Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Patent
1996-10-03
1998-12-01
Horabik, Michael
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
341 20, 341 33, 345173, 178 1901, H03K 1794
Patent
active
058445064
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a multiple input proximity detector/touchpad system which may comprise, for example, a keypad array, digitising tablet, touchscreen or an electronic mouse which may be operated through a variable thickness of glass or other dielectric medium, and more particularly to the design of a multiple input proximity detector/touchpad system in which a large matrix of keys or a large touch sensitive area may be formed using the superposition of, for example, orthogonally arranged conducting elements. The conducting elements, and the electronic scanning system to service the conducting elements are particularly arranged to obtain optimized sensitivity.
In European Patent No. EP-0185671 there is described a touch operated keyboard for attachment to one face of a sheet of glass comprising a plurality of keypads disposed adjacent each other in a desired pattern, together with interrogation means for assessing the condition of the keypads, indicating when a keypad, or keypads have been operated by a user, and an electronic scanning and processing system for providing means for threshold value generation and drift compensation.
The threshold value generation means is operative to determine repeatedly at predetermined intervals the required capacitance level associated with any keypad in order to indicate that that keypad has been operated by a user.
The drift compensation means is operative to offset variations in capacitance caused by varying background conditions.
The present invention is directed towards the construction of a multiple input proximity detector/touchpad system, which may comprise a keypad array, digitising tablet, touchscreen or an electronic mouse, wherein the position of a user's finger or other object touching, or in close proximity to the "touch sensitive" surface area, hereinafter referred to as a touchpad, is determined by means of the capacitive effect of that finger on multiple conductor elements (hereinafter referred to as a keystroke), and to the optimisation of sensitivity of the touchpad, particularly when the touch sensitive area becomes relatively large. It is intended that throughout the present specification, reference to a "finger" is intended to include any object that would exert sufficient capacitive influence to be detected by the touchpad.
It should be noted that the activation of a "keypad" or area of the touchpad can be achieved without pressure on, or even without physical contact with, the surface of the touchpad, although in normal mode of operation, the user's finger would contact the touchpad surface or a surface associated therewith.
Other known types of touchpad, such as membrane switches having two sets of conductors face to face, require the use of pressure on two conducting elements at an intersection of those conducting elements. Pairs of conducting elements may be scanned in systematic manner to determine which, if any, intersection has been pressed. Disadvantages of this system are that there are moving parts (eg. the upper surface presented to the user's finger) which can therefore be subject to damage, and also that the positioning of the user's finger must coincide with the conducting element intersection. This method employs a set of driver conductors and a set of sensing conductors.
U.S. Pat. No. 4,686,332 discloses a touchpad comprising a horizontal and vertical grid of transparent conductors which are plated onto a substrate and which provide unique finger touch sensing and unique stylus location sensing.
The present invention uses only sensing conductors and has no moving parts. It can thus be well protected from damage by users by the glass or other dielectric medium covering the touchpad. The electronic scanning of the conducting elements requires connection to only one element at a time, and all other elements can be placed in condition to reduce interference when not being scanned. The present invention further permits detection of the user's finger at any point on the touchpad's active surface, and the electronic scanning
REFERENCES:
patent: 4686332 (1987-08-01), Greanias et al.
Hill Andrew
Horabik Michael
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