Sensor with diffusing resistor

• US 9,921,696 B2
• Filed: 09/26/2015
• Issued: 03/20/2018
• Est. Priority Date: 04/24/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hotelling, Steven P., Pant, Vivek, Bugnait, Prathit, Chan, Isaac
• Primary Examiner(s): HONG, RICHARD J
• Application Number:
  US14/866,846
• Publication Number:
  US 20160313825A1
• Time in Patent Office: 906 Days
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Electrode configurations for reducing wobble error for a stylus translating on a surface over and between electrodes of a touch sensor panel is disclosed. In some examples, electrodes associated with a more linear signal profile are correlated with lower wobble error. In some examples, electrodes are coupled to adjacent electrodes via diffusing resistors such that the signal profile for each electrode is spread to be more linear. In some configurations, the value of the diffusing resistors and series resistance associated with an electrode is selected based on a desired signal profile for that electrode. In some examples, the series resistance can include a trace resistance and a compensating resistance. The compensating resistance can compensate for a variance in trace resistance between electrodes, thus making series resistance substantially equal for each of the electrodes.

Claims

1. An apparatus comprising:

a touch sensor panel including;

a plurality of sense electrodes, including a first sense electrode and a second sense electrode;

a plurality of diffusing resistors, including a first diffusing resistor coupled between the first sense electrode and the second sense electrode;

a plurality of conductive traces, including a first conductive trace coupling the first sense electrode to the sense circuitry, and a second conductive trace coupling the second sense electrode to the sense circuitry;

a plurality of compensating resistances, including a first compensating resistance in series with the first conductive trace and a second compensating resistance in series with the second conductive trace; and

sense circuitry coupled to the first and second sense electrodes and configured to detect a touch signal using the first sense electrode and the second sense electrode,

wherein;

a first series resistance associated with the first conductive trace and the first compensating resistor is substantially equal to a common series resistance; and

a second series resistance associated with the second conductive trace and the second compensating resistor is substantially equal to the common series resistance.

2. The apparatus of claim 1, wherein:

the first sense electrode and second sense electrode of the plurality of sense electrodes are formed on a first layer of a first conductive material; and

the first diffusing resistor is formed on the first layer of the first conductive material.

3. The apparatus of claim 1, wherein the touch sensor panel includes:

a third sense electrode of the plurality of sense electrodes;

a second diffusing resistor coupled between the first sense electrode and the third sense electrode;

wherein

the second sense electrode is proximate to the first sense electrode in a first direction, and the third sense electrode is proximate to the first sense electrode in a second direction different from the first.

4. The apparatus of claim 1, wherein:

the first sense electrode of the plurality of sense electrodes includes a plurality of component electrodes.

5. The apparatus of claim 4, wherein the touch sensor panel includes:

a second diffusing resistor of the plurality of diffusing resistors coupled between at least two component electrodes of the plurality of component electrodes of the first sense electrode.

6. The apparatus of claim 1, wherein:

the first compensating resistor is formed of a first segment of conductive material, the first segment of conductive material having a first cross sectional area; and

the second compensating resistor is formed of a second segment of conductive material, the second segment of conductive material having a second cross sectional area, different than the first cross sectional area;

the first compensating resistance is different than the second compensating resistance.

7. The apparatus of claim 6, wherein:

the conductive material forming the first segment is a different conductive material than a conductive material forming the first conductive trace.

8. The apparatus of claim 7, wherein:

the conductive material forming the first segment has a lower conductivity than a conductivity of the conductive material forming the first conductive trace.

9. The apparatus of claim 7, wherein:

the conductive material forming the first segment has a conductivity at least 1000 times lower than a conductivity of the conductive material forming the first conductive trace.

10. The apparatus of claim 6, wherein:

the first segment of conductive material is formed by removing portions of a first larger segment of conductive material having a pre-determined cross sectional area;

the second segment of conductive material is formed by removing portions of a second larger segment of conductive material having the pre-determined cross sectional area.

11. The apparatus of claim 1, wherein:

the common series resistance is substantially equal to a largest conductive trace resistance associated with one of the plurality of conductive traces.

12. The apparatus of claim 1, wherein:

the plurality of diffusing resistors substantially share a diffusing resistance; and

the diffusing resistance is selected such that the diffusing resistance and the common series resistance satisfy a threshold ratio between the diffusing resistance and the common series resistance.

13. The apparatus of claim 12, wherein the threshold ratio between the diffusing resistance and the common series resistance is greater than 3.

14. The apparatus of claim 12, wherein the threshold ratio between the diffusing resistance and the common series resistance is greater than 3 and less than 8.

15. The apparatus of claim 12, wherein the threshold ratio between the diffusing resistance and the common series resistance is greater than 3 and less than 5.

16. The apparatus of claim 12, wherein:

the first sense electrode is configured to receive a signal from an object; and

the threshold ratio between the diffusing resistance and the common series resistance is selected such that the first sense electrode diffuses a first portion of the signal to the second sense electrode, the first portion having more than 5 percent of the signal.

17. The apparatus of claim 16, wherein:

a third sense electrode is adjacent to the second sense electrode and distal to the first sense electrode; and

the threshold ratio between the diffusing resistance and the common series resistance is selected such that the second sense electrode diffuses less than 10 percent of the first portion of the signal to a third sense electrode.

18. A method for detecting an object proximate to a touch sensor panel, the method comprising:

detecting, at a first sense electrode, a first portion of a signal originating from a coupling between the first sense electrode and the object;

detecting, at a second sense electrode, a second portion of the signal originating from the coupling between the first sense electrode and the object, wherein the second portion of the signal is diffused by a diffusing resistance from the first sense electrode to the second sense electrode; and

determining a location of the object from the first and second portions of the signal at sense circuitry,

wherein;

a first conductive trace couples the first sense electrode to the sense circuitry and a second conductive trace couples the second sense electrode to the sense circuitry;

a first compensating resistance in series with the first conductive trace wherein a first series resistance associated with the first conductive trace and the first compensating resistor is substantially equal to a common series resistance;

and a second compensating resistance in series with the second conductive trace wherein a second series resistance associated with the second conductive trace and the second compensating resistor is substantially equal to the common series resistance.

19. The method of claim 18, wherein the second portion of the signal contains at least 5 percent of the signal.

20. The method of claim 19, further comprising:

detecting, at a third sense electrode, a third portion of the signal originating from the coupling between the first sense electrode and the object, wherein;

the third portion of the signal is diffused from the second sense electrode to the third sense electrode through a second diffusing resistor coupled between the second sense electrode and the third sense electrode; and

the third portion of the signal contains less than 1 percent of the signal.

21. The method of claim 18, further comprising:

selecting the common series resistance to be substantially equal to a largest of the first conductive trace resistance and the second conductive trace resistance.

22. The method of claim 18, wherein:

a percentage of signal in the second portion of the signal is determined by a ratio between the diffusing resistance and the common series resistance.

23. The method of claim 22, further comprising:

selecting the ratio between the diffusing resistance and the common series resistance such that the percentage of signal in the second portion of the signal is greater than 5 percent; and

selecting the diffusing resistance to satisfy the ratio.

24. The method of claim 22, further comprising:

selecting the ratio between the diffusing resistance and the common series resistance to be greater than 3 and less than 8;

selecting the diffusing resistance to satisfy the ratio.

25. The method of claim 22, further comprising:

selecting the ratio between the diffusing resistance and the common series resistance to be greater than 3 and less than 5; and

selecting the diffusing resistance to satisfy the ratio.