Magneto-optical apparatus and method for the spatially-resolved detection of weak magnetic fields
First Claim
1. A detection apparatus to detect magnetic fields comprising:
- an first alteration element having a response curve to an applied electromagnetic field, the response curve exhibiting hysteresis between a plurality of stable states such that transition regions exist between the stable states;
a source of electromagnetic radiation, the electromagnetic radiation impinging on the first alteration element;
a source of an alternating electromagnetic field applied to the first alteration element, the alternating electromagnetic field of sufficient strength to switch the first alteration element between the stable states, a characteristic of the electromagnetic radiation being altered dependent on the alternating electromagnetic field and an electromagnetic field of a subject; and
a detector configured to detect the characteristic of the electromagnetic radiation impinging on the detector, the electromagnetic radiation impinging on the detector having been altered when the first alteration element was in one of the transition regions.
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Accused Products
Abstract
A detector uses the magneto-optical Kerr effect and exploits the transition region between two magnetization states of a magneto-optical film to detect magnetic fields of less than 100 pT. The magnetic field of a subject is determined by examining the polarization of light reflected from the magneto-optical film. A several μm thick, bismuth doped, YIG film is used for detection as the transition regions are steep, providing large changes in the polarization rotation angle for small variations in the applied magnetic field. The apparatus may be used in the functional imaging of various organs and systems in humans and animals or for the spatial and temporal tracking of nano or micro magnetic particles intentionally introduced into the circulatory or intestinal systems for diagnostic or research purposes.
45 Citations
65 Claims
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1. A detection apparatus to detect magnetic fields comprising:
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an first alteration element having a response curve to an applied electromagnetic field, the response curve exhibiting hysteresis between a plurality of stable states such that transition regions exist between the stable states;
a source of electromagnetic radiation, the electromagnetic radiation impinging on the first alteration element;
a source of an alternating electromagnetic field applied to the first alteration element, the alternating electromagnetic field of sufficient strength to switch the first alteration element between the stable states, a characteristic of the electromagnetic radiation being altered dependent on the alternating electromagnetic field and an electromagnetic field of a subject; and
a detector configured to detect the characteristic of the electromagnetic radiation impinging on the detector, the electromagnetic radiation impinging on the detector having been altered when the first alteration element was in one of the transition regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 15)
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11. A detection apparatus to detect magnetic fields comprising:
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a first magneto-optical element that exhibits a response, in the form of Faraday rotation, to an applied magnetic field, a hysteresis characteristic of the Faraday rotation exhibiting transition regions between a plurality of stable states;
a light source to emit light that impinges on the first magneto-optical element;
a modulation element to apply a time-varying magnetic field of sufficient strength to switch the first magneto-optical element between the stable states; and
a detector configured to detect a change in the light caused by a reaction of the first magneto-optical element to a magnetic field of a subject that occurred when the first magneto-optical element was in one of the transition regions. - View Dependent Claims (12, 13, 14, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method of detecting magnetic fields comprising:
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providing a first magneto-optical element that exhibiting a response, in the form of Faraday rotation, to an applied magnetic field, a hysteresis characteristic of the Faraday rotation exhibiting transition regions between a plurality of stable states;
emitting light from a light source that impinges on the first magneto-optical element;
applying a time-varying magnetic field of sufficient strength to switch the first magneto-optical element between the stable states; and
detecting a change in the light caused by a reaction of the first magneto-optical element to a magnetic field of a subject that occurred when the first magneto-optical element was in one of the transition regions. - View Dependent Claims (41, 42, 43, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65)
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44. The detection method of claim 44, further comprising providing a second magneto-optical element upon which the light impinges and that is affected substantially the same as the first magneto-optical element by the time-varying magnetic field, the second first magneto-optical element configured to be substantially unaffected by the magnetic field of the subject and supplying the background signal.
Specification