Large-aperture internal focusing optical system

Abstract

The present invention relates to a large-aperture internally focusing optical system, which includes a first lens group with a positive optical power, a second lens group with a negative optical power, and a third lens group with a positive optical power, sequentially arranged from the object side to the imaging surface; at least the second lens group moves along the optical axis from the object side to the imaging surface for focusing; the second lens group consists of a single negative lens; the first lens group includes at least two lenses, and satisfies the following conditional formula: (1) 3.20 < T1 / D12 < 17.0; where D12 is the central air gap between the first lens and the second lens sequentially arranged from the object side to the imaging side in the first lens group, and T1 is the total length of the first lens group. The present invention has a medium-long focal length in terms of 35mm camera conversion, and is large-aperture, small-sized, lightweight, and has excellent imaging performance.

Description

Technical Field

[0001] The present invention relates to an optical system, and in particular to a large-aperture inner-focus optical system suitable for use in digital still cameras, digital video cameras and other imaging devices using solid-state imaging elements. Background Art

[0002] As solid-state imaging elements have become popular in digital still cameras, digital video cameras and other imaging devices, the performance and miniaturization of imaging optical systems have been rapidly promoted, and many internal focusing optical systems with medium and longer focal lengths have been proposed.

[0003] For example, Chinese patent application document with publication number CN102789042A (Patent Document 1) discloses an inner focus lens, which sequentially arranges a first lens group with positive focal power, a second lens group with negative focal power, and a third lens group with positive focal power from the object side, and focuses by moving the second lens group, and specifically arranges each lens group to meet Wherein, f3 represents the focal length of the third lens group, f represents the focal length of the entire optical system, f1 represents the focal length of the first lens group, and Fno represents the F number of the entire optical system.

[0004] The above patent documents still have the following problems when used:

[0005] 1. The shortest shooting distance is relatively long, which is not suitable for close-up shooting;

[0006] 2. It is difficult to realize a large-aperture optical system with a medium-long focal length when converted to a 35mm camera. If the invention in Patent Document 1 is used to realize a large-aperture optical system with a medium-long focal length when converted to a 35mm camera, the diameter of the front lens will be large, making it difficult to miniaturize the optical system.

[0007] In response to the above problems, the designer conducted in-depth thinking and active research and development, which resulted in this project. Summary of the Invention

[0008] The object of the present invention is to provide a large-aperture internal focusing optical system having a medium-long focal length when converted to a 35mm camera, and being compact, lightweight, large-aperture and having excellent imaging performance.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] A large-aperture inner-focus optical system comprising a first lens group with positive focal power, a second lens group with negative focal power, and a third lens group with positive focal power, which are arranged in sequence from the object side to the imaging plane;

[0011] At least a second lens group moves along the optical axis from the object side to the imaging plane to perform focusing;

[0012] The second lens group consists of a negative lens;

[0013] The first lens group includes at least two lenses and satisfies the following conditional formula:

[0014] (1)3.20 <T1 / D12<17.0

[0015] Wherein, D12 is the central air gap between the first lens and the second lens arranged sequentially from the object side to the imaging side in the first lens group, and T1 is the total length of the first lens group.

[0016] The optical system also meets the following conditions:

[0017] (2)0.4 <f3 / f<2.0

[0018] Wherein, f3 is the focal length of the lens with the weakest positive refractive power in the third lens group, and f is the focal length of the optical system.

[0019] The optical system meets the following conditions:

[0020] (3)fL / f<-0.3

[0021] Where fL is the focal length of the lens closest to the imaging surface in the optical system, and f is the focal length of the optical system.

[0022] The second lens group meets the following conditions:

[0023] (4)-1.0 <f2 / f<-0.2

[0024] Wherein, f2 is the focal length of the second lens group, and f is the focal length of the optical system. At least one lens in the first lens group meets the following conditions:

[0025] (5)V1≥60

[0026] Where V1 is the Abbe number of the lens.

[0027] The optical system meets the following conditions:

[0028] (6)0.1 <DL / f<0.33

[0029] DL is the distance from the center of the image-side mirror surface of the lens closest to the imaging surface in the optical system to the imaging surface on the optical axis.

[0030] With the above-described solution, the optical system of the present invention includes a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged sequentially from the object side to the image side. At least the second lens group moves along the optical axis from the object side to the image plane, thereby adjusting the focus from infinity to the closest object. By ensuring that the optical system satisfies specified conditional expressions, the present invention achieves a medium-long focal length equivalent to a 35mm camera, while also achieving a large aperture, lightweight, compact size, and excellent imaging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of Embodiment 1 of the present invention;

[0032] Figure 2 This is a diagram of spherical aberration, astigmatism, and distortion in an embodiment of the present invention, with an object distance of infinity, an imaging magnification of 1 / 40, and the closest focusing distance;

[0033] Figure 3 This is a structural diagram of embodiment 2 of the present invention;

[0034] Figure 4 This is a diagram of spherical aberration, astigmatism, and distortion in the second embodiment of the present invention when the object distance is infinite, the imaging magnification is 1 / 40, and the focus state is at the minimum distance;

[0035] Figure 5 This is a structural diagram of embodiment 3 of the present invention;

[0036] Figure 6 Graphs of spherical aberration, astigmatism, and distortion for the third embodiment of the present invention, with the object distance being infinite, the imaging magnification being 1 / 40, and the closest focusing distance;

[0037] Figure 7 This is a structural diagram of a fourth embodiment of the present invention;

[0038] Figure 8 Graphs of spherical aberration, astigmatism, and distortion for the fourth embodiment of the present invention, with the object distance being infinite, the imaging magnification being 1 / 40, and the closest focusing distance;

[0039] Figure 9 This is a structural diagram of Embodiment 5 of the present invention;

[0040] Figure 10 Graphs of spherical aberration, astigmatism, and distortion for the fifth embodiment of the present invention, with the object distance being infinite, the imaging magnification being 1 / 40, and the closest focusing distance;

[0041] Figure 11 This is a structural diagram of embodiment 6 of the present invention;

[0042] Figure 12Schematic diagrams of spherical aberration, astigmatism, and distortion in Example 6 of the present invention when the object distance is infinite, the imaging magnification is 1 / 40, and the focusing state is at the minimum distance.

[0043] Description of labels:

[0044] First lens group G1; second lens group G2; third lens group G3; imaging surface IMG; protective glass CG. DETAILED DESCRIPTION

[0045] The inner focusing optical system according to the present invention will be described in detail below with reference to the accompanying drawings.

[0046] The present invention discloses an internal focusing optical system comprising a first lens group G1 with positive focal power, a second lens group G2 with negative focal power, and a third lens group G3 with positive focal power, arranged sequentially from the object side to the image side. At least the second lens group G2 moves along the optical axis from the object side to the image plane IMG, thereby adjusting the focus from an infinity focus state to a focus state at the closest object. By arranging at least the second lens group G2, the present invention achieves focusing of the optical system without moving the entire optical system during focusing, thereby achieving miniaturization, lightweighting, and high-speed focusing while maintaining the same length of the optical system.

[0047] To achieve high-speed focusing, at least the second lens group G2 consists of a negative lens L21. To maintain high-speed focusing without increasing lens size, achieve a medium-long focal length in 35mm terms, and achieve excellent imaging performance with a large aperture, the optical system of the present invention also meets the following conditions.

[0048] (1)3.20 <T1 / D12<17.0

[0049] Wherein, D12 is the central air gap between the first lens and the second lens in the first lens group G1, and T1 is the total length of the first lens group G1.

[0050] If the optical system satisfies conditional equation (1), the system will be miniaturized and lightweight. If conditional equation (1) is not satisfied, part of the spherical aberration curve will drift to the right (positive direction). In other words, the spherical aberration of at least a portion of the points corresponding to the same vertical coordinate on the spherical aberration curve will increase, which is not conducive to the quality of the lens shooting. To further improve this quality, the refractive power of the lens needs to be increased, which will lead to a deterioration in the sensitivity between the lenses and the chromatic aberration of the lens. When improving the sensitivity and chromatic aberration, at least one low-dispersion lens needs to be added, which will significantly increase the total optical length and weight of the lens.

[0051] If the optical system according to each embodiment satisfies at least one of the following conditions (1a) and (1b) in addition to the above condition (1), the above advantageous effects are more significantly exhibited.

[0052] (1a)4.0 <T1 / D12

[0053] (1b)T1 / D12<10.0

[0054] On the basis of the above, the optical system also meets the following conditions:

[0055] (2)0.4 <f3 / f<2.0

[0056] Here, f3 is the focal length of the lens with the weakest positive refractive power in the third lens group G3, and f is the focal length of the optical system.

[0057] If the optical system satisfies conditional formula (2), the optical system can be miniaturized on the basis of the above while maintaining high-speed focusing. If conditional formula (2) is not satisfied, the refractive power of the positive lens in the rear half of the lens will increase, which will lead to an increase in the exit pupil diameter, further causing the relative illumination of the lens to deteriorate. In order to improve the relative illumination, the effective diameter of the lens after the aperture needs to be increased, that is, the weight of the focusing lens will increase. The increase in the outer diameter of the lens after the focusing lens will also lead to an increase in the diameter of the entire lens. The increase in the weight of the focusing lens is not conducive to high-speed focusing.

[0058] If the optical system according to each embodiment satisfies at least one of the following conditions (2a) and (2b) in addition to the above condition (2), the above advantageous effects are more significantly exhibited.

[0059] (2a)0.70 <f3 / f

[0060] (2b)f3 / f<1.50

[0061] In order to shorten the overall length of the lens and further miniaturize the lens, the following settings are made:

[0062] (3)fL / f<-0.3

[0063] Here, fL is the focal length of the lens closest to the imaging surface IMG within the optical system. A concave lens (negative lens) helps diverge light, expanding the angle of emitted light within a limited distance. However, when the imaging surface size is constant, a convex lens (positive lens) that facilitates light convergence requires a longer back focus distance and a larger effective lens diameter, resulting in a longer total optical length and lens outer diameter. Therefore, compared to a positive lens, a negative lens can effectively shorten the overall lens length.

[0064] If the optical system according to each embodiment satisfies the following condition (3a) in addition to the above condition (3), the above advantageous effects can be more significantly exerted.

[0065] (3a)fL / f<-0.4

[0066] Furthermore, the second lens group G2 is configured as follows:

[0067] (4)-1.0 <f2 / f<-0.2

[0068] Where f2 is the focal length of the second lens group G2. Meeting this conditional expression ensures good performance from infinity to the shortest shooting distance, shortens the range of focus lens movement, and effectively reduces the overall optical length of the lens.

[0069] If the optical system according to each embodiment satisfies at least one of the following conditions (4a) and (4b) in addition to the above condition (4), the above advantageous effects are more significantly exhibited.

[0070] (4a)-0.9 <f2 / f

[0071] (4b)f2 / f<-0.5

[0072] To reduce chromatic aberration, the first lens group G1 is configured as follows:

[0073] (5)V1≥60

[0074] The Abbe number of at least one lens in the first lens group G1 satisfies the conditional expression (5). Selecting a material with the above Abbe number can reduce the chromatic aberration of the optical system.

[0075] If the optical system according to each embodiment satisfies the following condition (5a) in addition to the above condition (5), the above advantageous effects can be more significantly exerted.

[0076] (5a)V1≥70.

[0077] (6)0.1 <DL / f<0.33

[0078] DL is the distance on the optical axis from the center of the image-side mirror surface of the lens closest to the imaging surface IMG in the optical system to the imaging surface IMG.

[0079] If the optical system according to each embodiment satisfies at least one of the following conditions (6a) and (6b) in addition to the above condition (6), the above advantageous effects can be more significantly exerted.

[0080] (6a)0.15 <DL / f

[0081] (6b)DL / f<0.30

[0082] To further elaborate on the technical content of the invention, the following embodiments are given to describe a large-aperture internal focusing optical system in detail. In the following embodiments, a protective glass CG is disposed between the optical system and the imaging surface IMG. The protective glass CG can be disposed as needed and can be omitted if not needed.

[0083] Example 1

[0084] like Figure 1 As shown, the large-aperture internal-focus optical system of this embodiment includes a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 comprises, in order from the object side toward the imaging plane IMG, a positive lens L11, a positive lens L12, a negative lens L13, and a positive lens L14. The second lens group G2 consists of a negative lens L21. The third lens group G3 comprises, in order from the object side toward the imaging side, a negative lens L31, a positive lens L32, a positive lens L33, and a negative lens L34.

[0085] In this embodiment, the second lens group G2 can move along the optical axis from the object side to the imaging plane IMG, thereby performing focusing from an infinity focused state to a minimum distance object focused state.

[0086] In this embodiment, the lens data of the optical system are set as follows:

[0087]

[0088]

[0089]

[0090]

[0091] T1 / D125.67

[0092]

[0093] According to the above lens parameters, the optical system of this embodiment satisfies the above conditional equations (1) to (6). In addition, the total length of the optical system of this embodiment is 103.00 mm, the focal length f of the optical system is 84.07 mm, and the shortest shooting distance is 793.0 mm.

[0094] Figure 2 The spherical aberration, astigmatism and distortion diagram of the optical system of this embodiment when the object distance is infinite, the imaging magnification is 1 / 40 times, and the closest focus state is shown. Figure 2 It can be seen that the imaging performance of this embodiment is excellent.

[0095] In summary, this embodiment can achieve a medium-long focal length when converted to a 35mm camera, and can also achieve a large aperture, small size, light weight and excellent imaging performance.

[0096] Example 2

[0097] like Figure 3 As shown, the large-aperture internal-focus optical system of this embodiment includes a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 comprises, in order from the object side toward the imaging plane IMG, a positive lens L11, a positive lens L12, a negative lens L13, and a positive lens L14. The second lens group G2 consists of a negative lens L21. The third lens group G3 comprises, in order from the object side toward the imaging side, a negative lens L31, a positive lens L32, a positive lens L33, and a negative lens L34.

[0098] In this embodiment, the second lens group G2 can move along the optical axis from the object side to the imaging plane IMG, thereby performing focusing from an infinity focused state to a minimum distance object focused state.

[0099] In this embodiment, the lens data of the optical system are set as follows:

[0100]

[0101]

[0102] Optical system length 101.0 Minimum shooting distance 800.0

[0103] f364.36

[0104] f 82.49

[0105] fL -68.77

[0106] T1 / D1216.68

[0107]

[0108]

[0109] According to the above lens parameters, the optical system of this embodiment satisfies the above conditional equations (1) to (6). In addition, the total length of the optical system of this embodiment is 101.0 mm, the focal length f of the optical system is 82.49 mm, and the shortest shooting distance is 800.0 mm.

[0110] like Figure 4 As shown in FIG, the spherical aberration, astigmatism and distortion diagram of the optical system of this embodiment is in the state of infinite distance, imaging magnification of 1 / 40 times and closest distance focus. Figure 4 It can be seen that the imaging performance of this embodiment is excellent.

[0111] In summary, this embodiment can achieve a medium-long focal length when converted to a 35mm camera, and can also achieve a large aperture, small size, light weight and excellent imaging performance.

[0112] Example 3

[0113] like Figure 5 As shown, the large-aperture internal-focus optical system of this embodiment includes a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 comprises, in order from the object side toward the imaging plane IMG, a positive lens L11, a positive lens L12, a negative lens L13, and a positive lens L14. The second lens group G2 consists of a negative lens L21. The third lens group G3 comprises, in order from the object side toward the imaging side, a negative lens L31, a positive lens L32, a positive lens L33, and a negative lens L34.

[0114] In this embodiment, the second lens group G2 can move along the optical axis from the object side to the imaging plane IMG, thereby performing focusing from an infinity focused state to a minimum distance object focused state.

[0115] In this embodiment, the lens data of the optical system are set as follows:

[0116]

[0117]

[0118] Optical system total length 100.5

[0119] Shortest shooting distance 788.9

[0120] f3120.82

[0121] f 82.45

[0122] fL -81.65

[0123] T1 / D129.42

[0124]

[0125] According to the above lens parameters, the optical system of this embodiment satisfies the above conditional equations (1) to (6). In addition, the total length of the optical system of this embodiment is 100.5 mm, the focal length f of the optical system is 82.45 mm, and the shortest shooting distance is 788.9 mm.

[0126] like Figure 6As shown in FIG, the spherical aberration, astigmatism and distortion diagram of the optical system of this embodiment is in the state of infinite distance, imaging magnification of 1 / 40 times and closest distance focus. Figure 6 It can be seen that the imaging performance of this embodiment is excellent.

[0127] In summary, this embodiment can achieve a medium-long focal length when converted to a 35mm camera, and can also achieve a large aperture, small size, light weight and excellent imaging performance.

[0128] Example 4

[0129] like Figure 7 As shown, the large-aperture internal-focus optical system of this embodiment includes a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 comprises, in order from the object side toward the imaging plane IMG, a positive lens L11, a positive lens L12, a negative lens L13, a negative lens L14, and a positive lens L15. The second lens group G2 consists of a negative lens L21. The third lens group G3 comprises, in order from the object side toward the imaging side, a positive lens L31, a positive lens L32, a negative lens L33, and a negative lens L34.

[0130] In this embodiment, the second lens group G2 can move along the optical axis from the object side to the imaging plane IMG, thereby performing focusing from an infinity focused state to a minimum distance object focused state.

[0131] In this embodiment, the lens data of the optical system are set as follows:

[0132]

[0133]

[0134]

[0135] Optical system total length 110.0

[0136] Minimum shooting distance 800.0

[0137] f346.60

[0138] f 83.55

[0139] fL -85.71

[0140] T1 / D127.19

[0141]

[0142] According to the above lens parameters, the optical system of this embodiment satisfies the above conditional equations (1) to (6). In addition, the total length of the optical system of this embodiment is 110.0 mm, the focal length f of the optical system is 83.55 mm, and the shortest shooting distance is 800.0 mm.

[0143] like Figure 8 As shown in FIG, the spherical aberration, astigmatism and distortion diagram of the optical system of this embodiment is in the state of infinite distance, imaging magnification of 1 / 40 times and closest distance focus. Figure 8 It can be seen that the imaging performance of this embodiment is excellent.

[0144] In summary, this embodiment can achieve a medium-long focal length when converted to a 35mm camera, and can also achieve a large aperture, small size, light weight and excellent imaging performance.

[0145] Example 5

[0146] like Figure 9 As shown, the large-aperture internal-focus optical system of this embodiment includes a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 comprises, in order from the object side toward the imaging plane IMG, a positive lens L11, a positive lens L12, a negative lens L13, and a positive lens L14. The second lens group G2 consists of a negative lens L21. The third lens group G3 comprises, in order from the object side toward the imaging side, a positive lens L31, a negative lens L32, a positive lens L33, a negative lens L34, a positive lens L35, and a negative lens L36.

[0147] In this embodiment, focusing can be performed by the second lens group G2 and the positive lens L33 of the third lens group G3, wherein the second lens group G2 moves along the optical axis from the object side to the imaging plane IMG, and the lens L33 moves along the optical axis from the imaging plane IMG to the object side, thereby performing focusing from the infinity focus state to the closest object focus state.

[0148] In this embodiment, the lens data of the optical system are set as follows:

[0149]

[0150]

[0151]

[0152] Optical system length 135.0

[0153] Minimum shooting distance 600.0

[0154] f380.51

[0155] f / 85.92

[0156] fL -66.54

[0157] T1 / D124.11

[0158]

[0159] According to the above lens parameters, the optical system of this embodiment satisfies the above conditional equations (1) to (6). In addition, the total length of the optical system of this embodiment is 135.0 mm, the focal length f of the optical system is 85.92 mm, and the shortest shooting distance is 600.0 mm.

[0160] like Figure 10 As shown in FIG, the spherical aberration, astigmatism and distortion diagram of the optical system of this embodiment is in the state of infinite distance, imaging magnification of 1 / 40 times and closest distance focus. Figure 10 It can be seen that the imaging performance of this embodiment is excellent.

[0161] In summary, this embodiment can achieve a medium-long focal length when converted to a 35mm camera, and can also achieve a large aperture, small size, light weight and excellent imaging performance.

[0162] Example 6

[0163] like Figure 11 As shown, the large-aperture internal-focus optical system of this embodiment includes a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 comprises, in order from the object side toward the imaging plane IMG, a positive lens L11, a positive lens L12, a negative lens L13, and a positive lens L14. The second lens group G2 consists of a negative lens L21. The third lens group G3 comprises, in order from the object side toward the imaging side, a positive lens L31, a negative lens L32, a positive lens L33, a negative lens L34, and a negative lens L35.

[0164] In this embodiment, focusing can be performed by the second lens group G2 and the positive lens L33 of the third lens group G3, wherein the second lens group G2 moves along the optical axis from the object side to the imaging plane IMG, and the lens L33 moves along the optical axis from the imaging plane IMG to the object side, thereby performing focusing from the infinity focus state to the closest object focus state.

[0165] In this embodiment, the lens data of the optical system are set as follows:

[0166]

[0167]

[0168]

[0169] Optical system total length 110.0

[0170] Minimum shooting distance 800.0

[0171] f3121.92

[0172] f 82.45

[0173] fL -143.57

[0174] T1 / D1211.85

[0175]

[0176] According to the above lens parameters, the optical system of this embodiment satisfies the above conditional equations (1) to (6). In addition, the total length of the optical system of this embodiment is 110.0 mm, the focal length f of the optical system is 82.45 mm, and the shortest shooting distance is 800.0 mm.

[0177] like Figure 12 As shown in FIG, the spherical aberration, astigmatism and distortion diagram of the optical system of this embodiment is in the state of infinite distance, imaging magnification of 1 / 40 times and closest distance focus. Figure 12 It can be seen that the imaging performance of this embodiment is excellent.

[0178] In summary, this embodiment can achieve a medium-long focal length when converted to a 35mm camera, and can also achieve a large aperture, small size, light weight and excellent imaging performance.

[0179] The above description is merely an embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A large-aperture internal focusing optical system, characterized by: The optical system comprises a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, which are arranged in sequence from the object side to the image side. The first lens group is located on the object side of the aperture stop, and the second and third lens groups are located on the image side of the aperture stop. At least a second lens group moves along the optical axis from the object side to the image side to perform focusing; The first lens group is composed of a positive lens, a positive lens, a negative lens and a positive lens arranged in sequence from the object side to the imaging side; The second lens group consists of a negative lens; The third lens group includes a first negative lens, a first positive lens, and a sub-lens group arranged in order from the imaging side to the object side, wherein the sub-lens group includes at least one positive lens and one negative lens, the first negative lens is the lens closest to the imaging side of the third lens group, and the first positive lens is the lens second closest to the imaging side of the third lens group; The first lens group satisfies the following conditional formula: (1) 3.20 < T1 / D12 < 17.0; Wherein, D12 is the central air gap between the first lens and the second lens arranged sequentially from the object side to the imaging side in the first lens group, and T1 is the total length of the first lens group.

2. The large-aperture internal focusing optical system according to claim 1, wherein: The optical system also meets the following conditions: (2) 0.4 < f3 / f < 2.0; Wherein, f3 is the focal length of the lens with the weakest positive refractive power in the third lens group, and f is the focal length of the optical system.

3. The large-aperture internal focusing optical system according to claim 1, wherein: The optical system meets the following conditions: (3) fL / f < -0.3; Where fL is the focal length of the lens closest to the image side in the optical system, and f is the focal length of the optical system.

4. The large-aperture internal focusing optical system according to claim 1, wherein: The second lens group meets the following conditions: (4) -1.0 < f2 / f < -0.2; Where f2 is the focal length of the second lens group, and f is the focal length of the optical system.

5. The large-aperture internal focusing optical system according to claim 1, wherein: At least one lens in the first lens group meets the following conditions: （5）V1 ≥ 60； Where V1 is the Abbe number of the lens.

6. The large-aperture internal focusing optical system according to claim 1, wherein: The optical system meets the following conditions: (6) 0.1 < DL / f < 0.33; DL is the distance from the center of the image-side mirror surface of the lens closest to the image side in the optical system to the image side on the optical axis.

7. A large-aperture internal-focus optical system, characterized in that: The optical system comprises a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, which are arranged in sequence from the object side to the image side. The first lens group is located on the object side of the aperture stop, and the second and third lens groups are located on the image side of the aperture stop. At least a second lens group moves along the optical axis from the object side to the image side to perform focusing; The first lens group consists of a positive lens, a positive lens, a negative lens, a negative lens, and a positive lens arranged in order from the object side to the image side; The second lens group consists of a negative lens; The third lens group consists of a positive lens, a positive lens, a negative lens, and a negative lens arranged in order from the object side to the image side; The first lens group satisfies the following conditional formula: (1) 3.20 < T1 / D12 < 17.0 Wherein, D12 is the central air gap between the first lens and the second lens arranged sequentially from the object side to the imaging side in the first lens group, and T1 is the total length of the first lens group.

8. The large-aperture inner-focusing optical system according to claim 7, wherein: The optical system also meets the following conditions: (2) 0.4 < f3 / f < 2.0; Wherein, f3 is the focal length of the lens with the weakest positive refractive power in the third lens group, and f is the focal length of the optical system.

9. The large-aperture inner-focusing optical system according to claim 7, wherein: The optical system meets the following conditions: (3) fL / f < -0.3; Where fL is the focal length of the lens closest to the image side in the optical system, and f is the focal length of the optical system.

10. The large-aperture inner-focusing optical system according to claim 7, wherein: The second lens group meets the following conditions: (4) -1.0 < f2 / f < -0.2; Where f2 is the focal length of the second lens group, and f is the focal length of the optical system.

11. The large-aperture inner-focusing optical system according to claim 7, wherein: At least one lens in the first lens group meets the following conditions: （5）V1 ≥ 60； Where V1 is the Abbe number of the lens.

12. The large-aperture internal focusing optical system according to claim 7, wherein: The optical system meets the following conditions: (6) 0.1 < DL / f < 0.33; DL is the distance from the center of the image-side mirror surface of the lens closest to the image side in the optical system to the image side on the optical axis.

13. A large-aperture internal-focus optical system, characterized in that: The optical system comprises a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, which are arranged in sequence from the object side to the image side. The first lens group is located on the object side of the aperture stop, and the second and third lens groups are located on the image side of the aperture stop. At least a second lens group moves along the optical axis from the object side to the image side to perform focusing; The first lens group consists of a positive lens, a positive lens, a negative lens, and a positive lens arranged in order from the object side to the image side; The second lens group consists of a negative lens; The third lens group consists of a positive lens, a negative lens, a positive lens, a negative lens, and a negative lens, arranged in order from the object side to the image side; The first lens group satisfies the following conditional formula: (1) 3.20 < T1 / D12 < 17.0 Wherein, D12 is the central air gap between the first lens and the second lens arranged sequentially from the object side to the imaging side in the first lens group, and T1 is the total length of the first lens group.

14. The large-aperture inner-focusing optical system according to claim 13, wherein: The optical system also meets the following conditions: (2) 0.4 < f3 / f < 2.0; Wherein, f3 is the focal length of the lens with the weakest positive refractive power in the third lens group, and f is the focal length of the optical system.

15. The large-aperture inner-focusing optical system according to claim 13, wherein: The optical system meets the following conditions: (3) fL / f < -0.3; Where fL is the focal length of the lens closest to the image side in the optical system, and f is the focal length of the optical system.

16. The large-aperture inner-focusing optical system according to claim 13, wherein: The second lens group meets the following conditions: (4) -1.0 < f2 / f < -0.2; Where f2 is the focal length of the second lens group, and f is the focal length of the optical system.

17. The large-aperture inner-focusing optical system according to claim 13, wherein: At least one lens in the first lens group meets the following conditions: （5）V1 ≥ 60； Where V1 is the Abbe number of the lens.

18. The large-aperture inner-focusing optical system according to claim 13, wherein: The optical system meets the following conditions: (6) 0.1 < DL / f < 0.33; DL is the distance from the center of the image-side mirror surface of the lens closest to the image side in the optical system to the image side on the optical axis.

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