| Along with the accelerating of the information-based progress, the human-computer interaction platform develops more and more personally. Since the touch screen technology was published, touch screen has developed with simple operation, flexible use and convenient portability etc, which become an indispensable part of people’s daily life instead of traditional hardware input device like the mouse, writing board, keyboard etc.As a branch of study on the touch screen, infrared touch screen stand out from lots of touch screen with its many advantages. Infrared touch screen judges infrared touch point position by blocking infrared light without the films on the touch screen. It has high transmission and strong anti electromagnetic interference ability, which is very suitable for high altitude and electronic interference working environment. But the infrared touch screen is worked by transmitting and receiving infrared light., and it is sensitive in the change of illumination environment. The use of infrared touch screen will be greatly disturbed in the external light environment, leading to abnormity of received intensity by infrared receiving tube, which can cause malfunction.To solve the problem of strong light interference on the infrared touch screen, this paper researches the operation principle, design and implementation of infrared touch screen. By analyzing and comparing several methods of infrared anti glare, this paper presents a new algorithm based on the phase-locked amplifying technology and anti glare infrared touch module design. First, this paper emits and receives high frequency infrared, and achieves modulation of light AD conversion and digital phase shifter by programmable chip system PSOC5. Then filtering the interference frequency band of sunlight in the lock in amplifier way. This paper achieves the way of interference of sunlight and verified result. In addition, by improving demodulation algorithm of lock in amplifier, removing the filter circuit of the traditional lock in amplification, which makes the circuit more simple and reliable.In the design process to achieve anti light interference infrared module, firstly feasibility of the overall design scheme should be proved through verification of the new algorithm of phase locked amplification technology. Secondly this paper verifies its effectiveness through the hardware circuit experiments. Finally it completes the overall design to test its performance of anti glare. After that, this paper put the anti light interference module into the overall design of the infrared touch screen, combines with the infrared touch screen signal generation module analysis and infrared transmitting, receiving, controlling module technology, designs the anti light interference infrared touch control module based on phase-locked frequency.Through the hardware platform experiments, using a new type of lock-in amplifier technique can achieve good anti glare effect. The Q value frequency selection can reach 145.985, which is improved by 9 times to unaltered lock-in amplifier anti glare effect, and it can work properly in the 50000 lux light intensity environment, largely filters the interference of external light and achieves the anti light interference. |
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