# Patent

## Title
Optical imaging lens and electronic device comprising the same

## Abstract

An optical imaging lens set includes a first lens element to a plastic fifth lens element from an object side toward an image side along an optical axis. The second lens element has an image-side surface with a convex portion in a vicinity of its periphery. The fourth lens element has an image-side surface with a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of its periphery.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority to China Application No. 201310288528.9, filed on Jul. 10, 2013.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an optical imaging lens set and an electronic device which includes such optical imaging lens set. Specifically speaking, the present invention is directed to an optical imaging lens set of five lens elements and an electronic device which includes such optical imaging lens set of five lens elements.
2. Description of the Prior Art
In recent years, the popularity of mobile phones and digital cameras makes the photography modules of various portable electronic products, such as optical imaging lens elements or an image sensor . . . develop quickly, and the shrinkage of mobile phones and digital cameras also makes a greater and greater demand for the miniaturization of the photography module. The current trend of research is to develop an optical imaging lens set of a shorter length with uncompromised good quality.
With the development and shrinkage of a charge coupled device (CCD) or a complementary metal oxide semiconductor element (CMOS), the optical imaging lens set installed in the photography module shrinks to meet the demands as well. However, good and necessary optical properties, such as the system aberration improvement, as well as production cost and production feasibility should be taken into consideration, too.
For example, JP 4197994, JP 2008-281760, TW M-369459, TW 200722785, US 2010-0254029 and U.S. Pat. No. 8,248,713 all disclose an optical imaging lens set made of five lens elements. However, the total length of the optical imaging lens set is longer than 9 mm so they are disadvantageous for a smaller design.
These disclosed dimensions do not show good examples of the shrinkage of portable electronic products, such as mobile phones and digital cameras. It is still a problem, on one hand, to reduce the system length efficiently and, on the other hand, to maintain a sufficient optical performance in this field.
SUMMARY OF THE INVENTION
In the light of the above, the present invention is capable of proposing an optical imaging lens set of lightweight, low production cost, reduced length, high resolution and high image quality. The optical imaging lens set of five lens elements of the present invention has a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element sequentially from an object side to an image side along an optical axis.
The second lens element has an image-side surface facing toward the image side and the image-side surface has a convex portion in a vicinity of a circular periphery of the second lens element. The fourth lens element has an image-side surface facing toward the image side and the image-side surface has a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of a circular periphery of the fourth lens element. The fifth lens element is made of plastic. The optical imaging lens set exclusively has five lens elements with refractive power. Each one of the first lens element, the second lens element, the third lens element, the fourth lens element, and the fifth lens element has an object-side surface facing toward said object side and an image-side surface facing toward said image side.
In the optical imaging lens set of five lens elements of the present invention, the first lens element has a first lens element thickness T1 along the optical axis, the second lens element has a second lens element thickness T2 along the optical axis, the third lens element has a third lens element thickness T3 along the optical axis, the fourth lens element has a fourth lens element thickness T4 along the optical axis, and the fifth lens element has a fifth lens element thickness T5 along the optical axis, the total thickness of all the lens elements in the optical imaging lens set along the optical axis is Tal=T1+T2+T3+T4+T5.
In the optical imaging lens set of five lens elements of the present invention, an air gap G12 is disposed between the first lens element and the second lens element, an air gap G23 is disposed between the second lens element and the third lens element, an air gap G34 is disposed between the third lens element and the fourth lens element, an air gap G45 is disposed between the fourth lens element and the fifth lens element, the sum of total four air gaps between adjacent lens elements from the first lens element to the fifth lens element along the optical axis is Gaa=G12+G23+G34+G45.
In the optical imaging lens set of five lens elements of the present invention, a thickness T4 of the fourth lens element along the optical axis and an air gap G12 between the first lens element and the second lens element along the optical axis satisfy a relationship T4/G12≦2.0.
In the optical imaging lens set of five lens elements of the present invention, a focal length Efl of the optical imaging lens set and an a thickness T2 of the second lens element along the optical axis satisfy a relationship 3.0≦(Efl/T2)≦7.0.
In the optical imaging lens set of five lens elements of the present invention, a thickness T1 of the first lens element along the optical axis and an air gap G12 between the first lens element and the second lens element along the optical axis satisfy a relationship T1/G12≦2.5.
In the optical imaging lens set of five lens elements of the present invention, a thickness T2 of the second lens element along the optical axis and a thickness T4 of the fourth lens element along the optical axis satisfy a relationship 1.4≦(T2/T4)≦3.5.
In the optical imaging lens set of five lens elements of the present invention, a focal length Efl of the optical imaging lens set and a thickness T2 of the second lens element along the optical axis satisfy a relationship (Efl/T2)≦7.0.
In the optical imaging lens set of five lens elements of the present invention, a maximal thickness Tmax among the five lens elements along the optical axis and an air gap G12 between the first lens element and the second lens element along the optical axis satisfy a relationship 0.7≦(Tmax/G12)≦2.3.
In the optical imaging lens set of five lens elements of the present invention, a thickness T1 of the first lens element along the optical axis and an air gap G12 between the first lens element and the second lens element along the optical axis satisfy a relationship 0.5≦T1/G12≦2.5.
In the optical imaging lens set of five lens elements of the present invention, a maximal thickness Tmax among the five lens elements along the optical axis and a thickness T2 of the second lens element along the optical axis satisfy a relationship Tmax/T2≦1.4.
In the optical imaging lens set of five lens elements of the present invention, a thickness T1 of the first lens element along the optical axis and the sum of all four air gaps Gaa between each lens element from the first lens element to the fifth lens element along the optical axis satisfy a relationship 1.5≦Gaa/T1≦4.0.
In the optical imaging lens set of five lens elements of the present invention, a thickness T2 of the second lens element along the optical axis satisfies a relationship T1/T2≦1.1.
In the optical imaging lens set of five lens elements of the present invention, a thickness T4 of the fourth lens element along the optical axis and the sum of all four air gaps Gaa between each lens element from the first lens element to the fifth lens element along the optical axis satisfies a relationship 2.0≦Gaa/T4≦8.0.
In the optical imaging lens set of five lens elements of the present invention, a thickness T2 of the second lens element along the optical axis satisfies a relationship 1.4≦T2/T4.
In the optical imaging lens set of five lens elements of the present invention, an Abbe number VD1 of the first lens element and an Abbe number VD2 of the second lens element satisfy a relationship 30≦VD2−VD1.
The present invention also proposes an electronic device which includes the optical imaging lens set as described above. The electronic device includes a case and an image module disposed in the case. The image module includes an optical imaging lens set as described above, a barrel for the installation of the optical imaging lens set, a module housing unit for the installation of the barrel, and an image sensor disposed at an image side of the optical imaging lens set.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a first example of the optical imaging lens set of the present invention.
FIG. 2A illustrates the longitudinal spherical aberration on the image plane of the first example.
FIG. 2B illustrates the astigmatic aberration on the sagittal direction of the first example.
FIG. 2C illustrates the astigmatic aberration on the tangential direction of the first example.
FIG. 2D illustrates the distortion aberration of the first example.
FIG. 3 illustrates a second example of the optical imaging lens set of five lens elements of the present invention.
FIG. 4A illustrates the longitudinal spherical aberration on the image plane of the second example.
FIG. 4B illustrates the astigmatic aberration on the sagittal direction of the second example.
FIG. 4C illustrates the astigmatic aberration on the tangential direction of the second example.
FIG. 4D illustrates the distortion aberration of the second example.
FIG. 5 illustrates a third example of the optical imaging lens set of five lens elements of the present invention.
FIG. 6A illustrates the longitudinal spherical aberration on the image plane of the third example.
FIG. 6B illustrates the astigmatic aberration on the sagittal direction of the third example.
FIG. 6C illustrates the astigmatic aberration on the tangential direction of the third example.
FIG. 6D illustrates the distortion aberration of the third example.
FIG. 7 illustrates a fourth example of the optical imaging lens set of five lens elements of the present invention.
FIG. 8A illustrates the longitudinal spherical aberration on the image plane of the fourth example.
FIG. 8B illustrates the astigmatic aberration on the sagittal direction of the fourth example.
FIG. 8C illustrates the astigmatic aberration on the tangential direction of the fourth example.
FIG. 8D illustrates the distortion aberration of the fourth example.
FIG. 9 illustrates a fifth example of the optical imaging lens set of five lens elements of the present invention.
FIG. 10A illustrates the longitudinal spherical aberration on the image plane of the fifth example.
FIG. 10B illustrates the astigmatic aberration on the sagittal direction of the fifth example.
FIG. 10C illustrates the astigmatic aberration on the tangential direction of the fifth example.
FIG. 10D illustrates the distortion aberration of the fifth example.
FIG. 11 illustrates a sixth example of the optical imaging lens set of five lens elements of the present invention.
FIG. 12A illustrates the longitudinal spherical aberration on the image plane of the sixth example.
FIG. 12B illustrates the astigmatic aberration on the sagittal direction of the sixth example.
FIG. 12C illustrates the astigmatic aberration on the tangential direction of the sixth example.
FIG. 12D illustrates the distortion aberration of the sixth example.
FIG. 13 illustrates a seventh example of the optical imaging lens set of five lens elements of the present invention.
FIG. 14A illustrates the longitudinal spherical aberration on the image plane of the seventh example.
FIG. 14B illustrates the astigmatic aberration on the sagittal direction of the seventh example.
FIG. 14C illustrates the astigmatic aberration on the tangential direction of the seventh example.
FIG. 14D illustrates the distortion aberration of the seventh example.
FIG. 15 illustrates exemplificative shapes of the optical imaging lens element of the present invention.
FIG. 16 illustrates a first preferred example of the portable electronic device with an optical imaging lens set of the present invention.
FIG. 17 illustrates a second preferred example of the portable electronic device with an optical imaging lens set of the present invention.
FIG. 18 shows the optical data of the first example of the optical imaging lens set.
FIG. 19 shows the aspheric surface data of the first example.
FIG. 20 shows the optical data of the second example of the optical imaging lens set.
FIG. 21 shows the aspheric surface data of the second example.
FIG. 22 shows the optical data of the third example of the optical imaging lens set.
FIG. 23 shows the aspheric surface data of the third example.
FIG. 24 shows the optical data of the fourth example of the optical imaging lens set.
FIG. 25 shows the aspheric surface data of the fourth example.
FIG. 26 shows the optical data of the fifth example of the optical imaging lens set.
FIG. 27 shows the aspheric surface data of the fifth example.
FIG. 28 shows the optical data of the sixth example of the optical imaging lens set.
FIG. 29 shows the aspheric surface data of the sixth example.
FIG. 30 shows the optical data of the seventh example of the optical imaging lens set.
FIG. 31 shows the aspheric surface data of the seventh example.
FIG. 32 shows some important ratios in the examples.



DETAILED DESCRIPTION
Before the detailed description of the present invention, the first thing to be noticed is that in the present invention, similar (not necessarily identical) elements share the same numeral references. In the entire present specification, “a certain lens element has negative/positive refractive power” refers to the part in a vicinity of the optical axis of the lens element has negative/positive refractive power. “An object-side/image-side surface of a certain lens element has a concave/convex part or concave/convex portion” refers to the part is more concave/convex in a direction parallel with the optical axis to be compared with an outer region next to the region. Take FIG. 15 for example, the optical axis is “I” and the lens element is symmetrical with respect to the optical axis I. The object side of the lens element has a convex part in the region A, a concave part in the region B, and a convex part in the region C because region A is more convex in a direction parallel with the optical axis than an outer region (region B) next to region A, region B is more concave than region C and region C is similarly more convex than region E. “A circular periphery of a certain lens element” refers to a circular periphery region of a surface on the lens element for light to pass through, that is, region C in the drawing. In the drawing, imaging light includes Lc (chief ray) and Lm (marginal ray). “A vicinity of the optical axis” refers to an optical axis region of a surface on the lens element for light to pass through, that is, the region A in FIG. 15. In addition, the lens element may include an extension part E for the lens element to be installed in an optical imaging lens set. Ideally speaking, no light would pass through the extension part, and the actual structure and shape of the extension part is not limited to this and may have other variations. For the reason of simplicity, the extension part is not illustrated in FIGS. 1, 3, 5, 7, 9, 11 and 13.
As shown in FIG. 1, the optical imaging lens set 1 of five lens elements of the present invention, sequentially from an object side 2 (where an object is located) to an image side 3 along an optical axis 4, has a first lens element 10, a second lens element 20, a third lens element 30, a fourth lens element 40, a fifth lens element 50, a filter 60 and an image plane 71. Generally speaking, the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40 and the fifth lens element 50 may be made of a transparent plastic material and each has an appropriate refractive power, but the present invention is not limited to this and the fifth lens element 50 is always made of a transparent plastic material. There are exclusively five lens elements with refractive power in the optical imaging lens set 1 of the present invention. The optical axis 4 is the optical axis of the entire optical imaging lens set 1, and the optical axis of each of the lens elements coincides with the optical axis of the optical imaging lens set 1.
Furthermore, the optical imaging lens set 1 includes an aperture stop (ape. stop) 80 disposed in an appropriate position. In FIG. 1, the aperture stop 80 is disposed between the first lens element 10 and the second lens element 20. When light emitted or reflected by an object (not shown) which is located at the object side 2 enters the optical imaging lens set 1 of the present invention, it forms a clear and sharp image on the image plane 71 at the image side 3 after passing through the first lens element 10, the aperture stop 80, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the filter 60.
In the embodiments of the present invention, the optional filter 60 may be a filter of various suitable functions, for example, the filter 60 may be an infrared cut filter (IR cut filter), placed between the fifth lens element 50 and the image plane 71.
Each lens element in the optical imaging lens set 1 of the present invention has an object-side surface facing toward the object side 2 as well as an image-side surface facing toward the image side 3. In addition, each object-side surface and image-side surface in the optical imaging lens set 1 of the present invention has a part in a vicinity of its circular periphery (circular periphery part) away from the optical axis 4 as well as a part in a vicinity of the optical axis (optical axis part) closer to the optical axis 4. For example, the first lens element 10 has an object-side surface 11 and an image-side surface 12; the second lens element 20 has an object-side surface 21 and an image-side surface 22; the third lens element 30 has an object-side surface 31 and an image-side surface 32; the fourth lens element 40 has an object-side surface 41 and an image-side surface 42; the fifth lens element 50 has an object-side surface 51 and an image-side surface 52.
Each lens element in the optical imaging lens set 1 of the present invention further has a central thickness T on the optical axis 4. For example, the first lens element 10 has a first lens element thickness T1, the second lens element 20 has a second lens element thickness T2, the third lens element 30 has a third lens element thickness T3, the fourth lens element 40 has a fourth lens element thickness T4, and the fifth lens element 50 has a fifth lens element thickness T5. Therefore, the total thickness of all the lens elements in the optical imaging lens set 1 along the optical axis 4 is Ta1=T1+T2+T3+T4+T5. At least one of the five lens elements has a maximal thickness Tmax among all along the optical axis.
In addition, between two adjacent lens elements in the optical imaging lens set 1 of the present invention there is an air gap G along the optical axis 4. For example, an air gap G12 is disposed between the first lens element 10 and the second lens element 20, an air gap G23 is disposed between the second lens element 20 and the third lens element 30, an air gap G34 is disposed between the third lens element 30 and the fourth lens element 40, an air gap G45 is disposed between the fourth lens element 40 and the fifth lens element 50. Therefore, the sum of total four air gaps between adjacent lens elements from the first lens element 10 to the fifth lens element 50 along the optical axis 4 is Gaa=G12+G23+G34+G45.
First Example
Please refer to FIG. 1 which illustrates the first example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 2A for the longitudinal spherical aberration on the image plane 71 of the first example; please refer to FIG. 2B for the astigmatic field aberration on the sagittal direction; please refer to FIG. 2C for the astigmatic field aberration on the tangential direction, and please refer to FIG. 2D for the distortion aberration. The Y axis of the spherical aberration in each example is “field of view” for 1.0. The Y axis of the astigmatic field and the distortion in each example stands for “image height”.
The optical imaging lens set 1 of the first example has five lens elements 10 to 50; each is made of a plastic material and has refractive power. The optical imaging lens set 1 also has a filter 60, an aperture stop 80, and an image plane 71. The aperture stop 80 is provided between the first lens element 10 and the second lens element 20. The filter 60 may be an infrared filter (IR cut filter) to prevent inevitable infrared in light reaching the image plane to adversely affect the imaging quality.
The first lens element 10 has positive refractive power. The object-side surface 11 of the first lens element 10 facing toward the object side 2 is a convex surface and the image-side surface 12 of the first lens element 10 facing toward the image side 3 is a concave surface. Both the object-side surface 11 and the image-side 12 of the first lens element 10 are aspherical surfaces.
The second lens element 20 has positive refractive power. The object-side surface 21 of the second lens element 20 facing toward the object side 2 is a convex surface and the image-side surface 22 of the second lens element 20 facing toward the image side 3 is a convex surface and has a convex part 27 (convex circular periphery part) in a vicinity of its circular periphery. In addition, both the object-side surface 21 and the image-side surface 22 of the second lens element 20 are aspherical surfaces.
The third lens element 30 has positive refractive power, an object-side surface 31 of the third lens element 30 facing toward the object side 2 and an image-side surface 32 of the third lens element 30 facing toward the image side 3. The object-side surface 31 is a concave surface. The image-side surface 32 has a convex part 36 (convex optical axis part) in the vicinity of the optical axis and a concave part 37 (concave circular periphery part) in a vicinity of its circular periphery. In addition, both the object-side surface 31 and the mage-side surface 32 of the third lens element 30 are aspherical surfaces.
The fourth lens element 40 has negative refractive power. The object-side surface 41 of the fourth lens element 40 facing toward the object side 2 has a convex part 43 (convex optical axis part) in the vicinity of the optical axis and a concave part 44 (concave circular periphery part) in a vicinity of its circular periphery. The image-side surface 42 of the fourth lens element 40 facing toward the image side 3 has a concave part 46 (concave optical axis part) in the vicinity of the optical axis and a convex part 47 (convex circular periphery part) in a vicinity of its circular periphery. In addition, both the object-side surface 41 and the image-side 42 of the fourth lens element 40 are aspherical surfaces.
The fifth lens element 50 has positive refractive power, an object-side surface 51 of the fifth lens element 50 facing toward the object side 2 and an image-side surface 52 of the fifth lens element 50 facing toward the image side 3. The object-side surface 51 has a convex part 53 (convex optical axis part) in the vicinity of the optical axis and a concave part 54 (concave circular periphery part) in a vicinity of its circular periphery. The image-side surface 52 has a concave part 56 (concave optical axis part) in the vicinity of the optical axis and a convex part 57 (convex circular periphery part) in a vicinity of its circular periphery. Further, both the object-side surface 51 and the image-side 52 of the fifth lens element 50 are aspherical surfaces. The filter 60 may be an infrared cut filter, and is disposed between the fifth lens element 50 and the image plane 71.
In the optical imaging lens element 1 of the present invention, the object side 11/21/31/41/51 and image side 12/22/32/42/52 from the first lens element 10 to the fifth lens element 50, total of ten surfaces are all aspherical. These aspheric coefficients are defined according to the following formula:




  
    Z
    ⁡
    
      (
      Y
      )
    
  
  =
  
    
      
        
          Y
          2
        
        R
      
      /
      
        (
        
          1
          +
          
            
              1
              -
              
                
                  (
                  
                    1
                    +
                    K
                  
                  )
                
                ⁢
                
                  
                    Y
                    2
                  
                  
                    R
                    2
                  
                
              
            
          
        
        )
      
    
    +
    
      
        ∑
        
          i
          =
          1
        
        n
      
      ⁢
      
        
      
      ⁢
      
        
          a
          
            2
            ⁢
            
              
            
            ⁢
            i
          
        
        ×
        
          Y
          
            2
            ⁢
            
              
            
            ⁢
            i
          
        
      
    
  




In which:
R represents the curvature radius of the lens element surface;
Z represents the depth of an 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 a vertical distance from a point on the aspherical surface to the optical axis;
K is a conic constant; a21 is the aspheric coefficient of the 2i order.
The optical data of the first example of the optical imaging lens set 1 are shown in FIG. 18 and the Abbe No. is the Abbe number while the aspheric surface data are shown in FIG. 19. In the following examples of the optical imaging lens set, the f-number of the entire optical lens element system is Fno, HFOV stands for the half field of view which is half of the field of view of the entire optical lens element system, and the unit for the curvature radius, the thickness and the focal length is in millimeters (mm), and F is a system focal length Efl of the optical imaging lens set 1. The length of the optical imaging lens set is 3.78 mm (from the first object-side surface to the image plane along the optical axis). The image height is 2.268 mm. Some important ratios of the first example are as follows:
T4/G12=1.906
Efl/T2=3.382
T2/T4=2.361
T1/G12=2.490
Tmax/G12=4.501
Tmax/T2=1.000
Gaa/T1=1.654
T1/T2=0.553
Gaa/T4=2.161
VD2−VD1=32.586
Second Example
Please refer to FIG. 3 which illustrates the second example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 4A for the longitudinal spherical aberration on the image plane 71 of the second example; please refer to FIG. 4B for the astigmatic aberration on the sagittal direction; please refer to FIG. 4C for the astigmatic aberration on the tangential direction, and please refer to FIG. 4D for the distortion aberration. The second example is similar with the first example, but the optical data, the object-side surface 21, the image-side surface 32 are different. The object-side surface 21 of the second lens element 20 is a concave surface and the image-side surface 32 of the third lens element 30 is a convex surface. The optical data of the second example of the optical imaging lens set are shown in FIG. 20 while the aspheric surface data are shown in FIG. 21. The length of the optical imaging lens set is 4.17 mm. The image height is 2.268 mm. Some important ratios of the second example are as follows:
T4/G12=0.360
Efl/T2=5.998
T2/T4=1.852
T1/G12=0.587
Tmax/G12=0.933
Tmax/T2=1.398
Gaa/T1=3.682
T1/T2=0.880
Gaa/T4=6.000
VD2−VD1=32.586
Third Example
Please refer to FIG. 5 which illustrates the third example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 6A for the longitudinal spherical aberration on the image plane 71 of the second example; please refer to FIG. 6B for the astigmatic aberration on the sagittal direction; please refer to FIG. 6C for the astigmatic aberration on the tangential direction, and please refer to FIG. 6D for the distortion aberration. The third example is similar with the first example, but the optical data, the object-side surface 21, and the image-side surface 32 are different, The object-side surface 21 of the second lens element 20 has a convex part 23 (convex optical axis part) in the vicinity of the optical axis and a concave part 24 (concave circular periphery part) in a vicinity of its circular periphery and the image-side surface 32 of the third lens element 30 is a convex surface. The optical data of the third example of the optical imaging lens set are shown in FIG. 22 while the aspheric surface data are shown in FIG. 23. The length of the optical imaging lens set is 4.04 mm. The image height is 2.268 mm. Some important ratios of the third example are as follows:
T4/G12=0.501
Efl/T2=4.417
T2/T4=1.811
T1/G12=0.699
Tmax/G12=0.973
Tmax/T2=1.072
Gaa/T1=2.844
T1/T2=0.770
Gaa/T4=3.966
VD2−VD1=32.586
Fourth Example
Please refer to FIG. 7 which illustrates the fourth example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 8A for the longitudinal spherical aberration on the image plane 71 of the second example; please refer to FIG. 8B for the astigmatic aberration on the sagittal direction; please refer to FIG. 8C for the astigmatic aberration on the tangential direction, and please refer to FIG. 8D for the distortion aberration. The fourth example is similar with the first example, but the optical data, the object-side surface 21, the image-side surface 32 are different. The object-side surface 21 of the second lens element 20 has a convex part 23 (convex optical axis part) in the vicinity of the optical axis and a concave part 24 (concave circular periphery part) in a vicinity of its circular periphery and the image-side surface 32 of the third lens element is a convex surface. The optical data of the fourth example of the optical imaging lens set are shown in FIG. 24 while the aspheric surface data are shown in FIG. 25. The length of the optical imaging lens set is 4.04 mm. The image height is 2.268 mm. Some important ratios of the fourth example are as follows:
T4/G12=0.767
Efl/T2=2.574
T2/T4=3.078
T1/G12=1.177
Tmax/G12=2.360
Tmax/T2=1.000
Gaa/T1=1.783
T1/T2=0.499
Gaa/T4=2.737
VD2−VD1=32.586
Fifth Example
Please refer to FIG. 9 which illustrates the fifth example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 10A for the longitudinal spherical aberration on the image plane 71 of the second example; please refer to FIG. 10B for the astigmatic aberration on the sagittal direction; please refer to FIG. 10C for the astigmatic aberration on the tangential direction, and please refer to FIG. 10D for the distortion aberration. The fifth example is similar with the first example, but the optical data and the image-side surface 32 are different. The image-side surface 32 of the third lens element 30 is a convex surface. The optical data of the fifth example of the optical imaging lens set are shown in FIG. 26 while the aspheric surface data are shown in FIG. 27. The length of the optical imaging lens set is 4.04 mm. The image height is 2.268 mm. Some important ratios of the fifth example are as follows:
T4/G12=0.981
Efl/T2=3.342
T2/T4=1.823
T1/G12=1.308
Tmax/G12=1.788
Tmax/T2=1.000
Gaa/T1=1.501
T1/T2=0.732
Gaa/T4=2.003
VD2−VD1=32.586
Sixth Example
Please refer to FIG. 11 which illustrates the sixth example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 12A for the longitudinal spherical aberration on the image plane 71 of the second example; please refer to FIG. 12B for the astigmatic aberration on the sagittal direction; please refer to FIG. 12C for the astigmatic aberration on the tangential direction, and please refer to FIG. 12D for the distortion aberration. The sixth example is similar with the first example, but the optical data and the image-side surface 32 are different. The image-side surface 32 of the third lens element 30 is a convex surface. The optical data of the sixth example of the optical imaging lens set are shown in FIG. 28 while the aspheric surface data are shown in FIG. 29. The length of the optical imaging lens set is 3.74 mm. The image height is 2.268 mm. Some important ratios of the sixth example are as follows:
T4/G12=0.971
Efl/T2=5.477
T2/T4=1.489
T1/G12=0.944
Tmax/G12=2.016
Tmax/T2=1.394
Gaa/T1=3.358
T1/T2=0.653
Gaa/T4=3.264
VD2−VD1=32.586
Seventh Example
Please refer to FIG. 13 which illustrates the seventh example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 14A for the longitudinal spherical aberration on the image plane 71 of the second example; please refer to FIG. 14B for the astigmatic aberration on the sagittal direction; please refer to FIG. 14C for the astigmatic aberration on the tangential direction, and please refer to FIG. 14D for the distortion aberration. The seventh example is similar with the first example, but the optical data, refractive power of the first lens element 10, the object-side surface 21 and the image-side surface 32 are different. The first lens element 10 has negative refractive power, the object-side surface 21 of the second lens element 20 has a convex part 23 (convex optical axis part) in the vicinity of the optical axis and a concave part 24 (concave circular periphery part) in a vicinity of its circular periphery and the image-side surface 32 of the third lens element 30 is a convex surface. The optical data of the seventh example of the optical imaging lens set are shown in FIG. 30 while the aspheric surface data are shown in FIG. 31. The length of the optical imaging lens set is 3.89 mm. The image height is 2.268 mm. Some important ratios of the sixth example are as follows:
T4/G12=0.673
Efl/T2=5.435
T2/T4=1.741
T1/G12=0.904
Tmax/G12=1.463
Tmax/T2=1.250
Gaa/T1=3.368
T1/T2=0.772
Gaa/T4=4.527
VD2−VD1=32.586
Some important ratios in each example are shown in FIG. 32.
In the light of the above examples, the inventors observe the following features:
1) The convex circular periphery part of the image-side surface of the second lens element and the concave optical axis part as well as the convex circular periphery part of the fourth image-side surface of the fourth lens element work together to minimize the aberrations.

2) The plastic fifth lens element facilitates the reduction of the production cost and the reduction of the weight of the optical imaging lens set.

In addition, it is found that there are some better ratio ranges for different optical data according to the above various important ratios. Better ratio ranges help the designers to design the better optical performance and an effectively reduced length of a practically possible optical imaging lens set. For example:
1. T4/G12 should be not greater than 2.0. When the optical imaging lens set is smaller, the total length should be shorter as well. However, because the concave optical axis part of the image-side surface of the fourth lens element, it may be thinner to satisfy this relationship. It is suggested that 0.1≦T4/G12≦2.0.

2. Efl/T2 should be not greater than 7.0. When the optical imaging lens set is shorter, the focal length should be shorter as well to satisfy this relationship. Preferably, it is 3.0≦Efl/T2≦7.0. A smaller T2 helps to optimize a better arrange of other lens thickness and gaps when the optical imaging lens set becomes shorter. Or, it is 2.0≦Efl/T2≦7.0.

3. T2/T4 should be not less than 1.4. When the optical imaging lens set is smaller, the total length should be shorter as well. However, because the concave optical axis part of the image-side surface of the fourth lens element, it may be thinner to satisfy this relationship. It is suggested that 1.4≦T2/T4≦3.5.

4. T1/G12 should be not greater than 2.5. When the optical imaging lens set is smaller, the total length should be shorter as well. When the optical performance and the productivity are taken into consideration, this relationship suggests better results. Preferably, it is 0.5≦T1/G12≦2.5.

5. Tmax/G12 should be between 0.7 and 2.3. When the optical imaging lens set is smaller, the total length should be shorter and the largest thickness should become smaller as well to satisfy this relationship.

6. Tmax/T2 should be not greater than 1.4. When the optical imaging lens set is smaller, the total length should be shorter and the largest thickness should become smaller as well to satisfy this relationship. Preferably, It is suggested that 0.8≦Tmax/T2≦1.4.

7. Gaa/T1 should be between 1.5 and 4.0. When the optical imaging lens set is smaller, the total length should be shorter as well. When the optical performance and the productivity are taken into consideration, this relationship suggests better results.

8. T1/T2 should be not greater than 1.1. When the optical imaging lens set is smaller, the total length should be shorter as well. When the optical performance and the productivity are taken into consideration, this relationship suggests better results. Preferably, It is suggested that 0.3≦T1/T2≦1.1.

9. Gaa/T4 should be between 2.0 and 8.0. When the optical imaging lens set is smaller, the total length should be shorter as well. When the optical performance and the productivity are taken into consideration, this relationship suggests better results.

10. VD2−VD1 should be not less than 30. Abbe Number is used to evaluate the dispersion properties of a lens. A shortened lens set would have worse dispersion properties. This relationship facilitates to reduce the dispersion properties. Preferably, It is suggested that 30≦VD2−VD1≦36.

The optical imaging lens set 1 of the present invention may be applied to a portable electronic device. Please refer to FIG. 16. FIG. 16 illustrates a first preferred example of the optical imaging lens set 1 of the present invention for use in a portable electronic device 100. The portable electronic device 100 includes a case 110, and an image module 120 mounted in the case 110. A mobile phone is illustrated in FIG. 16 as an example, but the portable electronic device 100 is not limited to a mobile phone.
As shown in FIG. 16, the image module 120 includes the optical imaging lens set 1 as described above. FIG. 16 illustrates the aforementioned first example of the optical imaging lens set 1. In addition, the portable electronic device 100 also contains a barrel 130 for the installation of the optical imaging lens set 1, a module housing unit 140 for the installation of the barrel 130, a substrate 172 for the installation of the module housing unit 140 and an image sensor 70 disposed at the substrate 172, and at the image side 3 of the optical imaging lens set 1. The image sensor 70 in the optical imaging lens set 1 may be an electronic photosensitive element, such as a charge coupled device or a complementary metal oxide semiconductor element. The image plane 71 forms at the image sensor 70.
The image sensor 70 used here is a product of chip on board (COB) package rather than a product of the conventional chip scale package (CSP) so it is directly attached to the substrate 172, and protective glass is not needed in front of the image sensor 70 in the optical imaging lens set 1, but the present invention is not limited to this.
To be noticed in particular, the optional filter 60 may be omitted in other examples although the optional filter 60 is present in this example. The case 110, the barrel 130, and/or the module housing unit 140 may be a single element or consist of a plurality of elements, but the present invention is not limited to this.
Each one of the five lens elements 10, 20, 30, 40 and 50 with refractive power is installed in the barrel 130 with air gaps disposed between two adjacent lens elements in an exemplary way. The module housing unit 140 has a lens element housing 141, and an image sensor housing 146 installed between the lens element housing 141 and the image sensor 70. However in other examples, the image sensor housing 146 is optional. The barrel 130 is installed coaxially along with the lens element housing 141 along the axis I-I′, and the barrel 130 is provided inside of the lens element housing 141.
Because the optical imaging lens set 1 of the present invention may be as short as 3.78 mm, this ideal length allows the dimensions and the size of the portable electronic device 100 to be smaller and lighter, but excellent optical performance and image quality are still possible. In such a way, the various examples of the present invention satisfy the need for economic benefits of using less raw materials in addition to satisfy the trend for a smaller and lighter product design and consumers' demands.
Please also refer to FIG. 17 for another application of the aforementioned optical imaging lens set 1 in a portable electronic device 200 in the second preferred example. The main differences between the portable electronic device 200 in the second preferred example and the portable electronic device 100 in the first preferred example are: the lens element housing 141 has a first seat element 142, a second seat element 143, a coil 144 and a magnetic component 145. The first seat element 142 is for the installation of the barrel 130, exteriorly attached to the barrel 130 and disposed along the axis I-I′. The second seat element 143 is disposed along the axis I-I′ and surrounds the exterior of the first seat element 142. The coil 144 is provided between the outside of the first seat element 142 and the inside of the second seat element 143. The magnetic component 145 is disposed between the outside of the coil 144 and the inside of the second seat element 143.
The first seat element 142 may pull the barrel 130 and the optical imaging lens set 1 which is disposed inside of the barrel 130 to move along the axis I-I′, namely the optical axis 4 in FIG. 1. The image sensor housing 146 is attached to the second seat element 143. The filter 60, such as an infrared filter, is installed at the image sensor housing 146. Other details of the portable electronic device 200 in the second preferred example are similar to those of the portable electronic device 100 in the first preferred example so they are not elaborated again.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

## Claims

1. An optical imaging lens set, comprising: a first lens element, a second lens element, a third lens element, a fourth lens element and a plastic fifth lens element from an object side toward an image side in order along an optical axis and each lens element having refractive power, wherein:
said first lens element having an object-side surface facing toward said object side and said object-side surface is a convex surface;
said second lens element having an image-side surface facing toward said image side and said image-side surface having a convex portion in a vicinity of a circular periphery of said second lens element;
said fourth lens element having an image-side surface facing toward said image side and said image-side surface having a concave portion in a vicinity of said optical axis and a convex portion in a vicinity of a circular periphery of said fourth lens element;
said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element each has an image-side surface facing toward said image side and an object-side surface facing toward said object side; and
said optical imaging lens set exclusively has five lens elements with refractive power, wherein a thickness T1 of said first lens element along said optical axis and an air gap G12 between said first lens element and said second lens element along said optical axis satisfy a relationship 0.5≦T1/G12≦2.5, and a thickness T4 of said fourth lens element along said optical axis and the air gap G12 between said first lens element and said second lens element along said optical axis satisfy a relationship T4/G12≦2.0.

2. The optical imaging lens set of claim 1, wherein a focal length Efl of said optical imaging lens set and an a thickness T2 of said second lens element along said optical axis satisfy a relationship 3.0≦(Efl/T2)≦7.0.

3. The optical imaging lens set of claim 1, wherein a thickness T2 of said second lens element along said optical axis and a thickness T4 of said fourth lens element along said optical axis satisfy a relationship 1.4≦(T2/T4)≦3.5.

4. The optical imaging lens set of claim 1, wherein a focal length Efl of said optical imaging lens set and an a thickness T2 of said second lens element along said optical axis satisfy a relationship (Efl/T2)≦7.0.

5. The optical imaging lens set of claim 4, wherein a maximal thickness Tmax among said five lens elements along said optical axis and an air gap G12 between said first lens element and said second lens element along said optical axis satisfy a relationship 0.7≦(Tmax/G12)≦2.3.

6. The optical imaging lens set of claim 1, wherein a maximal thickness Tmax among said five lens elements along said optical axis and a thickness T2 of said second lens element along said optical axis satisfy a relationship Tmax/T2≦1.4.

7. The optical imaging lens set of claim 1, wherein a thickness T1 of said first lens element along said optical axis and the sum of all four air gaps Gaa between each lens element from said first lens element to said fifth lens element along the optical axis satisfy a relationship 1.5≦Gaa/T1≦4.0.

8. The optical imaging lens set of claim 7, wherein a thickness T2 of said second lens element along said optical axis satisfies a relationship T1/T2≦1.1.

9. The optical imaging lens set of claim 1, wherein a thickness T4 of said fourth lens element along said optical axis and the sum of all four air gaps Gaa between each lens element from said first lens element to said fifth lens element along the optical axis satisfy a relationship 2.0≦Gaa/T4≦8.0.

10. The optical imaging lens set of claim 9, wherein a thickness T2 of said second lens element along said optical axis satisfies a relationship 1.4≦T2/T4.

11. The optical imaging lens set of claim 1, wherein an abbe number VD1 of said first lens element and an abbe number VD2 of said second lens element satisfy a relationship 30≦VD2-VD1.

12. An electronic device, comprising:
a case; and
an image module disposed in said case and comprising:
an optical imaging lens set of claim 1;
a barrel for the installation of said optical imaging lens set;
a module housing unit for the installation of said barrel; and
an image sensor disposed at an image side of said optical imaging lens set.