Principle of capacitive touchscreen

Principle of capacitive Touchscreen

The surface type used to be the mainstream capacitance method, but with the emergence of the projection type and its use in smartphones and tablets, the leading role has changed. Nowadays, capacitance method refers to projected capacitance method.

Detection principle of projected capacitance method

ITO electrode patterns form a matrix

It consists of a combination of ITO electrode patterns deployed vertically and horizontally, and allows input with just a light touch of a finger. The inside of the touchscreen consists of an orthogonal arrangement of transparent X-axis and Y-axis electrodes, forming a matrix. The number of electrodes ranges from a dozen to several dozen, and the capacitance value is detected for each electrode.

Locate by capacity coupling

This transparent ITO electrode is not located on the top surface of the sensor, but is stored inside the sensor, and when a finger approaches, capacitive coupling with the electrode occurs through a transparent substrate (dielectric material) such as glass or film.

Judges touch by electrode difference in capacitance value

When a human body such as a finger approaches the electrodes in the touchscreen, the capacitance values of the X and Y electrodes at the point of approach change. By reading the capacitance values, it is possible to determine which electrode area is touched.