Light distribution for illuminated keyboard switches and displays
US5397867A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 23, 1993 |
| Grant date | Mar 14, 1995 |
| Priority date | — |
| Expiry date | Mar 23, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01H2219/064
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Disclosed is the backlit display and/or backlit keyboard display which have a controlled level of illumination at the surface thereof. Where such switch and/or display are illuminated by a light emitting diode, the present invention interposes an optical filter between the light emitting diode and the surface of the cover. The optical filter contains a pattern thereon having a variable density distribution of opaque material which in a preferred embodiment is densest in the area closest to the light emitting diode and decreases in density in areas away from the light emitting diode. In a preferred embodiment the optical filter is a "negative" of the illumination without a filter present. The result in both the switch and display embodiments is a substantially constant level of illumination across the surface of the cover. Further disclosed is at least one slot in translucent layers which may be incorporated in a switch or display which reduces "crosstalk" between switches and/or displays. Additionally the use of a reflective material as the optical filter, in combination with and separated from a reflective layer near the LED by a separator layer, provides increased illumination of…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.