Voice coil motor
A VCM is disclosed, the motor including a stator including a first driving unit, a rotor arranged inside the stator, including a second driving unit responding to the first driving unit and mounted therein with a lens, a base fixing the stator, and an elastic member coupled to the rotor to float the rotor from the base in a case a driving signal for driving the first and second driving units is not applied to the first and second driving units.
1. A lens driving device comprising:
a base;
a bobbin disposed over the base;
a coil block disposed outside of the bobbin;
a magnet facing the coil block;
an elastic member coupled to the bobbin and configured to distance the bobbin from the base at an initial position when no current is applied to the coil block,
wherein the bobbin is configured to travel from the initial position in a first direction approaching the base when a forward current is applied to the coil block and to travel from the initial position in a second direction distancing from the base when a backward current is applied to the coil block, and
wherein the lens driving device is configured such that a first stroke length of the bobbin in the first direction is different from a second stroke length of the bobbin in the second direction.
2. The lens driving device of claim 1 , wherein the lens driving device is configured such that a maximum of the first stroke length of the bobbin in the first direction is different from a maximum of the second stroke length of the bobbin in the second direction.
3. The lens driving device of claim 2 , wherein the lens driving device is configured such that the maximum of the first stroke length is determined by the bobbin and the base.
4. The lens driving device of claim 2 , wherein the maximum of the first stroke length is a distance traveled by the bobbin from the initial position until the bobbin contacts a first stopper.
5. The lens driving device of claim 4 , wherein the maximum of the second stroke length is a distance traveled by the bobbin from the initial position until the bobbin contacts a second stopper.
6. The lens driving device of claim 4 , wherein the first stopper includes an upper surface of the base or a shock absorber disposed on the upper surface of the base.
7. The lens driving device of claim 5 , further comprising a cover disposed over the bobbin, wherein the second stopper includes a portion of the cover, an inner surface of the cover, or a shock absorber disposed on the inner surface of the cover.
8. The lens driving device of claim 7 , wherein the bobbin is configured to travel from a position where the bobbin contacts the first stopper to a position where the bobbin contacts the second stopper.
9. The lens driving device of claim 1 , wherein the lens driving device is configured such that the base is configured to limit a movement of the bobbin in the first direction.
10. The lens driving device of claim 1 , wherein the coil block is disposed around an outer surface of the bobbin.
11. The lens driving device of claim 1 , wherein the magnet is mounted on the bobbin.
12. The lens driving device of claim 1 , wherein the bobbin includes a hole formed therethrough and has a screw thread on an inner surface thereof for fixing a lens.
13. The lens driving device of claim 1 , further comprising:
a cover disposed over the bobbin, wherein the cover is configured to surround the bobbin, the coil block and the magnet.
14. The lens driving device of claim 13 , wherein the cover includes:
an upper plate having an opening; and
a lateral plate extended from an edge of the upper plate toward the base.
15. The lens driving device of claim 14 , wherein the lateral plate of the cover is coupled to the base.
16. The lens driving device of claim 13 , wherein the lens driving device is configured such that a maximum of the second stroke length is determined by the bobbin and the cover.
17. The lens driving device of claim 13 , wherein the lens driving device is configured such that the cover is configured to limit a movement of the bobbin in the second direction.
18. The lens driving device of claim 13 , wherein a first imaginary line, which is perpendicular to the first direction and bisects a second imaginary line that is parallel to the first direction and has as its endpoints an upper surface of the bobbin and a lower surface of the bobbin, is dislocated from a third imaginary line, which is perpendicular to the first direction and bisects a fourth imaginary line that is parallel to the first direction and has as its endpoints an upper surface of the base and an inner surface of an upper plate of the cover.
19. The lens driving device of claim 18 , wherein the coil block is disposed around an outer surface of the bobbin.
20. The lens driving device of claim 18 , wherein the magnet is mounted on the bobbin.
21. The lens driving device of claim 18 , wherein the first imaginary line is positioned closer to the base than the third imaginary line is.
22. The lens driving device of claim 18 , wherein the first imaginary line is positioned farther from the base than the third imaginary line is.
23. The lens driving device of claim 13 , wherein, when the bobbin is at the initial position, a distance from a lower surface of the bobbin to an upper surface of the base is different from a distance from the upper surface of the bobbin to an inner surface of the upper plate of the cover.
24. The lens driving device of claim 23 , wherein the distance between the lower surface of the bobbin and the upper surface of the base is shorter than the distance between the upper surface of the bobbin and the inner surface of the upper plate of the cover.
25. The lens driving device of claim 1 , wherein the first stroke length is shorter than the second stroke length.
26. The lens driving device of claim 25 , wherein the second stroke length is from two to three times longer than the first stroke length.
27. The lens driving device of claim 1 , wherein the first stroke length is longer than the second stroke length.
28. The lens driving device of claim 1 , wherein a groove is concavely formed on an upper surface of the base, and
wherein the bobbin and the base are configured such that the bobbin is partially disposed in the groove when the forward current is applied to the coil block and the bobbin has traveled a maximum of the first stroke length in the first direction.
29. A camera comprising a lens and the lens driving device for driving the lens according to claim 1 .
30. A digital apparatus comprising the camera according to claim 29 .