Position detection unit, lens module, and imaging apparatus
A position detection unit includes a magnetic sensor, a first magnetic field generator, and a second magnetic field generator. The first magnetic field generator includes a first magnet and a second magnet spaced apart from each other in a first direction, and generates a first magnetic field. The second magnetic field generator generates a second magnetic field and is movable along a second direction orthogonal to the first direction with respect to the first magnetic field generator and the magnetic sensor. In the first direction, a center position of the magnetic sensor lies at a position in a region between the first magnet and the second magnet other than a midpoint position between the first magnet and the second magnet. The magnetic sensor generates a detection signal corresponding to a direction of a magnetic field to be detected, and detects a positional change of the second magnetic field generator.
1. A position detection unit comprising:
a magnetic sensor;
a first magnetic field generator that includes a first magnet and a second magnet and generates a first magnetic field, the first magnet and the second magnet being spaced apart from each other in a first direction; and
a second magnetic field generator that generates a second magnetic field and is movable along a second direction orthogonal to the first direction with respect to the first magnetic field generator and the magnetic sensor, wherein
in the first direction, a center position of the magnetic sensor lies at a position in a region between the first magnet and the second magnet other than a midpoint position between the first magnet and the second magnet,
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 second magnetic field generator, the detection-target magnetic field being a magnetic field to be detected, and being a composite of the first magnetic field along a plane orthogonal to the second direction and the second magnetic field along the plane,
the first magnet and the second magnet each include a vertex defined by a first plane and a second plane, the first plane and the second plane meeting together to form the vertex, the first plane forming an angle of 90 degrees plus or minus 5 degrees with respect to the plane and an angle of 45 degrees plus or minus 5 degrees with respect to the first direction, the second plane forming an angle of 90 degrees plus or minus 5 degrees with respect to the plane and an angle of 90 degrees plus or minus 5 degrees with respect to the first plane,
the second plane at the first magnet and the second plane at the second magnet form an angle of 90 degrees plus or minus 5 degrees with respect to each other,
the first magnet and the second magnet are arranged in orientations that allow a distance from the magnetic sensor to the first magnet and a distance from the magnetic sensor to the second magnet to be smallest at their respective vertexes, and
an expression (1) is satisfied:
0 <D< ( G× 2/5) (1)
where
D represents a distance from the midpoint position between the vertex of the first magnet and the vertex of the second magnet in the first direction to the center position of the magnetic sensor in the first direction, and
G represents a distance between the vertex of the first magnet and the vertex of the second magnet in the first direction.
2. The position detection unit according to claim 1 , wherein, in the first direction, an entirety of the magnetic sensor is disposed at a position in the region between the first magnet and the second magnet other than the midpoint position between the first magnet and the second magnet.
3. The position detection unit according to claim 1 , wherein, in the first direction, the second magnetic field generator is disposed in the region between the first magnet and the second magnet, with a portion of the second magnetic field generator lying at the midpoint position between the first magnet and the second magnet.
4. The position detection unit according to claim 1 , wherein a center position of the second magnetic field generator in the first direction lies at the midpoint position between the first magnet and the second magnet in the first direction.
5. The position detection unit according to claim 1 , wherein an expression (2) is satisfied:
( G/ 6)< D <( G/ 3) (2).
6. The position detection unit according to claim 1 , wherein
the first magnet and the second magnet each include a first magnetic material and have a first shape, and
the second magnetic field generator includes a third magnet including a second magnetic material and having a second shape.
7. The position detection unit according to claim 6 , wherein the first magnet has a first temperature coefficient of residual magnetic flux density, and the second magnet has a second temperature coefficient of residual magnetic flux density, the second temperature coefficient of residual magnetic flux density being smaller in absolute value than the first temperature coefficient of residual magnetic flux density.
8. The position detection unit according to claim 6 , wherein
the first magnetic material includes NdFeB, and
the second magnetic material includes SmCo.
9. The position detection unit according to claim 1 , further comprising:
a first holding member holding the first magnetic field generator; and
a second holding member holding the second magnetic field generator and movable along the second direction with respect to the first holding member.
10. The position detection unit according to claim 9 , wherein the second holding member is configured to hold a lens having an optical axis along the second direction.
11. The position detection unit according to claim 1 , wherein the magnetic sensor has a sensitive axis parallel to the plane orthogonal to the second direction.
12. A lens module comprising:
the position detection unit according to claim 1 ; and
a lens movable along the second direction in conjunction with the second magnetic field generator with respect to the first magnetic field generator and the magnetic sensor.
13. The lens module according to claim 12 , further comprising:
a first holding member holding the first magnetic field generator; and
a second holding member holding the second magnetic field generator and the lens, and movable along the second direction with respect to the first holding member.
14. An imaging apparatus including
the lens module according to claim 12 , and
an imaging element.
15. A position detection unit comprising: 7 .
a magnetic sensor;
a first magnetic field generator that includes a first magnet and a second magnet and generates a first magnetic field, the first magnet and the second magnet being spaced apart from each other in a first direction; and
a second magnetic field generator that generates a second magnetic field and is movable along a second direction orthogonal to the first direction with respect to the first magnetic field generator and the magnetic sensor, wherein
in the first direction, a center position of the magnetic sensor lies at a position in a region between the first magnet and the second magnet other than a midpoint position between the first magnet and the second magnet,
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 second magnetic field generator, the detection-target magnetic field being a magnetic field to be detected, and being a composite of the first magnetic field along a plane orthogonal to the second direction and the second magnetic field along the plane,
the first magnet and the second magnet each include:
a first plane that forms an angle of 90 degrees plus or minus 5 degrees with respect to the plane and is along the first direction; and
a second plane including a portion that forms an angle of 90 degrees plus or minus 5 degrees with respect to the plane and forms an angle of less than or equal to 45 degrees plus or minus 5 degrees with respect to the first plane,
the second plane of the first magnet and the second plane of the second magnet are opposed to each other in the first direction and increase in distance from each other in the first direction as a distance from the first plane to the second plane in the first magnet and a distance from the first plane to the second plane in the second magnet increase, and
an expression (3) is satisfied:
0< D <( G/ 4) (3)
where
D represents a distance from the midpoint position between the first magnet and the second magnet in the first direction to the center position of the magnetic sensor in the first direction, and
G represents a shortest distance between the first magnet and the second magnet in the first direction.
16. The position detection unit according to claim 15 , wherein an expression (4) is satisfied:
( G/ 12)< D <( G/ 5) (4).