Unambiguous capacitance sensing using shared inputs

• US 7,965,281 B2
• Filed: 10/03/2006
• Issued: 06/21/2011
• Est. Priority Date: 10/03/2006
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Mackey, Bob Lee
• Primary Examiner(s): Liang; Regina
• Application Number:
  US11/543,397
• Publication Number:
  US 20080079699A1
• Time in Patent Office: 1,722 Days
• Field of Search: 345173-179, 178/18.01, 178/18.06, 178/18.03
• 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 comprising first, second, third and fourth capacitance sensor elements that traverse a region, wherein a change in capacitance is induced in at least one of said capacitance sensor elements when an object is proximate to said 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 region corresponds to said value of said first variable and said value of said second variable.

2. The apparatus of claim 1 wherein said first, second, third and fourth 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 that traverses said region orthogonally to said first plurality of capacitance sensor elements.

4. The apparatus of claim 1 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 region.

5. The apparatus of claim 1 wherein said value of said first variable and said value of said second variable uniquely identify a sub-region of said 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.

6. A method of determining a position in a 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 region and said second measure produced by a second capacitance sensor element that traverses said 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 region and said fourth measure produced by a fourth capacitance sensor element that traverses said region;

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

7. The method of claim 6 wherein said first, second, third and fourth capacitance sensor elements have widths that vary along their respective lengths.

8. The method of claim 6 further comprising sensing measures of at a second plurality of second capacitance sensor elements that traverses said region orthogonally to said first plurality of capacitance sensor elements.

9. The method of claim 6 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 region.

10. The method of claim 6 wherein said value of said first variable and said value of said second variable uniquely identify a sub-region of said 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.

11. A 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 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 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 region can be determined.

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

13. The apparatus of claim 11 further comprising a second plurality of second capacitance sensor elements that traverses said region orthogonally to said first plurality of capacitance sensor elements.

14. The apparatus of claim 11 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.

15. The apparatus of claim 14 comprising 2N inputs, 2^N sub-regions and N capacitance sensor elements per sub-region, where N is a positive integer.

16. A capacitance sensing apparatus comprising:

capacitance sensor elements traversing a region, wherein said capacitance sensor elements are configured with widths that vary along their respective lengths to identify a position of said object along a second axis of said 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 a first axis of said region is identified according to which subset of a plurality of subsets of said first plurality of inputs senses a change in capacitance that is induced when said object is proximate to said region, and

wherein said capacitance sensor elements are configured for identifying a position of said object along a second axis of said region, said second axis being non-parallel to said first axis.

17. The capacitance sensing apparatus of claim 16 wherein said capacitance sensor elements, which are configured for identifying a position of said object along a second axis of said region, comprise capacitance sensor elements that are disposed non-parallel to said first axis;

and

a second plurality of inputs, wherein more than one of said capacitance sensor elements that are disposed non-parallel to said first axis are coupled to a same input of said second plurality of inputs.

18. A capacitance sensing apparatus comprising:

capacitance sensor elements traversing a 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 subset of said first plurality of inputs uniquely identifying a sub-region of said region, wherein said subset of said first plurality of inputs is encoded as a number value that is unique to said sub-region,

wherein a position of an object along a first axis of said region is identified according to which subset of a plurality of subsets of said first plurality of inputs senses a change in capacitance that is induced when said object is proximate to said region, and

wherein said capacitance sensor elements are configured for identifying a position of said object along a second axis of said region, said second axis being non-parallel to said first axis.

19. The capacitance sensing apparatus of claim 18 wherein said number value is a binary number.

20. The capacitance sensing apparatus of claim 19 wherein said region comprises a plurality of sub-regions, wherein said capacitance sensor elements and said first plurality of inputs are connected such that adjacent sub-regions of said plurality of sub-regions are identified by encoded number values that have a Hamming distance of one.

21. The capacitance sensing apparatus of claim 19 wherein said region comprises a plurality of sub-regions, wherein said capacitance sensor elements and said first plurality of inputs are connected such that adjacent sub-regions of said plurality of sub-regions are identified by encoded number values that have a Hamming distance of at least two.

22. The capacitance sensing apparatus of claim 19 wherein said region comprises a plurality of sub-regions, wherein said capacitance sensor elements and said first plurality of inputs are connected such that adjacent sub-regions of said plurality of sub-regions are identified by encoded number values that are run length limited with a run length of at least two.

23. A capacitance sensing apparatus comprising:

capacitance sensor elements traversing a 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 subset of said first plurality of inputs uniquely identifies a sub-region of said region, wherein said sub-region is traversed by a plurality of pairs of capacitance sensor elements, wherein both capacitance sensor elements in a pair of said plurality of pairs are electrically coupled to a same input of said subset 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 capacitance sensor elements of said plurality of pairs in said sub-region are arranged in a symmetrical pattern according to which inputs of said subset of inputs said capacitance sensor elements of said plurality of pairs are electrically coupled,

wherein a position of an object along a first axis of said region is identified according to which subset of a plurality of subsets of said first plurality of inputs senses a change in that is induced when said object is proximate to said region, and

wherein said capacitance sensor elements are configured for identifying a position of said object along a second axis of said region, said second axis being non-parallel to said first axis.

24. A method of sensing a position of an object proximate to a 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 region, wherein more than one capacitance sensor element of said capacitance sensor elements are electrically coupled to a same input of said first plurality of inputs, wherein said capacitance sensor elements have widths that vary along their respective lengths, wherein a change in capacitance is induced in one or more of said more than one capacitance sensor element of said capacitance sensor elements when said object is proximate to said region; and

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

25. The method of claim 24 further comprising sensing measures of capacitance at a second plurality of inputs coupled to a second plurality of capacitance sensor elements that traverses said region orthogonally to said first plurality of capacitance sensor elements, wherein more than one of said second plurality of capacitance sensor elements are coupled to a same input of said second plurality of inputs.

26. A method of sensing a position of an object proximate to a 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 region, wherein more than one capacitance sensor element 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 more than one capacitance sensor element of said capacitance sensor elements when said object is proximate to said region;

comparing capacitance measures between selected combinations of said first plurality of inputs to identify which subset of said first plurality of inputs senses said change in capacitance;

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

encoding said subset of said first plurality of inputs as a number value that is unique to said sub-region, wherein a position of said object along an axis of said region unambiguously corresponds to which of said first plurality of inputs are members of said subset.

27. A method of sensing a position of an object proximate to a 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 region, wherein more than one capacitance sensor element 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 more than one capacitance sensor element of said capacitance sensor elements when said object is proximate to said region;

comparing capacitance measures between selected combinations of said first plurality of inputs to identify which subset of said first plurality of inputs senses said change in capacitance; and

identifying a unique sub-region of said region using said subset of said first plurality of inputs, wherein said sub-region is traversed by a plurality of pairs of said first plurality of capacitance sensor elements, wherein both capacitance sensor elements in a pair of said plurality of pairs are electrically coupled to a same input of said subset 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 capacitance sensor elements of said plurality of pairs in said sub-region are arranged in a symmetrical pattern according to which inputs of said subset of inputs said capacitance sensor elements of said plurality of pairs are electrically coupled, wherein a position of said object along an axis of said region unambiguously corresponds to which of said first plurality of inputs are members of said subset.