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Electroluminescent Keyboard Lamp

IP.com Disclosure Number: IPCOM000036823D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 4 page(s) / 68K

Publishing Venue

IBM

Related People

Najjar, LJ: AUTHOR

Abstract

This article describes an electroluminescent keyboard lamp to illuminate a full travel keyboard. A full travel keyboard is one in which the keys travel generally at least 2.5 mm. Full travel keyboards are preferred by typists because they provide obvious tactile feedback of key switch activation.

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Electroluminescent Keyboard Lamp

This article describes an electroluminescent keyboard lamp to illuminate a full travel keyboard. A full travel keyboard is one in which the keys travel generally at least 2.5 mm. Full travel keyboards are preferred by typists because they provide obvious tactile feedback of key switch activation.

Some jobs require that a full travel keyboard be used in a dimly lit ambient environment. For example, to maintain their ability to see aircraft and runways at night, air traffic controllers will use a full travel keyboard in a dimly illuminated tower cab. Full travel keyboards are also used in the dim environments of specialized work stations on submarines and military aircraft.

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Two techniques exist currently to illuminate a full travel keyboard in a dimly lit ambient environment: back lighting and front lighting. Back lighting requires that an incandescent light bulb or light-emitting diode (LED) be placed inside each keyboard key. When power is applied, the bulb or LED illuminates from the rear the legend on that key cap. Front lighting requires that a light source, typically a gooseneck desk lamp with an adjustable brightness incandescent light bulb, be placed above the keyboard. When power is applied, light from the lamp illuminates from the front the legends on the key caps.

Each keyboard-lighting technique has advantages and disadvantages. Back lighting has the advantage in that it is integrated with the keyboard to eliminate annoying cables and reach and vision obstructions onto and behind the keyboard. In back lighting, each key is illuminated to avoid finger shadows on the key caps and provide good key cap legend readability. Also, the brightness of the keyboard can be easily adjusted to avoid display reflections and suit different lighting conditions and user preferences.

However, back lighting has disadvantages in that the keyboard itself is usually quite heavy and thick due to deeper keys necessary to accommodate incandescent light bulbs or LEDs and other support electronics. Back lit keyboards are also quite expensive due to low volume and unusual, customized electronics. They suffer from low reliability due to electronic complexity and relatively short life of incandescent light bulbs, and require relatively large amounts of power.

Front lighting has an advantage in that it is much lower in cost to implement because a commercially available lamp can be used. The lamp's incandescent light bulb can be adjusted if it is interfaced with a rheostat. A lamp can be adjusted if a flexible mount is provided.

Front lighting has disadvantages in that the lamp obstructs the user's view and access to keys on the keyboard because, to get adequate light on the keyboard key caps, the lamp has to be positioned above the keyboard in the user's line of sight. Uneven lighting of keys occurs in front lighting the keyboard because the incandescent light bulb serves as a single, small, nonuniform s...