Large aperture inner focusing optical system

Abstract

The present application relates to a kind of large aperture inner focusing optical system, it includes the first lens group with positive optical power, the second lens group with negative optical power and the third lens group with optical power in order from object side to image side direction;The first lens group includes the first lens group, aperture and second lens group in order from object side to image side direction;The first lens group at least includes the positive lens, negative lens and object side face concave lens in order from object side to image side direction;The second lens group at least includes a negative lens;The second lens group is single lens for focusing along optical axis;The optical system satisfies condition formula (1): 0.0<D1b / D1a<2.0;Wherein, D1a is the length of first lens group in optical axis direction, D1b is the length of second lens group in optical axis direction.The present application makes the optical system satisfy specified condition formula, so that the optical system can shorten the shortest shooting distance, while realizing large aperture, small and excellent imaging performance.

Description

Technical Field

[0001] This invention relates to optical systems, and more specifically to a large-aperture internal focusing optical system, which is suitable for imaging devices using solid-state imaging elements, such as digital still cameras and digital camcorders. Background Technology

[0002] The widespread adoption of solid-state imaging elements in digital still cameras, digital camcorders, and other imaging devices has led to rapid advancements in the performance and miniaturization of imaging optical systems, and has resulted in the development of many internal focusing optical systems with medium to high focal lengths.

[0003] For example, Chinese patent application CN112198644A (hereinafter referred to as Document 1) discloses an imaging lens and a camera device, which reduces spherical aberration and astigmatism by setting a rear lens group and a second lens group, and enables the imaging lens to have high-quality imaging performance by limiting the focal length of the front lens group and the combined focal length of the second and third lens groups.

[0004] However, the internal focusing optical system disclosed in Reference 1 has a relatively long minimum shooting distance, making it unsuitable for close-up shooting.

[0005] In response to the above problems, the designer conducted in-depth conceptualization and active research and development, resulting in this project. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a large-aperture internal focusing optical system to achieve a bright and miniaturized lens with excellent imaging performance at an extremely short shooting distance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A large-aperture internal focusing optical system includes a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with optical power arranged sequentially from the object side to the image side.

[0009] The first lens group includes a first lens group, an aperture, and a second lens group arranged sequentially from the object side to the image side; the first lens group includes at least a positive lens, a negative lens, and a lens with an inwardly concave object side arranged sequentially from the object side to the image side; the second lens group includes at least one negative lens;

[0010] The second lens group consists of a single lens that can be moved along the optical axis for focusing.

[0011] The optical system satisfies condition (1):

[0012] (1) 0.0 < D1b / D1a < 2.0;

[0013] Where D1a is the length of the first lens group in the optical axis direction, and D1b is the length of the second lens group in the optical axis direction.

[0014] The optical system also satisfies condition (2):

[0015] (2) 0.1 < D1b / L < 0.5;

[0016] Where D1b is the length of the second lens group in the optical axis direction, and L is the total length of all lens elements in the optical axis direction from the lens surface closest to the object side to the lens surface closest to the image side.

[0017] The optical system also satisfies conditions (3) and (4):

[0018] (3) -50 < f1a / f < 20;

[0019] (4) 1.0 < f11 / f < 9.0;

[0020] Where f1a is the focal distance of the first lens group; f11 is the focal distance of the positive lens closest to the object side in the first lens group; and f is the focal distance of the entire optical system.

[0021] The optical system also satisfies condition (5):

[0022] (5) |f1b / f1a| < 1.5;

[0023] f1a is the focal distance of the first lens group, and flb is the focal distance of the second lens group.

[0024] The optical system also satisfies condition (6):

[0025] (6) 1 < fL1 / D1b < 11;

[0026] Where fL1 is the focal distance of the lens closest to the image side in the first lens group, and D1a is the length of the first lens group in the optical axis direction.

[0027] The optical system also satisfies conditions (7) and (8):

[0028] (7) 0.10 < Df / D < 0.3;

[0029] (8) Nd max - Nd min < 0.3;

[0030] Df is the distance on the optical axis from the lens surface closest to the image side in the first lens group to the lens surface closest to the object side in the third lens group; D is the distance on the optical axis from the lens surface closest to the object side to the imaging plane in the optical system, i.e., the total length of the optical system; Ndmax and Ndmin refer to the maximum and minimum refractive indices of the lens elements between the lens element closest to the image side in the first lens group and the lens element closest to the object side in the third lens group.

[0031] The optical system also satisfies condition (9):

[0032] (9) 0.05 < BF / Y < 1.5;

[0033] Where BF is the distance from the lens surface closest to the image side to the imaging surface along the optical axis, and Y is the maximum image height at the imaging surface position.

[0034] By adopting the above scheme, the present invention enables the optical system to shorten the minimum shooting distance and achieve large-aperture, miniaturized and excellent imaging performance by making the optical system meet the specified conditions. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the optical system structure in Example 1;

[0036] Figure 2 The images shown are of spherical aberration, astigmatism, and distortion under the closest focusing state of the optical system in Example 1, with the object distance being infinite and the imaging magnification being 1 / 40 (where a corresponds to the spherical aberration image, b corresponds to the astigmatism image, and c corresponds to the distortion image).

[0037] Figure 3 This is a schematic diagram of the optical system structure in Example 2;

[0038] Figure 4 The images shown are of spherical aberration, astigmatism, and distortion under the closest focusing state of the optical system in Example 2, with the object distance being infinite and the imaging magnification being 1 / 40 (where a corresponds to the spherical aberration image, b corresponds to the astigmatism image, and c corresponds to the distortion image).

[0039] Figure 5 This is a schematic diagram of the optical system structure in Example 3;

[0040] Figure 6 The images shown are of spherical aberration, astigmatism, and distortion under the closest focusing state of the optical system in Example 3, with the object distance being infinite and the imaging magnification being 1 / 40 (where a corresponds to the spherical aberration image, b corresponds to the astigmatism image, and c corresponds to the distortion image).

[0041] Figure 7 This is a schematic diagram of the optical system structure in Example 4;

[0042] Figure 8The images shown are spherical aberration, astigmatism, and distortion at the closest focusing distance of the optical system in Example 4, with the object distance being infinite and the imaging magnification being 1 / 40 (where a corresponds to the spherical aberration image, b corresponds to the astigmatism image, and c corresponds to the distortion image). Detailed Implementation

[0043] The internal focusing optical system of the present invention will now be described in detail.

[0044] This invention discloses a large-aperture internal focusing optical system, comprising a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with optical power arranged sequentially from the object side to the image side. The first lens group includes a first lens assembly, an aperture, and a second lens assembly arranged sequentially from the object side to the image side. The first lens assembly includes at least a positive lens, a negative lens, and a lens with an inwardly concave object side arranged sequentially from the object side to the image side. The second lens group includes at least one negative lens. The second lens group is a single lens that can be moved along the optical axis for focusing. The spacing between the first and second lens groups, and the spacing between the second and third lens groups, changes as the second lens group moves along the optical axis. By configuring the second lens group G2, focusing of the optical system is achieved, eliminating the need to move the entire optical system during focusing. This results in miniaturization and high-speed focusing of the optical system while maintaining its length.

[0045] Based on the above, the optical system can achieve quasi-wide-angle, bright and miniaturized lens at extremely short shooting distances and excellent imaging performance by satisfying the specified conditions (1)-(9).

[0046] The conditional expression (1) is as follows:

[0047] (1) 0.0 < D1b / D1a < 2.0;

[0048] Where D1a is the length of the first lens group in the optical axis direction, and D1b is the length of the second lens group in the optical axis direction. Satisfying condition (1) can reduce the outer diameter of the lens elements in the first lens group, which is a condition for realizing large aperture and miniaturization of optical systems.

[0049] By controlling the values ​​of D1b / D1a within the aforementioned range, the placement area of ​​the aperture on the optical path can be restricted, allowing for an effective balance between the overall optical system length and peripheral aberrations. If the values ​​exceed the aforementioned range, the deterioration of peripheral aberrations necessitates compensation by increasing the number of lenses and the overall optical system length, making miniaturization difficult.

[0050] If the optical system involved in each embodiment satisfies at least one of the following conditions (1a) and (1b) in addition to satisfying the above-mentioned condition (1), the above-mentioned advantageous effects will be more obviously realized.

[0051] (1a) 0.2 < D1b / D1a;

[0052] (1b)D1b / D1a<1.2.

[0053] Condition (2) is as follows:

[0054] (2) 0.1 < D1b / L < 0.5;

[0055] Where D1b is the length of the second lens group in the optical axis direction, and L is the total length of all lens elements in the optical axis direction from the lens surface closest to the object side to the lens surface closest to the image side. When condition (2) is met, miniaturization of the optical system can be made easier while satisfying optical performance requirements.

[0056] If the optical system involved in each embodiment satisfies at least one of the following conditions (2a) and (2b) in addition to satisfying the above-mentioned condition (2), the above-mentioned advantageous effects will be more obviously realized.

[0057] (2a) 0.12 < D1b / L;

[0058] (2b)D1b / L<0.32.

[0059] Conditional expressions (3)-(4) are as follows:

[0060] (3) -50 < f1a / f < 20;

[0061] (4) 1.0 < f11 / f < 9.0;

[0062] Where f1a is the focal distance of the first lens group; f11 is the focal distance of the positive lens closest to the object side in the first lens group; and f is the focal distance of the entire optical system. Satisfying conditions (3) and (4) allows for effective control of the aberrations of the optical system without increasing the overall size of the optical system.

[0063] If the optical system involved in each embodiment satisfies at least one of the following conditions (3a) and (3b) in addition to satisfying the above-mentioned condition (3), the above-mentioned advantageous effects will be more obviously realized.

[0064] (3a)-35<f1a / f;

[0065] (3b)fla / f<13.

[0066] If the optical system involved in each embodiment satisfies at least one of the following conditions (4a) and (4b) in addition to satisfying the above-mentioned condition (4), the above-mentioned advantageous effects will be more obviously realized.

[0067] (4a) 1.2 < f11 / f;

[0068] (4b)f11 / f<5.0.

[0069] Conditional expression (5) is shown below:

[0070] (5) |f1b / f1a| < 1.5;

[0071] f1a is the focal distance of the first lens group, and f1b is the focal distance of the second lens group. When condition (5) is met, the size of the first lens group and the magnitude of the aberration can be balanced relatively well, which helps to miniaturize the overall optical system.

[0072] If the optical system involved in each implementation method satisfies the above conditions... In addition, the following conditions must be met. and If at least one of the conditions is met, the aforementioned beneficial effects will be more clearly realized.

[0073] -0.8 < f1b / f1a;

[0074] f1b / f1a < 0.8.

[0075] The condition (6) is as follows:

[0076] (6) 1 < fL1 / D1b < 11;

[0077] Where fL1 is the focal distance of the lens closest to the image side in the first lens group, and D1a is the length of the first lens group in the optical axis direction. Satisfying condition (6) can easily balance the size of the first lens group and the magnitude of the aberration.

[0078] If the optical system involved in each implementation method satisfies the above conditions... In addition, the following conditions must be met. and If at least one of the conditions is met, the aforementioned beneficial effects will be more clearly realized.

[0079] 2 < fL1 / D1b;

[0080] fL1 / D1b < 9.

[0081] Conditions (7)-(8) are shown below:

[0082] (7) 0.10 < Df / D < 0.3;

[0083] (8) Nd max - Nd min < 0.3;

[0084] Df is the distance on the optical axis from the lens surface closest to the image side in the first lens group to the lens surface closest to the object side in the third lens group; D is the distance on the optical axis from the lens surface closest to the object side to the imaging plane, i.e., the total length of the optical system; Ndmax and Ndmin refer to the maximum and minimum refractive indices of the lens elements between the lens elements closest to the image side in the first lens group and the lens elements closest to the object side in the third lens group. It satisfies condition (7), which is extremely advantageous for shortening the shortest shooting distance; it satisfies condition (8), which is advantageous for correcting spherical aberration and coma.

[0085] If the optical system involved in each embodiment satisfies at least one of the following conditions (7a) and (7b) in addition to satisfying the above-mentioned condition (7), the above-mentioned advantageous effects will be more obviously realized.

[0086] (7a) 0.12 < Df / D;

[0087] (7b) DffD < 0.2.

[0088] The conditional expression (9) is shown below:

[0089] (9) 0.05 < BF / Y < 1.5

[0090] Where BF is the distance from the lens surface closest to the image side to the imaging surface along the optical axis, and Y is the maximum image height at the imaging surface position. It satisfies condition (9), making it easy to miniaturize the optical system.

[0091] If the optical system involved in each embodiment satisfies at least one of the following conditions (9a) and (9b) in addition to satisfying the above-mentioned condition (9), the above-mentioned advantageous effects will be more obviously realized.

[0092] (9a) 0.40 < BF / Y;

[0093] (9b)BF / Y < 1.2.

[0094] To further elaborate on the technical content of the invention, the following embodiments will be provided to describe the large-aperture internal focusing optical system in detail.

[0095] In the following embodiments, a protective glass CG is disposed between the optical system and the imaging plane IMG. The protective glass CG can be configured as needed and can be omitted if not needed.

[0096] Example 1

[0097] like Figure 1As shown, the large-aperture internal focusing optical system of this embodiment includes a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with optical power arranged sequentially from the object side to the image side.

[0098] The first lens group G1 includes a first lens group G1a, an aperture S, and a second lens group G1b.

[0099] The first lens group G1a includes, in sequence from the object side to the image side, a meniscus lens L11 with positive optical power and convex towards the object side, a lens L12 with negative optical power and concave image side, a lens L13 with negative optical power and concave object side, a meniscus lens L14 convex towards the image side, and a biconvex lens L15. The image side of lens L13 is in contact with the object side of lens L14.

[0100] The second lens group G1b includes a biconvex lens L16, a lens L17 convex to the image side, and a meniscus lens L18 convex to the image side, arranged sequentially from the object side to the image side. The image side of the biconvex lens L16 is in contact with the object side of the lens L17.

[0101] The second lens group G2 consists of a single lens that can be moved along the optical axis for focusing. This single lens is a lens L21 with a concave surface facing the image side and having negative optical power.

[0102] The third lens group G3 includes a biconvex lens L31 arranged from the object side to the image side, and a lens L32 with negative optical power and concave surface facing the object side.

[0103] In this embodiment, the lens data settings for each lens in the optical system are as follows:

[0104] Optical parameters

[0105]

[0106]

[0107] Aspherical data

[0108] Page 19

[0109] K = 0.00000E+00

[0110] Page 20

[0111] K = 0.00000E+00

[0112] Page 21

[0113] K = 0.00000E+00

[0114] Page 22

[0115] K = 0.00000E+00 A8 = 2.84101E-10

[0116] No. noodle

[0117] K = 0.00000E+00.

[0118] No. noodle

[0119] K = 0.00000E+00

[0120]

[0121] Based on the lens parameters described above, the optical system of this embodiment satisfies conditions (1)-(9), and the shortest imaging distance is 0.24m. Furthermore, combined with... Figure 2 It can be seen that the imaging performance of this embodiment is excellent, that is, this embodiment can still have a large aperture, a near-wide angle and excellent imaging performance while reducing the minimum shooting distance.

[0122] Example 2

[0123] like Figure 3 As shown, the large-aperture internal focusing optical system of this embodiment includes a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with optical power arranged sequentially from the object side to the image side.

[0124] The first lens group G1 includes a first lens group G1a, an aperture S, and a second lens group G1b.

[0125] The first lens group G1a includes, in sequence from the object side to the image side, a meniscus lens L11 with positive optical power and convex towards the object side, a lens L12 with negative optical power and concave image side, a biconcave lens L13 with negative optical power, and a biconvex lens L14, with the object side of the biconvex lens L14 and the image side of the biconcave lens L13 in contact.

[0126] The second lens group G1b includes a biconvex lens L15, a lens L16 convex towards the image side, and a biconvex lens L17 arranged sequentially from the object side to the image side. The object sides of the biconvex lens L15 and the lens L16 are attached to each other.

[0127] The second lens group G2 consists of a single lens that can be moved along the optical axis for focusing. This single lens is a lens L21 with a concave surface facing the image side and having negative optical power.

[0128] The third lens group G3 includes a biconvex lens L31 arranged from the object side to the image side, and a lens L32 with negative optical power and concave surface facing the object side.

[0129] In this embodiment, the lens data settings for each lens in the optical system are as follows:

[0130] Optical parameters

[0131]

[0132]

[0133] Aspherical data

[0134] Page 16

[0135] K = 0.00000E+00, A4 = -1.39545E-05, A6 = -3.41613E-08, A8 = 1.72932E-10 (Page 17) K = 0.00000E+00, A4 = 6.18861E-06, A6 = -3.37027E-08, A8 = 1.82306E-10

[0136] Page 18

[0137] K=0.00000E+00,A4=5.25225E-05,A6=-2.73366E-07,A8=4.54054E-10

[0138] Page 19

[0139] K=2.08816E+00,A4=5.59839E-05,A6=-2.82317E-07,A8=-1.59565E-11

[0140] Page 22

[0141] K=0.00000E+00,A4=3.08220E-05,A6=9.21039E-09,A8=-4.86887E-11

[0142] Page 23

[0143] K=0.00000E+00,A4=2.02244E-05,A6=9.08868E-09,A8=-1.05038E-11

[0144]

[0145] Based on the lens parameters described above, the optical system of this embodiment satisfies conditions (1)-(9), and the shortest imaging distance is 0.24m. Furthermore, combined with... Figure 4 It can be seen that the imaging performance of this embodiment is excellent, that is, this embodiment can still have a large aperture, a near-wide angle and excellent imaging performance while reducing the minimum shooting distance.

[0146] Example 3

[0147] As shown in the figure As shown, the large-aperture internal focusing optical system of this embodiment includes a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with optical power arranged sequentially from the object side to the image side.

[0148] The first lens group G1 includes a first lens group G1a, an aperture S, and a second lens group G1b.

[0149] The first lens group G1a includes, in sequence from the object side to the image side, a meniscus lens L11 with positive optical power and convex towards the object side, a lens L12 with negative optical power and concave image side, a biconcave lens L13 with negative optical power, a biconvex lens L14, and a biconvex lens L15, with the object side of the biconvex lens L14 and the image side of the biconcave lens L13 in contact.

[0150] The second lens group G1b includes a biconvex lens L16, a lens L17 convex to the image side, and a meniscus lens L18 convex to the image side, arranged sequentially from the object side to the image side. The object sides of the biconvex lens L16 and the lens L17 are attached to each other.

[0151] The second lens group G2 consists of a single lens that can be moved along the optical axis for focusing. This single lens is a lens L21 with a concave surface facing the image side and having negative optical power.

[0152] The third lens group G3 includes a biconvex lens L31 arranged from the object side to the image side and a lens L32 with its concave surface facing the object side.

[0153] In this embodiment, the lens data settings for each lens in the optical system are as follows:

[0154] Optical parameters

[0155]

[0156]

[0157] Aspherical data

[0158] Page 19

[0159] K=0.00000E+00,A4=-2.28340E-05,A6=-1.29895E-08,A8=3.20275E-11,A10=2.59389E-13

[0160] Page 20

[0161] K=0.00000E+00,A4=-7.81578E-06,A6=1.06120E-08,A8=-1.01209E-10,A10=4.93994E-13

[0162] Page 21

[0163] K=0.00000E+00,A4=6.47783E-05,A6=-2.51210E-07,A8=3.86520E-10

[0164] Page 22

[0165] K=0.00000E+00,A4=8.84804E-05,A6=-2.56600E-07,A8=3.49647E-10

[0166] Page 25

[0167] K=0.00000E+00,A4=3.46765E-05,A6=-1.41966E-08,A8=-3.36923E-11

[0168] Page 26

[0169] K=0.00000E+00,A4=1.79667E-05,A6=-7.86515E-09,A8=-4.87158E-11

[0170]

[0171] Based on the lens parameters described above, the optical system of this embodiment satisfies conditions (1)-(9), and the shortest imaging distance is 0.24m. Furthermore, combined with... Figure 6 It can be seen that the imaging performance of this embodiment is excellent, that is, this embodiment can still have a large aperture, a near-wide angle and excellent imaging performance while reducing the minimum shooting distance.

[0172] Example 4

[0173] like Figure 7 As shown, the large-aperture internal focusing optical system of this embodiment includes a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with optical power arranged sequentially from the object side to the image side.

[0174] The first lens group G1 includes a first lens group G1a, an aperture S, and a second lens group G1b.

[0175] The first lens group G1a includes, in sequence from the object side to the image side, a meniscus lens L11 with positive optical power and convex to the object side, a lens L12 with the image side concave, a biconcave lens L13 with negative optical power, and a lens L14 convex to the image side.

[0176] The second lens group G1b includes a biconvex lens L15, a biconcave lens L16, a biconvex lens L17, and a meniscus lens L18 convex towards the image side, arranged sequentially from the object side to the image side. The object sides of the biconvex lens L15 and the biconcave lens L16 are in contact.

[0177] The second lens group G2 consists of a single lens that can be moved along the optical axis for focusing. This single lens is a biconcave lens L21 with negative optical power.

[0178] The third lens group G3 includes a biconvex lens L31 and a biconcave lens L32 arranged from the object side to the image side.

[0179] In this embodiment, the lens data settings for each lens in the optical system are as follows:

[0180] Optical parameters

[0181]

[0182]

[0183] Aspherical data

[0184] Page 8

[0185] K = 0.00000E+00

[0186] Page 9

[0187] K = 0.00000E+00 A8=3.81781E-09A10=-1.37422E-11,

[0188] Page 22

[0189] K = 0.00000E+00.

[0190] Page 23

[0191] K = 0.00000E+00.

[0192] No. noodle

[0193] K=0.00000E+00,A4=1.93178E-04,

[0194] No. noodle

[0195] K = 0.00000E+00

[0196] Page 27

[0197] K = 0.00000E+00.

[0198] Page 28

[0199] K = 0.00000E+00.

[0200]

[0201] Based on the lens parameters described above, the optical system of this embodiment satisfies conditions (1)-(9), and the shortest imaging distance is 0.24m. Furthermore, combined with... Figure 8 It can be seen that the imaging performance of this embodiment is excellent, that is, this embodiment can still have a large aperture, a near-wide angle and excellent imaging performance while reducing the minimum shooting distance.

[0202] The above description is merely an embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A large-aperture internal focusing optical system, characterized in that: It includes a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with optical power arranged sequentially from the object side to the image side; The first lens group includes a first lens group, an aperture, and a second lens group arranged sequentially from the object side to the image side; the first lens group includes at least a positive lens, a negative lens, and a lens with an inwardly concave object side arranged sequentially from the object side to the image side; the second lens group includes at least one negative lens; The second lens group consists of a single lens that can be moved along the optical axis for focusing. The optical system satisfies condition (1): (1) 0.0 < D1b / D1a < 2.0; Where D1a is the length of the first lens group in the optical axis direction, and D1b is the length of the second lens group in the optical axis direction.

2. The large-aperture internal focusing optical system according to claim 1, characterized in that: The optical system also satisfies condition (2): (2) 0.1 < D1b / L < 0.5; Where D1b is the length of the second lens group in the optical axis direction, and L is the total length of all lens elements in the optical axis direction from the lens surface closest to the object side to the lens surface closest to the image side.

3. The large-aperture internal focusing optical system according to claim 1, characterized in that: The optical system also satisfies condition (3) and condition (4): (3) -50 < f1a / f < 20; (4) 1.0 < f11 / f < 9.0; Where f1a is the focal distance of the first lens group; f11 is the focal distance of the positive lens closest to the object side in the first lens group; and f is the focal distance of the entire optical system.

4. The large-aperture internal focusing optical system according to claim 1, characterized in that: The optical system also satisfies condition (5): (5) |f1b / f1a| < 1.5; f1a is the focal distance of the first lens group, and f1b is the focal distance of the second lens group.

5. The large-aperture internal focusing optical system according to claim 1, characterized in that: The optical system also satisfies condition (6): (6) 1 < fL1 / D1b < 11; Where fL1 is the focal distance of the lens closest to the image side in the first lens group, and D1a is the length of the first lens group in the optical axis direction.

6. The large-aperture internal focusing optical system according to claim 1, characterized in that: The optical system also satisfies conditions (7) and (8): (7) 0.10 < Df / D < 0.3; (8) Nd max - Nd min < 0.3; Df is the distance on the optical axis from the lens surface closest to the image side in the first lens group to the lens surface closest to the object side in the third lens group; D is the distance on the optical axis from the lens surface closest to the object side to the imaging plane in the optical system, i.e., the total length of the optical system; Ndmax and Ndmin refer to the maximum and minimum refractive indices of the lens elements between the lens element closest to the image side in the first lens group and the lens element closest to the object side in the third lens group.

7. The large-aperture internal focusing optical system according to claim 1, characterized in that: The optical system also satisfies condition (9): (9) 0.05 < BF / Y < 1.5; Where BF is the distance from the lens surface closest to the image side to the imaging surface along the optical axis, and Y is the maximum image height at the imaging surface position.

Images