Actuator and camera module including same

1. An actuator, comprising:

a detection target disposed on a surface of a lens barrel; and

a position detecting unit comprising two or more sensing coils and configured to detect a displacement of the detection target in a first direction perpendicular to an optical axis,

wherein when the detection target moves in a second direction perpendicular to the optical axis, an area of overlap between each of the two or more sensing coils and the detection target is maintained constant.

2. The actuator of claim 1 , wherein the first direction corresponds to a direction perpendicular to a surface on which the two or more sensing coils are disposed.

3. The actuator of claim 1 , wherein the second direction corresponds to a direction parallel with a surface on which the two or more sensing coils are disposed.

4. The actuator of claim 1 , wherein the two or more sensing coils comprise a main-sensing coil and a sub-sensing coil.

5. The actuator of claim 4 , wherein an inductance of the main-sensing coil is greater than that of the sub-sensing coil.

6. The actuator of claim 5 , wherein the main-sensing coil and the sub-sensing coil are disposed to face the detection target.

7. The actuator of claim 5 , wherein a range in which the detection target is movable in the second direction is positioned to overlap in a hollow portion of the main-sensing coil, and the sub-sensing coil is disposed inside the hollow portion of the main-sensing coil.

8. The actuator of claim 4 , wherein the main-sensing coil is disposed to face the detection target, and the sub-sensing coil is disposed outside a range in which the detection target is movable in the second direction.

9. The actuator of claim 4 , wherein a range in which the detection target is movable in the second direction is positioned to overlap in a hollow portion of the main-sensing coil, and the sub-sensing coil is disposed outside of the hollow portion of the main-sensing coil.

10. An actuator, comprising:

a detection target disposed on a surface of a lens barrel;

an oscillating unit comprising two or more oscillation circuits, each of the two or more oscillation circuits comprising a sensing coil; and

a detecting unit configured to calculate a position of the detection target in a first direction perpendicular to an optical axis in response to a difference between frequencies of two or more oscillation signals output from the two or more oscillation circuits, respectively,

wherein when the detection target moves in a second direction perpendicular to the optical axis, the frequencies of the two or more oscillation signals are maintained constant.

11. The actuator of claim 10 , wherein the two or more sensing coils comprise a main-sensing coil and a sub-sensing coil, and

when the detection target moves in the second direction, an area of overlap between each of the main-sensing coil and the sub-sensing coil and the detection target is maintained constant.

12. The actuator of claim 11 , wherein an inductance of the main-sensing coil is greater than that of the sub-sensing coil.

13. The actuator of claim 12 , wherein the main-sensing coil and the sub-sensing coil are disposed to face the detection target.

14. The actuator of claim 12 , wherein a range in which the detection target is movable in the second direction is positioned to overlap in a hollow portion of the main-sensing coil, and the sub-sensing coil is disposed inside the hollow portion of the main-sensing coil.

15. The actuator of claim 11 , wherein the main-sensing coil is disposed to face the detection target, and the sub-sensing coil is disposed outside a range in which the detection target is movable in the second direction.

16. The actuator of claim 11 , wherein a range in which the detection target is movable in the second direction is positioned to overlap in a hollow portion of the main-sensing coil, and the sub-sensing coil is disposed outside of the hollow portion of the main-sensing coil.

17. An actuator, comprising:

a first detection target disposed on a lateral surface of a body and a second detection target disposed on an other surface of the body; and

a detecting unit comprising two or more first sensing coils configured to detect a displacement of the first detection target perpendicular to the lateral surface and two or more second sensing coils configured to detect a displacement of the second detection target perpendicular to the other surface,

wherein overlap area of the first detection target with the first sensing coils remains constant when the body moves perpendicular to the lateral surface and overlap area of the second detection target with the second sensing coils remains constant when the body moves perpendicular to the other surface.

18. The actuator of claim 17 , wherein the body comprises a lens barrel comprising an optical axis parallel to the lateral surface and the other surface.

19. The actuator of claim 17 , wherein the two or more first sensing coils comprise coils of different inductances, and

wherein the two or more second sensing coils comprise coils of different inductances.

20. The actuator of claim 17 , further comprising a computing unit configured to receive oscillation signals from circuits comprising the first and second sensing coils, and to output a frequency corresponding to each received signal,

wherein the detecting unit is further configured to calculate a position of the body in a direction perpendicular to the lateral surface in response to a difference between frequencies corresponding to the two or more first sensing coils, and in a direction perpendicular to the other surface in response to a difference between frequencies corresponding to the two or more second sensing coils.