Optical touch input device
US5838308A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 15, 1992 |
| Grant date | Nov 17, 1998 |
| Priority date | — |
| Expiry date | Apr 15, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/042
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An optical touch input device comprises an array of actively addressed sensing elements (18) for sensing a light input, e.g. from a light pen, each of which comprises a capacitor (25) which is charged periodically through operation of a switch device (24) and a discharge circuit, including a photosensitive device (28) and a further switch device (27) connected across the capacitor, which circuit in operation demonstrates an optical threshold characteristic whereby the capacitor (25) is discharged in response to the sensing elements being subjected to light which is at or above a predetermined intensity level so as to discriminate from ambient light. Elements written into are determined by detecting the charge stage of their capacitors. The sensing element array can be integrated with a matrix display device with the sensing elements (18) and display elements components (12) provided on a common support using thin film technology.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.