Optical imaging system

Abstract

An optical imaging system includes a first lens group including a plurality of lenses and having a negative refractive power, a second lens group including a plurality of lenses and having a positive refractive power, and a third lens group including a plurality of lenses and having a negative refractive power, wherein the first lens group, the second lens group, and the third lens group are sequentially disposed from an object side and collectively include seven lenses, wherein at least one of the first lens group to the third lens group is movable in an optical axis direction, and wherein 0.11 < Nd6 - Nd7 < 0.13, wherein Nd6 is a refractive index of a sixth lens disposed from the object side among the seven lenses, and Nd7 is a refractive index of a seventh lens disposed from the object side among the seven lenses.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2018-0044964, filed with the Korean Intellectual Property Office on April 18, 2018, and Korean Patent Application No. 10-2018-0115988, filed with the Korean Intellectual Property Office on September 28, 2018, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0002] The following description relates to an optical imaging system capable of adjusting the focal length. Background Technology

[0003] One type of optical path folding imaging system involves multiple lenses aligned in columns, constructed such that the more lenses there are, the longer the overall length of the optical imaging system. For example, it may be more difficult to reduce the size of an optical imaging system comprising five lenses compared to one comprising three lenses. For this reason, there may be limitations to installing an optical path folding imaging system in a small, portable terminal device.

[0004] Unlike optical path folding imaging systems, curved optical imaging systems can be constructed such that prisms bend the optical direction, thus reducing the length from the foremost lens to the imaging plane. However, in curved optical imaging systems, the displacement of the lens group used to adjust the focus can be large, making it difficult to reduce the size of the curved optical imaging system. Summary of the Invention

[0005] The present invention is provided to introduce, in a simplified form, the selected concepts that will be further described in the detailed embodiments below. The present invention is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter. In one general aspect, an optical imaging system includes: a first lens group movable in an optical direction and having negative refractive power; a second lens group movable in the optical direction and having positive refractive power; and a third lens group movable in the optical direction and having negative refractive power. The first lens group, the second lens group, and the third lens group collectively comprise seven lenses, and at least one of the seven lenses includes an aspherical surface. The first lens group, the second lens group, and the third lens group are arranged sequentially from the object side to the image side in the optical direction.

[0006] At least one of the seven lenses may be made of plastic material.

[0007] The first lens group may include two lenses with refractive powers having different signs.

[0008] The second lens group may include three lenses, and the three lenses of the second lens group may be arranged such that adjacent lenses have refractive powers of different signs.

[0009] The third lens group may include two lenses having refractive powers of different signs.

[0010] The optical imaging system may include a refracting prism disposed in front of the first lens group.

[0011] In another general aspect, an optical imaging system includes: a prism; a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power; a fifth lens having positive refractive power; a sixth lens having positive refractive power; and a seventh lens having negative refractive power. The prism and the first to seventh lenses are arranged sequentially from the object side.

[0012] The first lens may include a convex image-side surface.

[0013] The second lens may include a convex object-side surface.

[0014] The third lens may include a convex image-side surface.

[0015] The fourth lens may include a concave object-side surface.

[0016] The sixth lens may include a concave object-side surface.

[0017] The seventh lens may include a concave image-side surface.

[0018] The optical imaging system may satisfy -1.0<(R1+R2) / (R1-R2)<-0.1, wherein R1 is a radius of curvature of an object-side surface of the third lens, and R2 is a radius of curvature of an image-side surface of the third lens.

[0019] The optical imaging system may satisfy 0.11<Nd6-Nd7<0.13, wherein Nd6 is a refractive index of the sixth lens, and Nd7 is a refractive index of the seventh lens.

[0020] At a wide-angle end of the optical imaging system, a distance D1 between the first lens group and the second lens group may be greater than a distance D3 between the third lens group and an imaging surface, and a distance D2 between the second lens group and the third lens group may be greater than D3.

[0021] D1 / D2 may range from 0.9 to 1.3, D2 / D3 may range from 1.5 to 2.2, and D1 / D3 may range from 1.5 to 3.5.

[0022] At the telephoto end of the optical imaging system, the distance D1 between the first lens group and the second lens group can be less than the distance D2 between the second lens group and the third lens group, and D2 can be less than the distance D3 between the third lens group and the imaging plane.

[0023] D1 / D2 can be in the range of 0.2 to 0.4, D2 / D3 can be in the range of 0.2 to 0.4, and D3 / D1 can be in the range of 14 to 16.

[0024] Other features and aspects will be apparent from the following detailed description, drawings and claims. Attached Figure Description

[0025] Figure 1 This is a diagram illustrating a first example of an optical imaging system.

[0026] Figure 2 It shows in Figure 1 The aberration curves at the first variable magnification position of the optical imaging system shown.

[0027] Figure 3 It shows in Figure 1 The aberration curves at the second variable magnification position of the optical imaging system are shown.

[0028] Figure 4 This is a diagram illustrating a second example of an optical imaging system.

[0029] Figure 5 It shows in Figure 4 The aberration curves at the first variable magnification position of the optical imaging system shown.

[0030] Figure 6 It shows in Figure 4 The aberration curves at the second variable magnification position of the optical imaging system are shown.

[0031] Throughout the accompanying drawings and detailed embodiments, the same reference numerals denote the same elements. The drawings may not be drawn to scale, and for clarity, illustration, and convenience, the relative dimensions, scale, and depiction of elements in the drawings may be exaggerated. Detailed Implementation

[0032] The following detailed description is provided to aid the reader in gaining a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various variations, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding the disclosure of this application. For example, the order of operations described herein is merely illustrative and is not limited to those set forth herein, but may be varied as will become apparent upon understanding the disclosure of this application, except for operations that must occur in a certain order. Furthermore, for clarity and conciseness, descriptions of features known in the art may be omitted. The features described herein may be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples provided herein are merely to illustrate some of the many possible ways in which the methods, apparatus, and / or systems described herein will become apparent upon understanding the disclosure of this application.

[0033] It should be noted here that the use of the term "may / may" in relation to examples or embodiments (e.g., regarding what an example or embodiment may include or implement) means that there exists at least one example or embodiment that includes or implements such a feature, but not all examples and embodiments are limited thereto.

[0034] Throughout the specification, when an element (such as a layer, region, or substrate) is described as "located on," "connected to," or "bonded to" another element, it may be directly "located on," "connected to," or "bonded to" said other element, or there may be one or more other elements in between. Conversely, when an element is described as "directly located on," "directly connected to," or "directly bonded to" another element, there may be no other elements in between.

[0035] As used herein, the term “and / or” includes any one of the relevant listed items and any combination of any two or more relevant listed items.

[0036] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, parts, areas, layers, or sections, these components, parts, areas, layers, or sections are not limited by these terms. Rather, these terms are used only to distinguish one component, part, area, layer, or section from another. Therefore, without departing from the teachings of the examples described herein, the first component, part, area, layer, or section mentioned in the examples may also be referred to as the second component, part, area, layer, or section.

[0037] For ease of description, spatial relative terms (such as "above," "above," "below," and "under") may be used herein to describe the relationship of one element to another as shown in the figures. In addition to including the orientation depicted in the figures, these spatial relative terms are intended to encompass different orientations of the device during use or operation. For example, if the device in the figures is flipped, an element described as "above" or "above" relative to another element will become "below" or "under" relative to said other element. Thus, the term "above" encompasses both upper and lower orientations depending on the spatial orientation of the device. The device may also be oriented in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relative terms used herein will be interpreted accordingly.

[0038] The terminology used herein is for the purpose of describing various examples only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms “comprising,” “including,” and “having” specify the presence of the stated features, quantities, operations, components, elements, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0039] The shapes shown in the accompanying drawings may vary due to manufacturing techniques and / or tolerances. Therefore, the examples described herein are not limited to the specific shapes shown in the accompanying drawings, but include shape variations that occur during manufacturing.

[0040] The features of the examples described herein can be combined in a variety of ways as will become apparent upon understanding the disclosure of this application. Furthermore, although the examples described herein have various constructions, other constructions are possible as will become apparent upon understanding the disclosure of this application.

[0041] In the following text, examples will be described with reference to the accompanying drawings.

[0042] The first lens can refer to the lens positioned closest to the object (or subject), and the seventh lens can refer to the lens positioned closest to the imaging plane (or image sensor). In the example, all of the following are expressed in millimeters (mm): radius of curvature, thickness, distance between lenses, TTL, IMG HT (half the diagonal length of the imaging plane), and focal length of the lens, where TTL refers to the distance from the object-side surface of the first lens to the imaging plane. Furthermore, the lens thickness, the gap between lenses, and TTL can be distances located along the optical axis of the lens. In the description of lens form, a convex surface of the lens indicates that the optical axis region of that surface is convex, while a concave surface of the lens indicates that the optical axis region of that surface is concave. Therefore, in a configuration where the surface of the lens is described as convex, the edge region of said surface of the lens can be concave. Similarly, in a configuration where the surface of the lens is described as concave, the edge region of said surface of the lens can be convex.

[0043] An optical imaging system may include an optical system comprising multiple lenses. For example, the optical system of an optical imaging system may include multiple lenses with refractive power. However, an optical imaging system includes more than just lenses with refractive power. For example, an optical imaging system may include a prism for refracting incident light and an aperture for adjusting the amount of light. An optical imaging system may also include an infrared blocking filter for blocking infrared light. An optical imaging system may also include an image sensor (imaging device) for converting an image of a subject incident through the optical system into an electrical signal. An optical imaging system may also include a gap-maintaining member for adjusting the distance between the lenses.

[0044] Multiple lenses can be made using materials with a refractive index different from that of air. For example, multiple lenses can be made using glass. At least one of the multiple lenses can be aspherical. An aspherical surface can be represented by Equation 1 below.

[0045] Equation 1

[0046]

[0047] In Equation 1, "c" is the reciprocal of the radius of curvature of each lens, "K" is the conic constant, "r" is the distance from a point on the aspherical surface of the lens in a direction perpendicular to the optical axis to the optical axis, "A" to "G" are aspherical constants, and "Z" (or SAG) is the distance from a point on the aspherical surface of the lens at a distance r from the optical axis to the vertex of the aspherical surface in the direction of the optical axis.

[0048] An optical imaging system may include multiple lens groups. For example, an optical imaging system may include a first lens group, a second lens group, and a third lens group. The first lens group, the second lens group, and the third lens group may be arranged sequentially along the optical axis.

[0049] The first lens group may include multiple lenses. For example, the first lens group may include multiple lenses with refractive powers of different signs. For example, the first lens group may include lenses with positive refractive power and lenses with negative refractive power. Generally, the lenses in the first lens group may have negative refractive power.

[0050] The second lens group may include multiple lenses. For example, the second lens group may include three lenses. The three lenses of the second lens group may be configured such that the sign of the refractive power of one of the three lenses may be different from the sign of the refractive power of the adjacent lens. For example, the second lens group may include a lens with positive refractive power, a lens with negative refractive power, and a lens with positive refractive power. Overall, the lenses of the second lens group may have positive refractive power.

[0051] The third lens group may include multiple lenses. For example, the third lens group may include multiple lenses with refractive powers of different signs. For example, the third lens group may include lenses with positive refractive power and lenses with negative refractive power. Generally, the lenses in the third lens group may have negative refractive power.

[0052] The first, second, and third lens groups can move in the optical direction. For example, one or more of the first, second, and third lens groups can move to change the focal length of the optical imaging system, and two or more of the first, second, and third lens groups can move to adjust the focus of the optical imaging system. Therefore, the optical imaging system can significantly change the variable magnification. Furthermore, in an optical imaging system, multiple lens groups can be driven to adjust the focus, thus enabling precise focus adjustment under any variable magnification condition and significantly reducing the displacement range of the lens groups used for focus adjustment.

[0053] Optical imaging systems may include lenses made of plastic materials. For example, an optical imaging system may be configured such that one of seven or more lenses included in a lens group may be made of plastic material.

[0054] Optical imaging systems may include aspherical lenses. For example, an optical imaging system may be configured such that one of the seven or more lenses included in a lens group is an aspherical lens. Optical imaging systems may include prisms, filters, apertures, and image sensors.

[0055] A prism can be positioned on the object side of the first lens group. The prism may contain a material with a relatively low Abbe number. For example, the prism material may be selected from materials with an Abbe number of 25 or lower.

[0056] The optical filter may be disposed between the third lens group and the image sensor. The optical filter can block incident light of a specific wavelength to improve the resolution of the optical imaging system. For example, the optical filter can block incident light of infrared wavelengths.

[0057] The diaphragm may be disposed between the first lens group and the second lens group.

[0058] The optical imaging system can satisfy one or more of the following first conditional expression to seventh conditional expression:

[0059] -1.5<R2 / f<-0.5 (Conditional Expression 1)

[0060] -1.0<(R1+R2) / (R1-R2)<-0.1 (Conditional Expression 2)

[0061] 0.1<f / f1<0.8 (Conditional Expression 3)

[0062] 1.0<f / f3<3.0 (Conditional Expression 4)

[0063] -1.5<f / f4<-0.2 (Conditional Expression 5)

[0064] 0.2<f / f5<1.0 (Conditional Expression 6)

[0065] 0.11<N6-N7<0.13 (Conditional Expression 7)

[0066] In the conditional expressions, "f" is the focal length of the optical imaging system, R1 is the curvature radius of the object-side surface of the third lens, R2 is the curvature radius of the image-side surface of the third lens, f1 is the focal length of the first lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, N6 is the refractive index of the sixth lens, and N7 is the refractive index of the seventh lens.

[0067] In the following description, various examples of the optical imaging system will be described.

[0068] Reference will be made to Figure 1 to describe the first example of the optical imaging system.

[0069] The optical imaging system 100 may include a prism 102, a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170, and may be divided into multiple lens groups. For example, the optical imaging system 100 may be divided into a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 may include two lenses. For example, the first lens group G1 may include a first lens 110 and a second lens 120. The first lens 110 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The second lens 120 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. The second lens group G2 may include three lenses. For example, the second lens group G2 may include a third lens 130, a fourth lens 140, and a fifth lens 150. The third lens 130 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fourth lens 140 may have negative refractive power and may have a concave object-side surface and a convex image-side surface. The fifth lens 150 may have positive refractive power and may have a concave object-side surface and a convex image-side surface. The third lens group G3 may include two lenses. For example, the third lens group G3 may include a sixth lens 160 and a seventh lens 170. The sixth lens 160 may have positive refractive power and may have a concave object-side surface and a convex image-side surface. The seventh lens 170 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. Lens groups G1, G2, and G3 may be moved in the optical direction to change the focal length of the optical imaging system. For example, as the focal length of the optical imaging system increases, the distance D1 between the first lens group G1 and the second lens group G2, and the distance D2 between the second lens group G2 and the third lens group G3, may decrease. Furthermore, as the focal length of the optical imaging system increases, the distance D3 between the third lens group G3 and the image plane may increase.

[0070] Lens groups G1, G2, and G3 can move in the optical direction to quickly adjust the focus of the optical imaging system. For example, one or more of the first lens group G1, the second lens group G2, and the third lens group G3 can move in the optical direction so that a sharp image of the subject can be imaged on the imaging plane. Furthermore, the first lens group G1, the second lens group G2, and the third lens group G3 can move different distances in the optical direction to significantly reduce the amount of displacement used for focus adjustment. The optical imaging system 100 may have… Figure 2 and Figure 3 The aberration characteristics shown are illustrated.

[0071] The optical imaging system 100 may include a prism 102, an aperture ST, a filter 180, and an image sensor 190.

[0072] The prism 102 can be positioned in front of the first lens 110. The prism 102 can refract light reflected from the object side onto the first lens 110.

[0073] A filter 180 can be positioned in front of the image sensor 190 and can block infrared light and other components included in the incident light. The image sensor 190 may include multiple optical sensors. The image sensor 190 can be configured to convert optical signals into electrical signals.

[0074] Table 1 lists the characteristics of the lenses of the optical imaging system 100, Table 2 lists the aspherical values ​​of the optical imaging system 100, and Table 3 lists the distance values ​​between the lens groups in the first and second positions of the optical imaging system 100. Here, EFL represents the effective focal length, and e-line represents the E-ray.

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079]

[0080] Table 3

[0081] D1 1.6775 0.2 D2 1.3325 0.6 D3 0.8 3

[0082] Reference Figure 4 A second example describing an optical imaging system.

[0083] Optical imaging system 200 may include a prism 202, a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixth lens 260, and a seventh lens 270, and may be divided into multiple lens groups. For example, optical imaging system 200 may be divided into a first lens group G1, a second lens group G2, and a third lens group G3. First lens group G1 may include two lenses. For example, first lens group G1 may include a first lens 210 and a second lens 220. First lens 210 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. Second lens 220 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. Second lens group G2 may include three lenses. For example, second lens group G2 may include a third lens 230, a fourth lens 240, and a fifth lens 250. Third lens 230 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fourth lens 240 may have negative refractive power and may have a concave object-side surface and a convex image-side surface. The fifth lens 250 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The third lens group G3 may include two lenses. For example, the third lens group G3 may include a sixth lens 260 and a seventh lens 270. The sixth lens 260 may have positive refractive power and may have a concave object-side surface and a convex image-side surface. The seventh lens 270 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. Lens groups G1, G2, and G3 may be moved in the optical direction to change the focal length of the optical imaging system. For example, as the focal length of the optical imaging system increases, the distance D1 between the first lens group G1 and the second lens group G2, and the distance D2 between the second lens group G2 and the third lens group G3, may decrease. Furthermore, as the focal length of the optical imaging system increases, the distance D3 between the third lens group G3 and the imaging plane may increase.

[0084] Lens groups G1, G2, and G3 can move in the optical direction to quickly adjust the focus of the optical imaging system. For example, one or more of the first lens group G1, the second lens group G2, and the third lens group G3 can move in the optical direction so that a sharp image of the subject can be imaged on the imaging plane. Furthermore, the first lens group G1, the second lens group G2, and the third lens group G3 can move different distances in the optical direction to significantly reduce the amount of displacement required for focus adjustment. The optical imaging system 200 may have… Figure 5 and Figure 6 The aberration characteristics shown are illustrated.

[0085] The optical imaging system 200 may include a prism 202, an aperture ST, a filter 280, and an image sensor 290.

[0086] The prism 202 can be positioned in front of the first lens 210. The prism 202 can refract light reflected from the object side onto the first lens 210.

[0087] A filter 280 can be positioned in front of the image sensor 290 and can block infrared light and other components included in the incident light. The image sensor 290 may include multiple optical sensors. The image sensor 290 can be configured to convert optical signals into electrical signals.

[0088] Table 4 lists the characteristics of the lenses of the optical imaging system 200, Table 5 lists the aspherical values ​​of the optical imaging system 200, and Table 6 lists the distance values ​​between the lens groups in the first and second positions of the optical imaging system 200.

[0089] Table 4

[0090]

[0091]

[0092] Table 5

[0093]

[0094] Table 6

[0095] D1 1.6378 0.2 D2 1.6826 0.9104 D3 0.8 3

[0096] The optical imaging systems in the examples may share the following common characteristics. For instance, the focal length of the first lens may be in the range of 20mm to 40mm, the focal length of the second lens may be in the range of -10mm to -6.0mm, the focal length of the third lens may be in the range of 2mm to 4mm, the focal length of the fourth lens may be in the range of -15mm to -8.0mm, the focal length of the fifth lens may be in the range of 8mm to 15mm, the focal length of the sixth lens may be 30mm or greater, and the focal length of the seventh lens may be in the range of -10mm to -4.0mm. As another example, the focal length of the optical imaging system at the wide-angle end may be in the range of 5.0mm to 7.0mm, and the focal length of the optical imaging system at the telephoto end may be in the range of 8.0mm to 10.0mm.

[0097] At the wide-angle end of the optical imaging system, the distance D1 between the first and second lens groups can be greater than the distance D3 between the third lens group and the imaging plane, and the distance D2 between the second and third lens groups can be greater than the distance D3 between the third lens group and the imaging plane. At the wide-angle end of the optical imaging system, D1 / D2 can be in the range of 0.9 to 1.3, D2 / D3 can be in the range of 1.5 to 2.2, and D1 / D3 can be in the range of 1.5 to 3.5.

[0098] At the telephoto end of the optical imaging system, the distance D1 between the first and second lens groups can be smaller than the distance D2 between the second and third lens groups, and the distance D2 between the second and third lens groups can be smaller than the distance D3 between the third lens group and the imaging plane. At the telephoto end of the optical imaging system, D1 / D2 can be in the range of 0.2 to 0.4, D2 / D3 can be in the range of 0.2 to 0.4, and D3 / D1 can be in the range of 14 to 16.

[0099] Table 7 lists the values ​​of the conditional expressions for the optical imaging systems in the first and second examples. As shown in Table 7, the optical imaging systems can satisfy all of the aforementioned conditional expressions.

[0100] Table 7

[0101]

[0102]

[0103] Based on the examples, a curved optical imaging system capable of changing the focal length and having a reduced size can be realized. These examples provide an optical imaging system with variable magnification capability while having a reduced size.

[0104] While this disclosure includes specific examples, it will be apparent upon understanding the disclosure of this application that various changes in form and detail may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered descriptive only and not for limiting purposes. The description of features or aspects in each example is to be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and / or if components in the described system, architecture, apparatus, or circuit are combined in a different manner and / or replaced or supplemented by other components or their equivalents. Therefore, the scope of this disclosure is not limited by the specific embodiments but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents should be construed as included in this disclosure.

Claims

1. An optical imaging system, comprising: The first lens group includes a first lens and a second lens arranged sequentially from the object side, and has negative refractive power; The second lens group includes a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side, and has positive refractive power; as well as The third lens group includes a sixth lens and a seventh lens arranged sequentially from the object side, and has negative refractive power. The first lens group, the second lens group, and the third lens group are arranged sequentially from the object side, and a total of seven lenses are included. At least one of the first to third lens groups is movable along the optical axis. Where 0.11 < Nd6-Nd7 < 0.13, Wherein, Nd6 is the refractive index of the sixth lens disposed from the object side among the seven lenses, and Nd7 is the refractive index of the seventh lens disposed from the object side among the seven lenses, and The first lens has positive refractive power, the second lens has negative refractive power, the third lens has positive refractive power, the fourth lens has negative refractive power, the fifth lens has positive refractive power, the sixth lens has positive refractive power, and the seventh lens has negative refractive power.

2. The optical imaging system according to claim 1, wherein, 0.1 < f / f1 < 0.8, Where f is the focal length of the optical imaging system, and f1 is the focal length of the first lens.

3. The optical imaging system according to claim 1, wherein: -1.0 < (R1+R2) / (R1-R2) < -0.1, Wherein, R1 is the radius of curvature of the object side of the first lens, and R2 is the radius of curvature of the image side of the first lens.

4. The optical imaging system according to claim 1, wherein, The sixth lens has a concave object-side surface and a convex image-side surface, and the seventh lens has a convex object-side surface and a concave image-side surface.

5. The optical imaging system according to claim 1, wherein, Both the object side and the image side of the first lens are convex.

6. The optical imaging system of claim 1, wherein, The second lens has a convex object-side surface and a concave image-side surface.

7. The optical imaging system of claim 1, wherein, The object side and image side of the third lens are both convex.

8. The optical imaging system of claim 1, wherein, The fifth lens has a concave object-side surface.

9. The optical imaging system according to claim 1 further includes a prism disposed in front of the first lens group.

10. The optical imaging system of claim 1, wherein, At least one of the seven lenses includes an aspherical surface and is formed of a plastic material.

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