CN107436478B

CN107436478B - Optical imaging lens

Info

Publication number: CN107436478B
Application number: CN201710828050.2A
Authority: CN
Inventors: 贾远林
Original assignee: Zhejiang Sunny Optics Co Ltd
Current assignee: Zhejiang Sunny Optics Co Ltd
Priority date: 2017-09-14
Filing date: 2017-09-14
Publication date: 2022-09-16
Anticipated expiration: 2037-09-14
Also published as: CN107436478A

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, a second lens, a third lens, and a fourth lens. The first lens has negative focal power; the third lens has positive focal power; at least one of the second lens and the fourth lens has positive optical power; the central thickness CT2 of the second lens element on the optical axis and the central thickness CT4 of the fourth lens element on the optical axis satisfy CT2/CT4 < 0.5.

Description

Optical imaging lens

Technical Field

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

Background

With the improvement of performance and size reduction of a common photosensitive device such as a photosensitive coupling device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS), higher requirements are made on miniaturization, weight reduction, high imaging quality, and the like of a corresponding imaging lens.

The conventional imaging lens is usually configured with an f-number Fno (total effective focal length of the lens/entrance pupil diameter of the lens) of 2.0 or more than 2.0, so as to achieve good optical performance while achieving miniaturization. However, with the continuous development of portable electronic products such as smart phones, higher requirements are put forward on matched imaging lenses, and particularly, under the conditions of insufficient light (such as overcast and rainy days, dusk, and the like), shaking hands, and the like, the imaging lens with the f-number Fno of 2.0 or more than 2.0 cannot meet the higher-order imaging requirements. Particularly, in the field of infrared cameras, an imaging lens is also required to have high relative illumination while ensuring small size and large aperture so as to meet the requirements of applications such as detection and identification on the lens.

Disclosure of Invention

The present application provides a large aperture image pickup lens applicable to a portable electronic product, which can solve at least or partially at least one of the above-mentioned disadvantages in the related art.

In one aspect, the present application provides an optical imaging lens, in order from an object side to an image side along an optical axis, comprising: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens may have a negative optical power; the third lens may have a positive optical power; at least one of the second lens and the fourth lens may have positive optical power; the central thickness CT2 of the second lens element on the optical axis and the central thickness CT4 of the fourth lens element on the optical axis satisfy CT2/CT4 < 0.5.

In one embodiment, the image side surface of the first lens may be concave.

In one embodiment, the radius of curvature R2 of the image side surface of the first lens and the total effective focal length f of the optical imaging lens can satisfy 0.7 < R2/f < 1.3.

In one embodiment, the image-side surface of the third lens element can be convex, and the radius of curvature R2 of the image-side surface of the first lens element and the radius of curvature R6 of the image-side surface of the third lens element can satisfy-1 < R2/R6 < -0.5.

In one embodiment, the central thickness CT2 of the second lens on the optical axis and the edge thickness ET2 of the second lens satisfy 0.5 < CT2/ET2 < 1.

In one embodiment, the effective half aperture DT21 of the object side surface of the second lens and the effective half aperture DT32 of the image side surface of the third lens can satisfy 0.8 < DT21/DT32 < 1.4.

In one embodiment, the object side surface of the fourth lens may be convex.

In one embodiment, the effective half aperture DT42 of the image side surface of the fourth lens and the half length ImgH of the diagonal line of the effective pixel area on the imaging surface of the optical imaging lens can satisfy 0.7 < DT42/ImgH ≦ 1.0.

In one embodiment, a distance SAG41 on the optical axis between an intersection point of the object-side surface of the fourth lens and the optical axis to an effective semi-aperture vertex of the object-side surface of the fourth lens and a distance SAG42 on the optical axis between an intersection point of the image-side surface of the fourth lens and the optical axis to an effective semi-aperture vertex of the image-side surface of the fourth lens may satisfy 1.0 < SAG41/SAG42 < 1.5.

In one embodiment, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens may satisfy-1.2 < f1/f3 < -0.5.

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 may satisfy f/EPD < 1.6.

In one embodiment, the ImgH of half of the diagonal length of the effective pixel area on the imaging surface of the optical imaging lens and the total effective focal length f of the optical imaging lens can satisfy ImgH/f > 1.

In another aspect, the present application further provides an optical imaging lens, in order from an object side to an image side along an optical axis, comprising: a first lens, a second lens, a third lens, and a fourth lens. The first lens may have a negative optical power; the second lens may have optical power; the third lens can have positive focal power, and both the object-side surface and the image-side surface of the third lens can be convex surfaces; the fourth lens can have focal power, and the object side surface of the fourth lens can be a convex surface; the total effective focal length f of the optical imaging lens and the entrance pupil diameter EPD of the optical imaging lens can satisfy f/EPD < 1.6.

In another aspect, the present application further provides an optical imaging lens, in order from an object side to an image side along an optical axis, comprising: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens may have a negative optical power; the second lens may have optical power; the third lens may have a positive optical power; the fourth lens may have optical power; wherein, the central thickness CT2 of the second lens on the optical axis and the edge thickness ET2 of the second lens can satisfy 0.5 < CT2/ET2 < 1.

In another aspect, the present application further provides an optical imaging lens, in order from an object side to an image side along an optical axis, comprising: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens may have a negative optical power; the second lens may have optical power; the third lens may have a positive optical power; the fourth lens may have optical power; the effective half aperture DT42 of the image side surface of the fourth lens and half of the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging lens can meet the condition that DT42/ImgH is more than 0.7 and less than or equal to 1.0.

In another aspect, the present application further provides an optical imaging lens, in order from an object side to an image side along an optical axis, comprising: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens may have a negative optical power; the second lens may have optical power; the third lens may have a positive optical power; the fourth lens may have optical power; and the distance SAG41 on the optical axis between the intersection point of the object-side surface of the fourth lens and the optical axis and the effective semi-aperture vertex of the object-side surface of the fourth lens and the distance SAG42 on the optical axis between the intersection point of the image-side surface of the fourth lens and the optical axis and the effective semi-aperture vertex of the image-side surface of the fourth lens can meet the requirement that 1.0 < SAG41/SAG42 < 1.5.

Through reasonable configuration, the optical imaging lens has at least one beneficial effect of miniaturization, large aperture, large field angle, high relative illumination and the like while realizing good imaging quality.

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 chromatic aberration of magnification curve, and a relative illuminance 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 chromatic aberration of magnification curve, and a relative illuminance 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 astigmatism curve, a magnification chromatic aberration curve, and a relative illuminance curve of the optical imaging lens of embodiment 3, respectively;

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 astigmatic curve, a chromatic aberration of magnification curve, and a relative illuminance 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;

fig. 10A to 10D show an on-axis chromatic aberration curve, an astigmatism curve, a magnification chromatic aberration curve, and a relative illuminance curve of the optical imaging lens of embodiment 5, respectively;

fig. 11 is a schematic structural view showing an optical imaging lens according to embodiment 6 of the present application;

fig. 12A to 12D show an on-axis chromatic aberration curve, an astigmatic curve, a chromatic aberration of magnification curve, and a relative illuminance curve, respectively, of the optical imaging lens of embodiment 6.

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, 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 the list of listed features, that 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, in the present application, the embodiments and features of the embodiments 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 includes, for example, four lenses having optical power, i.e., a first lens, a second lens, a third lens, and a fourth lens. The four lenses are arranged in order from the object side to the image side along the optical axis. The optical imaging lens can further comprise a photosensitive element arranged on the imaging surface.

The first lens may have a negative optical power, and at least one of the object-side surface and the image-side surface thereof may be concave. In one embodiment, the image side surface of the first lens may be concave. The image side surface of the first lens is arranged to be concave, so that the first lens has larger negative focal power under the condition of ensuring better processing manufacturability, and the imaging system has the advantages of large field angle and high image quality.

The radius of curvature R2 of the image side surface of the first lens and the total effective focal length f of the optical imaging lens can satisfy 0.7 < R2/f < 1.3, and more specifically, R2 and f can further satisfy 0.85 < R2/f < 1.11. The condition that R2/f is more than 0.7 and less than 1.3 is met, the wide-angle characteristic of an imaging system can be realized, the first lens is ensured to have larger negative focal power, and meanwhile, the first lens is further ensured to have better processing manufacturability.

The second lens may have a positive or negative power, and at least one of the object-side surface and the image-side surface thereof may be convex. In one embodiment, the object side surface of the second lens can be convex.

The central thickness CT2 of the second lens on the optical axis and the edge thickness ET2 of the second lens can satisfy 0.5 < CT2/ET2 < 1, and more specifically, CT2 and ET2 can further satisfy 0.57 < CT2/ET2 < 0.98. The condition formula of 0.5 < CT2/ET2 < 1 is satisfied, the processing manufacturability of the second lens is favorably ensured, and the processing precision of the second lens is improved.

The third lens may have a negative optical power. The effective focal length f1 of the first lens and the effective focal length f3 of the third lens can satisfy-1.2 < f1/f3 < -0.5, more specifically, f1 and f3 can further satisfy-1.14 < f1/f3 < 0.73. Satisfying the conditional expression-1.2 < f1/f3 < -0.5, the first lens and the third lens have opposite signs and approximately equivalent powers, and a reverse telephoto optical structure consisting of a front negative lens group and a rear positive lens group is formed. Such a configuration is advantageous for enlarging the field of view of the imaging system and improving the imaging quality.

The object-side surface of the third lens element can be convex, and the image-side surface can be convex. The curvature radius R2 of the image side surface of the first lens and the curvature radius R6 of the image side surface of the third lens can satisfy-1 < R2/R6 < -0.5, more specifically, R2 and R6 can further satisfy-0.90 < R2/R6 < 0.51. The image side surface of the first lens and the image side surface of the third lens have curvature radii with opposite signs and approximately equivalent sizes, which can be beneficial to the compensation of aberration and the improvement of imaging quality.

The effective half caliber DT21 of the object side surface of the second lens and the effective half caliber DT32 of the image side surface of the third lens can satisfy 0.8 < DT21/DT32 < 1.4, and more specifically, DT21 and DT32 further satisfy 0.82 < DT21/DT32 < 1.30. The object side surface of the second lens and the image side surface of the third lens have effective half apertures with the same size, so that the assembly of an imaging system is facilitated, and the assembly precision is improved; at the same time, such an arrangement is also advantageous for improving the imaging quality of the imaging system.

The fourth lens has positive power or negative power. Alternatively, the fourth lens may have a positive optical power.

At least one of the object-side surface and the image-side surface of the fourth lens may be convex. In one embodiment, the object side surface of the fourth lens may be convex. The object side surface of the fourth lens is arranged to be a convex surface, so that the chief ray of the imaging system is favorably ensured to have a smaller incident angle when being incident to the imaging surface, and the relative illumination of the imaging surface is favorably improved.

The central thickness CT2 of the second lens on the optical axis and the central thickness CT4 of the fourth lens on the optical axis can satisfy CT2/CT4 < 0.5, more specifically, CT2 and CT4 can further satisfy 0.10 ≦ CT2/CT4 ≦ 0.44. The central thicknesses of the second lens and the fourth lens are reasonably distributed, so that each lens has better manufacturability on the premise of ensuring the imaging quality of the lens.

The distance SAG41 on the optical axis between the intersection point of the object side surface of the fourth lens and the optical axis and the effective semi-caliber vertex of the object side surface of the fourth lens and the distance SAG42 on the optical axis between the intersection point of the image side surface of the fourth lens and the optical axis and the effective semi-caliber vertex of the image side surface of the fourth lens can satisfy 1.0 < SAG41/SAG42 < 1.5, more specifically, SAG41 and SAG42 can further satisfy 1.10 < SAG41/SAG42 < 1.44. The condition 1 < SAG41/SAG42 < 1.5 is satisfied, which is beneficial to enabling the imaging system to have smaller chief ray angle and higher relative illumination. In addition, the reasonable configuration of SAG41 and SAG42 is also beneficial to the fourth lens to have better processability.

The effective half aperture DT42 of the image side surface of the fourth lens and the half of the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging lens can satisfy 0.7 < DT42/ImgH < 1.0, and more specifically, DT42 and ImgH further satisfy 0.73 < DT42/ImgH < 0.95. The conditional expression that DT42/ImgH is more than 0.7 and less than or equal to 1.0 is satisfied, the effective half aperture of the fourth lens is approximately equal to half of the diagonal length of the effective pixel area on the imaging surface, the chief ray angle of the imaging system is ensured to have a smaller angle when the chief ray angle enters the imaging surface, and the relative illumination of the imaging system is improved.

f/EPD < 1.6 can be satisfied between the total effective focal length f of the optical imaging lens and the entrance pupil diameter EPD of the optical imaging lens, and more specifically, f and EPD further satisfy 1.19 ≦ f/EPD ≦ 1.48. The condition f/EPD is less than 1.6, the image surface energy density on an imaging surface can be effectively improved, and the signal-to-noise ratio of the output signal of the image sensor is further improved, namely, the precision of measuring depth is improved.

The ImgH/f between half of the diagonal length of the effective pixel area on the imaging surface of the optical imaging lens and the total effective focal length f of the optical imaging lens can be more than 1, and more specifically, the ImgH and f can further satisfy the condition that the ImgH/f is more than or equal to 1.34 and less than or equal to 1.91. The condition formula ImgH/f is more than 1, the imaging system can be ensured to have a larger field angle, and the wide-angle characteristic of the lens is realized.

Optionally, the optical imaging lens may further include at least one diaphragm to improve imaging quality. The diaphragm may be disposed at any position as needed, for example, the diaphragm may be disposed between the second lens and the third lens.

Optionally, the optical imaging lens may further include an optical filter and/or a protective glass.

The optical imaging lens according to the above-described embodiment of the present application may employ a plurality of lenses, for example, four 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 volume of the lens can be effectively reduced, the sensitivity of the lens is reduced, and the machinability of the lens is improved, so that the lens is more beneficial to production and processing and can be suitable for portable electronic products. Meanwhile, the optical imaging lens with the configuration has the beneficial effects of large aperture, large field angle, high imaging quality and the like, and can be well applied to the fields of infrared detection, identification and the like.

In the embodiment of the present application, at least one of the mirror surfaces of each lens is an aspherical 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 a better curvature radius characteristic, and has advantages of improving distortion aberration and improving astigmatism aberration. After the aspheric lens is adopted, the aberration generated during imaging can be eliminated as much as possible, thereby improving the imaging quality.

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 four lenses are exemplified in the embodiment, the optical imaging lens is not limited to include four 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 shows a schematic structural diagram of an optical imaging lens according to embodiment 1 of the present application.

As shown in fig. 1, the optical imaging lens includes, in order from an object side to an imaging side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and an imaging surface S11. The optical imaging lens may further include a photosensitive element disposed on the imaging surface S11.

The first lens element L1 has negative power, the object-side surface S1 is convex, the image-side surface S2 is concave, and both the object-side surface S1 and the image-side surface S2 of the first lens element L1 are aspheric.

The second lens L2 has positive power, the object-side surface S3 is convex, the image-side surface S4 is concave, and both the object-side surface S3 and the image-side surface S4 of the second lens L2 are aspheric.

The third lens element L3 has positive power, and has a convex object-side surface S5 and a convex image-side surface S6, and both the object-side surface S5 and the image-side surface S6 of the third lens element L3 are aspheric.

The fourth lens element L4 has positive power, and has a convex object-side surface S7 and a concave image-side surface S8, and the object-side surface S7 and the image-side surface S8 of the fourth lens element L4 are aspheric.

Optionally, the optical imaging lens may further include a filter L5 having an object side S9 and an image side S10. The light from the object sequentially passes through the respective surfaces S1 to S10 and is finally imaged on the imaging surface S11.

Alternatively, a stop STO may be provided between the second lens L2 and the third lens L3 to improve the imaging quality.

Table 1 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the optical imaging lens of example 1, wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

TABLE 1

As can be seen from table 1, the radius of curvature R2 of the image-side surface S2 of the first lens L1 and the radius of curvature R6 of the image-side surface S6 of the third lens L3 satisfy the relationship of-0.63 for R2/R6; the central thickness CT2 of the second lens L2 on the optical axis and the central thickness CT4 of the fourth lens on the optical axis satisfy CT2/CT4 being 0.25.

In embodiment 1, each lens may be an aspherical lens, and each aspherical surface type x is defined by the following 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 the conic coefficient (given in table 1); ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 below gives the coefficients A of the higher-order terms that can be used for the aspherical mirrors S1-S8 in example 1 ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ And A ₁₆ 。

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

2.3881E-02

-1.0376E-02

2.3068E-03

-3.0035E-04

2.3028E-05

-9.5925E-07

1.6728E-08

S2

5.5580E-02

6.7232E-02

-1.5390E-01

1.2259E-01

-5.3244E-02

1.1872E-02

-1.0351E-03

S3

-6.0199E-02

1.2438E-02

-3.6378E-02

7.0939E-02

-4.7642E-02

1.4781E-02

-1.8372E-03

S4

-5.5698E-02

2.4854E-01

-9.5137E-01

2.3584E+00

-3.0815E+00

2.0701E+00

-5.3969E-01

S5

-6.3203E-02

7.6266E-02

-1.4136E-01

1.5507E-01

-9.9525E-02

3.7971E-02

-6.5824E-03

S6

-6.0869E-02

1.8807E-02

-2.3483E-02

1.1263E-02

2.4715E-03

-4.6087E-03

1.2545E-03

S7

-3.8045E-02

1.5354E-02

-1.1502E-02

4.6124E-03

-1.0751E-03

1.2745E-04

-5.5876E-06

S8

9.2110E-02

-5.0657E-02

2.3420E-02

-8.2491E-03

1.8216E-03

-2.2155E-04

1.1284E-05

TABLE 2

Table 3 below gives the total effective focal length f of the optical imaging lens, the effective focal lengths f1 to f4 of the respective lenses, half ImgH of the diagonal length of the effective pixel region on the imaging plane S11, and the maximum half field angle HFOV in embodiment 1.

TABLE 3

As can be seen from tables 1 and 3, f1/f3 ═ 0.86 is satisfied between the effective focal length f1 of the first lens L1 and the effective focal length f3 of the third lens L3; the ImgH/f between half of the diagonal length of the effective pixel area on the imaging surface S11 and the total effective focal length f of the optical imaging lens is 1.79; the radius of curvature R2 of the image side S2 of the first lens L1 and the total effective focal length f of the optical imaging lens satisfy the relationship of R2/f equal to 0.85.

In embodiment 1, f/EPD of 1.37 is satisfied between the total effective focal length f of the optical imaging lens and the entrance pupil diameter EPD of the optical imaging lens; the central thickness CT2 of the second lens L2 on the optical axis and the edge thickness ET2 of the second lens L2 satisfy CT2/ET2 of 0.79; the effective half-aperture DT21 of the object side S3 of the second lens L2 and the effective half-aperture DT32 of the image side S6 of the third lens L3 meet the requirement that DT21/DT32 is 0.98; the effective half-aperture DT42 of the image side surface S8 of the fourth lens L4 and the half ImgH of the diagonal length of the effective pixel region on the image plane S11 satisfy that DT42/ImgH is 0.91; an on-axis distance SAG41 from an intersection point of an object side surface S7 of the fourth lens L4 and the optical axis to an effective semi-aperture vertex of an object side surface S7 of the fourth lens L4 and an on-axis distance SAG42 from an intersection point of an image side surface S8 of the fourth lens L4 and the optical axis to an effective semi-aperture vertex of an image side surface S8 of the fourth lens L4 satisfy SAG41/SAG42 as 1.44.

In embodiment 1, the maximum half field angle HFOV of the optical imaging lens is 80.1 °, and has a wide-angle characteristic.

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 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. Fig. 2D shows a relative illuminance curve of the optical imaging lens of embodiment 1, which represents relative illuminance corresponding to different angles of view. 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. In this embodiment and the following embodiments, a description 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 imaging lens according to embodiment 2 of the present application.

As shown in fig. 3, the optical imaging 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, and an image plane S11. The optical imaging lens may further include a photosensitive element disposed on the imaging surface S11.

The second lens L2 has positive power, the object-side surface S3 is convex, the image-side surface S4 is convex, and both the object-side surface S3 and the image-side surface S4 of the second lens L2 are aspheric.

Table 4 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the optical imaging lens of example 2, wherein the unit of the radius of curvature and the thickness are both millimeters (mm). Table 5 shows high-order term coefficients that can be used for each aspherical mirror surface in example 2, wherein each aspherical mirror surface type can be defined by formula (1) given in example 1 above. Table 6 shows the total effective focal length f of the optical imaging lens, the effective focal lengths f1 to f4 of the respective lenses, half the diagonal length ImgH of the effective pixel region on the imaging plane S11, and the maximum half field angle HFOV in embodiment 2.

TABLE 4

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

2.7776E-02

-9.4783E-03

1.7128E-03

-1.8409E-04

1.1936E-05

-4.2886E-07

6.5065E-09

S2

6.6834E-02

-2.4077E-02

-1.1094E-02

9.6166E-03

-3.3734E-03

7.4245E-04

-7.1898E-05

S3

-1.9620E-02

-3.7381E-02

7.3131E-02

-6.1671E-02

2.9243E-02

-7.1735E-03

6.9348E-04

S4

-5.9313E-02

3.8040E-01

-1.7185E+00

4.4836E+00

-6.4092E+00

4.7316E+00

-1.4060E+00

S5

-6.5877E-02

6.9202E-02

-1.7761E-01

2.6497E-01

-2.3735E-01

1.1387E-01

-2.3129E-02

S6

-7.7150E-02

3.9368E-02

-1.3219E-02

4.0253E-04

1.5308E-03

-5.5756E-04

6.4620E-05

S7

-7.9211E-02

3.8506E-02

-2.2380E-02

8.3239E-03

-1.9424E-03

2.5064E-04

-1.3752E-05

S8

8.8430E-02

-5.8249E-02

2.5311E-02

-8.0056E-03

1.5952E-03

-1.7339E-04

7.7465E-06

TABLE 5

TABLE 6

Fig. 4A shows on-axis chromatic aberration curves of the optical imaging lens of embodiment 2, which represent 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 chromatic aberration of magnification curve of the optical imaging lens of embodiment 2, which represents a deviation of different image heights on the imaging plane after light passes through the lens. Fig. 4D shows a relative illuminance curve of the optical imaging lens of embodiment 2, which represents relative illuminance corresponding to different angles of view. 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 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, and an image plane S11. The optical imaging lens may further include a photosensitive element disposed on the imaging surface S11.

The first lens element L1 has negative power, the object-side surface S1 is concave, the image-side surface S2 is concave, and both the object-side surface S1 and the image-side surface S2 of the first lens element L1 are aspheric.

The third lens L3 has positive power, the object-side surface S5 is convex, the image-side surface S6 is convex, and both the object-side surface S5 and the image-side surface S6 of the third lens L3 are aspheric.

Optionally, the optical imaging lens may further include a filter L5 having an object-side surface S9 and an image-side surface S10. The light from the object sequentially passes through the respective surfaces S1 to S10 and is finally imaged on the imaging surface S11.

Table 7 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the optical imaging lens of example 3, wherein the unit of the radius of curvature and the thickness are both millimeters (mm). Table 8 shows high-order term coefficients that can be used for each aspherical mirror surface in example 3, wherein each aspherical mirror surface type can be defined by formula (1) given in example 1 above. Table 9 shows the total effective focal length f of the optical imaging lens, the effective focal lengths f1 to f4 of the respective lenses, half ImgH of the diagonal length of the effective pixel region on the imaging plane S11, and the maximum half field angle HFOV in embodiment 3.

TABLE 7

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

7.8114E-03

-8.7117E-04

7.7884E-05

-4.6945E-06

1.6850E-07

-3.2499E-09

2.6435E-11

S2

7.9625E-02

-2.7186E-02

7.6673E-03

-1.4753E-03

1.8897E-04

-1.8010E-05

9.2952E-07

S3

1.6752E-03

-4.9169E-02

4.3065E-02

-2.0018E-02

5.8328E-03

-9.4966E-04

6.3067E-05

S4

9.2638E-02

-2.2513E-01

3.9866E-01

-4.1070E-01

2.5288E-01

-8.4070E-02

1.1798E-02

S5

9.0718E-03

-3.3073E-02

7.5884E-02

-1.0921E-01

8.2668E-02

-3.1478E-02

4.7208E-03

S6

4.8323E-02

-7.3135E-02

6.9179E-02

-4.2669E-02

1.6199E-02

-3.4309E-03

3.0463E-04

S7

4.6008E-02

-3.1320E-02

1.6428E-02

-5.7079E-03

1.2064E-03

-1.4127E-04

6.9419E-06

S8

3.1256E-02

-1.0354E-02

2.9840E-03

-1.0454E-03

2.5780E-04

-3.6544E-05

2.1305E-06

TABLE 8

TABLE 9

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 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. Fig. 6D shows a relative illuminance curve of the optical imaging lens of embodiment 3, which represents relative illuminance corresponding to different angles of view. 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 includes, in order from the object side to the imaging side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and an imaging surface S11. The optical imaging lens may further include a photosensitive element disposed on the imaging surface S11.

The second lens element L2 has negative power, the object-side surface S3 is convex, the image-side surface S4 is concave, and the object-side surface S3 and the image-side surface S4 of the second lens element L2 are aspheric.

The fourth lens element L4 has positive power, and has a convex object-side surface S7 and a convex image-side surface S8, and the object-side surface S7 and the image-side surface S8 of the fourth lens element L4 are aspheric.

Table 10 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the optical imaging lens of example 4, wherein the unit of the radius of curvature and the thickness are both millimeters (mm). Table 11 shows high-order term coefficients that can be used for each aspherical mirror surface in embodiment 4, wherein each aspherical mirror surface type can be defined by the formula (1) given in embodiment 1 above. Table 12 shows the total effective focal length f of the optical imaging lens, the effective focal lengths f1 to f4 of the respective lenses, half the diagonal length ImgH of the effective pixel region on the imaging plane S11, and the maximum half field angle HFOV in embodiment 4.

Watch 10

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

2.1333E-03

8.7601E-04

-3.0458E-04

5.2519E-05

-5.0687E-06

2.5785E-07

-5.3999E-09

S2

4.7766E-02

-6.9272E-02

1.1528E-01

-9.4857E-02

4.2403E-02

-9.4150E-03

7.9327E-04

S3

-7.5276E-02

2.8128E-02

-2.3937E-02

3.6464E-02

-2.9086E-02

1.1107E-02

-1.6234E-03

S4

-5.9739E-02

1.0183E-01

-2.3753E-01

4.1965E-01

-4.0250E-01

1.9828E-01

-3.9125E-02

S5

-9.1203E-03

1.0113E-02

-1.1411E-02

6.1062E-03

-1.6721E-03

2.7059E-04

-2.4307E-05

S6

9.3936E-03

-3.4242E-03

-4.6735E-03

5.8714E-03

-3.1370E-03

7.9506E-04

-7.4892E-05

S7

1.4023E-02

-9.9200E-03

4.4130E-03

-1.5485E-03

3.3519E-04

-3.9104E-05

1.8133E-06

S8

2.4576E-02

4.1503E-04

-1.7959E-03

1.0955E-03

-3.8345E-04

6.2629E-05

-3.8958E-06

TABLE 11

TABLE 12

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 chromatic aberration of magnification curve of the optical imaging lens of embodiment 4, which represents a deviation of different image heights on the imaging plane after light passes through the lens. Fig. 8D shows a relative illuminance curve of the optical imaging lens of embodiment 4, which represents the relative illuminance corresponding to different angles of view. 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 includes, in order from the object side to the imaging side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and an imaging surface S11. The optical imaging lens may further include a photosensitive element disposed on the imaging surface S11.

Table 13 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the optical imaging lens of example 5, wherein the unit of the radius of curvature and the thickness are both millimeters (mm). Table 14 shows high-order term coefficients that can be used for each aspherical mirror surface in example 5, wherein each aspherical mirror surface type can be defined by formula (1) given in example 1 above. Table 15 shows the total effective focal length f of the optical imaging lens, the effective focal lengths f1 to f4 of the respective lenses, half ImgH of the diagonal length of the effective pixel region on the imaging plane S11, and the maximum half field angle HFOV in embodiment 5.

Watch 13

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

4.5400E-03

-5.3624E-04

-1.4910E-05

1.7887E-05

-2.5896E-06

1.5808E-07

-3.6392E-09

S2

4.4641E-02

-3.2483E-02

5.6725E-02

-4.9217E-02

2.3141E-02

-5.3211E-03

4.5733E-04

S3

-3.2870E-02

-9.5164E-03

4.7532E-02

-6.8414E-02

4.8439E-02

-1.6496E-02

2.1575E-03

S4

-3.1480E-02

1.4375E-01

-3.7668E-01

6.5893E-01

-6.6403E-01

3.5847E-01

-7.8597E-02

S5

-1.2423E-02

4.0228E-03

-8.0603E-04

-4.3021E-03

4.1936E-03

-1.4591E-03

1.7929E-04

S6

8.3009E-03

-5.1026E-03

8.2095E-04

1.1760E-04

-1.2137E-04

1.6078E-05

8.7169E-07

S7

5.2285E-03

-2.0828E-03

-1.4501E-03

1.0758E-03

-3.3693E-04

4.9948E-05

-2.8871E-06

S8

1.5788E-02

2.8522E-03

-2.9971E-03

1.5274E-03

-4.8658E-04

7.6796E-05

-4.6875E-06

TABLE 14

Watch 15

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 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. Fig. 10D shows a relative illuminance curve of the optical imaging lens of example 5, which represents relative illuminance corresponding to different angles of view. As can be seen from fig. 10A to 10D, the optical imaging lens according to embodiment 5 can achieve good imaging quality.

Example 6

An optical imaging lens according to embodiment 6 of the present application is described below with reference to fig. 11 to 12D. Fig. 11 shows a schematic structural view of an optical imaging lens according to embodiment 6 of the present application.

As shown in fig. 11, the optical imaging lens includes, in order from the object side to the imaging side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and an imaging surface S11. The optical imaging lens may further include a photosensitive element disposed on the imaging surface S11.

Table 16 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the optical imaging lens of example 6, wherein the unit of the radius of curvature and the thickness are both millimeters (mm). Table 17 shows high-order term coefficients that can be used for each aspherical mirror surface in example 6, wherein each aspherical mirror surface type can be defined by formula (1) given in example 1 above. Table 18 shows the total effective focal length f of the optical imaging lens, the effective focal lengths f1 to f4 of the respective lenses, half the diagonal length ImgH of the effective pixel region on the imaging plane S11, and the maximum half field angle HFOV in embodiment 6.

TABLE 16

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

2.3757E-02

-7.2283E-03

1.3820E-03

-1.6669E-04

1.2338E-05

-5.0722E-07

8.8125E-09

S2

2.5422E-02

8.7594E-02

-1.6320E-01

1.4784E-01

-7.5523E-02

2.0181E-02

-2.1608E-03

S3

-3.7117E-02

1.1130E-02

-6.4491E-02

1.2129E-01

-1.0089E-01

4.1578E-02

-6.8791E-03

S4

-2.9738E-02

-5.3272E-02

6.4035E-01

-2.1272E+00

3.5357E+00

-2.8668E+00

9.1160E-01

S5

-5.5391E-02

2.8572E-02

-3.5312E-02

2.7512E-02

-1.2867E-02

4.4917E-03

-7.8006E-04

S6

-1.0383E-01

3.3561E-02

2.4952E-02

-5.5329E-02

3.9310E-02

-1.3183E-02

1.7516E-03

S7

-9.9204E-02

4.8038E-02

-2.6240E-02

9.0335E-03

-1.9715E-03

2.4638E-04

-1.3575E-05

S8

5.0984E-02

-1.9611E-02

4.8247E-03

-1.4225E-03

3.4463E-04

-4.6596E-05

2.5287E-06

TABLE 17

Watch 18

Fig. 12A shows an on-axis chromatic aberration curve of the optical imaging lens of embodiment 6, which represents the deviation of the convergent focal points of light rays of different wavelengths after passing through the lens. Fig. 12B shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the optical imaging lens of embodiment 6. Fig. 12C shows a chromatic aberration of magnification curve of the optical imaging lens of embodiment 6, which represents deviation of different image heights on the imaging surface after light passes through the lens. Fig. 12D shows a relative illuminance curve of the optical imaging lens of example 6, which represents relative illuminance corresponding to different angles of view. As can be seen from fig. 12A to 12D, the optical imaging lens according to embodiment 6 can achieve good imaging quality.

In summary, examples 1 to 6 each satisfy the relationship shown in table 19 below.

Conditional formula (I)	1	2	3	4	5	6
							f/EPD	1.37	1.28	1.19	1.38	1.38	1.48
f1/f3	-0.86	-0.92	-1.05	-0.97	-1.14	-0.73
							ImgH/f	1.79	1.71	1.91	1.54	1.34	1.62
R2/R6	-0.63	-0.55	-0.87	-0.82	-0.90	-0.51
							R2/f	0.85	1.06	1.11	0.94	0.94	0.98
CT2/CT4	0.25	0.44	0.37	0.10	0.30	0.38
							CT2/ET2	0.79	0.96	0.98	0.57	0.79	0.97
DT21/DT32	0.98	0.87	1.30	0.87	0.83	0.82
							DT42/ImgH	0.91	0.95	0.73	0.90	0.90	0.95
SAG41/SAG42	1.44	1.18	1.10	1.43	1.20	1.27

Watch 19

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, a tablet computer, or the like. The imaging device is equipped with the imaging lens described above.

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 imaging lens sequentially comprises from an object side to an image side along an optical axis: a first lens, a second lens, a third lens, and a fourth lens, the number of lenses having power in the optical imaging lens being four,

the first lens has a negative focal power;

the second lens has optical power;

the third lens has positive optical power;

the fourth lens has positive optical power;

a central thickness CT2 of the second lens on the optical axis and a central thickness CT4 of the fourth lens on the optical axis satisfy CT2/CT4 < 0.5, an

1.0＜SAG41/SAG42＜1.5，

SAG41 is the distance between the intersection point of the object side surface of the fourth lens and the optical axis and the effective semi-aperture vertex of the object side surface of the fourth lens on the optical axis; and

SAG42 is the distance on the optical axis between the intersection point of the image side surface of the fourth lens and the optical axis and the effective semi-aperture vertex of the image side surface of the fourth lens.

2. The optical imaging lens of claim 1, wherein the image side surface of the first lens is concave.

3. The optical imaging lens of claim 2, wherein the radius of curvature R2 of the image side surface of the first lens and the total effective focal length f of the optical imaging lens satisfy 0.7 < R2/f < 1.3.

4. The optical imaging lens of claim 2, wherein the image-side surface of the third lens element is convex, and the radius of curvature R2 of the image-side surface of the first lens element and the radius of curvature R6 of the image-side surface of the third lens element satisfy-1 < R2/R6 < -0.5.

5. The optical imaging lens of claim 1, wherein a central thickness CT2 of the second lens on the optical axis and an edge thickness ET2 of the second lens satisfy 0.5 < CT2/ET2 < 1.

6. The optical imaging lens of claim 1, wherein the effective half aperture DT21 of the object side surface of the second lens and the effective half aperture DT32 of the image side surface of the third lens satisfy 0.8 < DT21/DT32 < 1.4.

7. The optical imaging lens of claim 2, wherein the object side surface of the fourth lens is convex.

8. The optical imaging lens of claim 7, wherein the effective half aperture DT42 of the image side surface of the fourth lens and the half of the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging lens satisfy 0.7 < DT42/ImgH ≦ 1.0.

9. The optical imaging lens according to any one of claims 1 to 4, characterized in that the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy-1.2 < f1/f3 < -0.5.

10. The optical imaging lens of any one of claims 1 to 8, 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 < 1.6.

11. The optical imaging lens according to any one of claims 1 to 8, wherein ImgH > 1 is satisfied by half the diagonal length ImgH of an effective pixel area on an imaging surface of the optical imaging lens and a total effective focal length f of the optical imaging lens.

12. The optical imaging lens sequentially comprises from an object side to an image side along an optical axis: a first lens, a second lens, a third lens, and a fourth lens, the number of lenses having power in the optical imaging lens being four,

the first lens has a negative optical power;

the second lens has optical power;

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

the fourth lens has positive focal power, and the object side surface of the fourth lens is a convex surface;

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 < 1.6, an

1.0＜SAG41/SAG42＜1.5，

13. The optical imaging lens of claim 12, wherein the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy-1.2 < f1/f3 < -0.5.

14. The optical imaging lens of claim 12, wherein the image side surface of the first lens is concave, and the radius of curvature of the image side surface R2 and the total effective focal length f of the optical imaging lens satisfy 0.7 < R2/f < 1.3.

15. The optical imaging lens of claim 12, wherein the radius of curvature R2 of the image-side surface of the first lens and the radius of curvature R6 of the image-side surface of the third lens satisfy-1 < R2/R6 < -0.5.

16. The optical imaging lens of claim 15, wherein the image side surface of the first lens is concave.

17. The optical imaging lens according to any one of claims 12 to 16, wherein ImgH > 1 is satisfied by half the diagonal length ImgH of an effective pixel area on an imaging surface of the optical imaging lens and a total effective focal length f of the optical imaging lens.

18. The optical imaging lens of claim 17, wherein a center thickness CT2 of the second lens on the optical axis and an edge thickness ET2 of the second lens satisfy 0.5 < CT2/ET2 < 1.

19. The optical imaging lens of claim 18, wherein a central thickness CT2 of the second lens element on the optical axis and a central thickness CT4 of the fourth lens element on the optical axis satisfy CT2/CT4 < 0.5.

20. The optical imaging lens of claim 17, wherein the effective half aperture DT21 of the object side surface of the second lens and the effective half aperture DT32 of the image side surface of the third lens satisfy 0.8 < DT21/DT32 < 1.4.

21. The optical imaging lens of claim 17, wherein the effective half aperture DT42 of the image side surface of the fourth lens element and the half ImgH of the diagonal length of the effective pixel area on the imaging surface of the optical imaging lens satisfy 0.7 < DT42/ImgH ≦ 1.0.