Patent Publication Number: US-2012033125-A1

Title: Imaging optical device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a miniaturized imaging optical device, and more particularly to a wafer-level photographic lens. 
     2. Description of Related Art 
     Wafer level optics is a technique of fabricating miniaturized optics such as lens module or camera module at the wafer level using semiconductor techniques. The wafer level optics is well adapted to mobile or handheld devices, to which photograph has become an indispensable function. 
     As the size of an image sensor, such as a charge-coupled devices (CCD) or a complementary metal-oxide-semiconductor image sensor (CIS), is scaled down, the photographic lens need be scaled down too. 
     Imaging lens design is a stringent process to achieve requirements such as low volume, light weight, low cost but high resolution. A general-purpose camera, either stand-alone or integrated with a handheld device such as a mobile phone, commonly uses two groups of imaging lenses in order to meet the high resolution demand. Each group includes two or more lenses that integrally accomplish required optical characteristics, and the two groups should also work together to achieve high performance. 
     Therefore, there is a need for a designer to propose a novel imaging optical device, particularly a wafer-level miniaturized optical device that has high image quality with low volume and light weight. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the embodiment of the present invention to provide an imaging optical device with high resolution and excellent optical characteristics suitable for modern handheld electronic devices. 
     According to one embodiment, the imaging optical device includes a first lens group and the second lens group disposed in an order from the object side to the image side. The first lens group has a positive refractive power, and includes at least a first lens, a second lens and a third lens in an order from an object side to an image side. Specifically, the first lens has an image-side surface in substantially contact with an object-side surface of the second lens, the second lens has an image-side surface in substantially contact with an object-side surface of the third lens, and the third lens has a convex image-side surface. The second lens group has a negative refractive power, and includes at least a fourth lens, a fifth lens and a sixth lens in an order from the object side to the image side. Specifically, the fourth lens has an image-side surface in substantially contact with an object-side surface of the fifth lens, and the fifth lens has an image-side surface in substantially contact with an object-side surface of the sixth lens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a lens arrangement of a wafer-level imaging optical device according to a first embodiment of the present invention; 
         FIG. 2A  and  FIG. 2B  show some performances of the imaging optical device according to the first embodiment; 
         FIG. 3  shows a lens arrangement of a wafer-level imaging optical device according to a second embodiment of the present invention; and 
         FIG. 4A  and  FIG. 4B  show some performances of the imaging optical device according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a lens arrangement of a wafer-level imaging optical device according to a first embodiment of the present invention. Although the optical devices of the following illustrated embodiments are fabricated by wafer level technique, it is appreciated by those skilled in the pertinent art that the embodiments may be generally adapted to a miniature optical device fabricated by either the wafer level technique or other fabrication techniques. According to present technology advancement, lens form of the wafer-level optics may be less than 1 μm. 
     In the drawing, the left side of the imaging optical device faces an object, and the right side of the imaging optical device faces an image (or an image plane). In the first embodiment, the imaging optical device includes two lens groups: a first lens group  1  and a second lens group  2  in the order from the object side to the image side. The first lens group  1  acts as a positive lens having a positive refractive power, and the second lens group  2  acts as a negative lens having a negative refractive power. Specifically, the first lens group  1  includes at least three lenses: a first lens  11 , a second lens  12  and a third lens  13  in the order from the object side to the image side. The first lens  11  has a concave object-side surface s 1 . The first lens  11  has an image-side surface s 2  in substantially contact with an object-side surface s 2  of the second lens  12 . The second lens  12  has an image-side surface s 3  in substantially contact with an object-side surface s 3  of the third lens  13 . The third lens  13  has a convex image-side surface s 4 . In the exemplary embodiment, the surface s 2  (i.e., the image-side surface of the first lens  11  and the object-side surface of the second lens  12 ) may, but not limited to, be planar. The surface s 3  (i.e., the image-side surface of the second lens  12  and the object-side surface of the third lens  13 ) may, but not limited to, be planar. 
     The second lens group  2  includes at least three lenses: a fourth lens  14 , a fifth lens  15  and a sixth lens  16  in the order from the object side to the image side. The fourth lens  14  has a convex object-side surface s 5 . The fourth lens  14  has an image-side surface s 6  in substantially contact with an object-side surface s 6  of the fifth lens  15 . The fifth lens  15  has an image-side surface s 7  in substantially contact with an object-side surface s 7  of the sixth lens  16 . The sixth lens  16  has a concave image-side surface s 8 . In the exemplary embodiment, the surface s 6  (i.e., the image-side surface of the fourth lens  14  and the object-side surface of the fifth lens  15 ) may, but not limited to, be planar. The surface s 7  (i.e., the image-side surface of the fifth lens  15  and the object-side surface of the sixth lens  16 ) may, but not limited to, be planar. 
     The imaging optical device may optionally include a cover glass  3  for an image sensor such as a charge-coupled device (CCD) or complementary metal-oxide-semiconductor image sensor (CIS). The cover glass  3  has, for example, a planar object-side surface s 9  and a planar image-side surface s 10 . 
     According to one aspect of the present embodiment, with respect to each lens group  1  or  2 , the refraction index of material of at least one lens is substantively different from the refraction index of material of other lens in the same lens group. 
     Table 1 shows some surface data according to the first embodiment, where the thickness and the radius may be unitless or in the unit, for example, of millimeter (mm). 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Material 
               
               
                   
                   
                   
                 nd: refraction index 
               
               
                 Surface 
                 Radius 
                 Thickness 
                 νd: dispersion index 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 s1 
                 −5.128 
                 0.0563 
                 nd = 1.52, νd = 50 
               
               
                 s2 
                 Infinity 
                 0.2567 
                 nd = 1.51, νd = 70 
               
               
                 s3 
                 Infinity 
                 0.1815 
                 nd = 1.52, νd = 50 
               
               
                 s4 
                 −0.513 
                 0.0428 
               
               
                 s5 
                  1.471 
                 0.1155 
                 nd = 1.52, νd = 50 
               
               
                 s6 
                 Infinity 
                 0.2567 
                 nd = 1.51, νd = 70 
               
               
                 s7 
                 Infinity 
                 0.0599 
                 nd = 1.52, νd = 50 
               
               
                 s8 
                  1.071 
                 0.3 
               
               
                 s9 
                 Infinity 
                 0.4 
                 nd = 1.5168, νd = 64.17 
               
               
                  s10 
                 Infinity 
                 0.061 
               
               
                   
               
            
           
         
       
     
     Table 2 shows some optical data according to the first embodiment. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
            
               
                   
                 F number (focal ratio) 
                 2.8 
               
               
                   
                 Effective focal length 
                 1 
               
               
                   
                 Field of view (FOV) 
                 60 degree 
               
               
                   
                 Effective focal length of first lens group 
                 1.05 
               
               
                   
                 Effective focal length of second lens group 
                 −12.04 
               
               
                   
                   
               
            
           
         
       
     
     The aspheric surface (e.g., s 1 , s 4 , s 5  or s 8 ) may be defined by the following equation: 
     
       
         
           
             z 
             = 
             
               
                 
                   cr 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                          
                         
                           c 
                           2 
                         
                          
                         
                           r 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   α 
                   1 
                 
                  
                 
                   r 
                   2 
                 
               
               + 
               
                 
                   α 
                   2 
                 
                  
                 
                   r 
                   6 
                 
               
               + 
               
                 
                   α 
                   3 
                 
                  
                 
                   r 
                   6 
                 
               
               + 
               
                 
                   α 
                   4 
                 
                  
                 
                   r 
                   8 
                 
               
               + 
               
                 
                   α 
                   5 
                 
                  
                 
                   r 
                   10 
                 
               
               + 
               
                 
                   α 
                   6 
                 
                  
                 
                   r 
                   12 
                 
               
               + 
               
                 
                   α 
                   7 
                 
                  
                 
                   r 
                   14 
                 
               
               + 
               
                 
                   α 
                   8 
                 
                  
                 
                   r 
                   16 
                 
               
             
           
         
       
     
     where α1=0 for all surfaces, z is a distance from the vertex of lens in the optical axis direction, r is a distance in the direction perpendicular to the optical axis, c is a reciprocal of radius of curvature on vertex of lens, k is a conic constant and α 1  to α 8  are aspheric coefficients. Table 3 shows exemplary constants and coefficients associated with the equation. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
             
            
               
                   
                 k 
                 α2 
                 α3 
                 α4 
               
               
                   
               
               
                 s1 
                 0 
                 −2.6132567 
                 73.09426 
                 −3041.4389 
               
               
                 s4 
                 −13.60203 
                 −9.6468524 
                 126.87827 
                 −1731.2702 
               
               
                 s5 
                 −49.9946 
                 4.1097678 
                 −64.356174 
                 596.94837 
               
               
                 s8 
                 1.095574 
                 1.859126 
                 −19.888752 
                 133.55797 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 α5 
                 α6 
                 α7 
                 α8 
               
               
                   
               
               
                 s1 
                 37217.507 
                 1144.2817 
                 −3587.0147 
                 228907.05 
               
               
                 s4 
                 12969.31 
                 2396.5052 
                 −737768.44 
                 3417732.6 
               
               
                 s5 
                 −1981.0921 
                 −11973.786 
                 115195.88 
                 −252363.83 
               
               
                 s8 
                 −398.74397 
                 −480.14211 
                 5863.3082 
                 −9972.8141 
               
               
                   
               
            
           
         
       
     
       FIG. 2A  and  FIG. 2B  show some performances of the imaging optical device according to the first embodiment. Specifically,  FIG. 2A  shows field curvature and  FIG. 2B  shows distortion. 
       FIG. 3  shows a lens arrangement of a wafer-level imaging optical device according to a second embodiment of the present invention. 
     In the drawing, the left side of the imaging optical device faces an object, and the right side of the imaging optical device faces an image (or an image plane). In the second embodiment, the imaging optical device includes two lens groups: a first lens group  4  and a second lens group  5  in the order from the object side to the image side. The first lens group  4  acts as a positive lens having a positive refractive power, and the second lens group  5  acts as a negative lens having a negative refractive power. Specifically, the first lens group  4  includes at least three lenses: a first lens  31 , a second lens  32  and a third lens  33  in the order from the object side to the image side. The first lens  31  has a convex object-side surface t 1 . The first lens  31  has an image-side surface t 2  in substantially contact with an object-side surface t 2  of the second lens  32 . The second lens  32  has an image-side surface t 3  in substantially contact with an object-side surface t 3  of the third lens  33 . The third lens  33  has a convex image-side surface t 4 . In the exemplary embodiment, the surface t 2  (i.e., the image-side surface of the first lens  31  and the object-side surface of the second lens  32 ) may, but not limited to, be planar. The surface t 3  (i.e., the image-side surface of the second lens  32  and the object-side surface of the third lens  33 ) may, but not limited to, be planar. 
     The second lens group  5  includes at least three lenses: a fourth lens  34 , a fifth lens  35  and a sixth lens  36  in the order from the object side to the image side. The fourth lens  34  has a concave object-side surface t 5 . The fourth lens  34  has an image-side surface t 6  in substantially contact with an object-side surface t 6  of the fifth lens  35 . The fifth lens  35  has an image-side surface t 7  in substantially contact with an object-side surface t 7  of the sixth lens  36 . The sixth lens  36  has a convex image-side surface t 8 . In the exemplary embodiment, the surface t 6  (i.e., the image-side surface of the fourth lens  34  and the object-side surface of the fifth lens  35 ) may, but not limited to, be planar. The surface t 7  (i.e., the image-side surface of the fifth lens  35  and the object-side surface of the sixth lens  36 ) may, but not limited to, be planar. 
     The imaging optical device may optionally include a cover glass  6  for an image sensor such as a charge-coupled device (CCD) or complementary metal-oxide-semiconductor image sensor (CIS). The cover glass  6  has, for example, a planar object-side surface t 9  and a planar image-side surface t 10 . 
     According to one aspect of the present embodiment, with respect to each lens group  4  or  5 , the refraction index of material of at least one lens is substantively different from the refraction index of material of other lens in the same lens group. 
     Table 4 shows some surface data according to the second embodiment, where the thickness and the radius may be unitless or in the unit, for example, of millimeter (mm). 
     
       
         
           
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                 Material 
               
               
                   
                   
                   
                 nd: refraction index 
               
               
                 Surface 
                 Radius 
                 Thickness 
                 νd: dispersion index 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 t1 
                  2.628 
                 0.0639 
                 nd = 1.52, νd = 50 
               
               
                 t2 
                 Infinity 
                 0.2515 
                 nd = 1.51, νd = 70 
               
               
                 t3 
                 Infinity 
                 0.2149 
                 nd = 1.52, νd = 50 
               
               
                 t4 
                 −0.265 
                 0.1354 
               
               
                 t5 
                 −0.283 
                 0.0713 
                 nd = 1.52, νd = 50 
               
               
                 t6 
                 Infinity 
                 0.2515 
                 nd = 1.51, νd = 70 
               
               
                 t7 
                 Infinity 
                 0.1382 
                 nd = 1.52, νd = 50 
               
               
                 t8 
                 −1.223 
                 0.1 
               
               
                 t9 
                 Infinity 
                 0.4 
                 nd = 1.5168, νd = 64.17 
               
               
                  t10 
                 Infinity 
                 0.077 
               
               
                   
               
            
           
         
       
     
     Table 5 shows some optical data according to the second embodiment. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
             
            
               
                   
                 F number (focal ratio) 
                 2.8 
               
               
                   
                 Effective focal length 
                 1 
               
               
                   
                 Field of view (FOV) 
                 60 degree 
               
               
                   
                 Effective focal length of first lens group 
                 0.49 
               
               
                   
                 Effective focal length of second lens group 
                 −0.85 
               
               
                   
                   
               
            
           
         
       
     
     The aspheric surface (e.g., t 1 , t 4 , t 5  or t 8 ) may be defined by the following equation: 
     
       
         
           
             z 
             = 
             
               
                 
                   cr 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                          
                         
                           c 
                           2 
                         
                          
                         
                           r 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   α 
                   1 
                 
                  
                 
                   r 
                   2 
                 
               
               + 
               
                 
                   α 
                   2 
                 
                  
                 
                   r 
                   4 
                 
               
               + 
               
                 
                   α 
                   3 
                 
                  
                 
                   r 
                   6 
                 
               
               + 
               
                 
                   α 
                   4 
                 
                  
                 
                   r 
                   8 
                 
               
               + 
               
                 
                   α 
                   5 
                 
                  
                 
                   r 
                   10 
                 
               
               + 
               
                 
                   α 
                   6 
                 
                  
                 
                   r 
                   12 
                 
               
               + 
               
                 
                   α 
                   7 
                 
                  
                 
                   r 
                   14 
                 
               
               + 
               
                 
                   α 
                   8 
                 
                  
                 
                   r 
                   16 
                 
               
             
           
         
       
     
     where α1=0 for all surfaces, z is a distance from the vertex of lens in the optical axis direction, r is a distance in the direction perpendicular to the optical axis, c is a reciprocal of radius of curvature on vertex of lens, k is a conic constant and α 1  to α 8  are aspheric coefficients. Table 6 shows exemplary constants and coefficients associated with the equation. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
             
            
               
                   
                 k 
                 α2 
                 α3 
                 α4 
               
               
                   
               
               
                 t1 
                 −31.60766 
                 −4.762182 
                 142.92806 
                 −5026.7395 
               
               
                 t4 
                 −6.540471 
                 −24.743838 
                 601.1817 
                 −9550.0428 
               
               
                 t5 
                 −1.535117 
                 15.340242 
                 −247.87977 
                 2421.9181 
               
               
                 t8 
                 2.965206 
                 5.7951023 
                 −30.400249 
                 114.99385 
               
               
                   
               
               
                   
                 α5 
                 α6 
                 α7 
                 α8 
               
               
                   
               
               
                 t1 
                 50330.12 
                 23.154433 
                 −1507.0367 
                 286.4907 
               
               
                 t4 
                 56336.211 
                 493979.31 
                 −9129582.1 
                 37986439 
               
               
                 t5 
                 −13831.562 
                 9674.4212 
                 291160.63 
                 −766184.37 
               
               
                 t8 
                 −402.756 
                 1035.8549 
                 131.372 
                 −4398.7019 
               
               
                   
               
            
           
         
       
     
       FIG. 4A  and  FIG. 4B  show some performances of the imaging optical device according to the second embodiment. Specifically,  FIG. 4A  shows field curvature and  FIG. 4B  shows distortion. 
     Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.