LucidTouch: A See-through 2-sided Touch Mobile Device
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LucidTouch is a mobile device that allows for direct touch input while minimizing occlusion by using pseudo-transparency. Its physical affordances allow for simultaneous direct-touch input from all 10 fingers.
Background & Objective: The project aims to extend our previous work in direct-touch tabletops to the mobile domain, and, as such, is related to the DiamondTouch, DiamondSpace, and DiamondSpin projects.
Touch is a compelling input modality for interactive devices; however, touch input on the small screen of a mobile device is problematic because a user's fingers occlude the graphical elements she wishes to work with. LucidTouch is a mobile device that addresses this limitation by allowing the user to control the application by touching the back of the device. The key to making this usable is what we call pseudo-transparency: by overlaying an image of the user's hands onto the screen, we create the illusion of the mobile device itself being semitransparent. This pseudo-transparency allows users to accurately acquire targets while not occluding the screen with their fingers and hand. LucidTouch also supports multi-touch input, allowing users to operate the device simultaneously with all 10 fingers. As a two-sided touch screen, the LucidTouch is a direct extension of our two-sided touch table, published previously as Under the Table Interaction (reference below).
Technical Discussion: Many direct touch input devices provide only two input states: out-of-range and dragging, the assumption being that the user's finger or stylus provides feedback in order to anticipate the point of interaction. When the hands are behind the display, this visual tracking is not possible. Our pseudo-transparency approach allows users to see their hands as they are attempting to acquire a target from the back of the device, thus solving not only the occlusion problem, but also the lack of tracking feedback. In order to overcome the fat finger problem, simple computer-vision techniques are applied, allowing each finger's touch points to be visualised prior to making contact with the touchpad. As a result, LucidTouch enables fast and intuitive land-on selection, in contrast to the take-off selection techniques other opaque devices employ.
Our research focus is on the development of interaction techniques, and the study of pseudo-transparency as a mechanism for enabling multi-touch mobile devices. We have developed techniques to address the issues of text entry, pointing/dragging, and multi-touch interaction.
Future Direction: There are two clear avenues for future research: first, the development of technologies which allow for imaging of the fingers while not in contact with the back of the device. Second, the development of a unified graphical user interface for a pseudo-transparent, multi-touch device provides exciting opportunities for increased parallelism and precision.
Wigdor, D.; Forlines, C.; Baudisch, P.; Barnwell, J.; Shen, C., “Lucid Touch: A See-through Mobile Device”, ACM Symposium on User Interface Software and Technology (UIST), ISBN: 978-1-59593-679-2, pp. 269-278, October 2007 (ACM Press, TR2007-075)
Wigdor, D.; Leigh, D.; Forlines, C.; Shipman, S.; Barnwell, J.; Balakrishnan, R.; Shen, C., “Under the Table Interaction”, ACM Symposium on User Interface Software and Technology (UIST), ISBN: 1-59593-313-1, pp. 259-268, October 2006 (ACM Press, TR2006-076)
Modification Date: October 3, 2008