Patent Publication Number: US-8970969-B2

Title: Image lens with high resolution and small distance

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to lenses and, particularly, to an image lens with high resolution and small distance. 
     2. Description of Related Art 
     Image sensors are used to capture an image. A size of an image sensor, such as a complementary metal oxide semiconductor device (CMOS), decreases with development of technology. For proper matching with the image sensor, an image lens, which is essentially comprised of a number of lenses, should be able to meet requirements, such as, high resolution and small distance. However, the existing image lenses cannot meet these requirements, thus, results in poor imaging effect. 
     Therefore, it is desirable to provide an image lens which can overcome the limitations described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an image lens in accordance with the present disclosure. 
         FIGS. 2˜5  are graphs respectively showing spherical aberration, field curvature, distortion, and characteristic curves of modulation transfer function occurring in the image lens, that is in a telephoto state, according to a first exemplary embodiment. 
         FIGS. 6˜9  are graphs respectively showing spherical aberration, field curvature, distortion, and characteristic curves of modulation transfer function occurring in the image lens, that is in a wide-angle state, according to the first exemplary embodiment. 
         FIGS. 10˜13  are graphs respectively showing spherical aberration, field curvature, distortion, and characteristic curves of modulation transfer function occurring in the image lens, that is in a telephoto state, according to a second exemplary embodiment. 
         FIGS. 14˜17  are graphs respectively showing spherical aberration, field curvature, distortion, and characteristic curves of modulation transfer function occurring in the image lens, that is in a wide-angle state, according to the second exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the disclosure will now be described in detail with reference to the accompanying drawings. 
       FIG. 1 , shows an image lens  100 , according to an exemplary embodiment, optically capturing an image of an object at an object side and forming a corresponding image on an image plane  20 . The image lens  100  includes, in an order from the object side to the image side, a first lens L 1  with positive refraction power, a second lens L 2  with negative refraction power, a third lens L 3  with positive refraction power, a fourth lens L 4  with positive refraction power, a fifth lens L 5  with negative refraction power, and IR-cut filter  10 . 
     The first lens L 1  includes a convex first surface S 1  facing the object side and a convex second surface S 2  facing the image side. 
     The second lens L 2  includes a convex third surface S 3  facing the object side and a concave fourth surface S 4  facing the image side. 
     The third lens L 3  includes a convex third surface S 5  facing the object side and a convex sixth surface S 6  facing the image side. 
     The fourth lens L 4  includes a concave seventh surface S 7  facing the object side and a convex eighth surface S 8  facing the image side. 
     The fifth lens L 5  includes a concave ninth surface S 9  facing the object side and a concave tenth surface S 10  facing the image side. 
     The IR-cut filter  10  includes an eleventh surface S 11  facing the object side and a twelfth surface S 12  facing the image side. 
     The image lens  100  further includes an aperture stop  30 . The aperture stop  30  is positioned between the first lens L 1  and the second lens L 2 . Light rays enter the image lens  100 , passing through the first lens L 1 , the aperture stop  30 , the second lens L 2 , the third lens L 3 , the fourth lens L 4 , the fifth lens L 5 , and the IR-cut filter  10 , finally forming optical images on the image plane  20 . The aperture stop  30  is for adjusting light flux from the first lens L 1  to the second lens L 2 . In addition, the aperture stop  30  facilitates uniform light transmission when light passes through the first lens L 1  to correct coma aberrations of the image lens  100 . The IR-cut filter  10  filters/removes infrared light from the light rays. 
     The image lens  100  satisfies the formulas:
 
 D/TTL&gt; 0.94;  (1)
 
 D/L&gt; 1.21;  (2)
 
     wherein D is the maximum image diameter of the image plane  20 ; TTL is a total length of the image lens  100 ; L is a distance from an outmost edge of the tenth surface S 10  to an optical axis of the image lens  100  along a direction perpendicular to the optical axis of the image lens  100 . 
     The formulas (1) to (2) are for shortening the length of the image lens  100 , and reducing the aberration of the field curvature and spherical aberration in the zoom process. If the image lens  100  does not satisfy the formulas (1) to (2), the distance of the image lens  100  cannot be maintained and the images captured by the image lens  100  cannot be corrected. 
     The image lens  100  further satisfies the formula:
 
 Z/Y&gt; 0;  (3)
 
     wherein Z is a distance from a central point of the seventh surface S 7  to an outmost edge of the eighth surface S 8  along the optical axis, Y is a distance from an outmost edge of the eighth surface S 8  to the optical axis along a direction perpendicular to the optical axis. 
     Formula (3) is for properly distributing the refraction power, while maintaining a relatively small spherical aberration. 
     The image lens  100  further satisfies the formulas:
 
 R 31 /F 3 &gt;R 11 /F 1&gt;0;  (4)
 
 R 12 /F 1 &lt;R 32 /F 3&lt;0;  (5)
 
     wherein R 11  is the curvature radius of the first surface S 1  of the first lens L 1 ; R 12  is the curvature radius of the second surface S 2  of the first lens L 1 ; R 31  is the curvature radius of the fifth surface S 5  of the third lens L 3 , R 32  is the curvature radius of the sixth surface S 6  of the third lens L 3 ; F 1  is focal length of the first lens L 1 , and F 3  is focal length of the third lens L 3 . 
     Formulas (4)-(5) are for maintaining quality of images captured by the image lens  100 . If the image lens  100  does not satisfy the formulas (4) to (5), the images captured by the image lens  100  cannot be corrected. 
     The image lens  100  further satisfies the formulas:
 
 R 51 /F 5 &lt;R 52 /F 5&lt;0;  (6)
 
     wherein R 51  is the curvature radius of the ninth surface S 9  of the fifth lens L 5 ; R 52  is the curvature radius of the tenth surface S 10  of the fifth lens L 5 ; F 5  is focal length of the fifth lens L 5 . 
     Formula (6) is for correcting chromatic aberration of the image lens  100 . If the image lens  100  does not satisfy the formula (6), the images captured by the image lens  100  will have a greater chromatic aberration. 
     All of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth surfaces S 1 , S 2 , S 3 , S 4 , S 5 , S 6 , S 7 , S 8 , S 9  and S 10  are aspherical surfaces. Each aspherical surface is shaped according to the formula: 
     
       
         
           
             Z 
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             k 
                             + 
                             1 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 ∑ 
                 
                   
                     A 
                     i 
                   
                   ⁢ 
                   
                     h 
                     i 
                   
                 
               
             
           
         
       
     
     wherein Z is the length of a line drawn from a point on the aspherical surface to the tangential plane of the aspherical surface, h is the height from the optical axis to the point on the aspherical surface, c is a vertex curvature (=1/R, the radius of curvature), k is a conic constant, and Ai are the correction coefficients, to the order of “i” of the aspherical surface. 
     Detailed examples of the imaging lens  100  are given below in accompany with  FIGS. 2-17 , but it should be noted that the imaging lens  100  is not limited by these examples. Listed below are the symbols used in these detailed examples: 
     FNo: F number; 
     2ω: field angle; 
     ri: radius of curvature of the surface Si; 
     Di: distance between surfaces on the optical axis of the surface Si and the surface Si+1; 
     Ni: refractive index of the surface Si; 
     Vi: Abbe constant of the surface Si; 
     Ki: Secondary curvature of the surface Si. 
     Example 1 
     Tables 1-4 show a first embodiment of the image lens  100 . 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 ri 
                 Di 
                   
                   
                   
               
               
                 Surface 
                 type 
                 (mm) 
                 (mm) 
                 ni 
                 Vi 
                 ki 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 first surface S1 
                 aspherical 
                 2.10 
                 0.70 
                 1.53 
                 56.0 
                 −0.54 
               
               
                 second surface S2 
                 aspherical 
                 −10.41 
                 0.05 
                 — 
                 — 
                 — 
               
               
                 aperture stop 30 
                 standard 
                 Infinity 
                 0.03 
                 — 
                 — 
                 — 
               
               
                 third surface S3 
                 aspherical 
                 5.41 
                 0.41 
                 1.63 
                 23.4 
                 −58.69  
               
               
                 fourth surface S4 
                 aspherical 
                 1.80 
                 0.33 
                 — 
                 — 
                 −0.33 
               
               
                 fifth surface S5 
                 aspherical 
                 9.69 
                 0.64 
                 1.53 
                 56.0 
                 — 
               
               
                 sixth surface S6 
                 aspherical 
                 −7.51 
                 0.45 
                 — 
                 — 
                 — 
               
               
                 seventh surface S7 
                 aspherical 
                 −1.82 
                 0.60 
                 1.53 
                 56.0 
                 −3.64 
               
               
                 eighth surface S8 
                 aspherical 
                 −0.98 
                 0.20 
                 — 
                 — 
                 −3.15 
               
               
                 ninth surface S9 
                 aspherical 
                 15.00 
                 0.58 
                 1.53 
                 56.0 
                 — 
               
               
                 tenth surface S10 
                 aspherical 
                 1.25 
                 0.65 
                 — 
                 — 
                 −7.68 
               
               
                 eleventh surface S11 
                 standard 
                 Infinity 
                 0.30 
                 1.52 
                 58.6 
                 — 
               
               
                 twelfth surface S12 
                 standard 
                 Infinity 
                 0.54 
                 — 
                 — 
                 — 
               
               
                 image plane 20 
                 standard 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 aspherical 
                 first 
                 second 
                 third 
                 fourth 
                 fifth 
               
               
                 coefficient 
                 surface S1 
                 surface S2 
                 surface S3 
                 surface S4 
                 surface S5 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 A4 
                 5.6E−03 
                 0.0171 
                 −3.5E−03 
                 −0.0865 
                 −0.0417 
               
               
                 A6 
                 −4.2E−03 
                 0.0159 
                 0.0403 
                 0.0969 
                 −0.0121 
               
               
                 A8 
                 1.5E−03 
                 −0.0154 
                 −5.7E−03 
                 −0.0452 
                 0.0271 
               
               
                 A10 
                 3.3E−03 
                 −0.0139 
                 −0.0558 
                 3.6E−04 
                 −2.2E−03 
               
               
                 A12 
                 −3.4E−03 
                 8.2E−03 
                 0.0246 
                 5.8E−04 
                 −1.9E−04 
               
               
                 A14 
                 −1.5E−04 
                 5.9E−04 
                 8.0E−03 
                 2.2E−04 
                 −1.2E−03 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 aspherical 
                 sixth 
                 seventh 
                 eighth 
                 ninth 
                 tenth 
               
               
                 coefficient 
                 surface S6 
                 surface S7 
                 surface S8 
                 surface S9 
                 surface S10 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 A4 
                 −0.0274 
                 −0.0165 
                 −0.0600 
                 −0.0860 
                 −0.0643 
               
               
                 A6 
                 −8.5E−03 
                 −0.0132 
                 0.0168 
                 3.0E−03 
                 0.0156 
               
               
                 A8 
                 −0.0122 
                 −1.7E−03 
                 4.9E−04 
                 6.1E−03 
                 −3.1E−03 
               
               
                 A10 
                 7.9E−03 
                 2.0E−03 
                 −2.6E−04 
                 −1.8E−03 
                 1.7E−04 
               
               
                 A12 
                 7.2E−06 
                 −4.7E−06 
                 3.3E−05 
                 −2.2E−04 
                 2.6E−05 
               
               
                 A14 
                 1.4E−05 
                 −8.5E−06 
                 −4.5E−06 
                 6.7E−05 
                 −4.1E−06 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 F(mm) 
                 F/No 
                 2ω 
               
               
                   
               
             
            
               
                 4.44 
                 2.50 
                 66.21° 
               
               
                   
               
            
           
         
       
     
     In the embodiment, D=5.867 mm; TTL=5.48 mm; Z=0.137 mm; Y=1.45 mm; L=4.47 mm; F 1 =3.32; F 3 =7.99 mm; F 5 =−2.57 mm. 
       FIGS. 2-5  are graphs of aberrations (spherical aberration, field curvature, distortion, and characteristic curves of modulation transfer function occurring in the first exemplary embodiment of the image lens  100  in a telephoto state.  FIGS. 6-9 , are graphs of aberrations (spherical aberration, field curvature, distortion, and lateral chromatic aberration) of the first exemplary embodiment of the image lens  100  in a wide angle state. In  FIGS. 2 and 6 , curves are spherical aberration characteristic curves of F light (wavelength: 486 nm), d light (wavelength: 588 nm) and C light (wavelength: 654 nm) of the image system  100 . The spherical aberration of the image lens  100  of the first exemplary embodiment is from −0.05 mm to 0.05 mm. As illustrated in  FIGS. 3 and 7 , the curves T and S are respectively the tangential field curvature curve and the sagittal field curvature curve. The field curvature of the first exemplary embodiment of the image lens  100  is from −0.05 mm to 0.05 mm. In  FIGS. 4 and 8 , the distortion of the first exemplary embodiment of the image lens system  100  is from −2.00% to 2.00%. Furthermore, as shown in  FIG. 5 , for half of the Nyquist frequency (about 2241 p/mm), the MTF of the central field is greater than 55% (see curve mc), the MTF of the 0.8 field is greater than 40% (see curve mp), the MTF between the central field and the 0.8 field is in a range of: 40%˜55% (see curve mt, for example). As shown in  FIG. 9 , for half of the Nyquist frequency (about 2241 p/mm), the MTF of the central field is greater than 42% (see curve mc). The MTF of the 0.8 field is greater than 14% (see curve mp). The MTF between the central field and the 0.8 field is in a range of: 14%˜42% (see curve mt, for example). 
     Example 2 
     Tables 5-8 show a second embodiment of the image lens  100 . 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 ri 
                 Di 
                   
                   
                   
               
               
                 Surface 
                 type 
                 (mm) 
                 (mm) 
                 ni 
                 vi 
                 ki 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 first surface S1 
                 aspherical 
                 2.14 
                 0.52 
                 1.53 
                 56.0 
                  0.42 
               
               
                 second surface S2 
                 aspherical 
                 −15.53 
                 0.07 
                 — 
                 — 
                 −58.87  
               
               
                 aperture stop 30 
                 standard 
                 Infinity 
                 0.06 
                 — 
                 — 
                 — 
               
               
                 third surface S3 
                 aspherical 
                 5.69 
                 0.39 
                 1.63 
                 23.4 
                 — 
               
               
                 fourth surface S4 
                 aspherical 
                 1.88 
                 0.35 
                 — 
                 — 
                 −7.00 
               
               
                 fifth surface S5 
                 aspherical 
                 7.16 
                 0.58 
                 1.53 
                 56.0 
                 — 
               
               
                 sixth surface S6 
                 aspherical 
                 −9.75 
                 0.41 
                 — 
                 — 
                 — 
               
               
                 seventh surface S7 
                 aspherical 
                 −1.89 
                 0.70 
                 1.53 
                 56.0 
                 — 
               
               
                 eighth surface S8 
                 aspherical 
                 −0.98 
                 0.25 
                 — 
                 — 
                 −2.80 
               
               
                 ninth surface S9 
                 aspherical 
                 423.22 
                 0.58 
                 1.53 
                 56.0 
                 — 
               
               
                 tenth surface S10 
                 aspherical 
                 1.41 
                 0.25 
                 — 
                 — 
                 −8.33 
               
               
                 eleventh surface S11 
                 standard 
                 Infinity 
                 0.30 
                 1.52 
                 58.6 
                 — 
               
               
                 twelfth surface S12 
                 standard 
                 Infinity 
                 1.07 
                 — 
                 — 
                 — 
               
               
                 image plane 20 
                 standard 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 aspherical 
                 first 
                 second 
                 third 
                 fourth 
                 fifth 
               
               
                 coefficient 
                 surface S1 
                 surface S2 
                 surface S3 
                 surface S4 
                 surface S5 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 A4 
                 −3.3E−03 
                 8.1E−03 
                 −0.0769 
                 9.4E−03 
                 −0.0589 
               
               
                 A6 
                 1.9E−03 
                 0.0370 
                 0.1175 
                 0.0456 
                 0.0127 
               
               
                 A8 
                 −4.1E−03 
                 −0.0326 
                 −0.0963 
                 −0.0436 
                 −9.0E−03 
               
               
                 A10 
                 8.3E−03 
                 7.4E−03 
                 0.0107 
                 0.0261 
                 0.0213 
               
               
                 A12 
                 −3.8E−03 
                 3.3E−06 
                 0.0117 
                 −0.0116 
                 −6.1E−03 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 7 
               
               
                   
               
               
                   
                 sixth 
                 seventh 
                 eighth 
                 ninth 
                 tenth 
               
               
                 aspherical 
                 surface 
                 surface 
                 surface 
                 surface 
                 surface 
               
               
                 coefficient 
                 S6 
                 S7 
                 S8 
                 S9 
                 S10 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 A4 
                 −0.0281 
                 0.0266 
                 −0.0672 
                 −0.0682 
                 −0.0679 
               
               
                 A6 
                 −9.0E−03 
                 −4.9E−03 
                 0.0131 
                 −6.0E−03 
                 0.0184 
               
               
                 A8 
                 1.5E−03 
                 −1.5E−03 
                 2.5E−03 
                 9.9E−03 
                 −4.8E−03 
               
               
                 A10 
                 −2.0E−03 
                 1.5E−03 
                 −1.7E−03 
                 −4.3E−03 
                 6.5E−04 
               
               
                 A12 
                 3.3E−03 
                 −4.9E−06 
                 4.2E−04 
                 5.5E−04 
                 −4.2E−05 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 F(mm) 
                 F/No 
                 2ω 
               
               
                   
               
             
            
               
                 4.52 
                 2.51 
                 65.43° 
               
               
                   
               
            
           
         
       
     
     In the embodiment, D=5.867 mm; TTL=5.66 mm; Z=0.121 mm; Y=1.44 mm; L=4.42 mm; F 1 =3.55 mm; F 3 =7.78 mm; F 5 =−2.63 mm. 
       FIGS. 10-13  are graphs of aberrations (spherical aberration, field curvature, distortion, and characteristic curves of modulation transfer function occurring in the image lens  100 ) of the second exemplary embodiment of the image lens  100  in the telephoto state.  FIGS. 14-17  are graphs of aberrations (spherical aberration, field curvature, distortion, and lateral chromatic aberration) of the second exemplary embodiment of the image lens  100  in the wide angle state. In  FIGS. 10 and 14 , curves are spherical aberration characteristic curves of F light (wavelength: 486 nm), d light (wavelength: 588 nm) and C light (wavelength: 654 nm) of the image system  100 . The spherical aberration of the image lens  100  of the second exemplary embodiment is from −0.05 mm to 0.05 mm. As illustrated in  FIGS. 11 and 15 , the curves T and S are respectively the tangential field curvature curve and the sagittal field curvature curve. The field curvature of the second exemplary embodiment of the image lens  100  is from −0.05 mm to 0.05 mm. In  FIGS. 12 and 16 , the distortion of the second exemplary embodiment of the image lens system  100  is from −2.00% to 2.00%. Furthermore, as shown in  FIG. 13 , for half of the Nyquist frequency (about 2241 p/mm), the MTF of the central field is greater than 55% (see curve mc), the MTF of the 0.8 field is greater than 40% (see curve mp), the MTF between the central field and the 0.8 field is in a range of: 40%˜55% (see curve mt, for example). As shown in  FIG. 17 , for half of the Nyquist frequency (about 2241 p/mm), the MTF of the central field is greater than 42% (see curve mc), the MTF of the 0.8 field is greater than 14% (see curve mp), the MTF between the central field and the 0.8 field is in a range of: 14%˜42% (see curve mt, for example). Overall, in this embodiment, the spherical aberration, the field curvature, the distortion, and the chief ray angle are limited in a small range. 
     Particular embodiments are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiments thereof without departing from the scope of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.