Apochromatic objective lens

Abstract

The utility model relates to an apochromatic objective lens. An apochromatic objective lens may include: a first optical module including, in order from a first side to a second side: a first concave lens; the concave surface of the second meniscus lens faces the first concave lens; the concave surface of the third meniscus lens faces the second meniscus lens; the second optical module is arranged on the second side of the first optical module and comprises a fourth convex lens, a fifth convex lens and a sixth convex lens which are arranged in sequence; a fifth concave lens; a sixth convex lens; a seventh convex lens; the convex surface of the eighth meniscus lens faces the seventh convex lens; the concave surface of the ninth meniscus lens faces the eighth meniscus lens; a tenth convex lens; and the convex surface of the eleventh meniscus lens faces the tenth convex lens. The distance between the lenses and the non-doublet structure avoid the interaction force between the lenses caused by thermal expansion and cold contraction, so that the apochromatic objective lens can work at low temperature and room temperature, and the reliability and stability of the apochromatic objective lens are improved.

Description

Technical Field

[0001] The utility model relates to an apochromatic objective lens with a long working distance which is suitable for low temperature and room temperature environments. Background Art

[0002] In recent years, with the development of quantum computing and superconducting materials technology, it has become more important to characterize the properties of some substances in extremely low temperature environments close to absolute zero in scientific research activities. In order to describe the changes in the morphology of an object, it is necessary to use an objective lens to photograph and observe its surface; and to characterize phenomena such as photoluminescence, it is necessary to use an objective lens to collect, process and analyze its fluorescence. The reliability and stability of the objective lens in a low temperature environment is directly related to the authenticity and efficiency of experiments or scientific research.

[0003] There are many objectives on the market, including those with long working distances, but they usually use double or triple cemented lenses. However, such objectives may crack when used in room temperature and low temperature environments for a long time, which will destroy the relative position between lenses, cause the position of components to change, and reduce image quality.

[0004] Therefore, there is still a need for an objective lens that has a long working distance and is suitable for use in extremely low temperature as well as room temperature environments and has improved reliability and stability. Utility Model Content

[0005] In order to observe and analyze samples in an extremely low temperature environment close to absolute zero (for example, liquid helium temperature of about 4K), and to avoid damage to double-cemented or multi-cemented lenses during high and low temperature cycles, which may lead to a decrease in image quality, the utility model proposes a new type of objective lens. The objective lens does not include a cemented lens, and the spacing between lenses can be greater than 0.4mm, at least greater than 0.2mm. The thickness of the air gap at the edge of the lens can be greater than 0.3mm. It has excellent tolerance performance and effectively avoids the interaction force between lenses caused by thermal expansion and contraction of the lens, thereby improving the reliability and stability of the objective lens. Based on this design, an objective lens with a modulation transfer function (MTF) close to the diffraction limit was developed, which achieves achromatic aberration in a low temperature environment and has good object telecentricity and full-field optical performance. In addition, the low-temperature objective lens can also work at room temperature.

[0006] According to one embodiment, an objective lens may include a first optical module and a second optical module. The first optical module may include: a first concave lens; a second meniscus lens, whose concave surface faces the first concave lens; and a third meniscus lens, whose concave surface faces the second meniscus lens, arranged in sequence from the first side to the second side. The second optical module is disposed on the second side of the first optical module and includes: a fourth convex lens; a fifth concave lens; a sixth convex lens; a seventh convex lens; an eighth meniscus lens, whose convex surface faces the seventh convex lens; a ninth meniscus lens, whose concave surface faces the eighth meniscus lens; a tenth convex lens; and an eleventh meniscus lens, whose convex surface faces the tenth convex lens.

[0007] In one embodiment, the center distance between adjacent lenses in the first optical module and the second optical module is greater than or equal to 0.2 mm, preferably greater than or equal to 0.3 mm, and more preferably greater than or equal to 0.4 mm.

[0008] In one embodiment, the ratio between the focal length of the first concave lens and the total focal length of the objective lens is in the range of 2.0-4.0, the second meniscus lens is a negative lens, and the ratio between the focal length of the second meniscus lens and the total focal length of the objective lens is in the range of 3.5-5.5, the third meniscus lens is a positive lens, and the ratio between the focal length of the third meniscus lens and the total focal length of the objective lens is in the range of 3.5-5.5. The first optical module including the first concave lens, the second meniscus lens and the third meniscus lens is formed as a negative lens, and the ratio between its focal length and the total focal length of the objective lens is in the range of 3.1-8.0, preferably in the range of 5.5-7.5.

[0009] In one embodiment, the ratio of the focal length of the fourth convex lens to the total focal length of the objective lens is in the range of 6.5-9.5, and the ratio of the focal length of the fifth concave lens to the total focal length of the objective lens is in the range of 2.5-5.5. The fourth convex lens and the fifth concave lens form a first submodule of the second optical module, and the ratio of the focal length of the first submodule to the total focal length of the objective lens is in the range of 7.5-10.0.

[0010] In one embodiment, the ratio of the focal length of the sixth convex lens to the total focal length of the objective lens is in the range of 7.0-15.0, the ratio of the focal length of the seventh convex lens to the total focal length of the objective lens is in the range of 8.0-16.0, the eighth meniscus lens is a positive lens, and the ratio of the focal length of the eighth meniscus lens to the total focal length of the objective lens is in the range of 6.0-15.0. The sixth convex lens, the seventh convex lens and the eighth meniscus lens form a second submodule of the second optical module, and the ratio of the focal length of the second submodule to the total focal length of the objective lens is in the range of 2.5-5.0, preferably in the range of 2.5-4.5.

[0011] In one embodiment, the ninth meniscus lens is a negative lens, and the ratio of the focal length of the ninth meniscus lens to the total focal length of the objective lens is in the range of 3.5-6.2, the ratio of the focal length of the tenth convex lens to the total focal length of the objective lens is in the range of 5.0-7.0, the eleventh meniscus lens is a positive lens, and the ratio of the focal length of the eleventh meniscus lens to the total focal length of the objective lens is in the range of 5.0-7.0. The ninth meniscus lens, the tenth convex lens and the eleventh meniscus lens form a third submodule of the second optical module, and the ratio of the focal length of the third submodule to the total focal length of the objective lens is in the range of 5.0-9.0.

[0012] In one embodiment, the refractive index of each of the third meniscus lens, the fifth concave lens, the ninth meniscus lens and the eleventh meniscus lens is greater than 1.7, and the refractive index of each of the sixth convex lens, the seventh convex lens, the eighth meniscus lens and the tenth convex lens is less than 1.65 and greater than 1.

[0013] In one embodiment, each of the first concave lens and the fifth concave lens is a biconcave lens, and each of the fourth convex lens, the sixth convex lens, the seventh convex lens and the tenth convex lens is a biconvex lens.

[0014] In one embodiment, two surfaces of each of the first concave lens to the eleventh meniscus lens are standard spherical surfaces.

[0015] In one embodiment, the second optical module further includes: a stop, which is arranged on the object plane side of the fourth convex lens.

[0016] In one embodiment, the distance between the first optical module and the second optical module is greater than the distance between any two adjacent lenses in the first optical module, and greater than the distance between any two adjacent lenses in the second optical module.

[0017] The above and other features and advantages of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram showing a first optical module of an objective lens according to an embodiment of the present utility model;

[0019] Figure 2 A schematic diagram showing a first optical module of an objective lens according to an embodiment of the present utility model;

[0020] Figure 3 A modulation transfer function (MTF) curve diagram of an objective lens according to an embodiment of the utility model is shown;

[0021] Figure 4 The figure shows an axial aberration curve of an objective lens according to an embodiment of the present utility model. DETAILED DESCRIPTION

[0022] Exemplary embodiments of the present invention are described below with reference to the accompanying drawings.

[0023] The objective lens of the present invention may include a first optical module 110 and a second optical module 120, the optical axes of which are aligned with each other, and the first optical module 110 may be arranged on a first side, such as an object plane side, and the second optical module 120 may be arranged on a second side, such as an image plane side. It should be understood that, depending on the specific application scenario, the first side may also be the image plane side, and the second side may also be the object plane side, and the present application does not have any specific restrictions on this. First, refer to Figure 1 , which shows a schematic diagram of a first optical module 110 of an objective lens according to an embodiment of the present utility model. Figure 1 As shown, the first optical module 110 may include a first concave lens L1, a second meniscus lens L2, and a third meniscus lens L3 which are sequentially arranged from a first side, such as an object plane side, toward a second side, such as an image plane side, wherein a concave surface of the second meniscus lens L2 faces the first concave lens L1, and a convex surface faces the third meniscus lens L3, and a concave surface of the third meniscus lens L3 faces the second meniscus lens L2, and a convex surface faces the image plane side, i.e., toward the second optical module 120 (see Figure 2 ).

[0024] The first concave lens L1 may be a double concave lens, both concave surfaces of which may be standard spherical surfaces, and the curvature radius of the object-side concave surface may be smaller than the curvature radius of the image-side concave surface. L1 The ratio to the total focal length F of the objective lens can be in the range of 2.0-4.0.

[0025] A meniscus lens is a lens with one concave surface and one convex surface. Depending on the degree of concavity and convexity of the two surfaces (i.e., the radius of curvature), the meniscus lens can have a positive focal length or a negative focal length. In one embodiment, the concave surface and the convex surface of the second meniscus lens L2 can both be standard spherical surfaces, and the radius of curvature of the concave surface can be smaller than the radius of curvature of the convex surface, that is, the edge of the second meniscus lens L2 can be thicker than the center, thereby forming a negative lens. In one embodiment, the focal length F of the second meniscus lens L2 is L2 The ratio to the total focal length F of the objective lens can be in the range of 3.5-5.5.

[0026] In one embodiment, the concave surface and the convex surface of the third meniscus lens L3 may also be standard spherical surfaces, but the curvature radius of the concave surface may be greater than the curvature radius of the convex surface, that is, the center of the third meniscus lens L3 may be thicker than the edge, thereby forming a positive lens. In one embodiment, the focal length F of the third meniscus lens L3 is L3 The ratio between the total focal length F of the objective lens can be in the range of 3.5-5.5. In one embodiment, the refractive index of the third meniscus lens L3, or the refractive index of the material forming the third meniscus lens L3, can be greater than 1.7. In the present application, if the refractive index of a lens is not specifically described, the lens can be formed of a material with a larger refractive index, such as a refractive index greater than 1.7, or can be formed of a material with a smaller refractive index, such as a refractive index less than 1.65, or can be between the two.

[0027] The first optical module 110 composed of the first concave lens L1, the second meniscus lens L2 and the third meniscus lens L3 can be formed as a negative lens. In the present application, a negative lens refers to a lens that diverges an incident light beam, and a positive lens refers to a lens that converges an incident light beam. The combined focal length of each lens in the first optical module 110, that is, the focal length F of the first optical module 110, is 110 , and the total focal length F of the objective lens may be in the range of 3.1-8.0, preferably in the range of 5.5-7.5. In the entire objective lens structure, the first optical module 110 is used to provide negative optical power.

[0028] Figure 2 FIG. 1 is a schematic diagram of a second optical module 120 of an objective lens according to an embodiment of the present invention. As mentioned above, the second optical module 120 can be arranged on a second side of the first optical module 110, such as an image plane side, and aligned with the optical axis of the first optical module 110. Figure 2As shown, from the first side, such as the object plane side, toward the second side, such as the image plane side, the second optical module 120 may include an aperture 121, a fourth convex lens L4, a fifth concave lens L5, a sixth convex lens L6, a seventh convex lens L7, an eighth meniscus lens L8, a ninth meniscus lens L9, a tenth convex lens L10, and an eleventh meniscus lens L11 arranged in sequence.

[0029] The aperture 121 is used to limit the size of the light beam passing through the objective lens, and it can be formed by an opaque material with a through hole at the center, such as a light barrier. The size of the central through hole of the aperture 121 can depend on the size of the entire objective lens, that is, the diameter of each lens. The aperture 121 can be regarded as a part of the second optical module 120, or it can also be regarded as a separate optical element arranged between the first optical module 110 and the second optical module 120. In one embodiment, the distance between the aperture 121 and the third meniscus lens L3 can be greater than the distance between the aperture 121 and the fourth convex lens L4. In one embodiment, the distance between the first optical module 110 and the second optical module 120, that is, the distance between the aperture 121 and the third meniscus lens L3, can be much greater than the distance between any adjacent lenses in the first optical module 110 and the second optical module 120. For example, as an example, the distance between the first optical module 110 and the second optical module 120 can be as high as tens of millimeters, such as about 20 mm, and the distance between adjacent lenses can be in the range of 0.2 mm to several mm, such as 10 mm.

[0030] like Figure 2 As shown, the fourth convex lens L4 may be a biconvex lens, and both convex surfaces thereof may be standard spherical surfaces, but the curvature radii may be different from each other. In one embodiment, the curvature radius of the convex surface on the object plane side may be greater than the curvature radius of the convex surface on the image plane side. The focal length F of the fourth convex lens L4 is L4 The ratio to the total focal length F of the objective lens can be in the range of 6.5-9.5.

[0031] The fifth concave lens L5 may be a double concave lens, and its two concave surfaces may both be standard spherical surfaces, but the sizes of the curvature radii may be different from each other. In one embodiment, the curvature radius of the concave surface on the object plane side may be smaller than the curvature radius of the concave surface on the image plane side. The fifth concave lens L5 may be formed of a material having a relatively large refractive index, for example, a refractive index greater than 1.7. In one embodiment, the focal length F of the fifth concave lens L5 is L5 The ratio to the total focal length F of the objective lens can be in the range of 2.5-5.5.

[0032] The fourth convex lens L4 and the fifth concave lens L5 form a first submodule 122 of the second optical module 120. In one embodiment, the focal length F of the first submodule 122 is 122The ratio between the total focal length F of the objective lens can be in the range of 7.5-10.0. In the objective lens structure, the first submodule 122 mainly bears a smaller optical focal length, and can contain special dispersion glass for achromatism.

[0033] The sixth convex lens L6 may be a biconvex lens, both convex surfaces of which may be standard spherical surfaces, but the radii of curvature may be different from each other. In one embodiment, the radius of curvature of the convex surface on the object plane side may be greater than the radius of curvature of the convex surface on the image plane side. The sixth convex lens L6 may be formed of a material having a relatively small refractive index, for example, the refractive index may be less than 1.65. In one embodiment, the focal length F of the sixth convex lens L6 is L6 The ratio to the total focal length F of the objective lens can be in the range of 7.0-15.0.

[0034] The seventh convex lens L7 may be a biconvex lens, both convex surfaces of which may be standard spherical surfaces and may have substantially the same or similar curvature radii, for example, the aberration amplitude of the curvature radius may be within the range of ±15%, preferably within the range of ±10%. The seventh convex lens L7 may be formed of a material having a relatively small refractive index, for example, the refractive index may be less than 1.65. In one embodiment, the focal length F of the seventh convex lens L7 is L7 The ratio to the total focal length F of the objective lens can be in the range of 8.0-16.0.

[0035] The concave surface and the convex surface of the eighth meniscus lens L8 may both be standard spherical surfaces, wherein the convex surface may face the seventh convex lens L7, and the concave surface may face the ninth meniscus lens L9, and the curvature radius of the convex surface may be smaller than the curvature radius of the concave surface, so that the eighth meniscus lens L8 may be formed as a positive lens. The eighth meniscus lens L8 may be formed of a material having a relatively small refractive index, for example, the refractive index may be less than 1.65. In one embodiment, the focal length F of the eighth meniscus lens L8 is L8 The ratio to the total focal length F of the objective lens can be in the range of 6.0-15.0.

[0036] The sixth convex lens L6, the seventh convex lens L7 and the eighth meniscus lens L8 may form a second submodule 124 of the second optical module 120. In one embodiment, the focal length F of the second submodule 124 is 124 The ratio to the total focal length of the objective lens may be in the range of 2.5-5.0, preferably in the range of 2.5-4.5. The second submodule 124 may be used to correct various aberrations in the optical path.

[0037] The concave surface and the convex surface of the ninth meniscus lens L9 may both be standard spherical surfaces, wherein the concave surface may face the eighth meniscus lens L8, and the convex surface may face the tenth convex lens L10, and the curvature radius of the concave surface may be smaller than the curvature radius of the convex surface, so that the ninth meniscus lens L9 may be formed as a negative lens. The ninth meniscus lens L9 may be formed of a material having a relatively large refractive index, for example, the refractive index may be greater than 1.7. In one embodiment, the focal length F of the ninth meniscus lens L9 is L9 The ratio to the total focal length F of the objective lens can be in the range of 3.5-6.2.

[0038] The tenth convex lens L10 may be a biconvex lens, both convex surfaces of which may be standard spherical surfaces, wherein the curvature radius of the convex surface facing the ninth meniscus lens L9 may be smaller than the curvature radius of the convex surface facing the eleventh meniscus lens L11. The tenth convex lens L10 may be formed of a material having a relatively small refractive index, for example, the refractive index may be less than 1.65. In one embodiment, the focal length F of the tenth convex lens L10 is L10 The ratio to the total focal length F of the objective lens can be in the range of 5.0-7.0.

[0039] The concave surface and the convex surface of the eleventh meniscus lens L11 can both be standard spherical surfaces, wherein the convex surface can face the tenth convex lens L10, and the concave surface can face the image plane side, and the curvature radius of the convex surface can be smaller than the curvature radius of the concave surface, so that the eleventh meniscus lens L11 can be formed as a positive lens. The eleventh meniscus lens L11 can be formed of a material with a relatively large refractive index, for example, the refractive index can be greater than 1.7. In one embodiment, the focal length F of the eleventh meniscus lens L11 is L11 The ratio to the total focal length F of the objective lens can be in the range of 5.0-7.0.

[0040] The ninth meniscus lens L9, the tenth convex lens L10, and the eleventh meniscus lens L11 may form a third submodule 126 of the second optical module 120. In one embodiment, the focal length F of the third submodule 126 is 126 The ratio between the total focal length F of the objective lens can be in the range of 5.0-9.0. The third submodule 126 can bear positive optical power to supplement the optical power required by the objective lens.

[0041] Figure 1 and Figure 2 Only the individual lenses and apertures in the objective lens are shown, but it should be understood that the individual lenses and apertures can be fixed at the edge by the lens barrel of the objective lens, for example, the lens barrel can be formed of opaque plastic, or a thin metal layer can be coated on the outer surface of the opaque plastic. Figure 1 and Figure 2As shown, the adjacent lenses in the first optical module 110 and the second optical module 120 can be spaced apart from each other, that is, they are not in contact with each other and are not glued. In one embodiment, the center spacing between adjacent lenses can be greater than or equal to 0.2mm, preferably greater than or equal to 0.3mm, and more preferably greater than or equal to 0.4mm. The spacing at the edge of the lens can be greater than or equal to 0.2mm, preferably greater than or equal to 0.3mm. It should be understood that if each lens is formed larger, that is, has a larger diameter, the spacing between the lenses can be set larger. In this way, even if each lens will expand and contract due to temperature changes, the lenses will not contact each other and generate stress, and this stress may cause irreversible damage to the lens. Since there is no glue structure between the lenses, the debonding phenomenon caused by low temperature or high and low temperature changes can be avoided. Therefore, the object lens of the utility model has excellent reliability and stability. The object lens of the utility model with the above-mentioned characteristics can achieve a numerical aperture (NA) of 0.5-0.7, can achieve achromatic aberration in a low temperature environment, and has good object telecentricity and full field optical performance. This objective can also operate at room temperature.

[0042] Table 1 below shows parameters of various lenses in an objective lens according to an embodiment.

[0043] Table 1

[0044] surface Surface type Radius of curvature Thickness(mm) Refractive Index Abbe number 1 Standard sphere -8.38 1.69 1.81 40.8 2 Standard sphere 224.19 0.91 3 Standard sphere -6.61 1.75 1.89 37.3 4 Standard sphere -17.63 0.47 5 Standard sphere -15.44 2.99 1.89 20 6 Standard sphere -9.77 21.80 Aperture flat Infinity 0.3 7 Standard sphere 68.62 4.42 1.54 74.7 8 Standard sphere -16.43 0.30 9 Standard sphere -18.82 1.00 1.89 40 10 Standard sphere 108.80 0.40 11 Standard sphere 162.17 4.22 1.54 74.7 12 Standard sphere -21.44 0.30 13 Standard sphere 40.79 4.10 1.62 63.3 14 Standard sphere -40.66 0.30 15 Standard sphere 21.01 4.19 1.60 62.5 16 Standard sphere 241.96 2.00 17 Standard sphere -24.98 1.00 1.72 24.5 18 Standard sphere -74.15 0.30 19 Standard sphere 19.49 4.96 1.64 67.7 20 Standard sphere -31.44 0.30 21 Standard sphere 10.81 3.65 1.89 21.2 22 Standard sphere 16.70 9.37

[0045] In Table 1, surfaces 1-22 are surfaces from the object plane side to the image plane side of the first concave lens L1 to the eleventh meniscus lens L11, respectively. For example, surfaces 1 and 2 define two surfaces of the first concave lens L1, wherein the radius of curvature of surface 1 is a negative value, indicating that surface 1 is concave toward the image plane side, and the radius of curvature of surface 2 is a positive value, indicating that surface 2 is concave toward the object plane side. The thickness of surface 1 is the distance between surface 1 and surface 2 at the optical axis position, that is, the center thickness of the first concave lens L1, and the thickness of surface 2 is the distance between surface 2 and surface 3 at the optical axis position, that is, the center distance between the first concave lens L1 and the second meniscus lens L2. The refractive index and Abbe number of surface 1 are the refractive index and Abbe number of the material forming the first concave lens L1 (that is, the material located between surface 1 and surface 2), and because there is an air gap between surface 2 and surface 3, the refractive index and Abbe number of surface 2 are not shown in Table 1. In the example shown in Table 1, the refractive index of the first concave lens L1 is 1.81, the Abbe number is 40.8, the center thickness is 1.69 mm, and the center distance between the first concave lens L1 and the second meniscus lens L2 is 0.91 mm.

[0046] Similarly, surfaces 3 and 4 define two surfaces of the second meniscus lens L2, wherein the radius of curvature of surface 3 is a negative value, indicating that surface 3 is concave toward the image plane side, and the radius of curvature of surface 4 is also a negative value, indicating that surface 4 is convex toward the image plane side, so surfaces 3 and 4 define a meniscus lens. In the example shown in Table 1, the refractive index of the second meniscus lens L2 is 1.89, the Abbe number is 37.3, the center thickness is 1.75 mm, and the center distance between the second meniscus lens L2 and the third meniscus lens L3 is 0.47 mm.

[0047] Surfaces 5 and 6 define two surfaces of the third meniscus lens L3, wherein surface 3 is concave toward the image plane side, and surface 4 is convex toward the image plane side, thereby defining a meniscus lens. In the example shown in Table 1, the refractive index of the third meniscus lens L3 is 1.89, the Abbe number is 20.0, the center thickness is 2.99 mm, and the center distance between the third meniscus lens L3 and the next optical element, namely the aperture, that is, the center distance between the first optical module 110 and the second optical module 120 is 21.80 mm.

[0048] In Table 1, for simplicity, the aperture is represented as an imaginary plane without thickness, that is, with an infinite radius of curvature, and its thickness of 0.3 mm refers to the center distance between the aperture and the next optical element, namely the fourth convex lens L4.

[0049] Surfaces 7 and 8 define two surfaces of the fourth convex lens L4, wherein the curvature radius of surface 7 is a positive value, indicating that surface 7 is convex toward the object plane side, and the curvature radius of surface 8 is a negative value, indicating that surface 8 is convex toward the image plane side, so surfaces 7 and 8 define a double convex lens. In the example shown in Table 1, the refractive index of the fourth convex lens L4 is 1.54, the Abbe number is 74.7, the center thickness is 4.42 mm, and the center distance between the fourth convex lens L4 and the fifth concave lens L5 is 0.30 mm.

[0050] Similarly, in the example shown in Table 1, the surface 9 of the fifth concave lens L5 is concave toward the image plane side, the surface 10 is concave toward the object plane side, the refractive index is 1.89, the Abbe number is 40, the center thickness is 1.00 mm, and the center distance from the sixth convex lens L6 is 0.40 mm; the surface 11 of the sixth convex lens L6 is convex toward the object plane side, the surface 12 is convex toward the image plane side, the refractive index is 1.54, the Abbe number is 74.7, the center thickness is 4.22 mm, and the center distance from the seventh convex lens L7 is 0.3 0mm; the surface 13 of the seventh convex lens L7 is convex toward the object plane side, the surface 14 is convex toward the image plane side, the refractive index is 1.62, the Abbe number is 63.3, the center thickness is 4.10mm, and the center distance from the eighth meniscus lens L8 is 0.30mm; the surface 15 of the eighth meniscus lens L8 is convex toward the object plane side, the surface 16 is concave toward the object plane side, the refractive index is 1.60, the Abbe number is 62.5, the center thickness is 4.19mm, and the center distance from the ninth meniscus lens L9 is 2.00mm;

[0051] The surface 17 of the ninth meniscus lens L9 is concave toward the image plane side, the surface 18 is convex toward the image plane side, the refractive index is 1.72, the Abbe number is 24.5, the center thickness is 1.00 mm, and the center distance from the tenth convex lens L10 is 0.30 mm; the surface 19 of the tenth convex lens L10 is convex toward the object plane side, the surface 20 is convex toward the image plane side, the refractive index is 1.64, the Abbe number is 67.7, the center thickness is 4.96 mm, and the center distance from the eleventh meniscus lens L11 is 0.30 mm; the surface 21 of the eleventh meniscus lens L11 is convex toward the object plane side, the surface 22 is concave toward the object plane side, the refractive index is 1.89, the Abbe number is 21.2, the center thickness is 3.65 mm, and the distance from the image plane is 9.37 mm.

[0052] The system focal length (i.e., total focal length) of the objective lens formed according to the characteristic values ​​shown in Table 1 can be about 4.0 mm, the working distance can be greater than about 8.0 mm, the entrance pupil diameter is 4.3 mm, and the total length of the objective lens can be less than 75 mm, which can achieve good apochromatic characteristics. The working distance of the existing objective lens with a numerical aperture of about 0.6 is generally 2-3 mm, so the utility model can provide an objective lens with a significantly longer working distance.

[0053] Figure 3 The modulation transfer function (MTF) curve of the objective lens example in Table 1 is shown, wherein the solid line is the MTF curve of the diffraction of complex light, i.e., the modulus of the optical transfer function (OTF), and the dotted line is the MTF curve of the objective lens example, and the wavelength is the weighted average of the three colors of red, green and blue. It can be understood that the optical transfer function OTF includes an amplitude part and a phase part, the amplitude part is represented by the modulation transfer function MTF, and the phase part is represented by the phase transfer function PTF. Figure 3 The OTF modulus, i.e., the MTF curve is shown. Figure 3 As shown in FIG. 1 , when the spatial frequency is 500 lp / mm, where lp represents a line pair, the diffraction-limited OTF value is 0.63, and the OTF value of the objective lens example in Table 1 is 0.61, which is close to the diffraction limit. Since the MTF curves of the light in the meridional direction and the sagittal direction are substantially overlapped, Figure 3 The corresponding MTF curves for the light in the tangential direction and the light in the sagittal direction are not shown.

[0054] Figure 4 The axial aberration curves of the objective lens examples are shown in Table 1. Figure 4 It can be seen that for the three colors of light with wavelengths of 0.486μm, 0.587μm and 0.656μm, the axial aberration is very small in the entire pupil range, and the red, blue and green lights are almost completely overlapped at the 0.7 pupil, which effectively corrects the secondary spectrum. Therefore, this objective is an apochromatic objective with excellent imaging performance and outstanding fluorescence collection ability.

[0055] It should be understood that the values ​​shown in Table 1 are only examples, and the present invention is not limited thereto. Instead, these values ​​can be adjusted under the teachings of the present invention. For example, when an objective lens with a larger diameter is formed, these values ​​can be changed accordingly.

[0056] Unless the context clearly requires otherwise, throughout the specification and claims, contrary to the exclusive or exhaustive meaning, the words "including", "comprising", etc. should be understood in an inclusive sense, that is, in the sense of "including but not limited to". In the embodiments described above, some commonly used known devices, operations, etc. in the relevant field may be omitted. The wording "connected" generally used here means that two or more elements can be directly connected or connected by means of one or more intermediate elements. In addition, when used in this application, the words "here", "above", "below" and words of similar meanings should refer to the application as a whole, rather than any specific part of the application. When the context permits, the words used in the above description in the singular or plural may also include the plural or singular, respectively. The wording "or" when referring to a list of two or more items covers all of the following interpretations thereof: any item in the list, all items in the list, and any combination of items in the list.

[0057] The above detailed description of the embodiment of the utility model is not intended to be exhaustive or to limit the utility model to the precise form disclosed above. Although the specific embodiment of the utility model and the example for the utility model are described above for the purpose of illustration, as will be appreciated by those skilled in the art, various equivalent modifications within the scope of the utility model are feasible. For example, although a process or block is presented in a given order, an alternative embodiment can perform a process with steps in different orders, or adopt a system with blocks in different orders, and some processes or blocks can be deleted, moved, added, subtracted, combined and / or modified. Each of these processes or blocks can be implemented in a variety of different ways. Similarly, although a process or block is sometimes shown as being executed serially, on the contrary, these processes or blocks can also be executed in parallel, or can be executed at different times.

[0058] Although some embodiments of the utility model have been described, these embodiments have been presented only by way of example, and the embodiments are not intended to limit the scope of the present disclosure. In fact, the novel methods and systems described herein can be implemented in a variety of other forms; in addition, various omissions, substitutions, and changes in the form of the methods and systems described herein can be made without departing from the spirit of the present disclosure. The drawings and their equivalents are intended to cover such forms or modifications that will fall within the scope and spirit of the present disclosure.

Claims

1. An apochromatic objective lens, characterized in that include: The first optical module comprises: First concave lens; a second meniscus lens, the concave surface of which faces the first concave lens; as well as a third meniscus lens, the concave surface of which faces the second meniscus lens; as well as The second optical module is disposed on the second side of the first optical module, and includes: a fourth convex lens; Fifth concave lens; Sixth convex lens; Seventh convex lens; an eighth meniscus lens, a convex surface of which faces the seventh convex lens; a ninth meniscus lens, whose concave surface faces the eighth meniscus lens; Tenth convex lens; as well as The eleventh meniscus lens has a convex surface facing the tenth convex lens.

2. The apochromatic objective lens according to claim 1, characterized in that: A center distance between adjacent lenses in the first optical module and the second optical module is greater than or equal to 0.2 mm.

3. The apochromatic objective lens according to claim 1, characterized in that: The ratio between the focal length of the first concave lens and the total focal length of the objective lens is in the range of 2.0-4.0, The second meniscus lens is a negative lens, and the ratio of the focal length of the second meniscus lens to the total focal length of the objective lens is in the range of 3.5-5.5, The third meniscus lens is a positive lens, and the ratio between the focal length of the third meniscus lens and the total focal length of the objective lens is in the range of 3.5-5.5, The first optical module including the first concave lens, the second meniscus lens and the third meniscus lens is formed as a negative lens, and a ratio between a focal length thereof and a total focal length of the objective lens is in the range of 3.1-8.

0.

4. The apochromatic objective lens according to claim 3, characterized in that: The ratio between the focal length of the fourth convex lens and the total focal length of the objective lens is in the range of 6.5-9.5, The ratio between the focal length of the fifth concave lens and the total focal length of the objective lens is in the range of 2.5-5.5, The fourth convex lens and the fifth concave lens form a first submodule of the second optical module, and a ratio between a focal length of the first submodule and a total focal length of the objective lens is in a range of 7.5-10.

0.

5. The apochromatic objective lens according to claim 4, characterized in that: The ratio of the focal length of the sixth convex lens to the total focal length of the objective lens is in the range of 7.0-15.0, The ratio between the focal length of the seventh convex lens and the total focal length of the objective lens is in the range of 8.0-16.0, The eighth meniscus lens is a positive lens, and the ratio of the focal length of the eighth meniscus lens to the total focal length of the objective lens is in the range of 6.0-15.0, The sixth convex lens, the seventh convex lens and the eighth meniscus lens form a second submodule of the second optical module, and a ratio between a focal length of the second submodule and a total focal length of the objective lens is in the range of 2.5-5.

0.

6. The apochromatic objective lens according to claim 5, characterized in that: The ninth meniscus lens is a negative lens, and the ratio of the focal length of the ninth meniscus lens to the total focal length of the objective lens is in the range of 3.5-6.2, The ratio between the focal length of the tenth convex lens and the total focal length of the objective lens is in the range of 5.0-7.0, The eleventh meniscus lens is a positive lens, and the ratio between the focal length of the eleventh meniscus lens and the total focal length of the objective lens is in the range of 5.0-7.0, The ninth meniscus lens, the tenth convex lens and the eleventh meniscus lens form a third submodule of the second optical module, and a ratio between a focal length of the third submodule and a total focal length of the objective lens is in the range of 5.0-9.

0.

7. The apochromatic objective lens according to any one of claims 1 to 6, characterized in that: The refractive index of each of the third meniscus lens, the fifth concave lens, the ninth meniscus lens and the eleventh meniscus lens is greater than 1.7, and A refractive index of each of the sixth convex lens, the seventh convex lens, the eighth meniscus lens, and the tenth convex lens is less than 1.65 and greater than 1.

8. The apochromatic objective lens according to any one of claims 1 to 6, characterized in that Each of the first concave lens and the fifth concave lens is a biconcave lens, and each of the fourth convex lens, the sixth convex lens, the seventh convex lens, and the tenth convex lens is a biconvex lens.

9. The apochromatic objective lens according to any one of claims 1 to 6, characterized in that Both surfaces of each of the first concave lens to the eleventh meniscus lens are standard spherical surfaces.

10. The apochromatic objective lens according to any one of claims 1 to 6, characterized in that: The second optical module also includes: An aperture stop is arranged on the object plane side of the fourth convex lens.

11. The apochromatic objective lens according to any one of claims 1 to 6, characterized in that: The distance between the first optical module and the second optical module is greater than the distance between any two adjacent lenses in the first optical module, and greater than the distance between any two adjacent lenses in the second optical module.

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