Magnetic position detection system
First Claim
1. A magnetic position detection system comprising:
- a magnetic target object,an array of magnetometric sensors for detecting the magnetic field from the target object in a detection space, anda data processor for receiving magnetic field measurements from the array of magnetometric sensors and calculating the position of the target object relative to the array,the data processor being adapted to detect whether or not the target object is present in the detection space by;
fitting a magnetic field model to the magnetic field measurements by minimising differences between the magnetic field model and the magnetic field measurements, determining remaining differences between the fitted magnetic field model and the magnetic field measurements, and determining from the remaining differences whether or not the target object is present in the detection space,wherein the magnetic field sensors and data processor are adapted to conduct periodically a background field measurement process comprising determining whether the target object is present in the detection space, and, if it is not present, storing the measurements as background measurements, and wherein the magnetic field sensors and data processor are further adapted to conduct a target object position sensing process following a determination that the target object is present in the detection space, the target object position sensing process comprising the steps of correcting the magnetic field measurements for a background magnetic field by reference to the stored background measurements and fitting the magnetic field model to the corrected magnetic field measurements to perform said calculation of the position of the target object relative to the array.
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Accused Products
Abstract
In a magnetic position detection system designed to detect a target object in a detection space using an array of magnetic sensors, the position of the target object can be determined by fitting a model of the target object'"'"'s magnetic field to the sensor measurements. A robust determination of whether a target object is present can be obtained by fitting the model to the sensor measurements and determining the remaining differences between the fitted model and the sensor measurements. If the differences are high then the model is not fitting well, suggesting that the target object is not present. If the differences are low, the model is fitting well and the target object can be determined as being present. Measurements made when the target object is determined as not being present can be regarded as background field measurements including any stray fields. These stray fields can then be deducted from subsequent sensor measurements to eliminate the effect of stray fields and allow more accurate determination of the position of the target object. A user indicator may be included to indicate whether stray fields are not present, or present and accurately detected, or whether stray fields are varying.
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Citations
45 Claims
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1. A magnetic position detection system comprising:
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a magnetic target object, an array of magnetometric sensors for detecting the magnetic field from the target object in a detection space, and a data processor for receiving magnetic field measurements from the array of magnetometric sensors and calculating the position of the target object relative to the array, the data processor being adapted to detect whether or not the target object is present in the detection space by;
fitting a magnetic field model to the magnetic field measurements by minimising differences between the magnetic field model and the magnetic field measurements, determining remaining differences between the fitted magnetic field model and the magnetic field measurements, and determining from the remaining differences whether or not the target object is present in the detection space,wherein the magnetic field sensors and data processor are adapted to conduct periodically a background field measurement process comprising determining whether the target object is present in the detection space, and, if it is not present, storing the measurements as background measurements, and wherein the magnetic field sensors and data processor are further adapted to conduct a target object position sensing process following a determination that the target object is present in the detection space, the target object position sensing process comprising the steps of correcting the magnetic field measurements for a background magnetic field by reference to the stored background measurements and fitting the magnetic field model to the corrected magnetic field measurements to perform said calculation of the position of the target object relative to the array. - 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, 25, 26, 27)
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28. An ultrasound imaging system comprising a magnetic position detection system, wherein the magnetic position detection system comprises:
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a magnetic target object, an array of magnetometric sensors for detecting the magnetic field from the target object in a detection space, and a data processor for receiving magnetic field measurements from the array of magnetometric sensors and calculating the position of the target object relative to the array, the data processor being adapted to detect whether or not the target object is present in the detection space by;
fitting a magnetic field model to the magnetic field measurements by minimising differences between the magnetic field model and the magnetic field measurements, determining remaining differences between the fitted magnetic field model and the magnetic field measurements, and determining from the remaining differences whether or not the target object is present in the detection space by calculating a ratio based on a sum of the remaining differences and a sum of the magnetic field measurements. - View Dependent Claims (29)
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30. A magnetic position detection system comprising:
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a magnetic target object, an array of magnetometric sensors for detecting the magnetic field from the target object in a detection space, and a data processor for receiving magnetic field measurements from the array of magnetometric sensors and calculating the position of the target object relative to the array, the data processor being adapted to detect whether or not the target object is present in the detection space by;
fitting a magnetic field model to the magnetic field measurements by minimising differences between the magnetic field model and the magnetic field measurements, determining remaining differences between the fitted magnetic field model and the magnetic field measurements, and determining from the remaining differences whether or not the target object is present in the detection space by calculating a ratio based on a sum of the remaining differences and a sum of the magnetic field measurements. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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Specification