Long working distance visible light near infrared microscope objective

Abstract

The present application relates to the field of lens, especially to a long working distance visible light near-infrared microscope objective lens, comprising a first group of negative focal length, a second group of negative focal length and a third group of positive focal length arranged in sequence along the optical axis from the object side to the image side; wherein the focal length of each group satisfies the following relationship: 1.8<|fA / fS|<3; 2.5<|fC / fS|<4.2; wherein: fA is the focal length of the first group, fC is the focal length of the third group; fS is the focal length of the objective lens; the focal length fA of the first group is: -30mm<fA<-18mm; the focal length fC of the third group is: 25mm<fC<42mm. The objective lens has long working distance and large numerical aperture, can be used for visible light and near-infrared wave band detection at the same time, and can greatly reduce the purchase cost of the objective lens.

Description

Technical Field

[0001] This invention relates to the field of lenses, and in particular to a long working distance visible light and near-infrared microscope objective. Background Technology

[0002] With the continuous development of processing technology, inspection technology is receiving increasing attention. Microscopic inspection technology has garnered significant interest due to its non-contact and high-precision characteristics. In addition to common visible light microscopy, infrared microscopy utilizes the penetrating power of near-infrared light into semiconductor materials to achieve non-destructive testing during the manufacturing process of chips and microelectronic devices. By penetrating silicon wafers with an infrared microscope, one can observe dislocations and hidden cracks during crystal growth, as well as analyze defects during chip dicing and packaging.

[0003] Conventional objectives have a very short working distance while meeting the requirements of large numerical aperture, and most objectives operate only in the visible or near-infrared regions.

[0004] From the perspective of ease of inspection, while meeting the specifications of the microscopy system, we desire objectives with a long working distance, large numerical aperture, and high resolution. Such objectives are ideal for industrial inspection to ensure the accuracy requirements of the inspected devices. Summary of the Invention

[0005] The purpose of this invention is to provide a long working distance visible and near-infrared microscope objective. This objective has a long working distance and a large numerical aperture, and can be used for detection in both visible and near-infrared bands, which can greatly reduce the purchase cost of the objective.

[0006] The present invention is achieved through the following technical solution: a long working distance visible light near-infrared microscope objective, characterized in that: it includes a first group of negative optical power, a second group of negative optical power, and a third group of positive optical power arranged sequentially along the optical axis from the object side to the image side;

[0007] The focal lengths of each group satisfy the following relationship:

[0008] 1.8 < |fA / fS| < 3;

[0009] 2.5 < |fC / fS| < 4.2;

[0010] Where: fA is the focal length of the first group, fC is the focal length of the third group; fS is the focal length of the objective lens;

[0011] The focal length fA of the first group is: -30mm < fA < -18mm;

[0012] The focal length fC of the third group is: 25mm < fC < 42mm.

[0013] As a further improvement, the first group adopts a cemented doublet lens structure, which is beneficial to eliminating chromatic aberration; the second group adopts two sets of cemented doublet lenses, which is beneficial to eliminating axial chromatic aberration of the system; and at least one meniscus single lens in the third group acts as a uniform lens, which can significantly improve the numerical aperture.

[0014] To improve resolution, at least one lens in the second group uses an ultra-low dispersion material with an Abbe number ranging from 90 to 100.

[0015] To further improve resolution, at least two lenses in the third group use ultra-low dispersion materials with an Abbe number ranging from 65 to 100.

[0016] As a preferred embodiment, the first group includes a first lens and a second lens arranged sequentially along the incident direction of light;

[0017] The first lens is a biconcave lens with negative optical power, and the second lens is a biconvex lens with positive optical power. The first lens and the second lens form a cemented doublet.

[0018] As a preferred embodiment, the second group includes a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially along the incident direction of the light;

[0019] The third lens is a biconcave lens with negative optical power, and the fourth lens is a biconvex lens with positive optical power. The third lens and the fourth lens form a cemented doublet.

[0020] The fifth lens is a meniscus lens with negative optical power, and the sixth lens is a biconvex lens with positive optical power. The fifth and sixth lenses also form a cemented doublet.

[0021] As a preferred embodiment, the third group includes a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged sequentially along the incident direction of light.

[0022] The seventh lens is a negative optical power biconcave lens, the eighth lens is a positive optical power biconvex lens, and the seventh and eighth lenses form a cemented doublet. The ninth and tenth lenses are a positive optical power biconvex lens and a positive optical power meniscus lens, respectively.

[0023] Compared with previous technologies, the beneficial effects of the present invention are as follows:

[0024] 1. The present invention provides a long working distance visible and near-infrared microscope objective, which has a long working distance (working distance greater than 20 mm) and a large numerical aperture (numerical aperture greater than 0.4), and can be used for detection in both visible and near-infrared bands, which can greatly reduce the purchase cost of the objective.

[0025] 2. The first group in this invention adopts a cemented doublet lens structure, which is beneficial to eliminating chromatic aberration; the second group adopts two sets of cemented doublet lenses, which is beneficial to eliminating axial chromatic aberration of the system; in the third group, at least one meniscus single lens acts as a uniform lens, which can significantly improve the numerical aperture. Attached Figure Description

[0026] Figure 1 This is a structural schematic diagram of Embodiment 1 of the present invention;

[0027] Figure 2 This is an optical path difference curve of Embodiment 1 of the present invention when it operates in the visible light band;

[0028] Figure 3 This is an optical path difference curve of Embodiment 1 of the present invention when it operates in the near-infrared band;

[0029] Figure 4 This is the MTF curve of Embodiment 1 of the present invention operating in the visible light band;

[0030] Figure 5 This is the MTF curve of Embodiment 1 of the present invention operating in the visible light band at 100 lp / mm;

[0031] Figure 6 This is the MTF curve of Embodiment 1 of the present invention operating in the near-infrared band;

[0032] Figure 7 This is the MTF curve of Embodiment 1 of the present invention operating in the near-infrared band at 100 lp / mm;

[0033] Figure 8 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0034] Figure 9 This is the optical path difference curve of Embodiment 2 of the present invention when it operates in the visible light band;

[0035] Figure 10 This is the optical path difference curve of Embodiment 2 of the present invention when it operates in the near-infrared band;

[0036] Figure 11 This is the MTF curve of Embodiment 2 of the present invention operating in the visible light band;

[0037] Figure 12 This is the MTF curve of Embodiment 2 of the present invention operating in the visible light band at 100 lp / mm;

[0038] Figure 13 This is the MTF curve of Embodiment 2 of the present invention operating in the near-infrared band;

[0039] Figure 14This is the MTF curve of Embodiment 2 of the present invention operating in the near-infrared band at 100 lp / mm.

[0040] Labeling explanation: A, Group 1; A1, Lens 1; A2, Lens 2; B, Group 2; B1, Lens 3; B2, Lens 4; B3, Lens 5; B4, Lens 6; C, Group 3; C1, Lens 7; C2, Lens 8; C3, Lens 9; C4, Lens 10. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings: Example

[0042] This embodiment relates to a long working distance visible and near-infrared microscope objective, such as... Figure 1-7 As shown, it includes a first group A of negative optical power, a second group B of negative optical power, and a third group C of positive optical power arranged sequentially along the optical axis from the object side to the image side;

[0043] The focal lengths of each group satisfy the following relationship:

[0044] 1.8 < |fA / fS| < 3;

[0045] 2.5 < |fC / fS| < 4.2;

[0046] Where: fA is the focal length of the first group, fC is the focal length of the third group; fS is the focal length of the objective lens;

[0047] The focal length fA of the first group is: -30mm < fA < -18mm;

[0048] The focal length fC of the third group is: 25mm < fC < 42mm.

[0049] As a further improvement, the first group A adopts a cemented doublet lens structure, which is beneficial to eliminating chromatic aberration; the second group B adopts two sets of cemented doublet lenses, which is beneficial to eliminating axial chromatic aberration of the system; and at least one meniscus single lens in the third group C acts as a uniform lens, which can significantly improve the numerical aperture.

[0050] To improve resolution, at least one lens in the second group B uses an ultra-low dispersion material with an Abbe number ranging from 90 to 100.

[0051] To further improve resolution, at least two lenses in the third group C use ultra-low dispersion materials with an Abbe number ranging from 65 to 100.

[0052] As a preferred embodiment, the first group A includes a first lens A1 and a second lens A2 arranged sequentially along the incident direction of light;

[0053] The first lens A1 is a biconcave lens with negative optical power, and the second lens A2 is a biconvex lens with positive optical power. The first lens A1 and the second lens A2 form a cemented doublet.

[0054] As a preferred embodiment, the second group B includes a third lens B1, a fourth lens B2, a fifth lens B3, and a sixth lens B4 arranged sequentially along the incident direction of light.

[0055] The third lens B1 is a biconcave lens with negative optical power, and the fourth lens B2 is a biconvex lens with positive optical power. The third lens B1 and the fourth lens B2 form a double cemented lens assembly.

[0056] The fifth lens B3 is a meniscus lens with negative optical power, and the sixth lens B4 is a biconvex lens with positive optical power. The fifth lens B3 and the sixth lens B4 also form a cemented doublet.

[0057] As a preferred embodiment, the third group C includes a seventh lens C1, an eighth lens C2, a ninth lens C3, and a tenth lens C4 arranged sequentially along the incident direction of light.

[0058] The seventh lens C1 is a negative optical power biconcave lens, the eighth lens C2 is a positive optical power biconvex lens, the seventh lens C1 and the eighth lens C2 form a cemented doublet, and the ninth lens C3 and the tenth lens C4 are a positive optical power biconvex lens and a positive optical power meniscus lens, respectively.

[0059] Specifically, the lens has a focal length fS of 10.3mm, a focal length NA of 0.41, an image plane diameter of 1.2mm, an entrance pupil diameter of 8.61mm, and a total lens length of 87.7mm. The data for the radius of curvature, center thickness, refractive index nd, and Abbe number vd of each lens are shown in the table below (the surface numbers in the table are set sequentially along the direction of light incidence).

[0060]

[0061] Based on the data in the table above and the relevant formulas, we can obtain:

[0062] fS=10.3; fA=-23.564; fC=35.33; |fA / fS|=2.288; |fC / fS|=3.43.

[0063] The lens provided in Embodiment 1 will be further described below through a detailed optical system analysis.

[0064] Figure 3This is a graph showing the optical path difference of the system when it is operating in the near-infrared band. It can be seen that the optical path difference of the system is within 1 wavelength in the visible light band and within 2 wavelengths in the near-infrared band, and the performance of each field of view almost reaches the diffraction limit. Figure 5 The MTF curve of the objective lens at 100 lp / mm shows that the MTF values ​​are all above 0.8. Figures 6 to 7 The images show the MTF curves for the objective lens in the near-infrared band and at 100 lp / mm. It can be seen that the MTF of the objective lens at 100 lp / mm in the near-infrared band is lower than that in the visible light band, but is still higher than 0.5, which is good for working with infrared detectors.

[0065] Example 2:

[0066] Another embodiment has the following specific structure: This embodiment relates to a long working distance visible and near-infrared microscope objective, such as... Figure 8-14 As shown, it includes a first group A of negative optical power, a second group B of negative optical power, and a third group C of positive optical power arranged sequentially along the optical axis from the object side to the image side;

[0067] The focal lengths of each group satisfy the following relationship:

[0068] 1.8 < |fA / fS| < 3;

[0069] 2.5 < |fC / fS| < 4.2;

[0070] Where: fA is the focal length of the first group, fC is the focal length of the third group; fS is the focal length of the objective lens;

[0071] The focal length fA of the first group is: -30mm < fA < -18mm;

[0072] The focal length fC of the third group is: 25mm < fC < 42mm.

[0073] As a further improvement, the first group A adopts a cemented doublet lens structure, which is beneficial to eliminating chromatic aberration; the second group B adopts two sets of cemented doublet lenses, which is beneficial to eliminating axial chromatic aberration of the system; and at least one meniscus single lens in the third group C acts as a uniform lens, which can significantly improve the numerical aperture.

[0074] To improve resolution, at least one lens in the second group B uses an ultra-low dispersion material with an Abbe number ranging from 90 to 100.

[0075] To further improve resolution, at least two lenses in the third group C use ultra-low dispersion materials with an Abbe number ranging from 65 to 100.

[0076] As a preferred embodiment, the first group A includes a first lens A1 and a second lens A2 arranged sequentially along the incident direction of light;

[0077] The first lens A1 is a biconcave lens with negative optical power, and the second lens A2 is a biconvex lens with positive optical power. The first lens A1 and the second lens A2 form a cemented doublet.

[0078] As a preferred embodiment, the second group B includes a third lens B1, a fourth lens B2, a fifth lens B3, and a sixth lens B4 arranged sequentially along the incident direction of light.

[0079] The third lens B1 is a biconcave lens with negative optical power, and the fourth lens B2 is a biconvex lens with positive optical power. The third lens B1 and the fourth lens B2 form a double cemented lens assembly.

[0080] The fifth lens B3 is a meniscus lens with negative optical power, and the sixth lens B4 is a biconvex lens with positive optical power. The fifth lens B3 and the sixth lens B4 also form a cemented doublet.

[0081] As a preferred embodiment, the third group C includes a seventh lens C1, an eighth lens C2, a ninth lens C3, and a tenth lens C4 arranged sequentially along the incident direction of light.

[0082] The seventh lens C1 is a negative optical power biconcave lens, the eighth lens C2 is a positive optical power biconvex lens, the seventh lens C1 and the eighth lens C2 form a cemented doublet, and the ninth lens C3 and the tenth lens C4 are a positive optical power biconvex lens and a positive optical power meniscus lens, respectively.

[0083] Specifically, the lens has a focal length fS of 10.25mm, a focal length NA of 0.42, an image plane diameter of 1.2mm, an entrance pupil diameter of 8.61mm, and a total lens length of 90.6mm. The data for the radius of curvature, center thickness, refractive index nd, and Abbe number vd of each lens are shown in the table below (the surface numbers in the table are set sequentially along the direction of light incidence).

[0084]

[0085] Based on the data in the table above and the relevant formulas, we can obtain:

[0086] fS=10.25; fA=-24.357; fC=33.572; |fA / fS|=2.376; |fC / fS|=3.275.

[0087] The lens provided in Embodiment 2 will be further described below through a detailed optical system analysis.

[0088] Figure 10 This is a graph showing the optical path difference of the system when it is operating in the near-infrared band. It can be seen that the optical path difference of the system is within 1 wavelength in the visible light band and within 2 wavelengths in the near-infrared band, and the performance of each field of view almost reaches the diffraction limit. Figure 12 The MTF curve of the objective lens at 100 lp / mm shows that the MTF values ​​are all above 0.8. Figures 13 to 14 The images show the MTF curves for the objective lens in the near-infrared band and at 100 lp / mm. It can be seen that the MTF of the objective lens at 100 lp / mm in the near-infrared band is lower than that in the visible light band, but is still higher than 0.48, which is good for working with infrared detectors.

[0089] Although the present invention has been illustrated and described through specific embodiments and alternative methods, it should be understood that various changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, it should be understood that the present invention is not limited in any sense except by the appended claims and their equivalents.

Claims

1. A long working distance visible and near-infrared microscope objective, characterized in that: It includes a first group (A) of negative optical power, a second group (B) of negative optical power, and a third group (C) of positive optical power arranged sequentially from the object side to the image side along the optical axis. The focal lengths of each group satisfy the following relationship: 1.8 < |fA / fS| < 3; 2.5 < |fC / fS| < 4.2; Where: fA is the focal length of the first group, fC is the focal length of the third group, and fS is the focal length of the objective lens; The focal length fA of the first group is: -30mm < fA < -18mm; The focal length fC of the third group is: 25mm < fC < 42mm; The first group (A) includes a first lens (A1) and a second lens (A2) arranged sequentially along the incident direction of light; the first lens (A1) is a biconcave lens with negative optical power, and the second lens (A2) is a biconvex lens with positive optical power. The first lens (A1) and the second lens (A2) form a cemented doublet. The second group (B) includes a third lens (B1), a fourth lens (B2), a fifth lens (B3), and a sixth lens (B4) arranged sequentially along the incident direction of light. The third lens (B1) is a biconcave lens with negative optical power, and the fourth lens (B2) is a biconvex lens with positive optical power. The third lens (B1) and the fourth lens (B2) form a cemented doublet. The fifth lens (B3) is a meniscus lens with negative optical power, and the sixth lens (B4) is a biconvex lens with positive optical power. The fifth lens (B3) and the sixth lens (B4) also form a cemented doublet. The third group (C) includes a seventh lens (C1), an eighth lens (C2), a ninth lens (C3), and a tenth lens (C4) arranged sequentially along the incident direction of light. The seventh lens (C1) is a biconcave lens with negative optical power, the eighth lens (C2) is a biconvex lens with positive optical power, the seventh lens (C1) and the eighth lens (C2) form a cemented doublet, and the ninth lens (C3) and the tenth lens (C4) are a biconvex lens with positive optical power and a meniscus lens with positive optical power, respectively.

2. The long working distance visible and near-infrared microscope objective according to claim 1, characterized in that: The first group (A) adopts a cemented doublet lens structure, which is beneficial to eliminating chromatic aberration; the second group (B) adopts two sets of cemented doublet lenses, which is beneficial to eliminating axial chromatic aberration of the system; at least one meniscus single lens in the third group (C) acts as a uniform lens, which greatly improves the numerical aperture.

3. The long working distance visible and near-infrared microscope objective according to claim 1, characterized in that: At least one lens in the second group (B) uses an ultra-low dispersion material with an Abbe number ranging from 90 to 100.

4. The long working distance visible and near-infrared microscope objective according to claim 1, characterized in that: At least two lenses in the third group (C) use ultra-low dispersion materials with an Abbe number ranging from 65 to 100.

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