Generally, 3-D interactive systems are used in systems with large displays and are not suitable for portable devices. To 'touch' a floating 3-D image displayed from a mobile device, we proposed a camera-free, 3D, interactive, virtual-touch system for bare fingers. By embedding optical sensors into the display pixels and adding angular scanning illuminators to the edge of the display, a flat panel can sense the images reflected off a bare finger. The three-axis (x, y, z) information of the fingertip can be determined by analyzing these reflected images. The proposed 3-D virtual-touch system successfully functions with a 4-in mobile display.