A 20 times long working distance infinity corrected microscope objective

Abstract

The application provides a 20 times long working distance infinite conjugate microscopic objective lens, relates to the technical field of microscopic imaging, and the microscopic objective lens comprises a first lens group, a second lens group, a third lens group and a diaphragm which are sequentially arranged along an optical axis from an object plane, chromatic aberration of the system in a visible light wave band is realized by adopting a plurality of lens groups, the system field number can reach 30 under the guarantee of a 95mm parfocal distance, the working distance is greater than 21mm, NA reaches 0.43, good machinability and adjustment are achieved, the use demand of large field of view, long working distance and high resolution is met, the complex chromatic aberration correction in the visible light 486nm-656nm wave band is realized, the overall imaging quality of the system reaches the diffraction limit, good imaging effect is achieved, and the technical problems that the defect detection speed, safety and high resolution of a semiconductor device are difficult to be considered in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of microscopic imaging technology, specifically to a 20x long working distance infinite conjugate microscope objective. Background Technology

[0002] With the continuous development of the semiconductor industry and the continuous expansion of production scale, the control of production yield plays a crucial role in production costs; and the control of production yield depends more on the early detection of defects in the production process.

[0003] As production capacity increases year by year, the standards for testing speed and accuracy also rise accordingly, with a focus on minimizing product defects introduced during the testing process. It is well known that the resolution of an optical microscopy system can be calculated as 0.61λ / NA. Therefore, to distinguish small defects and improve accuracy, a large NA is required. However, a large NA results in a shorter working distance, making it prone to contact with the device under test during inspection, introducing adverse effects. Conversely, increasing testing speed requires the testing equipment to cover a large area, but current technologies struggle to simultaneously handle large fields of view, leading to a trade-off between various usage requirements. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing a 20x long working distance infinite conjugate microscope objective.

[0005] A 20x long working distance infinite conjugate microscope objective comprises: a first lens group, a second lens group, a third lens group, and an aperture stop arranged sequentially along the optical axis from the object plane. The first lens group has positive optical power, the second lens group has positive optical power, and the third lens group has negative optical power. The focal lengths among the first, second, and third lens groups satisfy: 0.3 < f G1 / f G2 <0.5, and -4 <f G2 / f G3 <-2, where f G1 f is the focal length of the first lens group. G2 f is the focal length of the second lens group. G3 This is the focal length of the third lens group.

[0006] Furthermore, the first lens group includes a first lens and a second lens arranged sequentially along the optical axis from the object surface, wherein the first lens is a meniscus lens and the second lens is a biconvex lens.

[0007] Furthermore, the second lens group includes a first cemented lens group, a second cemented lens group, and a third cemented lens group arranged sequentially along the optical axis from the object surface. The first cemented lens group has positive optical power, the second cemented lens group has negative optical power, and the third cemented lens group has positive optical power.

[0008] Furthermore, the third lens group includes a tenth lens, a fourth cemented lens group, and a thirteenth lens arranged sequentially along the optical axis from the object surface. The tenth lens is a meniscus lens, the thirteenth lens is a biconcave lens, and the fourth cemented lens group has positive optical power.

[0009] Furthermore, the first cemented lens group includes a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the object surface. The third lens and the fifth lens are both biconvex lenses, and the fourth lens is a biconcave lens.

[0010] Furthermore, the second cemented lens group includes a sixth lens and a seventh lens arranged sequentially along the optical axis from the object surface, wherein the sixth lens is a meniscus lens and the seventh lens is a biconvex lens.

[0011] Furthermore, the third cemented lens group includes an eighth lens and a ninth lens arranged sequentially along the optical axis from the object surface, wherein the eighth lens is a biconvex lens and the ninth lens is a biconcave lens.

[0012] Furthermore, the fourth cemented lens group includes an eleventh lens and a twelfth lens arranged sequentially along the optical axis from the object surface. The eleventh lens is a biconvex lens, and the twelfth lens is a biconcave lens.

[0013] Furthermore, both the first lens and the second lens have positive optical power.

[0014] Furthermore, both the tenth and thirteenth lenses have negative optical power.

[0015] The technical solution of this invention has the following advantages:

[0016] The technical solution provided by this invention uses a combination of multiple lenses to achieve achromatic correction in the visible light band. While maintaining a parfocal distance of 95mm, the system can achieve a field of view of 30, a working distance of more than 21mm, and an achromatic NA of 0.43. It has good manufacturability and configurability, meeting the requirements of large field of view, long working distance, and high resolution. In the visible light 486nm-656nm band, the system achieves apochromatic correction, and the overall imaging quality reaches the diffraction limit, resulting in excellent imaging performance. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 This is a modulation transfer function diagram of the microscope objective of the present invention;

[0020] Figure 3 This is an axial aberration diagram of the microscope objective of this invention.

[0021] 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-Object plane; G1-First lens group; G2-Second lens group; G3-Third lens group. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] like Figure 1 The diagram illustrates a 20x long working distance infinite conjugate microscope objective. The objective comprises a first lens group G1, a second lens group G2, a third lens group G3, and an aperture stop, arranged sequentially along the optical axis from the object plane 14. The aperture stop is located on the far left of the system, coinciding with the exit pupil position, thus facilitating pupil alignment and controlling the system's numerical aperture. The first lens group G1 has positive optical power, the second lens group G2 has positive optical power, and the third lens group G3 has negative optical power. The focal lengths among the first lens group G1, the second lens group G2, and the third lens group G3 satisfy: 0.3 < f. G1 / f G2 <0.5, and -4 <f G2 / f G3 <-2, where f G1 f is the focal length of the first lens group G1. G2 f is the focal length of the second lens group G2. G3 The focal length of the third lens group G3 is used. The system operates in the visible light band with a wavelength of 486nm-656nm. The light emitted from the microscope objective is parallel. The microscope objective is used in conjunction with a 200mm tube lens to achieve 20x magnification.

[0027] The aforementioned 20x long working distance infinite conjugate microscope objective uses multiple lens combinations to achieve achromatic correction in the visible light band. While maintaining a parfocal distance of 95mm, the system can achieve a field of view of 30, a working distance greater than 21mm, and an achromatic NA of 0.43. It has good workability and adjustability, meeting the requirements of large field of view, long working distance, and high resolution. With apochromatic correction in the visible light 486nm-656nm band, the overall imaging quality of the system reaches the diffraction limit, resulting in excellent imaging performance.

[0028] like Figure 1As shown, in this embodiment, the first lens group G1 includes a first lens 1 and a second lens 2 arranged sequentially along the optical axis from the object surface 14. The first lens 1 is a meniscus lens and the second lens 2 is a biconvex lens. The meniscus direction of the first lens 1 faces the object surface 14. Both the first lens 1 and the second lens 2 have positive optical power. The two lenses are used together to converge light and achieve a long working distance and a large numerical aperture.

[0029] like Figure 1 As shown, in this embodiment, the second lens group G2 includes a first cemented lens group, a second cemented lens group, and a third cemented lens group arranged sequentially along the optical axis from the object surface 14. The first cemented lens group has positive optical power, the second cemented lens group has negative optical power, and the third cemented lens group has positive optical power. The first cemented lens group includes a third lens 3, a fourth lens 4, and a fifth lens 5 arranged sequentially along the optical axis from the object surface 14. The third lens 3 and the fifth lens 5 are both biconvex lenses, and the fourth lens 4 is a biconcave lens. The second cemented lens group... The system includes a sixth lens 6 and a seventh lens 7 arranged sequentially along the optical axis from the object surface 14. The sixth lens 6 is a meniscus lens, and the seventh lens 7 is a biconvex lens. The third cemented lens group includes an eighth lens 8 and a ninth lens 9 arranged sequentially along the optical axis from the object surface 14. The eighth lens 8 is a biconvex lens, and the ninth lens 9 is a biconcave lens. The first cemented lens group is used to correct the chromatic aberration and apochromatic aberration of the system and to converge light rays. The second cemented lens group is used to correct the chromatic aberration of the system and to diverge light rays. The third cemented lens group is used to correct the chromatic aberration of the system and to converge light rays.

[0030] like Figure 1 As shown, in this embodiment, the third lens group G3 includes a tenth lens 10, a fourth cemented lens group, and a thirteenth lens 13 arranged sequentially along the optical axis from the object surface 14. The tenth lens 10 is a meniscus lens, the thirteenth lens 13 is a biconcave lens, and the fourth cemented lens group has positive optical power. Both the tenth lens 10 and the thirteenth lens 13 have negative optical power. The tenth lens 10 is used to diverge light. The fourth cemented lens group includes an eleventh lens 11 and a twelfth lens 12 arranged sequentially along the optical axis from the object surface 14. The eleventh lens 11 is a biconvex lens, and the twelfth lens 12 is a biconcave lens. The fourth cemented lens group is used to converge light, and the thirteenth lens 13 is used to diverge light.

[0031] like Figures 1-3As shown, in this embodiment, the light incident from the object surface 14 passes through each lens in sequence and then exits parallel from the exit pupil, achieving the infinite conjugate of the objective lens. When used in conjunction with a 200-mm tube lens, a system magnification of 20 times can be achieved. The numerical aperture NA of the microscopic objective lens satisfies 0.35 < NA < 0.5. The microscopic objective lens has a long working distance, a large field of view, and the maximum NA value can reach 0.5, meeting the usage requirements of existing microscopic objective lenses, being compatible with existing microscopic equipment, and enabling the switching detection of different objective lenses with different magnifications. By adopting a combination of multiple groups of cemented lenses, apochromatic correction in the visible light band of 486 nm - 656 nm is achieved, and all lenses are spherical lenses made of common optical materials, which is convenient for processing and detection. Figure 2 It is the modulation transfer function graph of the microscopic objective lens. It can be seen that the designed value of the objective lens is close to the limit and the performance of the objective lens is good. Figure 3 It is the axial aberration graph of the microscopic objective lens. It can be seen that the axial chromatic aberration is small, the overall imaging quality of the system reaches the diffraction limit, and at the same time, it has a good imaging effect. Table 1 gives the specific parameters of the 20-fold long working distance infinite conjugate microscopic objective lens. A positive radius value R indicates that the center of curvature is close to the object side, and a negative radius value R indicates that the center of curvature is close to the image side. The units of the radius, thickness, and aperture are all millimeters.

[0032] Table 1 Specific parameters of the 20-fold long working distance infinite conjugate microscopic objective lens

[0033]

[0034] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A 20x long working distance infinite conjugate microscope objective, characterized in that, The microscope objective comprises a first lens group (G1), a second lens group (G2), a third lens group (G3), and an aperture, arranged sequentially along the optical axis from the object plane (14). The first lens group (G1) has positive optical power, the second lens group (G2) has positive optical power, and the third lens group (G3) has negative optical power. The focal lengths between the first lens group (G1), the second lens group (G2), and the third lens group (G3) satisfy: 0.3 < f G1 / f G2 <0.5, and -4 <f G2 / f G3 <-2, where f G1 f is the focal length of the first lens group (G1). G2 f is the focal length of the second lens group (G2). G3 The focal length of the third lens group (G3); the first lens group (G1) includes a first lens (1) and a second lens (2) arranged sequentially along the optical axis from the object surface (14), the first lens (1) is a meniscus lens, and the second lens (2) is a biconvex lens; the second lens group (G2) includes a first cemented lens group, a second cemented lens group and a third cemented lens group arranged sequentially along the optical axis from the object surface (14), the first cemented lens group has positive optical power, the second cemented lens group has negative optical power, and the third cemented lens group has positive optical power; the third lens group (G3) includes a tenth lens (10), a fourth cemented lens group and a thirteenth lens (13) arranged sequentially along the optical axis from the object surface (14), the tenth lens (10) is a meniscus lens, the thirteenth lens (13) is a biconcave lens, and the fourth cemented lens group has positive optical power; the first cemented lens group includes a third lens (3), a fourth cemented lens group and a fourth cemented lens group arranged sequentially along the optical axis from the object surface (14). Lens (4) and fifth lens (5), third lens (3) and fifth lens (5) are both biconvex lenses, and fourth lens (4) is a biconcave lens; the second cemented lens group includes a sixth lens (6) and a seventh lens (7) arranged sequentially along the optical axis from the object surface (14), the sixth lens (6) is a meniscus lens, and the seventh lens (7) is a biconvex lens; the third cemented lens group includes an eighth lens (8) and a ninth lens (9) arranged sequentially along the optical axis from the object surface (14), the eighth lens (8) is a biconvex lens, and the ninth lens (9) is a biconcave lens; the fourth cemented lens group includes an eleventh lens (11) and a twelfth lens (12) arranged sequentially along the optical axis from the object surface (14), the eleventh lens (11) is a biconvex lens, and the twelfth lens (12) is a biconcave lens; the first lens (1) and the second lens (2) both have positive optical power; the tenth lens (10) and the thirteenth lens (13) both have negative optical power.

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