CN110412743B

CN110412743B - Lens

Info

Publication number: CN110412743B
Application number: CN201910615112.0A
Authority: CN
Inventors: 林法官; 刘凯; 丁洪兴
Original assignee: Zhejiang Dahua Technology Co Ltd
Current assignee: Zhejiang Dahua Technology Co Ltd
Priority date: 2019-07-09
Filing date: 2019-07-09
Publication date: 2021-04-16
Anticipated expiration: 2039-07-09
Also published as: CN110412743A

Abstract

The invention discloses a lens, which comprises a first lens group, a second lens group and an imaging surface, wherein the first lens group, the second lens group and the imaging surface are sequentially arranged from an object side to an image side; the lens group satisfies the following conditions: 1.6< | f2/f system | < 2.0; 1.15< (TTL Fno NL)/20000< 1.25; wherein f2 is the focal length of the second lens group, f system is the system focal length of the lens, TTL is the total optical length of the lens, Fno is the aperture value of the lens, and NL is the number of lenses. Since, in the embodiment of the present invention, two lens groups are arranged in order from the object side to the image side in the lens barrel in a specific order, and the lens groups in the lens barrel satisfy: 1.6< | f2/f system | < 2.0; 1.15< (TTL Fno NL)/20000< 1.25; therefore, the lens provided by the embodiment of the invention has a large aperture and high resolution.

Description

Lens

Technical Field

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

Background

Machine vision lens is widely applied to the fields of production and manufacturing, quality detection, logistics, medicine, scientific research and the like. The actual aperture of the general traffic lens in the market is mostly F1.6 to 1.8 at present, and under the low light scene, the imaging brightness is lower, and the noise of image is more, influences the image definition, needs a large amount of light supplements in order to improve luminance, and this also makes light pollution great. In addition, the resolution ratio of a few large-aperture lenses in the market is low, generally 500 ten thousand pixel levels, and the quality of the acquired image is poor. With the advance of security protection to high definition, the lens is required to achieve higher performance. Therefore, it is important to develop a lens with a large aperture and a high resolution.

Disclosure of Invention

The embodiment of the invention provides a lens, which is used for solving the problem of small aperture of the lens in the prior art.

The embodiment of the present invention provides a lens barrel, including a first lens group, a second lens group and an image plane arranged in sequence from an object side to an image side;

the lens group satisfies the following conditions:

1.6< | f2/f system | < 2.0;

1.15＜(TTL*Fno*Fno*NL*NL)/20000＜1.25；

wherein f2 is the focal length of the second lens group, f system is the system focal length of the lens, TTL is the total optical length of the lens, Fno is the aperture value of the lens, and NL is the number of lenses.

The first lens group comprises a first negative power lens, a second negative power lens, a third negative power lens group, a first sub lens group, a second positive power lens and a second sub lens group which are sequentially arranged from the object side to the image side;

the first sub-lens group comprises a first positive focal power lens or comprises a first positive focal power lens and a fourth negative focal power lens;

the second sub-lens group includes a third positive power lens and a fifth negative power lens.

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

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

the third negative power lens comprises a meniscus lens, and the surface of the third negative power lens facing the image side is a convex surface or comprises a biconcave lens;

the first positive power lens comprises a biconvex lens;

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

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

the third positive power lens comprises a biconvex lens;

the fifth negative power lens comprises a meniscus lens, and the surface of the fifth negative power lens facing the image side is a convex surface or comprises a biconcave lens.

Further, the second lens group comprises a third sub-lens group, a fifth positive power lens and a fourth sub-lens group which are arranged in sequence from the object side to the image side;

the third sub-lens group comprises a sixth negative power lens and a fourth positive power lens;

the fourth sub-lens group includes a seventh negative power lens, a sixth positive power lens, and an eighth negative power lens.

Further, the sixth negative power lens includes a biconcave lens;

the fourth positive power lens comprises a biconvex lens;

the fifth positive power lens includes a biconvex lens;

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

the sixth positive power lens includes a biconvex lens;

the eighth negative power lens comprises a meniscus lens, and the surface of the eighth negative power lens facing the image side is a convex surface.

Further, the refractive indexes of the second positive power lenses are all larger than 1.90, and the refractive indexes of the fifth positive power lenses are all larger than 1.80.

Further, the third negative focal power lens, the first positive focal power lens, the third positive focal power lens and the sixth positive focal power lens are made of low-dispersion materials.

Further, the abbe numbers of the third negative focal power lens, the first positive focal power lens, the third positive focal power lens and the sixth positive focal power lens are all more than 60.

Further, an optical filter is arranged between the second lens group and the imaging surface.

Further, a diaphragm is arranged between the first lens group and the second lens group.

The embodiment of the present invention provides a lens barrel, including a first lens group, a second lens group and an image plane arranged in sequence from an object side to an image side; the lens group satisfies the following conditions: 1.6< | f2/f system | < 2.0; 1.15< (TTL Fno NL)/20000< 1.25; wherein f2 is the focal length of the second lens group, f system is the system focal length of the lens, TTL is the total optical length of the lens, Fno is the aperture value of the lens, and NL is the number of lenses. Since, in the embodiment of the present invention, two lens groups are arranged in order from the object side to the image side in the lens barrel in a specific order, and the lens groups in the lens barrel satisfy: 1.6< | f2/f system | < 2.0; 1.15< (TTL Fno NL)/20000< 1.25; therefore, the lens provided by the embodiment of the invention has a large aperture and higher resolution.

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 schematic view of a lens structure according to an embodiment of the present invention;

fig. 3 is a schematic view of a lens structure provided in embodiment 1 of the present invention;

fig. 4 is a transfer function graph of a lens provided in embodiment 1 of the present invention in a white light scene;

fig. 5 is a schematic view of a lens structure provided in embodiment 2 of the present invention;

fig. 6 is a transfer function curve diagram of a lens provided in embodiment 2 of the present invention in a white light scene;

fig. 7 is a schematic view of a lens structure according to embodiment 3 of the present invention;

fig. 8 is a transfer function graph of a lens provided in embodiment 3 of the present invention in a white light scene.

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 disclosure, the lens barrel including a first lens group G1, a second lens group G2, and an image plane N arranged in order from an object side to an image side;

the lens group satisfies the following conditions:

1.6< | f2/f system | < 2.0;

1.15＜(TTL*Fno*Fno*NL*NL)/20000＜1.25；

Embodiments of the present invention provide a lens barrel in which each lens group has a corresponding focal length f, and since in the embodiments of the present invention, two lens groups are arranged in the lens barrel in order from an object side to an image side in a specific order, and the lens groups in the lens barrel satisfy: 1.6< | f2/f system | < 2.0; 1.15< (TTL Fno NL)/20000< 1.25; therefore, the lens provided by the embodiment of the invention has a large aperture.

In an embodiment of the present invention, an absolute value of a ratio of a focal length of the second lens group to a focal length of the lens barrel is greater than 1.6 and less than 2.0. The absolute value of the ratio of the focal length of the second lens group to the focal length of the lens is too small, and although the lens length can be shortened, spherical aberration increases, image quality is affected, and manufacturability of the lens decreases. The absolute value of the ratio of the focal length of the second lens group to the focal length of the lens is too large, so that the spherical aberration can be reduced, the image quality and the manufacturability of the lens are improved, but the length of the lens is larger. In order to take into account the lens length and the spherical aberration and manufacturability of the lens, a range of absolute values of the ratio of the focal length of the second lens group to the focal length of the lens is provided in the embodiment of the present invention. In an embodiment of the present invention, an absolute value of a ratio of a focal length of the second lens group to a focal length of the lens is greater than 1.6 and less than 2.0. The lens length, the spherical aberration and the manufacturability of the lens can be better considered.

For example, the absolute value of the ratio of the focal length of the second lens group to the focal length of the lens may be 1.7, 1.8, or the like.

Fig. 2 is a schematic structural diagram of a lens barrel according to an embodiment of the present invention, in order to further improve the imaging quality of the lens barrel, the first lens group includes a first negative power lens 1, a second negative power lens 2, a third negative power lens group 3, a first sub-lens group, a second positive power lens 5, and a second sub-lens group C1, which are arranged in order from an object side to an image side;

the first sub-lens group comprises a first positive focal power lens 4, or comprises a first positive focal power lens and a fourth negative focal power lens;

the second sub-lens group includes a third positive power lens 6 and a fifth negative power lens 7.

The first sub-lens group shown in fig. 2 includes a first positive power lens 4, which may be cemented or cemented in order to enable a compact system if the first sub-lens group includes a first positive power lens and a fourth negative power lens.

Specifically, in order to further improve the imaging quality of the lens barrel, as shown in fig. 2, the first negative power lens includes a meniscus lens, and a surface of the first negative power lens facing the image side is a concave surface; the second negative focal power lens comprises a meniscus lens, and the surface of the second negative focal power lens facing the image side is a concave surface; the third negative power lens comprises a meniscus lens, and the surface of the third negative power lens facing the image side is a convex surface or comprises a biconcave lens; the first positive power lens comprises a biconvex lens; the fourth negative power lens comprises a meniscus lens, and the surface of the fourth negative power lens facing the image side is a convex surface; the second positive focal power lens comprises a meniscus lens, and the surface of the second positive focal power lens facing the image side is a concave surface; the third positive power lens comprises a biconvex lens; the fifth negative power lens comprises a meniscus lens, and the surface of the fifth negative power lens facing the image side is a convex surface or comprises a biconcave lens.

The second lens group comprises a third sub-lens group C2, a fifth positive power lens 10 and a fourth sub-lens group which are arranged in sequence from the object side to the image side; the third sub-lens group C3 includes a sixth negative power lens 8 and a fourth positive power lens 9; the fourth sub-lens group includes a seventh negative power lens 11, a sixth positive power lens 12, and an eighth negative power lens 13.

To further enable the system to be compact, the sixth negative power lens 8 and the fourth positive power lens 9 may be cemented or cemented; the fourth sub-lens group including the seventh negative power lens 11, the sixth positive power lens 12, and the eighth negative power lens 13 may be cemented or cemented.

In order to further improve the imaging quality of the image, the sixth negative-power lens comprises a biconcave lens; the fourth positive power lens comprises a biconvex lens; the fifth positive power lens includes a biconvex lens; the seventh negative power lens comprises a meniscus lens, and the surface of the seventh negative power lens facing the image side is a concave surface; the sixth positive power lens includes a biconvex lens; the eighth negative power lens comprises a meniscus lens, and the surface of the eighth negative power lens facing the image side is a convex surface.

In order to improve the refractive index of the lens and reduce the total length of the lens, the refractive index of the second positive focal power lenses is greater than 1.90, and the refractive index of the fifth positive focal power lenses is greater than 1.80. For example, the refractive index of the second positive power lens may be 2.0, 2.1, etc., the refractive index of the fifth positive power lens may be 1.9, 2.0, etc., and the refractive indices of the second positive power lens and the fifth positive power lens may be the same or different.

In addition, when light rays of a spherical lens enter the lens and then reach a focal plane, serious refraction and bending are easy to occur at the edge part of the spherical lens than at the central part of the spherical lens, and the phenomenon can cause the reduction of sharpness and contrast and the generation of light spots, thereby causing the reduction of image quality. And such aberrations are called spherical aberrations. In the embodiment of the invention, the refractive indexes of the second positive power lens are all larger than 1.90, and the refractive indexes of the fifth positive power lens are all larger than 1.80, so that the spherical aberration can be reduced, and the image quality can be improved.

The refractive index of the second positive power lens is nd5, and the refractive index of the fifth positive power lens is nd 10. Wherein nd5 is more than 1.90, and nd10 is more than 1.80.

The second positive focal power lens and the fifth positive focal power lens are made of ultrahigh refractive index materials, so that the refractive index of the lens can be improved, and the resolution of the lens is further improved. And moreover, by adopting the ultrahigh-refractive-index material, the thicknesses of the second positive focal power lens and the fifth positive focal power lens can be reduced, and the total length of the lens is further reduced.

In order to adapt the lens to a wide range of working temperatures, namely, to enable the lens to clearly image at-40 ℃ to 80 ℃, in the embodiment of the invention, the third negative power lens, the first positive power lens, the third positive power lens and the sixth positive power lens are made of low dispersion materials. The abbe numbers of the third negative focal power lens, the first positive focal power lens, the third positive focal power lens and the sixth positive focal power lens are all larger than 60. In addition, the abbe numbers of the third negative focal power lens, the first positive focal power lens, the third positive focal power lens and the sixth positive focal power lens are all larger than 60, so that the chromatic aberration of an image can be reduced, and the image quality is improved. For example, the abbe numbers of the third negative power lens, the first positive power lens, the third positive power lens, and the sixth positive power lens may be 65, 68, 70, and the like. The abbe numbers of the third negative power lens, the first positive power lens, the third positive power lens and the sixth positive power lens may be the same or different.

The abbe number of the third negative power lens is Vd3, the abbe number of the first positive power lens is Vd4, the abbe number of the third positive power lens is Vd6, and the abbe number of the sixth positive power lens is Vd 12. Wherein, Vd3>60, Vd4>60, Vd6>60 and Vd12> 60.

An optical filter M is arranged between the second lens group and the imaging surface, and a diaphragm P is arranged between the first lens group and the second lens group.

The diaphragm P may be a fixed, unchanging device; the diaphragm P can also be automatically and continuously adjusted, so that the intelligent requirement of modern optical instruments is met. The filter M is an optical device for selecting a desired wavelength band of radiation. And the right side of the filter M is an image surface N.

The optical performance of the lens provided by the embodiment of the invention is as follows: the focal length is about 12mm, the aperture Fno <1.25, the field angle 2 ω is about 75 degrees, and the image plane size y' is φ 17.5 mm. The technical requirements of high resolution, super starlight, no thermalization and the like are realized, and the system is suitable for the monitoring requirement of road traffic on lanes.

In summary, the embodiments of the present invention provide a lens, which employs 13 or 14 optical lenses, and sequentially arranges the optical lenses from left to right in a specific order, and matches the structural form of the lens system, the refractive index, abbe number, and other parameters of the lenses with the imaging conditions by distributing the focal power of each optical lens, and simultaneously using a reasonable optical glass material, so as to better correct the spherical aberration, coma aberration, astigmatism, field curvature, chromatic aberration of magnification, and chromatic aberration of position of the lens system, thereby achieving the resolution of an ultra-large aperture and ten million pixels, and good environmental suitability (from-40 degrees to 80 degrees). The optical imaging resolution is high, and the optical imaging device can be matched with a CMOS imaging chip with more than 2 million pixels; and compact structure, overall dimension is little, and all optical lens all adopt spherical design, and cold working technology performance is good, low in production cost.

The lens provided by the embodiment of the invention has the advantages of large aperture, large light flux of the lens, high imaging brightness, small image noise and high image definition in a low-light environment, and can reduce the required light supplement intensity and reduce light pollution even if light supplement is required to a certain degree, thereby achieving the effects of power saving and environmental protection. The lens provided by the embodiment of the invention has high resolution, and can reach more than 1600 ten thousand pixel levels.

For the relation: 1.6< | f2/f system | <2.0, when the value is greater than the upper limit, the imaging will be improved, but the total length of the system is not reduced; when the value is less than the lower limit, although the system is more compact, the poor imaging performance of the system can not meet the use requirement of ten million pixels.

In addition, in order to make the system compact and achieve high imaging performance, the total optical length of the lens, the number of lenses and the aperture value should satisfy the relation: 1.15< (TTL Fno NL)/20000< 1.25. Wherein, TTL is the total optical length of the lens, Fno is the aperture value of the lens, and NL is the number of lenses.

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

Example 1:

fig. 3 is a schematic view of a lens structure provided in an embodiment of the present invention, where a focal length of the lens is 12.58mm, an aperture Fno is 1.20, and a total lens length TTL is about 99.8 mm.

Data of curvature radius, center thickness, refractive index nd, and abbe constant Vd of each lens are shown in table 1:

TABLE 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.

From the data in table 1 and the associated equations, one can obtain: f2 is 24.65 mm; NL-13; 1.96 in the system of | f 2/f; (TTL × Fno × NL)/20000 ═ 1.21; nd5 is 2.051; nd10 is 1.804; vd3 ═ 61.25; vd 4-68.62; vd 6-68.62; vd 12-68.62.

The lens provided in embodiment 1 will be further described below by performing detailed optical system analysis on embodiment 1.

The optical transfer function is used for evaluating the imaging quality of an optical system in a more accurate, visual and common mode, and the higher and smoother curve of the optical transfer function indicates that the imaging quality of the system is better, and aberration is well corrected.

Fig. 4 is a plot of the transfer function (MTF) of the system in white light with the resolution on the abscissa in lp/mm and the MTF value on the ordinate, and similar curves below are not repeated and are not repeated. As in fig. 4, it can be seen that the curve falls smoothly and converges. At 140lp/mm, the MTF value is greater than 0.3 within 7.48mm of image height. Therefore, the lens can be matched with a CMOS imaging chip with the resolution of more than 2 million pixels under white light of the system.

Example 2:

fig. 5 is a schematic view of a lens structure provided in an embodiment of the present invention, where a focal length of the lens is 12.13mm, an aperture Fno is 1.02, and a total lens length TTL is 138 mm.

Data of curvature radius, center thickness, refractive index nd, and abbe constant Vd of each lens are shown in table 2:

TABLE 2

From the data in table 2 and the associated equations, one can obtain: f2 ═ 21.65 mm; NL-13; the system | f2/f 1.78; (TTL × Fno × NL)/20000 ═ 1.21; nd5 is 2.003; nd10 is 1.804; vd 3-81.56; vd 4-68.35; vd 6-68.35; vd 12-68.35.

The lens provided in embodiment 2 will be further described below by performing a detailed optical system analysis on embodiment 2.

Fig. 6 is a transfer function (MTF) graph with curves falling smoothly and converging. At 140lp/mm, the MTF value is greater than 0.3 within 7.48mm of image height. Therefore, the lens can be matched with a CMOS imaging chip with the resolution of more than 2 million pixels under white light of the system.

Example 3:

fig. 7 is a schematic view of a lens structure provided in the embodiment of the present invention, where a focal length of the lens is 12.5mm, an aperture Fno is 1.02, and a total lens length TTL is 118 mm.

Data of the radius of curvature, center thickness, refractive index nd, and abbe constant Vd of each lens are shown in table 3:

TABLE 3

From the data in table 3 and the associated equations, one can obtain: f2 ═ 21.99 mm; NL is 14; the system | f2/f 1.76; (TTL × Fno × NL)/20000 ═ 1.20; nd5 is 1.923; nd10 is 2.003; vd 3-81.56; vd 4-68.62; vd 6-68.62; vd 12-68.62.

The lens provided in embodiment 3 will be further described below by performing a detailed optical system analysis on embodiment 3.

Fig. 8 is a transfer function (MTF) graph with curves falling smoothly and converging. At 140lp/mm, the MTF value is greater than 0.3 within 7.48mm of image height. Therefore, the lens can be matched with a CMOS imaging chip with the resolution of more than 2 million pixels under white light of the system.

The embodiment of the present invention provides a lens barrel, including a first lens group, a second lens group and an image plane arranged in sequence from an object side to an image side; the lens group satisfies the following conditions: 1.6< | f2/f system | < 2.0; 1.15< (TTL Fno NL)/20000< 1.25; wherein f2 is the focal length of the second lens group, f system is the system focal length of the lens, TTL is the total optical length of the lens, Fno is the aperture value of the lens, and NL is the number of lenses. Since, in the embodiment of the present invention, two lens groups are arranged in order from the object side to the image side in the lens barrel in a specific order, and the lens groups in the lens barrel satisfy: 1.6< | f2/f system | < 2.0; 1.15< (TTL Fno NL)/20000< 1.25; therefore, the lens provided by the embodiment of the invention has a large aperture.

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 lens group, a second lens group and an imaging surface which are sequentially arranged from an object side to an image side;

the lens group satisfies the following conditions:

1.6< | f2/f system | < 2.0;

1.15＜(TTL*Fno*Fno*NL*NL)/20000＜1.25；

wherein f2 is the focal length of the second lens group, f system is the system focal length of the lens, TTL is the optical total length of the lens, Fno is the aperture value of the lens, and NL is the number of lenses;

the first lens group comprises a first negative focal power lens, a second negative focal power lens, a third negative focal power lens, a first sub lens group, a second positive focal power lens and a second sub lens group which are sequentially arranged from the object side to the image side;

2. The lens barrel according to claim 1, wherein the first negative power lens includes a meniscus lens, and a surface of the first negative power lens facing the image side is a concave surface;

the first positive power lens comprises a biconvex lens;

the third positive power lens comprises a biconvex lens and the fifth negative power lens comprises a biconcave lens; or the third positive focal power lens comprises a convex lens, the surface of the third positive focal power lens facing the object side is a convex surface, the fifth negative focal power lens comprises a concave lens, and the surface of the fifth negative focal power lens facing the image side is a concave surface.

3. The lens barrel according to claim 1, wherein the second lens group includes a third sub-lens group, a fifth positive power lens, and a fourth sub-lens group arranged in order from an object side to an image side;

4. The lens barrel as claimed in claim 3, wherein the sixth negative power lens includes a biconcave lens;

the fourth positive power lens comprises a biconvex lens;

the fifth positive power lens includes a biconvex lens;

the sixth positive power lens includes a biconvex lens;

5. The lens barrel as claimed in claim 4, wherein the refractive indices of the second positive power lenses are each greater than 1.90, and the refractive indices of the fifth positive power lenses are each greater than 1.80.

6. The lens barrel as claimed in claim 4, wherein the third negative power lens, the first positive power lens, the third positive power lens and the sixth positive power lens use low dispersion materials.

7. The lens barrel as claimed in claim 6, wherein the third negative power lens, the first positive power lens, the third positive power lens and the sixth positive power lens have abbe numbers greater than 60.

8. The lens barrel according to claim 1, wherein a filter is provided between the second lens group and the imaging surface.

9. The lens barrel according to claim 1, wherein a diaphragm is disposed between the first lens group and the second lens group.