4 Types of Touch Panel Sensing Technologies

Label:Touch Panel

Feb 20, 20242420

4 Types of Touch Panel Sensing Technologies

1. Optical type


For optical touch panels, the light source reception and interruption principle covers the panel with light sources and receivers forming a matrix. When the light is blocked, you can know the location of the receiver where the signal cannot be received, and then determine its precise location.


The optical touch panel is made of a glass substrate, an infrared emission source, and an infrared receiver. What about the installation? Place the infrared transmitting device on the left and lower sides of the glass panel, and set up infrared receivers on the right and upper sides. When the infrared rays are blocked by fingers or contact objects, the information received can be detected.


There are advantages. The surface is pure glass, which does not affect the light transmittance. There are more: high reliability, scratch resistance, and good fire resistance. On the other hand, there are disadvantages. It has poor waterproof and antifouling properties.


Generally speaking, we put this type of touch panel on ATMs, OA business machines, and medical equipment.


2. Sonic type


The sonic touch panel is composed of a transmitting transducer, a receiving transducer, a reflective plate and a controller. We install transmitting transducers, reflective plates, and receiving transducers on the X and Y axes of the glass and on the opposite sides.


When keeping running, the controller first transmits a 5MHz electronic signal to the transmission transducer, which converts it into ultrasonic waves and directly transmits them through the surface of the touch panel to the reflective plate array. After the reflector receives the ultrasonic wave, it collects the sound wave and sends it to the receiving transducer to convert it into an electronic signal, and then transmits it to the controller to store the signal information in the normal state.


When this touch panel is working, the contact pointer object will absorb ultrasonic waves and cause attenuation, so the signal when receiving is different from when it is not in action. The controller compares the attenuation before and after use, and calculates the exact position.


There are advantages: good fire resistance, poor waterproof, anti-fouling and scratch resistance, suitable for large sizes. However, the cost is high. We always put sonic touch panels on automatic ticket vending machines.


3. Capacitive type


The capacitive touch panel uses the capacitance change generated by the electrostatic combination between the arranged transparent electrodes and the human body to detect its coordinates from the induced current. The induction principle uses voltage to act on the four corners of the screen sensing area and form fixed electric field.


When a finger touches the screen, it causes the electric field to induce current, which is measured by the controller. Based on the difference in the ratio of the current distance to the four corners, the contact position can be calculated.


However, this touch panel must overcome the influence of noise caused by static electricity in the pointer. When subjected to touch pressure, the position can be calculated based on the current ratio.


4. Resistive type


The main components of a resistive touch panel are two upper and lower groups of ITO conductive layers, spacers, and electrodes. It uses ITO glass as the substrate, with spacer supports in the middle, so that the upper and lower plates will not cause conduction and induction due to the close distance. Silver electrodes are printed on the edges to provide voltage.


During use, pressure is used to conduct the upper and lower electrodes, and the controller detects the panel voltage change and calculates the contact point position for input.


The advantages are good waterproof, anti-fouling properties and low price, but the disadvantages are poor scratch resistance and fire resistance. We always put this touch panel on small and medium-sized portable handheld devices.


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