The multi-touch of capacitive touch screen means to detect multiple touch points simultaneously or continuously and map them accurately to the corresponding position on the screen. The emergence of multi-touch technology has greatly expanded the application field of capacitive touch screen, and provided users with more abundant and flexible interactive operation methods. In this paper, we will briefly describe the implementation principle and technical architecture of capacitive touch screen multi-touch.
Implementation principle
The principle of capacitive touch screen multi-touch is based on the detection and analysis of capacitance changes. On a normal capacitive touch screen, only one touch point can be detected. Multi-touch requires detecting and analyzing capacitance changes between multiple touch points and determining their location and number.
Generally, the implementation principle of capacitive touch screen multi-touch can be divided into two types:
(1) Double-layer capacitor structure: there are two sets of capacitor layers on the touch screen, which are used for horizontal and vertical detection respectively. Each set of capacitor layers is composed of multiple capacitor nodes, which are independent of each other. When there are multiple touch points touching the screen, each touch point causes a capacitance change on the capacitor layer. The controller will collect capacitance values on multiple sets of capacitor layers and process them algorithmically to determine the position and number of multiple touch points on the screen.
(2) Mutual inductance capacitor structure: The capacitor layer on the touch screen communicates with the controller through mutual inductance. When multiple capacitive nodes on the touch screen change capacitance at the same time, different electromagnetic signals will be generated, and the controller can identify these signals to determine the position and number of multiple touch points on the screen.
Technical architecture
In order to realize multi-touch capacitive touch screen, it is necessary to adopt a certain technical architecture and algorithm. The common capacitive touch screen multi-touch technology architecture includes the following parts:
(1) Inductive capacitor layer: The inductive capacitor layer composed of multiple capacitor nodes on the capacitive touch screen is used to detect the position and number of touch points.
(2) Touch screen controller: The controller located below the capacitive touch screen is responsible for collecting and processing the capacitance change information on the capacitor layer, and converting it into the corresponding position and action information.
(3) Driver chip: the controller's instructions are transferred to the capacitor layer to control the charge change of the capacitor layer.
(4) Algorithm: used for data processing and multi-touch detection and recognition. Commonly used algorithms include difference algorithm, least square method, polynomial fitting and so on.
Implementation process
The multi-touch implementation process of capacitive touch screens usually includes the following steps:
(1) Establish a benchmark reference value: When no touch point touches the touch screen, the system needs to establish a benchmark reference value. This reference value can be used for subsequent multi-touch detection and calibration.
(2) Detect and identify touch points: When a touch point touches the touch screen, multiple capacitor nodes will change capacitance at the same time. The controller takes these capacitance values and processes them using algorithms to determine the position and number of touch points on the screen.
Mapping touch points: By determining the position and number of touch points, they are correctly mapped to the corresponding position on the screen. In this way, users can implement various interactive operations through multi-touch, such as zooming, rotating, dragging, and so on.
(4) Calibration and adjustment: Because the size, thickness, temperature and other factors of the touch screen will affect the accuracy and stability of the capacitance value, it is necessary to regularly calibrate and adjust to ensure that the multi-touch of the touch screen is always accurate and reliable.
In short, the implementation principle and technical architecture of capacitive touch screen multi-touch technology are very complex, and advanced algorithms and efficient hardware design are needed to achieve accurate, smooth and stable multi-touch experience.