A low-power large field of view long working distance lens

Abstract

This invention discloses a low-magnification, large-field-of-view, long-working-distance lens, comprising a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged sequentially along the optical axis from the object side to the image side. Through the rational allocation of optical power among the three lens groups, this invention enables the lens to achieve an ultra-long working distance of more than 31mm on the object side while maintaining a parfocal distance of 95mm, and supports ultra-large field-of-view observation with an object diameter of 35mm. It also possesses good manufacturability, meeting the high-precision observation and measurement needs of the semiconductor field under large field-of-view and long working-distance conditions.

Description

Technical Field

[0001] This invention relates to the field of microscope objective technology, specifically to a low-magnification, large-field-of-view, long-working-distance lens. Background Technology

[0002] With the rapid development of the semiconductor industry, the feature size of integrated circuits continues to shrink and the wafer size continues to increase, which puts forward higher requirements for the performance of microscopic imaging systems, especially in rapid detection and large field of view observation. Ultra-large field of view can cover a wider observation area, significantly reduce the number of mechanical scans, greatly improve detection efficiency, and long working distance can provide more space for objective lens installation and focusing, adapt to various complex working conditions such as complex fixtures or non-ideal lighting environments, and avoid collision between objective lens and sample.

[0003] For most lenses on the market, as long as the working distance is longer, the design space of the lens group becomes shorter, provided that the focal length of 95mm is met. In this case, to achieve a large field of view, the light must be deflected at a larger angle inside the lens group. A larger angle of light deflection introduces more aberrations. The limited space of the lens group also restricts the degree of freedom in correcting aberrations. Therefore, conventional designs are unlikely to achieve near-diffraction-limited imaging quality under the conditions of focal length, working distance and large field of view. Summary of the Invention

[0004] Technical objective: To address the shortcomings of existing microscope objectives, this invention discloses a low-magnification, large-field-of-view, long-working-distance lens that achieves an ultra-large field of view of 35mm on the object side and an ultra-long working distance of 31mm while maintaining image quality, under the premise of satisfying 95mm parfocal focus.

[0005] Technical solution: To achieve the above technical objectives, the present invention adopts the following technical solution: A low-magnification, large-field-of-view, long-working-distance lens comprises a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged sequentially along the optical axis from the object side to the image side. The focal length of the first lens group is F1, the focal length of the second lens group is F2, the focal length of the third lens group is F3, the focal length of the lens is F, and the following conditions apply: 0.5 ≥ F1 / F > 0, 0 > F2 / F ≥ -0.5, 0.5 ≥ F3 / F > 0, and 0.5 ≥ F1 / F3 ≥ 0.4.

[0006] Preferably, the first lens group of the present invention consists of a first lens with positive optical power, a second lens with positive optical power, a third lens with positive optical power, and a fourth lens with negative optical power, arranged sequentially along the optical path starting from the object side.

[0007] Preferably, the third lens and the fourth lens of the present invention form a cemented doublet lens group.

[0008] Preferably, the refractive index and Abbe number of the first lens of the present invention are n1 and v1, respectively, 1.9≥n1≥1.8, 50≥v1≥40; The refractive index and Abbe number of the second lens are n2 and v2, respectively, 2.0≥n2≥1.9, 40≥v2≥30; The refractive index and Abbe number of the third lens are n3 and v3, respectively, 1.7≥n3≥1.6, 40≥v3≥30; The refractive index and Abbe number of the fourth lens are n4 and v4, respectively, 1.9≥n4≥1.8, 30≥v4≥20.

[0009] Preferably, the second lens group of the present invention consists of a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, a fifteenth lens, and a sixteenth lens arranged sequentially along the optical path direction. Each lens in the second lens group is arranged with alternating positive and negative optical powers along the optical path direction.

[0010] Preferably, the fifth and sixth lenses of the present invention form a cemented doublet lens group; the eighth and ninth lenses form a cemented doublet lens group; the eleventh, twelfth, and thirteenth lenses form a cemented triplet lens group; and the fourteenth, fifteenth, and sixteenth lenses form a cemented triplet lens group.

[0011] Preferably, the refractive index and Abbe number of the fifth lens of the present invention are n5 and v5, respectively, 1.7≥n5≥1.6, 50≥v5≥40; The refractive index and Abbe number of the sixth lens are n6 and v6, respectively, 1.9≥n6≥1.8, 50≥v6≥40; The refractive index and Abbe number of the seventh lens are n7 and v7, respectively, 1.6≥n7≥1.5, 50≥v7≥40; The refractive index and Abbe number of the eighth lens are n8 and v8, respectively, with 2.1≥n8≥2.0 and 30≥v8≥20. The refractive index and Abbe number of the ninth lens are n9 and v9, respectively, 1.8≥n9≥1.7, 30≥v9≥20; The refractive index and Abbe number of the tenth lens are n10 and v10, respectively, with 1.9 ≥ n10 ≥ 1.8 and 50 ≥ v10 ≥ 40. The refractive index and Abbe number of the eleventh lens are n11 and v11, respectively, 1.7≥n11≥1.6, 40≥v11≥30; The refractive index and Abbe number of the twelfth lens are n12 and v12, respectively, 1.8≥n12≥1.7, 60≥v12≥50; The refractive index and Abbe number of the thirteenth lens are n13 and v13, respectively, 1.9≥n13≥1.8, 30≥v13≥20; The refractive index and Abbe number of the fourteenth lens are n14 and v14, respectively, 1.8≥n14≥1.7, 60≥v14≥50; The refractive index and Abbe number of the fifteenth lens are n15 and v15, respectively, 1.6≥n15≥1.5, 60≥v15≥50; The refractive index and Abbe number of the sixteenth lens are n16 and v16, respectively, with 2.0 ≥ n16 ≥ 1.9 and 40 ≥ v16 ≥ 30.

[0012] Preferably, the third lens group of the present invention consists of a seventeenth lens with negative optical power, an eighteenth lens with positive optical power, and a nineteenth lens with positive optical power arranged sequentially along the optical path direction.

[0013] Preferably, the seventeenth lens and the eighteenth lens of the present invention form a cemented doublet lens group.

[0014] Preferably, the refractive index and Abbe number of the seventeenth lens of the present invention are n17 and v17, respectively, 1.8≥n17≥1.7, 60≥v17≥50; The refractive index and Abbe number of the eighteenth lens are n18 and v18, respectively, with 1.5≥n18≥1.4 and 100≥v18≥90; The refractive index and Abbe number of the nineteenth lens are n19 and v19, respectively, with 1.5≥n19≥1.4 and 100≥v19≥90.

[0015] Beneficial effects: The low-magnification, large-field-of-view, long-working-distance lens disclosed in this invention has the following beneficial effects: 1. This invention forms a positive-negative-positive optical architecture by sequentially arranging a first lens group, a second lens group, and a third lens group from the object side. The first lens group collects and initially converges light. The second lens group, with a specific range of negative optical power ratio, ensures moderate divergence to extend the working distance without causing subsequent aberrations to be difficult to correct due to excessive divergence. The third lens group converges again and corrects residual aberrations, achieving a good balance of aberrations and optimizing system performance. This structure not only effectively corrects field curvature and chromatic aberration, but also achieves optical distortion of less than 0.5% across the entire field of view, thereby ensuring clear imaging with high resolution, high contrast, and low distortion at both the image edges and center throughout the entire field of view.

[0016] 2. The optical power design of the first and third lens groups of this invention can effectively control the distortion of the entire field of view, ensuring that the image edges and center remain low under ultra-large field of view, thus guaranteeing the imaging quality of the lens.

[0017] 3. The first lens group of the present invention consists of two single lenses and one cemented doublet meniscus lens. The cemented doublet meniscus lens can effectively control the incident angle of light in a large field of view, thereby reducing the difficulty of aberration correction of the entire system, especially the difficulty of field curvature and astigmatism correction, while providing good light incident conditions for subsequent lens groups.

[0018] 4. The second lens group of the present invention consists of two single lenses, two cemented doublet lenses, and two cemented triplet lenses, which can realize the apochromatic function of the system. The multiple cemented structures, through the alternating combination of high dispersion materials and low dispersion materials, achieve chromatic aberration correction across the entire spectral band, improve the image quality at the edge of the large field of view, and ensure the consistency of imaging quality across the entire field of view. Spherical aberration correction is achieved through the alternating arrangement of positive and negative optical power lenses.

[0019] 5. The third lens group of the present invention consists of a single lens and a cemented doublet lens, which can balance the residual aberrations after correction by the first two lens groups, mainly correcting spherical aberration and chromatic aberration, ensuring that the overall imaging quality meets the design requirements, and guaranteeing the imaging quality of the lens in a large field of view and long working distance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0021] Figure 1 This is a schematic diagram of the lens structure of the present invention; Figure 2 This is a graph of the modulation transfer function of the lens of the present invention; Figure 3 This is a wave aberration diagram of the lens of the present invention; Figure 4 This is a field curvature and distortion diagram of the lens of the present invention; Among them, 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-fourteenth lens, 15-fifteenth lens, 16-sixteenth lens, 17-seventeenth lens, 18-eighteenth lens, 19-nineteenth lens, 20-first lens group, 21-second lens group, 22-third lens group. Detailed Implementation

[0022] Reference will now be made in detail to embodiments of the present disclosure, one or more of which are set forth herein. Each embodiment and example is provided by way of explanation of the apparatus, composition, and materials of the present disclosure, and not by way of limitation. Rather, the following description provides convenient illustrations for implementing exemplary embodiments of the present disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made to the teachings of the present disclosure without departing from the scope or spirit of the present disclosure.

[0023] like Figure 1 As shown, this invention discloses a low-magnification, large-field-of-view, long-working-distance lens, comprising a first lens group 20 with positive refractive power, a second lens group 21 with negative refractive power, and a third lens group 22 with positive refractive power, arranged sequentially along the optical axis from the object side to the image side. The focal length of the first lens group 20 is F1, the second lens group 21 is F2, and the third lens group 22 is F3. The lens focal length is F, with the following parameters: 0.5 ≥ F1 / F > 0, 0 > F2 / F ≥ -0.5, 0.5 ≥ F3 / F > 0, and 0.5 ≥ F1 / F3 ≥ 0.4. The optical power design of the first lens group 20 and the third lens group 22 effectively controls the distortion across the entire field of view on both sides of the second lens group 21, ensuring low distortion at both the edge and center of the image under a very large field of view, thus facilitating image quality.

[0024] This invention achieves a balance between a large field of view, a long working distance, and apochromatic performance through the rational configuration and structural coordination of the three lens groups. The positive-negative-positive optical structure of the lens enables a longer working distance, while the first lens group 20 provides a larger light deflection angle to achieve a large field of view for light incidence.

[0025] The first lens group 20 of the present invention consists of a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with positive optical power, and a fourth lens 4 with negative optical power, arranged sequentially along the optical path starting from the object side.

[0026] The third lens 3 and the fourth lens 4 of the present invention form a cemented doublet lens group. In the embodiment of the present invention, the third lens 3 and the fourth lens 4 form a cemented doublet meniscus lens, which can effectively control the incident angle of light with a large field of view, thereby reducing the difficulty of correcting aberrations in the whole system.

[0027] Specifically, the refractive index and Abbe number of the first lens 1 of the present invention are n1 and v1, respectively, 1.9≥n1≥1.8, 50≥v1≥40; The refractive index and Abbe number of the second lens 2 are n2 and v2, respectively, 2.0≥n2≥1.9, 40≥v2≥30; The refractive index and Abbe number of the third lens 3 are n3 and v3, respectively, 1.7≥n3≥1.6, 40≥v3≥30; The refractive index and Abbe number of the fourth lens 4 are n4 and v4, respectively, 1.9≥n4≥1.8, 30≥v4≥20.

[0028] The second lens group 21 of the present invention is used to appropriately diverge light and extend the working distance. It consists of a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12, a thirteenth lens 13, a fourteenth lens 14, a fifteenth lens 15, and a sixteenth lens 16 arranged sequentially along the optical path. Each lens of the second lens group 21 is arranged with alternating positive and negative optical powers along the optical path to correct spherical aberration in imaging.

[0029] Under a large field of view, off-axis aberrations will increase significantly. The fifth lens 5 and the sixth lens 6 of this invention form a cemented doublet lens group, the eighth lens 8 and the ninth lens 9 form a cemented doublet lens group, the eleventh lens 11, the twelfth lens 12 and the thirteenth lens 13 form a cemented triplet lens group, and the fourteenth lens 14, the fifteenth lens 15 and the sixteenth lens 16 form a cemented triplet lens group. The multiple cemented structures formed by the lenses achieve chromatic aberration correction across the entire wavelength range through the alternating combination of high-dispersion materials and low-dispersion materials, while the two cemented triplet lens groups can effectively correct higher-order aberrations to ensure image quality.

[0030] Specifically, the refractive index and Abbe number of the fifth lens 5 of the present invention are n5 and v5, respectively, 1.7≥n5≥1.6, 50≥v5≥40; The refractive index and Abbe number of the sixth lens 6 are n6 and v6, respectively, 1.9≥n6≥1.8, 50≥v6≥40; The refractive index and Abbe number of the seventh lens 7 are n7 and v7, respectively, 1.6≥n7≥1.5, 50≥v7≥40; The refractive index and Abbe number of the eighth lens 8 are n8 and v8, respectively, 2.1≥n8≥2.0, 30≥v8≥20; The refractive index and Abbe number of the ninth lens 9 are n9 and v9, respectively, 1.8≥n9≥1.7, 30≥v9≥20; The refractive index and Abbe number of the tenth lens 10 are n10 and v10, respectively, 1.9≥n10≥1.8, 50≥v10≥40; The refractive index and Abbe number of the eleventh lens 11 are n11 and v11, respectively, 1.7≥n11≥1.6, 40≥v11≥30; The refractive index and Abbe number of the twelfth lens 12 are n12 and v12, respectively, 1.8≥n12≥1.7, 60≥v12≥50; The refractive index and Abbe number of the thirteenth lens 13 are n13 and v13, respectively, 1.9≥n13≥1.8, 30≥v13≥20; The refractive index and Abbe number of the fourteenth lens 14 are n14 and v14, respectively, 1.8≥n14≥1.7, 60≥v14≥50; The refractive index and Abbe number of the fifteenth lens 15 are n15 and v15, respectively, 1.6≥n15≥1.5, 60≥v15≥50; The refractive index and Abbe number of the sixteenth lens 16 are n16 and v16, respectively, with 2.0≥n16≥1.9 and 40≥v16≥30.

[0031] The third lens group 22 of the present invention consists of a seventeenth lens 17 with negative optical power, an eighteenth lens 18 with positive optical power and a nineteenth lens 19 with positive optical power arranged sequentially along the optical path direction. The seventeenth lens 17 and the eighteenth lens 18 form a cemented doublet lens group.

[0032] The third lens group 22 of the present invention is used to balance the corrected residual aberrations, correct the spherical aberration and chromatic aberration of the image, balance the spherical aberration, coma and chromatic aberration of the imaging system, ensure the consistency of the full field of view imaging, and make the imaging quality meet the design requirements.

[0033] Specifically, the refractive index and Abbe number of the seventeenth lens 17 of the present invention are n17 and v17, respectively, 1.8≥n17≥1.7, 60≥v17≥50; The refractive index and Abbe number of the eighteenth lens 18 are n18 and v18, respectively, 1.5≥n18≥1.4, 100≥v18≥90; The refractive index and Abbe number of the nineteenth lens 19 are n19 and v19, respectively, 1.5≥n19≥1.4, 100≥v19≥90.

[0034] Through the lens structure design of this invention, the lens can achieve an ultra-large field of view of 35mm object diameter and an ultra-long working distance of more than 31mm while ensuring 95mm parfocal focus. The lens parameters of this invention are shown in Table 1.

[0035] Table 1 Lens Parameter Table Surface serial number radius of curvature (mm) Thickness (mm) Refractive index Abbe number IMA Infinity Infinity R1 15.86 3.13 1.46 98.3 R2 -271.20 0.12 R3 11.07 3.23 1.43 95.2 R4 -180.45 0.84 1.73 54.7 R5 40.85 4.83 R6 813.68 1.51 1.91 35.3 R7 6.12 2.62 1.57 56.0 R8 -9.25 0.61 1.70 56.2 R9 -14.99 0.17 R10 -53.90 1.67 1.81 25.5 R11 -8.06 0.93 1.75 52.3 R12 4.39 3.14 1.62 36.3 R13 -7.00 0.13 R14 -7.24 0.81 1.88 40.2 R15 65.07 0.10 R16 11.92 2.83 1.76 26.6 R17 -4.54 1.12 2.00 25.4 R18 12.40 0.53 R19 16.76 2.71 1.57 42.8 R20 -5.59 0.14 R21 -8.87 0.76 1.88 40.8 R22 15.18 1.32 1.61 40.0 R23 58.02 13.76 R24 -10.86 1.77 1.85 23.8 R25 -61.99 7.01 1.60 39.2 R26 -17.90 0.58 R27 -41.77 6.54 1.95 32.3 R28 -23.18 0.25 R29 87.88 3.81 1.82 46.6 R30 Infinity 32.16 OBJ Infinity The surface numbers represent different lens surfaces in the order of the nineteenth lens 19 to the first lens 1. Cemented doublet lenses share the same surface number. OBJ is the object plane, IMA is the image plane, and the thickness indicates the distance from the current surface to the next surface along the marking direction. For example, the thickness corresponding to R1 represents the maximum distance between surface R1 and surface R2, which is also the lens thickness of the nineteenth lens 19. The thickness corresponding to R2 represents the distance between surface R2 and the eighteenth lens 18.

[0036] like Figure 2 As shown, Figure 2 The horizontal axis represents the spatial frequency (lp / mm), and the vertical axis represents the magnitude of the optical modulation function. From the figure, it can be seen that the MTF curves of each field of view of the lens basically coincide with the diffraction limit curve, which proves that the lens imaging performance in this embodiment is excellent.

[0037] like Figure 3 As shown, the horizontal axis represents the field of view in mm, and the vertical axis represents the RMS wavefront difference, expressed as a fraction of the reference wavelength λ, for example, 0.03λ. Figure 3 The lines from top to bottom are labeled as curves A, B, C, and D. Curve A represents the RMS wavefront difference of 420nm monochromatic light under different fields of view; curve C represents the RMS wavefront difference of 600nm monochromatic light under different fields of view; curve D represents the RMS wavefront difference of 700nm monochromatic light under different fields of view; and curve B represents the RMS wavefront difference of the lens under polychromatic light under different fields of view. Polychromatic light refers to the superposition of 420nm, 600nm, and 700nm monochromatic light. Figure 3 It can be seen that the RMS wavefront difference of the lens for different bands is less than 0.06λ throughout the entire field of view, indicating that the imaging performance of the lens is basically close to the diffraction limit.

[0038] like Figure 4 The diagram shows the field curvature and distortion curves of the lens in this embodiment. The vertical axis represents the field of view. The left side is the field curvature diagram, and the horizontal axis represents the field curvature. The solid curves in the field curvature diagram, from left to right, are curves E, F, and G. The dashed curves, from left to right, are curves E1, F1, and G1. Curve E is the field curvature in the meridional direction of the lens under 420nm monochromatic light conditions, and curve E1 is the field curvature in the sagittal direction of the lens under 420nm monochromatic light conditions. Curve F is the field curvature in the meridional direction of the lens under 600nm monochromatic light conditions, and curve F1 is the field curvature in the sagittal direction of the lens under 600nm monochromatic light conditions. Curve G is the field curvature in the meridional direction of the lens under 700nm monochromatic light conditions, and curve G1 is the field curvature in the sagittal direction of the lens under 700nm monochromatic light conditions.

[0039] The plane formed by the principal ray passing through the off-axis object point and the lens principal axis is called the meridional plane, and the field curvature in the meridional direction is called the meridional field curvature. The plane perpendicular to the meridional plane and passing through the principal ray passing through the off-axis object point is called the sagittal plane, and the field curvature in the sagittal direction is called the sagittal field curvature. Figure 4 As can be seen from the field curvature diagram, the field curvature is less than 0.2 mm.

[0040] Figure 4The right side of the image shows the distortion curves. The horizontal axis represents the percentage of distortion. From left to right, the three solid curves are curve H, curve J, and curve K. Curve H represents the distortion curve corresponding to the lens under 600nm monochromatic light, curve J represents the distortion curve corresponding to 700nm monochromatic light, and curve K represents the distortion curve corresponding to 420nm monochromatic light. The distortion of all three curves is less than 0.2%, indicating that the lens in this example has corrected for field curvature and distortion, achieving better image quality.

[0041] The objective lens that can be achieved by the lens parameters of the embodiments of the present invention meets the following optical indicators, and the lens parameters are shown in Table 2.

[0042] Table 2 Objective Lens Parameters

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-magnification, large-field-of-view, long-working-distance lens, characterized in that, It consists of a first lens group (20) with positive refractive power, a second lens group (21) with negative refractive power, and a third lens group (22) with positive refractive power, arranged sequentially along the optical axis from the object side to the image side of the lens. The focal length of the first lens group (20) is F1, the focal length of the second lens group (21) is F2, the focal length of the third lens group (22) is F3, the focal length of the lens is F, 0.5≥F1 / F>0, 0>F2 / F≥-0.5, 0.5≥F3 / F>0, and 0.5≥F1 / F3≥0.

4.

2. The low-magnification, large-field-of-view, long-working-distance lens according to claim 1, characterized in that, The first lens group (20) consists of a first lens (1) with positive optical power, a second lens (2) with positive optical power, a third lens (3) with positive optical power, and a fourth lens (4) with negative optical power, arranged sequentially along the optical path starting from the object side.

3. A low-magnification, large-field-of-view, long-working-distance lens according to claim 2, characterized in that, The third lens (3) and the fourth lens (4) form a doublet lens group.

4. A low-magnification, large-field-of-view, long-working-distance lens according to claim 2, characterized in that, The refractive index and Abbe number of the first lens (1) are n1 and v1, respectively, 1.9≥n1≥1.8, 50≥v1≥40; The refractive index and Abbe number of the second lens (2) are n2 and v2, respectively, 2.0≥n2≥1.9, 40≥v2≥30; The refractive index and Abbe number of the third lens (3) are n3 and v3, respectively, 1.7≥n3≥1.6, 40≥v3≥30; The refractive index and Abbe number of the fourth lens (4) are n4 and v4, respectively, 1.9≥n4≥1.8, 30≥v4≥20.

5. A low-magnification, large-field-of-view, long-working-distance lens according to claim 1, characterized in that, The second lens group (21) consists of the fifth lens (5), the sixth lens (6), the seventh lens (7), the eighth lens (8), the ninth lens (9), the tenth lens (10), the eleventh lens (11), the twelfth lens (12), the thirteenth lens (13), the fourteenth lens (14), the fifteenth lens (15), and the sixteenth lens (16) arranged sequentially along the optical path. Each lens in the second lens group (21) is arranged in an alternating manner of positive and negative optical power along the optical path.

6. A low-magnification, large-field-of-view, long-working-distance lens according to claim 5, characterized in that, The fifth lens (5) and the sixth lens (6) form a cemented doublet lens group; the eighth lens (8) and the ninth lens (9) form a cemented doublet lens group; the eleventh lens (11), the twelfth lens (12) and the thirteenth lens (13) form a cemented triplet lens group; the fourteenth lens (14), the fifteenth lens (15) and the sixteenth lens (16) form a cemented triplet lens group.

7. A low-magnification, large-field-of-view, long-working-distance lens according to claim 5, characterized in that, The refractive index and Abbe number of the fifth lens (5) are n5 and v5, respectively, 1.7≥n5≥1.6, 50≥v5≥40; The refractive index and Abbe number of the sixth lens (6) are n6 and v6, respectively, 1.9≥n6≥1.8, 50≥v6≥40; The refractive index and Abbe number of the seventh lens (7) are n7 and v7, respectively, 1.6≥n7≥1.5, 50≥v7≥40; The refractive index and Abbe number of the eighth lens (8) are n8 and v8, respectively, 2.1≥n8≥2.0, 30≥v8≥20; The refractive index and Abbe number of the ninth lens (9) are n9 and v9, respectively, 1.8≥n9≥1.7, 30≥v9≥20; The refractive index and Abbe number of the tenth lens (10) are n10 and v10, respectively, 1.9≥n10≥1.8, 50≥v10≥40; The refractive index and Abbe number of the eleventh lens (11) are n11 and v11, respectively, 1.7≥n11≥1.6, 40≥v11≥30; The refractive index and Abbe number of the twelfth lens (12) are n12 and v12, respectively, 1.8≥n12≥1.7, 60≥v12≥50; The refractive index and Abbe number of the thirteenth lens (13) are n13 and v13, respectively, 1.9≥n13≥1.8, 30≥v13≥20; The refractive index and Abbe number of the fourteenth lens (14) are n14 and v14, respectively, 1.8≥n14≥1.7, 60≥v14≥50; The refractive index and Abbe number of the fifteenth lens (15) are n15 and v15, respectively, 1.6≥n15≥1.5, 60≥v15≥50; The refractive index and Abbe number of the sixteenth lens (16) are n16 and v16, respectively, 2.0≥n16≥1.9, 40≥v16≥30.

8. A low-magnification, large-field-of-view, long-working-distance lens according to claim 1, characterized in that, The third lens group (22) consists of a seventeenth lens (17) with negative optical power, an eighteenth lens (18) with positive optical power, and a nineteenth lens (19) with positive optical power arranged sequentially along the optical path.

9. A low-magnification, large-field-of-view, long-working-distance lens according to claim 8, characterized in that, The seventeenth lens (17) and the eighteenth lens (18) form a doublet lens group.

10. A low-magnification, large-field-of-view, long-working-distance lens according to claim 8, characterized in that, The refractive index and Abbe number of the seventeenth lens (17) are n17 and v17, respectively, 1.8≥n17≥1.7, 60≥v17≥50; The refractive index and Abbe number of the eighteenth lens (18) are n18 and v18, respectively, 1.5≥n18≥1.4, 100≥v18≥90; The refractive index and Abbe number of the nineteenth lens (19) are n19 and v19, respectively, 1.5≥n19≥1.4, 100≥v19≥90.

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