Tracking motion of a writing instrument

Abstract

Motion of a writing instrument is tracked from sensors located in the vicinity. The signals generated from the sensors are processed and used in a wide variety of ways.

1 - 23 . (canceled)  
     
     
         24 . A method comprising 
 conveying light from a moving writing instrument in a time-changing pattern of directions,    sensing the light at two or more sensors located at two or more different locations spaced from the writing instrument, and    determining the location of the writing instrument by detecting a phase difference between signals measured at the two or more sensors.    
     
     
         25 . The method of  claim 24  in which the time-changing pattern of directions includes a rotating pattern with respect to an X-Y plane on which the writing instrument is moving.  
     
     
         26 . The method of  claim 25  in which the signal radiated in the positive X direction is in phase quadrature to the signal radiated in the Y direction.  
     
     
         27 - 82 . (canceled)  
     
     
         83 . A method comprising 
 locating a writing instrument at a succession of locations on a writing surface,    generating signals at sensors from light received from the writing instruments at the succession of locations, and    determining calibration parameters for the writing instrument for use in calibrating a process that determines the locations of the writing instrument as it is being moved.    
     
     
         84 . The method of  claim 83  in which the calibration parameters comprise coefficients used in polynomial series that are part of the location determining process.  
     
     
         85 . The method of  claim 83  in which the locations do not lie on a regular rectangular grid.  
     
     
         86 - 112 . (canceled)