Optical imaging system

Abstract

An optical imaging system is provided comprising a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive or negative power; and a fourth lens group having a positive or negative power.

What is claimed is: 
     
       1. An optical imaging system comprising an image sensor for photoelectric conversion, the optical imaging system further comprising:
 a first lens group having a positive refractive power closest to a subject;   a second lens group closest to the first lens group and having a negative refractive power;   a third lens group having one of a positive or negative power; and   a fourth lens group having one of a positive or negative power,   wherein each of the first to fourth lens groups comprises an aspheric lens having at least one aspheric surface thereof; and   one of a thin film filter or an optical filter for restricting the transmission of a portion of light between the second and third lens groups or between the third and fourth lens groups.   
     
     
       2. An optical imaging system according to  claim 1 , wherein the first lens group comprises at least one lens of a positive refractive power. 
     
     
       3. An optical imaging system according to  claim 1 , wherein the second lens group comprises at least one lens of a negative refractive power. 
     
     
       4. An optical imaging system according to  claim 1 , wherein the third lens group comprises at least one lens of a positive or negative refractive power. 
     
     
       5. An optical imaging system according to  claim 1 , wherein a fourth lens group comprises at least one lens of a positive or negative refractive power. 
     
     
       6. An optical imaging system according to  claim 1 , wherein the optical imaging system satisfies 
       
         
           
             
               
                 0.3 
                 < 
                 
                   
                     f 
                     1 
                   
                   f 
                 
                 < 
                 3.1 
               
               , 
             
           
         
         wherein f denotes synthetic focus distance of the optical imaging system and f 1  denotes focus distance of the first lens group. 
       
     
     
       7. An optical imaging system according to  claim 1 , wherein the optical imaging system satisfies 
       
         
           
             
               
                 0.3 
                 < 
                 
                   
                      
                     
                       f 
                       2 
                     
                      
                   
                   f 
                 
                 < 
                 8.99 
               
               , 
             
           
         
         wherein f denotes a synthetic focus distance of the optical imaging system and f 2  denotes a focus distance of the second lens group. 
       
     
     
       8. An optical imaging system according to  claim 1 , wherein the optical imaging system satisfies 
       
         
           
             
               
                 0.19 
                 < 
                 
                   
                      
                     
                       f 
                       3 
                     
                      
                   
                   f 
                 
                 < 
                 ∞ 
               
               , 
             
           
         
         wherein f denotes a synthetic focus distance of the optical imaging system and f 3  denotes a focus distance of the third lens group. 
       
     
     
       9. An optical imaging system according to  claim 1 , wherein the optical imaging system satisfies 
       
         
           
             
               
                 0.15 
                 < 
                 
                   
                      
                     
                       f 
                       4 
                     
                      
                   
                   f 
                 
                 < 
                 ∞ 
               
               , 
             
           
         
       
       wherein f denotes a synthetic focus distance of the optical imaging system and f 4  denotes a focus distance of the second lens group. 
     
     
       10. An optical imaging system comprising an image sensor for photoelectric conversion, the optical imaging system further comprising:
 a first lens group having a positive refractive power;   a second lens group having a negative refractive power;   a third lens group having one of a positive or negative power; and   a fourth lens group having one of a positive or negative power, wherein the optical imaging system satisfies   
       
         
           
             
               
                 0.45 
                 < 
                 
                   f 
                   TTL 
                 
                 < 
                 1.01 
               
               , 
             
           
         
       
       wherein f denotes a synthetic focus distance of die optical imaging system and TTL denotes a distance from an iris surface to an imaging surface;
 wherein a lens located in the first lens group and having at least one aspheric surface; and 
 one of a thin film filter or an optical filter for restricting the transmission of a portion of light between the second and third lens groups or between the third and fourth lens groups. 
 
     
     
       11. An optical imaging system according to  claim 10 , further comprising a parallel flat glass disposed between the image sensor and the fourth lens group. 
     
     
       12. An optical imaging system comprising an image sensor for photoelectric conversion, the optical imaging system further comprising:
 a first lens group having a positive refractive power;   a second lens group having a negative refractive power;   a third lens group having one of a positive or negative power; and   a fourth lens group having one of a positive or negative power, wherein the first and second lens groups satisfy an optical axis direction size according to   
       
         
           
             
               
                 0 
                 < 
                 
                   
                     d 
                     1 
                   
                   TTL 
                 
                 < 
                 0.26 
               
               , 
             
           
         
       
       wherein d 1  denotes a separated distance between the first lens group and the second lens group on the optical axis and TTL denotes a distance from an iris surface to an imaging surface;
 wherein a lens located in the first lens group and having at least one aspheric surface; and 
 one of a thin film filter or an optical filter for restricting the transmission of a portion of light between the second and third lens groups or between the third and fourth lens groups. 
 
     
     
       13. An optical imaging system according to  claim 12 , further comprising a parallel flat glass disposed between the image sensor and the fourth lens group. 
     
     
       14. An optical imaging system comprising an image sensor for photoelectric conversion, the optical imaging system further comprising:
 a first lens group having a positive refractive power;   a second lens group having a negative refractive power;   a third lens group having one of a positive or negative power; and   a fourth lens group having one of a positive or negative power, wherein the third and fourth lens groups satisfy an optical axis direction size according to   
       
         
           
             
               
                 0 
                 < 
                 
                   
                     d 
                     3 
                   
                   TTL 
                 
                 < 
                 0.40 
               
               , 
             
           
         
         wherein d 3  denotes a separated distance between the third lens group and the fourth lens group on the optical axis and TIL denotes a distance from an iris surface to an imaging surface; 
       
       wherein a lens located in the first lens group and having at least one aspheric surface; and
 one of a thin film filter or an optical filter for restricting the transmission of a portion of light between the second and third lens groups or between the third and fourth lens groups. 
 
     
     
       15. An optical imaging system according to  claim 14 , further comprising a parallel flat glass disposed between the image sensor and the fourth lens group. 
     
     
       16. An optical imaging system comprising an image sensor for photoelectric conversion, the optical imaging system further comprising:
 a first lens group having a positive refractive power closest to a subject;   a second lens group closest to the first lens group and having a negative refractive power;   a third lens group having one of a positive or negative power; and   a fourth lens group having one of a positive or negative power,   wherein each of the first to fourth lens groups comprises an aspheric lens having at least one aspheric surface thereof, and   wherein the Abbe's numbers of the first and second lens groups G 1  and G 2  satisfy
   28.2<υ1−υ2<42.8,
 
   
       wherein υ 1  and υ 2  denote Abbe's numbers representing the distribution characteristics of the first and second lens groups respectively. 
     
     
       17. An optical imaging system for pickup comprising, in order from object side to image side:
 a first lens with a positive refractive power having an object side surface with a positive curvature;   a second lens with a negative refractive power having an object side surface with a negative curvature and an image side surface with a positive curvature;   a third lens with a refractive power having an object side surface with negative curvature and an image side surface with negative curvature; and   a fourth lens with a negative refractive power;   wherein each of the first lens, the second lens, the third lens, the fourth lens is an aspheric lens having at least one aspheric surface thereof,   wherein an Abbe number of the first lens is v1, an Abbe number of the second lens is v2, and the following condition is satisfied:
   28.2<v1−v2<42.8.
 
   
     
     
       18. The optical imaging system of claim 17, wherein the first lens comprises an image side surface with a negative or positive curvature. 
     
     
       19. The optical imaging system of claim 17, wherein the first lens and the second lens contact each other. 
     
     
       20. The optical imaging system of claim 17, wherein the third lens is a lens with a positive refractive power. 
     
     
       21. The optical imaging system of claim 17, wherein an object side surface and an image side surface of the fourth lens are aspheric. 
     
     
       22. The optical imaging system of claim 17, wherein the fourth lens comprises an object side surface with a negative curvature and an image side surface with a positive curvature. 
     
     
       23. The optical imaging system of claim 22, wherein a sign of the curvature of at least one of the object side surface or the image side surface of the fourth lens is changed from an optical axis towards an edge of the fourth lens. 
     
     
       24. The optical imaging system of claim 17, wherein the optical imaging system satisfies the following equation:
   0.45<f/TTL<1.01,   wherein f denotes a total focal length of the optical imaging system and TTL denotes a distance from an iris to an imaging surface.   
     
     
       25. The optical imaging system of claim 17, wherein the optical imaging system satisfies the following equations:
   0.3<f1/f<3.1     0.3<|f2|/f<8.99,   wherein f denotes a total focal length of the optical imaging system, f1 denotes a focal length of the first lens, and f2 denotes a focal length of the second lens.   
     
     
       26. The optical imaging system of claim 17, wherein the optical imaging system satisfies the following equations:
   0.19<|f3|/f<∞
     0.15<|f4|/f<∞,
   wherein f denotes a total focal length of the optical imaging system, f3 denotes a focal length of the third lens, and f4 denotes a focal length of the fourth lens.   
     
     
       27. The optical imaging system of claim 17, wherein an iris is disposed at an object side of the first lens. 
     
     
       28. The optical imaging system of claim 17, wherein the optical imaging system satisfies the following equation:
   0<d1/TTL<0.26,   wherein d1 denotes a separated distance between the first lens and the second lens on the optical axis and TTL denotes a distance from an iris to an imaging surface.   
     
     
       29. The optical imaging system of claim 17, wherein the optical imaging system satisfies the following equation:
   0<d3/TTL<0.40,   wherein d3 denotes a separated distance between the third lens and the fourth lens on the optical axis and TTL denotes a distance from an iris to an imaging surface.   
     
     
       30. An optical imaging system for pickup comprising, in order from object side to image side:
 a first lens with a positive refractive power;   a second lens with a negative refractive power having an object side surface with a negative curvature and an image side surface with a positive curvature;   a third lens with a refractive power; and   a fourth lens with a negative refractive power;   wherein each of the first lens, the second lens, the third lens, the fourth lens is an aspheric lens having at least one aspheric surface thereof,   wherein an Abbe number of the first lens is v1, an Abbe number of the second lens is v2, and the following condition is satisfied:
   28.2<v1−v2<42.8.
 
   
       
        
       
     
     
       31. The optical imaging system of claim 30, wherein the first lens comprises an object side surface with a positive curvature and an image side surface with a negative curvature. 
     
     
       32. The optical imaging system of claim 30, wherein the third lens is a lens with a positive refractive power. 
     
     
       33. The optical imaging system of claim 30, wherein the third lens comprises an object side surface with a negative curvature and an image side surface with a negative curvature. 
     
     
       34. The optical imaging system of claim 30, wherein the fourth lens comprises an object side surface with a negative curvature and an image side surface with a positive curvature. 
     
     
       35. The optical imaging system of claim 34, wherein a sign of the curvature of at least one of the object side surface or the image side surface of the fourth lens is changed from an optical axis towards an edge of the fourth lens. 
     
     
       36. The optical imaging system of claim 30, wherein an object side surface and an image side surface of the fourth lens are aspheric.