Method of increasing the spatial resolution of touch sensitive devices

• US 7,932,897 B2
• Filed: 08/15/2005
• Issued: 04/26/2011
• Est. Priority Date: 08/16/2004
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Orr, James Edmund IV, Elias, John Greer, Westerman, Wayne Carl
• Primary Examiner(s): Nguyen; Chanh
• Assistant Examiner(s): JOHNSON, ALLISON WALTHALL
• Application Number:
  US11/203,692
• Publication Number:
  US 20060032680A1
• Time in Patent Office: 2,080 Days
• Field of Search: 345173-174, 178/18.03, 178/18.06, 178 2001- 2004, 178/18.01, 178/18.05
• US Class Current: 345/174
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

Disclosed herein is a capacitive touch sensitive device. One aspect of the touch sensitive device described herein is a reduction in the number of sensor circuits needed for circular or linear capacitive touch sensitive devices while maintaining the same resolution and absolute position determination for a single object. A related aspect of the touch sensitive device described herein a coding pattern that allows each sensor circuit of a capacitive touch sensitive device to share multiple electrodes at specially chosen locations in a sensor array such that the ability to determine the absolute position of a single object over the array is not compromised.

Claims

1. A touch sensitive device configured to track a finger, the device comprising:

a first plurality of touch sensitive electrodes, each of the touch sensitive electrodes being associated with one of at least a first electrode group and a second electrode group; and

a second plurality of sense circuits,

wherein the second plurality of sense circuits is less than the first plurality of touch sensitive electrodes such that at least one sense circuit is shared between more than one of the touch sensitive electrodes;

wherein each of the touch sensitive electrodes that share the at least one sense circuit are spatially separated from each other by a dispersal distance and are associated with a different one of the first and second electrode groups,

wherein each of the touch sensitive electrodes is directly connected to the at least one sense circuit through a common conductor without multiplexing switches,

wherein the touch sensitive electrodes are configured to enable the finger to overlap multiple adjacent electrodes and the dispersal distance is large enough to prevent the finger from overlapping the touch sensitive electrodes that share a sense circuit,

wherein the plurality of sense circuits are configured to be scanned to collect a signal value corresponding to each of the plurality of sense circuits,

wherein a sense circuit having a maximum signal value and first and second touch sensitive electrodes that share the sense circuit having the maximum signal value are identified,

the first and second identified touch sensitive electrodes being spatially separated from each other by a dispersal distance and being associated with a different one of the first and second electrode groups,

wherein one of the first and second identified touch sensitive electrodes is identified as a touched electrode by comparing a signal strength of electrodes on either side of the first identified touch sensitive electrode with a signal strength of electrodes on either side of the second identified touch sensitive electrode, and

wherein a centroid of the finger being tracked is computed with reference to the touched electrode.

2. The touch sensitive device of claim 1 wherein the dispersal distance is approximately one-third of a characteristic dimension of the touch sensitive device.

3. The touch sensitive device of claim 1 wherein each sense circuit is directly connected to two touch sensitive electrodes.

4. The touch sensitive device of claim 1 wherein the plurality of touch sensitive electrodes are arranged in a circular array.

5. The touch sensitive device of claim 4 wherein the dispersal distance is approximately one-third the circumference of the circular array.

6. The touch sensitive device of claim 4 wherein each sense circuit is directly connected to two touch sensitive electrodes.

7. The touch sensitive device of claim 1 wherein the touch sensitive electrodes are arranged in a linear array.

8. The touch sensitive device of claim 7 wherein the dispersal distance is approximately one-third the length of the linear array.

9. A method of tracking a finger used in conjunction with a touch sensitive device, wherein the touch sensitive device comprises a plurality of electrodes and a plurality of sense circuits, wherein each of the electrodes is associated with one of at least a first electrode group and a second electrode group and wherein at least one of the sense circuits is directly connected to more than one electrode through a common conductor without multiplexing switches, the method comprising:

configuring the electrodes to enable the finger to overlap multiple adjacent electrodes;

spatially separating each of the electrodes that share a sense circuit by a dispersal distance large enough to prevent the finger from overlapping the electrodes that share the sense circuit and associating each of the electrodes that share a sense circuit with a different one of the first and second electrode groups;

scanning the plurality of sense circuits to collect a signal value corresponding to each of the plurality of sense circuits;

identifying, from the plurality of sense circuits, a sense circuit having a maximum signal value and first and second electrodes that share the sense circuit having the maximum signal value, the first and second identified electrodes being spatially separated from each other by a dispersal distance and being associated with a different one of the first and second electrode groups;

identifying one of the first and second identified electrodes as a touched electrode by comparing a signal strength of electrodes on either side of the first identified electrode with a signal strength of electrodes on either side of the second identified electrode; and

computing a centroid of the finger being tracked with reference to the touched electrode.

10. The method of claim 9 wherein sensor and electrode mappings required for identifying the sense circuit and identifying the electrode are stored in look up tables.

11. A capacitive touch sensitive device configured to determine a position of a finger, the device comprising:

a first plurality of electrodes arranged in an array, the array having at least a first dimension, each of the electrodes being associated with one of at least a first electrode group and a second electrode group,

a second plurality of sensor circuits, the first plurality of electrodes being greater than the second plurality of sensor circuits,

each sensor circuit being associated with at least two non-adjacent electrodes, the two non-adjacent electrodes being spaced by a dispersal distance equal to less than half of the first dimension and being associated with a different one of the first and second electrode groups,

wherein at least one of the sensor circuits is directly connected to more than one electrode through a common conductor without multiplexing switches,

wherein the electrodes are configured to enable the finger to overlap multiple adjacent electrodes and the dispersal distance is large enough to prevent the finger from overlapping the non-adjacent electrodes associated with the sensor circuit,

wherein the plurality of sense circuits are configured to be scanned to collect a signal value corresponding to each of the plurality of sense circuits,

wherein a sense circuit having a maximum signal value and first and second electrodes that share the sense circuit having the maximum signal value are identified,

the first and second identified electrodes being spatially separated from each other by a dispersal distance and being associated with a different one of the first and second electrode groups,

wherein one of the first and second identified electrodes is identified as a touched electrode by comparing a signal strength of electrodes on either side of the first identified electrode with a signal strength of electrodes on either side of the second identified electrode, and

wherein a centroid of the finger being tracked is computed with reference to the touched electrode.

12. The device of claim 11 wherein the first plurality of electrodes is equal to twice the second plurality of sensor circuits.

13. The device of claim 11 wherein the dispersal distance is equal to approximately one-third the first dimension.

14. The device of claim 11 wherein approximately one third of the electrodes are disposed between the two non-adjacent electrodes.

15. A method of tracking a finger using the device of claim 11, the method comprising:

identifying a sensor circuit associated with a maximum signal value,

identifying an electrode associated with a maximum signal value, the electrode corresponding to the sensor circuit having a maximum signal value, wherein the sensor circuit is directly connected to the electrode through a common conductor without multiplexing switches, and

computing a centroid of the finger being tracked with reference to the electrode having the maximum signal value and adjacent electrodes.

16. A method of tracking a finger used in conjunction with a touch sensitive device,

the touch sensitive device comprising multiple electrodes and multiple sense circuits, the multiple electrodes being individually associated with one of at least a first electrode group and a second electrode group, at least one of the sense circuits being connected to more than one electrode through a common conductor, the electrodes configured to enable the finger to overlap multiple adjacent electrodes, the touch sensitive electrodes that share a sense circuit being spatially separated from each other by a dispersal distance large enough to prevent the finger from overlapping the touch sensitive electrodes that share a sense circuit, and the electrodes that share a sense circuit being associated with a different one of the first and second electrode groups,

the method comprising:

scanning the multiple sense circuits to collect signal values corresponding to the multiple sense circuits,

identifying, from the multiple sense circuits, a sense circuit having a maximum signal value and first and second electrodes that share the sense circuit having the maximum signal value, the first and second identified electrodes being spatially separated from each other by a dispersal distance and being associated with a different one of the first and second electrode groups,

identifying one of the first and second identified electrodes as a touched electrode by comparing a signal strength of electrodes on either side of the first identified electrode with a signal strength of electrodes on either side of the second identified electrode, and

computing a centroid of the finger being tracked with reference to the touched electrode.

17. The method of claim 16 wherein the multiple electrodes are arranged in a circle and a portion of the electrodes in the first group are adjacent other electrodes in the first group and a portion of the electrodes in the first group are adjacent electrodes in the second group.

18. A capacitive touch sensitive device configured to determine a position of a finger, the device comprising:

multiple electrodes arranged in an array, the multiple electrodes being individually associated with one of at least a first electrode group and a second electrode group,

multiple sensor circuits, the multiple electrodes being greater in number than the multiple sensor circuits,

individual sensor circuits being associated with at least two non-adjacent electrodes, the two non-adjacent electrodes being spaced by a dispersal distance equal to less than half of a first dimension and being associated with a different one of the first and second electrode groups,

at least one of the sensor circuits being connected to more than one electrode through a common conductor,

the electrodes being configured to enable the finger to overlap multiple adjacent electrodes and the dispersal distance being large enough to prevent the finger from overlapping the non-adjacent electrodes associated with the sensor circuit,

the multiple sense circuits being configured to be scanned to collect a signal value corresponding to each of the multiple of sense circuits,

wherein a sense circuit having a maximum signal value and first and second electrodes that share the sense circuit having the maximum signal value are identified, the first and second identified electrodes being spatially separated from each other by a dispersal distance and being associated with a different one of the first and second electrode groups,

wherein one of the first and second identified electrodes is identified as a touched electrode by comparing a signal strength of electrodes on either side of the first identified electrode with a signal strength of electrodes on either side of the second identified electrode, and

wherein a centroid of the finger being tracked is computed with reference to the touched electrode.

19. The device of claim 18 wherein the multiple electrodes are arranged in a circle and a portion of the electrodes in the first group are adjacent other electrodes in the first group and a portion of the electrodes in the first group are adjacent electrodes in the second group.

20. A capacitive touch sensitive device configured to determine a position of a finger, the device comprising:

multiple electrodes arranged in a circle, each multiple electrode being associated with a first electrode group or a second electrode group, a portion of the electrodes in the first group being adjacent other electrodes in the first group and a portion of the electrodes in the first group being adjacent electrodes in the second group,

multiple sensor circuits, individual sensor circuits being associated with at least two non-adjacent electrodes spaced by a dispersal distance and associated with a different one of the first and second electrode groups,

at least one of the sensor circuits being connected to more than one electrode through a common conductor,

the electrodes being configured to enable the finger to overlap multiple adjacent electrodes and the dispersal distance being large enough to prevent the finger from overlapping the non-adjacent electrodes associated with the sensor circuit,

the multiple sense circuits being configured to be scanned to collect a signal value corresponding to each of the multiple of sense circuits,

wherein a sense circuit having a maximum signal value and first and second electrodes that share the sense circuit having the maximum signal value are identified, the first and second identified electrodes being spatially separated from each other by a dispersal distance and being associated with a different one of the first and second electrode groups,

wherein one of the first and second identified electrodes is identified as a touched electrode by comparing a signal strength of electrodes on either side of the first identified electrode with a signal strength of electrodes on either side of the second identified electrode, and

wherein a centroid of the finger being tracked is computed with reference to the touched electrode.