Instrument Detection with an Optical Touch Sensitive Device

An optical touch-sensitive device comprising:

• a surface for which touch events are to be detected;
• emitters and detectors arranged around a periphery of the surface, the emitters producing optical beams received by the detectors, the touch events disturbing the optical beam;
• and
• a touch event processor coupled, directly or indirectly, to the emitters and detectors, the touch event processor receiving information indicating which beams have been disturbed by actual touch events and when the optical beams have been disturbed;
• analyzing the received information to detect one or more touch events;
• and, based on said analysis, identifying at least one of the touch events as an instrument touch event rather than a finger touch event, wherein the instrument touch event is distinguished from finger touch events based on a temporal behavior of a touch interaction for the instrument touch event.