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The touch screen system generally consists of two parts: the touch detection device and the touch screen manipulator. The touch detection device is installed in front of the display screen, is used for detecting the user's touch direction, and accepts and sends the touch screen controller back; The primary function of the touch screen manipulator is to take the touch information from the touch point detection device, convert it into contact coordinates, and then send it to the CPU, which can accept the commands sent by the CPU and execute them. With the advancement of science and technology, touch screen skills have also experienced the process of gradual promotion and development from low level to high level. According to its operating principle, it is generally divided into four categories: resistive touch screen, capacitive touch screen, * touch screen and external acoustic touch screen.
Resistive touch screen The screen part of the resistive touch screen is a multi-layer composite film, which is made of a layer of glass or plexiglass as the base layer, coated with a transparent conductive layer (ITO film) on the surface, and covered with a layer of hardened, lubricated and scratch-resistant plastic layer on the outside. The inside and outside of it are also coated with an ITO layer, and there are a number of subtle (less than thousandth of an inch) bright separation points between the two conductive layers. When the finger touches the screen, the two-layer ITO touches and the resistance changes, and the controller calculates the coordinates of the touch point according to the detected resistance change, and then operates accordingly according to this coordinate. According to the number of lead-out wires, resistive screens are divided into four-wire, five-wire and other types. The appearance of the five-wire resistive touch screen is conductive glass instead of conductive coating, which has a longer life and higher light transmittance. If the ITO coating of resistive touch screen is too thin, it will be simple and brittle, and if the coating is too thick, it will reduce light transmission and internal reflection and reduce clarity. Because it is often affected, the surface ITO will show micro-cracks and even deformation after the use of time, so its life span is not long. Resistive touch screens are inexpensive and easy to produce, so they are still a common choice. The presentation of four-wire, five-line, seven-line and eight-line touch screens makes it more reliable and improves its optical properties. Capacitive touch screen The four sides of the capacitive touch screen are plated with slender electrodes, which form a low-voltage communication electric field. The touch screen is pasted with a transparent film layer, which is a special metal conductive substance. When the user touches the capacitive screen, the user's finger and the working surface form a coupling capacitor, because the working surface is connected with a high-frequency signal, so the finger will suck away a small current, and this current flows out of the electrodes on the four corners of the screen; Theoretically, the current flowing through the four electrodes is divided into the interval from the finger to the four corners, and the manipulator can obtain the direction of the touch point after fine calculation of the four current shares. The double glass of the capacitive touch screen not only maintains the conductor and sensor, but also effectively prevents the external environmental elements from affecting the touch screen, even if the screen is stained with dirt, dust or oil, the capacitive touch screen can still accurately calculate the touch orientation. However, because the capacitance changes with temperature, humidity or grounding conditions, its stability is poor, and drift often occurs. Although not as widespread as resistive applications, capacitive touch screens are also a popular alternative. These devices are precise, responsive, have a higher resolution at a slightly larger size, and are more resistant to scratches, making them suitable for use as touchscreens for gaming consoles. Moreover, the newly presented near-field imaging skills improve the functionality of capacitive touchscreens, reducing the drift that may occur in them and resistive touchscreens. * Touch screen The four sides of the infrared touch screen are arranged with infrared emitting tubes and infrared receiving tubes, which correspond to each other to form a horizontal and vertical interspersed * matrix. When the user touches the screen, the finger will block the horizontal and vertical two * passing through the direction, and the controller can determine the direction of the touch point after calculation. Infrared touch screens are also immune to current, voltage and static electricity, making them suitable for some harsh environments. Its primary advantage is its low price, convenient installation, and can be used on accounting machines at all levels. In addition, because there is no capacitive charging and discharging process, the response speed is faster than that of capacitive type, but the resolution is lower. Exterior sonic touch screen Exterior sound waves are a type of ultrasound waves, which are mechanical energy waves that are transmitted in the superficial layers of a medium (such as a rigid material such as glass or metal). Through the wedge-shaped triangular base (strictly designed according to the wavelength of the surface wave), the energy emission of the surface sound wave can be directed and at a small angle. The surface acoustic wave function is stable, easy to analyze, and has very sharp frequency characteristics in the shear wave transmission process, which has been rapidly developed in applications such as non-destructive testing, contrast and removal. The four corners of the display are equipped with an ultrasonic emitting transducer and an receiving transducer, which can emit a kind of ultrasonic wave and cover the surface of the screen. When the finger touches the display, because part of the sound wave energy is absorbed, the accepted waveform changes, that is, there is an attenuation gap in the waveform at a certain time, and the controller can calculate the direction of the touch point according to the attenuated signal. The appearance of the sonic touch screen is not affected by environmental factors such as temperature and humidity, with extremely high resolution, excellent scratch resistance, long life (50 million times without failure), high light transmittance (92%), and can adhere to clear and transparent pictures; There is no drift, only one correction is required when the device is installed; There is a third axis (i.e. pressure axis) to echo, * suitable for use in public places. Exterior sonic touchscreens are susceptible to water droplets and dust, which can be improved by adding dust strips or by increasing the monitoring of dirt to accurately identify useful operations and differences between dirt. In addition, because the sound wave screen can feel the pressure, it invisibly increases the control technique, which is very beneficial to the expansion of the function of the screen, and its application range is greatly expanded.
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