Browse Prior Art Database

Touch Sensitive Device

IP.com Disclosure Number: IPCOM000091365D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Fischler, AS: AUTHOR [+2]

Abstract

This touch sensitive device responds to light finger pressure and is free from contact bounce. Light emitting diode 12 is mounted on substrate 14. Pressure plate 16 is supported above substrate 14 by a resilient member 18, a sylphon bellows. Light sensor 22 is imbedded in plate 16. The latter is made of light transmitting material throughout. Alternately the boss in which sensor 22 is embedded can be the only part which needs be capable of transmitting light. This material has an index of refraction of the order of two. A gallium-arsenide light emitting diode 12 has an index of refraction of the order of 3.3. With the sensor bearing material spaced apart from diode 12, a large portion of the light incident on the surface of such diode from the junction is internally reflected.

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Touch Sensitive Device

This touch sensitive device responds to light finger pressure and is free from contact bounce. Light emitting diode 12 is mounted on substrate 14. Pressure plate 16 is supported above substrate 14 by a resilient member 18, a sylphon bellows. Light sensor 22 is imbedded in plate 16. The latter is made of light transmitting material throughout. Alternately the boss in which sensor 22 is embedded can be the only part which needs be capable of transmitting light. This material has an index of refraction of the order of two. A gallium-arsenide light emitting diode 12 has an index of refraction of the order of 3.3. With the sensor bearing material spaced apart from diode 12, a large portion of the light incident on the surface of such diode from the junction is internally reflected. Only a small portion is active with respect to member 22.

The latter is biased electrically, by conventional circuitry not shown, to treat this small portion of light as background. When finger pressure is applied to bring plate 16 into contact with diode 12, the increase in light impinging on member 22 provides a positive signal.

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