Microobjective

Abstract

The invention provides a microscope objective, and relates to the technical field of optical lenses, the microscope objective comprises a first lens group, a second lens group, a third lens group, a fourth lens group and a plane mirror which are sequentially arranged from an object space to an image space along an incident light direction, and the first lens group has negative focal power and is used for diverging incident light; the second lens group has positive focal power and is used for deflecting incident light and balancing spherical aberration generated by the first lens group; the third lens group comprises a plurality of lens groups, and each lens group is provided with at least two lenses which are arranged in a glued mode and used for achromatism in a wide spectrum range. The fourth lens group is a positive flush lens group and is used for correcting spherical aberration; the plane mirror is used for imaging after refraction. In a light path, the main surface of the lens moves backwards through the combination of the positive lens and the negative lens, a longer working distance is realized while the focal length is ensured, the microscope objective has the characteristics of long working distance and large NA, apoachromatism of a near-infrared band of 750nm-1100nm is realized, and an entrance pupil is effectively increased.

Description

Technical Field

[0001] This application relates to the technical field of optical lenses, and particularly to a microscope objective lens. Background Art

[0002] With the development of the semiconductor industry, there is an increasing demand for high-resolution and long-working-distance microscope objective lenses. In some high-demand laser processing and semiconductor fields, microscope objective lenses with long working distances, large numerical apertures (NAs), and large entrance pupils are required. However, the performance of current products on the market cannot fully meet the various index requirements of customers.

[0003] Currently, for microscope objective lenses with long working distances on the market, their NAs and entrance pupils are not large enough; for microscope objective lenses with large NAs, their working distances and entrance pupils are also not large enough. For example, the working distance of a 20x magnification microscope objective lens on the market is 20 mm, but its NA is only 0.42 and the entrance pupil is 8.4 mm. For microscope objective lenses with an NA of 0.6, their working distances are all less than 12 mm. That is, current products are difficult to meet the requirements of long working distance, large NA, and large entrance pupil simultaneously. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a microscope objective lens that can simultaneously meet the requirements of long working distance, large NA, large entrance pupil, and achromatism.

[0005] On the one hand, the embodiments of this application provide a microscope objective lens, which includes a first lens group, a second lens group, a third lens group, a fourth lens group, and a plane mirror arranged in sequence from the object side to the image side along the incident light direction. The first lens group has a negative focal power and is used to diverge the incident light; the second lens group has a positive focal power and is used to deflect the incident light and balance the spherical aberration generated by the first lens group; the third lens group includes multiple lens groups, and each lens group has at least two lenses glued together for apochromatism in a wide spectral range; the fourth lens group is a positive aplanatic lens group for correcting spherical aberration; the plane mirror is used for imaging after refraction.

[0006] Optionally, the first lens group includes a first lens and a second lens, and both the first lens and the second lens are meniscus negative lenses.

[0007] Optionally, the refractive indices of both the first lens and the second lens are greater than 1.8.

[0008] Optionally, the second lens group includes a third lens and a fourth lens, and both the third lens and the fourth lens are meniscus positive lenses.

[0009] Optionally, the third lens group includes a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, and an eleventh lens. The fifth lens is a meniscus positive lens, the sixth lens is a biconvex positive lens, and the fifth lens and the sixth lens are adhesively disposed; the seventh lens is a meniscus negative lens, the eighth lens is a biconvex positive lens, the ninth lens is a meniscus positive lens, and the seventh lens, the eighth lens, and the ninth lens are adhesively disposed; the tenth lens is a biconvex positive lens, the eleventh lens is a biconcave negative lens, and the tenth lens and the eleventh lens are adhesively disposed.

[0010] Optionally, the refractive index of the fourth lens is less than that of the fifth lens, and the Abbe number of the fourth lens is greater than that of the fifth lens.

[0011] Optionally, the fourth lens group includes a twelfth lens, a thirteenth lens, and a fourteenth lens, and the twelfth lens, the thirteenth lens, and the fourteenth lens are all meniscus positive lenses.

[0012] Optionally, the materials of the third lens, the fourth lens, the sixth lens, the eighth lens, the twelfth lens, the thirteenth lens, and the fourteenth lens are ultra-low dispersion glass materials.

[0013] Optionally, the first lens group, the second lens group, the third lens group, and the fourth lens group are sequentially attached, and there is a spacing between the fourth lens group and the flat mirror.

[0014] Optionally, the total optical path length of the microscopic objective lens from the object side to the image side is 85 nm to 90 nm.

[0015] The microscopic objective lens provided by the embodiment of the present application realizes the rear shift of the main plane of the lens through the combination of positive and negative lenses in the optical path, realizes a longer working distance while ensuring the focal length, enables the microscopic objective lens to have the characteristics of a long working distance and a large NA at the same time, complicates the lens optical path while meeting the parfocal distance, and enables the object to be clearly imaged; the third lens group can realize apochromatism in the near-infrared band of 750 nm to 1100 nm; by using multiple lens groups, the number of lenses is effectively increased, and in combination with the arrangement of the lenses, the entrance pupil is effectively increased, so that the entrance pupil of the lens is large. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0017] Figure 1 is the optical path schematic diagram of the microscope objective lens provided in this embodiment;

[0018] Figures 2a to 2d is the spot diagram of the microscope objective lens provided in this embodiment;

[0019] Figure 3 is the distortion diagram of the microscope objective lens provided in this embodiment;

[0020] Figure 4 is the chromatic aberration diagram of the microscope objective lens provided in this embodiment.

[0021] Icon: 1 - First lens; 2 - Second lens; 3 - Third lens; 4 - Fourth lens; 5 - Fifth lens; 6 - Sixth lens; 7 - Seventh lens; 8 - Eighth lens; 9 - Ninth lens; 10 - Tenth lens; 11 - Eleventh lens; 12 - Twelfth lens; 13 - Thirteenth lens; 14 - Fourteenth lens; 15 - Plane mirror. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application.

[0023] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "inside", "outside", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this application is usually placed during use. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. In addition, terms such as "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0024] It should also be noted that unless otherwise clearly specified and limited, the terms "set", "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0025] Please refer to Figure 1As shown in the figure, an embodiment of the present application provides a microscope objective lens, including: a first lens group, a second lens group, a third lens group, a fourth lens group, and a plane mirror 15 arranged in sequence from the object side to the image side along the incident light direction. The first lens group has a negative optical power and is used to diverge the incident light; the second lens group has a positive optical power and is used to deflect the incident light and balance the spherical aberration generated by the first lens group; the third lens group includes multiple lens groups, and each lens group has at least two lenses arranged in a glued manner for apochromatism in a wide spectral range; the fourth lens group is a positive aplanatic lens group for correcting spherical aberration; the plane mirror 15 is used for imaging after refraction.

[0026] Among them, the first lens group includes a first lens 1 and a second lens 2. The first lens 1 is a meniscus negative lens, and the first lens 1 and the second lens 2 are used to diverge the incident light.

[0027] It can be seen from Figure 1 that the incident light is parallel light. The surface shapes of the first lens 1 and the second lens 2 are the same. The incident surfaces and the exit surfaces of the first lens 1 and the second lens 2 are both bent towards the image side, but their heights in the vertical direction are different. The height of the second lens 2 is greater than that of the first lens 1. In this way, the light diverged by the first lens 1 can enter the second lens 2 and continue to be diverged by the second lens 2 and then propagate towards the second lens group.

[0028] In addition, both the first lens 1 and the second lens 2 are made of high-refractive-index glass, and their refractive indices are both greater than 1.8.

[0029] The second lens group includes a third lens 3 and a fourth lens 4. The third lens 3 and the fourth lens 4 are both meniscus positive lenses. The third lens 3 and the fourth lens 4 deflect the light and at the same time balance the spherical aberration generated by the first lens 1 and the second lens 2.

[0030] The third lens group includes a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, a tenth lens 10, and an eleventh lens 11. The fifth lens 5 and the sixth lens 6 are arranged in a glued manner to form a lens group for achromatism in a wide spectral range; the seventh lens 7, the eighth lens 8, and the ninth lens 9 are arranged in a glued manner to form a lens group, and the three glued lenses of the seventh lens 7, the eighth lens 8, and the ninth lens 9 cooperate with each other to achieve an apochromatic effect in the range of 750 nm to 1100 nm; the tenth lens 10 and the eleventh lens 11 are arranged in a glued manner to form a lens group for achromatism in a wide spectral range.

[0031] The fifth lens 5 is a meniscus positive lens, the sixth lens 6 is a biconvex positive lens, the seventh lens 7 is a meniscus negative lens, the eighth lens 8 is a biconvex positive lens, the ninth lens 9 is a meniscus positive lens, the tenth lens 10 is a biconvex positive lens, and the eleventh lens 11 is a biconcave negative lens.

[0032] The fourth lens 4 and the fifth lens 5 have certain differences in refractive index and Abbe number, and can correct spherical aberration and chromatic aberration simultaneously; the refractive index of the fourth lens 4 is less than that of the fifth lens 5, and the Abbe number of the fourth lens 4 is greater than that of the fifth lens 5. For specific values, see Table 1 below.

[0033] The fourth lens group includes the twelfth lens 12, the thirteenth lens 13, and the fourteenth lens 14. The twelfth lens 12, the thirteenth lens 13, and the fourteenth lens 14 are all meniscus positive lenses. The twelfth lens 12, the thirteenth lens 13, and the fourteenth lens 14 form a positive aplanatic lens group, which can effectively correct spherical aberration and achieve a large NA output.

[0034] The materials of the third lens 3, the fourth lens 4, the sixth lens 6, the eighth lens 8, the twelfth lens 12, the thirteenth lens 13, and the fourteenth lens 14 are ultra-low dispersion glass materials. When using this kind of material, the dispersion property is small, which can significantly reduce the dispersion phenomenon when light passes through the lens, effectively correct the chromatic aberration in the optical system, make the imaging clearer and sharper, and thus improve the imaging performance of the system. At the same time, it can also reduce the loss of light when passing through the lens, and increase the entrance pupil to a certain extent.

[0035] It should be noted that calcium fluoride material is avoided for each lens in this application, which can reduce the material cost of the microscope objective.

[0036] Furthermore, the first lens group, the second lens group, the third lens group, and the fourth lens group are sequentially attached, and there is a spacing between the fourth lens group and the flat mirror 15.

[0037] From Figure 1 it can be seen that the first lens group, the second lens group, the third lens group, and the fourth lens group are basically attached, while the flat mirror 15 is at a certain distance from the fourteenth lens 14 of the fourth lens group, so that light can form an image after passing through the flat mirror 15.

[0038] Exemplarily, the flat mirror 15 can be a glass protection sheet. After the light emitted from the fourteenth lens 14 passes through the flat mirror 15 for two refractions of incidence and exit, an image is formed in the image space.

[0039] Therefore, for the microscope objective provided by the embodiment of this application, the main plane of the lens is moved backward through the combination of positive and negative lenses in the optical path, while ensuring a focal length of 10 mm, a longer working distance is achieved, so that the microscope objective has the characteristics of a long working distance and a large NA at the same time. While the optical path of the lens is complicated, the parfocal distance is less than 95 mm, enabling the object to be clearly imaged; the third lens group can achieve apochromatism in the near-infrared band of 750 nm to 1100 nm; by using multiple lens groups and combining with the arrangement of the lenses, the entrance pupil is effectively increased, so that the entrance pupil of the lens is large.

[0040] In some embodiments, the total optical path length of the microscopic objective lens from the object side to the image side is 85 nm to 90 nm, the working distance is 17 mm, the numerical aperture (NA) is 0.6, the entrance pupil is 12 mm, the working wavelength is 750 nm to 1100 nm, and the magnification is 20 times.

[0041] In the microscopic objective lens provided by the embodiment of the present application, the radius of curvature, thickness, refractive index, and Abbe number of each lens are shown in Table 1 below. In Table 1, the radius of curvature 1 is the entrance surface of the lens along the incident direction, and the radius of curvature 2 is the exit surface of the lens along the incident direction; the positive and negative signs in the radius of curvature represent the direction of surface bending, with a positive value indicating that the spherical surface bends towards the object side and a negative value indicating that the spherical surface bends towards the image side.

[0042] Table 1

[0043] Lens serial number Radius of curvature 1 Radius of curvature 2 Thickness Refractive index Abbe number First lens －12.18 －108.2 1.7 1.92 21 Second lens －16.27 －67 1.7 1.95 18 Third lens －22.35 －16.87 4.3 1.59 68 Fourth lens －178.6 －23 7 1.62 63 Fifth lens 957 96.2 1.5 1.66 51 Sixth lens 96.2 －163.2 3.8 1.59 68 Seventh lens 172.8 30.28 1.5 1.58 41 Eighth lens 30.28 －29.48 13.5 1.5 81 Ninth lens －29.48 －41.15 1.5 1.52 64 Tenth lens 142.8 －281.12 3.3 1.69 49 Eleventh lens －281.12 160.6 1.5 1.73 51 Twelfth lens 54.2 158.8 3.8 1.59 68 Thirteenth lens 31.65 60 4.4 1.59 68 Fourteenth lens 17.8 46.68 7.6 1.5 81 Plane mirror INF INF 3.5 1.52 64

[0044] In summary, in the microscopic objective lens provided by the embodiment of the present application, the lens powers of the lenses in the lens optical path show the characteristics of negative in the front and positive in the back, which can move the principal plane of the lens backward, facilitating the increase of the working distance of the lens. By reasonably distributing the positive and negative lens powers of each lens in the optical path, as Figures 2a to 2d shown, the blur spot of the lens is close to the diffraction limit, and the lens has a good imaging effect. Multiple ultra-low dispersion glass lenses are used in the lens optical path. The ultra-low dispersion glass has anomalous dispersion, which can effectively reduce chromatic aberration. In the third lens group in the lens optical path, two sets of two cemented lenses (the fifth lens 5 and the sixth lens 6 are cemented, and the tenth lens 10 and the eleventh lens 11 are cemented) and one three-cemented lens (the seventh lens 7, the eighth lens 8, and the ninth lens 9 are cemented) are adopted. There are certain differences in the Abbe numbers between the lenses. After cementing, the residual chromatic aberration of the lens can be corrected; as Figure 4 shown, the chromatic aberration of the overall lens is small. The positive meniscus lens group composed of the twelfth lens 12, the thirteenth lens 13, and the fourteenth lens 14 can greatly reduce spherical aberration and achieve the output of high-NA light. As Figure 3 shown, through the setting of the present application, the distortion of the lens of the microscopic objective lens is small, which is suitable for the observation field.

[0045] The above are only the embodiments of the present application and are not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A microscope objective lens, characterized in that: include: A first lens group, a second lens group, a third lens group, a fourth lens group and a plane mirror are sequentially arranged from the object side to the image side along the direction of the incident light, wherein the first lens group has a negative optical power and is used to diverge the incident light; The second lens group has positive power and is used to deflect the incident light and balance the spherical aberration generated by the first lens group; The third lens group includes a plurality of lens groups, each of which has at least two cemented lenses for apochromatism in a wide spectral range; The fourth lens group is a positive lens group for correcting spherical aberration; the plane mirror is used for imaging after refraction.

2. The microscope objective lens according to claim 1, characterized in that The first lens group includes a first lens and a second lens, and both the first lens and the second lens are meniscus negative lenses.

3. The microscope objective lens according to claim 2, characterized in that: The refractive indexes of the first lens and the second lens are both greater than 1.

8.

4. The microscope objective according to any one of claims 1 to 3, characterized in that: The second lens group includes a third lens and a fourth lens, and both the third lens and the fourth lens are meniscus positive lenses.

5. The microscope objective lens according to claim 4, characterized in that: The third lens group includes a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens and an eleventh lens, the fifth lens is a meniscus positive lens, the sixth lens is a biconvex positive lens, and the fifth lens and the sixth lens are cemented together; the seventh lens is a meniscus negative lens, the eighth lens is a biconvex positive lens, the ninth lens is a meniscus positive lens, and the seventh lens, the eighth lens and the ninth lens are cemented together; the tenth lens is a biconvex positive lens, the eleventh lens is a biconcave negative lens, and the tenth lens and the eleventh lens are cemented together.

6. The microscope objective lens according to claim 5, characterized in that: A refractive index of the fourth lens is smaller than a refractive index of the fifth lens, and an Abbe number of the fourth lens is larger than an Abbe number of the fifth lens.

7. The microscope objective lens according to claim 5 or 6, characterized in that: The fourth lens group includes a twelfth lens, a thirteenth lens and a fourteenth lens, and the twelfth lens, the thirteenth lens and the fourteenth lens are all meniscus positive lenses.

8. The microscope objective lens according to claim 7, characterized in that: The third lens, the fourth lens, the sixth lens, the eighth lens, the twelfth lens, the thirteenth lens, and the fourteenth lens are made of ultra-low dispersion glass.

9. The microscope objective lens according to claim 1, characterized in that: The first lens group, the second lens group, the third lens group and the fourth lens group are sequentially arranged in contact with each other, and there is a distance between the fourth lens group and the plane mirror.

10. The microscope objective lens according to claim 1, characterized in that: The total length of the optical path from the object side to the image side of the microscope objective lens is 85nm-90nm.

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