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, and ultra-portable or ultra-mobile PCs, where it replaces touchpads, pointing sticks or trackballs as pointing device.
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 touchpads, it detects actual skin displacement, instead of displacement of the center of the area being touched, and more similar to pointing sticks or compact trackballs by using experience, but with less physical feedback.
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