Infrared touch input device having ambient compensation
US4855590A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 25, 1987 |
| Grant date | Aug 8, 1989 |
| Priority date | — |
| Expiry date | Jun 25, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/0421
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An input device which can be employed to input commands to a computer directly through a CRT display is disclosed. The input device employs a plurality of infrared light emitting diodes and phototransistors aligned in individual emitter-detector pairs. Infrared beams from the emitter cross the display field before striking the corresponding detector. Emitters and detectors are sequentially activated and each emitter is pulsed or modulated at a frequency different from the variation of ambient conditions during each emitter activation interval. The detection circuitry thus can distinguish the varying emitter signal from ambient or spurious variations. A number of pulses at the pulsed or modulated emitter frequency would be detected unless an opaque element were blocking the particular beam.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.