1. Field of the Invention
The present invention is in the field of computer input devices and pertains particularly to illumination of individual keys of a computer input device such as a keyboard or keypad.
2. Discussion of the State of the Art
Advances in illumination technology have led to a variety of types of backlighting techniques for consumer electronics. One application for illumination technology is illuminating keyboards so that the keys are discernable under low-light or no light conditions.
Typically, for more advanced products an electro-luminescent (EL) sheet is used as a low power source of illumination. An EL sheet or panel, sometimes referred to as a lamp, is a flexible translucent polymer sheet containing electrical leads and conductive surface areas treated with coatings of phosphorous or other chemicals that illuminate when exposed to an electrical charge from a power source.
The inventor is aware of a method and apparatus taught by Andrew J. Katrinecz U.S. Pat. No. 6,199,996 entitled “Low Power, Low Cost Illuminated Keyboards and Keypads” hereinafter termed Andrew et al. Andrew et al illustrates manufacturing processes for non-illuminated data-entry devices and mice to the manufacture of illuminated data-entry devices. The method calls for luminescent sheets of one or more colors integrated into a typical manufacturing process for keyboards whereby the sheet is incorporated underlying optically translucent device components to provide illumination of the components visual to a user of the device. The optically translucent components may be doped with phosphors or tinted to provide components that emit light of different colors. The intensity of illumination of the luminescent sheet may be controlled by the user and may vary in response to the background light of the environment.
Although illumination may be adequately produced from the source EL sheet of Andrew, the mechanics of the keyboard and more importantly the keys render the illumination effect produced undesirable in that shadows attributed to overlying keyboard components hinder a user's ability to well discern the correct key characters printed on the key faces above the illumination panel.
The general problem is that the illumination panel is setting to far below the face of the keys and therefore, parallax happens where one cannot see the characters well enough because of shadowing from the underlying mechanics of the keys set above the illumination or EL panel.
Therefore what is clearly needed is a system and method for illuminating the keyboard or keypad in a way that eliminates any parallax or shadowing from key components or other elements of the keyboard architecture.