CN217332985U - Imaging system - Google Patents

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 refractive power; a first spacer element in contact with an image side surface of the first lens; a second lens having a negative focal power; a second spacer element in contact with the image side surface of the second lens; a third lens having a positive refractive power; a third spacer element in contact with the image side surface of the third lens; a fourth lens having a positive refractive power, the object-side surface of which is convex; a fourth spacer element in contact with an image side surface of the fourth lens element; a fifth lens, which has negative focal power and a convex image-side surface; a fifth spacer element in contact with an image side surface of the fifth lens; a sixth lens having a negative focal power; wherein, the curvature radius R2 of the image side surface of the first lens, the curvature radius R12 of the image side surface of the sixth lens, the outer diameter D2m of the image side surface of the second spacing element and the outer diameter D5m of the image side surface of the fifth spacing element D5m satisfy: 13.0 < (R2/D2m) + (R12/D5m) < 13.0.

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 of the image sensors is reduced, the corresponding imaging system also needs to meet the requirements of high imaging quality and miniaturization, and meanwhile, the currently emerging double-shot technology generally needs to use a telephoto lens to obtain higher spatial and angular resolutions. And the stray light index and the automatic assembly stability of the imaging system play an important role in the imaging quality.

That is to say, the existing six-piece optical imaging system cannot simultaneously satisfy the design requirement of long focus and also consider the stability of stray light and assembly.

SUMMERY OF THE UTILITY MODEL

The present application provides an imaging system, in order from an object side to an image side along an optical axis, comprising: a first lens having a positive refractive power; a first spacer element in contact with an image side surface of the first lens; a second lens having a negative focal power; a second spacer element in contact with an image side surface of the second lens; a third lens having a positive refractive power; a third spacer element in contact with an image side surface of the third lens; a fourth lens having a positive focal power, the object-side surface of which is convex; a fourth spacer element in contact with an image side surface of the fourth lens; a fifth lens, which has negative focal power and a convex image-side surface; a fifth spacer element in contact with an image side surface of the fifth lens; a sixth lens having a negative focal power; wherein a radius of curvature R2 of the image-side surface of the first lens, a radius of curvature R12 of the image-side surface of the sixth lens, an outer diameter D2m of the image-side surface of the second spacer element, and an outer diameter D5m of the image-side surface of the fifth spacer element D5m satisfy: 13.0 < (R2/D2m) + (R12/D5m) < 13.0.

In one embodiment of the present application, an effective focal length f1 of the first lens, an effective focal length f5 of the fifth lens, a thickness CP1 of the first spacer element, and a thickness CP5 of the fifth spacer element are satisfied between: 230 < f5/CP5+ f1/CP1< -18.0.

In one embodiment of the present application, a distance EP34 of the third spacer element and the fourth spacer element on the optical axis, a distance EP45 of the fourth spacer element and the fifth spacer element on the optical axis, a center thickness CT3 of the third lens on the optical axis, and a center thickness CT4 of the fourth lens on the optical axis satisfy: -7.0 < (EP34+ EP45)/(CT3-CT4) < -3.0.

In one embodiment of the present application, the radius of curvature R8 of the image side surface of the fourth lens, the inner diameter d2m of the image side surface of the second spacer element, and the inner diameter d3m of the image side surface of the third spacer element satisfy: 4.0 < | R8/(d3m + d2m) | < 9.0.

In an embodiment of the application, a thickness CP3 of the third spacer element, a distance EP23 of the second spacer element and the third spacer element on the optical axis, a distance T23 of the second and third lenses on the optical axis, and a center thickness CT3 of the third lens on the optical axis satisfy: 1.5 < T23/CP3+ EP23/CT3 < 61.0.

In one embodiment of the application, a distance T45 between the fourth lens and the fifth lens on the optical axis, an outer diameter D4s of an object-side surface of the fourth spacer element, an inner diameter D4s of an object-side surface of the fourth spacer element and a thickness CP4 of the fourth spacer element satisfies: 7.0 < (D4s + D4s)/(CP4+ T45) < 16.0.

In one embodiment of the present application, a radius of curvature R5 of an object-side surface of the third lens, a sum Σ AT of distances on the optical axis of any two adjacent lenses of the first lens to the sixth lens, and a sum Σ EP of distances on the optical axis of any two adjacent spacing elements of the first spacing element to the fifth spacing element satisfy: 24.0 < | R5/(∑ EP- Σ AT) | < 45.0.

In one embodiment of the present application, a sum Σ CP of thicknesses of the respective first to fifth spacing elements, a radius of curvature R11 of an object-side surface of the sixth lens, and a sum Σ CT of center thicknesses of the respective first to sixth lenses on the optical axis satisfy: 0< | R11/(∑ CP +. Sigma CT) | < 13.0.

In one embodiment of the present application, an effective focal length f3 of the third lens, an effective focal length f5 of the fifth lens, a center thickness CT3 of the third lens on the optical axis, a center thickness CT5 of the fifth lens on the optical axis, a thickness CP3 of the third spacer element, a thickness CP5 of the fifth spacer element, an outer diameter D5s of an object-side surface of the fifth spacer element, and an inner diameter D5m of an image-side surface of the fifth spacer element satisfy: -24.0 ≦ (f5 × CP3 × CT5 × CT3-f3 × CP5 × CT5 × CT3)/(CP3 × CP5 × D5s × D5m) < -10.0.

In one embodiment of the present application, a lens barrel for accommodating each lens and each spacer element, wherein a dimension L of the lens barrel in the optical axis direction, a curvature radius R2 of an image-side surface of the first lens, and a curvature radius R12 of an image-side surface of the sixth lens satisfy: the ratio of (R2-R12)/L is more than or equal to-15.0 and less than 7.0.

The imaging system comprises the lens barrel, the plurality of lenses and the plurality of spacing elements, redundant light can be effectively shielded by arranging the spacing elements between every two adjacent lenses, stray light is improved, furthermore, the bearing between every two adjacent lenses and the spacing elements improves the stability and consistency of the lenses in the assembling process, and yield loss in the production process can be avoided. In addition, the imaging system has excellent bearing stability and reliability improvement performance by reasonably distributing the focal power of each lens and adjusting the relation between the curvature radius of the image side surface of the first lens and the curvature radius of the image side surface of the sixth lens and the radius of the adjacent spacing element.

Drawings

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

FIG. 1 shows a schematic view of a spacer element comprised by an imaging system according to the present application for parasitic light elimination;

FIG. 2 shows a parametric annotation schematic of an imaging system according to the present application;

fig. 3 shows a schematic cross-sectional view of an imaging system 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;

fig. 5 shows a schematic cross-sectional view of yet another imaging system according to embodiment 1 of the present application;

fig. 6A to 6D respectively show an astigmatism curve, a distortion curve, a magnification chromatic aberration curve, and an on-axis chromatic aberration curve of an imaging system according to embodiment 1 of the present application;

fig. 7 shows a schematic cross-sectional view of an imaging system according to embodiment 2 of the present application;

fig. 8 shows a schematic cross-sectional view of another imaging system according to embodiment 2 of the present application;

fig. 9 shows a schematic cross-sectional view of yet another imaging system according to embodiment 2 of the present application;

fig. 10A to 10D respectively show an astigmatism curve, a distortion curve, a magnification chromatic aberration curve, and an on-axis chromatic aberration curve of an imaging system according to embodiment 2 of the present application;

fig. 11 shows a schematic cross-sectional view of an imaging system according to embodiment 3 of the present application;

fig. 12 shows a schematic cross-sectional view of another imaging system according to embodiment 3 of the present application;

fig. 13 shows a schematic cross-sectional view of yet another imaging system according to embodiment 3 of the present application;

fig. 14A to 14D show an astigmatism curve, a distortion curve, a magnification chromatic aberration curve, and an on-axis chromatic aberration curve, respectively, of an imaging system 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.

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 a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The following examples are merely illustrative of several embodiments of the present invention, which are described in more 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 application, which all fall within the protection scope of the present invention, for example, any combination between the lens group, the spacing element and the structure of the lens barrel in the embodiments of the present application may be adopted, and the lens group in one embodiment is not limited to only be combined with the structure, the spacing element and the like of the lens barrel in the embodiment. 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.

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 a lens group 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, a fifth lens, and a sixth lens, each having power, a plurality of spacing elements, and a lens barrel for accommodating the lens group and the spacing elements.

In an exemplary embodiment, the first lens element may have a positive power, the object-side surface may be convex, and the image-side surface may be convex or concave, and the second lens element may have a negative power, the object-side surface may be convex, and the image-side surface may be concave, thereby forming a meniscus shape convex toward the object side; the third lens element can have positive focal power, and the object-side surface can be convex or concave, and the image-side surface can be convex; 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 negative power, and can have a concave object-side surface and a convex image-side surface, thereby forming a meniscus shape convex toward the image side; the sixth lens element can have a negative power, and can have a convex or concave object-side surface and a concave image-side surface. By reasonably distributing the surface type and the focal power of each lens of the imaging system, the image pickup effect can be effectively improved. In addition, the path of light rays in the optical system can be further adjusted by reasonably controlling the surface type of each lens, so that the image resolution of the imaging system is effectively improved, and the aberration of the imaging system is balanced.

In an exemplary embodiment, the plurality of spacer elements includes a first spacer element between the first lens and the second lens, a second spacer element between the second lens and the third lens, a third spacer element between the third lens and the fourth lens, a fourth spacer element between the fourth lens and the fifth lens, and a fifth spacer element between the fifth lens and the sixth lens. Optionally, the first spacer element is in contact with an image side surface of the first lens, the second spacer element is in contact with an image side surface of the second lens, the third spacer element is in contact with an image side surface of the third lens, the third spacer element is in contact with an image side surface of the fourth lens, and the fifth spacer element is in contact with an image side surface of the fifth lens. Optionally, at least one further spacer element may be provided between the third lens and the fourth lens in addition to the third spacer element. In an example where the at least one further spacing element is one spacing element, the one spacing element may be in contact with the third spacing element and may be in contact with the object side surface of the third lens. In an example where the at least one further spacer element is two spacer elements, one of the two spacer elements adjacent the third spacer element is in contact with the third spacer element and with the other spacer element, which may be in contact with the object side surface of the third lens. Through a plurality of spacer elements of reasonable setting, help intercepting unnecessary reflection light path, promote imaging system's formation of image definition, reduce the production of veiling glare, ghost to can guarantee the stability of lens part assemblage in-process, for example, when a plurality of spacer elements assemble with lens cone, lens in order, can guarantee assembly stability, and then promote the manufacturing yield of lens.

Fig. 1 shows a schematic view of a spacer element of the present application for eliminating veiling glare. It should be understood that, in order to make the structure and the labels of the drawings clearer, only the fourth spacing element P4 is taken as an example in fig. 1 to eliminate the stray light, and the rest of the spacing elements also have the function of eliminating the stray light, and the principle of eliminating the stray light is the same as that of the fourth spacing element. As is clear from fig. 1, the spacer element 4 is able to eliminate veiling glare G of light rays at the edge of the lens via multiple reflections.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the radius of curvature R2 of the image-side face of the first lens, the radius of curvature R12 of the image-side face of the sixth lens, the outer diameter D2m of the image-side face of the second spacing element and the outer diameter D5m of the image-side face of the fifth spacing element D5m satisfy: 13.0 < (R2/D2m) + (R12/D5m) < 13.0. The radius of the first lens and the radius of the sixth lens are reasonably set, so that the ratio of the first lens and the sixth lens is in an optimal range. The lens surface type mutation points are reduced, the molding difficulty is reduced, the molding consistency and stability of the lenses are improved, the assembly yield is improved, meanwhile, reasonable gradients are arranged between the sixth lens and the first lens, the outer diameters of the rest lenses are ensured to be stably changed, large-section-difference structures are reduced, the lens bearing stability is improved, and the reliability performance is improved; in addition, controlling the curvature of the image-side surface of the sixth lens is beneficial to achieving a large field angle of the imaging system by controlling the curvature of the image-side surface of the first lens, and is beneficial to balancing chromatic aberration and the ability to control distortion. The outer diameter of the image side surface of the second spacing element can be matched with the outer diameter of the image side surface of the fifth spacing element when the conditions are met, and a stray light path generated by image side reflection of the first lens and the second lens and a stray light path generated by image side reflection of the fifth lens and the sixth lens can be shielded, so that the imaging quality of the imaging system is improved.

It is understood that, in order to make the structures and labels in the drawings clearer, the dimension labels of the structures of the individual lenses and the individual spacing elements are only used as examples in fig. 2, and for the dimension definitions of the similar structures of the remaining lenses and the remaining spacing elements, reference may be made to the above-mentioned labeled related dimension structures and labels, which are not described herein in detail.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the effective focal length f1 of the first lens, the effective focal length f5 of the fifth lens, the thickness CP1 of the first spacer element and the thickness CP5 of the fifth spacer element are satisfied between: -230 < f5/CP5+ f1/CP1< -18.0. Further, the above conditional expressions may also satisfy: -230.0< f5/CP5+ f1/CP1<0 or 0< f5/CP5+ f1/CP1< -18.0. By reasonably setting the thicknesses of the first spacing element and the fifth spacing element, the internal stress of the lens can be effectively reduced, and the deformation quantity generated by the release of the baking stress is reduced, so that the variation of the curvature of field of the lens after high temperature and high humidity in reliability is reduced, the problem of the deformation of the lens barrel caused by the matching of the lens and the lens barrel is reduced, and the performance yield is improved; the reasonable control of the focal length of the first lens is beneficial to enabling the object side end to have enough convergence capacity so as to adjust the focusing position of the light beam, further shorten the total length of the system, and the reasonable control of the focal length of the fifth lens is beneficial to correcting the astigmatism in the arc loss direction and the meridional direction.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the distance EP34 of the third spacer element from the fourth spacer element on the optical axis, the distance EP45 of the fourth spacer element from the fifth spacer element on the optical axis, the central thickness CT3 of the third lens on the optical axis and the central thickness CT4 of the fourth lens on the optical axis satisfy: -7.0 < (EP34+ EP45)/(CT3-CT4) < -3.0. The ratio of the distance between each adjacent spacer element in the third spacer element, the fourth spacer element and the fifth spacer element to the difference of the thicknesses of the third lens and the fourth lens is reasonably set, so that the influence of air gap change on the lens can be reduced; in addition, the thickness ratio of the third lens and the fourth lens can be further controlled, the structural stability of the third lens and the fourth lens is enhanced, and the field curvature sensitivity is reduced.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the radius of curvature R8 of the image-side face of the fourth lens, the inner diameter d2m of the image-side face of the second spacer element and the inner diameter d3m of the image-side face of the third spacer element satisfy between: 4.0 < | R8/(d3m + d2m) | < 9.0. By controlling the ratio of the curvature radius of the image side surface of the fourth lens to the sum of the inner diameter of the image side surface of the second spacing element P2 and the inner diameter of the image side surface of the third spacing element P3 within a reasonable range, the light leakage phenomenon can be effectively improved, the generation of large-energy-value light spots is prevented, and the imaging quality of the lens is improved. Meanwhile, the second spacing element and the third spacing element have reasonable inner diameters, so that the flatness can be improved, and the inclination in the assembling process is reduced.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the thickness CP3 of the third spacer element, the distance EP23 of the second spacer element from the third spacer element on the optical axis, the distance T23 of the second lens and the third lens on the optical axis and the central thickness CT3 of the third lens on the optical axis are satisfied: 1.5 < T23/CP3+ EP23/CT3 < 61.0. Through the thickness ratio of the distance between the second lens and the third spacing element and the ratio of the thickness between the third lens and the distance between the second spacing element and the third spacing element, the light convergence can be effectively improved, the relative illumination is improved, and the imaging performance of the lens is improved.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the distance T45 between the fourth lens and the fifth lens on the optical axis, the outer diameter D4s of the object-side face of the fourth spacer element, the inner diameter D4s of the object-side face of the fourth spacer element and the thickness CP4 of the fourth spacer element are satisfied: 7.0 < (D4s + D4s)/(CP4+ T45) < 16.0. By reasonably controlling the distance between the fourth lens and the fifth lens and the ratio of the thickness sum of the fourth spacing element to the inner diameter sum and the outer diameter sum of the object side surface of the fourth spacing element, arc stray light can be effectively avoided, and the thickness ratio of the fifth lens is improved, so that the molding process of the two rear large image surface lenses is milder, and the lens outer diameter deformation caused by internal stress is reduced.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the radius of curvature R5 of the object-side surface of the third lens, the sum Σ AT of the distances on the optical axis of any two adjacent lenses of the first to sixth lenses, and the sum Σ EP of the distances on the optical axis of any two adjacent spacing elements of the first to fifth spacing elements satisfy: 24.0 < | R5/(∑ EP- Σ AT) | < 45.0. The smoothness of the lens of the third lens can be improved by reasonably controlling the curvature of the object side surface of the third lens, ghost images of an optical system are reduced, and the imaging capacity of the optical imaging lens is improved; in addition, the product yield loss caused by unstable assembly of each element can be effectively reduced by reasonably controlling the difference between the sum of the distances between the lenses and the sum of the distances between the spacing elements, and the stray light problem is improved by further controlling the balance of the axial thicknesses of the spacing elements and the lenses, so that the imaging quality is improved.

In an exemplary embodiment, referring to the dimensioning of fig. 2, a sum Σ CP of thicknesses of any one of the first to fifth spacing elements, a radius of curvature R11 of the object-side surface of the sixth lens, and a sum Σ CT of center thicknesses of any one of the first to sixth lenses on the optical axis satisfy: 0< | R11/(∑ CP +. Sigma CT) | < 13.0. Through the relation between the camber of the object side face of the reasonable control sixth lens and the thickness of each lens and each interval element, the risk of weld marks is reduced, the flatness of the lens is improved, and the assembly is not easy to incline, so that the optical imaging lens is stable.

In an exemplary embodiment, with reference to the dimensioning of fig. 2, the effective focal length f3 of the third lens, the effective focal length f5 of the fifth lens, the central thickness CT3 of the third lens on the optical axis, the central thickness CT5 of the fifth lens on the optical axis, the thickness CP3 of the third spacing element, the thickness CP5 of the fifth spacing element, the outer diameter D5s of the object-side face of the fifth spacing element and the inner diameter D5m of the image-side face of the fifth spacing element are such that: -24.0 ≦ (f5 × CP3 × CT5 × CT3-f3 × CP5 × CT5 × CT3)/(CP3 × CP5 × D5s × D5m) < -10.0. Thickness through reasonable control third interval component and fifth interval component, the external diameter of object side face and the internal diameter of image side face and the effective focal length and the thickness of third lens and fifth lens, can avoid dragging out the parasitic light that arouses by third lens and fifth lens, the central thickness of third lens and fifth lens is controlled simultaneously, be favorable to promoting the curvature of field stability, promote overall structure intensity, thereby obtain better reliability performance, the focal power of control fifth lens is favorable to realizing the long focal characteristic.

In an exemplary embodiment, the imaging lens further comprises a barrel for accommodating each lens and each spacer element, as referenced in the dimensioning of fig. 2, wherein a dimension L of the barrel in the optical axis direction, a radius of curvature R2 of the image-side surface of the first lens, and a radius of curvature R12 of the image-side surface of the sixth lens are satisfied between: the ratio of (R2-R12)/L is more than or equal to-15.0 and less than 7.0. Further, the above conditional expressions may also satisfy: -15.0 ≦ (R2-R12)/L <0 or 0 ≦ (R2-R12)/L < 7.0. The curvature of the image side surface of the first lens and the curvature of the image side surface of the sixth lens are reasonably arranged, so that the risk that the image side surface of the first lens and the image surface of the sixth lens are convex can be avoided, and the abrasion of the lens is reduced. In addition, the lens barrel can be made to have a miniaturization characteristic by limiting the axial dimension of the lens barrel.

In an exemplary embodiment, the imaging system according to the present application may further include a filter for correcting color deviation and/or a protective glass for protecting the photosensitive element located on the imaging surface.

The lens group according to the above-described embodiment of the present application may employ a plurality of lenses, for example, the above six lenses. By reasonably distributing the focal power of each lens, the surface type, the central thickness of each lens, the on-axis distance between each lens and the like, the low-order aberration of the imaging system can be effectively balanced and controlled, meanwhile, the tolerance sensitivity can be reduced, and the miniaturization of the imaging system can be kept.

In the embodiment of the present application, at least one of the mirror surfaces of each of the first to sixth 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 to sixth lenses 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 six lenses are exemplified in the embodiment, the imaging system is not limited to including six 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 imaging system according to embodiment 1 of the present application is described below with reference to fig. 3 to 6D. Fig. 3 to 5 respectively show cross-sectional schematic views of three imaging systems according to embodiment 1 of the present application. The three imaging systems may each include a lens group, a plurality of spacing elements, and a lens barrel for housing the lens group and the spacing elements. The three imaging systems described above may include lens groups having the same optical structure.

Taking the lens assembly included in the imaging system 110 shown in fig. 3 as an example, the lens assembly, in order from an object side to an image side along an optical axis, includes: stop STO, first lens E1, second lens E2, third lens E3, fourth lens E4, fifth lens E5, and sixth lens E6. Illustratively, the lens group may further include a filter (not shown) disposed on an image side surface of the sixth lens E6 along the optical axis and an image plane S15 (not shown).

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 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 convex object-side surface S5 and a convex 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 negative power, and has a concave object-side surface S9 and a convex image-side surface S10. The sixth lens element E6 has negative power, and has a concave object-side surface S11 and a concave image-side surface S12. The filter has an object side S13 and an image side S14. The light from the object sequentially passes through the respective surfaces S1 to S12 and is finally imaged on the imaging surface S15.

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

TABLE 1

In the present embodiment, the effective focal length f1 of the first lens E1 is 8.89mm, the effective focal length f3 of the third lens E3 is 14.49mm, and the effective focal length f5 of the fifth lens E5 is-13.02 mm.

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 sixth lens E6 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, and c is 1/R (i.e., paraxial curvature c is the reciprocal 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. Table 2 below gives the high-order coefficient coefficients a4, a6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each of the aspherical mirror surfaces S1 to S12 in example 1.

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

-7.0753E-03

-3.7969E-03

2.2237E-04

3.9397E-04

1.7269E-04

6.6902E-05

2.1235E-05

1.0415E-05

5.5167E-06

S2

1.1090E-01

-1.3132E-02

2.7557E-03

-4.1979E-04

-3.1383E-05

2.7182E-05

1.0263E-04

-6.5427E-07

-9.0539E-07

S3

-1.9959E-01

2.1712E-02

-2.6489E-03

-1.0698E-04

-1.4245E-04

-4.1377E-05

6.0514E-05

-7.0790E-06

-5.4337E-07

S4

-3.2151E-01

2.8733E-02

-7.3604E-04

9.5421E-05

-2.6575E-04

-8.0156E-05

1.9570E-05

-1.4557E-06

-6.8046E-07

S5

1.8974E-02

-5.5985E-03

4.0905E-03

-6.7427E-06

-3.2933E-04

-1.6601E-04

3.3756E-05

1.5079E-06

-5.2724E-06

S6

-2.3393E-02

-1.0882E-02

1.0083E-03

3.4494E-04

-1.6517E-04

-5.5229E-05

2.8324E-05

-5.1704E-06

1.2035E-07

S7

-4.5093E-02

8.6535E-03

8.4957E-04

5.2704E-04

-1.3122E-04

1.1613E-05

2.7866E-05

-7.7168E-06

9.3403E-07

S8

-1.4126E-01

1.3313E-02

-1.2811E-04

5.2301E-04

5.7951E-06

1.0478E-05

1.1708E-05

-2.2719E-06

1.6133E-06

S9

1.3371E-02

-1.5321E-02

7.9117E-04

7.6569E-04

-6.5961E-05

3.9770E-05

4.6520E-06

-2.5733E-06

9.9060E-07

S10

2.2215E-01

-1.7613E-02

-8.0935E-04

7.1245E-04

-1.2530E-04

7.9230E-06

-3.4681E-07

-5.0749E-06

1.1909E-06

S11

-3.7101E-01

7.9723E-03

-5.8021E-03

3.8982E-04

-1.8755E-04

-8.3902E-06

-1.0185E-05

-1.2925E-05

-3.1236E-06

S12

-6.2220E-01

1.9190E-02

-8.4937E-03

7.8485E-04

-2.9685E-04

1.0753E-05

-5.7138E-06

-1.2251E-05

2.8925E-06

TABLE 2

With continued reference to fig. 3, the imaging system 110 includes a barrel P0, the plurality of spacer elements including a first spacer element P1 located between the first lens E1 and the second lens E2, a second spacer element P2 located between the second lens E2 and the third lens E3, a third spacer element P3 located between the third lens E3 and the fourth lens E4, a fourth spacer element P4 located between the fourth lens E4 and the fifth lens E5, and a fifth spacer element P5 located between the fourth lens E4 and the fifth lens E5. Illustratively, the first spacer element P1 is in contact with the image-side surface S2 of the first lens E1, the second spacer element P2 is in contact with the image-side surface S4 of the second lens E2, and the third spacer element P3 is in contact with the image-side surface S6 of the third lens E3. The plurality of spacer elements further includes a spacer element P3b located between the third lens E3 and the fourth lens E4, the spacer element P3b being in contact with an image-side surface of the third spacer element P3 and an object-side surface of the fourth lens E4. The fourth spacing element P4 is in contact with the image-side surface S8 of the fourth lens E4, and the fifth spacing element P5 is in contact with the image-side surface S10 of the fifth lens E5. In the imaging system 110, the first spacer element P1, the second spacer element P2, the third spacer element P3, the fourth spacer element P4 and the fifth spacer element P5 are spacers and the spacer element P3b is a spacer. The spacing elements can be used for coupling adjacent lenses and preventing external redundant light from entering, and the structural stability of the imaging system can be enhanced by reasonably arranging the positions of the spacing elements and the lenses.

Referring to fig. 4, the imaging system 120 may have a similar structure to the imaging system 110, except that in the imaging system 120, the third and fourth spacing elements P3 and P4 are spacers, and the first, second, fifth, and spacing elements P1, P2, P5, and P3b are spacers.

Referring to fig. 5, the imaging system 130 may have a similar structure to the imaging system 110 and the imaging system 120, and unlike the two imaging systems described above, in the imaging system 130, the plurality of spacer elements further include a spacer element P3c between the third lens E3 and the fourth lens E4. Alternatively, the spacer element P3b may be in contact with the image-side surface of the third spacer element P3, and the spacer element P3c may be in contact with the image-side surface of the spacer element P3b and the object-side surface of the fourth lens E4. In imaging system 130, first spacer element P1, second spacer element P2, third spacer element P3, spacer element P3c, and fifth spacer element P5 are spacers, and spacer elements P3b and fourth spacer element P4 are spacers.

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 deviations of different image heights on the imaging plane after the light rays pass through the lens, and fig. 6D shows an on-axis chromatic aberration curve of the imaging system of embodiment 1, which represents the convergent focus deviations of the light rays of different wavelengths after the lens. As can be seen from fig. 6A to 6D, the imaging system according to embodiment 1 can achieve good imaging quality.

Example 2

An imaging system according to embodiment 1 of the present application is described below with reference to fig. 7 to 10D. Fig. 7 to 9 respectively show schematic sectional views of three imaging systems according to embodiment 2 of the present application. The three imaging systems may each include a lens group, a plurality of spacing elements, and a lens barrel for housing the lens group and the spacing elements. The three imaging systems described above may include lens groups having the same optical structure.

Taking the lens assembly included in the imaging system 210 shown in fig. 7 as an example, the lens assembly, in order from an object side to an image side along an optical axis, comprises: stop STO, first lens E1, second lens E2, third lens E3, fourth lens E4, fifth lens E5, and sixth lens E6. Illustratively, the lens group may further include a filter (not shown) disposed on an image side surface of the sixth lens E6 along the optical axis and an image plane S15 (not shown).

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 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 positive power, and has a convex object-side surface S7 and a concave image-side surface S8. The fifth lens element E5 has negative power, and has a concave object-side surface S9 and a convex image-side surface S10. The sixth lens element E6 has negative power, and has a convex object-side surface S11 and a concave image-side surface S12. The filter has an object side S13 and an image side S14. The light from the object sequentially passes through the respective surfaces S1 to S12 and is finally imaged on the imaging surface S15.

Table 3 shows a basic parameter table of the lens group of example 2, in which the unit of the radius of curvature and the thickness/distance are both millimeters (mm).

TABLE 3

In the present embodiment, the effective focal length f1 of the first lens E1 is 8.92mm, the effective focal length f3 of the third lens E3 is 15.59mm, and the effective focal length f5 of the fifth lens E5 is-10.96 mm.

Table 4 shows the high-order term coefficients a4, a6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each of the aspherical mirror surfaces S1 to S12 in example 2, wherein each aspherical mirror surface type can be defined by the formula (1) given in example 1 above.

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

-1.1489E-02

-2.0658E-03

1.0491E-03

5.2253E-04

1.5322E-04

3.9849E-05

4.4965E-06

3.4305E-06

-1.2001E-06

S2

1.1119E-01

-6.8254E-03

6.9645E-03

3.5852E-04

7.4354E-04

-3.8068E-05

2.1442E-04

-5.6872E-05

2.4443E-05

S3

-2.0456E-01

2.2543E-02

-2.3600E-03

-8.0034E-05

2.4780E-04

-1.4848E-04

1.2882E-04

-4.7091E-05

7.7252E-06

S4

-3.3104E-01

2.9012E-02

-1.2630E-03

7.0569E-04

1.2514E-04

6.1212E-05

5.5614E-05

-2.8484E-07

-2.5438E-06

S5

2.3196E-02

-5.4348E-03

4.8222E-03

4.2815E-04

-1.0622E-04

-4.9204E-05

8.4745E-05

2.0297E-06

-3.1974E-06

S6

-2.2427E-02

-1.1013E-02

9.0496E-04

4.0582E-04

-1.6073E-04

-5.8325E-05

3.2855E-05

-4.6862E-06

1.1389E-07

S7

-4.4812E-02

8.7406E-03

6.3470E-04

4.7058E-04

-1.3964E-04

1.1249E-05

2.4419E-05

-7.3171E-06

6.4657E-07

S8

-1.4823E-01

1.3433E-02

-6.8095E-04

4.8180E-04

-1.7840E-05

-2.9675E-06

1.3546E-05

-3.2991E-06

6.1348E-07

S9

9.3778E-03

-1.7182E-02

-4.7743E-05

7.1107E-04

-9.5148E-05

1.8708E-05

5.6889E-06

-3.5066E-06

2.9904E-07

S10

4.0590E-01

-5.0065E-02

1.7404E-03

2.0550E-03

-6.4463E-04

3.8222E-06

-2.4192E-05

-4.2295E-06

2.2317E-06

S11

-3.5745E-01

7.6035E-03

-5.7700E-03

4.5564E-04

-1.2979E-04

2.7947E-05

6.7596E-06

-6.3017E-06

6.6105E-07

S12

-6.2812E-01

1.7719E-02

-8.2169E-03

7.9397E-04

-2.4560E-04

3.0720E-05

8.7418E-06

-1.0094E-05

1.3599E-06

TABLE 4

With continued reference to fig. 7, the imaging system 210 includes a lens barrel P0, the plurality of spacer elements including a first spacer element P1 located between the first lens E1 and the second lens E2, a second spacer element P2 located between the second lens E2 and the third lens E3, a third spacer element P3 located between the third lens E3 and the fourth lens E4, a fourth spacer element P4 located between the fourth lens E4 and the fifth lens E5, and a fifth spacer element P5 located between the fourth lens E4 and the fifth lens E5. Illustratively, the first spacer element P1 is in contact with the image-side surface S2 of the first lens E1, the second spacer element P2 is in contact with the image-side surface S4 of the second lens E2, and the third spacer element P3 is in contact with the image-side surface S6 of the third lens E3. The plurality of spacer elements further includes a spacer element P3b located between the third lens E3 and the fourth lens E4, the spacer element P3b being in contact with an image-side surface of the third spacer element P3 and an object-side surface of the fourth lens E4. The fourth spacing element P4 is in contact with the image-side surface S8 of the fourth lens E4, and the fifth spacing element P5 is in contact with the image-side surface S10 of the fifth lens E5. In the imaging system 210, the first spacer element P1, the second spacer element P2, the third spacer element P3, the fourth spacer element P4, and the fifth spacer element P5 are spacers, and the spacer element P3b is a spacer. The spacing element can be used for coupling adjacent lenses and blocking external redundant light from entering, and the structural stability of the imaging system can be enhanced by reasonably setting the positions of the spacing element and each lens.

Referring to fig. 8, the imaging system 220 may have a similar structure to the imaging system 210, except that in the imaging system 220, the first, second, third, and fifth spacing elements P1, P2, P3, and P5 are spacers, and the spacing elements P3b and the fourth spacing element P4 are spacers.

Referring to fig. 9, the imaging system 230 may have a similar structure to the imaging system 210 and the imaging system 220, and unlike the two imaging systems described above, in the imaging system 230, the plurality of spacer elements further include a spacer element P3c between the third lens E3 and the fourth lens E4. Alternatively, the spacer element P3b may be in contact with the image-side surface of the third spacer element P3, and the spacer element P3c may be in contact with the image-side surface of the spacer element P3b and the object-side surface of the fourth lens E4. In imaging system 230, first spacer element P1, second spacer element P2, third spacer element P3, spacer element P3c, and fifth spacer element P5 are spacers, and spacer elements P3b and fourth spacer element P4 are spacers.

Fig. 10A shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the imaging system of embodiment 2. Fig. 10B shows a distortion curve of the imaging system of embodiment 2, which represents distortion magnitude values corresponding to different image heights. Fig. 10C shows a chromatic aberration of magnification curve of the imaging system of embodiment 2, which represents deviations of different image heights on the imaging plane after the light rays pass through the lens, and fig. 10D shows an on-axis chromatic aberration curve of the imaging system of embodiment 2, which represents the convergent focus deviations of the light rays of different wavelengths after the lens. As can be seen from fig. 10A to 10D, the imaging system according to embodiment 2 can achieve good imaging quality.

Example 3

An imaging system according to embodiment 3 of the present application is described below with reference to fig. 11 to 14D. Fig. 11 to 13 respectively show cross-sectional schematic views of three imaging systems according to embodiment 3 of the present application. The three imaging systems may each include a lens group, a plurality of spacing elements, and a lens barrel for housing the lens group and the spacing elements. The three imaging systems described above may include lens groups having the same optical structure.

Taking the lens assembly included in the imaging system 310 shown in fig. 11 as an example, the lens assembly, in order from an object side to an image side along an optical axis, comprises: stop STO, first lens E1, second lens E2, third lens E3, fourth lens E4, fifth lens E5, and sixth lens E6. Illustratively, the lens group may further include a filter (not shown) disposed on an image side surface of the sixth lens E6 along the optical axis and an image plane S15 (not shown).

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 positive power, and has a convex object-side surface S7 and a convex image-side surface S8. The fifth lens element E5 has negative power, and has a concave object-side surface S9 and a convex image-side surface S10. The sixth lens element E6 has negative power, and has a convex object-side surface S11 and a concave image-side surface S12. The filter has an object side S13 and an image side S14. The light from the object sequentially passes through the respective surfaces S1 to S12 and is finally imaged on the imaging surface S15.

Table 5 shows a basic parameter table of the lens group of example 3, in which the unit of the radius of curvature and the thickness/distance are both millimeters (mm).

TABLE 5

In the present embodiment, the effective focal length f1 of the first lens E1 is 9.68mm, the effective focal length f3 of the third lens E3 is 13.81mm, and the effective focal length f5 of the fifth lens E5 is-10.02 mm.

Table 6 shows the high-order term coefficients a4, a6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each of the aspherical mirror surfaces S1 to S12 in example 3, wherein each aspherical mirror surface type can be defined by the formula (1) given in example 1 above.

Flour mark

A4

A6

A8

A10

A12

A14

A16

A18

A20

S1

-7.1638E-03

-4.2463E-04

1.5239E-03

6.4160E-04

1.5755E-04

2.3529E-05

1.8482E-06

3.9986E-07

-7.5012E-07

S2

1.0448E-01

7.6458E-03

6.1379E-03

8.8517E-04

-1.2667E-03

-1.4308E-04

-1.5550E-04

-1.8566E-05

2.7501E-05

S3

-2.0951E-01

2.7843E-02

-3.7139E-03

9.5083E-04

-5.8412E-04

6.4471E-05

-3.2409E-05

-3.2659E-05

1.1289E-05

S4

-3.3004E-01

3.2004E-02

-2.1209E-04

9.6773E-04

1.4962E-04

1.3549E-04

4.2757E-05

-1.8362E-05

-3.3001E-06

S5

3.4309E-02

-6.1085E-03

4.9677E-03

5.2183E-04

-1.1463E-04

7.1737E-06

1.0010E-04

2.7466E-07

-4.7224E-06

S6

-2.7348E-02

-1.1469E-02

5.9230E-04

4.1396E-04

-1.7845E-04

-6.1571E-05

3.3698E-05

-3.1844E-06

-3.4152E-07

S7

-4.7944E-02

7.9991E-03

5.1444E-04

4.9064E-04

-1.2687E-04

1.3374E-05

2.2766E-05

-7.2549E-06

5.3440E-07

S8

-1.5244E-01

1.3415E-02

-1.1282E-03

4.8505E-04

-5.6634E-06

-7.4584E-06

9.8331E-06

-2.1168E-06

4.0947E-07

S9

1.4361E-02

-1.6478E-02

5.7250E-05

8.6422E-04

-9.1564E-05

1.2409E-05

8.8133E-06

-3.1178E-06

1.7289E-07

S10

4.0445E-01

-5.4951E-02

9.4811E-04

1.8039E-03

-4.2341E-04

4.5493E-05

1.3307E-05

-8.9749E-06

-3.9117E-08

S11

-3.1072E-01

6.8812E-04

-5.6248E-03

6.7523E-06

-1.4281E-04

-4.1978E-06

1.8675E-06

-3.7797E-06

1.2998E-06

S12

-1.2521E+00

-2.1954E-02

-3.0662E-02

-1.5071E-03

-1.4313E-03

-4.7666E-05

-6.3090E-05

-3.3040E-06

3.8007E-06

TABLE 6

With continued reference to fig. 11, the imaging system 310 includes a barrel P0, the plurality of spacer elements including a first spacer element P1 located between the first lens E1 and the second lens E2, a second spacer element P2 located between the second lens E2 and the third lens E3, a third spacer element P3 located between the third lens E3 and the fourth lens E4, a fourth spacer element P4 located between the fourth lens E4 and the fifth lens E5, and a fifth spacer element P5 located between the fourth lens E4 and the fifth lens E5. Illustratively, the first spacer element P1 is in contact with the image-side surface S2 of the first lens E1, the second spacer element P2 is in contact with the image-side surface S4 of the second lens E2, and the third spacer element P3 is in contact with the image-side surface S6 of the third lens E3. The plurality of spacer elements further includes a spacer element P3b located between the third lens E3 and the fourth lens E4, the spacer element P3b being in contact with an image-side surface of the third spacer element P3 and an object-side surface of the fourth lens E4. The fourth spacing element P4 is in contact with the image-side surface S8 of the fourth lens E4, and the fifth spacing element P5 is in contact with the image-side surface S10 of the fifth lens E5. In imaging system 310, first spacer element P1, second spacer element P2, third spacer element P3, fourth spacer element P4, and fifth spacer element P5 are spacers and spacer element P3b is a spacer. The spacing elements can be used for coupling adjacent lenses and preventing external redundant light from entering, and the structural stability of the imaging system can be enhanced by reasonably arranging the positions of the spacing elements and the lenses.

Referring to fig. 12, the imaging system 320 may have a similar structure to the imaging system 310, except that in the imaging system 320, the first, second, third, and fourth spacing elements P1, P2, P3b, and P5 are spacers, and the third and fourth spacing elements P3 and P4 are spacers.

Referring to fig. 13, the imaging system 330 may have a similar structure to the imaging system 310 and the imaging system 320, and unlike the two imaging systems described above, in the imaging system 330, the plurality of spacer elements further include a spacer element P3c between the third lens E3 and the fourth lens E4. Alternatively, spacer element P3b may be in contact with the image-side surface of the third spacer element P3, and spacer element P3c may be in contact with the image-side surface of spacer element P3b and the object-side surface of the fourth lens E4. In imaging system 330, first spacer element P1, second spacer element P2, third spacer element P3, spacer element P3c, and fifth spacer element P5 are spacers, and spacer elements P3b and fourth spacer element P4 are spacers.

Fig. 14A shows an astigmatism curve representing meridional field curvature and sagittal field curvature of the imaging system of embodiment 3. Fig. 14B shows a distortion curve of the imaging system of embodiment 3, which represents distortion magnitude values corresponding to different image heights. Fig. 14C shows a chromatic aberration of magnification curve of the imaging system of embodiment 3, which represents deviations of different image heights on the imaging plane after the light rays pass through the lens, and fig. 14D shows an on-axis chromatic aberration curve of the imaging system of embodiment 3, which represents the convergent focus deviations of the light rays of different wavelengths after the lens. As can be seen from fig. 14A to 14D, the imaging system according to embodiment 3 can achieve good imaging quality.

Table 7 shows a basic parameter table of the lens barrel and the spacer element in the imaging systems of embodiments 1 to 3, and the unit of each parameter in table 7 is millimeters (mm).

TABLE 7

In summary, examples 1 to 3 each satisfy the relationship shown in table 8.

TABLE 8

The foregoing description is only exemplary of the preferred embodiments of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of protection covered by the present application is not limited to the embodiments with a specific combination of the features described above, but also covers other embodiments with any combination of the features described above or their equivalents without departing from the scope of the present application. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims (10)

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 refractive power;

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

a second lens having a negative focal power;

a second spacer element in contact with an image side surface of the second lens;

a third lens having a positive refractive power;

a third spacer element in contact with an image side surface of the third lens;

a fourth lens having a positive focal power, the object-side surface of which is convex;

a fourth spacer element in contact with an image side surface of the fourth lens;

a fifth lens element having a negative refractive power and a convex image-side surface;

a fifth spacer element in contact with an image side surface of the fifth lens;

a sixth lens having a negative focal power; wherein a radius of curvature R2 of the image-side surface of the first lens, a radius of curvature R12 of the image-side surface of the sixth lens, an outer diameter D2m of the image-side surface of the second spacer element, and an outer diameter D5m of the image-side surface of the fifth spacer element D5m satisfy: 13.0 < (R2/D2m) + (R12/D5m) < 13.0.

2. The imaging system of claim 1, wherein an effective focal length f1 of the first lens, an effective focal length f5 of the fifth lens, a thickness CP1 of the first spacer element, and a thickness CP5 of the fifth spacer element are satisfied between: 230 < f5/CP5+ f1/CP1< -18.0.

3. The imaging system of claim 1, wherein a distance EP34 of the third and fourth spacer elements on the optical axis, a distance EP45 of the fourth and fifth spacer elements on the optical axis, a center thickness CT3 of the third lens on the optical axis, and a center thickness CT4 of the fourth lens on the optical axis satisfy: -7.0 < (EP34+ EP45)/(CT3-CT4) < -3.0.

4. The imaging system of claim 1, wherein a radius of curvature R8 of an image-side surface of the fourth lens, an inner diameter d2m of an image-side surface of the second spacer element, and an inner diameter d3m of an image-side surface of the third spacer element satisfy between: 4.0 < | R8/(d3m + d2m) | < 9.0.

5. The imaging system of claim 1, wherein a thickness CP3 of the third spacer element, a distance EP23 of the second spacer element from the third spacer element on the optical axis, a distance T23 of the second and third lenses on the optical axis, and a center thickness CT3 of the third lens on the optical axis satisfy: 1.5 < T23/CP3+ EP23/CT3 < 61.0.

6. The imaging system of claim 1, wherein a distance T45 between the fourth lens and the fifth lens on the optical axis, an outer diameter D4s of an object-side surface of the fourth spacer element, an inner diameter D4s of the object-side surface of the fourth spacer element, and a thickness CP4 of the fourth spacer element satisfies: 7.0 < (D4s + D4s)/(CP4+ T45) < 16.0.

7. The imaging system according to claim 1, characterized in that a radius of curvature R5 of an object-side surface of the third lens, a sum Σ AT of distances on the optical axis of any two adjacent lenses from the first lens to the sixth lens, and a sum Σ EP of distances on the optical axis of any two adjacent spacing elements from the first spacing element to the fifth spacing element satisfy: 24.0 < | R5/(∑ EP- Σ AT) | < 45.0.

8. The imaging system according to claim 1, wherein a sum Σ CP of thicknesses of respective spacer elements of the first to fifth spacer elements, a radius of curvature R11 of an object-side surface of the sixth lens, and a sum Σ CT of center thicknesses of respective lenses of the first to sixth lenses on the optical axis satisfy: 0< | R11/(∑ CP + ∑ CT) | < 13.0.

9. The imaging system of claim 1, wherein an effective focal length f3 of the third lens, an effective focal length f5 of the fifth lens, a center thickness CT3 of the third lens on the optical axis, a center thickness CT5 of the fifth lens on the optical axis, a thickness CP3 of the third spacing element, a thickness CP5 of the fifth spacing element, an outer diameter D5s of an object-side surface of the fifth spacing element, and an inner diameter D5m of an image-side surface of the fifth spacing element satisfy:

-24.0≤(f5*CP3*CT5*CT3-f3*CP5*CT5*CT3)/(CP3*CP5*D5s*d5m)＜-10.0。

10. the imaging system of claim 1, further comprising: a lens barrel for accommodating each lens and each spacer element, wherein a dimension L of the lens barrel in the optical axis direction, a radius of curvature R2 of an image-side surface of the first lens, and a radius of curvature R12 of an image-side surface of the sixth lens satisfy: -15.0 (R2-R12)/L is less than 7.0.

Images