Noiseproof digitizing apparatus with low power cordless pen

Details Noiseproof digitizing apparatus with low power cordless pen Noiseproof digitizing apparatus with low power cordless pen

1994-07-12

1996-06-18

Chin, Stephen

Telegraphy

Systems

Position coordinate determination for writing

178 19, 178 20, 345156, 345179, 345182, G08C 2100, G09G 302

Patent

active

055280021

ABSTRACT:
A noiseproof digitizing apparatus for digitizing the coordinates of a point on a tablet having grid conductors disposed along X and Y coordinate axes includes a cordless pen having a conductive end for transmitting an electrical signal to the grid conductors through of electrostatic capacitive coupling. An AC signal generator generates an AC signal and applies a balanced output of the AC signal to the conductive end, such that electrostatic capacitive coupling between the conductive end and the grid conductors causes a major balanced AC signal component and two minor unbalanced AC signal components to be produced in the grid conductors in response to the AC signal on the conductive end. A power supply supplies electrical power to the AC signal generator. A signal level measuring device measures the level of a signal current resulting from a sum of the major balanced AC signal component and the two minor unbalanced AC signal components produced in the grid conductors. A processor is provided for processing the measured signal level to determine a coordinate of the conductive end of the cordless pen.

REFERENCES:
patent: 4217649 (1980-08-01), Doundoulakis
patent: 4473717 (1984-09-01), Parnell
patent: 4479032 (1984-10-01), Parnell
patent: 4672154 (1987-06-01), Rodgers
patent: 5072076 (1991-12-01), Camp, Jr.

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