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For support (Eason Tsang):
Surface acoustic touch scren structure:
The surface acoustic touch screen part of the touch screen can be a flat, spherical or cylindrical glass plate, installed in front of the CRT,LED,LCD or plasma display screen. This glass plate is reinforced glass without any film or coating. The upper left corner and the lower right corner of the glass screen are respectively fixed with vertical and horizontal ultrasonic emission transducers, and the upper right corner with two corresponding ultrasonic receiving transducers. The rim of the glass screen is engraved with a 45-degree reflection stripe from sparsely to densely spaced.
How it works:
The transmitter converts the electrical signals sent by the controller through the touch screen cable into acoustic energy to the left surface, and then transmits the acoustic energy to the upper uniform surface by a set of precise reflection stripes at the bottom of the glass plate. The acoustic energy passes through the surface of the screen and then gathers from the reflection stripes on the upper side into a line to the right to transmit to the receiving transducer of the x axis. The received transducer converts the returned surface acoustic energy into an electric signal.
When the transmitter emits a narrow pulse, the sonic energy goes through different paths to the receiver, to the far right, to the latest, to the leftmost. The early arrival and the late arrival of these acoustic energy add up to a wider waveform signal, and the received signal is a collection of acoustic energy that goes through different paths in the x-axis direction, and they travel the same distance on the Y-axis. But on the x axis, the furthest is twice as far as the nearest axis. Therefore, the time axis of the waveform signal reflects the position of the original waveform before superposition, that is, the x axis coordinates. The received signal waveform is exactly the same as the reference waveform without touch.
When the finger touches, the energy of the sound wave is partially absorbed when the x axis of the finger walks upward, and there is a gap in the received waveform, that is, at a certain moment, and the touch coordinate is obtained by calculating the position of the notch. The controller analyzes the attenuation of the received signal and determines the x-axis coordinates from the position of the notch. Then the y-axis coordinates are determined by the same process of the y-axis.
The surface acoustic touch screen also responds to the third axis coordinate, which is the magnitude of the user's touch pressure. The principle is calculated by the attenuation at the attenuation of the received signal. Once the three axes are determined, the controller passes them to the host.
Advantages and disadvantages:
surface acoustic touch screen features anti-riot; fast response speed, it is the fastest of all touch screens; stable performance; automatic identification of interference; with a third axis of pressure axis, etc. The downside is that the dust and dirt on the touch screen will block the sound waves on the surface.