In the last few years alone, computing demands have increased dramatically. Such significant increases have given rise to a vast amount of new computing technologies. For example, a keyboard, mouse, or some other pointing (e.g., a stylus) used to be required for data entry as well as data manipulation. However, nowadays, users also have the option to utilize a variety of other means to enter, access, and/or manipulate data displayed on or stored in a computer. One primary example is touch screen technology. In general, a touch screen is an input device that allows users to operate a computer by simply touching the display screen.
Unfortunately common touch screen technologies are limited in capability. For example, most are not able to track more than a small number of objects on the screen at a time, and typically they report only the two dimensional (2D) position of the object and no shape information. This can be due in part to superficial limitations of the particular hardware implementation, which in turn are driven by the emphasis on emulating pointer input for common GUI (graphical user interface) interactions. Typically, today's applications are only able to handle one 2D pointer input.
Recently, a number of systems have introduced the concept of imaging touch screens, where instead of a small list of discrete points, a full touch image is computed, whereby each ‘pixel’ of the output image indicates the presence of an object on the touch screen's surface. The utility of the touch image thus computed has been demonstrated in gesture-based interactions for application on wall and table form factors. For example, the DiamondTouch system uses horizontal and vertical rows of electrodes to sense the capacitively coupled touch of the users' hands at electrode intersections. (Dietz, P. H., D. L. Leigh, DiamondTouch: A Multi-User Touch Technology. in ACM Symposium on User Interface Software and Technology (UIST), (2001), 219-226).
MetaDesk (see Ullmer, B., H. Ishii, The metaDESK: Models and Prototypes for Tangible User Interfaces. in ACM Symposium on User Interface Software and Technology, (1997), 223-232), HoloWall (see Matsushita, N., J. Rekimoto, HoloWall: Designing a Finger, Hand, Body and Object Sensitive Wall in ACM Symposium on User Interface Software and Technology (UIST), (1997)) and Designer's Outpost (see Klemmer, S. R., M. W. Newman, R. Farrell, M. Bilezikjian, J. A. Landay, The Designer's Output: A Tangible Interface for Collaborative Web Site Design in ACM Syposium on User Interface Software and Technology, (2001), 1 -10)) each use video cameras and computer vision techniques to compute a touch image. These systems permit simultaneous video projection and surface sensing by using a diffusing screen material which, from the camera view, only resolves those objects that are on or very near the surface. The touch image produced by these camera-based systems reveals the appearance of the object as it is viewed from behind the surface.
Thus, there remains a need to further develop and improve touch screen technology for better viewing quality and for greater flexibility regarding an object's distance from the screen material.