Touch panel system and method

Apparatus for detecting the position of a selected touch point on a current-conducting surface comprising,

• edge termination means defining two or more spaced apart edges of said current-conducting surface, the distance between said two or more spaced edges being predetermined, said edge termination means having terminals for connection to an external circuit,
• circuit means connected to said terminals of said edge termination means for maintaining said terminals at a predetermined instantaneous electrical potential at any time a linearized electrical current flows through said edges to any point on said surface between said edges,
• means for detecting a parameter of the linearized electrical currents through said terminals, and
• means for determining from the values of said detected parameter the location of said selected touch point on said surface at which said current is flowing from said edges, and producing at least one electrical signal corresponding to the said location of said selected touch point relative to at least one of said edges.

In a touch panel system having a resistive surface defined by two opposed pairs of edge terminations on said surface, a line passing through each edge pair being orthogonal to a line passing through the other edge pair, and having means for maintaining the terminals of said edge terminations of said surface at a predetermined instantaneous electrical potential, the method of locating a position on said surface comprising

• creating a potential difference between the terminals of said surface and a point touched on said surface by a human finger,
• placing said finger in proximity to said surface at any selected point such that current flows through said finger and said point to the terminals of said edge termination of said surface,
• measuring a parameter of said current flowing through said terminals,
• and converting said current measurements to a utilization signal and applying same to a utilization device.

A method of determining the location on an extended current-conducting impedance surface, of a current-conducting pathway between said impedance surface and a point of common electrical potential comprising:

• establishing at least two electrical connections to said impedance surface, said impedance surface possessing an electrical impedance that (1) is constant as a function of location or (2) is a known function of location,
• establishing potential differences between said electrical connections and said point of common electrical potential,
• linearizing current flow through said connections,
• measuring the electrical currents that flow through said electrical connections, and
• determining the location of said current-conducting pathway from the electrical measurements.

An apparatus for simultaneously locating a selected touch point on each of at least two separate touchable surfaces, comprising:

• at least two current-conducting impedance surfaces, each of said impedance surfaces being bounded by edge-termination means with at least two terminals for connecting said edge-terminations means to an external circuit,
• means connected to said terminals for maintaining said terminals at predetermined instantaneous electrical potentials,
• means for creating an instantaneous difference in net electrical potential between said terminals of a first impedance surface and said terminals of at least one other impedance surface, such that when a current-conducting means is provided between a selected touch point on said first impedance surface and a selected touch point on said other impedance surface, electrical currents are caused to flow through said terminals of both said first impedance surface and said other impedance surface,
• means for detecting a parameter of the electrical currents through said terminals of both said first impedance surface and said other impedance surface, and
• means for determining from the values of said detected parameter the locations of said selected touch points on said impedance surfaces, and producing at least two electrical signals corresponding to said locations of said selected touch points.

Apparatus for determining the location in two dimensions of a point through which electrical current flows in a current-conductive impedance surface, comprising

• means making at least three spced apart electrical connections to said current conductive impedance surface,
• means for linearizing current flow through said at least three connections,
• means for simultaneously measuring the electrical currents flowing through said at least three connections to said point, and
• ratiometric means for determining the location of said point from said measurements of electrical current.