Digitizing tablet system
First Claim
1. A digitizing tablet for use with a position indicating structure having a field generating element, said tablet comprising:
- a housing having a two-dimensional work surface;
a first plurality of spaced parallel conductive elements disposed in a plane parallel to said work surface;
a second plurality of conductive elements disposed in the plane of said first plurality of conductive elements and spaced in parallel and alternately with said first plurality of conductive elements;
a first multiplexor connected to each of said first plurality of spaced parallel conductive elements;
a second multiplexor connected to each of said second plurality of conductive elements;
a differential amplifier having one input connected to the output of said first multiplexor and a second input connected to the output of said second multiplexor; and
processing means connected to the output of said differential amplifier for processing signals received from said differential amplifier to produce data signals corresponding to the position of the position indicating structure relative to the two-dimensional work surface.
8 Assignments
0 Petitions
Accused Products
Abstract
A digitizing tablet is disclosed in which two multiplexors are connected to alternate conductive loop elements in each plane of elements. The two multiplexors are connected to a differential amplifier. The signals from the differential amplifier are demodulated. The demodulated signal is provided to an integrator. A microprocessor controlled reset switch is connected across the integrator to reset the integrator after the completion of each measurement. Grounded copper strips are used in the space formed within and between the conductive loop elements of the digitizing tablet to shield the loop elements from capacitive interference.
32 Citations
13 Claims
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1. A digitizing tablet for use with a position indicating structure having a field generating element, said tablet comprising:
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a housing having a two-dimensional work surface; a first plurality of spaced parallel conductive elements disposed in a plane parallel to said work surface; a second plurality of conductive elements disposed in the plane of said first plurality of conductive elements and spaced in parallel and alternately with said first plurality of conductive elements; a first multiplexor connected to each of said first plurality of spaced parallel conductive elements; a second multiplexor connected to each of said second plurality of conductive elements; a differential amplifier having one input connected to the output of said first multiplexor and a second input connected to the output of said second multiplexor; and processing means connected to the output of said differential amplifier for processing signals received from said differential amplifier to produce data signals corresponding to the position of the position indicating structure relative to the two-dimensional work surface. - View Dependent Claims (2, 3, 4, 5)
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6. A digitizing tablet for use with a position indicating structure having a field generating element, said tablet comprising:
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a grid of conductive elements in which a signal is induced by said field generating element; multiplexor means for providing induced signals from said conductive elements to an output one at a time; amplifier means for amplifying the signals received from said multiplexor means; means for demodulating the signals provided by said amplifier means filter means for removing the AC component from the demodulated signals; means for converting the signals from said filter means into digital signals; processor means for converting said digital signals into data signals corresponding to the position of the position indicating structure relative to the two-dimensional work surface; and a reset switch controlled by said processor means for resetting said filter means. - View Dependent Claims (7, 8, 9)
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10. A digitizing tablet for use with a position indicating structure having a field generating element said tablet comprising:
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a housing having a two-dimensional work surface; a grid structure in the housing, said grid structure including a first plurality of spaced parallel conductive loop elements equal in size disposed in a plane parallel to said work surface and defining a first coordinate axis and a second plurality of spaced parallel conductive loop elements equal in size disposed in a plane parallel to said work surface and defining a second coordinate axis; a plurality of grounded copper strips located in the space formed within said conductive loops to shield said loops from capacitive interference; and processing means for processing signals induced in said conductive loops to produce data signals corresponding to the position of the position indicating structure relative to the grid structure. - View Dependent Claims (11, 12, 13)
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Specification