Position resolving system

Abstract

A position resolving system is described incorporating a cordless pointing instrument such as a pen having an oscillator and battery supply therein. Electromagnetic radiations from the pen are directed onto a tablet grid having a plurality of grid loops therein. When the pen is in contact with the tablet, signals of maximum amplitude are radiated; when the pen is raised out of contact with the tablet, signal radiation is maintained but at a decreased amplitude for a predetermined time and then reduced to zero. Each loop is formed of parallel conductors joined at one end thereof by an end conductor; each loop is placed adjacent corresponding loops in the X and in the Y directions. The electromagnetic radiations are non-coherently amplitude detected to select the grid loop in the X direction and the grid loop in the Y direction having the maximum amplitudes thereon. When an X loop and a Y loop are detected each of which have signal amplitudes thereon that are higher than the remaining X and Y loops, and wherein the signal amplitudes are above a predetermined threshold amplitude, the system subsequently scans selected loops in the vicinity of the max loops in accordance with automatically selected routines. The routines are selected in accordance with criteria that include pen speed, signal strength and pen location. The routines may either rely upon the signal strength on a subset of three grid loops in each of the X and Y directions or a subset of four grid loops in the X and Y directions.