Optical imaging system

Abstract

The present application discloses an optical imaging system, which includes: a lens group that sequentially includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens with optical power from the object side to the image side along a first direction; a first prism disposed on the object side of the lens group for reflecting light incident on the first prism along a second direction to exit from the first prism along the first direction; a second prism disposed on the image side of the lens group for reflecting light incident on the second prism along the first direction to exit from the second prism along a third direction; wherein the first direction, the second direction, and the third direction are perpendicular to each other pairwise; wherein at least one lens in the lens group is a plastic lens, and at least one mirror surface of the plastic lens is an aspherical surface; and wherein the total effective focal length f of the optical imaging system satisfies f > 20 mm.

Description

Technical Field

[0001] The present application relates to the field of optical elements, and more specifically, to an optical imaging system. Background Art

[0002] Camera modules are usually provided on portable devices such as mobile phones, so that the mobile phones have camera functions. In recent years, with the upgrading of consumer electronic products and the development of image software functions and video software functions on consumer electronic products. The market demand for camera modules applicable to portable electronic products has gradually increased. An image sensor of Charge-coupled Device (CCD) type or Complementary Metal Oxide Semiconductor (CMOS) type is usually provided in the camera module, and an optical imaging system is provided. The optical imaging system can converge the light beam on the object side, and the imaging light travels along the optical path of the optical imaging system and irradiates on the image sensor, and then the image sensor converts the optical signal into an electrical signal to form image data.

[0003] As the requirements for imaging functions of miniaturized electronic products such as smart phones are getting higher and higher, higher requirements are also put forward for the optical performance of the optical imaging system. At present, mobile terminals pursue the optical zoom ratio. When its value increases, the imaging magnification of the optical imaging system increases, and distant scenes can be photographed more clearly and visibly. However, when the focal length of the optical imaging system increases, its overall optical length will also increase accordingly. A larger-sized optical imaging system is disadvantageous for the miniaturization of electronic products such as mobile phones.

[0004] In order to meet the miniaturization requirements and imaging requirements, an optical imaging system that can balance miniaturization, long focal length, and good imaging quality is needed. Summary of the Invention

[0005] The present application provides an optical imaging system applicable to portable electronic products, which can at least solve or partially solve at least one of the above disadvantages in the prior art.

[0006] The first aspect of the present application provides an optical imaging system, which includes: a lens group, the lens group sequentially includes a first lens with a focal power, a second lens, a third lens, a fourth lens, and a fifth lens from the object side to the image side along a first direction; a first prism, disposed on the object side of the lens group, for reflecting the light incident on the first prism along a second direction to exit from the first prism along the first direction; a second prism, disposed on the image side of the lens group, for reflecting the light incident on the second prism along the first direction to exit from the second prism along a third direction; wherein, the first direction, the second direction, and the third direction are perpendicular to each other pairwise; wherein, at least one lens in the lens group is a plastic lens, and at least one mirror surface of the plastic lens is an aspherical surface; and wherein, the total effective focal length f of the optical imaging system satisfies f > 20 mm.

[0007] In one embodiment, the total effective focal length f of the optical imaging system and the length Ty of the optical imaging system in the third direction may satisfy 1.0 < f / Ty < 3.0.

[0008] In one embodiment, the total effective focal length f of the optical imaging system and the length Tz of the optical imaging system in the second direction may satisfy 2.0 < f / Tz < 4.0.

[0009] In one embodiment, the total effective focal length f of the optical imaging system and half of the diagonal length ImgH of the effective pixel region on the imaging surface of the optical imaging system may satisfy f / ImgH > 8.

[0010] In one embodiment, the total effective focal length f of the optical imaging system and the entrance pupil diameter EPD of the optical imaging system may satisfy f / EPD ≤ 4.0.

[0011] In one embodiment, the refractive index N1 of the first lens and the refractive index N2 of the second lens may satisfy 0 < N2 - N1 < 0.2; the dispersion coefficient V1 of the first lens and the dispersion coefficient V2 of the second lens may satisfy 0 < V1 - V2 < 10.

[0012] In one embodiment, the dispersion coefficient V4 of the fourth lens and the dispersion coefficient V5 of the fifth lens may satisfy 50 < (V4 + V5) / 2 < 60.

[0013] In one embodiment, the first lens has a positive focal power; the second lens has a positive focal power; the third lens has a negative focal power; the fourth lens has a positive focal power; the fifth lens has a negative focal power.

[0014] In one embodiment, the effective focal length f1 of the first lens and the effective focal length f2 of the second lens may satisfy 0.1 < f1 / f2 < 0.3.

[0015] In one embodiment, the total effective focal length f of the optical imaging system and the effective focal length f4 of the fourth lens may satisfy 1.0 < f / f4 < 3.0.

[0016] In one embodiment, the effective focal length f3 of the third lens and the effective focal length f5 of the fifth lens may satisfy 2.0 < f3 / f5 < 3.0.

[0017] In one embodiment, the sum ∑CT of the central thicknesses of the lenses in the first lens to the fifth lens may satisfy 1.0 mm < ∑CT / 5 < 1.5 mm.

[0018] A second aspect of the present application provides an optical imaging system, which includes: a lens group, the lens group sequentially includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens having optical power from the object side to the image side along a first direction; a first prism, disposed on the object side of the lens group, for reflecting the light incident on the first prism along a second direction to exit from the first prism along the first direction; a second prism, disposed on the image side of the lens group, for reflecting the light incident on the second prism along the first direction to exit from the second prism along a third direction; wherein, the first direction, the second direction, and the third direction are perpendicular to each other pairwise; wherein, at least one lens in the lens group is a plastic lens, and at least one mirror surface of the plastic lens is an aspherical surface; and wherein, the total effective focal length f of the optical imaging system and half of the diagonal length ImgH of the effective pixel region on the imaging surface of the optical imaging system satisfy f / ImgH > 8.

[0019] In one embodiment, the total effective focal length f of the optical imaging system and the length Ty of the optical imaging system in the third direction satisfy 1.0 < f / Ty < 3.0.

[0020] In one embodiment, the total effective focal length f of the optical imaging system and the length Tz of the optical imaging system in the second direction satisfy 2.0 < f / Tz < 4.0.

[0021] In one embodiment, the total effective focal length f of the optical imaging system satisfies f > 20 mm.

[0022] In one embodiment, the total effective focal length f of the optical imaging system and the entrance pupil diameter EPD of the optical imaging system satisfy f / EPD ≤ 4.0.

[0023] In one embodiment, the refractive index N1 of the first lens and the refractive index N2 of the second lens satisfy 0 < N2 - N1 < 0.2; the dispersion coefficient V1 of the first lens and the dispersion coefficient V2 of the second lens satisfy 0 < V1 - V2 < 10.

[0024] In one embodiment, the dispersion coefficient V4 of the fourth lens and the dispersion coefficient V5 of the fifth lens satisfy 50 < (V4 + V5) / 2 < 60.

[0025] In one embodiment, the first lens has a positive optical power; the second lens has a positive optical power; the third lens has a negative optical power; the fourth lens has a positive optical power; the fifth lens has a negative optical power.

[0026] In one embodiment, the effective focal length f1 of the first lens and the effective focal length f2 of the second lens satisfy 0.1 < f1 / f2 < 0.3.

[0027] In one embodiment, the total effective focal length f of the optical imaging system and the effective focal length f4 of the fourth lens satisfy 1.0 < f / f4 < 3.0.

[0028] In one embodiment, the effective focal length f3 of the third lens and the effective focal length f5 of the fifth lens satisfy 2.0 < f3 / f5 < 3.0.

[0029] In one embodiment, the sum ∑CT of the central thicknesses of the lenses from the first lens to the fifth lens satisfies 1.0 mm < ∑CT / 5 < 1.5 mm.

[0030] This application uses a first prism and a second prism to fold back the optical path, so that there is an angle of 90° between the object plane and the imaging plane, thereby making the optical length of the optical imaging system shorter in the first direction and miniaturizing the volume of the optical imaging system. At the same time, it can also make the optical imaging system have a longer focal length, and thus can have a better optical zoom ratio. And the optical imaging system has good optical imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In conjunction with the accompanying drawings, through the following detailed description of non-limiting embodiments, other features, objects, and advantages of this application will become more apparent. In the drawings:

[0032] Figure 1 Shows a schematic front view of the optical imaging system according to Embodiment 1 of this application;

[0033] Figure 2 Shows a schematic top view of the optical imaging system according to Embodiment 1 of this application;

[0034] Figure 3 and Figure 4 Respectively show the astigmatism curve and distortion curve of the optical imaging system of Embodiment 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] To better understand 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 these detailed descriptions are only descriptions of exemplary embodiments of the present application and do not limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] It should be noted that in this specification, the expressions such as first, second, third, etc. are only used to distinguish one feature from another feature and do not represent any limitation on the features. Therefore, without departing from the teachings of the present application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0037] In the drawings, for the sake of clarity, the thickness, dimensions, and shape of the lens have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are shown by way of example. That is, the spherical or aspherical shapes are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are only examples and are not drawn to an exact scale.

[0038] In this document, 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 not defined, 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 not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object being photographed is called the object side surface of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

[0039] It should also be understood that the terms "comprises", "comprising", "has", "including" and / or "including having", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of listed features rather than an individual element in the list. In addition, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". And the term "exemplary" is intended to refer to an example or illustration.

[0040] 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 should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning 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.

[0041] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will describe the present application in detail with reference to the drawings and in combination with the embodiments.

[0042] The features, principles and other aspects of the present application will be described in detail below.

[0043] The optical imaging system according to an exemplary embodiment of the present application may include a first prism, a lens group, and a second prism. The three are arranged in sequence from the object side to the image side along a first direction. The lens group may include, for example, five lenses with optical power, that is, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. These five lenses are arranged in sequence from the object side to the image side along the optical axis in the first direction. There may be an air gap between any two adjacent lenses among the first lens to the fifth lens. There may be an air gap between the first lens and the first prism. There may be an air gap between the fifth lens and the second prism.

[0044] The first prism is disposed on the object side of the lens group. Exemplarily, the first prism may be a triangular prism, including a first incident surface, a first reflection surface, and a first exit surface. The angle between the first reflection surface and the first direction is 45°. The first exit surface may be perpendicular to the first direction. A second direction is perpendicular to the first direction and the angle between it and the first reflection surface is 45°. The first reflection surface is used to reflect the light incident along the second direction into the light exiting along the first direction. The first incident surface may be perpendicular to the second direction. Exemplarily, the first prism may also be a mirror, which generally has a first reflection surface.

[0045] The second prism is disposed on the image side of the lens group. Exemplarily, the second prism may be a triangular prism, including a second incident surface, a second reflection surface, and a second exit surface. The angle between the second reflection surface and the first direction is 45°. The second incident surface may be perpendicular to the first direction. A third direction is perpendicular to the first direction and the angle between it and the second reflection surface is 45°, and at the same time the third direction is perpendicular to the second direction. The second reflection surface is used to reflect the light incident along the first direction into the light exiting along the third direction. The second exit surface may be perpendicular to the third direction.

[0046] The optical path is folded back twice through the first prism and the second prism, and the emission surface of the first prism and the reflection surface of the second prism have an angle of approximately 30°, so that there is an angle of 90° between the object surface and the imaging surface, thereby making the optical length of the optical imaging system shorter in the first direction and miniaturizing the volume of the optical imaging system. At the same time, it can also make the optical imaging system have a longer focal length, and thus can have a better optical zoom ratio.

[0047] In an exemplary embodiment, the above optical imaging system may further include at least one aperture. The aperture can be disposed at an appropriate position as needed. For example, it can be disposed between the first prism and the first lens. Optionally, the above optical imaging system 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 filter and / or the protective glass can be located on the image side of the second prism.

[0048] In an exemplary embodiment, at least one lens in the lens group is a plastic lens, and at least one surface of the plastic lens is an aspherical surface. Using a plastic lens with an aspherical surface is beneficial to improving the design freedom of the lens, and at the same time can further reduce the axial spherical aberration of the optical imaging system and its off-axis meridional coma aberration. Exemplarily, the first lens is a plastic lens, and the object side surface of the first lens is an aspherical surface.

[0049] In an embodiment of the present application, at least one of the surfaces of each lens is an aspherical surface, that is, at least one of the object side surface of the first lens to the image side surface of the fifth lens is an aspherical surface. The characteristic of an aspherical lens is that the curvature changes continuously from the center of the lens to the periphery of the lens. Different from a spherical lens with a constant curvature from the center of the lens to the periphery, an aspherical lens has better curvature radius characteristics and has the advantages of improving distortion aberration and astigmatism aberration. After using an aspherical lens, it is possible to eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality. Optionally, at least one of the object side surface and the image side surface of each of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens is an aspherical surface. Optionally, both the object side surface and the image side surface of each of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are aspherical surfaces.

[0050] In an exemplary embodiment, the optical imaging system of the present application may satisfy the condition f > 20 mm, where f is the total effective focal length of the optical imaging system. By controlling this condition, the optical imaging system can have the characteristics of a long focal length. Exemplarily, f may satisfy f > 22 mm. More specifically, f may satisfy 23 mm < f < 25 mm.

[0051] In an exemplary embodiment, the lens group includes five lenses. Among them, the first lens may have a positive optical power; the second lens may have a positive optical power; the third lens may have a negative optical power; the fourth lens may have a positive optical power; the fifth lens may have a negative optical power. By reasonably distributing the positive and negative of the optical power of each component of the control system and the curvature of the lens surface type, the temperature drift offset of the long focal length optical imaging system can be effectively reduced, and further the imaging quality of the optical imaging system at different temperatures can be improved.

[0052] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional expression 1.0 < f / Ty < 3.0, where f is the total effective focal length of the optical imaging system, and Ty is the length of the optical imaging system in the third direction. By restricting this conditional expression, when the total effective focal length of the optical imaging system reaches the required magnification, the optical path in the third direction is shorter, and thus the size of the optical imaging system can be reduced. More specifically, f and Ty can satisfy 1.3 < f / Ty < 2.0.

[0053] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional expression 2.0 < f / Tz < 4.0, where f is the total effective focal length of the optical imaging system, and Tz is the length of the optical imaging system in the second direction. By restricting this conditional expression, when the total effective focal length of the optical imaging system reaches the required magnification, the optical path in the second direction is shorter, and thus the size of the optical imaging system can be reduced. More specifically, f and Tz can satisfy 2.5 < f / Tz < 3.5.

[0054] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional expression f / ImgH > 8, where f is the total effective focal length of the optical imaging system, and ImgH is half of the diagonal length of the effective pixel region on the imaging surface of the optical imaging system. By controlling the ratio of the total effective focal length to the image height, it is beneficial for the optical imaging system to have sufficient telephoto ability and improve the magnification of the object being photographed. More specifically, f and ImgH can satisfy f / ImgH > 9.0.

[0055] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional expression f / EPD ≤ 4.0, where f is the total effective focal length of the optical imaging system, and EPD is the entrance pupil diameter of the optical imaging system. By controlling the ratio of the total effective focal length to the entrance pupil diameter, the light passing amount of the ultra-long focal length optical imaging lens can be increased, and the signal-to-noise ratio of the image data can be improved. More specifically, f and EPD can satisfy 3.0 < f / EPD ≤ 4.0.

[0056] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional expression 0 < N2 - N1 < 0.2, where N1 is the refractive index of the first lens and N2 is the refractive index of the second lens. Exemplarily, the optical imaging system of the present application can satisfy the conditional expression 0 < V1 - V2 < 10, where V1 is the dispersion coefficient of the first lens and V2 is the dispersion coefficient of the second lens. By controlling the refractive index and dispersion coefficient of the first lens and the refractive index and dispersion coefficient of the second lens to satisfy the foregoing relationships, it is beneficial to reduce the lateral chromatic aberration of the optical imaging system and improve the imaging quality of the optical imaging system. More specifically, N1 and N2 can satisfy 0 < N2 - N1 < 0.1. More specifically, V1 and V2 can satisfy 5.0 < V1 - V2 < 9.0.

[0057] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional formula 50 < (V4 + V5) / 2 < 60, where V4 is the dispersion coefficient of the fourth lens and V5 is the dispersion coefficient of the fifth lens. By controlling the dispersion coefficients of the fourth lens and the fifth lens, it is beneficial to reduce the chromatic aberration of magnification of the optical imaging system, improve the imaging quality of the optical imaging system, and increase the value of the Modulation Transfer Function (MTF). More specifically, V4 and V5 can satisfy 55 < (V4 + V5) / 2 < 59.

[0058] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional formula 0.1 < f1 / f2 < 0.3, where f1 is the effective focal length of the first lens and f2 is the effective focal length of the second lens. By controlling the ratio of the effective focal lengths of the first lens and the second lens, it is beneficial to reduce the distortion of the optical imaging system, and thus reduce the deformation of the object being photographed in the image. More specifically, f1 and f2 can satisfy 0.15 < f1 / f2 < 0.20.

[0059] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional formula 1.0 < f / f4 < 3.0, where f is the total effective focal length of the optical imaging system and f4 is the effective focal length of the fourth lens. By controlling the ratio of the total effective focal length and the effective focal length of the fourth lens, it is beneficial to reduce the tilt sensitivity of the fourth lens, and thus reduce the tolerance sensitivity of the optical imaging system to tilt. More specifically, f and f4 can satisfy 1.5 < f / f4 < 2.0.

[0060] In an exemplary embodiment, the optical imaging system of the present application can satisfy the conditional formula 2.0 < f3 / f5 < 3.0, where f3 is the effective focal length of the third lens and f5 is the effective focal length of the fifth lens. By controlling the ratio of the effective focal lengths of the third lens and the fifth lens, it is beneficial to reduce the decentration sensitivity of the third lens and the fifth lens, and overall improve the yield distribution of the optical imaging system, which is beneficial to the manufacturing and production of the optical imaging system. More specifically, f3 and f5 can satisfy 2.1 < f3 / f5 < 2.5.

[0061] In an exemplary embodiment, the optical imaging system of the present application may satisfy the condition 1.0 mm < ∑CT / 5 < 1.5 mm, where ∑CT is the sum of the central thicknesses of the lenses from the first lens to the fifth lens. By controlling this condition, the back focal length size of the optical imaging system can be significantly increased, which is beneficial for arranging complex optical path imaging auxiliary systems such as prisms and mirrors in the optical imaging system. Exemplarily, ∑CT = CT1 + CT2 + CT3 + CT4 + CT5, where CT1 is the central thickness of the first lens. More specifically, ∑CT may satisfy 1.15 mm < ∑CT / 5 < 1.45 mm.

[0062] In the lens group of the optical imaging system according to the above embodiment of the present application, multiple lenses can be used, such as the five lenses described above. By reasonably distributing the optical power, surface shape, central thickness of each lens, and the on-axis spacing between each lens, etc., the system focal length can be effectively increased, the sensitivity of the imaging system can be reduced, and the processability of the imaging system can be improved, making the optical imaging system more conducive to production and processing and applicable to portable electronic products. At the same time, through the cooperation with the first prism and the second prism, it is beneficial to achieve the compression of the optical length in the first direction. The optical imaging system of the present application can also be used for functions such as optical zoom.

[0063] However, those skilled in the art should understand that without departing from the technical solution claimed in the present application, the number of lenses constituting the optical imaging system can be changed to obtain the various results and advantages described in this specification. For example, although five lenses are described as an example in the embodiment, the optical imaging system is not limited to including five lenses. If necessary, the optical imaging system may also include other numbers of lenses.

[0064] The following further describes specific embodiments of the optical imaging system applicable to the above embodiment with reference to the drawings.

[0065] Example 1

[0066] The following refers to Figures 1 to 4 Describe the optical imaging system according to Embodiment 1 of the present application. Figure 1 A schematic front view of the optical imaging system according to Embodiment 1 of the present application is shown. Figure 2 A schematic top view is shown.

[0067] As Figure 1 shown, the optical imaging system sequentially includes, from the object side to the image side along the first direction X: a first prism P1, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a second prism P2, and a filter E6.

[0068] The first prism P1 includes a first incident surface S1, a first reflection surface S2, and a first exit surface S3. The angle between the first reflection surface S1 and the first direction X is 45°. The light L2 incident along the second direction Z is deflected at the first reflection surface S2 to propagate along the first direction X as the light ray L1. There is also a diaphragm between the first prism P1 and the first lens E1.

[0069] The first lens E1 has a positive optical power. Its object side surface S4 is convex, and its image side surface S5 is concave. The second lens E2 has a positive optical power. Its object side surface S6 is concave, and its image side surface S7 is convex. The third lens E3 has a negative optical power. Its object side surface S8 is concave, and its image side surface S9 is convex. The fourth lens E4 has a positive optical power. Its object side surface S10 is convex, and its image side surface S11 is convex. The fifth lens E5 has a negative optical power. Its object side surface S12 is convex, and its image side surface S13 is concave.

[0070] The second prism P2 includes a second incident surface S14, a second reflection surface S15, and a second exit surface S16. The angle between the second reflection surface S15 and the first direction X is 45°. The light L1 incident along the first direction X is deflected at the second reflection surface S15 to propagate along the third direction Y as the light ray L3. At the same time, the third direction Y is perpendicular to the second direction Z.

[0071] The filter E6 has an object side surface S17 and an image side surface S18. The optical imaging system has an imaging surface S19. The light from the object (including the light L1 on the optical axis in the second direction Z and the marginal rays) sequentially passes through (or traverses) the surfaces S1 to S18 and finally forms an image on the imaging surface S19.

[0072] Table 1 shows the basic parameter table of the optical imaging system in Embodiment 1, where the units of the radius of curvature, thickness / distance, and focal length are all millimeters (mm).

[0073]

[0074]

[0075] Table 1

[0076] In Embodiment 1, the value of the total effective focal length f of the optical imaging system is 24.00 mm, and the value of the maximum field of view FOV is 12.6°.

[0077] In Embodiment 1, the object side surface and the image side surface of any one of the first lens E1 to the fifth lens E5 are aspherical surfaces. The surface profile x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0078]

[0079] Wherein, x is the sagitta, which is the distance from the vertex of the aspherical surface to the position along the optical axis at a height of h; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic coefficient; Ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 below gives the higher-order coefficients A4, A6, A8, A 10 、A 12 、A 14 、A 16 、A 18 and A 20 .

[0080] Surface number A4 A6 A8 A10 A12 A14 A16 A18 A20 S4 6.5018E-02 1.9356E-02 4.9292E-04 -6.4124E-05 -1.0449E-04 -3.7724E-05 -4.3844E-05 -2.4528E-05 -8.8362E-06 S5 4.6680E-02 2.7299E-02 -9.0126E-03 -2.8068E-03 -3.4874E-04 6.0546E-05 2.4585E-04 3.1587E-04 7.7389E-05 S6 -6.7682E-02 -2.8107E-02 -1.0635E-03 -5.6094E-04 2.3210E-03 1.0103E-03 1.0544E-03 5.8282E-04 5.2065E-05 S7 -2.5958E-01 5.4885E-02 -2.2406E-02 6.0319E-03 -8.7768E-03 3.6553E-03 -1.4870E-03 -2.0575E-03 1.1907E-03 S8 -2.9115E-02 3.0192E-02 1.7983E-03 -6.0309E-03 -6.9128E-04 -5.4877E-04 2.0005E-04 -1.3706E-04 -1.1574E-04 S9 1.7447E-01 -9.0705E-02 5.2802E-02 -2.1087E-02 4.8637E-03 -2.4433E-03 1.2569E-03 -2.0754E-04 -1.3693E-04 S10 1.1088E-02 4.1038E-03 -6.7942E-03 3.5531E-04 -1.5298E-04 1.0088E-04 -4.0030E-04 2.9430E-05 6.4232E-05 S11 1.6933E-03 -1.0495E-02 6.8909E-03 -5.0012E-04 2.3296E-04 -6.9774E-04 -2.4324E-04 1.1347E-04 7.3324E-05 S12 -3.3023E-01 3.2598E-03 1.9951E-02 -2.5149E-02 1.2605E-02 -2.3112E-03 -1.5124E-03 3.7053E-04 1.6117E-04 S13 -4.4666E-01 -5.2210E-02 8.3730E-03 -1.4385E-02 5.6913E-03 -1.3423E-03 1.3683E-04 -6.2066E-04 3.2276E-04

[0081] Table 2

[0082] Figure 3 shows the astigmatism curve of the optical imaging system of Embodiment 1, which represents the meridional image plane curvature and the sagittal image plane curvature. Figure 4 shows the distortion curve of the optical imaging system of Embodiment 1, which represents the distortion magnitude values corresponding to different image heights. According to Figure 3 and Figure 4 it can be seen that the optical imaging system given in Embodiment 1 can achieve good imaging quality.

[0083] In summary, Embodiment 1 satisfies the relationships shown in Table 3.

[0084]

[0085]

[0086] Table 3

[0087] This application also provides an imaging device, which is provided with an electronic photosensitive element for imaging. The electronic photosensitive element can be a charge coupled device (CCD) or a complementary metal oxide semiconductor element (CMOS). The imaging device can be an independent imaging device such as a digital camera, or an imaging module integrated on a mobile electronic device such as a mobile phone. The imaging device is equipped with the optical imaging system described above.

[0088] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of protection involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the concept of the present application. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) disclosed in the present application that have similar functions.

Claims

1. An optical imaging system, characterized in that, Comprising: A lens group, which sequentially includes a first lens with a focal power, a second lens, a third lens, a fourth lens, and a fifth lens from the object side to the image side along a first direction; A first prism, disposed on the object side of the lens group, for reflecting light incident on the first prism along a second direction to exit from the first prism along the first direction; A second prism, disposed on the image side of the lens group, for reflecting light incident on the second prism along the first direction to exit from the second prism along a third direction; Wherein, the number of lenses with focal power in the optical imaging system is five; The first lens has a positive focal power, its object side is convex, and its image side is concave; The second lens has a positive focal power, its object side is concave, and its image side is convex; The third lens has a negative focal power, its object side is concave, and its image side is convex; The fourth lens has a positive focal power, its object side is convex, and its image side is convex; The fifth lens has a negative focal power, its object side is convex, and its image side is concave; Wherein, the first direction, the second direction, and the third direction are perpendicular to each other in pairs; Wherein, at least one lens in the lens group is a plastic lens, and at least one mirror surface of the plastic lens is an aspherical surface; and Wherein, the total effective focal length f of the optical imaging system and half of the diagonal length ImgH of the effective pixel region on the imaging surface of the optical imaging system satisfy f / ImgH > 9.0; The total effective focal length f of the optical imaging system and the length Ty of the optical imaging system in the third direction satisfy 1.3 < f / Ty < 2.

0.

2. The optical imaging system according to claim 1, characterized in that, The total effective focal length f of the optical imaging system and the length Tz of the optical imaging system in the second direction satisfy 2.5 < f / Tz < 3.

5.

3. The optical imaging system according to claim 1, characterized in that, The total effective focal length f of the optical imaging system satisfies 23 mm < f < 25 mm.

4. The optical imaging system according to claim 1, characterized in that, The total effective focal length f of the optical imaging system and the entrance pupil diameter EPD of the optical imaging system satisfy 3.0 < f / EPD ≤ 4.

0.

5. The optical imaging system according to claim 1, characterized in that, The refractive index N1 of the first lens and the refractive index N2 of the second lens satisfy 0 < N2 - N1 < 0.1; The dispersion coefficient V1 of the first lens and the dispersion coefficient V2 of the second lens satisfy 5.0 < V1 - V2 < 9.

0.

6. The optical imaging system according to claim 1, characterized in that, The dispersion coefficient V4 of the fourth lens and the dispersion coefficient V5 of the fifth lens satisfy 55 < (V4 + V5) / 2 < 59.

7. The optical imaging system according to any one of claims 1 - 6, characterized in that, The effective focal length f1 of the first lens and the effective focal length f2 of the second lens satisfy 0.15 < f1 / f2 < 0.

20.

8. The optical imaging system according to any one of claims 1 - 6, characterized in that, The total effective focal length f of the optical imaging system and the effective focal length f4 of the fourth lens satisfy 1.5 < f / f4 < 2.

0.

9. The optical imaging system according to any one of claims 1 - 6, characterized in that, The effective focal length f3 of the third lens and the effective focal length f5 of the fifth lens satisfy 2.1 < f3 / f5 < 2.

5.

10. The optical imaging system according to any one of claims 1 - 6, characterized in that, The sum ∑CT of the central thicknesses of each lens from the first lens to the fifth lens satisfies 1.15 mm < ∑CT / 5 < 1.45 mm.

11. The optical imaging system according to any one of claims 1 - 6, characterized in that, The total effective focal length f of the optical imaging system and half of the diagonal length ImgH of the effective pixel region on the imaging surface of the optical imaging system satisfy 9.0 < f / ImgH ≤ 9.06.

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