Improved stylus sensing system.

摘要

An improved finger touch and stylus detection system for use on the surface of a display device is disclosed. An overlay having horizontal and vertical transparent conductors is coupled to the other elements of the system through a bus having a minimum number of bus wires. A control processor issues command signals which selectively couples the transparent conductors to a capacitive measuring device and a radiative measuring device to determine finger and stylus position respectively. The improvements to the system include a radiative stylus having a spherical antenna which receives the overlay signal independent of the angle at which it is held. Further, a contact detecting mode has been added to eliminate spurious stylus positions measured between strokes, when the stylus is proximate to but not in contact with the overlay.