Large NA ultraviolet collimating optical system

Abstract

The application discloses a large-NA ultraviolet collimating optical system and relates to the technical field of optics. The large-NA ultraviolet collimating optical system comprises a first mirror group, the first mirror group has negative optical power, and the first mirror group pre-diverges an incident light beam when the incident light beam is projected onto the first mirror group; a second mirror group, the second mirror group has positive optical power, the first mirror group and the second mirror group are sequentially arranged in the direction of an optical axis, and the second mirror group converges light projected from the first mirror group; wherein the first mirror group comprises a first lens, a second lens and a third lens sequentially arranged along the optical axis, the second lens with positive optical power is arranged between the first lens with negative optical power and the third lens with negative optical power, so as to correct aberration and constrain the divergence angle of the light beam; the first mirror group formed by the first lens with negative optical power, the second lens with positive optical power and the third lens with negative optical power realizes the pre-divergence of the incident light beam.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a large nanometer ultraviolet collimating optical system. Background Technology

[0002] In core processes such as photolithography, wafer inspection, and etching in the semiconductor industry, ultraviolet (UV) collimating optical systems are key components. Large numerical aperture (NA) UV collimating systems have become the mainstream research and application direction in the industry due to their ability to improve beam focusing accuracy and resolution. Existing large NA UV collimating optical systems mainly consist of UV transmission lenses, a lens barrel support, a focusing assembly, and a mounting base. Each lens is coaxially mounted within the lens barrel support, and the focusing assembly adjusts the spacing in conjunction with the lens group. The entire device is fixed to the base. During operation, the UV beam passes sequentially through each lens to achieve collimation and modulation, providing a highly parallel UV beam for semiconductor processes.

[0003] Currently, most mainstream large-NA ultraviolet collimating optical systems use traditional ultraviolet optical materials such as quartz and calcium fluoride as lens substrates, and achieve large NA through folding or immersion methods. However, the assembly precision and manufacturing cost of these two methods are relatively high, and the folding method is large in size and the immersion method is complex to maintain. Summary of the Invention

[0004] The main objective of this invention is to propose a large numerical aperture (NA) ultraviolet collimating optical system, which aims to solve the technical problems of high assembly accuracy and high cost of existing large numerical aperture ultraviolet collimating systems.

[0005] To achieve the above objectives, the present invention proposes a large-NA ultraviolet collimating optical system, comprising: The first lens group has negative optical power, and when the incident light beam is projected onto the first lens group, the first lens group prediversifies the incident light beam. The second lens group has positive optical power. The first lens group and the second lens group are distributed sequentially along the optical axis. The second lens group converges the light projected from the first lens group. The first lens group includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis. The second lens with positive optical power is disposed between the first lens with negative optical power and the third lens with negative optical power to correct aberrations and constrain the beam divergence angle.

[0006] In one embodiment, the first lens is a meniscus lens, and the radius of curvature of the surface of the first lens facing the second lens is smaller than the radius of curvature of the surface of the first lens away from the second lens, so as to pre-diverge the incident light beam and reduce the incident angle of the light.

[0007] In one embodiment, the second lens is a spherical meniscus lens, and there is a gap between the first lens and the second lens. The radius of curvature of the surface of the second lens facing the first lens is greater than the radius of curvature of the surface of the second lens facing the third lens, so as to converge the pre-divergent beam and smooth the beam angle.

[0008] In one embodiment, the third lens is a meniscus lens, and the radius of curvature of the surface of the third lens facing the second lens is smaller than the radius of curvature of the surface of the third lens away from the second lens, so as to optimize the light angle.

[0009] In one embodiment, the second lens group includes a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis, wherein the convex surfaces of the fifth lens, the sixth lens, the seventh lens, and the eighth lens all face the fourth lens.

[0010] In one embodiment, the fourth lens is a biconvex lens, wherein the radius of curvature of the surface of the fourth lens facing the third lens is greater than the radius of curvature of the surface of the fourth lens away from the third lens, and the surface of the fourth lens away from the third lens deflects the light rays converged by the radius of curvature of the surface of the fourth lens facing the third lens a second time. The side of the fourth lens with the larger radius of curvature faces the concave surface of the third lens.

[0011] In one embodiment, the fifth lens is a meniscus lens, and the radius of curvature of the surface of the fifth lens facing the fourth lens is smaller than the radius of curvature of the surface of the fifth lens facing away from the fourth lens.

[0012] In one embodiment, the sixth lens is a meniscus lens, wherein the radius of curvature of the sixth lens facing the fifth lens is smaller than the radius of curvature of the sixth lens away from the fifth lens, and the radius of curvature of the fifth lens away from the fourth lens is larger than the radius of curvature of the sixth lens facing the fifth lens.

[0013] In one embodiment, the seventh lens is a meniscus lens, wherein the radius of curvature of the seventh lens facing the sixth lens is smaller than the radius of curvature of the seventh lens away from the sixth lens, and the radius of curvature of the sixth lens away from the fifth lens is larger than the radius of curvature of the seventh lens facing the sixth lens.

[0014] In one embodiment, the eighth lens is a meniscus lens, wherein the radius of curvature of the eighth lens facing the seventh lens is smaller than the radius of curvature of the eighth lens away from the seventh lens, and the radius of curvature of the seventh lens away from the sixth lens is larger than the radius of curvature of the eighth lens facing the seventh lens.

[0015] The technical solution of this invention uses a first lens group formed by a first lens with negative optical power, a second lens with positive optical power, and a third lens with negative optical power to achieve pre-divergence of the incident beam. The second lens with positive optical power compensates for the spherical aberration and chromatic aberration caused by the first and third lenses, thus canceling the dispersion of ultraviolet materials. At the same time, it constrains excessive beam divergence, avoids excessively large apertures of the rear lens, and achieves miniaturization of the whole device. The second lens group with positive optical power is set on the coaxial side of the first lens to receive the divergent beam projected by the first lens group and gradually converges and corrects the divergent beam. By replacing the existing reflection and immersion structure with the second lens group, a large NA design can be achieved without reflective elements and immersion media, simplifying the auxiliary structure of the whole device and reducing the difficulty of equipment operation and maintenance. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of an embodiment of the large NA ultraviolet collimating optical system provided by the present invention; Figure 2 This is a schematic diagram of the optical path of an embodiment of the large nanometer ultraviolet collimating optical system provided by the present invention; Figure 3 Data charts for each lens in one embodiment of the large NA ultraviolet collimating optical system provided by the present invention.

[0018] Explanation of icon numbers: 100, First lens group; 200, Second lens group; 10, First lens; 20, Second lens; 30, Third lens; 40, Fourth lens; 50, Fifth lens; 60, Sixth lens; 70, Seventh lens; 80, Eighth lens.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] In core processes such as photolithography, wafer inspection, and etching in the semiconductor industry, ultraviolet (UV) collimating optical systems are key components. Large numerical aperture (NA) UV collimating systems have become the mainstream research and application direction in the industry due to their ability to improve beam focusing accuracy and resolution. Existing large NA UV collimating optical systems mainly consist of UV transmission lenses, a lens barrel support, a focusing assembly, and a mounting base. Each lens is coaxially mounted within the lens barrel support, and the focusing assembly adjusts the spacing in conjunction with the lens group. The entire device is fixed to the base. During operation, the UV beam passes sequentially through each lens to achieve collimation and modulation, providing a highly parallel UV beam for semiconductor processes.

[0024] Currently, most mainstream large-NA ultraviolet collimating optical systems use traditional ultraviolet optical materials such as quartz and calcium fluoride as lens substrates, and achieve large NA through folding or immersion methods. However, the assembly precision and manufacturing cost of these two methods are relatively high, and the folding method is large in size and the immersion method is complex to maintain.

[0025] This invention proposes a large-NA ultraviolet collimating optical system.

[0026] Please see Figure 1 In one embodiment of the present invention, the large NA ultraviolet collimating optical system includes: The first lens group 100 has a negative optical power, and when the incident light beam is projected onto the first lens group 100, the first lens group 100 prediversifies the incident light beam. The second lens group 200 has positive optical power. The first lens group 100 and the second lens group 200 are distributed sequentially in the optical axis direction. The second lens group 200 converges the light projected from the first lens group 100. The first lens group 100 includes a first lens 10, a second lens 20 and a third lens 30 arranged sequentially along the optical axis. The second lens 20 with positive optical power is disposed between the first lens 10 with negative optical power and the third lens 30 with negative optical power to correct aberrations and constrain the beam divergence angle.

[0027] It should be noted that most mainstream large-NA ultraviolet collimating optical systems currently use traditional ultraviolet optical materials such as quartz and calcium fluoride as lens substrates. However, the incident light has a large incident angle and the material has a large dispersion coefficient, which leads to wavefront distortion and insufficient parallelism accuracy of the collimated beam.

[0028] To this end, a first lens group 100 is set up. The incident light is first projected onto the first lens group 100. The negative optical power of the first lens group will disperse the incident light and pre-diverge the incident light to reduce the incident angle of the light from the rear lens, thereby reducing the dispersion and wavefront distortion caused by the large-angle incident deep ultraviolet light.

[0029] Furthermore, the first lens group 100 includes a first lens 10 with negative optical power, a second lens 20 with positive optical power, and a third lens 30 with negative optical power, and the first lens 10, the second lens 20, and the third lens 30 are arranged at intervals.

[0030] It is understandable that the first lens 10 and the third lens 30 are set to achieve pre-divergence of the beam, while the second lens 20 is set to compensate for the spherical aberration and chromatic aberration generated by the first lens 10 and the third lens 30. By correcting optical aberrations, the problems of large dispersion of deep ultraviolet materials and poor beam parallelism are solved.

[0031] Furthermore, by using a second lens with positive optical power to limit excessive beam divergence, control the lens aperture, and compress the overall length of the system, it is beneficial to achieve structural miniaturization.

[0032] like Figure 1 As shown, a second mirror group 200 with the same optical axis as the first mirror group 100 is provided on one side of the first mirror group 100.

[0033] Understandably, the second lens group 200 with positive optical power receives the divergent beam projected by the first lens group 100 and gradually converges and corrects the divergent beam, correcting the pre-divergent incident ultraviolet beam into a parallel collimated beam, thereby simplifying the overall structure and facilitating the miniaturization of the structure.

[0034] The technical solution of this invention uses a first lens group 100 formed by a first lens 10 with negative optical power, a second lens 20 with positive optical power, and a third lens 30 with negative optical power to achieve pre-divergence of the incident beam. The second lens 20 with positive optical power compensates for the spherical aberration and chromatic aberration caused by the first lens 10 and the third lens 30, and cancels the dispersion of ultraviolet materials. At the same time, it constrains excessive beam divergence, avoids excessively large aperture of the rear lens, and achieves miniaturization of the whole machine. A second lens group 200 with positive optical power is set on the coaxial side of the first lens 10 to receive the divergent beam projected by the first lens group 100 and gradually converges and corrects the divergent beam. By replacing the existing reflection and immersion structure with the second lens group 200, a large NA design can be achieved without the need for reflective elements and immersion media, simplifying the auxiliary structure of the whole machine and reducing the difficulty of equipment operation and maintenance.

[0035] In one embodiment, the first lens 10 is a meniscus lens, and the radius of curvature of the surface of the first lens 10 facing the second lens 20 is smaller than the radius of curvature of the surface of the first lens 10 away from the second lens 20, so as to pre-diverge the incident light beam and reduce the incident angle of the light.

[0036] It should be noted that the incident light contains stray beams from the edges at large tilt angles. If these beams are directly incident on the subsequent converging positive lens, the off-axis light will have an excessively high incident height, which can easily induce large amounts of spherical aberration, coma, and deep ultraviolet dispersion aberration.

[0037] like Figure 2 As shown, it can be understood that the first lens 10 is a crescent moon lens, with the radius of curvature of the front surface being smaller than that of the rear surface, forming a strong negative optical power structure that is steep at the front and flat at the rear. This structure is used to pre-diverge the incident deep ultraviolet beam, reduce the incident angle of the light from the subsequent lens group, suppress high-order spherical aberration and wavefront distortion from the source, adapt to the working conditions of large numerical aperture, and at the same time reduce the difficulty of system assembly and adjustment.

[0038] In another embodiment, the first lens 10 uses a calcium fluoride optical substrate combined with a quartz material to form a dispersion complementary combination. Relying on the difference in the Abbe coefficients of the two materials in the deep ultraviolet band, the primary axial chromatic aberration of the system is pre-canceled, improving the dispersion defects of deep ultraviolet wide-band imaging and ensuring coaxial focusing of multi-wavelength deep ultraviolet light.

[0039] like Figure 1As shown, the first lens 10 includes a first concave surface and a first convex surface. The first concave surface faces the incident light, and the side of the first lens 10 near the second lens 20 is the first convex surface. The surface radius of curvature of the first concave surface is smaller than that of the first convex surface.

[0040] Understandably, the first concave surface with a small curvature on the incident side preferentially diverges the scattered light from the edge with a large tilt angle, quickly reducing the incident slope of the edge light and reducing the spherical aberration and coma caused by the edge light from the source. The first convex surface with a large radius of curvature has a gentle curvature, which makes gentle fine adjustments to the beam after it has diverged through the front surface, avoiding excessive beam expansion that would cause the outer diameter of the system to exceed the limit, and balancing the divergence of the central beam and the edge beam.

[0041] Understandably, the asymmetric concave-convex surface uniformly adjusts the beam divergence, balances the optical paths of the central and peripheral fields of view, and achieves a smooth transition of light across a large field of view while constraining the overall size of the optical system.

[0042] In one embodiment, the second lens 20 is a spherical meniscus lens, and there is a gap between the first lens 10 and the second lens 20. The radius of curvature of the surface of the second lens 20 facing the first lens 10 is greater than the radius of curvature of the surface of the second lens 20 facing the third lens 30, so as to converge the pre-divergent beam and smooth the beam angle.

[0043] It is understandable that the second lens 20 has a positive optical power, which is used to receive the light path diverging from G1 and to perform beam shaping, thereby converging the diverging beam, gathering the diverging beam from G1, and reasonably controlling the beam aperture to provide incident conditions for subsequent lens groups.

[0044] like Figure 1 As shown, the second lens 20 includes a second concave surface and a second convex surface, with the second convex surface facing the first lens 10 and the second concave surface facing the third lens 30.

[0045] Understandably, the second concave surface has a large radius of curvature and a gentle curvature, resulting in a small deflection of light rays. This allows it to smoothly receive a wide range of incident light beams, reduce the incident deflection angle, decrease interface reflection loss, and avoid additional coma caused by the sharp deflection of light rays in some areas due to the excessively steep curvature of the incident surface.

[0046] Understandably, the second convex surface has a small radius of curvature and strong bending ability, which enables it to focus the beam, gradually compress the beam aperture, narrow the optical path, and share the initial focusing load of the system.

[0047] In this way, a progressively converging structure is formed by the asymmetrical curvature at the front and back. Combined with the negative optical power of the first lens 10, the dispersion in the deep ultraviolet band is initially offset, achieving primary achromatic aberration and solving the problem of wide-band imaging dispersion.

[0048] In one embodiment, the third lens 30 is a meniscus lens, and the radius of curvature of the surface of the third lens 30 facing the second lens 20 is smaller than the radius of curvature of the surface of the third lens 30 away from the second lens 20, so as to optimize the light angle.

[0049] It is understandable that the third lens 30 is a meniscus lens with negative optical power. After being converged by the second lens 20, the overall convergence of the beam is too high, and the edge rays converge too quickly, which easily produces spherical aberration and field curvature. Therefore, after the beam passes through the negative optical power third lens 30, the beam is appropriately diverged, the optical power ratio of the entire group is finely adjusted, the residual spherical aberration and field curvature caused by the excessive convergence of the second lens 20 are offset, and the incident tilt angle of the beam is changed to optimize the incident conditions of the subsequent second lens group 200 main converging lens.

[0050] like Figure 1 As shown, the third lens 30 includes a third convex surface and a third concave surface, with the third convex surface facing the second lens 20 and the third concave surface facing the second lens group 200.

[0051] Understandably, the third convex surface has a large radius of curvature and is planar, so as to gently receive the beam emitted from the second lens 20, thereby reducing the incident angle of light and thus reducing interface reflection loss, preventing local light rays from being sharply deflected and adding coma.

[0052] The radius of curvature of the third concave surface decreases, and the surface becomes steeper, thereby achieving beam divergence, specifically breaking up overly dense beams at the edges, and balancing the convergence difference between the center and the edges.

[0053] In one embodiment, the second lens group 200 includes a fourth lens 40, a fifth lens 50, a sixth lens 60, a seventh lens 70, and an eighth lens 80 arranged sequentially along the optical axis, wherein the convex surfaces of the fifth lens 50, the sixth lens 60, the seventh lens 70, and the eighth lens 80 all face the fourth lens 40.

[0054] like Figure 1 As shown, along the direction of light propagation, the fifth lens 50, the sixth lens 60, the seventh lens 70, and the eighth lens 80 all point their convex surfaces toward the fourth lens 40 upstream of the light path, so that the light-facing surfaces of each group of lenses are all convex structures.

[0055] Understandably, after the beam passes through the fourth lens 40, it forms a directional convergent optical path. The convex surfaces arranged in the same direction allow the incident light to be incident on the surface of each lens at a smaller incident angle, which greatly reduces the reflection loss and scattered stray light at the lens interface.

[0056] At the same time, the continuous convex surfaces form a progressive continuous refractive structure, which gradually and gently converges and shapes the light beam, avoiding the generation of higher aberrations such as spherical aberration and coma caused by large-angle deflection of light rays by a single lens.

[0057] Furthermore, the uniformly oriented convex structure shapes the upstream beam in an orderly manner, regulating the beam aperture and propagation angle, providing a stable and uniform incident beam for the downstream optical components, ensuring the overall imaging accuracy of the entire optical system, and meeting the high-precision detection requirements for tiny defects in wafers.

[0058] In one embodiment, the fourth lens 40 is a biconvex lens, and the radius of curvature of the surface of the fourth lens 40 facing the third lens 30 is greater than the radius of curvature of the surface of the fourth lens 40 away from the third lens 30. The surface of the fourth lens 40 away from the third lens 30 deflects the light rays converged by the radius of curvature of the surface of the fourth lens 40 facing the third lens 30 for a second time. The side of the fourth lens 40 with a large radius of curvature faces the concave surface of the third lens 30.

[0059] like Figure 1 As shown, the fourth lens 40 adopts an asymmetrical biconvex structure with a steep front and a gentle rear. The curvature radius of the surface upstream of the optical path (away from the third lens 30) is smaller and the degree of curvature is greater. As the main converging surface, it takes the lead in significantly converging the incident beam and undertakes the main converging task of the system.

[0060] Understandably, a smaller radius of curvature on the light-facing surface has a stronger light-gathering ability, which can efficiently compress the beam aperture, significantly improve the numerical aperture of the system, and ensure the resolution of wafer defect detection under large NA conditions.

[0061] Meanwhile, downstream of the optical path (towards the third lens 30) is a gently curved surface with a larger radius of curvature. On the one hand, it receives the light beam that has been initially converged and performs a secondary small deflection and angle correction on the light, weakening the excessive bending effect caused by the strong convergence at the front. On the other hand, this gently curved surface is directly opposite the concave surface of the third lens 30. The two surfaces are compatible with each other, so that the light beam is incident on the next stage lens at a matching angle, avoiding a sudden change in the incident angle of the light.

[0062] Understandably, the flat side of the fourth lens with a large radius of curvature faces the concave surface of the third lens at 30°. The two sets of optical surfaces match each other, reducing the incident angle of light at the interface, improving the transmission efficiency of deep ultraviolet beams, and optimizing the optical path connection.

[0063] Furthermore, the main light focusing is achieved by a steep surface with a small radius of curvature, and the light angle is corrected a second time by a gentle surface with a large radius of curvature. The fourth lens 40 rationally distributes the optical power load on both sides of the single lens through an asymmetrical biconvex structure, avoiding local stress concentration, reducing surface distortion caused by temperature and assembly deviations, and enhancing the overall working stability of the optical system.

[0064] In one embodiment, the fifth lens 50 is a meniscus lens, and the radius of curvature of the surface of the fifth lens 50 facing the fourth lens 40 is smaller than the radius of curvature of the surface of the fifth lens 50 away from the fourth lens 40.

[0065] like Figure 2 As shown, after the beam exits from the fourth lens 40, it first enters the steep curved surface of the fifth lens 50. This curved surface can receive the beam converged by the previous stage and continue to slightly converge the light, continuing the progressive convergence optical path design of the system. Then the light exits after the angle is finely adjusted by the gentle curved surface on the rear side.

[0066] Understandably, the small curvature surface on the light-facing side continuously converges the light beam, forming a coherent gradient convergence structure with the fourth lens, avoiding sudden changes in the convergence intensity of the light beam, and effectively reducing coma and higher-order spherical aberration caused by large-scale light deflection.

[0067] Meanwhile, the gentle curved surface with a large radius of curvature on the rear side makes the change in the refraction angle of the emitted light softer, reduces the reflection loss of light at the lens interface, reduces the generation of stray light, and adapts to the light energy requirements of the deep ultraviolet detection optical path.

[0068] Furthermore, the fifth lens 50 rationally distributes the beam deflection through its overall asymmetric meniscus shape, while relying on the optical characteristics of the meniscus lens itself to compensate for the residual spherical aberration and field curvature of the preceding lens, thus smoothly connecting the front and rear optical paths.

[0069] In one embodiment, the sixth lens 60 is a meniscus lens, the radius of curvature of the sixth lens 60 facing the fifth lens 50 is smaller than the radius of curvature of the sixth lens 60 away from the fifth lens 50, and the radius of curvature of the fifth lens 50 away from the fourth lens 40 is larger than the radius of curvature of the sixth lens 60 facing the fifth lens 50.

[0070] like Figure 1 As shown, the sixth lens 60 adopts an asymmetrical meniscus structure with a steeper front and a gentler rear. The curvature on the light-facing side is more pronounced, while the curvature on the back-facing side is gentler. Combined with the attached... Figure 3 It can be seen that the fifth lens 50 has a larger curvature and a flatter surface, while the sixth lens 60 has a smaller curvature and a steeper surface. The adjacent optical surfaces of the two lenses form a continuous transition structure with a gentle transition to a steep one.

[0071] like Figure 2As shown, after exiting the gently curved surface of the fifth lens 50, the beam smoothly enters the steep curved surface of the sixth lens 60, where it continues to converge and adjust its angle, before exiting gently through the gentle curved surface behind the sixth lens 60.

[0072] Understandably, the fifth lens 50 has a large curvature and a flat surface on its exit surface, while the sixth lens 60 has a small curvature and a steeper surface on its incident surface. The curvature of adjacent surfaces changes gradually to avoid abrupt changes in the incident angle between the two lenses, effectively suppressing stray light and additional refractive aberrations at the interface, and improving the transmission stability of deep ultraviolet beams.

[0073] Furthermore, the meniscus configuration of the sixth lens 60, with its steep front and gentle rear, deflects the beam in stages, continuously distributing the system's focusing power and preventing single large-angle refraction. This further reduces advanced monochromatic aberrations such as spherical aberration and coma, ensuring beam quality under large numerical apertures and wide fields of view. At the same time, the beam aperture and propagation angle are more uniform after curvature matching and shaping by the fifth lens 50 and the sixth lens 60, providing a stable incident beam for the seventh lens 70 and the eighth lens 80. This effectively reduces the pressure on the power distribution and aberration correction of the rear lens group, improving the overall reliability of the entire optical system.

[0074] In one embodiment, the seventh lens 70 is a meniscus lens, the radius of curvature of the surface of the seventh lens 70 facing the sixth lens 60 is smaller than the radius of curvature of the surface of the seventh lens 70 away from the sixth lens 60, and the radius of curvature of the surface of the sixth lens 60 away from the fifth lens 50 is larger than the radius of curvature of the surface of the seventh lens 70 facing the sixth lens 60.

[0075] like Figure 1 As shown, the seventh lens 70 adopts the same asymmetrical meniscus structure as the front lenses, with a steeper front and gentler rear. The incident side surface has a higher degree of curvature, while the exit side surface is more gently curved. (The last sentence appears to be incomplete and possibly refers to a different feature.) Figure 3 It can be seen that the sixth lens 60 has a large radius of curvature and a smooth surface on its exit surface, while the seventh lens 70 has a small radius of curvature and a steep surface on its incident surface. The adjacent optical surfaces of the two lenses form a continuous curvature gradient connection.

[0076] like Figure 2 As shown, after the beam exits smoothly from the sixth lens 60, it enters the steep curved surface of the seventh lens 70 at a uniform angle. The beam continues to converge and the angle is corrected by this curved surface, and then it is gently output through the rear gentle curved surface.

[0077] Understandably, the seventh lens 70 continues the design concept of graded convergence and step-by-step correction of the entire lens group. Relying on the optical characteristics of the meniscus lens, it continuously compensates for the spherical aberration and field curvature accumulated in the optical path. At the same time, it relies on the curvature matching of adjacent surfaces to constrain the light deflection amplitude and ensure the continuity and stability of the optical path.

[0078] At the same time, in conjunction with multiple sets of meniscus lenses in the preceding sequence, residual field curvature and monochromatic aberration in the optical path are continuously offset, and the image plane is gradually flattened to ensure that the imaging effect of the central field of view and the edge field of view is consistent, which is suitable for the needs of large field of view wafer defect detection.

[0079] In one embodiment, the eighth lens 80 is a meniscus lens, the radius of curvature of the eighth lens 80 facing the seventh lens 70 is smaller than the radius of curvature of the eighth lens 80 away from the seventh lens 70, and the radius of curvature of the seventh lens 70 away from the sixth lens 60 is larger than the radius of curvature of the eighth lens 80 facing the seventh lens 70.

[0080] like Figure 1 As shown, the eighth lens 80 continues the unified asymmetrical meniscus structure of the lens group, which is steep at the front and gentle at the back. The incident side surface is highly curved, while the exit side surface is more gently curved.

[0081] The seventh lens 70 has a large radius of curvature and a smooth surface on its exit surface, while the eighth lens 80 has a small radius of curvature and a steep surface on its incident surface. The two lenses form a smooth curvature gradient connection, allowing light to propagate smoothly across the lenses.

[0082] Understandably, as the end element of the second lens group, the eighth lens 80 receives the beam after multiple convergence stages from the preceding stages, relies on the steep incident surface to complete the final round of beam convergence and angle calibration, and then uses the exiting gentle surface to perform the final smoothing process on the light. At the same time, it utilizes the optical characteristics of the meniscus lens to perform the final correction of the residual spherical aberration and field curvature accumulated by the entire lens group, ensuring that the shape of the outgoing beam is uniform and the propagation direction is stable.

[0083] Furthermore, the eighth lens 80, relying on its steep front and gentle rear surface structure, completes the final stage of progressive focusing of the entire lens group, adjusting the beam aperture and convergence angle to the design standard, stabilizing the system numerical aperture, and meeting the large NA imaging requirements.

[0084] Meanwhile, as the final meniscus lens in the lens group, it concentrates on compensating for the residual spherical aberration, field curvature, and slight coma of the preceding lenses, further flattening the image plane and ensuring the clarity and uniformity of the entire field of view.

[0085] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A large nanometer ultraviolet collimating optical system, characterized in that, include: The first lens group has negative optical power, and when the incident light beam is projected onto the first lens group, the first lens group prediversifies the incident light beam. The second lens group has positive optical power. The first lens group and the second lens group are distributed sequentially along the optical axis. The second lens group converges the light projected from the first lens group. The first lens group includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis. The second lens with positive optical power is disposed between the first lens with negative optical power and the third lens with negative optical power to correct aberrations and constrain the beam divergence angle.

2. The large-NA ultraviolet collimating optical system as described in claim 1, characterized in that, The first lens is a meniscus lens, and the radius of curvature of the surface of the first lens facing the second lens is smaller than the radius of curvature of the surface of the first lens away from the second lens, so as to pre-diverge the incident beam and reduce the incident angle of the light.

3. The large-NA ultraviolet collimating optical system as described in claim 1, characterized in that, The second lens is a spherical meniscus lens. There is a gap between the first lens and the second lens. The surface curvature radius of the second lens facing the first lens is greater than the surface curvature radius of the second lens facing the third lens, so as to converge the pre-divergent beam and smooth the fiber angle.

4. The large-NA ultraviolet collimating optical system as described in claim 1, characterized in that, The third lens is a meniscus lens, and the radius of curvature of the surface of the third lens facing the second lens is smaller than the radius of curvature of the surface of the third lens away from the second lens, so as to optimize the light angle.

5. The large-NA ultraviolet collimating optical system as described in claim 1, characterized in that, The second lens group includes a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis. The convex surfaces of the fifth lens, the sixth lens, the seventh lens, and the eighth lens all face the fourth lens.

6. The large-NA ultraviolet collimating optical system as described in claim 5, characterized in that, The fourth lens is a biconvex lens. The radius of curvature of the surface of the fourth lens facing the third lens is greater than the radius of curvature of the surface of the fourth lens away from the third lens. The surface of the fourth lens away from the third lens deflects the light rays converged by the radius of curvature of the surface of the fourth lens facing the third lens for the second time. The side of the fourth lens with the larger radius of curvature faces the concave surface of the third lens.

7. The large-NA ultraviolet collimating optical system as described in claim 6, characterized in that, The fifth lens is a meniscus lens, and the radius of curvature of the surface of the fifth lens facing the fourth lens is smaller than the radius of curvature of the surface of the fifth lens facing away from the fourth lens.

8. The large-NA ultraviolet collimating optical system as described in claim 7, characterized in that, The sixth lens is a meniscus lens, and the radius of curvature of the surface of the sixth lens facing the fifth lens is smaller than the radius of curvature of the surface of the sixth lens away from the fifth lens, and the radius of curvature of the surface of the fifth lens away from the fourth lens is larger than the radius of curvature of the surface of the sixth lens facing the fifth lens.

9. The large-NA ultraviolet collimating optical system as described in claim 8, characterized in that, The seventh lens is a meniscus lens, and the radius of curvature of the surface of the seventh lens facing the sixth lens is smaller than the radius of curvature of the surface of the seventh lens away from the sixth lens, and the radius of curvature of the surface of the sixth lens away from the fifth lens is larger than the radius of curvature of the surface of the seventh lens facing the sixth lens.

10. The large-NA ultraviolet collimating optical system as described in claim 9, characterized in that, The eighth lens is a meniscus lens. The radius of curvature of the eighth lens facing the seventh lens is smaller than the radius of curvature of the eighth lens away from the seventh lens, and the radius of curvature of the seventh lens away from the sixth lens is larger than the radius of curvature of the eighth lens facing the seventh lens.

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