Metal detection methods and apparatus
First Claim
1. An apparatus, comprising:
- a sense coil defining a sensing volume;
an analog to digital converter coupled to the sense coil, and configured to receive a sense signal that includes a contribution associated with a conductive object situated in the sensing volume and to produce a numeric representation of the sense signal; and
a signal processor configured to receive the numeric representation of the sense signal and produce a numeric representation of a noise contribution to the sense signal.
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Accused Products
Abstract
Metal detectors include a sense coil coupled to an analog to digital converter that produces a numeric representation of an electrical signal associated with a conductive object situated in an active region of a sense coil. The numeric representation is processed to obtain a noise contribution associated with random noise, fixed pattern noise, and/or thermal drift. The noise is subtracted from the numeric representation to produce a numeric difference. The numeric difference includes contributions associated with conductive objects located in a sense volume defined by the sense coil. The numeric difference (or the numeric representation) can be digitally processed with, for example, a matched filter to enhance the conductive object contribution. The matched filter can be based on a measured sense coil speed or can be based on typical sense coil speeds.
16 Citations
25 Claims
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1. An apparatus, comprising:
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a sense coil defining a sensing volume; an analog to digital converter coupled to the sense coil, and configured to receive a sense signal that includes a contribution associated with a conductive object situated in the sensing volume and to produce a numeric representation of the sense signal; and a signal processor configured to receive the numeric representation of the sense signal and produce a numeric representation of a noise contribution to the sense signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A detection method for detection of a conductive object, comprising:
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obtaining a detection signal associated with a presence of the conductive object in a sense volume; digitizing the detection signal to produce a numeric representation of the detection signal; processing the numeric representation of the detection signal to produce an estimated noise contribution to the numeric representation; and estimating a conductive object contribution to the numeric representation based on a difference between the numeric representation of the detection signal and the estimated noise contribution. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A conductive object detection system, comprising:
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a first sense coil and a second sense coil; a sense coil selector configured to select one or more of the first sense coil and the second sense coil so as to produce a sense signal; and an analog to digital converter configured to produce a numeric representation of the sense signal; a signal processor configured to produce an indication associated with a presence of a conductive object based on a difference of the numeric representation of the sense signal and a low pass filtered numeric representation of the sense signal. - View Dependent Claims (24, 25)
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Specification