Touch Sensing for a Projected Screen Using Slope Disparity Gating

This paper introduces a novel touch sensing system for a projected screen with a single camera. To achieve touch sensing with camera image, there are two challenges to overcome. One is to establish robustness against image processing being misled by projected contents. The other is to realize both touch detection and fingertips localization with a single-camera image. In this work, we use Slope Disparity Gating and capture only the region slightly above the projected screen. This selected region is set geometrically so that a part of the finger is captured when touching, and no finger is captured when not touching. A key feature of this study is that the projector can enable this selective imaging capability in the camera while still displaying a normal projected image to the user's eyes. The projector is both a programmable light source for capturing system and an interface display device for the users. We built a prototype system and touch sensing algorithm, evaluated the touch accuracy, demonstrated robustness to a projected content.