Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Patent
1987-11-18
1989-09-19
Yusko, Donald J.
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
341 32, 250221, H03M 1100, H03K 17968
Patent
active
048685682
DESCRIPTION:
BRIEF SUMMARY
The present invention relates more particularly to scanning optical keyboards, i.e. to keyboards in which information is conveyed by light rays reflected on mirrors, and in which a number of optical components serves to handle a quantity of keys which is greater than would be possible using keys each fitted with individual detection and connection elements.
Because of the proliferation of microprocessors, scanning keyboards have become common on devices such as calculators, typewriters, word processor systems, computers, music synthesizers, vending machines, etc. Instead of using individually detected keys, i.e. keys each provided with their own particular connections to the system using them, the keys are connected in a logical matrix with a scanning interface which informs the system to which the keyboard is connected of the results of its inspections concerning the states of the keys. Each key is connected at an individual intersection in a matrix. It operates by producing two distinct states: a state in which the corresponding inlet and outlet are coupled and a second state in which they are not coupled.
In an optical keyboard, the signals used are visible light, or more generally any form of radiant energy (e.g. infrared or ultraviolet rays). These signals are applied to the keyboard inlets and its outlets are inspected to determine whether or not there is any coupling with the inlet signals. The coupling or noncoupling state at each intersection of the matrix is governed by an element which moves under the action of the corresponding key. This element is generally in the form of a shutter or of a moving mirror. In an electrical keyboard, coupling or noncoupling between electrically conductive materials is generally provided by on/off switches, but other components such as capacitive switches or Hall effect switches are also widespread.
A priori, optical keyboards offer considerable advantages over electrical keyboards. For example, they are free from electrical interference (both as emitters of interference and as receivers of interference). By their very nature, they offer improved safety (no sparks in explosive atmospheres), key bounce is reduced at source, component life is increased (no contact wear), . . .
The major problem with matrix optical keyboards lies in the frequently random results that may occur when two or more keys are depressed simultaneously. This problem arises during high speed typing: operators are capable of typing at speeds of more than 10 characters per second. As a result, several keys may be depressed simultaneously at any given moment. The person skilled in the art refers to this problem by the English term "key rollover": it is important for the user system to be able to identify keys reliably and the order in which they are depressed, even if several keys happen to be simultaneously depressed at any given moment. Further, even without high speed typing, many keyboards require a plurality of keys to be depressed simultaneously, for example the shift key and some other key in order to gain access to particular symbols or functions. This problem is thus quite general. Another problem, related to the first, is the problem of "ghost" keys: the depression of a key which the operator is not touching can be simulated by a combination of other keys, and the user system has no way of establishing which keys are really being depressed.
In an optical keyboard, the problem of reliably identifying any key even in the presence of a plurality of keys being depressed simultaneously, is solved provided it can be guaranteed firstly that every key has access to light regardless of the states of any other keys (coupling or noncoupling), and secondly that each photodetector can "see" all of the keys which are associated therewith, again regardless of the states of any other keys. This comes to saying that the optical path between each light source and each of the keys which are associated therewith must never be totally obstructed, and also that the optical path connecting each photodetector
REFERENCES:
patent: 3886544 (1975-05-01), Narodny
patent: 4113353 (1978-09-01), Matsushita
patent: 4379968 (1983-04-01), Ely et al.
patent: 4641026 (1987-02-01), Garcia, Jr.
"Opto-Magnetic Input Tablet or Keyboard" by S. C. Tseng, IBM Tech. Discl. Bulletin, vol. 22, No. 12, 5/80.
Queen Tyrone
Yusko Donald J.
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