The structure of the surface elastic wave touch screen is that X, y light-emitting units and light-receiving units are installed on the corners of the transparent glass, and a reflective array is formed on 4 sides. Usually X, y light-emitting units are located at the opposite corners. The reflector array is installed at an angle of 45°. The spacing of the reflective arrays shown in Figure 3>4 ist relativ gleich, aber in tatsächlichen Situationen ändert sich der Abstand der reflektierenden Anordnungen gemäß einer bestimmten Regel. Dies geschieht, um die Dämpfung des Signals zu verringern. Ein kurzes - Impulssignal wird in den Sender (den Eingangssignalsensor) eingegeben, so dass Ultraschallwellen (elastische Oberflächenwellen) in seitlicher Richtung des Glases erzeugt werden, die in Richtung des Glases reflektiert werden Oberfläche durch das reflektierende Array, und das reflektierende Array in der entgegengesetzten Richtung wird verwendet, um es zu machen. Auf der anderen Seite reflektiert, wird der Empfänger (Empfangssensor) verwendet, um es zu empfangen und in ein elektrisches Signal umzuwandeln. Da die Wellenform des elektrischen Signals der Berührung gedämpft wird, wird die Position der Berührung durch die Dämpfungszeit erfasst.
For the surface elastic wave touch screen, the way it detects the degree of absorption based on the touch, while the bending wave touch screen detects the vibration generated by the touch panel or the friction vibration generated by the drag operation. Acoustic waves are propagated by mixing longitudinal waves and transverse waves, so it seems that the entire panel is vibrating, which can be transmitted over long distances. The time that the bending wave travels in the glass is proportional to its distance. The vibration wave during touch expands outward with concentric circles centered on the touch. Using the characteristic of different arrival times of the vibration of the touch, the position of the touch where the vibration occurs can be checked. The pressure sensor receives the vibration of each touch position, and converts the pulse signal into electronic signal data through the converter. According to the manufacturer, it can be divided into Acoustic Pulse Recognition (APR) and vibration detection (Dispersive Signal Technology, DST). Both methods use bending waves, but the detection principles are different.
APR type is that the pressure sensor is unevenly arranged outside, so that the arrival time of the bending wave is different. But according to the vibration frequency, the propagation speed will be different, so the position cannot be accurately selected, so the reference waveform corresponding to the touch position must be prepared in advance and compared with the actual waveform to detect the accurate position.
The DST type also uses the difference in vibration arrival time. The principle of detection is the same as that of GPS, which uses triangulation detection. In this way, the natural vibration of the glass will be specified as the frequency generated by the touch, and everything else will be regarded as noise, so it can cancel the error input other than the touch. Bending waves propagate inside glass, etc., so unlike surface elastic waves, they are rarely affected by scratches and foreign objects. However, the problem of incorrect input caused by falling objects or residual problems in the performance of software, touchpad, and dragging operations need to be resolved urgently. And because of the characteristics of its detection method, this method is not suitable for small machines.
