Method and apparatus for calibration of a charge ratio digitizer
US4831566A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 20, 1987 |
| Grant date | May 16, 1989 |
| Priority date | — |
| Expiry date | Mar 20, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/0441
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A conventional three-electrode wedge-and-strip pattern in a digitizer tablet surface is used with a conventional cursor or stylus. A phantom cursor electrode is located at predetermined coordinates of the active area of the digitizer tablet beneath the X, Y and balance (B) electrodes and separated therefrom by a layer of dielectric material, preferably an air gap. Prior to use of the digitizer apparatus, the phantom cursor electrode is electrostatically coupled to the X, Y and B electrodes in order to obtain data signals representing the phantom cursor's measured coordinates without compensation for resolution distortion. A microprocessor produces a correction factor using the data signals and the predefined coordinates of the phantom cursor electrode, which correction factor is applied in normal use to compensate for resolution distortion resulting from the unavoidable gaps between the X, Y and B electrodes. Also raw measured data obtained from the electrostatically coupled electrodes is adjusted to compensate for environmental and inherent noise and an offset corresponding to the difference in the reference potentials of the integrator and comparator.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.