Position measurement apparatus for capacitive touch panel system
US4853498A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 13, 1988 |
| Grant date | Aug 1, 1989 |
| Priority date | — |
| Expiry date | Jun 13, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/0444
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A capacitive touch panel system (10) having a faceplate (14) with an electrically conductive layer (20) of a consistent resistivity employs a position measurement apparatus (12) to generate an address signal indicative of a position (46) on the faceplate in contact with a stylus (48). The position measurement apparatus includes a position measurement signal source (62) that generates a square-wave measurement signal of substantially constant frequency and a preselected magnitude. The position measurement signal is applied to a first pair of opposed electrodes (36) and (40) and a second pair of opposed electrodes (38) and (42) positioned along respective side margins (26, 30, 28, and 32) of the faceplate. The resistivity of the conductive layer establishes effective resistances of R.sub.x and R.sub.y between the respective first and second pairs of electrodes. Position measurement subcircuits (60a-60d) measure currents drawn through the electrodes whenever the stylus contacts the conductive layer, thereby to form an address signal indicative of the location at which the stylus contacts the faceplate.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.