Low magnification long working distance telecentric objective

Abstract

The application discloses a low-magnification long-working-distance telecentric objective lens, which comprises a first lens group, a second lens group and a third lens group arranged along an optical axis in sequence, the first lens group has positive refractive power, the second lens group has negative refractive power, the third lens group has positive refractive power, and the following conditional expressions are satisfied: 0.0<|f1 / f|<3.3; 0.0<|f2 / f|<3.1; 0.0<|f3 / f|<3.3; 0.0<|f2 / f1|<3.3; 0.0<|f1 / f3|<6.1; 0.0<|f2 / f3|<3.3; wherein f is the focal distance of the objective lens, f1 is the focal distance of the first lens group, f2 is the focal distance of the second lens group, and f3 is the focal distance of the third lens group. The first lens group, the second lens group and the third lens group are arranged, and the focal distances of the first lens group, the second lens group and the third lens group are limited, so that the field curvature, the distortion and the chromatic aberration of the objective lens optical system are corrected, and the problems of insufficient working distance, insufficient low magnification and telecentricity of the objective lens are solved.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and specifically to a low magnification, long working distance telecentric objective lens. Background Technology

[0002] With the rapid development of the biotechnology and electronics industries in recent years, optical microscopes have played an important role in many fields such as biomedicine, especially in the areas of industrial material structure, device surface defects, machine vision inspection, and real-time microscopic observation. Optical systems with low magnification, long working distance, and telecentric objectives can provide more and faster possibilities for optical microscopes.

[0003] In the field of microscopic imaging, low magnification and long working distance are particularly important. Telecentric objectives are irreplaceable in the inspection industry, as ordinary microscope objectives cannot simultaneously achieve low magnification, long working distance, and telecentric capability. It is difficult to find an objective that simultaneously possesses low magnification, long working distance, and object-side telecentricity. For such an optical system to meet overall high-resolution imaging requirements, achieving low on-axis aberrations, low magnification, low chromatic aberration at magnification, low field curvature, and low distortion is even more challenging. For example, the prior art disclosed in application publication number CN115343832A is a large field-of-view plan telecentric microscope objective with a focal length of 50.12mm, which is insufficient, meaning the magnification is not low enough.

[0004] Therefore, how to provide a telecentric objective lens with low magnification and long working distance is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a low magnification, long working distance, telecentric objective lens to solve the problems of insufficient working distance, insufficient magnification, and telecentricity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A low-magnification, long-working-distance telecentric objective lens includes a first lens group, a second lens group, and a third lens group arranged sequentially along an optical axis. The first lens group has positive refractive power, the second lens group has negative refractive power, and the third lens group has positive refractive power, satisfying the following condition:

[0008] 0.0<|f1 / f|<3.3; 0.0<|f2 / f|<3.1; 0.0<|f3 / f|<3.3;

[0009] 0.0<|f2 / f1|<3.3; 0.0<|f1 / f3|<6.1; 0.0<|f2 / f3|<3.3;

[0010] Where f is the focal distance of the objective lens, f1 is the focal distance of the first lens group, f2 is the focal distance of the second lens group, and f3 is the focal distance of the third lens group.

[0011] Furthermore, the first lens group is located near the object side, and the first lens group includes a first lens having positive refractive power.

[0012] Furthermore, the second lens group has one or more cemented lenses. The second lens group includes a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially from the object side to the image side. The second lens has negative refractive power, the third lens has positive refractive power, the fourth lens has negative refractive power, the fifth lens has positive refractive power, the sixth lens has positive refractive power, the seventh lens has negative refractive power, the eighth lens has positive refractive power, and the ninth lens has negative refractive power.

[0013] Furthermore, the second lens group has three cemented lenses.

[0014] Furthermore, the second lens group satisfies the following condition:

[0015] 0.0<|f2 / f21|<3.6; 0.0<|f2 / f22|<6.3;

[0016] 0.0<|f2 / f23|<7.4; 0.0<|f2 / f24|<6.7;

[0017] 0.0<|f2 / f25|<6.1; 0.0<|f2 / f26|<6.5;

[0018] 0.0<|f2 / f27|<4.6; 0.0<|f2 / f28|<3.3;

[0019] Where f2 is the focal distance of the second lens group, f21 is the focal distance of the second lens, f22 is the focal distance of the third lens, f23 is the focal distance of the fourth lens, f24 is the focal distance of the fifth lens, f25 is the focal distance of the sixth lens, f26 is the focal distance of the seventh lens, f27 is the focal distance of the eighth lens, and f28 is the focal distance of the ninth lens.

[0020] Furthermore, the third lens group is located near the image side, and the third lens group includes a tenth lens, which has positive refractive power.

[0021] Furthermore, each of the first to tenth lenses includes an object-side surface facing the object side and through which imaging light passes, and an image-side surface facing the image side and through which imaging light passes. The object-side surface and image-side surface of the first lens are convex, the image-side surface and image-side surface of the second lens are concave, the object-side surface and image-side surface of the third lens are convex, the object-side surface and image-side surface of the fourth lens are concave, the object-side surface and image-side surface of the fifth lens are convex and the image-side surface of the fifth lens are concave, the object-side surface and image-side surface of the sixth lens are convex, the object-side surface and image-side surface of the sixth lens are convex, the object-side surface and image-side surface of the seventh lens are concave, the image-side surface of the eighth lens are convex, the object-side surface and image-side surface of the ninth lens are concave and the image-side surface of the ninth lens are convex, and the object-side surface and image-side surface of the tenth lens are concave and the image-side surface of the tenth lens are convex.

[0022] Furthermore, the first to tenth lenses satisfy the following conditional expression:

[0023] N11≥1.40; N21≥1.45; N22≤1.80; N23≥1.45; N24≥1.40;

[0024] N25 ≥ 1.50; N26 ≤ 1.90; N27 ≥ 1.45; N28 ≤ 2.01; N31 ≥ 1.40;

[0025] Wherein, N11 is the refractive index of the first lens, N21 is the refractive index of the second lens, N22 is the refractive index of the third lens, N23 is the refractive index of the fourth lens, N24 is the refractive index of the fifth lens, N25 is the refractive index of the sixth lens, N26 is the refractive index of the seventh lens, N27 is the refractive index of the eighth lens, N28 is the refractive index of the ninth lens, and N31 is the refractive index of the tenth lens.

[0026] Furthermore, the first to tenth lenses satisfy the following conditional expression:

[0027] V11≥30; V21≤95; V22≥20; V23≤95; V24≤95;

[0028] V25≥20; V26≤95; V27≤95; V28≥15; V31≤95;

[0029] Wherein, V11 is the Abbe number of the first lens, V21 is the Abbe number of the second lens, V22 is the Abbe number of the third lens, V23 is the Abbe number of the fourth lens, V24 is the Abbe number of the fifth lens, V25 is the Abbe number of the sixth lens, V26 is the Abbe number of the seventh lens, V27 is the Abbe number of the eighth lens, V28 is the Abbe number of the ninth lens, and V31 is the Abbe number of the tenth lens.

[0030] Furthermore, the first to tenth lenses satisfy the following conditional expression:

[0031] 1.08<T11 / T31<1.58; 0.30<T21 / T22<0.70;

[0032] 0.75<T21 / T23<1.25; 0.28<T21 / T24<0.78;

[0033] 0.17<T21 / T25<0.67; 0.75<T21 / T26<1.25;

[0034] 0.09<T21 / T27<0.59; 0.75<T21 / T28<1.25;

[0035] Wherein, T11 is the thickness of the first lens on the optical axis, T31 is the thickness of the tenth lens on the optical axis, T21 is the thickness of the second lens on the optical axis, T22 is the thickness of the third lens on the optical axis, T23 is the thickness of the fourth lens on the optical axis, T24 is the thickness of the fifth lens on the optical axis, T25 is the thickness of the sixth lens on the optical axis, T26 is the thickness of the seventh lens on the optical axis, T27 is the thickness of the eighth lens on the optical axis, and T28 is the thickness of the ninth lens on the optical axis.

[0036] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0037] 1. This invention uses a first lens group, a second lens group, and a third lens group to set up the first lens group to have positive refractive power, the second lens group to have negative refractive power, and the third lens group to have positive refractive power. By limiting the focal distance of the first lens group, the second lens group, and the third lens group, the field curvature, distortion, and chromatic aberration of the objective lens optical system are corrected, thereby solving the problems of insufficient working distance, insufficient magnification, and telecentricity of the objective lens.

[0038] 2. By limiting the refractive index, Abbe number, thickness, etc. of the lenses in the first lens group, the second lens group, and the third lens group, this invention further corrects the chromatic aberration, field curvature, and dispersion of the objective lens optical system, achieving good telecentricity and thus improving the optical performance of the objective lens. This results in the objective lens optical system possessing the characteristics of high-resolution imaging, low magnification, long working distance, telecentricity, small chromatic aberration, and small distortion. Attached Figure Description

[0039] Figure 1 This is a lens configuration diagram of the objective lens optical system according to Embodiment 1 of the present invention;

[0040] Figure 2 This is a spherical aberration diagram of the objective lens optical system of Embodiment 1 of the present invention;

[0041] Figure 3 This is a field curvature diagram of the objective lens optical system of Embodiment 1 of the present invention;

[0042] Figure 4 This is a distortion diagram of the objective lens optical system in Embodiment 1 of the present invention;

[0043] Figure 5 This is a lens configuration diagram of the objective optical system of Embodiment 2 of the present invention;

[0044] Figure 6 This is a spherical aberration diagram of the objective lens optical system in Embodiment 2 of the present invention;

[0045] Figure 7 This is a field curvature diagram of the objective lens optical system of Embodiment 2 of the present invention;

[0046] Figure 8 This is a distortion diagram of the objective lens optical system in Embodiment 2 of the present invention;

[0047] Figure 9 This is a lens configuration diagram of the objective lens optical system of Embodiment 3 of the present invention;

[0048] Figure 10 This is a spherical aberration diagram of the objective lens optical system in Embodiment 3 of the present invention;

[0049] Figure 11 This is a field curvature diagram of the objective lens optical system of Embodiment 3 of the present invention;

[0050] Figure 12 This is a distortion diagram of the objective lens optical system in Embodiment 3 of the present invention.

[0051] Explanation of reference numerals in the attached figures:

[0052] Object side 700, first lens group 81, first lens 711, second lens group 82, second lens 721, third lens 722, fourth lens 723, fifth lens 724, sixth lens 725, seventh lens 726, eighth lens 727, ninth lens 728, third lens group 83, tenth lens 731. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0054] In this specification, the phrase "the lens has positive (or negative) refractive power" means that the paraxial refractive power of the lens, calculated using Gaussian optics theory, is positive (or negative). The "object-side surface (or image-side surface)" is defined as the specific area through which imaging rays pass on the lens surface. The convexity or concavity of a lens surface can be determined using methods commonly known in the field, namely, by the sign of the radius of curvature (R-value). The R-value is commonly used in optical design software, such as Zemax or Code V. The R-value is also frequently found in lens datasheets within optical design software. For the object-side surface, a positive R-value indicates a convex surface, while a negative R-value indicates a concave surface. Conversely, for the image-side surface, a positive R-value indicates a concave surface, while a negative R-value indicates a convex surface.

[0055] Cooperate Figure 1 , Figure 5 ,and Figure 9 As shown, this invention discloses a low-magnification, long-working-distance telecentric objective lens, comprising a first lens group 81, a second lens group 82, and a third lens group 83 arranged sequentially along an optical axis from the object side 700. The first lens group 81 has positive refractive power, the second lens group 82 has negative refractive power, and the third lens group 83 has positive refractive power. To enable this objective lens to have low magnification and a long working distance, it satisfies the following condition:

[0056] 0.0<|f1 / f|<3.3; 0.0<|f2 / f|<3.1; 0.0<|f3 / f|<3.3;

[0057] 0.0<|f2 / f1|<3.3; 0.0<|f1 / f3|<6.1; 0.0<|f2 / f3|<3.3;

[0058] Where f is the focal distance of the objective lens optical system OB, f1 is the focal distance of the first lens group 81, f2 is the focal distance of the second lens group 82, and f3 is the focal distance of the third lens group 83.

[0059] The first lens group 81 of the objective lens is located near the object side, and the first lens group 81 includes a first lens 711, which has positive refractive power.

[0060] The second lens group 82 of the objective lens has one or more cemented lenses. The second lens group 82 includes a second lens 721, a third lens 722, a fourth lens 723, a fifth lens 724, a sixth lens 725, a seventh lens 726, an eighth lens 727, and a ninth lens 728 arranged sequentially from the object side to the image side. The second lens 721 has negative refractive power, the third lens 722 has positive refractive power, the fourth lens 723 has negative refractive power, the fifth lens 724 has positive refractive power, the sixth lens 725 has positive refractive power, the seventh lens 726 has negative refractive power, the eighth lens 727 has positive refractive power, and the ninth lens 728 has negative refractive power.

[0061] In this embodiment, the second lens group 82 of the objective lens has three cemented lenses. Preferably, the third lens 722, the fourth lens 723 and the fifth lens 724 form a cemented lens, the sixth lens 725 and the seventh lens 726 form a cemented lens, and the eighth lens 727 and the ninth lens 728 form a cemented lens.

[0062] To ensure good telecentricity of the objective lens optical system, the second lens group 82 satisfies the following condition:

[0063] 0.0<|f2 / f21|<3.6; 0.0<|f2 / f22|<6.3; 0.0<|f2 / f23|<7.4;

[0064] 0.0<|f2 / f24|<6.7; 0.0<|f2 / f25|<6.1; 0.0<|f2 / f26|<6.5;

[0065] 0.0<|f2 / f27|<4.6; 0.0<|f2 / f28|<3.3;

[0066] Wherein, f2 is the focal distance of the second lens group 82, f21 is the focal distance of the second lens 721, f22 is the focal distance of the third lens 722, f23 is the focal distance of the fourth lens 723, f24 is the focal distance of the fifth lens 724, f25 is the focal distance of the sixth lens 725, f26 is the focal distance of the seventh lens 726, f27 is the focal distance of the eighth lens 727, and f28 is the focal distance of the ninth lens 728.

[0067] The third lens group 83 of the objective lens is located near the image side, and the third lens group 83 includes a tenth lens 731, which has positive refractive power.

[0068] The objective lens comprises a first lens 711 to a tenth lens 731, each including an object-side surface (i.e., a first surface) facing the object side and allowing imaging light to pass through, and an image-side surface (i.e., a second surface) facing the image side and allowing imaging light to pass through. The object-side surface and image-side surface of the first lens 711 are convex, the image-side surface and image-side surface of the second lens 721 are concave, the object-side surface and image-side surface of the third lens 722 are convex, the image-side surface of the fourth lens 723 are concave, the object-side surface and image-side surface of the fifth lens 724 are convex, the image-side surface of the sixth lens 725 are convex, the image-side surface of the sixth lens 725 are convex, the object-side surface and image-side surface of the seventh lens 726 are concave, the image-side surface of the seventh lens 726 are concave, the object-side surface and image-side surface of the eighth lens 727 are convex, the image-side surface of the ninth lens 728 are concave, and the object-side surface of the tenth lens 731 are concave and the image-side surface of the tenth lens 731.

[0069] To ensure that the objective lens system has high resolution, low chromatic aberration, and low distortion, the first lens 711 to the tenth lens 731 satisfy the following conditional expression:

[0070] N11≥1.40; N21≥1.45; N22≤1.80; N23≥1.45;

[0071] N24 ≥ 1.40; N25 ≥ 1.50; N26 ≤ 1.90; N27 ≥ 1.45;

[0072] N28≤2.01; N31≥1.40;

[0073] Wherein, N11 is the refractive index of the first lens 711, N21 is the refractive index of the second lens 721, N22 is the refractive index of the third lens 722, N23 is the refractive index of the fourth lens 723, N24 is the refractive index of the fifth lens 724, N25 is the refractive index of the sixth lens 725, N26 is the refractive index of the seventh lens 726, N27 is the refractive index of the eighth lens 727, N28 is the refractive index of the ninth lens 728, and N31 is the refractive index of the tenth lens 731.

[0074] To further reduce chromatic aberration and field curvature in the objective lens optical system, the first lens 711 to the tenth lens 731 satisfy the following conditional expression:

[0075] V11≥30; V21≤95; V22≥20; V23≤95;

[0076] V24≤95; V25≥20; V26≤95; V27≤95;

[0077] V28≥15; V31≤95;

[0078] Wherein, V11 is the Abbe number of the first lens 711, V21 is the Abbe number of the second lens 721, V22 is the Abbe number of the third lens 722, V23 is the Abbe number of the fourth lens 723, V24 is the Abbe number of the fifth lens 724, V25 is the Abbe number of the sixth lens 725, V26 is the Abbe number of the seventh lens 726, V27 is the Abbe number of the eighth lens 727, V28 is the Abbe number of the ninth lens 728, and V31 is the Abbe number of the tenth lens 731.

[0079] The first lens 711 to the tenth lens 731 of the objective lens satisfy the following condition:

[0080] 1.08<T11 / T31<1.58; 0.30<T21 / T22<0.70;

[0081] 0.75<T21 / T23<1.25; 0.28<T21 / T24<0.78;

[0082] 0.17<T21 / T25<0.67; 0.75<T21 / T26<1.25;

[0083] 0.09<T21 / T27<0.59; 0.75<T21 / T28<1.25;

[0084] Wherein, T11 is the thickness of the first lens 711 on the optical axis, T31 is the thickness of the tenth lens 731 on the optical axis, T21 is the thickness of the second lens 721 on the optical axis, T22 is the thickness of the third lens 722 on the optical axis, T23 is the thickness of the fourth lens 723 on the optical axis, T24 is the thickness of the fifth lens 724 on the optical axis, T25 is the thickness of the sixth lens 725 on the optical axis, T26 is the thickness of the seventh lens 726 on the optical axis, T27 is the thickness of the eighth lens 727 on the optical axis, and T28 is the thickness of the ninth lens 728 on the optical axis.

[0085] To further elaborate on the technical content of the invention, three embodiments will be listed below to describe in detail the low magnification long working distance telecentric objective lens.

[0086] Example 1

[0087] like Figure 1 As shown, the objective lens optical system OB01 includes an object side 700, a first lens group 81, a second lens group 82, and a third lens group 83. The object-side numerical aperture (NAO) is 0.03, the object height diameter is 13.5 mm, the focal distance f of the objective lens optical system OB01 is 89.7 mm, the magnification is 2X, the maximum field of view telecentricity is 0.18°, and the working distance is 10 mm. In the optical system of the objective lens in this embodiment:

[0088] The first lens 711 has a focal length f11 of 26.46, a refractive index N11 of 1.50, an Abbe number V11 of 81.6, and a thickness T11 of 3.75.

[0089] The second lens 721 has a focal length f21 of -11.85, a refractive index N21 of 1.49, an Abbe number V21 of 70.4, and a thickness T21 of 1.00.

[0090] The third lens 722 has a focal length f22 of 6.05, a refractive index N22 of 1.67, an Abbe number V22 of 32.2, and a thickness T22 of 2.53.

[0091] The fourth lens 723 has a focal length f23 of -3.15, a refractive index N23 of 1.80, an Abbe number V23 of 46.6, and a thickness T23 of 1.06.

[0092] The fifth lens 724 has a focal length f24 of 14.15, a refractive index N24 of 1.50, an Abbe number V24 of 81.6, and a thickness T24 of 2.06.

[0093] The sixth lens 725 has a focal length f25 of 6.83, a refractive index N25 of 1.76, an Abbe number V25 of 27.5, and a thickness T25 of 2.68.

[0094] The seventh lens 726 has a focal length f26 of -5.18, a refractive index N26 of 1.80, an Abbe number V26 of 39.6, and a thickness T26 of 1.05.

[0095] The eighth lens 727 has a focal length f27 of 12.17, a refractive index N27 of 1.50, an Abbe number V27 of 81.6, and a thickness T27 of 3.49.

[0096] The ninth lens 728 has a focal length f28 of -25.26, a refractive index N28 of 1.81, an Abbe number V28 of 25.5, and a thickness T28 of 1.05.

[0097] The tenth lens 731 has a focal length f31 of 24.84, a refractive index N31 of 1.50, an Abbe number V31 of 81.6, and a thickness T31 of 2.93.

[0098] In this embodiment, other optical parameters of the objective lens are shown in Table 1-1.

[0099] Table 1-1

[0100] radius of curvature Thickness / Gap Refractive index Abbe number focal length surface unlimited 10.00 1.00 First lens First page 16.212 3.75 1.50 81.6 26.46 Second side -65.318 17.22 Second lens First page -9.419 1.00 1.49 70.4 11.85 Second side 15.600 1.84 Third lens First page 29.321 2.53 1.67 32.2 6.05 Second side -4.603 0.00 Fourth lens First page -4.603 1.06 1.80 46.6 -3.15 Second side 6.274 0.00 Fifth lens First page 6.274 2.06 1.50 81.6 14.15 Second side 50.590 0.82 Sixth lens First page 43.069 2.68 1.76 27.5 6.83 Second side -5.753 0.00 Seventh Lens First page -5.753 1.05 1.80 39.6 5.18 Second side 16.700 1.20 Eighth lens First page 69.631 3.49 1.50 81.6 12.17 Second side -6.534 0.00 Ninth Lens First page -6.534 1.05 1.81 25.48 -25.26 Second side -10.277 0.30 Tenth Lens First page -30.110 2.93 1.50 81.6 24.84 Second side -9.057

[0101] As shown in the table above, in the objective lens optical system OB01 of this embodiment, the focal length of the first lens group 81 is 26.46, the focal length of the second lens group 82 is the combined focal length of the second lens 721 to the ninth lens 728, i.e., f2 is -7.46; the focal length of the third lens group 83 is the focal length of the tenth lens 731, i.e., f3 is 24.84.

[0102] Therefore, |f1 / f| is 0.29, |f2 / f| is 0.08, |f3 / f| is 0.28, |f2 / f1| is 0.28, |f1 / f3| is 1.07, |f2 / f3| is 0.30, |f2 / f21| is 0.63, |f2 / f22| is 1.23, |f2 / f23| is 2.37, |f2 / f24| is 0.53, |f2 / f25| is 1.09, |f2 / f26| is 1.44, |f2 / f27| is 0.61, and |f2 / f28| is 0.30.

[0103] Figures 1 to 4 The diagram shows the lens configuration, spherical aberration diagram, field curvature diagram, and distortion diagram of the objective optical system in Example 1. These diagrams represent various aberrations, and when the aberrations are relatively small, a higher quality image can be observed.

[0104] Specifically, Figure 1 This is a diagram of the lens configuration in Example 1. Figure 2 The spherical aberration diagram of the objective lens optical system in Example 1 is shown below. Figure 2 As shown in the figure, the horizontal axis represents spherical aberration in mm, and the vertical axis represents image height in mm. The solid line represents the d-line, the dashed line represents the C-line, the single-dotted line represents the F-line, and the double-dotted line represents the g-line. It can be seen from the figure that the spherical aberration of the objective lens optical system is controlled within ±1.2 mm, which makes the center resolution of the objective lens optical system optimal.

[0105] Figure 3 The field curvature diagram of the objective lens optical system in Example 1 is shown below. Figure 3 As shown, the horizontal axis represents the object plane movement in mm, and the vertical axis represents the image height in mm. The solid line represents the sagitta relative to each wavelength of light, and the dashed line represents the meridion relative to each wavelength. From the distribution of field curvature, it can be seen that the field curvature of this objective optical system is controlled within ±2.0 mm, which makes the center resolution of the objective optical system optimal.

[0106] Figure 4 This is a distortion diagram of the objective lens optical system in Example 1, such as... Figure 4 As shown, the horizontal axis represents the distortion (%), and the vertical axis represents the image height (mm). The distortion distribution shows that the distortion of the objective lens optical system is controlled within ±2%, resulting in the optimal center resolution of the objective lens optical system.

[0107] Example 2

[0108] like Figure 5 As shown, the objective lens optical system OB02 includes an object side 700, a first lens group 81, a second lens group 82, and a third lens group 83. The object-side numerical aperture (NAO) is 0.03, the object height diameter is 13.5 mm, the focal distance f of the objective lens optical system OB02 is 89.7 mm, the magnification is 2X, the maximum field of view telecentricity is 0°, and the working distance is 10 mm. In the optical system of the objective lens in this embodiment:

[0109] The first lens 711 has a focal length f11 of 22.12, a refractive index N11 of 1.68, an Abbe number V11 of 53.0, and a thickness T11 of 3.45.

[0110] The second lens 721 has a focal length f21 of -11.50, a refractive index N21 of 1.49, an Abbe number V21 of 70.4, and a thickness T21 of 1.00.

[0111] The third lens 722 has a focal length f22 of 10.15, a refractive index N22 of 1.59, an Abbe number V22 of 35.3, and a thickness T22 of 2.15.

[0112] The fourth lens 723 has a focal length f23 of -3.31, a refractive index N23 of 1.85, an Abbe number V23 of 32.7, and a thickness T23 of 1.00.

[0113] The fifth lens 724 has a focal length f24 of 7.45, a refractive index N24 of 1.72, an Abbe number V24 of 24.9, and a thickness T24 of 2.38.

[0114] The sixth lens 725 has a focal length f25 of 6.95, a refractive index N25 of 1.72, an Abbe number V25 of 24.7, and a thickness T25 of 2.76.

[0115] The seventh lens 726 has a focal length f26 of -5.08, a refractive index N26 of 1.86, an Abbe number V26 of 30.4, and a thickness T26 of 1.00.

[0116] The eighth lens 727 has a focal length f27 of 12.35, a refractive index N27 of 1.50, an Abbe number V27 of 81.6, and a thickness T27 of 3.48.

[0117] The ninth lens 728 has a focal length f28 of -22.91, a refractive index N28 of 1.83, an Abbe number V28 of 37.9, and a thickness T28 of 1.00.

[0118] The tenth lens 731 has a focal length f31 of 25.59, a refractive index N31 of 1.50, an Abbe number V31 of 81.6, and a thickness T31 of 3.02.

[0119] In this embodiment, other optical parameters of the objective lens are shown in Table 2-1.

[0120] Table 2-1

[0121] radius of curvature Thickness / Gap Refractive index Abbe number focal length surface unlimited 10.00 1.00 First lens First page 15.813 3.45 1.68 53.0 22.12 Second side -314.172 13.25 Second lens First page -9.489 1.00 1.49 70.4 -11.50 Second side 14.301 5.07 Third lens First page -65.866 2.15 1.59 35.3 10.15 Second side -5.598 0.00 Fourth lens First page -5.598 1.00 1.85 32.7 3.31 Second side 6.168 0.00 Fifth lens First page 6.168 2.38 1.72 24.9 7.45 Second side -36.605 0.30 Sixth lens First page 36.649 2.76 1.72 24.7 6.95 Second side -5.699 0.00 Seventh Lens First page -5.699 1.00 1.86 30.4 -5.08 Second side 20.912 1. 35 Eighth lens First page -1056.596 3.48 1.50 81.6 12.35 Second side -6.128 0.00 Ninth Lens First page -6.128 1.00 1.83 37.94 -22.91 Second side -9.699 0.30 Tenth Lens First page -31.813 3.02 1.50 81.6 25.59 Second side -9.392

[0122] As shown in the table above, in the objective lens optical system OB02 of this embodiment, the focal length of the first lens group 81 is 22.12, the focal length of the second lens group 82 is the combined focal length of the second lens 721 to the ninth lens 728, i.e., f2 is -6.45; the focal length of the third lens group 83 is the focal length of the tenth lens 731, i.e., f3 is 25.59.

[0123] Therefore, |f1 / f| is 0.20, |f2 / f| is 0.06, |f3 / f| is 0.29, |f2 / f1| is 0.29, |f1 / f3| is 0.69, |f2 / f3| is 0.20, |f2 / f21| is 0.47, |f2 / f22| is 0.52, |f2 / f23| is 1.74, |f2 / f24| is 0.81, |f2 / f25| is 0.71, |f2 / f26| is 1.06, |f2 / f27| is 0.42, and |f2 / f28| is 0.21.

[0124] Figures 5 to 8 The diagram shows the lens configuration, spherical aberration diagram, field curvature diagram, and distortion diagram of the objective optical system in Example 2. These diagrams represent various aberrations, and when the aberrations are relatively small, a higher quality image can be observed.

[0125] Specifically, Figure 5 This is a diagram showing the lens configuration in Example 2. Figure 6 The spherical aberration diagram of the objective lens optical system in Example 2 is shown below. Figure 6 As shown, the horizontal axis represents spherical aberration in mm, and the vertical axis represents image height in mm. Solid lines represent the d-line, dashed lines represent the C-line, single-dotted lines represent the F-line, and double-dotted lines represent... g As can be seen from the figure, the spherical aberration of the objective lens optical system is controlled within ±1.2mm, resulting in the optimal center resolution of the objective lens optical system.

[0126] Figure 7 The field curvature diagram of the objective lens optical system in Example 2 is shown below. Figure 7 As shown, the horizontal axis represents the object plane movement in mm, and the vertical axis represents the image height in mm. The solid line represents the sagitta relative to each wavelength of light, and the dashed line represents the meridion relative to each wavelength. From the distribution of field curvature, it can be seen that the field curvature of this objective optical system is controlled within ±2.0 mm, which makes the center resolution of the objective optical system optimal.

[0127] Figure 8 This is a distortion diagram of the objective lens optical system in Example 2, such as... Figure 8 As shown, the horizontal axis represents the distortion (%), and the vertical axis represents the image height (mm). The distortion distribution shows that the distortion of the objective lens optical system is controlled within ±2%, resulting in the optimal center resolution of the objective lens optical system.

[0128] Example 3

[0129] like Figure 9 As shown, the objective lens optical system OB03 includes an object side 700, a first lens group 81, a second lens group 82, and a third lens group 83. The object-side numerical aperture (NAO) is 0.03, the object height diameter is 13.5 mm, the focal distance f of the objective lens optical system OB03 is 89.7 mm, the magnification is 2X, the maximum field of view telecentricity is 0°, and the working distance is 10 mm. In the optical system of the objective lens in this embodiment:

[0130] The first lens 711 has a focal length f11 of 26.46, a refractive index N11 of 1.50, an Abbe number V11 of 81.6, and a thickness T11 of 3.75.

[0131] The second lens 721 has a focal length f21 of -11.85, a refractive index N21 of 1.49, an Abbe number V21 of 70.4, and a thickness T21 of 1.00.

[0132] The third lens 722 has a focal length f22 of 6.05, a refractive index N22 of 1.67, an Abbe number V22 of 32.2, and a thickness T22 of 2.53.

[0133] The fourth lens 723 has a focal length f23 of -3.15, a refractive index N23 of 1.80, an Abbe number V23 of 46.6, and a thickness T23 of 1.06.

[0134] The fifth lens 724 has a focal length f24 of 14.15, a refractive index N24 of 1.50, an Abbe number V24 of 81.6, and a thickness T24 of 2.06.

[0135] The sixth lens 725 has a focal length f25 of 6.83, a refractive index N25 of 1.76, an Abbe number V25 of 27.5, and a thickness T25 of 2.68.

[0136] The seventh lens 726 has a focal length f26 of -5.18, a refractive index N26 of 1.80, an Abbe number V26 of 39.6, and a thickness T26 of 1.05.

[0137] The eighth lens 727 has a focal length f27 of 12.17, a refractive index N27 of 1.50, an Abbe number V27 of 81.6, and a thickness T27 of 3.49.

[0138] The ninth lens 728 has a focal length f28 of -25.26, a refractive index N28 of 1.81, an Abbe number V28 of 25.5, and a thickness T28 of 1.05.

[0139] The tenth lens 731 has a focal length f31 of 24.84, a refractive index N31 of 1.50, an Abbe number V31 of 81.6, and a thickness T31 of 2.93.

[0140] In this embodiment, other optical parameters of the objective lens are shown in Table 3-1.

[0141] Table 3-1

[0142] radius of curvature Thickness / Gap Refractive index Abbe number focal length surface unlimited 10.00 1.00 First lens First page 16.212 3.75 1.50 81.6 26.46 Second side -65.318 17.22 Second lens First page -9.419 1.00 1.49 70.4 -11.85 Second side 15.600 1.84 Third lens First page 29.321 2.53 1.67 32.2 6.05 Second side -4.603 0.00 Fourth lens First page -4.603 1.06 1.80 46.6 -3.15 Second side 6.274 0.00 Fifth lens First page 6.274 2.06 1.50 81.6 14.15 Second side 50.590 0.82 Sixth lens First page 43.069 2.68 1.76 27.5 6.83 Second side -5.753 0.00 Seventh Lens First page -5.753 1.05 1.80 39.6 -5.18 Second side 16.700 1.20 Eighth lens First page 69.631 3.49 1.50 81.6 12.17 Second side -6.534 0.00 Ninth Lens First page -6.534 1.05 1.81 25.48 -25.26 Second side -10.277 0.30 Tenth Lens First page -30.110 2.93 1.50 81.6 24.84 Second side -9.057

[0143] As shown in the table above, in the objective lens optical system OB03 of this embodiment, the focal length of the first lens group 81 is 26.46, the focal length of the second lens group 82 is the combined focal length of the second lens 721 to the ninth lens 728, i.e., f2 is -7.46; the focal length of the third lens group 83 is the focal length of the tenth lens 731, i.e., f3 is 24.84.

[0144] The values ​​of |f1 / f| are 0.29, |f2 / f| are 0.08, |f3 / f| are 0.28, |f2 / f1| are 0.28, |f1 / f3| are 1.07, |f2 / f3| are 0.30, |f2 / f21| are 0.63, |f2 / f22| are 1.23, |f2 / f23| are 2.37, |f2 / f24| are 0.53, |f2 / f25| are 1.09, |f2 / f26| are 1.44, |f2 / f27| are 0.61, and |f2 / f28| are 0.30.

[0145] Figures 9 to 12 The diagram shows the lens configuration, spherical aberration diagram, field curvature diagram, and distortion diagram of the three-mirror optical system in this embodiment. It presents various aberrations, and when the aberrations are relatively small, a better quality image can be observed.

[0146] Specifically, Figure 9 This is a diagram of the lens configuration in Example 3. Figure 10 The spherical aberration diagram of the objective lens optical system in Example 3 is shown below. Figure 10 As shown in the figure, the horizontal axis represents spherical aberration in mm, and the vertical axis represents image height in mm. The solid line represents the d-line, the dashed line represents the C-line, the single-dotted line represents the F-line, and the double-dotted line represents the g-line. It can be seen from the figure that the spherical aberration of the objective lens optical system is controlled within ±1.2 mm, which makes the center resolution of the objective lens optical system optimal.

[0147] Figure 11 The field curvature diagram of the objective lens optical system in Example 3 is shown below. Figure 11As shown, the horizontal axis represents the object plane movement in mm, and the vertical axis represents the image height in mm. The solid line represents the sagitta relative to each wavelength of light, and the dashed line represents the meridion relative to each wavelength. From the distribution of field curvature, it can be seen that the field curvature of this objective optical system is controlled within ±2.0 mm, which makes the center resolution of the objective optical system optimal.

[0148] Figure 12 This is a distortion diagram of the objective lens optical system in Example 3, such as... Figure 12 As shown, the horizontal axis represents the distortion (%), and the vertical axis represents the image height (mm). The distortion distribution shows that the distortion of the objective lens optical system is controlled within ±2%, resulting in the optimal center resolution of the objective lens optical system.

[0149] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low-magnification, long-working-distance telecentric objective lens, characterized in that, It consists of a first lens group, a second lens group, and a third lens group arranged sequentially along an optical axis. The first lens group has positive refractive power and includes a first lens, which has positive refractive power. The second lens group has negative refractive power. The second lens group includes a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially from the object side to the image side. The second lens has negative refractive power, the third lens has positive refractive power, the fourth lens has negative refractive power, the fifth lens has positive refractive power, the sixth lens has positive refractive power, the seventh lens has negative refractive power, the eighth lens has positive refractive power, and the ninth lens has negative refractive power. The third lens group has positive refractive power and includes a tenth lens, which has positive refractive power. It satisfies the following condition: 0.0<|f1 / f|<3.3; 0.0<|f2 / f|<3.1; 0.0<|f3 / f|<3.3; 0.0<|f2 / f1|<3.3; 0.0<|f1 / f3|<6.1; 0.0<|f2 / f3|<3.3; Where f is the focal distance of the objective lens, f1 is the focal distance of the first lens group, f2 is the focal distance of the second lens group, and f3 is the focal distance of the third lens group.

2. The low magnification, long working distance telecentric objective lens as described in claim 1, characterized in that, The first lens group is located near the object side.

3. The low magnification, long working distance telecentric objective lens as described in claim 2, characterized in that, The second lens group has one or more cemented lenses.

4. A low magnification, long working distance telecentric objective lens as described in claim 3, characterized in that, The second lens group has three cemented lenses.

5. A low magnification, long working distance telecentric objective lens as described in claim 3, characterized in that, The second lens group satisfies the following condition: 0.0<|f2 / f21|<3.6; 0.0<|f2 / f22|<6.3; 0.0<|f2 / f23|<7.4; 0.0<|f2 / f24|<6.7; 0.0<|f2 / f25|<6.1; 0.0<|f2 / f26|<6.5; 0.0<|f2 / f27|<4.6; 0.0<|f2 / f28|<3.3; Where f2 is the focal distance of the second lens group, f21 is the focal distance of the second lens, f22 is the focal distance of the third lens, f23 is the focal distance of the fourth lens, f24 is the focal distance of the fifth lens, f25 is the focal distance of the sixth lens, f26 is the focal distance of the seventh lens, f27 is the focal distance of the eighth lens, and f28 is the focal distance of the ninth lens.

6. A low magnification, long working distance telecentric objective lens as described in claim 3, characterized in that, The third lens group is located near the image side.

7. A low magnification, long working distance telecentric objective lens as described in claim 6, characterized in that, Each of the first to tenth lenses includes an object-side surface facing the object side and through which imaging light passes, and an image-side surface facing the image side and through which imaging light passes. The object-side surface and image-side surface of the first lens are convex, the image-side surface and image-side surface of the second lens are concave, the object-side surface and image-side surface of the third lens are convex, the object-side surface and image-side surface of the fourth lens are concave, the object-side surface and image-side surface of the fifth lens are convex and the image-side surface of the fifth lens are concave, the object-side surface and image-side surface of the sixth lens are convex, the object-side surface and image-side surface of the seventh lens are concave, the image-side surface of the eighth lens are convex, the object-side surface and image-side surface of the ninth lens are concave and the image-side surface of the tenth lens are concave and the image-side surface of the tenth lens are concave.

8. A low magnification, long working distance telecentric objective lens as described in claim 6, characterized in that, The first through tenth lenses satisfy the following condition: 1.68≥N11≥1.40; 1.49≥N21≥1.45; 1.67≤N22≤1.80; 1.85≥N23≥1.45; 1.72≥N24≥1.40; 1.76≥N25≥1.50; 1.8≤N26≤1.90; 1.5≥N27≥1.45; 1.81≤N28≤2.01; 1.5≥N31≥1.40; Wherein, N11 is the refractive index of the first lens, N21 is the refractive index of the second lens, N22 is the refractive index of the third lens, N23 is the refractive index of the fourth lens, N24 is the refractive index of the fifth lens, N25 is the refractive index of the sixth lens, N26 is the refractive index of the seventh lens, N27 is the refractive index of the eighth lens, N28 is the refractive index of the ninth lens, and N31 is the refractive index of the tenth lens.

9. A low magnification, long working distance telecentric objective lens as described in claim 6, characterized in that, The first through tenth lenses satisfy the following condition: 81.6 ≥ V11 ≥ 30; 70.4 ≤ V21 ≤ 95; 35.3 ≥ V22 ≥ 20; 32.7 ≤ V23 ≤ 95; 24.9 ≤ V24 ≤ 95; 27.5 ≥ V25 ≥ 20; 30.4 ≤ V26 ≤ 95; 81.6 ≤ V27 ≤ 95; 37.9 ≥ V28 ≥ 15; 81.6 ≤ V31 ≤ 95; Wherein, V11 is the Abbe number of the first lens, V21 is the Abbe number of the second lens, V22 is the Abbe number of the third lens, V23 is the Abbe number of the fourth lens, V24 is the Abbe number of the fifth lens, V25 is the Abbe number of the sixth lens, V26 is the Abbe number of the seventh lens, V27 is the Abbe number of the eighth lens, V28 is the Abbe number of the ninth lens, and V31 is the Abbe number of the tenth lens.

10. A low magnification, long working distance telecentric objective lens as described in claim 6, characterized in that, The first through tenth lenses satisfy the following condition: 1.08<T11 / T31<1.58; 0.30<T21 / T22<0.70; 0.75<T21 / T23<1.25; 0.28<T21 / T24<0.78; 0.17<T21 / T25<0.67; 0.75<T21 / T26<1.25; 0.09<T21 / T27<0.59; 0.75<T21 / T28<1.25; Wherein, T11 is the thickness of the first lens on the optical axis, T31 is the thickness of the tenth lens on the optical axis, T21 is the thickness of the second lens on the optical axis, T22 is the thickness of the third lens on the optical axis, T23 is the thickness of the fourth lens on the optical axis, T24 is the thickness of the fifth lens on the optical axis, T25 is the thickness of the sixth lens on the optical axis, T26 is the thickness of the seventh lens on the optical axis, T27 is the thickness of the eighth lens on the optical axis, and T28 is the thickness of the ninth lens on the optical axis.

Images