CN109031588B

CN109031588B - Optical lens

Info

Publication number: CN109031588B
Application number: CN201710438657.XA
Authority: CN
Inventors: 姚波; 王东方; 张野
Original assignee: Ningbo Sunny Automotive Optech Co Ltd
Current assignee: Ningbo Sunny Automotive Optech Co Ltd
Priority date: 2017-06-12
Filing date: 2017-06-12
Publication date: 2021-05-28
Anticipated expiration: 2037-06-12
Also published as: CN109031588A

Abstract

The present application discloses an optical lens, sequentially from an object side to an image side along an optical axis, comprising: the lens comprises a first lens, a second lens, a third lens and a fourth lens. The first lens has negative focal power, 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 second lens has positive focal power, and both the object side surface and the image side surface of the second lens are convex surfaces; the third lens has negative focal power; and the fourth lens has positive focal power, and the object side surface of the fourth lens is a convex surface and the image side surface of the fourth lens is a concave surface.

Description

Optical lens

Technical Field

The present application relates to an optical lens, and more particularly, to an optical lens including four lenses.

Background

With the widespread use of cameras, the variety of chips that can be selected is increasing. The angle CRA (chief ray angle) of chief ray incident on the chip required by part of special chips in design reaches about 25 degrees, which exceeds the conventional requirement. The chief ray angle CRA of a general lens cannot be the value, so that the lens cannot be matched with a chip, and the conditions of chromatic aberration and the like occur.

Also, for applications where certain mounting locations are limited, it is desirable for the lens to have a smaller rear end size. For example, a vehicle-mounted lens that needs to be installed in a vehicle needs to meet the requirements of small size of the rear end and large chief ray angle CRA simultaneously by using a special lens design due to the limitation of the installation position.

Therefore, it is desirable to provide an optical lens having a large principal ray angle CRA, a small rear end size, and a high resolving power.

Disclosure of Invention

The technical solution provided by the present application at least partially solves the technical problems described above.

According to an aspect of the present application, an optical lens is disclosed, which includes, in order from an object side to an image side along an optical axis: the lens comprises a first lens, a second lens, a third lens and a fourth lens. The first lens can have negative focal power, and the object side surface of the first lens can be a convex surface, and the image side surface of the first lens can be a concave surface; the second lens can have positive focal power, and both the object side surface and the image side surface of the second lens can be convex surfaces; the third lens may have a negative optical power; and the fourth lens element can have positive optical power, and its object side surface can be convex surface and its image side surface can be concave surface.

In one embodiment, the optical lens further includes an aperture stop, and the aperture stop may be located between the second lens and the third lens.

In one embodiment, the on-axis distance T from the object-side surface of the first lens to the stop_{Front side}On-axis distance T from diaphragm to imaging surface of optical lens_{Rear end}Can satisfy T_{Front side}/T_{Rear end}≥1.5。

According to another aspect of the present application, there is also disclosed an optical lens, in order from an object side to an image side along an optical axis, comprising: a first lens, a second lens, a diaphragm, and at least one subsequent lens. The first lens can have negative focal power, and the object side surface of the first lens can be a convex surface, and the image side surface of the first lens can be a concave surface; the second lens can have positive focal power, and both the object side surface and the image side surface of the second lens can be convex surfaces; and the on-axis distance T from the object side surface of the first lens to the diaphragm_{Front side}On-axis distance T from diaphragm to imaging surface of optical lens_{Rear end}Can satisfy T_{Front side}/T_{Rear end}≥1.5。

In one embodiment, the at least one subsequent lens of the optical lens may include: a third lens, which may have a negative focal power; and a fourth lens element with positive focal power, wherein the object-side surface of the fourth lens element can be convex and the image-side surface of the fourth lens element can be concave.

In one embodiment, the image-side surface of the third lens element can be concave and the object-side surface can be convex.

In one embodiment, both the object-side surface and the image-side surface of the third lens can be concave.

In one embodiment, the third lens and the fourth lens may be cemented to form a cemented lens.

In one embodiment, at least one of the second lens and the fourth lens is an aspherical lens.

In one embodiment, a focal length value f1 of the first lens and a total focal length value f of the optical lens may satisfy-3.0 ≦ f1/f ≦ -1.5.

In one embodiment, f2/f ≧ 0.9 can be satisfied between the focal length value f2 of the second lens and the total focal length value f of the optical lens.

In one embodiment, the distance T12 between the first lens and the second lens on the optical axis and the total focal length f of the optical lens can satisfy T12/f ≧ 1.5.

In one embodiment, the radius of curvature R4i of the image side surface of the fourth lens and the total focal length f of the optical lens can satisfy R4i/f ≧ 1.3.

In one embodiment, the maximum clear aperture D4i of the image side surface of the fourth lens corresponding to the maximum field angle, the image height h corresponding to the maximum field angle and the maximum field angle FOV can satisfy D4i/h/FOV ≦ 0.01.

The present application adopts a plurality of (for example, four) lenses, and through reasonable lens arrangement, power distribution, air space distribution between lenses, and design of the meniscus lens with the concave surface of the fourth lens facing the image side, the optical lens has at least one of the following advantages while ensuring large imaging size and high pixel:

under the same imaging plane, the chief ray angle CRA is increased;

reducing the size of the rear end of the lens; and

the resolution and the imaging quality of the lens are improved.

Drawings

Other features, objects and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments thereof, when taken in conjunction with the accompanying drawings. In the drawings:

fig. 1 is a schematic view showing a structure of an optical lens according to embodiment 1 of the present application;

fig. 2 is a schematic view showing a structure of an optical lens according to embodiment 2 of the present application.

Detailed Description

For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the present application and does not limit the scope of the present application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that in this specification, the expressions first, second, third, etc. are used only to distinguish one feature from another, and do not represent any limitation on the features. Thus, the first lens discussed below may also be referred to as the second lens or the third lens without departing from the teachings of the present application.

In the drawings, the thickness, size, and shape of the lens have been slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shape of the spherical surface or the aspherical surface is not limited to the shape of the spherical surface or the aspherical surface shown in the drawings. The figures are purely diagrammatic and not drawn to scale.

The paraxial region refers to a region near the optical axis. Herein, a surface closest to the object in each lens is referred to as an object side surface, and a surface closest to the imaging surface in each lens is referred to as an image side surface.

It will be further understood that the terms "comprises," "comprising," "includes," "including," "has," "including," and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.

Unless otherwise defined, all terms (including 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. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

The features, principles, and other aspects of the present application are described in detail below.

An optical lens according to an exemplary embodiment of the present application may include, for example, four lenses, i.e., a first lens, a second lens, a third lens, and a fourth lens. The four lenses are arranged in order from the object side to the image side along the optical axis.

According to embodiments of the present disclosure, the first lens element can have a negative power, and the object-side surface can be convex and the image-side surface can be concave. Arranging the first lens as a meniscus lens convex to the object facilitates collecting as much light as possible into the rear optical system. The focal length value f1 of the first lens and the total focal length value f of the optical lens can satisfy-3.0 ≤ f1/f ≤ 1.5, and more specifically, f1 and f can further satisfy-2.56 ≤ f1/f ≤ 2.08.

The second lens can have positive optical power, and both the object side surface and the image side surface of the second lens can be convex. The double convex second lens can compress the light collected by the first lens and make the light trend to be smoothly transited. The focal length value f2 of the second lens and the total focal length value f of the optical lens can satisfy f2/f ≥ 0.9, more specifically, f2/f ≤ 1.15 can further satisfy between f2 and f.

The third lens may have a negative optical power. In some embodiments, the image-side surface of the third lens element can be concave and the object-side surface can be convex. In other embodiments, the image-side surface of the third lens element can be concave and the object-side surface can be concave. The third lens can be used for diverging the light rays, so that the light rays can smoothly enter the rear optical system. The arrangement of the third lens as a meniscus lens convex towards the object side or as a biconcave lens may advantageously increase the chief ray angle CRA.

The fourth lens element can have a positive power, and can have a convex object-side surface and a concave image-side surface. The fourth lens may be used to converge light. Arranging the fourth lens with the meniscus lens concave towards the image side facilitates increasing the chief ray angle CRA; at the same time, such an arrangement is also advantageous in reducing the aperture of the fourth lens. In an exemplary embodiment, a radius of curvature R4i of an image-side surface of the fourth lens and a total focal length value f of the optical lens may satisfy R4i/f ≧ 1.3, and more specifically, between R4i and f, may further satisfy 1.58 ≦ R4i/f ≦ 5.77. The increase of the chief ray angle CRA is facilitated by the reasonable design of the curvature of the image side surface of the fourth lens.

Alternatively, the third lens may be cemented with the fourth lens to form a cemented lens. The use of the cemented lens is advantageous for correcting aberrations, and for compacting the overall structure of the optical system.

According to an embodiment of the present application, the optical lens may further include, for example, a stop disposed between the second lens and the third lens. Arranging the stop between, for example, the second lens and the third lens, can collect light before and after the stop, reduce the lens group aperture before and after the stop, and increase the chief ray angle CRA.

In an exemplary embodiment, the on-axis distance T from the object-side surface of the first lens to the stop_{Front side}On-axis distance T from diaphragm to imaging surface of optical lens_{Rear end}Can satisfy T_{Front side}/T_{Rear end}More specifically, T is ≧ 1.5_{Front side}And T_{Rear end}Further satisfies T being more than or equal to 1.89_{Front side}/T_{Rear end}Less than or equal to 1.90. With T_{Front side}The increase of the/T rear ratio reduces the size of the rear end of the lens, which is beneficial to increasing the chief ray angle CRA of the lens.

In application, at least one of the second lens or the fourth lens can be arranged as an aspheric lens to further improve the imaging quality of the lens. The aspheric lens is characterized in that: the curvature varies continuously from the center to the periphery of the lens. Unlike a spherical lens having a constant curvature from the center to the periphery of the lens, an aspherical lens has better curvature radius characteristics, and has advantages of improving distortion aberration and improving astigmatic aberration. After the aspheric lens is adopted, the aberration generated during imaging can be eliminated as much as possible, thereby improving the imaging quality.

In the exemplary embodiment, a distance T12 between the first lens and the second lens on the optical axis and a total focal length value f of the optical lens may satisfy T12/f ≧ 1.5, and more specifically, between T12 and f, may further satisfy 1.86 ≦ T12/f ≦ 2.44. When the diaphragm is arranged between the second lens and the third lens, the distance T12 between the first lens and the second lens on the optical axis is increased, so that the ratio between the distance between the object side surface of the first lens and the diaphragm on the axis and the distance between the diaphragm and the imaging surface on the axis is increased, the diaphragm moves towards the direction close to the imaging surface, and the purpose of reducing the aperture at the rear end of the lens is achieved.

In an exemplary embodiment, the optical lens has a maximum field angle FOV, the maximum clear aperture D4i of the image side surface of the fourth lens corresponding to the maximum field angle, and the distance between the image height h and the maximum field angle FOV corresponding to the maximum field angle may satisfy D4i/h/FOV ≦ 0.01, and more specifically, between D4i, h and the FOV may further satisfy 0.0085 ≦ D4i/h/FOV ≦ 0.0096. When the conditional expression D4i/h/FOV satisfies D4i/h/FOV less than or equal to 0.01, the lens can be embodied to have a smaller rear end aperture.

The lens barrel according to the above-described embodiment of the present application may employ a plurality of lenses, for example, four lenses as described above. Through reasonable lens arrangement, focal power distribution and air interval distribution, and the arrangement of the fourth lens as a meniscus lens with the concave surface facing the image side, the chief ray angle CRA can be increased under the condition of ensuring large imaging size and high pixels of the lens; meanwhile, the lens configured in the mode can also achieve the effect of reducing the size of the rear end, so that the lens can be matched with a chip, and can be better suitable for the installation limitation requirement of a vehicle-mounted lens.

However, it will be appreciated by those skilled in the art that the number of lenses constituting the lens barrel may be varied to achieve the various results and advantages described in the present specification without departing from the claimed subject matter. For example, although four lenses are exemplified in the embodiment, the optical lens is not limited to including four lenses. The optical lens may also include other numbers of lenses, if desired.

Specific examples of an optical lens applicable to the above-described embodiments are further described below with reference to the drawings.

Example 1

An optical lens according to embodiment 1 of the present application is described below with reference to fig. 1. Fig. 1 shows a schematic structural diagram of an optical lens according to embodiment 1 of the present application.

As shown in fig. 1, the optical lens includes four lenses L1-L4 arranged in order from the object side to the image side along the optical axis. The first lens L1 is a meniscus lens with negative power, with the object-side S1 being convex and the image-side S2 being concave; the second lens L2 is a biconvex lens with positive refractive power, and has a convex object-side surface S3 and a convex image-side surface S4; the third lens L3 is a meniscus lens with negative power, with the object-side S6 being convex and the image-side S7 being concave; and the fourth lens L4 is a meniscus lens with positive power, with the object side S7 being convex and the image side S8 being concave. Wherein, the third lens L3 and the fourth lens L4 are cemented to form a cemented lens. Optionally, the optical lens may further include a color filter L5 having an object side S9 and an image side S10. Optionally, the optical lens may further include a protective glass L5 having an object-side surface S9 and an image-side surface S10. The light from the object sequentially passes through the respective surfaces S1 to S10 and is finally imaged on the imaging surface S11.

In the optical lens of the present embodiment, a stop STO may be further provided between the second lens L2 and the third lens L3 to improve the imaging quality of the optical lens.

Table 1 shows the radius of curvature R, thickness T, refractive index Nd, and abbe number Vd of each lens of the optical lens of example 1.

Flour mark	Radius of curvature R (mm)	Thickness T (mm)	Refractive index Nd	Abbe number Vd
					S1	21.9216	1.0000	1.52	64.21
S2	2.9275	5.9538
					S3	3.6183	4.0138	1.62	63.41
S4	-9.8106	0.0000
					STO	Infinity	0.1000
S6	5.2306	0.5500	1.92	20.88
					S7	2.9542	3.0000	1.62	63.41
S8	5.0500	1.0000
					S9	Infinity	0.7000	1.52	64.21
S10	Infinity	0.4162
					S11	Infinity

TABLE 1

From the data in Table 1, the on-axis distance T from the object-side surface of the first lens L1 to the stop STO can be obtained_{Front side}On-axis distance T from stop STO to image forming surface S11_{Rear end}Satisfy T_{Front side}/T_{Rear end}＝1.90。

In the embodiment, four lenses are used as an example, and by reasonably distributing the focal length and the surface type of each lens, the incident angle of the chief ray incident on the electronic photosensitive element on the imaging surface is increased under the condition of ensuring the large imaging size and high pixel of the lens; meanwhile, the size of the rear end of the lens is reduced, so that the lens is matched with the chip. In embodiment 1, the second lens L2 is an aspherical lens, and its surface shape Z is defined by the following formula:

wherein Z is the distance rise from the vertex of the aspheric surface when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius of curvature R in table 1 above); k is a conic constant; A. b, C, D, E are all high order term coefficients. Table 2 below shows the conic constant k and the high-order term coefficients A, B, C, D and E that can be used for each of the aspherical lens surfaces S3 and S4 in example 1.

Flour mark

k

A

B

C

D

E

S3

0.1213

-7.2237E-05

-4.7353E-04

1.4290E-04

-1.9938E-05

1.1187E-06

S4

17.9223

2.7830E-02

-4.3746E-02

5.2936E-02

-3.0322E-02

6.7156E-03

TABLE 2

Table 3 shows the focal length value f1 of the first lens L1, the focal length value f2 of the second lens L2, the total focal length value f of the optical lenses, the maximum field angle FOV of the optical lenses, the maximum clear aperture D4i of the image-side surface S8 of the fourth lens L4 corresponding to the maximum field angle, and the image height h corresponding to the maximum field angle in example 1.

Parameter(s)	f1(mm)	f2(mm)	f(mm)	FOV(°)	D4i(mm)	h(mm)
							Numerical value	-6.63	4.81	3.19	73	2.97	4.24

TABLE 3

In embodiment 1, the radius of curvature R4i of the image side surface of the fourth lens L4 and the total focal length f of the optical lens satisfy R4i/f of 1.58; the separation distance T12 between the first lens L1 and the second lens L2 on the optical axis and the total focal length f of the optical lens satisfy T12/f-1.86; the focal length value f2 of the second lens L2 and the total focal length value f of the optical lens satisfy f 2/f-1.51; the focal length value f1 of the first lens L1 and the total focal length value f of the optical lens satisfy f 1/f-2.08; the maximum field angle FOV of the optical lens is 73 °; the maximum light-passing aperture D4i of the image-side surface S8 of the fourth lens L4 corresponding to the maximum field angle, the image height h corresponding to the maximum field angle, and the maximum field angle FOV satisfy D4i/h/FOV of 0.0096.

Example 2

An optical lens according to embodiment 2 of the present application is described below with reference to fig. 2. Fig. 2 shows a schematic structural diagram of an optical lens according to embodiment 2 of the present application.

As shown in fig. 2, the optical lens includes four lenses L1-L4 arranged in order from the object side to the image side along the optical axis. The first lens L1 is a meniscus lens with negative power, with the object-side S1 being convex and the image-side S2 being concave; the second lens L2 is a biconvex lens with positive refractive power, and has a convex object-side surface S3 and a convex image-side surface S4; the third lens L3 is a biconcave lens with negative power, and has a concave object-side surface S6 and a concave image-side surface S7; and the fourth lens L4 is a meniscus lens with positive power, with the object side S8 being convex and the image side S9 being concave. Optionally, the optical lens may further include a color filter L5 having an object side S10 and an image side S11. Optionally, the optical lens may further include a protective glass L5 having an object-side surface S10 and an image-side surface S11. The light from the object sequentially passes through the respective surfaces S1 to S11 and is finally imaged on the imaging surface S12.

Table 4 shows the radius of curvature R, thickness T, refractive index Nd, and abbe number Vd of each lens of the optical lens of example 2. Table 5 shows the conic constant k and the high-order term coefficients A, B, C, D and E that can be used for each of the aspherical lens surfaces S8 and S9 in embodiment 2. Table 6 shows the focal length value f1 of the first lens L1, the focal length value f2 of the second lens L2, the total focal length value f of the optical lenses, the maximum field angle FOV of the optical lenses, the maximum clear aperture D4i of the image-side surface S9 of the fourth lens L4 corresponding to the maximum field angle, and the image height h corresponding to the maximum field angle in example 2. Wherein each aspherical surface type can be defined by the formula (1) given in the above-described embodiment 1.

TABLE 4

Flour mark

k

A

B

C

D

E

S8

-1.9000

-5.6659E-04

-1.4477E-03

-1.3711E-03

2.6902E-04

-2.3599E-04

S9

33.9630

1.2993E-02

-3.1812E-03

2.5322E-05

1.8578E-04

-1.9325E-04

TABLE 5

Parameter(s)	f1(mm)	f2(mm)	f(mm)	FOV(°)	D4i(mm)	h(mm)
							Numerical value	-8.67	3.38	3.39	72.9	2.82	4.55

TABLE 6

In example 2, the on-axis distance T from the object-side surface of the first lens L1 to the stop STO_{Front side}On-axis distance T from stop STO to image forming surface S11_{Rear end}Satisfy T_{Front side}/T_{Rear end}1.89; the curvature radius R4i of the image side surface of the fourth lens L4 and the total focal length f of the optical lens satisfy that R4i/f is 5.77; the first lens L1 and the second lens L2 are separated by a distance T12 on the optical axis from the optical lensThe total focal length value f satisfies T12/f-2.44; the focal length value f2 of the second lens L2 and the total focal length value f of the optical lens satisfy f 2/f-1.00; the focal length value f1 of the first lens L1 and the total focal length value f of the optical lens satisfy f 1/f-2.56; the maximum field angle FOV of the optical lens is 72.9 °; the maximum light-passing aperture D4i of the image-side surface S9 of the fourth lens L4 corresponding to the maximum field angle, the image height h corresponding to the maximum field angle, and the maximum field angle FOV satisfy D4i/h/FOV of 0.0085.

In summary, example 1 and example 2 each satisfy the relationship shown in table 7 below.

Conditional expression (A) example	1	2
			R4i/f	1.58	5.77
T_{Front side}/T_{Rear end}	1.90	1.89
			T12/f	1.86	2.44
f2/f	1.51	1.00
			f1/f	-2.08	-2.56
D4i/h/FOV	0.0096	0.0085

TABLE 7

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features and the technical features (but not limited to) having similar functions disclosed in the present application are mutually replaced to constitute the technical solution.

Claims

1. The optical lens sequentially comprises from an object side to an image side along an optical axis: a first lens, a second lens, a third lens and a fourth lens,

it is characterized in that the preparation method is characterized in that,

the first lens has negative focal power, 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 second lens has positive focal power, and both the object side surface and the image side surface of the second lens are convex surfaces;

the third lens has negative focal power, and the image side surface of the third lens is a concave surface; and

the fourth lens has positive focal power, the object side surface of the fourth lens is a convex surface, the image side surface of the fourth lens is a concave surface,

wherein the optical lens is a four-piece lens, an

Wherein D4i/h/FOV is less than or equal to 0.01,

wherein D4i is the maximum clear aperture of the image-side surface of the fourth lens corresponding to the maximum field angle of the optical lens;

h is the image height corresponding to the maximum field angle of the optical lens; and

the FOV is the maximum field angle of the optical lens.

2. An optical lens barrel according to claim 1, wherein the object side surface of the third lens is convex.

3. An optical lens barrel according to claim 1, wherein the object side surface of the third lens is concave.

4. An optical lens according to claim 1, wherein the third lens and the fourth lens are cemented to form a cemented lens.

5. An optical lens barrel according to claim 1, wherein at least one of the second lens and the fourth lens is an aspherical lens.

6. An optical lens according to claim 1, characterized in that a diaphragm is arranged between the second lens and the third lens.

7. An optical lens barrel according to claim 6, wherein the on-axis distance T from the object side of the first lens to the stop_{Front side}On-axis distance T from the diaphragm to the imaging surface of the optical lens_{Rear end}Satisfies 1.90 ≥ T_{Front side}/T_{Rear end}≥1.5。

8. An optical lens barrel according to any one of claims 1 to 7, wherein a radius of curvature R4i of an image side surface of the fourth lens and a total focal length value f of the optical lens satisfy R4i/f ≧ 1.3.

9. An optical lens according to any one of claims 1 to 7, wherein a separation distance T12 between the first lens and the second lens on the optical axis and a total focal length f of the optical lens satisfy T12/f ≧ 1.5.

10. An optical lens according to any one of claims 1 to 7, characterized in that the focal length value f2 of the second lens and the total focal length value f of the optical lens satisfy f2/f ≧ 0.9.

11. An optical lens according to any one of claims 1 to 7, characterized in that a focal length value f1 of the first lens and a total focal length value f of the optical lens satisfy-3.0 ≦ f1/f ≦ -1.5.

12. The optical lens sequentially comprises from an object side to an image side along an optical axis: a first lens, a second lens, a diaphragm, a third lens and a fourth lens,

it is characterized in that the preparation method is characterized in that,

an on-axis distance T from the object side surface of the first lens to the diaphragm_{Front side}On-axis distance T from the diaphragm to the imaging surface of the optical lens_{Rear end}Satisfy T_{Front side}/T_{Rear end}≥1.5，

Wherein the optical lens is a four-piece lens, an

Wherein D4i/h/FOV is less than or equal to 0.01,

the FOV is the maximum field angle of the optical lens.

13. An optical lens according to claim 12, wherein the first lens and the second lens are spaced apart on the optical axis by a distance T12 which satisfies T12/f ≧ 1.5 together with the total focal length f of the optical lens.

14. An optical lens according to claim 12, characterized in that a focal length value f1 of the first lens and a total focal length value f of the optical lens satisfy-3.0 ≦ f1/f ≦ -1.5.

15. An optical lens according to claim 12, wherein the focal length value f2 of the second lens and the total focal length value f of the optical lens satisfy f2/f ≧ 0.9.

16. An optical lens barrel according to claim 12, wherein at least one of the second lens and the fourth lens is an aspherical lens.

17. An optical lens barrel according to claim 12, wherein the object side surface of the third lens is convex.

18. An optical lens barrel according to claim 12, wherein the object side surface of the third lens is concave.

19. An optical lens according to claim 17 or 18, characterized in that the third lens and the fourth lens are cemented to constitute a cemented lens.

20. An optical lens barrel according to claim 12, wherein the radius of curvature R4i of the image side surface of the fourth lens element and the total focal length f of the optical lens barrel satisfy R4i/f ≧ 1.3.