The electrowetting display (EWD) has a low gray level, and there are some phenomena that affect the display quality, such as oil backflow and charge trapping. In this paper, an error diffusion algorithm based on pixel neighborhood gray information and direct current (DC)‐balanced driving waveform are proposed for display quality of EWD. The proposed algorithm and driving waveform are implemented in the proposed driving system based on Digital Visual Interface (DVI) video codec system and field‐programmable gate array (FPGA) control system. The experiment results show that the driving waveform suppresses the oil backflow, charge trapping and keeps DC balance, and the proposed error diffusion preserves the edges and richness of image. The whole driving system successfully plays video in real time with computer and improves the display quality of EWD.
This paper proposes a kind of periodic complex ramp pulse driving waveform in the electrowetting display system with suitable viscosity ink. Firstly, considering the fluid-motion characteristics of different viscosity inks, the relationship between the contact angle and viscosity of inks in the liquid-oil-solid three-phase contact display system is calculated to obtain the suitable viscosity range and driving voltage range. Secondly, the physical model of ink motion with different viscosity is established by COMSOL simulation. Then, During the ink shrinkage movement after applying voltage, the change of the meniscus height at the oil-liquid interface is calculated. Finally, the appropriate viscosity range of the ink movement is verified and obtained based on the meniscus height. On this basis, after applying the driving voltage of different amplitude and frequency respectively, the ink movement situation is observed to design a suitable driving waveform. The results show that when the viscosity of ink fluid is between 0.005 and 0.015Pa·s, the higher the voltage amplitude and the lower the frequency, the higher the meniscus height of ink shrinkage, which is consistent with the characteristics of magenta ink tested in the experiment. Experimental tests show that the driving waveform designed in this paper can not only suppress the phenomenon of oil film splitting, backflow and contact angle saturation hysteresis, but also improve the ink response speed and pixel aperture ratio, in which the aperture ratio is increased to 68.69%. This research is of great significance to optimize the structure of fluid material and the design of driving in electrowetting display.
This paper proposes a kind of periodic complex ramp pulse driving waveform in the electrowetting display system with suitable viscosity ink. Firstly, considering the fluid-motion characteristics of different viscosity inks, the relationship between the contact angle and viscosity of inks in the liquid-oil-solid three-phase contact display system is calculated to obtain the suitable viscosity range and driving voltage range. Secondly, the physical model of ink motion with different viscosity is established by COMSOL simulation. Then, During the ink shrinkage movement after applying voltage, the change of the meniscus height at the oil-liquid interface is calculated. Finally, the appropriate viscosity range of the ink movement is verified and obtained based on the meniscus height. On this basis, after applying the driving voltage of different amplitude and frequency respectively, the ink movement situation is observed to design a suitable driving waveform. The results show that when the viscosity of ink fluid is between 0.005 and 0.015Pa·s, the higher the voltage amplitude and the lower the frequency, the higher the meniscus height of ink shrinkage, which is consistent with the characteristics of magenta ink tested in the experiment. Experimental tests show that the driving waveform designed in this paper can not only suppress the phenomenon of oil film splitting, backflow and contact angle saturation hysteresis, but also improve the ink response speed and pixel aperture ratio, in which the aperture ratio is increased to 68.69%. This research is of great significance to optimize the structure of fluid material and the design of driving in electrowetting display.
Due to the phenomenon of contact angle saturation and charge trapping, contrast of the electrowetting display will be decreased, and the details of the image will be lost. A histogram equalization algorithm is commonly used to improve the image contrast enhancement. Therefore, in order to improve the display quality of the electrowetting display, this article proposes an extension of dynamic histogram equalization (DHE) techniques, called intensity preservation-based dynamic histogram equalization (IPDHE). Initially, the proposed IPDHE technique separates the histogram into four subhistograms based on intensity preservation. Then, the resultant subhistograms are reshaped by the nonzero bins as the amount of emphasis given on total pixels. Mathematically, the intensity preservation measure of each subhistogram stands for the density and boosted level of the subhistogram. Finally, each subhistogram is equalized. Simulation results show that, for the dataset of test images, the proposed algorithm successfully enhances the contrast of images while preserving the maximum average information content (entropy), presents more image details, and applies to the electrowetting display.
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