Optical imaging system

Abstract

The present invention provides an optical imaging system. The optical imaging system includes a lens barrel and a lens group and a spacer element group disposed in the lens barrel. The lens group is composed of four lenses. The four lenses are, from the object side to the image side, a first lens with negative optical focal length, a second lens with optical focal length, a third lens with positive optical focal length, and a fourth lens with positive optical focal length. The object side surface of the fourth lens is convex. The spacer element group includes a first spacer element, a second spacer element, and a third spacer element. The following conditions are satisfied: 2.21≤L / ImgH≤2.90; 2.13≤f1 / f≤1.51; and 0.81≤(CT1+T12) / EP01≤1.74. The present invention solves the problem in the prior art of four-lens optical imaging systems that the optical focal length of the front lens is controlled, which easily leads to improper design of the front lens size, thereby resulting in poor assembly stability.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging equipment, and in particular to an optical imaging system. Background Art

[0002] In the field of modern optical imaging technology, four-element optical imaging systems are widely used in various imaging devices, such as mobile phone cameras and surveillance cameras, due to their simple structure and low cost. However, with the development of technology and increasing user needs, the requirements for optical imaging systems are also increasing, especially in terms of image size and device miniaturization.

[0003] Currently, four-lens optical imaging systems, while ensuring image size and miniaturization, control the focal length of the front-end lens to rationally control its ability to focus light, thereby controlling the light trajectory and ensuring that imaging requirements are met. However, this can easily lead to improper front-end lens sizing, resulting in stress concentration during assembly and affecting assembly stability.

[0004] That is to say, the four-lens optical imaging system in the prior art has the problem of controlling the optical focal length of the front lens, which easily leads to improper design of the front lens size and thus poor assembly stability. Summary of the Invention

[0005] The main purpose of the present invention is to provide an optical imaging system to solve the problem in the prior art of four-lens optical imaging systems that the optical focal length of the front lens is controlled, which easily leads to improper design of the front lens size and thus poor assembly stability.

[0006] To achieve the above-mentioned purpose, according to one aspect of the present invention, an optical imaging system is provided, comprising a lens barrel and a lens group and a spacer element group arranged in the lens barrel, wherein the lens group is composed of four lenses, and the four lenses are, from the object side to the image side, a first lens with negative optical power, a second lens with optical power, a third lens with positive optical power, and a fourth lens with positive optical power; the object side surface of the fourth lens is a convex surface; the spacer element group comprises a first spacer element located between the first lens and the second lens and partially supporting the image side surface of the first lens, a second spacer element located between the second lens and the third lens and partially supporting the image side surface of the second lens, a spacer element located between the third lens and the fourth lens and partially supporting the image side surface of the third lens, and a spacer element located between the third lens and the fourth lens and partially supporting the image side surface of the third lens. a third spacing element close to the lens; wherein, a spacing distance L from the object side surface of the lens barrel to the image side surface of the lens barrel on the optical axis of the optical imaging system and half of the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system satisfy: 2.21≤L / ImgH≤2.90; an effective focal length f1 of the first lens and an effective focal length f of the optical imaging system satisfy: -2.13≤f1 / f≤-1.51; a center thickness CT1 of the first lens on the optical axis, an air gap T12 between the first lens and the second lens on the optical axis, and a spacing distance EP01 from the object side surface of the lens barrel to the object side surface of the first spacing element on the optical axis satisfy: 0.81≤(CT1+T12) / EP01≤1.74.

[0007] According to another aspect of the present invention, an optical imaging system is also provided, comprising a lens barrel and a lens group and a spacer element group arranged in the lens barrel, wherein the lens group is composed of four lenses, and the four lenses are, from the object side to the image side, a first lens with negative optical focal length, a second lens with optical focal length, a third lens with positive optical focal length and a fourth lens with positive optical focal length; the image side surface of the first lens is concave; the object side surface of the third lens is concave and the image side surface is convex; the object side surface of the fourth lens is convex; the spacer element group comprises a first spacer element located between the first lens and the second lens and partially supporting the image side surface of the first lens, a second spacer element located between the second lens and the third lens and partially supporting the image side surface of the second lens, and a spacer element located between the second lens and the third lens and partially supporting the image side surface of the second lens. a third spacer element between the third lens and the fourth lens and partially supported by the image side surface of the third lens; wherein, the spacing distance L from the object side surface of the lens barrel to the image side surface of the lens barrel on the optical axis of the optical imaging system and the effective focal length f of the optical imaging system satisfy: 1.74≤L / f≤3.15; the effective focal length f4 of the fourth lens, the curvature radius R5 of the object side surface of the third lens and the curvature radius R6 of the image side surface of the third lens satisfy: -2.95≤f4 / (R5+R6)≤-0.60; the inner diameter d1s of the object side surface of the first spacer element, the outer diameter D0s of the object side surface of the lens barrel and the inner diameter d0s of the object side surface of the lens barrel satisfy: 0.47≤d1s / (D0s-d0s)≤4.48.

[0008] According to another aspect of the present invention, an optical imaging system is also provided, comprising a lens barrel and a lens group and a spacer element group arranged in the lens barrel, wherein the lens group is composed of four lenses, and the four lenses are, from the object side to the image side, a first lens with negative optical focal length, a second lens with optical focal length, a third lens with positive optical focal length and a fourth lens with positive optical focal length; the image side surface of the first lens is concave; the object side surface of the third lens is concave and the image side surface is convex; the object side surface of the fourth lens is convex; the spacer element group comprises a first spacer element located between the first lens and the second lens and partially supporting the image side surface of the first lens, a second spacer element located between the second lens and the third lens and partially supporting the image side surface of the second lens, and a spacer element located between the third lens and the second lens and partially supporting the image side surface of the second lens. a third spacer element between the third lens and the fourth lens and supported by the image side surface of the third lens; wherein, the spacing distance L from the object side surface of the lens barrel to the image side surface of the lens barrel on the optical axis of the optical imaging system and half the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system satisfy the following: 2.21≤L / ImgH≤2.90; the effective focal length f1 of the first lens and the effective focal length f of the optical imaging system satisfy the following: -2.13≤f1 / f≤-1.51; the curvature radius R1 of the object side surface of the first lens, the curvature radius R2 of the image side surface of the first lens and the inner diameter d1s of the object side surface of the first spacer element satisfy the following: -4.91≤(R1+R2) / d1s≤1.87.

[0009] Furthermore, the inner diameter d1s of the object-side surface of the first spacer element, the outer diameter D0s of the object-side surface of the lens barrel, and the inner diameter d0s of the object-side surface of the lens barrel satisfy the following relationship: 0.47≤d1s / (D0s-d0s)≤4.48.

[0010] Furthermore, the object-side surface of the third lens is concave, and the image-side surface is convex; the curvature radius R5 of the object-side surface of the third lens, the curvature radius R6 of the image-side surface of the third lens, and the inner diameter d3s of the object-side surface of the third spacer element satisfy the following relationship: -3.48≤(R5+R6) / d3s≤-0.87.

[0011] Furthermore, the distance TD on the optical axis from the object side surface of the first lens to the image side surface of the fourth lens, the spacing distance EP12 on the optical axis from the image side surface of the first spacer element to the object side surface of the second spacer element, and the spacing distance EP23 on the optical axis from the image side surface of the second spacer element to the object side surface of the third spacer element satisfy the following: 2.35≤TD / (EP12+EP23)≤4.79.

[0012] Furthermore, the image side surface of the first lens is concave; the outer diameter D1s of the object side surface of the first spacer element, the inner diameter d1s of the object side surface of the first spacer element and the curvature radius R2 of the image side surface of the first lens satisfy: 1.45≤(D1s-d1s) / R2≤4.27.

[0013] Furthermore, an inner diameter d3m of the image-side surface of the third spacer element and an inner diameter d2m of the image-side surface of the second spacer element satisfy the following relationship: 1.34≤d3m / d2m≤2.40.

[0014] Furthermore, a distance L between the object side surface of the lens barrel and the image side surface of the lens barrel on the optical axis, a sum ∑AT of air gaps on the optical axis between two adjacent lenses among the first to fourth lenses, and a center thickness CT2 of the second lens on the optical axis satisfy the following relationship: 3.55≤(L-∑AT) / CT2≤7.43.

[0015] Furthermore, an inner diameter d2s of the object-side surface of the second spacer element and an inner diameter d1m of the image-side surface of the first spacer element satisfy the following relationship: 0.49≤d2s / d1m≤1.87.

[0016] Furthermore, the spacer element group also includes a third auxiliary spacer element located between the third spacer element and the fourth lens and partially supported by the third spacer element. The sum of the thicknesses ∑CP3 of all spacer elements located between the third lens and the fourth lens, the center thickness CT3 of the third lens on the optical axis, the center thickness CT4 of the fourth lens on the optical axis, and the air gap T34 between the third lens and the fourth lens on the optical axis satisfy the following: 0.43≤∑CP3 / (CT4+CT3+T34)≤0.91.

[0017] Furthermore, the spacer element group also includes a second auxiliary spacer element selectively arranged between the second spacer element and the third lens and partially supported by the second spacer element, and the sum of the thicknesses ∑CP2 of all spacer elements located between the second lens and the third lens and the air gap T23 on the optical axis between the second lens and the third lens satisfy the following: 0.08≤∑CP2 / T23≤1.52.

[0018] Furthermore, an outer diameter D3s of the object-side surface of the third spacer element, an inner diameter d3s of the object-side surface of the third spacer element, and an effective focal length f3 of the third lens satisfy the following relationship: 0.06≤(D3s-d3s) / f3≤1.70.

[0019] Furthermore, the spacer element group also includes a third auxiliary spacer element located between the third spacer element and the fourth lens and partially supported by the third spacer element, and the curvature radius R7 of the object-side surface of the fourth lens and the inner diameter d3bm of the image-side surface of the third auxiliary spacer element satisfy the following relationship: 0.52≤R7 / d3bm≤2.40.

[0020] Furthermore, an inner diameter d0m of the image-side surface of the lens barrel and an effective focal length f4 of the fourth lens element satisfy the following relationship: 0.58≤d0m / f4≤1.62.

[0021] Furthermore, a center thickness CT2 of the second lens on the optical axis and a spacing distance EP12 from the image side surface of the first spacer element to the object side surface of the second spacer element on the optical axis satisfy: 0.66≤CT2 / EP12≤2.41.

[0022] Furthermore, the inner diameter d1m of the image side surface of the first spacer element, the curvature radius R3 of the object side surface of the second lens and the refractive index N2 of the second lens satisfy: -0.33≤d1m / R3 N2≤1.37.

[0023] By applying the technical solution of the present invention, the optical imaging system of the present application is composed of a lens barrel, four lenses arranged in the lens barrel, and multiple spacer elements. By reasonably arranging the optical power of each lens, the surface shape of the fourth lens, and the positions of the first spacer element to the third spacer element, and setting the optical imaging system to meet 2.21≤L / ImgH≤2.90 and -2.13≤f1 / f≤-1.51, it can be seen that by setting the optical power of the first lens to a negative value, if the thickness ratio of the first lens is improperly designed, it is easy for the first lens to experience stress concentration during assembly, resulting in large assembly internal stress, thereby affecting the assembly stability of the optical imaging system. Therefore, the present application constrains 0.81≤(CT1+T12) / EP01≤1.74, and controls the ratio of the center thickness of the first lens on the optical axis, the sum of the air gaps between the first lens and the second lens on the optical axis, and the spacing distance between the object side of the lens barrel and the object side of the first spacing element on the optical axis within a certain range. This is conducive to reasonably controlling the center thickness and edge thickness of the first lens, facilitating the design of the structural dimensions of the first lens, reducing the internal stress of the assembly of the first lens and the front end of the lens barrel, avoiding the risk of deformation of the first lens during assembly, ensuring the assembly stability of the first lens, and thus ensuring the assembly stability of the optical imaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 A dimensioned diagram illustrating an optical imaging system according to an alternative embodiment of the present invention;

[0026] Figure 2 A schematic structural diagram of an optical imaging system according to embodiment 1-1 of the present invention is shown;

[0027] Figure 3 A schematic structural diagram of an optical imaging system according to Embodiment 1-2 of the present invention is shown;

[0028] Figure 4Schematic diagrams showing the structures of optical imaging systems according to embodiments 1-3 of the present invention;

[0029] Figures 5 to 8 chromatic aberration of magnification curve, axial chromatic aberration curve, astigmatism curve and distortion curve of the optical imaging system of embodiment 1 of the present invention are respectively shown;

[0030] Figure 9 A schematic structural diagram of an optical imaging system according to embodiment 2-1 of the present invention is shown;

[0031] Figure 10 A schematic structural diagram of an optical imaging system according to embodiment 2-2 of the present invention is shown;

[0032] Figure 11 A schematic structural diagram of an optical imaging system according to Embodiment 2-3 of the present invention is shown;

[0033] Figures 12 to 15 chromatic aberration curve, axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical imaging system of the second embodiment of the present invention are respectively shown;

[0034] Figure 16 A schematic structural diagram of an optical imaging system according to embodiment 3-1 of the present invention is shown;

[0035] Figure 17 A schematic structural diagram of an optical imaging system according to embodiment 3-2 of the present invention is shown;

[0036] Figure 18 A schematic structural diagram of an optical imaging system according to embodiment 3-3 of the present invention is shown;

[0037] Figures 19 to 22 chromatic aberration curve, axial chromatic aberration curve, astigmatism curve, and distortion curve of the optical imaging system of Example 3 of the present invention are respectively shown;

[0038] Figure 23 An assembly stress diagram is shown for an optical imaging system according to an optional example 1 of the present invention when 2.21≤L / ImgH≤2.90, -2.13≤f1 / f≤-1.51, and (CT1+T12) / EP01=1.00 is satisfied;

[0039] Figure 24 An assembly stress diagram is shown for an optical imaging system according to optional example 2 of the present invention when 2.21≤L / ImgH≤2.90, -2.13≤f1 / f≤-1.51, and (CT1+T12) / EP01=1.48 is satisfied;

[0040] Figure 25An assembly stress diagram is shown for the optical imaging system of Example 3 when 2.21≤L / ImgH≤2.90, -2.13≤f1 / f≤-1.51, and (CT1+T12) / EP01=1.90 is satisfied;

[0041] Figure 26 An assembly stress diagram is shown for the optical imaging system of Example 4 when 2.21≤L / ImgH≤2.90, -2.13≤f1 / f≤-1.51, and (CT1+T12) / EP01=0.50 is satisfied.

[0042] The above drawings include the following reference numerals:

[0043] P0, lens barrel; E1, first lens; S1, object-side surface of the first lens; S2, image-side surface of the first lens; E2, second lens; S3, object-side surface of the second lens; S4, image-side surface of the second lens; E3, third lens; S5, object-side surface of the third lens; S6, image-side surface of the third lens; E4, fourth lens; S7, object-side surface of the fourth lens; S8, image-side surface of the fourth lens; P1, first spacer; P2, second spacer; P2b, second auxiliary spacer; P3, third spacer; P3b, third auxiliary spacer. DETAILED DESCRIPTION

[0044] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0045] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0046] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity direction; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above directional words are not used to limit the present invention.

[0047] It should be noted that in this specification, the terms "first," "second," "third," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, the first lens discussed below could also be referred to as the second lens or the third lens without departing from the teachings of this application.

[0048] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical and aspherical surfaces shown in the drawings are provided by way of example. That is, the shapes of the spherical and aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0049] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is undefined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is undefined, it means that the lens surface is concave at least in the paraxial region. The surface shape in the paraxial region can be determined according to the judgment method of ordinary knowledge in this field, using the positive and negative R value (R refers to the radius of curvature of the paraxial region, usually refers to the R value in the lens database (lens data) in optical software) to determine the convexity and concavity. For the object side, when the R value is positive, it is determined to be convex, and when the R value is negative, it is determined to be concave. For the image side, when the R value is positive, it is determined to be concave, and when the R value is negative, it is determined to be convex. In this application, the left side is the object side and the right side is the image side.

[0050] In order to solve the problem in the prior art of a four-lens optical imaging system that the optical focal length of the front lens is controlled, which easily leads to improper design of the front lens size and thus poor assembly stability, the present invention provides an optical imaging system.

[0051] like Figures 1 to 26As shown, in an optional embodiment of the present application, the optical imaging system includes a lens barrel and a lens group and a spacer element group arranged in the lens barrel, the lens group consists of four lenses, and the four lenses are, from the object side to the image side, a first lens with negative optical focal length, a second lens with optical focal length, a third lens with positive optical focal length and a fourth lens with positive optical focal length; the object side surface of the fourth lens is a convex surface; the spacer element group includes a first spacer element located between the first lens and the second lens and partially supported by the image side surface of the first lens, a second spacer element located between the second lens and the third lens and partially supported by the image side surface of the second lens, a third spacer element located between the third lens and the fourth lens and partially supported by the image side surface of the third lens Three spacer elements; wherein, the spacing distance L from the object side surface of the lens barrel to the image side surface of the lens barrel on the optical axis of the optical imaging system and half of the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system satisfy: 2.21≤L / ImgH≤2.90; the effective focal length f1 of the first lens and the effective focal length f of the optical imaging system satisfy: -2.13≤f1 / f≤-1.51; the center thickness CT1 of the first lens on the optical axis, the air gap T12 between the first lens and the second lens on the optical axis, and the spacing distance EP01 from the object side surface of the lens barrel to the object side surface of the first spacer element on the optical axis satisfy: 0.81≤(CT1+T12) / EP01≤1.74.

[0052] The optical imaging system of the present application consists of a lens barrel, four lenses arranged in the lens barrel, and multiple spacer elements. By rationally arranging the optical power of each lens, the surface shape of the fourth lens, and the positions of the first to third spacer elements, and setting the optical imaging system to satisfy 2.21≤L / ImgH≤2.90 and -2.13≤f1 / f≤-1.51, it can be seen that by setting the optical power of the first lens to a negative value, if the thickness ratio of the first lens is improperly designed, stress concentration is likely to occur in the first lens during assembly, resulting in large assembly internal stress, thereby affecting the assembly stability of the optical imaging system. Therefore, the present application constrains 0.81≤(CT1+T12) / EP01≤1.74, and controls the ratio of the center thickness of the first lens on the optical axis, the sum of the air gaps between the first lens and the second lens on the optical axis, and the spacing distance between the object side of the lens barrel and the object side of the first spacing element on the optical axis within a certain range. This is conducive to reasonably controlling the center thickness and edge thickness of the first lens, facilitating the design of the structural dimensions of the first lens, reducing the internal stress of the assembly of the first lens and the front end of the lens barrel, avoiding the risk of deformation of the first lens during assembly, ensuring the assembly stability of the first lens, and thus ensuring the assembly stability of the optical imaging system.

[0053] In addition, refer to Table 1 below. Figures 23 to 26As shown, under the premise that the optical imaging system satisfies 2.21≤L / ImgH≤2.90 and -2.13≤f1 / f≤-1.51, for example, L / ImgH=2.88, f1 / f=-1.98, or L / ImgH=2.32, f1 / f=-2.13. Figure 23 An assembly stress diagram is shown when the optical imaging system of Optional Example 1 of the present application satisfies (CT1+T12) / EP01=1.00. Figure 24 An assembly stress diagram is shown when the optical imaging system of optional example 2 of the present application satisfies (CT1+T12) / EP01=1.48. Figure 25 An assembly stress diagram is shown for the optical imaging system of Example 3 when (CT1+T12) / EP01=1.90 is satisfied. Figure 26 An assembly stress diagram is shown for the optical imaging system of Example 4 when (CT1+T12) / EP01=0.50 is satisfied. Figures 23 to 26 In the middle, the upper side is the object side and the lower side is the image side.

[0054] Depend on Figures 23 to 26 It can be seen that when (CT1+T12) / EP01=1.00 or (CT1+T12) / EP01=1.48 is satisfied, the assembly stress of the structure of the first lens and the object side end of the lens barrel is small. Figure 23 In the optical imaging system, the maximum and minimum values of the assembly stress are 78.624MPa and 0.020097MPa respectively; Figure 24 In the optical imaging system, the maximum and minimum values of the assembly stress are 66.881MPa and 0.031016MPa respectively; Figure 23 and Figure 24 It can be seen that the assembly stability of the optical imaging system is good. When (CT1+T12) / EP01=1.90 is met, a large internal stress will occur at the edge flange position of the first lens, which will make the flange surface position of the first lens easily crushed by the assembly nozzle during the assembly process. At this time, the maximum and minimum values of the assembly stress in the optical imaging system are 101.61MPa and 0.5656MPa respectively, and the assembly stability is poor. When (CT1+T12) / EP01=0.50 is met, the object side end structure of the lens barrel is squeezed by the first lens, and the object side end structure of the lens barrel will have a large internal stress, which will easily cause the object side end structure of the lens barrel and the supporting surface of the first lens to deform, affecting the flatness of the supporting surface with the first lens, thereby affecting the assembly stability of the first lens. At this time, the maximum and minimum values of the assembly stress in the optical imaging system are 99.852MPa and 0.46327MPa respectively, and the assembly stability is poor.

[0055] It can be seen that under the premise of satisfying 2.21≤L / ImgH≤2.90 and -2.13≤f1 / f≤-1.51 and controlling (CT1+T12) / EP01 within the range of 0.81 to 1.74, the assembly stress between the first lens and the lens barrel is minimized, the assembly stress in the optical imaging system is minimized, the assembly performance is optimal, and the overall assembly stability is optimal. Therefore, the present application reasonably controls the center thickness and edge thickness of the first lens on the optical axis by constraining 0.81≤(CT1+T12) / EP01≤1.74, by controlling the ratio of the sum of the center thickness of the first lens on the optical axis, the air gap between the first lens and the second lens on the optical axis, and the spacing distance between the object side of the lens barrel and the object side of the first spacing element on the optical axis within a certain range, which is conducive to the reasonable design of the structure of the first lens, reduces the internal stress of the assembly of the first lens and the front end of the lens barrel, avoids the risk of deformation of the first lens during assembly, ensures the assembly stability of the first lens, and thus ensures the assembly stability of the optical imaging system.

[0056] Table 1

[0057]

[0058] In this embodiment, the relationship between the inner diameter d1s of the object-side surface of the first spacer element, the outer diameter D0s of the object-side surface of the lens barrel, and the inner diameter d0s of the object-side surface of the lens barrel satisfies the following equation: 0.47 ≤ d1s / (D0s - d0s) ≤ 4.48. This expression ensures the supporting width of the structure on the object-side end of the lens barrel, preventing significant supporting misalignment between the structure on the object-side end of the lens barrel and the edge flange position of the first lens during assembly, thereby avoiding affecting the assembly stability of the first lens and ensuring the overall assembly stability of the optical imaging system. Furthermore, limiting d1s ensures that reflected stray light from the first lens can be intercepted by the first spacer element, which is beneficial for improving reflected stray light from the first lens.

[0059] In this embodiment, the object-side surface of the third lens is concave, and the image-side surface is convex. The curvature radius R5 of the object-side surface of the third lens, the curvature radius R6 of the image-side surface of the third lens, and the inner diameter d3s of the object-side surface of the third spacer element satisfy the following relationship: -3.48≤(R5+R6) / d3s≤-0.87. By controlling the surface shape of the third lens and this expression, a reasonable shape of the third lens is ensured, ensuring the third lens's light refraction effect and accurate light transmission within the third lens. Furthermore, stray light reflected from the flange of the object-side surface of the third lens is intercepted by the third spacer element, thereby improving stray light and ensuring the imaging quality of the optical imaging system.

[0060] In this embodiment, the distance TD on the optical axis from the object side surface of the first lens to the image side surface of the fourth lens, the distance EP12 on the optical axis from the image side surface of the first spacer element to the object side surface of the second spacer element, and the distance EP23 on the optical axis from the image side surface of the second spacer element to the object side surface of the third spacer element satisfy the following relationship: 2.35 ≤ TD / (EP12 + EP23) ≤ 4.79. This expression ensures the resolution of the optical imaging system by limiting TD, ensuring that the optical imaging system presents a clear image in all fields of view. Furthermore, limiting the edge thickness of the second and third lenses ensures the notch width of the second and third lenses, preventing molding problems with the second and third lenses and ensuring molding stability of the second and third lenses.

[0061] In this embodiment, the image-side surface of the first lens is concave; the outer diameter D1s of the object-side surface of the first spacer element, the inner diameter d1s of the object-side surface of the first spacer element, and the radius of curvature R2 of the image-side surface of the first lens satisfy the following relationship: 1.45 ≤ (D1s - d1s) / R2 ≤ 4.27. By controlling the difference between the outer and inner diameters of the object-side surface of the first spacer element, the first spacer element can effectively intercept stray light at the edge of the effective diameter of the image-side surface of the first lens. Simultaneously, controlling the radius of curvature of the image-side surface of the first lens can limit the curvature of the image-side surface of the first lens, ensuring the convergence of light.

[0062] In this embodiment, the inner diameter d3m of the image-side surface of the third spacer element and the inner diameter d2m of the image-side surface of the second spacer element satisfy the following relationship: 1.34 ≤ d3m / d2m ≤ 2.40. This expression controls the ratio of the inner diameter of the image-side surface of the third spacer element to the inner diameter of the image-side surface of the second spacer element, ensuring the final image brightness of the optical imaging system, thereby meeting the chip's specification requirements and ultimately producing a clear image.

[0063] In this embodiment, the optical axis distance L between the object-side surface and the image-side surface of the lens barrel, the sum of the air gaps ΣAT between adjacent lenses from the first to fourth lenses, and the center thickness CT2 of the second lens on the optical axis satisfy the following relationship: 3.55 ≤ (L - ΣAT) / CT2 ≤ 7.43. By controlling the ratio of the difference between the maximum axial height of the lens barrel and the sum of the air gaps between all lenses to the center thickness of the second lens, the ratio of the sum of the center thicknesses of all lenses to the center thickness of the second lens is indirectly controlled, thereby achieving the purpose of controlling the position of the second lens in the entire optical imaging system and ensuring good formability of the second lens.

[0064] In this embodiment, the inner diameter d2s of the object-side surface of the second spacer element and the inner diameter d1m of the image-side surface of the first spacer element satisfy the following relationship: 0.49 ≤ d2s / d1m ≤ 1.87. Controlling the inner diameters of the object-side surface of the second spacer element and the image-side surface of the first spacer element using this expression facilitates the first and second spacer elements to intercept stray light incident on the edge, ensuring the first and second spacer elements' effectiveness in improving stray light in the optical imaging system, preventing strong reflected stray light from the inner diameter surfaces of the spacer elements, and ensuring ultimate imaging quality.

[0065] In this embodiment, the spacer element assembly further includes a third auxiliary spacer element positioned between the third spacer element and the fourth lens and partially abutting the third spacer element. The sum of the thicknesses ∑CP3 of all spacer elements between the third and fourth lenses, the center thickness CT3 of the third lens on the optical axis, the center thickness CT4 of the fourth lens on the optical axis, and the air gap T34 between the third and fourth lenses on the optical axis satisfy the following equation: 0.43 ≤ ∑CP3 / (CT4 + CT3 + T34) ≤ 0.91. This expression controls the sum of the thicknesses of all spacer elements between the third and fourth lenses, ensuring margin for stray light improvement between the third and fourth lenses. It also controls the proper distribution of the center thicknesses and air gaps of the third and fourth lenses, limiting variations in the air gap of the optical imaging system during assembly and ensuring assembly yield.

[0066] It should be noted that ΣCP3 is the center thickness of the third spacer element on the optical axis, or the sum of the center thickness of the third spacer element on the optical axis and the center thickness of the third auxiliary spacer element on the optical axis.

[0067] In this embodiment, the spacer assembly further includes a second auxiliary spacer selectively positioned between the second spacer and the third lens, partially abutting the second spacer. The sum of the thicknesses ∑CP2 of all spacer elements between the second and third lenses and the air spacing T23 between the second and third lenses on the optical axis satisfy the following relationship: 0.08 ≤ ∑CP2 / T23 ≤ 1.52. By controlling the ratio of the sum of the thicknesses of all spacer elements between the second and third lenses to the air spacing between the second and third lenses on the optical axis, this expression can prevent excessive spacing between the second and third lenses, which can lead to multiple reflections of stray light between the lenses. This improves stray light and enhances final image quality.

[0068] It should be noted here that ΣCP2 is the center thickness of the second spacer element on the optical axis, or the sum of the center thickness of the second spacer element on the optical axis and the center thickness of the second auxiliary spacer element on the optical axis.

[0069] In this embodiment, the outer diameter D3s of the object-side surface of the third spacer element, the inner diameter d3s of the object-side surface of the third spacer element, and the effective focal length f3 of the third lens satisfy the following relationship: 0.06 ≤ (D3s - d3s) / f3 ≤ 1.70. Controlling the difference between the outer and inner diameters of the object-side surface of the third spacer element facilitates the third spacer element's interception of excess stray light, thereby lowering the energy threshold of the ultimately emitted stray light. This also limits the effective focal length of the third lens, helping to ensure a secure light transmission path.

[0070] In this embodiment, the radius of curvature R7 of the object-side surface of the fourth lens element and the inner diameter d3bm of the image-side surface of the third auxiliary spacer element satisfy the following relationship: 0.52 ≤ R7 / d3bm ≤ 2.40. By limiting the ratio of the radius of curvature of the object-side surface of the fourth lens element to the inner diameter of the image-side surface of the third auxiliary spacer element to a certain range, the third auxiliary spacer element can effectively block stray light generated by the first three lenses, ensuring the stable transmission of imaging light entering the fourth lens element, thereby ensuring the ultimate imaging quality of the lens.

[0071] In this embodiment, the relationship between the inner diameter d0m of the image-side surface of the lens barrel and the effective focal length f4 of the fourth lens element satisfies the following: 0.58≤d0m / f4≤1.62. This expression ensures that the emitted light from the optical imaging system converges at the imaging chip, ensuring that most of the light is received by the imaging chip, thereby maintaining the imaging quality of the optical imaging system. At the same time, limiting the inner diameter of the image-side surface of the lens barrel ensures that the size of the optical imaging system meets the image plane size of the imaging chip, ensuring the adaptability of the optical imaging system.

[0072] In this embodiment, the central thickness CT2 of the second lens on the optical axis and the distance EP12 between the image-side surface of the first spacer element and the object-side surface of the second spacer element on the optical axis satisfy the following relationship: 0.66 ≤ CT2 / EP12 ≤ 2.41. This expression constrains the central and edge thicknesses of the second lens, ensuring uniformity in shape and size, and thus ensuring the feasibility of molding the second lens.

[0073] In this embodiment, the inner diameter d1m of the image side surface of the first spacer, the curvature radius R3 of the object side surface of the second lens, and the refractive index N2 of the second lens satisfy: -0.33≤d1m / R3 N2 ≤ 1.37. By controlling the relationship between the inner diameter of the image-side surface of the first spacer, the radius of curvature of the object-side surface of the second lens, and the refractive index of the second lens, the curvature of the effective diameter of the object-side surface of the second lens is guaranteed. This prevents mutual reflection between the first spacer and the effective diameter of the first lens, which can generate high-energy optical ghost images, while also ensuring that the first spacer can intercept excess stray light from the first lens.

[0074] In this embodiment, the image side surface of the first lens is concave; the object side surface of the third lens is concave, and the image side surface is convex. By rationally planning the lens surface shape, it is helpful to control the direction of light, eliminate aberrations, and ensure image quality.

[0075] Optionally, the optical imaging system in the embodiments of the present application can be simulated using software and / or tools such as ZEMAX and CODEV. During the simulation using the aforementioned software and / or tools, the surface profile of each lens can be appropriately adjusted based on the surface profile provided by the software and / or tool used.

[0076] In addition, in another optional embodiment of the present application, an optical imaging system is also provided, including a lens barrel and a lens group and a spacer element group arranged in the lens barrel, the lens group consisting of four lenses, and the four lenses are, from the object side to the image side, a first lens with negative optical focal length, a second lens with optical focal length, a third lens with positive optical focal length and a fourth lens with positive optical focal length; the image side surface of the first lens is concave; the object side surface of the third lens is concave, and the image side surface is convex; the object side surface of the fourth lens is convex; the spacer element group includes a first spacer element located between the first lens and the second lens and partially supporting the image side surface of the first lens, a second spacer element located between the second lens and the third lens and partially supporting the image side surface of the second lens a third spacer element located between the third lens and the fourth lens and partially supporting the image side surface of the third lens; wherein, a spacing distance L from the object side surface of the lens barrel to the image side surface of the lens barrel on the optical axis of the optical imaging system and an effective focal length f of the optical imaging system satisfy the following relationship: 1.74≤L / f≤3.15; an effective focal length f4 of the fourth lens, a curvature radius R5 of the object side surface of the third lens, and a curvature radius R6 of the image side surface of the third lens satisfy the following relationship: -2.95≤f4 / (R5+R6)≤-0.60; an inner diameter d1s of the object side surface of the first spacer element, an outer diameter D0s of the object side surface of the lens barrel, and an inner diameter d0s of the object side surface of the lens barrel satisfy the following relationship: 0.47≤d1s / (D0s-d0s)≤4.48.

[0077] The optical imaging system of the present application consists of a lens barrel, four lenses arranged in the lens barrel, and multiple spacer elements. By reasonably arranging the optical power and surface shape of each lens, the positions of the first to third spacer elements, and setting the optical imaging system to meet 1.74≤L / f≤3.15 and -2.95≤f4 / (R5+R6)≤-0.60, it can be seen that under the condition of controlling the effective focal length of the fourth lens and the curvature radii of the object side and image side of the third lens, if the first lens and the lens barrel are not properly supported, it is easy to cause the first lens and the lens barrel to be misaligned, thereby causing invalid light to be incident on the edge structure of the first lens and reflect to generate new stray light. Therefore, the present application ensures the supporting width of the structure at the object side end of the lens barrel by constraining 0.47≤d1s / (D0s-d0s)≤4.48, prevents a large supporting misalignment between the structure at the object side end of the lens barrel and the edge flange position of the first lens during the assembly process, limits d1s, and ensures that the reflected stray light of the first lens can be intercepted by the first spacing element, which is beneficial to improving the reflected stray light of the first lens.

[0078] Of course, this embodiment may also include other parameter formulas in the above embodiment, which will not be described one by one here.

[0079] In addition, in another optional embodiment of the present application, an optical imaging system is also provided, including a lens barrel and a lens group and a spacer element group arranged in the lens barrel, the lens group is composed of four lenses, and the four lenses are, from the object side to the image side, a first lens with negative optical focal length, a second lens with optical focal length, a third lens with positive optical focal length and a fourth lens with positive optical focal length; the image side surface of the first lens is concave; the object side surface of the third lens is concave, and the image side surface is convex; the object side surface of the fourth lens is convex; the spacer element group includes a first spacer element located between the first lens and the second lens and partially supported by the image side surface of the first lens, a second spacer element located between the second lens and the third lens and partially supported by the image side surface of the second lens , a third spacing element located between the third lens and the fourth lens and resting against the image side surface of the third lens; wherein, the spacing distance L from the object side surface of the lens barrel to the image side surface of the lens barrel on the optical axis of the optical imaging system and half of the diagonal length of the effective pixel area on the imaging surface of the optical imaging system ImgH satisfy: 2.21≤L / ImgH≤2.90; the effective focal length f1 of the first lens and the effective focal length f of the optical imaging system satisfy: -2.13≤f1 / f≤-1.51; the curvature radius R1 of the object side surface of the first lens, the curvature radius R2 of the image side surface of the first lens and the inner diameter d1s of the object side surface of the first spacing element satisfy: -4.91≤(R1+R2) / d1s≤1.87.

[0080] The optical imaging system of the present application is composed of a lens barrel, four lenses arranged in the lens barrel, and a plurality of spacer elements. By reasonably arranging the optical focal length and surface shape of each lens, the positions of the first to third spacer elements, and setting the optical imaging system to meet 2.21≤L / ImgH≤2.90 and -2.13≤f1 / f≤-1.51, it can be seen that when the optical focal length of the first lens is set to a negative value, if the surface shape of the first lens is unreasonable, it is difficult to control the deflection angle and divergence degree of the first lens on the incident light from the front. Large-angle light is easily reflected at the edge position of the first lens to form new stray light, affecting the clarity and contrast of the final image. Therefore, the present application, by constraining -4.91≤(R1+R2) / d1s≤1.87, on the one hand, ensures that the surface shape of the first lens is relatively reasonable, ensures the refraction effect of the first lens on light, ensures the accurate transmission of light in the first lens, and at the same time ensures that the stray light generated at the edge position of the first lens can be intercepted by the first spacer element, thereby ensuring the imaging quality of the optical imaging system.

[0081] Of course, this embodiment may also include other parameter formulas in the above embodiment, which will not be described one by one here.

[0082] Optionally, the optical imaging system may further include a protective glass for protecting the photosensitive element located on the imaging surface.

[0083] The optical imaging system in the present application may use multiple lenses, such as the four lenses described above. In the present application, at least one of the mirror surfaces of each lens is an aspheric mirror surface. The characteristic of an aspheric lens is that the curvature changes continuously from the center of the lens to the periphery. Unlike a spherical lens that has a constant curvature from the center of the lens to the periphery, an aspheric lens has a better curvature radius characteristic, with the advantages of improving distortion aberration and improving astigmatism aberration. After using an aspheric lens, the aberrations that occur during imaging can be eliminated as much as possible, thereby improving the imaging quality.

[0084] However, those skilled in the art will appreciate that the number of lenses comprising the optical imaging system can be varied to achieve the various results and advantages described herein without departing from the technical solutions claimed herein. For example, while the embodiments describe four lenses as an example, the optical imaging system is not limited to four lenses. If desired, the optical imaging system can also include other numbers of lenses.

[0085] Figure 1 A schematic diagram of the dimensions of an optical imaging system of the present application is shown. Figure 1Parameters such as D0s, d0s, d2s, D1s, d1m, d1s, d3s, d3m, D3s, d3bm, d0m, ∑CP2, ∑CP3, L, EP01, EP12, and EP23 are labeled to provide a clear and intuitive understanding of their significance. To facilitate the description of the optical imaging system and specific lens profiles, these parameters will not be reflected in the accompanying drawings when describing specific embodiments.

[0086] The following further describes examples of specific surface shapes and parameters of the optical imaging system applicable to the above-mentioned embodiments with reference to the accompanying drawings.

[0087] It should be noted that in the following Example 1, there are three examples: Example 1-1, Example 1-2, and Example 1-3; in Example 2, there are three examples: Example 2-1, Example 2-2, and Example 2-3; and in Example 3, there are three examples: Example 3-1, Example 3-2, and Example 3-3. While the optical imaging systems of the three examples in the same embodiment have the same parameters, such as the radius of curvature and center thickness of the first through fourth lenses, as well as the spacing between the lenses and the higher-order coefficients, they differ in parameters such as the thickness, inner diameter, and outer diameter of the lens barrel and the first through third spacer elements. In other words, the primary imaging structure is the same, while the auxiliary imaging structures are different.

[0088] It should be noted that any one of the following examples 1 to 3 is applicable to all implementation methods of the present application.

[0089] Example 1

[0090] like Figures 2 to 8 As shown, the optical imaging system of embodiment 1 is described. Figure 2 shows a schematic structural diagram of the optical imaging system of Example 1-1, Figure 3 shows a schematic structural diagram of the optical imaging system of Example 1-2, Figure 4 Schematic diagrams of the structures of the optical imaging systems of Examples 1-3 are shown.

[0091] like Figures 2 to 4 As shown, the optical imaging system includes a lens barrel P0 and a first lens E1, a first spacer element P1, a second lens E2, a second spacer element P2, a third lens E3, a third spacer element P3, a third auxiliary spacer element P3b, and a fourth lens E4, which are arranged in the lens barrel P0 in sequence from the object side to the image side along the optical axis.

[0092] like Figure 2, which is a schematic structural diagram of the optical imaging system of Example 1-1. In this example, the image side of the second spacer element P2 is further provided with a second auxiliary spacer element P2b. The object-side and image-side surfaces of the first spacer element P1 partially abut against the image-side surface S2 of the first lens and the object-side surface S3 of the second lens, respectively. The object-side and image-side surfaces of the second spacer element P2 partially abut against the image-side surface S4 of the second lens and the object-side surface of the second auxiliary spacer element P2b, respectively. The image-side surface of the second auxiliary spacer element P2b partially abuts against the object-side surface S5 of the third lens. The object-side and image-side surfaces of the third spacer element P3 partially abut against the image-side surface S6 of the third lens and the object-side surface of the third auxiliary spacer element P3b, respectively. The image-side surface of the third auxiliary spacer element P3b partially abuts against the object-side surface S7 of the fourth lens.

[0093] like Figure 3 Figure 2 is a schematic structural diagram of the optical imaging system of Example 1-2. This example differs from Example 1-1 in that the second auxiliary spacer element P2b is not provided. Therefore, the object-side and image-side surfaces of the second spacer element P2 partially abut against the image-side surface S4 of the second lens element and the object-side surface S5 of the third lens element, respectively. The abutment mechanism of the remaining spacer elements is the same as that of Example 1-1, and reference is made to the relevant description of Example 1-1, which will not be repeated here.

[0094] like Figure 4 FIG. 3 is a schematic structural diagram of an optical imaging system according to embodiment 1-3. In this example, the supporting and abutting manner of each spacer element is the same as that of embodiment 1-1, and reference may be made to the relevant description in embodiment 1-1, which will not be repeated here.

[0095] In summary, the structural parameters of the optical imaging system of Example 1 in Example 1-1, Example 1-2, and Example 1-3 are shown in Table 2 (unit: mm).

[0096] Table 2

[0097]

[0098] In Example 1, the object-side surface S1 of the first lens is convex, and the image-side surface S2 of the first lens is concave. The object-side surface S3 of the second lens is concave, and the image-side surface S4 of the second lens is convex. The object-side surface S5 of the third lens is concave, and the image-side surface S6 of the third lens is convex. The object-side surface S7 of the fourth lens is convex, and the image-side surface S8 of the fourth lens is concave.

[0099] In Example 1, half the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system is 0.81 mm, the effective focal length f of the optical imaging system is 1.10 mm, the effective focal length f1 of the first lens is -2.18 mm, the effective focal length f2 of the second lens is 1.42 mm, the effective focal length f3 of the third lens is 7.04 mm, and the effective focal length f4 of the fourth lens is 3.17 mm.

[0100] Table 3 shows the basic structural parameters of the optical imaging system of Example 1, where the units for the radius of curvature and thickness / distance are all in millimeters. In the table below, OBJ (not shown) represents the object distance. STO (not shown) represents the aperture stop, located between the first lens E1 and the second lens E2. S9 and S10 (not shown) can be the object-side and image-side surfaces of a filter or the object-side and image-side surfaces of a protective glass. S11 (not shown) represents the imaging surface.

[0101] Table 3

[0102]

[0103] In Example 1, the object-side surface and the image-side surface of the first lens E1 to the fourth lens E4 are all aspherical surfaces. The surface shape of each aspherical lens can be defined by, but not limited to, the following aspherical surface formula:

[0104] Formula (1).

[0105] Where x is the distance from the vertex of the aspheric surface at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c = 1 / R, i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 3 above; k is the conic coefficient; Ai is the correction coefficient for the i-th order of the aspheric surface. Table 4 below lists the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for each aspheric mirror surface S1-S8 in Example 1.

[0106] Table 4

[0107]

[0108] Figure 5 The magnification chromatic aberration curve of the optical imaging system of Example 1 is shown, which represents the deviation of different image heights on the imaging surface after the light passes through the optical imaging system. Figure 6 The axial chromatic aberration curve of the optical imaging system of the first embodiment is shown, which indicates the deviation of the focal point of light of different wavelengths after passing through the imaging lens. Figure 7 The astigmatism curve of the optical imaging system of the first embodiment is shown, which represents the meridional image curvature and the sagittal image curvature. Figure 8The distortion curve of the optical imaging system of the first embodiment is shown, which represents the distortion magnitude values corresponding to different image heights.

[0109] according to Figures 5 to 8 It can be seen that the optical imaging system provided in the first embodiment can achieve good imaging quality.

[0110] Example 2

[0111] like Figures 9 to 15 As shown, the optical imaging system of the second embodiment is described. Figure 9 2-1 shows a schematic structural diagram of the optical imaging system of Example 2-1. Figure 10 2-2 shows a schematic structural diagram of the optical imaging system of Example 2-2, Figure 11 A schematic structural diagram of the optical imaging system of Example 2-3 is shown.

[0112] like Figures 9 to 11 As shown, the optical imaging system includes a lens barrel P0 and a first lens E1, a first spacer element P1, a second lens E2, a second spacer element P2, a third lens E3, a third spacer element P3, a third auxiliary spacer element P3b, and a fourth lens E4, which are arranged in the lens barrel P0 in sequence from the object side to the image side along the optical axis.

[0113] like Figure 9 , which is a schematic structural diagram of the optical imaging system of Example 2-1. In this example, a second auxiliary spacer element P2b is further provided on the image side of the second spacer element P2. The object-side surface and image-side surface of the first spacer element P1 partially abut against the image-side surface S2 of the first lens and the object-side surface S3 of the second lens, respectively. The object-side surface and image-side surface of the second spacer element P2 partially abut against the image-side surface S4 of the second lens and the object-side surface of the second auxiliary spacer element P2b, respectively. The image-side surface of the second auxiliary spacer element P2b partially abuts against the object-side surface S5 of the third lens. The object-side surface and image-side surface of the third spacer element P3 partially abut against the image-side surface S6 of the third lens and the object-side surface of the third auxiliary spacer element P3b, respectively. The image-side surface of the third auxiliary spacer element P3b partially abuts against the object-side surface S7 of the fourth lens.

[0114] like Figure 10 Figure 2 shows a schematic structural diagram of the optical imaging system of Example 2-2. This example differs from Example 2-1 in that the second auxiliary spacer element P2b is not provided. Therefore, the object-side and image-side surfaces of the second spacer element P2 partially abut against the image-side surface S4 of the second lens element and the object-side surface S5 of the third lens element, respectively. The abutment mechanism of the remaining spacer elements is the same as that of Example 2-1, and reference is made to the relevant description of Example 2-1, which will not be repeated here.

[0115] like Figure 11FIG2 is a schematic diagram of the structure of the optical imaging system of Example 2-3. In this example, the supporting and abutting manner of each spacer element is the same as that of Example 2-1. Please refer to the relevant description of Example 2-1 and will not be repeated here.

[0116] In summary, the structural parameters of the optical imaging system of the second embodiment in embodiments 2-1, 2-2, and 2-3 are shown in Table 5 (unit: mm).

[0117] Table 5

[0118]

[0119] In Example 2, the object-side surface S1 of the first lens is convex, and the image-side surface S2 of the first lens is concave. The object-side surface S3 of the second lens is convex, and the image-side surface S4 of the second lens is convex. The object-side surface S5 of the third lens is concave, and the image-side surface S6 of the third lens is convex. The object-side surface S7 of the fourth lens is convex, and the image-side surface S8 of the fourth lens is concave.

[0120] In Example 2, half the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system is 0.81 mm, the effective focal length f of the optical imaging system is 1.13 mm, the effective focal length f1 of the first lens is -1.71 mm, the effective focal length f2 of the second lens is 1.19 mm, the effective focal length f3 of the third lens is 7.09 mm, and the effective focal length f4 of the fourth lens is 3.85 mm.

[0121] Table 6 shows the basic structural parameters of the optical imaging system of Example 2, where the units for the radius of curvature and thickness / distance are all in millimeters. In the table below, OBJ (not shown) represents the object distance. STO (not shown) represents the aperture stop, located between the first lens E1 and the second lens E2. S9 and S10 (not shown) can be the object-side and image-side surfaces of a filter or the object-side and image-side surfaces of a protective glass. S11 (not shown) represents the imaging surface.

[0122] Table 6

[0123]

[0124] Table 7 below lists the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for the aspheric mirror surfaces S1-S8 in Example 2.

[0125] Table 7

[0126]

[0127] Figure 12The magnification chromatic aberration curve of the optical imaging system of Example 2 is shown, which represents the deviation of different image heights on the imaging surface after the light passes through the optical imaging system. Figure 13 The axial chromatic aberration curve of the optical imaging system of the second embodiment is shown, which indicates the deviation of the focal point of light of different wavelengths after passing through the imaging lens. Figure 14 The astigmatism curve of the optical imaging system of the second embodiment is shown, which represents the meridional image curvature and the sagittal image curvature. Figure 15 The distortion curve of the optical imaging system of the second embodiment is shown, which represents the distortion magnitude values corresponding to different image heights.

[0128] according to Figures 12 to 15 It can be seen that the optical imaging system provided in the second embodiment can achieve good imaging quality.

[0129] Example 3

[0130] like Figures 16 to 22 As shown, the optical imaging system of embodiment 3 is described. Figure 16 Schematic diagram of the structure of the optical imaging system of Example 3-1 is shown. Figure 17 Schematic diagram of the structure of the optical imaging system of Example 3-2 is shown. Figure 18 A schematic structural diagram of the optical imaging system of Example 3-3 is shown.

[0131] like Figures 16 to 18 As shown, the optical imaging system includes a lens barrel P0 and a first lens E1, a first spacer element P1, a second lens E2, a second spacer element P2, a third lens E3, a third spacer element P3, a third auxiliary spacer element P3b, and a fourth lens E4, which are arranged in the lens barrel P0 in sequence from the object side to the image side along the optical axis.

[0132] like Figure 16 , which is a schematic diagram of the structure of the optical imaging system of Example 3-1. In this example, the object-side and image-side surfaces of the first spacer element P1 partially abut against the image-side surface S2 of the first lens and the object-side surface S3 of the second lens, respectively. The object-side and image-side surfaces of the second spacer element P2 partially abut against the image-side surface S4 of the second lens and the object-side surface S5 of the third lens, respectively. The object-side and image-side surfaces of the third spacer element P3 partially abut against the image-side surface S6 of the third lens and the object-side surface of the third auxiliary spacer element P3b, respectively. The image-side surface of the third auxiliary spacer element P3b partially abuts against the object-side surface S7 of the fourth lens.

[0133] like Figure 17 FIG3 is a schematic diagram of the structure of the optical imaging system of Example 3-2. The supporting and abutting manner of each spacer element is the same as that of Example 3-1, and the relevant description in Example 3-1 can be referred to and will not be repeated here.

[0134] like Figure 18 FIG3 is a schematic diagram of the structure of the optical imaging system of Example 3-3. In this example, the supporting and abutting manner of each spacer element is the same as that of Example 3-1. Please refer to the relevant description of Example 3-1 and will not be repeated here.

[0135] In summary, the structural parameters of the optical imaging system of Example 3 in Example 3-1, Example 3-2, and Example 3-3 are shown in Table 8 (unit: mm).

[0136] Table 8

[0137]

[0138] In Example 3, the object-side surface S1 of the first lens is concave, and the image-side surface S2 of the first lens is concave. The object-side surface S3 of the second lens is convex, and the image-side surface S4 of the second lens is concave. The object-side surface S5 of the third lens is concave, and the image-side surface S6 of the third lens is convex. The object-side surface S7 of the fourth lens is convex, and the image-side surface S8 of the fourth lens is convex.

[0139] In Example 3, half the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system is 0.81 mm, the effective focal length f of the optical imaging system is 0.60 mm, the effective focal length f1 of the first lens is -1.28 mm, the effective focal length f2 of the second lens is -9.23 mm, the effective focal length f3 of the third lens is 0.96 mm, and the effective focal length f4 of the fourth lens is 1.77 mm.

[0140] Table 9 shows the basic structural parameters of the optical imaging system of Example 3, where the units for the radius of curvature and thickness / distance are all in millimeters. In the table below, OBJ (not shown) represents the object distance. STO (not shown) represents the aperture stop, located between the first lens E1 and the second lens E2. S9 and S10 (not shown) can be the object-side and image-side surfaces of a filter or the object-side and image-side surfaces of a protective glass. S11 (not shown) represents the imaging surface.

[0141] Table 9

[0142]

[0143] Table 10 below lists the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for the aspheric mirror surfaces S1-S8 in Example 3.

[0144] Table 10

[0145]

[0146] Figure 19The magnification chromatic aberration curve of the optical imaging system of Example 3 is shown, which represents the deviation of different image heights on the imaging surface after the light passes through the optical imaging system. Figure 20 The axial chromatic aberration curve of the optical imaging system of the third embodiment is shown, which indicates the deviation of the focal point of light of different wavelengths after passing through the imaging lens. Figure 21 The astigmatism curve of the optical imaging system of the third embodiment is shown, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 22 The distortion curve of the optical imaging system of the third embodiment is shown, which represents the distortion magnitude values corresponding to different image heights.

[0147] according to Figures 19 to 22 It can be seen that the optical imaging system provided in the third embodiment can achieve good imaging quality.

[0148] In summary, Examples 1 to 3 respectively satisfy the relationships shown in Table 11.

[0149] Table 11

[0150]

[0151] Table 12 shows half the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system of Examples 1 to 3, the effective focal length f of the optical imaging system, and the effective focal length of each lens of the optical imaging system.

[0152] Table 12

[0153]

[0154] This application also provides an imaging device, whose electronic photosensitive element can be a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). The imaging device can be a standalone imaging device such as a digital camera, or an imaging module integrated into a mobile electronic device such as a mobile phone. The imaging device is equipped with the optical imaging system described above.

[0155] Specifically, the optical imaging system of the present application can be used in an eye tracking system as an infrared lens. That is, the operating wavelength of the optical imaging system of the present application can be the infrared wavelength band. The optical imaging system of the present application has good optical performance stability, so that eye movement signals can be quickly captured.

[0156] Obviously, the embodiments described above are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0157] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, tasks, devices, components and / or combinations thereof.

[0158] It should be noted that the terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0159] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An optical imaging system, characterized in that: comprising a lens barrel and a lens group and a spacer element group arranged in the lens barrel, The lens group is composed of four lenses, which are, from the object side to the image side, a first lens with negative optical power, a second lens with optical power, a third lens with positive optical power, and a fourth lens with positive optical power; the object side surface of the fourth lens is a convex surface; The spacer element group includes a first spacer element located between the first lens and the second lens and resting against the image-side surface of the first lens, a second spacer element located between the second lens and the third lens and resting against the image-side surface of the second lens, and a third spacer element located between the third lens and the fourth lens and resting against the image-side surface of the third lens; The distance L between the object side surface of the lens barrel and the image side surface of the lens barrel on the optical axis of the optical imaging system and half of the diagonal length ImgH of the effective pixel area on the imaging surface of the optical imaging system satisfy the following relationship: 2.21≤L / ImgH≤2.90; the effective focal length f1 of the first lens and the effective focal length f of the optical imaging system satisfy the following relationship: -2.13≤f1 / f≤-1.51; The center thickness CT1 of the first lens on the optical axis, the air gap T12 between the first lens and the second lens on the optical axis, and the spacing distance EP01 from the object side surface of the lens barrel to the object side surface of the first spacing element on the optical axis satisfy the following: 0.81≤(CT1+T12) / EP01≤1.

74.

2. The optical imaging system according to claim 1, wherein: The inner diameter d1s of the object-side surface of the first spacer, the outer diameter D0s of the object-side surface of the lens barrel, and the inner diameter d0s of the object-side surface of the lens barrel satisfy the following relationship: 0.47≤d1s / (D0s-d0s)≤4.

48.

3. The optical imaging system according to claim 1, wherein: The object side surface of the third lens is concave, and the image side surface is convex; the curvature radius R5 of the object side surface of the third lens, the curvature radius R6 of the image side surface of the third lens and the inner diameter d3s of the object side surface of the third spacer element satisfy the following relationship: -3.48≤(R5+R6) / d3s≤-0.

87.

4. The optical imaging system according to claim 1, wherein: The distance TD from the object side surface of the first lens to the image side surface of the fourth lens on the optical axis, the spacing distance EP12 from the image side surface of the first spacer element to the object side surface of the second spacer element on the optical axis, and the spacing distance EP23 from the image side surface of the second spacer element to the object side surface of the third spacer element on the optical axis satisfy the following: 2.35≤TD / (EP12+EP23)≤4.

79.

5. The optical imaging system according to claim 1, wherein: The image side surface of the first lens is concave; the outer diameter D1s of the object side surface of the first spacer element, the inner diameter d1s of the object side surface of the first spacer element and the curvature radius R2 of the image side surface of the first lens satisfy: 1.45≤(D1s-d1s) / R2≤4.

27.

6. The optical imaging system according to claim 1, wherein: An inner diameter d3m of the image-side surface of the third spacer element and an inner diameter d2m of the image-side surface of the second spacer element satisfy the following relationship: 1.34≤d3m / d2m≤2.

40.

7. The optical imaging system according to claim 1, wherein: The spacing distance L between the object side surface of the lens barrel and the image side surface of the lens barrel on the optical axis, the sum ΣAT of the air gaps between two adjacent lenses among the first lens to the fourth lens on the optical axis, and the center thickness CT2 of the second lens on the optical axis satisfy the following: 3.55≤(L-ΣAT) / CT2≤7.

43.

8. The optical imaging system according to claim 1, wherein: The inner diameter d2s of the object-side surface of the second spacer element and the inner diameter d1m of the image-side surface of the first spacer element satisfy the following relationship: 0.49≤d2s / d1m≤1.

87.

9. The optical imaging system according to claim 1, wherein: The spacer element group further includes a third auxiliary spacer element located between the third spacer element and the fourth lens and partially in contact with the third spacer element. The sum of the thicknesses ∑CP3 of all spacing elements between the third lens and the fourth lens, the center thickness CT3 of the third lens on the optical axis, the center thickness CT4 of the fourth lens on the optical axis, and the air gap T34 between the third lens and the fourth lens on the optical axis satisfy the following: 0.43≤∑CP3 / (CT4+CT3+T34)≤0.

91.

10. The optical imaging system according to claim 1, wherein: The spacer element group further includes a second auxiliary spacer element selectively disposed between the second spacer element and the third lens and partially in contact with the second spacer element. A sum ΣCP2 of thicknesses of all spacer elements between the second lens and the third lens and an air space T23 between the second lens and the third lens on the optical axis satisfy the following relationship: 0.08≤ΣCP2 / T23≤1.

52.

11. The optical imaging system according to claim 1, wherein: An outer diameter D3s of the object-side surface of the third spacer element, an inner diameter d3s of the object-side surface of the third spacer element, and an effective focal length f3 of the third lens satisfy the following relationship: 0.06≤(D3s-d3s) / f3≤1.

70.

12. The optical imaging system according to claim 1, wherein: The spacer element group also includes a third auxiliary spacer element located between the third spacer element and the fourth lens and partially supported by the third spacer element. The curvature radius R7 of the object side surface of the fourth lens and the inner diameter d3bm of the image side surface of the third auxiliary spacer element satisfy the following relationship: 0.52≤R7 / d3bm≤2.

40.

13. The optical imaging system according to claim 1, wherein: The inner diameter d0m of the image-side surface of the lens barrel and the effective focal length f4 of the fourth lens satisfy the following: 0.58≤d0m / f4≤1.

62.

14. The optical imaging system according to claim 1, wherein: A center thickness CT2 of the second lens on the optical axis and a spacing distance EP12 from the image side surface of the first spacer element to the object side surface of the second spacer element on the optical axis satisfy the following: 0.66≤CT2 / EP12≤2.

41.

15. The optical imaging system according to claim 1, wherein: The inner diameter d1m of the image-side surface of the first spacer element, the curvature radius R3 of the object-side surface of the second lens, and the refractive index N2 of the second lens satisfy: .

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