Method and apparatus for finding the location of a pointing instrument on a tablet
US5428192A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 10, 1993 |
| Grant date | Jun 27, 1995 |
| Priority date | — |
| Expiry date | May 10, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/046
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for producing a digital number representing the location of a pointing instrument with respect to a plurality of spaced conductors is disclosed. The instrument has a coil unit which produces an alternating magnetic field for inducing a plurality of alternating current signals in the plurality of spaced conductors, respectively, when an alternating current electrical signal is applied thereto. The conductors are sampled in a predetermined order so as to sense the induced alternating current signals. A phase sensitive detector is employed to detect a phase reversal between the induced alternating current signals induced in ones of the conductors located on opposite sides of the coil to produce a signal waveform which changes polarity in response to the phase reversal. A position counter is then incremented at a predetermined rate upon detection of the phase reversal until sampling of a succeeding one of the conductors which immediately follows the detection of the phase reversal is to be initiated. A processor deducts a digital number in the position counter from a digital number corresponding to a predetermined distance of the succeeding one of the conductors …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.