Unambiguous capacitance sensing using shared inputs

• US 20080079699A1
• Filed: 10/03/2006
• Published: 04/03/2008
• Est. Priority Date: 10/03/2006
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Mackey, Bob Lee
• Granted Patent: US 7,965,281 B2
• Time in Patent Office: Days
• 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
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

Capacitance sensing apparatuses are described. The apparatus includes capacitance sensor elements that traverse a sensing region. The apparatus also includes sensor circuitry that has multiple inputs. More than one of the capacitance sensor elements are electrically coupled to the same input. A position of an object along an axis of the sensing region is unambiguously identified according to which subset of the inputs senses a change in capacitance that is induced when the object is proximate to the sensing region.

Claims

1. A capacitance sensing apparatus comprising:

a first plurality of capacitance sensor elements traversing a sensing region; and

sensor circuitry having a first plurality of inputs, wherein more than one of said capacitance sensor elements are electrically coupled to a same input of said first plurality of inputs;

wherein a position of an object along an axis of said sensing region is identified according to which subset of said inputs senses a change in capacitance that is induced when said object is proximate to said sensing region.

2. The apparatus of claim 1 wherein said capacitance sensor elements have widths that vary along their respective lengths.

3. The apparatus of claim 1 further comprising:

a second plurality of second capacitance sensor elements traversing said sensing region orthogonally to said first plurality of capacitance sensor elements; and

a second plurality of inputs, wherein more than one of said second capacitance sensor elements are coupled to a same input of said second plurality of inputs.

4. The apparatus of claim 1 wherein said subset of inputs uniquely identifies a sub-region of said sensing region, wherein said subset is encoded as a number value that is unique to said sub-region.

5. The apparatus of claim 4 wherein said number value is a binary number.

6. The apparatus of claim 5 wherein said region comprises a plurality of sub-regions, wherein said capacitance sensor elements and said inputs are connected such that adjacent sub-regions are identified by encoded number values that have a Hamming distance of one.

7. The apparatus of claim 5 wherein said region comprises a plurality of sub-regions, wherein said capacitance sensor elements and said inputs are connected such that adjacent sub-regions are identified by encoded number values that have a Hamming distance of at least two.

8. The apparatus of claim 5 wherein said region comprises a plurality of sub-regions, wherein said capacitance sensor elements and said inputs are connected such that adjacent sub-regions are identified by encoded number values that are run length limited with a run length of at least two.

9. The apparatus of claim 1 wherein said subset of inputs uniquely identifies a sub-region of said sensing region, wherein said sub-region is traversed by a plurality of pairs of capacitance sensor elements, wherein both capacitance sensor elements in a pair are electrically coupled to a same input and wherein one capacitance sensor element of said pair is disposed on one side of a line of symmetry that intersects said sub-region and the other capacitance sensor element of said pair is disposed on the other side of said line of symmetry, and wherein said capacitance sensor elements in said sub-region are arranged in a symmetrical pattern according to which of said inputs said capacitance sensor elements are electrically coupled.

10. A method of sensing a position of an object proximate to a sensing region, said method comprising:

sensing measures of capacitance at a first plurality of inputs coupled to a first plurality of capacitance sensor elements that traverse said sensing region, wherein more than one of said capacitance sensor elements are electrically coupled to a same input of said first plurality of inputs, wherein a change in capacitance is induced in one or more of said capacitance sensor elements when said object is proximate to said sensing region; and

comparing capacitance measures between selected combinations of said first plurality of inputs to identify which subset of said inputs senses said change in capacitance, wherein a position of said object along an axis of said sensing region unambiguously corresponds to which of said inputs are members of said subset.

11. The method of claim 10 wherein said capacitance sensor elements have widths that vary along their respective lengths.

12. The method of claim 10 further comprising sensing measures of capacitance at a second plurality of inputs coupled to a second plurality of second capacitance sensor elements that traverses said sensing region orthogonally to said first plurality of capacitance sensor elements, wherein more than one of said second capacitance sensor elements are coupled to a same input of said second plurality of inputs.

13. The method of claim 10 further comprising:

identifying a sub-region of said sensing region using said subset of inputs; and

encoding said subset of inputs as a number value that is unique to said sub-region.

14. The method of claim 10 further comprising identifying a unique sub-region of said sensing region using said subset of inputs, wherein said sub-region is traversed by a plurality of pairs of capacitance sensor elements, wherein both capacitance sensor elements in a pair are electrically coupled to a same input and wherein one capacitance sensor element of said pair is disposed on one side of a line of symmetry that intersects said sub-region and the other capacitance sensor element of said pair is disposed on the other side of said line of symmetry, and wherein said capacitance sensor elements in said sub-region are arranged in a symmetrical pattern according to which of said inputs said capacitance sensor elements are electrically coupled.

15. A capacitance sensing apparatus comprising:

a first plurality of capacitance sensor elements comprising first, second, third and fourth capacitance sensor elements that traverse a sensing region, wherein a change in capacitance is induced in at least one of said capacitance sensor elements when an object is proximate to said sensing region; and

sensor circuitry having a first plurality of inputs comprising first, second, third and fourth inputs;

wherein a comparison of a first measure of capacitance received at said first input and a second measure of capacitance received at said second input is used in setting a value of a first variable, said first and second measures respectively produced by said first and second capacitance sensor elements, and wherein a comparison of a third measure of capacitance sensed at said third input and a fourth measure of capacitance sensed at said fourth input is used in setting a value of a second variable, said third and fourth measures respectively produced by said third and fourth capacitance sensor elements; and

wherein a position along an axis of said sensing region corresponds to said value of said first variable and said value of said second variable.

16. The apparatus of claim 15 wherein said first, second, third and fourth capacitance sensor elements have widths that vary along their respective lengths.

17. The apparatus of claim 15 further comprising a second plurality of second capacitance sensor elements that traverses said sensing region orthogonally to said first plurality of capacitance sensor elements.

18. The apparatus of claim 15 wherein said value of said first variable and said value of said second variable comprise a number value that uniquely identifies a sub-region of said sensing region.

19. The apparatus of claim 15 wherein said value of said first variable and said value of said second variable uniquely identify a sub-region of said sensing region, wherein said sub-region is traversed by a plurality of pairs of capacitance sensor elements, wherein both capacitance sensor elements in a pair are electrically coupled to a same input and wherein one capacitance sensor element of said pair is disposed on one side of a line of symmetry that intersects said sub-region and the other capacitance sensor element of said pair is disposed on the other side of said line of symmetry, and wherein said capacitance sensor elements in said sub-region are arranged in a symmetrical pattern according to which of said inputs said capacitance sensor elements are electrically coupled.

20. A method of determining a position in a sensing region of a capacitance sensing apparatus, said method comprising:

setting a value of a first variable by comparing a first measure of capacitance received at a first input and a second measure of capacitance received at a second input, said first measure produced by a first capacitance sensor element that traverses said sensing region and said second measure produced by a second capacitance sensor element that traverses said sensing region; and

setting a value of a second variable by comparing a third measure of capacitance sensed at a third input and a fourth measure of capacitance sensed at a fourth input, said third measure produced by a third capacitance sensor element that traverses said sensing region and said fourth measure produced by a fourth capacitance sensor element that traverses said sensing region;

wherein a position along an axis of said sensing region corresponds to said value of said first variable and said value of said second variable.

21. The method of claim 20 wherein said first, second, third and fourth capacitance sensor elements have widths that vary along their respective lengths.

22. The method of claim 20 further comprising sensing measures of capacitance at a second plurality of second capacitance sensor elements that traverses said sensing region orthogonally to said first plurality of capacitance sensor elements.

23. The method of claim 20 wherein said value of said first variable and said value of said second variable comprise a number value that uniquely identifies a sub-region of said sensing region.

24. The method of claim 20 wherein said value of said first variable and said value of said second variable uniquely identify a sub-region of said sensing region, wherein said sub-region is traversed by a plurality of pairs of capacitance sensor elements, wherein both capacitance sensor elements in a pair are electrically coupled to a same input and wherein one capacitance sensor element of said pair is disposed on one side of a line of symmetry that intersects said sub-region and the other capacitance sensor element of said pair is disposed on the other side of said line of symmetry, and wherein said capacitance sensor elements in said sub-region are arranged in a symmetrical pattern according to which of said inputs said capacitance sensor elements are electrically coupled.

25. A capacitance sensing apparatus comprising:

sensor circuitry having a plurality of inputs comprising a first input, a second input, a third input and a fourth input; and

a sensing region having a plurality of sub-regions and a first plurality of capacitance sensor elements, said sub-regions comprising a first sub-region comprising a first capacitance sensor element electrically coupled to said second input and a second capacitance sensor element electrically coupled to said fourth input, a second sub-region comprising a third capacitance sensor element electrically coupled to said second input and a fourth capacitance sensor element electrically coupled to said third input, a third sub-region comprising a fifth capacitance sensor element electrically coupled to said first input and a sixth capacitance sensor element electrically coupled to said third input, and a fourth sub-region comprising a seventh capacitance sensor element electrically coupled to said first input and an eighth capacitance sensor element electrically coupled to said fourth input;

wherein a change in capacitance is induced in one or more of said capacitance sensor elements when an object is proximate to said sensing region;

wherein said sensor circuitry compares a first measure of capacitance sensed at said first input and a second measure of capacitance sensed at said second input to set a value for a first variable, and wherein said sensor circuitry compares a third measure of capacitance sensed at said third input and a fourth measure of capacitance sensed at said fourth input to set a value for a second variable; and

wherein a sub-region of said plurality of sub-regions is uniquely identifiable according to values of said first and second variables such that a position of said object along an axis of said sensing region can be determined.

26. The apparatus of claim 25 wherein said capacitance sensor elements have widths that vary along their respective lengths.

27. The apparatus of claim 25 further comprising a second plurality of second capacitance sensor elements that traverses said sensing region orthogonally to said first plurality of capacitance sensor elements.

28. The apparatus of claim 25 wherein said first sub-region further comprises a ninth capacitance sensor element electrically coupled to said second input and a tenth capacitance sensor element electrically coupled to said fourth input, and wherein said first and second capacitance sensor elements are disposed on one side of a line of symmetry that intersects said sub-region and said ninth and tenth capacitance sensor elements are disposed on the other side of said line of symmetry in a mirror-image pattern according to which of said second and fourth inputs said first, second, ninth and tenth capacitance sensor elements are electrically coupled.

29. The apparatus of claim 28 comprising 2N inputs, 2^N sub-regions and N capacitance sensor elements per sub-region, where N is a positive integer.