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Method for improving the Solar tolerance of an IR touch system Disclosure Number: IPCOM000202195D
Publication Date: 2010-Dec-08
Document File: 1 page(s) / 23K

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IR touch systems work by forming a grid of infrared (IR) light beams that are projected from an LED into a phototransistor. The IR LEDs are usually placed on the right and bottom sides of the screens with matching IR phototransistors on the top. When an object such as a finger is placed within the IR grid it is detected when the IR beam is broken. Disclosed is a solution to the problem when light from the sun shines into the touch grid from the left at an angle close to the LEDs the phototransistors can be blinded making the touch system fail.

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Method for improving the Solar tolerance of an IR touch system

The solution to this problem is to add an extra set of LEDs and phototransistors to the sides making two sets of IR beams, a left to right and a right to left as shown in the figure. If the controller is using the left to right set of beams and it detects it is saturated it can flip to the second set of right to left beams. Due to the angle of sun required to saturate the phototransistors it is impossible to saturate both sets of beams.


Figure 1.