Technologies of Touch Screen

Basic Infrared technology

Structure

The basic infrared touch screen consists of light emitting elements and light receiving elements located on the four sides of the panel vis-a-vis in pairs. The light emitting elements consist of LEDs while receiving elements are composed of phototransistors.

I see, then there are beams of infrared light over the panel in matrix?

Exactly. Let's see the sensing method for detail.

Sensing Method

As the figure indicates, infrared lights are raying over the panel in the X and Y directions in matrix. When the infrared LEDs are turned on, the phototransistors located opposite to the LEDs will receive the infrared light and be turned on. If an infrared light is blocked by a finger, the light will not reach to the opposite phototransistor, then the phototransistor will be off.

I got it! The sensor will detect the touched locations by recognizing which phototransistors are off, doesn't it?

You are right. Naturally, it can detect whatever blocks the lights.

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