阅读说明：本技术 一种变焦镜头 (Zoom lens ) 是由 上官秋和 刘青天 李雪慧 李志鹏 于 2019-12-13 设计创作，主要内容包括：本发明涉及镜头技术领域。本发明公开了一种变焦镜头,具有十二片透镜,第一透镜至第三透镜构成第一固定透镜组,第四透镜至第六透镜构成变倍透镜组,第七透镜至第九透镜构成补偿透镜组,第十透镜至第十二透镜构成第二固定透镜组,光阑设置在补偿透镜组和变倍透镜组之间,并对第一透镜至第十二透镜的屈光率和面型进行相应限定,且第一透镜和第二透镜组成胶合透镜,第五透镜和第六透镜组成胶合透镜。本发明具有焦距段跨度大,视野范围跨度大,对传递函数的管控好,解析度高,色差小、畸变小,成像质量高的优点。(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.)

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 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.

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.

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.