Magneto-optical apparatus and method for the spatially-resolved detection of weak magnetic fields
First Claim
1. A detection apparatus to detect weak magnetic fields comprising:
- 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 comprising a coil adjacent to the first magneto-optical element, the modulation element being a source of 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 weak magnetic field of an organ or bodily system, the change occurring when the first magneto-optical element is in one of the transition regions,wherein the detection apparatus has a sensitivity sufficient to detect the weak magnetic field.
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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.
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Citations
50 Claims
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1. A detection apparatus to detect weak 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 comprising a coil adjacent to the first magneto-optical element, the modulation element being a source of 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 weak magnetic field of an organ or bodily system, the change occurring when the first magneto-optical element is in one of the transition regions, wherein the detection apparatus has a sensitivity sufficient to detect the weak magnetic field. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 49)
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25. A method of detecting weak magnetic fields comprising:
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providing a first magneto-optical element 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 stable states, wherein the first magneto-optical element is in the presence of a weak magnetic field; impinging light from a light source on the first magneto-optical element; applying a time-varying magnetic field from a modulation element to the first magneto-optical element; switching 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 the weak magnetic field of an organ or bodily system, the change occurring when the first magneto-optical element is in one of the transition regions. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 50)
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Specification