Harit Doshi

31.2: A5 Sized Electronic Paper Display for Document Viewing

A new active matrix electronic paper display (EPD) prototype targeting medium format document viewing applications has been developed using electrophoretic technology manufactured by E Ink Corporation. The prototype panel represents an unprecedented step upward in absolute resolution and total viewable area over commercially available products, while also introducing a novel controller architecture for image stable displays. 1. Overview The past several years have born witness to a steady advancement in the capabilities and performance of electrophoretic displays. Resolutions have grown from QVGA to SVGA [3], image update time has decreased, and final image quality has improved. E Ink has previously demonstrated the largest active matrix electrophoretic display in terms of diagonal size [4]. While the display presented here is approximately 30% smaller in terms of area, it represents an 85% increase in terms of absolute number of pixels and is believed to be the world’s highest total pixel count electrophoretic paper display. Given these improvements, electronic paper displays (EPD) have emerged as an ideal imaging technology for electronic reading applications. However, the aspect ratios and diagonal sizes typical in the display industry are not necessarily best suited for viewing print content. This panel is purpose-built for reader applications, and adopts a common paper size for print compatibility. Most bi-stable or multi-stable imaging technologies differ from standard LCDs in the data and logic level processing required to perform a display update. Since the display only needs to be driven when a change in state is desired, some system is needed first to detect on a per pixel level when a change is indeed requested and second to effect this change in an efficient and expeditious manner. Several approaches exist to building this system. One approach, employed in conjunction with this new panel, is to utilize as much as possible the LCD related hardware and interfaces already in place on many host platforms. For evaluation and development of this panel and controller, a host system was constructed based on a system on chip processor commonly used for portable products. A Linux operating system was chosen as typical of the environment available in the target products. This choice also allowed for straightforward driver software and applications prototyping. A block diagram of the complete A5 display system described is shown in Figure 1. 2. Application Specific Display Requirements Since the products targeted by this display are chiefly concerned with viewing content traditionally conveyed by print on paper, the dimensions of the active area were closely matched to A5 ISO paper size. Breaking away from the confines of the popular industry 4:3 aspect ratio resulted in a display markedly better A5 Panel Xscale Host Bluetooth MMC Im pu ls e D at a Display Controller Im ag e D at a