CN113484980A

CN113484980A - Lens

Info

Publication number: CN113484980A
Application number: CN202110641248.6A
Authority: CN
Inventors: 邢圆圆; 刘凯; 丁洪兴; 杜艳芬; 白雪
Original assignee: Zhejiang Dahua Technology Co Ltd
Current assignee: Zhejiang Dahua Technology Co Ltd
Priority date: 2021-06-09
Filing date: 2021-06-09
Publication date: 2021-10-08
Anticipated expiration: 2041-06-09
Also published as: CN113484980B

Abstract

The invention discloses a lens, which comprises a first positive focal power lens, a first lens group, a second lens group, a third negative focal power lens, a fourth negative focal power lens, a fifth negative focal power lens, a fourth positive focal power lens, an optical filter and an imaging surface which are sequentially arranged from an object side to an image side; the lens satisfies the following conditions: 50< (fg1/fg2) > f system < 60; wherein fg1 is the focal length of the first lens group, fg2 is the focal length of the second lens group, and the f system is the system focal length of the lens. Since in the embodiment of the present invention, the lens and the lens group of which the power is set are arranged in order from the object side to the image side in the lens barrel in a specific order, and the lens group in the lens barrel satisfies: 50< (fg1/fg2) > f system < 60; therefore, the embodiment of the invention provides a telephoto lens with a large target surface.

Description

Lens

Technical Field

The invention relates to the technical field of optical imaging, in particular to a lens.

Background

With the development of security monitoring technology, the application scenes of the fixed focus lens are more and more, but the conventional security monitoring and road condition monitoring device has the following defects: in an intelligent traffic system, the resolution requirement of an optical imaging lens is higher and higher, the target surface is larger and larger, and the target surfaces of the lenses in the market are mainly concentrated on 1/1.8 inch and 1/1.2 inch, so that the current use requirements cannot be met. In addition, the lens has more lenses, large structural size, poor processability and higher cost. Therefore, it becomes important to develop a telephoto lens with a large target surface.

Disclosure of Invention

The embodiment of the invention provides a lens, which is used for providing a telephoto lens with a large target surface.

The embodiment of the present invention provides a lens assembly, which includes a first positive power lens, a first lens group, a second lens group, a third negative power lens, a fourth negative power lens, a fifth negative power lens, a fourth positive power lens, an optical filter, and an image plane, which are sequentially arranged from an object side to an image side;

the lens satisfies the following conditions:

50< (fg1/fg2) > f system < 60;

wherein fg1 is the focal length of the first lens group, fg2 is the focal length of the second lens group, and the f system is the system focal length of the lens.

Further, the first lens group includes a second positive power lens and a first negative power lens arranged in order from the object side to the image side.

Further, the second lens group includes a second negative power lens and a third positive power lens arranged in order from the object side to the image side.

Further, the first positive power lens includes a meniscus lens, and a surface of the meniscus lens facing the object side is convex;

the second positive power lens comprises a convex lens, and one surface of the convex lens facing the object side is a convex surface;

the first negative focal power lens comprises a concave lens, and one surface of the concave lens facing the image side is a concave surface;

the second negative focal power lens comprises a concave lens, and one surface of the concave lens facing the image side is a concave surface;

the third positive power lens comprises a convex lens, and one surface of the convex lens facing the object side is a convex surface;

the third negative-power lens comprises a meniscus lens, and one surface of the meniscus lens facing the image side is a concave surface;

the fourth negative-power lens comprises a meniscus lens, and one surface of the meniscus lens facing the image side is a concave surface;

the fifth negative-power lens comprises a meniscus lens, and one surface of the meniscus lens facing the image side is a convex surface;

the fourth positive power lens includes a double convex lens.

Further, the curvature radius of one surface of the second positive power lens facing the image side is the same as that of one surface of the first negative power lens facing the object side;

and the curvature radius of one surface of the second negative focal power lens facing the image side is the same as that of one surface of the third positive focal power lens facing the object side.

Furthermore, one surface of the second positive power lens facing the image side, one surface of the first negative power lens facing the object side, and one surface of the second negative power lens facing the object side are planes or curved surfaces.

Further, the focal length f1 of the first positive focal power lens is not more than 55, the focal length f6 of the third negative focal power lens is not less than 70, and the focal length f9 of the fourth positive focal power lens is not less than 35.

Furthermore, the Abbe number Vd2 of the second positive focal power lens is more than or equal to 60; the Abbe number Vd5 of the third positive focal power lens is not less than 55; and the Abbe number Vd8 of the fifth negative-power lens is not less than 63.

Further, the refractive index Nd1 of the first positive focal power lens is more than or equal to 1.90; the refractive index Nd3 of the first negative-power lens is less than or equal to 1.86; the refractive index Nd4 of the second negative-power lens is less than or equal to 1.88; the refractive index Nd7 of the fourth negative-power lens is more than or equal to 1.90.

Further, an aperture stop is disposed between the third positive power lens and the third negative power lens.

The embodiment of the present invention provides a lens assembly, which includes a first positive power lens, a first lens group, a second lens group, a third negative power lens, a fourth negative power lens, a fifth negative power lens, a fourth positive power lens, an optical filter, and an image plane, which are sequentially arranged from an object side to an image side; the lens satisfies the following conditions: 50< (fg1/fg2) > f system < 60; wherein fg1 is the focal length of the first lens group, fg2 is the focal length of the second lens group, and the f system is the system focal length of the lens. Since in the embodiment of the present invention, the lens and the lens group of which the power is set are arranged in order from the object side to the image side in the lens barrel in a specific order, and the lens group in the lens barrel satisfies: 50< (fg1/fg2) > f system < 60; therefore, the embodiment of the invention provides a telephoto lens with a large target surface.

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 view of a lens provided in an embodiment of the present invention;

fig. 2 is a graph of an optical transfer function (MTF) of the lens provided in the embodiment of the present invention in a normal temperature state of a visible light band;

fig. 3 is a graph of curvature of field and distortion of a lens in a visible light band according to an embodiment of the present invention;

fig. 4 is a transverse fan diagram of the lens provided by the embodiment of the invention in the visible light band;

fig. 5 is a dot-column diagram of a lens provided in an embodiment of the present invention in a visible light band;

fig. 6 is a graph of an optical transfer function (MTF) of the lens in an infrared band normal temperature state according to the embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the attached drawings, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 is a schematic view of a lens barrel according to an embodiment of the present invention, the lens barrel includes, in order from an object side to an image side, a first positive power lens L1, a first lens group G1, a second lens group G2, a third negative power lens L6, a fourth negative power lens L7, a fifth negative power lens L8, a fourth positive power lens L9, a filter M, and an image plane N;

the lens satisfies the following conditions:

50< (fg1/fg2) > f system < 60;

Filters are optical devices used to select a desired wavelength band of radiation.

Since a lens and a lens group of which power is set are arranged in order from an object side to an image side in a lens barrel in a specific order, and the lens group in the lens barrel satisfies: 50< (fg1/fg2) > f system < 60; therefore, the embodiment of the invention provides a telephoto lens with a large target surface.

In order to further improve the imaging quality of the lens, in the embodiment of the invention, the first lens group G1 comprises a second positive power lens L2 and a first negative power lens L3 which are arranged in order from the object side to the image side.

In order to further improve the imaging quality of the lens, in the embodiment of the invention, the second lens group G2 comprises a second negative power lens L4 and a third positive power lens L5 which are arranged in order from the object side to the image side.

In order to further improve the imaging quality of the lens barrel, in the embodiment of the invention, the first positive power lens includes a meniscus lens, and one surface of the meniscus lens facing the object side is a convex surface;

the fourth positive power lens includes a double convex lens.

In order to further enable the system to be compact, the curvature radius of the surface of the second positive power lens facing the image side is the same as that of the surface of the first negative power lens facing the object side. The second positive power lens and the first negative power lens can be attached or glued.

And the curvature radius of one surface of the second negative focal power lens facing the image side is the same as that of one surface of the third positive focal power lens facing the object side. The second negative power lens and the third positive power lens can be attached or glued.

In order to further improve the imaging quality of the lens barrel, in the embodiment of the present invention, a surface of the second positive power lens facing the image side, a surface of the first negative power lens facing the object side, and a surface of the second negative power lens facing the object side are flat or curved.

In order to further improve the imaging quality of the lens, in the embodiment of the invention, the focal length f1 of the first positive focal power lens is not less than 55, the focal length f6 of the third negative focal power lens is not less than 70, and the focal length f9 of the fourth positive focal power lens is not less than 35.

In the embodiment of the invention, in order to realize clear imaging at the lens between minus 30 ℃ and 70 ℃, in the embodiment of the invention, the Abbe number Vd2 of the second positive power lens is more than or equal to 60; the Abbe number Vd5 of the third positive focal power lens is not less than 55; and the Abbe number Vd8 of the fifth negative-power lens is not less than 63. In addition, the Abbe number Vd2 of the second positive focal power lens is not less than 60; the Abbe number Vd5 of the third positive focal power lens is not less than 55; the Abbe number Vd8 of the fifth negative focal power lens is not less than 63, and the chromatic aberration of the image can be reduced, so that the imaging quality is improved.

In order to improve the imaging quality of the lens and reduce the total length of the lens, in the embodiment of the invention, the refractive index Nd1 of the first positive power lens is more than or equal to 1.90; the refractive index Nd3 of the first negative-power lens is less than or equal to 1.86; the refractive index Nd4 of the second negative-power lens is less than or equal to 1.88; the refractive index Nd7 of the fourth negative-power lens is more than or equal to 1.90. The refractive index Nd1 of the first positive focal power lens is more than or equal to 1.90; the refractive index Nd3 of the first negative-power lens is less than or equal to 1.86; the refractive index Nd4 of the second negative-power lens is less than or equal to 1.88; the refractive index Nd7 of the fourth negative-power lens is larger than or equal to 1.90, the spherical aberration can be reduced, and the imaging quality is improved.

The design scheme of the lens provided by the embodiment of the invention can support 1.1 inch at most, effectively realizes the miniaturization of the lens structure, ensures the imaging quality, performs the design of eliminating the heat difference and can adapt to the environment of-30-70 ℃. The imaging can support the use of a Sensor with the maximum size of 1.1 inches, the aperture F is 1.8, and the total length of the system does not exceed 79.5 mm; under the condition that the MTF value of the full field of view is 100lp/mm, the MTF value reaches more than 0.55, and the resolution requirement of a 1200 ten thousand pixel camera can be supported at the highest; the lens takes the design of infrared confocal, can be compatible with the scene demand of day and night dual-purpose.

The embodiment of the invention adopts the technical scheme, effectively controls the cost of the lens and realizes a long-focus imaging system with low cost, large target surface and high resolution.

The following exemplifies the lens parameters provided by the embodiment of the present invention.

Example 1:

in a specific implementation, the radius of curvature R, the center thickness Tc, the refractive index Nd, and the abbe constant Vd of each lens of the imaging system satisfy the conditions listed in table 1:

TABLE 1

The lens provided by the embodiment of the invention has the following optical technical indexes:

the total optical length TTL is less than or equal to 79.5 mm;

focal length f' of the lens: 70 mm;

angle of view of lens: 12.8 degrees;

optical distortion of the lens: 1.2 percent;

aperture fno of lens system: FNO is less than or equal to 1.8;

size of a lens image plane: more than or equal to 1 ".

Note that the surface numbers in table 1 are surface numbers of the lenses from left to right in the lens configuration diagram shown in fig. 1.

The lens structure of the embodiment of the present invention is shown in fig. 1, and the lens provided in embodiment 1 is further described below by performing detailed optical system analysis on embodiment 1.

The optical transfer function is used for evaluating the imaging quality of the imaging system in a more accurate, visual and common mode, the higher and smoother curve of the optical transfer function shows that the imaging quality of the system is better, and various aberrations (such as spherical aberration, coma aberration, astigmatism, field curvature, axial chromatic aberration, vertical axis chromatic aberration and the like) are well corrected.

As shown in fig. 2, it is a graph of an optical transfer function (MTF) of the lens in a normal temperature state in a visible light band; as shown in fig. 3, the field curvature and distortion diagram of the lens in the visible light band is shown; as shown in fig. 4, it is a transverse light fan diagram of the lens in the visible light band; as shown in fig. 5, it is a dot-sequence diagram of the lens in the visible light band; as shown in fig. 6, it is a graph of optical transfer function (MTF) of the lens in the infrared band at normal temperature.

As can be seen from fig. 2, the optical transfer function (MTF) curve of the lens in the normal temperature state in the visible light portion is relatively smooth and concentrated, and the average MTF value of the full field of view (half-image height Y' is 8mm) is more than 0.55; therefore, the imaging system provided by the embodiment can achieve high resolution and meet the imaging requirement of a 1-inch 1200-ten-thousand-pixel camera.

As can be seen from fig. 3 and 4, the lens distortion is well controlled within 1.2%, and the field curvature is controlled within ± 5 um. Light aberration control is also better.

As can be seen from fig. 5, the lens has a small and concentrated light spot radius, and the corresponding aberration and coma are also good.

As can be seen from fig. 6, in the infrared 850nm band, the optical transfer function (MTF) curve of the lens is smoother and more concentrated, except that the MTF value in the marginal field is slightly decreased, and the average MTF value in the remaining fields (half-image height Y ═ 8mm) is more than 0.55. The infrared confocal lens can be obtained, and the requirement of a day and night dual-purpose scene can be met.

The embodiment of the invention provides an optical lens with low cost, large target surface and high imaging definition. The imaging system has the advantages that the imaging system can realize better distortion control and excellent imaging characteristics by adopting 9 optical lenses with specific structural shapes, sequentially arranging the optical lenses from the object side to the image side according to a specific sequence and distributing and combining specific focal power of each optical lens, has excellent environmental adaptability, and can be widely applied to the field of security monitoring, particularly the fields of intelligent transportation, road monitoring and the like. The focal power of each lens of the lens is distributed reasonably, the shape of the lens is convenient to process, and the cost of the lens is low.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. The lens is characterized by comprising a first positive focal power lens, a first lens group, a second lens group, a third negative focal power lens, a fourth negative focal power lens, a fifth negative focal power lens, a fourth positive focal power lens, an optical filter and an imaging surface which are sequentially arranged from an object side to an image side;

the lens satisfies the following conditions:

50< (fg1/fg2) > f system < 60;

2. The lens barrel according to claim 1, wherein the first lens group includes a second positive power lens and a first negative power lens arranged in order from the object side to the image side.

3. The lens barrel according to claim 2, wherein the second lens group includes a second negative power lens and a third positive power lens arranged in order from the object side to the image side.

4. The lens barrel as claimed in claim 3, wherein the first positive power lens includes a meniscus lens whose object side surface is convex;

the fourth positive power lens includes a double convex lens.

5. The lens barrel according to claim 4, wherein a surface of the second positive power lens facing the image side has the same radius of curvature as a surface of the first negative power lens facing the object side;

6. The lens barrel according to claim 5, wherein a surface of the second positive power lens facing the image side, a surface of the first negative power lens facing the object side, and a surface of the second negative power lens facing the object side are flat or curved.

7. The lens barrel as claimed in claim 1, wherein the first positive power lens has a focal length f1 ≤ 55, the third negative power lens has a focal length f6 ≥ 70, and the fourth positive power lens has a focal length f9 ≥ 35.

8. The lens barrel as claimed in claim 3, wherein the second positive power lens has an Abbe number Vd2 ≥ 60; the Abbe number Vd5 of the third positive focal power lens is not less than 55; and the Abbe number Vd8 of the fifth negative-power lens is not less than 63.

9. The lens barrel as claimed in claim 3, wherein the refractive index Nd1 of the first positive power lens is 1.90 or more; the refractive index Nd3 of the first negative-power lens is less than or equal to 1.86; the refractive index Nd4 of the second negative-power lens is less than or equal to 1.88; the refractive index Nd7 of the fourth negative-power lens is more than or equal to 1.90.

10. The lens barrel as claimed in claim 1, wherein an aperture stop is disposed between the third positive power lens and the third negative power lens.