US 6,271,830 B1 · Three- point capacitor trackpoint

Abstract

A capacitive trackpoint device employs three capacitive sensors rather than four to increase sensitivity while reducing power consumption. Use of capacitive rather than resistive sensors provides a more sensitive and consistent signal with respect to pressure and a greater dynamic range than can be obtained from a resistive or strain gauge sensor, while use of larger area capacitive sensors for a given total area reduces the power requirements for reading the sensors both by having fewer capacitive sensors to read and by reducing the oscillating frequency. Because a more sensitive sensor is utilized, sampling of the signal may be made for a shorter time during periods of inactivity. The overall reduction in power consumption is particularly important for battery operated, hand-held input devices. Use of three sensors rather than four allows sampling of only two in a power-saving mode during periods of inactivity. Normalized force signals measured from the sensing electrodes are translated into displacement-type signals in at least two independent directions through simple trigonometric computations, with the normalized, translated signals being transformed to conventional displacement signals for a pointing device. The reduced power consumption is especially significant for infrared remote control devices of the type employed to control a set-top box, in which battery life is an important consideration.

Claims11

Dependent claims

A method of operating an input device for a data processing system, comprising:

measuring an oscillation frequency for at least two of three variable capacitances within the input device;
translating the oscillation frequency for the at least two variable capacitances into predetermined signals corresponding to displacement in any of at least two independent directions by:
calculating normalized gain signals for three oscillators each including one of the variable capacitances;
calculating a first signal corresponding to displacement along a first axis from a normalized gain signal for an oscillator including a first of the three variable capacitances minus a normalized gain signal for an oscillator including a second of the three variable capacitances;
and
calculating a second signal corresponding to displacement along a second axis from a normalized gain signal for an oscillator including the first of the three variable capacitances plus a normalized gain signal for an oscillator including the second of the three variable capacitances minus a normalized gain signal for an oscillator including a third of the variable capacitances;
and
transforming the predetermined signals into displacement signals for a cursor within a graphical user interface in the data processing system.

5 more elements

Dependencies are inferred from the claim text.

Three- point capacitor trackpoint

Life of this patent

Three- point capacitor trackpoint

Life of this patent

Abstract

Claims11