A 25x liquid immersion objective for microscopic imaging

Abstract

The present invention discloses a 25x liquid immersion objective lens for microscopic imaging. Silicone oil is used as an immersion medium. By selecting the focal lengths of each lens group and the structures of the middle lens group and the rear lens group, the refractive indices of the first and last lenses in the front lens group, and the range of variation of the air gap between the third cemented lens in the middle lens group and the last lens in the front lens group, the third cemented lens is moved back and forth relative to the last lens in the lens group to adjust system aberrations caused by changes in cover glass thickness. At the same time, the refractive index, focal length, and focal length-to-outer diameter ratio of the last lens in the front lens group are selected to control the spherical aberration of marginal light. The fifth cemented lens is selected to have a negative optical power to correct system field curvature. The sixteenth lens is combined with the fifth cemented lens to reduce system astigmatism, thereby solving problems in living cell imaging.

Description

Technical Field

[0001] The invention relates to a microscopic imaging objective lens, in particular to a 25x liquid immersion objective lens for microscopic imaging. Background Art

[0002] Live cell imaging is an optical technique for studying real-time dynamic physiological processes in living cells. It can provide spatial and temporal information about dynamic molecular events occurring in single cells, intracellular networks, and even entire organisms. These properties make it an essential technique for studying dynamic physiological processes in cell biology, cancer, developmental biology, and neuroscience.

[0003] With the rapid advancements in electronics, optics, and biochemistry in recent years, researchers have been able to more easily image live cells. However, this has also placed higher demands on the image quality of the microscope objectives used in imaging systems. In live-cell microscopy, liquid immersion objectives are commonly used to observe cells. Liquid immersion objectives are those that have a liquid or other medium between the objective lens and the specimen. This design primarily aims to increase the numerical aperture, thereby improving image quality and resolution. Currently, the most commonly used liquid immersion objectives are oil and water immersion objectives. These objectives are mature and commercially available, but they have some drawbacks in live-cell microscopy applications. Due to the difference in the refractive index of oil (ne≈1.52) and that of living tissue cells (ne≈1.38), this refractive index mismatch causes spherical aberration and degrades image quality. Researchers cannot obtain deeper, brighter cell images using oil immersion objectives. The numerical aperture of a water-immersion objective is smaller than that of an oil-immersion objective, resulting in lower imaging resolution. Furthermore, some live-cell microscopy imaging requires long-term monitoring at a stable 37°C environment. Water-immersion objectives require regular rehydration due to water evaporation, making long-term, stable, real-time observation impossible. Furthermore, existing medium-magnification objectives around 25× in China lack an adjustment ring for spherical aberration compensation, making it impossible to compensate for spherical aberration caused by variations in coverslip thickness, thus affecting cell observation. The objective's quadratic field of view is also only 22 mm in diameter, making it impossible to observe a larger field of view of cells in real time. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a 25x silicone oil immersion objective lens suitable for microscopic imaging of living cells, which can better adapt to the variation of cover glass thickness from 0.11mm to 0.23mm, match the refractive index of living tissue, and at the same time have a large image field of view and wide spectrum chromatic aberration correction.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a 25x liquid immersion objective lens for microscopic imaging, wherein the liquid immersion in the liquid immersion objective lens is silicone oil immersion, and the objective lens is composed of a front lens group with positive focal power, an intermediate lens group with negative focal power, and a rear lens group with positive focal power, which are arranged in sequence on the same optical axis from the object side to the image side. The focal length fobj of the entire 25x liquid immersion objective lens is 7.6mm~8.4mm, the focal length fm1 of the front lens group satisfies: 7mm≤fm1≤9mm, the focal length fm2 of the intermediate lens group satisfies: -200mm≤fm2≤-60mm, and the focal length fm3 of the rear lens group satisfies: 80mm≤fm3≤120mm; the refractive index of the first lens in the front lens group is nd1 satisfies: 1.4<nd1<1.5, the middle lens group consists of a third cemented lens with a focal length of 40mm~70mm that can be moved along the optical axis and a fourth cemented lens with a focal length of -20mm~-10mm that is fixed in position; the air gap between the third cemented lens and the last lens in the front lens group varies in the range of 0.7mm~0.9mm, the last lens in the front lens group is a positive lens with a refractive index greater than 1.9, a focal length of 45mm~60mm, and a focal length to outer diameter ratio greater than 2, the rear lens group consists of a fifth cemented lens with negative focal power, a sixteenth lens with positive focal power, and a seventeenth lens with positive focal power, and the refractive index of the sixteenth lens is greater than 1.75.

[0006] Compared with the prior art, the advantages of the present invention are that silicone oil is used as the immersion medium (silicone oil refractive index ne≈1.4), the focal length of each lens group and the structure of the middle lens group and the rear lens group are selected, the refractive index of the first lens and the last lens in the front lens group and the range of variation of the air gap between the third cemented lens in the middle lens group and the last lens in the front lens group are selected, the third cemented lens is adjusted for system aberrations caused by changes in cover glass thickness by moving back and forth relative to the last lens in the lens group, and the spherical aberration of marginal light is controlled by selecting the refractive index, focal length and focal length to outer diameter ratio of the last lens in the front lens group, and the fifth cemented lens is selected as a negative The optical power is used to correct the field curvature of the system, and the astigmatism of the system is reduced by cooperating with the sixteenth lens and the fifth cemented lens. This solves the problems of the refractive index mismatch of the immersion medium, insufficient numerical aperture, insufficient field of view, insufficient stability of the immersion medium, and inability to correct aberrations for changes in cover glass thickness in conventional oil immersion and water immersion objectives in the prior art in living cell imaging. The numerical aperture of the liquid immersion objective of the present invention reaches 1.05, which can adapt to cover glass thickness changes of 0.11 mm to 0.23 mm. The refractive index of the immersion medium can be effectively matched with the refractive index of living tissue (ne≈1.38), while also achieving a large 25 mm field of view on the image side and wide-spectrum chromatic aberration correction.

[0007] Preferably, the front lens group consists of a first cemented lens with a focal length of 20 mm to 40 mm, a third lens with a focal length of 15 mm to 30 mm, a second cemented lens, and a seventh lens with a focal length of 45 mm to 60 mm. The first cemented lens consists of a first lens and a second lens. The refractive index of the first lens satisfies: 1.4<nd1<1.5, the refractive index nd1 of the first lens and the refractive index nd2 of the second lens satisfy: nd2-nd1>0.35, and the Abbe number vd1 of the first lens and the Abbe number vd2 of the second lens satisfy: | vd1-vd2|≥25. The second cemented lens is composed of a fourth lens, a fifth lens, and a sixth lens. The fourth lens L4 is a positive lens, the fifth lens L5 is a negative lens, and the sixth lens L6 is a positive lens. The following conditions are met: |vd4-vd5|≥40 and |vd5-vd6|≥40, where vd4 is the Abbe number of the fourth lens, vd5 is the Abbe number of the fifth lens, and vd6 is the Abbe number of the sixth lens. The air gap between the seventh lens and the second cemented lens varies in the range of 0.7mm to 0.9mm. The combination of the first and second lenses can effectively collect object-side light and reduce the angle of incident light. The second cemented lens uses a positive-negative-positive lens structure and corrects chromatic aberration by increasing the difference in the dispersion coefficients of adjacent lenses.

[0008] Preferably, the third cemented lens is composed of an eighth lens with positive power, a ninth lens with negative power, and a tenth lens with positive power; and the fourth cemented lens is composed of an eleventh lens with negative power, a twelfth lens with positive power, and a thirteenth lens with negative power. The third cemented lens is a triplet with a positive-negative-positive structure, and the fourth cemented lens is a triplet with a negative-positive-negative structure. The combination of the two can correct the secondary spectrum and achieve wide-spectrum apochromatism.

[0009] Preferably, the first lens is a hemispherical lens with a flat object side, the second lens is a meniscus lens with a concave object side, the third lens is a meniscus lens with a concave object side, the eleventh lens has a convex object side and a concave image side, the twelfth lens has a convex object side and a convex image side, the sixteenth lens is a meniscus lens with a concave object side and a convex image side, and the seventeenth lens has a convex object side and a convex image side.

[0010] Preferably, the fifth cemented lens is composed of a fourteenth lens with negative optical power and a fifteenth lens with positive optical power, the fourteenth lens has a concave surface on the object side and a concave surface on the image side, and the fifteenth lens has a convex surface on the object side and a convex surface on the image side.

[0011] Preferably, the Abbe number vd8 of the eighth lens, the Abbe number vd9 of the ninth lens, and the Abbe number vd10 of the tenth lens satisfy: |vd8-vd9|≥40 and |vd9-vd10|≥40, and the Abbe number vd11 of the eleventh lens, the Abbe number vd12 of the twelfth lens, and the Abbe number vd13 of the thirteenth lens satisfy: |vd11-vd12|≥40 and |vd12-vd13|≥40.

[0012] Preferably, the air gap between the first cemented lens and the third lens is 0.1 mm to 0.2 mm, the air gap between the third lens and the second cemented lens is 0.1 mm to 0.2 mm, the air gap between the second cemented lens and the seventh lens is 0.1 mm to 0.2 mm, the air gap between the fifth cemented lens and the sixteenth lens is 1 mm to 2 mm, and the air gap between the sixteenth lens and the seventeenth lens is 0.1 mm to 0.2 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the structure of a 25x liquid immersion objective lens according to Example 1 of the embodiment of the present invention;

[0014] Figure 2 This is a graph of field curvature for Example 1 of the present invention, where the cover glass thickness is 0.17 mm. The ordinate in the graph is the angle of the incident light, which corresponds to the field number of the objective lens, and the abscissa is the magnitude of the field curvature. Different curves correspond to different wavelengths.

[0015] Figure 3 This is a field curvature curve diagram of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0016] Figure 4 This is a field curvature curve diagram of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0017] Figure 5 This is a distortion curve diagram for Example 1 of the present invention, where the cover glass thickness is 0.17 mm. The ordinate in the diagram is the angle of the incident light, which corresponds to the field of view of the objective lens, and the abscissa is the magnitude of the distortion. Different curves correspond to different wavelengths.

[0018] Figure 6 This is a distortion curve diagram of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0019] Figure 7 This is a distortion curve diagram of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0020] Figure 8This is an optical transfer function (MTF) curve for Example 1 of the embodiment of the present invention with a cover glass thickness of 0.17 mm. The ordinate represents the MTF value, and the abscissa represents the spatial frequency.

[0021] Figure 9 This is the optical transfer function (MTF) curve of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0022] Figure 10 This is the optical transfer function (MTF) curve of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0023] Figure 11 This is a graph of the axial aberration of Example 1 of the embodiment of the present invention with a cover glass thickness of 0.17 mm. The ordinate represents the normalized pupil, and the abscissa represents the spherical aberration value of different color lights in the on-axis field of view.

[0024] Figure 12 This is a graph showing the axial aberration of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0025] Figure 13 This is a graph showing the axial aberration of Example 1 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0026] Figure 14 Schematic diagram of the structure of a 25x liquid immersion objective lens according to Example 2 of the embodiment of the present invention;

[0027] Figure 15 This is a graph of field curvature for Example 2 of the present invention, where the cover glass thickness is 0.17 mm. The ordinate in the graph is the angle of the incident light, which corresponds to the field number of the objective lens, and the abscissa is the magnitude of the field curvature. Different curves correspond to different wavelengths.

[0028] Figure 16 This is a field curvature curve diagram of Example 2 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0029] Figure 17 This is a field curvature curve diagram of Example 2 of the embodiment of the present invention with a cover glass thickness of 0.23 mm;

[0030] Figure 18 This is a distortion curve diagram for Example 2 of the present invention, where the cover glass thickness is 0.17 mm. The ordinate in the diagram is the angle of the incident light, which corresponds to the field of view of the objective lens, and the abscissa is the magnitude of the distortion. Different curves correspond to different wavelengths.

[0031] Figure 19 This is a distortion curve diagram of Example 2 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0032] Figure 20This is a distortion curve diagram of Example 2 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0033] Figure 21 This is an optical transfer function (MTF) curve for Example 2 of the embodiment of the present invention with a cover glass thickness of 0.17 mm. The ordinate represents the MTF value, and the abscissa represents the spatial frequency.

[0034] Figure 22 This is the optical transfer function (MTF) curve of Example 2 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0035] Figure 23 This is the optical transfer function (MTF) curve of Example 2 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0036] Figure 24 This is a graph of the axial aberration of Example 2 of the embodiment of the present invention with a cover glass thickness of 0.17 mm. The ordinate represents the normalized pupil, and the abscissa represents the spherical aberration values ​​of different color lights in the on-axis field of view.

[0037] Figure 25 This is an axial aberration curve diagram for Example 2 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0038] Figure 26 This is a graph showing the axial aberration of Example 2 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0039] Figure 27 Schematic diagram of the structure of a 25x liquid immersion objective lens according to Example 3 of the embodiment of the present invention;

[0040] Figure 28 This is a graph of field curvature for Example 3 of the present invention, where the cover glass thickness is 0.17 mm. The ordinate in the graph is the angle of the incident light, which corresponds to the field number of the objective lens, and the abscissa is the magnitude of the field curvature. Different curves correspond to different wavelengths.

[0041] Figure 29 This is a field curvature curve diagram of Example 3 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0042] Figure 30 This is a field curvature curve diagram of Example 3 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0043] Figure 31 This is a distortion curve diagram for Example 3 of the present invention, where the cover glass thickness is 0.17 mm. The ordinate in the diagram is the angle of the incident light, which corresponds to the field of view of the objective lens, and the abscissa is the magnitude of the distortion. Different curves correspond to different wavelengths.

[0044] Figure 32This is a distortion curve diagram of Example 3 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0045] Figure 33 This is a distortion curve diagram of Example 3 of the embodiment of the present invention when the cover glass thickness is 0.23 mm;

[0046] Figure 34 This is an MTF curve of the optical transfer function of Example 3 of the embodiment of the present invention with a cover glass thickness of 0.17 mm, where the ordinate represents the magnitude of the MTF value and the abscissa represents the spatial frequency;

[0047] Figure 35 This is the optical transfer function MTF curve of Example 3 of the embodiment of the present invention with a cover glass thickness of 0.11 mm;

[0048] Figure 36 This is the optical transfer function MTF curve of Example 3 of the embodiment of the present invention with a cover glass thickness of 0.23 mm;

[0049] Figure 37 This is a graph of the axial aberration of Example 3 of the embodiment of the present invention with a cover glass thickness of 0.17 mm. The ordinate represents the normalized pupil, and the abscissa represents the spherical aberration value of different color lights in the on-axis field of view.

[0050] Figure 38 This is a graph showing the axial aberration of Example 3 of the embodiment of the present invention when the cover glass thickness is 0.11 mm;

[0051] Figure 39 This is an axial aberration curve diagram of Example 3 of the embodiment of the present invention when the cover glass thickness is 0.23 mm. DETAILED DESCRIPTION

[0052] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0053] like Figure 1 、 14 As shown in Figure 27, a 25x liquid immersion objective lens for microscopic imaging, wherein the immersion liquid in the liquid immersion objective lens is silicone oil immersion, and the objective lens is composed of a front lens group M1 with positive optical power, an intermediate lens group M2 with negative optical power, and a rear lens group M3 with positive optical power, which are arranged in sequence on the same optical axis from the object side to the image side. The focal length fobj of the entire 25x liquid immersion objective lens is 7.6mm~8.4mm, the focal length fm1 of the front lens group M1 satisfies: 7mm≤fm1≤9mm, the focal length fm2 of the intermediate lens group M2 satisfies: -200mm≤fm2≤-60mm, and the focal length fm3 of the rear lens group M3 satisfies: 80mm≤fm3≤120mm.

[0054] The front lens group M1 consists of a first cemented lens GL1 with a focal length of 20mm~40mm, a third lens L3 with a focal length of 15mm~30mm, a second cemented lens GL2 and a seventh lens L7 with a focal length of 45mm~60mm. The first cemented lens GL1 consists of a first lens L1 and a second lens L2. The first lens L1 is a hemispherical lens with a flat surface facing the object, and the second lens L2 is a meniscus lens with a concave surface facing the object. The refractive index nd1 of the first lens L1 and the refractive index nd2 of the second lens L2 satisfy: 1.4<nd1<1.5, nd2-nd1>0.35, the Abbe number vd1 of the first lens L1 and the Abbe number vd2 of the second lens L2 satisfy: |vd1-vd2|≥25, the second cemented lens GL2 is composed of the fourth lens L4, the fifth lens L5 and the sixth lens L6, the fourth lens L4 is a positive lens, the fifth lens L5 is a negative lens, and the sixth lens L6 is a positive lens, satisfying: |vd4-vd5|≥40 and |vd5-vd6|≥40, where vd4 is the value of the fourth lens L 4, vd5 is the Abbe number of the fifth lens L5, vd6 is the Abbe number of the sixth lens L6, the refractive index nd7 of the seventh lens L7 satisfies: nd7>1.9, the focal length fl7 of the seventh lens L7 is 45 mm~60 mm, the outer diameter d of the seventh lens L7 satisfies: fl7 / d>2, the air gap between the first cemented lens GL1 and the third lens L3 is 0.1 mm~0.2 mm, the air gap between the third lens L3 and the second cemented lens GL2 is 0.1 mm~0.2 mm, and the air gap between the second cemented lens GL2 and the seventh lens L7 is 0.1 mm~0.2 mm.

[0055] The middle lens group M2 consists of a third cemented lens GL3 with a focal length of 40mm~70mm that can be moved along the optical axis, and a fourth cemented lens GL4 with a focal length of -20mm~-10mm that is fixed in position. The third cemented lens GL3 adjusts the system aberration caused by changes in the cover glass thickness by moving back and forth relative to the seventh lens L7. The air gap between the seventh lens L7 and the second cemented lens GL2 varies in the range of 0.7mm~0.9mm. The third cemented lens GL3 is composed of an eighth lens L8, a ninth lens L9 and a tenth lens L10. The eighth lens L8 is a positive lens, the ninth lens L9 is a negative lens, and the tenth lens L10 is a positive lens. The Abbe number vd8 of the eighth lens L8, the Abbe number vd9 of the ninth lens L9 and the Abbe number vd10 of the tenth lens L10 satisfy the following conditions: |vd8-vd9|≥40 and |vd9-vd10|≥40. The eighth lens L8 has a convex surface facing the object side and a concave surface facing the image side. The ninth lens L9 has a convex surface facing the object side and a concave surface facing the image side. The fourth cemented lens GL4 is composed of an eleventh lens L8. Lens L11, a twelfth lens L12, and a thirteenth lens L13 are composed. The eleventh lens L11 is a negative lens, the twelfth lens L12 is a positive lens, and the thirteenth lens L13 is a negative lens. The Abbe number vd11 of the eleventh lens L11, the Abbe number vd12 of the twelfth lens L12, and the Abbe number vd13 of the thirteenth lens L13 satisfy: |vd11-vd12|≥40 and |vd12-vd13|≥40. The eleventh lens L11 has a convex surface facing the object side and a concave surface facing the image side. The twelfth lens L12 has a convex surface facing the object side and a convex surface facing the image side.

[0056] The rear lens group M3 consists of a negative-power fifth cemented lens GL5, a positive-power sixteenth lens L16, and a positive-power seventeenth lens L17. The fifth cemented lens GL5 is composed of a fourteenth lens L14 and a fifteenth lens L15. The fourteenth lens L14 is a negative lens, and the fifteenth lens L15 is a positive lens. The fourteenth lens L14 has a concave surface facing both the object and image sides. The fifteenth lens L15 has a convex surface facing both the object and image sides. The sixteenth lens L16 is a meniscus lens with positive refractive power, with its surface concave facing the object side and its surface convex facing the image side. The refractive index nd16 of the sixteenth lens L16 satisfies the following: nd16>1.75. The seventeenth lens L17 is a positive lens, with its surface convex facing the object side and its surface convex facing the image side. The air gap between the fifth cemented lens GL5 and the sixteenth lens L16 is 1 mm to 2 mm, and the air gap between the sixteenth lens L16 and the seventeenth lens L17 is 0.1 mm to 0.2 mm.

[0057] The present embodiment is described in detail below through three examples.

[0058] Example 1: Structural description and embodiment of the 25x liquid immersion objective in this example Figure 1The 25x liquid immersion objective is identical, consisting of a front lens group M1, a middle lens group M2, and a rear lens group M3. The focal length fobj of this 25x liquid immersion objective is 7.99 mm, the numerical aperture NA is 1.05, the magnification β is -25×, the immersion layer thickness is 0.55 mm, the cover glass thickness is 0.17 mm, the spectral range is 410 nm to 656 nm, the field of view is 25 mm, and the immersion medium is silicone oil 100. This 25x liquid immersion objective has the following characteristics:

[0059] The focal length of the front lens group M1 is fm1 = 8.61mm, the focal length of the middle lens group M2 is fm2 = -197.86mm, and the focal length of the rear lens group M3 is fm3 = 114.55mm. The refractive index of the first lens L1 is nd1 = 1.45, and the refractive index of the second lens L2 is nd2 = 1.88, with nd2-nd1 = 0.43. The Abbe number of the first lens L1 is vd1 = 67.8, and the Abbe number of the second lens L2 is vd2 = 40.8, with |vd1-vd2| = 27. The focal length of the first cemented lens GL1 is 36.46mm. The focal length fl3 of the third lens L3 is 24.47mm. The Abbe number vd4 of the fourth lens L4 is 95, the Abbe number vd5 of the fifth lens L5 is 44.3, the Abbe number vd6 of the sixth lens L6 is 95, |vd4-vd5| is 50.7, and |vd5-vd6| is 50.7.

[0060] The refractive index of the seventh lens element L7 is nd7 = 1.92, the focal length fl7 is 53.71 mm, the outer diameter is d = 20.4 mm, and the value fl7 / d = 2.6. The air gap between the first cemented lens GL1 and the third lens element L3 is 0.15 mm, the air gap between the third lens element L3 and the second cemented lens GL2 is 0.11 mm, and the air gap between the second cemented lens GL2 and the seventh lens element L7 is 0.12 mm. The Abbe number vd8 of the eighth lens element L8 is 95, the Abbe number vd9 of the ninth lens element L9 is 44.3, and the Abbe number vd10 of the tenth lens element L10 is 95. |vd8 - vd9| = 50.7 and |vd9 - vd10| = 50.7. The focal length fgl3 of the third cemented lens GL3 is 43.2 mm, and the air gap between the seventh lens L7 and the third cemented lens GL3 is 0.71 mm.

[0061] The Abbe number vd11 of the eleventh lens L11 is 44.3, the Abbe number vd12 of the twelfth lens L12 is 95, the Abbe number vd13 of the thirteenth lens L13 is 26.6, |vd11-vd12| is 50.7, and |vd12-vd13| is 68.4. The focal length fgl4 of the fourth cemented lens GL4 is -15.4 mm.

[0062] The refractive index nd16 of the sixteenth lens L16 is 1.8, the focal length fl17 of the seventeenth lens L17 is 42.66 mm, the air gap between the fifth cemented lens GL5 and the sixteenth lens L16 is 1.1 mm, and the air gap between the sixteenth lens L16 and the seventeenth lens L17 is 0.13 mm.

[0063] The lens parameters of the 25x liquid immersion objective lens of Example 1 are shown in Table 1.

[0064] Table 1

[0065] Here, radius refers to the radius of curvature of the surface, and thickness refers to the on-axis distance from the current surface to the next surface. For example, the thickness of the object plane of surface L1 is the distance from the object plane L1 to the object plane L2. It can be the on-axis thickness of the medium or lens, or the on-axis air gap between them.

[0066] In this example, when the cover glass thickness becomes 0.11 mm, the distance d1 between the seventh lens L7 and the third cemented lens GL3 is 0.75 mm, and the distance d2 between the third cemented lens GL3 and the fourth cemented lens GL4 is 0.9 mm.

[0067] When the cover glass thickness becomes 0.23 mm, the distance d1 between the seventh lens L7 and the third cemented lens GL3 is 0.67 mm, and the distance d2 between the third cemented lens GL3 and the fourth cemented lens GL4 is 0.98 mm.

[0068] from Figures 2 to 4 Field curvature curves and Figures 5 to 7 From the distortion curve, we can see that the maximum field curvature at the edge of the field of view within the full aperture range under different cover glass thicknesses is no more than 1um, and the maximum distortion is within 0.1%. Both field curvature and distortion are well corrected.

[0069] from Figures 8 to 10 It can be seen from the optical transfer function MTF curve that the cutoff frequency of the optical system is 4000lp / mm, and the MTF curves of each field of view under different cover glass thicknesses are close to the diffraction limit, and the system can achieve good imaging quality.

[0070] from Figures 11 to 13 As can be seen from the axial aberration curve, spherical aberration has been strictly corrected within the full aperture range, and the spectrum covers 410nm~656nm, meeting the requirements of apochromatism.

[0071] Example 2: Figure 14As shown, the 25x liquid immersion objective consists of a front lens group M1, a middle lens group M2, and a rear lens group M3. The 25x liquid immersion objective has a focal length fobj = 8 mm, an NA = 1.05, a magnification β = -25×, an immersion layer thickness of 0.55 mm, a cover glass thickness of 0.17 mm, a spectral range of 410 nm to 656 nm, a field of view of 25 mm, and an immersion medium of silicone oil 100. The 25x liquid immersion objective has the following features:

[0072] The focal length of the front lens group M1 is fm1 = 8.46mm, the focal length of the middle lens group M2 is fm2 = -164.24mm, and the focal length of the rear lens group M3 is fm3 = 109.14mm. The refractive index of the first lens L1 is nd1 = 1.45, and the refractive index of the second lens L2 is nd2 = 1.88, with nd2-nd1 = 0.43. The Abbe number of the first lens L1 is vd1 = 67.8, and the Abbe number of the second lens L2 is vd2 = 40.8, with |vd1-vd2| = 27. The focal length of the first cemented lens doublet GL1 is 23.28mm, and the focal length fl3 of the third lens L3 is 25.23mm. The Abbe number vd4 of the fourth lens L4 is 95, the Abbe number vd5 of the fifth lens L5 is 44.1, the Abbe number vd6 of the sixth lens L6 is 90.9, |vd4-vd5| is 50.9, and |vd5-vd6| is 46.8.

[0073] The seventh lens element L7 has a refractive index of nd7 = 1.92, a focal length fl7 of 49.48 mm, an outer diameter of d = 20.5 mm, and a value of fl7 / d = 2.4. The air gap between the first cemented lens GL1 and the third lens L3 is 0.2 mm, the air gap between the third lens L3 and the second cemented lens GL2 is 0.15 mm, and the air gap between the second cemented lens GL2 and the seventh lens L7 is 0.17 mm.

[0074] The Abbe number vd8 of the eighth lens element L8 is 95, the Abbe number vd9 of the ninth lens element L9 is 39.1, and the Abbe number vd10 of the tenth lens element L10 is 95, with |vd8 - vd9| equal to 55.9 and |vd9 - vd10| equal to 55.9. The focal length fgl3 of the third cemented lens GL3 is 42.74 mm, and the air gap between the seventh lens element L7 and the third cemented lens GL3 is 0.74 mm.

[0075] The Abbe number vd11 of the eleventh lens L11 is 46.6, the Abbe number vd12 of the twelfth lens L12 is 94.8, and the Abbe number vd13 of the thirteenth lens L13 is 27.5. |vd11-vd12| is 48.2, and |vd12-vd13| is 67.3. The focal length fgl4 of the fourth cemented lens GL4 is -14.24 mm.

[0076] The refractive index nd16 of the sixteenth lens L16 is 1.8, the focal length fl17 of the seventeenth lens L17 is 54.15 mm, the air gap between the fifth cemented lens GL5 and the sixteenth lens L16 is 1.5 mm, and the air gap between the sixteenth lens L16 and the seventeenth lens L17 is 0.15 mm.

[0077] The lens parameters of the 25x liquid immersion objective lens of Example 2 are shown in Table 2.

[0078] Table 2

[0079] In this example, when the cover glass thickness becomes 0.11 mm, the distance d1 between the seventh lens L7 and the third cemented lens GL3 is 0.78 mm, and the distance d2 between the third cemented lens GL3 and the fourth cemented lens GL4 is 0.9 mm.

[0080] When the thickness of the cover glass becomes 0.23 mm, the distance d1 between the seventh lens L7 and the third cemented lens GL3 is 0.7 mm, and the distance d2 between the third cemented lens GL3 and the fourth cemented lens GL4 is 0.98 mm.

[0081] from Figures 15 to 17 Field curvature curves and Figures 18 to 20 From the distortion curve, we can see that the maximum field curvature at the edge of the field of view within the full aperture range under different cover glass thicknesses is no more than 2um, and the maximum distortion is within 0.3%. Both field curvature and distortion are well corrected.

[0082] from Figure 21 to Figure 23 It can be seen from the optical transfer function MTF curve that the cutoff frequency of the optical system is 4000lp / mm, and the MTF curves of each field of view under different cover glass thicknesses are close to the diffraction limit, and the system can achieve good imaging quality.

[0083] from Figures 24 to 26 As can be seen from the axial aberration curve, spherical aberration has been strictly corrected within the full aperture range, and the spectrum covers 410nm~656nm, meeting the requirements of apochromatism.

[0084] Example 3: Figure 27 As shown, the 25x liquid immersion objective consists of a front lens group M1, a middle lens group M2, and a rear lens group M3. The focal length of the 25x liquid immersion objective is fobj = 7.99mm, NA = 1.05, magnification β = -25×, immersion layer thickness is 0.55mm, cover glass thickness is 0.17mm, spectral range is 410nm-656nm, field of view range is 25mm, and the immersion medium is silicone oil. The 25x liquid immersion objective has the following features:

[0085] The focal length of the front lens group M1 is fm1=7.62mm, the focal length of the middle lens group M2 is fm2=-73.82mm, the focal length of the rear lens group M3 is fm3=80.97mm, the refractive index of the first lens L1 is nd1=1.5, the refractive index of the second lens L2 is nd2=1.88, and nd2-nd1=0.38. The Abbe number of the first lens L1 is vd1=69.5, the Abbe number of the second lens L2 is vd2=40.8, and |vd1-vd2|=28.7; the focal length of the first cemented lens GL1 is 24.88 mm, the focal length fl3 of the third lens L3 is 17.68 mm, the Abbe number of the fourth lens L4 is vd4=95, the Abbe number of the fifth lens L5 is vd5=44.1, and the Abbe number of the sixth lens L6 is vd6=90.9, with |vd4-vd5|=50.9 and |vd5-vd6|=46.8.

[0086] The seventh lens element L7 has a refractive index of nd7 = 1.95, a focal length fl7 of 55.68 mm, an outer diameter of d = 20 mm, and a value of fl7 / d = 2.78. The air gap between the first cemented lens GL1 and the third lens L3 is 0.1 mm, the air gap between the third lens L3 and the second cemented lens GL2 is 0.13 mm, and the air gap between the second cemented lens GL2 and the seventh lens L7 is 0.2 mm.

[0087] The Abbe number vd8 of the eighth lens element L8 is 90.2, the Abbe number vd9 of the ninth lens element L9 is 36.4, and the Abbe number vd10 of the tenth lens element L10 is 94.9, with |vd8 - vd9| equal to 53.8 and |vd9 - vd10| equal to 58.5. The focal length fgl3 of the third cemented lens GL3 is 68.07 mm, and the air gap between the seventh lens element L7 and the third cemented lens GL3 is 0.8 mm.

[0088] The Abbe number vd11 of the eleventh lens L11 is 46.6, the Abbe number vd12 of the twelfth lens L12 is 94.8, and the Abbe number vd13 of the thirteenth lens L13 is 27.5. |vd11-vd12| is 48.2, and |vd12-vd13| is 67.3. The focal length fgl4 of the fourth cemented lens GL4 is -18.68 mm.

[0089] The refractive index nd16 of the sixteenth lens L16 is 1.78, the focal length fl17 of the seventeenth lens L17 is 52.48 mm, the air gap between the fifth cemented lens GL5 and the sixteenth lens L16 is 2 mm, and the air gap between the sixteenth lens L16 and the seventeenth lens L17 is 0.1 mm.

[0090] The lens parameters of the 25x liquid immersion objective lens of Example 3 are shown in Table 3.

[0091] Table 3

[0092] In this example, when the cover glass thickness becomes 0.11 mm, the distance d1 between the seventh lens L7 and the third cemented lens GL3 is 0.9 mm, and the distance d2 between the third cemented lens GL3 and the fourth cemented lens GL4 is 0.9 mm.

[0093] When the thickness of the cover glass becomes 0.23 mm, the distance d1 between the seventh lens L7 and the third cemented lens GL3 is 0.7 mm, and the distance d2 between the third cemented lens GL3 and the fourth cemented lens GL4 is 1.1 mm.

[0094] from Figures 28 to 30 Field curvature curves and Figure 31 to Figure 33 From the distortion curve, we can see that the maximum field curvature at the edge of the field of view within the full aperture range under different cover glass thicknesses is no more than 4um, and the maximum distortion is within 0.2%. Both field curvature and distortion are well corrected.

[0095] from Figures 34 to 36 It can be seen from the optical transfer function MTF curve that the cutoff frequency of the optical system is 4000lp / mm, and the MTF curves of each field of view under different cover glass thicknesses are close to the diffraction limit, and the system can achieve good imaging quality.

[0096] from Figures 37 to 39 As can be seen from the axial aberration curve, spherical aberration has been strictly corrected within the full aperture range, and the spectrum covers 410nm~656nm, meeting the requirements of apochromatism.

Claims

1. A 25x liquid immersion objective lens for microscopic imaging, wherein the immersion liquid in the liquid immersion objective lens is silicone oil immersion, characterized in that From the object side to the image side, the lens comprises a front lens group with positive focal power, an intermediate lens group with negative focal power, and a rear lens group with positive focal power, which are arranged in sequence on the same optical axis. The focal length fobj of the entire 25x liquid immersion objective lens is 7.6mm~8.4mm. The focal length fm1 of the front lens group satisfies: 7mm≤fm1≤9mm, the focal length fm2 of the intermediate lens group satisfies: -200mm≤fm2≤-60mm, and the focal length fm3 of the rear lens group satisfies: 80mm≤fm3≤120mm. The refractive index nd1 of the first lens in the front lens group satisfies: 1.4<nd1<1.5, and the refractive index nd1 of the first lens in the intermediate lens group satisfies: 1.4<nd1<1.

5. The invention comprises a third cemented lens with a focal length of 40 mm to 70 mm that is movable along the optical axis, and a fourth cemented lens with a focal length of -20 mm to -10 mm that is fixed in position; the air gap between the third cemented lens and the last lens in the front lens group varies in the range of 0.7 mm to 0.9 mm; the last lens in the front lens group is a positive lens with a refractive index greater than 1.9, a focal length of 45 mm to 60 mm, and a focal length to outer diameter ratio greater than 2; the rear lens group comprises a fifth cemented lens with negative focal power, a sixteenth lens with positive focal power, and a seventeenth lens with positive focal power; the refractive index of the sixteenth lens is greater than 1.

75.

2. A 25x liquid immersion objective lens for microscopic imaging according to claim 1, characterized in that The front lens group consists of a first cemented lens with a focal length of 20mm to 40mm, a third lens with a focal length of 15mm to 30mm, a second cemented lens, and a seventh lens with a focal length of 45mm to 60mm. The first cemented lens consists of a first lens and a second lens. The refractive index of the first lens satisfies: 1.4<nd1<1.5, the refractive index nd1 of the first lens and the refractive index nd2 of the second lens satisfy: nd2-nd1>0.35, and the Abbe number vd1 of the first lens and the Abbe number vd2 of the second lens satisfy: | vd1-vd2|≥25, the second cemented lens consists of a fourth lens, a fifth lens and a sixth lens, the fourth lens is a positive lens, the fifth lens is a negative lens, and the sixth lens is a positive lens, satisfying the following: |vd4-vd5|≥40 and |vd5-vd6|≥40, wherein vd4 is the Abbe number of the fourth lens, vd5 is the Abbe number of the fifth lens, and vd6 is the Abbe number of the sixth lens. The air gap between the seventh lens and the second cemented lens varies in the range of 0.7 mm to 0.9 mm.

3. A 25x liquid immersion objective lens for microscopic imaging according to claim 2, characterized in that The third cemented lens is composed of an eighth lens with positive focal power, a ninth lens with negative focal power and a tenth lens with positive focal power, and the fourth cemented lens is composed of an eleventh lens with negative focal power, a twelfth lens with positive focal power and a thirteenth lens with negative focal power.

4. A 25x liquid immersion objective lens for microscopic imaging according to claim 3, characterized in that The first lens is a hemispherical lens with a flat object side, the second lens is a meniscus lens with a concave object side, the third lens is a meniscus lens with a concave object side, the eleventh lens has a convex object side and a concave image side, the twelfth lens has a convex object side and a convex image side, the sixteenth lens is a meniscus lens with a concave object side and a convex image side, and the seventeenth lens has a convex object side and a convex image side.

5. A 25x liquid immersion objective lens for microscopic imaging according to claim 2, characterized in that The fifth cemented lens is composed of a fourteenth lens with negative optical power and a fifteenth lens with positive optical power. The fourteenth lens has a concave surface on the object side and a concave surface on the image side, and the fifteenth lens has a convex surface on the object side and a convex surface on the image side.

6. A 25x liquid immersion objective lens for microscopic imaging according to claim 3, characterized in that The Abbe number vd8 of the eighth lens, the Abbe number vd9 of the ninth lens, and the Abbe number vd10 of the tenth lens satisfy: |vd8-vd9|≥40 and |vd9-vd10|≥40, and the Abbe number vd11 of the eleventh lens, the Abbe number vd12 of the twelfth lens, and the Abbe number vd13 of the thirteenth lens satisfy: |vd11-vd12|≥40 and |vd12-vd13|≥40.

7. A 25x liquid immersion objective lens for microscopic imaging according to claim 2, characterized in that The air gap between the first cemented lens and the third lens is 0.1mm~0.2mm, the air gap between the third lens and the second cemented lens is 0.1mm~0.2mm, the air gap between the second cemented lens and the seventh lens is 0.1mm~0.2mm, the air gap between the fifth cemented lens and the sixteenth lens is 1mm~2mm, and the air gap between the sixteenth lens and the seventeenth lens is 0.1mm~0.2mm.

Images