Research Of Optical Touch Screen Based On Cmos Image Sensor

As a new kind of computer input device, touch screen unified the tactile and visual, and made the computer interaction more intuitive and convenient. The huge success of iPhone, made the wave of touch screen application to an unprecedented height. At present, the situation of development of touch screen technology as follows. The resistive and capacitive touch screen for leading in the small and medium sized filed. There are a variety of techniques in the large sized field, including infrared, surface acoustic wave and optical touch technology.The emerging optical touch technology broke the bottleneck of the traditional touch technology, and had greatly improved in accuracy, speed of response, service life and other aspects. Two digital cameras installed in the top corners of the display could detect the position of multiple touches, so people can not only click and drag, rotate and zoom the picture, but also control the movements of three-dimensional objects by gently touching the screen.In this paper, we introduced a design method of optical touch screen based on CMOS image sensor, in-depth studied the key parts of optical touch screen-coordinate operations and HID device, and wrote codes for the achievement of the sine function and arctangent function on the FPGA and the realization of HID device on the ARM.Firstly, discussed the principle of the CMOS intersection measuring, deduced the calculation formula of the physical coordinates of the touch points, and provided a basis for the follow coordinate operations.Secondly, designed the linear CMOS circuit and image signal processing circuit, and verified them in TINA. Completed a0to999counter on the FPGA using Verilog language to count the numbers of pixels on the image signal, and got the image position of the touch points in the CMOS.Thirdly, implemented the sine function and arctangent function on the FPGA using13levels pipeline CORDIC architecture, and verified.Finally, designed the USB interface circuit using the PDIUSBD12, and wrote codes on the ARM follow the HID class specification to achieve the automatic identification and communication on the host, and implement click, double-click and drag three types of interaction.