Telegraphy – Systems – Position coordinate determination for writing
Patent
1993-05-10
1995-06-27
Chin, Stephen
Telegraphy
Systems
Position coordinate determination for writing
178 18, 178 20, 345179, G08C 2100
Patent
active
054281920
ABSTRACT:
A method and apparatus for producing a digital number representing the location of a pointing instrument with respect to a plurality of spaced conductors is disclosed. The instrument has a coil unit which produces an alternating magnetic field for inducing a plurality of alternating current signals in the plurality of spaced conductors, respectively, when an alternating current electrical signal is applied thereto. The conductors are sampled in a predetermined order so as to sense the induced alternating current signals. A phase sensitive detector is employed to detect a phase reversal between the induced alternating current signals induced in ones of the conductors located on opposite sides of the coil to produce a signal waveform which changes polarity in response to the phase reversal. A position counter is then incremented at a predetermined rate upon detection of the phase reversal until sampling of a succeeding one of the conductors which immediately follows the detection of the phase reversal is to be initiated. A processor deducts a digital number in the position counter from a digital number corresponding to a predetermined distance of the succeeding one of the conductors from a marginal one of the conductors in order to determine the location of the pointing instrument.
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Chen Chien-Hung
Hsu Jung-Chih
Ace Cad Enterprise Co., Ltd.
Chin Stephen
Shankar Vijay
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