CN110780431A

CN110780431A - Zoom lens

Info

Publication number: CN110780431A
Application number: CN201911279846.2A
Authority: CN
Inventors: 上官秋和; 刘青天; 李雪慧; 李志鹏
Original assignee: Xiamen Li Ding Au Optronics Co
Current assignee: Xiamen Li Ding Au Optronics Co; Xiamen Leading Optics Co Ltd
Priority date: 2019-12-13
Filing date: 2019-12-13
Publication date: 2020-02-11

Abstract

The invention relates to the technical field of lenses. The invention discloses a zoom lens which is provided with twelve lenses, wherein a first lens to a third lens form a first fixed lens group, a fourth lens to a sixth lens form a variable power lens group, a seventh lens to a ninth lens form a compensation lens group, a tenth lens to a twelfth lens form a second fixed lens group, a diaphragm is arranged between the compensation lens group and the variable power lens group and correspondingly limits the refractive index and the surface type of the first lens to the twelfth lens, the first lens and the second lens form a cemented lens, and the fifth lens and the sixth lens form a cemented lens. The invention has the advantages of large focal length span, large visual field span, good control on the transfer function, high resolution, small chromatic aberration, small distortion and high imaging quality.

Description

Zoom lens

Technical Field

The invention belongs to the technical field of lenses, and particularly relates to a zoom lens.

Background

With the continuous progress of the technology, in recent years, the optical imaging lens is also rapidly developed and widely applied to various fields such as smart phones, tablet computers, video conferences, security monitoring and the like.

The zoom lens is a camera lens which can change focal length in a certain range, thereby obtaining different field angles, images with different sizes and different scene ranges. The zoom lens can change the shooting range by varying the focal length without changing the shooting distance, and thus is very convenient to use.

However, the zoom lens for security monitoring in the current market has the following defects: the span of the focal length section is small, so that the span of a visual field range is small, and the switching flexibility is poor under different use environments; the resolution is low, the resolving power of different focal length sections is poor, and the image is not uniform; the chromatic aberration is large, the color reduction is inaccurate, and the blue-violet edge phenomenon is easy to generate; the short focus distortion is large, the image deformation is large, the reducibility is poor, the requirements of users which are increased day by day cannot be met, and the requirements need to be improved.

Disclosure of Invention

The present invention is directed to a zoom lens to solve the above problems.

In order to achieve the purpose, the invention adopts the technical scheme that: a zoom lens comprises first to sixth lenses, a diaphragm, and seventh to twelfth lenses in sequence from an object side to an image side along an optical axis; the first lens element to the twelfth lens element each include an object-side surface facing the object side and allowing the imaging light to pass therethrough and an image-side surface facing the image side and allowing the imaging light to pass therethrough;

the first lens element with negative refractive index has a convex object-side surface and a concave image-side surface; the second lens element with positive refractive index has a convex object-side surface; the image side surface of the first lens and the object side surface of the second lens are mutually glued; the third lens element with positive refractive index has a convex object-side surface and a concave image-side surface; the first lens to the third lens form a first fixed lens group;

the fourth lens element with negative refractive index has a concave object-side surface and a concave image-side surface; the fifth lens element with negative refractive index has a concave object-side surface and a concave image-side surface; the sixth lens element with positive refractive index has a convex object-side surface and a concave image-side surface; the image side surface of the fifth lens is mutually glued with the object side surface of the sixth lens; the fourth lens to the sixth lens form a variable power lens group;

the seventh lens element with positive refractive power has a convex object-side surface and a convex image-side surface; the eighth lens element with positive refractive index has a convex object-side surface and a concave or planar image-side surface; the ninth lens element with negative refractive index has a concave object-side surface and a concave image-side surface; the seventh lens to the ninth lens form a compensation lens group;

the tenth lens element with positive refractive power has a convex object-side surface and a convex image-side surface; the eleventh lens element with negative refractive power has a convex object-side surface and a concave image-side surface; the twelfth lens element with a positive refractive index has a convex object-side surface; the tenth lens to the twelfth lens constitute a second fixed lens group;

the zoom lens has only the twelve lenses with the refractive index.

Further, the zoom lens further satisfies: | vd1-vd2 | 30, where vd1 and vd2 represent the abbe numbers of the first and second lenses, respectively.

Further, the zoom lens further satisfies: | vd5-vd6 | 30, where vd5 and vd6 represent the abbe numbers of the fifth lens and the sixth lens, respectively.

Further, the zoom lens further satisfies: r31 < 25mm, wherein R31 is the radius of curvature of the object side of the third lens.

Further, the zoom lens further satisfies: nd1 is more than 1.8, nd6 is more than 1.8, and nd11 is more than 1.8, wherein nd1, nd6 and nd11 are refractive indexes of the first lens, the sixth lens and the eleventh lens respectively.

Further, the zoom lens further satisfies: vd7 > 80, vd10 > 80 and vd12 > 80, wherein vd7, vd10 and vd12 are the abbe numbers of the seventh lens, the tenth lens and the twelfth lens, respectively.

Further, the seventh lens, the tenth lens and the twelfth lens are all made of materials with a temperature coefficient of relative refractive index Dn/Dt < 0.

Further, the zoom lens further satisfies: 0.8< | f11/f10 | < 1.2, wherein f10 and f11 are focal lengths of the tenth lens and the eleventh lens, respectively.

Further, the zoom lens further satisfies: 0.8< BFLt/BFLw <1.5, wherein BFLw is the back focal length at the shortest focal length and BFLt is the back focal length at the longest focal length.

The invention has the beneficial technical effects that:

the invention has the advantages of large span of focal length section, large span of visual field range, and flexible switching of far and near monitoring; the design transfer function control is good, the resolution ratio is high, and high resolution is kept for different focal length sections; the color difference control is good, the serious blue-violet phenomenon is avoided, and the color reducibility is good; small short-focus distortion and small object image deformation.

In addition, the invention has the advantages of small temperature drift amount, no coke loss at high and low temperature; the optical system has the advantages of good manufacturability and low sensitivity.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a first embodiment of the present invention at a shortest focal length;

fig. 2 is a schematic structural diagram of the first embodiment of the present invention at the longest focal length;

FIG. 3 is a graph of MTF of 0.435-0.656um at the shortest focal length according to the first embodiment of the present invention;

FIG. 4 is a graph of MTF of 0.435-0.656um at the intermediate focal length according to the first embodiment of the present invention;

FIG. 5 is a graph of MTF of 0.435-0.656um at the longest focal length according to the first embodiment of the present invention;

FIG. 6 is a diagram illustrating curvature of field and distortion at the shortest focal length according to the first embodiment of the present invention;

FIG. 7 is a diagram illustrating curvature of field and distortion at a middle focal length according to a first embodiment of the present invention;

FIG. 8 is a diagram illustrating curvature of field and distortion at the longest focal length according to the first embodiment of the present invention;

FIG. 9 is a schematic diagram illustrating a lateral chromatic aberration at a shortest focal length according to a first embodiment of the present invention;

FIG. 10 is a schematic diagram of lateral chromatic aberration at a middle focal length according to a first embodiment of the present invention;

FIG. 11 is a schematic diagram illustrating a chromatic aberration along the horizontal axis when the focal length is longest according to the first embodiment of the present invention;

FIG. 12 is a schematic structural diagram of the second embodiment of the present invention at the shortest focal length;

fig. 13 is a schematic structural view of the second embodiment of the present invention at the longest focal length;

FIG. 14 is a graph of MTF of 0.435-0.656um at the shortest focal length according to the second embodiment of the present invention;

FIG. 15 is a graph of MTF of 0.435-0.656um at intermediate focal length according to example two of the present invention;

FIG. 16 is a graph of MTF of 0.435-0.656um at the longest focal length according to example two of the present invention;

FIG. 17 is a diagram illustrating curvature of field and distortion at the shortest focal length according to the second embodiment of the present invention;

FIG. 18 is a diagram showing curvature of field and distortion at a middle focal length according to a second embodiment of the present invention;

FIG. 19 is a diagram illustrating curvature of field and distortion at the longest focal length for example two of the present invention;

FIG. 20 is a schematic diagram illustrating the lateral chromatic aberration at the shortest focal length according to the second embodiment of the present invention;

FIG. 21 is a schematic diagram of lateral chromatic aberration at an intermediate focal length according to a second embodiment of the present invention;

FIG. 22 is a schematic diagram illustrating the chromatic aberration along the horizontal axis at the longest focal length according to the second embodiment of the present invention;

FIG. 23 is a schematic structural diagram of a third embodiment of the present invention at the shortest focal length;

FIG. 24 is a schematic structural diagram of a third embodiment of the present invention at the longest focal length;

FIG. 25 is a graph of MTF of 0.435-0.656um at the shortest focal length according to the third embodiment of the present invention;

FIG. 26 is a graph of MTF of 0.435-0.656um at intermediate focal length according to example three of the present invention;

FIG. 27 is a graph of MTF of 0.435-0.656um at the longest focal length for example three of the present invention;

FIG. 28 is a diagram illustrating curvature of field and distortion at the shortest focal length according to the third embodiment of the present invention;

FIG. 29 is a schematic view of field curvature and distortion at a middle focal length for a third embodiment of the present invention;

FIG. 30 is a diagram illustrating curvature of field and distortion at the longest focal length for example three of the present invention;

FIG. 31 is a schematic diagram of lateral chromatic aberration at the shortest focal length according to the third embodiment of the present invention;

FIG. 32 is a schematic diagram of lateral chromatic aberration at intermediate focal length according to a third embodiment of the present invention;

FIG. 33 is a schematic diagram of chromatic aberration along the horizontal axis at the longest focal length according to the third embodiment of the present invention;

FIG. 34 is a schematic structural diagram of a fourth embodiment of the present invention at the shortest focal length;

FIG. 35 is a schematic structural diagram of a fourth embodiment of the present invention at the longest focal length;

FIG. 36 is a graph of MTF of 0.435-0.656um at the shortest focal length according to the fourth embodiment of the present invention;

FIG. 37 is a graph of MTF of 0.435-0.656um at intermediate focus for example four of the present invention;

FIG. 38 is a graph of MTF of 0.435-0.656um at the longest focal length for example four of the present invention;

FIG. 39 is a diagram illustrating field curvature and distortion at the shortest focal length according to a fourth embodiment of the present invention;

FIG. 40 is a graph showing curvature of field and distortion at a middle focal length for a fourth embodiment of the present invention;

FIG. 41 is a graph showing curvature of field and distortion at the longest focal length for a fourth embodiment of the present invention;

FIG. 42 is a schematic diagram of lateral chromatic aberration at the shortest focal length according to the fourth embodiment of the present invention;

FIG. 43 is a schematic diagram of lateral chromatic aberration at intermediate focal length according to a fourth embodiment of the present invention;

FIG. 44 is a schematic diagram of chromatic aberration along the horizontal axis at the longest focal length according to the fourth embodiment of the present invention;

FIG. 45 is a table of values for various parameters of interest for four embodiments of the present invention.

Detailed Description

To further illustrate the various embodiments, the invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. Those skilled in the art will appreciate still other possible embodiments and advantages of the present invention with reference to these figures. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

The invention will now be further described with reference to the accompanying drawings and detailed description.

The term "a lens element having positive refractive index (or negative refractive index)" means that the paraxial refractive index of the lens element calculated by Gaussian optics theory is positive (or negative). The term "object-side (or image-side) of a lens" is defined as the specific range of imaging light rays passing through the lens surface. The determination of the surface shape of the lens can be performed by the judgment method of a person skilled in the art, i.e., by the sign of the curvature radius (abbreviated as R value). The R value may be commonly used in optical design software, such as Zemax or CodeV. The R value is also commonly found in lens data sheets (lens data sheets) of optical design software. When the R value is positive, the object side is judged to be a convex surface; and when the R value is negative, judging that the object side surface is a concave surface. On the contrary, regarding the image side surface, when the R value is positive, the image side surface is judged to be a concave surface; when the R value is negative, the image side surface is judged to be convex.

The invention provides a zoom lens which sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a diaphragm, a seventh lens, a sixth lens, a seventh lens, a twelfth lens and a fourth lens from an object side to an image side along an optical axis; the first lens element to the twelfth lens element each include an object-side surface facing the object side and passing the image light and an image-side surface facing the image side and passing the image light.

The first lens element with negative refractive index has a convex object-side surface and a concave image-side surface, and has a meniscus structure to optimize distortion; the second lens element with positive refractive index has a convex object-side surface; the image side surface of the first lens and the object side surface of the second lens are mutually glued; the third lens element with positive refractive index has a convex object-side surface and a concave image-side surface; the first lens to the third lens form a first fixed lens group.

The fourth lens element with negative refractive index has a concave object-side surface and a concave image-side surface; the fifth lens element with negative refractive index has a concave object-side surface and a concave image-side surface; the sixth lens element with positive refractive index has a convex object-side surface and a concave image-side surface; the image side surface of the fifth lens is mutually glued with the object side surface of the sixth lens; the fourth lens to the sixth lens constitute a variable power lens group.

The seventh lens element with positive refractive power has a convex object-side surface and a convex image-side surface; the eighth lens element with positive refractive index has a convex object-side surface and a concave or planar image-side surface; the ninth lens element with negative refractive index has a concave object-side surface and a concave image-side surface; the seventh lens to the ninth lens constitute a compensation lens group.

The tenth lens element with positive refractive power has a convex object-side surface and a convex image-side surface; the eleventh lens element with negative refractive power has a convex object-side surface and a concave image-side surface; the twelfth lens element with a positive refractive index has a convex object-side surface; the tenth to twelfth lenses constitute a second fixed lens group.

The zoom lens has only twelve lenses with refractive index, and the zoom lens has the advantages of large focal length span, large visual field span and flexible switching of distance monitoring and near monitoring; the design transfer function is well controlled and high in resolution, and high resolution is kept for different focal length sections; the color difference control is good, the serious blue-violet phenomenon is avoided, and the color reducibility is good; small short-focus distortion and small object image deformation.

Preferably, the zoom lens further satisfies: | vd1-vd2 | 30, where vd1 and vd2 respectively represent the abbe numbers of the first and second lenses, further correcting chromatic aberration.

Preferably, the zoom lens further satisfies: | vd5-vd6 | 30, where vd5 and vd6 respectively represent the abbe numbers of the fifth and sixth lenses, further correcting chromatic aberration.

Preferably, the zoom lens further satisfies: r31 is less than 25mm, wherein R31 is the curvature radius of the object side surface of the third lens, and the focal length is further optimized.

Preferably, the zoom lens further satisfies: nd1 is more than 1.8, nd6 is more than 1.8, nd11 is more than 1.8, wherein nd1, nd6 and nd11 are refractive indexes of the first lens, the sixth lens and the eleventh lens respectively, so that the optical structure can be optimized well, and the outer diameter of the system can be controlled.

Preferably, the zoom lens further satisfies: vd7 is more than 80, vd10 is more than 80, and vd12 is more than 80, wherein vd7, vd10 and vd12 are respectively the dispersion coefficients of a seventh lens, a tenth lens and a twelfth lens, so that the chromatic dispersion of light is effectively reduced, and the chromatic aberration is further optimized.

Preferably, the seventh lens, the tenth lens and the twelfth lens are all made of materials with a temperature coefficient Dn/Dt of relative refractive index being less than 0, so that the temperature drift is controlled, and the temperature drift of the optical system is better matched with the structural component and the camera.

Preferably, the zoom lens further satisfies: 0.8< | f11/f10 | < 1.2, wherein f10 and f11 are the focal lengths of the tenth lens and the eleventh lens, respectively, to further control the temperature drift.

Preferably, the zoom lens further satisfies: 0.8< BFLt/BFLw <1.5, wherein BFLw is the back focal length at the shortest focal length, BFLt is the back focal length at the longest focal length, and the temperature drift of the long focus and the short focus is controlled.

The zoom lens of the present invention will be described in detail below with specific embodiments.

Example one

As shown in fig. 1 and 2, the present invention provides a zoom lens, which includes, in order from an object side a1 to an image side a2 along an optical axis I, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a stop 130, a seventh lens 7, an eighth lens 8, a ninth lens 9, a tenth lens 100, an eleventh lens 110, a twelfth lens 120, a protective glass 140, and an image plane 150; the first lens element 1 to the twelfth lens element 120 each include an object-side surface facing the object side a1 and passing the image light, and an image-side surface facing the image side a2 and passing the image light.

The first lens element 1 has a negative refractive index, the object-side surface 11 of the first lens element 1 is a convex surface, and the image-side surface 12 of the first lens element 1 is a concave surface; the second lens element 2 has a positive refractive index, the object-side surface 21 of the second lens element 2 is convex, and the image-side surface 22 of the second lens element 2 is concave; the image side surface 21 of the first lens 1 and the object side surface 22 of the second lens 2 are mutually glued; the third lens element 3 with positive refractive index has a convex object-side surface 31 of the third lens element 3 and a concave image-side surface 32 of the third lens element 3; the first lens 1 to the third lens 3 constitute a first fixed lens group.

The fourth lens element 4 has a negative refractive index, the object-side surface 41 of the fourth lens element 4 is concave, and the image-side surface 42 of the fourth lens element 4 is concave; the fifth lens element 5 has a negative refractive index, the object-side surface 51 of the fifth lens element 5 is concave, and the image-side surface 52 of the fifth lens element 5 is concave; the sixth lens element 6 with positive refractive index has a convex object-side surface 61 of the sixth lens element 6 and a concave image-side surface 62 of the sixth lens element 6; the image side surface 52 of the fifth lens 5 and the object side surface 61 of the sixth lens 6 are cemented with each other; the fourth lens 4 to the sixth lens 6 constitute a variable power lens group.

The seventh lens element 7 with positive refractive index has a convex object-side surface 71 of the seventh lens element 7 and a convex image-side surface 72 of the seventh lens element 7; the eighth lens element 8 with positive refractive index has a convex object-side surface 81 of the eighth lens element 8 and a planar image-side surface 82 of the eighth lens element 8; the ninth lens element 9 with negative refractive index has a concave object-side surface 91 of the ninth lens element 9 and a concave image-side surface 92 of the ninth lens element 9; the seventh lens 7 to the ninth lens 9 constitute a compensation lens group.

The tenth lens element 100 with positive refractive power has a convex object-side surface 101 of the tenth lens element 100 and a convex image-side surface 102 of the tenth lens element 100; the eleventh lens element 110 with negative refractive index has a convex object-side surface 111 of the eleventh lens element 110 and a concave image-side surface 112 of the eleventh lens element 110; the twelfth lens element 120 with a positive refractive index has a convex object-side surface 121 of the twelfth lens element 120 and a concave image-side surface 122 of the twelfth lens element 120; the tenth to twelfth lenses 100 to 120 constitute a second fixed lens group.

In this embodiment, the seventh lens 7, the tenth lens 100 and the twelfth lens 120 are made of a material having a temperature coefficient of relative refractive index Dn/Dt < 0.

In this embodiment, the first lens element 1 to the twelfth lens element 120 are made of a glass material, but not limited thereto.

Of course, in other embodiments, the image-side surface 22 of the second lens element 2 may be concave or planar, the image-side surface 82 of the eighth lens element 8 may be concave, and the image-side surface 122 of the twelfth lens element 120 may be convex or planar.

Detailed optical data at the shortest focal length of this embodiment are shown in table 1-1.

TABLE 1-1 detailed optical data at shortest focal length of example one

Detailed optical data at the longest focal length for this particular embodiment are shown in tables 1-2.

TABLE 1-2 detailed optical data at longest focal length of example one

Please refer to fig. 45 for some values of the conditional expressions in this embodiment.

Referring to fig. 3 to 5, it can be seen from the drawings that the resolution of the present embodiment is well controlled, the resolution and the imaging quality are high, the MTF value of 160lp/mm spatial frequency is greater than 0.3 at the shortest focal length, the MTF value of 160lp/mm spatial frequency is greater than 0.25 at the middle focal length, and the MTF value of 160lp/mm spatial frequency is greater than 0.2 at the longest focal length; the field curvature and distortion diagram are shown in detail in fig. 6, fig. 7 and (a) and (B) of fig. 8, and it can be seen that the distortion is small, the optical distortion is less than ± 13.5% at the shortest focal length and less than ± 0.3% at the longest focal length; the horizontal axis chromatic aberration diagram is shown in detail in fig. 9, fig. 10 and fig. 11, and it can be seen that the chromatic aberration is small, and the horizontal axis chromatic aberration is less than +/-0.007 mm.

In the specific embodiment, the focal length f of the zoom lens is 6-42 mm; the aperture value FNO is 2.25, the field angle FOV is 63 ° -9 °, and the image plane height IMH is 6.5 mm.

Example two

As shown in fig. 12 and 13, in this embodiment, the surface-type convexities and concavities and refractive indexes of the lenses are substantially the same as those of the first embodiment, only the image-side surface 22 of the second lens element 2 is convex, the image-side surface 82 of the eighth lens element 8 is concave, and the optical parameters such as the curvature radius of the lens surfaces and the lens thickness are different.

The detailed optical data at the shortest focal length of this embodiment is shown in table 2-1.

TABLE 2-1 detailed optical data at shortest focal Length for example two

The detailed optical data at the longest focal length for this particular embodiment is shown in table 2-2.

TABLE 2-2 detailed optical data at longest focal Length for example two

Referring to fig. 14 to 16, it can be seen that the resolution of the present embodiment is good for the transfer function control, the resolution and the imaging quality are high, the MTF value of 160lp/mm spatial frequency is greater than 0.3 at the shortest focal length, greater than 0.25 at the middle focal length, and greater than 0.2 at the longest focal length; the field curvature and distortion diagram are shown in detail in fig. 17, fig. 18 and (a) and (B) of fig. 19, and it can be seen that the distortion is small, the optical distortion is less than ± 13.5% at the shortest focal length and less than ± 0.3% at the longest focal length; the horizontal axis color difference diagram is shown in detail in fig. 20, fig. 21 and fig. 22, and it can be seen that the color difference is small, and the horizontal axis color difference is less than ± 0.007 mm.

In the specific embodiment, the focal length f of the zoom lens is 6-42 mm; the aperture value FNO is 2.25, the field angle FOV is 63 ° -9 °, and the image plane height IMH is 6.46 mm.

EXAMPLE III

As shown in fig. 23 and 24, the lens of this embodiment has the same surface type convexo-concave and refractive index as the lens of the first embodiment, and only the optical parameters such as the curvature radius of the surface of each lens and the thickness of the lens are different.

The detailed optical data at the shortest focal length of this embodiment is shown in table 3-1.

TABLE 3-1 detailed optical data at shortest focal length for example III

The detailed optical data at the longest focal length of this embodiment is shown in table 3-2.

TABLE 3-2 detailed optical data at longest focal length for example III

Referring to fig. 25 to 27, it can be seen that the resolution of the present embodiment is better controlled by transfer function, the resolution and the imaging quality are high, the MTF value of 160lp/mm spatial frequency is greater than 0.3 at the shortest focal length, greater than 0.25 at the middle focal length, and greater than 0.2 at the longest focal length; the field curvature and distortion diagram are shown in detail in fig. 28, fig. 29 and (a) and (B) of fig. 30, and it can be seen that the distortion is small, the optical distortion is less than ± 13.5% at the shortest focal length and less than ± 0.3% at the longest focal length; the horizontal axis color difference diagram is shown in detail in fig. 31, fig. 32 and fig. 33, and it can be seen that the color difference is small, and the horizontal axis color difference is less than ± 0.007 mm.

Example four

As shown in fig. 34 and 35, the lens of this embodiment has the same surface type convexo-concave and refractive index as those of the lens of the first embodiment, and only the optical parameters such as the curvature radius of the surface of each lens and the thickness of the lens are different.

The detailed optical data at the shortest focal length of this embodiment is shown in table 4-1.

TABLE 4-1 detailed optical data at shortest focal length for example four

The detailed optical data at the longest focal length of this embodiment is shown in table 4-2.

TABLE 4-2 detailed optical data at longest focal length for example four

Please refer to fig. 36 to 38 for the resolution of the present embodiment, which shows that the transfer function is well controlled, the resolution and the imaging quality are high, the MTF value of 160lp/mm spatial frequency is greater than 0.3 at the shortest focal length, the MTF value of 160lp/mm spatial frequency is greater than 0.25 at the middle focal length, and the MTF value of 160lp/mm spatial frequency is greater than 0.2 at the longest focal length; the field curvature and distortion diagram are shown in detail in fig. 39, fig. 40 and (a) and (B) of fig. 41, and it can be seen that the distortion is small, the optical distortion is less than ± 13.5% at the shortest focal length and less than ± 0.3% at the longest focal length; the horizontal axis color difference diagram is shown in detail in fig. 42, fig. 43 and fig. 44, and it can be seen that the color difference is small, and the horizontal axis color difference is less than ± 0.007 mm.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A zoom lens, characterized in that: the optical lens assembly sequentially comprises first to sixth lenses, a diaphragm and seventh to twelfth lenses from an object side to an image side along an optical axis; the first lens element to the twelfth lens element each include an object-side surface facing the object side and allowing the imaging light to pass therethrough and an image-side surface facing the image side and allowing the imaging light to pass therethrough;

the zoom lens has only the twelve lenses with the refractive index.

2. A zoom lens according to claim 1, further satisfying: | vd1-vd2 | 30, where vd1 and vd2 represent the abbe numbers of the first and second lenses, respectively.

3. A zoom lens according to claim 1, further satisfying: | vd5-vd6 | 30, where vd5 and vd6 represent the abbe numbers of the fifth lens and the sixth lens, respectively.

4. A zoom lens according to claim 1, further satisfying: r31 < 25mm, wherein R31 is the radius of curvature of the object side of the third lens.

5. A zoom lens according to claim 1, further satisfying: nd1 is more than 1.8, nd6 is more than 1.8, and nd11 is more than 1.8, wherein nd1, nd6 and nd11 are refractive indexes of the first lens, the sixth lens and the eleventh lens respectively.

6. A zoom lens according to claim 1, further satisfying: vd7 > 80, vd10 > 80 and vd12 > 80, wherein vd7, vd10 and vd12 are the abbe numbers of the seventh lens, the tenth lens and the twelfth lens, respectively.

7. The zoom lens according to claim 1, wherein: the seventh lens, the tenth lens and the twelfth lens are all made of materials with a temperature coefficient Dn/Dt <0 of relative refractive index.

8. A zoom lens according to claim 1, further satisfying: 0.8< | f11/f10 | < 1.2, wherein f10 and f11 are focal lengths of the tenth lens and the eleventh lens, respectively.

9. A zoom lens according to claim 1, further satisfying: 0.8< BFLt/BFLw <1.5, wherein BFLw is the back focal length at the shortest focal length and BFLt is the back focal length at the longest focal length.