CN217034397U

CN217034397U - Imaging system

Info

Publication number: CN217034397U
Application number: CN202221009267.3U
Authority: CN
Inventors: 杨世勇; 方荣波; 陈莉; 闻人建科; 戴付建; 赵烈烽
Original assignee: Zhejiang Sunny Optics Co Ltd
Current assignee: Zhejiang Sunny Optics Co Ltd
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2022-07-22
Anticipated expiration: 2032-04-28

Abstract

The application discloses an imaging system, include in order from object side to image side along the optical axis: a first lens having a positive optical power; a first spacer element in contact with at least a portion of the image side surface of the first lens; a second spacer element in contact with at least a portion of the image side surface of the first spacer element; a second lens; a third spacer element in contact with at least a portion of the image side surface of the second lens; a third lens element having one of an object-side surface and an image-side surface that has a positive curvature and the other of the object-side surface and the image-side surface that has a negative curvature; a fourth spacing element; a fourth lens; a fifth spacing element; a fifth lens element with positive refractive power having a concave object-side surface and a convex image-side surface; and the imaging system satisfies: 2< (CP1+ CP2+ CP3+ CP4+ CP5)/(Σat tan (Semi-FOV)) <5, where CP1 is the thickness of the first spacer element, CP2 is the thickness of the second spacer element, CP3 is the thickness of the third spacer element, CP4 is the thickness of the fourth spacer element, CP5 is the thickness of the fifth spacer element, Σ AT is the sum of the distances on the optical axis of any two adjacent lenses of the first to fifth lenses, and Semi-FOV is half of the maximum field angle of the imaging system.

Description

Imaging system

Technical Field

The present application relates to the field of optical elements, and in particular, to an imaging system.

Background

As the performance of charge-coupled devices (CCDs) and complementary metal-oxide semiconductor (CMOS) image sensors is improved and the size thereof is reduced, the corresponding imaging systems also need to meet the requirements of high imaging quality and miniaturization.

Imaging systems typically include multiple lenses and spacing elements for coupling adjacent lenses, and for imaging systems including five or more lenses, assembly stability problems due to large step differences between lenses can occur. And the problem of assembly stability seriously affects the imaging quality of the imaging system. Therefore, how to reasonably set the optical parameters of the imaging system and the lenses included therein and the thickness of the spacer element to improve the assembly stability is a problem to be solved in the art.

It is to be appreciated that this background section is intended in part to provide a useful background for understanding the technology, however, it is not necessary for these matters to be within the knowledge or understanding of those skilled in the art prior to the filing date of the present application.

SUMMERY OF THE UTILITY MODEL

The present application provides an imaging system, sequentially comprising from an object side to an image side along an optical axis: a first lens having a positive optical power; a first spacer element in contact with at least a portion of an image side surface of the first lens; a second spacer element in contact with at least a portion of the image side surface of the first spacer element; a second lens; a third spacing element in contact with at least a portion of an image side surface of the second lens; a third lens element having one of an object-side surface and an image-side surface that has a positive curvature and the other of the object-side surface and the image-side surface that has a negative curvature; a fourth spacer element in contact with at least a portion of an image side surface of the third lens; a fourth lens; a fifth spacer element in contact with at least a portion of an image side surface of the fourth lens; a fifth lens element with positive refractive power having a concave object-side surface and a convex image-side surface; and the imaging system satisfies: 2< (CP1+ CP2+ CP3+ CP4+ CP5)/(Σat tan (Semi-FOV)) <5, wherein CP1 is a thickness of the first spacer element, CP2 is a thickness of the second spacer element, CP3 is a thickness of the third spacer element, CP4 is a thickness of the fourth spacer element, CP5 is a thickness of the fifth spacer element, Σ AT is a sum of distances on the optical axis of any two adjacent lenses of the first lens to the fifth lens, and Semi-FOV is half of a maximum field angle of the imaging system.

In one embodiment of the application, the first spacer element is in contact with an image side surface of the first lens and at least a portion of the second spacer element, respectively, and the imaging system satisfies: 0< CT1/(CP1+ CP2) <5, where CP1 is the thickness of the first spacer element, CP2 is the thickness of the second spacer element, and CT1 is the center thickness of the first lens on the optical axis.

In one embodiment of the present application, the object-side surface of the second lens is in contact with at least a portion of the second spacer element and the image-side surface of the second lens is in contact with at least a portion of the third spacer element, and the side of the second lens closer to the second spacer element is convex and the side of the second lens closer to the third spacer element is concave.

In one embodiment of the present application, the fourth lens has positive optical power, and at least one of the object-side surface and the image-side surface thereof is convex.

In one embodiment of the application, the fourth spacer element is in contact with at least a portion of an image-side surface of the third lens and an object-side surface of the fourth lens, respectively, and the imaging system satisfies: 0< CP4/(CT4+ CT5)/tan (Semi-FOV) <5, where CP4 is the thickness of the fourth spacer element, CT4 is the center thickness of the fourth lens on the optical axis, CT5 is the center thickness of the fifth lens on the optical axis, and Semi-FOV is half of the maximum field angle of the imaging system.

In one embodiment of the present application, a lens barrel for accommodating each lens and each spacer element is further included, and the imaging system satisfies: 3< (L- Σ CT)/CP1 × Fno <15, where CP1 is a thickness of the first spacing element, L is a distance on the optical axis from an object side end to an image side end of the lens barrel, Σ CT is a sum of thicknesses on the optical axis of the respective first to fifth lenses, and Fno is an aperture value of the imaging system.

In one embodiment of the application, the fourth spacer element is in contact with at least a portion of an image-side surface of the third lens and an object-side surface of the fourth lens, respectively, and the imaging system satisfies: 0< CP4/(d4s + d4m) + (R6/R7) <8, where CP4 is the thickness of the fourth spacing element, d4s is the minimum inner diameter of the object-side surface of the fourth spacing element, d4m is the minimum inner diameter of the image-side surface of the fourth spacing element, R6 is the radius of curvature of the image-side surface of the third lens, and R7 is the radius of curvature of the object-side surface of the fourth lens.

In one embodiment of the application, the fifth spacer element is in contact with at least a portion of an image-side surface of the fourth lens and an object-side surface of the fifth lens, respectively, and the imaging system satisfies: 2< f45/(D5s-D5s) <20, wherein D5s is the maximum outer diameter of the object-side surface of the fifth spacing element, D5s is the minimum inner diameter of the object-side surface of the fifth spacing element, and f45 is the combined focal length of the fourth lens and the fifth lens.

In one embodiment of the application, the fourth lens is in contact with at least a portion of an image side surface of the fourth spacer element and an object side surface of the fifth spacer element, respectively, the fifth lens is in contact with at least a portion of an image side surface of the fifth spacer element, and the imaging system satisfies: 0< (f4/D5s) - (f45/D4m) <5, wherein D5s is the maximum inner diameter of the object side surface of the fifth spacing element, D4m is the maximum outer diameter of the image side surface of the fourth spacing element, f4 is the focal length of the fourth lens, and f45 is the combined focal length of the fourth lens and the fifth lens.

In one embodiment of the application, the fourth lens is in contact with at least a portion of an image-side surface of the fourth spacer element and an object-side surface of the fifth spacer element, respectively, and the imaging system satisfies: 1< (CT4+ CP4)/EP45<5, wherein EP45 is a distance between the fourth spacing element and the fifth spacing element on the optical axis, CP4 is a thickness of the fourth spacing element, and CT4 is a central thickness of the fourth lens on the optical axis.

In one embodiment of the present application, the imaging system satisfies: 0< (EP23+ T23)/(EP34+ T34) <2, wherein EP23 is a distance between the second and third spacing elements on the optical axis, EP34 is a distance between the third and fourth spacing elements on the optical axis, T23 is a distance between the second and third lenses on the optical axis, and T34 is a distance between the third and fourth lenses on the optical axis.

In one embodiment of the application, the second spacer element is the same thickness as the third and fifth spacer elements, and the first spacer element has a thickness greater than the thickness of any of the second to fifth spacer elements.

In one embodiment of the present application, the first lens is made of glass, and any one of the second lens to the fifth lens is made of plastic.

The imaging system comprises a plurality of lenses and spacing elements arranged between the lenses, and the number of the spacing elements between the lenses is reasonably set, the thickness of each spacing element is controlled, and the assembling stability of the imaging system can be improved. In addition, by reasonably setting the relationship between the field angle of the imaging system and the distance between the lenses and the thickness of the spacing elements, the maximum aperture of incident light can be adjusted, the imaging system is ensured to have enough light incoming amount, and the deformation amount of assembly stress is further reduced, so that the field curvature sensitivity of the sensitive lens is effectively reduced.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:

FIG. 1 shows a parametric annotation schematic of an imaging system according to the present application;

fig. 2 shows a schematic structural diagram of an optical lens group according to embodiment 1 of the present application;

FIG. 3 shows a schematic cross-sectional view of an imaging system comprising an optical lens group as shown in FIG. 2 according to embodiment 1 of the present application;

FIG. 4 shows a schematic cross-sectional view of another imaging system according to embodiment 1 of the present application comprising an optical lens group as shown in FIG. 2;

FIG. 5 shows a schematic cross-sectional view of yet another imaging system according to embodiment 1 of the present application comprising an optical lens group as shown in FIG. 2;

fig. 6A to 6C respectively show an astigmatism curve, a distortion curve, and a chromatic aberration of magnification curve of an optical lens group according to embodiment 2 of the present application;

fig. 7 shows a schematic structural diagram of an optical lens group according to embodiment 2 of the present application;

FIG. 8 shows a schematic cross-sectional view of an imaging system comprising an optical lens group as shown in FIG. 7 according to embodiment 2 of the present application;

FIG. 9 shows a schematic cross-sectional view of another imaging system according to embodiment 2 of the present application comprising an optical lens group as shown in FIG. 7;

FIG. 10 shows a schematic cross-sectional view of a further imaging system according to embodiment 2 of the present application comprising an optical lens group as shown in FIG. 7;

fig. 11A to 11C respectively show an astigmatism curve, a distortion curve, and a chromatic aberration of magnification curve of an optical lens group according to embodiment 2 of the present application;

fig. 12 shows a schematic structural diagram of an optical lens group according to embodiment 3 of the present application;

FIG. 13 shows a schematic cross-sectional view of an imaging system comprising an optical lens group as shown in FIG. 12 according to embodiment 3 of the present application;

FIG. 14 shows a schematic cross-sectional view of another imaging system according to embodiment 3 of the present application comprising an optical lens group as shown in FIG. 12;

FIG. 15 shows a schematic cross-sectional view of yet another imaging system including an optical lens group as shown in FIG. 12 according to embodiment 3 of the present application;

fig. 16A to 16C show an astigmatism curve, a distortion curve, and a chromatic aberration of magnification curve, respectively, of an optical lens group according to embodiment 3 of the present application.

Detailed Description

For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the present application and does not limit the scope of the present application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

In the drawings, the thickness, size, and shape of the lens have been slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shape of the spherical surface or the aspherical surface is not limited to the shape of the spherical surface or the aspherical surface shown in the drawings. The figures are purely diagrammatic and not drawn to scale.

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

It 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.

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 examples or illustrations.

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 following examples, which are intended to represent only a few embodiments of the present invention, are described in greater detail and detail, but are not to be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, it is possible to make several variations and modifications without departing from the concept of the present invention, and these are all within the protection scope of the present invention, for example, any combination between the optical lens group, the lens barrel structure and the spacing element in the embodiments of the present application may be used, and the optical lens group in one embodiment is not limited to be combined with the lens barrel structure, the spacing element and the like in the embodiment. 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 imaging system according to an exemplary embodiment of the present application may include an optical lens group including a plurality of lenses including, in order from an object side to an image side along an optical axis, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, each having power, a plurality of spacing elements, and a lens barrel for accommodating the optical lens group and the plurality of spacing elements.

In an exemplary embodiment, the first lens element can have a positive optical power, the object-side surface can be convex and the image-side surface can be convex or concave, the second lens element can have a positive or negative optical power, the object-side surface can be convex and the image-side surface can be concave; the third lens element can have a negative focal power, and the object-side surface and the image-side surface can be concave; the fourth lens has positive focal power, and the object side surface of the fourth lens can be a convex surface, and the image side surface of the fourth lens can be a convex surface or a concave surface; the fifth lens element can have a positive optical power, and can have a concave object-side surface and a convex image-side surface. The image pickup effect can be effectively improved by reasonably distributing the surface type and the focal power of each lens of the imaging system. In addition, the surface shape of each lens can be reasonably controlled, and the image resolution of the imaging system can be effectively improved and the aberration of the imaging system can be balanced by adjusting the path of light rays in the optical system.

In an exemplary embodiment, the imaging system further includes a prism disposed within the lens barrel, and the prism may be disposed on an object side surface of the first lens along the optical axis. The prism may have two optical axes that are orthogonal, an incident optical axis perpendicular to the incident surface of the prism and an exit optical axis perpendicular to the exit surface of the prism. The light from the object can sequentially pass through the incident surface of the prism along the incident optical axis, is reflected and deflected by 90 degrees by the reflecting surface of the prism, and then is emitted in the direction vertical to the emergent surface. The emergent optical axis of the prism and the optical axis of the optical lens group are positioned on the same straight line, and light emitted through the emergent surface of the prism can sequentially pass through the second lens, the third lens, the fourth lens and the fifth lens and is finally projected onto an imaging surface. The optical axes are fused together to form the main optical axis of the periscopic telephoto lens. The reflection direction of light rays is changed through the prism, so that the telephoto lens can be laid horizontally (placed backwards relative to vertical placement), a periscopic structure can be realized, and the thickness of a device carrying the telephoto lens is reduced.

In an exemplary embodiment, the plurality of spacer elements includes at least one spacer element positioned between any adjacent two lenses, the at least one spacer element being in contact with at least a portion of an adjacent lens. Optionally, the at least one spacer element may be in contact with a non-active optical portion of an adjacent lens (e.g., an edge region of the lens). Illustratively, the plurality of spacer elements includes, for example, a first spacer element and a second spacer element between the first lens and the second lens, a third spacer element between the second lens and the third lens, a fourth spacer element between the third lens and the fourth lens, and a fifth spacer element between the fourth lens and the fifth lens. Optionally, at least a portion of the first spacer element and the second spacer element are in contact, e.g. the image side of the first spacer element is in contact with at least a portion of the object side of the second spacer element. The electrostatic repulsion of the PC component in the assembling process can be reduced by controlling at least one part of the first spacing element to be in contact with the second spacing element, the stability of the component in the assembling process is ensured, and the manufacturing yield of the imaging system is improved. Through setting up a plurality of spacer elements, help intercepting unnecessary reflection light path, promote imaging system's formation of image cleanliness, reduce the production of miscellaneous light, ghost to can guarantee that a plurality of spacer elements assemble with lens cone, lens in order, and guarantee that the assembly is stable.

In an exemplary embodiment, the image-side surface of the first lens may be in contact with at least a portion of the object-side surface of the first spacer element, the object-side surface of the second lens may be in contact with at least a portion of the image-side surface of the second spacer element, and the image-side surface of the second lens may be in contact with at least a portion of the object-side surface of the third spacer element. The second spacing element is arranged on the object side face of the second lens, and the third spacing element is arranged on the image side face of the second lens, so that the incident light range can be reasonably limited, light with poor edge quality is eliminated, off-axis aberration is reduced, a stray light path generated by reflection of the second lens can be shielded, and the imaging quality of the optical system is improved.

In some examples, the second lens has a convex object-side surface (i.e., a side close to the second spacer element) contacting at least a portion of the image-side surface of the second spacer element and a concave image-side surface (i.e., a side close to the third spacer element) contacting at least a portion of the object-side surface of the third spacer element, so that the path of the light path in the optical system can be reasonably limited, the manufacturability of lens molding can be increased, and the image resolution of the imaging system can be effectively improved. In addition, the reasonable distribution of the surface shape of the second lens is helpful for ensuring the good convergence of light rays on an imaging surface, and the second lens is in stacked contact with the adjacent spacing elements, so that the stability of the assembled lens can be improved, and the reliability of an imaging system can be improved.

Alternatively, the object-side surface of the third lens may be in contact with at least a portion of the image-side surface of the third spacer element, the image-side surface of the third lens may be in contact with at least a portion of the object-side surface of the fourth spacer element, the object-side surface of the fourth lens may be in contact with at least a portion of the image-side surface of the fourth spacer element, the object-side surface of the fourth lens may be in contact with at least a portion of the object-side surface of the fifth spacer element, and the object-side surface of the fifth lens may be in contact with at least a portion of the image-side surface of the fifth spacer element.

In an exemplary embodiment, the second spacer element is the same thickness as the third and fifth spacer elements, and the thickness of the first spacer element is greater than the thickness of any of the second to fifth spacer elements. In order to ensure that the light paths of the imaging system converge, the distances between adjacent lenses in the optical system are different, the stress influence generated by the lens assembly can be reduced by setting the thickness of the first spacing element to be larger than the thicknesses of other spacing elements, the thicknesses of other spacing elements are adjusted to be the same, the stability of the assembly of the imaging system and the stability of the lens gap can be improved, and meanwhile, the finished product yield and the imaging quality of the imaging system are improved.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 2< (CP1+ CP2+ CP3+ CP4+ CP5)/(∑ AT tan (Semi-FOV)) <5, wherein CP1 is the thickness of the first spacer element, CP2 is the thickness of the second spacer element, CP3 is the thickness of the third spacer element, CP4 is the thickness of the fourth spacer element, CP5 is the thickness of the fifth spacer element, Σ AT is the sum of the distances on the optical axis of any two adjacent lenses of the first lens E1 through the fifth lens E5, and Semi-FOV is half of the maximum field angle of the imaging system. The sum of the thickness of each spacing element and the distance of each adjacent lens on the optical axis and half of the maximum field angle of the imaging system are reasonably controlled, so that the maximum aperture of incident light can be adjusted, and the imaging system is ensured to have enough light incoming amount; and further, the deformation of the assembly stress is reduced by reasonably controlling the thickness of the spacing element, so that the field curvature sensitivity of the sensitive lens is effectively reduced.

It is understood that, in order to make the structure and the labels of the drawings clearer, the labels of the sizes of the components in fig. 1 are simplified, only a group of sizes of the first spacing element and the distance between the first spacing element and the second spacing element on the optical axis are taken as examples, and the first spacing element can be referred to for the size limitation of each of the second spacing element to the fifth spacing element, which is not described herein in detail.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 0< CT1/(CP1+ CP2) <5, where CP1 is the thickness of the first spacer element, CP2 is the thickness of the second spacer element, and CT1 is the center thickness of the first lens E1 on the optical axis. The field curvature is adjusted by restricting the thicknesses of the first spacing element and the second spacing element, the sensitivity of the field curvature is reduced, the assembly performance yield of the imaging system is improved, the thickness uniformity of the middle thickness and the edge mechanism part of the first lens is adjusted, and the formability of the lens is improved.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 0< CP4/(CT4+ CT5)/tan (Semi-FOV) <5, where CP4 is the thickness of the fourth spacer element, CT4 is the center thickness of the fourth lens on the optical axis, CT5 is the center thickness of the fifth lens on the optical axis, and the Semi-FOV is half of the maximum field angle of the imaging system. The range of the conditional expressions is met, the forming manufacturability of the third lens E3 and the fourth lens E4 can be improved, the assembly stability is improved, and the size of the lens barrel is controlled; meanwhile, the stray light problem between the third lens E3 and the fourth lens E4 is improved, and the yield of the system is improved.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 3< (L- Σ CT)/CP1 × Fno <15, where CP1 is the thickness of the first spacing element, L is the distance on the optical axis from the object side end to the image side end of the lens barrel P0, Σ CT is the sum of the thicknesses of the respective first lens E1 to fifth lens E5 on the optical axis, and Fno is the aperture value of the imaging system. Satisfying above-mentioned conditional expression scope, can guaranteeing under imaging system's the condition of aperture value, managing and controlling the ratio of lens thickness and the thickness of thicker spacer element for imaging system has miniaturized characteristics, thereby can adapt to the full screen.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 0< CP4/(d4s + d4m) + (R6/R7) <8, where CP4 is the thickness of the fourth spacing element, d4s is the smallest inner diameter of the object side surface of the fourth spacing element, d4m is the smallest inner diameter of the image side surface of the fourth spacing element, R6 is the radius of curvature of the image side surface of the third lens E3, and R7 is the radius of curvature of the object side surface of the fourth lens E4. Satisfying the above conditional expression ranges, it is possible to restrict the distribution of the powers of the respective lenses by controlling the curvatures of the image-side surface of the third lens E3 and the object-side surface of the fourth lens E4, and further improve the upper limit of the performance of the optical system; meanwhile, the thickness of the spacing elements with large spacing is ensured to be within a reasonable range, the structural strength of the spacing elements and the stability of lens assembly can be improved, and the assembly yield of the imaging system is improved. In addition, the curvature of the image side surface of the third lens E3 and the curvature of the object side surface of the fourth lens are matched with the inner diameter of the fourth spacing element, so that the aberration of the system is balanced, the contact width of the image side surface and the object side surface of the fourth spacing element and at least one part of the lens can limit the partial reflection of the lens mechanism to generate redundant light, the assembly deformation of the first lens is optimized, the second lens is better supported in the front-back direction, and the assembly yield of the whole system is improved.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 2< f45/(D5s-D5s) <20, where D5s is the maximum outer diameter of the object-side face of the fifth spacing element, D5s is the minimum inner diameter of the object-side face of the fifth spacing element, and f45 is the combined focal length of fourth lens E4 and fifth lens E5. By controlling the combined effective focal length of the fourth lens E4 and the fifth lens E5 within a reasonable range, the amount of astigmatism of the system can be effectively controlled, thereby improving the imaging quality of the off-axis field. By further controlling the size of the fifth spacing element, the parasitic light path can be intercepted, thereby reducing parasitic light caused by reflection by the fifth spacing element. In addition, by controlling the outer diameter of the fifth spacer element, the wall thickness of the lens barrel P0 at this portion can be adjusted, so that the moldability and structural strength thereof can be improved, and in the case of performing convergence of the entire optical power, the curvature of field sensitivity of the fourth lens E4 can be reduced, and the imaging quality of the imaging system can be further improved.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 0< (f4/D5s) - (f45/D4m) <5, wherein D5s is the maximum inner diameter of the object side surface of the fifth spacing element, D4m is the maximum outer diameter of the image side surface of the fourth spacing element, f4 is the focal length of the fourth lens E4, and f45 is the combined focal length of the fourth lens E4 and the fifth lens E5. By controlling the outer diameter of the fourth spacer, the wall thickness of the lens barrel at this portion can be adjusted, so that the moldability and structural strength thereof can be improved, and the yield of the system can be further improved in the case where the focal powers of the fourth lens E4 and the fifth lens E5 are combined to be converged.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 1< (CT4+ CP4)/EP45<5, wherein EP45 is the distance between the fourth spacing element and the fifth spacing element on the optical axis, CP4 is the thickness of the fourth spacing element, and CT4 is the central thickness of the fourth lens on the optical axis. The range of the conditional expressions is satisfied, the uniformity of the central thickness and the mechanism part thickness of the fourth lens E4 can be controlled, and the formability of the fourth lens E4 is improved; by controlling the thickness of the fourth spacing element and the fifth spacing element and the thickness of the lens edge mechanism, the sensitivity of field curvature can be reduced, the stability of the fourth spacing element, the fifth spacing element and the fourth lens in the assembling process can be ensured, and the yield and the imaging quality of the system can be improved.

In an exemplary embodiment, with reference to the dimensioning of fig. 1, the imaging system satisfies: 0< (EP23+ T23)/(EP34+ T34) <2, where EP23 is the distance between the second and third spacing elements on the optical axis, EP34 is the distance between the third and fourth spacing elements on the optical axis, T23 is the distance between the second lens E2 and the third lens E3 on the optical axis, and T34 is the distance between the third lens E3 and the fourth lens E4 on the optical axis. Satisfying above-mentioned conditional expression scope, can guaranteeing imaging system's assembly stability, avoiding imaging system inside to have the unstable product yield loss that causes of spacing component assemblage of big interval to further guarantee the equilibrium of the axial thickness of a plurality of spacing components, be favorable to improving the parasitic light between the spacing component, promote imaging quality.

In an exemplary embodiment, a material of the first lens is glass, and a material of any one of the second lens to the fifth lens is plastic. The first lens is made of glass materials, so that the first lens has a high Abbe number and a high refractive index, and the size of the optical lens group can be reduced; any one of the second lens, the third lens and the fourth lens is made of plastic materials, so that the cost of the optical lens group is saved, the cost of an imaging system is reduced, and the processing difficulty of the lenses is reduced while high imaging quality is obtained. In an exemplary embodiment, the optical lens group according to the present application may further include a filter for correcting color deviation and/or a protective glass for protecting a photosensitive element located on an image forming surface.

In the embodiment of the present application, at least one of the mirror surfaces of each of the first to fifth lenses 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 better curvature radius characteristics, and has advantages of improving distortion aberration and improving astigmatic aberration. After the aspheric lens is adopted, the aberration generated in imaging can be eliminated as much as possible, and the imaging quality is further improved. Optionally, the object-side surface and the image-side surface of each of the first lens to the fifth lens are aspheric mirror surfaces.

However, it will be appreciated by those skilled in the art that the number of lenses making up the imaging system can be varied to achieve the various results and advantages described in this specification without departing from the claimed subject matter. For example, although five lenses are exemplified in the embodiments, the imaging system is not limited to include five lenses. The imaging system may also include other numbers of lenses, if desired.

Specific examples of imaging systems that can be adapted to the above-described embodiments are further described below with reference to the accompanying drawings.

Example 1

An optical lens group and an imaging system according to embodiment 1 of the present application are described below with reference to fig. 2 to 6C. Fig. 2 shows a schematic structural diagram of an optical lens group according to embodiment 1 of the present application. Fig. 3 to 5 respectively show schematic cross-sectional views of three imaging systems including the optical lens group shown in fig. 2 according to embodiment 1 of the present application.

As shown in fig. 2, the optical lens assembly includes, in order from an object side to an image side: a first lens E1, a stop STO, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a filter E6, and an image plane S13.

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

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

TABLE 1

In this embodiment, the total effective focal length f of the optical lens group is 17.50mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens element E1 to the imaging surface S13 is 19.00mm, the half ImgH of the diagonal length of the effective pixel area on the imaging surface S13 is 3.67mm, the aperture value Fno of the optical lens group is 3.53, and the half Semi-FOV of the maximum field angle of the optical lens group is 11.80 °.

In the present embodiment, the aspheric surface type x included in the object-side surface and the image-side surface of the lenses of the first lens E1 to the fifth lens E5 may be defined using, but not limited to, the following aspheric surface formula:

wherein x is the rise of the distance from the aspheric surface vertex to the aspheric surface vertex when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius of curvature R in table 1 above); k is a conic coefficient; ai is the correction coefficient of the i-th order of the aspheric surface. Tables 2 and 3 below show the coefficients of high-order terms a4, A6, A8, a10, a11, a12, a13, a14, a15, a16, a17, a18, and a19 of the respective mirrors usable for the aspherical surfaces S1 through S10 in example 1.

Flour mark

A4

A6

A8

A10

A11

A12

A13

S1

0.0000E+00

S2

0.0000E+00

S3

-1.2509E-04

7.1678E-04

-5.1620E-04

9.8696E-05

6.0653E-05

-4.4978E-05

1.2808E-05

S4

-3.9926E-03

1.1612E-02

-1.0570E-02

3.5170E-03

1.4184E-03

-1.9903E-03

9.5327E-04

S5

-2.7159E-02

8.3560E-02

-1.1627E-01

9.9887E-02

-5.6527E-02

2.1425E-02

-5.2532E-03

S6

-4.6769E-02

1.2046E-01

-1.6120E-01

1.3576E-01

-7.5099E-02

2.7788E-02

-6.7281E-03

S7

-3.4242E-02

4.6192E-02

-2.3956E-02

-3.7055E-02

1.0070E-01

-1.2576E-01

1.0317E-01

S8

-2.1323E-02

4.8760E-03

6.5270E-02

-1.8755E-01

2.8997E-01

-2.9862E-01

2.1615E-01

S9

-7.2155E-03

-9.8585E-03

5.6360E-02

-1.1660E-01

1.4580E-01

-1.2273E-01

7.2027E-02

S10

-8.1114E-04

-9.8461E-03

2.9761E-02

-5.1478E-02

5.8862E-02

-4.6500E-02

2.5836E-02

TABLE 2

Flour mark

A14

A15

A16

A17

A18

A19

S1

0.0000E+00

S2

0.0000E+00

S3

-1.7959E-06

1.0246E-07

0.0000E+00

S4

-2.3359E-04

2.4070E-05

0.0000E+00

S5

7.4792E-04

-4.6151E-05

0.0000E+00

S6

9.7315E-04

-6.3968E-05

0.0000E+00

S7

-5.9126E-02

2.3774E-02

-6.5638E-03

1.1834E-03

-1.2532E-04

5.9041E-06

S8

-1.1138E-01

4.0580E-02

-1.0202E-02

1.6817E-03

-1.6340E-04

7.0871E-06

S9

-2.9570E-02

8.3237E-03

-1.5300E-03

1.6534E-04

-7.9638E-06

0.0000E+00

S10

-1.0069E-02

2.6923E-03

-4.6995E-04

4.8190E-05

-2.2001E-06

0.0000E+00

TABLE 3

As shown in fig. 3, the imaging system 110 includes the above-described optical lens group, a lens barrel 111 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. As shown in fig. 4, the imaging system 120 includes the above-described optical lens group, a lens barrel 121 for accommodating the above-described optical lens group, and a plurality of spacing elements P1 to P5 located between any adjacent two of the plurality of lenses. As shown in fig. 5, the imaging system 130 includes the above-described optical lens group, a lens barrel 131 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. In the imaging system as shown in fig. 3 to 5, the first and second spacer elements P1 and P2 are located between the first and second lenses E1 and E2, and the first spacer element P1 is in contact with at least a portion of the image-side surface S2 of the first lens E1, and the image-side surface of the second spacer element P2 is in contact with at least a portion of the object-side surface S3 of the second lens E2. A third spacing element P3 is located between the second lens E2 and the third lens E3, the object side surface of the third spacing element P3 is in contact with at least a portion of the image side surface of the second lens E2, a fourth spacing element P4 is located between the third lens E3 and the fourth lens E4, and a fifth spacing element P5 is located between the fourth lens E5 and the fifth lens E5. In the present embodiment, the first P1 and fourth P4 spacer elements are spacers, and the second P2, third P3 and fifth P5 spacer elements are spacers. The first to fifth spacing elements P1 to P5 may block the entry of external unwanted light, make the lens and the barrel better bear, and enhance the structural stability of the imaging system.

In the imaging system as shown in fig. 3 to 5, the second spacer element P2, the third spacer element P3 and the fifth spacer element P5 have the same thickness, and the thickness of the first spacer element P1 is greater than the thickness of any of the second spacer element P2 to the fifth spacer element P5.

Table 4 shows a basic parameter table of the lens barrel and the spacer element of the three imaging systems of embodiment 1, and the unit of each parameter in table 4 is millimeter (mm).

System numbering	d4s	d4m	D4m	d5s	D5s	CP1	CP2	CP3	CP4	CP5	L	EP23	EP34	EP45
																110	3.96	3.99	5.09	3.71	5.20	0.53	0.02	0.02	0.48	0.02	8.20	1.45	1.00	0.75
120	3.76	3.89	5.29	3.61	5.40	0.53	0.02	0.02	0.48	0.02	8.20	1.45	1.00	0.75
															130	3.56	3.79	5.49	3.41	5.60	0.53	0.02	0.02	0.48	0.02	8.20	1.45	1.00	0.75

TABLE 4

Fig. 6A shows an astigmatism curve representing a meridional field curvature and a sagittal field curvature of the imaging system of embodiment 1. Fig. 6B shows a distortion curve of the imaging system of embodiment 1, which represents distortion magnitude values corresponding to different image heights. Fig. 6C shows a chromatic aberration of magnification curve of the imaging system of embodiment 1, which represents the deviation of different image heights on the imaging plane after the light passes through the system. As can be seen from fig. 6A to 6C, the imaging system according to embodiment 1 can achieve good imaging quality.

Example 2

An optical lens group and an imaging system according to embodiment 2 of the present application are described below with reference to fig. 7 to 11C. Fig. 7 shows a schematic structural diagram of an optical lens group according to embodiment 2 of the present application. Fig. 8 to 10 respectively show schematic sectional views of three imaging systems including the optical lens group shown in fig. 7 according to embodiment 2 of the present application.

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

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

Table 5 shows a basic parameter table of the optical lens group of example 2, in which the units of the radius of curvature, the thickness/distance, and the focal length are all millimeters (mm).

TABLE 5

In this embodiment, the total effective focal length f of the optical lens group is 18.40mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens E1 to the imaging surface S13 is 18.72mm, the ImgH, which is half the diagonal length of the effective pixel area on the imaging surface S13, is 3.47mm, the aperture value Fno of the optical lens group is 3.34, and the Semi-FOV, which is the maximum field angle of the optical lens group, is 10.08 °.

Table 6 shows the high-order term coefficients a4, a6, a8, and a10 of the mirror surface usable for the aspherical surface S7 in example 2, wherein the surface shape of the aspherical surface can be defined by the formula (1) given in example 1 above.

Flour mark	A4	A6	A8	A10
					S7	8.7328E-05	-8.0647E-05	-3.4070E-05	-1.3156E-06

TABLE 6

As shown in fig. 8, the imaging system 210 includes the above-described optical lens group, a lens barrel 211 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. As shown in fig. 9, the imaging system 220 includes the above-described optical lens group, a lens barrel 221 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. As shown in fig. 10, the imaging system 230 includes the above-described optical lens group, a lens barrel 231 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. In the imaging system as shown in fig. 8-10, the first and second spacer elements P1 and P2 are located between the first and second lenses E1 and E2, with the first spacer element P1 in contact with at least a portion of the image-side surface S2 of the first lens E1 and the second spacer element P2 in contact with at least a portion of the object-side surface S3 of the second lens E2. A third spacing element P3 is located between the second lens E2 and the third lens E3, the object side surface of the third spacing element P3 is in contact with at least a portion of the image side surface of the second lens E2, a fourth spacing element P4 is located between the third lens E3 and the fourth lens E4, and a fifth spacing element P5 is located between the fourth lens E5 and the fifth lens E5. In the present embodiment, the first P1 and fourth P4 spacer elements are spacers, and the second P2, third P3 and fifth P5 spacer elements are spacers. The first to fifth spacing elements P1 to P5 may block the entry of external unwanted light, make the lens and the barrel better bear, and enhance the structural stability of the imaging system.

In the imaging system shown in fig. 3-5, second and third spacing elements P2, P3 and fifth spacing element P5 have the same thickness, and the thickness of first spacing element P1 is greater than the thickness of any of second to fifth spacing elements P2-P5.

Table 7 shows a basic parameter table of the lens barrel and the spacer of three imaging systems of embodiment 2, and the unit of each parameter in table 7 is millimeter (mm).

System numbering	d4s	d4m	D4m	d5s	D5s	CP1	CP2	CP3	CP4	CP5	L	EP23	EP34	EP45
																210	4.78	5.14	5.60	4.44	5.80	1.38	0.02	0.02	0.68	0.02	7.70	0.88	1.37	0.38
220	4.68	5.04	5.80	4.34	6.00	1.38	0.02	0.02	0.68	0.02	7.70	0.88	1.37	0.38
															230	4.68	5.04	5.90	4.34	6.10	1.38	0.02	0.02	0.68	0.02	7.70	0.88	1.37	0.38

TABLE 7

Fig. 11A shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the imaging system of embodiment 2. Fig. 11B shows a distortion curve of the imaging system of embodiment 2, which represents distortion magnitude values corresponding to different image heights. Fig. 11C shows a chromatic aberration of magnification curve of the imaging system of embodiment 2, which represents the deviation of different image heights on the imaging plane after the light passes through the system. As can be seen from fig. 11A to 11C, the imaging system according to embodiment 2 can achieve good imaging quality.

Example 3

An optical lens group and an imaging system according to embodiment 3 of the present application are described below with reference to fig. 12 to 16C. Fig. 11 shows a schematic structural diagram of an optical lens group according to embodiment 3 of the present application. Fig. 13 to 15 respectively show cross-sectional schematic views of three imaging systems including the optical lens group shown in fig. 12 according to embodiment 3 of the present application.

As shown in fig. 12, the optical lens assembly includes, in order from an object side to an image side: a first lens E1, a stop STO, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a filter E6, and an image plane S13.

Table 8 shows a basic parameter table of the optical lens group of example 3 in which the units of the radius of curvature, thickness/distance, and focal length are millimeters (mm).

TABLE 8

In this embodiment, the total effective focal length f of the optical lens group is 19.36mm, the distance TTL on the optical axis from the object-side surface S1 of the first lens element E1 to the imaging surface S13 is 19.26mm, the half ImgH of the diagonal length of the effective pixel area on the imaging surface S13 is 3.47mm, the aperture value Fno of the optical lens group is 3.47, and the half Semi-FOV of the maximum field angle of the optical lens group is 9.86 °.

Table 9 shows the high-order term coefficients a4, a6, A8, a10, a11, and a12 of the respective mirror surfaces usable for the aspherical surfaces S7 through S10 in example 3, wherein the respective aspherical surface types can be defined by the formula (1) given in example 1 above.

Flour mark

A4

A6

A8

A10

A11

A12

S7

-8.7238E-04

-6.3695E-04

2.6713E-04

-2.4668E-05

0.0000E+00

S8

6.0455E-04

-5.3345E-04

1.9482E-04

7.7895E-06

-5.3821E-06

2.5748E-07

S9

5.7688E-04

-1.6141E-04

2.7833E-06

-2.1491E-06

-1.6595E-06

0.0000E+00

S10

4.9443E-05

7.7557E-06

-2.8035E-05

-3.1061E-06

1.1323E-07

0.0000E+00

TABLE 9

As shown in fig. 13, the imaging system 310 includes the above-described optical lens group, a lens barrel 311 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. As shown in fig. 14, the imaging system 320 includes the above-described optical lens group, a lens barrel 321 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. As shown in fig. 15, the imaging system 330 includes the above-described optical lens group, a lens barrel 331 for accommodating the above-described optical lens group, and a plurality of spacer elements P1 to P5 located between any adjacent two of the plurality of lenses. In the imaging system as shown in fig. 13 to 15, the first and second spacer elements P1 and P2 are located between the first and second lenses E1 and E2, and the first spacer element P1 is in contact with at least a portion of the image-side surface S2 of the first lens E1, and the image-side surface of the second spacer element P2 is in contact with at least a portion of the object-side surface S3 of the second lens E2. A third spacer element P3 is positioned between second lens E2 and third lens E3, with the object-side surface of third spacer element P3 in contact with at least a portion of the image-side surface of second lens E2, a fourth spacer element P4 is positioned between third lens E3 and fourth lens E4, and a fifth spacer element P5 is positioned between fourth lens E5 and fifth lens E5. In the present embodiment, first spacing element P1 is a cage and second through fifth spacing elements P2 through P5 are spacers. The first to fifth spacing elements P1 to P5 may block the entry of external unwanted light, make the lens and the barrel better bear, and enhance the structural stability of the imaging system.

Table 10 shows a basic parameter table of the lens barrel and the spacer of three imaging systems of embodiment 3, and the unit of each parameter in table 10 is millimeters (mm).

System numbering	d4s	d4m	D4m	d5s	D5s	CP1	CP2	CP3	CP4	CP5	L	EP23	EP34	EP45
																310	4.29	4.29	6.00	4.52	5.90	1.77	0.02	0.02	0.02	0.02	7.70	1.19	1.09	0.83
320	4.19	4.19	6.20	4.42	6.10	1.77	0.02	0.02	0.02	0.02	7.70	1.19	1.09	0.83
															330	4.05	4.05	6.40	4.22	6.30	1.77	0.02	0.02	0.02	0.02	7.70	1.19	1.09	0.83

TABLE 10

Fig. 16A shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the imaging system of embodiment 3. Fig. 16B shows a distortion curve of the imaging system of embodiment 3, which represents distortion magnitude values corresponding to different image heights. Fig. 16C shows a chromatic aberration of magnification curve of the imaging system of embodiment 3, which represents the deviation of different image heights on the imaging plane after the light passes through the system. As can be seen from fig. 16A to 16C, the imaging system according to embodiment 3 can achieve good imaging quality.

In summary, examples 1 to 3 satisfy the relationships shown in table 11, respectively.

TABLE 11

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the invention herein disclosed is not limited to the particular combination of features described above, but also encompasses other arrangements formed by any combination of the above 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 imaging system, in order from an object side to an image side along an optical axis, comprises:

a first lens having a positive optical power;

a first spacer element in contact with at least a portion of an image side surface of the first lens;

a second spacer element in contact with at least a portion of the image side surface of the first spacer element;

a second lens;

a third spacing element in contact with at least a portion of an image side surface of the second lens;

a third lens element having a positive curvature of one of the object-side surface and the image-side surface and a negative curvature of the other;

a fourth spacer element in contact with at least a portion of an image side surface of the third lens;

a fourth lens;

a fifth spacer element in contact with at least a portion of an image side surface of the fourth lens;

a fifth lens element with positive refractive power having a concave object-side surface and a convex image-side surface; and the imaging system satisfies: 2< (CP1+ CP2+ CP3+ CP4+ CP5)/(∑ AT tan (Semi-FOV)) <5,

wherein CP1 is a thickness of the first spacer element, CP2 is a thickness of the second spacer element, CP3 is a thickness of the third spacer element, CP4 is a thickness of the fourth spacer element, CP5 is a thickness of the fifth spacer element, Σ AT is a sum of distances on the optical axis of any two adjacent lenses among the first lens to the fifth lens, and Semi-FOV is half of a maximum field angle of the imaging system.

2. The imaging system of claim 1, wherein the first spacer element is in contact with an image side surface of the first lens and at least a portion of the second spacer element, respectively, and the imaging system satisfies:

0＜CT1/(CP1+CP2)＜5，

wherein CP1 is a thickness of the first spacer element, CP2 is a thickness of the second spacer element, and CT1 is a center thickness of the first lens on the optical axis.

3. The imaging system of claim 2, wherein an object side surface of the second lens is in contact with at least a portion of the second spacing element and an image side surface of the second lens is in contact with at least a portion of the third spacing element, and wherein a side of the second lens proximate the second spacing element is convex and a side of the second lens proximate the third spacing element is concave.

4. The imaging system of claim 2, wherein the fourth lens has a positive optical power and at least one of the object-side surface and the image-side surface is convex.

5. The imaging system of any of claims 1 to 4, wherein the fourth spacer element is in contact with at least a portion of an image-side surface of the third lens and an object-side surface of the fourth lens, respectively, and the imaging system satisfies:

0＜CP4/(CT4+CT5)/tan(Semi-FOV)＜5，

wherein CP4 is a thickness of the fourth spacer element, CT4 is a center thickness of the fourth lens on the optical axis, CT5 is a center thickness of the fifth lens on the optical axis, and the Semi-FOV is half of a maximum field angle of the imaging system.

6. The imaging system according to any one of claims 1 to 4, further comprising a lens barrel for accommodating the respective lenses and the respective spacer elements, and wherein the imaging system satisfies:

3＜(L-∑CT)/CP1*Fno＜15，

wherein CP1 is a thickness of the first spacer element, L is a distance on the optical axis from the object side end to the image side end of the lens barrel, Σ CT is a sum of thicknesses on the optical axis of each of the first to fifth lenses, and Fno is an aperture value of the imaging system.

7. The imaging system of any of claims 1 to 4, wherein the fourth spacer element is in contact with at least a portion of an image-side surface of the third lens and an object-side surface of the fourth lens, respectively, and the imaging system satisfies:

0＜CP4/(d4s+d4m)+(R6/R7)＜8，

wherein CP4 is a thickness of the fourth spacer element, d4s is a minimum inner diameter of an object-side surface of the fourth spacer element, d4m is a minimum inner diameter of an image-side surface of the fourth spacer element, R6 is a radius of curvature of an image-side surface of the third lens, and R7 is a radius of curvature of an object-side surface of the fourth lens.

8. The imaging system of any of claims 1 to 4, wherein the fifth spacer element is in contact with at least a portion of an image-side surface of the fourth lens and an object-side surface of the fifth lens, respectively, and the imaging system satisfies:

2＜f45/(D5s-d5s)＜20，

wherein D5s is the maximum outer diameter of the object side surface of the fifth spacing element, D5s is the minimum inner diameter of the object side surface of the fifth spacing element, and f45 is the combined focal length of the fourth lens and the fifth lens.

9. An imaging system according to any one of claims 1 to 4, characterized in that the fourth lens is in contact with at least a part of an image side surface of the fourth spacer element and an object side surface of the fifth spacer element, respectively, the fifth lens is in contact with at least a part of an image side surface of the fifth spacer element, and the imaging system satisfies:

0＜(f4/D5s)-(f45/D4m)＜5，

wherein D5s is the maximum inner diameter of the object side surface of the fifth spacing element, D4m is the maximum outer diameter of the image side surface of the fourth spacing element, f4 is the focal length of the fourth lens, and f45 is the combined focal length of the fourth lens and the fifth lens.

10. An imaging system according to any one of claims 1 to 4, wherein the fourth lens is in contact with at least a portion of an image side surface of the fourth spacer element and an object side surface of the fifth spacer element, respectively, the imaging system satisfying:

1＜(CT4+CP4)/EP45＜5，

wherein EP45 is the distance of the fourth and fifth spacing elements on the optical axis, CP4 is the thickness of the fourth spacing element, and CT4 is the center thickness of the fourth lens on the optical axis.

11. The imaging system of any of claims 1 to 4, wherein the imaging system satisfies:

0＜(EP23+T23)/(EP34+T34)＜2，

wherein EP23 is the distance between the second and third spacing elements on the optical axis, EP34 is the distance between the third and fourth spacing elements on the optical axis, T23 is the distance between the second and third lenses on the optical axis, and T34 is the distance between the third and fourth lenses on the optical axis.

12. The imaging system of any of claims 1 to 4, wherein the second spacer element is the same thickness as the third and fifth spacer elements, and the first spacer element has a thickness greater than any of the second to fifth spacer elements.

13. The imaging system of claim 1, wherein the first lens is made of glass, and any one of the second lens to the fifth lens is made of plastic.