CN112180558A

CN112180558A - Optical imaging lens

Info

Publication number: CN112180558A
Application number: CN202011163556.4A
Authority: CN
Inventors: 徐武超; 戴付建; 赵烈烽
Original assignee: Zhejiang Sunny Optics Co Ltd
Current assignee: Zhejiang Sunny Optics Co Ltd
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2021-01-05

Abstract

The application discloses an optical imaging lens, this optical imaging lens includes along the optical axis from the object side to the image side in proper order: a first lens having a refractive power, an image-side surface of which is concave; a second lens element having a negative refractive power, the object-side surface of which is concave and the image-side surface of which is concave; a third lens having a negative optical power; the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; and a fifth lens having optical power. The total effective focal length f of the optical imaging lens and the entrance pupil diameter EPD of the optical imaging lens meet the following conditions: f/EPD is less than or equal to 2.08; an air interval T23 of the second lens and the third lens on the optical axis, an air interval T34 of the third lens and the fourth lens on the optical axis, and an air interval T45 of the fourth lens and the fifth lens on the optical axis satisfy: 1.16 ≤ T45/(T23+ T34) < 3; and the maximum effective semi-aperture DT21 of the object side surface of the second lens and the maximum effective semi-aperture DT31 of the object side surface of the third lens meet the following conditions: DT31/DT21 is less than or equal to 0.90.

Description

Optical imaging lens

Technical Field

The present application relates to the field of optical elements, and in particular, to an optical imaging lens including five lenses.

Background

In recent years, with the continuous development of camera module technology and the market trend of ultra-thin mobile phones, users have increasingly high requirements for the imaging quality of optical imaging lenses used in mobile phones. To meet the above requirements, the mobile phone lens is composed of more lenses, for example, 6 lenses or 7 lenses. However, the cost of the mobile phone lens increases due to excessive lens composition, and the structure of the lenses does not have enough adjustment space in the subsequent assembly process. Therefore, for some optical imaging lens manufacturers, it is necessary to not only follow the mainstream trend to produce an optical imaging lens for a mobile phone with large image plane, large aperture and ultra-thin characteristics, but also pursue higher cost performance.

Therefore, how to make the optical imaging lens have ultra-thin, large aperture, large image plane, large aperture and high imaging quality even in dark environment is one of the problems to be solved by many optical imaging lens designs.

Disclosure of Invention

The present application provides an optical imaging lens applicable to portable electronic products, for example, an optical imaging lens having an ultra-thin, large image plane, which can at least solve or partially solve at least one of the above-mentioned disadvantages of the prior art.

An aspect of the present application provides an optical imaging lens, which may include, in order from an object side to an image side along an optical axis: a first lens having a refractive power, an image-side surface of which is concave; a second lens element having a negative refractive power, the object-side surface of which is concave and the image-side surface of which is concave; a third lens having a negative optical power; the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; and a fifth lens having a focal power, wherein the total effective focal length f of the optical imaging lens and the entrance pupil diameter EPD of the optical imaging lens satisfy: f/EPD is less than or equal to 2.08; an air interval T23 of the second lens and the third lens on the optical axis, an air interval T34 of the third lens and the fourth lens on the optical axis, and an air interval T45 of the fourth lens and the fifth lens on the optical axis satisfy: 1.16 is less than or equal to T45/(T23+ T34) < 3; and the maximum effective semi-aperture DT21 of the object side surface of the second lens and the maximum effective semi-aperture DT31 of the object side surface of the third lens meet the following conditions: DT31/DT21 is less than or equal to 0.90.

In one embodiment, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, and the total effective focal length f of the optical imaging lens may satisfy: -1.6 < (f1+ f2)/f < -1.

In one embodiment, the total effective focal length f of the optical imaging lens and the radius of curvature R2 of the image side surface of the first lens can satisfy: 1 < R2/f < 3.

In one embodiment, the radius of curvature R7 of the object-side surface of the fourth lens, the radius of curvature R8 of the image-side surface of the fourth lens, and the effective focal length f4 of the fourth lens may satisfy: -1.1 < (R7+ R8)/f4 < -0.5.

In one embodiment, the radius of curvature R3 of the object-side surface of the second lens and the radius of curvature R4 of the image-side surface of the second lens may satisfy: 0 < (R3+ R4)/(R3-R4) < 1.1.

In one embodiment, the central thickness CT1 of the first lens on the optical axis, the central thickness CT2 of the second lens on the optical axis, and the central thickness CT3 of the third lens on the optical axis may satisfy: 1 < CT1/(CT2+ CT3) < 1.5.

In one embodiment, an on-axis distance SAG51 from an intersection point of an object-side surface of the fifth lens and the optical axis to an effective radius vertex of the object-side surface of the fifth lens and an on-axis distance SAG52 from an intersection point of an image-side surface of the fifth lens and the optical axis to an effective radius vertex of the image-side surface of the fifth lens may satisfy: 0.9 < SAG51/SAG52 is less than or equal to 1.35.

In one embodiment, the maximum effective half aperture DT22 of the image-side surface of the second lens and the maximum effective half aperture DT31 of the object-side surface of the third lens satisfy: DT22/DT31 is less than or equal to 1.

In one embodiment, the central thickness CT3 of the third lens on the optical axis and the central thickness CT4 of the fourth lens on the optical axis may satisfy: 0.3 < CT3/CT4 < 0.5.

In one embodiment, the central thickness CT4 of the fourth lens on the optical axis and the edge thickness ET4 of the fourth lens can satisfy: 0.4 < ET4/CT4 < 0.85.

In one embodiment, the maximum effective half aperture DT41 of the object-side surface of the fourth lens and the maximum effective half aperture DT42 of the image-side surface of the fourth lens satisfy: DT41/DT42 of more than 0.6 and less than or equal to 1.02.

Another aspect of the present application provides an optical imaging lens, which may include, in order from an object side to an image side along an optical axis: a first lens having a refractive power, an image-side surface of which is concave; a second lens element having a negative refractive power, the object-side surface of which is concave and the image-side surface of which is concave; a third lens having a negative optical power; the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; and a fifth lens having optical power, wherein the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, and the total effective focal length f of the optical imaging lens satisfy: -1.6 < (f1+ f2)/f < -1; an air interval T23 of the second lens and the third lens on the optical axis, an air interval T34 of the third lens and the fourth lens on the optical axis, and an air interval T45 of the fourth lens and the fifth lens on the optical axis satisfy: 1.16 is less than or equal to T45/(T23+ T34) < 3; and the maximum effective semi-aperture DT21 of the object side surface of the second lens and the maximum effective semi-aperture DT31 of the object side surface of the third lens meet the following conditions: DT31/DT21 is less than or equal to 0.90.

In one embodiment, the total effective focal length f of the optical imaging lens and the entrance pupil diameter EPD of the optical imaging lens satisfy: f/EPD is less than or equal to 2.08.

The application provides an optical imaging lens adopts a plurality of lenses, for example first lens to fifth lens, through the focal power, face type, curvature radius and the effective focal length of each lens of reasonable control optical imaging system, make optical imaging lens have characteristics such as big image plane, high image quality, low-cost, big light ring when realizing ultra-thin, the compact structure of each lens simultaneously, the shaping processing performance is good, can promote the production yield of making a video recording module.

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 shows a schematic structural view of an optical imaging lens according to embodiment 1 of the present application;

fig. 2A to 2D show an on-axis chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, of the optical imaging lens of embodiment 1;

fig. 3 is a schematic structural view showing an optical imaging lens according to embodiment 2 of the present application;

fig. 4A to 4D show an on-axis chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, of the optical imaging lens of embodiment 2;

fig. 5 is a schematic structural view showing an optical imaging lens according to embodiment 3 of the present application;

fig. 6A to 6D show an on-axis chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, of the optical imaging lens of embodiment 3;

fig. 7 is a schematic structural view showing an optical imaging lens according to embodiment 4 of the present application;

fig. 8A to 8D show an on-axis chromatic aberration curve, an astigmatism curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, of the optical imaging lens of embodiment 4;

fig. 9 is a schematic structural view showing an optical imaging lens according to embodiment 5 of the present application; and

fig. 10A to 10D show an axial chromatic aberration curve, an astigmatism curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, of the optical imaging lens of embodiment 5.

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.

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 of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

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 imaging lens according to an exemplary embodiment of the present application may include five lenses having optical powers, i.e., a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The five lenses are arranged in sequence from the object side to the image side along the optical axis. In the first to fifth lenses, each of adjacent two lenses may have an air space therebetween.

In an exemplary embodiment, the first lens has a positive or negative power, and the image-side surface thereof is concave; the second lens can have negative focal power, and the object side surface of the second lens is a concave surface; the third lens may have a negative optical power; the fourth lens can have positive focal power, and the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; and the fifth lens has positive power or negative power. The reasonable configuration of the surface type and focal power of each lens can ensure the performance of the optical system, and simultaneously, the optical system has the characteristics of high pixel, large aperture and easy processing.

In an exemplary embodiment, the object side surface of the first lens may be convex.

In an exemplary embodiment, an image side surface of the fifth lens may be concave.

In an exemplary embodiment, the total effective focal length f of the optical imaging lens and the entrance pupil diameter EPD of the optical imaging lens satisfy: f/EPD is less than or equal to 2.08. For example, 1.5 < f/EPD ≦ 2.08. The ratio of the total effective focal length of the optical imaging lens to the entrance pupil diameter of the optical imaging lens is controlled within a reasonable numerical range, so that the optical imaging lens can obtain a larger aperture, and the light inlet quantity of the optical imaging system is increased.

In the exemplary embodiment, an air interval T23 of the second lens and the third lens on the optical axis, an air interval T34 of the third lens and the fourth lens on the optical axis, and an air interval T45 of the fourth lens and the fifth lens on the optical axis satisfy: 1.16 is less than or equal to T45/(T23+ T34) < 3. For example, 1.7 < T45/(T23+ T34) < 2.5. The air space of the second lens and the third lens on the optical axis, the air space T34 of the third lens and the fourth lens on the optical axis and the air space of the fourth lens and the fifth lens on the optical axis are reasonably controlled, so that the sensitivity of the air space to tolerance in an optical imaging system is favorably reduced, the manufacturing yield of the optical imaging lens is improved, and the stability of the curvature of field of the optical imaging lens is controlled.

In an exemplary embodiment, the maximum effective half aperture DT21 of the object side surface of the second lens and the maximum effective half aperture DT31 of the object side surface of the third lens satisfy: DT31/DT21 is less than or equal to 0.90. For example, 0.7 < DT31/DT21 ≦ 0.90. The ratio of the maximum effective half aperture of the object side surface of the second lens to the maximum effective half aperture of the object side surface of the third lens is controlled within a reasonable numerical range, so that off-axis aberration of an optical imaging system is reduced, and the imaging quality of the optical imaging lens is improved.

In an exemplary embodiment, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, and the total effective focal length f of the optical imaging lens may satisfy: -1.6 < (f1+ f2)/f < -1. For example, -1.5 < (f1+ f2)/f < -1.2. The mutual relation among the effective focal length of the first lens, the effective focal length of the second lens and the total effective focal length of the optical imaging lens is reasonably controlled, the axial chromatic aberration of the optical imaging system is favorably corrected, and the resolution capability of the optical imaging system is improved.

In an exemplary embodiment, the total effective focal length f of the optical imaging lens and the radius of curvature R2 of the image side surface of the first lens may satisfy: 1 < R2/f < 3. For example, 1.5 < R2/f < 3. The ratio of the total effective focal length of the optical imaging lens to the curvature radius of the image side surface of the first lens is controlled within a reasonable numerical range, so that the processability of the first lens is improved, and the sensitivity of the first air space to back focus is reduced.

In an exemplary embodiment, the radius of curvature R7 of the object-side surface of the fourth lens, the radius of curvature R8 of the image-side surface of the fourth lens, and the effective focal length f4 of the fourth lens may satisfy: -1.1 < (R7+ R8)/f4 < -0.5. The mutual relation among the curvature radius of the object side surface, the curvature radius of the image side surface and the effective focal length of the fourth lens is reasonably controlled, the astigmatism values of the object image surface and the image side surface of the fourth lens can be effectively controlled, and the imaging quality in the aperture band of the central view field of the optical imaging lens is effectively and reasonably controlled.

In an exemplary embodiment, the radius of curvature R3 of the object-side surface of the second lens and the radius of curvature R4 of the image-side surface of the second lens may satisfy: 0 < (R3+ R4)/(R3-R4) < 1.1. For example, 0.5 < (R3+ R4)/(R3-R4) < 1.1. The ratio of the curvature radius of the object side surface and the curvature radius of the image side surface of the second lens is controlled within a reasonable numerical range, so that the spherical aberration and the axial chromatic aberration of the optical imaging system are corrected, and the imaging quality of the optical imaging lens is improved.

In an exemplary embodiment, the central thickness CT1 of the first lens on the optical axis, the central thickness CT2 of the second lens on the optical axis, and the central thickness CT3 of the third lens on the optical axis may satisfy: 1 < CT1/(CT2+ CT3) < 1.5. For example, 1.1 < CT1/(CT2+ CT3) < 1.4. The mutual relation among the central thicknesses of the first lens, the second lens and the third lens on the optical axis is reasonably controlled, the structural compactness of an optical imaging system is favorably ensured, meanwhile, the sensitivity of the central thickness of each lens in the optical imaging lens to field curvature is reduced, and the assembly yield of the optical imaging lens is favorably improved.

In an exemplary embodiment, an on-axis distance SAG51 from an intersection of an object-side surface of the fifth lens and the optical axis to an effective radius vertex of the object-side surface of the fifth lens and an on-axis distance SAG52 from an intersection of an image-side surface of the fifth lens and the optical axis to an effective radius vertex of the image-side surface of the fifth lens may satisfy: 0.9 < SAG51/SAG52 is less than or equal to 1.35. The ratio of the rise of the object side surface to the rise of the image side surface of the fifth lens is controlled within a reasonable numerical range, so that the surface type transition of the fifth lens is smooth, and the processability and manufacturability of the fifth lens are met.

In an exemplary embodiment, the maximum effective half aperture DT22 of the image-side surface of the second lens and the maximum effective half aperture DT31 of the object-side surface of the third lens may satisfy: DT22/DT31 is less than or equal to 1. For example, 0.5 < DT22/DT31 ≦ 1. The ratio of the maximum effective half aperture of the image side surface of the second lens to the maximum effective half aperture of the object side surface of the third lens is controlled within a reasonable numerical range, so that the relative brightness of the marginal field of view of the optical imaging lens is favorably improved, and the photosensitive chip is well matched.

In an exemplary embodiment, the central thickness CT3 of the third lens on the optical axis and the central thickness CT4 of the fourth lens on the optical axis may satisfy: 0.3 < CT3/CT4 < 0.5. By controlling the ratio of the central thicknesses of the third lens and the fourth lens on the optical axis within a reasonable numerical range, the curvature of field of the optical imaging lens can be effectively corrected while the processability of the optical imaging lens is ensured.

In an exemplary embodiment, the central thickness CT4 of the fourth lens on the optical axis and the edge thickness ET4 of the fourth lens may satisfy: 0.4 < ET4/CT4 < 0.85. By controlling the ratio of the center thickness to the edge thickness of the fourth lens on the optical axis within a reasonable numerical range, it is advantageous to satisfy the workability of the fourth lens and to correct curvature of field and distortion of the optical imaging system.

In an exemplary embodiment, the maximum effective half aperture DT41 of the object-side surface of the fourth lens and the maximum effective half aperture DT42 of the image-side surface of the fourth lens may satisfy: DT41/DT42 of more than 0.6 and less than or equal to 1.02. The ratio of the maximum effective half aperture of the object side surface to the maximum effective half aperture of the image side surface of the fourth lens is controlled within a reasonable numerical range, so that the fourth lens can be prevented from being excessively bent, the processing difficulty is reduced, and the matching degree of the Chief Ray incident Angle (CRA) of the optical imaging lens and the photosensitive chip is increased.

In an exemplary embodiment, the optical imaging lens may further include a diaphragm. The diaphragm may be disposed at an appropriate position as required. For example, a diaphragm may be disposed between the object side and the first lens. Optionally, the optical imaging lens may further include a filter for correcting color deviation and/or a protective glass for protecting a photosensitive element on the imaging surface.

The application provides an optical imaging lens with characteristics of ultrathin property, large image plane and the like. The optical imaging lens according to the above-described embodiment of the present application may employ a plurality of lenses, for example, five lenses as described above. By reasonably distributing the focal power, the surface type, the central thickness of each lens, the on-axis distance between each lens and the like, the incident light can be effectively converged, the optical total length of the imaging lens is reduced, the machinability of the imaging lens is improved, and the optical imaging lens is more favorable for production and processing.

In an exemplary embodiment, at least one of the mirror surfaces of each lens is an aspheric mirror surface, i.e., at least one of the object side surface of the first lens to the image side surface of the fifth lens is an aspheric mirror surface. The aspheric lens is characterized in that: the curvature varies continuously from the center of the lens to the periphery of the lens. Unlike a spherical lens having a constant curvature from the center of the lens 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. Optionally, at least one of an object-side surface and an image-side surface of each of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens is an aspheric mirror surface. Optionally, each of the first, second, third, fourth, and fifth lenses has an object-side surface and an image-side surface that are aspheric mirror surfaces.

The present application also provides an imaging device whose electron photosensitive element may be a photo-coupled device (CCD) or a complementary metal oxide semiconductor device (CMOS). The imaging device may be a stand-alone imaging device such as a digital camera, or may be an imaging module integrated on a mobile electronic device such as a mobile phone. The imaging device is equipped with the optical imaging lens described above.

However, it will be appreciated by those skilled in the art that the number of lenses constituting an optical imaging lens 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 five lenses are exemplified in the embodiment, the optical imaging lens is not limited to include five lenses. The optical imaging lens may also include other numbers of lenses, if desired.

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

Example 1

An optical imaging lens according to embodiment 1 of the present application is described below with reference to fig. 1 to 2D. Fig. 1 is a schematic view showing a structure of an optical imaging lens according to embodiment 1 of the present application.

As shown in fig. 1, the optical imaging lens, in order from an object side to an image side along an optical axis, comprises: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a filter E6, and an image forming surface S13.

The first lens element E1 has positive power, and has a convex object-side surface S1 and a concave image-side surface S2. The second lens element E2 has negative power, and has a concave object-side surface S3 and a concave image-side surface S4. The third lens element E3 has negative power, and has a convex object-side surface S5 and a concave image-side surface S6. The fourth lens element E4 has positive power, and has a concave object-side surface S7 and a convex image-side surface S8. The fifth lens element E5 has negative power, and has a convex object-side surface S9 and a concave image-side surface S10. Filter E6 has an object side S11 and an image side S12. The light from the object sequentially passes through the respective surfaces S1 to S12 and is finally imaged on the imaging surface S13.

Table 1 shows a basic parameter table of the optical imaging lens of embodiment 1, in which the units of the radius of curvature, the thickness/distance, and the focal length are all millimeters (mm).

TABLE 1

In the present embodiment, the total effective focal length f of the optical imaging lens is 3.80mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens E1 to the imaging surface S13 is 3.40mm, and the half ImgH of the diagonal length of the effective pixel area on the imaging surface S13 is 4.34mm, and the maximum half field angle Semi-FOV of the optical imaging lens is 40.86 °.

In embodiment 1, the object-side surface and the image-side surface of any one of the first lens E1 to the fifth lens E5 are aspheric surfaces, and the surface shape x of each aspheric lens can be defined by, but is not limited to, the following aspheric surface formula:

wherein x is the rise of the distance from the aspheric surface vertex to the aspheric surface vertex 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 coefficient; ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 below shows the high-order coefficient A of each of the aspherical mirror surfaces S1 to S10 used in example 1₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈And A₂₀。

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

2.2993E-02

1.7955E-02

3.7445E-02

-4.2462E-01

1.7891E+00

-4.1311E+00

5.3973E+00

-3.7942E+00

1.0843E+00

S2

-9.8772E-02

5.8070E-02

-1.2116E-01

1.1884E+00

-4.4964E+00

7.6346E+00

-5.7469E+00

7.8964E-01

7.7372E-01

S3

-7.3613E-02

8.6522E-02

1.3346E+00

-7.7286E+00

2.5817E+01

-5.5058E+01

7.2650E+01

-5.3450E+01

1.6763E+01

S4

-2.1790E-02

5.3304E-01

-3.3749E+00

2.1770E+01

-8.7974E+01

2.1888E+02

-3.2619E+02

2.6763E+02

-9.2402E+01

S5

-3.1220E-01

5.5047E-01

-5.5229E+00

3.4644E+01

-1.3797E+02

3.4330E+02

-5.1951E+02

4.3747E+02

-1.5750E+02

S6

-2.6406E-01

3.6711E-01

-2.0434E+00

8.0064E+00

-1.9563E+01

3.0803E+01

-3.0126E+01

1.6498E+01

-3.8242E+00

S7

-1.7197E-01

1.3165E-01

-1.0661E-01

-2.4763E-02

1.4823E+00

-3.2928E+00

3.0042E+00

-1.2789E+00

2.1088E-01

S8

-2.6391E-02

4.2767E-02

2.6268E-03

-8.4620E-02

2.6916E-01

-2.9868E-01

1.5465E-01

-3.8763E-02

3.8214E-03

S9

-4.0711E-01

3.6201E-01

-2.1862E-01

9.4374E-02

-2.7371E-02

5.1458E-03

-6.0122E-04

3.9739E-05

-1.1376E-06

S10

-1.7504E-01

1.2467E-01

-6.1975E-02

2.0810E-02

-4.7305E-03

7.0743E-04

-6.5595E-05

3.3918E-06

-7.4659E-08

TABLE 2

Fig. 2A shows an on-axis chromatic aberration curve of the optical imaging lens of embodiment 1, which represents the deviation of the convergent focal points of light rays of different wavelengths after passing through the lens. Fig. 2B shows an astigmatism curve representing a meridional field curvature and a sagittal field curvature of the optical imaging lens of embodiment 1. Fig. 2C shows a distortion curve of the optical imaging lens of embodiment 1, which represents distortion magnitude values corresponding to different image heights. Fig. 2D shows a chromatic aberration of magnification curve of the optical imaging lens of embodiment 1, which represents a deviation of different image heights on the imaging plane after light passes through the lens. As can be seen from fig. 2A to 2D, the optical imaging lens according to embodiment 1 can achieve good imaging quality.

Example 2

An optical imaging lens according to embodiment 2 of the present application is described below with reference to fig. 3 to 4D. Fig. 3 shows a schematic structural diagram of an optical imaging lens according to embodiment 2 of the present application.

As shown in fig. 3, the optical imaging lens, in order from an object side to an image side along an optical axis, comprises: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a filter E6, and an image forming surface S13.

The first lens element E1 has positive power, and has a convex object-side surface S1 and a concave image-side surface S2. The second lens element E2 has negative power, and has a concave object-side surface S3 and a concave image-side surface S4. The third lens element E3 has negative power, and has a concave object-side surface S5 and a concave image-side surface S6. The fourth lens element E4 has positive power, and has a concave object-side surface S7 and a convex image-side surface S8. The fifth lens element E5 has negative power, and has a convex object-side surface S9 and a concave image-side surface S10. Filter E6 has an object side S11 and an image side S12. The light from the object sequentially passes through the respective surfaces S1 to S12 and is finally imaged on the imaging surface S13.

In the present embodiment, the total effective focal length f of the optical imaging lens is 3.79mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens E1 to the imaging surface S13 is 3.40mm, the half ImgH of the diagonal length of the effective pixel area on the imaging surface S13 is 4.30mm, and the maximum half field angle Semi-FOV of the optical imaging lens is 40.86 °.

Table 3 shows a basic parameter table of the optical imaging lens of embodiment 2, in which the units of the radius of curvature, the thickness/distance, and the focal length are all millimeters (mm).

TABLE 3

In embodiment 2, both the object-side surface and the image-side surface of any one of the first lens E1 through the fifth lens E5 are aspheric. Table 4 below shows the high-order coefficient A of each of the aspherical mirror surfaces S1-S10 used in example 2₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈And A₂₀。

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

1.9870E-02

6.1187E-02

-2.1202E-01

4.4080E-01

2.0233E-02

-2.0596E+00

4.1686E+00

-3.5803E+00

1.1403E+00

S2

-9.5093E-02

5.5814E-02

1.5601E-04

2.5266E-01

-1.0429E+00

3.5248E-01

2.8828E+00

-4.3771E+00

1.9286E+00

S3

-7.1479E-02

1.1839E-01

1.1948E+00

-7.3155E+00

2.4522E+01

-5.1481E+01

6.6190E+01

-4.7033E+01

1.4158E+01

S4

-2.1614E-02

5.9031E-01

-4.4696E+00

3.1710E+01

-1.3879E+02

3.7102E+02

-5.9159E+02

5.1781E+02

-1.9094E+02

S5

-3.4870E-01

9.4290E-01

-9.8589E+00

6.3362E+01

-2.5754E+02

6.5704E+02

-1.0219E+03

8.8529E+02

-3.2774E+02

S6

-3.0676E-01

5.8352E-01

-3.3831E+00

1.3397E+01

-3.3350E+01

5.3647E+01

-5.3762E+01

3.0314E+01

-7.2782E+00

S7

-2.0643E-01

2.8614E-01

-7.5096E-01

1.7068E+00

-1.0561E+00

-1.2532E+00

2.1424E+00

-1.1220E+00

2.0733E-01

S8

-6.0288E-02

1.3467E-01

-1.9329E-01

2.0237E-01

8.4913E-02

-2.9079E-01

2.0081E-01

-5.9371E-02

6.6277E-03

S9

-3.9884E-01

3.6077E-01

-2.3342E-01

1.0915E-01

-3.3955E-02

6.7766E-03

-8.3446E-04

5.7845E-05

-1.7305E-06

S10

-1.6414E-01

1.1326E-01

-5.4670E-02

1.7299E-02

-3.5819E-03

4.6496E-04

-3.4243E-05

1.1464E-06

-6.7143E-09

TABLE 4

Fig. 4A shows an on-axis chromatic aberration curve of the optical imaging lens of embodiment 2, which represents the deviation of the convergent focal points of light rays of different wavelengths after passing through the lens. Fig. 4B shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the optical imaging lens of embodiment 2. Fig. 4C shows a distortion curve of the optical imaging lens of embodiment 2, which represents distortion magnitude values corresponding to different image heights. Fig. 4D shows a chromatic aberration of magnification curve of the optical imaging lens of embodiment 2, which represents the deviation of different image heights on the imaging plane after light passes through the lens. As can be seen from fig. 4A to 4D, the optical imaging lens according to embodiment 2 can achieve good imaging quality.

Example 3

An optical imaging lens according to embodiment 3 of the present application is described below with reference to fig. 5 to 6D. Fig. 5 shows a schematic structural diagram of an optical imaging lens according to embodiment 3 of the present application.

As shown in fig. 5, the optical imaging lens, in order from an object side to an image side along an optical axis, comprises: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a filter E6, and an image forming surface S13.

The first lens element E1 has positive power, and has a convex object-side surface S1 and a concave image-side surface S2. The second lens element E2 has negative power, and has a concave object-side surface S3 and a concave image-side surface S4. The third lens element E3 has negative power, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element E4 has positive power, and has a concave object-side surface S7 and a convex image-side surface S8. The fifth lens element E5 has negative power, and has a concave object-side surface S9 and a concave image-side surface S10. Filter E6 has an object side S11 and an image side S12. The light from the object sequentially passes through the respective surfaces S1 to S12 and is finally imaged on the imaging surface S13.

In the present embodiment, the total effective focal length f of the optical imaging lens is 3.68mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens E1 to the imaging surface S13 is 3.40mm, and the half ImgH of the diagonal line length of the effective pixel area on the imaging surface S13 is 4.23mm, and the maximum half field angle Semi-FOV of the optical imaging lens is 41.63 °.

Table 5 shows a basic parameter table of the optical imaging lens of embodiment 3, in which the units of the radius of curvature, the thickness/distance, and the focal length are all millimeters (mm).

TABLE 5

In embodiment 3, both the object-side surface and the image-side surface of any one of the first lens E1 to the fifth lens E5 are aspheric. Table 6 below shows the high-order coefficient A of each of the aspherical mirror surfaces S1-S10 used in example 3₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈And A₂₀。

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

1.8289E-02

1.0779E-01

-5.1701E-01

1.6275E+00

-2.6107E+00

1.1109E+00

2.5421E+00

-3.7883E+00

1.5011E+00

S2

-8.5471E-02

7.0016E-02

-3.6993E-01

2.2404E+00

-6.6423E+00

8.8115E+00

-2.9231E+00

-4.0829E+00

3.0097E+00

S3

-6.1410E-02

9.3017E-02

1.1281E+00

-7.3002E+00

2.7143E+01

-6.3310E+01

8.9667E+01

-6.9581E+01

2.2712E+01

S4

-7.8780E-03

4.9687E-01

-4.1538E+00

3.2199E+01

-1.4989E+02

4.2259E+02

-7.0765E+02

6.4907E+02

-2.5048E+02

S5

-3.1391E-01

7.4271E-01

-9.0371E+00

6.1409E+01

-2.5935E+02

6.8495E+02

-1.1020E+03

9.8784E+02

-3.7863E+02

S6

-2.3577E-01

2.7114E-01

-2.0441E+00

9.4030E+00

-2.5737E+01

4.5197E+01

-4.9062E+01

2.9670E+01

-7.5740E+00

S7

-1.6979E-01

1.5833E-01

-3.4489E-01

6.8005E-01

6.4482E-01

-2.9281E+00

3.0977E+00

-1.4173E+00

2.4580E-01

S8

-3.1462E-02

3.7909E-04

2.0240E-01

-6.1091E-01

1.0938E+00

-1.0231E+00

5.0732E-01

-1.2815E-01

1.3049E-02

S9

-3.5692E-01

3.0021E-01

-1.8918E-01

8.9960E-02

-2.8685E-02

5.8539E-03

-7.3552E-04

5.2023E-05

-1.5914E-06

S10

-1.5541E-01

1.0654E-01

-5.4747E-02

1.9219E-02

-4.6247E-03

7.5041E-04

-7.8752E-05

4.8806E-06

-1.3685E-07

TABLE 6

Fig. 6A shows an on-axis chromatic aberration curve of the optical imaging lens of embodiment 3, which represents the deviation of the convergent focal points of light rays of different wavelengths after passing through the lens. Fig. 6B shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the optical imaging lens of embodiment 3. Fig. 6C shows a distortion curve of the optical imaging lens of embodiment 3, which represents distortion magnitude values corresponding to different image heights. Fig. 6D shows a chromatic aberration of magnification curve of the optical imaging lens of embodiment 3, which represents a deviation of different image heights on the imaging plane after light passes through the lens. As can be seen from fig. 6A to 6D, the optical imaging lens according to embodiment 3 can achieve good imaging quality.

Example 4

An optical imaging lens according to embodiment 4 of the present application is described below with reference to fig. 7 to 8D. Fig. 7 shows a schematic structural diagram of an optical imaging lens according to embodiment 4 of the present application.

As shown in fig. 7, the optical imaging lens, in order from an object side to an image side along an optical axis, comprises: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a filter E6, and an image forming surface S13.

The first lens element E1 has positive power, and has a convex object-side surface S1 and a concave image-side surface S2. The second lens element E2 has negative power, and has a concave object-side surface S3 and a concave image-side surface S4. The third lens element E3 has negative power, and has a convex object-side surface S5 and a concave image-side surface S6. The fourth lens element E4 has positive power, and has a concave object-side surface S7 and a convex image-side surface S8. The fifth lens element E5 has negative power, and has a concave object-side surface S9 and a concave image-side surface S10. Filter E6 has an object side S11 and an image side S12. The light from the object sequentially passes through the respective surfaces S1 to S12 and is finally imaged on the imaging surface S13.

In the present embodiment, the total effective focal length f of the optical imaging lens is 3.60mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens E1 to the imaging surface S13 is 3.40mm, and the half ImgH of the diagonal line length of the effective pixel area on the imaging surface S13 is 4.20mm, and the maximum half field angle Semi-FOV of the optical imaging lens is 42.29 °.

Table 7 shows a basic parameter table of the optical imaging lens of embodiment 4, in which the units of the radius of curvature, the thickness/distance, and the focal length are all millimeters (mm).

TABLE 7

In embodiment 4, both the object-side surface and the image-side surface of any one of the first lens E1 to the fifth lens E5 are aspheric. Table 8 below shows the high-order coefficient A of each of the aspherical mirror surfaces S1-S10 used in example 4₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈And A₂₀。

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

1.0795E-02

1.4364E-01

-9.3066E-01

3.8939E+00

-1.0162E+01

1.6161E+01

-1.5048E+01

7.1697E+00

-1.2771E+00

S2

-5.1949E-02

1.3009E-01

-1.2238E+00

7.6609E+00

-2.7982E+01

5.8506E+01

-6.9888E+01

4.4489E+01

-1.1686E+01

S3

6.3192E-03

1.3366E-01

8.3430E-02

-1.1319E+00

4.3143E+00

-1.0640E+01

1.7382E+01

-1.5266E+01

5.4901E+00

S4

2.4960E-02

2.8212E-01

-1.7705E+00

1.2053E+01

-5.3831E+01

1.4854E+02

-2.4327E+02

2.1723E+02

-8.0650E+01

S5

-3.1757E-01

8.9191E-01

-1.0508E+01

6.8000E+01

-2.7661E+02

7.0264E+02

-1.0858E+03

9.3352E+02

-3.4182E+02

S6

-2.1966E-01

3.0039E-01

-2.0883E+00

8.7077E+00

-2.2645E+01

4.0620E+01

-4.7500E+01

3.1341E+01

-8.5958E+00

S7

-2.1929E-01

1.4154E-02

1.8270E+00

-1.0050E+01

3.1709E+01

-5.5049E+01

5.2588E+01

-2.6266E+01

5.4079E+00

S8

-1.5968E-02

-2.0213E-01

1.1364E+00

-2.9743E+00

4.7677E+00

-4.4233E+00

2.3164E+00

-6.3910E-01

7.2458E-02

S9

-3.8644E-01

3.3538E-01

-2.1899E-01

1.0857E-01

-3.6178E-02

7.7121E-03

-1.0103E-03

7.4307E-05

-2.3552E-06

S10

-1.5987E-01

1.1075E-01

-5.8649E-02

2.1324E-02

-5.2862E-03

8.7423E-04

-9.2444E-05

5.7297E-06

-1.6068E-07

TABLE 8

Fig. 8A shows an on-axis chromatic aberration curve of the optical imaging lens of embodiment 4, which represents the deviation of the convergent focal points of light rays of different wavelengths after passing through the lens. Fig. 8B shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the optical imaging lens of embodiment 4. Fig. 8C shows a distortion curve of the optical imaging lens of embodiment 4, which represents distortion magnitude values corresponding to different image heights. Fig. 8D shows a chromatic aberration of magnification curve of the optical imaging lens of embodiment 4, which represents the deviation of different image heights on the imaging plane after light passes through the lens. As can be seen from fig. 8A to 8D, the optical imaging lens according to embodiment 4 can achieve good imaging quality.

Example 5

An optical imaging lens according to embodiment 5 of the present application is described below with reference to fig. 9 to 10D. Fig. 9 shows a schematic structural diagram of an optical imaging lens according to embodiment 5 of the present application.

As shown in fig. 9, the optical imaging lens, in order from an object side to an image side along an optical axis, comprises: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a filter E6, and an image forming surface S13.

In the present embodiment, the total effective focal length f of the optical imaging lens is 3.80mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens E1 to the imaging surface S13 is 3.39mm, and the half ImgH of the diagonal line length of the effective pixel area on the imaging surface S13 is 4.40mm, and the maximum half field angle Semi-FOV of the optical imaging lens is 40.64 °.

Table 9 shows a basic parameter table of the optical imaging lens of embodiment 5, in which the units of the radius of curvature, the thickness/distance, and the focal length are all millimeters (mm).

TABLE 9

In embodiment 5, both the object-side surface and the image-side surface of any one of the first lens E1 to the fifth lens E5 are aspheric. Table 10 below shows the high-order coefficient A of each of the aspherical mirror surfaces S1-S10 used in example 5₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈And A₂₀。

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

1.4867E-02

5.8693E-02

-2.5151E-01

7.3403E-01

-1.1215E+00

6.1336E-01

4.7859E-01

-8.0411E-01

2.8820E-01

S2

-9.6509E-02

6.3115E-02

7.3555E-02

-3.2339E-01

8.0097E-01

-2.1110E+00

3.3856E+00

-2.7019E+00

8.4410E-01

S3

-8.9665E-02

1.5529E-01

8.0302E-01

-4.7287E+00

1.4057E+01

-2.5882E+01

2.9094E+01

-1.8052E+01

4.7500E+00

S4

-4.1796E-02

4.6841E-01

-2.6142E+00

1.6156E+01

-6.3386E+01

1.5181E+02

-2.1644E+02

1.6913E+02

-5.5530E+01

S5

-3.4015E-01

9.8323E-01

-9.2654E+00

5.2262E+01

-1.8566E+02

4.1350E+02

-5.6173E+02

4.2523E+02

-1.3743E+02

S6

-2.8390E-01

7.1577E-01

-4.5021E+00

1.7513E+01

-4.2309E+01

6.4855E+01

-6.1061E+01

3.1992E+01

-7.0758E+00

S7

-1.9550E-01

3.0071E-01

-9.2860E-01

2.1055E+00

-1.6646E+00

-3.7974E-01

1.2685E+00

-6.6705E-01

1.1565E-01

S8

-3.0274E-02

-3.5945E-02

3.6779E-01

-1.0006E+00

1.6487E+00

-1.4942E+00

7.3840E-01

-1.8865E-01

1.9599E-02

S9

-3.6533E-01

3.1382E-01

-1.8563E-01

7.8375E-02

-2.2139E-02

4.0465E-03

-4.5963E-04

2.9559E-05

-8.2431E-07

S10

-1.6082E-01

1.1183E-01

-5.4637E-02

1.7863E-02

-3.9090E-03

5.5340E-04

-4.7142E-05

2.1232E-06

-3.6839E-08

Watch 10

Fig. 10A shows an on-axis chromatic aberration curve of the optical imaging lens of embodiment 5, which represents the deviation of the convergent focal points of light rays of different wavelengths after passing through the lens. Fig. 10B shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the optical imaging lens of embodiment 5. Fig. 10C shows a distortion curve of the optical imaging lens of embodiment 5, which represents distortion magnitude values corresponding to different image heights. Fig. 10D shows a chromatic aberration of magnification curve of the optical imaging lens of embodiment 5, which represents a deviation of different image heights on the imaging surface after light passes through the lens. As can be seen from fig. 10A to 10D, the optical imaging lens according to embodiment 5 can achieve good imaging quality.

In summary, examples 1 to 5 satisfy the relationships shown in table 11, respectively.

TABLE 11

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. An optical imaging lens, in order from an object side to an image side along an optical axis, comprising:

a first lens having a refractive power, an image-side surface of which is concave;

a second lens element having a negative refractive power, the object-side surface of which is concave and the image-side surface of which is concave;

a third lens having a negative optical power;

the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; and

a fifth lens having an optical power,

wherein f/EPD is less than or equal to 2.08;

1.16 is less than or equal to T45/(T23+ T34) < 3; and

DT31/DT21≤0.90，

wherein f is the total effective focal length of the optical imaging lens; EPD is the entrance pupil diameter of the optical imaging lens; t23 is an air space on the optical axis between the second lens and the third lens; t34 is an air space on the optical axis between the third lens and the fourth lens; t45 is an air space on the optical axis between the fourth lens and the fifth lens; DT21 is the maximum effective half aperture of the object side surface of the second lens and DT31 is the maximum effective half aperture of the object side surface of the third lens.

2. The optical imaging lens of claim 1, wherein the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, and the total effective focal length f of the optical imaging lens satisfy:

-1.6＜(f1+f2)/f＜-1。

3. the optical imaging lens of claim 1, wherein the total effective focal length f of the optical imaging lens and the radius of curvature R2 of the image side surface of the first lens satisfy:

1＜R2/f＜3。

4. the optical imaging lens of claim 1, wherein the radius of curvature R7 of the object-side surface of the fourth lens, the radius of curvature R8 of the image-side surface of the fourth lens, and the effective focal length f4 of the fourth lens satisfy:

-1.1＜(R7+R8)/f4＜-0.5。

5. the optical imaging lens according to any one of claims 1 to 4, wherein a radius of curvature R3 of an object-side surface of the second lens and a radius of curvature R4 of an image-side surface of the second lens satisfy:

0＜(R3+R4)/(R3-R4)＜1.1。

6. the optical imaging lens according to any one of claims 1 to 4, wherein a center thickness CT1 of the first lens on the optical axis, a center thickness CT2 of the second lens on the optical axis, and a center thickness CT3 of the third lens on the optical axis satisfy:

1＜CT1/(CT2+CT3)＜1.5。

7. the optical imaging lens according to any one of claims 1 to 4, wherein an on-axis distance from an intersection point of an object-side surface of the fifth lens and the optical axis to an effective radius vertex of the object-side surface of the fifth lens, SAG51, and an intersection point of an image-side surface of the fifth lens and the optical axis to an effective radius vertex of the image-side surface of the fifth lens, SAG52 satisfies:

0.9＜SAG51/SAG52≤1.35。

8. the optical imaging lens according to any one of claims 1 to 4, wherein the maximum effective semi-aperture DT22 of the image side surface of the second lens and the maximum effective semi-aperture DT31 of the object side surface of the third lens satisfy:

DT22/DT31≤1。

9. the optical imaging lens according to any one of claims 1 to 4, wherein a center thickness CT3 of the third lens on the optical axis and a center thickness CT4 of the fourth lens on the optical axis satisfy:

0.3＜CT3/CT4＜0.5。

10. an optical imaging lens, in order from an object side to an image side along an optical axis, comprising:

a third lens having a negative optical power;

a fifth lens having an optical power,

wherein-1.6 < (f1+ f2)/f < -1;

1.16 is less than or equal to T45/(T23+ T34) < 3; and

DT31/DT21≤0.90，

wherein f1 is the effective focal length of the first lens; f2 is the effective focal length of the second lens; f is the total effective focal length of the optical imaging lens; t23 is an air space on the optical axis between the second lens and the third lens; t34 is an air space on the optical axis between the third lens and the fourth lens; t45 is the air space between the fourth lens and the fifth lens on the optical axis; DT21 is the maximum effective half aperture of the object side surface of the second lens and DT31 is the maximum effective half aperture of the object side surface of the third lens.