| 主权项 |
1. A stylus comprising:
a housing elongated along a longitudinal axis, and including a body portion and a tip portion at one end of the housing, the tip portion being attached to or integral with the body portion; a tip at the tip portion for pointing at a working surface, the tip having an end for placing on the working surface; a cavity extending longitudinally within the housing, and having a first end closest to the tip and a second end longitudinally opposite the first end, the first end including a plurality of holes; a transmitter of acoustic waves located at the second end of the cavity and having front emitting surface facing the first end forming said second end, the acoustic-wave transmitter configured to transmit acoustic waves at a main wavelength within the cavity towards the first end having the holes, the holes forming ports having exits from the cavity through which the acoustic waves can travel from the cavity towards the end of the tip; and electronics to drive the transmitter of acoustic waves, including a power source for the electronics; wherein the acoustic transmitter is arranged such that when driven by the electronics, and the end of the tip is in contact with the working surface, acoustic waves emanate from the front emitting surface of the acoustic transducer towards the holes in the cavity, and out of the port exits towards the end of the tip, wherein the distance between the exit of the ports and the end of the tip is less than a quarter of the main wavelength, and wherein the acoustic waves emitted from the exit of the ports are reflected by the working surface, travel through the air away from the working surface, and after reflection are detectible by a plurality of acoustic sensors that are spaced from the surface, the acoustic waves detected by the sensors being usable to determine the location of the end of the tip on the working surface. |
