Optical system

Abstract

The present invention relates to an optical system, comprising a first fixed group (G1), a zoom group (G2), a stop (STOP), a second fixed group (G3), and a focusing group (G4) arranged in sequence from the object side to the image side along the optical axis. The second fixed group (G3) includes at least one cemented lens group. The optical system of the present invention has an ultra-large constant aperture, a large target surface, and ultra-high resolution, so that it can well meet the performance requirements of zoom lenses in the field of security monitoring.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and particularly to an optical system. Background Art

[0002] Zoom lenses can meet the needs of diverse monitoring scenarios due to their variable focal lengths, and have attracted attention especially in the security monitoring market. With the development of AI face recognition technology, higher requirements have been put forward for the resolution, aperture, infrared performance, and high and low temperature performance of zoom lenses applied to the security monitoring field. However, currently available zoom lenses often cannot balance the above characteristics due to performance defects, which limits their usage scenarios. For example, some zoom lenses have low resolution and cannot meet the high pixel requirements for face recognition. Or the aperture is small, and the brightness of the image in low illumination environments cannot be guaranteed. In addition, the performance of existing lenses is unstable under high and low temperature conditions, making it impossible to always ensure clear imaging in outdoor environments with large temperature differences. Summary of the Invention

[0003] The purpose of the present invention is to provide a variable-focus optical system whose performance is sufficient to meet the requirements of the security monitoring field.

[0004] To achieve the above-mentioned invention purpose, the present invention provides an optical system, which includes a first fixed group, a zoom group, a diaphragm, a second fixed group, and a focusing group arranged in sequence from the object side to the image side along the optical axis, and the second fixed group includes at least one cemented lens group.

[0005] According to one aspect of the present invention, the optical power of the first fixed group is positive, the optical power of the zoom group is negative, the optical power of the second fixed group is positive, and the optical power of the focusing group is positive.

[0006] According to one aspect of the present invention, the first fixed group includes a first lens with negative optical power, a second lens with positive optical power, and a third lens with positive optical power arranged in sequence from the object side to the image side;

[0007] The zoom group includes a fourth lens with negative optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, and a seventh lens with negative optical power arranged in sequence from the object side to the image side, and the fifth lens is a biconcave lens;

[0008] The second fixed group includes an eighth lens with positive optical power, a ninth lens with negative optical power, a tenth lens with positive optical power, an eleventh lens with negative optical power, a twelfth lens with positive optical power, a thirteenth lens with negative optical power, and a fourteenth lens with positive optical power arranged in sequence from the object side to the image side, the tenth lens is a biconvex lens, the eleventh lens is a biconcave lens, and the twelfth lens is a biconvex lens;

[0009] The focusing group includes a fifteenth lens with a positive optical power, a sixteenth lens with a negative optical power, a seventeenth lens with a positive optical power, and an eighteenth lens with a negative optical power, which are arranged in sequence from the object side to the image side. The sixteenth lens is a biconcave lens.

[0010] According to one aspect of the present invention, the focal lengths fⅠ of the first fixed group, fⅡ of the zoom group, fⅢ of the second fixed group, and fⅣ of the focusing group respectively satisfy the following relationships with the focal length fw of the wide-angle end of the optical system:

[0011] 4.0 ≤ fⅠ:fw ≤ 6.5, -2.4 ≤ fⅡ:fw ≤ -1.0, 1.5 ≤ fⅢ:fw ≤ 3.0, 2.2 ≤ fⅣ:fw ≤ 5.8.

[0012] According to one aspect of the present invention, the distance ΔD that the zoom group moves from the wide-angle end to the telephoto end of the optical system satisfies the following relationship with the total length TTL of the optical system:

[0013] 0.1 < ΔD / TTL < 0.3.

[0014] According to one aspect of the present invention, the ratio of the focal length f7 of the seventh lens to the focal length fⅡ of the zoom group satisfies the following relationship:

[0015] 1.5 < f7 / fⅡ < 3.6;

[0016] The ratio of the focal length f15 of the fifteenth lens to the focal length fⅣ of the focusing group satisfies the following relationship:

[0017] 0.4 < f15 / fⅣ < 1.0;

[0018] The focal lengths f9 and f10 of the ninth lens and the tenth lens satisfy the following relationship:

[0019] -2.0 < f9 / f10 < -0.9.

[0020] According to one aspect of the present invention, the Abbe number difference Vd5 - Vd6 between the fifth lens and the sixth lens satisfies the following relationship:

[0021] 30 < Vd5 - Vd6 < 65.

[0022] According to one aspect of the present invention, the refractive indices Nd8 and Nd10 of the eighth lens and the tenth lens satisfy the following relationship:

[0023] 0.4 < (Nd10 - 1) / (Nd8 - 1) < 1.2.

[0024] According to one aspect of the present invention, the radius of curvature R3b of the image side surface of the third lens and the radius of curvature R4a of the object side surface of the fourth lens satisfy the following relational expression:

[0025] 1.5 < R3b / R4a < 12.

[0026] According to one aspect of the present invention, the second fixed group includes an aspherical lens;

[0027] The cemented lens group in the second fixed group is at least composed of two adjacent lenses cemented together, and at least two adjacent lenses in the focusing group are cemented together to form a cemented lens group.

[0028] According to the solution of the present invention, an optical system is provided, which has a constant aperture and can reach up to FNO1.0 at most, so as to have the ability to clearly image under ultra-low illumination conditions. By reasonably configuring the optical power of each lens in the optical system, at least 3 times zoom can be achieved under a certain total length condition, while having high resolution and a large aperture at the same time. In addition, by specifically selecting the materials of each lens, the optical system can still ensure good resolution at a high temperature of 80°C and a low temperature of -40°C. Thus, a zoom optical system with a super-large constant aperture, a large target surface, and ultra-high resolution is formed.

[0029] According to one solution of the present invention, by reasonably distributing the focal lengths of each group and the wide-angle end of the optical lens, it is beneficial to improve the light transmittance and better realize focusing and zooming.

[0030] According to one solution of the present invention, by reasonably setting the relationship between the moving distance during the zooming of the zoom group and the total length of the optical system, a large zoom ratio can be realized as much as possible, thereby better restricting the total length of the lens.

[0031] According to one solution of the present application, the ratio of the focal length f7 of the seventh lens to the focal length fⅡ of the zoom group satisfies the following relational expression: 1.5 < f7 / fⅡ < 3.6. The ratio of the focal length f15 of the fifteenth lens to the focal length fⅣ of the focusing group satisfies the following relational expression: 0.4 < f15 / fⅣ < 1.0. The distribution of the above optical power is beneficial to correcting the field curvature and astigmatism of the wide-angle end, thereby improving the image quality.

[0032] According to one solution of the present invention, the focal lengths of the ninth lens and the tenth lens satisfy the following relational expression: -2.0 < f9 / f10 < -0.9. This lens combination method and optical power distribution can reduce the degree of deflection of light during transmission, thereby minimizing the tolerance sensitivity of the system.

[0033] According to one embodiment of the present invention, the Abbe number difference between the fifth lens and the sixth lens satisfies the following relationship: 30 < Vd5 - Vd6 < 65. This material combination can result in a relatively large Abbe number difference between adjacent lenses, thereby effectively improving the chromatic aberration of the system.

[0034] According to one embodiment of the present invention, the refractive indices of the eighth lens and the tenth lens satisfy the following relationship: 0.4 < (Nd10 - 1) / (Nd8 - 1) < 1.2. This material combination can effectively improve the light transmissibility of the varifocal group and is beneficial to enhancing the image quality.

[0035] According to one embodiment of the present invention, the radius of curvature of the image side of the third lens and the radius of curvature of the object side of the fourth lens satisfy the following relationship: 1.5 < R3b / R4a < 12. This relationship between the radii of curvature of the lenses can improve the efficiency of converging light between the first fixed group and the varifocal group, which is beneficial to better realizing the zoom process and ensuring the image quality.

[0036] According to one embodiment of the present invention, the second fixed group includes an aspherical lens. This can reduce the spherical aberration and, while achieving a super large aperture, greatly reduce the total length of the optical system. At least two adjacent lenses in the focusing group are cemented to form a cemented lens group. This way of forming a cemented lens group by lenses can also effectively reduce the high-order chromatic aberration of the system and ensure ultra-high resolution while achieving a super large aperture. Description of the Drawings

[0037] Figure 1 Schematic diagram showing the structure of the wide-angle end of the optical system according to the first embodiment of the present invention;

[0038] Figure 2 Schematic diagram showing the structure of the telephoto end of the optical system according to the first embodiment of the present invention;

[0039] Figure 3 Schematic diagram showing the visible light MTF of the wide-angle end of the optical system according to the first embodiment of the present invention;

[0040] Figure 4 Schematic diagram showing the visible light MTF of the telephoto end of the optical system according to the first embodiment of the present invention;

[0041] Figure 5 Schematic diagram showing the structure of the wide-angle end of the optical system according to the second embodiment of the present invention;

[0042] Figure 6 Schematic diagram showing the structure of the telephoto end of the optical system according to the second embodiment of the present invention;

[0043] Figure 7Schematically shows the visible light MTF graph of the wide-angle end of the optical system according to the second embodiment of the present invention;

[0044] Figure 8 Schematically shows the visible light MTF graph of the telephoto end of the optical system according to the second embodiment of the present invention;

[0045] Figure 9 Schematically shows the structural diagram of the wide-angle end of the optical system according to the third embodiment of the present invention;

[0046] Figure 10 Schematically shows the structural diagram of the telephoto end of the optical system according to the third embodiment of the present invention;

[0047] Figure 11 Schematically shows the visible light MTF graph of the wide-angle end of the optical system according to the third embodiment of the present invention;

[0048] Figure 12 Schematically shows the visible light MTF graph of the telephoto end of the optical system according to the third embodiment of the present invention;

[0049] Figure 13 Schematically shows the structural diagram of the wide-angle end of the optical system according to the fourth embodiment of the present invention;

[0050] Figure 14 Schematically shows the structural diagram of the telephoto end of the optical system according to the fourth embodiment of the present invention;

[0051] Figure 15 Schematically shows the visible light MTF graph of the wide-angle end of the optical system according to the fourth embodiment of the present invention;

[0052] Figure 16 Schematically shows the visible light MTF graph of the telephoto end of the optical system according to the fourth embodiment of the present invention. Detailed implementation manners

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0054] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" is based on the orientation or positional relationship shown in the relevant drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0055] The present invention will be described in detail below with reference to the drawings and specific embodiments. The embodiments cannot be enumerated one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0056] See Figure 1 , the (zoom) optical system of the present invention includes a first fixed group G1, a variable magnification group G2, a diaphragm STOP (fixed in position), a second fixed group G3, and a focusing group G4 arranged in sequence from the object side to the image side along the optical axis. Among them, the variable magnification group G2 can move along the optical axis to realize the switching between the wide-angle end and the telephoto end. Of course, a filter / color filter C can also be provided in front of the image plane IMA. The optical power of the first fixed group G1 is positive, the optical power of the variable magnification group G2 is negative, the optical power of the second fixed group G3 is positive, and the optical power of the focusing group G4 is positive. According to the concept of the present invention, the second fixed group G3 includes at least one cemented lens group. Preferably, the cemented lens group in the second fixed group G3 is at least composed of two lenses cemented together, that is, at least includes a doublet or a triplet. Thus, by setting a cemented lens group in the second fixed group G3, the high-order chromatic aberration of the system can be effectively reduced, ensuring ultra-high resolution while achieving a super large aperture, so that the optical system can better adapt to the applications in the field of security monitoring.

[0057] In the present invention, the first fixed group G1 includes a first lens L1 with a negative focal power, a second lens L2 with a positive focal power, and a third lens L3 with a positive focal power, which are arranged in sequence from the object side to the image side. The zoom group G2 includes a fourth lens L4 with a negative focal power, a fifth lens L5 with a negative focal power, a sixth lens L6 with a positive focal power, and a seventh lens L7 with a negative focal power, which are arranged in sequence from the object side to the image side. Among them, the fifth lens L5 is a biconcave lens. The second fixed group G3 includes an eighth lens L8 with a positive focal power, a ninth lens L9 with a negative focal power, a tenth lens L10 with a positive focal power, an eleventh lens L11 with a negative focal power, a twelfth lens L12 with a positive focal power, a thirteenth lens L13 with a negative focal power, and a fourteenth lens L14 with a positive focal power, which are arranged in sequence from the object side to the image side. Among them, the tenth lens L10 is a biconvex lens, the eleventh lens L11 is a biconcave lens, and the twelfth lens L12 is a biconvex lens. The focusing group G4 includes a fifteenth lens L15 with a positive focal power, a sixteenth lens L16 with a negative focal power, a seventeenth lens L17 with a positive focal power, and an eighteenth lens L18 with a negative focal power, which are arranged in sequence from the object side to the image side. Among them, the sixteenth lens L16 is a biconcave lens.

[0058] In the present invention, the focal lengths fⅠ of the first fixed group G1, fⅡ of the zoom group G2, fⅢ of the second fixed group G3, and fⅣ of the focusing group G4 respectively satisfy the following relationships with the focal length fw of the wide-angle end of the optical system: 4.0 ≤ fⅠ:fw ≤ 6.5, -2.4 ≤ fⅡ:fw ≤ -1.0, 1.5 ≤ fⅢ:fw ≤ 3.0, 2.2 ≤ fⅣ:fw ≤ 5.8. This distribution method of the focal power among the groups is beneficial to improving the light transmittance and better achieving focusing and zooming.

[0059] In the present invention, the distance ΔD that the zoom group G2 moves from the wide-angle end to the telephoto end of the optical system and the total length TTL of the optical system satisfy the following relationship: 0.1 < ΔD / TTL < 0.3. Under this condition, a large zoom ratio can be achieved as much as possible, thereby better limiting the total length of the lens.

[0060] In the present invention, the ratio of the focal length f7 of the seventh lens L7 to the focal length fⅡ of the zoom group G2 satisfies the following relationship: 1.5 < f7 / fⅡ < 3.6. The ratio of the focal length f15 of the fifteenth lens L15 to the focal length fⅣ of the focusing group G4 satisfies the following relationship: 0.4 < f15 / fⅣ < 1.0. The above distribution of the focal power is beneficial to correcting the field curvature and astigmatism at the wide-angle end, thereby improving the image quality. The focal lengths f9 and f10 of the ninth lens L9 and the tenth lens L10 satisfy the following relationship: -2.0 < f9 / f10 < -0.9. This combination method of the lenses and the distribution of the focal power can reduce the degree of deflection of the light during transmission, thereby minimizing the tolerance sensitivity of the system.

[0061] In the present invention, the Abbe number difference Vd5 - Vd6 between the fifth lens L5 and the sixth lens L6 satisfies the following relationship: 30 < Vd5 - Vd6 < 65. This material combination can result in a relatively large Abbe number difference between adjacent lenses, thereby effectively improving the chromatic aberration of the system. The refractive indices Nd8 and Nd10 of the eighth lens L8 and the tenth lens L10 satisfy the following relational expression: 0.4 < (Nd10 - 1) / (Nd8 - 1) < 1.2. This material combination can effectively improve the light transmissibility of the variable magnification group G2 and is beneficial to enhancing the image quality.

[0062] In the present invention, the radius of curvature R3b of the image side (or the rear surface) of the third lens L3 and the radius of curvature R4a of the object side (or the front surface) of the fourth lens L4 satisfy the following relational expression: 1.5 < R3b / R4a < 12. This relationship between the radii of curvature of the lenses can improve the efficiency of converging light between the first fixed group G1 and the variable magnification group G2, which is beneficial for better realizing the zoom process and ensuring the image quality.

[0063] In the present invention, the second fixed group G3 includes an aspherical lens. Thereby, it can reduce the spherical aberration, and while achieving a super large aperture, it can greatly reduce the total length of the optical system. At least two adjacent lenses in the focusing group G4 are glued together to form a glued lens group, that is, it can include a doublet or a triplet lens group. This way of making the lenses form a glued lens group can also effectively reduce the high-order chromatic aberration of the system, ensuring an ultra-high resolution while achieving a super large aperture.

[0064] The aperture of the optical system set as above is constant, up to FNO1.0 at most, and it has the effect of being able to clearly image under ultra-low illumination conditions. Moreover, by reasonably configuring the optical power of each lens, at least 3-fold zoom can be achieved under a certain total length condition, while having both high resolution and a super large aperture. The material selection of each lens in the optical system is also specific, which can ensure good resolution of the system at a high temperature of 80 °C and a low temperature of -40 °C.

[0065] The following gives four sets of embodiments according to the above settings of the present invention to specifically illustrate the optical system of the present invention. In the following embodiments, 1, 2,..., N are used to represent the surfaces of each lens, where the glued surface of the glued lens group is denoted as one surface, and the aperture stop STOP can also be denoted as STO, and the image plane is IMA. In each embodiment, the aspherical lens surface shape satisfies the following formula:

[0066] Z = cy 2 / {1 + [1 - (1 + k)c 2 y 2 1 / 2}+a 4 y 4 +a 6 y​6 +a 8 y 8 +a 10 y 10 +a 12 y 12

[0067] Wherein, Z is the axial distance from the vertex to the surface at a position with a height h perpendicular to the optical axis along the optical axis direction; c represents the curvature at the vertex of the aspherical surface; y is the radial coordinate of the aspherical lens; k is the conic coefficient; a 4 、a 6 、a 8 、a 10 、a 12 、a 14 、a 16 respectively represent the aspherical coefficients of the fourth order, sixth order, eighth order, tenth order, twelfth order, fourteenth order, and sixteenth order.

[0068] The parameter settings of each embodiment satisfy Table 1 below:

[0069]

[0070] Table 1

[0071] The first embodiment:

[0072] As Figure 1 and Figure 2 shown, in this embodiment, the fifth lens L5 and the sixth lens L6 in the zoom group G2 of the optical system are cemented to form a cemented lens group, the tenth lens L10 and the eleventh lens L11 in the second fixed group G3 are cemented to form a doublet lens group, the twelfth lens L12, the thirteenth lens L13, and the fourteenth lens L14 are cemented to form a triplet lens group, and the seventeenth lens L17 and the eighteenth lens L18 in the focusing group G4 are cemented to form a doublet lens group.

[0073] Wherein, the parameters of the optical system are as follows: focal length: 12.5 - 38 mm; F number = 1.0; TTL = 122 mm. The relevant parameters of each lens, including the surface type, radius of curvature, thickness, and refractive index, are shown in Table 2 below:

[0074]

[0075]

[0076] Table 2 Table 3 shows the aspherical coefficients of each aspherical lens in this embodiment:

[0077] Surface serial number 14 15 k 0.0900 22.5000 a4 4.4117E-006 1.4433E-05 a6 3.3482E-008 2.7046E-08 a8 -2.5983E-010 -3.2200E-10 a10 9.6065E-012 1.6154E-12 a12 -1.6401E-013 -9.5920E-15 a14 1.3526E-015 1.5390E-16 a16 -4.8425E-018 -1.8327E-18

[0078] Table 3

[0079] When, as Figures 1 to 2 shown, the variable magnification group G2 changes from the wide-angle end to the telephoto end, the variable interval values are as shown in Table 4 below:

[0080]

[0081]

[0082] Table 4

[0083] Combined with Figure 3 and Figure 4 shown, the optical system of this embodiment can achieve an ultra-large aperture while greatly reducing the total length of the optical system, effectively reducing the high-order chromatic aberration of the system, and ensuring ultra-high resolution while achieving an ultra-large aperture.

[0084] The second embodiment:

[0085] As Figure 5 and Figure 6 shown, in the optical system of this embodiment, the fifth lens L5 and the sixth lens L6 in the variable magnification group G2 are cemented to form a doublet lens group, the tenth lens L10, the eleventh lens L11, and the twelfth lens L12 in the second fixed group G3 are cemented to form a triplet lens group, the thirteenth lens L13 and the fourteenth lens L14 are cemented to form a doublet lens group, and the seventeenth lens L17 and the eighteenth lens L18 in the focusing group G4 are cemented to form a doublet lens group.

[0086] Among them, the parameters of the optical system are as follows: focal length: 14 - 42 mm; F number = 1.1; TTL = 130 mm. The relevant parameters of each lens, including the surface type, radius of curvature, thickness, and refractive index, are as shown in Table 5 below:

[0087]

[0088]

[0089]

[0090] Table 5 Table 6 shows the aspherical coefficients of each aspherical lens in this embodiment:

[0091] Surface serial number 14 15 k -7.8422E-02 -8.566E+01 a4 4.9381E-07 1.3869E-05 a6 3.1376E-08 -3.9436E-09 a8 -5.3329E-10 -6.3746E-11 a10 1.1809E-11 3.0348E-12 a12 -1.1586E-13 -4.4923E-14 a14 6.2888E-16 3.3931E-16 a16 -1.4651E-18 -9.6554E-19

[0092] Table 6

[0093] When, as Figures 5 to 6 shown, the variable magnification group G2 changes from the wide-angle end to the telephoto end, the variable interval values are as shown in Table 7 below:

[0094] Surface serial number Thickness Wide-angle end Telephoto end 5 D1 0.50 31.98 12 D2 31.98 0.50 24 D3 2.54 2.77 31 D4 6.31 6.08

[0095] Table 7

[0096] Combined with Figure 7 and Figure 8 As shown, the optical system of this embodiment can achieve an ultra-large aperture while greatly reducing the total length of the optical system, effectively reducing the higher-order chromatic aberration of the system, and ensuring ultra-high resolution while achieving an ultra-large aperture.

[0097] The third embodiment:

[0098] As Figure 9 and Figure 10 shown, in the optical system of this embodiment, the fifth lens L5 and the sixth lens L6 in the zoom group G2 are cemented to form a doublet lens group, the tenth lens L10, the eleventh lens L11, and the twelfth lens L12 in the second fixed group G3 are cemented to form a triplet lens group, the thirteenth lens L13 and the fourteenth lens L14 are cemented to form a doublet lens group, and the sixteenth lens L16, the seventeenth lens L17, and the eighteenth lens L18 in the focusing group G4 are cemented to form a triplet lens group.

[0099] Among them, the parameters of the optical system are as follows: focal length: 17 - 51 mm; F number = 1.1; TTL = 135 mm. The relevant parameters of each lens, including surface type, radius of curvature, thickness, and refractive index, are shown in Table 8 below:

[0100]

[0101]

[0102] Table 8

[0103] Table 9 shows the aspheric coefficients of each aspheric lens in this embodiment:

[0104]

[0105]

[0106] Table 9

[0107] When changing from the wide-angle end to the telephoto end according to Figures 9 to 10 as shown, the variable interval values are shown in Table 10 below:

[0108] Surface serial number Thickness Wide-angle end Telephoto end 5 D1 0.80 33.43 12 D2 33.03 0.40 24 D3 2.34 2.76 30 D4 8.94 8.52

[0109] Table 10

[0110] Combined with Figure 11 and Figure 12As shown, the optical system of this embodiment can achieve a super large aperture while greatly reducing the total length of the optical system, effectively reducing the high-order chromatic aberration of the system, and ensuring ultra-high resolution while achieving a super large aperture.

[0111] Fourth Embodiment:

[0112] As Figure 13 and Figure 14 shown, in the second fixed group G3 of the optical system of this embodiment, the tenth lens L10, the eleventh lens L11, and the twelfth lens L12 are glued together to form a triplet lens group, the thirteenth lens L13 and the fourteenth lens L14 are glued together to form a doublet lens group, and the sixteenth lens L16, the seventeenth lens L17, and the eighteenth lens L18 in the focusing group G4 are glued together to form a triplet lens group.

[0113] Among them, the parameters of the optical system are as follows: focal length: 20 - 60 mm; F number = 1.2; TTL = 135 mm. The relevant parameters of each lens, including surface type, radius of curvature, thickness, and refractive index, are shown in Table 11 below:

[0114]

[0115]

[0116] Table 11

[0117] Table 12 shows the aspheric coefficients of each aspheric lens in this embodiment:

[0118] Surface serial number 15 16 k -7.9400E-02 -8.5023E+02 a4 -1.9301E-07 1.1626E-05 a6 3.7534E-08 -1.7101E-08 a8 -8.8871E-10 9.4374E-11 a10 1.4747E-11 2.7630E-12 a12 -1.1886E-13 -4.5919E-14 a14 4.8620E-16 2.8109E-16 a16 -7.5953E-19 -6.0117E-19

[0119] Table 12

[0120] When, as Figures 13 to 14 shown, the variable magnification group G2 changes from the wide-angle end to the telephoto end, the variable interval values are as shown in Table 13 below:

[0121] Surface serial number Thickness Wide-angle end Telephoto end 5 D1 0.80 31.56 13 D2 31.56 0.80 25 D3 1.68 4.97 31 D4 10.44 7.15

[0122] Table 13

[0123] Combining Figure 15 and Figure 16 shown, the optical system of this embodiment can achieve a super large aperture while greatly reducing the total length of the optical system, effectively reducing the high-order chromatic aberration of the system, and ensuring ultra-high resolution while achieving a super large aperture.

[0124] The above is only one solution of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optical system includes a first fixed group (G1), a zoom group (G2), a stop (STOP), a second fixed group (G3), and a focusing group (G4) arranged in sequence from the object side to the image side along the optical axis, with a total of 4 lens groups. Characterized in that, The second fixed group (G3) includes at least one cemented lens group; The optical power of the first fixed group (G1) is positive, the optical power of the zoom group (G2) is negative, the optical power of the second fixed group (G3) is positive, and the optical power of the focusing group (G4) is positive; The zoom group (G2) includes a fourth lens (L4) with negative optical power, a fifth lens (L5) with negative optical power, a sixth lens (L6) with positive optical power, and a seventh lens (L7) with negative optical power arranged in sequence from the object side to the image side, with a total of 4 lenses; The focusing group (G4) includes a fifteenth lens (L15) with positive optical power, a sixteenth lens (L16) with negative optical power, a seventeenth lens (L17) with positive optical power, and an eighteenth lens (L18) with negative optical power arranged in sequence from the object side to the image side, with a total of 4 lenses.

2. The optical system according to claim 1, Characterized in that, The first fixed group (G1) includes a first lens (L1) with negative optical power, a second lens (L2) with positive optical power, and a third lens (L3) with positive optical power arranged in sequence from the object side to the image side, with a total of 3 lenses.

3. The optical system according to claim 2, Characterized in that, The fifth lens (L5) is a biconcave lens.

4. The optical system according to claim 1, Characterized in that, The second fixed group (G3) includes an eighth lens (L8) with positive optical power, a ninth lens (L9) with negative optical power, a tenth lens (L10) with positive optical power, an eleventh lens (L11) with negative optical power, a twelfth lens (L12) with positive optical power, a thirteenth lens (L13) with negative optical power, and a fourteenth lens (L14) with positive optical power arranged in sequence from the object side to the image side. The tenth lens (L10) is a biconvex lens, the eleventh lens (L11) is a biconcave lens, and the twelfth lens (L12) is a biconvex lens, with a total of 7 lenses.

5. The optical system according to claim 1, Characterized in that, The sixteenth lens (L16) is a biconcave lens.

6. The optical system according to any one of claims 1-5, Characterized in that, The focal length fⅠ of the first fixed group (G1), the focal length fⅡ of the zoom group (G2), the focal length fⅢ of the second fixed group (G3), and the focal length fⅣ of the focusing group (G4) respectively satisfy the following relationships with the focal length fw of the wide-angle end of the optical system: 4.0≤fⅠ:fw≤6.5, -2.4≤fⅡ:fw≤-1.0, 1.5≤fⅢ:fw≤3.0, 2.2≤fⅣ:fw≤5.

8.

7. The optical system according to any one of claims 1-6, Characterized in that, The distance ΔD that the zoom group (G2) moves from the wide-angle end to the telephoto end of the optical system and the total length TTL of the optical system satisfy the following relational expression: 0.1 < ΔD / TTL < 0.

3.

8. The optical system according to claim 1, wherein, the ratio of the focal length f7 of the seventh lens (L7) to the focal length fⅡ of the zoom group (G2) satisfies the following relational expression: 1.5 < f7 / fⅡ < 3.

6.

9. The optical system according to claim 1, wherein, the ratio of the focal length f15 of the fifteenth lens (L15) to the focal length fⅣ of the focusing group (G4) satisfies the following relational expression: 0.4 < f15 / fⅣ < 1.

0.

10. The optical system according to claim 4, wherein, the focal lengths f9 and f10 of the ninth lens (L9) and the tenth lens (L10) satisfy the following relational expression: -2.0 < f9 / f10 < -0.

9.

11. The optical system according to claim 1, wherein, the Abbe number difference Vd5 - Vd6 between the fifth lens (L5) and the sixth lens (L6) satisfies the following relationship: 30 < Vd5 - Vd6 < 65.

12. The optical system according to claim 4, wherein, the refractive indices Nd8 and Nd10 of the eighth lens (L8) and the tenth lens (L10) satisfy the following relational expression: 0.4 < (Nd10 - 1) / (Nd8 - 1) < 1.

2.

13. The optical system according to claim 2, wherein, the curvature radius R3b of the image side of the third lens (L3) and the curvature radius R4a of the object side of the fourth lens (L4) satisfy the following relational expression: 1.5 < R3b / R4a < 12.

14. The optical system according to any one of claims 1-6, wherein, the second fixed group (G3) includes an aspherical lens; the cemented lens group in the second fixed group (G3) is at least composed of two adjacent lenses cemented together, and at least two adjacent lenses in the focusing group (G4) are cemented together to form a cemented lens group.

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