Optical trackpad
An optical trackpad is an input device based on an optical sensor, which detects the displacement of a finger that is moving on top of it. The sensor is used typically in smartphones where it replaces the D-pad. The main advantages over a D-pad are:
Next to browsing through menus, it can drive a mouse cursor in point&click interfaces.
In comparison with trackpads, it detects actual skin displacement, instead of displacement of the center of the area being touched.
