CN110646916B

CN110646916B - Optical lens

Info

Publication number: CN110646916B
Application number: CN201810676366.9A
Authority: CN
Inventors: 张俊明; 徐超; 杨佳
Original assignee: Ningbo Sunny Automotive Optech Co Ltd
Current assignee: Ningbo Sunny Automotive Optech Co Ltd
Priority date: 2018-06-27
Filing date: 2018-06-27
Publication date: 2021-12-17
Anticipated expiration: 2038-06-27
Also published as: CN110646916A

Abstract

The present application discloses an optical lens, which sequentially comprises, from an object side to an image side along an optical axis: the lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens can have positive focal power, and 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 can have negative focal power, and the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the third lens can have negative focal power, and both the object side surface and the image side surface of the third lens are concave; the fourth lens can have positive focal power, and both the object side surface and the image side surface of the fourth lens are convex surfaces; the fifth lens may have a positive optical power; and the sixth lens element can have a negative power, and the object-side surface of the sixth lens element is concave and the image-side surface of the sixth lens element is convex. According to the optical lens, at least one beneficial effect of miniaturization, small FNO, good temperature performance, low cost, high relative illumination and the like can be achieved.

Description

Optical lens

Technical Field

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

Background

At present, the application of the optical lens is more and more extensive, and the requirement of miniaturization of the lens is more and more prominent. In order to increase the light entering amount, a small FNO lens is generally required, but the imaging quality of the lens of the small FNO is not high; in order to improve the image quality, the number of lenses generally needs to be increased, but the volume and weight of the lens are increased accordingly, which is not favorable for the miniaturization of the lens and causes the increase of the manufacturing cost. In addition, some lenses used in special applications are affected by harsh environments, and the image quality is deteriorated, so that the requirements for stable imaging of the lens in a large temperature difference range are high.

Disclosure of Invention

The present application provides an optical lens that is adaptable for on-board installation and that overcomes, at least in part, at least one of the above-identified deficiencies in the prior art.

An aspect of the present application provides an optical lens that may include, in order from an object side to an image side along an optical axis: the lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens can have positive focal power, and 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 can have negative focal power, and the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the third lens can have negative focal power, and both the object side surface and the image side surface of the third lens are concave; the fourth lens can have positive focal power, and both the object side surface and the image side surface of the fourth lens are convex surfaces; the fifth lens may have a positive optical power; and the sixth lens element can have a negative power, and the object-side surface of the sixth lens element is concave and the image-side surface of the sixth lens element is convex.

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

In another embodiment, the object-side surface of the fifth lens element can be convex, and the image-side surface can be planar.

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

In one embodiment, the third lens and the fourth lens may be cemented with each other to constitute a cemented lens.

In one embodiment, each of the first to sixth lenses may be a glass spherical lens.

In one embodiment, the optical lens may further include a stop disposed before the third lens.

In one embodiment, a distance TTL between a center of an object side surface of the first lens element and an imaging surface of the optical lens on an optical axis and a full-group focal length value f of the optical lens may satisfy: TTL/f is less than or equal to 2.

In one embodiment, the radius of curvature R3 of the object-side surface of the second lens, the radius of curvature R4 of the image-side surface of the second lens, and the center thickness d3 of the second lens may satisfy: the absolute value of R3 absolute/(| R4| + d3) is more than or equal to 0.6 and less than or equal to 1.2.

In one embodiment, the focal length value f3 of the third lens and the focal length value f of the whole group of the optical lens satisfy: and | f3/f | ≧ 0.45.

In one embodiment, the focal length value f3 of the third lens and the focal length value f4 of the fourth lens satisfy: f3/f4 is not less than-1.5 and not more than-0.7.

In one embodiment, the focal length value f5 of the fifth lens and the focal length value f of the whole group of the optical lens satisfy: f5/f is not less than 0.65.

In one embodiment, a radius of curvature R11 of the object-side surface and a radius of curvature R12 of the image-side surface of the sixth lens may satisfy: R11/R12 is more than or equal to 0.05 and less than or equal to 0.5.

Another aspect of the present application provides an optical lens that may include, in order from an object side to an image side along an optical axis: the lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens, the fourth lens and the fifth lens all have positive focal power; the second lens, the third lens and the sixth lens may each have a negative focal power; the third lens and the fourth lens can be mutually glued to form a cemented lens; and the distance TTL from the center of the object side surface of the first lens to the imaging surface of the optical lens on the optical axis and the whole group of focal length values f of the optical lens can satisfy the following conditions: TTL/f is less than or equal to 2.

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

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

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

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

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

The optical lens adopts six lenses, the shape of the lenses is set through optimization, the focal power of each lens is distributed reasonably, and at least one of the beneficial effects of miniaturization, small FNO, good temperature performance, low cost, high relative illumination and the like of the optical lens is achieved.

Drawings

Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments 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 structural view showing an optical lens according to embodiment 2 of the present application; and

fig. 3 is a schematic view showing a structure of an optical lens according to embodiment 3 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, and the first cemented lens may also be referred to as the second cemented 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.

Herein, the paraxial region refers to a region near the optical axis. If the lens surface is convex and the convex position is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the concave position is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is called the object side surface, and the surface of each lens closest to the image plane is called the image side surface.

It will be further understood that the terms "comprises," "comprising," "has," "having," "includes" and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, 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 includes, for example, six lenses having optical power, i.e., a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The six lenses are arranged in order from the object side to the image side along the optical axis.

The optical lens according to the exemplary embodiment of the present application may further include a photosensitive element disposed on the image plane. Alternatively, the photosensitive element provided to the imaging surface may be a photosensitive coupling element (CCD) or a complementary metal oxide semiconductor element (CMOS).

The first lens element can have a positive power, and can have a convex object-side surface and a concave image-side surface. The first lens is arranged in a meniscus shape which is convex towards the object side, so that light rays with a large field of view can be collected as far as possible and enter a rear optical system. The object side surface of the first lens is a convex surface, so that TTL can be effectively controlled, and the angle of collected light rays can be enlarged; the image side surface of the first lens is set to be a concave surface, a larger placing space can be provided for the second lens at the rear, the interval between the first lens and the second lens can be shortened, and therefore short TTL is achieved.

The second lens element can have a negative power, and can have a convex object-side surface and a concave image-side surface. The second lens can smoothly transit the light to the third lens at the rear. Further, the second lens can adopt a material with a large refractive index, for example, the refractive index Nd2 ≧ 1.7 of the second lens, so as to help reduce the center thickness of the third lens and shorten TTL.

The third lens element can have a negative optical power, and can have a concave object-side surface and a concave image-side surface.

The fourth lens element can have a positive optical power, and can have a convex object-side surface and a convex image-side surface. Further, the fourth lens can adopt a material with a large refractive index, for example, the refractive index Nd4 of the fourth lens is more than or equal to 1.7, so as to contribute to reducing the central thickness of the fourth lens, shortening TTL, and providing more favorable guarantee for realizing small FNO and miniaturization of the lens.

The fifth lens element can have a positive optical power, and can have a convex object-side surface and a convex or planar image-side surface. The fifth lens can smoothly transit the light to the rear optical system, so that the relative illumination of the lens is high.

The sixth lens element can have a negative power, and can have a concave object-side surface and a convex image-side surface. Further, the sixth lens can adopt a material with a large refractive index, for example, the refractive index Nd6 ≧ 1.65 of the sixth lens, so as to help reduce the center thickness of the sixth lens and shorten TTL.

As known to those skilled in the art, cemented lenses may be used to minimize or eliminate chromatic aberration. The use of the cemented lens in the optical lens can improve the image quality and reduce the reflection loss of light energy, thereby improving the imaging definition of the lens. In addition, the use of the cemented lens can also simplify the assembly process in the lens manufacturing process.

In an exemplary embodiment, the third lens and the fourth lens may be combined into a cemented lens by cementing the image-side surface of the third lens with the object-side surface of the fourth lens. By introducing the cemented lens consisting of the third lens and the fourth lens, the chromatic aberration influence can be eliminated, the field curvature is reduced, and the coma is corrected; meanwhile, the cemented lens may also retain a part of chromatic aberration to balance the entire chromatic aberration of the optical system. The air space between the two lenses is omitted by gluing the lenses, so that the optical system is compact as a whole, and the requirement of system miniaturization is met. In addition, the gluing of the lenses can reduce tolerance sensitivity problems of lens units due to tilt/decentration during assembly.

In the cemented lens, the third lens close to the object side has negative focal power, the fourth lens close to the image side has positive focal power, and the positive and negative lenses are cemented to reduce aberration and TTL. The third lens is a biconcave lens, which can help to glue the third lens and the fourth lens together, shorten the distance between the lenses, reduce TTL and realize miniaturization; the fourth lens is a biconvex lens, so that the third lens and the fourth lens can be glued, and the aperture of the light ray can be further compressed.

In an exemplary embodiment, a stop for limiting the light beam may be disposed before the third lens (e.g., between the second lens and the third lens) to ensure a small FNO, further improving the imaging quality of the lens. When the diaphragm is arranged at the position, the front and the rear light rays can be effectively converged, the total length of the optical system is shortened, and the calibers of the front and the rear lens groups are reduced. It should be noted, however, that the positions of the diaphragms disclosed herein are merely examples and not limitations; in alternative embodiments, the diaphragm may be disposed at other positions according to actual needs.

In an exemplary embodiment, the optical lens according to the present application may further include a filter disposed between the sixth lens and the imaging surface to filter light rays having different wavelengths, as necessary; and may further include a protective glass disposed between the optical filter and the imaging surface to prevent internal elements (e.g., chips) of the optical lens from being damaged.

In an exemplary embodiment, an optical total length TTL of the optical lens and a whole set focal length value f of the optical lens satisfy: TTL/f is less than or equal to 2, and more ideally, TTL/f is less than or equal to 1.8. With such an arrangement, the miniaturization characteristic is facilitated.

In an exemplary embodiment, the radius of curvature R3 of the object-side surface of the second lens, the radius of curvature R4 of the image-side surface of the second lens, and the center thickness d3 of the second lens may satisfy: the absolute value of R3 is more than or equal to 0.6 and less than or equal to (| R4| + d3) and less than or equal to 1.2, and more ideally, the absolute value of R3|/(| R4| + d3) is more than or equal to 0.7 and less than or equal to 1. The design configuration that the second lens is close to the concentric circles can be beneficial to eliminating distortion and improving the resolution power of the system.

In an exemplary embodiment, a focal length value f3 of the third lens and a focal length value f of the entire group of the optical lens may satisfy: the | f3/f | is more than or equal to 0.45, and more preferably, the | f3/f | is more than or equal to 0.55. Through the configuration, the smooth transition of light can be realized, and the realization of a large-aperture diaphragm is facilitated, so that the small FNO is realized.

In an exemplary embodiment, a focal length value f3 of the third lens and a focal length value f4 of the fourth lens may satisfy: f3/f4 is more preferably not less than-1.5 and not more than-0.7, and more preferably, f3/f4 is more preferably not less than-1.2 and not more than-0.8. By the configuration, chromatic aberration can be eliminated to the maximum extent, and the resolution quality is improved.

In an exemplary embodiment, a focal length value f5 of the fifth lens and a focal length value f of the entire group of the optical lens may satisfy: f5/f is not less than 0.65, more preferably, f5/f is not less than 0.75. By the configuration, light can be smoothly transited, and relative illumination of the system is favorably improved.

In an exemplary embodiment, the radius of curvature R11 and R12 of the object-side and image-side surfaces of the sixth lens may satisfy: R11/R12 is 0.05. ltoreq.0.5, and more preferably, R11/R12 is 0.1. ltoreq.0.4. Through such configuration, can be favorable to the convergence of light, promote the quality of resolution, realize like high compression of image simultaneously, form an image on the chip of appointed size.

In an exemplary embodiment, the lens used in the optical lens may be a plastic lens, or may be a glass lens. The lens made of plastic has a large thermal expansion coefficient, and when the ambient temperature change of the lens is large, the lens made of plastic causes a large amount of change of the optical back focus of the lens. The glass lens can reduce the influence of temperature on the optical back focus of the lens. According to the optical lens, the first lens to the sixth lens can adopt glass lenses so as to enhance the performance of the lens under the conditions of high temperature and low temperature, reduce the influence of the environment on the whole system and improve the overall performance of the optical lens. Furthermore, the first lens to the sixth lens can all adopt glass spherical lenses so as to realize the characteristics of low cost and good thermal stability.

According to the optical lens of the above embodiment of the present application, by placing the diaphragm in front of the third lens, FNO can be effectively reduced, and more incident light can be collected, which is particularly suitable for a lens requiring a large incident light; by reasonably distributing lens materials and focal lengths, the length of the lens can be greatly reduced, the miniaturization of the lens is realized, and the assembly of a limited space in some special fields is convenient to realize; through the reasonable collocation of the positive focal length and the negative focal length of the lens and the lens gluing, the aberration can be reduced, meanwhile, the TTL is compressed, the FNO is reduced, and the resolution quality is improved; through reasonable distribution of the shape and focal power of the lens, high relative illumination can be realized, so that the lens can uniformly collect energy of each view field angle; the lens is designed by adopting an all-glass spherical surface, so that the lens is low in cost, wide in working temperature range and stable in optical performance at-40-105 ℃.

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 six lenses are exemplified in the embodiment, the optical lens is not limited to including six 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, in order from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6.

The first lens L1 is a meniscus lens with positive power, with the object side S1 being convex and the image side S2 being concave.

The second lens L2 is a meniscus lens with negative power, with the object side S3 being convex and the image side S4 being concave.

The third lens L3 is a biconcave lens with negative optical power, and both the object-side surface S6 and the image-side surface S7 are concave. The fourth lens L4 is a biconvex lens with positive optical power, and has both the object-side surface S7 and the image-side surface S8 convex. Wherein the third lens L3 and the fourth lens L4 are cemented with each other to form a cemented lens.

The fifth lens L5 is a biconvex lens with positive optical power, and has both the object-side surface S9 and the image-side surface S10 convex.

The sixth lens L6 is a meniscus lens with negative power, and has a concave object-side surface S11 and a convex image-side surface S12.

The first lens L1 to the sixth lens L6 are all glass spherical lenses.

Optionally, the optical lens may further include a filter L7 and/or a protective lens L7' having an object side S13 and an image side S14. Filter L7 can be used to correct for color deviations. The protective lens L7' may be used to protect the image sensing chip on the imaging plane IMA. Light from the object passes through each of the surfaces S1 to S14 in sequence and is finally imaged on the imaging plane IMA.

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

Table 1 shows a radius of curvature R, a thickness T, a refractive index Nd, and an abbe number Vd of each lens of the optical lens of example 1, where the radius of curvature R and the thickness T are both in units of millimeters (mm).

TABLE 1

The present embodiment adopts six lenses as an example, and by reasonably distributing the focal power and the surface type of each lens, the center thickness of each lens and the air space between each lens, the lens has at least one of the advantages of miniaturization, small FNO, good temperature performance, low cost, high relative illumination and the like.

Table 2 below gives the entire group focal length value f of the optical lens of embodiment 1, the total optical length TTL of the optical lens (i.e., the on-axis distance from the center of the object-side surface S1 of the first lens L1 to the imaging surface IMA), the radii of curvature R3 and R4 of the object-side surface S3 and the image-side surface S4 of the second lens L2, the center thickness d3 of the second lens L2, the focal length values f3-f5 of the third lens L3 to the fifth lens L5, the radii of curvature R11 and R12 of the object-side surface S11 and the image-side surface S12 of the sixth lens L6, the refractive index Nd2 of the second lens L2, the refractive index Nd4 of the fourth lens L4, and the refractive index Nd6 of the sixth lens L6.

TABLE 2

f(mm)	24.7641	R11(mm)	-19.7875
				TTL(mm)	41.1214	R12(mm)	-123.6127
R3(mm)	18.0121	f5(mm)	20.9342
				R4(mm)	14.6153	Nd2	1.90
d3(mm)	6.1050	Nd4	1.90
				f3(mm)	-14.9536	Nd6	1.72
f4(mm)	14.5155

In the present embodiment, TTL/f is 1.661, which is satisfied between the total optical length TTL of the optical lens and the whole focal length f of the optical lens; the radius of curvature R3 of the object-side surface S3 of the second lens L2, the radius of curvature R4 of the image-side surface S4 of the second lens L2, and the center thickness d3 of the second lens L2 satisfy | R3|/(| R4| + d3) ═ 0.869; a focal length value f3 of the third lens L3 and a focal length value f of the whole group of the optical lens satisfy | f3/f | > -0.604; f3/f4 is-1.030 between the focal length value f3 of the third lens L3 and the focal length value f4 of the fourth lens L4; the curvature radii R11 and R12 of the object side surface S11 and the image side surface S12 of the sixth lens L6 satisfy R11/R12 of 0.160; and f5/f is equal to 0.845 between the focal length value f5 of the fifth lens L5 and the focal length value f of the whole group of the optical lens.

Example 2

An optical lens according to embodiment 2 of the present application is described below with reference to fig. 2. In this embodiment and the following embodiments, descriptions of parts similar to those of embodiment 1 will be omitted for the sake of brevity. 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, in order from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6.

The fifth lens L5 is a plano-convex lens with positive power, and has a convex object-side surface S9 and a flat image-side surface S10.

The first lens L1 to the sixth lens L6 are all glass spherical lenses.

Table 3 below shows a radius of curvature R, a thickness T, a refractive index Nd, and an abbe number Vd of each lens of the optical lens of example 2, where the radius of curvature R and the thickness T are both in units of millimeters (mm). Table 4 below gives the entire group focal length value f of the optical lens of embodiment 2, the total optical length TTL of the optical lens (i.e., the on-axis distance from the center of the object-side surface S1 of the first lens L1 to the imaging surface IMA), the radii of curvature R3 and R4 of the object-side surface S3 and the image-side surface S4 of the second lens L2, the center thickness d3 of the second lens L2, the focal length values f3-f5 of the third lens L3 to the fifth lens L5, the radii of curvature R11 and R12 of the object-side surface S11 and the image-side surface S12 of the sixth lens L6, the refractive index Nd2 of the second lens L2, the refractive index Nd4 of the fourth lens L4, and the refractive index Nd6 of the sixth lens L6.

TABLE 3

Flour mark	Radius of curvature R	Thickness T	Refractive index Nd	Abbe number Vd
					1	29.7659	4.5135	1.80	46.57
2	216.7939	0.0994
					3	18.5311	6.1486	1.90	31.32
4	15.2742	3.7401
					STO	All-round	2.8668
6	-18.6314	2.2639	1.60	38.01
					7	19.9379	7.3028	1.90	31.32
8	-32.1621	2.0146
					9	21.7110	4.2720	1.90	37.12
10	All-round	2.1270
					11	-19.8899	0.9831	1.72	29.50
12	-71.3840	4.0891
					13	All-round	1.0000	1.52	64.17
14	All-round	0.0000
					IMA	All-round

TABLE 4

In the present embodiment, TTL/f is 1.672, which is satisfied between the total optical length TTL of the optical lens and the entire focal length f of the optical lens; the radius of curvature R3 of the object-side surface S3 of the second lens L2, the radius of curvature R4 of the image-side surface S4 of the second lens L2, and the center thickness d3 of the second lens L2 satisfy | R3|/(| R4| + d3) ═ 0.865; the focal length value f3 of the third lens L3 and the entire group of focal length values f of the optical lens satisfy | f3/f | -0.645; f3/f4 is-1.067 between the focal length value f3 of the third lens L3 and the focal length value f4 of the fourth lens L4; the curvature radii R11 and R12 of the object side S11 and the image side S12 of the sixth lens L6 satisfy R11/R12 of 0.279; and f5/f is equal to 0.997 between the focal length value f5 of the fifth lens L5 and the focal length value f of the whole group of the optical lens.

Example 3

An optical lens according to embodiment 3 of the present application is described below with reference to fig. 3. In this embodiment and the following embodiments, descriptions of parts similar to those of embodiment 1 will be omitted for the sake of brevity. Fig. 3 shows a schematic structural diagram of an optical lens according to embodiment 3 of the present application.

As shown in fig. 3, the optical lens includes, in order from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6.

The fifth lens L5 is a meniscus lens with positive power, with the object side S9 being convex and the image side S10 being concave.

The first lens L1 to the sixth lens L6 are all glass spherical lenses.

Table 5 below shows a radius of curvature R, a thickness T, a refractive index Nd, and an abbe number Vd of each lens of the optical lens of example 3, where the radius of curvature R and the thickness T are both in units of millimeters (mm). Table 6 below gives the entire group focal length value f of the optical lens of embodiment 3, the total optical length TTL of the optical lens (i.e., the on-axis distance from the center of the object-side surface S1 of the first lens L1 to the imaging surface IMA), the radii of curvature R3 and R4 of the object-side surface S3 and the image-side surface S4 of the second lens L2, the center thickness d3 of the second lens L2, the focal length values f3-f5 of the third lens L3 to the fifth lens L5, the radii of curvature R11 and R12 of the object-side surface S11 and the image-side surface S12 of the sixth lens L6, the refractive index Nd2 of the second lens L2, the refractive index Nd4 of the fourth lens L4, and the refractive index Nd6 of the sixth lens L6.

TABLE 5

Flour mark	Radius of curvature R	Thickness T	Refractive index Nd	Abbe number Vd
					1	29.4976	4.4796	1.80	46.57
2	213.0472	0.0700
					3	18.6965	6.1331	1.90	31.32
4	15.3478	3.9117
					STO	All-round	2.6738
6	-18.5954	2.2851	1.60	38.01
					7	19.3367	7.3097	1.90	31.32
8	-32.2764	1.9754
					9	21.0503	4.3939	1.90	37.12
10	214.2530	2.1858
					11	-19.8404	0.9461	1.72	29.50
12	-61.7340	4.0704
					13	All-round	1.0000	1.52	64.17
14	All-round	0.0000
					IMA	All-round

TABLE 6

f(mm)	24.8376	R11(mm)	-19.8404
				TTL(mm)	41.4346	R12(mm)	-61.7340
R3(mm)	18.6965	f5(mm)	26.2657
				R4(mm)	15.3478	Nd2	1.90
d3(mm)	6.1331	Nd4	1.90
				f3(mm)	-15.7242	Nd6	1.72
f4(mm)	14.7290

In the present embodiment, TTL/f is 1.668 between the total optical length TTL of the optical lens and the whole focal length f of the optical lens; the radius of curvature R3 of the object-side surface S3 of the second lens L2, the radius of curvature R4 of the image-side surface S4 of the second lens L2, and the center thickness d3 of the second lens L2 satisfy | R3|/(| R4| + d3) ═ 0.870; the focal length value f3 of the third lens L3 and the entire group focal length value f of the optical lens satisfy | f3/f | -0.633; f3/f4 is-1.068 between the focal length value f3 of the third lens L3 and the focal length value f4 of the fourth lens L4; the curvature radii R11 and R12 of the object side surface S11 and the image side surface S12 of the sixth lens L6 satisfy R11/R12 of 0.321; and f5/f is 1.057 between the focal length value f5 of the fifth lens L5 and the focal length value f of the whole group of the optical lens.

In summary, examples 1 to 3 each satisfy the relationship shown in table 7 below.

TABLE 7

Conditions/examples	1	2	3
				TTL/f	1.661	1.672	1.668
\|R3\|/(\|R4\|+d3)	0.869	0.865	0.870
				\|f3/f\|	0.604	0.645	0.633
f3/f4	-1.030	-1.067	-1.068
				R11/R12	0.160	0.279	0.321
f5/f	0.845	0.997	1.057

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 may be replaced with (but not limited to) features having similar functions disclosed in the present application.

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, a fourth lens, a fifth lens, and a sixth lens,

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

the first lens has positive 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 negative focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface;

the third lens has negative focal power, and both the object side surface and the image side surface of the third lens are concave;

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

the fifth lens has positive focal power; and

the sixth lens element has negative focal power, a concave object-side surface and a convex image-side surface,

wherein the optical lens is a six-piece lens,

wherein the radius of curvature R3 of the object side surface of the second lens, the radius of curvature R4 of the image side surface of the second lens and the center thickness d3 of the second lens satisfy: the absolute value of R3 absolute/(| R4| + d3) is more than or equal to 0.6 and less than or equal to 1.2.

2. An optical lens barrel according to claim 1, wherein the object-side surface and the image-side surface of the fifth lens element are convex.

3. An optical lens barrel according to claim 1, wherein the fifth lens element has a convex object-side surface and a planar image-side surface.

4. An optical lens barrel according to claim 1, wherein the fifth lens element has a convex object-side surface and a concave image-side surface.

5. An optical lens according to claim 1, wherein the third lens and the fourth lens are cemented to each other to constitute a cemented lens.

6. An optical lens according to claim 1, wherein the first lens to the sixth lens are all glass spherical lenses.

7. An optical lens barrel according to claim 1, further comprising a stop disposed before the third lens.

8. An optical lens barrel according to any one of claims 1 to 7, wherein a distance TTL between a center of an object side surface of the first lens and an imaging surface of the optical lens on the optical axis and a full group focal length value f of the optical lens satisfy: TTL/f is less than or equal to 2.

9. An optical lens according to any one of claims 1 to 7, characterized in that the focal length value f3 of the third lens and the entire group of focal length values f of the optical lens satisfy: and | f3/f | ≧ 0.45.

10. An optical lens according to any one of claims 1 to 7, characterized in that a focal length value f3 of the third lens and a focal length value f4 of the fourth lens satisfy: f3/f4 is not less than-1.5 and not more than-0.7.

11. An optical lens according to any one of claims 1 to 7, characterized in that the focal length value f5 of the fifth lens and the entire group of focal length values f of the optical lens satisfy: f5/f is not less than 0.65.

12. An optical lens barrel according to any one of claims 1 to 7, wherein a radius of curvature R11 of an object side surface and a radius of curvature R12 of an image side surface of the sixth lens satisfy: R11/R12 is more than or equal to 0.05 and less than or equal to 0.5.

13. 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, a fourth lens, a fifth lens, and a sixth lens,

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

the first lens, the fourth lens and the fifth lens each have positive optical power;

the second lens, the third lens and the sixth lens each have a negative optical power;

the third lens and the fourth lens are mutually glued to form a cemented lens;

the optical lens is a six-piece lens;

the distance TTL from the center of the object side surface of the first lens to the imaging surface of the optical lens on the optical axis and the whole group of focal length values f of the optical lens satisfy the following condition: TTL/f is less than or equal to 2, and

the radius of curvature R3 of the object side surface of the second lens, the radius of curvature R4 of the image side surface of the second lens and the center thickness d3 of the second lens are satisfied: the absolute value of R3 absolute/(| R4| + d3) is more than or equal to 0.6 and less than or equal to 1.2.

14. An optical lens barrel according to claim 13, wherein the first lens element has a convex object-side surface and a concave image-side surface.

15. An optical lens barrel according to claim 13, wherein the second lens element has a convex object-side surface and a concave image-side surface.

16. An optical lens barrel according to claim 13, wherein the object side surface and the image side surface of the third lens are both concave.

17. An optical lens barrel according to claim 13, wherein the object side surface and the image side surface of the fourth lens are convex.

18. An optical lens barrel according to claim 13, wherein the object-side surface and the image-side surface of the fifth lens element are convex.

19. An optical lens barrel according to claim 13, wherein the fifth lens element has a convex object-side surface and a planar image-side surface.

20. An optical lens barrel according to claim 13, wherein the fifth lens element has a convex object-side surface and a concave image-side surface.

21. An optical lens barrel according to claim 13, wherein the sixth lens element has a concave object-side surface and a convex image-side surface.

22. An optical lens barrel according to any one of claims 13 to 21, wherein the first lens to the sixth lens are all glass spherical lenses.

23. An optical lens barrel according to any one of claims 13 to 21, further comprising a diaphragm disposed before the third lens.

24. An optical lens element according to any one of claims 13-21, characterized in that the focal length value f3 of the third lens element and the entire set of focal length values f of the optical lens element satisfy: and | f3/f | ≧ 0.45.

25. An optical lens element according to any of claims 13-21, characterized in that between the focal length value f3 of the third lens element and the focal length value f4 of the fourth lens element: f3/f4 is not less than-1.5 and not more than-0.7.

26. An optical lens element according to any one of claims 13 to 21, characterized in that the focal length value f5 of the fifth lens element and the focal length value f of the entire group of the optical lens element satisfy: f5/f is not less than 0.65.

27. An optical lens barrel according to any one of claims 13 to 21, wherein a radius of curvature R11 of the object side surface and a radius of curvature R12 of the image side surface of the sixth lens satisfy: R11/R12 is more than or equal to 0.05 and less than or equal to 0.5.