OBJECT POSITION SENSING APPARATUS

• US 20090322355A1
• Filed: 06/27/2008
• Published: 12/31/2009
• Est. Priority Date: 06/27/2008
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Day, Shawn P., Ely, David, Mackey, Bob L.
• Granted Patent: US 8,120,371 B2
• Time in Patent Office: Days
• US Class Current: 324/691
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• 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 3/0443 using a single layer of sensing electrodes

Abstract

An object position sensing apparatus including a substrate, a conductive crossbar, and a plurality of resistive elements coupled to the crossbar is described. The resistive elements are coupled to circuitry that can apply an excitation signal, such as a voltage change, to the resistive elements. For each resistive element, an electrical effect responsive to the excitation signal, such as a change in charge flowing to the resistive element, is determined. When an object is proximate to the plurality of resistive elements, the electrical effects change, and a position of the object in one or multiple dimensions can be determined from changes in the electrical effects.

Claims

1. An object position sensing apparatus having a sensing region, said object position sensing apparatus comprising:

a substrate;

a conductive crossbar disposed on said substrate;

a plurality of elongate resistive elements disposed on said substrate, each of said plurality of elongate resistive elements having a first end coupled to said crossbar and a second end; and

circuitry, wherein each of said plurality of elongate resistive elements is coupled to said circuitry at said second end, and wherein said circuitry is configured for

concurrently applying a voltage change to each of said plurality of elongate resistive elements, and

determining an amount of charge flowing to each of said plurality of elongate resistive elements due to said voltage change.

2. The apparatus of claim 1 further comprising a common trace coupled with said conductive crossbar and said circuitry.

3. The apparatus of claim 1 wherein said circuitry is further configured for determining a position of said object in a first dimension of said sensing region based on said amount of charge flowing to each of said plurality of elongate resistive elements.

4. The apparatus of claim 1 wherein said conductive crossbar is made from a? same resistive material as said elongate resistive elements.

5. The apparatus of claim 1 further comprising a separate conductor, wherein said separate conductor electrically couples to both a first end portion of said conductive crossbar and a second end portion of said conductive crossbar.

6. The apparatus of claim 5 wherein said separate conductor establishes an electrical path such that an electrical resistance between a first elongate resistive element and a second elongate resistive element adjacent to said first elongate resistive element is substantially the same as an electrical resistance between said first elongate resistive element and a third elongate resistive element non-adjacent to said first elongate resistive element.

7. The apparatus of claim 1 further comprising a guard resistive element disposed adjacent to said plurality of elongate resistive elements.

8. The apparatus of claim 1 further comprising a plurality of electrical resistors coupled between said plurality of elongate resistive elements and said conductive crossbar.

9. The apparatus of claim 8 wherein said electrical resistors and said elongate resistive elements are made of a same resistive material.

10. The apparatus of claim 1 wherein said circuitry is further configured to determine a position of said object in a first dimension of said sensing region by:

interpolating said position using variations in electrical charge flow due to said object in said sensing region for at least a first elongate resistive element of said plurality of resistive elements and a second elongate resistive element of said plurality of resistive elements, wherein said first resistive element has a greatest change in electrical charge due to said object and said second resistive element is proximate to said first resistive element.

11. The apparatus of claim 1 wherein said circuitry is further configured to determine a position of said object in a first dimension of said sensing region based on a ratio comparing n*K to L, wherein n is a total count of said plurality of elongate resistive elements and K is a variation in said amount of charge flowing to one of said plurality of elongate resistive elements substantially uninfluenced by said object, such that n*k is a product of these two values, and wherein L substantially totals all variations in said amounts of charge flowing to each of said plurality of resistive elements

12. The apparatus of claim 2 wherein said circuitry is further configured to determine a position of said object in a first dimension of said sensing region by comparing a variation in a total amount of charge flowing to said plurality of resistive elements without flowing through said common trace with a variation in a total amount of charge flowing through said common trace to said plurality of resistive elements.

13. The apparatus of claim 1 wherein said circuitry is also operable for one of testing said plurality of elongate resistive elements for electrical continuity and ascertaining correction factors for determining a position of an object in said sensing region.

14. The apparatus of claim 1 wherein said substrate and said plurality of elongate resistive elements are transparent.

15. An object position sensing apparatus having a sensing region, said object position sensing apparatus comprising:

a substrate; and

a comb-shaped sensor array disposed on said substrate, said comb-shaped sensor array comprising;

a conductive crossbar;

a plurality of resistive elements, wherein a first end of each of said plurality of resistive elements is electrically coupled with said conductive crossbar; and

circuitry, wherein a second end of each of said plurality of resistive elements is electrically coupled to said circuitry, and wherein said circuitry is configured for

concurrently applying an excitation signal to each of said plurality of resistive elements, and

determining an electrical effect due to said excitation signal for each of said plurality of resistive elements.

16. The electronic system of claim 15, wherein said circuitry of said object position sensing apparatus is configured to concurrently apply an excitation signal to each of said plurality of elongate resistive elements by applying a voltage change, and wherein said circuitry of said object position sensing apparatus is configured to determine an electrical effect for each of said plurality of elongate resistive elements by determining an amount of charge flowing to each of said plurality of elongate resistive elements.

17. The electronic system of claim 15, wherein said circuitry of said object position sensing apparatus is configured to concurrently apply an excitation signal to each of said plurality of elongate resistive elements by supplying a current, and wherein said circuitry of said object position sensing apparatus is configured to determine an electrical effect for each of said plurality of elongate resistive elements by determining a voltage for each of said plurality of elongate resistive elements.

18. The apparatus of claim 15 further comprising a common trace coupled to both said crossbar and said circuitry.

19. The apparatus of claim 15 further comprising a separate conductor that electrically couples a first end portion of said crossbar to a second end portion of said crossbar.

20. The apparatus of claim 15 further comprising a guard resistive element disposed on said substrate, wherein said guard resistive element is disposed proximate to said plurality of resistive elements.

21. The apparatus of claim 15 further comprising a plurality of electrical resistors coupled between said plurality of resistive elements and said crossbar.

22. The apparatus of claim 15 wherein said circuitry is further configured for determining a position of an object in said sensing region by:

determining changes in said electrical effect caused by said object for at least two resistive elements of said plurality of resistive elements, and

interpolating said position using said changes.

23. The apparatus of claim 15 wherein said circuitry is further configured for determining a position of an object in said sensing region by:

determining changes in said electrical effect caused by said object for at least two resistive elements of said plurality of resistive elements, and

identifying a location of greatest electrical effect change as said position.

24. The apparatus of claim 15 wherein said circuitry is further configured for determining a position of an object in said sensing region by examining a ratio of changes in said electrical effect due to said object.

25. A method of determining a position of an object proximate to a comb-shaped sensor, said method comprising:

concurrently applying a voltage change to a plurality of resistive elements that form portions of said comb-shaped sensor;

measuring a change in electrical charge per resistive element for each of said plurality of resistive elements; and

using said change in electrical charge per resistive element to determine said position of said object relative to said sensing region.

26. The method of claim 25, further comprising:

ascertaining correction factors for determining said position of said object in said sensing region.

27. The method of claim 25 wherein using said change in electrical charge per resistive element to determine said position of said object relative to said sensing region comprises:

interpolating said position using said change in electrical charge per resistive element for at least a first resistive element of said plurality of resistive elements and second resistive element of said plurality of resistive elements, wherein said first resistive element has a greatest change in electrical charge due to said object and said second resistive element is proximate to said first resistive element.

28. The method of claim 25 wherein using said change in electrical charge per resistive element to determine said position of said object relative to said sensing region further comprises:

identifying a location of estimated greatest change in electrical charge due to said object as said position.

29. The method of claim 25 wherein using said change in electrical charge per resistive element to determine said position of said object relative to said sensing region further comprises:

examining a ratio involving said change in electrical charge per resistive element.

30. The method of claim 29, wherein determining said position along a second dimension by examining a ratio involving said change in electrical charge per resistive element comprises:

comparing n*K to L, wherein n is a total count of said plurality of resistive elements and K is a change in electrical charge for one of said plurality of resistive elements substantially uninfluenced by said object, such that n*k is a product of these two values, and wherein L substantially totals all changes in electrical charge per resistive element for said plurality of resistive elements

31. The method of claim 29, wherein determining said position along a second dimension by examining a ratio involving said change in electrical charge per resistive element comprises:

comparing a total amount of charge flowing to said plurality of resistive elements without flowing through said common trace with a variation in a total amount of charge flowing through said common trace to said plurality of resistive elements.

32. An electronic system comprising:

a processor;

a memory coupled to said processor; and

an object position sensing apparatus coupled to said processor and having a sensing region, said object position sensing apparatus comprising;

a substrate,

a plurality of elongate resistive elements disposed on said substrate,

a crossbar connected to said plurality of resistive elements, wherein a first end of each of said plurality of resistive elements is coupled to said crossbar, and

circuitry, wherein a second end of each of said plurality of resistive elements is coupled to said circuitry, and wherein said circuitry is configured to

concurrently apply an excitation signal to each of said plurality of elongate resistive elements,

determine an electrical effect for each of said plurality of elongate resistive elements due to said excitation signal, and

determine a position of an object in said sensing region based on changes in said electrical effect due to said object.

33. The electronic system of claim 32, wherein said object position sensing apparatus is substantially transparent, said electronic system further comprising:

a display device positioned under said object position sensing apparatus such that material shown by the display device is viewable through said object position sensing apparatus.