US 5,528,002 A · Noiseproof digitizing apparatus with low power cordless pen

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.

Claims24

Dependent claims

A noiseproof digitizing apparatus, comprising:

a tablet having a plurality of grid conductors disposed along X and Y coordinate axes;
a cordless pen for transmitting an electric signal to the grid conductors by electrostatic capacity coupling;
an AC signal generator disposed within the cordless pen for generating an AC signal and applying an output of the AC signal to the cordless pen;
power supplying means for supplying power to the AC signal generator;
two conductors disposed at the extreme end of the cordless pen and driven in balance or driven in pseudo balance by the AC signal generator such that electrostatic capacitive coupling between the cordless pen 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 cordless pen;
signal level measuring means for measuring the level of a signal current resulting from a sum of the major balanced AC signal and a difference of the two minor unbalanced AC signal components produced in the grid conductors;
means for measuring a frequency of the AC signal;
and means for processing signal values measured by the signal level measuring means to digitally output a coordinate of the extreme end of the cordless pen.

5 more elements

A noiseproof digitizing apparatus for digitizing coordinates of a point on a tablet having grid conductors disposed along X and Y coordinate axes, the noiseproof digitizing apparatus comprising:

a cordless pen having a conductive end for transmitting an electrical signal to the grid conductors by electrostatic capacitive coupling, and AC signal generating means for generating an AC signal and applying 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;
power supplying means for supplying electrical power to the AC signal generating means;
signal level measuring means for measuring 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;
and
means for processing the signal current level measured by the signal level measuring means to determine a coordinate of the conductive end of the cordless pen.

2 more elements

Dependencies are inferred from the claim text.

Noiseproof digitizing apparatus with low power cordless pen

Life of this patent

Noiseproof digitizing apparatus with low power cordless pen

Life of this patent

Abstract

Claims24