Stylus-input computing system with erasure

摘要

A handheld computing device has a planar display (12) and a superimposed, transparent digitizer (10). The combination is arranged to simulate writing or drawing with pencil on paper: the writing end of a passive stylus (18) is pressed on and moved across the digitizer surface and a line on the display (12) is produced directly under the stylus path. In order to complete the analogy to pencil and paper, display erasure is also provided. Under the display (12) is located an inductive winding (26). The other end of the stylus (18) contains a small permanent magnet (22). When the magnet end of the stylus (18) is pressed against the digitizer (10) and moved over a display line, a small voltage is induced in the inductive winding (26). This voltage is converted into a logic signal. The assertion of this signal together with a signal from the digitizer (10) results in the erasure of display traces in the region inferred from the digitizer signal.