Electronic sketch pad
US4639720A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 12, 1981 |
| Grant date | Jan 27, 1987 |
| Priority date | — |
| Expiry date | Jan 12, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G3/3685
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A graphics input/output device contains a graphics input pad having an array of transparent capacitive pixels the capacitance characteristics of which are changed in response to the passing of a conductive-tipped stylus over the surface of the pad. This change in capacitance is sensed by sense buffers disposed along the columns of the matrix, as the rows are scanned at a prescribed scanning rate. The sensed data is read out of the sense buffer and loaded into a RAM. An array of display pixels formed of an LCD matrix is addressed by a scan sequence control unit, and the energization of the display pixels is multiplexed with the read-out scanning of the sensed data, so as to present to the user a real time generated image of the graphics created by the stylus. As a result, it appears to the user that the stylus is actually "writing" on the display pad.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.