Digitizer tablet
First Claim
1. A system for locating the position of a cursor along a coordinate axis, said system comprising:
- a plurality of parallel conductors spaced along the axis and defining a locus;
means for sequentially energizing said conductors in simultaneously energized lesser pluralities with a fixed energization pattern which steps along said plurality of conductors, thereby generating a current sheet which translates along the locus of and parallel to said conductors;
means for sensing the passage of a particular portion of the current sheet across a reference point carried by the cursor; and
means responsive to the time of passage of the particular portion of the current sheet for generating an output signal representing the position of the cursor along the coordinate axis.
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Accused Products
Abstract
A system for precisely determining the location of a cursor on a work surface with respect to a grid of coordinate conductors. The system is based on the time-distance relationship of current sheets caused to move sequentially along each axis of the work surface, and the detection of each current sheet as it approaches and passes an operator-movable sensor. A number of the grid wires are simultaneously energized with a fixed energization pattern which steps along the conductors, thereby generating the current sheet and consequent magnetic field which translate along the plane of the conductors parallel to the conductors. A preferred means responsive to the time of passage of the current sheet comprises an inductive pickup coil having a diameter approximately equal to the width of the current sheet and means for sensing current induced in the pickup coil. Preferably, the grid conductors are energized with substantially fixed constant currents. Among the important advantages of the invention are enhanced signal levels with improved signal to noise ratios, improved immunity to extraneous noise, relative insensitivity to minor inaccuracies in the placement of the grid wires in the manufacture of the tablet, excellent resolution, and a high degree of stability. Moreover, the system, through several discoveries, is characterized by a relative lack of undue complexity, while serving well its intended function.
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Citations
32 Claims
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1. A system for locating the position of a cursor along a coordinate axis, said system comprising:
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a plurality of parallel conductors spaced along the axis and defining a locus; means for sequentially energizing said conductors in simultaneously energized lesser pluralities with a fixed energization pattern which steps along said plurality of conductors, thereby generating a current sheet which translates along the locus of and parallel to said conductors; means for sensing the passage of a particular portion of the current sheet across a reference point carried by the cursor; and means responsive to the time of passage of the particular portion of the current sheet for generating an output signal representing the position of the cursor along the coordinate axis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A system for locating the position of a cursor on a surface, said system comprising:
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a conductor grid including a first plurality of parallel conductors spaced along a first axis in a plane parallel to the surface, and including a second plurality of parallel conductors spaced along a second axis perpendicular to said first axis, also in a plane parallel to the surface, such that the conductors of said second plurality are perpendicular to the conductors of said first plurality; means for sequentially energizing the conductors in simultaneously energized lesser pluralities with a fixed energization pattern which steps first along said first plurality of conductors and then along said second plurality of conductors, thereby generating a first current sheet which translates along the plane of and parallel to the conductors of the first plurality followed by a second current sheet which translates along the plane of and parallel to the conductors of the second plurality; means for sensing the passage of a particular portion of each of the current sheets across a reference point carried by the cursor; means responsive to the times of passage of the particular portions of the current sheets for generating an output signal representing the coordinate position of the cursor on the surface. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. A sensing arrangement for use in a system for locating the position of a cursor along a coordinate axis of the type which sequentially energizes a plurality of parallel conductors spaced along the axis to produce a current wave which translates along the axis, and which responds to the time of passage of the current wave across the cursor to generate an output signal representing the position of the cursor along the coordinate axis, said sensing arrangement comprising:
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an inductive pickup coil carried by the cursor; and means for sensing current induced in said inductive pickup coil. - View Dependent Claims (30)
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31. In a system for locating the position of a cursor along a coordinate axis of the general type which sequentially energizes a plurality of parallel conductors spaced along the axis to produce a current wave which translates along the axis, and which includes means responsive to the time of passage of the current wave across the cursor to generate an output signal representing the position of the cursor along the coordinate axis, means for sensing the time of passage of a particular portion of the current sheet across a reference point carried by the cursor, which means for sensing comprises:
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an inductive pickup coil carried by the cursor; means responsive to a signal induced in said pickup coil as the current wave passes for generating a waveform envelope; a first comparator responsive to the waveform envelope crossing a threshold; a second comparator responsive to the waveform envelope crossing another threshold for generating a timing signal; and means for enabling said second comparator only in response to said first comparator. - View Dependent Claims (32)
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Specification