FIREBIRD: Fully Integrated Bidirectional Infrared Displays

苹果iPhone、微软的多用户触摸台和其他类似设备最近的发展表明，人们对不依赖键盘或鼠标进行交互、但通过直接触摸显示屏工作的电子设备有真正的需求。人们也在努力提高能效，特别是在移动设备中，在这方面，基于有机发光二极管(OLED)技术的显示器比现有的液晶显示器(LCD)技术具有明显的优势。Firebird项目旨在直接将多点触摸表面与OLED显示器相结合。多点触控表面将通过光学手段实现。红外OLED发射器将以矩阵形式排列在显示器上，并与有机光电探测器(OPD)阵列耦合。接近显示器表面的物体会将发射器发出的红外光反射回传感器，以便进行检测。这项技术的一个关键优势是，它还可以用于识别有图案的表面，因此也可以用于文档扫描。开发Firebird多点触控显示屏需要三个关键元素：OLED发射器和OPD传感器，用于驱动发射器和传感器的有源矩阵底板，以及带有软件的控制器。剑桥大学工程系(CUED)在该项目中的主要作用将是开发背板技术，并与其他合作伙伴在系统集成方面进行合作。为了驱动将位于每个显示像素的各种设备(显示元件、红外发射器和传感器)，背板电子设备将需要具有良好的性能特性。氢化非晶硅(a-Si：H)已成为大面积电子产品(包括有源矩阵液晶显示器)的首选材料。然而，它的器件稳定性和电子迁移率都很差。氧化锌是一种光学透明的半导体材料，可以与其他材料合金化，从而获得优异的电学性能。事实上，基于反应磁控溅射非晶氧化铟锌(a-IZO)的薄膜晶体管(TFT)器件已经被证明具有约10 cm^2/(V.S)的场效应迁移率，这比a-Si：H提高了一个数量级。这要归功于一个关于氧化锌薄膜晶体管(HiPZOT)的项目，该项目由EPSRC资助的“剑桥先进制造技术光电子集成知识中心”(CIKC)与英国的等离子Quest Ltd.(PQL)共同资助。在该项目中，通过HiPZOT项目开发的平台氧化锌技术将应用于这一新的应用领域。这将需要仔细的设备开发，以确保实现多点触摸显示屏背板区域的要求。具体地说，可以使用氧化锌技术来制造全透明TFT，这对于与显示元件集成具有特殊的优势。然而，人们认识到，氧化锌技术处于相对较早的开发阶段，因此也将开发a-Si：H以确保项目的成功，尽管这将导致最终器件的性能降低，并不允许制造完全透明的器件。

The recent development of the Apple iPhone, Microsoft's multi-user touch table and other similar devices has shown that there is a real demand for electronic devices that do not rely on keyboards or mice to allow interaction, but which work by directly touching a display. There is also a drive towards greater energy efficiency, particularly in mobile devices, and in this regard, displays based on organic light emitting diode (OLED) technology have a clear advantage over the incumbant liquid crystal display (LCD) technology.The FIREBIRD project aims to integrate a multi-touch surface diretly with an OLED display. The multi-touch surface will be realised by optical means. Infrared OLED emitters will be arranged in a matrix over the display and coupled with an array of organic photodetectors (OPDs). Objects in close proximity to the display surface will reflect the infrared light from the emitters back onto the sensors to allow detection. A key advantage of this technology is that it can also be used to recognise patterned surfaces, and so could also be used for document scanning, for example.Three key elements are required to enable the development of the FIREBIRD multi-touch display: the OLED emitters and OPD sensors, an active matrix backplane for driving the emitters and sensors and a controller with software. The main role of Cambridge University Engineering Department (CUED) within this project will be to develop the backplane technology and to collaborate with the other partners in system integration. In order to drive the various devices that will be locted at each display pixel (display element, infrared emitter and sensor) the backplane electronics will need to have good peformance characteristics. Hydrogenated amorphous silicon (a-Si:H) has been dominant as the material of choice for large area electronics (including active matrix liquid crystal displays). However, it suffers from poor device stability and poor electron mobility. Zinc oxide is an optically transparent semiconducting material that can be alloyed with other materials to give excellent electonic properties. Indeed, thin film transistor (TFT) devices based on reactive magnetron sputtered amorphous indium zinc oxide (a-IZO) have been demonstrated at CUED with field effect mobilities ~10 cm^2/(V.s) - an order of magnitude improvement over a-Si:H. This has been enabled by a project on ZnO TFTs (HiPZOT) that has been funded through the EPSRC-funded 'Cambridge Integrated knowledge Centre for Advanced Manufacturing Technologies for Photonics and Electronics' (CIKC) in collaboration with UK-based Plasma Quest Ltd. (PQL). In this project, the platform ZnO technology that has been developed through the HiPZOT project will be applied to this new application area. This will require careful device development to ensure that the requirements of the multi-touch display backplane area realised. In particular, fully transparent TFTs can be produced using the ZnO technology, which would have particular advantages for integration with the display element. However, it is recognised that the ZnO technology is at a relatively early stae of development, and therefore a-Si:H will also be developed to ensure the success of the project, although this will lead to reduced performance of the final device and would not permit the fabrication of fully-transparent devices.