| With the simple and visual operating feature as well as flexible input characteristic, touch screen has played an increasingly significant role in the field of human-computer interaction. Advanced properties of touch screen have been required as the further widespread application in all fields. As one of the most common touch techniques, infrared touch screen has many advantages, such as100%light transmittance, immune to electromagnetic interference, easy to install and maintain, suitable for severe conditions and so on. Consequently, infrared touch screen has been widely concerned and become an important trend of the development of touch techniques. Nonetheless, there are also some unsolved problems of infrared touch screen, such as susceptible to interference of light, low resolution and long response time due to its hardware construction and operating mode, which has resulted in the restrictions in some certain fields.In order to solve the above problems and improve other aspects of performance, the design of this project has made following major innovations.(a)This project has adopted the scheme of double backup configuration of infrared tubes to provide switchable circuit for the infrared touch screen. Through this design, the device can avoid direct sunlight and be detectable. In addition, the project has designed subtraction circuit and adds the infrared filter strip to the installation structure in order to reduce interference produced by the change of the ambient light. (b) This project has increased the resolution with one-to-many scanning mode and the scheme of double backup configuration. It also has improved the stability of touch and moving smoothness with the application of multiple scanning and filtering algorithm.(c) This project has researched on multi-touch subject and has proposed to truly achieve the two-points identification through zigzag scanning, calculating the inclined blocking distance of the touch points to eliminate ghost points, and adding auxiliary algorithm to improve the detection accuracy.(d) This project has shorten the response time of touch screen by introducing the scanning solution combining rough scanning and partial fine scanning.(e) This project has applied low power mode in order to reduce system power consumption. Furthermore, this scheme has designed the detection of bad tubes and alternative algorithm to improve system stability and service life.(f) This project has chosen STM32series processor as main control chips and completed hardware circuit and embedded software design of the infrared touch screen. In addition, the verifying experiment of scheme has also been conducted.There are several advantages of the infrared touch screen in this project. Firstly, the infrared touch screen of this project has good light resistance which can be applied in direct sunlight. Secondly, the resolution of the touch screen has reached4096×4096without jittering. Thirdly, the maximum response time is less than15ms. In addition, the two-points touch identification can be effectively conducted and gestures movement can be responded accurately. |
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