Flat-field apochromatic large-view-field large-numerical-aperture objective lens

Abstract

The invention relates to the field of microscopic imaging, in particular to a flat-field apochromatic large-view-field large-numerical-aperture objective lens. The objective lens is composed of 14 convex lenses and concave lenses made of conventional optical glass, and each lens is coaxial with the center of an object plane. From left to right, the object plane, the first concave lens, the second convex lens, the third concave lens and the fourth convex lens are glued to form a glued lens, the fifth convex lens, the sixth concave lens, the seventh convex lens and the eighth concave lens are glued to form a glued lens, and the ninth convex lens and the tenth concave lens are glued to form a glued lens. And the diaphragm, the thirteenth convex lens and the fourteenth concave lens are imaged at infinity, and a balsaming lens formed by gluing the eleventh convex lens and the twelfth concave lens is formed by gluing the diaphragm, the thirteenth convex lens and the fourteenth concave lens. The working distance WD is larger than 15 mm, the amplification factor beta is equal to 8 *-10 *, the focal length f 'is equal to 20-25 mm, the numerical aperture NA is larger than 0.32, and the object view field phi is equal to 4 mm.

Description

Technical Field

[0001] The present invention relates to the field of microscopic imaging, and specifically to a large-field and large-numerical-aperture objective lens with flat-field apochromatism. Background Art

[0002] In a microscopic imaging system, imaging is usually carried out by means of a microscopic objective lens plus a tube lens. The core design parameters of the objective lens itself are divided into magnification (focal length); numerical aperture; object field of view; working distance; aberration correction, etc. In different applications, the requirements for the above core design parameters are different or even completely opposite. In a planar array scanning detection device, a common and important requirement is a relatively fast scanning speed and clear and stable images. Moreover, since the wafer is generally very thin and some materials are transparent, it is not desired that the patterns on the back and the front overlap during imaging, and a smaller depth of field is required. Therefore, for the corresponding optical system, the objective lens is required to have a larger field of view, a larger numerical aperture, and excellent aberration correction. However, the existing objective lens systems are difficult to meet the above technical requirements. Summary of the Invention

[0003] In order to solve the technical problem that the existing objective lens cannot simultaneously have a large field of view, a large numerical aperture, and excellent aberration correction, the present invention provides a large-field and large-numerical-aperture objective lens with flat-field apochromatism.

[0004] The present invention is implemented by adopting the following technical solutions: A large-field and large-numerical-aperture objective lens with flat-field apochromatism includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens arranged in sequence from the object plane to the image plane direction, and the optical axes of each lens are coaxial with the center of the object plane; The first lens has a first focal length f1' and f1'<0, 1<|f1' / f'|<10; The second lens has a second focal length f2' and f2'>0, 1<|f2' / f'|<2; The third lens has a third focal length f3' and f3'<0, 1<|f3' / f'|<2; The fourth lens has a fourth focal length f4' and f4'>0, 2<|f4' / f'|<3; The fifth lens has a fifth focal length f5' and f5'>0, 1<|f5' / f'|<10; The sixth lens has a sixth focal length f6' and f6'<0, 1<|f6' / f'|<5.5; The seventh lens has a seventh focal length f7' and f7'>0, 1<|f7' / f'|<8.5; The eighth lens, having an eighth focal length f8' and f8' < 0, 1 < |f8' / f'| < 10; The ninth lens, having a ninth focal length f9' and f9' > 0, 1 < |f9' / f'| < 4.5; The tenth lens, having a tenth focal length f10' and f10' < 0, 5 < |f10' / f'| < 20; The eleventh lens, having an eleventh focal length f11' and f11' > 0, 2 < |f11' / f'| < 3; The twelfth lens, having a twelfth focal length f12' and f12' < 0, 2 < |f12' / f'| < 3; The thirteenth lens, having a thirteenth focal length f13' and f13' > 0, 1 < |f13' / f'| < 5; The fourteenth lens, having a fourteenth focal length f14' and f14' < 0, 1 < |f14' / f'| < 5; Wherein, f' is the total focal length of the large field of view and large numerical aperture objective lens composed of the above lenses.

[0005] The present invention provides an objective lens suitable for a detection device of a matrix scanning type. Compared with the existing solutions provided by objective lens suppliers on the market, according to specific applications, the present invention further improves the numerical aperture and the field of view at the cost of compressing the working distance, so as to improve the scanning speed and the clarity and stability of the image.

[0006] Further, when the objective lens is applicable to a differential interference optical path, a diaphragm is placed between the thirteenth lens and the fourteenth lens, and the position of the diaphragm ensures that the position of the entrance pupil of the objective lens is 8 mm in front of the fourteenth lens, that is, inside the thirteenth lens, and the pupil plane is required to be flat.

[0007] Further, the second lens, the fourth lens, the seventh lens, and the ninth lens are made of a low refractive index and high dispersion coefficient material, and their dispersion coefficients are all required to be greater than 80.

[0008] Further, the fifth lens and the thirteenth lens are made of a high refractive index and low dispersion coefficient material, and their refractive indices are all required to be greater than 1.7.

[0009] Further, the third lens and the fourth lens form a cemented lens, the seventh lens and the eighth lens form a cemented lens, the ninth lens and the tenth lens form a cemented lens, and the eleventh lens and the twelfth lens form a cemented lens.

[0010] The invention discloses a plan-apochromatic objective lens with a large field of view and a large numerical aperture that is more suitable for array scanning equipment. The objective lens is composed of 14 conventional optical glass convex lenses and concave lenses, and each lens is coaxial with the center of the object plane, and the image is formed at infinity. The working distance WD of the invention is greater than 15mm, the magnification β is 8×~10×, the focal length f' is 20~25mm, the numerical aperture NA is greater than 0.32, and the object field of view φ is 4mm.

[0011] The advantages of the present invention are: using glass materials that are easy to obtain, reasonably distributing the focal length of concave and convex lenses, using 4 cemented lenses, and distributing glass materials, so that the microscope objective lens can achieve a flat field apochromatic effect. In terms of overall structure, the working distance of common objective lenses (Sanfeng) on ​​the market is approximately in the range of 30mm-40mm, and the numerical aperture is within 0.2. This design index is suitable for most microscopic imaging scenes, but for some special imaging objects, especially very thin transparent objects, an ultra-long working distance is not necessary, and a small numerical aperture will bring a larger depth of field, thereby causing the back image of the transparent object to also be imaged, and the images of the front and back sides are superimposed together, which is not conducive to analysis. Therefore, by compressing the working distance to a reasonable 15mm, there is design space, and improvements can be made in more important fields of view and numerical apertures. Moreover, as long as the use scenario can compress the working distance, the present invention can improve the scanning speed and image clarity and stability compared to common objective lenses on the market.

[0012] Compared with the common microscope objective lenses on the market, the present invention focuses on improving the field of view and numerical aperture. Without sacrificing the imaging quality, the field of view is increased by more than 20%, the numerical aperture is increased by more than 100%, the scanning speed is significantly improved, the depth of field is reduced, and the image is clearer and more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the structure of the present invention.

[0014] Figure 2 MTF graph (Modulation Transfer Function graph) for the wavelength range of 400nm-650nm.

[0015] Figure 3 MTF graph (Modulation Transfer Function graph) for the wavelength range of 650nm-820nm.

[0016] 1-object plane, 2-first lens, 3-second lens, 4-third lens, 5-fourth lens, 6-fifth lens, 7-sixth lens, 8-seventh lens, 9-eighth lens, 10-ninth lens, 11-tenth lens, 12-eleventh lens, 13-twelfth lens, 14-aperture, 15-thirteenth lens, 16-fourteenth lens. DETAILED DESCRIPTION

[0017] The present invention discloses an optical architecture of a microscope objective lens, specifically a large-field and large numerical aperture objective lens with flat-field apochromatism. The tube lens focal lengths used in conjunction with this objective lens include, but are not limited to, 200 mm.

[0018] The following further describes the embodiments of the present invention with reference to the accompanying drawings. As Figure 1 shown, a large-field and large numerical aperture objective lens with flat-field apochromatism includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens arranged in sequence from the object plane along the image plane direction. The optical axes of all lenses are coaxial with the center of the object plane; The first lens has a first focal length f1' and f1' < 0, 1 < |f1' / f'| < 10; The second lens has a second focal length f2' and f2' > 0, 1 < |f2' / f'| < 2; The third lens has a third focal length f3' and f3' < 0, 1 < |f3' / f'| < 2; The fourth lens has a fourth focal length f4' and f4' > 0, 2 < |f4' / f'| < 3; The fifth lens has a fifth focal length f5' and f5' > 0, 1 < |f5' / f'| < 10; The sixth lens has a sixth focal length f6' and f6' < 0, 1 < |f6' / f'| < 5.5; The seventh lens has a seventh focal length f7' and f7' > 0, 1 < |f7' / f'| < 8.5; The eighth lens has an eighth focal length f8' and f8' < 0, 1 < |f8' / f'| < 10; The ninth lens has a ninth focal length f9' and f9' > 0, 1 < |f9' / f'| < 4.5; The tenth lens has a tenth focal length f10' and f10' < 0, 5 < |f10' / f'| < 20; The eleventh lens has an eleventh focal length f11' and f11' > 0, 2 < |f11' / f'| < 3; The twelfth lens has a twelfth focal length f12' and f12' < 0, 2 < |f12' / f'| < 3; The thirteenth lens has a thirteenth focal length f13' and f13' > 0, 1 < |f13' / f'| < 5; The fourteenth lens has a fourteenth focal length f14' and f14' < 0, 1 < |f14' / f'| < 5; Among them, f' is the total focal length of the large-field-of-view and large-numerical-aperture objective lens formed by the above lenses; the third lens and the fourth lens form a cemented lens, the seventh lens and the eighth lens form a cemented lens, the ninth lens and the tenth lens form a cemented lens, and the eleventh lens and the twelfth lens form a cemented lens.

[0019] As an implementation scheme, the objective lens can be applied to both telecentric and non-telecentric microscopic imaging architectures. The objective lens is applicable to a DIC (differential interference contrast) optical path, and the objective lens entrance pupil position is located about 8 mm in front of the fourteenth lens, inside the thirteenth lens, and the pupil surface is flat.

[0020] As a preferred implementation, the second lens, the fourth lens, the seventh lens, and the ninth lens are made of low-refractive-index and high-abbe number materials, and their abe number should be greater than 80; the fifth lens and the thirteenth lens are made of high-refractive-index and low-abbe number materials, and their refractive indices should be greater than 1.7.

[0021] The working distance WD of the present invention is greater than 15 mm, the magnification β=8×~10× (preferably 9 times), the focal length f'=20~25 mm (preferably 22.5 mm), the numerical aperture NA>0.32, and the object field of view φ=4 mm.

[0022] Figure 2 This is the MTF curve of the objective lens of the present invention in the wavelength range of 400nm~650nm. Each field of view is very close to the diffraction limit, which represents extremely high image resolution capability and high resolution.

[0023] Figure 3 This is the MTF curve of the objective lens of the present invention in the wavelength range of 650nm~820nm. Each field of view is very close to the diffraction limit, which represents extremely high image resolution capability and high resolution.

[0024] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the implementation method. Those skilled in the art can also make modifications or substitutions based on this structure, and these modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A plan apochromatic objective lens with a large field of view and a large numerical aperture, characterized in that: It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens, which are arranged in sequence from the object plane to the image plane. The optical axes of all lenses are coaxial with the center of the object plane. The first lens has a first focal length f1' and f1' < 0, 1 < |f1' / f'| < 10. The second lens has a second focal length f2' and f2' > 0, 1 < |f2' / f'| < 2. The third lens has a third focal length f3' and f3' < 0, 1 < |f3' / f'| < 2. The fourth lens has a fourth focal length f4' and f4' > 0, 2 < |f4' / f'| < 3. The fifth lens has a fifth focal length f5' and f5' > 0, 1 < |f5' / f'| < 10. The sixth lens has a sixth focal length f6' and f6' < 0, 1 < |f6' / f'| < 5.

5. The seventh lens has a seventh focal length f7' and f7' > 0, 1 < |f7' / f'| < 8.

5. The eighth lens has an eighth focal length f8' and f8' < 0, 1 < |f8' / f'| < 10. The ninth lens has a ninth focal length f9' and f9' > 0, 1 < |f9' / f'| < 4.

5. The tenth lens has a tenth focal length f10' and f10' < 0, 5 < |f10' / f'| < 20. The eleventh lens has an eleventh focal length f11' and f11' > 0, 2 < |f11' / f'| < 3. The twelfth lens has a twelfth focal length f12' and f12' < 0, 2 < |f12' / f'| < 3. The thirteenth lens has a thirteenth focal length f13' and f13' > 0, 1 < |f13' / f'| < 5. The fourteenth lens has a fourteenth focal length f14' and f14' < 0, 1 < |f14' / f'| < 5. Wherein, f' is the total focal length of the large field of view and large numerical aperture objective lens composed of the above lenses.

2. A plan apochromatic objective lens with a large field of view and a large numerical aperture according to claim 1, characterized in that: When the objective lens is applicable to the differential interference optical path, a diaphragm is placed between the thirteenth lens and the fourteenth lens, and the position of the diaphragm ensures that the position of the entrance pupil of the objective lens is 8 mm in front of the fourteenth lens, that is, inside the thirteenth lens, and the pupil plane is required to be flat.

3. A plan apochromatic objective lens with a large field of view and a large numerical aperture according to claim 1, characterized in that: The second lens, the fourth lens, the seventh lens, and the ninth lens are made of materials with low refractive index and high dispersion coefficient, and their dispersion coefficients are all required to be greater than 80.

4. A plan apochromatic objective lens with a large field of view and a large numerical aperture according to claim 1, characterized in that: The fifth lens and the thirteenth lens are made of materials with high refractive index and low dispersion coefficient, and their refractive indices are all required to be greater than 1.

7.

5. A plan apochromatic objective lens with a large field of view and a large numerical aperture according to any one of claims 1 to 4, characterized in that: The third lens and the fourth lens form a cemented lens, the seventh lens and the eighth lens form a cemented lens, the ninth lens and the tenth lens form a cemented lens, and the eleventh lens and the twelfth lens form a cemented lens.

6. A plan apochromatic objective lens with a large field of view and a large numerical aperture according to any one of claims 1 to 4, characterized in that: The working distance WD > 15 mm, the magnification β = 8× - 10×, the focal length f' = 20 - 25 mm, and the numerical aperture NA > 0.

32.

7. The plan-apochromatic objective lens with a large field of view and a large numerical aperture according to claim 5, characterized in that: Working distance WD>15mm, magnification β=8×~10×, focal length f'=20~25mm, numerical aperture NA>0.32.

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