Electrostatic pattern-coupled digitizer
First Claim
1. A digitizer tablet having a pattern of conductive electrode portions arranged in a plane, said pattern comprising a set of generally rectangular conductive areas each including at least one planar electrode, the longer sides of said generally rectangular conductive areas being arranged parallel to a first coordinate axis and the shorter sides of said generally rectangular surface areas having a length which increases incrementally in a direction parallel to a second coordinate axis for successive generally rectangular surface areas, and a set of generally triangular conductive areas each including at least one planar electrode, said generally triangular conductive areas being interleaved between said generally rectangular conductive areas, the shortest side of said generally triangular conductive areas being arranged parallel to said second coordinate axis and the remaining two sides of each generally triangular conductive area being separated by a distance in a direction parallel to said second coordinate axis which increases linearly in a direction parallel to said first coordinate axis.
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Abstract
A digitizer in which position of a free moving cursor or stylus over a digitizing surface is determined by electrostatic coupling of the cursor with three coplanar electrodes imbedded in the digitizing tablet. The electrodes consist of a repetitive sawtooth pattern to determine position in one axis, the sawtooths interleaved with progressively wider, repetitive stripes to determine position in another axis. The third electrode covers the remainder of the coplanar surface area. Only three electrode signals are required to be electronically processed to determine absolute vertical and horizontal position of the cursor over the digitizing tablet by a ratiometric measurement. The signals from the electrodes are processed synchronously to reject noise.
81 Citations
32 Claims
- 1. A digitizer tablet having a pattern of conductive electrode portions arranged in a plane, said pattern comprising a set of generally rectangular conductive areas each including at least one planar electrode, the longer sides of said generally rectangular conductive areas being arranged parallel to a first coordinate axis and the shorter sides of said generally rectangular surface areas having a length which increases incrementally in a direction parallel to a second coordinate axis for successive generally rectangular surface areas, and a set of generally triangular conductive areas each including at least one planar electrode, said generally triangular conductive areas being interleaved between said generally rectangular conductive areas, the shortest side of said generally triangular conductive areas being arranged parallel to said second coordinate axis and the remaining two sides of each generally triangular conductive area being separated by a distance in a direction parallel to said second coordinate axis which increases linearly in a direction parallel to said first coordinate axis.
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5. A digitizer comprising:
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(a) a digitizer tablet having first coupling electrode means arranged in a pattern in a plane; (b) second coupling electrode means movable over said plane; (c) signal generating means coupled to one of said first and second coupling electrode means for driving said one coupling electrode means; and (d) processing means coupled to the other of said first and second coupling electrode means for processing the signals electrostatically induced in said other coupling electrode means in response to driving of said one coupling electrode means, the processing means being adapted to determine the coordinates of a point on said second coupling electrode means relative to a reference system on said plane having first and second coordinate axes; wherein said pattern comprises a set of generally rectangular conductive areas each including at least one planar electrode, the longer sides of said generally rectangular conductive areas being arranged parallel to a first coordinate axis and the shorter sides of said generally rectangular surface areas having a length which increases incrementally in a direction parallel to a second coordinate axis for successive generally rectangular surface areas, and a set of generally triangular conductive areas each including at least one planar electrode, said generally triangular conductive areas being interleaved between said generally rectangular conductive areas, the shortest side of said generally triangular conductive areas being arranged parallel to said second coordinate axis and the remaining two sides of each generally triangular conductive area being separated by a distance in a direction parallel to said second coordinate axis which increases linearly in a direction parallel to said first coordinate axis. - View Dependent Claims (6, 7, 8)
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9. A digitizer comprising:
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(a) a digitizer tablet having first coupling electrode means arranged in a pattern in a plane; (b) second coupling electrode means movable over said plane; (c) signal generating means coupled to one of said first and second coupling electrode means for driving said one coupling electrode means; and (d) processing means coupled to the other of said first and second coupling electrode means for processing the signals electrostatically induced in said other coupling electrode means in response to driving of said one coupling electrode means, the processing means being adapted to determine the coordinates of a point on said second coupling electrode means relative to a reference system on said plane having first and second coordinate axes; wherein said pattern is defined in part by first and second pluralities of straight edge lines, said straight edge lines of said first plurality being parallel to said first coordinate axis and said straight edge lines of said second plurality being oblique to said first coordinate axis, said first coordinate being determined by said processing means by detecting an induced signal corresponding to the amount of electrostatic coupling between said first coupling electrode means and a portion of said second coupling electrode means formed by a plurality of conductive areas each defined in party by a pair of straight edge lines, at least one of which is of said second plurality, the distance in a direction parallel to said second coordinate axis between said straight edge lines of said pair increasing linearly in a direction parallel to said first coordinate axis, and said second coordinate being determined by said processing means by detecting an induced signal corresponding to the amount of electrostatic coupling between said first coupling electrode means and a portion of said second coupling electrode means formed by a plurality of conductive areas each lying between a pair of straight edge lines of said first plurality, the distance in said direction parallel to said second coordinate axis between said straight edge lines of successive pairs of straight edges of said first plurality increasing incrementally in said direction parallel to said second coordinate axis.
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10. A digitizer tablet comprising a plurality of conductive elements deployed in a common plane, wherein:
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(a) the areas of first selected ones of said conductive elements varying as a function of position in a first coordinate of said common plane; (b) the areas of second selected ones of said conductive elements varying as a function of position in a second coordinate of said common plane; and (c) the combined areas of selected ones of the conductive elements are independent of position on the common plane. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A digitizer comprising:
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(a) a digitizer tablet having a first electrode having a pattern that varies with a first coordinate in an orthogonal X - Y coordinate system including a plurality of conductive stripes connected together along one end, the stripes having progressively increasing width starting from a side of the tablet and extending toward an opposite side of the tablet, and a second coplanar electrode having a pattern that varies with the second coordinate in the orthogonal X - Y coordinate system including a plurality of elongated sawtooths interleaved between the stripes, the sawtooths also being connected together at one end thereof; (b) a coupling electrode movable on the digitizer tablet for coupling with the first and second patterned electrodes of the digitizer tablet; (c) signal generating means connected for inputting an electrical signal alternately to the first and second patterned electrodes of the digitizer tablet, thereby establishing electrostatic field coupling with an electrical signal on the coupling electrode, the signal on the coupling electrode being alternately indicative of the position of the coupling electrode in each coordinate of the orthogonal X - Y coordinate system; and (d) electronic means for calculating the coordinates of the coupling electrode in the orthogonal X - Y coordinate system from the signals coupled to the coupling electrode from the first and second patterned electrodes. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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Specification