Objective lens

Abstract

The utility model relates to the technical field of optics and relates to an objective lens. The objective lens comprises a first lens group, a second lens group, a third lens group, a fourth lens group and a fifth lens group which are sequentially arranged from an object space to an image space, a second lens group that corrects the chromatic aberration of the incident beam by using a positive and negative lens combination having a dispersion difference; the third lens group is of a double-agglutination negative lens group structure and is used for adjusting the incident light beam to be bent relative to the upper part of the optical axis; the fourth lens group is a convex lens and concave lens combined lens and is used for optimizing the telecentricity of the incident light beam and correcting distortion; the first lens group and the second lens group form a front lens group, the third lens group and the fourth lens group form a rear lens group, and diaphragms are arranged on the rear focal plane of the front lens group and the front focal plane of the rear lens group to form a double-telecentric lens structure. According to the invention, ultraviolet wavelength high-resolution imaging can be satisfied, high light collection efficiency can be ensured, and weak ultraviolet imaging and a large imaging field of view can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, and relates to an objective lens. BACKGROUND

[0002] In semiconductor measurement or detection applications, an ultraviolet light source is often used. According to the Rayleigh criterion, the limit resolution of a lens is σ = 0.61λ / NA; where λ represents the wavelength, and NA represents the numerical aperture of the lens. According to the above formula, compared with visible light, using ultraviolet light of a short wavelength to image can distinguish smaller details and achieve higher resolution under the same numerical aperture.

[0003] Current industrial lenses are generally designed and optimized for visible light, and these lenses may be general for ultraviolet light imaging. With the development of semiconductor measurement and detection technology, the requirements for lens imaging performance are becoming higher and higher, and it is required to meet high resolution, large target surface imaging, and high magnification requirements. Because there are few optical materials with high transmittance in the ultraviolet band, it is difficult to correct the chromatic aberration of the ultraviolet lens, and it is difficult to improve the imaging quality. In addition, compared with general microscope lenses, the object distance requirement of industrial lenses is also generally higher. These all increase the design difficulty of the ultraviolet lens. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a high-resolution, large-target-surface imaging, high-object-distance, high-magnification double-telecentric optical system.

[0005] In a first aspect, an embodiment of the present application provides an objective lens, comprising, in order from the object side to the image side: a first lens group for controlling the divergence angle of an incident light beam and the bending angle of the incident light beam to reduce the spherical aberration and coma of the incident light beam; a second lens group for correcting the chromatic aberration of the incident light beam by using a positive and negative lens combination with different dispersion; a third lens group, which is a double-cemented negative lens group structure, for adjusting the bending of the incident light beam relative to the upper part of the optical axis and correcting the astigmatism of the incident light beam; and a fourth lens group, which is a convex lens, a concave lens combination lens, for optimizing the telecentricity of the incident light beam and correcting the distortion; the first lens group and the second lens group form a front lens group, the third lens group and the fourth lens group form a rear lens group, and a diaphragm is arranged on the rear focal plane of the front lens group and the front focal plane of the rear lens group to form a double-telecentric lens structure.

[0006] In some specific implementations, the first lens group includes a first positive lens group with positive focal power, which is mainly composed of a first lens, a second lens and a third lens in order of decreasing bending degree of the light entrance surface, the first lens and the second lens are concave mirrors, and the third lens is a plano-convex lens, and the first positive lens group is used to bend the large-angle incident light beam.

[0007] In some specific implementations, the first mirror group further comprises a second positive lens group with positive focal power mainly composed of a biconvex lens and a meniscus lens, and the second positive lens group is used for gently bending light rays and controlling spherical aberration and coma.

[0008] In some specific implementations, the second mirror group comprises two doublet lens groups, the first doublet lens group is sequentially provided with a positive meniscus lens and a negative meniscus lens along the light beam incident direction, the second doublet lens group is sequentially provided with a double-concave lens and a double-convex lens along the light beam incident direction, and the dispersion coefficient of the positive meniscus lens is greater than that of the negative meniscus lens, and the dispersion coefficient of the double-concave lens is less than that of the double-convex lens.

[0009] In some specific implementations, the dispersion coefficients of the positive meniscus lens, the negative meniscus lens, the double-concave lens and the double-convex lens are respectively within the following intervals: [58, 62], [33, 37], [28, 32], [62, 64].

[0010] In some specific implementations, the third mirror group is sequentially provided with a positive meniscus lens and a double-concave lens along the light beam incident direction, and the concave surface of the positive meniscus lens is the light entrance surface.

[0011] In some specific implementations, the fourth mirror group is sequentially provided with a positive meniscus lens and a plano-convex lens along the light beam incident direction, and the concave surface of the positive meniscus lens is the light entrance surface.

[0012] In some specific implementations, the total length of the objective lens is less than or equal to 720 mm, the object-side numerical aperture is greater than or equal to 0.35, and the magnification is 6X.

[0013] In some specific implementations, the object-side working distance of the objective lens is greater than 80 mm, and the diameter of the object-side field of view is 45 mm.

[0014] In some specific implementations, the object-side resolution of the objective lens is greater than or equal to 0.83 um.

[0015] The embodiment of the present application brings the following beneficial effects:

[0016] The embodiment of the present application provides an objective lens, which forms a double-telecentric optical system by setting four lens groups, and realizes optimization and correction of spherical aberration, coma, chromatic aberration, astigmatism, telecentricity and distortion of the incident laser beam through the four lens groups. It can meet the requirements of ultraviolet wavelength high-resolution imaging and ensure high light collection efficiency, and can realize weak ultraviolet light imaging and large imaging field of view.

[0017] Additional features and advantages of the present disclosure will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the present disclosure according to the following claims.

[0018] In order to make the above objectives, features and advantages of the present disclosure more obvious and comprehensible, the following preferred embodiments are specifically described below, and the accompanying drawings are referred to for a detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 The structural schematic diagram of the objective lens provided by the embodiment of the present application is shown in the figure.

[0021] Figure 2 The MTF schematic diagram of the objective lens provided by the embodiment of the present application is shown in the figure.

[0022] Figure 3 The point column diagram of the objective lens provided by the embodiment of the present application is shown in the figure.

[0023] Figure legend: O- object side; ST- stop; I- image side;

[0024] G1- first lens group; G2- second lens group; G3- third lens group; G4- fourth lens group;

[0025] G11- first positive lens group; G12- second positive lens group;

[0026] 1- first lens; 2- second lens; 3- third lens; 4- fourth lens; 5- fifth lens; 6- sixth lens; 7- seventh lens; 8- eighth lens; 9- ninth lens; 10- tenth lens; 11- eleventh lens; 12- twelfth lens; 13- thirteenth lens; 14- filter device. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0028] The objective lens provided by the embodiment of the present application is applied to an optical detection and measurement scene, and provides a light source for a to-be-detected measurement object. The optical detection and measurement scene can be a semiconductor product, and in particular, a wafer optical detection and measurement scene. That is, in the embodiment, the to-be-detected measurement object is a wafer. The light source is a laser light source, that is, the wafer is subjected to projection of a laser beam.

[0029] In the prior art, with the development of semiconductor measurement and detection technology, the requirements for the imaging performance of the lens become higher and higher, and it is required to meet high resolution, large target surface imaging, and high magnification. Due to the fact that there are few optical materials with high transmittance in the ultraviolet band, it is difficult to correct the chromatic aberration of the ultraviolet lens, and it is difficult to improve the imaging quality. In addition, compared with general microscope lenses, the requirements for the objective lens of an industrial lens are usually also increased, which increases the design difficulty of the ultraviolet lens.

[0030] Therefore, in view of the above background art, the embodiment of the present application provides an objective lens which can meet the above lens requirements in the optical detection and measurement scene.

[0031] Specifically, referring to Figure 1 The present application provides a structure diagram of the projection objective lens of the first embodiment. The total length of the projection objective lens of the embodiment is not more than 720 mm, it is suitable for the ultraviolet spectral range, the numerical aperture of the object side is greater than or equal to 0.35, the magnification is 6X, the object side working distance is greater than 80 mm, and the diameter of the object side field of view is 45 mm.

[0032] In the embodiment, the objective lens is sequentially provided with a first lens group G1, a second lens group G2, a third lens group G3 and a fourth lens group G4 from the direction of the light beam incidence. The first lens group G1 and the second lens group G2 form a front lens group, which is used to reduce the spherical aberration and chromatic aberration of the incident light beam. The third lens group G3 and the fourth lens group G4 form a rear lens group, which is used to correct the spherical aberration, coma, astigmatism and telecentricity of the incident light beam, and to optimize and correct the distortion.

[0033] Specifically, the first lens group G1 controls the spherical aberration and coma by controlling the divergence angle and bending angle of the incident light beam. The second lens group G2 corrects the chromatic aberration of the incident light beam by using a combination of positive and negative lens groups with different dispersion. The third lens group G3 adjusts the relative position of the incident light beam relative to the optical axis to correct the astigmatism. Specifically, the third lens group G3 adjusts the incident light beam to bend relative to the upper part of the optical axis, so that the astigmatism is corrected. The fourth lens group G4 realizes the optimization of the telecentricity of the incident light beam and the correction of the distortion by combining convex and concave lenses.

[0034] In the embodiment, a diaphragm ST is arranged on the rear focal surface of the front lens group and the front focal surface of the rear lens group, so that the overall objective lens system forms a double-telecentric lens structure.

[0035] In the embodiment, the first mirror group is composed of two positive lens groups, which are the first positive lens group G11 and the second positive lens group G12. The first positive lens group G11 is used to bend the large-angle incident light beam, and the second positive lens group G12 is used to gently bend the light rays, thereby controlling the spherical aberration and coma.

[0036] The first positive lens group G11 is a positive focal length lens group composed of three lenses, which are the first lens 1, the second lens 2, and the third lens 3. The three lenses have decreasing bending degrees of the entrance surface along the optical axis direction, specifically, the first lens 1 is a concave mirror, the second lens 2 is a concave mirror, and the third lens 3 is a plano-convex lens. The concave direction and the convex direction of the above-mentioned lenses are determined according to the corresponding curvature radius of the entrance surface and the curvature radius of the exit surface.

[0037] Specifically, the curvature radius of the entrance surface and the curvature radius of the exit surface of the first lens 1 are negative values, so the concave surface of the first lens 1 faces the object side, the curvature radius of the entrance surface and the curvature radius of the exit surface of the second lens 2 are negative values, so the concave surface of the second lens 2 faces the object side, the curvature radius of the entrance surface of the third lens 3 is infinite, and the curvature radius of the exit surface of the third lens 3 is negative, so the convex surface of the third lens faces the image side. Moreover, the absolute values of the curvature radius of the first lens 1, the curvature radius of the second lens 2, and the curvature radius of the entrance surface of the third lens 3 increase in turn, which means that the bending degrees of the entrance surfaces of the first lens 1, the second lens 2, and the third lens 3 decrease in turn.

[0038] In the embodiment, the curvature radii of the first lens 1, the second lens 2, and the third lens 3 are adjusted and set, so that the bending degrees of the first lens 1, the second lens 2, and the third lens 3 for the incident light beam are adjusted, thereby bending the large-angle incident light beam.

[0039] The second positive lens group G12 is also a positive focal length lens group composed of two lenses, which are the fourth lens 4 and the fifth lens 5.

[0040] Specifically, the fourth lens 4 is a double convex lens, and the fifth lens 5 is a meniscus lens. The meniscus lens is a positive meniscus lens, and its concave surface is set to face the image side. In the embodiment, the second positive lens group G12 is used to gently bend the light rays, thereby controlling the spherical aberration and coma of the incident light beam.

[0041] In the embodiment, the second mirror group G2 includes two doublet lens groups. The first doublet lens group is sequentially provided with the sixth lens 6 and the seventh lens 7 along the incident direction of the incident light beam, wherein the sixth lens 6 is a positive meniscus lens, and the seventh lens 7 is a negative meniscus lens. The second doublet lens group is sequentially provided with the eighth lens 8 and the ninth lens 9 along the incident direction of the incident light beam, wherein the eighth lens 8 is a double concave lens, and the ninth lens 9 is a double convex lens.

[0042] Wherein, the refractive index and the dispersion coefficient of the positive meniscus lens, the negative meniscus lens, the double concave lens and the double convex lens in the embodiment are different.

[0043] Specifically, the dispersion coefficient of the positive meniscus lens is greater than that of the negative meniscus lens, the dispersion coefficient of the double concave lens is less than that of the double convex lens, the refractive index of the positive meniscus lens is less than that of the negative meniscus lens, the refractive index of the negative meniscus lens is greater than that of the double concave lens, and the refractive index of the double concave lens is less than that of the negative meniscus lens.

[0044] Specifically, the dispersion coefficient of the positive meniscus lens is any one value in [58, 62], the dispersion coefficient of the negative meniscus lens is any one value in [33, 37], the dispersion coefficient of the double concave lens is any one value in [28, 32], and the dispersion coefficient of the double convex lens is any one value in [62, 64]. The refractive index of the positive meniscus lens is any one value in [1.62, 1.66], the refractive index of the negative meniscus lens is any one value in [1.73, 1.77], the refractive index of the double concave lens is any one value in [1.70, 1.74], and the refractive index of the double convex lens is any one value in [1.60, 1.64].

[0045] From the above, it can be seen that in the embodiment, the convex-concave lenses with different refractive indices and dispersion rates are combined to reduce the chromatic aberration of the incident light beam.

[0046] In the embodiment, the third lens group G3 is a double cemented negative lens group structure, and the tenth lens 10 and the eleventh lens 11 are sequentially arranged along the incident direction of the incident light beam, wherein the tenth lens 10 is a positive meniscus lens, and the eleventh lens 11 is a double concave lens. Wherein, the concave surface of the positive meniscus lens is the light entrance surface.

[0047] Wherein, the dispersion coefficients of the tenth lens 10 and the eleventh lens 11 are the same, but the refractive indices are different, and the refractive index of the tenth lens 10 is greater than that of the eleventh lens 11. By so arranging, the bending trend of the incident light beam can be adjusted, the bending of the incident light beam relative to the upper part of the optical axis is adjusted, and the astigmatism of the incident light beam is corrected.

[0048] Specifically, the refractive index of the tenth lens is any one value in [1.63, 1.67], and the refractive index of the eleventh lens is any one value in [1.49, 1.53].

[0049] In the embodiment, the fourth lens group G4 is a combination lens of convex lenses and concave lenses, and the twelfth lens 12 and the thirteenth lens 13 are sequentially arranged along the incident direction of the incident light beam.

[0050] In the embodiment, the twelfth lens 12 is a concave lens, specifically a positive meniscus lens, and the concave surface of the twelfth lens 12 is arranged at the light entrance surface; the thirteenth lens 13 is a convex lens, specifically a plano-convex lens, and the convex surface of the thirteenth lens 13 is arranged at the light entrance surface. In the embodiment, the refractive index of the twelfth lens 12 is less than the refractive index of the thirteenth lens 13.

[0051] Specifically, the refractive index of the twelfth lens 12 in the embodiment is any one value in [1.82, 1.86], and the refractive index of the thirteenth lens 13 is any one value in [1.48, 1.52].

[0052] Since the projection objective lens has a double-telecentric structure, the chief rays of each field of view on the object side are approximately parallel to the optical axis and are incident on the front surface of the objective lens; the chief rays of each field of view on the image side are approximately parallel to the optical axis and are emitted and converge on the image plane.

[0053] Table 1 shows the specific parameters of the objective lens in the above embodiment. The radius R is positive, indicating that the center of curvature is on the side close to the object side; the radius R is negative, indicating that the center of curvature is on the side close to the image side. The size unit of the radius R and the thickness d is millimeter; in the serial number, “O” represents the object side, “I” represents the image side, “ST” represents the stop, “a” represents the mirror surface on the side close to the object side, and “b” represents the mirror surface on the side close to the image side. For example, “11a” represents the mirror surface on the side close to the object side of the eleventh lens.

[0054] Table 1. Parameters of the objective lens in the embodiment

[0055] Number Surface type Radius R Thickness d Refractive index / Abbe number O STANDARD Infinite 86.925 1a STANDARD -118.600 6.500 1.65；55.89 1b STANDARD -70.060 0.200 2a STANDARD -173.650 5.500 1.62；63.39 2b STANDARD -101.650 0.200 3a STANDARD Infinite 5.200 1.52；64.17 3b STANDARD -241.670 18.000 4a STANDARD 223.810 25.000 1.49；70.41 4b STANDARD -505.260 30.000 5a STANDARD 113.280 25.000 1.55；63.46 5b STANDARD 519.330 0.900 6a STANDARD 66.940 10.100 1.64；60.10 6b STANDARD 281.270 23.200 1.75；34.95 7a STANDARD 281.270 23.200 1.75；34.95 7b STANDARD 41.950 6.800 8a STANDARD -312.600 21.850 1.72；29.51 8b STANDARD 46.150 25.000 1.62；63.39 9a STANDARD 46.150 25.000 1.62；63.39 9b STANDARD -163.180 30.000 ST STANDARD Infinite 30.000 10a STANDARD -69.270 25.000 1.65；33.85 10b STANDARD -36.780 25.000 1.51；61.04 11a STANDARD -36.780 25.000 1.51；61.04 11b STANDARD 68.440 31.100 12a STANDARD -109.290 25.000 1.84；43.13 12b STANDARD -88.780 30.700 13a STANDARD 115.410 25.000 1.50；66.95 13b STANDARD Infinite 108.700 I STANDARD Infinite 0.000

[0056] In the embodiment, a filter device is arranged between the thirteenth lens and the image side to realize the filtering of the incident light beam.

[0057] Specifically, the filter device can be any one of an optical attenuation sheet, an optical filter, and a dustproof sheet having a refractive index and a thickness similar to those of the thirteenth lens.

[0058] For the above objective lens structure, the first lens to the thirteenth lens are spherical mirrors, and in order to further reduce the chromatic aberration of the objective lens, the corresponding dispersion coefficients of the lenses in the above objective lens should satisfy the following conditions: 54≤v1≤58, 62≤v2≤66, 62≤v3≤66, 68≤v4≤72, 62≤v5≤66, 58≤v6≤62, 33≤v7≤37, 28≤v8≤32, 62≤v9≤64, 62≤v10≤66, 62≤v11≤66, 40≤v12≤44, 65≤v13≤69, 62≤v14≤66. Wherein, v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13 are respectively the dispersion coefficient expressions of the first lens to the thirteenth lens, and v14 is the dispersion coefficient expression of the filter device.

[0059] And, for the corresponding refractive index of the lenses in the above objective lens should satisfy the following conditions: 1.63≤n1≤1.67, 1.60≤n2≤1.64, 1.50≤n3≤1.54, 1.48≤n4≤1.52, 1.53≤n5≤1.57, 1.62≤n6≤1.66, 1.73≤n7≤1.77, 1.70≤n8≤1.74, 1.60≤n9≤1.64, 1.63≤n10≤1.67, 1.49≤n11≤1.53, 1.82≤n12≤1.86, 1.48≤n13≤1.52, 1.50≤n14≤1.54. Wherein, n1, n2, n3, n4, n5, n6, n7, n8, n9, n10, n11, n12, n13 are respectively the reflectivity expressions of the first lens to the thirteenth lens, and n14 is the reflectivity expression of the filter device.

[0060] Referring to Figure 2 The MTF diagram of the objective lens in the above embodiment is shown in the figure, and it can be seen from the figure that the contrast of the objective lens in the embodiment is still above 40% at a high spatial frequency, for example, at a spatial frequency of 100 lp / mm, which fully illustrates that the imaging effect of the objective lens in the embodiment is still very good in the case of a large target surface.

[0061] Referring to Figure 3For the point array diagram of the objective lens in the above embodiment, five different spot diagrams are included in the diagram, and the five diagrams respectively indicate the spot array diagrams corresponding to the spots formed by the object image under different field of view ranges. Among them, the different field of view ranges refer to different offset amounts of the object side relative to the detection surface of the sensor, for example, the image surface: 0.000 mm surface object side center is concentric with the detection surface center, and the image surface: 5.625 mm surface center is offset by 5.625 mm. Regarding the Airy spot radius of 3.702 μm in the diagram, the RMS radii of the above five different fields of view are 2.772 μm, 3.194 μm, 3.799 μm, 4.076 μm and 4.856 μm, respectively; and the corresponding GEO halves are 4.692 μm, 7.590 μm, 12.669 μm, 16.832 μm and 20.898 μm, respectively.

[0062] The objective lens provided by the embodiment can realize large target surface imaging. For the objective lens with a numerical aperture of 0.35 on the object side, the objective lens can accept light rays with a larger range of incident angles, thereby having higher light receiving capacity and focusing capacity, so that the objective lens has higher resolution and better imaging quality, and the resolution on the object side can reach 0.83 um. Moreover, under the premise of ensuring a large target surface, the objective lens can realize a relatively high object distance, so that the objective lens has sufficient space for installation between the objective lens and the object surface; and the large target surface optimization design of the embodiment enables the objective lens to have a maximum imaging target surface diameter of 45 mm, and still maintain relatively high imaging quality.

[0063] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0064] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An objective, characterized in that The first mirror group is used for controlling the divergence angle of the incident light beam and the bending angle of the incident light beam, so as to reduce the spherical aberration and coma of the incident light beam. The second mirror group is used for correcting the chromatic aberration of the incident light beam by using the positive and negative lens combination with different dispersion. The third mirror group is a double-cemented negative lens group structure, which is used for adjusting the bending of the incident light beam relative to the upper part of the optical axis and correcting the astigmatism of the incident light beam. The fourth mirror group is a convex lens and a concave lens combination lens, which is used for optimizing the telecentricity of the incident light beam and correcting the distortion. The first mirror group and the second mirror group form a front lens group, and the third mirror group and the fourth mirror group form a rear lens group. The first mirror group includes a first positive lens group with positive focal power, which is mainly composed of a first lens, a second lens and a third lens with the bending degree of the light entrance surface decreasing in turn.

2. The objective according to claim 1, characterized in that The first mirror group further includes a second positive lens group with positive focal power, which is mainly composed of a double convex lens and a meniscus lens.

3. The objective according to claim 2, characterized in that The second mirror group includes two double-cemented lens groups.

4. The objective according to claim 1, characterized in that The dispersion coefficients of the positive meniscus lens, the negative meniscus lens, the double concave lens and the double convex lens are respectively within the following intervals: [58, 62], [33, 37], [28, 32] and [62, 64].

5. The objective according to claim 4, characterized in that The third mirror group includes a positive meniscus lens and a double concave lens arranged in turn along the light beam incidence direction, and the concave surface of the positive meniscus lens is the light entrance surface.

6. The objective according to claim 1, characterized in that The fourth mirror group includes a positive meniscus lens and a plano-convex lens arranged in turn along the light beam incidence direction, and the concave surface of the positive meniscus lens is the light entrance surface.

7. The objective according to claim 1, characterized in that The total length of the objective lens is less than or equal to 720 mm, the numerical aperture on the object side is greater than or equal to 0.35, and the magnification is 6X.

8. The objective according to claim 1, characterized in that The object side working distance of the objective lens is greater than 80 mm, and the diameter of the object side field of view is 45 mm.

9. The objective according to claim 1, characterized in that The object side resolution of the objective lens is greater than or equal to 0.83 um.

10. The objective according to claim 1, characterized in that ​

Images