Touch panel using modulated light
US4893120A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 18, 1988 |
| Grant date | Jan 9, 1990 |
| Priority date | — |
| Expiry date | Nov 18, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/0421
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A touch panel system using modulated light beams to enable the system to detect when one or more of the light beams are blocked even in bright ambient light conditions. The system has a "touch sensitive" display surface with a defined perimeter. Surrounding the display surface are a multiplicity of light emitting elements and light receiving elements. These elements are located so that the light paths defined by selected pairs of light emitting and light receiving elements cross the display surface and define a grid of intersecting light paths. A scanning circuit sequentially enables selected pairs of the light emitting and light receiving elements, modulating the amplitude of the light emitted in accordance with a predetermined pattern. A filter generates a blocked path signal if the currently enabled light receiving element is not generating an output signal modulated in accordance with the predetermined pattern. Finally a computer is used to determine if an object is adjacent to the display surface and the location of the object, by determining if the filter is generating at least two blocked path signals corresponding to light paths which intersect each other within the perimet…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.