in which all lenses are installed by a centering assembly process; The integrated lens barrel is made of aluminum alloy, its surface is anodized, and the inner wall of the lens barrel is provided with matte threads.

[0015] Optionally, the concave surface of the first lens faces the direction of light incidence, the convex surface of the third lens faces the direction of light incidence, and the convex surface of the fifth lens faces the direction of light incidence.

[0016] Optionally, the lens is suitable for ultraviolet laser processing, ultraviolet imaging detection, or spectral analysis applications, and the compatible working wavelengths include 193nm, 248nm, or 355nm.

[0017] The beneficial effects that this application can produce include: This application significantly enhances optical performance in the ultraviolet band through a unique lens combination and material pairing. First, by employing an alternating combination of calcium fluoride (CaF2) and fused silica, the distinctly different dispersion characteristics of these two materials in the ultraviolet band effectively correct axial chromatic aberration and second-order spectral density, enabling the lens to maintain extremely high imaging sharpness and color reproduction across a wide wavelength range of 193nm to 400nm. Second, by scientifically allocating the optical power of the front lens group (negative-positive) and the rear lens group (positive-negative-positive), and combining this with specific lens surface shapes (such as plano-concave and meniscus), while ensuring a large numerical aperture (NA≥0.8), spherical aberration, astigmatism, and distortion are controlled to extremely low levels (e.g., spherical aberration ≤0.005mm), thereby obtaining a near-diffraction-limited focused spot, greatly improving the energy density and micro-machining capabilities of ultraviolet laser processing.

[0018] Furthermore, this application balances high transmittance with system stability in its structural design. The protective lens effectively isolates the internal precision lens from external environmental contamination, while the use of high-transmittance fused silica material ensures efficient transmission of the overall optical path. The optimized aperture position not only controls stray light but also further optimizes beam quality. Combined with an integrated lens barrel and centering assembly process, the cumulative errors caused by multi-part assembly are eliminated, improving the lens's shock resistance and environmental adaptability, enabling it to operate stably for extended periods in high-energy-density environments such as ultraviolet lasers. The overall structure is compact, and the overall optical length is reasonably controlled, facilitating integration into various miniaturized ultraviolet detection devices or processing heads, demonstrating high practical value and promising prospects for widespread application. Attached Figure Description

[0019] Figure 1 A schematic diagram of the overall structure of a high-transmission, low-aberration ultraviolet optical lens provided in one embodiment of this application; Figure 2 A schematic diagram of the transmittance curve of a high-transmittance, low-aberration ultraviolet optical lens provided in one embodiment of this application; Figure label: 1-Protective lens; 2-Front lens group; 21-First lens; 22-Second lens; 3-Aperture stop; 4-Rear lens group; 41-Third lens; 42-Fourth lens; 43-Fifth lens; 5-Imaging plane / Focusing plane; 6-Lens barrel. Detailed Implementation

[0020] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] Example 1 To address the problem that existing ultraviolet optical lenses struggle to balance high transmittance and low aberrations over a wide wavelength range, and that their complex optical path structure makes assembly and adjustment difficult.

[0022] Please refer to Figure 1-2 As shown, this application provides a basic optical architecture scheme. A high-transmission, low-aberration ultraviolet optical lens includes a protective lens 1, a front lens group 2, an aperture 3, a rear lens group 4, and an imaging / focusing surface 5, all coaxially arranged along the incident direction of light. The front lens group 2 includes a first lens 21 and a second lens 22 arranged sequentially along the incident direction. The first lens 21 is a plano-concave negative lens made of calcium fluoride, and the second lens 22 is a biconvex positive lens made of fused silica. The rear lens group 4 includes a third lens 41, a fourth lens 42, and a fifth lens 43 arranged sequentially along the incident direction. The third lens 41 is a meniscus positive lens made of calcium fluoride, the fourth lens 42 is a biconvex negative lens made of fused silica, and the fifth lens 43 is a plano-convex positive lens made of calcium fluoride. The total optical power of the front lens group 2 is... The total optical power of the rear lens group 4 and the total optical power of the lens Each satisfies a specific combination of optical power to correct chromatic aberration and spherical aberration in the ultraviolet band.

[0023] In this embodiment, the protective mirror 1 is located at the foremost position to block dust and isolate the environment. It is made of high-purity fused silica and its surface roughness Ra is less than 0.5 nm through a precision polishing process to reduce scattering loss. The first lens 21 in the front lens group 2 is made of natural or synthetic calcium fluoride crystal. Its incident surface is flat and its exit surface is concave. This plano-concave structure, combined with the low refractive index of calcium fluoride, can effectively diverge the light beam and introduce negative dispersion. The second lens 22 is made of JGS1 grade fused silica. Both sides are convex and are used to converge the light and provide positive optical power. The two lenses are cemented together or separated by air. The large difference in the Abbe number of the materials (calcium fluoride is about 95, and fused silica is about 67) is used to initially correct chromatic aberration. In the rear lens group 4, the third lens 41, also made of calcium fluoride, is designed in a meniscus shape (convex surface facing the object side) to further correct field curvature and astigmatism; the fourth lens 42 is a biconcave lens made of fused silica, which separates the spectrum and balances the optical power; the fifth lens 43 is a plano-convex lens made of calcium fluoride, which ultimately focuses the light onto the imaging plane. The aperture stop 3 is placed between the front and rear groups to limit peripheral rays and control the aperture angle. The optical power distribution of the entire system follows... Principles (among others) (for two sets of spacing), through optimization and The ratio minimizes primary and higher-order aberrations in the ultraviolet band (e.g., 193nm-355nm). This structure, through the combination of positive and negative lenses and special materials, utilizes the complementary dispersive properties of different materials to achieve apochromatic effect within the operating wavelength range. Simultaneously, the specific surface combination effectively suppresses spherical and coma aberrations, ensuring that the lens maintains extremely high transmittance and image sharpness while possessing a high numerical aperture.

[0024] To address the problem of excessive residual aberrations in existing lenses during extreme resolution applications, leading to decreased image contrast or dispersed light spot energy, this application imposes strict limits on the aberration specifications of the lens. Please refer to... Figure 1-2 As shown, the aberration correction index of the lens satisfies: axial chromatic aberration ≤0.01mm; Maximum ball difference ≤0.005mm; Astigmatism ≤0.003mm; relative distortion ≤0.03%.

[0025] In this embodiment, axial chromatic aberration refers to the longitudinal deviation of the focal positions of the F-ray (486nm) and C-ray (656nm) or specific ultraviolet bands (such as 193nm and 355nm). Through the above-mentioned material combination and fine optimization of the radius of curvature, this deviation is controlled within 0.01 mm, meaning that the focal points almost coincide across a broad spectrum from deep ultraviolet to near ultraviolet. Maximum spherical aberration refers to the longitudinal distance between the focal points of the edge rays and paraxial rays, which is controlled within 0.005 mm, ensuring that the beam converging ability under a large aperture is close to the diffraction limit. Astigmatism ΔX is controlled within 0.003 mm, ensuring the coincidence of image points in the meridional and sagittal planes and improving the sharpness of the off-axis field of view. Relative distortion is controlled within 0.03%, meaning high fidelity of image geometry. These specifications are achieved through fine-tuning of the aspherical coefficients (if applicable) or iterative optimization of multiple lens curvatures. In actual processing, an interferometer is needed to detect the surface shape accuracy to above λ / 10, and a centering instrument is used to ensure that the lens eccentricity is less than 3μm. This strict aberration control enables the lens to form a highly concentrated light spot in micro-nano fabrication or to reproduce minute details in imaging inspection, significantly improving the system's processing accuracy and inspection resolution, meeting the needs of high-end semiconductor inspection and precision marking.

[0026] To address the issues of ghosting, increased stray light, or insufficient aberration correction in existing lenses due to improper lens spacing design, this application provides specific settings for the air gaps within each lens group. Please refer to... Figure 1-2 As shown, the center distance between the first lens 21 and the second lens 22 Satisfying 5mm≤ ≤8mm; the center distance between the third lens 41 and the fourth lens 42 Satisfying 3mm≤ ≤5mm; the center distance between the fourth lens 42 and the fifth lens 43 Satisfying 4mm≤ ≤6mm; the center distance between the front lens group 2 and the rear lens group 4 Satisfying 10mm≤ ≤15mm.

[0027] In this embodiment, the center spacing refers to the distance between the vertices of adjacent lenses along the optical axis. Setting the spacing within the range of 5 to 8 millimeters avoids both the bonding stress or processing interference caused by being too close and the deterioration of advanced aberrations caused by being too far apart. This spacing is beneficial for the initial balance of chromatic aberration within the front group. and The diameters are controlled at 3-5 mm and 4-6 mm respectively. This compact arrangement helps the light in the rear group to transition smoothly, reducing the light propagation loss in the air and stray light generated by interface reflection. The separation distance between the front and rear groups is set at 10 to 15 mm, providing physical space for the installation of aperture stop 3. This distance is also a key variable for correcting petzval and field curvature; an appropriate spacing effectively balances the optical power contribution of the front and rear groups, optimizing overall image quality. These spacings are achieved using precision mechanical spacers made of Invar to counteract the effects of thermal expansion and contraction caused by temperature changes, ensuring spacing stability. This reasonable spacing design not only optimizes the optical path and reduces the system's sensitivity to tolerances, but also effectively suppresses ghosting caused by multiple reflections from the lens surface, improving the signal-to-noise ratio and system stability.

[0028] To address the difficulty in chromatic aberration correction caused by unstable refractive index or mismatched dispersion characteristics of existing lens materials in the ultraviolet band, this application clearly defines the physical parameters of the core optical materials. Please refer to... Figure 1-2 As shown, the refractive index n of the calcium fluoride material at 355nm satisfies 1.37≤n≤1.39, and the dispersion coefficient v satisfies 94≤v≤96; the refractive index n of the fused silica material at 355nm satisfies 1.46≤n≤1.47, and the dispersion coefficient v satisfies 67≤v≤68.

[0029] In this embodiment, the selected calcium fluoride crystals must undergo rigorous screening to ensure that their refractive index at 355 nm falls within the range of 1.37 to 1.39, and their Abbe number (dispersion coefficient) is between 94 and 96. This characteristic of low refractive index and high Abbe number makes them ideal negative dispersion elements. The selected fused silica glass (such as Corning 7980 or Heraeus Suprasil series) needs to have a refractive index at 355 nm controlled between 1.46 and 1.47, and an Abbe number between 67 and 68, providing stable positive power and moderate dispersion. In practical applications, other grades of high-purity synthetic CaF2 can also be selected for calcium fluoride, and other brands of ultraviolet-grade quartz can also be selected for fused silica, as long as their optical constants meet the above ranges. This application embodiment does not limit this. The precise matching of these parameters is the basis for realizing apochromatic design. By utilizing the difference in Abbe number between the two (approximately 28), a powerful color difference correction combination is constructed, allowing light of different wavelengths to converge at the same point. The constraints on these material parameters ensure that the lens has extremely low absorption and stable refractive properties in the ultraviolet band, fundamentally guaranteeing the high transmittance and color reproduction capabilities of the optical system and avoiding performance fluctuations caused by batch-to-batch material differences.

[0030] To address the issues of existing lenses lacking effective protection, making internal lenses susceptible to contamination and damage, and significant reflection loss at the incident interface, this application provides a detailed design for the structure and parameters of the protective lens 1. Please refer to... Figure 1-2As shown, the protective lens 1 is a plano-convex lens made of fused silica material, with a center thickness of 1.5mm to 2.5mm, and a transmittance of greater than or equal to 90% in the 193nm to 400nm wavelength band; the center distance between the protective lens 1 and the front lens group 2 is... Satisfying 2mm≤ ≤3mm.

[0031] In this embodiment, the protective mirror 1 adopts a plano-convex structure, with the flat surface facing the harsh external environment and the convex surface facing the internal optical system. This design can withstand a certain amount of external pressure while reducing wavefront distortion of the internal beam. The material used is ultraviolet-grade fused silica, and an antireflective coating (AR Coating) is applied to both sides, resulting in a single-sided reflectivity of less than 0.5% across the entire wavelength range of 193nm to 400nm, thus ensuring an overall transmittance of ≥90%. The center thickness is set between 1.5mm and 2.5mm, ensuring sufficient mechanical strength to resist cleaning or accidental impacts while avoiding material absorption loss due to excessive thickness. The spacing is controlled at 2 to 3 millimeters. This tiny gap is sufficient to prevent physical contact between the protective mirror 1 and the first lens 21 of the front group, while also limiting the angle of stray light entering the system. In practical applications, the coating process of the protective mirror 1 can also be ion beam sputtering (IBS) or other high-energy deposition techniques; this embodiment does not limit this. This design effectively isolates the core lens group from contamination by dust, oil, and laser ablation products, extending the lens's lifespan. Simultaneously, the high transmittance design minimizes light energy loss and improves the system's energy utilization rate.

[0032] To address the problem of severe vignetting or poor stray light control caused by improperly positioned aperture stop 3 in existing lenses, this application optimizes the position and size of aperture stop 3. Please refer to... Figure 1-2 As shown, the aperture stop 3 is disposed between the front lens group 2 and the rear lens group 4, and is located close to the rear lens group 4. The aperture D of the aperture stop 3 satisfies 2mm≤D≤5mm.

[0033] In this embodiment, the aperture 3 acts as a solid light-shielding plate, typically made of a thin sheet of black anodized aluminum or stainless steel, with a high-precision circular aperture at its center. Its placement between the front and rear lens groups, close to the rear group, is based on optical path tracing optimization. This position is an area with an appropriate beam waist or principal ray height, effectively blocking stray light and advanced aberration rays that deviate from the optical axis, while avoiding unnecessary obstruction (vignetting) of the effective field of view. The aperture D is adjustable from 2 to 5 mm, with the specific value determined by the required numerical aperture (NA) and focal length. For example, when NA=0.8, the aperture needs to be precisely calculated in conjunction with the focal length to obtain the optimal cutoff frequency. The edges of the aperture 3 are chamfered and blackened to eliminate edge diffraction effects. This layout not only defines the system's entrance and exit pupils and optimizes beam quality but also significantly reduces background noise, improves imaging contrast and laser focusing purity, making the system more stable in high-precision applications.

[0034] To address the limitations of existing lenses, such as their narrow applicability and limited parameters, which fail to meet the diverse needs of ultraviolet applications, this application systematically defines the overall operating parameters of the lens. Please refer to... Figure 1-2 As shown, the working wavelength of the lens covers 193nm to 400nm, the focal length f satisfies 100mm≤f≤150mm, the numerical aperture NA satisfies 0.8≤NA≤1.0, the entrance pupil diameter Din satisfies 8mm≤Din≤12mm, and the total optical length TTL satisfies 180mm≤TTL≤220mm.

[0035] In this embodiment, the working wavelength ranges from deep ultraviolet (193nm, ArF excimer laser) to near ultraviolet (400nm, frequency-doubled solid-state laser), indicating that the lens has an extremely wide achromatic capability. The focal length, set at 100 to 150 mm, provides a suitable working distance, facilitating the integration of robotic arms or sensors. A numerical aperture (NA) as high as 0.8 to 1.0 (potentially involving immersion or special designs) signifies extremely strong light-gathering and resolving power, suitable for micron-level and even submicron-level processing and inspection. An entrance pupil diameter of 8 to 12 mm matches the high NA, ensuring sufficient light throughput. The overall optical length is controlled at 180 to 220 mm, reflecting the compact design and facilitating device miniaturization. These parameters are a balance point obtained through a global optimization algorithm, ensuring consistent performance across all wavelengths. This parameter system allows the lens to flexibly adapt to various scenarios such as 193nm lithography inspection, 248nm micro-drilling, and 355nm precision scribing, demonstrating broad versatility and high application value.

[0036] To address the issues of low assembly precision and susceptibility to vibration-induced optical axis misalignment in existing lenses, this application introduces a high-precision mechanical support structure. Please refer to... Figure 1-2As shown, it also includes an integrated lens barrel 6, and all lenses are installed in the integrated lens barrel 6 through a centering assembly process; the integrated lens barrel 6 is made of aluminum alloy material, its surface is anodized, and the inner wall of the lens barrel 6 is provided with matte threads.

[0037] In this embodiment, the integrated lens barrel 6 is integrally machined from high-strength aluminum alloy (such as 7075-T6) using a CNC machine tool, avoiding the cumulative errors and insufficient rigidity problems caused by multi-segment splicing. Surface anodizing treatment not only improves corrosion resistance and wear resistance but also forms an insulating layer. The matting threads (serrated structure) on the inner wall are coated with a high-absorption black paint to absorb stray light reflected from the lens edges, preventing multiple reflections within the lens barrel 6 and the formation of halos. The centering assembly process refers to using a high-precision centering instrument to monitor the concentricity of the lens's optical axis and the mechanical axis of the lens barrel 6 in real time during the installation of each lens, and fixing it by adjusting washers or applying adhesive to ensure that the eccentricity is controlled within the micrometer level. In practical applications, the lens barrel 6 material can also be titanium alloy or stainless steel to meet special environmental requirements; this embodiment does not limit this. This structural design greatly improves the lens's mechanical stability and shock resistance, ensuring the long-term stability of the optical axis. Simultaneously, the matting design further enhances the imaging signal-to-noise ratio, ensuring reliable operation in harsh industrial environments.

[0038] To address the problem of low aberration correction efficiency or assembly confusion caused by the arbitrary orientation of lens surfaces in existing lenses, this application clarifies the orientation of key lenses. Please refer to... Figure 1-2 As shown, the concave surface of the first lens 21 faces the direction of light incidence, the convex surface of the third lens 41 faces the direction of light incidence, and the convex surface of the fifth lens 43 faces the direction of light incidence.

[0039] In this embodiment, the first lens 21 serves as a negative lens, with its concave surface facing the incident light (i.e., the plane faces backward or the concave surface faces forward; here, it is explicitly stated that the concave surface faces the incident direction. Combined with the plano-concave description in claim 1, this should be understood as the concave surface acting as the primary refractive surface facing the light, or depending on the specific optical path design, strictly following the claim description: if the first lens 21 is plano-concave and the concave surface faces the incident direction, then the light passes through the concave surface first). This orientation is beneficial for diverging light and correcting spherical aberration. The third lens 41 serves as a meniscus positive lens, with its convex surface facing the incident direction, effectively converging light and correcting field curvature. The fifth lens 43 serves as a plano-convex positive lens, with its convex surface facing the incident direction (or, depending on the optical path, the plane may face forward; here, strictly following the claim: the convex surface faces the incident direction). This arrangement ensures that light undergoes primary refraction upon entering the lens, which helps reduce higher-order aberrations. Each lens's orientation is defined within the lens barrel 6 by positioning steps or spacers; the markings must be strictly checked during assembly. Correct surface orientation is crucial for maximizing lens design performance; incorrect orientation can lead to a sharp increase in aberrations or even prevent image formation. This clear orientation specification simplifies the assembly process, reduces the difficulty of assembly and adjustment, and ensures that each lens works in its optimal state as designed, thereby guaranteeing the achievement of overall optical performance.

[0040] To address the limitations of existing lenses in their application areas and their inability to adapt to various wavelength lasers, this application expands the specific application scenarios of the lens. Specifically, the lens is suitable for ultraviolet laser processing, ultraviolet imaging detection, or spectral analysis applications, and its compatible operating wavelengths include 193nm, 248nm, or 355nm.

[0041] In this embodiment, the lens can be widely used in semiconductor wafer defect detection (using a 193nm light source), PCB board drilling and cutting (using a 355nm light source), biofluorescence microscopy (using 248nm or 355nm excitation), and Raman spectroscopy analysis. For different wavelengths, the coating parameters inside the lens can be fine-tuned to adapt to the peak transmittance, but the basic optical architecture remains unchanged. For example, in 193nm applications, special attention needs to be paid to the radiation damage resistance of the material; in 355nm applications, more attention is paid to thermal stability under high power. In practical applications, the lens can also be adapted to other ultraviolet bands such as 266nm and 405nm, as long as they are within the designed wavelength range; this application embodiment does not limit this. This multi-scenario, multi-wavelength adaptability design makes the lens a universal core component of ultraviolet optics, greatly reducing the cost of equipment replacement for users, improving the flexibility and compatibility of production lines, and yielding significant economic and social benefits.

[0042] Example 2 Please refer to Figure 1-2As shown, this application provides a high-transmittance, low-aberration ultraviolet optical lens suitable for 355nm ultraviolet laser processing scenarios. Specific parameters are as follows: Protective mirror 1: The plano-convex lens is made of fused silica (SiO2) material, with a center thickness of 2.0 mm and a transmittance of ≥92% in the 193nm-400nm wavelength range; the center-to-center distance between the protective lens 1 and the first lens 21 is... =2.5mm.

[0043] Front lens group 2: First lens 21: Plano-concave negative lens, made of calcium fluoride (CaF2) material, refractive index n1=1.38 (355nm band), dispersion coefficient v1=95, focal length f1=-50mm, optical power φ1=-0.02mm -1 Center thickness d1 = 3.0 mm; Second lens 22: Biconvex positive lens, made of fused silica (SiO2) material, refractive index n2=1.465 (355nm band), dispersion coefficient v2=67.5, focal length f2=30mm, optical power φ2≈0.0333mm -1 Center thickness d2 = 4.0 mm; The center distance d between the first lens 21 and the second lens 22 12 =6.5mm; The total optical power φ of the front lens group is calculated according to formula (1). 12 :

[0044] Rear lens group 4: Third lens 41: Meniscus positive lens, calcium fluoride (CaF2) material, refractive index n3=1.38 (355nm band), dispersion coefficient v3=95, focal length f3=40mm, optical power φ3=0.025mm -1 Center thickness d3 = 3.5 mm; Fourth lens 42: Biconcave negative lens, made of fused silica (SiO2), refractive index n4=1.465 (355nm band), dispersion coefficient v4=67.5, focal length f4=-25mm, optical power φ4=-0.04mm -1 Center thickness d4 = 2.5 mm; Fifth Lens 43: Plano-convex positive lens, made of calcium fluoride (CaF2), refractive index n5=1.38 (355nm band), dispersion coefficient v5=95, focal length f5=35mm, optical power φ5≈0.0286mm -1 Center thickness d5 = 3.0 mm; The center distance d between the third lens 41 and the fourth lens 42 34=4.0mm, the center distance d between the fourth lens 42 and the fifth lens 43 45 =5.0mm, the center distance d between the third lens 41 and the fifth lens 43 35 =9.0mm; The total optical power φ of the rear lens group is calculated according to formula (3). 345 :

[0045] Aperture 3: Located between the front lens group 2 and the rear lens group 4, close to the rear lens group 4, with an aperture D = 3.5 mm; the center distance d between the front lens group 2 and the rear lens group 4. 23 =12.5mm; Calculate the total optical power φ of the lens according to formula (4):

[0046] The total focal length of the lens is f = 1 / φ ≈ 28.74mm (compatible with the 355nm band). Aberration correction results (calculated according to formulas (5)-(8)): Axial color difference =0.008mm≤0.01mm; Maximum ball difference =0.003mm≤0.005mm; Like scattered =0.002mm≤0.003mm; Relative distortion Dist = -0.02%, |Dist| ≤ 0.03%; Other parameters: operating wavelength 193nm-400nm, numerical aperture NA=0.9, entrance pupil diameter Din=10mm, total optical length TTL=200mm; the lens barrel 6 is made of aluminum alloy with anodized surface and matting threads on the inner wall; all lenses adopt a centering assembly process with an assembly accuracy ≤0.001mm.

[0047] The lens in this embodiment has a transmittance of ≥92% in the 355nm ultraviolet band, a focused spot size of 1.0μm (diffraction limit), and an MTF value of ≥0.85 at 50lp / mm. It provides clear imaging and precise focusing, making it suitable for applications such as 355nm ultraviolet laser precision cutting and semiconductor chip drilling. Example 3 Please refer to Figure 1-2 As shown, this embodiment provides a high-transmittance, low-aberration ultraviolet optical lens suitable for 193nm ultraviolet spectral analysis scenarios. The specific parameters differ from those in Embodiment 2 in that: Lens material refractive index adjustment (for 193nm band): The refractive index of calcium fluoride material is n1=n3=n5=1.375, and the refractive index of fused silica material is n2=n4=1.46; Focal length and optical power adjustment: The first lens 21 has a focal length f1 = -45mm and an optical power φ1 ≈ -0.0222mm. -1 ; The second lens has a focal length of f2 = 28 mm and an optical power of φ2 ≈ 0.0357 mm. -1 ; The third lens 41 has a focal length f3 = 38mm and an optical power φ3 ≈ 0.0263mm. -1 ; The fourth lens has a focal length of f4 = -22mm and an optical power of φ4 ≈ -0.0455mm. -1 ; The fifth lens has a focal length of f5 = 32mm and an optical power of φ5 ≈ 0.03125mm. -1 ; Spacing adjustment: d 12 =5.5mm, d 34 =3.5mm, d 45 =4.5mm, d 23 =11.0mm; Aperture diameter D=2.5mm, entrance pupil diameter Din=8mm, numerical aperture NA=0.85, total optical length TTL=185mm; Aberration correction results: Axial color difference =0.007mm≤0.01mm; Maximum ball difference =0.004mm≤0.005mm; Like scattered =0.0025mm≤0.003mm; The relative distortion Dist = 0.025%, |Dist| ≤ 0.03%.

[0048] The lens in this embodiment has a transmittance of ≥90% in the 193nm ultraviolet band, high imaging resolution, and low stray light interference, making it suitable for scenarios such as ultraviolet spectral analysis and environmental pollutant detection.

[0049] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A high-transmission, low-aberration ultraviolet optical lens, characterized in that, It includes a protective mirror (1), a front lens group (2), an aperture (3), a rear lens group (4), and an imaging surface / focusing surface (5) arranged coaxially along the incident direction of light. The front lens group (2) includes a first lens (21) and a second lens (22) arranged sequentially along the incident direction. The first lens (21) is a plano-concave negative lens and is made of calcium fluoride material. The second lens (22) is a biconvex positive lens and is made of fused silica material. The rear lens group (4) includes a third lens (41), a fourth lens (42) and a fifth lens (43) arranged sequentially along the incident direction. The third lens (41) is a meniscus positive lens and is made of calcium fluoride material. The fourth lens (42) is a biconcave negative lens and is made of fused silica material. The fifth lens (43) is a plano-convex positive lens and is made of calcium fluoride material. The total optical power of the front lens group (2) The total optical power of the rear lens group (4) and the total optical power of the lens Each satisfies a specific combination of optical power to correct chromatic aberration and spherical aberration in the ultraviolet band.

2. The high-transmission, low-aberration ultraviolet optical lens according to claim 1, characterized in that, The aberration correction index of the lens meets the following requirements: Axial color difference ≤0.01mm; Maximum ball difference ≤0.005mm; Like scattered ≤0.003mm; Relative distortion ≤0.03%.

3. The high-transmission, low-aberration ultraviolet optical lens according to claim 1, characterized in that, The center distance between the first lens (21) and the second lens (22) Satisfying 5mm≤ ≤8mm; The center distance between the third lens (41) and the fourth lens (42) Satisfying 3mm≤ ≤5mm; The center distance between the fourth lens (42) and the fifth lens (43) Satisfying 4mm≤ ≤6mm; The center distance between the front lens group (2) and the rear lens group (4) Satisfying 10mm≤ ≤15mm.

4. The high-transmission, low-aberration ultraviolet optical lens according to claim 1, characterized in that, The refractive index n of the calcium fluoride material at 355nm wavelength satisfies 1.37≤n≤1.39, and the dispersion coefficient v satisfies 94≤v≤96. The refractive index n of the fused silica material at 355nm wavelength satisfies 1.46≤n≤1.47, and the dispersion coefficient v satisfies 67≤v≤68.

5. The high-transmission, low-aberration ultraviolet optical lens according to claim 1, characterized in that, The protective lens (1) is a plano-convex lens made of fused silica material, with a center thickness of 1.5 mm to 2.5 mm and a transmittance of greater than or equal to 90% in the 193 nm to 400 nm wavelength band; The center distance between the protective mirror (1) and the front lens group (2) Satisfying 2mm≤ ≤3mm.

6. The high-transmission, low-aberration ultraviolet optical lens according to claim 1, characterized in that, The aperture stop (3) is located between the front lens group (2) and the rear lens group (4), and is close to the rear lens group (4). The aperture D of the aperture stop (3) satisfies 2mm≤D≤5mm.

7. The high-transmission, low-aberration ultraviolet optical lens according to claim 1, characterized in that, The lens operates in a wavelength range of 193nm to 400nm, with a focal length f of 100mm ≤ f ≤ 150mm, a numerical aperture NA of 0.8 ≤ NA ≤ 1.0, an entrance pupil diameter Din of 8mm ≤ Din ≤ 12mm, and an optical total length TTL of 180mm ≤ TTL ≤ 220mm.

8. The high-transmission, low-aberration ultraviolet optical lens according to claim 1, characterized in that, It also includes an integrated lens barrel (6), in which all lenses are installed by a centering assembly process; The integrated lens barrel (6) is made of aluminum alloy material, its surface is anodized, and the inner wall of the lens barrel (6) is provided with matte threads.

9. The high-transmission, low-aberration ultraviolet optical lens according to any one of claims 1 to 8, characterized in that, The concave surface of the first lens (21) faces the direction of light incidence, the convex surface of the third lens (41) faces the direction of light incidence, and the convex surface of the fifth lens (43) faces the direction of light incidence.

10. The high-transmission, low-aberration ultraviolet optical lens according to any one of claims 1 to 8, characterized in that, The lens is suitable for ultraviolet laser processing, ultraviolet imaging detection, or spectral analysis applications, and is compatible with working wavelengths including 193nm, 248nm, or 355nm.

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