Augmented optical waveguide for use in an optical touch sensitive device

An optical touch-sensitive device for use with a display, the touch-sensitive device comprising:

• a planar optical waveguide extending over a surface of the display, the waveguide having a top surface and a bottom surface;
• emitters and detectors arranged along a periphery of the display;
• an optical coupler assembly positioned along the periphery of the display, the optical coupler assembly coupling optical beams produced by the emitters into the waveguide and out of the waveguide to the detectors, wherein touches on the top surface of the waveguide disturb the optical beams, the touch-sensitive device determining touch events based on the disturbances;
• and
• at least one static dead zone, the static dead zone comprising:
• a cover layer having a top surface and a bottom surface, the bottom surface of the cover layer directly coupled to the top surface of the waveguide, the cover layer preserving optical beam propagation in the waveguide by reflecting optical beams propagating in the waveguide at the cover layer's bottom surface, wherein the cover layer makes the dead zone insensitive to touches;
• and
• a dark layer that is opaque to visible light, wherein a bottom surface of the dark layer is coupled to the top surface of the cover layer.