Method and apparatus for performing magnetic field measurements using magneto-optic Kerr effect sensors
First Claim
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1. A magneto-optic Kerr effect magnetic field sensor comprising:
- a light source;
a magneto-optic Kerr effect magnetic field sensing element, said sensing element comprising a plurality of thin-film layers disposed on a substrate, at least one of said layers being of a reflective magnetic material and having;
an in-plane magnetization orientation;
a well-defined in-plane uniaxial anisotropy; and
known magneto-optic Kerr effect and in-plane uniaxial anisotropy field values, wherein said sensing element is disposed such that an in-plane hard axis of said at least one layer of reflective magnetic material lies in a light plane of incidence and collinear to an external magnetic field to be measured, wherein said at least one reflective magnetic material layer has at least one domain having a rotatable magnetization vector that rotates in response to said external magnetic field, and said at least one layer of reflective magnetic material is disposed such that a polarization characteristic of incident light is altered upon reflectance from said sensing element;
a first polarizing element disposed between said light source and said magneto-optic Kerr effect magnetic field sensing element wherein said light source directs a light beam to said first polarizing element and said first polarizing element transmits a first polarized light beam having a first predetermined polarization characteristic to said magneto-optic Kerr effect magnetic field sensing element;
a second polarizing element disposed to intercept light reflected from said magneto-optic Kerr effect magnetic field sensing element and to transmit a second polarized light beam having a second predetermined polarization characteristic; and
a detector disposed to intercept said second polarized light beam from said second polarizing element.
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Abstract
A sensor system includes a magneto-optic Kerr effect magnetic field sensing element and an optical system including a light source, at least one polarizer or polarizing element and a detector disposed about the sensing element. The sensing element is responsive to an external magnetic field. In one embodiment, the optical system and sensing element can be arranged to measure the strength of a magnetic field. In another embodiment the optical system and sensing element can be arranged to measure the rotational speed of rotating members.
81 Citations
68 Claims
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1. A magneto-optic Kerr effect magnetic field sensor comprising:
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a light source; a magneto-optic Kerr effect magnetic field sensing element, said sensing element comprising a plurality of thin-film layers disposed on a substrate, at least one of said layers being of a reflective magnetic material and having;
an in-plane magnetization orientation;
a well-defined in-plane uniaxial anisotropy; and
known magneto-optic Kerr effect and in-plane uniaxial anisotropy field values, wherein said sensing element is disposed such that an in-plane hard axis of said at least one layer of reflective magnetic material lies in a light plane of incidence and collinear to an external magnetic field to be measured, wherein said at least one reflective magnetic material layer has at least one domain having a rotatable magnetization vector that rotates in response to said external magnetic field, and said at least one layer of reflective magnetic material is disposed such that a polarization characteristic of incident light is altered upon reflectance from said sensing element;a first polarizing element disposed between said light source and said magneto-optic Kerr effect magnetic field sensing element wherein said light source directs a light beam to said first polarizing element and said first polarizing element transmits a first polarized light beam having a first predetermined polarization characteristic to said magneto-optic Kerr effect magnetic field sensing element; a second polarizing element disposed to intercept light reflected from said magneto-optic Kerr effect magnetic field sensing element and to transmit a second polarized light beam having a second predetermined polarization characteristic; and a detector disposed to intercept said second polarized light beam from said second polarizing element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A magneto-optic Kerr effect magnetic field sensing system comprising:
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a light source; a polarizing beamsplitter disposed to receive a light beam from said light source and to transmit a light beam having a predetermined polarization characteristic; a magneto-optic Kerr effect magnetic field sensing element, said sensing element disposed to receive said light beam having said predetermined polarization characteristic from said polarizing beamsplitter, said sensing element comprising a plurality of thin film layers disposed on a substrate, at least one layer of which being a layer of reflective magnetic material and having;
an in-plane magnetization orientation;
a well-defined in-plane uniaxial anisotropy; and
known magneto-optic Kerr effect and in-plane uniaxial anisotropy field values, wherein said sensing element is disposed such that an in-plane hard axis of said at least one layer of reflective magnetic material lies in a light plane of incidence and collinear to an external magnetic field to be measured, wherein said at least one reflective magnetic material layer has at least one domain having a rotatable magnetization vector that rotates in response to said external magnetic field, and said at least one layer of reflective magnetic material is disposed such that said predetermined polarization characteristic of said light beam from said polarizing beamsplitter is altered upon reflectance from said sensing element;a highly reflective element disposed to intercept light reflected from said sensing element and reflect light back to said sensing element, wherein said reflected light is then reflected towards said beamsplitter; a detector disposed to intercept light that reflects from said beamsplitter after being reflected from said sensing element. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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48. A magneto-optic Kerr effect magnetic field sensor comprising:
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a light source; a magneto-optic Kerr effect magnetic field sensing element, said sensing element comprising a plurality of thin-film layers disposed on a substrate, at least one of said layers being of a reflective magnetic material and having;
an in-plane magnetization orientation;
a well-defined in-plane uniaxial anisotropy; and
known magneto-optic Kerr effect and in-plane uniaxial anisotropy field values, wherein said sensing element is disposed such that an in-plane hard axis of said at least one layer of reflective magnetic material lies in a light plane of incidence and collinear to an external magnetic field to be measured, wherein said at least one reflective magnetic material layer has at least one domain having a rotatable magnetization vector that rotates in response to said external magnetic field, and said at least one layer of reflective magnetic material is disposed such that a polarization characteristic of incident light is altered upon reflectance from said sensing element;a first polarizing element disposed between said light source and said magneto-optic Kerr effect magnetic field sensing element wherein said light source directs a light beam to said first polarizing element and said first polarizing element transmits a first polarized light beam having a first predetermined polarization characteristic to said magneto-optic Kerr effect magnetic field sensing element; a second polarizing element disposed to intercept light reflected from said magneto-optic Kerr effect magnetic field sensing element, to transmit light having a second predetermined polarization characteristic, and to reflect light having a third predetermined polarization characteristic; a first detector disposed to intercept light having said second predetermined polarization characteristic that is transmitted through said second polarizing element; and a second detector disposed to intercept light having said third predetermined polarization characteristic that is reflected from said second polarizing element. - View Dependent Claims (49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68)
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Specification