CN113467057A

CN113467057A - Optical imaging system

Info

Publication number: CN113467057A
Application number: CN202110906585.3A
Authority: CN
Inventors: 龚停停; 宋立通; 戴付建; 赵烈烽
Original assignee: Zhejiang Sunny Optics Co Ltd
Current assignee: Zhejiang Sunny Optics Co Ltd
Priority date: 2021-08-09
Filing date: 2021-08-09
Publication date: 2021-10-01

Abstract

The invention discloses an optical imaging system, which sequentially comprises the following components from an object side to an image side along an optical axis: a first lens having positive refractive power, a convex object side surface and a concave image side surface; a second lens having an optical power; a third lens having positive refractive power, a concave object side surface, and a convex image side surface; a fourth lens; the on-axis distance TTL from the object side surface of the first lens to the imaging surface and the distance BFL from the image side surface of the last lens of the optical imaging system to the imaging surface on the optical axis satisfy the following conditions: TTL/BFL < 2.5; the value CT2 at which the center thickness is the smallest among all the lenses is the center thickness of the second lens on the optical axis. The reasonable matching of focal power and surface curvature among the lenses can effectively balance various aberrations of the system and ensure the requirement of high imaging quality of the system. The system can be ensured to have the characteristic of ultra-thinness by controlling the ratio of the distance from the object side surface of the first lens to the image side surface of the last lens to the imaging surface on the optical axis.

Description

Optical imaging system

Technical Field

The invention belongs to the field of optical imaging, and particularly relates to an optical imaging system comprising four lenses.

Background

Along with the development of science and technology, the miniaturization trend of portable electronic products is more and more obvious, the functions of equipment such as cell-phone, notebook computer, intelligence dress are more integrated and perfect, the corresponding higher requirement of having proposed to the imaging lens who carries on, and common imaging lens is for satisfying the demand of high imaging quality, hi-lite etc. can obtain more regulation spaces through increasing lens figure, increase system overall length etc. usually, hardly compromise characteristics such as ultra-thin, high quality, light, low price simultaneously.

In order to solve the problems, the invention aims to design an ultrathin, small-distortion and high-definition 4-piece imaging lens.

Disclosure of Invention

The invention aims to provide an optical imaging system consisting of four lenses, which has the characteristics of effectively balancing various aberrations of the system and ensuring the requirement of high imaging quality of the system.

The present invention provides an optical imaging system, in order from an object side to an image side along an optical axis, comprising:

a first lens having positive refractive power, a convex object side surface and a concave image side surface;

a second lens having an optical power;

a third lens having positive refractive power, a concave object side surface, and a convex image side surface;

a fourth lens;

the on-axis distance TTL from the object side surface of the first lens to the imaging surface and the distance BFL from the image side surface of the last lens of the optical imaging system to the imaging surface on the optical axis satisfy the following conditions: TTL/BFL < 2.5; the value CT2 at which the center thickness is the smallest among all the lenses is the center thickness of the second lens on the optical axis.

According to one embodiment of the invention, the maximum effective radius DT11 of the object-side surface of the first lens and the maximum effective radius DT21 of the object-side surface of the second lens satisfy: DT11/DT21< 1.0.

According to one embodiment of the invention, the effective focal length F, the relative F-number Fno of the optical imaging system and half of the maximum field angle Semi-FOV of the optical imaging system satisfy: 3.3mm ≦ f × tan (Semi-FOV). times.Fno ≦ 4.5 mm.

According to an embodiment of the present invention, a central thickness CT1 of the first lens on the optical axis, a central thickness CT2 of the second lens on the optical axis, a central thickness CT3 of the third lens on the optical axis, an air interval T12 of the first lens and the second lens on the optical axis, and an air interval T34 of the third lens and the fourth lens on the optical axis satisfy: 1.4 ≦ (CT1+ CT2+ T12)/(CT3+ T34) ≦ 2.1.

According to one embodiment of the present invention, the effective focal length f of the optical imaging system, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: l (f3-f1)/f | ≦ 3.0.

According to one embodiment of the invention, the effective focal length f1 of the first lens and the combined focal length f234 of the second, third and fourth lenses satisfy: 1.5 ≦ f234/f1 ≦ 3.5.

According to one embodiment of the present invention, the radius of curvature R5 of the object-side surface of the third lens, the radius of curvature R6 of the image-side surface of the third lens, the radius of curvature R7 of the object-side surface of the fourth lens, and the radius of curvature R8 of the image-side surface of the fourth lens satisfy: 1.0 ≦ R6 × R8|/| R5 × R7| ≦ 2.0.

According to an embodiment of the present invention, a sum Σ AT of air intervals on the optical axis between any adjacent two lenses having optical powers of the first lens to the closest imaging surface lens and a sum Σ CT of center thicknesses on the optical axis of all the lenses satisfy: 2.0 ≦ Σ CT/Σ AT ≦ 4.0.

According to an embodiment of the present invention, an on-axis distance between the object-side surface of the first lens element and the image-side surface of the second last lens element, wherein the on-axis distance between the object-side surface of the first lens element and the image plane, TTL, satisfies: 2.0 ≦ TTL/InTL ≦ 2.5.

According to one embodiment of the present invention, an on-axis distance SAG41 between an intersection point of the fourth lens object-side surface and the optical axis and an effective radius vertex of the fourth lens object-side surface, and an on-axis distance SAG32 between an intersection point of the third lens image-side surface and the optical axis and an effective radius vertex of the third lens image-side surface satisfy: 1.0 ≦ (SAG32+ SAG41)/(SAG32-SAG41) ≦ 4.5.

According to an embodiment of the present invention, an edge thickness maximum value ETmax of the first to fourth lenses and an edge thickness ET1 of the first lens satisfy: 1.0 ≦ ETmax/ET1 ≦ 1.8.

According to one embodiment of the present invention, the effective focal length f of the optical imaging system and the combined focal length f234 of the second lens, the third lens and the fourth lens satisfy: 2.0 ≦ f234/f ≦ 5.5.

The present invention also provides an optical imaging system comprising:

a second lens having an optical power;

a fourth lens having a negative optical power;

wherein, the on-axis distance TTL from the object side surface of the first lens to the imaging surface and the half of the diagonal length ImgH of the effective pixel area on the imaging surface satisfy: TTL/ImgH ≦ 1.35.

The invention has the beneficial effects that:

the optical imaging system provided by the invention comprises a plurality of lenses, such as a first lens, a second lens and a third lens. The reasonable matching of focal power and surface curvature among the lenses can effectively balance various aberrations of the system and ensure the requirement of high imaging quality of the system. The system can be ensured to have the characteristic of ultra-thinness by controlling the ratio of the distance from the object side surface of the first lens to the image side surface of the last lens to the imaging surface on the optical axis.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

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

FIGS. 2a to 2d are an axial chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, in an embodiment 1 of an optical imaging system according to the present invention;

FIG. 3 is a schematic diagram of a lens assembly of an optical imaging system according to embodiment 2 of the present invention;

FIGS. 4a to 4d are an axial chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, in an embodiment 2 of an optical imaging system according to the present invention;

FIG. 5 is a schematic diagram of a lens assembly of an optical imaging system according to embodiment 3 of the present invention;

FIGS. 6a to 6d are an axial chromatic aberration curve, an astigmatic curve, a distortion curve, and a magnification chromatic aberration curve, respectively, of an optical imaging system in accordance with embodiment 3 of the present invention;

FIG. 7 is a schematic diagram of a lens assembly of an optical imaging system according to embodiment 4 of the present invention;

FIGS. 8a to 8d are an axial chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, in an optical imaging system according to embodiment 4 of the present invention;

FIG. 9 is a schematic diagram of a lens assembly of an optical imaging system according to embodiment 5 of the present invention;

FIGS. 10a to 10d are an axial chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, in an optical imaging system according to embodiment 5 of the present invention;

FIG. 11 is a schematic diagram of a lens assembly of an optical imaging system according to embodiment 6 of the present invention;

fig. 12a to 12d are an axial chromatic aberration curve, an astigmatic curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, in an optical imaging system according to embodiment 6 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

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 invention.

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.

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.

In the description of the present invention, 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.

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 may be combined with each other without conflict. Features, principles and other aspects of the present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Exemplary embodiments

The optical imaging system according to an exemplary embodiment of the present invention includes four lenses, in order from an object side to an image side along an optical axis: the lens comprises a first lens, a second lens, a third lens and a fourth lens, wherein the lenses are independent from each other, and an air space is formed between the lenses on an optical axis.

In this exemplary embodiment, the image sensor, in order from an object side to an image side along an optical axis, comprises: a first lens having positive refractive power, a convex object side surface and a concave image side surface; a second lens having an optical power; a third lens having positive refractive power, a concave object side surface, and a convex image side surface; a fourth lens; the on-axis distance TTL from the object side surface of the first lens to the imaging surface and the distance BFL from the image side surface of the last lens of the optical imaging system to the imaging surface on the optical axis satisfy the following conditions: TTL/BFL < 2.5; the value CT2 at which the center thickness is the smallest among all the lenses is the center thickness of the second lens on the optical axis. The reasonable matching of focal power and surface curvature among the lenses can effectively balance various aberrations of the system and ensure the requirement of high imaging quality of the system. The system can be ensured to have the characteristic of ultra-thinness by controlling the ratio of the distance from the object side surface of the first lens to the image side surface of the last lens to the imaging surface on the optical axis.

According to one embodiment of the invention, the maximum effective radius DT11 of the object-side surface of the first lens and the maximum effective radius DT21 of the object-side surface of the second lens satisfy: DT11/DT21< 1.0. By controlling the ratio of the maximum effective radius of the object side surface of the first lens to the maximum effective radius of the object side surface of the second lens, on one hand, the distortion and astigmatism of the system can be effectively corrected, and on the other hand, the molding assembly of each lens is facilitated, so that the finished system has better processability. More specifically, the maximum effective radius DT11 of the object-side surface of the first lens and the maximum effective radius DT21 of the object-side surface of the second lens satisfy: DT11/DT21< 0.9.

According to one embodiment of the invention, the effective focal length F, the relative F-number Fno of the optical imaging system and half of the maximum field angle Semi-FOV of the optical imaging system satisfy: 3.3mm ≦ f × tan (Semi-FOV). times.Fno ≦ 4.5 mm. By controlling the product of the effective focal length, the relative F number and half of the maximum field angle of the optical imaging system in a certain range, the characteristic that the system has large aperture in a certain imaging range can be ensured, the imaging quality of the system in a dark environment is improved, and the size of the optical imaging system is favorably compressed. More specifically, the effective focal length F, the relative F-number Fno of the optical imaging system and a half of the maximum field angle Semi-FOV of the optical imaging system satisfy: 3.2mm ≦ f × tan (Semi-FOV). times.Fno ≦ 4.3 mm.

According to an embodiment of the present invention, a central thickness CT1 of the first lens on the optical axis, a central thickness CT2 of the second lens on the optical axis, a central thickness CT3 of the third lens on the optical axis, an air interval T12 of the first lens and the second lens on the optical axis, and an air interval T34 of the third lens and the fourth lens on the optical axis satisfy: 1.4 ≦ (CT1+ CT2+ T12)/(CT3+ T34) ≦ 2.1. The ratio of the sum of the air intervals of the first lens, the second lens, the first lens and the second lens on the optical axis to the sum of the central thickness of the third lens on the optical axis and the air intervals of the third lens and the fourth lens on the optical axis is favorable for correcting the primary aberration of the optical imaging lens and weakening the intensity of a ghost image, and in addition, the system can be ensured to have better assemblage. More specifically, the central thickness CT1 of the first lens on the optical axis, the central thickness CT2 of the second lens on the optical axis, the central thickness CT3 of the third lens on the optical axis, the air interval T12 of the first lens and the second lens on the optical axis, and the air interval T34 of the third lens and the fourth lens on the optical axis satisfy: 1.3 ≦ (CT1+ CT2+ T12)/(CT3+ T34) ≦ 2.0.

According to one embodiment of the present invention, the effective focal length f of the optical imaging system, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: l (f3-f1)/f | ≦ 3.0. By controlling the ratio of the difference between the effective focal lengths of the third lens and the first lens of the optical imaging system to the effective focal length of the optical imaging system, the contribution of the first lens and the third lens to the focal length of the optical imaging system can be effectively restrained, the off-axis aberration of the optical system can be balanced, and the system can obtain higher imaging quality. More specifically, the effective focal length f of the optical imaging system, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy: l (f3-f1)/f | ≦ 2.9.

According to one embodiment of the invention, the effective focal length f1 of the first lens and the combined focal length f234 of the second, third and fourth lenses satisfy: 1.5 ≦ f234/f1 ≦ 3.5. By controlling the ratio of the combined focal length of the second lens, the third lens and the fourth lens to the effective focal length of the first lens within a certain range, on one hand, the focal power of the system can be reasonably distributed, the aberration of the system is balanced, on the other hand, the sensitivity of the system can be effectively reduced, and the production yield is improved. More specifically, the effective focal length f1 of the first lens and the combined focal length f234 of the second lens, the third lens and the fourth lens satisfy: 1.4 ≦ f234/f1 ≦ 3.4.

According to one embodiment of the present invention, the radius of curvature R5 of the object-side surface of the third lens, the radius of curvature R6 of the image-side surface of the third lens, the radius of curvature R7 of the object-side surface of the fourth lens, and the radius of curvature R8 of the image-side surface of the fourth lens satisfy: 1.0 ≦ R6 × R8|/| R5 × R7| ≦ 2.0. By controlling the lens curvatures of the third lens and the fourth lens, the chromatic aberration of magnification and distortion of the system can be effectively corrected, and the deflection of light rays on the third lens and the fourth lens can be favorably controlled, so that the ghost image of the system can be weakened or eliminated. More specifically, the radius of curvature R5 of the object-side surface of the third lens, the radius of curvature R6 of the image-side surface of the third lens, the radius of curvature R7 of the object-side surface of the fourth lens, and the radius of curvature R8 of the image-side surface of the fourth lens satisfy: 0.9 ≦ R6 × R8|/| R5 × R7| ≦ 1.9.

According to an embodiment of the present invention, a sum Σ AT of air intervals on the optical axis between any adjacent two lenses having optical powers of the first lens to the closest imaging surface lens and a sum Σ CT of center thicknesses on the optical axis of all the lenses satisfy: 2.0 ≦ Σ CT/Σ AT ≦ 4.0. By controlling the ratio of the central thickness of all the lenses on the optical axis to the sum of the air intervals on the optical axis between the first lens and any two adjacent lenses with focal power from the first lens to the lens closest to the imaging surface, the processing and the assembly of each lens of the system are facilitated, and the system can be ensured to have smaller optical total length. More specifically, the sum Σ AT of the air intervals on the optical axis between any adjacent two lenses having optical powers of the first lens to the lens closest to the imaging surface and the sum Σ CT of the center thicknesses on the optical axis of all the lenses satisfy: 1.9 ≦ Σ CT/Σ AT ≦ 3.9.

According to an embodiment of the present invention, an on-axis distance between the object-side surface of the first lens element and the image-side surface of the second last lens element, wherein the on-axis distance between the object-side surface of the first lens element and the image plane, TTL, satisfies: 2.0 ≦ TTL/InTL ≦ 2.5. By controlling the ratio of the axial distance from the object side surface of the first lens to the imaging surface to the axial distance from the object side surface of the first lens to the penultimate mirror image side surface, the size of the system can be effectively compressed, the adjustment of the emergent ray of the system by the last lens is facilitated, and the system is better matched with a chip. More specifically, an on-axis distance inll from the object-side surface of the first lens element to the image-side surface of the penultimate lens element and an on-axis distance TTL from the object-side surface of the first lens element to the image plane satisfy: 1.9 ≦ TTL/InTL ≦ 2.4.

According to one embodiment of the present invention, an on-axis distance SAG41 between an intersection point of the fourth lens object-side surface and the optical axis and an effective radius vertex of the fourth lens object-side surface, and an on-axis distance SAG32 between an intersection point of the third lens image-side surface and the optical axis and an effective radius vertex of the third lens image-side surface satisfy: 1.0 ≦ (SAG32+ SAG41)/(SAG32-SAG41) ≦ 4.5. By controlling the distance between the third lens and the fourth lens on the relevant axis, the inclination angles of the third lens and the fourth lens can be effectively controlled, the processing and forming of the lens are ensured, the field curvature and distortion of the system can be corrected, and the imaging quality of the system is improved. More specifically, an on-axis distance SAG41 between an intersection point of the fourth lens object-side surface and the optical axis and an effective radius vertex of the fourth lens object-side surface, and an on-axis distance SAG32 between an intersection point of the third lens image-side surface and the optical axis and an effective radius vertex of the third lens image-side surface satisfy: 0.9 ≦ (SAG32+ SAG41)/(SAG32-SAG41) ≦ 4.4.

According to an embodiment of the present invention, an edge thickness maximum value ETmax of the first to fourth lenses and an edge thickness ET1 of the first lens satisfy: 1.0 ≦ ETmax/ET1 ≦ 1.8. By controlling the ratio of the maximum edge thickness of the first lens to the edge thickness of the fourth lens to the edge thickness of the first lens within a certain range, the thickness distribution of each lens of the system is uniform, the structural arrangement and later-stage assembly are facilitated, and in addition, the optical size of the system is reduced. More specifically, the maximum value ETmax of the edge thicknesses of the first to fourth lenses and the edge thickness ET1 of the first lens satisfy: 0.9 ≦ ETmax/ET1 ≦ 1.7.

According to one embodiment of the present invention, the effective focal length f of the optical imaging system and the combined focal length f234 of the second lens, the third lens and the fourth lens satisfy: 2.0 ≦ f234/f ≦ 5.5. By controlling the ratio of the combined focal length of the second lens, the third lens and the fourth lens to the effective focal length of the optical imaging system, the spherical aberration and chromatic aberration of the system can be effectively corrected, and the definition of the optical imaging system is improved. More specifically, the effective focal length f of the optical imaging system and the combined focal length f234 of the second lens, the third lens and the fourth lens satisfy: 1.9 ≦ f234/f ≦ 5.4.

In this exemplary embodiment, the image sensor, in order from an object side to an image side along an optical axis, comprises: the method comprises the following steps: a first lens having positive refractive power, a convex object side surface and a concave image side surface; a second lens having an optical power; a third lens having positive refractive power, a concave object side surface, and a convex image side surface; a fourth lens having a negative optical power; wherein, the on-axis distance TTL from the object side surface of the first lens to the imaging surface and the half of the diagonal length ImgH of the effective pixel area on the imaging surface satisfy: TTL/ImgH ≦ 1.35.

In the present exemplary embodiment, the object-side surface and the image-side surface of any one of the first lens E1 through the fourth lens E4 are aspheric, and the profile x of each aspheric lens can be defined using, but not limited to, the following aspheric 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); k is a conic coefficient; ai is the correction coefficient of the i-th order of the aspheric surface.

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

The optical imaging system according to the above-described embodiment of the present invention may employ a plurality of lenses, for example, four lenses as described above. The optical imaging system has a large imaging image surface by reasonably distributing the focal power and the surface type of each lens, the central thickness of each lens, the on-axis distance between each lens and the like, has the characteristics of wide imaging range and high imaging quality, and ensures the ultrathin property of the mobile phone.

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 fourth lens is an aspheric mirror surface. The aspheric lens is characterized in that: the aspherical lens has a better curvature radius characteristic, and has advantages of improving distortion aberration and astigmatic aberration, unlike a spherical lens having a constant curvature from the lens center to the lens periphery, in which the curvature is continuously varied from the lens center to the lens periphery. 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 the object-side surface and the image-side surface of each of the first lens, the second lens, the third lens, and the fourth lens is an aspheric mirror surface. Optionally, each of the first lens, the second lens, the third lens and the fourth lens has an object-side surface and an image-side surface which are aspheric mirror surfaces.

However, it will be appreciated by those skilled in the art that the number of lenses constituting the optical imaging system 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 system is not limited to include four lenses, and the optical imaging system may include other numbers of lenses if necessary.

Specific embodiments of an optical imaging system suitable for use in the above-described embodiments are further described below with reference to the drawings.

Detailed description of the preferred embodiment 1

Fig. 1 is a schematic view of a lens assembly structure of an optical imaging system according to embodiment 1 of the present invention, the optical imaging system, in order from an object side to an image side along an optical axis, comprising: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a filter E5, and an image plane S11.

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 positive power, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element E4 has negative power, and has a convex object-side surface S7 and a concave image-side surface S8. Filter E5 has 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 plane S11.

As shown in table 1, a basic parameter table of the optical imaging system of example 1 is shown, in which the units of the radius of curvature, the thickness, and the focal length are all millimeters (mm).

TABLE 1

As shown in table 2, in embodiment 1, the total effective focal length f of the optical imaging system is 1.82mm, the distance TTL on the optical axis from the object side surface S1 of the first lens E1 to the imaging surface S11 of the optical imaging system is 2.40mm, and the half ImgH of the diagonal length of the effective pixel region on the imaging surface S11 is 1.88 mm. Half of the maximum field angle Semi-FOV of the optical imaging lens is 45.51 °.

TABLE 2

The optical imaging system in embodiment 1 satisfies:

TTL/BFL is 2.46. Wherein, TTL is the axial distance from the object side surface of the first lens to the imaging surface; BFL is the distance from the image side surface of the last lens of the optical imaging system to the imaging surface on the optical axis.

And the TTL/ImgH is 1.28, wherein the TTL is the on-axis distance from the object side surface of the first lens to the imaging surface, and the ImgH is half of the diagonal length of the effective pixel area on the imaging surface.

DT11/DT21 is 0.90, where DT11 is the maximum effective radius of the object-side face of the first lens; DT21 is the maximum effective radius of the object side of the second lens.

F × tan (Semi-FOV) × Fno is 4.17, where F is the effective focal length of the optical imaging system, Fno is the relative F-number, and Semi-FOV is half of the maximum field angle of the optical imaging system.

(CT1+ CT2+ T12)/(CT3+ T34) ═ 1.41, where CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, CT3 is the central thickness of the third lens on the optical axis, T12 is the air space between the first lens and the second lens on the optical axis, and T34 is the air space between the third lens and the fourth lens on the optical axis.

And | f3-f1)/f | -1.72, wherein f is the effective focal length of the optical imaging system, f1 is the effective focal length of the first lens, and f3 is the effective focal length of the third lens.

f234/f1 is 3.24, where f1 is the effective focal length of the first lens and f234 is the combined focal length of the second, third and fourth lenses.

L R6 × R8 l/l R5 × R7 l is 1.46, where R5 is the radius of curvature of the object-side surface of the third lens and R6 is the radius of curvature of the image-side surface of the third lens; r7 is the radius of curvature of the object-side surface of the fourth lens, and R8 is the radius of curvature of the image-side surface of the fourth lens.

Σ CT/Σ AT is 2.29, where Σ AT is the sum of the air intervals on the optical axis between any adjacent two lenses having optical powers of the first lens to the lens closest to the imaging surface; Σ CT is the sum of the central thicknesses of all lenses on the optical axis.

TTL/instl is 2.27, where instl is the on-axis distance from the object-side surface of the first lens to the image-side surface of the second last lens.

(SAG32+ SAG41)/(SAG32-SAG41) ═ 4.14, where SAG41 is the on-axis distance between the intersection of the fourth lens object-side surface and the optical axis and the effective radius vertex of the fourth lens object-side surface, and SAG32 is the on-axis distance between the intersection of the third lens image-side surface and the optical axis and the effective radius vertex of the third lens image-side surface.

ETmax/ET1 is 1.38, where ETmax is the maximum value of the edge thickness of the first to fourth lenses, and ET1 is the edge thickness of the first lens.

f234/f is 4.00, wherein f is the effective focal length of the optical imaging system, and f234 is the combined focal length of the second lens, the third lens and the fourth lens.

In example 1, the object-side surface and the image-side surface of any one of the first lens E1 through the fourth lens E4 are aspheric, and table 3 shows the high-order term coefficients a that can be used for the aspheric mirror surfaces S1 through S8 in example 1₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈、A₂₀And A₂₂。

Flour mark	A4	A6	A8	A10	A12
						S1	-3.7532E-01	2.4999E+01	-7.5999E+02	1.3258E+04	-1.3827E+05
S2	7.1255E-02	-1.3305E+01	4.3416E+02	-8.4561E+03	9.1906E+04
						S3	-1.4886E+00	1.4033E+01	-3.6025E+02	4.2171E+03	-2.8681E+04
S4	-7.2276E-01	7.3283E+00	-1.0387E+02	7.5541E+02	-3.1787E+03
						S5	3.6241E-01	-4.2360E-01	1.6155E+01	-5.3782E+01	2.9620E+01
S6	-2.2810E+00	1.5757E+01	-2.7598E+01	-2.8765E+02	2.3809E+03
						S7	-5.2282E+00	2.0674E+01	-6.7007E+01	1.5584E+02	-2.4855E+02
S8	-4.4824E+00	1.5488E+01	-4.4131E+01	9.2627E+01	-1.3915E+02
						Flour mark	A14	A16	A18	A20	A22
S1	8.4743E+05	-2.8117E+06	3.8864E+06	0.0000E+00	0.0000E+00
						S2	-5.6603E+05	1.8401E+06	-2.4590E+06	0.0000E+00	0.0000E+00
S3	1.0299E+05	-1.4824E+05	0.0000E+00	0.0000E+00	0.0000E+00
						S4	7.3053E+03	-6.7064E+03	0.0000E+00	0.0000E+00	0.0000E+00
S5	1.4243E+02	-2.3836E+02	0.0000E+00	0.0000E+00	0.0000E+00
						S6	-7.7233E+03	1.2837E+04	-1.0847E+04	3.7006E+03	0.0000E+00
S7	2.6382E+02	-1.7675E+02	6.7241E+01	-1.1033E+01	0.0000E+00
						S8	1.4657E+02	-1.0526E+02	4.8963E+01	-1.3284E+01	1.5963E+00

TABLE 3

Fig. 2a shows an on-axis chromatic aberration curve of the optical imaging system 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 of the optical imaging system of embodiment 1, which represents a meridional field curvature and a sagittal field curvature. Fig. 2c shows a distortion curve of the optical imaging system 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 system of embodiment 1, which represents the deviation of different image heights on the imaging plane after the light passes through the lens. As can be seen from fig. 2a to 2d, the optical imaging system according to embodiment 1 can achieve good imaging quality.

Specific example 2

Fig. 3 is a schematic view of a lens assembly structure of an optical imaging system in embodiment 2, the optical imaging system, in order from an object side to an image side along an optical axis, including: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a filter E5, and an image plane S11.

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 convex object-side surface S3 and a concave image-side surface S4. The third lens element E3 has positive power, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element E4 has negative power, and has a convex object-side surface S7 and a concave image-side surface S8. Filter E5 has 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 plane S11.

As shown in table 4, a basic parameter table of the optical imaging system of example 2 is shown, in which the units of the radius of curvature, the thickness, and the focal length are all millimeters (mm).

TABLE 4

As shown in table 5, in embodiment 2, the total effective focal length f of the optical imaging system is 1.61mm, the distance TTL on the optical axis from the object side surface S1 of the first lens E1 to the imaging surface S11 of the optical imaging system is 2.25mm, and the half ImgH of the diagonal length of the effective pixel region on the imaging surface S11 is 1.75 mm. Half of the maximum field angle Semi-FOV of the optical imaging lens is 46.44 °.

TABLE 5

In example 2, the object-side surface and the image-side surface of any one of the first lens E1 to the fourth lens E4 are aspheric, and table 6 shows the high-order term coefficients a that can be used for the aspheric mirror surfaces S1 to S8 in example 2₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈、A₂₀And A₂₂。

Flour mark

A4

A6

A8

A10

A12

A14

S1

3.1624E+02

-2.5849E+04

1.3223E+06

-4.5217E+07

1.0778E+09

-1.8375E+10

S2

-6.9234E+01

3.8204E+03

-9.3862E+04

-8.9168E+05

1.3534E+08

-4.5648E+09

S3

3.1781E+02

-2.5626E+04

1.2820E+06

-4.3115E+07

1.0150E+09

-1.7125E+10

S4

2.2130E+01

-1.6881E+03

5.6960E+04

-1.2300E+06

1.8357E+07

-1.9595E+08

S5

-5.7695E+01

8.2449E+02

-7.5055E+03

2.7326E+04

2.0305E+05

-3.2524E+06

S6

-1.6672E+01

1.2512E+03

-2.5558E+04

3.1340E+05

-2.6069E+06

1.5423E+07

S7

4.5900E+01

-2.7861E+02

1.2555E+03

-3.8082E+03

6.7385E+03

-2.1125E+03

S8

6.9931E+00

4.9227E+01

-6.0185E+02

3.3424E+03

-1.1978E+04

2.9969E+04

Flour mark

A16

A18

A20

A22

A24

S1

2.2694E+11

-2.0336E+12

1.3082E+13

-5.8817E+13

1.7532E+14

S2

8.8532E+10

-1.1234E+12

9.6430E+12

-5.5670E+13

2.0742E+14

S3

2.0950E+11

-1.8602E+12

1.1860E+13

-5.2883E+13

1.5647E+14

S4

1.5203E+09

-8.5994E+09

3.5117E+10

-1.0084E+11

1.9312E+11

S5

1.9148E+07

-5.6742E+07

5.6317E+07

1.5161E+08

-5.3945E+08

S6

-6.6159E+07

2.0641E+08

-4.6360E+08

7.3000E+08

-7.6451E+08

S7

-2.2979E+04

6.8231E+04

-1.0490E+05

1.0023E+05

-5.9894E+04

S8

-5.3849E+04

6.9973E+04

-6.5211E+04

4.2489E+04

-1.8371E+04

TABLE 6

Fig. 4a shows an on-axis chromatic aberration curve of the optical imaging system 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 of the optical imaging system of embodiment 2, which represents a meridional field curvature and a sagittal field curvature. Fig. 4c shows a distortion curve of the optical imaging system 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 system of embodiment 2, which represents the deviation of different image heights on the imaging plane after the light passes through the lens. As can be seen from fig. 4a to 4d, the optical imaging system according to embodiment 2 can achieve good imaging quality.

Specific example 3

Fig. 5 is a schematic view of a lens assembly structure of an optical imaging system in embodiment 3, the optical imaging system, in order from an object side to an image side along an optical axis, including: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a filter E5, and an image plane S11.

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 positive power, and has a convex object-side surface S3 and a concave image-side surface S4. The third lens element E3 has positive power, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element E4 has negative power, and has a convex object-side surface S7 and a concave image-side surface S8. Filter E5 has 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 plane S11.

As shown in table 7, a basic parameter table of the optical imaging system of example 3 is shown, in which the units of the radius of curvature, the thickness, and the focal length are all millimeters (mm).

TABLE 7

As shown in table 8, in embodiment 3, the total effective focal length f of the optical imaging system is 1.74mm, the distance TTL on the optical axis from the object side surface S1 of the first lens E1 to the imaging surface S11 of the optical imaging system is 2.46mm, and the half ImgH of the diagonal length of the effective pixel region on the imaging surface S11 is 1.83 mm. Half of the maximum field angle Semi-FOV of the optical imaging lens is 45.40 °.

TABLE 8

In example 3, the object-side surface and the image-side surface of any one of the first lens E1 to the fourth lens E4 are aspheric, and table 9 shows the high-order term coefficients a usable for the aspheric mirror surfaces S1 to S8 in example 3₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈、A₂₀And A₂₂。

TABLE 9

Fig. 6a shows an on-axis chromatic aberration curve of the optical imaging system 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 of the optical imaging system of embodiment 3, which represents a meridional field curvature and a sagittal field curvature. Fig. 6c shows a distortion curve of the optical imaging system 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 system of embodiment 3, which represents the deviation of different image heights on the imaging plane after the light passes through the lens. As can be seen from fig. 6a to 6d, the optical imaging system according to embodiment 3 can achieve good imaging quality.

Specific example 4

Fig. 7 is a lens assembly structure of an optical imaging system in accordance with embodiment 4 of the present invention, the optical imaging system, in order from an object side to an image side along an optical axis, includes: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a filter E5, and an image plane S11.

As shown in table 10, the basic parameter table of the optical imaging system of example 4 is shown, in which the units of the radius of curvature, the thickness, and the focal length are all millimeters (mm).

Watch 10

As shown in table 11, in embodiment 4, the total effective focal length f of the optical imaging system is 1.76mm, the distance TTL on the optical axis from the object side surface S1 of the first lens E1 to the imaging surface S11 of the optical imaging system is 2.46mm, and the half ImgH of the diagonal length of the effective pixel region on the imaging surface S11 is 1.83 mm. Half of the maximum field angle Semi-FOV of the optical imaging lens is 45.29 °.

TABLE 11

In example 4, the object-side surface and the image-side surface of any one of the first lens E1 to the fourth lens E4 are aspheric, and table 12 shows the high-order term coefficients a that can be used for the aspheric mirror surfaces S1 to S8 in example 4₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈、A₂₀And A₂₂。

Flour mark	A4	A6	A8	A10	A12
						S1	-1.4854E-03	2.7217E+00	-9.7057E+01	1.5020E+03	-1.2834E+04
S2	-2.1038E-01	9.0160E-01	-7.6459E+01	9.4545E+02	-6.7093E+03
						S3	-4.2964E-01	-2.9929E+01	6.1390E+02	-7.9018E+03	6.1915E+04
S4	9.3597E-01	-2.7352E+01	2.5135E+02	-1.0985E+03	1.0065E+03
						S5	2.8592E+00	-2.2381E+01	-1.4314E+02	3.4892E+03	-2.3971E+04
S6	3.3318E-01	-6.0829E+00	7.8135E+01	-6.1438E+02	2.8921E+03
						S7	-3.8922E+00	8.5330E+00	-1.5904E+01	2.7314E+01	-3.8144E+01
S8	-4.7552E+00	1.4179E+01	-3.4818E+01	6.3523E+01	-8.2734E+01
						Flour mark	A14	A16	A18	A20	A22
S1	5.6063E+04	-9.9356E+04	0.0000E+00	0.0000E+00	0.0000E+00
						S2	2.3509E+04	-2.8838E+04	-1.5517E+04	0.0000E+00	0.0000E+00
S3	-3.1008E+05	9.6769E+05	-1.6723E+06	1.1862E+06	0.0000E+00
						S4	1.2330E+04	-6.0256E+04	1.1627E+05	-8.5063E+04	0.0000E+00
S5	8.5980E+04	-1.7545E+05	1.9376E+05	-9.0280E+04	0.0000E+00
						S6	-7.5679E+03	1.0979E+04	-8.3339E+03	2.6008E+03	0.0000E+00
S7	3.7054E+01	-2.2475E+01	7.5745E+00	-1.0800E+00	0.0000E+00
						S8	7.4996E+01	-4.5943E+01	1.8067E+01	-4.1068E+00	4.0992E-01

TABLE 12

Fig. 8a shows an on-axis chromatic aberration curve of the optical imaging system 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 system of example 4. Fig. 8c shows a distortion curve of the optical imaging system 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 system of embodiment 4, which represents the deviation of different image heights on the imaging plane after the light passes through the lens. As can be seen from fig. 8a to 8d, the optical imaging system according to embodiment 4 can achieve good imaging quality.

Specific example 5

Fig. 9 is a lens assembly structure of the optical imaging system according to embodiment 5 of the present invention, the optical imaging system, in order from an object side to an image side along an optical axis, includes: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a filter E5, and an image plane S11.

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 convex image-side surface S4. The third lens element E3 has positive power, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element E4 has negative power, and has a convex object-side surface S7 and a concave image-side surface S8. Filter E5 has 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 plane S11.

As shown in table 13, the basic parameter table of the optical imaging system of example 5 is shown, in which the units of the radius of curvature, the thickness, and the focal length are all millimeters (mm).

Watch 13

As shown in table 14, in embodiment 5, the total effective focal length f of the optical imaging system is 1.82mm, the distance TTL on the optical axis from the object side surface S1 of the first lens E1 to the imaging surface S11 of the optical imaging system is 2.39mm, and the half ImgH of the diagonal length of the effective pixel region on the imaging surface S11 is 1.88 mm. Half of the maximum field angle Semi-FOV of the optical imaging lens is 45.28 °.

TABLE 14

In example 5, the object-side surface and the image-side surface of any one of the first lens element E1 through the fourth lens element E4 are aspheric, and table 15 shows the high-order term coefficients a that can be used for the aspheric mirror surfaces S1 through S8 in example 5₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈And A₂₀。

Flour mark	A4	A6	A8	A10	A12
						S1	-1.0828E-01	1.2081E+01	-2.4792E+02	2.4197E+03	-7.2865E+03
S2	-9.2067E-02	-5.5141E-01	-2.0616E+01	3.2143E+02	-4.2326E+03
						S3	-1.5671E+00	3.5553E+01	-1.4597E+03	3.0103E+04	-3.7694E+05
S4	1.2816E-01	-5.8000E+00	-8.6667E+01	2.2845E+03	-2.2648E+04
						S5	7.0077E-01	7.1349E+00	-3.4199E+02	4.4844E+03	-2.8344E+04
S6	-2.1729E+00	1.5495E+01	-3.5008E+01	-2.9097E+02	2.8337E+03
						S7	-5.3441E+00	2.0863E+01	-7.1646E+01	1.8877E+02	-3.4661E+02
S8	-4.5089E+00	1.4938E+01	-4.0208E+01	7.8782E+01	-1.0735E+02
						Flour mark	A14	A16	A18	A20
S1	-5.1881E+04	4.4749E+05	-9.4961E+05	0.0000E+00
						S2	3.0705E+04	-1.1862E+05	1.7328E+05	0.0000E+00
S3	2.9171E+06	-1.3698E+07	3.5845E+07	-4.0120E+07
						S4	1.2762E+05	-4.2742E+05	7.9026E+05	-6.1535E+05
S5	1.0143E+05	-2.1254E+05	2.4522E+05	-1.2102E+05
						S6	-9.9550E+03	1.7525E+04	-1.5526E+04	5.5267E+03
S7	4.1838E+02	-3.1271E+02	1.3053E+02	-2.3224E+01
						S8	9.7892E+01	-5.6637E+01	1.8702E+01	-2.6699E+00

Watch 15

Fig. 10a shows an on-axis chromatic aberration curve of the optical imaging system 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 system of example 5. Fig. 10c shows a distortion curve of the optical imaging system 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 system of embodiment 5, which represents the deviation of different image heights on the imaging plane after the light passes through the lens. As can be seen from fig. 10a to 10d, the optical imaging system according to embodiment 5 can achieve good imaging quality.

Specific example 6

Fig. 11 is a lens assembly structure of an optical imaging system according to embodiment 6 of the present invention, the optical imaging system, in order from an object side to an image side along an optical axis, comprising: a stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a filter E5, and an image plane S11.

As shown in table 16, the basic parameter table of the optical imaging system of example 6 is shown, in which the units of the radius of curvature, the thickness, and the focal length are all millimeters (mm).

TABLE 16

As shown in table 17, in embodiment 6, the total effective focal length f of the optical imaging system is 1.81mm, the distance TTL on the optical axis from the object side surface S1 of the first lens E1 to the imaging surface S11 of the optical imaging system is 2.39mm, and the half ImgH of the diagonal length of the effective pixel region on the imaging surface S11 is 1.88 mm. Half of the maximum field angle Semi-FOV of the optical imaging lens is 45.30 °.

TABLE 17

In example 6, the object-side surface and the image-side surface of any one of the first lens element E1 to the fourth lens element E4 are aspheric, and table 18 shows the high-order term coefficients a that can be used for the aspheric mirror surfaces S1 to S8 in example 6₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆、A₁₈、A₂₀、A₂₂、A₂₄And A₂₆。

Watch 18

Fig. 12a shows an on-axis chromatic aberration curve of the optical imaging system 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 system of example 6. Fig. 12c shows a distortion curve of the optical imaging system of embodiment 6, which represents distortion magnitude values corresponding to different image heights. Fig. 12d shows a chromatic aberration of magnification curve of the optical imaging system of embodiment 6, which represents the deviation of different image heights on the imaging plane after the light passes through the lens. As can be seen from fig. 12a to 12d, the optical imaging system according to embodiment 6 can achieve good imaging quality.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, improvements, equivalents and the like that fall within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

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

a second lens having an optical power;

a fourth lens;

2. The optical imaging system of claim 1, wherein the maximum effective radius DT11 of the first lens object-side surface and the maximum effective radius DT21 of the second lens object-side surface satisfy: DT11/DT21< 1.0.

3. The optical imaging system of claim 1, wherein the effective focal length F, the relative F-number Fno of the optical imaging system and half of the Semi-FOV of the maximum field angle of the optical imaging system satisfy: 3.3mm ≦ f × tan (Semi-FOV). times.Fno ≦ 4.5 mm.

4. The optical imaging system according to claim 1, wherein a central thickness CT1 of the first lens on the optical axis, a central thickness CT2 of the second lens on the optical axis, a central thickness CT3 of the third lens on the optical axis, an air interval T12 of the first lens and the second lens on the optical axis, and an air interval T34 of the third lens and the fourth lens on the optical axis satisfy: 1.4 ≦ (CT1+ CT2+ T12)/(CT3+ T34) ≦ 2.1.

5. The optical imaging system of claim 1, wherein the effective focal length f of the optical imaging system, the effective focal length f1 of the first lens, and the effective focal length f3 of the third lens satisfy: l (f3-f1)/f | ≦ 3.0.

6. An optical imaging system characterized by: in order from an object side to an image side along an optical axis:

a second lens having an optical power;

a fourth lens having a negative optical power;

7. The optical imaging system of claim 2, wherein the on-axis distance between the object-side surface of the first lens element and the image-side surface of the second last lens element, InTL, and the on-axis distance between the object-side surface of the first lens element and the imaging surface, TTL, satisfy: 2.0 ≦ TTL/InTL ≦ 2.5.

8. The optical imaging system of claim 2, wherein an on-axis distance SAG41 from the intersection of the fourth lens object-side surface and the optical axis to the effective radius vertex of the fourth lens object-side surface and an on-axis distance SAG32 from the intersection of the third lens image-side surface and the optical axis to the effective radius vertex of the third lens image-side surface satisfy: 1.0 ≦ (SAG32+ SAG41)/(SAG32-SAG41) ≦ 4.5.

9. The optical imaging system of claim 2, wherein the maximum value ETmax of the edge thickness of the first to fourth lenses and the edge thickness ET1 of the first lens satisfy: 1.0 ≦ ETmax/ET1 ≦ 1.8.

10. The optical imaging system of claim 2, wherein an effective focal length f of the optical imaging system and a combined focal length f234 of the second lens, the third lens, and the fourth lens satisfy: 2.0 ≦ f234/f ≦ 5.5.