Pen position and tilt estimators for a digitizer tablet
First Claim
1. A digitizer tablet comprising a fixed array of inductors for use with an external moveable inductor and including means for determining a magnitude of a mutual inductance between the array of inductors and the moveable inductor, the digitizer tablet further including means, coupled to an output of the determining means and responsive to the determined magnitude, for deriving an estimate of the position of the moveable inductor relative to a coordinate system associated with the fixed array of inductors, wherein the determining means includes measurement means for measuring a magnitude of an induced electrical signal from individual ones of the fixed array of inductors, and wherein the estimating means includes means for weighting a plurality of the measurements in accordance with a first weighting function for determining an estimated position of the moveable inductor in accordance with a least squares line fit of the plurality of weighted measurements.
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Accused Products
Abstract
A digitizer tablet (10) has an array of conductors that define a sensing plane (12) for sensing an electromagnetic signal generated by a pointing device (16) disposed external to the plane. The tablet includes circuitry, coupled to the array of conductors, for determining a magnitude of an electrical signal or signals induced within the array of conductors by the pointing device. The tablet also includes a data processor (30) that is responsive to the determined magnitude for accurately estimating both a position and an angular orientation of the pointing device relative to a coordinate system associated with the sensing plane. A first position estimate derived from a zero-crossing estimator is used to position a weighting function, which is employed in a weighted least squares fit of a line to the data, resulting in a second zero-crossing estimate of the position of the pointing device. On this second position estimate another weighting function is centered and a tilt estimation is obtained. The tilt estimation is employed to derive a correction for the position estimate.
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Citations
17 Claims
- 1. A digitizer tablet comprising a fixed array of inductors for use with an external moveable inductor and including means for determining a magnitude of a mutual inductance between the array of inductors and the moveable inductor, the digitizer tablet further including means, coupled to an output of the determining means and responsive to the determined magnitude, for deriving an estimate of the position of the moveable inductor relative to a coordinate system associated with the fixed array of inductors, wherein the determining means includes measurement means for measuring a magnitude of an induced electrical signal from individual ones of the fixed array of inductors, and wherein the estimating means includes means for weighting a plurality of the measurements in accordance with a first weighting function for determining an estimated position of the moveable inductor in accordance with a least squares line fit of the plurality of weighted measurements.
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3. A method of operating a digitizer tablet to determine a location of a pointing means relative to a surface of the tablet, the method comprising, for each dimension x and y, the steps of:
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determining a first position estimate of a location of the pointing means relative to a plurality of sensor grid coils disposed beneath the surface of the tablet; centering a first curve representing a first weighting function on the first position estimate; weighting a plurality of electrical signal measurements of adjacent coils in accordance with the first weighting function; and employing a least squares line fit, using the weighted measurements, to derive a second position estimate of the location of the pointing means relative to the plurality of sensor grid coils. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification