Capacitive touch screen to achieve multi-touch, rely on the mutual capacitance is to increase the electrode, simply put, is the screen block, in each area set up a set of mutual capacitance modules are independent work, Capacitive Touch Screen so capacitive touch screen You can independently detect the touch of the region, after processing, simply achieve multi-touch.
, Capacitive technology Touch screen CTP (Capacity Touch Panel) is the use of the body's current sensing work. Capacitive touch screen is a four-layer composite glass screen, Capacitive Touch Screen the inner surface of the glass screen and the interlayer coated with a layer of ITO (nano indium tin metal oxide), the outermost layer is only 0.0015mm thick silica glass protective layer, Layer for the face, four corners lead to four electrodes, the inner layer of ITO screen layer to ensure that the working environment.
When the user touches the capacitive touch screen, due to the human body electric field, the user's finger and the working surface form a coupling capacitance, Capacitive Touch Screen because the work surface is connected with the high frequency signal, so the finger absorption takes a very small current, the current from the screen four And theoretically flowing through the four electrodes is proportional to the distance from the finger to the four corners, Capacitive Touch Screen and the controller obtains the position by the precise calculation of the four current proportions. Can achieve 99% accuracy, with less than 3ms response speed.
Capacitive touch screen works
However, the real smartphone is a capacitive touch screen, which is a double-sided conductive film coated with a glass substrate, and in the upper plate covered with a thin layer of SiO2 dielectric layer. Capacitive Touch Screen As shown in the figure, where the upper electrode is used to form a plate capacitance with the human body (ground) capacitance changes, and the lower plate used to shield the external signal interference.
When working, the transparent electrode needs to pick up the voltage and draw four electrodes on the four corners. Therefore, when the finger touches the upper SiO2 layer, because the body is conductive, there is enough coupling capacitance between the body and the transparent electrode , Capacitive Touch Screen And the touch position coordinates (the larger the capacitance is closer to the touch position) are calculated based on the change in the capacitance value measured with the four corners (or the surroundings). Capacitive Touch Screen But this surface capacitive touch (Surface Capacitive) or can not meet the now popular multi-touch, if you want to achieve multi-touch must use the new technology called Projected-Capacitive Touch, it is mainly to change the surface of the induction electrode Layed into a layer or two layers and patterned (mainly diamond), a layer responsible for the X direction, a layer responsible for the Y direction. And then through the X direction and Y direction of the electrode capacitance changes to locate.
As the mainstream is now multi-touch (Multi-Touch), so I talk a little more about his evolution process, multi-touch Projected Capacitive there are two: self-capacitance (Self-Capacitive) and mutual capacitance (Mutual Capacitive.
Self-capacitance It is a direct scan of each X and Y electrode capacitance, so when two touch points will be generated when two additional virtual points (Ghost Points).