Touch Sensing Using Shadow and Reflective Modes

A touch panel system for detecting one or more objects in proximity with a touchable surface of the touch panel system, the touch panel system comprising:

• a touch panel having integrated therein infrared sensors distributed throughout the touch panel parallel to the touchable surface;
• at least one infrared source configured to illuminate objects through the touchable surface;
• and
• a control element arranged to:
• scan at least a portion of the touch panel to measure a level of ambient infrared radiation;
• switch to a shadow mode of operation if a level of ambient infrared radiation exceeds a first threshold;
• switch to a reflective mode of operation if the level of ambient infrared radiation does not exceed both the first threshold and a second threshold, wherein the switching between the shadow mode and the reflective mode changes an angle of illumination of an object adjacent to the touch panel;
• and
• determining the three-dimensional shape and thickness of the object based in part on the changes in the angle of illumination.

A method of operating a touch panel system for detecting an object in proximity with a touchable surface of the touch panel system, the method comprising:

• detecting a level of ambient infrared light over a portion of the touchable surface;
• selecting between a first mode of operation and a second mode of operation for a region of the touch panel system according to said level, wherein said first mode comprises detecting said object by detecting infrared radiation reflected from said object and wherein said second mode comprises detecting said object by detecting ambient infrared radiation;
• switching to the shadow mode of operation after the level of ambient infrared radiation surpasses a threshold;
• and
• switching to the reflective mode of operation after the level of ambient infrared radiation drops below the threshold, wherein the switching between the first mode and the second mode changes an angle of illumination of an object adjacent to the touch panel;
• and
• determining the three-dimensional shape and thickness of the object based in part on the changes in the angle of illumination.