Eddy current imaging system using spatial derivatives for flow detection
First Claim
1. A method for contrast imaging a workpiece with eddy current imaging means including an eddy current sensing coil positioned proximate said workpiece by traversing said workpiece in an arbitrary pattern independently of velocity or direction, thus to scan said workpiece and produce a signal indicative of the impedance of said workpiece proximate said eddy current sensing coil and the location of said sensing coil, said method including:
- providing a signal from said impedance indicative signal representative of the amplitude of said signal for selected scan positions;
calculating a spatial derivative in one or more dimensions of said amplitude indicative signal;
providing an image of said spatial derivative for said selected scan positions; and
recording true sensor position for said selected scan positions.
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0 Petitions
Accused Products
Abstract
An eddy current imaging system includes an eddy current sensing coil positioned proximate a workpiece for scanning the workpiece to produce a signal indicative of the integrity of the workpiece for regions in an x,y array of data. Such a signal may be a complex impedance signal representative of the amplitude and/or the phase of the signal. Two data processing techniques are disclosed for enhancing the display of a flay in the workpiece. The first includes the step of calculating a spatial derivative of the amplitude and/or phase indicative signal from the coil and providing an image of the spatial derivative to produce a C scan of the spatial derivative. The second includes the steps of determining the regions of maximum ascent and/or descent of the signal for regions in the scan and calculating an impedance plane trajectory from the data array of path points for displaying a reconstructed optimum signal independent of path pattern.
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Citations
26 Claims
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1. A method for contrast imaging a workpiece with eddy current imaging means including an eddy current sensing coil positioned proximate said workpiece by traversing said workpiece in an arbitrary pattern independently of velocity or direction, thus to scan said workpiece and produce a signal indicative of the impedance of said workpiece proximate said eddy current sensing coil and the location of said sensing coil, said method including:
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providing a signal from said impedance indicative signal representative of the amplitude of said signal for selected scan positions; calculating a spatial derivative in one or more dimensions of said amplitude indicative signal; providing an image of said spatial derivative for said selected scan positions; and recording true sensor position for said selected scan positions. - View Dependent Claims (2, 3, 4, 14, 15, 21)
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5. A method of displaying a contrast image of a flaw in a workpiece which is scanned in an arbitrary pattern independently of velocity or direction by an eddy current coil to produce a quadrature impedance amplitude indicative signal, comprising the steps of:
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deriving a spatial derivative in one or more dimensions of said amplitude indicative signal for selected positions in said arbitrary pattern; and producing said contrast image by displaying said spatial derivative in one or more selected dimensions. - View Dependent Claims (6, 23)
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7. The method for contrast imaging a workpiece with eddy current imaging means including an eddy current sensing coil positioned proximate said workpiece and traversing said workpiece in a pattern, thus to scan said workpiece ad produce a signal indicative of the impedance of said workpiece proximate said eddy current sensing coil for each scanned position of interest, said method including:
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determining for said signal indicative of the impedance of said workpiece the maximum rate of change of the scanned image sections by spatial operators; and detecting true flaw signals in the presence of background noise form said regions of maximum rate of change. - View Dependent Claims (8, 9, 16, 17, 18)
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10. A method for contrast imaging a workpiece, comprising the steps of;
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scanning said workpiece with an eddy current imaging means including an eddy current sensing coil positioned proximate said workpiece to produce data representative of the integrity of said workpiece in an x, y group; determining from said x, y group of data the regions of maximum rate of change of the scanned image sections; calculating from said x, y group of data and the maximum rate of change of the scanned image sections an impedance plane trajectory; and determining an optimum signal independent of an original scan pattern. - View Dependent Claims (11, 12, 13, 19, 20)
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22. A method for contrast imaging a workpiece with eddy current imaging means including an eddy current sensing coil positioned proximate said workpiece by traversing said workpiece in an arbitrary pattern independently of velocity or direction, thus to scan said workpiece and produce a signal indicative of the impedance of said workpiece proximate said eddy current sensing coil and the location of sensing coil, said method including:
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providing a signal from said impedance indicative signal representative of the phase of said signal for selected scan positions; calculating a spatial derivative in one or more dimensions of said phase indicative signal; providing an image of said spatial derivative for said selected scan positions; and recording true sensor position for said selected scan positions. - View Dependent Claims (25, 26)
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24. A method of displaying a contrast image of a flaw in a workpiece which is scanned in an arbitrary pattern independently of velocity or direction by an eddy current coil to produce an in phase indicative signal, comprising the steps;
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deriving a spatial derivative in one or more dimensions of said phase indicative signal for selected positions in said arbitrary pattern; and producing said contrast image by displaying said spatial derivative in one or more selected dimensions.
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Specification