High-magnification microscopic coaxial illumination optical system

Abstract

The invention relates to a high-magnification microscopic coaxial illumination optical system. The system comprises a front lens group, a diaphragm, a rear lens group and a beam splitter prism which are sequentially arranged along a light incidence direction, the front lens group comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged in the light incidence direction. The rear lens group comprises a fifth lens and a sixth lens which are sequentially arranged in the light incidence direction. Wherein the first lens adopts a concave-convex positive lens, the second lens adopts a biconvex positive lens, the third lens adopts a convex-concave negative lens, the fourth lens adopts a biconvex positive lens, the fifth lens adopts a convex-concave meniscus lens, and the sixth lens adopts a convex-concave positive lens; the third lens and the fourth lens form a doublet lens; on the premise of low cost and small size, the comprehensive performance of high magnification, low chromatic aberration and high image quality is realized, and the contradiction between high precision and equipment compatibility in industrial detection is solved.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and particularly to a high-magnification microscopic coaxial illumination optical system. Background Art

[0002] With the rapid development of technology, microscopes are increasingly widely used in fields such as biomedicine, materials science, and electronic detection. Traditional microscope optical systems usually adopt simple lens combinations, but when performing high-magnification imaging, there are often significant chromatic aberration phenomena, which seriously affect the imaging quality. Chromatic aberration is caused by different refractive indices of light with different wavelengths when passing through a lens, resulting in inconsistent imaging positions. In addition, traditional microscopes are large in volume and high in cost, which brings great troubles to users in some application scenarios with strict restrictions on equipment volume and cost, such as PCB board detection and miniaturized detection equipment.

[0003] In existing microscope optical systems, although some designs adopt apochromatic techniques to improve chromatic aberration problems, these designs are often complex in structure, require the use of a variety of special materials and complex processing techniques, resulting in high costs. At the same time, these systems usually cannot balance the optimization of volume and cost, and it is difficult to meet the market demand for low-cost and miniaturized microscopes.

[0004] In addition, the traditional illumination method of microscopes is mostly non-coaxial illumination. This illumination method is prone to shadows and uneven illumination effects during high-magnification imaging, further affecting the imaging quality. Therefore, developing a microscope optical system that can effectively correct chromatic aberration at high magnifications, has a coaxial illumination function at the same time, is small in volume and low in cost is of great practical significance for meeting market demands. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to overcome the defects or deficiencies of the prior art and provide a high-magnification microscopic coaxial illumination optical system.

[0006] A high-magnification microscopic coaxial illumination optical system includes a front lens group, a diaphragm, a rear lens group, and a beam splitter prism arranged in sequence along the light incident direction; the front lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence along the light incident direction, and the rear lens group includes a fifth lens and a sixth lens arranged in sequence along the light incident direction;

[0007] Among them, the first lens is a positive lens with a convex-concave shape, the second lens is a positive lens with a double-convex shape, the third lens is a negative lens with a convex-concave shape, the fourth lens is a positive lens with a double-convex shape, the fifth lens is a meniscus lens with a convex-concave shape, and the sixth lens is a positive lens with a convex-concave shape; the third lens and the fourth lens form a doublet lens.

[0008] Compared with the prior art, the optical system of the present invention achieves comprehensive performance of high magnification, low chromatic aberration, and high image quality on the premise of low cost and small volume, and solves the contradiction between high precision and equipment compatibility in industrial inspection.

[0009] In one embodiment, the magnification PMAG of the optical system is 12X, its relative aperture F..NO is 18, its effective focal length EFL is 8.8 mm, and its total optical length TTL is 119 mm.

[0010] In one embodiment, the relationship between the focal length of each lens and the effective focal length EFL of the optical system satisfies the following conditions:

[0011]

[0012] Wherein, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, and f6 is the focal length of the sixth lens.

[0013] In one embodiment, the distance D1 between the second lens and the first lens along the optical axis direction is 3.25 mm; the distance D2 between the third lens and the second lens along the optical axis direction is 0.1 mm; the distance D3 between the diaphragm and the fourth lens along the optical axis direction is 1.69 mm; the fifth lens is next to the diaphragm, and the distance D4 between the fifth lens and the diaphragm along the optical axis direction is 0 mm; the distance D5 between the sixth lens and the fifth lens along the optical axis direction is 19.37 mm; the distance D6 between the beam splitter prism and the sixth lens along the optical axis direction is 5.25 mm.

[0014] In one embodiment, the materials of each lens satisfy the following conditions:

[0015] The refractive index coefficient Nd1 of the first lens has a value range of Nd1 ∈ (1.75, 1.95), and its dispersion coefficient Vd1 has a value range of Vd1 ∈ (15, 50);

[0016] The refractive index coefficient Nd2 of the second lens has a value range of Nd2 ∈ (1.45, 1.75), and its dispersion coefficient Vd2 has a value range of Vd1 ∈ (45, 90);

[0017] The refractive index coefficient Nd3 of the third lens has a value range of Nd3 ∈ (1.75, 1.95), and its dispersion coefficient Vd3 has a value range of Vd3 ∈ (15, 50);

[0018] The refractive index coefficient Nd4 of the fourth lens has a value range of Nd4 ∈ (1.45, 1.75), and its dispersion coefficient Vd4 has a value range of Vd4 ∈ (45, 90);

[0019] The refractive index coefficient Nd5 of the fifth lens has a value range of Nd5 ∈ (1.75, 1.95), and its dispersion coefficient Vd5 has a value range of Vd5 ∈ (15, 50);

[0020] The refractive index coefficient Nd6 of the sixth lens has a value range of Nd6 ∈ (1.75, 1.95), and its dispersion coefficient Vd6 has a value range of Vd6 ∈ (15, 50);

[0021] The refractive index coefficient Nd7 of the beam splitting prism has a value range of Nd7 ∈ (1.45, 1.75), and its dispersion coefficient Vd7 has a value range of Vd7 ∈ (45, 90).

[0022] In one embodiment, the refractive index coefficients Nd of the first lens, the third lens, the fifth lens, and the sixth lens all have a value of 1.94, and the dispersion coefficients Vd all have a value of 17.9;

[0023] The refractive index coefficients Nd of the second lens and the fourth lens all have a value of 1.49, and the dispersion coefficients Vd all have a value of 81;

[0024] The refractive index coefficient Nd7 of the beam splitting prism has a value of 1.51, and its dispersion coefficient Vd7 has a value of 64.1.

[0025] In one embodiment, the dimensions of each lens satisfy the following conditions:

[0026] The value range of the front surface curvature radius R11 of the first lens is R11 ∈ (-35, -15) mm, the value range of the rear surface curvature radius R12 is R12 ∈ (-15, -6) mm, and the value range of its core thickness d1 along the optical axis direction is d1 ∈ (1, 3.5) mm;

[0027] The value range of the front surface curvature radius R21 of the second lens is R21 ∈ (5, 20) mm, the value range of the rear surface curvature radius R22 is R22 ∈ (10, 30) mm, and the value range of its core thickness d2 along the optical axis direction is d2 ∈ (1, 5) mm;

[0028] The value range of the front surface curvature radius R31 of the third lens is R31 ∈ (20, 40) mm, the value range of the rear surface curvature radius R32 is R32 ∈ (3, 15) mm, and the value range of its core thickness d3 along the optical axis direction is d3 ∈ (1, 5) mm;

[0029] The radius of curvature of the front surface of the fourth lens is R41, and the value range is R41 ∈ (3, 15) mm. The radius of curvature of the rear surface is R42, and the value range is R42 ∈ (20, 100) mm. The core thickness along the optical axis is d4, and the value range is d4 ∈ (1, 6) mm;

[0030] The radius of curvature of the front surface of the fifth lens is R51, and the value range is R51 ∈ (4, 15) mm. The radius of curvature of the rear surface is R52, and the value range is R52 ∈ (3, 12) mm. The core thickness along the optical axis is d5, and the value range is d5 ∈ (1, 10) mm;

[0031] The radius of curvature of the front surface of the sixth lens is R61, and the value range is R61 ∈ (20, 100) mm. The radius of curvature of the rear surface is R62, and the value range is R62 ∈ (50, 150) mm. The core thickness along the optical axis is d6, and the value range is d6 ∈ (1, 5) mm.

[0032] In an embodiment, the value of R11 is -28.25774 mm, the value of R12 is -9.366924 mm, and the value of d1 is 1.59 mm;

[0033] The value of R21 is 10.48226 mm, the value of R22 is -22.9771 mm, and the value of d2 is 2.5 mm;

[0034] The value of R31 is 27.80004 mm, the value of R32 is 5.471564 mm, and the value of d3 is 0.786 mm;

[0035] The value of R41 is 5.471564 mm, the value of R42 is -53.94242 mm, and the value of d4 is 2.73 mm;

[0036] The value of R51 is 6.34324 mm, the value of R52 is 3.9905 mm, and the value of d5 is 5.545 mm;

[0037] The value of R61 is 34.27038 mm, the value of R62 is 86.39184 mm, and the value of d6 is 1.797 mm;

[0038] The radius of curvature of the front surface of the beam splitter prism is R71 and is infinity ∞. The radius of curvature of the rear surface is R72 and is infinity ∞. Both the front and rear surfaces of the beam splitter prism are flat. The core thickness along the optical axis is d7, and the value is 8.5 mm.

[0039] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0040] Figure 1 Schematic diagrams of the structures of the components in the optical system of the present invention;

[0041] Figure 2 Schematic diagram of the light conduction of the optical system of the present invention;

[0042] Figure 3 Optical transfer function curve graph of the optical system of the present invention;

[0043] Figure 4 Distortion diagram of the optical system of the present invention;

[0044] Figure 5 Spot diagram of the optical system of the present invention. Specific embodiments

[0045] The following further details the solution of the present invention with reference to the accompanying drawings.

[0046] As Figure 1 and Figure 2 shown, a high-magnification microscopic coaxial illumination optical system of the present invention includes a front lens group 10, a diaphragm 2, a rear lens group 30, and a beam splitter prism 4 arranged in sequence along the light incident direction; wherein, the front lens group 10 includes a first lens 11, a second lens 12, a third lens 13, and a fourth lens 14 arranged in sequence along the light incident direction, and the rear lens group 30 includes a fifth lens 31 and a sixth lens 32 arranged in sequence along the light incident direction.

[0047] Specifically, the first lens 11 is a positive lens with a concave-convex shape, the second lens 12 is a positive lens with a double-convex shape, the third lens 13 is a negative lens with a convex-concave shape, the fourth lens 14 is a positive lens with a double-convex shape, the fifth lens 31 is a meniscus lens with a convex-concave shape, and the sixth lens 32 is a positive lens with a convex-concave shape; wherein, the third lens 13 and the fourth lens 14 form a doublet lens.

[0048] Specifically, the distance D1 between the second lens 12 and the first lens 11 along the optical axis direction is 3.25 mm; the distance D2 between the third lens 13 and the second lens 12 along the optical axis direction is 0.1 mm; the distance D3 between the diaphragm 2 and the fourth lens 14 along the optical axis direction is 1.69 mm; the fifth lens 31 is adjacent to the diaphragm 2, and the distance D4 between the fifth lens 31 and the diaphragm 2 along the optical axis direction is 0 mm; the distance D5 between the sixth lens 32 and the fifth lens 31 along the optical axis direction is 19.37 mm; the distance D6 between the beam splitter prism 4 and the sixth lens 32 along the optical axis direction is 5.25 mm.

[0049] Specifically, as shown in Table 1 below, the materials of the respective lenses satisfy the following conditions:

[0050]

[0051]

[0052] Specifically, for the first lens 11, the refractive index coefficient Nd1 has a value range of Nd1 ∈ (1.75, 1.95), and its dispersion coefficient Vd1 has a value range of Vd1 ∈ (15, 50);

[0053] For the second lens 12, the refractive index coefficient Nd2 has a value range of Nd2 ∈ (1.45, 1.75), and its dispersion coefficient Vd2 has a value range of Vd1 ∈ (45, 90);

[0054] For the third lens 13, the refractive index coefficient Nd3 has a value range of Nd3 ∈ (1.75, 1.95), and its dispersion coefficient Vd3 has a value range of Vd3 ∈ (15, 50);

[0055] For the fourth lens 14, the refractive index coefficient Nd4 has a value range of Nd4 ∈ (1.45, 1.75), and its dispersion coefficient Vd4 has a value range of Vd4 ∈ (45, 90);

[0056] For the fifth lens 31, the refractive index coefficient Nd5 has a value range of Nd5 ∈ (1.75, 1.95), and its dispersion coefficient Vd5 has a value range of Vd5 ∈ (15, 50);

[0057] For the sixth lens 32, the refractive index coefficient Nd6 has a value range of Nd6 ∈ (1.75, 1.95), and its dispersion coefficient Vd6 has a value range of Vd6 ∈ (15, 50);

[0058] For the beam splitting prism 4, the refractive index coefficient Nd7 has a value range of Nd7 ∈ (1.45, 1.75), and its dispersion coefficient Vd7 has a value range of Vd7 ∈ (45, 90).

[0059] In this application, preferably, the refractive index coefficient Nd1 of the first lens 11 has a value of 1.94, and its dispersion coefficient Vd1 has a value of 17.9.

[0060] In this application, preferably, the refractive index coefficient Nd2 of the second lens 12 has a value of 1.49, and its dispersion coefficient Vd2 has a value of 81.

[0061] In this application, preferably, the refractive index coefficient Nd3 of the third lens 13 has a value of 1.94, and its dispersion coefficient Vd3 has a value of 17.9.

[0062] In the present application, preferably, the refractive index coefficient Nd4 of the fourth lens 14 is 1.49 and its dispersion coefficient Vd4 is 81.

[0063] In the present application, preferably, the refractive index coefficient Nd5 of the fifth lens 31 is 1.94 and its dispersion coefficient Vd5 is 17.9.

[0064] In the present application, preferably, the refractive index coefficient Nd6 of the sixth lens 32 is 1.94 and its dispersion coefficient Vd6 is 17.9.

[0065] In the present application, preferably, the refractive index coefficient Nd7 of the beam splitting prism 4 is 1.51 and its dispersion coefficient Vd7 is 64.1.

[0066] Specifically, as shown in Table 2 below, the dimensions of each lens satisfy the following conditions:

[0067]

[0068] Specifically, the front surface curvature radius of the first lens 11 is R11, the rear surface curvature radius is R12, and its core thickness along the optical axis direction is d1, where the value range of R11 is R11 ∈ (-35, -15) mm; the value range of R12 is R12 ∈ (-15, -6) mm; the value range of d1 is d1 ∈ (1, 3.5) mm.

[0069] In the present application, preferably, the value of R11 is -28.25774 mm, the value of R12 is -9.366924 mm, and the value of d1 is 1.59 mm.

[0070] Specifically, the front surface curvature radius of the second lens 12 is R21, the rear surface curvature radius is R22, and its core thickness along the optical axis direction is d2, where the value range of R21 is R21 ∈ (5, 20) mm; the value range of R22 is R22 ∈ (10, 30) mm; the value range of d2 is d2 ∈ (1, 5) mm.

[0071] In the present application, preferably, the value of R21 is 10.48226 mm, the value of R22 is -22.9771 mm, and the value of d2 is 2.5 mm.

[0072] Specifically, the front surface curvature radius of the third lens 13 is R31, the rear surface curvature radius is R32, and its core thickness along the optical axis direction is d3, where the value range of R31 is R31 ∈ (20, 40) mm; the value range of R32 is R32 ∈ (3, 15) mm; the value range of d3 is d3 ∈ (1, 5) mm.

[0073] In this application, preferably, the value of R31 is 27.80004 mm, the value of R32 is 5.471564 mm, and the value of d3 is 0.786 mm.

[0074] Specifically, the front surface curvature radius of the fourth lens 14 is R41, the rear surface curvature radius is R42, and its core thickness along the optical axis direction is d4, where the value range of R41 is R41 ∈ (3, 15) mm; the value range of R42 is R42 ∈ (20, 100) mm; the value range of d4 is d4 ∈ (1, 6) mm.

[0075] In this application, preferably, the value of R41 is 5.471564 mm, the value of R42 is -53.94242 mm, and the value of d4 is 2.73 mm.

[0076] Specifically, the front surface curvature radius of the fifth lens 31 is R51, the rear surface curvature radius is R52, and its core thickness along the optical axis direction is d5, where the value range of R51 is R51 ∈ (4, 15) mm; the value range of R52 is R52 ∈ (3, 12) mm; the value range of d5 is d5 ∈ (1, 10) mm.

[0077] In this application, preferably, the value of R51 is 6.34 sixth lens 324 mm, the value of R52 is 3.9905 mm, and the value of d5 is 5.545 mm.

[0078] Specifically, the front surface curvature radius of the sixth lens 32 is R61, the rear surface curvature radius is R62, and its core thickness along the optical axis direction is d6, where the value range of R61 is R61 ∈ (20, 100) mm; the value range of R62 is R62 ∈ (50, 150) mm; the value range of d6 is d6 ∈ (1, 5) mm.

[0079] In this application, preferably, the value of R61 is 34.27038 mm, the value of R62 is 86.39184 mm, and the value of d6 is 1.797 mm.

[0080] Specifically, the front surface curvature radius of the beam splitter prism 4 is R71, the rear surface curvature radius is R72, and its core thickness along the optical axis direction is d7; in this application, the front and rear surface curvature radii of the beam splitter prism 4 are both infinity ∞, that is, flat surfaces; preferably, the value of d7 is 8.5 mm.

[0081] In this embodiment, according to the parameter design requirements, an optical system for low-cost, high-magnification microscopic coaxial illumination is designed, and the technical indicators achieved by this optical system are:

[0082]

[0083] Specifically, the focal lengths of the respective lenses satisfy the following conditions:

[0084]

[0085]

[0086] As Figure 3 shown, it is the optical transfer function curve graph of this optical system, indicating that this system has met the basic requirements of industrial inspection, and its performance is excellent especially under the constraint of low cost.

[0087] As Figure 4 shown, it is the distortion graph of this optical system, indicating that the distortion of this system is extremely low, meeting the requirements of high-precision inspection. At the same time, the influence of chromatic aberration on distortion is weak, verifying the effectiveness of the apochromatic design.

[0088] As Figure 5 shown, it is the spot diagram of this optical system, indicating that the core aberrations of this system have been effectively corrected, and the spot size meets the requirements of microscopic inspection. Although the image quality at the edge decreases slightly, it is controllable, meeting the design goals of low cost and compactness.

[0089] In summary, based on the comprehensive data of MTF, distortion, and spot diagram, this system has achieved an industrial-level balance in terms of resolution, geometric accuracy, and image quality uniformity.

[0090] Compared with the prior art, the optical system provided by the present invention realizes the comprehensive performance of high magnification, low chromatic aberration, and high image quality on the premise of low cost and small volume, and solves the contradiction between high precision and equipment compatibility in industrial inspection.

[0091] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms "a", "the", and "said" used in the embodiments of the present application and the claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that unless otherwise stated, "plural" means two or more; the terms "first", "second", "third", etc. are only used for distinction, and are not used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. The term "and / or" used herein means and includes any or all possible combinations of one or more of the associated listed items. When the above description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present application, 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 circumstances.

[0092] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. A high magnification microscopic coaxial illumination optical system, characterized in that Including: A front lens group, a diaphragm, a rear lens group, and a beam splitter prism arranged in sequence along the light incident direction; the front lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence along the light incident direction, and the rear lens group includes a fifth lens and a sixth lens arranged in sequence along the light incident direction; Wherein, the first lens is a positive lens with a convex-concave shape, the second lens is a positive lens with a double-convex shape, the third lens is a negative lens with a convex-concave shape, the fourth lens is a positive lens with a double-convex shape, the fifth lens is a meniscus lens with a convex-concave shape, and the sixth lens is a positive lens with a convex-concave shape; the third lens and the fourth lens form a doublet lens.

2. The optical system according to claim 1, wherein: The magnification PMAG of the optical system is 12X, its relative aperture F..NO is 18, its effective focal length EFL is 8.8 mm, and its total optical length TTL is 119 mm.

3. The optical system according to claim 2, characterized in that, The relationship between the focal length of each lens and the effective focal length EFL of the optical system satisfies the following conditions: Wherein, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, and f6 is the focal length of the sixth lens.

4. The optical system according to claim 3, wherein: The distance D1 between the second lens and the first lens along the optical axis direction is 3.25 mm; the distance D2 between the third lens and the second lens along the optical axis direction is 0.1 mm; the distance D3 between the diaphragm and the fourth lens along the optical axis direction is 1.69 mm; the fifth lens is adjacent to the diaphragm, and the distance D4 between the fifth lens and the diaphragm along the optical axis direction is 0 mm; the distance D5 between the sixth lens and the fifth lens along the optical axis direction is 19.37 mm; the distance D6 between the beam splitter prism and the sixth lens along the optical axis direction is 5.25 mm.

5. The optical system according to claim 4, wherein The materials of each lens satisfy the following conditions: The refractive index coefficient Nd1 of the first lens has a value range of Nd1 ∈ (1.75, 1.95), and its dispersion coefficient Vd1 has a value range of Vd1 ∈ (15, 50); The refractive index coefficient Nd2 of the second lens has a value range of Nd2 ∈ (1.45, 1.75), and its dispersion coefficient Vd2 has a value range of Vd1 ∈ (45, 90); The refractive index coefficient Nd3 of the third lens has a value range of Nd3 ∈ (1.75, 1.95), and its dispersion coefficient Vd3 has a value range of Vd3 ∈ (15, 50); The refractive index coefficient Nd4 of the fourth lens has a value range of Nd4 ∈ (1.45, 1.75), and its dispersion coefficient Vd4 has a value range of Vd4 ∈ (45, 90); The refractive index coefficient Nd5 of the fifth lens has a value range of Nd5 ∈ (1.75, 1.95), and its dispersion coefficient Vd5 has a value range of Vd5 ∈ (15, 50); The refractive index coefficient Nd6 of the sixth lens has a value range of Nd6 ∈ (1.75, 1.95), and its dispersion coefficient Vd6 has a value range of Vd6 ∈ (15, 50); The refractive index coefficient Nd7 of the beam splitting prism has a value range of Nd7 ∈ (1.45, 1.75), and its dispersion coefficient Vd7 has a value range of Vd7 ∈ (45, 90).

6. The optical system according to claim 5, wherein: The refractive index coefficients Nd of the first lens, the third lens, the fifth lens, and the sixth lens all have a value of 1.94, and the dispersion coefficients Vd all have a value of 17.9; The refractive index coefficients Nd of the second lens and the fourth lens all have a value of 1.49, and the dispersion coefficients Vd all have a value of 81; The refractive index coefficient Nd7 of the beam splitting prism has a value of 1.51, and its dispersion coefficient Vd7 has a value of 64.

1.

7. The optical system according to claim 6, characterized in that, The dimensions of each lens satisfy the following conditions: The value range of the front surface curvature radius R11 of the first lens is R11 ∈ (-35, -15) mm, the value range of the rear surface curvature radius R12 is R12 ∈ (-15, -6) mm, and the value range of the core thickness d1 in the optical axis direction is d1 ∈ (1, 3.5) mm; The value range of the front surface curvature radius R21 of the second lens is R21 ∈ (5, 20) mm, the value range of the rear surface curvature radius R22 is R22 ∈ (10, 30) mm, and the value range of the core thickness d2 in the optical axis direction is d2 ∈ (1, 5) mm; The value range of the front surface curvature radius R31 of the third lens is R31 ∈ (20, 40) mm, the value range of the rear surface curvature radius R32 is R32 ∈ (3, 15) mm, and the value range of the core thickness d3 in the optical axis direction is d3 ∈ (1, 5) mm; The value range of the front surface curvature radius R41 of the fourth lens is R41 ∈ (3, 15) mm, the value range of the rear surface curvature radius R42 is R42 ∈ (20, 100) mm, and the value range of the core thickness d4 in the optical axis direction is d4 ∈ (1, 6) mm; The value range of the front surface curvature radius R51 of the fifth lens is R51 ∈ (4, 15) mm, the value range of the rear surface curvature radius R52 is R52 ∈ (3, 12) mm, and the value range of the core thickness d5 in the optical axis direction is d5 ∈ (1, 10) mm; The value range of the front surface curvature radius R61 of the sixth lens is R61 ∈ (20, 100) mm, the value range of the rear surface curvature radius R62 is R62 ∈ (50, 150) mm, and the value range of the core thickness d6 in the optical axis direction is d6 ∈ (1, 5) mm.

8. The optical system according to claim 7, wherein: The value of R11 is -28.25774 mm, the value of R12 is -9.366924 mm, and the value of d1 is 1.59 mm; The value of R21 is 10.48226 mm, the value of R22 is -22.9771 mm, and the value of d2 is 2.5 mm; The value of R31 is 27.80004 mm, the value of R32 is 5.471564 mm, and the value of d3 is 0.786 mm; The value of R41 is 5.471564 mm, the value of R42 is -53.94242 mm, and the value of d4 is 2.73 mm; The value of R51 is 6.34324 mm, the value of R52 is 3.9905 mm, and the value of d5 is 5.545 mm; The value of R61 is 34.27038 mm, the value of R62 is 86.39184 mm, and the value of d6 is 1.797 mm; The front surface curvature radius of the beam splitting prism is R71 which is infinity ∞, the rear surface curvature radius is R72 which is infinity ∞, both the front and rear surfaces of the beam splitting prism are flat, and its core thickness along the optical axis direction is d7 with a value of 8.5 mm.

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