Method and apparatus for data input

• US 6,222,528 B1
• Filed: 03/07/1997
• Issued: 04/24/2001
• Est. Priority Date: 03/07/1997
• Status: Expired due to Term

• Current Assignee: Cirque Corporation (Alps Alpine Co., Ltd.)
• Original Assignee: Cirque Corporation (Alps Alpine Co., Ltd.)
• Inventors: Johnson, Rick L., McDonald, Marty, Gerpheide, George E.
• Primary Examiner(s): Luu, Matthew
• Application Number:
  US08/813,158
• Time in Patent Office: 1,509 Days
• Field of Search: 345/173, 345/174, 345/178, 345/179
• US Class Current: 345/173
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A method and apparatus for providing accelerated X and Y axis position determination of a probe relative to a touchpad surface by enabling determination of the X and Y axis coordinates independent of each other. The apparatus of the present invention enables simplification of the electronics of the touchpad because fewer sense lines are required to achieve position resolution which is finer than the electrode pitch. Position determination is further accelerated because fewer position measurements are then required to compensate for such problems as probe symmetry duplication.

Claims

1. A data input device for sensing a position of a probe relative to a touchpad surface, wherein the data input device comprises:

a pad means for sensing the position of the probe, and wherein the pad means further comprises;

a plurality of first electrode strips disposed in a first parallel direction and spaced apart in at least a first electrode array, wherein at least a portion of the touchpad surface overlaps at least a portion of the first electrode array;

a sense electrode disposed co-planar with the first electrode array, and including fringe electric fields between the first electrode array and the sense electrode to thereby develop capacitive balances, wherein the probe disrupts the fringe electric fields when the probe comes in proximity to the pad means, thereby altering the capacitive balances, and wherein the at least a portion of the touchpad surface overlaps at least a portion of the common sense electrode;

measuring means electrically coupled to the pad means for measuring the capacitive balances in the pad means to thereby determine the position of the probe relative to the pad means; and

interpolation means electrically coupled to the measuring means for determining probe position at a resolution which is less than a distance between individual electrodes of the at least a first electrode array.

2. The data input device as defined in claim 1 wherein the pad means further comprises:

a plurality of second electrode strips electrically insulated from but in a same plane as the first electrode strips, and spaced apart in a second electrode array which is disposed generally at a 90 degree angle relative to the first parallel direction, wherein at least a portion of the touchpad surface overlaps at least a portion of the second electrode array; and

wherein the sense electrode is a common sense electrode disposed co-planar with the second electrode array, and including fringe electric fields between the second electrode array and the common sense electrode to thereby develop capacitive balances, wherein the probe disrupts the fringe electric fields when the probe comes in proximity to the pad means, thereby altering the capacitive balances.

3. The data input device as defined in claim 1 wherein the pad means further comprises means for selecting which electrode strips of the first electrode array and which electrode strips of the second electrode array are to have capacitive balances measured thereon.

4. The data input device as defined in claim 1 wherein the pad means further comprises means for causing development of electric fields between the first electrode array and the common sense electrode, and the second electrode array and the common sense electrode.

5. The data input device as defined in claim 3 wherein the pad means further comprises means for detecting changes in capacitive balances in the pad means, and the locations of said changes.

6. The data input device as defined in claim 1 wherein the pad means further comprises insulator means between the first electrode array, the second electrode array, the common sense electrode and the touchpad surface.

7. The data input device as defined in claim 1 wherein the common sense electrode is combined into a single sheet with the first electrode array or the second electrode array, but remains electrically isolated therefrom.

8. The data input device as defined in claim 7 wherein the common sense electrode is further comprised of a plurality of electrodes which are electrically coupled together and which are interdigitated with the plurality of electrode strips of the first electrode array or with the plurality of electrode strips of the second electrode array disposed in the single sheet.

9. The data input device as defined in claim 1 wherein the position of the probe is determinable only when the probe is disposed over an area of the touchpad surface which overlaps the first electrode array, the second electrode array and the common sense electrode.

10. The data input device as defined in claim 1 wherein the measurement means determines the capacitive balances in the pad means for the first electrode array independent of determining the capacitive balances in the pad means for the second electrode array.

11. The data input device as defined in claim 5 wherein the means for selecting which electrode strips are to have capacitive balances measured thereon further comprises means for supplying signals to selected pairs of electrode strips in the first electrode array to thereby form selected virtual dipole electrodes, and for supplying signals to selected pairs of electrode strips in the second electrode array to thereby form selected virtual dipole electrodes, each virtual dipole electrode having a positive half electrode strip and a negative half electrode strip such that electric fields are established between selected halves of one polarity in the first electrode array, and selected halves of the opposite polarity in the second electrode array.

12. The data input device as defined in claim 11 wherein the means for detecting further comprises:

means for successively calculating capacitive balances between selected halves of virtual dipole electrodes in the first electrode array and halves of virtual dipole electrodes in the second electrode array;

means for calculating capacitive balance ratios for selected pairs of calculated capacitive balances; and

means for calculating the position of the probe relative to the pad means from the calculated capacitance balance ratios and the locations of the virtual dipole electrodes producing the calculated capacitive balances.

13. The data input device as defined in claim 12 wherein the data input device is mounted to a keyboard input device of a computer.

14. The data input device as defined in claim 13 wherein the data input device is electrically passive.

15. The data input device as defined in claim 1 wherein the common sense electrode is disposed nearest the touchpad surface.

16. The data input device as defined in claim 1 wherein the common sense electrode is disposed between the first electrode array and the second electrode array.

17. The data input device as defined in claim 1 wherein the common sense electrode is disposed furthest from the touchpad surface relative to the first and the second electrode array.

18. The data input device as defined in claim 1 wherein the interpolation means is further comprised of a linear interpolation means.

19. The data input device as defined in claim 1 wherein the interpolation means is further comprised of a centroid interpolation means.

20. A data input device for sensing a position of a probe relative to a touchpad surface, wherein the data input device comprises:

a pad means for sensing the position of the probe, and wherein the pad means further comprises;

a first electrode array;

a second electrode array disposed beneath the first electrode array in a co-planar arrangement;

a common sense electrode disposed beneath the second electrode array in a co-planar arrangement, and including fringe electric fields between the first electrode array and the common sense electrode and the between the second electrode array and the common sense electrode to thereby develop capacitive balances, wherein the probe disrupts the fringe electric fields when the probe comes in proximity to the pad means, thereby altering the capacitive balances;

measurement means electrically coupled to the pad means for measuring the capacitive balances in the pad means to thereby determine the position of the probe relative to the pad means; and

interpolation means electrically coupled to the measurement means for determining probe position at a resolution which is less than a distance between individual electrodes of the first or the second electrode array.

21. A method for measuring a probe'"'"'s position relative to a touch-sensitive surface, wherein the touch-sensitive surface functions by measuring the probe'"'"'s position utilizing detection of a decrease in mutual capacitance in electrode arrays of the touchpad, said method comprising the steps of:

(1) providing a first electrode array disposed beneath and co-planar with the touch-sensitive surface, wherein the first electrode array measures a decrease in mutual capacitance to detect the probe'"'"'s position;

(2) providing a second electrode array disposed beneath and co-planar with the touch-sensitive surface, wherein the second electrode array measures a decrease in mutual capacitance to detect the probe'"'"'s position;

(3) providing a shared sense electrode disposed beneath and co-planar with the touch-sensitive surface; and

(4) determining the position of the probe utilizing an interpolation algorithm.

22. The method for measuring a probe'"'"'s position as defined in claim 21 wherein the method further comprises the step of disposing the shared sense electrode nearest to the touch-sensitive surface.

23. The method for measuring a probe'"'"'s position as defined in claim 21 wherein the method further comprises the step of disposing the shared sense electrode between the first electrode array and the second electrode array.

24. The method for measuring a probe'"'"'s position as defined in claim 21 wherein the method further comprises the step of disposing the shared sense electrode furthest from the touch-sensitive surface relative to the first electrode array and the second electrode array.

25. The method for measuring a probe'"'"'s position as defined in claim 23 wherein the method further comprises the steps of:

(1) determining a coarse position of the probe independent of the interpolation algorithm; and

(2) determining a fine position of the probe utilizing the interpolation algorithm.

26. The method for measuring a probe'"'"'s position as defined in claim 25 wherein the method further comprises the step of interpolating using linear interpolation.

27. The method for measuring a probe'"'"'s position as defined in claim 25 wherein the method further comprises the step of interpolating using centroid interpolation.

28. A method of measuring a probe'"'"'s position relative to a touch-sensitive surface, said method comprising the steps of:

(1) providing an electrically sensitive touchpad comprising;

insulator means for providing an insulating substrate;

first electrode means for establishing an electrical field;

second electrode means for establishing an electrical field; and

a common sense electrode means for establishing the electrical fields relative to the first electrode means and the second electrode means;

(2) measuring electrical balances between the first and the common sense electrode means;

(3) measuring electrical balances between the second and the common sense electrode means; and

(4) calculating the probe'"'"'s position based on the measured balances between the first electrode means, the second electrode means and the common sense electrode means utilizing an interpolation algorithm.