Prismodule

The multi-touch interface is essential for smartphone user experience; however many issues such as a lack of physical feedback, the occlusion problem, and the reachability problem still remain. The back-of-device (BoD) approach is a way to address these issues; nevertheless, there are problems such as that the user finger or external landscape affects the view of the camera and that simultaneous input is difficult in the technique using the acceleration sensor. We propose a thin and low-cost method using internal reflection to actualize an additional physical UI on the back of the smartphone. No special devices such as mirrors are needed only acrylic panels and plastic parts. This method extends the smartphone input UI to include a physical button, dial, pointing stick, and also a slider. In addition, the method supports simultaneous input and overcome the effect of the user finger and external landscape.