Combined finger touch and stylus detection system for use on the viewing surface of a visual display device

A combined finger touch and stylus detection system for use on the viewing surface of a visual device, comprising:

• an array of horizontal and vertical conductors arranged on the viewing surface of the visual display device, having an I/O terminal coupled thereto, for conducting electrical signals between said terminal and the vicinity of said viewing surface;
• a radiative pickup stylus, having an output terminal, for receiving electromagnetic signals radiated from said array;
• a selection means having a switchable path connected to said I/O terminal of said array and having a control input, for connecting selected patterns of a plurality of said horizontal and vertical conductors to said switchable path in response to control signals applied to said control input;
• a capacitance measuring means having an input coupled to said switchable path of said selection means, for measuring the capacitance of selected ones of said conductors in said array, in response to said control signals applied to said control inputs;
• a radiative signal source having an output coupled to said switchable path of said selection means, for driving selected ones of said conductors in said array, in response to said control signals applied to said control input;
• a radiative signal measuring means coupled to said radiative pickup stylus, for measuring said electromagnetic signals received by said stylus;
• a control processor connected to said control input of said selection means, for executing a sequence of stored program instructions to sequentially output said control signals to said selection means;
• said control processor connected to said capacitance measuring means, for receiving measured capacitance values of said conductors when said selection means, in response to said control signals, has connected a first pattern of a plurality of said conductors in said array to said capacitance measuring means, to detect the location of a finger touch with respect to said viewing surface of said display device;
• said control processor connected to said radiative signal measuring means, for receiving measured radiative signal values when said selection means, in response to said control signals, has connected a second pattern of a plurality of said conductors in said array to said radiative signal source, to detect the location of said stylus with respect to said viewing surface of said display device;
• whereby, both finger touch location and stylus location with respect to said viewing surface of said display, can be detected.