Finger operable control device

• US 5,657,012 A
• Filed: 12/20/1991
• Issued: 08/12/1997
• Est. Priority Date: 06/21/1989
• Status: Expired due to Fees

• Current Assignee: David Adams Gilmour Tait
• Original Assignee: David Adams Gilmour Tait
• Inventors: Tait, David Adams Gilmour
• Primary Examiner(s): Swarthout, Brent
• Assistant Examiner(s): HILL, ANDREW M
• Application Number:
  US07/778,160
• Time in Patent Office: 2,062 Days
• Field of Search: 341/20, 341/33, 340/709, 340/710, 324/659, 324/672, 324/686, 361/278, 361/280, 361/288, 361/328, 361/330, 361/283, 361/283.3, 307/113, 345/173
• US Class Current: 341/20
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard

Abstract

A finger operable control device that includes a sensor having five conductive plates. The conductive plates are coupled to a detector circuit arranged to sense capacity imbalance due to the presence of a finger or an earthed object on or by one or more of the conductive plates. The device is utilized as a mouse or joystick.

Claims

1. A finger operable control device comprising a sensor having a central electrically conductive plate, a first pair of electrically conductive plates on a first axis and spaced from opposite edges of the central plate to form a first pair of capacitors therewith having substantially equal capacitance, a second pair of electrically conductive plates on a second axis different from the first axis and spaced from opposite edges of the central plate to form a second pair of capacitors therewith having substantially equal capacitance, characterised in that opposite members of each pair of plates are driven by antiphase outputs of a quadrature-phase generator and the central plate is connected to a detector capable of sensing the magnitude and/or phase of the signal therefrom caused by capacitive imbalance induced by presence of either a finger or a finger-operable earthed object placed on or near the conductive plates when the finger or object is displaced laterally from the intersection of the two axes.

2. A device as claimed in claim 1 wherein the generator includes an oscillator operative at a frequency of twice the frequency of the quadrature phase signals.

3. A device as claimed in claim 1 wherein the detector is preceded by an amplifier.

4. A device as claimed in claim 3 wherein a dead-zone is provided by appropriately biassing the amplifier.

5. A device as claimed in claim 3 wherein a dead-zone is provided by connecting the output of the amplifier to a comparator, the second input of the comparator being connected to a reference signal to provide the dead-zone.

6. A device as claimed in claim 1 wherein the detector circuit comprises at least one phase sensitive detector having reference input coupled to an output of the first quadrature phase generator.

7. A device as claimed in claim 6 wherein the output of the phase sensitive detector is coupled to an input of a second quadrature phase generator.

8. A device as claimed in claim 7 wherein a clock pulsing means is coupled between said phase sensitive detector and said second generator.

9. A device as claimed in claim 6, wherein said phase sensitive detector produces at its output a signal indicating displacement of the finger or object relative to at least the first axis.

10. A device as claimed in claim 4 or 5 wherein the amplifier is biassed to a level lower than the threshold of the phase sensitive detectors, and wherein a ramp is applied to the amplifier bias whereby the dead-zone is at least partially eliminated.

11. A device as claimed in claim 4 or claim 5 wherein a random noise signal is applied to the amplifier whereby the dead-zone is at least partially eliminated.

12. A device as claimed in claim 1 wherein an electrical lead extends from the central plate between a plate of the first pair and a plate of the second pair, and a dummy lead extends between the other plates of the first and second pairs.

13. A device claimed in claim 1 comprising at least two said sensors.

14. A mouse emulator comprising a finger operable device as claimed in claim 1.

15. A joystick emulator comprising a finger operable device as claimed in claim 1.