Optical imaging system

Abstract

An optical imaging system is disclosed, comprising: a first lens having a positive refractive power, a convex object-side surface, and a convex image-side surface; a second lens having a negative refractive power, a convex object-side surface, and a concave image-side surface; a third lens having a refractive power; and a fourth lens having a positive refractive power; wherein the first lens to the fourth lens are sequentially arranged on the optical axis from the object side towards the image side, wherein 1.3 < TTL / BFL < 3.5 is satisfied, where TTL is the distance from the object-side surface of the first lens to the imaging surface, BFL is the distance from the image-side surface of the fourth lens to the imaging surface, and wherein FOV ≤ 40° is satisfied, where FOV is the field of view of the optical imaging system.

Description

[0001] This application claims the priority and benefit of Korean Patent Application No. 10-2017-0105365, filed on Aug. 21, 2017 with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0002] This application relates to an optical imaging system. Background Art

[0003] In recent years, mobile communication terminals have generally been provided with camera modules, enabling video calls and image capture. As the use of camera modules installed in mobile communication terminals has increased, camera modules for mobile communication terminals have gradually been required to have higher resolution and higher performance.

[0004] However, due to the trend of gradually miniaturizing and lightening mobile communication terminals, there seem to be limitations in implementing camera modules with higher resolution and higher performance.

[0005] In particular, a telephoto lens may have a relatively long focal length. In this case, the total track length (TTL) is also increased. Therefore, when a telephoto lens is installed in a small mobile electronic device, the size (thickness) of the mobile electronic device also increases.

[0006] The above information disclosed in the background art section is only for enhancing the understanding of the background of the present disclosure, and thus the above information may include information that neither forms any part of the prior art nor forms information of the prior art that may be taught to a person of ordinary skill in the art. Summary of the Invention

[0007] The present invention content is provided to introduce selected concepts that will be further described in the detailed description below in a simplified form. The present invention content is neither intended to identify the key features or essential features of the claimed subject matter nor intended to be used to help determine the scope of the claimed subject matter.

[0008] In one general aspect, an optical imaging system includes: a first lens, a second lens, a third lens, and a fourth lens sequentially arranged on an optical axis from an object side toward an image side; and a reflection member disposed closer to the object side than the first lens and having a reflection surface configured to change a path of light so that the light is incident on the first lens to the fourth lens. The first lens to the fourth lens are arranged to be separated from each other by a preset distance along the optical axis, and 1.3 < TTL / BFL < 3.5, where TTL is the distance from the object-side surface of the first lens to the imaging surface of an image sensor, and BFL is the distance from the image-side surface of the fourth lens to the imaging surface of the image sensor.

[0009] In the optical imaging system, the FOV may be less than or equal to 40°, where the FOV is the field of view of the optical system including the first lens to the fourth lens.

[0010] In the optical imaging system, DF / DC may be greater than 0.9 and less than 1.3, wherein DF is the effective aperture radius of the image-side surface of the fourth lens, and DC is the effective aperture radius of the object-side surface of the first lens.

[0011] In the optical imaging system, TTL / f may be greater than 0.8 and less than 1.5, where f is a total focal length of the optical system including the first to fourth lenses.

[0012] In the optical imaging system, f12 / f may be greater than 0.75 and less than 1.8, wherein f12 is the composite focal length of the first lens and the second lens, and f is the total focal length of the optical system including the first lens to the fourth lens.

[0013] The first lens may have positive refractive power and a convex object-side surface, and the second lens may have negative refractive power and a concave image-side surface.

[0014] The first lens may have positive refractive power, the second lens may have negative refractive power, the third lens may have negative refractive power, and the fourth lens may have positive refractive power.

[0015] The first lens may have a convex object-side surface and a convex image-side surface.

[0016] The first lens may have a convex object-side surface and a concave image-side surface.

[0017] The second lens may have a convex object-side surface and a concave image-side surface.

[0018] The third lens may have a concave object-side surface and a convex image-side surface.

[0019] The fourth lens may have a convex object-side surface and a concave image-side surface.

[0020] The first and fourth lenses may include a first plastic material, and the second and third lenses may include a plastic material having optical properties different from those of the first plastic material.

[0021] The plastic material of the second lens may include different optical properties from the plastic material of the third lens.

[0022] In another general aspect, an optical imaging system includes: a reflecting member having a reflecting surface configured to change the path of light; and a lens sequentially arranged from an object side toward an image side on an optical axis, and the changed path of the light is configured to be incident on the lens. The reflecting member is disposed on the object side of the lens. TTL / BFL is greater than 1.3 and less than 3.5, where TTL is the distance from the object-side surface of the lens closest to the reflecting member to the imaging surface of an image sensor, BFL is the distance from the image-side surface of the lens closest to the image sensor to the imaging surface of the image sensor, and 0.9 < DF / DC < 1.3, where DF is the effective aperture radius of the image-side surface of the lens closest to the image sensor, and DC is the effective aperture radius of the object-side surface of the lens closest to the reflecting member.

[0023] The lens may include: a first lens having a positive refractive power and a convex object-side surface; a second lens having a negative refractive power and a concave image-side surface; a third lens having a refractive power; and a fourth lens having a refractive power. The first lens to the fourth lens may be sequentially arranged from the object side toward the image side.

[0024] The first lens may be the lens closest to the reflecting member, and the fourth lens may be the lens closest to the image sensor.

[0025] In another general aspect, an optical imaging system includes: a reflecting member configured to change the path of light so that the light is incident on the object side of a lens; and an image sensor configured to receive light from the image side of the lens. The lens includes a first lens, a second lens, a third lens, and a fourth lens sequentially arranged from the object side toward the image side on the optical axis. Any one or any combination of any two or more of the following expressions are satisfied: FOV ≤ 40°, 0.9 < DF / DC < 1.3, 1.3 < TTL / BFL < 3.5, 0.8 < TTL / f < 1.5, 0.75 < f12 / f < 1.8, and CRA_max < 25°, where FOV is the field of view of the optical imaging system, DF is the effective aperture radius of the image-side surface of the fourth lens, DC is the effective aperture radius of the object-side surface of the first lens, TTL is the distance from the object-side surface of the first lens to the imaging surface of the image sensor, BFL is the distance from the image-side surface of the fourth lens to the imaging surface of the image sensor, f is the total focal length of the optical imaging system, f12 is the combined focal length of the first lens and the second lens, and CRA_max is the maximum value of the incident angle of the chief ray incident on the imaging surface.

[0026] The first lens may include positive refractive power, the second lens may include negative refractive power, the third lens may include negative refractive power, and the fourth lens may include positive refractive power.

[0027] The first lens may include a convex object-side surface and a convex or concave image-side surface; the second lens may include a convex object-side surface and a concave image-side surface; the third lens may include a concave object-side surface and a convex image-side surface; and / or the fourth lens may include a convex object-side surface and a concave image-side surface.

[0028] Other features and aspects will be apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a diagram illustrating a first example of an optical imaging system.

[0030] Figure 2 and Figure 3 Shown with presentation Figure 1 An example graph of a curve of aberration characteristics of an optical imaging system is shown in FIG.

[0031] Figure 4 is a diagram illustrating a second example of the optical imaging system.

[0032] Figure 5 and Figure 6 Shown with presentation Figure 4 An example graph of a curve of aberration characteristics of an optical imaging system is shown in FIG.

[0033] Throughout the drawings and detailed description, like reference numerals refer to like elements. The drawings may not be drawn to scale, and the relative sizes, proportions, and depictions of elements in the drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0034] The following detailed description is provided to help the reader gain a comprehensive understanding of the methods, devices, and / or systems described herein. However, after understanding the disclosure of the present application, various permutations, modifications, and equivalents of the methods, devices, and / or systems described herein will be apparent. For example, the order of operations described herein is merely an example and is not limited to the order set forth herein. Instead, except for operations that must occur in a particular order, changes that will be apparent after understanding the disclosure of the present application may be made. In addition, for clarity and brevity, descriptions of features known in the art may be omitted.

[0035] The features described herein may be implemented in different forms and are not to be construed as limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many possible ways of implementing the methods, devices, and / or systems described herein that will be apparent upon understanding the disclosure of this application.

[0036] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings.

[0037] An aspect of the present disclosure provides an optical imaging system capable of preventing an increase in size (eg, thickness) of a mobile electronic device while having a relatively narrow field of view and a relatively large total track length (TTL).

[0038] An optical imaging system according to an example of the present application includes lenses arranged on an optical axis, wherein the lenses are arranged to be separated from each other by a predetermined distance on the optical axis.

[0039] As an example, the optical imaging system includes four lenses.

[0040] In an example where the optical imaging system includes four lenses, the first lens refers to the lens closest to the object, and the fourth lens refers to the lens closest to the image sensor.

[0041] The first surface of each lens refers to the surface of the lens closest to the object side (also called the object side surface), and the second surface of each lens refers to the surface of the lens closest to the image side (also called the image side surface). In addition, in this specification, all numerical values of lens curvature radius, thickness, distance, etc. are expressed in millimeters (mm), and angles are expressed in degrees. In addition, in the following, lens thickness, spacing between lenses, TTL, BFL, etc. are distances measured based on the optical axis. IMG HT is half the diagonal length of the imaging surface of the image sensor.

[0042] Furthermore, in the description of the shape of each lens, a lens surface being convex means that the paraxial region of the corresponding surface is partially convex, and a lens surface being concave means that the paraxial region of the corresponding surface is partially concave. Therefore, even when a lens surface is described as convex, the edge portion of the surface may be concave. Similarly, even when a lens surface is described as concave, the edge portion of the surface may be convex.

[0043] The paraxial region refers to the narrow region near the optical axis.

[0044] When the optical imaging system is installed in a mobile electronic device, the optical axis of the lens of the optical imaging system is formed in a direction perpendicular to the thickness direction of the mobile electronic device (a direction from the front surface of the mobile electronic device toward the rear surface of the mobile electronic device or a direction opposite to the direction from the front surface of the mobile electronic device toward the rear surface of the mobile electronic device).

[0045] As an example, the optical axis of the lens constituting the optical imaging system is formed in the width direction or the length direction of the mobile electronic device.

[0046] Therefore, the total track length (TTL) of the optical imaging system (e.g., the distance from the object-side surface of the first lens to the imaging plane of the image sensor) may not affect the thickness of the mobile electronic device. Therefore, even if the TTL of the optical imaging system is relatively large, the TTL does not affect the thickness of the mobile electronic device, and the mobile electronic device can be minimized.

[0047] External light is incident on the mobile electronic device in a direction approximately equal to the thickness of the mobile electronic device, and the optical axis of the lens is formed in a direction perpendicular to the thickness of the mobile electronic device. Therefore, the optical imaging system is configured to change the path of light.

[0048] As an example, the optical imaging system includes a reflective member having a reflective surface to change the path of light. The reflective member may be a prism or a mirror that changes the path of light.

[0049] Examples of optical imaging systems have been described as including four lenses.

[0050] For example, the optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence from the object side.

[0051] However, the optical imaging system is not limited to including only four lenses, but may also include other components.

[0052] For example, the optical imaging system further includes a reflective member having a reflective surface that changes the path of light. The reflective member changes the path of light by 90°. As an example, the reflective member can be a mirror or a prism.

[0053] Compared to the lens, the reflective member is closer to the object side. As an example, between the reflective member and the lens, the reflective member is closest to the object side.

[0054] Among the lenses, the lens closest to the object side (for example, the first lens) is closest to the reflecting member.

[0055] Furthermore, the optical imaging system further includes an image sensor configured to convert an image of a subject incident on the image sensor into an electric signal.

[0056] The optical imaging system further includes an infrared cut filter configured to filter out infrared light. The infrared cut filter is disposed between a lens closest to the image sensor (for example, the fourth lens) and the image sensor.

[0057] In the exemplary optical imaging system, all lenses are formed using plastic materials.

[0058] Among the lenses constituting the optical imaging system, the lens closest to the reflective member and the lens closest to the image sensor are formed using a first plastic material, the other lenses are formed using a plastic material having optical properties different from the optical properties of the first plastic material, and the other lenses are formed using plastic materials having optical properties different from each other.

[0059] As an example, in an optical imaging system including four lenses, the first lens and the fourth lens are formed using a first plastic material, the second lens and the third lens are formed using a plastic material having optical properties different from the optical properties of the first plastic material, and the second lens and the third lens are formed using plastic materials having optical properties different from each other.

[0060] The lens has at least one aspherical surface.

[0061] That is, at least one of the first and second surfaces of all lenses from the first to fourth lenses is aspherical. Here, any aspherical surface among the aspherical surfaces of the first to fourth lenses is expressed by the following equation 1:

[0062]

[0063] Here, c is the curvature of the lens (the inverse of the radius of curvature R), k is the conic constant, and r is the distance from a point on the aspheric surface of the lens to the optical axis, perpendicular to the optical axis. Constants A through F are aspheric coefficients. Z is the distance between a point on the aspheric surface of the lens at a distance r from the optical axis and the tangent plane, where the tangent plane intersects the vertex of the aspheric surface of the lens.

[0064] The first to fourth lenses included in the optical imaging system have positive refractive power / negative refractive power / negative refractive power / positive refractive power in sequence from the object side.

[0065] The optical imaging system according to the example satisfies any one or any combination of any two or more of the following conditional expressions:

[0066] FOV≤40°

[0067] 0.9 <DF / DC<1.3

[0068] 1.3 <TTL / BFL<3.5

[0069] 0.8 <TTL / f<1.5

[0070] 0.75 <f12 / f<1.8

[0071] CRA_max<25°.

[0072] In the above conditional expressions, FOV is the field of view of the optical imaging system, DF is the effective aperture radius of the image-side surface of the lens closest to the image sensor, DC is the effective aperture radius of the object-side surface of the lens closest to the object (or reflective component), TTL is the distance from the object-side surface of the first lens to the imaging plane of the image sensor, BFL is the distance from the image-side surface of the lens closest to the image sensor to the imaging plane of the image sensor, f is the total focal length of the optical imaging system, f12 is the composite focal length of the first lens and the second lens, and CRA_max is the maximum value of the incident angle of the principal light ray incident on the imaging plane.

[0073] The effective aperture radius refers to the radius of one surface of each lens (object surface or image surface) through which light actually passes.

[0074] Next, first to fourth lenses constituting the optical imaging system according to an example will be described.

[0075] The first lens has positive refractive power.

[0076] The first lens has two convex surfaces. For example, the first surface and the second surface of the first lens are convex. Optionally, the first lens has a meniscus shape with a convex object-side surface. For example, the first surface of the first lens is convex and the second surface of the first lens is concave.

[0077] At least one of the first surface and the second surface of the first lens is aspherical. For example, both surfaces of the first lens are aspherical.

[0078] The second lens has negative refractive power. The second lens has a meniscus shape with a convex object-side surface. For example, the first surface of the second lens is convex and the second surface of the second lens is concave.

[0079] At least one of the first surface and the second surface of the second lens is aspherical. For example, both surfaces of the second lens are aspherical.

[0080] The third lens element has negative refractive power. The third lens element has a meniscus shape with a convex image-side surface. For example, the first surface of the third lens element is concave, and the second surface of the third lens element is convex.

[0081] At least one of the first surface and the second surface of the third lens is aspherical. For example, both surfaces of the third lens are aspherical.

[0082] The fourth lens element has positive refractive power and has a meniscus shape with a convex object-side surface. For example, the first surface of the fourth lens element is convex and the second surface of the fourth lens element is concave.

[0083] At least one of the first surface and the second surface of the fourth lens is aspherical. For example, both surfaces of the fourth lens are aspherical.

[0084] The first to fourth lenses are lenses on which no inflection point is formed.

[0085] In the optical imaging system configured as described above, the lens performs an aberration correction function to thereby enhance aberration improvement performance.

[0086] The optical imaging system has the characteristics of a telephoto lens with a field of view of 40 degrees or less. The optical imaging system has a relatively narrow field of view and a relatively long total focal length.

[0087] Will refer to Figures 1 to 3 A first example of an optical imaging system is described.

[0088] The optical imaging system according to the first example includes an optical system including a first lens 110 , a second lens 120 , a third lens 130 , and a fourth lens 140 , and further includes an infrared cut filter 150 and an image sensor 160 .

[0089] The optical imaging system further includes a reflective member P that is closer to the object side than the first lens 110 and has a reflective surface that changes the path of light.

[0090] Here, Table 1 shows the lens characteristics of each lens (curvature radius, thickness of the lens or distance between lenses, refractive index, Abbe number, and effective aperture radius).

[0091] Table 1

[0092] Surface marking Radius of curvature Thickness or distance Refractive index Abbe number Effective hole radius Prism infinity 4.300 1.5167 64.17 Prism infinity 1.000 1 3.254501135 1.134841384 1.5441 56.11 1.862 2 -152.590894 0.030001661 1.722 3 4.820975086 0.900080445 1.6349 23.97 1.632 4 2.048937542 0.960625226 1.312 5 -2.46741293 0.817889534 1.6144 25.95 1.366 6 -3.11220229 0.030892447 1.634 7 3.323254281 0.700000126 1.5441 56.11 1.845 8 5.614984106 0.967508944 1.887 9 infinity 0.11 1.5167 64.17 10 infinity 5.72105725 11 infinity

[0093] In the first example, the total focal length f of the optical imaging system is 10.6893 mm, the focal length f1 of the first lens 110 is 5.871596 mm, the focal length f2 of the second lens 120 is -6.421992 mm, the focal length f3 of the third lens 130 is -37.4734 mm, and the focal length f4 of the fourth lens 140 is 13.510605 mm.

[0094] The field of view (FOV) of the optical imaging system is 30.24°, the effective aperture radius (DC) of the object-side surface of the first lens 110 is 1.862 mm, the effective aperture radius (DF) of the image-side surface of the fourth lens 140 is 1.887 mm, the distance (TTL) from the object-side surface of the first lens 110 to the imaging plane of the image sensor 160 is 11.373 mm, the distance (BFL) from the image-side surface of the fourth lens 140 to the imaging plane of the image sensor 160 is 6.799 mm, the composite focal length (f12) of the first lens 110 and the second lens 120 is 15.7264 mm, and the maximum incident angle (CRA_max) of the chief ray incident on the imaging plane is 16.63°.

[0095] In the first example, the first lens 110 has positive refractive power, and the first surface and the second surface of the first lens 110 are convex in the paraxial region.

[0096] The second lens 120 has negative refractive power, a first surface of the second lens 120 is convex in the paraxial region, and a second surface of the second lens 120 is concave in the paraxial region.

[0097] The third lens 130 has negative refractive power, a first surface of the third lens 130 is concave in a paraxial region, and a second surface of the third lens 130 is convex in the paraxial region.

[0098] The fourth lens 140 has positive refractive power, a first surface of the fourth lens 140 is convex in the paraxial region, and a second surface of the fourth lens 140 is concave in the paraxial region.

[0099] The first lens 110 and the fourth lens 140 are formed using a first plastic material, the second lens 120 and the third lens 130 are formed using a plastic material having optical properties different from those of the first plastic material, and the second lens 120 and the third lens 130 are formed using plastic materials having optical properties different from each other.

[0100] All of the first to fourth lenses 110 to 140 are lenses on which no inflection point is formed.

[0101] Each surface of the first to fourth lenses 110 to 140 has an aspheric coefficient as shown in Table 2. For example, all of the object-side surfaces and image-side surfaces of the first to fourth lenses 110 to 140 are aspheric.

[0102] Table 2

[0103] surface S1 S2 S3 S4 R 3.25450114E+00 -1.52590894E+02 4.82097509E+00 2.04893754E+00 k 1.12247811E+00 0.00000000E+00 0.00000000E+00 0.00000000E+00 A -2.93087621E-03 3.08885231E-03 -9.71881812E-03 -1.67492903E-02 B -6.03090776E-04 -1.55177834E-03 -7.75346961E-04 1.12149397E-03 C -9.43451358E-05 1.35090893E-03 1.46983797E-03 -2.38906969E-04 D 1.54995264E-05 -4.95921618E-04 -5.84288723E-04 7.49703655E-04 E -8.14345763E-06 6.88446582E-05 7.69230485E-05 -2.01012950E-04

[0104] Table 2 (continued)

[0105] surface S5 S6 S7 S8 R -2.46741293E+00 -3.11220229E+00 3.32325428E+00 5.61498411E+00 k 0.00000000E+00 0.00000000E+00 0.00000000E+00 0.00000000E+00 A 4.27481176E-02 4.14217107E-03 -3.44593845E-02 -1.23689361E-02 B -1.87912212E-02 -2.67943122E-03 6.49482597E-03 -6.92154503E-04 C 9.02786550E-03 2.38752870E-03 -5.91158915E-04 7.76013714E-04 D -1.54167364E-03 -5.79265734E-04 2.84559575E-05 -5.04688822E-05 E 7.24405414E-07 2.64231849E-06 -5.93158735E-05 -5.27842068E-05 F 1.22461623E-05 9.64415333E-06

[0106] The optical imaging system constructed as described above has the following features: Figure 2 and Figure 3 Aberration characteristics shown.

[0107] Will refer to Figures 4 to 6 A second example of an optical imaging system is described.

[0108] The optical imaging system according to the second example includes an optical system including a first lens 210 , a second lens 220 , a third lens 230 , and a fourth lens 240 , and further includes an infrared cut filter 250 and an image sensor 260 .

[0109] The optical imaging system further includes a reflective member P that is closer to the object side than the first lens 210 and has a reflective surface that changes the path of light.

[0110] Here, Table 3 shows the lens characteristics of each lens (curvature radius, thickness of the lens or distance between lenses, refractive index, Abbe number, and effective aperture radius).

[0111] Table 3

[0112] Surface marking Radius of curvature Thickness or distance Refractive index Abbe number Effective hole radius Prism infinity 4.300 1.5167 64.17 Prism infinity 1.000 1 3.229258844 1.122792676 1.5441 56.11 1.850 2 3091.218237 0.03 1.705 3 4.748586431 0.886922529 1.6349 23.97 1.620 4 2.024253753 0.9614216 1.257 5 -2.46875098 0.788079933 1.6144 25.95 1.359 6 -3.07358344 0.03 1.617 7 3.367820575 0.700602456 1.5441 56.11 1.822 8 5.775095248 0.95657511 1.867 9 infinity 0.11 1.5167 64.17 10 infinity 5.856604534 11 infinity

[0113] In the second example, the total focal length f of the optical imaging system is 10.7822 mm, the focal length f1 of the first lens 210 is 5.940492 mm, the focal length f2 of the second lens 220 is -6.401719 mm, the focal length f3 of the third lens 230 is -40.50323 mm, and the focal length f4 of the fourth lens 240 is 13.468033 mm.

[0114] The field of view (FOV) of the optical imaging system is 30.04°, the effective aperture radius (DC) of the object-side surface of the first lens 210 is 1.850 mm, the effective aperture radius (DF) of the image-side surface of the fourth lens 240 is 1.867 mm, the distance (TTL) from the object-side surface of the first lens 210 to the imaging plane of the image sensor 260 is 11.443 mm, the distance (BFL) from the image-side surface of the fourth lens 240 to the imaging plane of the image sensor 260 is 6.923 mm, the composite focal length (f12) of the first lens 210 and the second lens 220 is 16.4729 mm, and the maximum incident angle (CRA_max) of the chief ray incident on the imaging plane is 16.568°.

[0115] In the second example, the first lens 210 has positive refractive power, a first surface of the first lens 210 is convex in the paraxial region, and a second surface of the first lens 210 is concave in the paraxial region.

[0116] The second lens 220 has negative refractive power, a first surface of the second lens 220 is convex in the paraxial region, and a second surface of the second lens 220 is concave in the paraxial region.

[0117] The third lens 230 has negative refractive power, a first surface of the third lens 230 is concave in a paraxial region, and a second surface of the third lens 230 is convex in the paraxial region.

[0118] The fourth lens 240 has positive refractive power, a first surface of the fourth lens 240 is convex in the paraxial region, and a second surface of the fourth lens 240 is concave in the paraxial region.

[0119] The first lens 210 and the fourth lens 240 are formed using a first plastic material, the second lens 220 and the third lens 230 are formed using a plastic material having optical properties different from those of the first plastic material, and the second lens 220 and the third lens 230 are formed using plastic materials having optical properties different from each other.

[0120] All of the first to fourth lenses 210 to 240 are lenses on which no inflection point is formed.

[0121] Each surface of the first to fourth lenses 210 to 240 has an aspheric coefficient as shown in Table 4. For example, all of the object-side surfaces and image-side surfaces of the first to fourth lenses 210 to 240 are aspheric.

[0122] Table 4

[0123] surface S1 S2 S3 S4 R 3.22925884E+00 3.09121824E+03 4.71858643E+00 2.02425375E+00 k 1.12733268E+00 0.00000000E+00 0.00000000E+00 0.00000000E+00 A -2.91252696E-03 3.18876500E-03 -1.01279285E-02 -1.77062176E-02 B -7.25411438E-04 -1.65034789E-03 -4.73706916E-04 2.29233274E-03 C -3.49226702E-05 1.49024285E-03 1.34520649E-03 -1.45352361E-03 D -2.092399959E-06 -5.70716275E-04 -5.77192419E-04 1.45712465E-03 E -6.95453838E-06 8.20730484E-05 7.98045969E-05 -3.45733760E-04

[0124] Table 4 (continued)

[0125] surface S5 S6 S7 S8 R -2.46875098E+00 -3.07358344E+00 3.36782058E+00 5.77509525E+00 k 0.00000000E+00 0.00000000E+00 0.00000000E+00 0.00000000E+00 A 4.28687352E-02 4.305664437E-03 -3.50692924E-02 -1.27288018E-02 B -1.85205970E-02 -3.07696460E-03 5.97266181E-03 -1.13580054E-03 C 8.30407571E-03 2.61783612E-03 6.34612226E-05 1.13730181E-03 D -8.88551012E-04 -5.64448011E-04 -2.35317915E-04 -1.83415130E-04 E -1.60139148E-04 -2.09965100E-05 -1.40750387E-05 -2.86613583E-05 F 9.70247802E-06 8.01109643E-06

[0126] The optical imaging system constructed as described above has the following features: Figure 5 and Figure 6 Aberration characteristics shown.

[0127] As explained above, the optical imaging system according to the examples in the present application can prevent the size (or thickness) of the mobile electronic device from increasing while having a relatively narrow field of view and a relatively large total track length (TTL).

[0128] Although the present disclosure includes specific examples, it will be apparent after understanding the disclosure of this application that various changes in form and detail can be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein will be considered as descriptive meanings only and not for limiting purposes. The description of the features or aspects in each example will be considered to be applicable to similar features or aspects in other examples. If the described techniques are performed in a different order, and / or if the components in the described systems, architectures, devices or circuits are combined in different ways and / or replaced or supplemented with other components or their equivalents, appropriate results can be obtained. Therefore, the scope of the present disclosure is not limited by specific embodiments, but by the claims and their equivalents, and all changes within the scope of the claims and their equivalents will be interpreted as being included in the present disclosure.

Claims

1. An optical imaging system, comprising: A first lens having a positive refractive power, a convex object-side surface, and a convex image-side surface; A second lens having a negative refractive power, a convex object-side surface, and a concave image-side surface; A third lens having a negative refractive power, a concave object-side surface, and a convex image-side surface; And A fourth lens having a positive refractive power, a convex object-side surface, and a concave image-side surface; Wherein, the optical imaging system includes a total of four lenses with refractive power, and the first lens to the fourth lens are arranged in sequence from the object side to the image side on the optical axis, Wherein, 1.3 < TTL / BFL < 11.373 / 6.799 is satisfied, where TTL is the distance from the object-side surface of the first lens to the imaging surface, and BFL is the distance from the image-side surface of the fourth lens to the imaging surface, Wherein, FOV ≤ 40° is satisfied, where FOV is the field of view of the optical imaging system, and Wherein, 15.7264 / 10.689 ≤ f12 / f < 1.8 is satisfied, where f is the total focal length of the optical imaging system, and f12 is the combined focal length of the first lens and the second lens.

2. The optical imaging system according to claim 1, wherein: 0.8 < TTL / f < 1.5 is satisfied.

3. The optical imaging system according to claim 1, wherein: The fourth lens has a convex object-side surface.

4. The optical imaging system according to claim 3, wherein: The fourth lens has a concave image-side surface.

5. The optical imaging system according to claim 1, wherein: The first lens to the fourth lens are arranged to be spaced apart from each other by a predetermined distance along the optical axis.

6. The optical imaging system according to claim 1, wherein: The first lens to the fourth lens are made of a plastic material.

7. The optical imaging system according to claim 6, wherein: The first lens includes a first plastic material; and The second lens and the third lens include a plastic material with optical properties different from those of the first plastic material.

8. The optical imaging system according to claim 7, wherein: The plastic material of the second lens has different optical properties from the plastic material of the third lens.

9. The optical imaging system according to claim 1, further comprising a reflecting element, the reflecting element being arranged closer to the object side than the first lens and having a reflecting surface for changing the optical path to the first lens to the fourth lens.

10. The optical imaging system according to claim 9, wherein: The first lens is the lens closest to the reflecting element, and the fourth lens is the lens closest to the image sensor.

Images