Capacitive touch screen

touch screen

Touch screen is a technology that allows you to use IT devices more intuitively by clicking or dragging the desired location on the screen.
There are several types of touch screens depending on the detection method.

  • Resistive touch panel: It is composed of two touch screens with resistance. When the touch screen is pressed, the two sheets are in contact with each other. By measuring the resistance value, you can know the coordinates. It is difficult to implement multi-touch.
  • Ultrasonic touch panel: It is composed of a speaker that outputs ultrasonic waves and a detection sensor. If there is an object(such as a finger) that interferes with the progress of the ultrasound, the coordinates are determined.
  • Infrared touch panel: It consists of an LED that outputs infrared light and a photoelectric device. If there is an object(such as a finger) that interferes with the progress of the infrared ray, the corresponding coordinates are determined.
  • Capacitive touch screen: Coordinates are sensed using the amount of change in capacitance on the screen. It is difficult to manipulate with a non-dielectric (leather gloves, nails, general stylus pen, etc.).

Capacitive touch screen

The capacitive touch screen is a structure in which two metal plates forming a capacitor are laid out horizontally. When a conductive object (finger, etc.) is placed on this metal plate, the capacitance changes.
If these structures are closely arranged on the screen, the device can obtain the coordinates of the touch point.
Transparent electrodes are used here, since this structure must be created on the display screen. Indium tin oxide is mainly used.

There are two types of capacitive touch screens: self-capacitive touch sensor and mutual-capacitive touch sensor.

  • self-capacitive touch sensor: Using a single electrode of the capacitor. Measures the degree of change in capacitance based on ground. When touched, capacitance increases.
  • mutual-capacitive touch sensor: Using both electrodes of the capacitor. Measure the change in capacitance between the two electrodes. When touched, capacitance decreases. Multi-touch is possible, but the detection algorithm becomes complex.

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