| 主权项 |
1. An apparatus comprising:
a signal generator having an input port and an output port; a transmit antenna electrically connected to said output port of said signal generator; a signal detector having an input port and output port; a receive antenna electrically connected to said input port of said electrical signal detector; a tablet comprising a plurality of light emitting devices and a plurality of light sensing devices, said light emitting devices and said light sensing devices arranged as an orthogonal grid; a controller electrically connected to said input port of said signal generator, said output port of said signal detector, a data base system, and separately, to each of said light emitting devices and said light sensing devices. |
