Method of increasing the spatial resolution of touch sensitive devices

• US 20060032680A1
• Filed: 08/15/2005
• Published: 02/16/2006
• Est. Priority Date: 08/16/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: FingerWorks Limited (Apple Inc.)
• Inventors: Westerman, Wayne Carl, Orr, James Edmund IV, Elias, John Greer
• Granted Patent: US 7,932,897 B2
• Time in Patent Office: Days
• US Class Current: 178/18.60
• 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 comprising:

a plurality of touch sensitive electrodes; and

a number of sense circuits, wherein the number of sense circuits is less than the number 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 a sense circuit are spatially separated from each other by a dispersal distance and wherein each touch sensitive electrode is directly connected to a sense circuit.

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 an object used in conjunction a touch sensitive device, wherein the touch sensitive device comprises a plurality of electrodes and a plurality of sense circuits, wherein at least one of the sense circuits is directly connected to more than one electrode, the method comprising:

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

identifying a sense circuit having a maximum signal value;

identifying an electrode having a maximum signal value, the electrode corresponding to the sense circuit having a maximum signal value; and

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

10. The method of claim 9 wherein sensor and electrode mappings required for identifying a sense circuit having a maximum signal value and identifying an electrode having a maximum signal value are stored in look up tables.

11. The method of claim 9 wherein identifying an electrode having a maximum signal value comprises:

picking out each electrode associated with the sense circuit having a maximum signal value;

finding each electrode adjacent the electrodes associated with the sense circuit having a maximum signal value;

comparing signal values associated with the adjacent electrodes; and

identifying the electrode having a maximum signal by selecting the electrode having adjacent electrodes with the highest signal value.