Capacitive sensing apparatus designs

• US 7,692,431 B2
• Filed: 04/23/2009
• Issued: 04/06/2010
• Est. Priority Date: 01/30/2006
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Mackey, Bob Lee
• Primary Examiner(s): Dole; Timothy J
• Application Number:
  US12/429,097
• Publication Number:
  US 20090206845A1
• Time in Patent Office: 348 Days
• Field of Search: 324/660, 324/662, 324/663, 324/686, 324/688, 345/173, 345/174
• US Class Current: 324/660
• CPC Class Codes: G01D 5/2415 adapted for encoders

Abstract

A capacitive sensing apparatus includes a plurality of electrically conductive sensing elements that have widths that vary and lengths that traverse a sensing region. The sensing elements include a first sensing element including a first variable-width portion and a second variable-width portion that in combination produce a combined first sensor signal, a second sensing element including a third variable-width portion and a fourth variable-width portion that in combination produce a combined second sensor signal, and a third sensing element including a fifth variable-width portion and a sixth variable-width portion that in combination produce a combined third sensor signal. The first, third and fifth variable-width portions are arranged in a first pattern and the second, fourth and sixth variable-width portions are arranged in a second pattern, wherein the first pattern and the second pattern are bilaterally symmetrical about a median that is substantially equidistant from opposite edges of the sensing region.

Claims

1. A capacitive sensing apparatus comprising:

a plurality of electrically conductive sensing elements that have widths that vary and lengths that traverse a sensing region, said sensing elements comprising;

a first sensing element comprising a first variable-width portion and a second variable-width portion that in combination produce a combined first sensor signal;

a second sensing element comprising a third variable-width portion and a fourth variable-width portion that in combination produce a combined second sensor signal; and

a third sensing element comprising a fifth variable-width portion and a sixth variable-width portion that in combination produce a combined third sensor signal;

wherein said first, third and fifth variable-width portions are arranged in a first pattern and said second, fourth and sixth variable-width portions are arranged in a second pattern, wherein said first pattern and said second pattern are bilaterally symmetrical about a median that is substantially equidistant from opposite edges of said sensing region.

2. The capacitive sensing apparatus of claim 1 wherein said first and second variable-width portions are connected to a same first electrical conductor to provide said first sensor signal.

3. The capacitive sensing apparatus of claim 2 wherein said third and fourth variable-width portions are connected to a same second electrical conductor to provide said second sensor signal, and wherein said fifth and sixth variable-width portions are connected to a same third electrical conductor to provide said third sensor signal.

4. The capacitive sensing apparatus of claim 1 wherein a measure of a sensor signal output from said first variable-width portion is added to a measure of a sensor signal output from said second variable-width portion to provide said first sensor signal.

5. The capacitive sensing apparatus of claim 1 further comprising circuitry coupled to said plurality of sensing elements, said circuitry operable to use said first, second and third sensor signals to determine an unambiguous position in a lengthwise dimension of said sensing region.

6. The capacitive sensing apparatus of claim 5 wherein said position is also determined in a widthwise dimension of said sensing region.

7. The capacitive sensing apparatus of claim 1 further comprising circuitry coupled to said plurality of sensing elements, said circuitry operable to use said first, second and third sensor signals to determine a rate of movement of an object proximate to said sensing region.

8. The capacitive sensing apparatus of claim 1 wherein surface areas of said first, second and third sensing elements are substantially equal.

9. The capacitive sensing apparatus of claim 1 wherein said sensing region has one of a ring-shape and a rectangle-shape.

10. A capacitive sensing method comprising:

receiving a first sensor signal output from a first sensing element of a plurality of electrically conductive sensing elements that have widths that vary and lengths that traverse a sensing region, said first sensing element comprising a first variable-width portion and a second variable-width portion that in combination produce said first sensor signal;

receiving a second sensor signal output from a second sensing element of said plurality of electrically conductive sensing elements, said second sensing element comprising a third variable-width portion and a fourth variable-width portion that in combination produce said second sensor signal;

receiving a third sensor signal output from a third sensing element of said plurality of electrically conductive sensing elements, said third sensing element comprising a fifth variable-width portion and a sixth variable-width portion that in combination produce said third sensor signal, wherein said first, third and fifth variable-width portions are arranged in a first pattern and said second, fourth and sixth variable-width portions are arranged in a second pattern, wherein said first pattern and said second pattern are bilaterally symmetrical about a median that is substantially equidistant from opposite edges of said sensing region; and

determining an unambiguous position of an object proximate to said sensing region in a lengthwise dimension of said sensing region using said first, second and third sensor signals.

11. The method of claim 10 further comprising:

determining an unambiguous position of said object in a widthwise dimension of said sensing region using said first, second and third sensor signals.

12. The method of claim 10 further comprising:

determining a rate of movement of said object relative to said plurality of electrically conducting sensing elements using said first, second and third sensor signals.

13. The method of claim 10 further comprising:

adding a measure of a sensor signal output from said first variable-width portion to a measure of a sensor signal output from said second variable-width portion to provide said first sensor signal;

adding a measure of a sensor signal output from said third variable-width portion to a measure of a sensor signal output from said fourth variable-width portion to provide said second sensor signal; and

adding a measure of a sensor signal output from said fifth variable-width portion to a measure of a sensor signal output from said sixth variable-width portion to provide said third sensor signal.

14. The method of claim 10 wherein surface areas of said first, second and third sensing elements are substantially equal.

15. A capacitive sensing system comprising:

a plurality of electrically conductive sensing elements that have widths that vary and lengths that traverse a sensing region, said sensing elements comprising;

a first sensing element comprising a first variable-width portion and a second variable-width portion connected to a same first electrical conductor to produce a first sensor signal;

a second sensing element comprising a third variable-width portion and a fourth variable-width portion connected to a same second electrical conductor to produce a second sensor signal; and

a third sensing element comprising a fifth variable-width portion and a sixth variable-width portion connected to a same third electrical conductor to produce a third sensor signal;

wherein said first, third and fifth variable-width portions are arranged in a first pattern and said second, fourth and sixth variable-width portions are arranged in a second pattern, wherein said first pattern and said second pattern are bilaterally symmetrical about a median that is substantially equidistant from opposite edges of said sensing region; and

sensing circuitry coupled to said plurality of sensing elements, said sensing circuitry operable for receiving said first, second and third sensor signals.

16. The capacitive sensing system of claim 15 wherein said sensing circuitry is operable to use said first, second and third sensor signals to determine an unambiguous position in a lengthwise dimension of said sensing region.

17. The capacitive sensing system of claim 16 wherein said unambiguous position is also determined in a widthwise dimension of said sensing region.

18. The capacitive sensing system of claim 15 wherein said circuitry is operable to use said first, second and third sensor signals to determine a rate of movement of an object proximate to said sensing region.

19. The capacitive sensing system of claim 15 wherein surface areas of said first, second and third sensing elements are substantially equal.

20. The capacitive sensing system of claim 15 wherein said sensing region has one of a ring-shape and a rectangle-shape.