Abstract: An input device for a computer detects movement of an object, such as a finger, within a selected field of space, and across the boundaries of the selected space. The input device is used to input commands into a computer, such as to control movement of a cursor over a display device or to mark certain portions of information displayed on the computer monitor. Directional transducers receive reflections of transmitted energy from an object in the field, and provide signals to an interpreter which maps the signals to control movement of the cursor or other device on the computer monitor. The input device includes an interpreter for detecting movements within the selected input space. Certain or selected detected movements within or through the input space are interpreted as input commands for controlling aspects of the computer.