Touch determination with interaction compensation

Abstract

A device implements a data processing method for an optical FTIR-based touch system. The touch system defines detection lines across a surface portion of a panel by propagating light inside the panel from a plurality of incoupling points to a plurality of outcoupling points, such that each location on the surface portion is illuminated by incident light rays. At least one light detector is coupled to the outcoupling points to generate an output signal. The device obtains signal values for the detection lines from the output signal and processes the signal values to at least partly compensate for variations in the apparent interaction among the subset of detection lines that interact with an object on the surface portion.

1 . A method of processing an output signal from a touch-sensitive apparatus, the touch-sensitive apparatus comprising a light transmissive panel configured to propagate light by internal reflections from a plurality of incoupling points to a plurality of outcoupling points, thereby defining detection lines that extend across a surface portion of the panel between pairs of incoupling and outcoupling points, wherein each location on the surface portion is illuminated by incident light rays such that an object in contact with the surface portion interacts with the incident light rays of a subset of the detection lines, the touch-sensitive apparatus further comprising at least one light detector coupled to the outcoupling points to generate the output signal, wherein the method comprises:
 obtaining, based on the output signal, signal values for the detection lines, the signal values being indicative of an apparent interaction between the object and light propagating on the respective detection line; and   processing the signal values to generate touch data indicative of the object on the surface portion;   wherein said processing comprises:
 generating compensated signal values by operating compensation data on the signal values to at least partly compensate for variations in the apparent interaction among the subset of the detection lines that interact with the object, wherein the compensation data is obtained to at least represent the variations that are caused by differences in incident power distribution among the subset of the detection lines, the incident power distribution being a distribution of power among the incident light rays on the respective detection line with respect to a normal direction of the surface portion; and 
 processing the compensated signal values to generate said touch data. 
   
     
     
         2 .- 21 . (canceled)