Telegraphy – Systems – Position coordinate determination for writing
Patent
1987-05-07
1989-01-24
Schreyer, Stafford D.
Telegraphy
Systems
Position coordinate determination for writing
382 3, G08C 2100
Patent
active
048002402
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for detecting the displacement of a writing implement from a proximity threshold which is determined relative to a writing surface, the instrument having, close to its writing tip, a permanent magnet the magnetisation of which is orientated so as to be generally parallel to the longitudinal axis of the said instrument and symmetrical about this axis, the device comprising, subjacent to the writing surface, at least two electric conductors in series extending parallel to the writing plane.
French Pat. No. 2 486 271 has already disclosed a device for measuring the characteristic parameters of the speed of handwriting using coils disposed beneath the writing surface in which coils electric voltages are induced by the magnetic field of a permanent magnet rigid with the writing implement. If consideration is given to this concept, it will be seen that voltages are induced at the terminals of the coils not only when one is writing, but also consequent upon movements of the writing implement some distance from the writing surface.
It has been proposed inter alia to use a device of this type to compare the speed signals of a signature with those of a reference signature. In a case where this is used, where the comparison is carried out automatically by comparing digitised signals, the signals which derive from movements of the writing implement preceding the signature are parasitic signals which must be eliminated. The distinction between parasitic signals and useful signals presents an awkward problem, the accuracy of which will to a large extent ensure successful comparison of signals.
European Pat. No. 0 030 224 discloses a solution to this problem by associating a piezo-electric detector with the writing surface, in order to set the start of the comparison at the moment the writing implement touches the writing surface. In practice, it has been shown that this system is frequently subject to malfunctioning in that it is sensitive to parasitic noise.
The aim of the invention is to obviate, at least in part, the disadvantages set out above.
To this end, the subject of the invention is a device for detecting the displacement of a writing implement according to claim 1.
The advantage of this device over other solutions previously proposed lies essentially in that only the magnetic field emanating from the permanent magnet rigid with the writing implement can induce a characteristic signal of the fixed proximity threshold. Consequently, false starts to the signature comparison process for example, caused by a variety of parasitic vibrations transmitted to the writing surface, are avoided. As a result, no other special precautions are necessary for determining the start of recording in order to proceed with the comparison of a signature with a reference signature. This feature is of great importance in a system intended for use by the general public, as would be the case if this method of comparing signatures were to be used for credit cards in order to verify that the holder of a given card is in fact the legal cardholder.
The accompanying drawings show diagrammatically and by way of example an embodiment of the device which is the subject of the present invention.
FIG. 1 is an exploded perspective view of this embodiment.
FIG. 2 is an electronic circuit diagram.
FIGS. 3a to 3c are diagrams of the processing of the signal by the circuit in FIG. 2.
FIG. 1 shows four electric conductors 1, 2 and 1', 2' each forming a series of rectangular loops 3, respectively 4, 3' or 4', adjacent on their long sides and open on the short side, the opening of the adjacent loops being located at the respective opposite ends of these loops. Having formed the loops 3, 4 respectively, the conductors 1 and 2 form a second series of rectangular loops 5, and 6 respectively, which are adjacent on their long sides, and open on their short sides, the openings of the adjacent loops being located at the respective opposite ends of these loops. The loops 5 or 6 respectively overlap the loops 3 and 4 resp
REFERENCES:
patent: 3647963 (1972-03-01), Bailey
IBM Technical Disclosure Bulletin, vol. 3, No. 6, Nov. 1960, (New York, US), K. A. Ahmad: "Signal Communication Apparatus", p. 22, See the Whole Document.
IBM Technical Disclosure Bulletin, vol. 22, No. 3, Aug. 1979, (New York, US), P. E. Stuckert: "Magnetic Pen and Tablet", pp. 1245-1251, See the Whole Document.
Abstracts of IECE Transactions, vol. 58, No. 5, N. Aoki et al.: "Data Tablet for Handwriting Characters", pp. 51-52, See Pages 51-52.
WO, A 80/02883 (Battelle Memorial Institute), Dec. 24, 1980, See p. 2, Line 21-p. 3, Line 13; FIGS.; p. 3, Line 23-p. 6, Line 27.
WO, A 79/00363, (Battelle Memorial Institute), Jun. 28, 1979, See the Whole Document, (Cited in the Application).
Battelle (Memorial Institute)
Schreyer Stafford D.
LandOfFree
Device for detecting the displacement of a writing implement does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for detecting the displacement of a writing implement, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for detecting the displacement of a writing implement will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-420199