Patent ID: 6288710
Filing Date: 2001-09-11
Classification: G06F

Abstract:
A method for detecting the position of a coordinate probe relative to a digitizing tablet, the coordinate probe radiating an electromagnetic coordinate signal, the method comprising:(a) providing a sensing coil grid on a working region of the digitizing tablet, the sensing coil grid including a plurality of sensing coils, each of which is U-shaped and has a front section and a grounded rear section, the sensing coils being arranged in parallel along an axis of the working region in an overlapping manner with the front sections of consecutive ones of the sensing coils being arranged in succession, and with the rear sections of the consecutive ones of the sensing coils also being arranged in succession, wherein electric currents are induced in the sensing coils by virtue of the coordinate signal when the coordinate probe is disposed on the working region;(b) performing a front scanning operation, includingscanning in sequence the sensing coils in order to detect the electric currents induced therein and to generate a grid signal,generating an inverted signal by inverting a predetermined one of front and rear half-cycles of the grid signal, anddetecting a predetermined transition of the inverted signal from a first logic state to a second logic state;(c) performing a rear scanning operation when the predetermined transition of the inverted signal is not detected after the front scanning operation has been completed, includingrepeating sequential scanning of the sensing coils in order to continue generation of the grid signal,generating the inverted signal by inverting the other one of the front and rear half-cycles of the grid signal, anddetecting the predetermined transition of the inverted signal from the first logic state to the second logic state;(d) generating a count output corresponding to time elapsed before the predetermined transition of the inverted signal is detected; and(e) converting the count output into a coordinate of the coordinate probe along the axis of the working region of the digitizing tablet.