Patent Publication Number: US-11644652-B2

Title: Mobile device and optical imaging lens thereof

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/852,242, filed Apr. 17, 2020, which is a continuation of U.S. patent application Ser. No. 15/652,569, filed Jul. 18, 2017, now U.S. Pat. No. 10,678,023, which is a continuation of U.S. patent application Ser. No. 14/795,801, filed on Jul. 9, 2015, now U.S. Pat. No. 9,746,639, which is a continuation of U.S. patent application Ser. No. 13/963,717, filed on Aug. 9, 2013, now U.S. Pat. No. 9,097,876, which claims priority to Chinese Patent Application No. 201310159899.7, filed on May 3, 2013, the disclosures of which are hereby incorporated by reference in their entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a mobile device and an optical imaging lens thereof, and particularly, relates to a mobile device applying an optical imaging lens having six lens elements and an optical imaging lens thereof. 
     BACKGROUND 
     The ever-increasing demand for smaller sized mobile devices, such as cell phones, digital cameras, etc. has correspondingly triggered a growing need for smaller sized photography modules contained therein. Size reductions may be contributed from various aspects of the mobile devices, which includes not only the charge coupled device (CCD) and the complementary metal-oxide semiconductor (CMOS), but also the optical imaging lens mounted therein. When reducing the size of the optical imaging lens, however, achieving good optical characteristics becomes a challenging problem. 
     The conventional optical imaging lenses generally have six lens elements. Since less number of the lens elements, the total length of the conventional optical imaging lenses could be limited to a certain length range. However, the ever-increasing demand for high standard productions, such as 12 million pixels smart phones or digital cameras, etc. has correspondingly triggered a growing need for high resolution and high quality. Therefore, there is needed to develop an optical imaging lens having six lens elements for high specification products. 
     SUMMARY 
     An object of the present invention is to provide a mobile device and an optical imaging lens thereof. With controlling the convex or concave shape of the surfaces of the lens elements, the length of the optical imaging lens is shortened and meanwhile the good optical characters, such as high resolution, are sustained. 
     In an exemplary embodiment, an optical imaging lens, sequentially from an object side to an image side, comprises first, second, third, fourth, fifth and sixth lens elements, each of the lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side, in which the object-side surface of the first lens element comprises a convex portion in a vicinity of the optical axis; the image-side surface of the second lens element comprises a concave portion in a vicinity of a periphery of the second lens element; the image-side surface of the third lens element comprises a convex portion in a vicinity of a periphery of the third lens element; the image-side surface of the fourth lens element comprises a convex portion in a vicinity of the optical axis; the image-side surface of the fifth lens element comprises a convex portion in a vicinity of a periphery of the fifth lens element; and the image-side surface of the sixth lens element comprises a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the sixth lens element; the optical imaging lens as a whole having only the six lens elements having refractive power. Accordingly, with controlling the convex or concave shape of the surfaces of these lens elements, the length of the optical imaging lens is shortened efficiently and meanwhile the aberration is eliminated for sustaining good optical characters. 
     In an exemplary embodiment, the object-side surface of the sixth lens element may be designed to have a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the sixth lens element, the image-side surface of the third lens element may be designed to have a convex portion in a vicinity of the optical axis, and the image-side surface of the fourth lens element may be designed to have a convex portion in a vicinity of a periphery of the fourth lens element. Accordingly, with controlling the convex or concave shape of the surfaces of these lens elements, the length of the optical imaging lens is shortened efficiently and meanwhile the aberration is eliminated for sustaining good optical characters. 
     In another exemplary embodiment, some equation(s), such as those relating to the ratio among parameters could be taken into consideration. For example, an effective focal length of the optical imaging lens, EFL, and a central thickness of the third lens element along the optical axis, CT3, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         6 
                         . 
                         0 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         E 
                         ⁢ 
                         F 
                         ⁢ 
                         L 
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         3 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a distance from the object-side surface of the first lens element to the image-side surface of the sixth lens element, TL, and a central thickness of the sixth lens element along the optical axis, CT6, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         7 
                         . 
                         6 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         T 
                         ⁢ 
                         L 
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         6 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the fifth lens element and the sixth lens element, AC56, a central thickness of the second lens element along the optical axis, CT2, and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         5 
                         . 
                         0 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         E 
                         ⁢ 
                         F 
                         ⁢ 
                         L 
                       
                       
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           2 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           5 
                           ⁢ 
                           6 
                         
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the second lens element and the third lens element, AC23, an air gap between the third lens element and the fourth lens element, AC34, and CT3 could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         2 
                         . 
                         3 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           2 
                           ⁢ 
                           3 
                         
                         + 
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           3 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           3 
                           ⁢ 
                           4 
                         
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         3 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a sum of all air gaps from the first lens element to the sixth lens element along the optical axis, AAG, AC23, and AC34 could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       A 
                       ⁢ 
                       A 
                       ⁢ 
                       G 
                     
                     
                       
                         A 
                         ⁢ 
                         C 
                         ⁢ 
                         2 
                         ⁢ 
                         3 
                       
                       + 
                       
                         A 
                         ⁢ 
                         C 
                         ⁢ 
                         3 
                         ⁢ 
                         4 
                       
                     
                   
                   ≤ 
                   
                     1.81 
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     5 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the first lens element and the second lens element, AC12, an air gap between the fourth lens element and the fifth lens element, AC45, AC34 and AC56 could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   1.20 
                   ≤ 
                   
                     
                       
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           2 
                           ⁢ 
                           3 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           3 
                           ⁢ 
                           4 
                         
                       
                       
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           1 
                           ⁢ 
                           2 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           4 
                           ⁢ 
                           5 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           5 
                           ⁢ 
                           6 
                         
                       
                     
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     6 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the fourth lens element along the optical axis, CT4, a central thickness of the fifth lens element along the optical axis, CT5, and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       E 
                       ⁢ 
                       F 
                       ⁢ 
                       L 
                     
                     
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         4 
                       
                       + 
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         5 
                       
                     
                   
                   ≤ 
                   
                     5.40 
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     7 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, the sum of the thickness of all six lens elements along the optical axis, ALT, and a central thickness of the sixth lens element along the optical axis, CT6, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         5 
                         . 
                         5 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         A 
                         ⁢ 
                         L 
                         ⁢ 
                         T 
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         6 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     8 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the fifth lens element and the sixth lens element, AC56, CT6 and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         6 
                         . 
                         3 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         E 
                         ⁢ 
                         F 
                         ⁢ 
                         L 
                       
                       
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           6 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           5 
                           ⁢ 
                           6 
                         
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     9 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the third lens element, CT3, and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         8 
                         . 
                         3 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         E 
                         ⁢ 
                         F 
                         ⁢ 
                         L 
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         3 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     
                       1 
                       ′ 
                     
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the second lens element, CT2, a central thickness of the fourth lens element, CT4, and a central thickness of the fifth lens element, CT5, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         2 
                         . 
                         8 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           4 
                         
                         + 
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           5 
                         
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         2 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     10 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the second lens element, CT2, an air gap between the fifth lens element and the sixth lens element, AC56, and TL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         5 
                         . 
                         5 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         T 
                         ⁢ 
                         L 
                       
                       
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           2 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           5 
                           ⁢ 
                           6 
                         
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     11 
                     ) 
                   
                 
               
             
           
         
       
     
     Aforesaid exemplary embodiments are not limited and could be selectively incorporated in other embodiments described herein. 
     In another exemplary embodiment, a mobile device comprises a housing and a photography module. The photography module is positioned in the housing and comprises a lens barrel, an optical imaging lens, a module housing unit, and an image sensor. The optical image lens is positioned in the lens barrel. The module housing unit is configured to provide a space where the lens barrel is positioned. The image sensor is positioned at the image side of the optical imaging lens. 
     In exemplary embodiments, the module housing unit comprises, but is not limited to, a lens backseat, which comprises a first lens seat and a second lens seat, in which the first lens seat is positioned close to the outside of the lens barrel and along with an axis, the second lens seat is positioned along the axis and around the outside of the first lens seat, and the lens barrel and the optical imaging lens positioned therein are driven by the first lens seat to move along the axis. 
     In exemplary embodiments, the module housing unit further comprises, but is not limited to, an image sensor backseat positioned between the first lens seat, the second lens seat and the image sensor, and close to the second lens seat. 
     Through controlling the arrangement of the convex or concave shape of the surface of the lens element(s) and/or refractive power, the mobile device and the optical imaging lens thereof in aforesaid exemplary embodiments achieve good optical characters and effectively shorten the lengths of the optical imaging lens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: 
         FIG.  1    is a cross-sectional view of a lens element of one embodiment of an optical imaging lens according to the present disclosures; 
         FIG.  2    is a cross-sectional view of a first embodiment of the optical imaging lens having six lens elements according to the present disclosures; 
         FIG.  3    is a chart of longitudinal spherical aberration and other kinds of optical aberrations of the first embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  4    is a table of optical data for each lens element of the optical imaging lens of the first embodiment of the present disclosures; 
         FIG.  5    is a table of aspherical data of the first embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  6    is a cross-sectional view of a second embodiment of an optical imaging lens having six lens elements according to the present disclosures; 
         FIG.  7    is a chart of longitudinal spherical aberration and other kinds of optical aberrations of the second embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  8    is a table of optical data for each lens element of the optical imaging lens of the second embodiment of the present disclosures; 
         FIG.  9    is a table of aspherical data of the second embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  10    is a cross-sectional view of a third embodiment of an optical imaging lens having six lens elements according to the present disclosures; 
         FIG.  11    is a chart of longitudinal spherical aberration and other kinds of optical aberrations of the third embodiment of the optical imaging lens according the present disclosures; 
         FIG.  12    is a table of optical data for each lens element of the optical imaging lens of the third embodiment of the present disclosures; 
         FIG.  13    is a table of aspherical data of the third embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  14    is a cross-sectional view of a fourth embodiment of an optical imaging lens having six lens elements according to the present disclosures; 
         FIG.  15    is a chart of longitudinal spherical aberration and other kinds of optical aberrations of the fourth embodiment of the optical imaging lens according the present disclosures; 
         FIG.  16    is a table of optical data for each lens element of the optical imaging lens of the fourth embodiment of the present disclosures; 
         FIG.  17    is a table of aspherical data of the fourth embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  18    is a cross-sectional view of a fifth embodiment of an optical imaging lens having six lens elements according to the present disclosures; 
         FIG.  19    is a chart of longitudinal spherical aberration and other kinds of optical aberrations of the fifth embodiment of the optical imaging lens according the present disclosures; 
         FIG.  20    is a table of optical data for each lens element of the optical imaging lens of the fifth embodiment of the present disclosures; 
         FIG.  21    is a table of aspherical data of a fifth embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  22    is a cross-sectional view of a sixth embodiment of an optical imaging lens having six lens elements according to the present disclosures; 
         FIG.  23    is a chart of longitudinal spherical aberration and other kinds of optical aberrations of the sixth embodiment of the optical imaging lens according the present disclosures; 
         FIG.  24    is a table of optical data for each lens element of the optical imaging lens of the sixth embodiment of the present disclosures; 
         FIG.  25    is a table of aspherical data of the sixth embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  26    is a cross-sectional view of a seventh embodiment of an optical imaging lens having six lens elements according to the present disclosures; 
         FIG.  27    is a chart of longitudinal spherical aberration and other kinds of optical aberrations of the seventh embodiment of the optical imaging lens according the present disclosures; 
         FIG.  28    is a table of optical data for each lens element of the optical imaging lens of the seventh embodiment of the present disclosures; 
         FIG.  29    is a table of aspherical data of the seventh embodiment of the optical imaging lens according to the present disclosures; 
         FIG.  30    is a table for the values of 
                   E   ⁢   F   ⁢   L       C   ⁢   T   ⁢   3       ,       T   ⁢   L       C   ⁢   T   ⁢   6       ,     EFL       CT   ⁢           ⁢   2     +     A   ⁢           ⁢   C   ⁢           ⁢   56         ,         A   ⁢   C   ⁢   2   ⁢   3     +     C   ⁢   T   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4         C   ⁢   T   ⁢   3       ,       A   ⁢   A   ⁢   G         A   ⁢   C   ⁢   2   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4         ,         A   ⁢   C   ⁢   2   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4           A   ⁢   C   ⁢   1   ⁢   2     +     A   ⁢   C   ⁢   4   ⁢   5     +     A   ⁢   C   ⁢   5   ⁢   6         ,       E   ⁢   F   ⁢   L         C   ⁢   T   ⁢   4     +     C   ⁢   T   ⁢   5         ,       A   ⁢   L   ⁢   T       C   ⁢   T   ⁢   6       ,       E   ⁢   F   ⁢   L         C   ⁢   T   ⁢   6     +     A   ⁢   C   ⁢   5   ⁢   6         ,         C   ⁢   T   ⁢   4     +     C   ⁢   T   ⁢   5         C   ⁢   T   ⁢   2       ,     and   ⁢           ⁢       T   ⁢   L         C   ⁢   T   ⁢   2     +     A   ⁢   C   ⁢   5   ⁢   6                 
of all seven example embodiments;
 
         FIG.  31    is a structure of an example embodiment of a mobile device; and 
         FIG.  32    is a partially enlarged view of the structure of another example embodiment of a mobile device. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features. Persons having ordinary skill in the art will understand other varieties for implementing example embodiments, including those described herein. The drawings are not limited to specific scale and similar reference numbers are used for representing similar elements. As used in the disclosures and the appended claims, the terms “example embodiment,” “exemplary embodiment,” and “present embodiment” do not necessarily refer to a single embodiment, although it may, and various example embodiments may be readily combined and interchanged, without departing from the scope or spirit of the present invention. Furthermore, the terminology as used herein is for the purpose of describing example embodiments only and is not intended to be a limitation of the invention. In this respect, as used herein, the term “in” may include “in” and “on”, and the terms “a”, “an” and “the” may include singular and plural references. Furthermore, as used herein, the term “by” may also mean “from”, depending on the context. Furthermore, as used herein, the term “if” may also mean “when” or “upon”, depending on the context. Furthermore, as used herein, the words “and/or” may refer to and encompass any and all possible combinations of one or more of the associated listed items. 
     As used in the disclosures, the description “a lens element has a positive refractive power (or a negative refractive power)” means a portion of the lens in a vicinity of the optical axis has a positive refractive power (or a negative refractive power). Furthermore, as used herein, the description “an object-side (or the image-side) of a lens element comprises a convex portion (or a concave portion) in a certain region” means the portion in the certain region parallel to the optical axis is more convex outward (or more concave inward) than that in the outside region close to the certain region in the radial direction. As shown in  FIG.  1   , the axis I represents the optical axis and the lens element is symmetric about the axis I in the radial direction. The object-side surface of the lens element comprises a convex portion in the A region, a concave portion in the B region, and a convex portion in the C region. The portion in the A region parallel to the optical axis is more convex outward than the portion in the outside region (B region) close to the A region in the radial direction. The portion in the B region is more concave inward than the portion in the C region. The portion in the C region is more convex outward than the E region. Furthermore, as used herein, the description “in a vicinity of a periphery of a lens element” means in the vicinity of the periphery region on the surface of the lens element only where the imaging light passes, such as the C region. The imaging light comprises a chief ray Lc and a marginal ray Lm. Furthermore, as used herein, the description “in a vicinity of the optical axis” means in the vicinity of the optical axis on the surface of the lens element only where the imaging light passes, such as the A region. Besides, the lens element further comprises a protruding part E for mounting the lens element in an optical imaging lens, and ideally, the imaging light will not pass through the protruding part E. The structure and the shape of the protruding part E is not limited to this configuration illustrated in the  FIG.  1   . To clearly illustrate the structure of each lens element, each portion of the protruding part E in the embodiments is omitted. 
     Example embodiments of an optical imaging lens may comprise a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element, in which each of the lens elements has an object-side surface facing toward the object side and an image-side surface facing toward the image side. These lens elements may be arranged sequentially from the object side to the image side, and example embodiments of the lens as a whole may comprise the six lens elements having refractive power. In an example embodiment: the object-side surface of the first lens element comprises a convex portion in a vicinity of the optical axis; the image-side surface of the second lens element comprises a concave portion in a vicinity of a periphery of the second lens element; the image-side surface of the third lens element comprises a convex portion in a vicinity of a periphery of the third lens element; the image-side surface of the fourth lens element comprises a convex portion in a vicinity of the optical axis; the image-side surface of the fifth lens element comprises a convex portion in a vicinity of a periphery of the fifth lens element; and the image-side surface of the sixth lens element comprises a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the sixth lens element. 
     The designed characteristics of the lens elements in aforesaid exemplary embodiments are taken the optical characters and the lengths of the optical imaging lens into consideration. For example, the first lens element has a positive refractive power, the object-side surface of the first lens element comprises a convex portion in a vicinity of the optical axis, and the image-side surface of the first lens element comprises a convex portion in a vicinity of a periphery of the first lens element for assisting the optical imaging lens to converge the light. In conjunction with the above-mention design on the surfaces of the lens elements, the image-side surface of the second lens element comprises a concave portion in a vicinity of a periphery of the second lens element, the image-side surface of the third lens element comprises a convex portion in a vicinity of a periphery of the third lens element, the image-side surface of the fourth lens element comprises a convex portion in a vicinity of the optical axis, the image-side surface of the fifth lens element comprises a convex portion in a vicinity of a periphery of the fifth lens element, and the image-side surface of the sixth lens element comprises a concave portion in a vicinity of the optical axis for eliminating the aberration. Further, the object-side surface of the second lens element comprises a convex portion in a vicinity of the optical axis, a convex portion in a vicinity of a periphery of the second lens element, and a concave portion between a vicinity of the optical axis and a vicinity of a periphery of the second lens element for improving the efficiency of aberration elimination. Besides, the image-side surface of the sixth lens element comprises a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the sixth lens element for assisting the optical imaging lens to correct the field curvature of the optical imaging lens, reduce the high order aberration of the optical imaging lens, and depress the angle of the chief ray (the incident angle of the light onto the image sensor), and then the sensitivity of the whole system is promoted. Additionally, the object-side surface of the sixth lens element comprises a convex portion in a vicinity of a periphery of the sixth lens element for assisting the optical imaging lens to eliminate edge aberration. Therefore, the present embodiment achieves great optical performance. 
     In another exemplary embodiment, the ratio of related parameters of the optical imaging lens could be controlled to satisfy equations for assisting the designer to design the optical imaging lens with good optical characteristics and short total length under practicable technic, such as an effective focal length of the optical imaging lens, EFL, and a central thickness of the third lens element along the optical axis, CT3, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         6 
                         . 
                         0 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         E 
                         ⁢ 
                         F 
                         ⁢ 
                         L 
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         3 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a distance from the object-side surface of the first lens element to the image-side surface of the sixth lens element, TL, and a central thickness of the sixth lens element along the optical axis, CT6, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         7 
                         . 
                         6 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         T 
                         ⁢ 
                         L 
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         6 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the fifth lens element and the sixth lens element, AC56, a central thickness of the second lens element along the optical axis, CT2, and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         5 
                         . 
                         0 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       EFL 
                       
                         
                           CT 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         + 
                         
                           A 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           C 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           56 
                         
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the second lens element and the third lens element, AC23, an air gap between the third lens element and the fourth lens element, AC34, and CT3 could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         2 
                         . 
                         3 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           2 
                           ⁢ 
                           3 
                         
                         + 
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           3 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           3 
                           ⁢ 
                           4 
                         
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         3 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a sum of all air gaps from the first lens element to the sixth lens element along the optical axis, AAG, AC23, and AC34 could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     AAG 
                     
                       
                         A 
                         ⁢ 
                         C 
                         ⁢ 
                         2 
                         ⁢ 
                         3 
                       
                       + 
                       
                         A 
                         ⁢ 
                         C 
                         ⁢ 
                         3 
                         ⁢ 
                         4 
                       
                     
                   
                   ≤ 
                   
                     1.81 
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     5 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the first lens element and the second lens element, AC12, an air gap between the fourth lens element and the fifth lens element, AC45, AC34 and AC56 could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   1.20 
                   ≤ 
                   
                     
                       
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           2 
                           ⁢ 
                           3 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           3 
                           ⁢ 
                           4 
                         
                       
                       
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           1 
                           ⁢ 
                           2 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           4 
                           ⁢ 
                           5 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           5 
                           ⁢ 
                           6 
                         
                       
                     
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     6 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the fourth lens element along the optical axis, CT4, a central thickness of the fifth lens element along the optical axis, CT5, and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     EFL 
                     
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         4 
                       
                       + 
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         5 
                       
                     
                   
                   ≤ 
                   
                     5.40 
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     7 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, the sum of the thickness of all six lens elements along the optical axis, ALT, and a central thickness of the sixth lens element along the optical axis, CT6, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         5 
                         . 
                         5 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         A 
                         ⁢ 
                         L 
                         ⁢ 
                         T 
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         6 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     8 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, an air gap between the fifth lens element and the sixth lens element, AC56, CT6 and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         6 
                         . 
                         3 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       EFL 
                       
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           6 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           5 
                           ⁢ 
                           6 
                         
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     9 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the third lens element, CT3, and EFL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         8 
                         . 
                         3 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       EFL 
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         3 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     
                       1 
                       ′ 
                     
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the second lens element, CT2, a central thickness of the fourth lens element, CT4, and a central thickness of the fifth lens element, CT5, could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         2 
                         . 
                         8 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           4 
                         
                         + 
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           5 
                         
                       
                       
                         C 
                         ⁢ 
                         T 
                         ⁢ 
                         2 
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     10 
                     ) 
                   
                 
               
             
           
         
       
     
     In another exemplary embodiment, a central thickness of the second lens element, CT2, an air gap between the fifth lens element and the sixth lens element, AC56, and TL could be controlled to satisfy the equation as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         5 
                         . 
                         5 
                       
                       ⁢ 
                       0 
                     
                     ≤ 
                     
                       
                         T 
                         ⁢ 
                         L 
                       
                       
                         
                           C 
                           ⁢ 
                           T 
                           ⁢ 
                           2 
                         
                         + 
                         
                           A 
                           ⁢ 
                           C 
                           ⁢ 
                           5 
                           ⁢ 
                           6 
                         
                       
                     
                   
                   . 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     11 
                     ) 
                   
                 
               
             
           
         
       
     
     Aforesaid exemplary embodiments are not limited and could be selectively incorporated in other embodiments described herein. 
     Reference is now made to Equation (1). The design for the value of 
               E   ⁢   F   ⁢   L       C   ⁢   T   ⁢   3           
is based on the effective focal length of the optical imaging lens, EFL. The effective focal length of the optical imaging lens, EFL, would be shrunken to meet the demand of small sized optical imaging lens. When
 
               E   ⁢   F   ⁢   L       C   ⁢   T   ⁢   3           
meets to Equation (1), the effective focal length of the optical imaging lens, EFL, and the central thickness of the third lens element along the optical axis, CT3, could be in proper range to prevent excessive central thickness of the third lens element along the optical axis, CT3, which is unfavorable for shortening the length of the optical imaging lens. If the value of
 
               E   ⁢   F   ⁢   L       C   ⁢   T   ⁢   3           
further satisfy the Equation (1′), the shorten range of the third lens element along the optical axis, CT3, is greater. More preferably, the value of
 
               E   ⁢   F   ⁢   L       C   ⁢   T   ⁢   3           
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             
               
                 
                   6 
                   . 
                   0 
                 
                 ⁢ 
                 0 
               
               ≤ 
               
                 
                   E 
                   ⁢ 
                   F 
                   ⁢ 
                   L 
                 
                 
                   C 
                   ⁢ 
                   T 
                   ⁢ 
                   3 
                 
               
               ≤ 
               
                 1 
                 ⁢ 
                 
                   5 
                   . 
                   0 
                 
                 ⁢ 
                 0 
               
             
             . 
           
         
       
     
     Reference is now made to Equation (2). The design for the value of 
               T   ⁢   L       C   ⁢   T   ⁢   6           
is based on the central thickness of the sixth lens element along the optical axis, CT6. The central thickness of the sixth lens element along the optical axis, CT6, would be shrunken to meet the demand of small sized optical imaging lens. When
 
               T   ⁢   L       C   ⁢   T   ⁢   6           
meets to Equation (2), the central thickness of the sixth lens element along the optical axis, CT6, and the distance from the object-side surface of the first lens element to the image-side surface of the sixth lens element, TL, could be in proper range to prevent excessive central thickness of the sixth lens element along the optical axis, CT6, which is unfavorable for shortening the length of the optical imaging lens. More preferably, the value of
 
               T   ⁢   L       C   ⁢   T   ⁢   6           
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             
               
                 
                   7 
                   . 
                   6 
                 
                 ⁢ 
                 0 
               
               ≤ 
               
                 
                   T 
                   ⁢ 
                   L 
                 
                 
                   C 
                   ⁢ 
                   T 
                   ⁢ 
                   6 
                 
               
               ≤ 
               
                 1 
                 ⁢ 
                 
                   3 
                   . 
                   0 
                 
                 ⁢ 
                 0 
               
             
             . 
           
         
       
     
     Reference is now made to Equation (3). The design for the value of 
               E   ⁢   F   ⁢   L         C   ⁢   T   ⁢   2     +     A   ⁢   C   ⁢   5   ⁢   6             
is based on the effective focal length of the optical imaging lens, EFL. The effective focal length of the optical imaging lens, EFL, would be shrunken to meet the demand of small sized optical imaging lens. When
 
               E   ⁢   F   ⁢   L         C   ⁢   T   ⁢   2     +     A   ⁢   C   ⁢   5   ⁢   6             
meets to Equation (3), the central thickness of the second lens element along the optical axis, CT2, and the air gap between the fifth lens element and the sixth lens element, AC56, could be in proper range to prevent excessive central thickness of the second lens element along the optical axis, CT2, and excessive air gap between the fifth lens element and the sixth lens element, AC56, that is unfavorable for shortening the length of the optical imaging lens. More preferably, the value of
 
               E   ⁢   F   ⁢   L         C   ⁢   T   ⁢   2     +     A   ⁢   C   ⁢   5   ⁢   6             
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             
               
                 
                   5 
                   . 
                   0 
                 
                 ⁢ 
                 0 
               
               ≤ 
               
                 
                   E 
                   ⁢ 
                   F 
                   ⁢ 
                   L 
                 
                 
                   
                     C 
                     ⁢ 
                     T 
                     ⁢ 
                     2 
                   
                   + 
                   
                     A 
                     ⁢ 
                     C 
                     ⁢ 
                     5 
                     ⁢ 
                     6 
                   
                 
               
               ≤ 
               
                 1 
                 ⁢ 
                 
                   5 
                   . 
                   0 
                 
                 ⁢ 
                 0 
               
             
             . 
           
         
       
     
     Reference is now made to Equation (4). The design for the value of 
                 A   ⁢   C   ⁢   2   ⁢   3     +     C   ⁢   T   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4         C   ⁢   T   ⁢   3           
is based on the path of light, the fabricating yield of each lens element, and the difficulties of assembling the optical imaging lens. When
 
                 A   ⁢   C   ⁢   2   ⁢   3     +     C   ⁢   T   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4         C   ⁢   T   ⁢   3           
meets to Equation (4), the air gap between the second lens element and the third lens element, AC23, the air gap between the third lens element and the fourth lens element, AC34, and the central thickness of the third lens element along the optical axis, CT3, could be in proper arrangement, that is favorable for shortening the length of the optical imaging lens. More preferably, the value of
 
                 A   ⁢   C   ⁢   2   ⁢   3     +     C   ⁢   T   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4         C   ⁢   T   ⁢   3           
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             
               
                 
                   2 
                   . 
                   3 
                 
                 ⁢ 
                 0 
               
               ≤ 
               
                 
                   
                     A 
                     ⁢ 
                     C 
                     ⁢ 
                     2 
                     ⁢ 
                     3 
                   
                   + 
                   
                     C 
                     ⁢ 
                     T 
                     ⁢ 
                     3 
                   
                   + 
                   
                     A 
                     ⁢ 
                     C 
                     ⁢ 
                     3 
                     ⁢ 
                     4 
                   
                 
                 
                   C 
                   ⁢ 
                   T 
                   ⁢ 
                   3 
                 
               
               ≤ 
               
                 
                   3 
                   . 
                   5 
                 
                 ⁢ 
                 0 
               
             
             . 
           
         
       
     
     Reference is now made to Equation (5). The design for the value of 
               A   ⁢   A   ⁢   G         A   ⁢   C   ⁢   2   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4             
is based on the air gap between the second lens element and the third lens element, AC23. Since the image-side surface of the second lens element comprises a concave portion in a vicinity of a periphery of the second lens element, the emitted light from the second lens element (imaging light) needs enough air gap to incident to a proper position on the third lens element. Hence, comparing to other air gaps, the shortened range of the air gap between the second lens element and the third lens element along the optical axis, A23, is under a considerable restriction. However, too small air gap between the second lens element and the third lens element along the optical axis, A23, would increase fabrication difficulties of each lens element. When
 
             AAG       A   ⁢   C   ⁢   2   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4             
meets to Equation (5) based on the path of light, and the fabricating difficulties of each lens element, the air gaps, AC23, AC34, and AAG could be in proper arrangement. More preferably, the value of
 
             AAG       A   ⁢   C   ⁢   2   ⁢   3     +     A   ⁢   C   ⁢   3   ⁢   4             
should be further restricted by an lower limit, for example but not limited to,
 
     
       
         
           
             1. 
             ≤ 
             
               AAG 
               
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   23 
                 
                 + 
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   34 
                 
               
             
             ≤ 
             
               1.81 
               . 
             
           
         
       
     
     Reference is now made to Equation (6). The design for the value of 
                 A   ⁢   C   ⁢   23     +     A   ⁢   C   ⁢   34           A   ⁢   C   ⁢   12     +     A   ⁢   C   ⁢   45     +     A   ⁢   C   ⁢   56             
is based on each air gap, the path of light, and the difficulties of assembling the optical imaging lens. When
 
                 A   ⁢   C   ⁢   23     +     A   ⁢   C   ⁢   34           A   ⁢   C   ⁢   12     +     A   ⁢   C   ⁢   45     +     A   ⁢   C   ⁢   56             
meets to Equation (6), each air gap could be in proper arrangement, which is favorable for shortening the length of the optical imaging lens. More preferably, the value of
 
                 A   ⁢   C   ⁢   23     +     A   ⁢   C   ⁢   34           A   ⁢   C   ⁢   12     +     A   ⁢   C   ⁢   45     +     A   ⁢   C   ⁢   56             
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             1.2 
             ≤ 
             
               
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   23 
                 
                 + 
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   34 
                 
               
               
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   12 
                 
                 + 
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   45 
                 
                 + 
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   56 
                 
               
             
             ≤ 
             
               2.5 
               . 
             
           
         
       
     
     Reference is now made to Equation (7). The design for the value of 
             EFL       CT   ⁢   4     +     CT   ⁢   5             
is based on the effective focal length of the optical imaging lens, EFL. The effective focal length of the optical imaging lens, EFL, would be shrunken to meet the demand of small sized optical imaging lens. When
 
             EFL       CT   ⁢   4     +     CT   ⁢   5             
meets to Equation (7), the central thickness of the fourth lens element along the optical axis, CT4, and the central thickness of the fifth lens element, CT5, would be in a proper range, which is favorable for shortening the length of the optical imaging lens. More preferably, the value of
 
             EFL       CT   ⁢   4     +     CT   ⁢   5             
should be further restricted by an lower limit, for example but not limited to,
 
     
       
         
           
             2.5 
             ≤ 
             
               EFL 
               
                 
                   CT 
                   ⁢ 
                   4 
                 
                 + 
                 
                   CT 
                   ⁢ 
                   5 
                 
               
             
             ≤ 
             
               5.4 
               . 
             
           
         
       
     
     Reference is now made to Equation (8). The design for the value of 
             ALT     CT   ⁢   6           
is based on the thickness of all six lens elements along the optical axis, ALT. The thickness of all six lens elements along the optical axis, ALT, would be shrunken to meet the demand of small sized optical imaging lens. When
 
             ALT     CT   ⁢   6           
meets to Equation (8), the central thickness of the sixth lens element along the optical axis, CT6, could be in proper range to prevent excessive central thickness of the sixth lens element along the optical axis, CT6. More preferably, the value of
 
             ALT     CT   ⁢   6           
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             5.5 
             ≤ 
             
               ALT 
               
                 CT 
                 ⁢ 
                 6 
               
             
             ≤ 
             
               8.5 
               . 
             
           
         
       
     
     Reference is now made to Equation (9). The design for the value of 
             EFL       CT   ⁢   6     +     A   ⁢   C   ⁢   56             
is based on the effective focal length of the optical imaging lens, EFL. The effective focal length of the optical imaging lens, EFL, would be shrunken to meet the demand of small sized optical imaging lens. When
 
             EFL       CT   ⁢   6     +     A   ⁢   C   ⁢   56             
meets to Equation (9), the central thickness of the sixth lens element along the optical axis, CT6, and the air gap between the fifth lens element and the sixth lens element, AC56, could be in proper range to prevent excessive central thickness of the sixth lens element along the optical axis, CT6, and excessive air gap between the fifth lens element and the sixth lens element, AC56. More preferably, the value of
 
             EFL       CT   ⁢   6     +     A   ⁢   C   ⁢   56             
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             6.3 
             ≤ 
             
               EFL 
               
                 
                   CT 
                   ⁢ 
                   6 
                 
                 + 
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   56 
                 
               
             
             ≤ 
             
               9.5 
               . 
             
           
         
       
     
     Reference is now made to Equation (10). The design for the value of 
                 CT   ⁢   4     +     CT   ⁢   5         CT   ⁢   2           
is based on the central thickness of the fourth lens element along the optical axis, CT4, and the central thickness of the fifth lens element along the optical axis, CT5. Since the fourth lens element and fifth lens element have larger effective optical diameters, the central thickness of the fourth lens element along the optical axis, CT4, and the central thickness of the fifth lens element along the optical axis, CT5, are thicker than the central thickness of the second lens element along the optical axis, CT2. When
 
                 CT   ⁢   4     +     CT   ⁢   5         CT   ⁢   2           
meets to Equation (10), the central thickness of the second lens element along the optical axis, CT2, could be in proper arrangement, which is favorable for shortening the length of the optical imaging lens. More preferably, the value of
 
                 CT   ⁢   4     +     CT   ⁢   5         CT   ⁢   2           
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             2.8 
             ≤ 
             
               
                 
                   CT 
                   ⁢ 
                   4 
                 
                 + 
                 
                   CT 
                   ⁢ 
                   5 
                 
               
               
                 CT 
                 ⁢ 
                 2 
               
             
             ≤ 
             
               6.5 
               . 
             
           
         
       
     
     Reference is now made to Equation (11). The design for the value of 
             TL       CT   ⁢   2     +     A   ⁢   C   ⁢   56             
is based on the distance between the object-side surface of the first lens element to the image-side surface of the sixth lens element, TL. The object-side surface of the first lens element to the image-side surface of the sixth lens element, TL, would be shrunken to meet the demand of small sized optical imaging lens. When
 
             TL       CT   ⁢   2     +     A   ⁢   C   ⁢   56             
meets to Equation (11), the central thickness of the second lens element along the optical axis, CT2, and the air gap between the fifth lens element and the sixth lens element, AC56, could be in proper arrangement to prevent excessive second lens element along the optical axis, CT2, and excessive air gap between the fifth lens element and the sixth lens element, AC56, that is favorable for shortening the length of the optical imaging lens. More preferably, the value of
 
             TL       CT   ⁢   2     +     A   ⁢   C   ⁢   56             
should be further restricted by an upper limit, for example but not limited to,
 
     
       
         
           
             5.5 
             ≤ 
             
               TL 
               
                 
                   CT 
                   ⁢ 
                   2 
                 
                 + 
                 
                   A 
                   ⁢ 
                   C 
                   ⁢ 
                   56 
                 
               
             
             ≤ 
             
               15. 
               . 
             
           
         
       
     
     When implementing example embodiments, more details about the convex or concave surface structure and/or the refractive power may be incorporated for one specific lens element or broadly for plural lens elements to enhance the control for the system performance and/or resolution, as illustrated in the following embodiments. It is noted that the details listed here could be incorporated in example embodiments if no inconsistency occurs. 
     Several exemplary embodiments and associated optical data will now be provided for illustrating example embodiments of optical imaging lens with good optical characters and a shortened length. Reference is now made to  FIGS.  2 - 5   .  FIG.  2    illustrates a cross-sectional view of a first embodiment of the optical imaging lens  1  having six lens elements according to the present disclosures.  FIGS.  3 ( a ) to  3 ( d )  show example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens  1  according to an example embodiment.  FIG.  4    illustrates an example table of optical data of each lens element of the optical imaging lens  1  according to an example embodiment.  FIG.  5    depicts an example table of aspherical data of the optical imaging lens  1  according to an example embodiment. 
     As shown in  FIG.  2   , the optical imaging lens  1  of the present embodiment comprises, in order from an object side A 1  to an image side A 2 , an aperture stop  100 , a first lens element  110 , a second lens element  120 , a third lens element  130 , a fourth lens element  140 , a fifth lens element  150 , and the sixth lens element  160 . The aperture stop  100  may be also disposed between the first lens element  110  and the second element  120  or other position. A filtering unit  170  and an image plane  180  of an image sensor are positioned at the image side A 2  of the optical image lens  1 . More specifically, the filtering unit  170  is an IR cut filter (infrared cut filter) positioned between the sixth lens  160  and the image plane  180  of the image sensor. The filtering unit  170  selectively absorbs light with specific wavelength from the light passing optical imaging lens  1 . For example, IR light is absorbed, and this will prohibit the IR light which is not seen by human eyes from producing an image on the image plane  180 . 
     Exemplary embodiments of each lens elements of the optical imaging lens  1  will now be described with reference to the drawings. Each of the first, second, third, fourth, fifth, and sixth lens elements  110 ,  120 ,  130 ,  140 ,  150 ,  160  has an object-side surface  111 / 121 / 131 / 141 / 151 / 161  facing toward the object side A 1  and an image-side surface  112 / 122 / 132 / 142 / 152 / 162  facing toward the image side A 2 . Both object-side surface  111 / 121 / 131 / 141 / 151 / 161  and image-side surface  112 / 122 / 132 / 142 / 152 / 162  may be aspherical surfaces. 
     The first lens element  110  has a positive refractive power, which may be constructed by plastic material. The object-side surface  111  is a convex surface, which comprises a convex portion  111  in a vicinity of the optical axis. The image-side surface  112  comprises a concave portion  1121  in a vicinity of the optical axis, and a convex portion  1122  in a vicinity of a periphery of the first lens element  110 . 
     The second lens element  120  may have a negative refractive power, which may be constructed by plastic material. The object-side surface  121  comprises a convex portion  1211  in a vicinity of the optical axis, a convex portion  1212  in a vicinity of a periphery of the second lens element  120 , and a concave portion  1213  between a vicinity of the optical axis and a vicinity of a periphery of the second lens element  120 . The image-side surface  122  is a concave surface and comprises a concave portion  1222  in a vicinity of a periphery of the second lens element  120 . 
     The third lens element  130  may have a positive refractive power, which may be constructed by plastic material. The object-side surface  131  comprises a convex portion  1311  in a vicinity of the optical axis, and a concave portion  1312  in a vicinity of a periphery of the third lens element  130 . The image-side surface  132  is a convex surface, which comprises a convex portion  1322  in a vicinity of a periphery of the third lens element  130 . 
     The fourth lens element  140  may have a positive refractive power, which may be constructed by plastic material. The object-side surface  141  is a concave surface. The image-side surface  142  is a convex surface, which comprises a concave portion  1421  in a vicinity of the optical axis, and a convex portion  1422  in a vicinity of a periphery of the fourth lens element  140 . 
     The fifth lens element  150  may have a negative refractive power, which may be constructed by plastic material. The object-side surface  151  is a concave surface. The image-side surface  152  is a convex surface, which comprises a convex portion  1522  in a vicinity of a periphery of the fifth lens element  150 . 
     The sixth lens element  160  may have a negative refractive power, which may be constructed by plastic material. The object-side surface  161  comprises a concave portion  1611  in a vicinity of the optical axis, a concave portion  1612  in a vicinity of a periphery of the sixth lens element  160 , and a convex portion  1613  between a vicinity of the optical axis and a vicinity of a periphery of the sixth lens element  160 . The image-side surface  162  comprises a concave portion  1621  in a vicinity of the optical axis and a convex portion  1622  in a vicinity of a periphery of the sixth lens element  160 . 
     In example embodiments, air gaps exist between the lens elements  110 - 160 , the filtering unit  160 , and the image plane  180  of the image sensor. For example,  FIG.  2    illustrates the air gap d 1  existing between the first lens element  110  and the second lens element  120 , the air gap d 2  existing between the second lens element  120  and the third lens element  130 , the air gap d 3  existing between the third lens element  130  and the fourth lens element  140  the air gap d 4  existing between the fourth lens element  140  and the fifth lens element  150 , the air gap d 5  existing between the fifth lens element  150  and the sixth lens element  160 , the air gap d 6  existing between the sixth lens element  160  and the filtering unit  170 , and the air gap d 7  existing between the filtering unit  170  and the image plane  180  of the image sensor. However, in other embodiments, any of the aforesaid air gaps may or may not exist. For example, the profiles of opposite surfaces of any two adjacent lens elements may correspond to each other, and in such situation, the air gaps may not exist. The air gap d 1  is denoted by AC12, the air gap d 2  is denoted by AC23, the air gaps d 3  is denoted by AC34, the air d 4  gap is denoted by AC45, the air gap d 5  is denoted by AC56, and the sum of all air gaps d 1 , d 2 , d 3 , d 4 , d 5  between the first though sixth lens elements is denoted by AAG. 
       FIG.  4    depicts the optical characteristics of each lens elements in the optical imaging lens  1  and thicknesses of the air gaps of the present embodiment. The distance from the object-side surface  111  of the first lens element  110  to the image plane  180  along the optical axis is 5.27 mm, and the length of the optical imaging lens  1  is indeed shortened. Besides the image height of the optical imaging lens  1  is 3.185 mm. 
     The aspherical surfaces, including the object-side surfaces  111 ,  121 ,  131 ,  141 ,  151 ,  161  and the image-side surfaces  112 ,  122 ,  132 ,  142 ,  152 ,  162  are all defined by the following aspherical formula: 
     
       
         
           
             
               Z 
               ⁡ 
               ( 
               Y 
               ) 
             
             = 
             
               
                 
                   
                     Y 
                     2 
                   
                   R 
                 
                 / 
                 
                   ( 
                   
                     1 
                     + 
                     
                       
                         1 
                         - 
                         
                           
                             ( 
                             
                               1 
                               + 
                               K 
                             
                             ) 
                           
                           ⁢ 
                           
                             
                               Y 
                               2 
                             
                             
                               R 
                               2 
                             
                           
                         
                       
                     
                   
                   ) 
                 
               
               + 
               
                 
                   ∑ 
                   
                     i 
                     = 
                     1 
                   
                   n 
                 
                 
                   
                     a 
                     
                       2 
                       ⁢ 
                       i 
                     
                   
                   × 
                   
                     Y 
                     
                       2 
                       ⁢ 
                       i 
                     
                   
                 
               
             
           
         
       
     
     R represents the radius of curvature of the surface of the lens element; 
     Z represents the depth of the aspherical surface (the perpendicular distance between the point of the aspherical surface at a distance Y from the optical axis and the tangent plane of the vertex on the optical axis of the aspherical surface); 
     Y represents the perpendicular distance between the point of the aspherical surface and the optical axis; 
     K represents a conic constant; and 
     a 2i  represents a aspherical coefficient of 2i th  order. 
     The values of each aspherical parameter, K, and a 4 -a 16  of each lens element  110 ,  120 ,  130 ,  140  are represented in  FIG.  5   . 
       FIG.  3 ( a )  illustrates the longitudinal spherical aberration of the present embodiment, in which curves of different wavelengths are distributed closely, that means the off-axis light with different height of different wavelengths converge in a vicinity of the imaging point.  FIG.  3 ( a )  shows that the offsets between the off-axis light with different light and the imaging point are controlled to be ±0.035 mm. Therefore, the present embodiment improves the spherical aberration in different wavelengths obviously. Additionally, the distances between the three represented wavelengths are quite close, that means the image positions of the different wavelengths converge with one another, such that the chromatic aberration is improved obviously. 
       FIG.  3 ( b )  illustrates an astigmatism aberration in the sagittal direction of the present embodiment, and  FIG.  3 ( c )  illustrates an astigmatism aberration in the tangential direction of the present embodiment. The focal lengths of the three represented wavelengths in the whole field of view are within ±0.05 mm, and the focal lengths of the sagittal direction are further controlled within ±0.05 mm. Therefore, the optical imaging lens  1  of the present embodiment could eliminate the aberration effectively. Additionally, the distances between the three represented wavelengths are quite close, that means the aberration is improved obviously. 
       FIG.  3 ( d )  illustrates a distortion aberration of the present embodiment. The distortion aberration of the present embodiment is maintained within the range of ±1%, that means the distortion aberration meets the image quality of optical system. Accordingly, the system length of the optical imaging lens  1  is shortened to be 5.27 mm approximately, which could overcome the chromatic aberration and provide better image quality. Therefore, the present embodiment achieves great optical performance and the length of the optical imaging lens  1  is effectively shortened. 
     Reference is now made to  FIGS.  6 - 9   .  FIG.  6    illustrates an example cross-sectional view of an optical imaging lens  2  having six lens elements of the optical imaging lens according to a second example embodiment.  FIG.  7    shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens  2  according to the second example embodiment.  FIG.  8    shows an example table of optical data of each lens element of the optical imaging lens  2  according to the second example embodiment.  FIG.  9    shows an example table of aspherical data of the optical imaging lens  2  according to the second example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with  2 , for example, reference number  231  for labeling the object-side surface of the third lens element  230 , reference number  232  for labeling the image-side surface of the third lens element  230 , etc. 
     As shown in  FIG.  6   , the second embodiment is similar to the first embodiment. The optical imaging lens  2 , in an order from an object side A 1  to an image side A 2 , comprises an aperture stop  200 , first lens element to sixth lens element  210 - 260 . A filtering unit  270  and an image plane  280  of an image sensor are positioned at the image side A 2  of the optical imaging lens  2 . The arrangement of the convex or concave surface structures, including the object-side surfaces  211 ,  231 ,  241 ,  251 ,  261  and image-side surfaces  212 ,  222 ,  232 ,  242 ,  252 ,  262 , and the refractive power of the lens elements  210 - 260  are generally same with the optical imaging lens  1 . The difference between the optical imaging lens  1  and the optical imaging lens  2  is the radius of curvature, the values of the central thicknesses of the lens elements  210 - 260  and the air gaps between the lens elements  210 - 260  are slight different from the values of the optical imaging lens  1 . Besides, the second lens element  210  and the sixth lens element  260  are slight different from these in the first embodiment. More specifically, the object-side surface  221  of the second lens element  220  is a convex surface, and the object-side  261  of the sixth lens element  260  is a concave surface. 
     Please refer to  FIG.  8    for the optical characteristics of each lens elements in the optical imaging lens  2  and thicknesses of the air gaps of the present embodiment. The distance from the object-side surface  211  of the first lens element  210  to the image plane  280  along the optical axis is 5.36 mm, and the length of the optical imaging lens  2  is indeed shortened. 
     As shown in  FIGS.  7 ( a )- 7 ( d ) , the optical imaging lens  2  of the present embodiment shows great characteristics in longitudinal spherical aberration  7 ( a ), astigmatism in the sagittal direction  7 ( b ), astigmatism in the tangential direction  7 ( c ), and distortion aberration  7 ( d ). Therefore, according to the above illustration, the optical imaging lens of the present embodiment indeed shows great optical performance and the length of the optical imaging lens  2  is effectively shortened. 
     Reference is now made to  FIGS.  10 - 13   .  FIG.  10    illustrates an example cross-sectional view of an optical imaging lens  3  having six lens elements of the optical imaging lens according to a third example embodiment.  FIG.  11    shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens  3  according to the third example embodiment.  FIG.  12    shows an example table of optical data of each lens element of the optical imaging lens  3  according to the third example embodiment.  FIG.  13    shows an example table of aspherical data of the optical imaging lens  3  according to the third example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with  3 , for example, reference number  331  for labeling the object-side surface of the third lens element  330 , reference number  332  for labeling the image-side surface of the third lens element  330 , etc. 
     As shown in  FIG.  10   , the third embodiment is similar to the first embodiment. The optical imaging lens  3 , in an order from an object side A 1  to an image side A 2 , comprises an aperture stop  300 , first lens element to sixth lens element  310 - 360 . A filtering unit  370  and an image plane  380  of an image sensor are positioned at the image side A 2  of the optical imaging lens  3 . The arrangement of the convex or concave surface structures, including the object-side surfaces  311 ,  341  and image-side surfaces  322 ,  332 ,  342 ,  352 ,  362 , and the refractive power of the lens elements  310 ,  320 ,  330 ,  360  are generally same with the optical imaging lens  1 . The difference between the optical imaging lens  1  and the optical imaging lens  3  is the radius of curvature, the values of the central thicknesses of the lens elements  310 - 360  and the air gaps between the lens elements  310 - 360  are slight different from the values of the optical imaging lens  1 . Besides, the lens elements  310 - 360  are slight different from these in the first embodiment. More specifically, the image-side surface  312  of the first lens element  310  is a convex surface, the object-side surface  321  of the second lens element  320  comprises a concave portion  3211  in a vicinity of the optical axis and a convex portion  3212  in a vicinity of a periphery of the second lens element  320 , the object-side surface  331  of the third lens element  330  is a concave surface, which comprises a concave portion  3311  in a vicinity of the optical axis, the fourth lens element  340  has a negative refractive power, the fifth lens element  350  has a positive refractive power, which comprises a convex portion  3511  in a vicinity of the optical axis and a concave portion  3512  in a vicinity of a periphery of the fifth lens element  350 , and the object-side surface  361  of the sixth lens element  360  comprises a concave portion  3611  in a vicinity of the optical axis and a convex portion  3612  in a vicinity of a periphery of the sixth lens element  360 . 
     Please refer to  FIG.  12    for the optical characteristics of each lens elements in the optical imaging lens  3  and thicknesses of the air gaps of the present embodiment. The distance from the object-side surface  311  of the first lens element  310  to the image plane  380  along the optical axis is 5.36 mm, and the length of the optical imaging lens  3  is indeed shortened. 
     As shown in  FIGS.  11 ( a )- 11 ( d ) , the optical imaging lens  3  of the present embodiment shows great characteristics in longitudinal spherical aberration  11 ( a ), astigmatism in the sagittal direction  11 ( b ), astigmatism in the tangential direction  11 ( c ), and distortion aberration  11 ( d ). Therefore, according to the above illustration, the optical imaging lens of the present embodiment indeed shows great optical performance and the length of the optical imaging lens  3  is effectively shortened. 
     Reference is now made to  FIGS.  14 - 17   .  FIG.  14    illustrates an example cross-sectional view of an optical imaging lens  4  having six lens elements of the optical imaging lens according to a fourth example embodiment.  FIG.  15    shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens  4  according to the fourth example embodiment.  FIG.  16    shows an example table of optical data of each lens element of the optical imaging lens  4  according to the fourth example embodiment.  FIG.  17    shows an example table of aspherical data of the optical imaging lens  4  according to the fourth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with  4 , for example, reference number  431  for labeling the object-side surface of the third lens element  430 , reference number  432  for labeling the image-side surface of the third lens element  430 , etc. 
     As shown in  FIG.  14   , the fourth embodiment is similar to the first embodiment. The optical imaging lens  4 , in an order from an object side A 1  to an image side A 2 , comprises an aperture stop  400 , first lens element to sixth lens element  410 - 460 . A filtering unit  470  and an image plane  480  of an image sensor are positioned at the image side A 2  of the optical imaging lens  4 . The arrangement of the convex or concave surface structures, including the object-side surfaces  411 ,  451  and image-side surfaces  422 ,  432 ,  442 ,  452 ,  462 , and the refractive power of the lens elements  410 ,  420 ,  430 ,  440 ,  460  are generally same with the optical imaging lens  1 . The difference between the optical imaging lens  1  and the optical imaging lens  4  is the radius of curvature, the values of the central thicknesses of the lens elements  410 - 460  and the air gaps between the lens elements  410 - 460  are slight different from the values of the optical imaging lens  1 . Besides, the lens elements  410 ,  420 ,  430 ,  450 ,  460  are slight different from these in the first embodiment. More specifically, the image-side surface  412  of the first lens element  410  is a convex surface, the object-side surface  421  of the second lens element  420  is a concave surface, the object-side surface  431  is of the third lens element  430  is a convex surface, the fifth lens element  450  has a positive refractive power, and the object-side surface  461  of the sixth lens element  460  is a concave surface. 
     Please refer to  FIG.  16    for the optical characteristics of each lens elements in the optical imaging lens  4  and thicknesses of the air gaps of the present embodiment. The distance from the object-side surface  411  of the first lens element  410  to the image plane  480  along the optical axis is 5.36 mm, and the length of the optical imaging lens  4  is indeed shortened. 
     As shown in  FIGS.  15 ( a )- 15 ( d ) , the optical imaging lens  4  of the present embodiment shows great characteristics in longitudinal spherical aberration  15 ( a ), astigmatism in the sagittal direction  15 ( b ), astigmatism in the tangential direction  15 ( c ), and distortion aberration  15 ( d ). Therefore, according to the above illustration, the optical imaging lens of the present embodiment indeed shows great optical performance and the length of the optical imaging lens  4  is effectively shortened. 
     Reference is now made to  FIGS.  18 - 21   .  FIG.  18    illustrates an example cross-sectional view of an optical imaging lens  5  having six lens elements of the optical imaging lens according to a fifth example embodiment.  FIG.  19    shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens  5  according to the fifth example embodiment.  FIG.  20    shows an example table of optical data of each lens element of the optical imaging lens  5  according to the fifth example embodiment.  FIG.  21    shows an example table of aspherical data of the optical imaging lens  5  according to the fifth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with  5 , for example, reference number  531  for labeling the object-side surface of the third lens element  530 , reference number  432  for labeling the image-side surface of the third lens element  530 , etc. 
     As shown in  FIG.  18   , the fifth embodiment is similar to the first embodiment. The optical imaging lens  5 , in an order from an object side A 1  to an image side A 2 , comprises an aperture stop  500 , first lens element to sixth lens element  510 - 560 . A filtering unit  570  and an image plane  580  of an image sensor are positioned at the image side A 2  of the optical imaging lens  5 . The arrangement of the convex or concave surface structures, including the object-side surfaces  511 ,  531 ,  541 ,  551  and image-side surfaces  512 ,  522 ,  532 ,  542 ,  552 ,  562 , and the refractive power of the lens elements  510 - 560  are generally same with the optical imaging lens  1 . The difference between the optical imaging lens  1  and the optical imaging lens  5  is the radius of curvature, the values of the central thicknesses of the lens elements  510 - 560  and the air gaps between the lens elements  510 - 560  are slight different from the values of the optical imaging lens  1 . Besides, the lens elements  520 ,  560  are slight different from these in the first embodiment. More specifically, the object-side surface  521  of the second lens element  520  is a convex surface, and the object-side surface  561  of the sixth lens element  560  is a concave surface. 
     Please refer to  FIG.  20    for the optical characteristics of each lens elements in the optical imaging lens  5  and thicknesses of the air gaps of the present embodiment. The distance from the object-side surface  511  of the first lens element  510  to the image plane  580  along the optical axis is 5.36 mm, and the length of the optical imaging lens  5  is indeed shortened. 
     As shown in  FIGS.  19 ( a )- 19 ( d ) , the optical imaging lens  5  of the present embodiment shows great characteristics in longitudinal spherical aberration  19 ( a ), astigmatism in the sagittal direction  19 ( b ), astigmatism in the tangential direction  19 ( c ), and distortion aberration  19 ( d ). Therefore, according to the above illustration, the optical imaging lens of the present embodiment indeed shows great optical performance and the length of the optical imaging lens  5  is effectively shortened. 
     Reference is now made to  FIGS.  22 - 25   .  FIG.  22    illustrates an example cross-sectional view of an optical imaging lens  6  having six lens elements of the optical imaging lens according to a sixth example embodiment.  FIG.  23    shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens  6  according to the sixth example embodiment.  FIG.  24    shows an example table of optical data of each lens element of the optical imaging lens  6  according to the sixth example embodiment.  FIG.  25    shows an example table of aspherical data of the optical imaging lens  6  according to the sixth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with  6 , for example, reference number  631  for labeling the object-side surface of the third lens element  630 , reference number  632  for labeling the image-side surface of the third lens element  630 , etc. 
     As shown in  FIG.  22   , the sixth embodiment is similar to the first embodiment. The optical imaging lens  6 , in an order from an object side A 1  to an image side A 2 , comprises an aperture stop  600 , first lens element to sixth lens element  610 - 660 . A filtering unit  670  and an image plane  680  of an image sensor are positioned at the image side A 2  of the optical imaging lens  6 . The arrangement of the convex or concave surface structures, including the object-side surfaces  611 ,  641 ,  551  and image-side surfaces  612 ,  622 ,  632 ,  642 ,  652 ,  662 , and the refractive power of the lens elements  610 - 660  are generally same with the optical imaging lens  1 . The difference between the optical imaging lens  1  and the optical imaging lens  6  is the radius of curvature, the values of the central thicknesses of the lens elements  610 - 660  and the air gaps between the lens elements  610 - 660  are slight different from the values of the optical imaging lens  1 . Besides, the lens elements  620 ,  630 ,  660  are slight different from these in the first embodiment. More specifically, the object-side surface  621  of the second lens element  620  is a convex surface, the object-side surface  631  of the third lens element  630  is a concave surface, and the object-side surface  661  of the sixth lens element  660  is a concave surface. 
     Please refer to  FIG.  24    for the optical characteristics of each lens elements in the optical imaging lens  6  and thicknesses of the air gaps of the present embodiment. The distance from the object-side surface  611  of the first lens element  610  to the image plane  680  along the optical axis is 5.21 mm, and the length of the optical imaging lens  6  is indeed shortened. 
     As shown in  FIGS.  23 ( a )- 23 ( d ) , the optical imaging lens  6  of the present embodiment shows great characteristics in longitudinal spherical aberration  23 ( a ), astigmatism in the sagittal direction  23 ( b ), astigmatism in the tangential direction  23 ( c ), and distortion aberration  23 ( d ). Therefore, according to the above illustration, the optical imaging lens of the present embodiment indeed shows great optical performance and the length of the optical imaging lens  6  is effectively shortened. 
     Reference is now made to  FIGS.  26 - 29   .  FIG.  26    illustrates an example cross-sectional view of an optical imaging lens  7  having six lens elements of the optical imaging lens according to a seventh example embodiment.  FIG.  27    shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens  7  according to the seventh example embodiment.  FIG.  28    shows an example table of optical data of each lens element of the optical imaging lens  7  according to the seventh example embodiment.  FIG.  29    shows an example table of aspherical data of the optical imaging lens  7  according to the seventh example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with  7 , for example, reference number  731  for labeling the object-side surface of the third lens element  730 , reference number  732  for labeling the image-side surface of the third lens element  730 , etc. 
     As shown in  FIG.  26   , the seventh embodiment is similar to the first embodiment. The optical imaging lens  7 , in an order from an object side A 1  to an image side A 2 , comprises an aperture stop  700 , first lens element to sixth lens element  710 - 760 . A filtering unit  770  and an image plane  780  of an image sensor are positioned at the image side A 2  of the optical imaging lens  7 . The arrangement of the convex or concave surface structures, including the object-side surfaces  711 ,  731 ,  741  and image-side surfaces  712 ,  722 ,  742 ,  752 ,  762 , and the refractive power of the lens elements  710 - 740 ,  760  are generally same with the optical imaging lens  1 . The difference between the optical imaging lens  1  and the optical imaging lens  7  is the radius of curvature, the values of the central thicknesses of the lens elements  710 - 760  and the air gaps between the lens elements  710 - 760  are slight different from the values of the optical imaging lens  1 . Besides, the lens elements  720 ,  730 ,  750 ,  760  are slight different from these in the first embodiment. More specifically, the object-side surface  721  of the second lens element  720  is a concave surface, the image-side surface  732  of the third lens element  730  comprises a concave portion  7321  in a vicinity of the optical axis and a convex portion  7322  in a vicinity of a periphery of the third lens element  730 , the fifth lens element  750  has a positive refractive power, which comprises a convex portion  7511  in a vicinity of the optical axis, the object-side surface  761  of the sixth lens element  760  comprises a convex portion  7611  in a vicinity of the optical axis, a convex portion  7612  in a vicinity of the a periphery of the sixth lens element  760 , and a concave portion  7613  between a vicinity of the optical axis and a vicinity of a periphery of the sixth lens element  760 . 
     Please refer to  FIG.  28    for the optical characteristics of each lens elements in the optical imaging lens  7  and thicknesses of the air gaps of the present embodiment. The distance from the object-side surface  711  of the first lens element  710  to the image plane  780  along the optical axis is 5.42 mm, and the length of the optical imaging lens  7  is indeed shortened. 
     As shown in  FIGS.  27 ( a )- 27 ( d ) , the optical imaging lens  7  of the present embodiment shows great characteristics in longitudinal spherical aberration  27 ( a ), astigmatism in the sagittal direction  27 ( b ), astigmatism in the tangential direction  27 ( c ), and distortion aberration  27 ( d ). Therefore, according to the above illustration, the optical imaging lens of the present embodiment indeed shows great optical performance and the length of the optical imaging lens  7  is effectively shortened. 
     Please refer to  FIG.  30    which shows the values of 
               EFL     CT   ⁢   3       ,     TL     CT   ⁢   6       ,     EFL       CT   ⁢   2     +     A   ⁢   C   ⁢   56         ,         A   ⁢   C   ⁢   23     +     CT   ⁢   3     +     A   ⁢   C   ⁢   34         CT   ⁢   3       ,     AAG       A   ⁢   C   ⁢   23     +     A   ⁢   C   ⁢   34         ,           A   ⁢   C   ⁢   23     +     A   ⁢   C   ⁢   34           A   ⁢   C   ⁢   12     +     A   ⁢   C   ⁢   45     +     A   ⁢   C   ⁢   56         +     EFL       CT   ⁢   4     +     CT   ⁢   5         +     ALT     CT   ⁢   6         ,       EFL       CT   ⁢   6     +     A   ⁢   C   ⁢   56         +         CT   ⁢   4     +     CT   ⁢   5         CT   ⁢   2         ,     and   ⁢           TL       CT   ⁢   2     +     A   ⁢   C   ⁢   56                 
of all seven embodiments, and it is clear that the optical imaging lens of the present invention satisfy the Equations (1) and/or (1′), (2), (3), (4), (5), (6), (7), (8), (9), (10) or (11).
 
     Please refer to  FIG.  31   , which shows an example structural view of a first embodiment of mobile device  20  applying an aforesaid optical imaging lens. The mobile device  20  comprises a housing  21  and a photography module  22  positioned in the housing  21 . An example of the mobile device  20  may be, but is not limited to, a mobile phone. 
     As shown in  FIG.  31   , the photography module  22  may comprise an aforesaid optical imaging lens, for example the optical imaging lens  1  of the first embodiment, a lens barrel  23  for positioning the optical imaging lens  1 , a module housing unit  24  for positioning the lens barrel  23 , a substrate  182  for positioning the module housing unit  24 , and an image sensor  181  which is positioned at an image side of the optical imaging lens  1 . The image plane  180  is formed on the image sensor  181 . 
     In some other example embodiments, the structure of the filtering unit  170  may be omitted. In some example embodiments, the housing  21 , the lens barrel  23 , and/or the module housing unit  24  may be integrated into a single component or assembled by multiple components. In some example embodiments, the image sensor  181  used in the present embodiment is directly attached to a substrate  182  in the form of a chip on board (COB) package, and such package is different from traditional chip scale packages (CSP) since COB package does not require a cover glass before the image sensor  181  in the optical imaging lens  1 . Aforesaid exemplary embodiments are not limited to this package type and could be selectively incorporated in other described embodiments. 
     The six lens elements  110 ,  120 ,  130 ,  140 ,  150 ,  160  are positioned in the lens barrel  23  in the way of separated by an air gap between any two adjacent lens elements. 
     The module housing unit  24  comprises a seat element  2401  for positioning the lens barrel  23  and an image sensor backseat  2406 , in which the image sensor backseat  2406  is not necessary in other embodiment. The lens barrel  23  and the seat element  2401  are positioned along a same axis I-I′, and the lens barrel  23  is positioned inside the seat element  2401 . 
     Because the length of the optical imaging lens  1  is merely 5.27 (mm), the size of the mobile device  20  may be quite small. Therefore, the embodiments described herein meet the market demand for smaller sized product designs. 
     Reference is now made to  FIG.  32   , which shows another structural view of a second embodiment of mobile device  20 ′ applying the aforesaid optical imaging lens  1 . One difference between the mobile device  20 ′ and the mobile device  20  may be the seat element  2401  further comprises a first lens seat  2402 , a second lens seat  2403 , a coil  2404 , and a magnetic unit  2405 . The first lens seat  2402 , which is close to the outside of the lens barrel  23 , and the lens barrel  23  are positioned along an axis II′. The second lens seat  2403  is positioned along the axis II′ and around the outside of the first lens seat  2402 . The coil  2404  is positioned between the outside of the first lens seat  2402  and the inside of the second lens seat  2403 . The magnetic unit  2405  is positioned between the outside of the coil  2404  and the inside of the second lens seat  2403 . The end facing to the image side of the image sensor backseat  2406  is close to the second lens seat  2403 . 
     The lens barrel  23  and the optical imaging lens  1  positioned therein are driven by the first lens seat  2402  to move along the axis II′. The rest structure of the mobile device  20 ′ is similar to the mobile device  20 . 
     Similarly, because the length of the optical imaging lens 5.27 mm, is shortened, the mobile device  20 ′ may be designed with a smaller size and meanwhile good optical performance is still provided. Therefore, the present embodiment meets the market demand for smaller sized product designs, and maintains good optical characteristics and image quality. Accordingly, the present embodiment not only reduces raw material amount of housing for economic benefits, but also meets smaller sized product design trend and consumer demand. 
     According to above illustration, it is clear that the mobile device and the optical imaging lens thereof in example embodiments, through controlling ratio of at least one central thickness of lens element to a sum of all air gaps along the optical axis between six lens elements in a predetermined range, and incorporated with detail structure and/or reflection power of the lens elements, the length of the optical imaging lens is effectively shortened and meanwhile good optical characters are still provided. 
     While various embodiments in accordance with the disclosed principles have been described above, it should be understood that they have been presented by way of example only, and are not limiting. Thus, the breadth and scope of exemplary embodiment(s) should not be limited by any of the above-described embodiments, but should be defined only in accordance with the claims and their equivalents issuing from this disclosure. Furthermore, the above advantages and features are provided in described embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages. 
     Additionally, the section headings herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any invention(s) in this disclosure. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of such claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings herein.