Where can you find touch-sensitive screens


How does a touch screen work?


A touch screen is a touch-sensitive screen that offers the possibility of touching and manipulating elements directly on the screen with your finger or pen. They are used, for example, in ATMs, cell phones, PCs, graphics tablets, PDAs, kiosk systems, navigation and multimedia systems or in copiers and measuring devices. There are various ways in which touch-sensitive screens can be implemented. Here I would like to briefly introduce four types of touch screens:

1) Resistive touch screens have two conductive layers on top of each other with a small gap. A voltage is applied to a layer that decreases from one edge of the screen to the other. If the layers are connected by touching the touch screen, a voltage can be read on the second layer that corresponds to the position of the pressure point on the screen. This is done every millisecond for both directions. Resistive touch screens do not require a special input device, since they only react to pressure.

2) Capacitive touch screens also have a conductive metal layer with 4 electrodes at the corners. A uniform, weak electric field is built up on the screen surface via the electrodes. If a finger comes close, the field is changed. The point of contact can be calculated using the resulting current flow from the corners of the touch screen to the finger. Capacitive touch screens only work with bare fingers or special pens.

3) Inductive touch screens have many small antenna coils underneath the display. The pen required for input contains a resonance circuit that is tuned to the antenna frequency. In the transmit mode, energy is emitted from the screen, which is coupled into the resonance circuit of the pen and, in the receive mode that follows shortly thereafter, is emitted again to the antenna coils below the display. The pen position is calculated from the strength with which the individual antennas receive a signal from the pen.

4) With optical touch screens, two or more cameras are installed, mostly in the corners of the screen, and aligned along the screen surface. Opposite them, in the field of vision of the camera, there are infrared lamps. When touched, the cameras can recognize the outline of the finger and use this to calculate the point of contact. A special input device is not necessary.

In the future, we will certainly encounter more and more touch-sensitive screens, as they simplify communication between people and machines and are very flexible at the same time.