Touch input device having digital ambient light sampling
US4943806A · kind A · utility
60Cited by
7References
5Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Dec 6, 1988 |
| Grant date | Jul 24, 1990 |
| Priority date | — |
| Expiry date | Dec 6, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/0421
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A touch input device which continuously samples and digitally stores ambient light readings and compares these with previously stored readings is taught. Briefly stated, a phototransistor is turned on before, during and after an LED emitter energization. An ambient value is calculated which is subtracted from the value obtained during LED firing so as to develop a signal indicative of the presence or absence of the LED pulse, irrespective of ambient light fluctuations. The ambient level is stored for comparison purposes during the next sampling of the associated phototransistor.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.