Auto-focusing apparatus having asymmetric supporting structure

Abstract

Disclosed is an auto-focusing apparatus having an asymmetric supporting structure, which includes a first frame having a magnet; a second frame having an AF coil for moving the first frame in an optical axis direction; a first ball group located between the first frame and the second frame and having a number of balls arranged along the optical axis direction; and a second ball group located between the first frame and the second frame at a position different from the first ball group and having a number of balls arranged along the optical axis direction. The first ball group include two first support balls having a greater size than the other balls in the first ball group, and the second ball group includes two second support balls having a greater size than the other balls in the second ball group.

What is claimed is: 
     
       1. An auto-focusing apparatus having an asymmetric supporting structure, comprising:
 a first frame having a magnet; 
 a second frame having an AF coil for moving the first frame in an optical axis direction; 
 a first ball group located between the first frame and the second frame and having a n (n is a natural number of 4 or above) number of balls arranged along the optical axis direction; and 
 a second ball group located between the first frame and the second frame at a position different from the first ball group and having a m (m is a natural number of 4 or above) number of balls arranged along the optical axis direction, 
 wherein the first ball group includes two first support balls having a greater size than the other balls in the first ball group, and the second ball group includes two second support balls having a greater size than the other balls in the second ball group; 
 wherein the first support balls are located at both ends of the first ball group, and 
 wherein the second support balls are located at a center of the second ball group and adjacent to each other. 
 
     
     
       2. The auto-focusing apparatus having an asymmetric supporting structure according to  claim 1 ,
 wherein the first support balls and the second support balls have the same size. 
 
     
     
       3. The auto-focusing apparatus having an asymmetric supporting structure according to  claim 1 ,
 wherein the n and the m are 4, and 
 wherein the first support balls are located at first and fourth positions in the first ball group based on the optical axis direction, and the second support balls are located at second and third positions in the second ball group based on the optical axis direction. 
 
     
     
       4. The auto-focusing apparatus having an asymmetric supporting structure according to  claim 1 ,
 wherein the first frame has first and second guiding grooves extending along the optical axis direction, 
 wherein the second frame has first and second accommodating grooves respectively facing the first and second guiding grooves, and 
 wherein the first ball group is located between the first guiding groove and the first accommodating groove, and the second ball group is located between the second guiding groove and the second accommodating groove. 
 
     
     
       5. The auto-focusing apparatus having an asymmetric supporting structure according to  claim 4 ,
 wherein at least one of the first guiding groove and the first accommodating groove has a V-shaped cross section. 
 
     
     
       6. An auto-focusing apparatus having an asymmetric supporting structure, comprising:
 a first frame having a magnet;   a second frame having an AF coil for moving the first frame in an optical axis direction;   a first ball group located between the first frame and the second frame and having a plurality of balls arranged along the optical axis direction; and   a second ball group located between the first frame and the second frame at a position different from the first ball group and having a plurality of balls arranged along the optical axis direction,   wherein the first ball group includes two first support balls making point contact with the first frame or the second frame, and the second ball group includes two second support balls making point contact with the first frame or the second frame; and   a pitch between the two second support balls is smaller than a pitch between the two first support balls,   wherein the two first support balls are located at both ends of the first ball group; and   the second support balls are located at a center of the second ball group and adjacent to each other.