An optical virtual keyboard was invented and patented by IBM engineers in 1992. It optically detects and analyses human hand and finger motions and interprets them as operations on a physically non-existent input device like a surface with painted or projected keys. In that way it can emulate unlimited types of manually operated input devices (such as a mouse, keyboard, and other devices). Mechanical input units can be replaced by such virtual devices, potentially optimized for a specific application and for the user's physiology, maintaining speed, simplicity and unambiguity of manual data input.