EP0288692A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Graphics input tablet
Assignee: International Business Machines Corp
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Filing: 1988-03-04
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Granted: —
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Expires: 2008-03-04
Abstract
Abstract A graphics input tablet has a conductive layer and a resistive layer with contacts (16, 17, 23, 24) arranged one along each edge of the resistive layer. The conductive layer is held at a negative potential relative to the resistive layer so current flows in each contact when localised pressure is applied to a region of the tablet (20) to bring the layers into electrical contact. The currents vary with both position and magnitude of the localised pressure. The position of the pressure is detected from the relative currents in opposed contacts and the magnitude of the pressure is detected from the total current in the contacts. The currents are measured by current sense amplifiers and processed in a computer. Analogue front-end processing of the currents is also possible.
Inventors
- 👤 Rafael Pascual
- 👤 Milan Miessler
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 20:09
CPC Classifications
G; G06; G06F; G06F3/00; G06F3/01; G06F3/03; G06F3/041; G06F3/045
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
183 words
A graphics input tablet comprising a layer of electrically resistive material (10) supported coextensively with a layer of electrically conductive material (11) to provide a flat tablet surface, first and second conductors (14, 15) connected respectively to first and second portions of the resistive layer (18, 19), said portions being spaced apart on a notional first line across the tablet surface, characterised in that: when an electrical potential is applied between the resistive layer and the conductive layer and localised pressure is applied to the tablet surface, currents flow from said first and second conductors through the resistive layer to the conductive layer, the relative magnitudes of these currents being related to the respective distances of the region of applied pressure from the first and second portions, the resistive material has the property that the electrical resistance between the layers in the region of the localised pressure applied thereto changes monotonically with the applied pressure and when the localised pressure is applied, the total current flowing between the resistive sheet and the conductive sheet is related to the magnitude of the applied pressure.
Claim 2
Dependent Claim
183 words
A graphics input tablet comprising a layer of electrically resistive material (10) supported coextensively with a layer of electrically conductive material (11) to provide a flat tablet surface, first and second conductors (14, 15) connected respectively to first and second portions of the resistive layer (18, 19), said portions being spaced apart on a notional first line across the tablet surface, characterised in that: when an electrical potential is applied between the resistive layer and the conductive layer and localised pressure is applied to the tablet surface, currents flow from said first and second conductors through the resistive layer to the conductive layer, the relative magnitudes of these currents being related to the respective distances of the region of applied pressure from the first and second portions, the resistive material has the property that the electrical resistance between the layers in the region of the localised pressure applied thereto changes monotonically with the applied pressure and when the localised pressure is applied, the total current flowing between the resistive sheet and the conductive sheet is related to the magnitude of the applied pressure.
Claim 3
Dependent Claim
99 words
A graphics input tablet as claimed in claim 1, further comprising third and fourth conductors (21, 22) connected respectively to third and fourth portions of the resistive layer (25, 26), said portions being spaced apart on a second notional line, intersecting said first notional line, across the tablet surface, such that when said localised pressure is applied in said region currents flow in said third and fourth conductors, the relative magnitudes of the currents in the third and fourth conductors being related to the respective distances of said third and fourth portions from the area of applied localised pressure.
Claim 4
Dependent Claim
32 words
A graphics input tablet as claimed in claim 1 or claim 2, further comprising electrical excitation means (44, 45) for applying said electrical potential between the resistive layer and the conductive layer.
Claim 5
Dependent Claim
43 words
A graphics input tablet as claimed in any preceding claim, further comprising electrical sensing means arranged to measure individually the current flowing in each of the said conductors and to evaluate the total current flowing between the resistive layer and the conductive layer.
Claim 6
Dependent Claim
36 words
A graphics input tablet as claimed in claim 4, in which said electrical sensing means (35 to 44) is arranged to evaluate said total current by summing the individual currents measured in each of said conductors.
Claim 7
Dependent Claim
41 words
A graphics input tablet as claimed in claim 4, in which said electrical sensing means (40 to 45) is arranged to evaluate said total current from a measurement of the current flowing between the electrical excitation means and the conductive layer.
Claim 8
Dependent Claim
54 words
A graphics input tablet as claimed in any preceding claim, in which said resistive layer is rectangular and said conductors are connected each to a different edge of said resistive layer such that each said portion (18, 19 or 18, 19, 25, 26) represents substantially the whole of an edge of the resistive layer.
Claim 9
Dependent Claim
75 words
A graphics input tablet as claimed in any preceding claim, in which the resistive layer comprises two sheets (10a, 10b), each of a resistive material, the conductors being connected to a first of said sheets (10b) and the second of said sheets (10a) providing the property as aforesaid that the electrical resistance between the layers in the region of localised pressure applied thereto changes monotonically with the magnitude of the pressure applied to the layers.
Claim 10
Dependent Claim
38 words
A graphics input tablet as claimed in any preceding claim, in which the electrical sensing means comprises analogue current measuring means (44), said tablet further comprising analogue summing means (35, 37, 39) and analogue dividing means (36, 38).
Claim 11
Dependent Claim
44 words
A graphics input tablet as claimed in any preceding claim, further comprising analogue to digital conversion means (41) and buffering means (42) for buffering an output of the analogue to digital conversion means onto a data bus (43) connected to a data processing means.
References Cited (Backward Citations)
No citation records indexed.
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