Design And Implementation Of Large Size Infrared Multi-touch System

With the development of multimedia technology,large size multi-touch technology is widely used in teaching,training,meetings and many other occasions,which is the key technology to realize interactive electronic whiteboard.Traditional resistance or capacitance touch technology is difficult to break through the size bottleneck,and the touch technology based on surface acoustic wave or CCD optics is easy to be disturbed by the environment.Infrared touch technology has become the mainstream technology,which benefits from the advantages of large application size,high touch precision,low hardware cost and long service life.However,the existing large-size infrared multi-point touch screen in the market is still plagued by the problems of low multi-point touch accuracy and poor tracking effect.According to the above questions,the thesis designed a large-size infrared multi-touch system with high multi-touch accuracy and good tracking effect,and used wireless communication to solve the problem of easy aging of the wired interface.The thesis completed the system design and the production,debugging and testing of 94,110 and 120 inch prototypes.The main tasks of hardware design includes: designed the main control module control system and processing data;designed the transmitting module and receiving module to realize the "one-transmit-multiple-receiving" scanning mechanism;designed the data acquisition module to collect infrared receiving signals;designed the communication module to realize the embedded terminal Wireless communication with PC.The main tasks of software design are as follows: realized touch point detection and tracking algorithms on the embedded side,designed multiple working modes and supporting tool software on the PC side;completed the data interaction between the embedded side and the PC side based on the USB HID protocol.The innovations of the thesis are as follows:(1)Aiming at the problem that short-distance multi-point touch is easy to produce tricky points and the touch accuracy is not high,the thesis proposes an algorithm for the weakest touch point in the neighborhood,which can better suppress the generation of tricky points and improve touch accuracy.(2)Aiming at the problem of poor tracking performance of multi-touch points in close range,the thesis improves the nearest neighbor algorithm and adopts the inertial prediction nearest neighbor algorithm to ensure the high real-time performance of the system and improves the accuracy of multi-touch point tracking in close range.(3)In order to further improve the stability and flexibility of the system,the thesis designs parameter configurable mode to improve the flexibility of the system,and uses wireless communication to solve the problem of easy aging of wired interface.After testing,the system designed in this thesis runs stably,and can well suppress the tricky points generated by the multi-touch point interval within 2cm?7cm,and when the multi-touch point interval is greater than 3cm,the tracking result is accurate,and the tracking accuracy rate reach 66.7% when the distance is less than 3cm.The scanning frame rate can reach 76 fps when single-point touch,and the scanning frame rate can reach 40 fps when 25-point simultaneous touch,with the test condition of 120 inches.All the performance indexes of the system have reached the expected research goal.