US3591718A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Graphical input tablet
Assignee: SHINTRON CO Inc
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Filing: 1968-04-18
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Granted: 1971-07-06
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Expires: 1988-04-18
Abstract
Abstract An AC potential field is established on an electrographic tablet. A stylus that may be used to write upon the tablet comprises a capacitive pickup to provide a potential representative of the stylus position. The potential field is alternately switched at a rapid rate between vertical equipotentials and horizontal equipotentials in synchronism with output analog switches coupled to the stylus to provide an X analog signal output and a Y analog signal output representative of the horizontal and vertical coordinates, respectively, of the stylus tip above the tablet.
Inventors
- 👤 Shintaro Asano
- 👤 Larry K Baxter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 20:18
CPC Classifications
G; G06; G06F; G06F3/00; G06F3/01; G06F3/03; G06F3/041; G06F3/044; G06F3/0441; G06F3/045; G06F3/0444
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
136 words
Electrographic apparatus comprising, tablet means defined by a quadrilateral conductive sheet of first high resistivity, a frame of material of second resistivity lower than said first resistivity surrounding and in contact with the edges of said conductive sheet, conductive electrode means at each corner of said frame, means including said frame and a controllable potential source coupled to respective ones of said electrode means for establishing first and second orthogonal electric fields in said conductive sheet during mutually exclusive time intervals, and stylus means for capacitively coupling the signal on a point of said sheet to first and second output terminals during mutually exclusive time intervals corresponding to the existence of said first and second electric fields respectively whereby the signals on said first and second Output terminals are representative of orthogonal coordinates of said point.
Claim 2
Dependent Claim
136 words
Electrographic apparatus comprising, tablet means defined by a quadrilateral conductive sheet of first high resistivity, a frame of material of second resistivity lower than said first resistivity surrounding and in contact with the edges of said conductive sheet, conductive electrode means at each corner of said frame, means including said frame and a controllable potential source coupled to respective ones of said electrode means for establishing first and second orthogonal electric fields in said conductive sheet during mutually exclusive time intervals, and stylus means for capacitively coupling the signal on a point of said sheet to first and second output terminals during mutually exclusive time intervals corresponding to the existence of said first and second electric fields respectively whereby the signals on said first and second Output terminals are representative of orthogonal coordinates of said point.
Claim 3
Dependent Claim
95 words
Electrographic apparatus in accordance with claim 1 whereby said frame comprises left and right side strips and top and bottom strips defining a rectangle, said electrode means being disposed at each corner of said rectangle, and means for applying through said electrode means a first potential waveform between said top strip and said bottom strip during a first of said time intervals and between said left and right side strips during a second of said time intervals whereby the signals on said first and second output terminals are representative of rectangular coordinates of said point.
Claim 4
Dependent Claim
92 words
Electrographic apparatus in accordance with claim 2 wherein said means for establishing includes means for applying a first potential waveform to a first of said top and bottom strips and to a first of said side strips and means for applying a second potential waveform to the other of said top and bottom strips and to the other of said side strips, said first and second potential waveforms having the same period but displaced in time by substantially a quarter of said period to differ in phase by substantially 90 electrical degrees.
Claim 5
Dependent Claim
13 words
Electrographic apparatus in accordance with claim 3 wherein said potential waveforms are rectangular.
Claim 6
Dependent Claim
14 words
Electrographic apparatus in accordance with claim 3 wherein said potential waveforms are substantially triangular.
Claim 7
Dependent Claim
72 words
Electrographic apparatus in accordance with claim 3 and further comprising, a source of a reference signal, means for comparing the signal provided by said stylus capacitively coupled from said point with said reference signal to provide first and second coordinate signals with a phase characteristic representative of respective rectangular coordinates of said point, and means responsive to said first and second coordinate signals for providing said first and second output signals respectively.
Claim 8
Dependent Claim
53 words
Electrographic apparatus in accordance with claim 6 and further comprising, first and second scalers, means responsive to said reference signal and said first and second coordinate signals for advancing the count in said first and second scalers respectively to first and second digital numbers respectively representative of respective rectangular coordinates of said point.
Claim 9
Dependent Claim
95 words
Electrographic apparatus in accordance with claim 6 and further comprising first and second integrating capacitors, means responsive to said reference signal for providing a signal derived from that provided by said stylus to said first integrating capacitor during a first subinterval when the latter signal is representative of a first of said rectangular coordinates and to said second integrating capacitor during a second subinterval when the latter signal is representative of a second of said rectangular coordinates, the potentials on said first and second integrating capacitors being representative of said first and second coordinates respectively.
Claim 10
Dependent Claim
118 words
Electrographic apparatus in accordance with claim 8 and further comprising, a source of a periodic sawtooth waveform synchronized with said reference signal, first and second scalers, first and second comparators for comparing said sawtooth waveform with the potentials on said first and second integrating capacitors respectively for providing first and second compare signals respectively when the sawtooth waveform potential bears a predetermined relationship to the potentials on said first and second integrating capacitors respectively, and means responsive to said reference signal and said first and second compare signals for advancing the count in said first and second scaler respectively to first and second digital numbers respectively representative of the potentials on said first and second integrating capacitors respectively.
Claim 11
Dependent Claim
34 words
Electrographic apparatus in accordance with claim 1 wherein the ratio of the resistivity of said first resistivIty sheet to the resistivity of said second resistivity material is on the order of 1000 to 1.
Claim 12
Dependent Claim
41 words
Electrographic apparatus in accordance with claim 10 wherein the resistivity of said conductive sheet is on the order of 10, 000 ohms per square and the resistivity of said second resistivity material is on the order of 10 ohms per square.
Claim 13
Dependent Claim
28 words
Electrographic apparatus in accordance with claim 1 wherein said frame comprises left and right side strips and top and bottom strips, each such strip having a concave shape.
Claim 14
Dependent Claim
21 words
Electrographic apparatus in accordance with claim 12 wherein each such strip includes at least one inwardly facing edge of parabolic shape.
Claim 15
Dependent Claim
99 words
A writing tablet capable of having a stylus means positioned thereover for selectively sensing the potential established at points on said tablet comprising, a quadrilaterial conductive sheet of first high resistivity material, a frame of material of second resistivity lower than said first resistivity surrounding and in contact with the edges of said conductive sheet, conductive electrode means at each corner of said frame, and means including said frame and a controllable potential source coupled to respective ones of said electrode means for establishing first and second orthogonal electric fields in said conductor sheet during mutually exclusive time intervals.
Claim 16
Dependent Claim
99 words
A writing tablet capable of having a stylus means positioned thereover for selectively sensing the potential established at points on said tablet comprising, a quadrilaterial conductive sheet of first high resistivity material, a frame of material of second resistivity lower than said first resistivity surrounding and in contact with the edges of said conductive sheet, conductive electrode means at each corner of said frame, and means including said frame and a controllable potential source coupled to respective ones of said electrode means for establishing first and second orthogonal electric fields in said conductor sheet during mutually exclusive time intervals.
Claim 17
Dependent Claim
35 words
A writing tablet in accordance with claim 14 wherein the ratio of the resistivity of said first resistivity sheet to the resistivity of said second resistivity material is on the order of 1000 to 1.
Claim 18
Dependent Claim
29 words
A writing tablet in accordance with claim 14 wherein said frame comprises left and right side strips and top and bottom strips, each such strip having a concave shape.
Claim 19
Dependent Claim
20 words
A writing tablet in accordance with claim 16 wherein each such strip includes an inwardly facing edge of parabolic shape.
Claim 20
Dependent Claim
92 words
A writing tablet in accordance with claim 14 further comprising probe means for coupling, a signal on a point of said tablet to first and second terminals, and phase controlled detection electronics comprising, a difference amplifier means having a pair of input terminals coupled to said probe means, a multiplier having one input coupled from said difference amplifier, an output amplifier coupled from the output of said multiplier, and a phase controlled square wave generator coupled from said output amplifier and having an output that couples to another input of said multiplier.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-07-05 | 1975-01-04 | 1975-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-05 | 1979-01-04 | 1979-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-05 | 1983-01-04 | 1983-07-06 | $7700.00 | Window Closed / Lapsed |