An inverted microscope objective

Abstract

The invention discloses an inverted microscope objective lens, which includes a first lens group and a second lens group; the first lens group includes a first lens with positive refractive power, the second lens group has positive refractive power, and the second lens group includes a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens in sequence, the second lens has positive refractive power, the third lens has negative refractive power, the fourth lens has positive refractive power, the fifth lens has positive refractive power, the sixth lens has negative refractive power, the seventh lens has positive refractive power, the eighth lens has negative refractive power, and the second lens group has at least two groups of cemented lenses. The invention includes a first lens group and a second lens group along the direction from the object side to the image side, and by designing eight lenses accordingly, the inverted objective lens optical system has the characteristics of large magnification, long working distance, large numerical aperture, high resolution performance, small chromatic aberration, large field of view, small number of lenses, and short total length of the optical system.

Description

Technical Field

[0001] The invention relates to the technical field of optical imaging, and in particular to an inverted microscope objective lens. Background Art

[0002] With the rapid development of the biological industry in recent years, there are more and more demands for observing the biology of culture dishes. The observation requirements are met by using the inverted observation method of the microscope. Generally speaking, due to the long working distance required for medical detection, the objective lens is prevented from being too close to the culture dish to affect the temperature of the culture dish, thereby affecting the observation results. At the same time, in order to observe more details on the microscope, a larger magnification and a larger numerical aperture are required. If a three-dimensional effect is required, a phase contrast plate is also required in the objective lens, which means that the rear focus of the lens or lens group needs to converge on the phase plate. For such a phase contrast objective optical system, it is difficult to compensate for axial aberrations, chromatic aberrations of magnification, and field curvature. The aberrations of large field numbers and large magnification objectives are even more difficult to control.

[0003] In the invention patent with publication number CN101271191A and the name of a microscope objective lens, a 10x phase contrast objective lens with a field number of 20 is described. The longitudinal chromatic aberration defined by the focus position deviation between the spectral lines C'-e and F'-e is 1.5 times the focal depth, where C' is 643.847nm, F' is 479.991nm and e is 546.074nm. The focal depth range is defined by λ / NA² (λ is the wavelength, NA is the numerical aperture). The defects are that the field number is not large enough, the longitudinal chromatic aberration is large, and only the C' line 643.847nm to the F' line 479.991nm is considered.

[0004] The patent with the announcement number KR10-1850999 and the name of a microscope objective lens describes a 50x phase contrast objective lens composed of 17 lenses. The defects of the objective lens are that the number of lenses used is large, the cost of the lens material is high, and the total length of the objective lens optical system is too long.

[0005] The patent with publication number CN202110574617.4 and titled "A Microscope Phase Contrast Objective" describes a 4x phase contrast objective consisting of 8 lenses and 2 phase contrast glasses. It has good resolution and chromatic aberration correction, but its defect is that due to the limitations of magnification and numerical aperture, it is impossible to observe smaller substances and details. Summary of the invention

[0006] The object of the present invention is to provide an inverted microscope objective lens, which can ensure that the objective lens has the characteristics of large magnification, long working distance, large numerical aperture, high resolution performance, small chromatic aberration, large field of view, small number of lenses, and short total length of the optical system.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An inverted microscope objective lens comprises a first lens group and a second lens group in sequence along an optical axis from an object side to an image side;

[0009] The first lens group includes a first lens having positive refractive power;

[0010] The second lens group has positive refractive power, and includes a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens in sequence. The second lens has positive refractive power, the third lens has negative refractive power, the fourth lens has positive refractive power, the fifth lens has positive refractive power, the sixth lens has negative refractive power, the seventh lens has positive refractive power, and the eighth lens has negative refractive power. The second lens group includes at least two groups of cemented lenses.

[0011] Preferably, each of the first to eighth lenses includes an object-side surface facing the object side and allowing imaging light to pass therethrough, and an image-side surface facing the image side and allowing imaging light to pass therethrough;

[0012] The object side surface of the first lens is concave, and the image side surface is convex; the image side surface of the second lens is convex; the object side surface of the third lens is concave, and the image side surface is concave; the object side surface of the fourth lens is convex, and the image side surface is convex; the object side surface of the fifth lens is convex, and the image side surface is convex; the object side surface of the sixth lens is concave, and the image side surface is a plane or a concave surface; the object side surface of the seventh lens is convex, and the image side surface is convex; the object side surface of the eighth lens is concave, and the image side surface is concave.

[0013] Preferably, the second lens, the third lens and the fourth lens form a cemented lens, the fifth lens and the sixth lens form a cemented lens, and the seventh lens and the eighth lens form a cemented lens.

[0014] Preferably, the inverted microscope objective satisfies the following condition: 0.5<|f×D0 / NA|<5.0, wherein f is the focal length of the inverted objective optical system, NA is the object-side numerical aperture of the inverted objective optical system, and D0 is the distance on the optical axis from the slide to the lens surface of the inverted objective optical system closest to the object.

[0015] Preferably, the inverted microscope objective lens satisfies the following conditional formula:

[0016] 0.16<|f / f1|<1.6, 0.17<|f / f2|<1.6, 0.19<|f2 / f1|<2.7,

[0017] Wherein, f is the focal length of the inverted objective optical system, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

[0018] Preferably, the inverted microscope objective lens satisfies the following conditional formula:

[0019] -0.26<f21 / f2<1.95, -1.60<f22 / f2<0.61, -0.43<f23 / f2<1.87,

[0020] -0.06<f24 / f2<2.32, -2.12<f25 / f2<0.26, -0.42<f28 / f2<1.89,

[0021] -1.49<f29 / f2<0.67,

[0022] Among them, f2 is the focal length of the second lens group, f21 is the focal length of the second lens, f22 is the focal length of the third lens, f23 is the focal length of the fourth lens, f24 is the focal length of the fifth lens, f25 is the focal length of the sixth lens, f28 is the focal length of the seventh lens, and f29 is the focal length of the eighth lens.

[0023] Preferably, the inverted microscope objective lens satisfies the following conditional formula:

[0024] N11≥1.80, N21≤1.90, N22≥1.50, N23≤1.85,

[0025] N24≤1.70, N25≥1.80, N28≥1.85, N29≥1.70,

[0026] Among them, 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, N28 is the refractive index of the seventh lens, and N29 is the refractive index of the eighth lens.

[0027] Preferably, the inverted microscope objective lens satisfies the following conditional formula:

[0028] V11≤30, V21≥35, V22≤50, V23≥30,

[0029] V24≥50, V25≤30, V28≤30, V29≤50,

[0030] Among them, 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, V28 is the Abbe number of the seventh lens, and V29 is the Abbe number of the eighth lens.

[0031] Preferably, the inverted microscope objective lens satisfies the following conditional formula:

[0032] 0.08<T1 / T2<0.21, 0.37<T11 / T1<0.95, 0.05<T21 / T2<0.66,

[0033] 0.01<T22 / T2<0.58, 0.03<T23 / T2<0.61, 0.03<T24 / T2<0.60,

[0034] 0.01<T25 / T2<0.54, 0.05<T28 / T2<0.66, 0.04<T29 / T2<0.65,

[0035] Among them, T1 is the length of the first lens group on the optical axis, T2 is the length of the second lens group on the optical axis, T11 is the thickness of the first 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, T28 is the thickness of the seventh lens on the optical axis, and T29 is the thickness of the eighth lens on the optical axis.

[0036] Preferably, the second lens group further includes a phase plate lens 1 and a phase plate lens 2, and the phase plate lens 1 and the phase plate lens 2 are arranged between the fourth lens and the seventh lens.

[0037] After adopting the above technical solution, the present invention has the following advantages compared with the background technology:

[0038] 1. The present invention includes a first lens group with positive refractive power and a second lens group with positive refractive power along the direction from the object side to the image side, and by correspondingly designing eight lenses, the inverted objective optical system has the characteristics of large magnification, long working distance, large numerical aperture, high resolution performance, small chromatic aberration, large field of view, small number of lenses, and short total length of the optical system.

[0039] 2. The present invention limits the focal length, refractive index, Abbe number and thickness of the first lens group and the second lens group, so that the field curvature, distortion and aberration sensitivity of the inverted objective optical system are further improved, thereby ensuring that the inverted optical microscope system has better optical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A lens composition diagram of an inverted objective optical system according to a first embodiment of the present invention;

[0041] Figure 2 is a spherical aberration diagram of the inverted objective optical system of the first embodiment of the present invention;

[0042] Figure 3 A field curvature diagram of an inverted objective optical system according to Embodiment 1 of the present invention;

[0043] Figure 4 is a distortion diagram of the inverted objective optical system of the first embodiment of the present invention;

[0044] Figure 5 is an MTF diagram of the inverted objective optical system of the first embodiment of the present invention;

[0045] Figure 6 is a lens composition diagram of an inverted objective optical system according to a second embodiment of the present invention;

[0046] Figure 7 is a spherical aberration diagram of the inverted objective optical system of the second embodiment of the present invention;

[0047] Figure 8 A field curvature diagram of an inverted objective optical system according to a second embodiment of the present invention;

[0048] Fig. 9 is a distortion diagram of the inverted objective optical system of the second embodiment of the present invention;

[0049] Fig.10 is an MTF diagram of the inverted objective optical system of the second embodiment of the present invention;

[0050] Fig.11 A lens composition diagram of an inverted objective optical system according to a third embodiment of the present invention;

[0051] Fig.12 is a spherical aberration diagram of the inverted objective optical system of the third embodiment of the present invention;

[0052] Fig.13 A field curvature diagram of an inverted objective optical system according to Embodiment 3 of the present invention;

[0053] Fig.14 is a distortion diagram of the inverted objective optical system of the third embodiment of the present invention;

[0054] Fig.15 is an MTF diagram of the inverted objective optical system of the third embodiment of the present invention;

[0055] Fig.16 is a lens composition diagram of an inverted objective optical system according to a fourth embodiment of the present invention;

[0056] Fig.17 is a spherical aberration diagram of the inverted objective optical system of the fourth embodiment of the present invention;

[0057] Fig.18 A field curvature diagram of an inverted objective optical system according to a fourth embodiment of the present invention;

[0058] Fig.19 is a distortion diagram of the inverted objective optical system of the fourth embodiment of the present invention;

[0059] Fig. 20 This is the MTF diagram of the inverted objective optical system of the fourth embodiment of the present invention.

[0060] Description of reference numerals:

[0061] A first lens 110;

[0062] A second lens 210, a third lens 220, a fourth lens 230, a fifth lens 240, a sixth lens 250, a seventh lens 280, an eighth lens 290, a phase plate lens 1 260, and a phase plate lens 2 270;

[0063] Object plane 300, slide glass 310;

[0064] A first lens holder 410, a second lens holder 420, a third lens holder 430, a phase plate glass cemented lens holder 440, and a fourth lens holder 450;

[0065] Main barrel 500;

[0066] Object side A1, image side A2. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0068] In this specification, "the lens has positive refractive power (or negative refractive power)" means that the paraxial refractive power of the lens calculated by Gaussian optical theory is positive (or negative). The "object side (or image side) of the lens" is defined as the specific range of the lens surface through which the imaging light passes. The concave and convex shape of the lens can be judged according to the judgment method of ordinary knowledge in this field, that is, the concave and convex shape of the lens surface can be judged by the positive and negative signs of the radius of curvature (abbreviated as R value). R value can be commonly used in optical design software, such as Ze max or Code V. R value is also commonly found in the lens datasheet of optical design software. For the object side, when the R value is positive, the object side is judged to be convex; when the R value is negative, the object side is judged to be concave. Conversely, for the image side, when the R value is positive, the image side is judged to be concave; when the R value is negative, the image side is judged to be convex.

[0069] Cooperate Figure 1 , Figure 6 , Fig.11 and Fig.16As shown, the present invention discloses an inverted microscope objective lens, which comprises a first lens group and a second lens group in sequence from the object side to the image side along an optical axis.

[0070] The first lens group includes a first lens 110, and the first lens 110 has a positive refractive power. The second lens group has a positive refractive power, and sequentially includes a second lens 210, a third lens 220, a fourth lens 230, a fifth lens 240, a sixth lens 250, a seventh lens 280, and an eighth lens 290. The second lens 210 has a positive refractive power, the third lens 220 has a negative refractive power, the fourth lens 230 has a positive refractive power, the fifth lens 240 has a positive refractive power, the sixth lens 250 has a negative refractive power, the seventh lens 280 has a positive refractive power, and the eighth lens 290 has a negative refractive power. The second lens group includes at least two groups of cemented lenses.

[0071] The first lens 110 to the eighth lens 290 each include an object-side surface facing the object side A1 and allowing imaging light to pass through, and an image-side surface facing the image side A2 and allowing imaging light to pass through; the object-side surface of the first lens 110 is a concave surface, and the image-side surface is a convex surface; the image-side surface of the second lens 210 is a convex surface (the object-side surface of the second lens 210 can be a concave surface, a convex surface, or a surface close to a plane); the object-side surface of the third lens 220 is a concave surface, and the image-side surface is a concave surface; the object-side surface of the fourth lens 230 is a convex surface, and the image-side surface is a convex surface; the object-side surface of the fifth lens 240 is a convex surface, and the image-side surface is a convex surface; the object-side surface of the sixth lens 250 is a concave surface, and the image-side surface is a plane or a concave surface; the object-side surface of the seventh lens 280 is a convex surface, and the image-side surface is a convex surface; the object-side surface of the eighth lens 290 is a concave surface, and the image-side surface is a concave surface.

[0072] The second lens 210, the third lens 220 and the fourth lens 230 form a cemented lens, the fifth lens 240 and the sixth lens 250 form a cemented lens, and the seventh lens 280 and the eighth lens 290 form a cemented lens. Through these cemented lenses, the total length of the objective optical system can be greatly shortened.

[0073] The inverted microscope objective meets the following condition: 0.5<|f×D0 / NA|<5.0, wherein f is the focal length of the inverted objective optical system, NA is the object-side numerical aperture of the inverted objective optical system, and D0 is the distance on the optical axis from the slide to the lens surface of the inverted objective optical system closest to the object.

[0074] The inverted microscope objective lens satisfies the following conditional formula:

[0075] 0.16<|f / f1|<1.6, 0.17<|f / f2|<1.6, 0.19<|f2 / f1|<2.7,

[0076] Wherein, f is the focal length of the inverted objective optical system, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

[0077] The inverted microscope objective lens satisfies the following conditional formula:

[0078] -0.26<f21 / f2<1.95, -1.60<f22 / f2<0.61, -0.43<f23 / f2<1.87,

[0079] -0.06<f24 / f2<2.32, -2.12<f25 / f2<0.26, -0.42<f28 / f2<1.89,

[0080] -1.49<f29 / f2<0.67,

[0081] Among them, f2 is the focal length of the second lens group, f21 is the focal length of the second lens 210, f22 is the focal length of the third lens 220, f23 is the focal length of the fourth lens 230, f24 is the focal length of the fifth lens 240, f25 is the focal length of the sixth lens 250, f28 is the focal length of the seventh lens 280, and f29 is the focal length of the eighth lens 290.

[0082] The inverted microscope objective lens satisfies the following conditional formula:

[0083] N11≥1.80, N21≤1.90, N22≥1.50, N23≤1.85,

[0084] N24≤1.70, N25≥1.80, N28≥1.85, N29≥1.70,

[0085] Among them, N11 is the refractive index of the first lens 110, N21 is the refractive index of the second lens 210, N22 is the refractive index of the third lens 220, N23 is the refractive index of the fourth lens 230, N24 is the refractive index of the fifth lens 240, N25 is the refractive index of the sixth lens 250, N28 is the refractive index of the seventh lens 280, and N29 is the refractive index of the eighth lens 290.

[0086] The inverted microscope objective lens satisfies the following conditional formula:

[0087] V11≤30, V21≥35, V22≤50, V23≥30,

[0088] V24≥50, V25≤30, V28≤30, V29≤50,

[0089] Among them, V11 is the Abbe number of the first lens 110, V21 is the Abbe number of the second lens 210, V22 is the Abbe number of the third lens 220, V23 is the Abbe number of the fourth lens 230, V24 is the Abbe number of the fifth lens 240, V25 is the Abbe number of the sixth lens 250, V28 is the Abbe number of the seventh lens 280, and V29 is the Abbe number of the eighth lens 290.

[0090] The inverted microscope objective lens satisfies the following conditional formula:

[0091] 0.08<T1 / T2<0.21, 0.37<T11 / T1<0.95, 0.05<T21 / T2<0.66,

[0092] 0.01<T22 / T2<0.58, 0.03<T23 / T2<0.61, 0.03<T24 / T2<0.60,

[0093] 0.01<T25 / T2<0.54, 0.05<T28 / T2<0.66, 0.04<T29 / T2<0.65,

[0094] Wherein, T1 is the length of the first lens group on the optical axis, T2 is the length of the second lens group on the optical axis, T11 is the thickness of the first lens 110 on the optical axis, T21 is the thickness of the second lens 210 on the optical axis, T22 is the thickness of the third lens 220 on the optical axis, T23 is the thickness of the fourth lens 230 on the optical axis, T24 is the thickness of the fifth lens 240 on the optical axis, T25 is the thickness of the sixth lens 250 on the optical axis, T28 is the thickness of the seventh lens on the optical axis, and T29 is the thickness of the eighth lens on the optical axis.

[0095] In the present invention, a phase plate lens 1 260 and a phase plate lens 2 270 may be provided in the second lens group as required, or may not be provided. The phase plate lens 1 260 and the phase plate lens 2 270 are provided between the fourth lens 230 and the seventh lens 280 .

[0096] In order to further elaborate the technical content of the invention, four embodiments are listed below to describe the objective optical system in detail.

[0097] Embodiment 1

[0098] like Figure 1 As shown, the inverted microscope objective lens includes an object plane 300, a glass slide 310, a first lens group and a second lens group in sequence from the object side to the image side along an optical axis.

[0099] The first lens group includes a first lens 110 with positive refractive power, and the second lens group has positive refractive power, which sequentially includes a second lens 210 with positive refractive power, a third lens 220 with negative refractive power, a fourth lens 230 with positive refractive power, a fifth lens 240 with positive refractive power, a sixth lens 250 with negative refractive power, a phase plate lens 1 260, a phase plate lens 2 270, a seventh lens 280 with positive refractive power and an eighth lens 290 with negative refractive power.

[0100] Among them, the object side surface of the first lens 210 is a receiving surface, which is placed in the first lens seat 410; the image side surface of the second lens 210 is glued to the object side surface of the third lens 220, and the image side surface of the third lens 220 is glued to the object side surface of the fourth lens 230. After the second lens 210, the third lens 220 and the fourth lens 230 are glued, the image side surface of the fourth lens 230 is used as a receiving surface and placed in the second lens seat 420. Through the cooperation of the first lens seat 410 and the second lens seat 420, the interval between the first lens 110 and the second lens 210 on the optical axis is guaranteed; the image side surface of the fifth lens 240 is glued to the object side surface of the sixth lens 250. After the fifth lens 240 and the sixth lens 250 are glued, the object side surface of the fifth lens 240 is used as a receiving surface and placed in the third lens seat 430. Through the cooperation of the second lens seat 420 and the third lens seat 430, the interval between the first lens 110 and the second lens 210 on the optical axis is guaranteed. The interval between the fourth lens 230 and the fifth lens 240 on the optical axis is ensured; the image side surface of the phase plate lens 1 260 is glued to the object side surface of the phase plate lens 2 270. After the phase plate lens 1 260 and the phase plate lens 2 270 are glued, the image side surface of the phase plate lens 2 270 is used as a receiving surface to be placed in the phase plate glass glued lens holder 440. Through the cooperation of the third lens holder 430 and the phase plate glass glued lens holder 440, the interval between the sixth lens 250 and the first phase plate glass 280 on the optical axis is ensured; the image side surface of the seventh lens 280 is glued to the object side surface of the eighth lens 290. After the seventh lens 280 and the eighth lens 290 are glued, the image side surface of the seventh lens 280 is used as a receiving surface to be placed in the fourth lens holder 450. Through the cooperation of the phase plate glass glued lens holder 440 and the fourth lens holder 450, the interval between the second phase plate glass 290 and the seventh lens 280 on the optical axis is ensured.

[0101] In the inverted objective optical system of this embodiment, the field number is 25mm, the magnification β is 40x, the longitudinal chromatic aberration defined by the focus position deviation between Ce is 1.03 times the focal depth, and the longitudinal chromatic aberration defined by the focus position deviation between ge is 0.74 times the focal depth, where C is 656.27nm, g is 435.84nm, and e is 546.07nm. The focal depth is λ / NA², where λ is the wavelength and NA is the numerical aperture.

[0102] The first lens 110 has a focal length f11 of 10.38, a refractive index N11 of 1.95, an Abbe number V11 of 21.0, and a thickness T11 of 4.53.

[0103] The second lens 210 has a focal length f21 of 11.68, a refractive index N21 of 1.50, an Abbe number V21 of 81.6, and a thickness T21 of 3.79.

[0104] The third lens 220 has a focal length f22 of -6.11, a refractive index N22 of 1.67, an Abbe number V22 of 32.2, and a thickness T22 of 1.00.

[0105] The fourth lens 230 has a focal length f23 of 9.05, a refractive index N23 of 1.80, an Abbe number V23 of 46.5, and a thickness T23 of 4.09.

[0106] The fifth lens 240 has a focal length f24 of 14.98, a refractive index N24 of 1.50, an Abbe number V24 of 81.6, and a thickness T24 of 3.79.

[0107] The sixth lens 250 has a focal length f25 of -11.75, a refractive index N25 of 1.92, an Abbe number V25 of 18.9, and a thickness T25 of 1.42.

[0108] The focal length f26 of the phase plate lens 260 is infinite, the refractive index N26 is 1.52, the Abbe number V26 is 64.2, and the thickness T26 is 0.70.

[0109] The focal length f27 of the second phase plate lens 270 is infinite, the refractive index N27 is 1.52, the Abbe number V27 is 64.2, and the thickness T27 is 0.70.

[0110] The seventh lens 280 has a focal length f28 of 9.18, a refractive index N28 of 1.95, an Abbe number V28 of 17.9, and a thickness T28 of 5.00.

[0111] The eighth lens 290 has a focal length f29 of -5.27, a refractive index N29 of 1.84, an Abbe number V29 of 25.2, and a thickness T29 of 5.00.

[0112] Other optical parameters of the new objective optical system are shown in Table 1-1.

[0113] Table 1-1

[0114]

[0115] From the above, it can be known that in the inverted objective optical system of this embodiment, f is the focal length of the inverted objective optical system, that is, f is 4.53; NA is the object side numerical aperture of the objective optical system, that is, NA is 0.55; D0 is the distance from the slide to the optical axis of the lens surface of the inverted objective optical system closest to the object, that is, D0 is 2.72, then |f×D0 / NA| is 3.03. This ensures that it has the characteristics of large magnification, large numerical aperture, high resolution performance, and large field of view.

[0116] The focal length of the first lens group is the focal length of the first lens 110, that is, f1 is equal to f11, which is 10.38. The focal length of the second lens group is the combined focal length of the second lens 210 to the eighth lens 290, that is, f2 is 10.85. The focal length f of the entire optical system is 4.53, then |f / f1| is 0.44, |f / f2| is 0.29, |f2 / f1| is 1.53, f21 / f2 is 0.74, f22 / f2 is -0.39, f23 / f2 is 0.57, f24 / f2 is 0.95, f25 / f2 is -0.74, f28 / f2 is 0.58, and f29 / f2 is -0.33. The objective optical system within the focal length numerical range has a large positive refractive power, so that the inverted objective has a large numerical aperture, and at the same time, it also makes it possible to better control distortion and field curvature.

[0117] In Embodiment 1, the thickness of the first lens group 1, i.e., T1, is 5.03 mm, the thickness T2 of the second lens group 2 is 36.81 mm, T1 / T2 is 0.14, T11 / T1 is 0.90, T21 / T2 is 0.10, T22 / T2 is 0.03, T23 / T2 is 0.11, T24 / T2 is 0.10, T25 / T2 is 0.04, T28 / T2 is 0.14, and T29 / T2 is 0.14.

[0118] Figures 2 to 5 The various aberration diagrams and MTF performance diagrams of the inverted objective optical system of Example 1 are shown. The various aberrations presented therein represent the resolution capability. When the aberrations are relatively small, images of better quality can be observed. Specifically:

[0119] Figure 2 is a spherical aberration diagram of the inverted objective optical system of the first embodiment of the present invention, Figure 2 In the figure, the horizontal axis is the spherical aberration, in mm, the vertical axis is the image height, in mm, the solid line represents the d line, the dotted line represents the C line, the single-point dash line represents the F line, and the double-point dash line represents the g line. Figure 2 As shown, the spherical aberration of the inverted objective optical system is controlled within ±0.005 mm, so that the center resolution of the inverted objective optical system is optimal.

[0120] Figure 3is a field curvature diagram of the inverted objective optical system according to the first embodiment of the present invention, Figure 3 In the figure, the horizontal axis is the object plane movement, in mm, the vertical axis is the image height, in mm, the solid line represents the sagittal relative to each wavelength of light, and the dotted line represents the meridian relative to each wavelength. From the distribution of field curvature, it can be seen that the field curvature of the inverted objective optical system is controlled within ±0.005mm, so that the central resolution of the inverted objective optical system is optimal.

[0121] Figure 4 is a distortion diagram of the inverted objective optical system of the first embodiment of the present invention, Figure 4 In the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image height, in mm. From the distribution of distortion, it can be seen that the distortion of the inverted objective optical system is controlled within ±2%, so that the central resolution of the inverted objective optical system is optimal.

[0122] Figure 5 is a diagram of the MTF (modulation transfer function) of the inverted objective optical system of the first embodiment of the present invention, Figure 5 In the figure, the horizontal axis is the spatial frequency in cycles / mm, and the vertical axis is the modulation, i.e., MTF. Figure 5 As shown, the solid line represents the modulation (MTF) of the central image plane of the inverted objective optical system, and the dotted line represents the diffraction limit.

[0123] Embodiment 2

[0124] like Figure 6 As shown, the structure of the inverted objective optical system in this embodiment is similar to that in the first embodiment, and also includes a first lens group and a second lens group, wherein the first lens group includes a first lens 110, and the second lens group includes a second lens 210, a third lens 220, a fourth lens 230, a fifth lens 240, a sixth lens 250, a seventh lens 280, and an eighth lens 290. The difference is that the first phase plate glass 280 and the second phase plate glass 290 are not placed, and the optical parameters of each lens are slightly different from those in the first embodiment.

[0125] Specifically, in the inverted objective optical system of the second embodiment, the field number is 25mm, the magnification β is 40x, the longitudinal chromatic aberration defined by the focus position deviation between Ce is 1.13 times the focal depth, and the longitudinal chromatic aberration defined by the focus position deviation between ge is 0.71 times the focal depth, where C is 656.27nm, g is 435.84nm, and e is 546.07nm. The focal depth is λ / NA², where λ is the wavelength and NA is the numerical aperture.

[0126] The first lens 110 has a focal length f11 of 12.05, a refractive index N11 of 1.92, an Abbe number V11 of 20.9, and a thickness T11 of 3.89.

[0127] The second lens 210 has a focal length f21 of 11.39, a refractive index N21 of 1.50, an Abbe number V21 of 81.6, and a thickness T21 of 3.89.

[0128] The third lens 220 has a focal length f22 of -7.22, a refractive index N22 of 1.62, an Abbe number V22 of 36.3, and a thickness T22 of 1.00.

[0129] The fourth lens 230 has a focal length f23 of 10.46, a refractive index N23 of 1.76, an Abbe number V23 of 50.8, and a thickness T23 of 3.91.

[0130] The fifth lens 240 has a focal length f24 of 15.21, a refractive index N24 of 1.50, an Abbe number V24 of 81.6, and a thickness T24 of 3.78.

[0131] The sixth lens 250 has a focal length f25 of -12.06, a refractive index N25 of 1.95, an Abbe number V25 of 17.9, and a thickness T25 of 1.00.

[0132] The seventh lens 280 has a focal length f28 of 8.89, a refractive index N28 of 1.95, an Abbe number V28 of 17.9, and a thickness T28 of 4.93.

[0133] The eighth lens 290 has a focal length f29 of -5.19, a refractive index N29 of 1.85, an Abbe number V29 of 23.8, and a thickness T29 of 4.64.

[0134] Other optical parameters of the inverted objective optical system are shown in Table 2-1.

[0135] Table 2-1

[0136]

[0137] As can be seen from the above, in the objective optical system of this embodiment, f is the focal length of the inverted objective optical system, that is, f is 4.52, NA is the object side numerical aperture of the objective optical system, that is, NA is 0.55, and D0 is the distance from the slide to the optical axis of the lens surface of the inverted objective optical system closest to the object, that is, D0 is 2.83, then |f×D0 / NA| is 2.90. This ensures that it has the characteristics of large magnification, large numerical aperture, high resolution performance, and large field of view.

[0138] The focal length of the first lens group is the focal length of the first lens 110, that is, f1 is equal to f11, which is 12.05. The focal length of the second lens group is the combined focal length of the second lens 210 to the eighth lens 290, that is, f2 is 12.69. The focal length f of the entire optical system is 4.52, then |f / f1| is 0.38, |f / f2| is 0.36, |f2 / f1| is 1.05, f21 / f2 is 0.95, f22 / f2 is -0.60, f23 / f2 is 0.87, f24 / f2 is 1.20, f25 / f2 is -0.95, f28 / f2 is 0.70, and f29 / f2 is -0.41. The objective optical system within the focal length numerical range has a large positive refractive power, so that the inverted objective has a large numerical aperture, and at the same time, it also makes it possible to better control distortion and field curvature.

[0139] In this embodiment 2, the thickness of the first lens group, i.e. T1, is 4.39 mm, the thickness T2 of the second lens group 2 is 37.68 mm, T1 / T2 is 0.10, T11 / T1 is 0.89, T21 / T2 is 0.10, T22 / T2 is 0.03, T23 / T2 is 0.10, T24 / T2 is 0.10, T25 / T2 is 0.03, T28 / T2 is 0.13, and T29 / T2 is 0.12.

[0140] Figures 7 to 10 The various aberration diagrams and MTF performance diagrams of the inverted objective optical system of Example 2 are shown. The various aberrations presented therein show the resolution capability. When the aberrations are relatively small, a better quality image can be observed. Specifically:

[0141] Figure 7 is a spherical aberration diagram of the inverted objective optical system of the second embodiment of the present invention, Figure 7 In the figure, the horizontal axis is the spherical aberration, in mm, and the vertical axis is the image height, in mm. Figure 7 As shown, the solid line represents the d line, the dotted line represents the C line, the single-dash line represents the F line, and the double-dash line represents the g line. The spherical aberration of the inverted objective optical system is controlled within ±0.005mm, so that the center resolution of the inverted objective optical system is optimal.

[0142] Figure 8 is a field curvature diagram of the inverted objective optical system of the second embodiment of the present invention, Figure 8 In the figure, the horizontal axis is the object plane movement, in mm, and the vertical axis is the image height, in mm. The solid line represents the sagittal relative to each wavelength of light, and the dotted line represents the meridian relative to each wavelength. From the distribution of field curvature, it can be seen that the field curvature of the inverted objective optical system is controlled within ±0.005mm, so that the central resolution of the inverted objective optical system is optimal.

[0143] Fig. 9is a distortion diagram of the inverted objective optical system of the second embodiment of the present invention, Fig. 9 In the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image height, in mm. From the distribution of distortion, it can be seen that the distortion of the inverted objective optical system is controlled within ±2%, so that the central resolution of the inverted objective optical system is optimal.

[0144] Fig.10 is a diagram of the MTF (modulation transfer function) of the inverted objective optical system of the second embodiment of the present invention, Fig.10 In the figure, the horizontal axis is the spatial frequency in cycles / mm, and the vertical axis is the modulation, i.e., MTF. Fig.10 As shown, the solid line represents the modulation (MTF) of the central image plane of the inverted objective optical system, and the dotted line represents the diffraction limit.

[0145] Embodiment 3

[0146] like Fig.11 As shown, the structure of the inverted objective optical system in this embodiment is similar to that of the first embodiment, and also includes a first lens group and a second lens group, wherein the first lens group includes a first lens 110, and the second lens group 2 includes a second lens 210, a third lens 220, a fourth lens 230, a first phase plate glass 280, a second phase plate glass 290, a fifth lens 240, a sixth lens 250, a seventh lens 280, and an eighth lens 290. Different from the first embodiment, the third embodiment has a larger magnification β, NA is 0.65, the positions of the first phase plate glass 280 and the second phase plate glass 290 are changed, and the optical parameters of each lens are slightly different from those of the first embodiment.

[0147] Specifically, in the inverted objective optical system of the third embodiment, the field number is 25mm, the magnification β is 60x, the longitudinal chromatic aberration defined by the focus position deviation between Ce is 1.14 times the focal depth, and the longitudinal chromatic aberration defined by the focus position deviation between ge is 0.77 times the focal depth, where C is 656.27nm, g is 435.84nm, and e is 546.07nm. The focal depth is λ / NA², where λ is the wavelength and NA is the numerical aperture.

[0148] The first lens 110 has a focal length f11 of 10.98, a refractive index N11 of 1.95, an Abbe number V11 of 17.9, and a thickness T11 of 3.35.

[0149] The second lens 210 has a focal length f21 of 8.15, a refractive index N21 of 1.81, an Abbe number V21 of 42.8, and a thickness T21 of 6.00.

[0150] The third lens 220 has a focal length f22 of -5.18, a refractive index N22 of 1.92, an Abbe number V22 of 20.9, and a thickness T22 of 2.56.

[0151] The fourth lens 230 has a focal length f23 of 8.94, a refractive index N23 of 1.72, an Abbe number V23 of 55.0, and a thickness T23 of 3.58.

[0152] The focal length f26 of the first phase plate glass 260 is infinite, the refractive index N26 is 1.52, the Abbe number V26 is 64.2, and the thickness T26 is 0.70.

[0153] The focal length f27 of the second phase plate glass 270 is infinite, the refractive index N27 is 1.52, the Abbe number V27 is 64.2, and the thickness T27 is 0.70.

[0154] The fifth lens 240 has a focal length f24 of 10.51, a refractive index N24 of 1.50, an Abbe number V24 of 81.6, and a thickness T24 of 3.58.

[0155] The sixth lens 250 has a focal length f25 of -9.10, a refractive index N25 of 1.95, an Abbe number V25 of 17.9, and a thickness T25 of 1.00.

[0156] The seventh lens 280 has a focal length f28 of 6.81, a refractive index N28 of 1.95, an Abbe number V28 of 17.9, and a thickness T28 of 6.00.

[0157] The eighth lens 290 has a focal length f29 of -3.85, a refractive index N29 of 1.83, an Abbe number V29 of 38.4, and a thickness T29 of 5.18.

[0158] Other optical parameters of the inverted objective optical system are shown in Table 3-1.

[0159] Table 3-1

[0160]

[0161] As can be seen from the above, in the objective optical system of this embodiment, f is the focal length of the inverted objective optical system, that is, f is 3.00, NA is the object side numerical aperture of the objective optical system, that is, NA is 0.65, and D0 is the distance from the slide to the optical axis of the lens surface of the inverted objective optical system closest to the object, that is, D0 is 2.79, then |f×D0 / NA| is 1.66. This ensures that it has the characteristics of large magnification, large numerical aperture, high resolution performance, and large field of view.

[0162] The focal length of the first lens group is the focal length of the first lens 110, that is, f1 is equal to f11, which is 10.98. The focal length of the second lens group is the combined focal length of the second lens 210 to the eighth lens 290, that is, f2 is 8.28. The focal length f of the entire optical system is 3.00, then |f / f1| is 0.27, |f / f2| is 0.36, |f2 / f1| is 0.75, f21 / f2 is 0.74, f22 / f2 is -0.47, f23 / f2 is 0.81, f24 / f2 is 1.27, f25 / f2 is -1.10, f28 / f2 is 0.82, and f29 / f2 is -0.47. The objective optical system within the focal length numerical range has a large positive refractive power, so that the inverted objective has a large numerical aperture, and at the same time, it also makes it possible to better control distortion and field curvature.

[0163] In this embodiment three, the thickness of the first lens group, i.e. T1, is 3.85 mm, the thickness T2 of the second lens group is 38.26 mm, T1 / T2 is 0.10, T11 / T1 is 0.87, T21 / T2 is 0.16, T22 / T2 is 0.07, T23 / T2 is 0.09, T24 / T2 is 0.09, T25 / T2 is 0.03, T28 / T2 is 0.16, and T29 / T2 is 0.14.

[0164] Figures 12 to 15 The various aberration diagrams and MTF performance diagrams of the inverted objective optical system of Example 3 are shown. The various aberrations presented therein show the resolution capability. When the aberrations are relatively small, a better quality image can be observed. Specifically:

[0165] Fig.12 is a spherical aberration diagram of the inverted objective optical system of the third embodiment of the present invention, Fig.12 In the figure, the horizontal axis is the spherical aberration, in mm, and the vertical axis is the image height, in mm. Figure 7 As shown, the solid line represents the d line, the dotted line represents the C line, the single-dash line represents the F line, and the double-dash line represents the g line. The spherical aberration of the inverted objective optical system is controlled within ±0.005mm, so that the center resolution of the inverted objective optical system is optimal.

[0166] Fig.13 is a field curvature diagram of the inverted objective optical system of the third embodiment of the present invention, Fig.13 In the figure, the horizontal axis is the object plane movement, in mm, the vertical axis is the image height, in mm, the solid line represents the sagittal relative to each wavelength, and the dotted line represents the meridian relative to each wavelength. From the distribution of field curvature, it can be seen that the field curvature of the inverted objective optical system is controlled within ±0.005mm, making the center resolution of the inverted objective optical system optimal.

[0167] Fig.14is a distortion diagram of the inverted objective optical system of the third embodiment of the present invention, Fig.14 In the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image height, in mm. From the distribution of distortion, it can be seen that the distortion of the inverted objective optical system is controlled within ±2%, making the central resolution of the inverted objective optical system optimal.

[0168] Fig.15 is a diagram of the MTF (modulation transfer function) of the inverted objective optical system of the third embodiment of the present invention, Fig.15 In the figure, the horizontal axis is the spatial frequency in cycles / mm, and the vertical axis is the modulation, i.e., MTF. Fig.15 As shown, the solid line represents the modulation (MTF) of the central image plane of the inverted objective optical system, and the dotted line represents the diffraction limit.

[0169] Embodiment 4

[0170] like Fig.16 As shown, the structure of the inverted objective optical system in the fourth embodiment is similar to that in the third embodiment, and also includes a first lens group and a second lens group, wherein the first lens group includes a first lens 110, and the second lens group includes a second lens 210, a third lens 220, a fourth lens 230, a fifth lens 240, a sixth lens 250, a seventh lens 260, and an eighth lens 270. The difference from the third embodiment is that the first phase plate glass 260 and the second phase plate glass 260 are not placed, and the optical parameters of each lens are slightly different from those in the third embodiment.

[0171] Specifically, in the inverted objective optical system of the fourth embodiment, the field number is 25mm, the magnification β is 60x, the longitudinal chromatic aberration defined by the focus position deviation between Ce is 1.21 times the focal depth, and the longitudinal chromatic aberration defined by the focus position deviation between ge is 0.84 times the focal depth, where C is 656.27nm, g is 435.84nm, and e is 546.07nm. The focal depth is λ / NA², where λ is the wavelength and NA is the numerical aperture.

[0172] The first lens 110 has a focal length f11 of 11.59, a refractive index N11 of 1.95, an Abbe number V11 of 17.9, and a thickness T11 of 3.35.

[0173] The second lens 210 has a focal length f21 of 8.78, a refractive index N21 of 1.81, an Abbe number V21 of 44.8, and a thickness T21 of 6.00.

[0174] The third lens 220 has a focal length f22 of -5.61, a refractive index N22 of 1.92, an Abbe number V22 of 20.9, and a thickness T22 of 3.04.

[0175] The fourth lens 230 has a focal length f23 of 8.96, a refractive index N23 of 1.73, an Abbe number V23 of 54.7, and a thickness T23 of 3.61.

[0176] The fifth lens 240 has a focal length f24 of 10.63, a refractive index N24 of 1.50, an Abbe number V24 of 81.6, and a thickness T24 of 3.66.

[0177] The sixth lens 250 has a focal length f25 of -8.99, a refractive index N25 of 1.95, an Abbe number V25 of 17.9, and a thickness T25 of 1.00.

[0178] The seventh lens 260 has a focal length f28 of 7.15, a refractive index N28 of 1.95, an Abbe number V28 of 17.9, and a thickness T28 of 6.00.

[0179] The eighth lens 270 has a focal length f29 of -3.97, a refractive index N29 of 1.82, an Abbe number V29 of 40.5, and a thickness T29 of 5.60.

[0180] Other optical parameters of the inverted objective optical system are shown in Table 4-1.

[0181] Table 4-1

[0182]

[0183] As can be seen from the above, in the objective optical system of this embodiment, f is the focal length of the inverted objective optical system, that is, f is 3.00, NA is the object side numerical aperture of the objective optical system, that is, NA is 0.65, and D0 is the distance from the slide to the optical axis of the lens surface of the inverted objective optical system closest to the object, that is, D0 is 2.84, then |f×D0 / NA| is 1.62. This ensures that it has the characteristics of large magnification, large numerical aperture, high resolution performance, and large field of view.

[0184] The focal length of the first lens group is the focal length of the first lens 110, that is, f1 is equal to f11, which is 11.59. The focal length of the second lens group is the combined focal length of the second lens 210 to the eighth lens 270, that is, f2 is 8.05. The focal length f of the entire optical system is 3.00, then |f / f1| is 0.26, |f / f2| is 0.37, |f2 / f1| is 0.69, f21 / f2 is 0.76, f22 / f2 is -0.48, f23 / f2 is 0.77, f24 / f2 is 1.32, f25 / f2 is -1.12, f28 / f2 is 0.89, and f29 / f2 is -0.49. The objective optical system within the focal length numerical range has a large positive refractive power, so that the inverted objective has a large numerical aperture, and at the same time, it also makes it possible to better control distortion and field curvature.

[0185] In this embodiment 4, the thickness of the first lens group, i.e. T1, is 3.85 mm, the thickness T2 of the second lens group 2 is 38.21 mm, T1 / T2 is 0.10, T11 / T1 is 0.87, T21 / T2 is 0.16, T22 / T2 is 0.08, T23 / T2 is 0.09, T24 / T2 is 0.10, T25 / T2 is 0.03, T28 / T2 is 0.16, and T29 / T2 is 0.15.

[0186] Figures 17 to 20 The aberration diagrams and MTF performance diagrams of the inverted objective optical system of the fourth embodiment show the resolution capability. When the aberration is relatively small, a better quality image can be observed. Specifically:

[0187] Fig.17 is a spherical aberration diagram of the inverted objective optical system of the fourth embodiment of the present invention, Fig.17 In the figure, the horizontal axis is the spherical aberration, in mm, and the vertical axis is the image height, in mm. Fig.17 As shown, the solid line represents the d line, the dotted line represents the C line, the single-dash line represents the F line, and the double-dash line represents the g line. The spherical aberration of the inverted objective optical system is controlled within ±0.005mm, so that the center resolution of the inverted objective optical system is optimal.

[0188] Fig.18 is a field curvature diagram of the inverted objective optical system of the fourth embodiment of the present invention, Fig.18 In the figure, the horizontal axis is the object plane movement, in mm, the vertical axis is the image height, in mm, the solid line represents the sagittal relative to each wavelength, and the dotted line represents the meridian relative to each wavelength. From the distribution of field curvature, it can be seen that the field curvature of the inverted objective optical system is controlled within ±0.005mm, making the center resolution of the inverted objective optical system optimal.

[0189] Fig.19 is a distortion diagram of the inverted objective optical system of the fourth embodiment of the present invention, Fig.19 In the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image height, in mm. From the distribution of distortion, it can be seen that the distortion of the inverted objective optical system is controlled within ±2%, making the central resolution of the inverted objective optical system optimal.

[0190] Fig. 20 is a diagram of the MTF (modulation transfer function) of the inverted objective optical system of the fourth embodiment of the present invention, Fig. 20 In the figure, the horizontal axis is the spatial frequency in cycles / mm, and the vertical axis is the modulation, i.e., MTF. Fig.15 As shown, the solid line represents the modulation (MTF) of the central image plane of the inverted objective optical system, and the dotted line represents the diffraction limit.

[0191] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An inverted microscope objective lens, characterized in that: The lens comprises a first lens group and a second lens group in sequence from the object side to the image side along an optical axis; The first lens group includes a first lens having positive refractive power; The second lens group has positive refractive power, and includes a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens in sequence, the second lens has positive refractive power, the third lens has negative refractive power, the fourth lens has positive refractive power, the fifth lens has positive refractive power, the sixth lens has negative refractive power, the seventh lens has positive refractive power, and the eighth lens has negative refractive power, and the second lens group includes at least two groups of cemented lenses; 0.16<|f / f1|<1.6, 0.17<|f / f2|<1.6, 0.19<|f2 / f1|<2.7, Wherein, f is the focal length of the inverted objective optical system, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group; The spherical aberration of the inverted objective optical system is controlled within ±0.005 mm, and the field curvature of the inverted objective optical system is controlled within ±0.005 mm.

2. An inverted microscope objective lens as claimed in claim 1, characterized in that: Each of the first to eighth lenses includes an object-side surface facing the object side and allowing imaging light to pass therethrough, and an image-side surface facing the image side and allowing imaging light to pass therethrough; The object side surface of the first lens is concave, and the image side surface is convex; the image side surface of the second lens is convex; the object side surface of the third lens is concave, and the image side surface is concave; the object side surface of the fourth lens is convex, and the image side surface is convex; the object side surface of the fifth lens is convex, and the image side surface is convex; the object side surface of the sixth lens is concave, and the image side surface is a plane or a concave surface; the object side surface of the seventh lens is convex, and the image side surface is convex; the object side surface of the eighth lens is concave, and the image side surface is concave.

3. An inverted microscope objective lens as claimed in claim 1, characterized in that: The second lens, the third lens and the fourth lens form a cemented lens, the fifth lens and the sixth lens form a cemented lens, and the seventh lens and the eighth lens form a cemented lens.

4. An inverted microscope objective lens as claimed in claim 1, characterized in that: The following condition is satisfied: 0.5<|f×D0 / NA|<5.0, wherein f is the focal length of the inverted objective optical system, NA is the object-side numerical aperture of the inverted objective optical system, and D0 is the distance on the optical axis from the glass slide to the lens surface of the inverted objective optical system closest to the object.

5. An inverted microscope objective lens as claimed in claim 1, characterized in that: The following conditions are met: -0.26<f21 / f2<1.95, -1.60<f22 / f2<0.61, -0.43<f23 / f2<1.87, -0.06<f24 / f2<2.32, -2.12<f25 / f2<0.26, -0.42<f28 / f2<1.89, -1.49<f29 / f2<0.67, Among them, f2 is the focal length of the second lens group, f21 is the focal length of the second lens, f22 is the focal length of the third lens, f23 is the focal length of the fourth lens, f24 is the focal length of the fifth lens, f25 is the focal length of the sixth lens, f28 is the focal length of the seventh lens, and f29 is the focal length of the eighth lens.

6. An inverted microscope objective lens as claimed in claim 1, characterized in that: The following conditions are met: N11≥1.80, N21≤1.90, N22≥1.50, N23≤1.85, N24≤1.70, N25≥1.80, N28≥1.85, N29≥1.70, Among them, 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, N28 is the refractive index of the seventh lens, and N29 is the refractive index of the eighth lens.

7. An inverted microscope objective lens as claimed in claim 1, characterized in that: The following conditions are met: V11≤30, V21≥35, V22≤50, V23≥30, V24≥50, V25≤30, V28≤30, V29≤50, Among them, 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, V28 is the Abbe number of the seventh lens, and V29 is the Abbe number of the eighth lens.

8. An inverted microscope objective lens as claimed in claim 1, characterized in that: The following conditions are met: 0.08<T1 / T2<0.21, 0.37<T11 / T1<0.95, 0.05<T21 / T2<0.66, 0.01<T22 / T2<0.58, 0.03<T23 / T2<0.61, 0.03<T24 / T2<0.60, 0.01<T25 / T2<0.54, 0.05<T28 / T2<0.66, 0.04<T29 / T2<0.65, Among them, T1 is the length of the first lens group on the optical axis, T2 is the length of the second lens group on the optical axis, T11 is the thickness of the first 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, T28 is the thickness of the seventh lens on the optical axis, and T29 is the thickness of the eighth lens on the optical axis.

9. An inverted microscope objective lens as claimed in claim 1, characterized in that: The second lens group further includes a phase plate lens 1 and a phase plate lens 2, and the phase plate lens 1 and the phase plate lens 2 are arranged between the fourth lens and the seventh lens.

Images