Four kinds of principles and techniques of contrast touch screen

Touch screen system generally consists of two parts : a touch detection devices and touch screen controller . Touch detection device is mounted in front of the monitor screen , for detecting a user touch position, a touch screen controller receiving evacuation ; touch screen controller 's main role is the touch point detecting means to receive touch information and convert it into contact coordinates , sending to the CPU, it also can receive commands sent to the CPU and executed .
With advances in technology , touch-screen technology also experienced a gradual upgrade from low to high and the development process. According to its working principle , its current is generally divided into four categories: resistive touch screen , capacitive touch screen , infrared touch screen and surface acoustic wave touch screen .
Resistive Touch Screen
Resistive touchscreen screen body part is a multi-layer composite film by a layer of glass or plexiglass as a grass surface is coated with a layer of transparent conductive layer (ITO film ) , above the outer surface and then covered with a layer of hardened , smooth scratch plastic layer . Its inner surface is also coated with a layer of ITO, a conductive layer between the two layers of many small ( less than one thousandth inch ) transparent isolation points separate them . When the finger touches the screen , the two ITO contact occurs , resistance changes , the controller detects a change in resistance to calculate the coordinates of the contact point , and then follow this coordinate to the corresponding operation . Lead resistance screen according to number of hours , divided into four or five lines and other types. Five-wire resistive touch screen is a conductive outer surface of the glass rather than the conductive coating layer, a longer life of this conductive glass , the transmittance is higher.
Resistive touch screen ITO-coated brittle fracture easily if too thin , thick coating will reduce internal reflection of light and the formation of reduced clarity. As has often been touched , use ITO surface after a certain time hairline cracks , and even variant, so its life did not last long .
Resistive touch screen is cheap and easy to produce , and thus it is still more common choice. Four -wire , five -wire and seven lines, eight -wire touch screen to make it appear more reliable , but also to improve its optical properties.
Capacitive touch screen
Capacitive touch screen are plated on the narrow sides of the electrode which is formed within a low-voltage AC electric field . Touch screen labeled with a transparent film layer , which is a special metal conductive materials . When the user touches the capacitive screen , the user's finger and face forming a capacitive coupling, because the work surface is connected with high-frequency signals , so fingers will suck a small current , respectively, from the current electrodes on the four corners of the screen in the outflow ; , and theoretically the current flowing through the four electrodes and the finger is proportional to the square of the distance from the controller through the four current ratio of precise calculation , the contact point can be derived .
Capacitive touch screen dual glass not only protect conductors and sensors , more effectively prevent external environmental factors affect the touch screen , even if the screen is stained filthy ,color lcd display module dust or grease, capacitive touch screen is still able to accurately calculate the touch location . However, since the capacitor with the temperature, humidity or changes in the different ground conditions , its stability is poor , often produce drift.
Although not so extensive application of resistive , capacitive touch screen is also popular for the election type. Such equipment precision , fast response, slightly larger size also has a higher resolution , more durable ( scratch resistant ) , and thus suitable for use as a touch screen consoles . Moreover , emerging near-field imaging technique improved performance capacitive touch screen , weakening it and the resistive touch screen drift may occur .
Infrared touch screen
Infrared touch screen arrangement of the four sides of the infrared emission control and infrared receiver tube , which correspond to the formation of horizontal and vertical cross- infrared matrix . When the user touches the screen , the finger will be blocked if they had been the location of two infrared controller can be judged by calculating the position of the touch point .
Infrared touch screen is also not current, voltage and electrostatic interference, suitable for certain harsh environments. Its main advantage is low cost, easy to install, can be used in various grades on the computer . In addition, since no capacitor charging and discharging process , the response speed faster than capacitive , but lower resolution .
Surface acoustic wave touch screen
A surface acoustic wave is an ultrasound , which is the medium (e.g., a rigid material such as glass or metal ) Surface Shallow mechanical energy wave propagation . By triangular wedge base ( designed strictly according to the wavelength of the surface wave ) , can be directed , a small surface acoustic wave energy emission angle . Surface acoustic performance, ease of analysis, and in the transverse transfer process has a very sharp frequency characteristics , in recent years, non-destructive testing, imaging and exit filter applications such as rapid development .
The four corners of the touch screen display has an ultrasonic transmitter transducer and the receiving transducer , and can send an ultrasonic cover the screen surface . When the fingers touch the display, due to absorption of some of the acoustic energy , the change in the received waveform , the waveform has an attenuation at a time gap, the controller can be calculated based on the signal attenuation of the touch point .
Surface acoustic wave touch screen independent of temperature, humidity and other environmental factors, high resolution , excellent scratch resistance , long life ( 50 million times without failure ) ,TFT LCD Displays high transmittance ( 92% ) , to maintain a clear translucent image ; does not drift , just installed a correction ; has a third axis ( ie pressure axis ) response , the most suitable for use in public places .
Surface acoustic wave touch screen susceptible to water droplets, dust, effects of improvement of the method is to add dust , dirt , or to increase the monitoring of the efficient operation accurately identify the difference between and dirt . In addition, the acoustic screen can feel the pressure , potentially increasing the means of control, on -screen feature is very beneficial expansion of its scope of application thus greatly expanded .