Ultraviolet broadband large-view-field detection objective lens

Abstract

The invention discloses an ultraviolet broadband large-view-field detection objective lens, and belongs to the technical field of optical instruments. In order to solve the problems that in the prior art, balance among short-wavelength, large-numerical-aperture, large-view-field and broadband detection is difficult to obtain, and meanwhile system complexity and manufacturing cost are considered, the invention provides an ultraviolet broadband large-view-field detection objective lens. Comprising a first lens group, a second lens group, a third lens group and a fourth lens group which are sequentially and coaxially arranged from an object plane, each lens group comprises a plurality of lenses, and the first lens group and the fourth lens group are variable lens groups. The method can simultaneously meet high requirements on resolution, detection range and detection efficiency, and is suitable for defect detection and quality control in the field of semiconductor wafer manufacturing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical instruments, and particularly relates to a wide-field detection objective lens for ultraviolet wide-band. BACKGROUND

[0002] In the semiconductor manufacturing industry, wafer manufacturing is a costly link. In order to effectively control costs and improve yield, it is crucial to detect defects such as particles, scratches and pattern deviations on the wafer in a timely and accurate manner. Traditional defect detection systems mostly use a shorter ultraviolet single wavelength for detection. Although a shorter wavelength can improve the resolution of the system, different types of defects have different sensitivities to different wavelengths of light. Therefore, single wavelength detection cannot comprehensively and effectively identify all defects. This makes it particularly necessary to develop a detection objective lens that can cover a wider wavelength band. In addition, as the size of semiconductor devices continues to shrink, higher resolution requirements are placed on detection systems. According to the resolution calculation formula of an optical microscopic system , shorter wavelengths and larger numerical apertures are the keys to improving resolution. However, it is difficult for existing technologies to achieve high resolution while also considering large field of view and wide-band detection, which has become a technical problem that needs to be solved urgently.

[0003] To solve the above technical bottlenecks, some solutions have been proposed in existing technologies. For example, Chinese patent document CN118732248A discloses a microscopic objective optical system that uses a catadioptric structure to overcome the problem of difficulty in balancing a large numerical aperture and a large field of view. It can achieve a numerical aperture of 0.9 and a maximum field of view of 1mm. The patent also proposes that all optical element surfaces are spherical to reduce processing difficulty. Another Chinese patent document CN120065493A provides a large-field, large-numerical-aperture ultraviolet wide-band microscopic optical system that includes a complex optical structure of a microscopic objective, a relay system and an imaging tube lens. It successfully achieves wide-band chromatic aberration correction from 250nm to 500nm, with a numerical aperture greater than or equal to 0.9 and a field of view greater than or equal to 1mm, and can even be increased to more than 2mm with the help of a magnifying optical system.

[0004] However, these existing technologies still have some deficiencies. Although the patent document CN118732248A makes improvements in numerical aperture and field of view range, it does not explicitly mention the effective coverage capability of the ultraviolet wide band, which has limitations for the semiconductor industry which needs sensitive detection of various defects. Although the patent document CN120065493A solves the problem of ultraviolet wide band, it adopts a complete optical system composed of a microscopic objective lens, a relay system and an imaging tube lens, which has a complex overall structure and a large number of components, which undoubtedly increases the design, processing and assembly difficulty and cost of the system.

[0005] Therefore, the present application aims to provide a more compact and simplified solution, i.e. a single ultraviolet wide band large field of view detection objective lens, in order to optimize the three key performance indicators of short wavelength, wide band, large numerical aperture and large field of view without relying on a complex relay system. The detection objective lens of the present application effectively solves the contradiction between high resolution, large field of view and wide band in the prior art, thereby significantly improving the comprehensiveness and efficiency of semiconductor wafer defect detection, while reducing the complexity and manufacturing cost of the system. SUMMARY

[0006] In order to solve the problem of balancing between short wavelength, large numerical aperture, large field of view and wide band detection in the prior art, while taking into account the system complexity and manufacturing cost, the present application proposes the following solution: An ultraviolet wide band large field of view detection objective lens, the detection objective lens comprising a first lens group G1, a second lens group G2, a third lens group G3 and a fourth lens group G4 coaxially arranged in sequence from the object plane; The second lens group G2 comprises a first double convex lens 4, a double concave lens 5 and a first plano-convex lens 6; The third lens group G3 comprises a second meniscus lens 7 and a second double convex lens 8; Further, the first lens group G1 comprises a first lens 1, a first meniscus lens 2 and a spherical bowl mirror 3 coaxially arranged in sequence from the object plane; The fourth lens group G4 comprises a third meniscus lens 10, a third double convex lens 11, a fourth meniscus lens 12, a fifth meniscus lens 13 and a fourth double convex lens 14 coaxially arranged in sequence from the third lens group G3.

[0007] Further, the first lens group G1 comprises a first lens 1, a first meniscus lens 2 and a second lens 31 coaxially arranged in sequence from the object plane; The fourth lens group G4 comprises a sixth meniscus lens 101, a second plano-convex lens 111, a fourth meniscus lens 12, a fifth meniscus lens 13 and a seventh meniscus lens 141 coaxially arranged in sequence from the third lens group G3.

[0008] Further, the second lenticular lens 8 is a thick lens, and the ratio of the diameter to the thickness is greater than 0.83.

[0009] Further, the bending direction of the first meniscus lens 2 is the same as that of the spherical mirror 3.

[0010] Further, the spherical mirror 3 has a central hole, and the area of the hole accounts for 5-25% of the surface area of the spherical mirror 3.

[0011] Further, a diaphragm 9 is arranged between the third mirror group G3 and the fourth mirror group G4.

[0012] Further, the second lens 31 has a light transmission hole in the center, the light transmission hole is coated with an anti-reflection film, the anti-reflection film is coated with a reflective film outside the range, and the transition area width of the anti-reflection film and the reflective film is less than 0.1mm.

[0013] Further, the first lens 1 has a light transmission hole in the center, the light transmission hole is coated with an anti-reflection film, the anti-reflection film is coated with a reflective film outside the range, and the transition area width of the anti-reflection film and the reflective film is less than 0.1mm.

[0014] Further, the first lens 1 can be any one of a lenticular lens, a plano-convex lens or a meniscus lens.

[0015] Compared with the prior art, the present application has the following beneficial effects: 1. The ultraviolet wide-band large-view-field detection objective lens has made a breakthrough in the wavelength coverage and resolution. By adopting the clever combination of the spherical mirror and the plurality of lens elements in the catadioptric hybrid structure, the detection objective lens realizes the imaging of the ultraviolet waveband from 255nm to 465nm, effectively corrects the chromatic aberration, and makes the objective lens have good imaging quality for light of different wavelengths. This not only far exceeds the waveband range of 320nm or more of the prior art, but also fully utilizes the sensitivity of light of different wavelengths to different defects, greatly improves the recognition ability of particles, scratches, pattern deviation and other defects. At the same time, the shorter cutoff wavelength also directly brings higher optical resolution, which can clearly capture smaller defect details.

[0016] 2. The ultraviolet wide-band large-field detection objective lens provided by the application effectively solves the problem that it is difficult to balance large numerical aperture and large field of view. In traditional designs, increasing the numerical aperture to improve resolution often leads to a sharp decrease in the field of view, limiting detection efficiency. The application optimizes the parameter configuration of the first lens group, the second lens group, the third lens group and the fourth lens group, and sets a diaphragm between the third lens group and the fourth lens group, so that the objective lens can maintain a larger imaging target surface while achieving a high numerical aperture. This directly brings the technical effect that the detection range is larger under the same detection conditions, thereby greatly improving the detection speed, and is particularly suitable for the demand for high efficiency and rapid detection in the semiconductor wafer manufacturing process.

[0017] 3. The ultraviolet wide-band large-field detection objective lens provided by the application is innovative in system integration and application flexibility. Compared with some complex prior art (such as CN120065493A), the application provides a single, compact detection objective lens that does not need to rely on a complex relay system or an imaging tube lens to achieve excellent optical performance. This modular design greatly simplifies the structure of the entire optical system, reduces the number of optical elements, not only effectively reduces the difficulty of design, processing and assembly, but also significantly reduces manufacturing costs. At the same time, the objective lens also has the ability to flexibly change the system magnification by replacing different focal length barrel lenses, so that it can easily adapt to different detection accuracies, different field sizes and different camera combinations, greatly expanding its application scenarios.

[0018] 4. The ultraviolet wide-band large-field detection objective lens provided by the application achieves excellent imaging quality through careful optical element design. For example, the first double convex lens in the claim has positive focal power, the double concave lens has negative focal power, and the plano-convex lens has positive focal power, etc. The combination of these lenses with different focal powers, together with other meniscus lenses and mirrors, can better correct various aberrations such as spherical aberration, astigmatism and distortion. Especially in the ultraviolet wide-band, this precise aberration control enables the objective lens to maintain clear and sharp imaging effects throughout the large field of view, ensuring the accuracy and reliability of defect detection and avoiding missed detection or misjudgment due to optical system defects.

[0019] 5. The ultraviolet wide-band large-field detection objective lens provided by the application is a highly innovative and practical solution. It systematically solves multiple technical bottlenecks in the prior art, such as high resolution, large field of view, wide band and short wavelength, and achieves comprehensive optimization of performance parameters. Compared with the prior art, the detection objective lens provided by the application has a shorter wavelength, a wider band, and a higher resolution, while its large field of view greatly improves detection efficiency.

[0020] The present application has the technical features of shorter wavelength, wider waveband, larger numerical aperture and larger field of view, and can simultaneously meet the high requirements on resolution, detection range and detection efficiency, and is particularly suitable for defect detection, quality control in semiconductor wafer manufacturing and other industrial detection and scientific research fields requiring high precision, large field of view and wide waveband optical imaging. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structure diagram of a wide waveband large field of view detection objective lens according to an embodiment of the present application, and the reference signs are: first lens group G1, second lens group G2, third lens group G3, fourth lens group G4, object plane 0, first lens 1, first meniscus lens 2, spherical bowl mirror 3, first double convex lens 4, double concave lens 5, first plano-convex lens 6, second meniscus lens 7, second double convex lens 8, diaphragm 9, third meniscus lens 10, third double convex lens 11, fourth meniscus lens 12, fifth meniscus lens 13, fourth double convex lens 14, mirror surface S11 of the side of the lens close to the object plane, and reflection surface S31 of the spherical bowl mirror; Figure 2 is a coating region diagram of a lens of a wide waveband large field of view detection objective lens according to an embodiment of the present application, and the reference signs are: annular reflection film A of the first lens, antireflection film B of the first lens, and annular transition region C of the first lens; Figure 3 is a modulation transfer function (MTF) curve diagram of a wide waveband large field of view detection objective lens according to an embodiment of the present application; Figure 4 is a wavefront aberration diagram of different fields of view of a wide waveband large field of view detection objective lens according to an embodiment of the present application; Figure 5 is an axial chromatic aberration curve diagram of a wide waveband large field of view detection objective lens according to an embodiment of the present application; Figure 6 is a structure diagram of a wide waveband large field of view detection objective lens according to an embodiment of the present application, and the reference signs are: second lens 31, sixth meniscus lens 101, second plano-convex lens 111, seventh meniscus lens 141, and surface S32 of the side of the second lens close to the convex surface; Figure 7 is a coating region diagram of a lens of a wide waveband large field of view detection objective lens according to an embodiment of the present application, and the reference signs are: annular reflection film D of the second lens, antireflection film E of the second lens, and annular transition region F of the second lens; Figure 8 is a modulation transfer function (MTF) curve diagram of a wide waveband large field of view detection objective lens according to an embodiment of the present application; Figure 9 is a wavefront aberration diagram of different fields of view of a wide waveband large field of view detection objective lens according to an embodiment of the present application Figure 10 This is a graph showing the axial chromatic aberration of an ultraviolet wide-band, large-field-of-view detection objective lens according to an embodiment of the present invention; DETAILED DESCRIPTION The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] Implementation Method 1 like Figure 1 As shown, an ultraviolet wide-band large-field detection objective lens comprises a first lens group G1, a second lens group G2, a third lens group G3 and a fourth lens group G4 which are coaxially arranged in sequence from the object plane; The second lens group G2 includes a first biconvex lens 4, a biconcave lens 5 and a first plano-convex lens 6; The third lens group G3 includes a second meniscus lens 7 and a second biconvex lens 8; This optical structure achieves wide-field imaging across a wide ultraviolet wavelength range through the coaxial arrangement and combination of multiple mirror groups, significantly improving aberration control and light flux uniformity. The inventive team expended considerable creative effort in designing the mirror group sequence, selecting lens types, and optimizing optical parameters, enabling the entire system to achieve high resolution, low distortion, and high imaging efficiency across a wide wavelength range, fully demonstrating their innovative design capabilities for complex optical systems.

[0023] Furthermore, the first lens group G1 includes a first lens 1, a first meniscus lens 2 and a bowl reflector 3 which are coaxially arranged in sequence from the object plane; The fourth lens group G4 includes a third meniscus lens 10 , a third biconvex lens 11 , a fourth meniscus lens 12 , a fifth meniscus lens 13 , and a fourth biconvex lens 14 , which are coaxially arranged in sequence from the third lens group G3 .

[0024] By precisely arranging the first and fourth mirror groups in a specific coaxial sequence, the present invention achieves high-quality imaging over a wide ultraviolet wavelength range, significantly reducing aberrations while maintaining the system's luminous flux and resolution. The inventive team expended considerable creative effort in designing the mirror group sequence, optimizing the curvature of the meniscus lens, and selecting an appropriate biconvex lens configuration. This not only addresses the aberration accumulation problem caused by multi-mirror group coupling but also ensures high signal-to-noise ratio imaging over a wide wavelength range.

[0025] Furthermore, the second biconvex lens 8 is a thick lens with a diameter-to-thickness ratio greater than 0.83.

[0026] The thick lens and the optimized diameter-thickness ratio can significantly improve the aberration control ability of the lens in the ultraviolet band, and enhance the heat resistance and mechanical stability of the system. The invention team has made creative efforts in determining the parameters of the thick lens, selecting the material and simulating the optical performance, which not only overcomes the problem of thermal lens effect of the conventional thin lens under high-power ultraviolet light, but also ensures the long-term stable imaging performance of the system.

[0027] Further, the bending direction of the first meniscus lens 2 is the same as that of the spherical bowl mirror 3.

[0028] By precisely matching the bending directions of the meniscus lens and the spherical bowl mirror, the optimization of light focusing and further compensation of aberration are realized. The invention team has made a lot of creative attempts in optical path simulation, curvature direction design and system optimization, which makes the whole optical system maintain high resolution and low distortion imaging under wide field of view.

[0029] Further, the spherical bowl mirror 3 has a central opening, and the area of the opening accounts for 5-25% of the surface area of the spherical bowl mirror 3.

[0030] The central opening design effectively reduces the occlusion of the optical system, while ensuring the balance between the imaging quality and the light flux of the mirror. The invention team has made creative efforts in determining the opening ratio, opening position and optimization of the influence on the optical performance of the system, which not only takes into account the feasibility of mechanical processing, but also maintains the high efficiency and high precision of optical design.

[0031] Further, the third mirror group G3 and the fourth mirror group G4 are provided with a diaphragm 9.

[0032] The diaphragm effectively controls the scattering and spot size of the incident light beam, improves the imaging clarity and the signal-to-noise ratio of the optical system. The invention team has made creative efforts in the optimization of the diaphragm position, size and optical shading effect, which realizes stable imaging effect under large field of view conditions.

[0033] Further, the first lens 1 has a central light transmission hole, the light transmission hole is coated with an anti-reflection film, the range outside the anti-reflection film is coated with a reflective film, and the transition area width of the anti-reflection film and the reflective film is less than 0.1mm.

[0034] This light transmission hole and film layer structure optimizes the optical efficiency of the lens, while reducing stray light and reflection loss. The invention team has made creative efforts in aperture design, film layer process and transition area precision control, so that the system can still maintain uniform imaging under high-power ultraviolet light conditions.

[0035] Further, the first lens 1 can be any one of a double convex lens, a plano-convex lens or a meniscus lens.

[0036] A plurality of lens selection schemes are provided, which improves the adaptability and adjustability of the optical system, and facilitates optimizing the imaging effect according to different application requirements. The invention team has made creative efforts in lens type evaluation, optical simulation and system compatibility testing, thereby realizing the flexibility and high performance of the system.

[0037] Embodiment two As shown in Figure 6 An ultraviolet wide-band large-field detection objective, the detection objective comprises a first lens group G1, a second lens group G2, a third lens group G3 and a fourth lens group G4 coaxially arranged in sequence from the object plane; The second lens group G2 comprises a first double convex lens 4, a double concave lens 5 and a first plano-convex lens 6; The third lens group G3 comprises a second meniscus lens 7 and a second double convex lens 8; The optical structure realizes large-field imaging under ultraviolet wide-band through the coaxial arrangement and combination of multiple lens groups, significantly improves the aberration control and light flux uniformity. The invention team has made a lot of creative efforts in lens group sequence design, lens type selection and optical parameter optimization, so that the whole system can balance high resolution, low distortion and high imaging efficiency under wide-band conditions, fully reflecting the innovative design ability of complex optical systems.

[0038] Further, the first lens group G1 comprises a first lens 1, a first meniscus lens 2 and a second lens 31 coaxially arranged in sequence from the object plane; The fourth lens group G4 comprises a sixth meniscus lens 101, a second plano-convex lens 111, a fourth meniscus lens 12, a fifth meniscus lens 13 and a seventh meniscus lens 141 coaxially arranged in sequence from the third lens group G3.

[0039] The innovative design of adding a second lens and a plurality of meniscus lens groups effectively improves the light path regulation ability of the system, realizes more uniform spot distribution and high-quality image field. The invention team has carried out systematic experimental and calculation verification in lens type selection, curvature matching and optical material optimization, reflecting the deep understanding and creative design ability of wide-band imaging, so that the whole optical system can still maintain excellent imaging performance under complex light path conditions.

[0040] Further, the second double convex lens 8 is a thick lens, and the diameter-thickness ratio is greater than 0.83.

[0041] The thick lens is adopted and the diameter-thickness ratio is optimized, so that the aberration control ability of the lens under ultraviolet band is significantly improved, and the heat resistance and mechanical stability of the system are enhanced. The invention team has made creative efforts in thick lens parameter determination, material selection and optical simulation, which not only overcomes the problem that the conventional thin lens is easy to produce thermal lens effect under high-power ultraviolet light, but also ensures the long-term stable imaging performance of the system.

[0042] Further, the center of the second lens 31 is left with an aperture, the aperture is coated with an anti-reflection film, the range outside the anti-reflection film is coated with a reflective film, and the transition area between the anti-reflection film and the reflective film is less than 0.1mm in width.

[0043] The aperture and the fine film layer design significantly improve the light flux utilization rate and reduce stray light, enhancing the system imaging contrast and resolution. The invention team has made a lot of creative exploration in aperture size design, film layer material selection and transition area precision control, so that the optical system still maintains excellent performance under complex wavebands.

[0044] Further, the center of the first lens 1 is left with an aperture, the aperture is coated with an anti-reflection film, the range outside the anti-reflection film is coated with a reflective film, and the transition area between the anti-reflection film and the reflective film is less than 0.1mm in width.

[0045] This aperture and film layer structure optimizes the optical efficiency of the lens, while reducing stray light and reflection loss. The invention team has made creative efforts in aperture design, film layer process and transition area precision control, so that the system can still maintain uniform imaging under high-power ultraviolet light conditions.

[0046] Further, the first lens 1 can be any one of a double-convex lens, a plano-convex lens or a meniscus lens.

[0047] Providing multiple lens selection schemes improves the adaptability and adjustability of the optical system, and facilitates optimization of imaging effects according to different application requirements. The invention team has made creative efforts in lens type evaluation, optical simulation and system compatibility testing, thus realizing the flexibility and high performance of the system.

[0048] Embodiment Three This embodiment combines the technical solutions described in the foregoing embodiments with actual application scenarios and the use process of the detection objective lens described in the invention, and further verifies and explains the technical effects of the invention through specific examples.

[0049] As shown in Figure 1 , it is a detection objective lens structure diagram in this embodiment, wherein all lenses are spherical lenses. The detection objective lens in this embodiment is applicable to a 255nm-465nm waveband, a numerical aperture of 0.9, and a field of view of From the object plane 0, the first lens group G1, the second lens group G2, the third lens group G3 and the fourth lens group G4 are sequentially arranged.

[0050] The first mirror group G1 includes a first lens 1, a first meniscus lens 2 and a spherical bowl mirror 3 coaxially arranged in sequence from an object plane; the first mirror group G1 has positive focal length in the embodiment, adopts catadioptric structure, can reduce system length and reduce the number of lenses.

[0051] As shown in Figure 2 The surface S11 of the first lens 1 close to the object plane 0 is coated with an annular reflecting film A, and a light transmission hole is left in the middle, the light transmission hole is coated with an anti-reflection film B, and the width of the annular transition area C between the reflecting film and the anti-reflection film is strictly controlled to be less than 0.1 mm.

[0052] In the detection objective lens in the embodiment, the annular reflecting surface of the first lens 1 is a plane; Preferably, the annular reflecting surface of the first lens 1 can be changed to a convex surface or a concave surface.

[0053] The spherical bowl mirror 3 has a hole in the center, and the size of the hole is determined according to the height of the light; in the embodiment, the area of the hole of the spherical bowl mirror 3 accounts for .

[0054] The reflecting surface S31 of the spherical bowl mirror 3 is coated with a wide-band ultraviolet reflecting film, and the back surface of the spherical bowl mirror 3 is processed as a plane, which is used as the mounting reference of the detection objective lens in the embodiment, and facilitates the assembly and adjustment of the whole system.

[0055] The second mirror group G2 includes a first biconvex lens 4, a biconcave lens 5 and a first plano-convex lens 6; the second mirror group G2 has positive focal length in the embodiment, the lenses are made of two different materials, and small interval design is used to correct chromatic aberration and secondary spectrum of the system.

[0056] The third mirror group G3 includes a second meniscus lens 7 and a second biconvex lens 8; the third mirror group G3 has positive focal length in the embodiment, the second biconvex lens 8 adopts a biconvex thick lens design, which can better converge light and compress the system aperture, and can also correct spherical aberration and part of field curvature of the system.

[0057] The detection objective lens in the embodiment adds a stop 9 between the third mirror group G3 and the fourth mirror group G4, which is used to limit the entrance pupil aperture of the optical system, and also limits the entry of stray light, and plays a part in eliminating stray light.

[0058] The fourth mirror group G4 includes, in sequence from the third mirror group G3, a third meniscus lens 10, a third lenticular lens 11, a fourth meniscus lens 12, a fifth meniscus lens 13, and a fourth lenticular lens 14. In the fourth mirror group G4, the third meniscus lens 10 has a negative focal power, the third lenticular lens 11 has a positive focal power, the fourth meniscus lens 12 has a negative focal power, the fifth meniscus lens 13 has a negative focal power, and the fourth lenticular lens 14 has a positive focal power. The fourth lenticular lens 14 is mainly used for converging light rays and compressing the system aperture, and can correct part of the system spherical aberration. The fourth meniscus lens 12 and the fifth meniscus lens 13 are thick meniscus lenses, and are oppositely installed, and are mainly used for correcting the field curvature of the system. The third meniscus lens 10 and the third lenticular lens 11 are used for controlling the light ray aperture and correcting the system aberration.

[0059] The system is difficult to assemble and adjust, so the translational adjustable link of the second mirror group G2 is reserved for aberration compensation during assembly and adjustment. The interval between the second mirror group G2 and the third mirror group G3 is reserved for axial compensation during assembly and adjustment.

[0060] In the embodiment, all the lenses of the detection objective lens are designed as spherical surfaces, which facilitates processing and detection.

[0061] As shown in Figure 3 , in the embodiment, the modulation transfer function MTF of the detection objective lens reaches the diffraction limit.

[0062] As shown in Figure 4 , in the embodiment, the wavefront aberration of the detection objective lens in the full field of view is less than .

[0063] As shown in Figure 5 , in the embodiment, the detection objective lens realizes complex achromatism.

[0064] Table 1 shows the specific parameters of the detection objective lens in the embodiment. The positive radius value indicates that the center of curvature is close to the image side, and the negative radius value indicates that the center of curvature is close to the object side. The units of the radius, thickness, and aperture are millimeters.

[0065] Table 1: Specific parameters of the ultraviolet wide-band large-field detection objective lens G2 / G3 / G4 in the first embodiment

[0066] Table 2: Specific parameters of the ultraviolet wide-band large-field detection objective lens G1 in the first embodiment

[0067] ​​The ultraviolet wide-band large field of view detection objective lens shown in the embodiment realizes high numerical aperture (0.9) and excellent imaging performance in the field of view in the 255nm-465nm wave band through coaxial arrangement of four lens groups and catadioptric structure The positive and negative focal lengths of the lens groups in the system are reasonably combined, thick lenses, meniscus lenses and spherical bowl mirror aperture designs are combined, the spherical aberration, field curvature and chromatic aberration are effectively corrected, the entrance pupil aperture is limited through the stop, the stray light is reduced, and the signal-to-noise ratio of the system is improved. The transition region width of the antireflection film and the annular reflection film of the first lens and the spherical bowl mirror is accurately controlled, the light flux is effectively improved, and the reflection loss is reduced. Through the reserved lens translation and interval adjustment, the aberration and axial compensation of the system can be realized in the adjustment stage, and the stability of the optical system is ensured. The overall design takes into account high resolution, low distortion and complex achromatism under the conditions of wide wave band and large field of view, and realizes excellent imaging effect.

[0068] Embodiment four The embodiment combines the technical solutions of the foregoing embodiments, combines the actual application scene and the use process of the detection objective lens, and further verifies and explains the technical effects of the application through specific examples.

[0069] The embodiment replaces some lenses on the basis of the embodiment two, and the specific embodiments are as follows: As Figure 6 shown, it is a detection objective lens structure diagram in the embodiment, wherein all the lenses are spherical lenses. The detection objective lens in the embodiment is suitable for the 255nm-465nm wave band, the numerical aperture is 0.9, and the field of view is . From the object plane 0, the first lens group G1, the second lens group G2, the third lens group G3 and the fourth lens group G4 are sequentially arranged coaxially.

[0070] The first lens group G1 includes the first lens 1, the first meniscus lens 2 and the second lens 31 sequentially arranged coaxially from the object plane. The first lens group G1 has positive focal power in the embodiment, adopts catadioptric structure, can reduce the system length, and reduce the number of lenses, wherein the first meniscus lens 2 is used to correct the spherical aberration of the system.

[0071] As Figure 7 shown, an annular reflection film D is coated on the surface S32 of the second lens 31 on the convex side, and a light transmission hole is left in the middle. The light transmission hole is coated with an antireflection film E, and the width of the annular transition region F between the reflection film and the antireflection film is strictly controlled to be less than 0.1mm.

[0072] The second lens group G2 includes the first biconvex lens 4, the biconcave lens 5 and the first plano-convex lens 6. The second lens group G2 has positive focal power in the embodiment, the lenses are made of two different materials, and small interval design is used to correct the chromatic aberration and secondary spectrum of the system.

[0073] The third mirror group G3 includes a second meniscus lens 7 and a second lenticular lens 8; in this embodiment, the third mirror group G3 has positive focal power, the second lenticular lens 8 adopts a lenticular thick lens design, which can better converge light rays, compress the system aperture, and correct the spherical aberration and part of the field curvature of the system.

[0074] The fourth mirror group G4 includes, in order from the third mirror group G3, a sixth meniscus lens 101, a second plano-convex lens 111, a fourth meniscus lens 12, a fifth meniscus lens 13, and a seventh meniscus lens 141; in this embodiment, the sixth meniscus lens 101 in the fourth mirror group G4 has negative focal power, the second plano-convex lens 111 has positive focal power, the fourth meniscus lens 12 has positive focal power, the fifth meniscus lens 13 has negative focal power, and the seventh meniscus lens 141 has negative focal power. The seventh meniscus lens 141 and the fifth meniscus lens 13 have opposite meniscus directions, and are mainly used to compress the system aperture, correct part of the field curvature and chromatic aberration of the system. The second plano-convex lens 111 and the fourth meniscus lens 12 are used to converge light rays and correct the spherical aberration of the system. The sixth meniscus lens 101 is mainly used to correct the spherical aberration and distortion of the system.

[0075] In this embodiment, a diaphragm 9 is arranged between the sixth meniscus lens 101 and the second plano-convex lens 111 of the fourth mirror group, which is used to limit the entrance pupil aperture of the optical system and also limit the entry of stray light, thereby playing a part in eliminating stray light.

[0076] The system is difficult to assemble and adjust, so the translational adjustable link of the second mirror group G2 is reserved for aberration compensation during assembly and adjustment. The interval between the second mirror group G2 and the third mirror group G3 is reserved for axial compensation during assembly and adjustment, and the eccentricity of the first meniscus lens 2 is reserved for system error correction.

[0077] In this embodiment, all the lenses of the detection objective lens adopt spherical surface design, which is convenient for processing and detection.

[0078] As shown in Figure 8 , the modulation transfer function MTF of the detection objective lens in this embodiment reaches the diffraction limit.

[0079] As shown in Figure 9 , the wavefront aberration of the full field of view of the detection objective lens in this embodiment is less than .

[0080] As shown in Figure 10 , the detection objective lens in this embodiment realizes complex achromatism.

[0081] Table 3 shows the specific parameters of the detection objective lens in this embodiment, and the radius value is positive, indicating that the curvature center is close to the image side. If the value is negative, it means that the center of curvature is close to the object side. The radius, thickness, and aperture are all in millimeters.

[0082] Table 3 Specific parameters of the ultraviolet wide-band large-field detection objective G2 / G3 / G4 in embodiment two

[0083] Table 4 Specific parameters of the first lens group G1 of the ultraviolet wide-band large-field detection objective in embodiment two

[0084] The detection objective in the embodiment further improves the overall optical performance by replacing and optimizing some lenses on the basis of maintaining a 255 nm-465 nm waveband, a numerical aperture of 0.9, and a field of view of 20°×20°. The system maintains a four-lens-group coaxial arrangement and a catadioptric structure, the first lens group is designed with positive focal power, the first meniscus lens is used to correct spherical aberration, the second lens is provided with an annular reflective film and an antireflection film to increase light flux and reduce reflection loss; the second lens group is combined with lenses made of two different materials in a small interval to correct chromatic aberration and secondary spectrum; the thick biconvex lens design of the third lens group can better converge light, compress the system aperture, and correct spherical aberration and part of the field curvature; the fourth lens group is combined with six meniscus lenses and a second plano-convex lens, and the positive and negative focal powers are reasonably matched to achieve comprehensive correction of spherical aberration, field curvature, chromatic aberration, and distortion, and a diaphragm is arranged between the sixth meniscus lens and the second plano-convex lens to effectively limit the entrance pupil aperture and suppress stray light. In terms of system adjustment, the lens translation, interval adjustment, and eccentricity setting of the first meniscus lens are used to achieve aberration and axial compensation, thereby ensuring the stability and debugging flexibility of the optical system. All lenses in the entire optical system are designed as spherical surfaces, which facilitates processing and detection, the modulation transfer function reaches the diffraction limit, the wavefront aberration in the full field of view is less than 0.05λ, and the system is achromatic.

[0085] On the basis of embodiment two, the ball lens reflector of the first lens group in embodiment two is replaced with a second lens and the reflective film design is optimized, the lens combination and focal power distribution of the fourth lens group are adjusted (a seventh meniscus lens and a second plano-convex lens are introduced), a diaphragm is arranged in the fourth lens group, and eccentric adjustment of the first meniscus lens is added to improve system error, thereby further optimizing the wavefront aberration and achromatism on the premise of maintaining the wide waveband and large field of view characteristics.

[0086] ​The above specific embodiments are used to further describe the technical solutions provided by the present application in detail, so as to highlight the advantages and benefits of the technical solutions provided by the present application. However, the above specific embodiments are not used to limit the protection scope of the present application, and any reasonable modifications, improvements, recombination and equivalent replacement of the embodiments of the present application within the spirit and principle of the present application should be included in the protection scope of the present application.

[0087] Those skilled in the art can understand that the above description is only the preferred embodiments of the present application, and the features described in each embodiment and / or claim of the present application can be combined or combined, even if such combination or combination is not explicitly described in the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacement to part of the technical features, and any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be considered to fall within the protection scope of the present application.

[0088] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application. Obviously, those skilled in the art can make various modifications and changes to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and changes of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and changes.

Claims

1. An ultraviolet wide-band large-field detection objective lens, characterized in that: The detection objective lens comprises a first lens group (G1), a second lens group (G2), a third lens group (G3) and a fourth lens group (G4) which are coaxially arranged in sequence from the object plane; The second lens group (G2) comprises a first biconvex lens (4), a biconcave lens (5) and a first plano-convex lens (6); The third lens group (G3) comprises a second meniscus lens (7) and a second biconvex lens (8).

2. The detection objective lens according to claim 1, characterized in that The first lens group (G1) comprises a first lens (1), a first meniscus lens (2), and a bowl reflector (3) which are coaxially arranged in sequence from the object plane; The fourth lens group (G4) comprises a third meniscus lens (10), a third biconvex lens (11), a fourth meniscus lens (12), a fifth meniscus lens (13), and a fourth biconvex lens (14), which are coaxially arranged in sequence from the third lens group (G3).

3. The detection objective lens according to claim 1, characterized in that The first lens group (G1) comprises a first lens (1), a first meniscus lens (2), and a second lens (31) which are coaxially arranged in sequence from the object plane; The fourth lens group (G4) comprises a sixth meniscus lens (101), a second plano-convex lens (111), a fourth meniscus lens (12), a fifth meniscus lens (13) and a seventh meniscus lens (141), which are coaxially arranged in sequence from the third lens group (G3).

4. The detection objective lens according to claim 1, characterized in that The second biconvex lens (8) is a thick lens with a diameter-to-thickness ratio greater than 0.

83.

5. The detection objective lens according to claim 2, characterized in that: The bending direction of the first meniscus lens (2) is the same as the bending direction of the bowl reflector (3).

6. The detection objective lens according to claim 2, characterized in that: The ball bowl reflector (3) has a central opening, and the area of ​​the opening accounts for 5-25% of the surface area of ​​the ball bowl reflector (3).

7. The detection objective lens according to claim 2, characterized in that: A diaphragm (9) is provided between the third lens group (G3) and the fourth lens group (G4).

8. The detection objective lens according to claim 3, characterized in that: A light hole is left at the center of the second lens (31), and the light hole is coated with an anti-reflection film. A reflective film is coated outside the range of the anti-reflection film, and the width of the transition area between the anti-reflection film and the reflective film is less than 0.1 mm.

9. The detection objective lens according to claim 2 or 3, characterized in that: A light hole is left at the center of the first lens (1), the light hole is coated with an anti-reflection film, a reflective film is coated outside the range of the anti-reflection film, and the width of the transition area between the anti-reflection film and the reflective film is less than 0.1 mm.

10. The detection objective lens according to claim 2 or 3, characterized in that: The first lens (1) can be any one of a biconvex lens, a plano-convex lens or a meniscus lens.

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