Patent Publication Number: US-2023139385-A1

Title: Optical imaging system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/891,279 filed on Jun. 3, 2020, which is a continuation of U.S. patent application Ser. No. 16/218,688 filed on Dec. 13, 2018, now U.S. Pat. No. 10,698,184 issued on Jun. 30, 2020, which is a continuation of U.S. patent application Ser. No. 15/594,686 filed on May 15, 2017, now U.S. Pat. No. 10,185,127 issued on Jan. 22, 2019, which claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application Nos. 10-2016-0117304 filed on Sep. 12, 2016, and 10-2016-0159277 filed on Nov. 28, 2016, in the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     1. Field 
     The following description relates to a telescopic optical imaging system including seven lenses. 
     2. Description of Related Art 
     Telescopic optical imaging systems capable of capturing images of distant objects may be significantly large. In detail, in terms of telescopic optical imaging systems, the ratio (TL/f) of the overall length TL of a telescopic optical imaging system to the overall focal length f may be greater than or equal to 1. Thus, it may be difficult to mount telescopic optical imaging systems in small electronic devices, such as portable terminals. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In one general aspect, an optical imaging system includes a first lens, a second lens, a third lens, a fourth lens having a negative refractive power, a fifth lens having a negative refractive power, a sixth lens, and a seventh lens having a positive refractive power. 
     The first lens of the optical imaging system may have a convex image-side surface along an optical axis. The second lens of the optical imaging system can have a convex object-side surface along an optical axis. The third lens of the optical imaging system may have a convex object-side surface along an optical axis. 
     The fourth lens of the optical imaging system may have a meniscus form in which one side surface is concave along an optical axis, and the other side surface is convex along the optical axis. The fifth lens of the optical imaging system can have a concave object-side surface along an optical axis. The sixth lens of the optical imaging system may have opposing concave surfaces along an optical axis. The seventh lens of the optical imaging system can have opposing convex surfaces along an optical axis. 
     In another general aspect, an optical imaging system includes first to seventh lenses, sequentially disposed from an object side to an imaging plane, wherein a ratio (TL/f) of a distance TL from an object-side surface of the first lens to an imaging plane to an overall focal length f is less than or equal to 1.0. 
     The optical imaging system may satisfy the expression BFL/f&lt;0.15, where BFL represents a distance from an image-side surface of the seventh lens to an imaging plane. The optical imaging system can satisfy the expression 0.1&lt;f/(IMG HT)&lt;2.5, where IMG HT is a half diagonal length of the imaging plane. The optical imaging system may satisfy the expression 1.5&lt;Nd7&lt;1.7, where Nd7 represents a refractive index of the seventh lens. 
     The optical imaging system may satisfy the expression −45&lt;f5/f&lt;45, where f5 represents a focal length of a fifth lens. The optical imaging system can satisfy the expression 2.0&lt;f/EPD&lt;2.8, where EPD represents a diameter of an entrance pupil. The second lens, fourth lens, and sixth lens of the optical imaging system may each have a negative refractive power. The sixth lens of the optical imaging system can have a concave object-side surface along an optical axis. 
     In another general aspect, an optical imaging system includes a first lens having a positive refractive power and a convex object-side surface along an optical axis, a second lens having a concave image-side surface along the optical axis, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. The first lens to seventh lens are sequentially disposed from an object side to an imaging plane. One or both surfaces of each of the first to seventh lenses are aspherical. 
     The object-side surface of the first lens of the optical imaging system may include a most convex point of the system. The image-side surface of the second lens of the optical imaging system can include a most concave point of the system. The third lens of the optical imaging system may have a meniscus form in which one side surface is concave and the other side surface is convex. The fifth lens of the optical imaging system can have a convex image-side surface. The seventh lens of the optical imaging system may be bi-convex with a positive refractive power or may be bi-concave with a negative refractive power. 
     In another general aspect, an optical imaging system includes a first lens to a seventh lens. The first lens and the seventh lens each have a positive refractive power, a convex object-side surface along an optical axis and a convex image-side surface along the optical axis. The first lens to seventh lens are sequentially disposed from an object side to an imaging plane. 
     The object-side surface of the first lens of the optical imaging system may include a most convex point of the optical imaging system. The second lens to sixth lens of the optical imaging system can each have a negative refractive power. The image-side surface of the second lens of the optical imaging system may be concave and may have a most concave point of the optical imaging system. 
     Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of an optical imaging system according to a first example. 
         FIG.  2    is a set of graphs illustrating aberration curves of the optical imaging system illustrated in  FIG.  1   . 
         FIG.  3    is a table listing aspherical characteristics of the optical imaging system illustrated in  FIG.  1   . 
         FIG.  4    is a diagram of an optical imaging system according to a second example. 
         FIG.  5    is a set of graphs illustrating aberration curves of the optical imaging system illustrated in  FIG.  4   . 
         FIG.  6    is a table listing aspherical characteristics of the optical imaging system illustrated in  FIG.  4   . 
         FIG.  7    is a diagram of an optical imaging system according to a third example. 
         FIG.  8    is a set of graphs illustrating aberration curves of the optical imaging system illustrated in  FIG.  7   . 
         FIG.  9    is a table listing aspherical characteristics of the optical imaging system illustrated in  FIG.  7   . 
         FIG.  10    is a diagram of an optical imaging system according to a fourth example. 
         FIG.  11    is a set of graphs illustrating aberration curves of the optical imaging system illustrated in  FIG.  10   . 
         FIG.  12    is a table listing aspherical characteristics of the optical imaging system illustrated in  FIG.  10   . 
         FIG.  13    is a rear view of a portable terminal including an optical imaging system mounted therein according to an example. 
         FIG.  14    is a cross-sectional view of the portable terminal illustrated in  FIG.  13   . 
     
    
    
     Throughout the drawings and the detailed description, the same reference numerals refer to the same elements, where applicable. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, or convenience. 
     DETAILED DESCRIPTION 
     Hereinafter, examples will be described as follows with reference to the attached drawings. Examples provide an optical imaging system capable of capturing images of distant objects and being mounted in a small terminal. The disclosure may, however, be exemplified in many different forms and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure after an understanding of this application. 
     Throughout the specification, it will be understood that when an element, such as a layer, region or wafer (substrate), is referred to as being “on,” “connected to,” or “coupled to” another element, it can be directly “on,” “connected to,” or “coupled to” the other element or other elements intervening therebetween may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element, there may be no elements or layers intervening therebetween. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although terms such as “first,” “second,” and “third” may be used herein to describe various components, regions, or sections, these components, regions, or sections are not to be limited by these terms. Rather, these terms are only used to distinguish one component, region, or section from another component, region, or section. Thus, a first component, region, or section referred to in examples described herein may also be referred to as a second component, region, or section without departing from the teachings of the examples. 
     The articles “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “includes,” and “has” specify the presence of stated features, numbers, operations, members, elements, and/or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, members, elements, and/or combinations thereof. 
     Due to manufacturing techniques and/or tolerances, variations of the shapes shown in the drawings may occur. Thus, the examples described herein are not limited to the specific shapes shown in the drawings, but include changes in shape that occur during manufacturing. 
     The features of the examples described herein may be combined in various ways as will be apparent after an understanding of the disclosure of this application. Further, although the examples described herein have a variety of configurations, other configurations are possible as will be apparent after an understanding of the disclosure of this application. 
     According to an example, a first lens refers to a lens closest to an object or a subject of which an image is captured. A seventh lens refers to a lens closest to an imaging plane or an image sensor. In the present specification, an entirety of a radius of curvature, a thickness, a distance from an object-side surface of a first lens to an imaging plane (TL), a half diagonal length of the imaging plane (IMG HT), and a focal length of a lens are indicated in millimeters (mm). A person skilled in the relevant art will appreciate that other units of measurement may be used. Further, in embodiments, all radii of curvature, thicknesses, OALs (optical axis distances from the first surface of the first lens to the image sensor), a distance on the optical axis between the stop and the image sensor (SLs), image heights (IMGHs) (image heights), and back focus lengths (BFLs) of the lenses, an overall focal length of an optical system, and a focal length of each lens are indicated in millimeters (mm). Further, thicknesses of lenses, gaps between the lenses, OALs, TLs, SLs are distances measured based on an optical axis of the lenses. 
     In a description of a form of a lens, a surface of a lens being convex means that an optical axis portion of a corresponding surface is convex, while a surface of a lens being concave means that an optical axis portion of a corresponding surface is concave. Therefore, in a configuration in which a surface of a lens is described as being convex, an edge portion of the lens may be concave. In a manner the same as the case described above, even in a configuration in which a surface of a lens is described as being concave, an edge portion of the lens may be convex. In other words, a paraxial region of a lens may be convex, while the remaining portion of the lens outside the paraxial region is either convex, concave, or flat. Further, a paraxial region of a lens may be concave, while the remaining portion of the lens outside the paraxial region is either convex, concave, or flat. In addition, in an embodiment, thicknesses and radii of curvatures of lenses are measured in relation to optical axes of the corresponding lenses. 
     In accordance with illustrative examples, the embodiments described of the optical system include seven lenses with a refractive power. However, the number of lenses in the optical system may vary, for example, between two to seven lenses, while achieving the various results and benefits described below. Also, although each lens is described with a particular refractive power, a different refractive power for at least one of the lenses may be used to achieve the intended result. 
     An optical imaging system includes seven lenses. For example, the optical imaging system may include the first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and the seventh lens, sequentially disposed from an object side. 
     The first lens has a refractive power. For example, the first lens has a positive refractive power. The first lens has at least one convex surface. In an embodiment, the first lens has a convex object-side surface. 
     The first lens has an aspherical surface. For example, both surfaces of the first lens are aspherical. The first lens may be formed using a material having a relatively high degree of light transmittance and excellent workability. In an example, the first lens is formed using a plastic material. However, a material of the first lens is not limited to being a plastic material. In another example, the first lens may be formed using a glass material. The first lens has a relatively low refractive index. For example, a refractive index of the first lens is less than 1.6. 
     The second lens has a refractive power. For example, the second lens has a negative refractive power. The second lens has a convex surface. In an embodiment, the second lens may have a convex object-side surface. 
     The second lens has an aspherical surface. For example, the second lens has an aspherical object-side surface. The second lens may be formed using a material having a relatively high degree of light transmittance and excellent workability. In an example, the second lens is formed using a plastic material. However, a material of the second lens is not limited to being plastic. In another example, the second lens may be formed using a glass material. The second lens has a reflective index higher than that of the first lens. For example, a refractive index of the second lens is greater than or equal to 1.65. 
     The third lens has a refractive power. For example, the third lens may have a positive or a negative refractive power. The third lens has a meniscus form in which one surface is concave, and the other surface is convex. In embodiments, the third lens has a form in which an object-side surface is convex and an image-side surface is concave, or has a form in which the object-side surface is concave and the image-side surface is convex. 
     The third lens has an aspherical surface. For example, the third lens has an aspherical image-side surface. The third lens may be formed using a material having a relatively high degree of light transmittance and excellent workability. In an example, the third lens is formed using a plastic material. However, a material of the third lens is not limited to being plastic. In another example, the third lens may be formed using a glass material. The third lens has a refractive index substantially similar to that of the first lens. In detail, the refractive index of the third lens is less than 1.6. 
     The fourth lens has a refractive power. For example, the fourth lens has a negative refractive power. The fourth lens has the meniscus form in which one surface is concave and the other surface is convex. In embodiments, the fourth lens has a form in which an object-side surface is convex and an image-side surface is concave, or has a form in which the object-side surface is concave and the image-side surface is convex. 
     The fourth lens has an aspherical surface. For example, both surfaces of the fourth lens are aspherical. The fourth lens may be formed using a material having a relatively high degree of light transmittance and excellent workability. In an example, the fourth lens is formed using a plastic material. However, a material of the fourth lens is not limited to being plastic. In another example, the fourth lens may be formed using a glass material. The fourth lens has a refractive index greater than or equal to that of the first lens. 
     The fifth lens has a refractive power. For example, the fifth lens may have a positive or a negative refractive power. The fifth lens has a concave surface. In an embodiment, the fifth lens has a concave object-side surface. 
     The fifth lens has an aspherical surface. For example, both surfaces of the fifth lens are aspherical. The fifth lens may be formed using a material having a relatively high degree of light transmittance and excellent workability. In an example, the fifth lens is formed using a plastic material. However, a material of the fifth lens is not limited to being plastic. In another example, the fifth lens may be formed using a glass material. The fifth lens has a refractive index higher than that of the first lens. In an embodiment, the refractive index of the fifth lens is greater than or equal to 1.6. 
     The sixth lens has a refractive power. For example, the sixth lens has a negative refractive power. The sixth lens may have a concave surface. For example, the sixth lens has a concave object-side surface. The sixth lens may have an inflection point. In an embodiment, the sixth lens includes one or more inflection points formed on opposing surfaces. 
     The sixth lens has an aspherical surface. For example, both surfaces of the sixth lens are aspherical. The sixth lens may be formed using a material having a relatively high degree of light transmittance and excellent workability. In an example, the sixth lens is formed using a plastic material. However, a material of the sixth lens is not limited to being plastic. In another example, the sixth lens may be formed using a glass material. The sixth lens has a refractive index substantially similar to that of the first lens. In an embodiment, the refractive index of the sixth lens is less than 1.6. 
     The seventh lens has a refractive power. For example, the seventh lens has a positive or a negative refractive power. The seventh lens may have opposing surfaces formed substantially in a symmetrical manner. For example, the seventh lens may have a convex object-side surface or opposing concave surfaces. The seventh lens may include an inflection point. In an embodiment, the seventh lens includes one or more inflection points formed on opposing surfaces. 
     The seventh lens may have an aspherical surface. For example, both surfaces of the seventh lens are aspherical. The seventh lens may be formed using a material having a relatively high degree of light transmittance and excellent workability. In an example, the seventh lens is formed using a plastic material. However, a material of the seventh lens is not limited to being plastic. In another example, the seventh lens may be formed using a glass material. The seventh lens has a refractive index lower than that of the first lens. In an embodiment, the refractive index of the seventh lens is less than 1.53. 
     Aspherical surfaces of the first to seventh lenses may be expressed using Formula 1. 
     
       
         
           
             
               
                 
                   z 
                   = 
                   
                     
                       
                         cr 
                         2 
                       
                       
                         1 
                         + 
                         
                           
                             1 
                             - 
                             
                               
                                 ( 
                                 
                                   1 
                                   + 
                                   k 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 c 
                                 2 
                               
                               ⁢ 
                               
                                 r 
                                 2 
                               
                             
                           
                         
                       
                     
                     + 
                     
                       Ar 
                       4 
                     
                     + 
                     
                       Br 
                       6 
                     
                     + 
                     
                       Cr 
                       8 
                     
                     + 
                     
                       Dr 
                       10 
                     
                     + 
                     
                       Er 
                       12 
                     
                     + 
                     
                       Fr 
                       14 
                     
                     + 
                     
                       Gr 
                       16 
                     
                     + 
                     
                       Hr 
                       18 
                     
                     + 
                     
                       Jr 
                       20 
                     
                   
                 
               
               
                 
                   Formula 
                   ⁢ 
                       
                   1 
                 
               
             
           
         
       
     
     In Formula 1, c represents an inverse of a radius of curvature of a lens, k represents a conic constant, r represents a distance from a certain point on an aspherical surface of the lens to an optical axis, A to J represent aspherical constants, and Z (or SAG) represents a distance between the certain point on the aspherical surface of the lens at the distance r and a tangential plane meeting the apex of the aspherical surface of the lens. 
     The optical imaging system further includes a filter, an image sensor, and a stop. The filter is disposed between the seventh lens and the image sensor. The filter may block a portion of wavelengths of visible light, in order to generate a clear image. For example, the filter blocks light of an infrared wavelength. 
     The image sensor forms an imaging plane. For example, a surface of the image sensor may form the imaging plane. The stop is disposed to adjust an amount of light incident on a lens. In detail, the stop may be interposed between the second lens and the third lens or between the third lens and the fourth lens. 
     The optical imaging system satisfies the following Conditional Equations: 
       0.7 &lt;TL/f&lt; 1.0  [Conditional Equation 1]
 
         BFL/f&lt; 0.15  [Conditional Equation 2]
 
       0.1 &lt;f /( IMG HT )&lt;2.5  [Conditional Equation 3]
 
       1.5 &lt;Nd 7&lt;1.7  [Conditional Equation 4]
 
       −45 &lt;f 5 /f&lt; 45  [Conditional Equation 5]
 
       2.0 &lt;f/EPD&lt; 2.8  [Conditional Equation 6]
 
     In the Conditional Equations, TL represents a distance from the object-side surface of the first lens to an imaging plane, f represents an overall focal length of the optical imaging system, BFL represents a distance from an image-side surface of the seventh lens to an imaging plane, and IMG HT represents a half diagonal length of the imaging plane. Nd7 represents a refractive index of the seventh lens, f5 represents a focal length of the fifth lens, and EPD represents a diameter of an entrance pupil. 
     Conditional Equation 1 is provided for the miniaturization of the optical imaging system. In detail, in cases in which the optical imaging system is beyond an upper limit value of Conditional Equation 1, it may be difficult to miniaturize the optical imaging system, so that it may be difficult to mount the optical imaging system in a portable terminal. In cases in which the optical imaging system is below a lower limit value of Conditional Equation 1, it may be difficult to manufacture the optical imaging system. 
     Conditional Equation 2 is provided for mounting the optical imaging system in a portable terminal. In detail, ease of manufacturing the optical imaging system beyond an upper limit value of Conditional Equation 2 is facilitated, but resolution of the optical imaging system may be relatively low. 
     Conditional Equation 3 is a parametric ratio for maintaining telescopic characteristics and relatively high resolution. In detail, the optical imaging system beyond an upper limit of Conditional Equation 3 may have excellent telescopic characteristics, but it may be difficult to implement relatively high resolution. The optical imaging system below a lower limit of Conditional Equation 3 may implement a relatively wide angle of view, but may have relatively poor telescopic characteristics. 
     Conditional Equation 4 is provided as a parameter of the seventh lens for a high-resolution optical imaging system. In detail, because the seventh lens satisfying a numerical range of Conditional Equation 4 has a relatively low Abbe number (less than or equal to 26), ease of correction of astigmatism, longitudinal chromatic aberrations, and chromatic aberrations of magnification is facilitated. 
     Conditional Equation 5 is provided as a parametric ratio of the fifth lens for a high-resolution optical imaging system. In detail, in cases in which the fifth lens is outside of a numerical range of Conditional Equation 5, the fifth lens may increase aberrations, so that it may be difficult to provide a high-resolution optical system. Conditional Equation 6 is provided as a numerical range of an F number for a high-resolution optical imaging system. 
     In the optical imaging system, a lens having a relatively high degree of positive refractive power may be disposed to be adjacent to an object. In detail, the first lens in the optical imaging system has the highest degree of positive refractive power. In the optical imaging system, a lens having a relatively high degree of negative refractive power may be disposed to be substantially adjacent to the imaging plane. In embodiments, the sixth lens has the highest degree of negative refractive power. However, in cases in which the seventh lens has a negative refractive power, the second lens may have the highest degree of negative refractive power. 
     In the optical imaging system, a relatively high degree of refractive power of a lens (an inverse value of a focal length) may be distributed in an object side and an image side. For example, in the optical imaging system, the first lens and the seventh lens may have relatively high degrees of refractive power, while the third lens, the fourth lens, and the fifth lens may have relatively low degrees of refractive power. 
     The first lens in the optical imaging system may have a surface including the most convex point of the system. In detail, the object-side surface of the first lens includes the most convex point. The second lens in the optical imaging system may have substantially a surface including the most concave point of the system. In embodiments, an image-side surface of the second lens includes the most concave point. 
     In the optical imaging system, the third lens may have substantially a refractive index similar to that of the sixth lens. For example, in cases in which the refractive index of the third lens is less than or equal to 1.55, the refractive index of the sixth lens is less than or equal to 1.55. In cases in which the refractive index of the third lens is more than or equal to 1.65, the refractive index of the sixth lens is more than or equal to 1.65. In a manner similar to the case described above, in the optical imaging system the fourth lens may have substantially a refractive index similar to that of the seventh lens. For example, in cases in which the refractive index of the fourth lens is less than or equal to 1.55, the refractive index of the seventh lens is less than or equal to 1.55. In cases in which the refractive index of the fourth lens is more than or equal to 1.64, the refractive index of the seventh lens is more than or equal to 1.64. 
     A focal length of lenses forming the optical imaging system may be selected from within a predetermined range. In an example, a focal length of the first lens is selected from within a range of 2.2 mm to 2.8 mm, a focal length of the second lens is selected from within a range of −7.0 mm to −3.0 mm, a focal length of the fourth lens is selected from within a range of −16 mm to −5.0 mm, and a focal length of the sixth lens is selected from within a range of −28 mm to −3.0 mm. 
     In the optical imaging system, effective diameters of lenses may be different. As an example, an effective diameter of the first lens is greater than that of the second lens. An effective diameter of the second lens may be greater than that of the third lens. In an embodiment, an effective diameter of the third lens is greater than or substantially similar to that of the fourth lens. In another example, an effective diameter of the fifth lens is greater than that of the fourth lens and less than that of the sixth lens. An effective diameter of the sixth lens may be greater than that of the fifth lens and less than that of the seventh lens. 
     In the optical imaging system, thicknesses of lenses may be different. In detail, among the first to seventh lenses, the first lens is the thickest, while the fourth lens or the fifth lens may be the thinnest. Odd-numbered lens may be substantially thicker than lenses disposed adjacently thereto. For example, the first lens is thicker than the second lens, while the third lens is thicker than the second lens and the fourth lens. 
     Distances between lenses in the optical imaging system may be different. Distances between lenses may be gradually reduced in directions away from the fourth lens and the fifth lens. For example, in the optical imaging system, a distance between the fourth lens and the fifth lens or a distance between the fifth lens and the sixth lens are longer than that between other lenses. Similarly in this configuration, a distance between the first lens and the second lens or a distance between the seventh lens and an imaging plane is less than that between other lenses. 
     Subsequently, an optical imaging system according to various examples will be described. First of all, the optical imaging system according to a first example will be described with reference to  FIG.  1   . An optical imaging system  100  includes 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 . 
     The first lens  110  has a positive refractive power and opposing convex surfaces. The second lens  120  has a negative refractive power, a convex object-side surface, and a concave image-side surface. The third lens  130  has a negative refractive power, a convex object-side surface, and a concave image-side surface. The fourth lens  140  has a negative refractive power, a concave object-side surface, and a convex image-side surface. 
     The fifth lens  150  has a negative refractive power, a concave object-side surface, and a convex image-side surface. The sixth lens  160  has a negative refractive power and opposing concave surfaces. In addition, the sixth lens  160  includes inflection points formed on opposing surfaces. The seventh lens  170  has a positive refractive power and opposing convex surfaces. In addition, the seventh lens  170  includes inflection points formed on opposing surfaces. 
     In the configuration described above, first lens  110  has the highest degree of positive refractive power, while sixth lens  160  has the highest degree of negative refractive power. In the example described above, an object-side surface of first lens  110  is more convex than surfaces of other lenses, while the image-side surface of second lens  120  is more concave than surfaces of other lenses. In the configuration described above, a paraxial region of first lens  110  is formed to be thicker than paraxial regions of other lenses. A paraxial region of fourth lens  140  is formed to be thinner than paraxial regions of other lenses. In the example described above, a distance between fifth lens  150  and sixth lens  160  is longer than that between other lenses. A distance between first lens  110  and second lens  120  may be shorter than that between other lenses. 
     The optical imaging system  100  further includes a filter  180 , an image sensor  190 , and a stop ST. Filter  180  is interposed between seventh lens  170  and image sensor  190 , while stop ST is interposed between third lens  130  and fourth lens  140 . 
     In optical imaging system  100 , first lens  110  and seventh lens  170  may have a higher degree of refractive power than that of other lenses. In a manner different from the embodiments described above, third lens  130 , fourth lens  140 , and fifth lens  150  may have a lower degree of refractive power than that of other lenses. 
     A refractive index of first lens  110 , a refractive index of third lens  130 , and a refractive index of sixth lens  160 , in optical imaging system  100 , may be less than or equal to 1.55. In this case, the refractive index of first lens  110  is substantially the same as that of the third lens  130 . The refractive index of second lens  120 , the refractive index of fourth lens  140 , the refractive index of fifth lens  150 , and the refractive index of seventh lens  170 , in optical imaging system  100 , may be higher than or equal to 1.64. In this case, the refractive index of fourth lens  140  is substantially the same as that of fifth lens  150 . In optical imaging system  100 , second lens  120  may have substantially the highest refractive index, while first lens  110  may have substantially the lowest refractive index. 
     An effective diameter of a lens in optical imaging system  100  may be gradually reduced in a direction toward stop ST. For example, an effective diameter of third lens  130  or fourth lens  140 , disposed adjacently to stop ST, may be smaller than that of lenses adjacent thereto. In a manner consistent with the case described above, a lens disposed distantly from stop ST may have a relatively large effective diameter. For example, seventh lens  170  disposed farthest from stop ST may has the largest effective diameter. 
     An optical imaging system having the configuration described above has aberration characteristics as illustrated in the graphs of  FIG.  2   .  FIG.  3    lists aspherical characteristics of the optical imaging system according to the example. Table 1 lists lens characteristics of the optical imaging system according to the example. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 First Example 
               
               
                 IMG HT = 2.75 f = 5.9976 TL = 5.195 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Surface 
                   
                 Radius of 
                 Thickness/ 
                 Focal 
                 Refractive 
                 Abbe 
               
               
                 No. 
                   
                 Curvature 
                 Distance 
                 Length 
                 Index 
                 Number 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S1 
                 First Lens 
                 1.4300 
                 0.7860 
                 2.580 
                 1.537 
                 55.8 
               
               
                 S2 
                   
                 −31.8100 
                 0.1000 
               
               
                 S3 
                 Second Lens 
                 5.2600 
                 0.1800 
                 −6.310 
                 1.684 
                 20.4 
               
               
                 S4 
                   
                 2.3000 
                 0.3080 
               
               
                 S5 
                 Third Lens 
                 3.0300 
                 0.2610 
                 −20.520 
                 1.537 
                 55.8 
               
               
                 S6 
                   
                 2.3000 
                 0.1210 
               
               
                 S7 
                 Stop 
                 infinity 
                 0.1960 
               
               
                 S8 
                 Fourth Lens 
                 −5.4000 
                 0.1600 
                 −12.120 
                 1.641 
                 23.9 
               
               
                 S9 
                   
                 −17.8700 
                 0.3100 
               
               
                 S10 
                 Fifth Lens 
                 −4.1600 
                 0.1900 
                 −13.570 
                 1.641 
                 23.9 
               
               
                 S11 
                   
                 −8.1100 
                 0.7890 
               
               
                 S12 
                 Sixth Lens 
                 −4.2000 
                 0.1640 
                 −5.520 
                 1.546 
                 56.0 
               
               
                 S13 
                   
                 10.8900 
                 0.1080 
               
               
                 S14 
                 Seventh Lens 
                 16.5500 
                 0.7220 
                 7.210 
                 1.657 
                 21.5 
               
               
                 S15 
                   
                 −6.5300 
                 0.1000 
               
               
                 S16 
                 Filter 
                 infinity 
                 0.1100 
                   
                 1.519 
                 64.2 
               
               
                 Imaging 
                   
                 infinity 
                 0.5900 
               
               
                 Plane 
               
               
                   
               
            
           
         
       
     
     An optical imaging system according to a second example will be described with reference to  FIG.  4   . An optical imaging system  200  includes 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 . 
     The first lens  210  has a positive refractive power and opposing convex surfaces. The second lens  220  has a negative refractive power, a convex object-side surface, and a concave image-side surface. The third lens  230  has a negative refractive power, a convex object-side surface, and a concave image-side surface. The fourth lens  240  has a negative refractive power, a concave object-side surface, and a convex image-side surface. 
     The fifth lens  250  has a negative refractive power, a concave object-side surface, and a convex image-side surface. The sixth lens  260  has a negative refractive power and opposing concave surfaces. In addition, the sixth lens  260  includes inflection points formed on opposing surfaces. The seventh lens  270  has a positive refractive power and opposing convex surfaces. In addition, the seventh lens  270  includes inflection points formed on opposing surfaces. 
     In the configuration described above, first lens  210  has the highest degree of positive refractive power, while sixth lens  260  has the highest degree of negative refractive power. In the example described above, an object-side surface of first lens  210  is more convex than surfaces of other lenses, while the image-side surface of third lens  230  is more concave than surfaces of other lenses. In the configuration described above, a paraxial region of first lens  210  is formed to be thicker than paraxial regions of other lenses. A paraxial region of the fourth lens  240  may be formed to be thinner than paraxial regions of other lenses. In the example described above, a distance between fifth lens  250  and sixth lens  260  is longer than that between other lenses. A distance between first lens  210  and second lens  220  may be shorter than that between other lenses. 
     The optical imaging system  200  further includes a filter  280 , an image sensor  290 , and a stop ST. Filter  280  is interposed between seventh lens  270  and image sensor  290 , while stop ST is interposed between third lens  230  and fourth lens  240 . 
     In the optical imaging system  200 , first lens  210  and seventh lens  270  may have a higher degree of refractive power than that of other lenses. In a manner different from the embodiments described above, third lens  230 , fourth lens  240 , and fifth lens  250  may have a lower degree of refractive power than that of other lenses. 
     A refractive index of first lens  210 , a refractive index of third lens  230 , and a refractive index of sixth lens  260 , in optical imaging system  200 , may be less than or equal to 1.55. In this case, the refractive index of first lens  210  is substantially the same as that of third lens  230 . The refractive index of second lens  220 , the refractive index of fourth lens  240 , the refractive index of fifth lens  250 , and the refractive index of seventh lens  270 , in optical imaging system  200 , may be higher than or equal to 1.64. In this case, the refractive index of fourth lens  240  is substantially the same as that of fifth lens  250 . In optical imaging system  200 , second lens  220  may have substantially the highest refractive index, while first lens  210  may have substantially the lowest refractive index. 
     An effective diameter of a lens in optical imaging system  200  may be gradually reduced in a direction toward stop ST. For example, an effective diameter of fourth lens  240  disposed adjacently to stop ST is smaller than that of lenses adjacent thereto. In a manner consistent with the embodiment described above, a lens disposed distantly from stop ST may have a relatively large effective diameter. For example, seventh lens  270  disposed farthest from stop ST has the largest effective diameter. 
     An optical imaging system having the configuration described above represents aberration characteristics as illustrated in the graphs of  FIG.  5   .  FIG.  6    lists aspherical characteristics of the optical imaging system according to the example. Table 2 lists lens characteristics of the optical imaging system according to the example. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Second Example 
               
               
                 IMG HT = 2.75 f = 5.9976 TL = 5.149 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Surface 
                   
                 Radius of 
                 Thickness/ 
                 Focal 
                 Refractive 
                 Abbe 
               
               
                 No. 
                   
                 Curvature 
                 Distance 
                 Length 
                 Index 
                 Number 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S1 
                 First Lens 
                 1.3700 
                 0.8040 
                 2.430 
                 1.537 
                 55.8 
               
               
                 S2 
                   
                 −22.7100 
                 0.0800 
               
               
                 S3 
                 Second Lens 
                 5.7100 
                 0.1500 
                 −5.980 
                 1.684 
                 20.4 
               
               
                 S4 
                   
                 2.3300 
                 0.3180 
               
               
                 S5 
                 Third Lens 
                 2.9000 
                 0.2300 
                 −11.950 
                 1.537 
                 55.8 
               
               
                 S6 
                   
                 1.9400 
                 0.1120 
               
               
                 S7 
                 Stop 
                 infinity 
                 0.1450 
               
               
                 S8 
                 Fourth Lens 
                 −7.6900 
                 0.1500 
                 −14.230 
                 1.641 
                 23.9 
               
               
                 S9 
                   
                 −49.4100 
                 0.2780 
               
               
                 S10 
                 Fifth Lens 
                 −5.5400 
                 0.1830 
                 −5.670 
                 1.641 
                 23.9 
               
               
                 S11 
                   
                 −12.5400 
                 0.8500 
               
               
                 S12 
                 Sixth Lens 
                 −3.7500 
                 0.1570 
                 −5.150 
                 1.546 
                 56.0 
               
               
                 S13 
                   
                 11.4600 
                 0.1000 
               
               
                 S14 
                 Seventh Lens 
                 53.8000 
                 0.7920 
                 7.000 
                 1.657 
                 21.5 
               
               
                 S15 
                   
                 −5.0000 
                 0.1000 
               
               
                 S16 
                 Filter 
                 infinity 
                 0.1100 
                   
                 1.519 
                 64.2 
               
               
                 Imaging 
                   
                 infinity 
                 0.5900 
               
               
                 Plane 
               
               
                   
               
            
           
         
       
     
     An optical imaging system according to a third example will be described with reference to  FIG.  7   . An optical imaging system  300  includes a first lens  310 , a second lens  320 , a third lens  330 , a fourth lens  340 , a fifth lens  350 , a sixth lens  360 , and a seventh lens  370 . 
     The first lens  310  has a positive refractive power and opposing convex surfaces. The second lens  320  has a negative refractive power, a convex object-side surface, and a concave image-side surface. The third lens  330  has a negative refractive power, a convex object-side surface, and a concave image-side surface. The fourth lens  340  has a negative refractive power, a convex object-side surface, and a concave image-side surface. 
     The fifth lens  350  has a negative refractive power, a concave object-side surface, and a convex image-side surface. The sixth lens  360  has a negative refractive power and opposing concave surfaces. In addition, the sixth lens  360  includes inflection points formed on opposing surfaces. The seventh lens  370  has a positive refractive power and opposing convex surfaces. In addition, the seventh lens  370  includes inflection points formed on opposing surfaces. 
     In the configuration described above, first lens  310  has the highest degree of positive refractive power, while sixth lens  360  has the highest degree of negative refractive power. In the example described above, an object-side surface of first lens  310  is more convex than surfaces of other lenses, while the image-side surface of third lens  330  is more concave than surfaces of other lenses. In the configuration described above, a paraxial region of first lens  310  is formed to be thicker than paraxial regions of other lenses. A paraxial region of the fifth lens  350  may be formed to be thinner than paraxial regions of other lenses. In the example described above, a distance between fifth lens  350  and sixth lens  360  is longer than that between other lenses. A distance between the first lens  310  and the second lens  320  and a distance between the sixth lens  360  and the seventh lens  370  may be shorter than that between other lenses. 
     The optical imaging system  300  further includes a filter  380 , an image sensor  390 , and a stop ST. Filter  380  is interposed between seventh lens  370  and image sensor  390 , while stop ST is interposed between third lens  330  and fourth lens  340 . 
     In optical imaging system  300 , first lens  310  and seventh lens  370  may have a higher degree of refractive power than that of other lenses. In a manner different from the case described above, third lens  330 , fourth lens  340 , and fifth lens  350  may have a lower degree of refractive power than that of other lenses. 
     A refractive index of first lens  310 , a refractive index of third lens  330 , and a refractive index of sixth lens  360 , in optical imaging system  300 , may be less than or equal to 1.55. In this case, the refractive index of first lens  310  is substantially the same as that of third lens  330 . The refractive index of second lens  320 , the refractive index of fourth lens  340 , the refractive index of fifth lens  350 , and the refractive index of seventh lens  370 , in optical imaging system  300 , may be greater than or equal to 1.64. In this case, the refractive index of fourth lens  340  is substantially the same as that of fifth lens  350 . In optical imaging system  300 , second lens  320  may have substantially the highest refractive index, while first lens  310  may have substantially the lowest refractive index. 
     An effective diameter of a lens in optical imaging system  300  may be gradually reduced in a direction toward stop ST. For example, an effective diameter of fourth lens  340  disposed adjacently to stop ST is smaller than that of lenses adjacent thereto. Similarly based on the configuration described above, a lens disposed distantly from stop ST has a relatively large effective diameter. In an embodiment, seventh lens  370  disposed farthest from stop ST has the largest effective diameter. 
     An optical imaging system having the configuration described above represents aberration characteristics as illustrated in the graphs of  FIG.  8   .  FIG.  9    lists aspherical characteristics of the optical imaging system according to the example. Table 3 lists lens characteristics of the optical imaging system according to the example. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Third Example 
               
               
                 IMG HT = 2.50 f = 5.9976 TL = 5.199 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Surface 
                   
                 Radius of 
                 Thickness/ 
                 Focal 
                 Refractive 
                 Abbe 
               
               
                 No. 
                   
                 Curvature 
                 Distance 
                 Length 
                 Index 
                 Number 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S1 
                 First Lens 
                 1.3700 
                 0.7970 
                 2.460 
                 1.537 
                 55.8 
               
               
                 S2 
                   
                 −29.1200 
                 0.1000 
               
               
                 S3 
                 Second Lens 
                 4.3100 
                 0.2000 
                 −5.770 
                 1.684 
                 20.4 
               
               
                 S4 
                   
                 2.0000 
                 0.1650 
               
               
                 S5 
                 Third Lens 
                 3.3500 
                 0.2630 
                 −11.180 
                 1.537 
                 55.8 
               
               
                 S6 
                   
                 2.0900 
                 0.1060 
               
               
                 S7 
                 Stop 
                 infinity 
                 0.1000 
               
               
                 S8 
                 Fourth Lens 
                 10.9900 
                 0.2000 
                 −8.550 
                 1.641 
                 23.9 
               
               
                 S9 
                   
                 3.6300 
                 0.3660 
               
               
                 S10 
                 Fifth Lens 
                 −18.1200 
                 0.1770 
                 −263.370 
                 1.641 
                 23.9 
               
               
                 S11 
                   
                 −20.3700 
                 0.8750 
               
               
                 S12 
                 Sixth Lens 
                 −3.4000 
                 0.2000 
                 −4.850 
                 1.546 
                 56.0 
               
               
                 S13 
                   
                 12.3100 
                 0.1000 
               
               
                 S14 
                 Seventh Lens 
                 15.2300 
                 0.7000 
                 6.300 
                 1.657 
                 21.5 
               
               
                 S15 
                   
                 −5.5800 
                 0.1000 
               
               
                 S16 
                 Filter 
                 infinity 
                 0.1100 
                   
                 1.519 
                 64.2 
               
               
                 Imaging 
                   
                 infinity 
                 0.6400 
               
               
                 Plane 
               
               
                   
               
            
           
         
       
     
     An optical imaging system according to a fourth example will be described with reference to  FIG.  10   . An optical imaging system  400  includes a first lens  410 , a second lens  420 , a third lens  430 , a fourth lens  440 , a fifth lens  450 , a sixth lens  460 , and a seventh lens  470 . 
     The first lens  410  has a positive refractive power and opposing convex surfaces. The second lens  420  has a negative refractive power, a convex object-side surface, and a concave image-side surface. The third lens  430  has a positive refractive power, a concave object-side surface, and a convex image-side surface. The fourth lens  440  has a negative refractive power, a convex object-side surface, and a concave image-side surface. 
     The fifth lens  450  has a positive refractive power, a concave object-side surface, and a convex image-side surface. The sixth lens  460  has a negative refractive power, a concave object-side surface, and a convex image-side surface. In addition, the sixth lens  460  includes inflection points formed on opposing surfaces. The seventh lens  470  has a negative refractive power and opposing concave surfaces. In addition, the seventh lens  470  includes inflection points formed on opposing surfaces. 
     In the configuration described above, first lens  410  has the highest degree of positive refractive power, while second lens  420  has the highest degree of negative refractive power. In the example described above, an object-side surface of first lens  410  is more convex than surfaces of other lenses, while the image-side surface of second lens  420  is more concave than surfaces of other lenses. In the configuration described above, a paraxial region of first lens  410  is formed to be thicker than paraxial regions of other lenses. A paraxial region of fifth lens  450  may be formed to be thinner than paraxial regions of other lenses. In the example described above, a distance between fourth lens  440  and fifth lens  450  is longer than that between other lenses. A distance between sixth lens  460  and seventh lens  470  or a distance between seventh lens  470  and an imaging plane may be shorter than that between other lenses. 
     The optical imaging system  400  further includes a filter  480 , an image sensor  490 , and a stop ST. Filter  480  is interposed between seventh lens  470  and image sensor  490 , while stop ST is interposed between second lens  420  and third lens  430 . 
     In optical imaging system  400 , first lens  410  may have a higher degree of refractive power than that of other lenses. In a manner different from the example described above, third lens  430 , fourth lens  440 , and fifth lens  450  may have a relatively low degree of refractive power. 
     A refractive index of first lens  410 , a refractive index of fourth lens  440 , and a refractive index of seventh lens  470 , in optical imaging system  400 , may be less than or equal to 1.55. In this case, the refractive index of first lens  410  is substantially the same as that of fourth lens  440 . The refractive index of second lens  420 , the refractive index of third lens  430 , the refractive index of fifth lens  450 , and the refractive index of sixth lens  460 , in optical imaging system  400 , may be greater than or equal to 1.65. In this case, the refractive index of third lens  430 , the refractive index of fifth lens  450 , and the refractive index of sixth lens  460  are substantially the same. In optical imaging system  400 , second lens  420  may have substantially the highest refractive index, while first lens  410  may have substantially the lowest refractive index. In optical imaging system  400 , one of fourth lens  440  and fifth lens  450  may have a refractive index greater than or equal to 1.6, and the other may have a refractive index less than or equal to 1.6. Fourth lens  440  and fifth lens  450 , having the configuration described above, increase an effect of aberration improvement 
     An effective diameter of a lens in optical imaging system  400  may be gradually reduced in a direction toward stop ST. For example, an effective diameter of third lens  430  disposed adjacently to stop ST may be smaller than that of lenses adjacent thereto. In a manner consistent with the configuration described above, a lens disposed distantly from stop ST may have a relatively large effective diameter. For example, seventh lens  470  disposed farthest from stop ST has the largest effective diameter. 
     An optical imaging system having the configuration described above represents aberration characteristics as illustrated in the graphs of  FIG.  11   .  FIG.  12    lists aspherical characteristics of the optical imaging system according to the example. Table 4 lists lens characteristics of the optical imaging system according to the example. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Fourth Example 
               
               
                 IMG HT = 2.40 f = 5.9976 TL = 5.296 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Surface 
                   
                 Radius of 
                 Thickness/ 
                 Focal 
                 Refractive 
                 Abbe 
               
               
                 No. 
                   
                 Curvature 
                 Distance 
                 Length 
                 Index 
                 Number 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S1 
                 First Lens 
                 1.4800 
                 0.8110 
                 2.460 
                 1.546 
                 56.0 
               
               
                 S2 
                   
                 −12.3700 
                 0.1330 
               
               
                 S3 
                 Second Lens 
                 9.2600 
                 0.2000 
                 −3.910 
                 1.684 
                 20.4 
               
               
                 S4 
                   
                 2.0200 
                 0.2220 
               
               
                 S5 
                 Third Lens 
                 infinity 
                 0.1000 
               
               
                 S6 
                   
                 −6.0300 
                 0.2480 
                 10.180 
                 1.657 
                 21.5 
               
               
                 S7 
                 Stop 
                 −3.2200 
                 0.1000 
               
               
                 S8 
                 Fourth Lens 
                 19.0700 
                 0.2000 
                 −6.000 
                 1.546 
                 56.0 
               
               
                 S9 
                   
                 2.7900 
                 0.7690 
               
               
                 S10 
                 Fifth Lens 
                 −14.1900 
                 0.1640 
                 47.550 
                 1.657 
                 21.5 
               
               
                 S11 
                   
                 −9.8000 
                 0.5920 
               
               
                 S12 
                 Sixth Lens 
                 −2.7600 
                 0.3850 
                 −24.760 
                 1.657 
                 21.5 
               
               
                 S13 
                   
                 −3.5000 
                 0.1000 
               
               
                 S14 
                 Seventh Lens 
                 −17.6100 
                 0.3770 
                 −9.25 
                 1.546 
                 56.0 
               
               
                 S15 
                   
                 7.1500 
                 0.1000 
               
               
                 S16 
                 Filter 
                 infinity 
                 0.1100 
                   
                 1.519 
                 64.2 
               
               
                 Imaging 
                   
                 infinity 
                 0.6850 
               
               
                 Plane 
               
               
                   
               
            
           
         
       
     
     Table 5 illustrates values of Conditional Equations of the optical imaging system according to first to fourth examples. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Conditional 
                 First 
                 Second 
                 Third 
                 Fourth 
               
               
                 Equation 
                 Example 
                 Example 
                 Example 
                 Example 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 TL/f 
                 0.8670 
                 0.8587 
                 0.8670 
                 0.8837 
               
               
                 BFL/f 
                 0.1334 
                 0.1334 
                 0.1417 
                 0.1493 
               
               
                 f/(IMG HT) 
                 2.181 
                 2.181 
                 2.399 
                 2.499 
               
               
                 Nd7 
                 1.657 
                 1.657 
                 1.657 
                 1.546 
               
               
                 f5/f 
                 −2.2628 
                 −0.9455 
                 −43.9127 
                 7.9280 
               
               
                 f/EPD 
                 2.40 
                 2.60 
                 2.60 
                 2.40 
               
               
                   
               
            
           
         
       
     
     Hereinafter, a portable terminal including an optical imaging system mounted therein, according to an example, will be described with reference to  FIGS.  13  and  14   . A portable terminal  10  includes a plurality of camera modules  20  and  30 . A first camera module  20  includes a first optical imaging system  101  configured to capture an image of a subject at a short distance. A second camera module  30  includes second optical imaging systems  100 ,  200 ,  300 , and  400 , configured to capture an image of a distant subject. 
     The first optical imaging system  101  includes a plurality of lenses. For example, first optical imaging system  101  includes four or more lenses. First optical imaging system  101  is configured to capture images of objects at short distance. In detail, first optical imaging system  101  has a relatively wide angle of view of 50° or more, while a ratio (TL/f) thereof may be higher than or equal to 1.0. 
     The second optical imaging systems  100 ,  200 ,  300 , and  400  include a plurality of lenses. For example, second optical imaging systems  100 ,  200 ,  300 , and  400  include seven lenses. Second optical imaging systems  100 ,  200 ,  300 , and  400  may be provided as one optical imaging system among optical imaging systems according to the first to fourth examples described above. Second optical imaging systems  100 ,  200 ,  300 , and  400  may be configured to capture an image of a distant object. In detail, second optical imaging systems  100 ,  200 ,  300 , and  400  have an angle of view of 40° or less, while a ratio (TL/f) thereof may be below 1.0. 
     First optical imaging system  101  and second optical imaging systems  100 ,  200 ,  300 , and  400  may have substantially the same size. In some embodiments, an overall length L 1  of first optical imaging system  101  is substantially the same as an overall length L 2  of second optical imaging systems  100 ,  200 ,  300 , and  400 . Alternatively, a ratio (L 1 /L 2 ) of the overall length L 1  of first optical imaging system  101  to the overall length L 2  of second optical imaging systems  100 ,  200 ,  300 , and  400  is from 0.8 to 1.0. As a further alternative, a ratio (L 2 /h) of the overall length L 2  of second optical imaging systems  100 ,  200 ,  300 , and  400  to a thickness h of portable terminal  10  may be less than or equal to 0.8. 
     As set forth above, according to examples, an optical imaging system capable of capturing images of distant objects and being mounted in a small terminal is provided. While this disclosure includes specific examples, it will be apparent after an understanding of the disclosure of this application that various changes in form and details 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 in a descriptive sense only, and not for purposes of limitation. Descriptions of features or aspects in each example are to be considered as being 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 a described system, architecture, device, or circuit are combined in a different manner, and/or replaced or supplemented by other components or their equivalents. Therefore, the scope of the disclosure is defined not by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as being included in the disclosure.