infrared method (touchscreen)
For multi-touch screens, there are various methods with which multiple touch points on the multi-touch screen can be detected. The infrared method is one of these methods, which is used in touch-sensitive touchscreens and with which the position at which the touchscreen is touched is determined. It is used in simple touchscreens and in multi-touch screens and is housed in a screen matrix that is attached to the LCD display or TFT display.
The infrared method uses an infrared matrix oflight-emittingdiodes and photodiodes placed on opposite sides of the touch or multi-touch screen. The light-emitting diodes and the photodetectors form a beam grid of infrared light( IR) that propagates across the display in both coordinates. As long as the individual infrared beams are not interrupted, the photodiodes receive the light beams from the light-emitting diodes. However, if the screen is touched by a finger or a pen, two light beams, the vertical and the horizontal, are interrupted and the corresponding photodiodes detect less light. The photodiodes are scanned at a constant speed and those that detect less light determine the vertical and horizontal position of the screen touch and thus the screen coordinates.
One of the advantages of the infrared method is that the coordinate value of the touch point is directly available as a digital value and does not have to be calculated first by analog-digital methods, as is the case with other multitouch methods. Comparable analog methods have the disadvantage that they have to be constantly recalibrated and, in addition, the analog values have to be converted into digital values. Therefore, touchscreens with infrared technology are characterized by a higher precision and accuracy.
The latter is determined by the beam width of the infrared rays. The infrared process is one of the versatile, flexible and durable touch technologies for displays with screen diagonals from 10" to 60". The process is equally suitable for single-touch, dual-touch, multi-touch and multi- user touch and can detect up to 32 touch points simultaneously. However, it is sensitive to dirt and liquids that alter the refraction of light.