Positioning a cursor on the display screen of a computer

A position input device comprising:

• an oscillator that generates an oscillating injection signal for coupling to a first body part of a human body;
• a first input operable to receive a first position signal from a first position sensing electrode that provides a first signal indicative of distance of the first position sensing electrode from a second body part in a non-contacting manner;
• a second input operable to receive a second position signal from a second position sensing electrode that provides a second signal indicative of distance of the second position sensing electrode from the second body part in a non-contacting manner, the first and second position sensing electrodes being spaced from each other;
• a differential amplifier having first and second differential inputs connected to the first and second inputs to receive the first and second signals;
• a processing device connected to the differential amplifier and operable to generate a distance signal based on evaluation of the first and second signals.

A position input device comprising:

• an oscillator that generates an oscillating injection signal for coupling to a first body part of a human body;
• a first input operable to receive a position signal from a position sensing electrode that provides a signal indicative of distance of the position sensing electrode from a second body part in a non-contacting manner;
• a differential amplifier having a first differential input connected to the first input to receive the signal indicative of distance;
• and
• a processing device connected to the differential amplifier and operable to generate a distance signal based on evaluation of the signal indicative of distance.

An input device for controlling the position of a cursor on a display of a computer, the input device comprising:

• at least one first position-sensing electrode positioned near a fixed reference frame defining an imaginary input boundary, for sensing the strength of a field established about a movable body part of an operator in a non-contacting manner and thereby to provide a first control variable corresponding to the position of the body part in the reference frame in a first direction;
• at least one second position-sensing electrode positioned near the fixed reference frame and spaced from the at least one first position-sensing electrode, for sensing the strength of the field about the movable body part in a non-contacting manner and thereby to provide a second control variable corresponding to the position of the body part in the reference frame in a second direction;
• and
• a control circuit operative in response to the first and second control variables to position the cursor on the display screen in accordance with the position of the body part in an active region defined by the reference frame;
• the cursor being positioned in response to the first and second control variables by movement of the body part in the active region.