Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Patent
1987-10-26
1990-12-25
Yusko, Donald J.
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
341 32, 250221, 25022722, H03M 1100, H03K 47969
Patent
active
049806858
DESCRIPTION:
BRIEF SUMMARY
The present invention relates more particularly to scanning optical keyboards, i.e. to keyboards in which the number of optical components serves to handle a greater quantity of keys than could be handled by using keys fitted with individual connection and detection elements.
Because of the proliferation of microprocessors, scanning keyboards have become usual on devices such as calculators, typewriters, word processors, computers, music synthesizers, automatic vending machines, etc. Rather than using keys which are detected individually, i.e. keys which are each fitted with their own connections to the system which uses the keys, the keys are connected in a logical matrix to a scanning interface which informs the system to which the keyboard is connected of the results of its observations concerning the states of the keys.
For example, a calculator may have sixteen keys disposed in a matrix of four inlets (or rows) by four outlets (or columns). Its keyboard will have an interface which periodically scans the keys by applying an interrogation signal on a first inlet and observing the result on all four outlets, etc. Thus, scanning a matrix of N.times.M keys provides the advantage of reducing the number of inlets and outlets required by the keyboard itself to M+N, instead of the M.times.N that would otherwise be required. Once the interface has determined that one or more keys have been depressed, it transmits this information in the form of an appropriate code to the user system. The interface may be connected in various different ways to the user system. If serial signals are used, then two or three lines suffice for any number of keys. If a parallel connection is used, then four lines suffice for a keyboard having up to sixteen keys, and eight lines enable up to 256 keys to be identified.
Each key is associated with its own intersection in the matrix. It preferably operates by producing two stable states: a state in which the corresponding inlet and outlet are coupled together and a second state in which they are not coupled. In an optical keyboard, the signals used are visible radiation or invisible radiation (infrared or ultraviolet rays, for example). These signals are applied to the inlets, and the outlets from the keyboard are observed to determine whether or not they are being coupled with the inlet signals. The state of the coupling at each intersection of the matrix is determined by an element which is actuated by the corresponding key. This element may be a shutter or a moving mirror. In an electrical keyboard, the coupling between electrically conductive materials is provided by on/off switches, although other components such as capacitive switches or Reed effect switches are also used.
Other methods may be used, such as varying the signal as described in the Journal of Research embodiment mentioned below.
A priori, optical keyboards provide several advantages over electrical keyboards. For example, they are free from electrical interference (both as transmitters of interference and as receivers of interference). By their very nature they provide greater safety (no sparks in explosive atmospheres), key bounce is reduced at source, component lifetime is increased (there is no contact wear), etc.
A fiber keyboard based transmission loss by bending two perpendicular optical fibers against each other under key pressure is described in 645 G.E.C. Journal of Research 2 (1986) No. 2 London, Great Britain. However this keyboard is constituted by a matrix which is not scanned, thus giving rise to a large number of inlets and outlets which are difficult to handle.
The major problem with matrix keyboards lies in the frequently random result of simultaneously depressing two or more keys. This problem often arises during high-speed typing: an operator may type at speeds in excess of ten characters per second. As a result several keys may be depressed simultaneously. This problem is commonly referred to as "key rollover": it is important for the user system to be able to identify keys reliably together with
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Fargette Alain
Marland Andre S.
Souloumiac Alain
Queen Tyrone
Yusko Donald J.
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