CN114114612A

CN114114612A - Optical lens and imaging apparatus

Info

Publication number: CN114114612A
Application number: CN202111216127.3A
Authority: CN
Inventors: 郭安峰; 刘凯; 丁洪兴
Original assignee: Zhejiang Dahua Technology Co Ltd
Current assignee: Zhejiang Dahua Technology Co Ltd
Priority date: 2021-10-19
Filing date: 2021-10-19
Publication date: 2022-03-01
Anticipated expiration: 2041-10-19
Also published as: CN114114612B

Abstract

The application discloses an optical lens and imaging equipment, wherein the optical lens comprises a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged from an object side to an image side; wherein the first lens, the second lens and the sixth lens are all negative focal power lenses, and the third lens, the fourth lens, the fifth lens and the seventh lens are all positive focal power lenses; one of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens is a spherical lens, and the rest are plastic aspheric lenses. The application provides an optical lens and imaging device, this optical lens have big target surface, big light ring, high resolving power and the lower characteristic of cost.

Description

Optical lens and imaging apparatus

Technical Field

The present disclosure relates to optical imaging technologies, and particularly to an optical lens and an imaging apparatus.

Background

The optical lens is an essential component in a machine vision system, directly influences the quality of imaging quality and influences the realization and effect of an algorithm. In recent years, optical lenses are increasingly used in the security field, and meanwhile, requirements on relevant parameters of the lenses are also increasingly strict, for example: volume, brightness, cost, etc.

However, the conventional optical imaging lens still has the following problems:

1. most of the glass glasses are designed by adopting a full glass scheme or a scheme of 2G5P (2 glass lenses and 5 plastic lenses) and a scheme of 5G3P (5 glass lenses and 3 plastic lenses), and although the performances such as imaging and reliability are ensured, the cost is higher;

2. the F number of the aperture is F1.2 or more, namely the aperture is smaller;

3. the imaging can only support the use of an image sensor with the target surface of 1/2.7 inches at most, namely the target surface is small;

4. the imaging quality of the lens is poor, and the requirement of an optical lens with high resolution cannot be supported.

Disclosure of Invention

The technical problem that this application mainly solved provides an optical lens and imaging device, and this optical lens has big target surface, big light ring, high resolving power and the lower characteristic of cost.

In order to solve the technical problem, the application adopts a technical scheme that: providing an optical lens, which comprises a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are arranged in sequence from an object side to an image side;

wherein the first lens, the second lens and the sixth lens are all negative focal power lenses, and the third lens, the fourth lens, the fifth lens and the seventh lens are all positive focal power lenses; one of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens is a spherical lens, and the rest are plastic aspheric lenses.

Further, the third lens is a spherical lens, and the first lens, the second lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all plastic aspheric lenses.

Further, the optical total length of the optical lens is less than or equal to 30.5 mm.

Further, the focal length of the lens group consisting of the fifth lens and the sixth lens is f_P56F, the focal length of the optical lens is f, the field angle of the optical lens is FOV, and then f_P56F and FOV satisfy the following formula:

further, a central radius of curvature R2 of the first lens image-side surface and a central radius of curvature R3 of the second lens object-side surface satisfy the following equation:

furthermore, the abbe number of the second lens material is Vd2, the abbe number of the fourth lens material is Vd4, the abbe number of the sixth lens material is Vd6, Vd2 is not more than 57, Vd4 is not less than 81, and Vd6 is not more than 25.

Furthermore, the third lens is made of glass, and the refractive index of the third lens is larger than or equal to 1.9.

Furthermore, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a convex surface; the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a convex surface; the object side surface of the sixth lens is a concave surface, and the image side surface of the sixth lens is a concave surface; the object side surface of the seventh lens element is a convex surface, and the image side surface of the seventh lens element is a convex surface.

Further, the object side surface of the first lens, the image side surface of the second lens and the image side surface of the seventh lens all have points of inflection.

In order to solve the above technical problem, another technical solution adopted by the present application is: there is provided an imaging apparatus including the optical lens according to any one of the above embodiments.

Different from the prior art, the beneficial effects of the application are that:

the optical lens provided by the embodiment of the application comprises seven lenses which are sequentially arranged, wherein only one of the seven lenses is a spherical lens, and the rest of the seven lenses are plastic aspheric lenses, so that the mass production consistency of the plastic aspheric lenses can be improved, the processability is optimized, and the cost is reduced.

Meanwhile, the maximum target surface size of the optical lens is 1/1.8 inch, and the F number of the maximum aperture is 1.0, namely the optical lens has a large target surface and a large aperture, is particularly suitable for monitoring requirements under a low illumination condition, and has high resolution and high resolution.

Drawings

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

fig. 1 is a schematic structural diagram of an optical lens provided in this embodiment;

fig. 2 is a schematic view of an MTF curve of an optical lens in a normal temperature state in a visible light band according to the present embodiment;

fig. 3 is a schematic view of a field curvature curve of an optical lens in a visible light band according to the present embodiment;

fig. 4 is a schematic diagram illustrating a distortion curve of an optical lens provided in this embodiment in a visible light band;

fig. 5A to 5E are schematic diagrams of a transverse fan of an optical lens in a visible light band according to the present embodiment, where an image height in fig. 5A is 0, a half-image height in fig. 5B is 1.4mm, a half-image height in fig. 5C is 2.5mm, a half-image height in fig. 5D is 3.8mm, and a half-image height in fig. 5E is 4.4 mm;

fig. 6A to 6E are schematic dot-line diagrams of an optical lens provided in this embodiment in a visible light band, where an image height in fig. 6A is 0, a unit of 40.00 is nm, a half-image height in fig. 6B is 1.4mm, a half-image height in fig. 6C is 2.5mm, a half-image height in fig. 6D is 3.8mm, and a half-image height in fig. 6E is 4.4 mm.

Description of reference numerals:

1. a first lens; 2. a second lens; 3. a third lens; 4. a fourth lens; 5. a fifth lens; 6. a sixth lens; 7. a seventh lens; 8. a diaphragm; 9. an optical filter; 10. an imaging plane; 11. an optical axis; 12. an object side; 13. and an image side.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, 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 application.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Please refer to fig. 1. The present invention provides an optical lens including a first lens 1, a second lens 2, a third lens 3, a stop 8, a fourth lens 4, a fifth lens 5, a sixth lens 6, and a seventh lens 7, which are arranged in order from an object side 12 to an image side 13.

The first lens 1, the second lens 2 and the sixth lens 6 are all negative focal power lenses, and the third lens 3, the fourth lens 4, the fifth lens 5 and the seventh lens 7 are all positive focal power lenses. One of the first lens element 1, the second lens element 2, the third lens element 3, the fourth lens element 4, the fifth lens element 5, the sixth lens element 6 and the seventh lens element 7 is a spherical lens element, and the rest are plastic aspheric lens elements. The maximum target surface size of the optical lens is 1/1.8 inch, and the F-number of the maximum aperture of the optical lens is 1.0.

In the present embodiment, the object-side surface of the first lens element 1 is convex, and the image-side surface of the first lens element 1 is concave. The object-side surface of the second lens element 2 is concave, and the image-side surface of the second lens element 2 is convex. The object-side surface of the third lens element 3 is concave, and the image-side surface of the third lens element 3 is convex. The object-side surface of the fourth lens element 4 is concave, and the image-side surface of the fourth lens element 4 is convex. The object-side surface of the fifth lens element 5 is convex, and the image-side surface of the fifth lens element 5 is convex. The object side surface of the sixth lens element 6 is a concave surface, and the image side surface of the sixth lens element 6 is a concave surface. The object-side surface of the seventh lens element 7 is convex, and the image-side surface of the seventh lens element 7 is convex.

Here, the "object side surface" refers to a surface facing the object side 12, and the "image side surface" refers to a surface facing the image side 13. The centers of the lenses are located on an optical axis 11, and the optical axis 11 extends from an object side 12 to an image side 13.

Specifically, the object side surface of the first lens element 1, the image side surface of the second lens element 2, and the image side surface of the seventh lens element 7 have inflection points for correcting aberrations, so that the optical lens system can operate normally. The first lens 1, the third lens 3, and the fourth lens 4 may be meniscus lenses.

In a preferred embodiment, the third lens 3 is a spherical lens, and the first lens 1, the second lens 2, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are all plastic aspheric lenses. The diaphragm 8 may be an aperture diaphragm.

Furthermore, the third lens 3 is made of glass, and the refractive index of the third lens 3 is greater than or equal to 1.9.

As shown in fig. 1, in the present embodiment, the optical lens may further include an optical filter 9 and an imaging surface 10. The filter 9 and the imaging surface 10 are positioned on the image side 13 of the seventh lens 7, and the filter 9 is positioned between the seventh lens 7 and the imaging surface 10. The optical total length of the optical lens is less than or equal to 30.5mm, namely the distance from the object side surface of the first lens 1 to the imaging surface 10 is less than or equal to 30.5mm, so that the overall size of the optical lens is smaller, and the miniaturization of the optical lens structure is effectively realized.

In the present embodiment, the focal length of the lens group consisting of the fifth lens 5 and the sixth lens 6 is f_P56F, when the focal length of the optical lens is f and the field angle of the optical lens is FOV_P56F and FOV satisfy the following formula:

in the present embodiment, the central radius of curvature R2 of the image-side surface of the first lens 1 and the central radius of curvature R3 of the object-side surface of the second lens 2 satisfy the following equation:

in the present embodiment, when the abbe number of the material of the second lens 2 is Vd2, the abbe number of the material of the fourth lens 4 is Vd4, and the abbe number of the material of the sixth lens 6 is Vd6, Vd2 is equal to or less than 57, Vd4 is equal to or greater than 81, and Vd6 is equal to or less than 25.

By limiting the parameter values, the optical lens provided by the embodiment has the advantages of low cost, large aperture, large target surface and high resolution. Specifically, when the spatial frequency value is 100lp/mm, the value of the full-field modulation transfer function of the optical lens is more than 0.5.

In the present embodiment, since each of the lenses and the filter 9 of the optical lens has an object-side surface and an image-side surface, respectively, and the aperture stop 8 occupies a single plane, and the image-forming surface 10 also occupies a single plane, the numbers of the object-side surface and the image-side surface of the first lens 1 are S1 and S2, respectively, the numbers of the object-side surface and the image-side surface of the second lens 2 are S3 and S4, respectively, the numbers of the object-side surface and the image-side surface of the third lens 3 are S5 and S6, respectively, the number of the aperture stop 8 is S7, the numbers of the object-side surface and the image-side surface of the fourth lens 4 are S8 and S9, the numbers of the object-side surface and the image-side surface of the fifth lens 5 are S10 and S11, respectively, the numbers of the object-side surface and the image-side surface of the sixth lens 6 are S12 and S13, respectively, the numbers of the object-side surface and the image-side surface of the seventh lens 7 are S14 and S15, respectively, and the number of the object-side surface of the filter 9 and the image-side surface of the filter 35 are S16, respectively, S17, the image forming surface 10 is given the surface number S18.

In one embodiment, the radii of curvature R, center thickness Tc, and conic index k of the surfaces S1-S18, as well as the refractive indices Nd, Abbe' S constants Vd of the respective lenses, are shown in Table 1 below. Where the radius of curvature R represents the radius of curvature at the center of each face (at a point on the optical axis 11). The center thickness Tc represents the distance between the surface and a point on the optical axis 11 of the adjacent surface on the surface image side 13, that is, the distance between the surface and the center point of the adjacent surface on the surface image side 13. For example, the center thickness Tc of the face S1 is equal to the distance from the midpoint of S1 to the midpoint of S2, and the center thickness Tc of the face S2 is equal to the distance from the midpoint of S2 to the midpoint of S3.

Table 1 example values of the parameters

The conic coefficient k of the aspheric surface in table 1 can be defined by the following formula (1) for the aspheric surface, but is not limited to the following expression method:

wherein, Z is the axial rise of the aspheric surface along the direction of the optical axis 11; r is the height from the point of the aspheric surface calculation vector height to the center; c is the curvature of the fitting sphere, and the value of c is the reciprocal of the curvature radius R of the center of the aspheric surface; k is a conic coefficient; A-F are respectively the coefficients of the aspheric polynomial in 4 th order, 6 th order, 8 th order, 10 th order, 12 th order and 14 th order, and the specific values are shown in the following table 2.

TABLE 2 EXAMPLES A-F values

In this embodiment, the total optical length TTL of the optical lens is less than or equal to 30.5mm, the focal length F of the optical lens is 4.17mm, the field angle of the optical lens is 134 °, the optical distortion of the optical lens is not more than-26.5%, the F value of the aperture of the optical lens is 1.0, and the image plane size of the optical lens is not less than Φ 8.8 mm.

The method for evaluating the imaging quality of an imaging system by using the optical transfer function is a relatively accurate, intuitive and common evaluation mode. The higher and smoother curve of the optical transfer function shows that the imaging quality of the imaging system is better, and the imaging system well corrects various aberrations (such as spherical aberration, coma aberration, astigmatism, field curvature, axial chromatic aberration, vertical axis chromatic aberration and the like). The optical transfer function consists of a modulation transfer function and a phase transfer function. At present, the types of instruments for testing the phase transfer function are few, the measurement precision is not high, and the influence of the phase transfer process on the influence is small, so that the influence of the phase transfer function can be not considered, and only the modulation transfer function is researched. The modulation Transfer function is abbreviated in english as mtf (modulation Transfer function), also called modulus Transfer function.

As shown in fig. 2, a schematic view of an MTF curve of the optical lens in a normal temperature state of a visible light band is shown. The MTF curve of the optical lens in a normal temperature state in a visible light part is smooth and concentrated, and the average MTF value of a full field of view (half image height Y' is 4.4mm) reaches above 0.5.

Fig. 3 is a schematic view of a field curvature curve of the optical lens in the visible light band. The curvature of field of the optical lens is controlled within +/-0.05 mm. When the lens has field curvature, the intersection point of the whole light beam is not superposed with an ideal image point, and although a clear image point can be obtained at each specific point, the whole image plane is a curved surface. T represents the meridional field curvature, and S represents the sagittal field curvature. The field curvature curve shows the distance of the current focal plane or image plane to the paraxial focal plane as a function of the field of view coordinates, and the meridional field curvature data is the distance from the currently determined focal plane to the paraxial focal plane measured along the optical axis 11 and measured in the meridional plane. Sagittal curvature of field data measures distances measured in a plane perpendicular to the meridian plane. The baseline in fig. 3 is on the optical axis 11, the top of the curve represents the maximum field of view (angle or height), and no units are set on the vertical axis, since the curve is always normalized with the maximum radial field of view.

Fig. 4 is a schematic diagram showing distortion curves of the optical lens in the visible light band. The optical lens has better distortion control within-26.5%. Fig. 4 coincides with reference to curves of a plurality of wavelengths (0.436mm, 0.486mm, 0.546mm, 0.587mm, and 0.656 mm). Generally, lens distortion is a general term of perspective distortion inherent to an optical lens, that is, distortion caused by perspective, which is very unfavorable for the imaging quality of a photograph, and after all, the purpose of photography is reproduction rather than exaggeration, but since the convergent light of a convex lens and the divergent light of a concave lens are inherent to the lens, the distortion cannot be eliminated, and only can be improved. As can be seen from fig. 4, the distortion of the optical lens provided by this embodiment is only-26.5%, and the distortion is set to balance the focal length, the field angle and the size of the target surface of the corresponding camera, and the distortion caused by the distortion can be corrected by the post-image processing.

As shown in fig. 5A to 5E, the optical lens is a schematic diagram of a transverse light fan in the visible light band. The curves in the figure are more concentrated, which shows that the spherical aberration and dispersion of the optical lens are better controlled.

Fig. 6A to 6E are schematic diagrams illustrating the optical lens in a dot arrangement in a visible light band. It can be seen that the optical lens has a small and concentrated light spot radius, and the corresponding aberration and coma are good.

In summary, the optical lens provided in this embodiment adopts 7 optical lenses with specific structural shapes, and the optical lenses are arranged in order from the object side 12 to the image side 13 according to a specific order, and through the distribution and combination of specific powers of the respective optical lenses, the optical lens can achieve better distortion control and have excellent imaging characteristics, and has good temperature stability.

In another embodiment, the radii of curvature R, center thickness Tc, and conic index k of the surfaces S1-S18, as well as the refractive indices Nd, Abbe' S constants Vd of the respective lenses are shown in Table 3 below.

Table 3 values of the parameters of example two

The conic coefficient k of the aspheric surface in table 3 can be defined by the above equation (1) for aspheric surfaces, and will not be described herein again. Wherein the specific values of A-F are shown in Table 4 below.

Number of noodles

A

B

C

D

E

F

S1

-1.31E-03

2.17E-05

-1.47E-07

-6.60E-10

1.05E-11

0.00E+00

S2

-2.70E-03

5.85E-05

-4.62E-06

1.78E-07

-4.84E-16

0.00E+00

S3

3.62E-03

-2.52E-04

1.36E-05

-6.01E-07

1.93E-08

-2.91E-10

S4

4.48E-03

-1.67E-04

3.58E-06

4.26E-08

-8.66E-10

-3.13E-11

S8

1.37E-03

-8.60E-05

2.01E-06

-9.82E-09

-1.19E-09

2.62E-11

S9

5.67E-04

-3.64E-05

1.09E-06

-1.14E-08

-1.12E-10

3.26E-13

S10

-5.46E-04

-2.49E-06

-2.05E-08

-1.41E-08

-3.85E-10

-1.91E-12

S11

-5.01E-04

1.23E-05

-2.32E-06

8.17E-08

6.41E-10

-5.78E-11

S12

5.43E-04

-6.68E-05

1.38E-06

3.30E-08

9.14E-10

-5.78E-11

S13

2.46E-04

3.59E-05

-2.63E-06

1.74E-07

-7.31E-09

6.98E-11

S14

5.52E-04

5.53E-06

2.68E-06

-4.08E-08

-1.92E-09

9.42E-11

S15

2.67E-04

-2.00E-05

6.30E-06

-2.52E-07

5.41E-09

1.07E-10

In this embodiment, the total optical length TTL of the optical lens is less than or equal to 30.01mm, the focal length F of the optical lens is 4.16mm, the field angle of the optical lens is 130 °, the optical distortion of the optical lens is not more than-25.2%, the F value of the aperture of the optical lens is 1.0, and the image plane size of the optical lens is not less than Φ 8.8 mm.

Embodiments of the present application further provide an imaging device, including an optical lens according to any of the above embodiments, and the detailed description of the related contents of the optical lens refers to the above contents, which are not described in detail herein. The imaging device may be a device having an image projection or image acquisition function, including but not limited to a communication device, a vehicle camera, a motion camera, a security camera, a surveillance device, a digital camera, or a projector.

The optical lens and the imaging device provided by the embodiment of the application have the following advantages:

1. the imaging surface 10 supports a sensor (CCD/CMOS) camera with the maximum size of phi 8.8mm, and the requirement of high resolution of equipment is met;

2. the full field MTF value can reach more than 0.6 under the condition of 100lp/mm, and the imaging characteristic is excellent;

3. the focal power of each lens is distributed reasonably, the shape of the lens is convenient to process, and the cost of the lens is low;

4. the aperture is large, the F number is 1.0, and the device is particularly suitable for monitoring requirements under the low-illumination condition;

5. the total length of the lens, for example, TTL can be 30.1mm, and the requirement of product miniaturization is met.

It should be noted that, in the description of the present specification, the terms "first", "second", and the like are used for descriptive purposes only and for distinguishing similar objects, and no order is present therebetween, and no indication or suggestion of relative importance is to be made. Further, in the description of the present specification, "a plurality" means two or more unless otherwise specified.

Any numerical value recited herein includes all values from the lower value to the upper value, in increments of one unit, provided that there is a separation of at least two units between any lower value and any higher value. For example, if it is stated that the number of a component or a value of a process variable (e.g., temperature, pressure, time, etc.) is from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, it is intended that equivalents such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also expressly enumerated in this specification. For values less than 1, one unit is suitably considered to be 0.0001, 0.001, 0.01, 0.1. These are only examples of what is intended to be explicitly recited, and all possible combinations of numerical values between the lowest value and the highest value that are explicitly recited in the specification in a similar manner are to be considered.

Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. The use of "about" or "approximately" with a range applies to both endpoints of the range. Thus, "about 20 to about 30" is intended to cover "about 20 to about 30", including at least the endpoints specified.

The term "consisting essentially of …" describing a combination shall include the identified element, ingredient, component or step as well as other elements, ingredients, components or steps that do not materially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, or steps herein also contemplates embodiments that consist essentially of such elements, components, or steps. By using the term "may" herein, it is intended to indicate that any of the described attributes that "may" include are optional.

A plurality of elements, components, parts or steps can be provided by a single integrated element, component, part or step. Alternatively, a single integrated element, component, part or step may be divided into separate plural elements, components, parts or steps. The disclosure of "a" or "an" to describe an element, ingredient, component or step is not intended to foreclose other elements, ingredients, components or steps.

The above description is only for the purpose of illustrating embodiments of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application or are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims

1. An optical lens includes a first lens element, a second lens element, a third lens element, a diaphragm, a fourth lens element, a fifth lens element, a sixth lens element, and a seventh lens element arranged in order from an object side to an image side;

2. An optical lens barrel according to claim 1, wherein the third lens is a spherical lens, and the first lens, the second lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are plastic aspheric lenses.

3. An optical lens according to claim 1, characterized in that the total optical length of the optical lens is less than or equal to 30.5 mm.

4. An optical lens barrel according to claim 1, wherein a focal length of a lens group consisting of the fifth lens and the sixth lens is f_P56F, the focal length of the optical lens is f, the field angle of the optical lens is FOV, and then f_P56F and FOV satisfy the following formula:

5. an optical lens as claimed in claim 1, characterized in that the central radius of curvature R2 of the image side surface of the first lens and the central radius of curvature R3 of the object side surface of the second lens satisfy the following formula:

6. an optical lens according to claim 1, characterized in that the abbe number of the second lens material is Vd2, the abbe number of the fourth lens material is Vd4, the abbe number of the sixth lens material is Vd6, and Vd2 ≤ 57, Vd4 ≥ 81, and Vd6 ≤ 25.

7. An optical lens according to claim 2, wherein the third lens is made of glass, and the refractive index of the third lens is greater than or equal to 1.9.

8. An optical lens barrel according to claim 1, wherein the object side surface of the first lens element is convex and the image side surface of the first lens element is concave; the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a convex surface; the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a convex surface; the object side surface of the sixth lens is a concave surface, and the image side surface of the sixth lens is a concave surface; the object side surface of the seventh lens element is a convex surface, and the image side surface of the seventh lens element is a convex surface.

9. An optical lens barrel according to claim 1, wherein the object side surface of the first lens, the image side surface of the second lens, and the image side surface of the seventh lens each have an inflection point.

10. An imaging apparatus, characterized by comprising the optical lens according to any one of claims 1 to 9.