performance comparison of touch screen resistive touch screen works in an environment completely isolated from the outside world. It is not afraid of dust, moisture and oil pollution, and can be touched by any object, which is more suitable for industrial control. The disadvantage is that because the outer layer of the composite film is made of plastic, too much force or sharp touch may scratch the touch screen. Capacitive touch screen has high resolution and good light transmittance, which can meet all requirements well. This kind of touch screen is common in public places. However, the capacitive touch screen uses the human body as an electrode of the capacitor. When a conductor approaches and couples a large enough capacitance with the ITO working surface of the interlayer, the flowing current will cause the misoperation of the capacitive touch screen. In addition, wearing gloves or holding an insulated object will not respond when touching it, because the insulated medium is added. The infrared touch screen determines the touch position by measuring the on-off of infrared rays, regardless of the material of the transparent baffle selected for the touch screen (some of them do not use any baffle at all). Therefore, a good visual effect can be obtained by selecting a baffle with good light transmission performance and anti-reflection treatment. However, due to the limitation of the volume of infrared emission tube, it is impossible to emit high-density infrared rays, so the resolution of this touch screen is not high. In addition, because the infrared touch screen works by infrared induction, the change of external light, such as sunlight or indoor lights, will affect its accuracy. Surface acoustic wave technology is very stable, and the controller of surface acoustic wave touch screen calculates the touch position by measuring the position of decay time on the time axis, so its accuracy is very high. The SAW touch screen also has a third axis (Z axis), that is, the pressure axis. By calculating the attenuation of the received signal, the user's touch force can be obtained, which can be divided into 2 5 6 levels at most. The greater the force, the wider and deeper the attenuation gap on the received signal waveform. Among all touch screens, only the surface acoustic wave touch screen has the performance of sensing touch pressure. Application According to the analysis of the structure, principle and performance characteristics of the touch screen, the application occasions of different touch screens are as follows. Four-wire resistive touch screen: it is not afraid of dust, oil pollution and photoelectric interference, and the fear of scratching is its main defect. Suitable for public places with fixed users, such as industrial control sites, offices, homes, etc. Five-wire resistive touch screen: excellent sensitivity and transmittance, long service life, no fear of dust, oil pollution and photoelectric interference, suitable for all kinds of public places, especially for industrial control sites that require precision. Capacitance-sensitive touch screen: Because the capacitance changes with the temperature, humidity or grounding, its stability is poor, and drift often occurs. Afraid of electromagnetic field interference and drift, it is not easy to use in industrial control places and places with interference. It can be used for public information inquiry with less precise requirements; Need frequent calibration and positioning. Infrared induction touch screen: low resolution, but not interfered by current, voltage and static electricity, suitable for some harsh environmental conditions; It is suitable for all kinds of public places, offices and industrial control sites without infrared and strong light interference. Surface acoustic wave touch screen: pure glass material, the best light transmission, long service life and good scratch resistance, suitable for all kinds of public places with unknown users. However, it is better to use it in a clean place for fear of dust accumulation and oil contamination for a long time. Otherwise, regular cleaning service is needed. Development trend Touch screen technology is convenient for people to operate and use computers, and it is a promising interactive input technology. Countries all over the world attach great importance to this and invest a lot of manpower and material resources in research and development, and new touch screens are constantly emerging. Touch pen: A touch screen operated by a touch pen is similar to a whiteboard. In addition to displaying interfaces, windows and icons, the touch pen also has the functions of signing and marking. This kind of touch pen is much more powerful than the light pen that only provided the selection menu in the early days. Touch panel: The touch panel adopts pressure-sensitive capacitive touch technology, with the largest screen area. It consists of three parts: the bottom layer is the center sensor, which is used to monitor whether the touch panel is touched and then process the information; the middle layer provides interactive graphics, characters and so on; and the outermost layer is the touch surface layer, which is made of high-strength plastic materials. When the finger touches the outer surface, this information can be sent to the sensor and registered in one thousandth of a second. Besides being compatible with PC, it also has the characteristics of high brightness, clear images and easy interaction, so it has been applied to pointing information inquiry systems (such as bulletin board system) and achieved very good results. In a word, the development of touch screen shows the trend of specialization, multimedia, three-dimensional and large screen. With the development of information society, people need to get all kinds of public information. With the touch screen technology as the interactive window, the public information transmission system introduces all kinds of information to people intuitively and vividly by using advanced computer technology and using various forms such as words, images, music, explanations, animations and videos, which brings great convenience to people. It can be predicted that with the rapid development of touch screen technology, the application field of touch screen will be wider and wider, and its performance will be better and better.