Classification of surface capacitive touch screen and projection capacitive touc
Date:2019-09-03
With the development of time and technology, capacitive touch screen has gradually become the mainstream application of mobile phones, touch displays and other products. Capacitive touch screen represents the mainstream technology of multi touch interface. Projective capacitive touch screen can accurately locate the position where the finger touches the screen by measuring the tiny change of capacitance. The most critical problem in the application of capacitive touch screen is the influence of electromagnetic interference on the system performance. At present, capacitive touch screen has gradually reduced this kind of interference problem. What is the classification of surface and projection touch screens? Next, we will discuss the working principle and classification of capacitive touch screen:
The working principle of capacitive touch screen is to make x-axis and y-axis electrode matrix with one or more layers of ITO on the glass surface. When the finger touches, a coupling capacitance is formed between the finger and ITO surface, which causes the weak change of current. By scanning the x-axis and y-axis electrode matrix, the change of electric capacity of the touch point is detected, and the position of the finger is calculated.
Capacitive touch screen can be divided into surface capacitive touch screen and projection capacitive touch screen. Projection capacitive touch screen can be divided into self capacitive touch screen and mutual capacitive touch screen. The x-axis and y-axis electrode matrix of self capacitive touch screen form capacitance with ground respectively. When finger touches capacitive touch screen, finger capacitance and electrode capacitance are superimposed to increase electrode capacitance.
When detecting, the self capacitive touch screen detects the x-axis and y-axis electrode matrix respectively. According to the change of capacitance before and after touching, the x-axis coordinates and y-axis coordinates are determined respectively, and the touch point coordinates of the capacitive touch screen are obtained.
The coordinates of a single touch point in x-axis and y-axis are unique. When there are two touch points and the two touch points are not in the same x-axis or the same y-axis, four coordinates are formed in the x-axis and y-axis, but only two of them are real, and the other two are commonly known as "ghost points", so the self capacitive touch screen can not achieve real multi-point touch.
The x-axis and y-axis electrode matrix of the mutual capacitive touch screen form capacitance at the intersection, that is, the x-axis and y-axis electrodes form the two poles of the capacitance respectively. When the finger touches the capacitive touch screen, it produces coupling capacitance with the two electrodes near the touch point, resulting in the capacitance change between the two electrodes.
When detecting, the y-axis electrode matrix sends out signals in time-sharing order, and the x-axis electrode matrix receives signals at the same time, so as to obtain the capacitance values of all the x-axis and y-axis electrode matrix intersection points. According to the change of capacitance, the coordinates of each touch point can be calculated. At present, it can support the touch of 10 fingers.
