Patent Publication Number: US-2021191093-A1

Title: Camera apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims benefit of priority to Chinese Patent Application No. 201911317865.X filed on Dec. 19, 2019 before the China National Intellectual Property Administration, the entire disclosure of which is incorporated herein by reference in its entity. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of optical apparatuses, and specifically, relates to a camera apparatus. 
     BACKGROUND 
     With the rapid development of the industry of portable electronic products, such as smart phones, the lens assembly of the portable electronic products has also developed rapidly. 
     Generally speaking, users expect to be able to use the portable electronic products to complete shooting tasks in a variety of scenes, such as distant shots, close shots and even macro shots. On the other hand, users expect to obtain images with the highest possible image quality in every scene. Considering the compact internal space of the portable electronic product, the above-mentioned user requirements pose a great challenge to the design of the camera apparatus. 
     SUMMARY 
     In one aspect, the present disclosure provides a camera apparatus, which includes a first optical system and a second optical system. The first optical system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, which are sequentially arranged from an object side to an image side along an optical axis. The second optical system includes a secondary reflecting mirror, a main reflecting mirror (with an opening in the center area), and a lens group, which are sequentially arranged from an object side to an image side. Light from the object side is sequentially reflected by the main reflecting mirror and the secondary reflecting mirror, and then enters the lens group through the opening. 
     In one embodiment, at least one lens of the lens group has an aspheric surface. 
     In one embodiment, a total effective focal length F 1  of the first optical system and a total effective focal length F 2  of the second optical system may satisfy: F 2 /F 1 &gt;10. 
     In one embodiment, the lens group of the second optical system includes: a first lens having positive refractive power; a second lens having negative refractive power; and a third lens having positive refractive power, which are sequentially arranged from the main reflecting mirror to the image side along the optical axis. 
     In one embodiment, a distance TTL 2  along the optical axis from the secondary reflecting mirror of the second optical system to an imaging plane of the second optical system and a total effective focal length F 2  of the second optical system may satisfy: TTL 2 /F 2 &lt;0.5. 
     In one embodiment, an effective radius DT 1  of an outer circumference of the main reflecting mirror of the second optical system and half of a diagonal length ImgH 2  of an effective pixel area on an imaging plane of the second optical system may satisfy: 3.0&lt;DT 1 /ImgH 2 &lt;3.5. 
     In one embodiment, an effective radius DT 2  of the secondary reflecting mirror of the second optical system and an effective radius DT 1  of an outer circumference of the main reflecting mirror of the second optical system may satisfy: 0.2&lt;DT 2 /DT 1 &lt;0.5. 
     In one embodiment, a conic coefficient of the secondary reflecting mirror of the second optical system and a conic coefficient of the main reflecting mirror of the second optical system may both be less than −1.0. 
     In one embodiment, a distance BFL along the optical axis from an image-side surface of the third lens of the second optical system to an imaging plane of the second optical system and half of a diagonal length ImgH 2  of an effective pixel area on the imaging plane of the second optical system may satisfy: 3.0&lt;BFL/ImgH 2 &lt;3.5. 
     In one embodiment, a refractive index N 1  of the first lens of the second optical system, a refractive index N 2  of the second lens of the second optical system and a refractive index N 3  of the third lens of the second optical system may satisfy: 1.5&lt;(N 1 +N 2 +N 3 )/3&lt;1.6. 
     In one embodiment, a total effective focal length F 2  of the second optical system and a radius of curvature R 1  of the main reflecting mirror of the second optical system may satisfy: −1.0&lt;F 2 /R 1 &lt;−0.5. 
     In one embodiment, a total effective focal length F 2  of the second optical system and a radius of curvature R 2  of the secondary reflecting mirror of the second optical system may satisfy: −1.2&lt;F 2 /R 2 &lt;−0.9. 
     In one embodiment, a total effective focal length F 2  of the second optical system and an effective focal length f 1  of the first lens of the second optical system may satisfy: 4.0&lt;F 2 /f 1 &lt;5.0. 
     In one embodiment, a total effective focal length F 2  of the second optical system and an effective focal length f 2  of the second lens of the second optical system may satisfy: −8.0&lt;F 2 /f 2 &lt;−7.0. 
     In one embodiment, a total effective focal length F 2  of the second optical system and an effective focal length f 3  of the third lens of the second optical system may satisfy: 3.0&lt;F 2 /f 3 &lt;4.0. 
     In one embodiment, a distance TTL 1  along the optical axis of the first optical system from an object-side surface of the first lens of the first optical system to an imaging plane of the first optical system and a total effective focal length F 1  of the first optical system may satisfy: TTL 1 /F 1 &lt;1.2. 
     In one embodiment, a total effective focal length F 1  of the first optical system and half of a diagonal length ImgH 1  of an effective pixel area on an imaging plane of the first optical system may satisfy: ImgH 1 /F 1 &gt;0.9. 
     The present disclosure combines the RC reflective optical system with aspheric lenses. The above camera apparatus has at least one beneficial effect, such as small size, long focal length, compact structure, high image quality, and low distortion and the like, by rationally configuring the refractive power, the refractive index of each lens and the like. The system is used in conjunction with another optical system to form a camera apparatus, which may achieve an optical zoom factor of more than  10  times and may achieve shooting tasks in a variety of scenes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features, objects, and advantages of the present disclosure will become more apparent by reading the detailed description of the non-limiting examples with reference to the accompanying drawings: 
         FIG. 1  illustrates a schematic structural view of a second optical system according to example 1 of the present disclosure; 
         FIGS. 2A to 2D  illustrate a longitudinal aberration curve, an astigmatic curve, a distortion curve, and a lateral color curve of the second optical system of the example 1, respectively; 
         FIG. 3  illustrates a schematic structural view of a second optical system according to example 2 of the present disclosure; 
         FIGS. 4A to 4D  illustrate a longitudinal aberration curve, an astigmatic curve, a distortion curve, and a lateral color curve of the second optical system of the example 2, respectively; 
         FIG. 5  illustrates a schematic structural view of a second optical system according to example 3 of the present disclosure; 
         FIGS. 6A to 6D  illustrate a longitudinal aberration curve, an astigmatic curve, a distortion curve, and a lateral color curve of the second optical system of the example 3, respectively; 
         FIG. 7  illustrates a schematic structural view of a first optical system according to example 4 of the present disclosure; 
         FIGS. 8A to 8D  illustrate a longitudinal aberration curve, an astigmatic curve, a distortion curve, and a lateral color curve of the first optical system of the example 4, respectively; 
         FIG. 9  illustrates a schematic structural view of a first optical system according to example 5 of the present disclosure; and 
         FIGS. 10A to 10D  illustrate a longitudinal aberration curve, an astigmatic curve, a distortion curve, and a lateral color curve of the first optical system of the example 5, respectively. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     For a better understanding of the present disclosure, various aspects of the present disclosure will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of the exemplary embodiments of the present disclosure and is not intended to limit the scope of the present disclosure in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression “and/or” includes any and all combinations of one or more of the associated listed items. 
     It should be noted that in the present specification, the expressions such as first, second, third are used merely for distinguishing one feature from another, without indicating any limitation on the features. Thus, a first lens discussed below may also be referred to as a second lens or a third lens without departing from the teachings of the present disclosure. 
     In the accompanying drawings, the thickness, size and shape of the lens have been somewhat exaggerated for the convenience of explanation. In particular, shapes of spherical surfaces or aspheric surfaces shown in the accompanying drawings are shown by way of example. That is, shapes of the spherical surfaces or the aspheric surfaces are not limited to the shapes of the spherical surfaces or the aspheric surfaces shown in the accompanying drawings. The accompanying drawings are merely illustrative and not strictly drawn to scale. 
     Herein, the paraxial area refers to an area near the optical axis. If a surface of a lens is a convex surface and the position of the convex is not defined, it indicates that the surface of the lens is convex at least in the paraxial region; and if a surface of a lens is a concave surface and the position of the concave is not defined, it indicates that the surface of the lens is concave at least in the paraxial region. In each lens, the surface closest to the object is referred to as an object-side surface of the lens, and the surface closest to the imaging plane is referred to as an image-side surface of the lens. 
     It should be further understood that the terms “comprising,” “including,” “having,” “containing” and/or “contain,” when used in the specification, specify the presence of stated features, elements and/or components, but do not exclude the presence or addition of one or more other features, elements, components and/or combinations thereof. In addition, expressions, such as “at least one of,” when preceding a list of features, modify the entire list of features rather than an individual element in the list. Further, the use of “may,” when describing embodiments of the present disclosure, refers to “one or more embodiments of the present disclosure.” Also, the term “exemplary” is intended to refer to an example or illustration. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with the meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
     It should also be noted that, the examples in the present disclosure and the features in the examples may be combined with each other on a non-conflict basis. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the examples. 
     The features, principles, and other aspects of the present disclosure are described in detail below. 
     A camera apparatus according to an exemplary embodiment of the present disclosure may include, for example, a first optical system and a second optical system. The first optical system may include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. The first optical system is a seven-piece lens. The seven lenses are arranged sequentially from an object side to an image side along an optical axis. Among the first lens to the seventh lens, there may be a spaced interval between each two adjacent lenses. The second optical system may include a secondary reflecting mirror, a main reflecting mirror (with an opening in the center area) and a lens group, which are sequentially arranged from an object side to an image side. Light from the object side is sequentially reflected by the main reflecting mirror and the secondary reflecting mirror, and then enters the lens group through the opening of the main reflecting mirror. Among the secondary reflecting mirror to the lens group, there may be a spaced interval between each two adjacent components. The lens group includes three lenses having refractive power, which are a first lens, a second lens and a third lens. The three lenses are arranged sequentially from an object side to an image side along an optical axis. Among the first lens to the third lens, there may be a spaced interval between each two adjacent lenses. 
     The first optical system and the second optical system are used together, so that the optical zoom of the camera apparatus may reach more than 10 times. By configuring two reflecting mirrors to fold the optical path, the second optical system has the characteristics of ultra-long equivalent focal length and high image quality, while also meeting the requirements of small size and compact structure. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: F 2 /F 1 &gt;10, where F 1  is a total effective focal length of the first optical system, and F 2  is a total effective focal length of the second optical system. When F 2 /F 1 &gt;10 is satisfied, the entire dual-camera lens group has a good zoom telephoto function. 
     In an exemplary embodiment, the lens group of the second optical system may include a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, which are sequentially arranged from the main reflecting mirror to the image side along the optical axis. By reasonably assigning the refractive power of the lenses of the second optical system, the second optical system having a long focal length may be used in conjunction with the first optical system to meet the optical zoom function of more than 10 times. At the same time, it may effectively reduce the system aberrations, so that the entire system has the characteristics of high image quality and long focal length. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: TTL 2 /F 2 &lt;0.5, where TTL 2  is a distance along an optical axis from the secondary reflecting mirror of the second optical system to an imaging plane of the second optical system, and F 2  is a total effective focal length of the second optical system. More specifically, TTL 2  and F 2  may further satisfy: TTL 2 /F 2 &lt;0.3. When TTL 2 /F 2 &lt;0.5 is satisfied, the ultra-long focal length characteristic of the second optical system is effectively guaranteed. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: 3.0&lt;DT 1 /ImgH 2 &lt;3.5, where DT 1  is an effective radius of an outer circumference of the main reflecting mirror of the second optical system, and ImgH 2  is half of a diagonal length of an effective pixel area on an imaging plane of the second optical system. More specifically, DT 1  and ImgH 2  may further satisfy: 3.0&lt;DT 1 /ImgH 2 &lt;3.3. Satisfying 3.0&lt;DT 1 /ImgH 2 &lt;3.5 effectively ensures the miniaturization of combined lens assembly. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: 0.2&lt;DT 2 /DT 1 &lt;0.5, where DT 2  is an effective radius of the secondary reflecting mirror of the second optical system, and DT 1  is an effective radius of an outer circumference of the main reflecting mirror of the second optical system. More specifically, DT 2  and DT 1  may further satisfy: 0.4&lt;DT 2 /DT 1 &lt;0.5. When 0.2&lt;DT 2 /DT 1 &lt;0.5 is satisfied, the total size of the system may be reasonably controlled, so that the system may satisfy the high requirements in performance, while also satisfying the requirements of miniaturization in structure. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: K&lt;−1.0, where K is a conic coefficient of one of the reflecting mirrors of the second optical system. When K&lt;−1.0 is satisfied, it is ensured that the reflecting mirror surface is a hyperboloid. It should be understood that the main reflecting mirror and the secondary reflecting mirror may have different conic coefficients, but both may be less than −1.0. With two hyperboloid mirrors, it may effectively reduce the spherical aberration, field curvature, coma and other aberrations in the system, and at the same time, make the system have the characteristics of long focal length and large aperture. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: 3.0&lt;BFL/ImgH 2 &lt;3.5, where BFL is a distance along the optical axis from an image-side surface of the third lens of the second optical system to an imaging plane of the second optical system, and ImgH 2  is half of a diagonal length of an effective pixel area on the imaging plane of the second optical system. More specifically, BFL and ImgH 2  may further satisfy: 3.0&lt;BFL/ImgH 2 &lt;3.3. Satisfying 3.0&lt;BFL/ImgH 2 &lt;3.5 makes the system more compact and miniaturized while meeting the characteristics of long focal length and high image quality. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: 1.5&lt;(N 1 +N 2 +N 3 )/3&lt;1.6, where N 1  is a refractive index of the first lens of the second optical system, N 2  is a refractive index of the second lens of the second optical system, and N 3  is a refractive index of the third lens of the second optical system. The camera apparatus satisfies the expression 1.5&lt;(N 1 +N 2 +N 3 )/3&lt;1.6. By reasonably selecting the material of the first to the third lenses, the effective focal length of the system may reach the required value, and the advantages of high image quality and small aberrations may be ensured. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: −1.0&lt;F 2 /R 1 &lt;−0.5, where F 2  is a total effective focal length of the second optical system, and R 1  is a radius of curvature of the main reflecting mirror of the second optical system. More specifically, F 2  and R 1  may further satisfy: −0.9&lt;F 2 /R 1 &lt;−0.8. Satisfying −1.0&lt;F 2 /R 1 &lt;−0.5 (that is, controlling the shape of the main reflecting mirror while meeting the effective focal length of the system) and cooperating with the secondary reflecting mirror and other lenses may effectively correct various aberrations of the system. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: −1.2&lt;F 2 /R 2 &lt;−0.9, where F 2  is a total effective focal length of the second optical system, and R 2  is a radius of curvature of the secondary reflecting mirror of the second optical system. More specifically, F 2  and R 2  may further satisfy: −1.2&lt;F 2 /R 2 &lt;−1.0. Satisfying −1.2&lt;F 2 /R 2 &lt;−0.9 (that is, controlling the shape of the secondary reflecting mirror while meeting the effective focal length of the system) and cooperating with the main reflecting mirror and other lenses may effectively correct various aberrations of the system. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: 4.0&lt;F 2 /f 1 &lt;5.0, where F 2  is a total effective focal length of the second optical system, and f 1  is an effective focal length of the first lens of the second optical system. More specifically, F 2  and f 1  may further satisfy: 4.4&lt;F 2 /f 1 &lt;4.7. When 4.0&lt;F 2 /f 1 &lt;5.0 is satisfied, the contribution of the effective focal length of the first lens to the effective focal length of the total system may be effectively controlled, so that the total effective focal length of the system may reach a larger ideal value. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: −8.0&lt;F 2 /f 2 &lt;−7.0, where F 2  is a total effective focal length of the second optical system, and f 2  is an effective focal length of the second lens of the second optical system. More specifically, F 2  and f 2  may further satisfy: −7.9&lt;F 2 /f 2 &lt;−7.3. When −8.0&lt;F 2 /f 2 &lt;−7.0 is satisfied, the contribution of the effective focal length of the second lens to the effective focal length of the total system may be effectively controlled, so that the total effective focal length of the system may reach a larger ideal value. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: 3.0&lt;F 2 /f 3 &lt;4.0, where F 2  is a total effective focal length of the second optical system, and f 3  is an effective focal length of the third lens of the second optical system. More specifically, F 2  and f 3  may further satisfy: 3.3&lt;F 2 /f 3 &lt;3.6. Satisfying 3.0&lt;F 2 /f 3 &lt;4.0 may effectively control the contribution of the effective focal length of the third lens to the effective focal length of the total system, so that the total effective focal length of the system may reach a larger ideal value. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: TTL 1 /F 1 &lt;1.2, where TTL 1  is a distance along the optical axis of the first optical system from an object-side surface of the first lens of the first optical system to an imaging plane of the first optical system, and F 1  is a total effective focal length of the first optical system. When TTL 1 /F 1 &lt;1.2 is satisfied, the long-focus characteristics of the system may be effectively guaranteed. 
     In an exemplary embodiment, the camera apparatus according to the present disclosure may satisfy: ImgH 1 /F 1 &gt;0.9, where F 1  is a total effective focal length of the first optical system, and ImgH 1  is half of a diagonal length of an effective pixel area on an imaging plane of the first optical system. When ImgH 1 /F 1 &gt;0.9 is satisfied, the ultra-thin characteristics of the system may be effectively guaranteed. 
     Optionally, the above camera apparatus may further include a stop disposed on the second lens of the second optical system. Optionally, the above camera apparatus may further include an optical filter for correcting the color deviation and/or a protective glass for protecting the photosensitive element located on an imaging plane. 
     The present disclosure proposes a seven-piece first optical system, a second optical system composed of an RC reflective optical system and a three-piece lens group, and a long-focus camera apparatus formed by combining the first optical system and the second optical system. By properly configuring the refractive power of each lens, the surface shape, the center thickness of each lens, the radius of curvature and spaced intervals along the optical axis between the lenses, it is possible to adopt less design freedom while ensuring that the camera apparatus has the characteristics of long focus and high resolution. 
     However, it will be understood by those skilled in the art that the number of lenses constituting the camera apparatus may be varied to achieve the various results and advantages described in this specification without departing from the technical solution claimed by the present disclosure. For example, although the first optical system and the second optical system are described as examples in the embodiment, the camera apparatus is not limited to including the first optical system and the second optical system. The camera apparatus may also include other numbers of optical systems if desired. 
     Some specific examples of a first optical system and a second optical system applicable to the camera apparatus of the above embodiment will be further described below with reference to the accompanying drawings. Examples 1 to 3 are examples of the second optical system, and examples 4 to 5 are examples of the first optical system. The following examples may be combined according to their lens group types to form 6 different camera apparatuses. The configurations of these camera apparatuses are as follows: 
     1) Example 1+Example 4; 
     2) Example 1+Example 5; 
     3) Example 2+Example 4; 
     4) Example 2+Example 5; 
     5) Example 3+Example 4; and 
     6) Example 3+Example 5. 
     EXAMPLE 1 
     A second optical system according to example 1 of the present disclosure is described below with reference to  FIG. 1  to  FIG. 2D .  FIG. 1  shows a schematic structural view of the second optical system according to example 1 of the present disclosure. 
     As shown in  FIG. 1 , the second optical system includes a secondary reflecting mirror E 2 , a main reflecting mirror E 1 , a first lens E 3 , a second lens E 4 , a third lens E 5  and an imaging plane S 9 , which are sequentially arranged from an object side to an image side. 
     The secondary reflecting mirror E 2  may have a hyperboloid S 2 . The main reflecting mirror E 1  may have a hyperboloid S 1 . The first lens E 3  has positive refractive power, an object-side surface S 3  thereof is a convex surface, and an image-side surface S 4  thereof is a convex surface. The second lens E 4  has negative refractive power, an object-side surface S 5  thereof is a concave surface, and an image-side surface S 6  thereof is a concave surface. The third lens E 5  has positive refractive power, an object-side surface S 7  thereof is a convex surface, and an image-side surface S 8  thereof is a concave surface. Light from an object sequentially passes through the respective surfaces S 1  to S 8  and is finally imaged on the imaging plane S 9 . 
     Table 1 is a table illustrating basic parameters of the second optical system of example 1, wherein the units for the radius of curvature, the thickness/distance and the focal length are millimeter (mm). 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Material 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                 Thickness/ 
                 Refractive 
                 Abbe 
                 Focal 
                 Conic 
               
               
                 number 
                 type 
                 curvature 
                 Distance 
                 index 
                 number 
                 length 
                 coefficient 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinite 
                 Infinite 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S1 
                 Hyperboloid 
                 −86.2770 
                 −23.4036 
                 Reflecting mirror 
                   
                 −1.8595 
               
               
                 S2 
                 Hyperboloid 
                 −67.4733 
                 24.4448 
                 Reflecting mirror 
                   
                 −16.3235 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 S3 (STO) 
                 Aspheric 
                 8.9867 
                 2.1764 
                 1.55 
                 72.24 
                 16.39 
                 −5.4967 
               
               
                 S4 
                 Spherical 
                 −661.7982 
                 0.5319 
                   
                   
                   
                 0.0000 
               
               
                 S5 
                 Aspheric 
                 −12.5684 
                 1.0112 
                 1.50 
                 56.41 
                 −9.86 
                 −28.0859 
               
               
                 S6 
                 Spherical 
                 8.1419 
                 1.4747 
                   
                   
                   
                 0.0000 
               
               
                 S7 
                 Aspheric 
                 6.1456 
                 1.7729 
                 1.59 
                 68.40 
                 21.88 
                 −4.3466 
               
               
                 S8 
                 Spherical 
                 10.5670 
                 9.7656 
               
               
                 S9 
                 Spherical 
                 Infinite 
               
               
                   
               
            
           
         
       
     
     In this example, a total effective focal length f of the second optical system is 72.94 mm, and a maximum field-of-view FOV of the second optical system is 4.9°. 
     In example 1, the image-side surface of any one of the first lens E 3  to the third lens E 5  are spherical. 
     In example 1, the object-side surface of any one of the first lens E 3  to the third lens E 5  are aspheric. The surface shape x of each aspheric lens may be defined by using, but not limited to, the following aspheric formula: 
     
       
         
           
             
               
                 
                   x 
                   = 
                   
                     
                       
                         c 
                          
                         
                           h 
                           2 
                         
                       
                       
                         1 
                         + 
                         
                           
                             1 
                             - 
                             
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                                
                               
                                 c 
                                 2 
                               
                                
                               
                                 h 
                                 2 
                               
                             
                           
                         
                       
                     
                     + 
                     
                       ∑ 
                       
                         Aih 
                         i 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     Where, x is the sag—the axis-component of the displacement of the surface from the aspheric vertex, when the surface is at height h from the optical axis; c is a paraxial curvature of the aspheric surface, c=1/R (that is, the paraxial curvature c is reciprocal of the radius of curvature R in the above Table 1); k is a conic coefficient; Ai is a correction coefficient for the i-th order of the aspheric surface. Table 2 below shows high-order coefficients A 4 , A 6 , A 8  and A 10  applicable to each aspheric surface S 3 , S 5  and S 7  in example 1. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Surface number 
                 A4 
                 A6 
                 A8 
                 A10 
               
               
                   
               
             
            
               
                 S3 
                 7.5502E−04 
                 −1.6509E−05 
                 3.0471E−07 
                 −2.1006E−09 
               
               
                 S5 
                 5.1074E−04 
                 −1.1288E−05 
                 9.9836E−08 
                 −1.4139E−10 
               
               
                 S7 
                 6.9146E−04 
                 −1.7754E−05 
                 5.8481E−07 
                 −8.5994E−09 
               
               
                   
               
            
           
         
       
     
       FIG. 2A  illustrates a longitudinal aberration curve of the second optical system according to example 1, representing deviations of focal points converged by light of different wavelengths after passing through the optical system.  FIG. 2B  illustrates an astigmatic curve of the second optical system according to example 1, representing a curvature of a tangential plane and a curvature of a sagittal plane.  FIG. 2C  illustrates a distortion curve of the second optical system according to example 1, representing amounts of distortion corresponding to different image heights.  FIG. 2D  illustrates a lateral color curve of the second optical system according to example 1, representing deviations of different image heights on an imaging plane after light passes through the optical system. It can be seen from  FIG. 2A  to  FIG. 2D  that the second optical system provided in example 1 may achieve good image quality. 
     EXAMPLE 2 
     A second optical system according to example 2 of the present disclosure is described below with reference to  FIG. 3  to  FIG. 4D . In this example, for the purpose of brevity, the description of parts similar to those in example 1 will be omitted.  FIG. 3  shows a schematic structural view of the second optical system according to example 2 of the present disclosure. 
     As shown in  FIG. 3 , the second optical system includes a secondary reflecting mirror E 2 , a main reflecting mirror E 1 , a first lens E 3 , a second lens E 4 , a third lens E 5  and an imaging plane S 9 , which are sequentially arranged from an object side to an image side. 
     The secondary reflecting mirror E 2  may have a hyperboloid S 2 . The main reflecting mirror E 1  may have a hyperboloid S 1 . The first lens E 3  has positive refractive power, an object-side surface S 3  thereof is a convex surface, and an image-side surface S 4  thereof is a convex surface. The second lens E 4  has negative refractive power, an object-side surface S 5  thereof is a concave surface, and an image-side surface S 6  thereof is a concave surface. The third lens E 5  has positive refractive power, an object-side surface S 7  thereof is a convex surface, and an image-side surface S 8  thereof is a concave surface. Light from an object sequentially passes through the respective surfaces S 1  to S 8  and is finally imaged on the imaging plane S 9 . 
     In this example, a total effective focal length f of the second optical system is 87.53 mm, and a maximum field-of-view FOV of the second optical system is 4.9°. The image-side surface of any one of the first lens E 3  to the third lens E 5  are spherical. 
     Table 3 is a table illustrating basic parameters of the second optical system of example 2, wherein the units for the radius of curvature, the thickness/distance and the focal length are millimeter (mm). Table 4 shows high-order coefficients applicable to each aspheric surface in example 2, wherein the surface shape of each aspheric surface may be defined by the formula (1) given in the above example 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
             
            
               
                   
                   
               
               
                   
                 Material 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                 Thickness/ 
                 Refractive 
                 Abbe 
                 Focal 
                 Conic 
               
               
                 number 
                 type 
                 curvature 
                 Distance 
                 index 
                 number 
                 length 
                 coefficient 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinite 
                 Infinite 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S1 
                 Hyperboloid 
                 −103.5324 
                 −28.0843 
                 Reflecting mirror 
                   
                 −1.8595 
               
               
                 S2 
                 Hyperboloid 
                 −80.9680 
                 29.3337 
                 Reflecting mirror 
                   
                 −16.3235 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 S3 (STO) 
                 Aspheric 
                 10.7840 
                 2.6117 
                 1.55 
                 72.24 
                 18.93 
                 −5.4967 
               
               
                 S4 
                 Spherical 
                 −794.1579 
                 0.6383 
                   
                   
                   
                 0.0000 
               
               
                 S5 
                 Aspheric 
                 −15.0821 
                 1.2134 
                 1.50 
                 56.41 
                 −11.24 
                 −28.0859 
               
               
                 S6 
                 Spherical 
                 9.7702 
                 1.7697 
                   
                   
                   
                 0.0000 
               
               
                 S7 
                 Aspheric 
                 7.3747 
                 2.1275 
                 1.59 
                 68.40 
                 25.11 
                 −4.3466 
               
               
                 S8 
                 Spherical 
                 12.6804 
                 11.7187 
               
               
                 S9 
                 Spherical 
                 Infinite 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Surface number 
                 A4 
                 A6 
                 A8 
                 A10 
               
               
                   
               
             
            
               
                 S3 
                 4.3693E−04 
                 −6.6346E−06 
                 8.5040E−08 
                 −4.0712E−10 
               
               
                 S5 
                 2.9557E−04 
                 −4.5364E−06 
                 2.7862E−08 
                 −2.7403E−11 
               
               
                 S7 
                 4.0015E−04 
                 −7.1350E−06 
                 1.6321E−07 
                 −1.6666E−09 
               
               
                   
               
            
           
         
       
     
       FIG. 4A  illustrates a longitudinal aberration curve of the second optical system according to example 2, representing deviations of focal points converged by light of different wavelengths after passing through the optical system.  FIG. 4B  illustrates an astigmatic curve of the second optical system according to example 2, representing a curvature of a tangential plane and a curvature of a sagittal plane.  FIG. 4C  illustrates a distortion curve of the second optical system according to example 2, representing amounts of distortion corresponding to different image heights.  FIG. 4D  illustrates a lateral color curve of the second optical system according to example 2, representing deviations of different image heights on an imaging plane after light passes through the optical system. It can be seen from  FIG. 4A  to  FIG. 4D  that the second optical system provided in example 2 may achieve good image quality. 
     EXAMPLE 3 
     A second optical system according to example 3 of the present disclosure is described below with reference to  FIG. 5  to  FIG. 6D .  FIG. 5  shows a schematic structural view of the second optical system according to example 3 of the present disclosure. 
     As shown in  FIG. 5 , the second optical system includes a secondary reflecting mirror E 2 , a main reflecting mirror E 1 , a first lens E 3 , a second lens E 4 , a third lens E 5  and an imaging plane S 9 , which are sequentially arranged from an object side to an image side. 
     The secondary reflecting mirror E 2  may have a hyperboloid S 2 . The main reflecting mirror E 1  may have a hyperboloid S 1 . The first lens E 3  has positive refractive power, an object-side surface S 3  thereof is a convex surface, and an image-side surface S 4  thereof is a convex surface. The second lens E 4  has negative refractive power, an object-side surface S 5  thereof is a concave surface, and an image-side surface S 6  thereof is a concave surface. The third lens E 5  has positive refractive power, an object-side surface S 7  thereof is a convex surface, and an image-side surface S 8  thereof is a concave surface. Light from an object sequentially passes through the respective surfaces S 1  to S 8  and is finally imaged on the imaging plane S 9 . 
     In this example, a total effective focal length f of the second optical system is 80.24 mm, and a maximum field-of-view FOV of the second optical system is 4.9°. The image-side surface of any one of the first lens E 3  to the third lens E 5  are spherical. 
     Table 5 is a table illustrating basic parameters of the second optical system of example 3, wherein the units for the radius of curvature, the thickness/distance and the focal length are millimeter (mm). Table 6 shows high-order coefficients applicable to each aspheric surface in example 3, wherein the surface shape of each aspheric surface may be defined by the formula (1) given in the above example 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
             
            
               
                   
                   
               
               
                   
                 Material 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                 Thickness/ 
                 Refractive 
                 Abbe 
                 Focal 
                 Conic 
               
               
                 number 
                 type 
                 curvature 
                 Distance 
                 index 
                 number 
                 length 
                 coefficient 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinite 
                 Infinite 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S1 
                 Hyperboloid 
                 −94.9047 
                 −25.7440 
                 Reflecting mirror 
                   
                 −1.8595 
               
               
                 S2 
                 Hyperboloid 
                 −74.2207 
                 26.8893 
                 Reflecting mirror 
                   
                 −16.3235 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 S3 (STO) 
                 Aspheric 
                 9.8853 
                 2.3941 
                 1.55 
                 72.24 
                 17.36 
                 −5.4967 
               
               
                 S4 
                 Spherical 
                 −727.9781 
                 0.5851 
                   
                   
                   
                 0.0000 
               
               
                 S5 
                 Aspheric 
                 −13.8252 
                 1.1123 
                 1.50 
                 56.41 
                 −10.30 
                 −28.0859 
               
               
                 S6 
                 Spherical 
                 8.9560 
                 1.6222 
                   
                   
                   
                 0.0000 
               
               
                 S7 
                 Aspheric 
                 6.7601 
                 1.9502 
                 1.59 
                 68.40 
                 23.02 
                 −4.3466 
               
               
                 S8 
                 Spherical 
                 11.6237 
                 10.7421 
               
               
                 S9 
                 Spherical 
                 Infinite 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 Surface number 
                 A4 
                 A6 
                 A8 
                 A10 
               
               
                   
               
             
            
               
                 S3 
                 5.6726E−04 
                 −1.0251E−05 
                 1.5637E−07 
                 −8.9088E−10 
               
               
                 S5 
                 3.8372E−04 
                 −7.0090E−06 
                 5.1232E−08 
                 −5.9964E−11 
               
               
                 S7 
                 5.1950E−04 
                 −1.1024E−05 
                 3.0010E−07 
                 −3.6470E−09 
               
               
                   
               
            
           
         
       
     
       FIG. 6A  illustrates a longitudinal aberration curve of the second optical system according to example 3, representing deviations of focal points converged by light of different wavelengths after passing through the optical system.  FIG. 6B  illustrates an astigmatic curve of the second optical system according to example 3, representing a curvature of a tangential plane and a curvature of a sagittal plane.  FIG. 6C  illustrates a distortion curve of the second optical system according to example 3, representing amounts of distortion corresponding to different image heights.  FIG. 6D  illustrates a lateral color curve of the second optical system according to example 3, representing deviations of different image heights on an imaging plane after light passes through the optical system. It can be seen from  FIG. 6A  to  FIG. 6D  that the second optical system provided in example 3 may achieve good image quality. 
     EXAMPLE 4 
     A first optical system according to example 4 of the present disclosure is described below with reference to  FIG. 7  to  FIG. 8D .  FIG. 7  shows a schematic structural view of the first optical system according to example 4 of the present disclosure. 
     As shown in  FIG. 7 , the first optical system includes a stop STO, a first lens E 1 , a second lens E 2 , a third lens E 3 , a fourth lens E 4 , a fifth lens E 5 , a sixth lens E 6 , a seventh lens E 7 , an optical filter E 8  and an imaging plane S 17 , which are sequentially arranged from an object side to an image side. 
     The first lens E 1  has positive refractive power, an object-side surface S 1  thereof is a convex surface, and an image-side surface S 2  thereof is a concave surface. The second lens E 2  has negative refractive power, an object-side surface S 3  thereof is a convex surface, and an image-side surface S 4  thereof is a concave surface. The third lens E 3  has positive refractive power, an object-side surface S 5  thereof is a convex surface, and an image-side surface S 6  thereof is a concave surface. The fourth lens E 4  has positive refractive power, an object-side surface S 7  thereof is a convex surface, and an image-side surface S 8  thereof is a convex surface. The fifth lens E 5  has negative refractive power, an object-side surface S 9  thereof is a convex surface, and an image-side surface S 10  thereof is a concave surface. The sixth lens E 6  has positive refractive power, an object-side surface S 11  thereof is a convex surface, and an image-side surface S 12  thereof is a convex surface. The seventh lens E 7  has negative refractive power, an object-side surface S 13  thereof is a concave surface, and an image-side surface S 14  thereof is a concave surface. The optical filter E 8  has an object-side surface S 15  and an image-side surface S 16 . Light from an object sequentially passes through the respective surfaces S 1  to S 16  and is finally imaged on the imaging plane S 17 . 
     Table 7 is a table illustrating basic parameters of the first optical system of example 4, wherein the units for the radius of curvature, the thickness/distance and the focal length are millimeter (mm). 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
             
            
               
                   
                   
               
               
                   
                 Material 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                 Thickness/ 
                 Refractive 
                 Abbe 
                 Focal 
                 Conic 
               
               
                 number 
                 type 
                 curvature 
                 Distance 
                 index 
                 number 
                 length 
                 coefficient 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinite 
                 Infinite 
                   
                   
                   
                   
               
               
                 STO 
                 Spherical 
                 Infinite 
                 −0.7151 
               
               
                 S1 
                 Aspheric 
                 2.3174 
                 0.9364 
                 1.546 
                 56.11 
                 5.19 
                 0.0263 
               
               
                 S2 
                 Aspheric 
                 10.9122 
                 0.0350 
                   
                   
                   
                 10.3469 
               
               
                 S3 
                 Aspheric 
                 5.9148 
                 0.3100 
                 1.678 
                 19.25 
                 −10.79 
                 9.7151 
               
               
                 S4 
                 Aspheric 
                 3.2000 
                 0.3626 
                   
                   
                   
                 2.3987 
               
               
                 S5 
                 Aspheric 
                 13.8233 
                 0.3100 
                 1.678 
                 19.25 
                 74.66 
                 90.9503 
               
               
                 S6 
                 Aspheric 
                 18.8484 
                 0.1978 
                   
                   
                   
                 −99.0000 
               
               
                 S7 
                 Aspheric 
                 91.6703 
                 0.4959 
                 1.546 
                 56.11 
                 41.26 
                 −38.9435 
               
               
                 S8 
                 Aspheric 
                 −29.8027 
                 0.5164 
                   
                   
                   
                 79.3889 
               
               
                 S9 
                 Aspheric 
                 19.1537 
                 0.5123 
                 1.645 
                 23.49 
                 −20.48 
                 59.6526 
               
               
                 S10 
                 Aspheric 
                 7.7338 
                 0.5163 
                   
                   
                   
                 −1.7482 
               
               
                 S11 
                 Aspheric 
                 5.3789 
                 1.0456 
                 1.546 
                 56.11 
                 6.48 
                 0.3838 
               
               
                 S12 
                 Aspheric 
                 −9.6233 
                 0.8366 
                   
                   
                   
                 −9.1234 
               
               
                 S13 
                 Aspheric 
                 −3.0672 
                 0.7016 
                 1.536 
                 55.74 
                 −4.18 
                 −1.1463 
               
               
                 S14 
                 Aspheric 
                 8.9859 
                 0.1797 
                   
                   
                   
                 −28.1695 
               
               
                 S15 
                 Spherical 
                 Infinite 
                 0.2100 
                 1.517 
                 64.17 
               
               
                 S16 
                 Spherical 
                 Infinite 
                 0.4463 
               
               
                 S17 
                 Spherical 
                 Infinite 
               
               
                   
               
            
           
         
       
     
     In this example, a total effective focal length f of the first optical system is 6.62 mm, and a maximum field-of-view FOV of the first optical system is 87.8°. 
     In example 4, the object-side surface and the image-side surface of any one of the first lens E 1  to the seventh lens E 7  are aspheric. The surface shape x of each aspheric lens may be defined by using, but not limited to, the following aspheric formula: 
     
       
         
           
             
               
                 
                   x 
                   = 
                   
                     
                       
                         c 
                          
                         
                           h 
                           2 
                         
                       
                       
                         1 
                         + 
                         
                           
                             1 
                             - 
                             
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                                
                               
                                 c 
                                 2 
                               
                                
                               
                                 h 
                                 2 
                               
                             
                           
                         
                       
                     
                     + 
                     
                       ∑ 
                       
                         A 
                          
                         i 
                          
                         
                           h 
                           i 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     Where, x is the sag—the axis-component of the displacement of the surface from the aspheric vertex, when the surface is at height h from the optical axis; c is a paraxial curvature of the aspheric surface, c=1/R (that is, the paraxial curvature c is reciprocal of the radius of curvature R in the above Table 1); k is a conic coefficient; Ai is a correction coefficient for the i-th order of the aspheric surface. Table 8 below shows high-order coefficients A 4 , A 6 , A 8 , A 10 , A 12 , A 14 , A 16 , A 18  and A 20  applicable to each aspheric surface S 1  to S 14  in example 4. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 8 
               
               
                   
               
             
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 A4 
                 A6 
                 A8 
                 A10 
                 A12 
               
               
                   
               
               
                 S1 
                 −1.2372E−03 
                  7.3054E−03 
                 −1.3673E−02  
                  1.6459E−02 
                 −1.2807E−02  
               
               
                 S2 
                 −3.0576E−03 
                 −1.6668E−04 
                 2.3119E−02 
                 −4.9249E−02 
                 5.2100E−02 
               
               
                 S3 
                 −1.2928E−02 
                  9.4709E−04 
                 3.0118E−02 
                 −6.6133E−02 
                 7.3832E−02 
               
               
                 S4 
                 −8.4167E−03 
                 −1.7363E−03 
                 3.3134E−02 
                 −8.7209E−02 
                 1.3230E−01 
               
               
                 S5 
                 −1.5335E−02 
                  5.7235E−03 
                 −3.1593E−02  
                  7.1237E−02 
                 −9.2544E−02  
               
               
                 S6 
                 −1.1271E−02 
                 −1.1075E−02 
                 3.8446E−02 
                 −8.3728E−02 
                 1.1228E−01 
               
               
                 S7 
                 −1.8906E−02 
                 −2.3317E−02 
                 5.9638E−02 
                 −1.0934E−01 
                 1.2169E−01 
               
               
                 S8 
                 −2.3027E−02 
                 −1.4783E−03 
                 4.7335E−03 
                 −1.0278E−02 
                 8.5400E−03 
               
               
                 S9 
                 −5.1036E−02 
                  1.9679E−02 
                 −1.0463E−02  
                  3.5983E−03 
                 −1.0105E−03  
               
               
                 S10 
                 −6.0065E−02 
                  2.2206E−02 
                 −7.8250E−03  
                  1.9909E−03 
                 −3.9141E−04  
               
               
                 S11 
                 −2.6145E−02 
                 −5.8706E−04 
                 1.7109E−03 
                 −8.0431E−04 
                 1.9874E−04 
               
               
                 S12 
                 −9.1447E−04 
                 −5.9431E−03 
                 1.7182E−03 
                 −2.6968E−04 
                 2.6043E−05 
               
               
                 S13 
                 −2.3444E−02 
                  2.5711E−03 
                 6.2884E−04 
                 −1.5368E−04 
                 1.4965E−05 
               
               
                 S14 
                 −2.2134E−02 
                  3.6695E−03 
                 −3.0028E−04  
                  5.4853E−06 
                 1.0764E−06 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Surface 
                   
                   
                   
                   
               
               
                   
                 number 
                 A14 
                 A16 
                 A18 
                 A20 
               
               
                   
                   
               
               
                   
                 S1 
                  6.4084E−03 
                 −1.9944E−03  
                  3.5053E−04 
                 −2.6732E−05  
               
               
                   
                 S2 
                 −3.2199E−02 
                 1.1754E−02 
                 −2.3498E−03 
                 1.9811E−04 
               
               
                   
                 S3 
                 −4.8466E−02 
                 1.8875E−02 
                 −4.0346E−03 
                 3.6429E−04 
               
               
                   
                 S4 
                 −1.2132E−01 
                 6.6837E−02 
                 −2.0312E−02 
                 2.6311E−03 
               
               
                   
                 S5 
                  7.1662E−02 
                 −3.2295E−02  
                  7.7706E−03 
                 −7.6699E−04  
               
               
                   
                 S6 
                 −9.1443E−02 
                 4.4544E−02 
                 −1.1809E−02 
                 1.3013E−03 
               
               
                   
                 S7 
                 −8.3008E−02 
                 3.3995E−02 
                 −7.5574E−03 
                 6.9403E−04 
               
               
                   
                 S8 
                 −3.7630E−03 
                 9.0962E−04 
                 −1.0174E−04 
                 2.9338E−06 
               
               
                   
                 S9 
                  1.9385E−04 
                 −1.3079E−05  
                 −1.0824E−06 
                 1.3434E−07 
               
               
                   
                 S10 
                  6.6262E−05 
                 −8.2700E−06  
                  5.9736E−07 
                 −1.8039E−08  
               
               
                   
                 S11 
                 −2.9562E−05 
                 2.6770E−06 
                 −1.3440E−07 
                 2.8370E−09 
               
               
                   
                 S12 
                 −1.2043E−06 
                 −1.3067E−08  
                  3.5055E−09 
                 −9.5188E−11  
               
               
                   
                 S13 
                 −8.1821E−07 
                 2.6359E−08 
                 −4.6946E−10 
                 3.5780E−12 
               
               
                   
                 S14 
                 −1.0642E−07 
                 4.5550E−09 
                 −9.6379E−11 
                 8.1094E−13 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 8A  illustrates a longitudinal aberration curve of the first optical system according to example 4, representing deviations of focal points converged by light of different wavelengths after passing through the optical system.  FIG. 8B  illustrates an astigmatic curve of the first optical system according to example 4, representing a curvature of a tangential plane and a curvature of a sagittal plane.  FIG. 8C  illustrates a distortion curve of the first optical system according to example 4, representing amounts of distortion corresponding to different image heights.  FIG. 8D  illustrates a lateral color curve of the first optical system according to example 4, representing deviations of different image heights on an imaging plane after light passes through the optical system. It can be seen from  FIG. 8A  to  FIG. 8D  that the first optical system provided in example 4 may achieve good image quality. 
     EXAMPLE 5 
     A first optical system according to example 5 of the present disclosure is described below with reference to  FIG. 9  to  FIG. 10D .  FIG. 9  shows a schematic structural view of the first optical system according to example 5 of the present disclosure. 
     As shown in  FIG. 9 , the first optical system includes a stop STO, a first lens E 1 , a second lens E 2 , a third lens E 3 , a fourth lens E 4 , a fifth lens E 5 , a sixth lens E 6 , a seventh lens E 7 , an optical filter E 8  and an imaging plane S 17 , which are sequentially arranged from an object side to an image side. 
     The first lens E 1  has positive refractive power, an object-side surface S 1  thereof is a convex surface, and an image-side surface S 2  thereof is a concave surface. The second lens E 2  has negative refractive power, an object-side surface S 3  thereof is a convex surface, and an image-side surface S 4  thereof is a concave surface. The third lens E 3  has negative refractive power, an object-side surface S 5  thereof is a convex surface, and an image-side surface S 6  thereof is a concave surface. The fourth lens E 4  has negative refractive power, an object-side surface S 7  thereof is a convex surface, and an image-side surface S 8  thereof is a concave surface. The fifth lens E 5  has negative refractive power, an object-side surface S 9  thereof is a convex surface, and an image-side surface S 10  thereof is a concave surface. The sixth lens E 6  has positive refractive power, an object-side surface S 11  thereof is a convex surface, and an image-side surface S 12  thereof is a convex surface. The seventh lens E 7  has negative refractive power, an object-side surface S 13  thereof is a concave surface, and an image-side surface S 14  thereof is a concave surface. The optical filter E 8  has an object-side surface S 15  and an image-side surface S 16 . Light from an object sequentially passes through the respective surfaces S 1  to S 16  and is finally imaged on the imaging plane S 17 . 
     In this example, a total effective focal length f of the first optical system is 6.85 mm, and a maximum field-of-view FOV of the first optical system is 85.5°. 
     Table 9 is a table illustrating basic parameters of the first optical system of example 5, wherein the units for the radius of curvature, the thickness/distance and the focal length are millimeter (mm). Table 10 shows high-order coefficients applicable to each aspheric surface in example 5, wherein the surface shape of each aspheric surface may be defined by the formula (2) given in the above example 5. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 9 
               
             
            
               
                   
                   
               
               
                   
                 Material 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                 Thickness/ 
                 Refractive 
                 Abbe 
                 Focal 
                 Conic 
               
               
                 number 
                 type 
                 curvature 
                 Distance 
                 index 
                 number 
                 length 
                 coefficient 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinite 
                 Infinite 
                   
                   
                   
                   
               
               
                 STO 
                 Spherical 
                 Infinite 
                 −0.7223 
               
               
                 S1 
                 Aspheric 
                 2.5356 
                 0.9675 
                 1.546 
                 56.11 
                 5.26 
                 0.0330 
               
               
                 S2 
                 Aspheric 
                 12.1943 
                 0.0350 
                   
                   
                   
                 −6.4427 
               
               
                 S3 
                 Aspheric 
                 8.3285 
                 0.3000 
                 1.666 
                 20.4 
                 −13.01 
                 6.6281 
               
               
                 S4 
                 Aspheric 
                 4.2297 
                 0.1827 
                   
                   
                   
                 1.5368 
               
               
                 S5 
                 Aspheric 
                 5.0485 
                 0.3429 
                 1.546 
                 56.11 
                 −666.67 
                 −14.6424 
               
               
                 S6 
                 Aspheric 
                 9.2536 
                 0.3641 
                   
                   
                   
                 34.1015 
               
               
                 S7 
                 Aspheric 
                 61.0782 
                 0.4300 
                 1.666 
                 20.4 
                 −500.00 
                 −99.0000 
               
               
                 S8 
                 Aspheric 
                 51.4796 
                 0.4414 
                   
                   
                   
                 −99.0000 
               
               
                 S9 
                 Aspheric 
                 11.1496 
                 0.4700 
                 1.645 
                 23.49 
                 −69.18 
                 5.8539 
               
               
                 S10 
                 Aspheric 
                 8.7720 
                 0.7363 
                   
                   
                   
                 −3.1326 
               
               
                 S11 
                 Aspheric 
                 7.1731 
                 0.8408 
                 1.546 
                 56.11 
                 7.47 
                 −12.2893 
               
               
                 S12 
                 Aspheric 
                 −9.0683 
                 1.0800 
                   
                   
                   
                 −13.9664 
               
               
                 S13 
                 Aspheric 
                 −5.0125 
                 0.6400 
                 1.536 
                 55.74 
                 −4.50 
                 −0.7279 
               
               
                 S14 
                 Aspheric 
                 4.8608 
                 0.2753 
                   
                   
                   
                 −28.1872 
               
               
                 S15 
                 Spherical 
                 Infinite 
                 0.2100 
                 1.517 
                 64.17 
               
               
                 S16 
                 Spherical 
                 Infinite 
                 0.4839 
               
               
                 S17 
                 Spherical 
                 Infinite 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 10 
               
               
                   
               
             
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 A4 
                 A6 
                 A8 
                 A10 
                 A12 
               
               
                   
               
               
                 S1 
                  8.5098E−02 
                 −3.5122E−02  
                 1.6756E−02 
                 −8.5459E−03 
                  5.2011E−03 
               
               
                 S2 
                  3.6270E−02 
                 −5.6464E−02  
                 3.4545E−02 
                  4.4092E−03 
                 −2.2870E−02 
               
               
                 S3 
                 −1.1660E−01 
                 −7.2716E−04  
                 1.8144E−02 
                 −7.7704E−03 
                 −9.4056E−04 
               
               
                 S4 
                  2.0467E−02 
                 −4.8404E−02  
                 3.5916E−04 
                  1.2100E−02 
                  6.5157E−03 
               
               
                 S5 
                 −2.4374E−01 
                 3.7291E−02 
                 −3.4405E−03  
                 −1.9955E−03 
                  9.4524E−05 
               
               
                 S6 
                 −2.3592E−01 
                 9.2749E−02 
                 −4.0701E−02  
                  1.9913E−02 
                 −1.1012E−02 
               
               
                 S7 
                 −1.9563E−01 
                 −1.6697E−02  
                 −3.2116E−03  
                 −5.1881E−04 
                 −5.9670E−04 
               
               
                 S8 
                 −3.5946E−01 
                 2.9270E−02 
                 2.4749E−02 
                  8.6791E−03 
                 −2.0694E−03 
               
               
                 S9 
                 −8.8536E−01 
                 1.9735E−02 
                 1.6185E−02 
                  1.4505E−02 
                 −4.4017E−03 
               
               
                 S10 
                 −9.6932E−01 
                 9.6506E−02 
                 −4.0832E−02  
                 −2.1075E−03 
                 −7.3852E−03 
               
               
                 S11 
                 −1.4147E+00 
                 3.2622E−01 
                 5.4739E−02 
                 −6.2351E−02 
                 −2.1931E−02 
               
               
                 S12 
                 −1.8000E−01 
                 −4.5397E−02  
                 1.4612E−01 
                 −3.2705E−03 
                 −3.5400E−02 
               
               
                 S13 
                  1.7402E+00 
                 6.2567E−02 
                 −1.8881E−01  
                  1.4519E−01 
                 −7.6250E−02 
               
               
                 S14 
                 −1.8384E+00 
                 2.2601E−01 
                 −1.3219E−01  
                  7.3591E−02 
                 −2.6020E−02 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Surface 
                   
                   
                   
                   
               
               
                   
                 number 
                 A14 
                 A16 
                 A18 
                 A20 
               
               
                   
                   
               
               
                   
                 S1 
                 −3.1564E−03 
                  1.6999E−03 
                 −6.9490E−04 
                  1.8696E−04 
               
               
                   
                 S2 
                  2.2743E−02 
                 −1.4483E−02 
                  5.1237E−03 
                 −1.1262E−03 
               
               
                   
                 S3 
                  4.3547E−03 
                 −4.7199E−03 
                  1.9168E−03 
                 −5.6998E−04 
               
               
                   
                 S4 
                 −2.0127E−02 
                  1.6108E−02 
                 −6.7866E−03 
                  1.2447E−03 
               
               
                   
                 S5 
                  5.4532E−04 
                 −4.5185E−04 
                  1.4262E−04 
                 −2.7852E−05 
               
               
                   
                 S6 
                  5.8940E−03 
                 −2.6674E−03 
                  8.5902E−04 
                 −1.3272E−04 
               
               
                   
                 S7 
                 −3.1702E−04 
                 −2.3772E−04 
                 −9.2162E−05 
                 −3.4690E−05 
               
               
                   
                 S8 
                 −3.0477E−03 
                 −2.1602E−03 
                 −8.2404E−04 
                 −2.2786E−04 
               
               
                   
                 S9 
                 −3.3705E−03 
                 −1.5746E−03 
                 −3.1236E−04 
                 −4.2786E−05 
               
               
                   
                 S10 
                 −3.5779E−04 
                 −7.4431E−04 
                 −3.4065E−04 
                 −1.1798E−04 
               
               
                   
                 S11 
                  6.5051E−03 
                 −2.1144E−03 
                 −3.9243E−03 
                 −5.7938E−04 
               
               
                   
                 S12 
                 −9.4872E−03 
                  2.3927E−04 
                  1.9463E−03 
                  2.7725E−03 
               
               
                   
                 S13 
                  2.8678E−02 
                 −7.8867E−03 
                  1.5676E−03 
                 −1.7318E−04 
               
               
                   
                 S14 
                  1.2456E−02 
                 −7.1777E−03 
                  8.1348E−04 
                  3.4130E−04 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 10A  illustrates a longitudinal aberration curve of the first optical system according to example 5, representing deviations of focal points converged by light of different wavelengths after passing through the optical system.  FIG. 10B  illustrates an astigmatic curve of the first optical system according to example 5, representing a curvature of a tangential plane and a curvature of a sagittal plane.  FIG. 10C  illustrates a distortion curve of the first optical system according to example 5, representing amounts of distortion corresponding to different image heights.  FIG. 10D  illustrates a lateral color curve of the first optical system according to example 5, representing deviations of different image heights on an imaging plane after light passes through the optical system. It can be seen from  FIG. 10A  to  FIG. 10D  that the first optical system provided in example 5 may achieve good image quality. 
     In view of the above, examples 1 to 5 respectively satisfy the relationship shown in Table 11. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 11 
               
               
                   
               
               
                 Condition/Example 
                 1 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 TTL2/F2 
                 0.24 
                 0.24 
                 0.24 
                   
                   
               
               
                 DT1/ImgH2 
                 3.18 
                 3.18 
                 3.18 
                   
                   
               
               
                 DT2/DT1 
                 0.46 
                 0.46 
                 0.46 
                   
                   
               
               
                 BFL/ImgH2 
                 3.10 
                 3.10 
                 3.10 
                   
                   
               
               
                 (N1 + N2 + N3)/3 
                 1.55 
                 1.55 
                 1.55 
                   
                   
               
               
                 F2/R1 
                 −0.85 
                 −0.85 
                 −0.85 
                   
                   
               
               
                 F2/R2 
                 −1.08 
                 −1.08 
                 −1.08 
                   
                   
               
               
                 F2/f1 
                 4.45 
                 4.62 
                 4.62 
                   
                   
               
               
                 F2/f2 
                 −7.40 
                 −7.79 
                 −7.79 
                   
                   
               
               
                 F2/f3 
                 3.33 
                 3.49 
                 3.49 
                   
                   
               
               
                 TTL1/F1 
                   
                   
                   
                 1.15 
                 1.14 
               
               
                 ImgH1/F1 
                   
                   
                   
                 0.97 
                 0.94 
               
               
                   
               
            
           
         
       
     
     The present disclosure further provides an imaging apparatus, having an electronic photosensitive element which may be a photosensitive Charge-Coupled Device (CCD) or a Complementary Metal-Oxide Semiconductor (CMOS). The imaging apparatus may be an independent imaging device such as a digital camera, or may be an imaging module integrated in a mobile electronic device such as a mobile phone. The imaging apparatus is equipped with the camera apparatus described above. 
     The foregoing is only a description of the preferred examples of the present disclosure and the applied technical principles. It should be appreciated by those skilled in the art that the inventive scope of the present disclosure is not limited to the technical solutions formed by the particular combinations of the above technical features. The inventive scope should also cover other technical solutions formed by any combinations of the above technical features or equivalent features thereof without departing from the concept of the invention, such as, technical solutions formed by replacing the features as disclosed in the present disclosure with (but not limited to), technical features with similar functions.