Touch panel coordinate determination

A system for determining coordinates of a contact point on a touch screen that comprises first and second input layers, spaced apart by a selected small distance, each layer containing a sequence of resistive lines that extend between an input layer voltage source and a no-current-flow point, the system comprising:

• a first selected voltage source, connected across a resistive line in the first input layer to an electrical contact point, common to the first input layer and the second input layer;
• a second selected voltage source, connected in series across a selected resistance and a resistive line in the second input layer to the contact point;
• a current measurement mechanism positioned to measure a current value for at least one resistive line that passes through the contact point;
• a voltage measurement mechanism positioned to measure a voltage value at the contact point;
• and
• a computer that is programmed:
• to receive the measured current value and the measured voltage value;
• to calculate a resistance of a resistive line that extends from the contact point to the first voltage source;
• and
• to calculate a resistance of a resistive line that extends from the contact point to the second voltage source.

A method for determining coordinates of a contact point on an input screen that comprises first and second input layers, spaced apart by a selected small distance, each layer containing a sequence of resistive lines that extend between first and second spaced apart electrodes for the input layer, the method comprising:

• providing a first selected voltage for a first layer first electrode and for a second layer first electrode, and providing a second selected voltage for a first layer second electrode and for a second layer second electrode;
• measuring a current value for at least one resistive line segment that extends from a contact point common to the first input layer and second input layer to the first layer first electrode;
• calculating a current value for that least two resistive lines that extend from the contact point to the first layer second electrode, to the second layer first electrode, and to the second layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the first layer first electrode and the first layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the second layer first electrode and the second layer second electrode;
• and
• using the estimated resistance values to estimate coordinates corresponding to location of the contact point on at least one of the first and second input layers.

A method for determining coordinates of a contact point on an input screen that comprises first and second input layers, spaced apart by a selected small distance, each input layer containing a sequence of resistive lines that extend between two spaced apart electrodes for the input layer, the method comprising:

• providing a first selected voltage and a second selected voltage for the first layer first electrode and first layer second electrode, and providing a third selected voltage and a fourth selected voltage for the second layer first electrode and second layer second electrode, respectively;
• measuring a current value for each of at least first and second resistive lines that extend from a contact point common to the first input layer and second input layer to the first layer first electrode and to the first layer second electrode, respectively;
• calculating a current value for two resistive lines that extend from the contact point to the second layer first electrode and to the second layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the first layer first electrode and the first layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the second layer first electrode and the second layer second electrode;
• and
• using the estimated resistance values to estimate coordinates corresponding to location of the contact point on at least one of the first and second input layers.

A method for determining coordinates of a contact point on an input screen that comprises first and second input layers, spaced apart by a selected small distance, each input layer containing a sequence of resistive lines that extend between two spaced apart electrodes for the input layer, the method comprising:

• providing a first selected voltage and a second selected voltage for the first layer first electrode and first layer second electrode, and providing a third selected voltage and a fourth selected voltage for the second layer first electrode and second layer second electrode, respectively;
• measuring a current value for each of at least first and second resistive lines that extend from a contact point common to the first input layer and second input layer to the first layer first electrode and to the second layer first electrode, respectively;
• calculating a current value for two resistive lines that extend from the contact point to the first layer second electrode and to the second layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the first layer first electrode and the first layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the second layer first electrode and the second layer second electrode;
• and
• using the estimated resistance values to estimate coordinates corresponding to location of the contact point on at least one of the first and second input layers.

A method for determining coordinates of a contact point on an input screen that comprises first and second input layers, spaced apart by a selected small distance, each input layer containing a sequence of resistive lines that extend between two spaced apart electrodes for the input layer, the method comprising:

• providing a first selected voltage and a second selected voltage for the first layer first electrode and first layer second electrode, and providing a third selected voltage and a fourth selected voltage for the second layer first electrode and second layer second electrode, respectively;
• measuring a current value for each of at least first, second and third resistive lines that extend from a contact point common to the first input layer and second input layer to the first layer first electrode, to the first layer second electrode and to the second layer first electrode, respectively;
• calculating a current value for two resistive lines that extend from the contact point to the first layer second electrode and to the second layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the first layer first electrode and the first layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the second layer first electrode and the second layer second electrode;
• and
• using the estimated resistance values to estimate coordinates corresponding to location of the contact point on at least one of the first and second input layers.

A method for determining coordinates of a contact point on an input screen that comprises first and second input layers, spaced apart by a selected small distance, each input layer containing a sequence of resistive lines that extend between a first electrode and a selected location in the input layer spaced apart from the first electrode, the method comprising:

• providing a first selected voltage for a first layer first electrode and for a second layer first electrode, and providing a second selected voltage for a first layer second electrode;
• measuring a current value for at least one resistive line segment that extends from a contact point common to the first input layer and the second input layer to a point drawn from the first layer first electrode, the first layer second electrode and the second layer first electrode;
• calculating a current value for at least one resistive line, drawn from lines that extend from the contact point to the first layer first electrode, to the first layer second electrode, and to the second layer first electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the first layer first electrode and the first layer second electrode;
• estimating a resistance value for the resistive line that extends from the contact point to at least one of the second layer first electrode and the second layer second electrode;
• and
• using the estimated resistance values to estimate coordinates corresponding to location of the contact point on at least one of the first and second input layers.