US4556871A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Touch sensing device
Assignee: Fujitsu Ltd
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Filing: 1983-06-20
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Granted: 1985-12-03
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Expires: 2003-06-20
Abstract
Abstract A transparent finger touch sensing device having a sensing circuit including a resonator for sensing a touch an oscillator for supplying an AC signal to the resonator, a buffer circuit for isolating an output of the oscillator from each selected touch electrodes and for supplying the oscillator output to the remaining non-selected touch electrodes when the sensing circuit is sequentially connected to the touch sensing electrodes, is disclosed. Thereby, the selected touch electrodes and non-selected touch electrodes are maintained at a voltage having the same phase and the same level and the inter-electrode impedance is substantially negligible.
Inventors
- 👤 Kazuo Yoshikawa
- 👤 Hisashi Yamaguchi
- 👤 Toru Asano
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:27
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/96; H03K17/9618
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
119 words
A touch sensing device having a plurality of touch sensing electrodes defining positions to be sensed and having an impedance between corresponding ones of the electrodes, said device comprising: a touch sensing circuit to which said touch sensing electrodes are sequentially and selectively connected, said touch sensing circuit including- an oscillator for supplying an AC signal to said selected touch sensing electrode; and a buffer circuit means for isolating the AC signal from the selected touch electrode and for supplying the AC signal to the non-selected touch sensing electrodes, so that the non-selected touch sensing electrodes are clampled to substantially the same potential as that of the selected electrodes and an impedance between the adjacent touch electrodes is negligible.
Claim 2
Dependent Claim
119 words
A touch sensing device having a plurality of touch sensing electrodes defining positions to be sensed and having an impedance between corresponding ones of the electrodes, said device comprising: a touch sensing circuit to which said touch sensing electrodes are sequentially and selectively connected, said touch sensing circuit including- an oscillator for supplying an AC signal to said selected touch sensing electrode; and a buffer circuit means for isolating the AC signal from the selected touch electrode and for supplying the AC signal to the non-selected touch sensing electrodes, so that the non-selected touch sensing electrodes are clampled to substantially the same potential as that of the selected electrodes and an impedance between the adjacent touch electrodes is negligible.
Claim 3
Dependent Claim
34 words
A touch sensing device according to claim (1), wherein said buffer circuit means comprises a non-inverting type amplifier having a voltage gain of about 1, a high input impedance and a low output impedance.
Claim 4
Dependent Claim
92 words
A touch sensing device for a touch keyboard having electrodes arranged to define key positions, each electrode having a selected and a non-selected state, said device comprising: oscillator means for generating an AC signal; selection means, operatively connected to said oscillator means, for placing in the selected state, desired ones of the electrodes and for applying said AC signal to said selected electrodes; and buffer means, operatively connected to said oscillator means and to said selection means, for amplifying said AC signal and for providing said amplified signal to the non-selected electrodes.
Claim 5
Dependent Claim
92 words
A touch sensing device for a touch keyboard having electrodes arranged to define key positions, each electrode having a selected and a non-selected state, said device comprising: oscillator means for generating an AC signal; selection means, operatively connected to said oscillator means, for placing in the selected state, desired ones of the electrodes and for applying said AC signal to said selected electrodes; and buffer means, operatively connected to said oscillator means and to said selection means, for amplifying said AC signal and for providing said amplified signal to the non-selected electrodes.
Claim 6
Dependent Claim
62 words
A touch sensing device according to claim 3, wherein said selection means includes: clock means for providing address signals; first switching means for connecting said selected ones of the electrodes to the oscillator means in response to the address signals; and second switching means for connecting the non-selected ones of the electrodes to said buffer means in response to the address signals.
Claim 7
Dependent Claim
97 words
A touch sensing device according to claim 3, wherein said selection means includes: first switching means, having a plurality of outputs, operatively connected to said oscillator means, for selectively applying said AC signal to said plurality of outputs; and second switching means having a first set of inputs operatively connected to said buffer means, and a second set of inputs each being operatively connected to a corresponding one of said plurality of outputs of said first switching means, for applying said AC signal to one of the electrodes and for applying said amplified signal to non-selected electrodes.
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) | 1988-12-02 | 1989-06-03 | 1989-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-02 | 1993-06-03 | 1993-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-02 | 1997-06-03 | 1997-12-03 | $7700.00 | Window Closed / Lapsed |