Position detection unit, lens module, and imaging apparatus

1. A position detection unit comprising:

a magnetic sensor; and

a first magnetic field generator spaced from and opposed to the magnetic sensor in a first-axis direction, including a first multipolar magnet and generating a first magnetic field to be exerted on the magnetic sensor, the first multipolar magnet including a plurality of N poles and a plurality of S poles, the N and S poles being adjacent to each other along a plane orthogonal to the first-axis direction, wherein

the magnetic sensor and the first magnetic field generator are relatively movable with respect to each other along a second-axis direction orthogonal to the first-axis direction, and

a center position of the magnetic sensor in a third-axis direction orthogonal to both of the first-axis direction and the second-axis direction is different from a position in the third-axis direction of an interface between the N and S poles adjacent to each other in the third-axis direction.

2. The position detection unit according to claim 1 , wherein

the first magnetic field includes a first magnetic field component, and a second magnetic field component having a phase difference from the first magnetic field component, and

the magnetic sensor is configured to generate a detection signal corresponding to a direction of a detection-target magnetic field, and configured to detect a positional change of the first magnetic field generator, the detection-target magnetic field being a magnetic field to be detected, and being a composite of the first magnetic field component and the second magnetic field component in the plane.

3. The position detection unit according to claim 1 , wherein

the first multipolar magnet includes a first N pole and a second N pole as the plurality of N poles, and a first S pole and a second S pole as the plurality of S poles,

the first N pole and the first S pole are adjacent to each other in the third-axis direction,

the second N pole and the second S pole are adjacent to each other in the third-axis direction,

the first N pole and the second S pole are adjacent to each other in the second-axis direction, and

the second N pole and the first S pole are adjacent to each other in the second-axis direction.

4. The position detection unit according to claim 1 , wherein the first multipolar magnet includes

a first region part magnetized in a first direction along the third-axis direction, and

a second region part magnetized in a second direction that is along the third-axis direction and opposite to the first direction.

5. The position detection unit according to claim 4 , wherein the first multipolar magnet further includes a neutral zone between the first region part and the second region part.

6. The position detection unit according to claim 5 , wherein the neutral zone extends along the third-axis direction.

7. The position detection unit according to claim 1 , wherein the first multipolar magnet has a longitudinal direction along the second-axis direction.

8. The position detection unit according to claim 1 , wherein the interface extends along the second-axis direction.

9. The position detection unit according to claim 1 , wherein the magnetic sensor and the first multipolar magnet are relatively movable with respect to each other along the second-axis direction while keeping a state of overlapping each other in the first-axis direction.

10. The position detection unit according to claim 1 , further comprising a second magnetic field generator generating a second magnetic field, wherein

the first magnetic field generator is movable along the second-axis direction with respect to the magnetic sensor and the second magnetic field generator owing to the second magnetic field.

11. The position detection unit according to claim 10 , wherein the second magnetic field generator includes a second multipolar magnet including a plurality of N poles and a plurality of S poles.

12. The position detection unit according to claim 11 , wherein

the second magnetic field generator includes a pair of the second multipolar magnets, the second multipolar magnets being opposed to each other in the third-axis direction and each extending along the first-axis direction, and

the magnetic sensor is interposed between the second multipolar magnets in the third-axis direction.

13. The position detection unit according to claim 10 , further comprising a first holding member holding the first magnetic field generator, wherein

the first holding member is movable in the second-axis direction owing to the second magnetic field.

14. The position detection unit according to claim 13 , wherein the first holding member is configured to hold a lens having an optical axis along the second-axis direction.

15. The position detection unit according to claim 10 , further comprising a second holding member holding the magnetic sensor and the second magnetic field generator.

16. The position detection unit according to claim 1 , wherein the magnetic sensor is configured to detect each of an intensity of a first magnetic field component along the second-axis direction and an intensity of a second magnetic field component along the third-axis direction.

17. The position detection unit according to claim 1 , wherein the magnetic sensor is configured to detect a direction of a composite magnetic field, the composite magnetic field being a composite of a first magnetic field component along the second-axis direction and a second magnetic field component along the third-axis direction.

18. A lens module comprising:

a magnetic sensor;

a first magnetic field generator spaced from and opposed to the magnetic sensor in a first-axis direction, including a first multipolar magnet and generating a first magnetic field to be exerted on the magnetic sensor, the first multipolar magnet including a plurality of N poles and a plurality of S poles, the N and S poles being adjacent to each other along a plane orthogonal to the first-axis direction;

a second magnetic field generator generating a second magnetic field; and

a lens, wherein

the first magnetic field generator and the lens are relatively movable with respect to the magnetic sensor and the second magnetic field generator along a second-axis direction orthogonal to the first-axis direction, and

a center position of the magnetic sensor in a third-axis direction orthogonal to both of the first-axis direction and the second-axis direction is different from a position in the third-axis direction of an interface between the N and S poles adjacent to each other in the third-axis direction.

19. The lens module according to claim 18 , further comprising:

a first holding member holding the first magnetic field generator and the lens; and

a second holding member holding the second magnetic field generator and the magnetic sensor, wherein

the first holding member is movable along the second-axis direction with respect to the second holding member.

20. An imaging apparatus including

an imaging element, and

a lens module,

the lens module comprising:

a magnetic sensor;

a first magnetic field generator spaced from and opposed to the magnetic sensor in a first-axis direction, including a first multipolar magnet and generating a first magnetic field to be exerted on the magnetic sensor, the first multipolar magnet including a plurality of N poles and a plurality of S poles, the N and S poles being adjacent to each other along a plane orthogonal to the first-axis direction;

a second magnetic field generator generating a second magnetic field; and

a lens, wherein

the first magnetic field generator and the lens are relatively movable with respect to the magnetic sensor and the second magnetic field generator along a second-axis direction orthogonal to the first-axis direction, and

a center position of the magnetic sensor in a third-axis direction orthogonal to both of the first-axis direction and the second-axis direction is different from a position in the third-axis direction of an interface between the N and S poles adjacent to each other in the third-axis direction.