Design And Implementation Of Scalable, Anti-light Interference Infrared Touch Module

With the development of information technology, people need a more convenientway to interact with smart devices. As a human-computer interaction device, touchscreen technology has been booming recently.Infrared touch screen does not require additional film on the display, so thetransmittance is100%. And infrared touch screen is less susceptible to electromagneticfields and electrostatic interference. It is suitable for working in harsh environment.Infrared touch screen dependent infrared light as working medium, infrared lightcomprise50％energy of the sunlight. So the sunlight can interface the operation ofinfrared touch screen.To solve the above shortcoming, this paper researches the operation principle,design and implementation of infrared touch screen. First research the infrared touchscreen which is suitable for indoor light environment. Base on that, research the infraredtouch screen which can work under high altitude strong light interference and propose aparallel scanning, received frequency selective infrared touch module. According tofrequency selective method, this paper researches crystal method and digitalcross-correlation phase lock amplification method to select received frequency.First, this paper researches the working principle and implementation of theinfrared touch screen which is suitable for indoor light environment, analyzes itsperformance while environmental light changing. The ARM7controls165pairs ofone-to-one corresponding infrared emitting diode and phototransistor transmitting andreceiving data sequentially. While data processing, this paper uses dynamic thresholdmethod to insure the infrared touch screen can work under370lux light intensity.Second, this paper researches the working principle and implementation of parallelscanning infrared touch screen which uses crystal to select certain frequency receivedsignal, analyzes its anti-light interference performance. Use C8051F930quantifying andprocessing received data on a single chip. Divide entire infrared touch screen intoseveral working independently scanning units. Thus the sequentially touch scanning ofentire infrared touch screen changes to the parallel scanning among scanning units. The scanning unit use extended UART protocol to communicate with master module. Usephotodiode as photoelectric conversion device to avoid saturation of received signal.Use converse piezoelectric-piezoelectric effect of passive crystal resonator toconstitute a narrow-band filter to achieve frequency selecting. Based on experiment thisinfrared touch screen can work under45Klux light intensity.At last, by using the touch coordinates generation method proposed by infraredtouch screen suitable for indoor light environment and the extended UART protocol toachieve parallel touch scanning and extensible module proposed by parallel scanninginfrared touch screen, this paper researches the working principle and implementation ofscalable, anti-light interference infrared touch module which uses cross-correlationphase lock amplification theory to select certain frequency received signal, analyzes itsanti-light interference performance. Use PSOC5, a programmable system-on-chip chip,to achieve digital cross-correlation phase lock amplification which can configurereceived frequency flexibly. Improve photodiode photoelectric conversion circuit bymulti-voltage domain method to increase the saturation voltage limit. Based onexperiment this infrared touch screen can work under100Klux light intensity.