Image analysis – Histogram processing – For setting a threshold
Patent
1981-02-12
1983-08-02
Boudreau, Leo H.
Image analysis
Histogram processing
For setting a threshold
178 19, 324228, 382 64, G06K 900, G08C 2100, G01R 3300
Patent
active
043970338
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a device for measuring characteristic parameters of the speed of handwriting based on electromotive forces induced by the writing instrument in pick-up coils.
STATE OF THE ART
Much work has already been carried out on the dynamic analysis of writing. Thus, the translation of the speed of writing into a proportional electrical signal has already been proposed. To achieve this object, it has been proposed, in particular, that the acceleration of the writing instrument be measured and the speed be deduced therefrom by integration of the measured acceleration. The presence of measuring elements on the writing instrument makes it necessary to connect the instrument to a data processing apparatus. This involves the presence of a wire, which is inconvenient. Moreover, accelerometers are sensitive to their orientation about the longitudinal axis of the writing instrument. This is why a solution in which the instrument is insensitive to its physical orientation is desirable.
It has already been proposed that this disadvantage be overcome by using a system of inductive pick-ups of the type described in PCT Application No. W079/00363. With this method of measurement, voltages are induced in two portions of crossed coils placed beneath the writing surface, by a permanent magnet placed in the pen.
Another problem inherent in this method of analysing writing involves the elimination of parasitic noise caused by displacements of the writing instrument which do not produce an outline, that is to say displacements which are communicated to this instrument when its writing point does not touch the writing substrate. Solutions utilizing systems of contacts have already been proposed as, for example, in U.S. Pat. No. 4,078,226. These systems are awkward as they have to be sensitive to slight pressures at any point on the writing substrate. It has also been proposed that the contact system be placed on the writing instrument, on the assumption that a source of current is coupled to the instrument or is connected thereto. Even in this case, the contact is a source of malfunctioning, not to mention the complication of the solution.
Moreover, U.S. Pat. No. 4,029,899 discloses a graphic detection device comprising a plurality of coils arranged alternatively in opposite directions to produce a signal when a magnetic flux passes from one coil to another, which is characteristic of the position of the writing instrument connected to the magnetic flux. Such a device is not therefore linked directly to the measurement of the dynamics of writing but, rather, is related to the graphical reproduction of the kinetics of the writing.
STATEMENT OF THE INVENTION
The object of the present invention is to overcome, at least in part, the disadvantages of the above-mentioned solutions.
For this purpose, the present invention relates to a device for measuring characteristics parameters of the speed of handwriting, characterised by the fact that it comprises, on the one hand, subjacent to the surface constituting the writing substrate, four superimposed windings of electrical conductors, coupled in series in pairs but with opposite winding directions, windings in the same pair containing two layers formed by rectilinear portions of conductors side by side, the rectilinear portions of conductors in one layer being parallel to and superimposed on the similar portions of the other layers, the remaining portions of the windings in this pair extending respectively on either side of their superimposed portions, the rectilinear portions of conductors of the layers in one pair of windings being orthogonal to those of the other pair, the zone of superimposition of these conductors defining the surface area of the said writing substrate and, on the other hand, a magnet adjacent to the writing point of the writing instrument of which the magnetization is selected so as to have a general orientation parallel to the longitudinal axis of the said instrument and symmetrical about this axis, all in such a way that, w
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Yoshida et al., "Input Pen Used for Electromagnetically Coupled Data Tablet", Trans. of the I.E.C.F., Japan, Section E, vol. E61, No. 7, Jul. 1978, pp. 561-562.
Stuckert, "Magnetic Pen and Tablet", IBM Tech. Disclosure Bulletin, vol. 22, No. 3, Aug., 1979, pp. 1245-1251.
Bechet, "Device for Measuring Characteristic Parameters of the Speed of Handwriting", International Publication #WO79/00363, Jun. 1979.
Battelle (Memorial Institute)
Boudreau Leo H.
Dunson Philip M.
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