The mutual capacitance mode is also called the transcapacitance mode, which generates capacitance through the coupling of adjacent electrodes. When the sensed finger approaches the electric field line from one electrode to another, the change of the mutual capacitance is sensed, thereby detecting the position. Mutual capacitance mode supports true multiple points, has higher light transmittance, and can also improve resolution and anti-electromagnetic interference capabilities. The technical principle of the mutual capacitance mode is that most conductive objects will generate charges when they are quite close. At this time, if another conductive object, such as a finger, is close to the first two conductive objects, because the human body absorbs some charge, The charge field (capacitance) between two conductive objects will change. The so-called mutual capacitance refers to the capacitance formed at the intersection of the horizontal and vertical ITO electrodes on the glass surface. The scanning method of mutual capacitance is to scan the capacitance change at each intersection to determine the position of the touch point. When touched, it will affect the coupling of adjacent electrodes, thereby changing the capacitance at the intersection.
Mutual capacitance scanning method can detect the capacitance value of each intersection and the capacitance change after touch, so the scanning time it needs is relatively longer compared with the self-capacitance scanning method. Need to scan and detect F data. It can truly detect multi-touch.
Related to self-capacitance is the recognition, tracking and interaction of gestures (Gestureinteraction), that is, detecting and distinguishing multi-touch behaviors, such as zooming, dragging, rotating, etc. The realization method is Axisintersect technology. It is to plan the diamond shape detection unit on the conductive layer, and a conductive layer is needed for each axis. Take the two-axis form as an example. When detecting touch behavior, the detection controller scans the horizontal axis and the vertical axis respectively. The horizontal and vertical detection points that produce capacitive coupling will have rising crests, and the intersection of the two axes is the touch point.
In fact, the axis-interleaved capacitive touch screen technology is the technology used on the touch panel of a notebook computer. The computer touch panel uses the X and Y axis sensing electrode arrays to form a sensing grid. When the finger is close to the touchpad, a small amount of charge will be generated between the finger and the sensing electrode. At this time, the position of the object can be determined by calculation. Of course, the biggest difference between a touchpad and a touch screen is that the former is opaque and the latter is transparent.
However, it should be pointed out that although the axis interleaving can realize the multi-touch gesture recognition function, it is still difficult to locate the correct position of the multi-touch. Because when scanning in two axes, the two touch points will generate two wave crests on the X axis and the F axis respectively. When they meet, 4 touch points will be generated. Two of them are false touch points. Make the system unable to make correct interpretation. The solution is to increase the axis to increase the position and number of identifiable contacts. For each additional axis, one more point can be identified (for example, 2 points can be identified for 3 axes, and 3 points can be identified for 4 axes). However, each additional axis requires an additional conductive layer, which will increase the thickness, weight and cost of the designed touch screen, which is not required for touch screens whose main application is portable products such as mobile phones.
