CN113341545B

CN113341545B - Optical lens

Info

Publication number: CN113341545B
Application number: CN202110905607.4A
Authority: CN
Inventors: 于笑枝; 曾昊杰; 曾吉勇
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Jiangxi Lianyi Optics Co Ltd
Priority date: 2021-08-09
Filing date: 2021-08-09
Publication date: 2021-10-26
Anticipated expiration: 2041-08-09
Also published as: CN113341545A

Abstract

The invention provides an optical lens, which sequentially comprises diaphragms from an object side to an imaging surface along an optical axis; the first lens, the object side is a convex surface, the image side is a concave surface; a second lens element having a convex object-side surface and a concave image-side surface; a third lens element having a convex object-side surface and a concave image-side surface at a paraxial region; a fourth lens element having a convex object-side surface and at least one inflection point at a paraxial region thereof, and a concave image-side surface at a paraxial region thereof; a fifth lens element having a concave object-side surface and a convex image-side surface; a sixth lens element having a concave object-side surface and a convex image-side surface; the seventh lens element has a concave object-side surface at a paraxial region and a concave image-side surface at a paraxial region. The first lens and the second lens are glass aspheric lenses, and the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are plastic aspheric lenses. The optical lens realizes the miniaturization of the lens and the balance of high pixels, and has the advantages of large image surface, large aperture and high imaging quality.

Description

Optical lens

Technical Field

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

Background

Because the internal space of the smart phone is smaller and smaller, and the number of the bearing functions and components is larger and larger, the plastic lens becomes the mainstream of the optical lens of the smart phone by virtue of the advantages of low cost, easiness in batch production and the like. However, with the increasingly higher pursuit of imaging by users, in the process of upgrading the smartphone towards a large aperture and an ultrahigh pixel direction, the problems of the plastic lens in the aspects of optical properties such as imaging definition, distortion rate, light transmittance and refractive index are more and more prominent, the requirements of the ultrahigh pixel lens cannot be well met, the problems of poor edge image quality, glare, ghost and the like frequently occur during photographing, and the protrusion thickness of the plastic lens is also more and more thick.

Compared with the prior art, the glass lens has the advantages of being lighter and thinner, better in light transmission, higher in refractive index, stronger in stability and the like, the problems of glare, ghost shadow and the like can be greatly reduced, and the glass-plastic hybrid lens combines the advantages of the glass lens and the plastic lens, can reduce the thickness and distortion rate of the lens, and improves the imaging definition and the aperture size.

Disclosure of Invention

Based on this, the present invention provides an optical lens to solve the above problems.

An embodiment of the present invention provides an optical lens, which includes seven lenses, in order from an object side to an image plane along an optical axis:

a diaphragm;

the first lens with positive focal power, the object side surface is a convex surface, and the image side surface is a concave surface;

the second lens with negative focal power, the object side surface is a convex surface, and the image side surface is a concave surface;

a third lens element having a positive optical power, the object side surface being convex and the image side surface being concave at the paraxial region;

a fourth lens having a power, the object side surface being convex at the paraxial region and having at least one inflection point, the image side surface being concave at the paraxial region;

the fifth lens with positive focal power, the object side surface is a concave surface, and the image side surface is a convex surface;

the sixth lens with negative focal power, the object side surface is a concave surface, and the image side surface is a convex surface;

a seventh lens element having a negative optical power, the object side surface being concave at the paraxial region, the image side surface being concave at the paraxial region;

the first lens and the second lens are glass aspheric lenses, and the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are plastic aspheric lenses.

Compared with the prior art, the optical lens provided by the invention has the advantages that the glass aspheric lens and the plastic aspheric lens are shared, so that the production cost is reduced. The optical lens provided by the invention can realize a large aperture, meet the requirement of high-pixel image output, ensure high resolution under the large aperture, meet high pixel and have a more compact structure, and is beneficial to improving the screen occupation ratio of portable electronic products. Therefore, the lens is miniaturized and balanced in high pixel, the advantages of large image surface, large aperture and high imaging quality are achieved, and the shooting experience of a user can be effectively improved.

Drawings

FIG. 1 is a schematic structural diagram of an optical lens system according to a first embodiment of the present invention;

FIG. 2 is a field curvature graph of an optical lens according to a first embodiment of the present invention;

FIG. 3 is a diagram illustrating a distortion curve of an optical lens according to a first embodiment of the present invention;

FIG. 4 is a vertical axis chromatic aberration diagram of an optical lens according to a first embodiment of the present invention;

FIG. 5 is a schematic structural diagram of an optical lens system according to a second embodiment of the present invention;

FIG. 6 is a field curvature graph of an optical lens according to a second embodiment of the present invention;

FIG. 7 is a diagram illustrating distortion curves of an optical lens according to a second embodiment of the present invention;

FIG. 8 is a vertical axis chromatic aberration diagram of an optical lens according to a second embodiment of the present invention;

FIG. 9 is a schematic structural diagram of an optical lens assembly according to a third embodiment of the present invention;

FIG. 10 is a field curvature graph of an optical lens according to a third embodiment of the present invention;

fig. 11 is a distortion graph of an optical lens in a third embodiment of the present invention;

fig. 12 is a vertical axis chromatic aberration diagram of an optical lens according to a third embodiment of the present invention.

Description of the main element symbols:

diaphragm	ST	First lens	L1
				Second lens	L2	Third lens	L3
Fourth lens	L4	Fifth lens element	L5
				Sixth lens element	L6	Seventh lens element	L7
Infrared filter	G1	Object side surface of the first lens	S1
				Image side surface of the first lens	S2	Object side surface of the second lens	S3
Image side surface of the second lens	S4	Object side of the third lens	S5
				Image side surface of the third lens	S6	Object side of the fourth lens	S7
Image side surface of the fourth lens	S8	Object side surface of fifth lens	S9
				Image side surface of the fifth lens element	S10	Object side surface of sixth lens	S11
Image side surface of sixth lens element	S12	Object side surface of seventh lens	S13
				Image side surface of seventh lens	S14	Object side of optical filter	S15
Image side of optical filter	S16	Image plane	S17

The following detailed description will further illustrate the invention in conjunction with the above-described figures.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Several embodiments of the invention are presented in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

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 invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In an optical lens system according to an embodiment of the present invention, the optical lens system includes seven lens elements, in order from an object side to an image side along an optical axis: the stop ST, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the filter G1, where the image side is on the image plane S17 side, and the object side is on the side opposite to the image side.

The first lens L1 has positive focal power, the object-side surface S1 of the first lens is convex, and the image-side surface S2 of the first lens is concave;

the second lens L2 has negative focal power, the object-side surface S3 of the second lens is convex, and the image-side surface S4 of the second lens is concave;

the third lens L3 has positive power, the object-side surface S5 of the third lens is convex, and the image-side surface S6 of the third lens is concave at the paraxial region;

the fourth lens element L4 has optical power, an object-side surface S7 of the fourth lens element being convex at a paraxial region and an image-side surface S8 of the fourth lens element being concave at a paraxial region;

the fifth lens L5 has positive power, the object-side surface S9 of the fifth lens is concave, and the image-side surface S10 of the fifth lens is convex;

the sixth lens L6 has negative power, and the object-side surface S11 of the sixth lens is concave, and the image-side surface S12 of the sixth lens is convex;

the seventh lens L7 has a negative power, and its object-side surface S13 is concave at the paraxial region and its image-side surface S14 is concave at the paraxial region.

In some embodiments, the effective focal length f of the optical lens and the distance TTL between the object-side surface of the first lens element and the imaging surface of the optical lens on the optical axis satisfy: f/TTL is more than 0.8 and less than 0.9. The optical lens can meet the requirement of the field angle range, and meanwhile, the optical total length is kept small, so that the optical lens meets the requirement of miniaturization.

In some embodiments, the effective focal length f of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy 1.75 < f/EPD < 1.85. Can reduce optical lens's aberration through the focal power of rational distribution lens, simultaneously through the specific value of restraint focal length and entrance pupil diameter, can increase the luminous flux of system, strengthen the imaging effect under the dark surrounds, reduce the aberration of marginal visual field.

In some embodiments, the object-side surface of the fourth lens has at least one inflection point, and the perpendicular distance Yc7 from the inflection point to the optical axis satisfies the following relationship with the center thickness CT4 of the fourth lens: 4.5 < CT4/Yc7 < 5.5. The shape of the fourth lens can be effectively controlled, the trend of light rays is controlled, and the lens is better matched with the chip.

In some embodiments, the second lens and the third lens are separated by a distance CT23 on the optical axis and a center thickness CT2 of the second lens and a center thickness CT3 of the third lens satisfy: 0.5 < CT 23/(CT 2+ CT 3) < 0.8. The distance between the second lens and the third lens can be effectively controlled, the advantages that the first lens and the second lens are made of glass aspheric lenses are fully exerted, the light turning trend of an off-axis field of view is reduced, optical distortion and field curvature can be corrected conveniently, the influence on lens sensitivity is reduced, and the imaging quality of the lens is improved.

In some embodiments, the refractive index ND2 of the second lens, the refractive index ND5 of the fifth lens, and the refractive index ND6 of the sixth lens satisfy: ND5 < ND6 < ND 2. The materials of the second lens, the fifth lens and the sixth lens are reasonably matched, so that chromatic aberration of the optical lens can be corrected, and the imaging quality of the optical lens can be improved.

In some embodiments, the combined focal length f12 of the first and second lenses and the effective focal length f of the optical lens satisfy: f12/f is more than 1.0 and less than 1.2. The combined focal length can be a reasonable positive focal length, which is beneficial to realizing the balance of large aperture and high resolution quality and improving the quality performance of the optical lens.

In some embodiments, the center thickness CT4 of the fourth lens and the edge thickness ET4 of the fourth lens satisfy: 0.75 < CT4/ET4 < 0.95. The sensitivity of the optical lens is reduced, the fourth lens is easier to process, and the production yield is improved.

In some embodiments, the edge SAGs 7 of the object-side surface of the fourth lens, the SAGs SAG7.1 of the inflection point of the object-side surface of the fourth lens, and the effective aperture DM7 of the object-side surface of the fourth lens satisfy: 0.14 < (SAG7.1-SAG7)/DM7 < 0.22. The light-passing aperture of the fourth lens can be effectively controlled, the incident range of incident light rays is reasonably limited, light rays with poor edge quality are eliminated, the off-axis aberration is reduced, the process difficulty of lens assembly can be reduced, and the resolving power of the optical lens is effectively improved.

In some embodiments, the fourth lens and the fifth lens are separated by a distance CT45 on the optical axis and a center thickness CT4 of the fourth lens that satisfy: 1.7 < CT45/CT4 < 2.1. The light turning trend of the off-axis field of view can be slowed down, and the chromatic aberration of the optical lens can be corrected.

In some embodiments, the distance CT23 between the second lens and the third lens on the optical axis, the distance CT45 between the fourth lens and the fifth lens on the optical axis, and the distance TTL between the object side surface of the first lens and the imaging surface of the optical lens on the optical axis satisfy: 0.1 < (CT23+ CT45)/TTL < 0.2. The sensitivity of the second lens and the sensitivity of the fourth lens are reduced, the total optical length of the optical lens is shortened, and the system is miniaturized.

In some embodiments, the central thickness CT4 of the fourth lens and the central thickness CT5 of the fifth lens satisfy: 0.4 < CT4/CT5 < 0.6. The chromatic aberration of the optical lens can be corrected, the sensitivity of the optical lens can be reduced, and the production yield can be improved.

In some embodiments, the focal length f of the optical lens and the focal length f5 of the fifth lens satisfy: f/f5 is more than 1.1 and less than 1.5. The optical total length of the optical lens can be reduced, the fifth lens can meet the requirement of thin lens type, and the field curvature can be corrected.

In some embodiments, the radius of curvature R9 of the object-side surface of the fifth lens and the focal length f of the optical lens satisfy: -2.1 < R9/f < -1.6. The high-order aberration of the optical lens can be corrected, and the imaging quality of the optical lens can be improved.

In some embodiments, the radius of curvature R9 of the object-side surface of the fifth lens and the saggital height SAG9 of the object-side surface of the fifth lens satisfy: 0.0 < SAG9/R9 < 0.1. The distortion of the off-axis field of view can be corrected, and the imaging quality of the optical lens can be improved.

In some embodiments, the focal length f of the optical lens and the focal length f6 of the sixth lens satisfy: -0.5 < f/f6 < -0.1. The total optical length of the optical lens can be reduced, the sixth lens can meet the requirement of thin lens type, and the field curvature can be corrected.

In some embodiments, the radius of curvature R11 of the object-side surface of the sixth lens and the focal length f of the optical lens satisfy: -5 < R11/f < 0. The method is beneficial to correcting the high-grade phase difference of the optical lens and improving the imaging quality of the optical lens.

In some embodiments, the radius of curvature R11 of the object-side surface of the sixth lens and the sago 11 of the object-side surface of the sixth lens satisfy: 0.1 < SAG11/R11 < 0.5. The angle of light rays entering the object side face of the sixth lens is controlled, ghost image energy is weakened, and imaging quality of the optical lens is improved.

In some embodiments, the focal length f6 of the sixth lens and the focal length f7 of the seventh lens satisfy: 5 < f6/f7 < 15. The method is favorable for reducing the sensitivity of the optical lens and the correction difficulty of high-grade aberration, improving the resolution quality of the optical lens and shortening the optical total length of the optical lens.

In some embodiments, the radius of curvature R14 of the image-side surface of the seventh lens and the focal length f of the optical lens satisfy: 4.5 < R14/f < 36. The matching degree of the optical lens and the sensor is improved, and the resolution quality of the optical lens is improved.

As an embodiment, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 may be aspheric lenses, and optionally, the first lens L1 and the second lens L2 are aspheric glass lenses, and the other lenses are aspheric plastic lenses. By adopting the aspheric lens, the number of the lenses can be effectively reduced, aberration can be corrected, and better optical performance can be provided.

In this embodiment, as an implementation manner, when each lens in the optical lens is an aspheric lens, each aspheric surface shape of the optical lens may satisfy the following equation:

wherein z is the distance rise from the aspheric surface vertex when the aspheric surface is at the position with the height h along the optical axis direction, c is the paraxial curvature of the surface, k is the quadric coefficient, A_2iIs the aspheric surface type coefficient of 2i order.

The optical lens provided by the embodiment of the invention adopts seven lenses with specific refractive power, and reasonably matches the lens shapes and focal power combinations among the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7, so that the structure of the optical lens is more compact on the premise that the lens has high pixels, the miniaturization of the lens and the balance of high pixels are better realized, and the shooting experience of a user can be effectively improved.

The invention is further illustrated below in the following examples. In the following embodiments, the thickness, the curvature radius, and the material selection of each lens in the optical lens are different, and specific differences can be referred to in the parameter tables of the embodiments. In each table, R represents a radius of curvature (unit: mm), d represents an optical surface distance (unit: mm), Nd represents a refractive index of the material, and Vd represents an Abbe number of the material.

First embodiment

Referring to fig. 1, an optical lens assembly according to a first embodiment of the present invention includes, in order from an object side to an image plane along an optical axis: the stop ST, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the filter G1.

The first lens L1 is a glass aspheric lens with positive power, the object-side surface S1 is convex, and the image-side surface S2 is concave;

the second lens L2 is a glass aspheric lens with negative power, the object-side surface S3 is convex, and the image-side surface S4 is concave;

the third lens element L3 is a plastic aspheric lens with positive power, with the object-side surface S5 being convex and the image-side surface S6 being concave at the paraxial region;

the fourth lens element L4 is a plastic aspheric lens with positive power, with the object-side surface S7 being convex at the paraxial region and the image-side surface S8 being concave at the paraxial region;

the fifth lens element L5 is a plastic aspheric lens with positive power, the object-side surface S9 is concave, and the image-side surface S10 is convex;

the sixth lens element L6 is a plastic aspheric lens with negative power, the object-side surface S11 is concave, and the image-side surface S12 is convex;

the seventh lens element L7 is a plastic aspheric lens with negative power, the object side surface S13 is concave at the paraxial region, and the image side surface S14 is concave at the paraxial region.

Table 1 shows relevant parameters of each lens in the optical lens system according to the first embodiment of the present invention.

The surface type coefficients of the aspheric surfaces of the optical lens according to the first embodiment of the present invention are shown in table 2:

TABLE 2

Referring to fig. 2, fig. 3 and fig. 4, an astigmatism graph, a distortion graph and a vertical axis chromatic aberration graph of the optical lens are shown, respectively.

The astigmatism curve of fig. 2 indicates the degree of curvature of the meridional image plane and the sagittal image plane. In fig. 2, the horizontal axis represents the offset amount (unit: mm) and the vertical axis represents the angle of view (unit: degree). As can be seen from fig. 2, astigmatism of the meridional image plane and the sagittal image plane is controlled within ± 0.15 mm, which indicates that astigmatism correction of the optical lens is good.

The distortion curve of fig. 3 represents the distortion at different image heights on the imaging surface S17. In fig. 3, the horizontal axis represents the f- θ distortion percentage, and the vertical axis represents the angle of view (unit: degree). As can be seen from fig. 3, the optical distortion at different image heights on the image plane S17 is controlled within ± 2%, which indicates that the distortion of the optical lens is well corrected.

The vertical axis chromatic aberration curve of fig. 4 shows chromatic aberration at different image heights on the image forming surface S17 for each wavelength with respect to the center wavelength (0.55 um). In fig. 4, the horizontal axis represents the homeotropic color difference (unit: μm) of each wavelength with respect to the center wavelength, and the vertical axis represents the normalized angle of view. As can be seen from FIG. 4, the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within + -1.5 μm, which indicates that the optical lens can effectively correct the aberration of the fringe field and the secondary spectrum of the whole image plane.

Second embodiment

Fig. 5 is a schematic structural diagram of an optical lens according to a second embodiment of the present invention, which is substantially the same as the optical lens according to the first embodiment, and mainly differs therefrom in that the fourth lens has negative refractive power, and the curvature radius and material selection of each lens are different. The optical lens sequentially comprises the following components from an object side to an imaging surface along an optical axis: the stop ST, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the filter G1.

the fourth lens element L4 is a plastic aspheric lens with negative power, the object-side surface S7 is convex at the paraxial region, and the image-side surface S8 is concave at the paraxial region;

Table 3 shows relevant parameters of each lens in the optical lens system according to the second embodiment of the present invention.

The second embodiment of the present invention provides an optical lens having aspheric surface coefficients as shown in table 4:

referring to fig. 6, 7 and 8, an astigmatism graph, a distortion graph and a vertical axis chromatic aberration graph of the optical lens are shown, respectively.

Fig. 6 shows the degree of curvature of the meridional image plane and the sagittal image plane. As can be seen from fig. 6, astigmatism of the meridional image plane and the sagittal image plane is controlled within ± 0.15 mm, which indicates that astigmatism correction of the optical lens is good.

Fig. 7 shows distortion at different image heights on the image forming surface S17. As can be seen from fig. 7, the optical distortion at different image heights on the image plane S17 is controlled to be within 2%, which indicates that the distortion of the optical lens is well corrected.

Fig. 8 shows the chromatic aberration at different image heights on the image forming surface S17 for the longest wavelength and the shortest wavelength. As can be seen from fig. 8, the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ± 1 micron, which indicates that the optical lens can effectively correct the aberration of the fringe field and the secondary spectrum of the entire image plane.

Third embodiment

Fig. 9 is a schematic structural diagram of an optical lens according to a third embodiment of the present invention, which is substantially the same as the optical lens according to the first embodiment, and mainly differs therefrom in that the fourth lens has negative refractive power, and the curvature radius and material selection of each lens are different. The optical lens sequentially comprises the following components from an object side to an imaging surface along an optical axis: the stop ST, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the filter G1.

Table 5 shows the relevant parameters of each lens in the optical lens system according to the third embodiment of the present invention.

The surface shape coefficients of the respective aspherical surfaces of the optical lens in the third embodiment of the present invention are shown in table 6:

referring to fig. 10, 11 and 12, an astigmatism graph, a distortion graph and a vertical axis chromatic aberration graph of the optical lens are shown, respectively.

Fig. 10 shows the degree of curvature of the meridional image plane and the sagittal image plane. As can be seen from fig. 10, astigmatism of the meridional image plane and the sagittal image plane is controlled to be within ± 0.15 mm, which indicates that astigmatism correction of the optical lens is good.

Fig. 11 shows distortion at different image heights on the image forming surface S17. As can be seen from fig. 11, the optical distortion at different image heights on the image plane S17 is controlled to be within 2%, indicating that the distortion of the optical lens is well corrected.

Fig. 12 shows the chromatic aberration at different image heights on the image forming surface S17 for the longest wavelength and the shortest wavelength. As can be seen from fig. 12, the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ± 1.5 microns, which indicates that the optical lens can effectively correct the aberration of the fringe field and the secondary spectrum of the entire image plane.

Referring to table 7, optical characteristics corresponding to the optical lenses provided in the three embodiments are shown. The optical characteristics mainly include an effective focal length F, an F # of the optical lens, an entrance pupil diameter EPD, a total optical length TTL, a field of view FOV, and the like, and a correlation value corresponding to each of the aforementioned conditional expressions.

In summary, the optical lens provided by the embodiment of the invention has the following advantages:

(1) because the shapes of the diaphragm and each lens are reasonably arranged, the optical lens has the requirements of larger aperture (FNO is less than or equal to 1.8) and larger imaging area (ImgH is more than or equal to 5.00 mm), and can better meet the requirements of portable intelligent electronic products.

(2) 2 glass aspheric lenses with specific refractive power are combined with 5 plastic aspheric lenses, and the lenses are matched through specific surface shapes, so that the optical lens has ultrahigh pixel imaging quality, and the invention can be matched with a chip with 5000 ten thousand pixels.

(3) The field angle of the optical lens can reach 81 degrees, the optical distortion can be effectively corrected, the optical distortion is controlled to be less than 2 percent, and the requirements of large field angle and high-definition imaging can be met.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An optical lens system comprising seven lens elements, comprising, in order from an object side to an image plane along an optical axis:

a diaphragm;

a fourth lens having a focal power, the object side surface being convex at the paraxial region and the image side surface being concave at the paraxial region;

the first lens and the second lens are glass aspheric lenses, and the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are plastic aspheric lenses;

the effective focal length f of the optical lens and the distance TTL from the object side surface of the first lens to the imaging surface of the optical lens on the optical axis satisfy the following conditions: f/TTL is more than 0.8 and less than 0.9;

the distance CT45 between the fourth lens and the fifth lens on the optical axis and the central thickness CT4 of the fourth lens satisfy that: 1.7 < CT45/CT4 < 2.1.

2. An optical lens barrel according to claim 1, wherein the object side surface of the fourth lens has at least one inflection point, and the perpendicular distance Yc7 from the inflection point to the optical axis satisfies the following relation with the central thickness CT4 of the fourth lens: 4.5 < CT4/Yc7 < 5.5.

3. An optical lens according to claim 1, wherein the second lens and the third lens are spaced apart by a distance CT23 on the optical axis and a center thickness CT2 of the second lens and a center thickness CT3 of the third lens satisfy: 0.5 < CT 23/(CT 2+ CT 3) < 0.8.

4. An optical lens according to claim 1, characterized in that the refractive index ND2 of the second lens, ND5 of the fifth lens and ND6 of the sixth lens satisfy: ND5 < ND6 < ND 2.

5. An optical lens according to claim 1, characterized in that the combined focal length f12 of the first and second lenses and the effective focal length f of the optical lens satisfy: f12/f is more than 1.0 and less than 1.2.

6. An optical lens according to claim 1, characterized in that the central thickness CT4 of the fourth lens and the edge thickness ET4 of the fourth lens satisfy: 0.75 < CT4/ET4 < 0.95.

7. The optical lens of claim 1, wherein the saggital height SAG7 of the edge of the object side of the fourth lens, the saggital height SAG7.1 of the inflection point of the object side of the fourth lens, and the effective aperture DM7 of the object side of the fourth lens satisfy: 0.14 < (SAG7.1-SAG7)/DM7 < 0.22.

8. An optical lens barrel according to claim 1, wherein an axial separation distance CT23 between the second lens and the third lens, an axial separation distance CT45 between the fourth lens and the fifth lens, and an axial distance TTL between the object-side surface of the first lens and the imaging surface of the optical lens barrel satisfy: 0.1 < (CT23+ CT45)/TTL < 0.2.

9. An optical lens according to claim 1, characterized in that the central thickness CT4 of the fourth lens and the central thickness CT5 of the fifth lens satisfy: 0.4 < CT4/CT5 < 0.6.