Patent ID: 8692807

Claim:
An apparatus for determining a location of at least one object on a touch surface, the apparatus comprising: a light transmissive panel defining the touch surface and an opposite surface; an illumination arrangement configured to introduce light into the light transmissive panel for propagation by internal reflection between the touch surface and the opposite surface; a light detection arrangement configured to receive the light propagating in the light transmissive panel; and a processor unit configured to iteratively, determine a current signal profile of light received by the light detection arrangement, update, when a condition is met, a background signal profile of light received by the light detection arrangement, calculate a current compensated signal profile as a function of the background signal profile and the current signal profile, and determine, when the at least one object touches the touch surface and thereby attenuates the light propagating in the light transmissive panel, the location as a function of the current compensated signal profile.