Driving System Of Electronic Paper Display Based On Image Enhancement Technology

Books are the ladder of human progress, the emergence of Electronic Paper Display has the potential to bring about the evolution of books. Electronic Paper has the advantages of ultra-thin, low power consumption, wide viewing angle, reading comfortability and so on. What’s more, with the development of flexible Electrophoretic Display material and the character of repeated use, the image shown on Electronic Paper is much closer to the traditional paper. It is praised as "a piece of paper to write forever". Since the inconsistent threshold voltage of Electronic Paper has led to the nonlinearity and unpredictability of optical response curve, the current way to solve this problem is to design the driving waveform based on pulse width modification (PWM) and use thin-film transistor (TFT) array as voltage switches. The driving waveform based on PWM can be achieved by scanning the TFT array and providing different voltage. As a result, the gray level of Electronic Paper Display dependent more on the frame frequency and further lead to the limitation of gray-scale. So the current Electronic Paper Display are mainly monochrome 16 level gray-scale display, and the quality of the image cannot meet the demands of the people.In this paper, we propose a kind of advanced digital halftone technology used on Electronic Paper to solve the problem of the limitation of gray-scale. It effectively improved the visual effect of image shown. The halftone technology is based on the improved error diffusion algorithm. The threshold is set dynamically according to the gray-scale range of the input image. The single threshold is expanded to 16 thresholds. Through utilizing the serpentine scanning path and adopting the corresponding error diffusion filter, the moire phenomenon and lagging phenomenon resulted from traditional halftone technology is significantly reduced and finally, the image of the Electronic Paper is enhanced.The paper has designed the software and hardware of the system, through rhe combination of halftone technology based on improved error diffusion algorithm, the quality of the image is significantly enhanced. ARM and the EPD controller chip are adopted to be the core of the hardware system. ARM is used to achieve the overall control, data procession and data transmission of the EPD system. EPD controller is responsible to provide data cache and display accurate images via calling the corresponding driving waveform according to the specific environment. Besides, power management module is added to the hardware system in order to reduce the power consumption by using Bootstrap circuit.μC/OS-II is utilized to be the kernel of the software system. The EPD-controller driving program is ported to μC/OS-II system. The halftone algorithm is tested and verified by displaying the images read from the memory card.The paper has finally fulfilled the driving system of Electronic Paper Display based on image enhancement technology. PSNR is used to evaluate the error diffusion algorithm by utilizing Matlab. Besides, the image processed by the halftone technology is tested in Electronic Paper Display system. All the results above prove the effectiveness and advancement of the improved error diffusion algorithm. The image, which is displayed in the EPD with monochrome 16 level gray-scale, is smoother. The final visual effect is significantly enhanced and the gray-scale level is effectively increased.