Principle of Electromagnetic Pen
The basic principle of electromagnetic induction technology is to transmit electromagnetic signals through an electromagnetic pen and interact with the electromagnetic induction board behind the display screen. When the electromagnetic pen is close to the touch screen, the electromagnetic induction board behind the touch screen will sense the electromagnetic signal of the pen. Therefore, the induction line under the electromagnetic induction board changes, and the X and Y coordinate positions of the pen are obtained by calculating the change of the magnetic flux according to the antenna array receiving signals in the horizontal direction and the vertical direction. And because the electromagnetic pen has a vertical pressure sensor, when the user writes and draws through the electromagnetic pen, when the pen tip is stressed, the pressure is transmitted to the pressure sensor through the pen core, and the change of the pressure causes the electromagnetic signal sent by the electromagnetic pen to change. , The electromagnetic induction board can show different pressure sensitivity according to the induction signal, so it is especially suitable for handwriting and painting.
passive electromagnetic pen
In order to sense the coordinates of the pen on the stylus, the initial electromagnetic induction technology had to supply power to the pen by means of wiring or built-in batteries, so that the electronic circuit on the pen could send out signals. However, the power supply through the cable will hinder the user's use, and the electromagnetic pen with built-in battery needs to be replaced frequently. The electromagnetic pen EMR technology using these two methods has a built-in electromagnetic induction board inside the LCD screen that can detect the pen movement. , There are many annular coils distributed vertically and horizontally on the induction plate. Within the range of the magnetic field generated by the induction plate, the movement of the pen can make the pen's resonance circuit accumulate weak electric energy. After the pen has accumulated energy, the control circuit will stop supplying the circulating coil. current and connect the circulating coil to the receiving loop. At this time, the energy accumulated by the pen will be sent back to the induction board from the coil of the pen tip through the free oscillation of the resonant circuit. At this time, the control loop firstly detects the approximate position of the pen by scanning the circulating coil on the induction board, and then scans multiple circulating coils around the pen, and calculates the detected signals, which can be very accurate. Calculate the coordinates of the pen. Such a cycle of action can sense the coordinates of the pen, the inclination, and the signals of the operation state (speed, pressure sensitivity of the pen).
Principle of capacitive pen
The capacitive touch screen works by using the current sensing of the human body. It is a four-layer composite glass screen. The inner surface and the interlayer of the glass screen are each coated with a layer of ITO (ie, coated conductive glass), and the outermost layer is a thin layer of silica glass protective layer. The ITO coating is used as the working surface, four electrodes are drawn from the four corners, and the inner layer of ITO is used as a shielding layer to ensure a good working environment.
When a finger touches the metal layer, a coupling capacitance is formed due to the electric field of the human body, the user and the surface of the touch screen. For high-frequency current, the capacitance is a direct conductor, so the finger draws a small current from the contact point. This current flows out from the electrodes on the four corners of the touch screen respectively, and the current flowing through these four electrodes is proportional to the distance from the finger to the four corners. location information.
A capacitive pen is an auxiliary device that uses conductor materials to imitate the human body (usually fingers) to complete man-machine dialogue.