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With the wide application of multimedia equipment, it is convenient for teachingand speech, but a problem is exposed: the speaker operation inconvenience. When thespeaker speaking use the PowerPoint (PPT), page and link point operations will causespeech incoherent and poor effect. To solve this problem, the paper designs ahuman-computer interactive system with projection screen based on laser pen. Thepurpose is that using the track of laser pen to control the PPT playing in the screen. Itprovides a new interactive teaching environment, convenient operation of the speaker.Firstly, the whole system is designed. The system uses CCD camera to capturethe screen information, and then transfers to a computer through the video capturecard for processing. Also the software structure is designed.Secondly, a series of discrete coordinates from the laser pen light track isextracted using of video image processing methods. The track is used operate PPT,besides instruction. So it is necessary to find out operating track and operating area isadopted to realize this objective. To get up speed, an improved Hough is put forwardto detect the area. Laser pen point is detected only in this area, an algorithm based onthe Top-hat and simplified PNLOG operator is adopted to detect light point, and thelight coordinates are tilted correction and transformed the coordinate system.Finally, the laser pen track recognition is realized. In order to improve the systemof real-time, it uses stroke direction of forming track process as the characteristicvalue, designs the neural network classifier to realize the track recognition. Accordingto the results, it sends command through the Windows API function to control thePPT’s action.The achievement of this system’s software is in VC++environment, combinedwith OpenCV library. Users make control actions through the laser pen in the PPT’soperating area to realize the paging up and down, operation link points, transition statebetween the mouse and brush, and erasing the ink. Through tests, the system achieves human-computer interaction, it has practical application value.
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