Zoom lens and imaging device

Abstract

This invention relates to the field of optics, specifically to a zoom lens and imaging device. The zoom lens, from the object plane side to the image plane side, consists of a first fixed lens group with positive optical power, a first zoom lens group with negative optical power, an aperture stop, a second fixed lens group with positive optical power, a focusing lens group with negative optical power, and a second zoom lens group with positive optical power. The zoom lens satisfies the following conditions: TTL < 110mm; ft / fw > 25; where TTL is the total optical length of the zoom lens, ft is the focal length of the zoom lens in telephoto mode, and fw is the focal length of the zoom lens in wide-angle mode. Through the above structure and parameter settings, a zoom lens with a high magnification can be achieved in a relatively small volume, increasing the applicability of the zoom lens.

Description

Technical Field

[0001] This invention relates to the field of optics, specifically to a zoom lens and an imaging device. Background Technology

[0002] Security lenses, also known as surveillance lenses, refer to the lenses of surveillance cameras. Since a surveillance camera is just a single video capture device, the pixels and resolution of its lenses are higher than those of a computer's video camera, but still cannot match those of a professional digital camera or DV.

[0003] With the booming development of the security industry, medium-magnification zoom lenses are favored by users due to their wide field of view. However, due to their high magnification, they require a large number of lenses and are also large in size, making them inconvenient to place and carry. They also have high requirements for applicable scenarios, causing a lot of inconvenience to customers. Summary of the Invention

[0004] This invention will solve the existing technical problems and provide a zoom lens and imaging device. By setting the above structure and parameters, a zoom lens with a large magnification can be achieved in a small volume, thereby increasing the applicability of the zoom lens.

[0005] The technical solution provided by this invention is as follows:

[0006] A zoom lens, wherein the zoom lens comprises, from the object plane side to the image plane side, a first fixed lens group with positive optical power, a first zoom lens group with negative optical power, an aperture stop, a second fixed lens group with positive optical power, a focusing lens group with negative optical power, and a second zoom lens group with positive optical power.

[0007] The first zoom lens group, the focusing lens group, and the second zoom lens group move along the principal optical axis of the zoom lens;

[0008] The first fixed lens group consists of a first fixed lens with negative optical power, a second fixed lens with positive optical power, a third fixed lens with positive optical power, and a fourth fixed lens with positive optical power, from the object plane side to the image plane side.

[0009] The first zoom lens group consists of a first zoom lens with negative optical power, a second zoom lens with negative optical power, and a third zoom lens with positive optical power, from the object plane side to the image plane side.

[0010] The focusing lens group is a first focusing lens with negative optical power;

[0011] The zoom lens satisfies the following condition:

[0012] TTL < 110mm;

[0013] ft / fw > 25;

[0014] Wherein, TTL is the total optical length of the zoom lens, ft is the focal length of the zoom lens in telephoto mode, and fw is the focal length of the zoom lens in wide-angle mode.

[0015] In this technical solution, by setting the above structure and parameters, a zoom lens with a large magnification can be achieved in a relatively small volume, thereby increasing the applicability of the zoom lens.

[0016] Preferably, the second fixed lens group consists of a fifth fixed lens with positive optical power, a sixth fixed lens with positive optical power, a seventh fixed lens with negative optical power, and an eighth fixed lens with positive optical power, arranged sequentially from the object plane side to the image plane side; the seventh fixed lens and the eighth fixed lens are cemented together.

[0017] Preferably, the second zoom lens group is a fourth zoom lens with positive optical power.

[0018] Preferably, the second fixed lens group consists of a fifth fixed lens with positive optical power, a sixth fixed lens with negative optical power, a seventh fixed lens with positive optical power, and an eighth fixed lens with negative optical power, arranged sequentially from the object plane side to the image plane side; the sixth fixed lens, the seventh fixed lens, and the eighth fixed lens form a cemented triplet lens.

[0019] Preferably, the second zoom lens group consists of a fourth zoom lens with positive optical power and a fifth zoom lens with negative optical power, sequentially from the object plane side to the image plane side.

[0020] Preferably, the zoom lens satisfies the following condition:

[0021] Da7 / fw > 1.4;

[0022] Wherein, Da7 is the thickness of the seventh fixed lens.

[0023] In this technical solution, by limiting the thickness of the seventh fixed lens, the use of lenses inside the zoom lens is reduced, thereby lowering the cost of the zoom lens.

[0024] Preferably, the zoom lens satisfies the following condition:

[0025] |(Rc12+Rb41) / (Rc12-Rb41)|>50;

[0026] Wherein, Rb41 is the radius of curvature of the fourth zoom lens near the object plane, and Rc12 is the radius of curvature of the first focusing lens near the image plane.

[0027] In this technical solution, by limiting the above parameters, the possibility of optical path changes during the focusing process of the first focusing lens is reduced, thereby reducing the coma of the zoom lens.

[0028] Preferably, the zoom lens satisfies the following condition:

[0029] 0.03 < S4 / S2 < 0.1;

[0030] Wherein, S2 is the moving distance of the first zoom lens group, and S4 is the moving distance of the focusing lens group.

[0031] In this technical solution, by limiting the above parameters, it is possible to achieve both focusing of the zoom lens and miniaturization of the zoom lens.

[0032] Preferably, the zoom lens satisfies the following condition:

[0033] |(Ra52+Ra61) / (Ra52-Ra61)|>2;

[0034] Wherein, Ra52 is the radius of curvature of the fifth fixed lens near the image plane side surface, and Ra61 is the radius of curvature of the sixth fixed lens near the object plane side surface.

[0035] In this technical solution, by limiting the above parameters, the optical path passing through the fifth fixed lens is adjusted, which facilitates the subsequent lens to receive light and increases the imaging quality of the zoom lens.

[0036] One of the objectives of this invention is to provide an imaging device, comprising: a zoom lens;

[0037] And an imaging element, configured to receive an image formed by the zoom lens.

[0038] Compared with the prior art, the zoom lens and imaging device provided by the present invention have the following beneficial effects:

[0039] 1. By setting the above structure and parameters, a zoom lens with a large magnification can be achieved in a relatively small volume, thus increasing the applicability of the zoom lens.

[0040] 2. By limiting the thickness of the seventh fixed lens, the number of lenses used in the zoom lens is reduced, thus lowering the cost of the zoom lens.

[0041] 3. By limiting the parameters mentioned above, the possibility of optical path changes during the focusing process of the first focusing lens is reduced, thereby reducing the coma of the zoom lens. Attached Figure Description

[0042] The preferred embodiments will now be described in a clear and easy-to-understand manner, with reference to the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of a zoom lens and imaging device.

[0043] Figure 1This is a schematic diagram of the structure of a zoom lens in telephoto mode according to the present invention;

[0044] Figure 2 This is a schematic diagram of the structure of a zoom lens in a wide-angle state according to the present invention;

[0045] Figure 3 This invention provides a coma diagram of a zoom lens in telephoto mode.

[0046] Figure 4 This invention relates to a coma diagram of a zoom lens in a wide-angle state.

[0047] Figure 5 This is an aberration diagram of a zoom lens in telephoto mode according to the present invention;

[0048] Figure 6 This is an aberration diagram of a zoom lens in a wide-angle state according to the present invention;

[0049] Figure 7 This is a schematic diagram of another zoom lens telephoto configuration according to the present invention;

[0050] Figure 8 This is a schematic diagram of another zoom lens in a wide-angle state according to the present invention;

[0051] Figure 9 This is another coma diagram of the zoom lens in telephoto mode according to the present invention;

[0052] Figure 10 This is another coma diagram of the zoom lens in the wide-angle state according to the present invention;

[0053] Figure 11 This is another aberration diagram of the zoom lens in telephoto mode according to the present invention;

[0054] Figure 12 This is another aberration diagram of the zoom lens in the wide-angle state according to the present invention.

[0055] Explanation of reference numerals: G1, First fixed lens group; G2, First zoom lens group; G3, Second fixed lens group; G4, Focusing lens group; G5, Second zoom lens group; G6, Auxiliary component; a1, First fixed lens; a2, Second fixed lens; a3, Third fixed lens; a4, Fourth fixed lens; a5, Fifth fixed lens; a6, Sixth fixed lens; a7, Seventh fixed lens; a8, Eighth fixed lens; b1, First zoom lens; b2, Second zoom lens; b3, Third zoom lens; b4, Fourth zoom lens; b5, Fifth zoom lens; c1, First focusing lens; STO, Aperture stop; CG, Protective glass. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] To keep the drawings concise, each figure only schematically shows the parts relevant to the invention, and these do not represent the actual structure of the product. Furthermore, to facilitate understanding, in some figures, only one of components with the same structure or function is schematically depicted, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one."

[0058] Example 1

[0059] like Figure 1 and Figure 7 As shown, a zoom lens is composed of, from the object plane side to the image plane side, a first fixed lens group G1 with positive optical power, a first zoom lens group G2 with negative optical power, an aperture stop STO, a second fixed lens group G3 with positive optical power, a focusing lens group G4 with negative optical power, and a second zoom lens group G5 with positive optical power.

[0060] The first zoom lens group G2, the focusing lens group G4, and the second zoom lens group G5 move along the principal optical axis of the zoom lens;

[0061] The first fixed lens group G1 consists of a first fixed lens a1 with negative optical power, a second fixed lens a2 with positive optical power, a third fixed lens a3 with positive optical power, and a fourth fixed lens a4 with positive optical power, from the object plane side to the image plane side.

[0062] The first zoom lens group G2 consists of a first zoom lens b1 with negative optical power, a second zoom lens b2 with negative optical power, and a third zoom lens b3 with positive optical power, from the object plane side to the image plane side.

[0063] The focusing lens group G4 is a first focusing lens c1 with negative optical power;

[0064] The zoom lens satisfies the following condition:

[0065] TTL < 110mm;

[0066] ft / fw > 25;

[0067] Wherein, TTL is the total optical length of the zoom lens, ft is the focal length of the zoom lens in telephoto mode, and fw is the focal length of the zoom lens in wide-angle mode.

[0068] By setting the above structure and parameters, a zoom lens with a large magnification can be achieved in a relatively small volume, thus increasing the applicability of the zoom lens.

[0069] The second fixed lens group G3 consists of a fifth fixed lens a5 with positive optical power, a sixth fixed lens a6 with positive optical power, a seventh fixed lens a7 with negative optical power, and an eighth fixed lens a8 with positive optical power, from the object plane side to the image plane side; the seventh fixed lens a7 and the eighth fixed lens a8 are cemented together.

[0070] The second zoom lens group G5 is a fourth zoom lens b4 with positive optical power.

[0071] The second fixed lens group G3 consists of a fifth fixed lens a5 with positive optical power, a sixth fixed lens a6 with negative optical power, a seventh fixed lens a7 with positive optical power, and an eighth fixed lens a8 with negative optical power, from the object plane side to the image plane side; the sixth fixed lens a6, the seventh fixed lens a7, and the eighth fixed lens a8 form a cemented three-layer lens.

[0072] The second zoom lens group G5 consists of a fourth zoom lens b4 with positive optical power and a fifth zoom lens b5 with negative optical power, arranged sequentially from the object plane side to the image plane side.

[0073] The zoom lens satisfies the following condition:

[0074] Da7 / fw > 1.4;

[0075] Wherein, Da7 is the thickness of the seventh fixed lens a7.

[0076] In this embodiment, by limiting the thickness of the seventh fixed lens a7, the use of lenses inside the zoom lens is reduced, thereby lowering the cost of the zoom lens.

[0077] The zoom lens satisfies the following condition:

[0078] |(Rc12+Rb41) / (Rc12-Rb41)|>50;

[0079] Wherein, Rb41 is the radius of curvature of the fourth zoom lens b4 near the object plane, and Rc12 is the radius of curvature of the first focusing lens c1 near the image plane.

[0080] In this embodiment, by limiting the above parameters, the possibility of optical path changes in the first focusing lens c1 during the focusing process is reduced, thereby reducing the coma of the zoom lens.

[0081] The zoom lens satisfies the following condition:

[0082] 0.03 < S4 / S2 < 0.1;

[0083] Wherein, S2 is the moving distance of the first zoom lens group G2, and S4 is the moving distance of the focusing lens group G4.

[0084] By limiting the parameters mentioned above, it is possible to achieve both focusing and miniaturization of the zoom lens.

[0085] The zoom lens satisfies the following condition:

[0086] |(Ra52+Ra61) / (Ra52-Ra61)|>2;

[0087] Wherein, Ra52 is the radius of curvature of the fifth fixed lens a5 near the image plane side surface, and Ra61 is the radius of curvature of the sixth fixed lens a6 near the object plane side surface.

[0088] By limiting the parameters mentioned above, the light path passing through the fifth fixed lens a5 was adjusted, which facilitates the subsequent lenses in receiving light and increases the imaging quality of the zoom lens.

[0089] Example 2

[0090] like Figures 1 to 6 As shown, a zoom lens is composed of, from the object plane side to the image plane side, a first fixed lens group G1 with positive optical power, a first zoom lens group G2 with negative optical power, an aperture stop STO, a second fixed lens group G3 with positive optical power, a focusing lens group G4 with negative optical power, a second zoom lens group G5 with positive optical power, and an auxiliary component G6.

[0091] The first zoom lens group G2, the focusing lens group G4, and the second zoom lens group G5 move along the principal optical axis of the zoom lens;

[0092] The first fixed lens group G1 consists of a first fixed lens a1 with negative optical power, a second fixed lens a2 with positive optical power, a third fixed lens a3 with positive optical power, and a fourth fixed lens a4 with positive optical power, from the object plane side to the image plane side.

[0093] The first zoom lens group G2 consists of a first zoom lens b1 with negative optical power, a second zoom lens b2 with negative optical power, and a third zoom lens b3 with positive optical power, from the object plane side to the image plane side.

[0094] The second fixed lens group G3 consists of a fifth fixed lens a5 with positive optical power, a sixth fixed lens a6 with positive optical power, a seventh fixed lens a7 with negative optical power, and an eighth fixed lens a8 with positive optical power, from the object plane side to the image plane side; the seventh fixed lens a7 and the eighth fixed lens a8 are cemented together.

[0095] The focusing lens group G4 is a first focusing lens c1 with negative optical power;

[0096] The second zoom lens group G5 is a fourth zoom lens b4 with positive optical power.

[0097] The auxiliary component G6 is a protective glass CG.

[0098] The basic lens data of the zoom lens in this embodiment is shown in Table 1, the variable parameters in Table 1 are shown in Table 2, and the aspherical coefficients are shown in Table 3.

[0099] The surface number column shows the surface number when the object-side surface is set as surface 1 and the numbering is increased sequentially towards the image side; the surface type column shows the surface type of a lens; the radius of curvature column shows the radius of curvature of a lens, where a positive radius of curvature indicates that the surface is curved towards the object side and a negative radius of curvature indicates that the surface is curved towards the image side; the center thickness column shows the surface spacing on the optical axis between each surface and the surface adjacent to it on the image side; the refractive index column shows the refractive index of a lens; and the Abbe number column shows the Abbe number of a lens.

[0100] In Table 2, the WIDE column indicates the specific values ​​of each variable parameter when the zoom lens is in wide-angle mode, and the TELE column indicates the specific values ​​of each variable parameter when the zoom lens is in telephoto mode.

[0101] In Table 3, K is the conic coefficient, and e is the scientific notation, for example, e-05 represents 10. -5 .

[0102] Table 1

[0103]

[0104]

[0105] Table 2

[0106] WIDE TELE D1 0.81 41.7 D2 41.42 0.53 D3 0.7 2.6 D4 11.81 13.67 D5 4.06 0.3

[0107] Table 3

[0108]

[0109]

[0110] In this embodiment, TTL = 108.02 mm, fw = 5.5 mm, ft = 140 mm, ft / fw = 25.5, and fno = 1.48 to 3.44;

[0111] Wherein, TTL is the total optical length of the zoom lens, ft is the focal length of the zoom lens in telephoto mode, fw is the focal length of the zoom lens in wide-angle mode, and fno is the aperture number of the zoom lens.

[0112] Rc12=11.70mm, Rb41=11.96mm;

[0113] |(Rc12+Rb41) / (Rc12-Rb41)|=91;

[0114] Wherein, Rb41 is the radius of curvature of the fourth zoom lens b4 near the object plane, and Rc12 is the radius of curvature of the first focusing lens c1 near the image plane.

[0115] S2 = 40.89 mm; S4 = 1.9 mm;

[0116] S4 / S2 = 0.046;

[0117] Wherein, S2 is the moving distance of the first zoom lens group G2, and S4 is the moving distance of the focusing lens group G4.

[0118] Ra52=63.58mm, Ra61=22.5mm;

[0119] (Ra52+Ra61) / (Ra52-Ra61)|=2.1;

[0120] Wherein, Ra52 is the radius of curvature of the fifth fixed lens a5 near the image plane side surface, and Ra61 is the radius of curvature of the sixth fixed lens a6 near the object plane side surface.

[0121] Example 3

[0122] like Figures 7 to 12 As shown, a zoom lens is composed of, from the object plane side to the image plane side, a first fixed lens group G1 with positive optical power, a first zoom lens group G2 with negative optical power, an aperture stop STO, a second fixed lens group G3 with positive optical power, a focusing lens group G4 with negative optical power, a second zoom lens group G5 with positive optical power, and an auxiliary component G6.

[0123] The first zoom lens group G2, the focusing lens group G4, and the second zoom lens group G5 move along the principal optical axis of the zoom lens;

[0124] The first fixed lens group G1 consists of a first fixed lens a1 with negative optical power, a second fixed lens a2 with positive optical power, a third fixed lens a3 with positive optical power, and a fourth fixed lens a4 with positive optical power, from the object plane side to the image plane side.

[0125] The first zoom lens group G2 consists of a first zoom lens b1 with negative optical power, a second zoom lens b2 with negative optical power, and a third zoom lens b3 with positive optical power, from the object plane side to the image plane side.

[0126] The second fixed lens group G3 consists of a fifth fixed lens a5 with positive optical power, a sixth fixed lens a6 with positive optical power, a seventh fixed lens a7 with negative optical power, and an eighth fixed lens a8 with positive optical power, from the object plane side to the image plane side; the seventh fixed lens a7 and the eighth fixed lens a8 are cemented together.

[0127] The focusing lens group G4 is a first focusing lens c1 with negative optical power;

[0128] The second zoom lens group G5 is a fourth zoom lens b4 with positive optical power.

[0129] The auxiliary component G6 is a protective glass CG.

[0130] The basic lens data of the zoom lens in this embodiment is shown in Table 4, the variable parameters in Table 4 are shown in Table 5, and the aspherical coefficients are shown in Table 6.

[0131] The surface number column shows the surface number when the object-side surface is set as surface 1 and the numbering is increased sequentially towards the image side; the surface type column shows the surface type of a lens; the radius of curvature column shows the radius of curvature of a lens, where a positive radius of curvature indicates that the surface is curved towards the object side and a negative radius of curvature indicates that the surface is curved towards the image side; the center thickness column shows the surface spacing on the optical axis between each surface and the surface adjacent to it on the image side; the refractive index column shows the refractive index of a lens; and the Abbe number column shows the Abbe number of a lens.

[0132] In Table 5, the WIDE column indicates the specific values ​​of each variable parameter when the zoom lens is in the wide-angle position, and the TELE column indicates the specific values ​​of each variable parameter when the zoom lens is in the telephoto position.

[0133] In Table 6, K is the conic coefficient, and e is the scientific notation, for example, e-05 represents 10. -5 .

[0134] Table 4

[0135] Face number Surface type radius of curvature / mm Center thickness / mm Refractive index Abbe number OBJ S1 spherical 67.60 0.70 1.91 24.78 S2 spherical 42.69 5.07 1.50 81.61 S3 spherical -1453.84 0.10 S4 spherical 37.11 3.81 1.50 81.61 S5 spherical 181.75 0.10 S6 spherical 29.11 3.13 1.44 95.10 S7 spherical 66.23 D1 S8 spherical 99.54 0.70 1.94 31.95 S9 spherical 8.32 2.52 S10 aspherical -11.49 0.70 1.69 53.20 S11 aspherical 13.76 0.91 S12 spherical 18.47 1.76 1.95 17.98 S13 spherical -70.86 D2 STO spherical INF 1.00 S15 aspherical 13.40 4.00 1.69 53.23 S16 aspherical -33.13 0.10 S17 spherical -113 0.70 1.52 64.20 S18 spherical 7.25 7.54 1.44 95.10 S19 spherical -8.62 0.70 1.77 49.05 S20 spherical -13.56 D3 S21 spherical 52.30 0.70 1.93 24.72 S22 spherical 13.18 D4 S23 spherical 12.68 3.89 1.50 81.61 S24 spherical -16.20 0.10 S25 aspherical -113.36 0.70 1.81 40.73 S26 aspherical 2471.53 D5 S27 spherical INF 1.90 S28 spherical INF 1.00 1.52 64.20 S29 spherical INF 1.00 IMG

[0136] Table 5

[0137]

[0138]

[0139] Table 6

[0140]

[0141] In this embodiment, TTL = 90.51 mm, fw = 5.3 mm, ft = 129.88 mm, ft / fw = 24.5, and fno = 1.66~4.56;

[0142] Wherein, TTL is the total optical length of the zoom lens, ft is the focal length of the zoom lens in telephoto mode, fw is the focal length of the zoom lens in wide-angle mode, and fno is the aperture number of the zoom lens.

[0143] Rc12=13.18mm, Rb41=12.68mm;

[0144] |(Rc12+Rb41) / (Rc12-Rb41)|=51.72;

[0145] Wherein, Rb41 is the radius of curvature of the fourth zoom lens b4 near the object plane, and Rc12 is the radius of curvature of the first focusing lens c1 near the image plane.

[0146] S2 = 28.23 mm; S4 = 2.08 mm;

[0147] S4 / S2 = 0.074;

[0148] Wherein, S2 is the moving distance of the first zoom lens group G2, and S4 is the moving distance of the focusing lens group G4.

[0149] Ra52=-33.13mm, Ra61=-113mm;

[0150] (Ra52+Ra61) / (Ra52-Ra61)|=1.83;

[0151] Wherein, Ra52 is the radius of curvature of the fifth fixed lens a5 near the image plane side surface, and Ra61 is the radius of curvature of the sixth fixed lens a6 near the object plane side surface.

[0152] Da7 = 7.54 mm;

[0153] Da7 / fw = 1.42;

[0154] Wherein, Da7 is the thickness of the seventh fixed lens a7.

[0155] Example 4

[0156] like Figures 1 to 12As shown, an imaging device includes: a zoom lens as described in any of the above embodiments, and an imaging element configured to receive an image formed by the zoom lens.

[0157] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A zoom lens, characterized in that, The zoom lens consists of, from the object plane side to the image plane side, a first fixed lens group with positive optical power, a first zoom lens group with negative optical power, an aperture stop, a second fixed lens group with positive optical power, a focusing lens group with negative optical power, and a second zoom lens group with positive optical power. The first zoom lens group, the focusing lens group, and the second zoom lens group move along the principal optical axis of the zoom lens; The first fixed lens group consists of a first fixed lens with negative optical power, a second fixed lens with positive optical power, a third fixed lens with positive optical power, and a fourth fixed lens with positive optical power, in sequence from the object plane side to the image plane side. The first zoom lens group consists of a first zoom lens with negative optical power, a second zoom lens with negative optical power, and a third zoom lens with positive optical power, sequentially from the object plane side to the image plane side. The focusing lens group is a first focusing lens with negative optical power; The zoom lens satisfies the following condition: TTL < 110mm; ft / fw ≥ 24.5; 0.03 < S4 / S2 < 0.1; Wherein, TTL is the total optical length of the zoom lens, ft is the focal length of the zoom lens in telephoto mode, fw is the focal length of the zoom lens in wide-angle mode, S2 is the moving distance of the first zoom lens group, and S4 is the moving distance of the focusing lens group.

2. A zoom lens according to claim 1, characterized in that: The second fixed lens group consists of a fifth fixed lens with positive optical power, a sixth fixed lens with positive optical power, a seventh fixed lens with negative optical power, and an eighth fixed lens with positive optical power, arranged sequentially from the object plane side to the image plane side; the seventh fixed lens and the eighth fixed lens are cemented together.

3. A zoom lens according to claim 2, characterized in that: The second zoom lens group is a fourth zoom lens with positive optical power.

4. A zoom lens according to claim 1, characterized in that: The second fixed lens group consists of a fifth fixed lens with positive optical power, a sixth fixed lens with negative optical power, a seventh fixed lens with positive optical power, and an eighth fixed lens with negative optical power, arranged sequentially from the object plane side to the image plane side; the sixth fixed lens, the seventh fixed lens, and the eighth fixed lens form a cemented three-layer lens.

5. A zoom lens according to claim 4, characterized in that: The second zoom lens group consists of a fourth zoom lens with positive optical power and a fifth zoom lens with negative optical power, arranged sequentially from the object plane side to the image plane side.

6. A zoom lens according to claim 4, characterized in that: The zoom lens satisfies the following condition: Da7 / fw > 1.4; Wherein, Da7 is the thickness of the seventh fixed lens.

7. A zoom lens according to claim 3 or 5, characterized in that: The zoom lens satisfies the following condition: |(Rc12+Rb41) / (Rc12-Rb41)|>50; Wherein, Rb41 is the radius of curvature of the fourth zoom lens near the object plane, and Rc12 is the radius of curvature of the first focusing lens near the image plane.

8. A zoom lens according to claim 2 or 4, characterized in that: The zoom lens satisfies the following condition: |(Ra52+Ra61) / (Ra52-Ra61)|≥1.83; Wherein, Ra52 is the radius of curvature of the fifth fixed lens near the image plane side surface, and Ra61 is the radius of curvature of the sixth fixed lens near the object plane side surface.

9. An image forming apparatus characterized by comprising: include: The zoom lens as described in any one of claims 1 to 8; And an imaging element, configured to receive an image formed by the zoom lens.

Images