Apparatus for sensing the position of a pointing object

• US 20040178995A1
• Filed: 12/29/2003
• Published: 09/16/2004
• Est. Priority Date: 06/29/2001
• Status: Active Grant

• Current Assignee: Ethertouch Limited
• Original Assignee: Ethertouch Limited
• Inventors: Sterling, Hans Rudolf
• Granted Patent: US 6,998,856 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

A computer system (10) includes a keyboard (11), a first pair of position-sensing electrodes (18.1 and 18.2), a second pair of position-sensing electrodes (20.1 and 20.2), a signal injection electrode (22) and an oscillator (27). The oscillator injects a signal via the electrode (22) and the operators left hand L, creating a field around the operator'"'"'s right hand R. The position electrodes are arranged underneath the keyboard and sense the strenght of the field enabling the position of the operator'"'"'s right hand R in an X-Y plane above the keyboard to be determined. Each position-sensing electrode is coupled to a difference amplifier (28 and 30) via a pair of buffer amplifiers (40.1, 40.2, 30.1, 30.2). The amplification factor of the buffer amplifiers can be varied so as to scale the field strength values sensed by the electrodes, thereby permitting the output of the difference amplifier to be varied so as to adjust the sensivity of the system to different positions of the operator'"'"'s hand R.

Claims

1. A method of sensing the position of a movable pointing object with respect to a reference frame, which includes:

establishing an electrical field about the pointing object;

sensing the strength of the field by arranging at least one pair of spaced sensor elements in the reference frame, the sensor elements being positioned adjacent one another, each sensor element being operable to sense the strength of the field at the location of the particular sensor element to provide a field strength value corresponding to the field strength sensed by the particular sensor element;

variably scaling the two field strength values with respect to one another; and

calculating the difference between the scaled field strength values to obtain a difference value providing a control variable corresponding to the position of the pointing object in the reference frame.

2. Apparatus for sensing the position of a movable pointing object with respect to a reference frame, the apparatus comprising:

electrical field generating means for establishing an electric field about the pointing object;

at least one pair of spaced sensor elements that are positionable in the reference frame in an arrangement wherein the sensor elements are adjacent one another, each sensor element being operable to sense the strength of the field at the location of the particular sensor element to provide a field strength value corresponding to the field strength sensed by the particular sensor element;

scaling means for variably scaling the two field strength values with respect to one another; and

difference calculation means for calculating the difference between the scaled field strength values to obtain a difference value providing a control variable corresponding to the position of the pointing object in the reference frame.

3. Apparatus as claimed in claim 2, wherein the sensor elements are in the form of a pair of spaced, parallel elongate electrodes.

4. Apparatus as claimed in claim 3, which includes two pairs of sensor elements, wherein the pairs of sensor elements are arranged orthogonally with respect to one another to provide for sensing of the position of the pointing object in a two-dimensional reference frame.

5. Apparatus as claimed in claim 3, including three pairs of sensor elements, wherein the pairs of sensor elements are arranged orthogonally with respect to one another to provide for sensing of the position of the pointing object in a three-dimensional reference frame.

6. A new method substantially as described in the specification.

7. A method substantially as described in the specification with reference to and as illustrated in the accompanying diagrammatic drawings.

8. A new apparatus substantially as described in the specification.

9. An apparatus substantially as described in the specification with reference to and as illustrated in the accompanying diagrammatic drawings.