Light distribution for illuminated keyboard switches and display

Details Light distribution for illuminated keyboard switches and display Light distribution for illuminated keyboard switches and display

1993-03-23

1995-03-14

Friedhofer, Michael A.

Electricity: circuit makers and breakers

Multiple circuit control

Multiple switch

200512, 200311, 200314, H01H 918

Patent

active

053978676

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 the display or switch.

REFERENCES:
patent: 3963489 (1975-04-01), Cho
patent: 4149773 (1979-04-01), Reid
patent: 4336978 (1982-06-01), Suzuki
patent: 4551598 (1985-11-01), Hamilton et al.
patent: 4811175 (1989-03-01), DeSmet
patent: 4963933 (1990-10-01), Brownlee

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