Methods and systems for detecting a position-based attribute of an object using digital codes

• US 9,696,863 B2
• Filed: 04/25/2016
• Issued: 07/04/2017
• Est. Priority Date: 11/15/2005
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Reynolds, Joseph Kurth
• Primary Examiner(s): Nguyen, Kevin M
• Application Number:
  US15/137,318
• Publication Number:
  US 20160306467A1
• Time in Patent Office: 435 Days
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

Methods, systems and devices are described for detecting a position-based attribute of a finger, stylus or other object with a touchpad or other sensor having a touch-sensitive region that includes a plurality of electrodes. Modulation signals for one or more electrodes are produced as a function of any number of distinct digital codes. The modulation signals are applied to an associated at least one of the plurality of electrodes to obtain a resultant signal that is electrically affected by the position of the object. The resultant signal is demodulated using the plurality of distinct digital codes to discriminate electrical effects produced by the object. The position-based attribute of the object is then determined with respect to the plurality of electrodes from the electrical effects.

Claims

1. A touch screen device configured to determine positions of a plurality of input objects, the touch screen device comprising:

a plurality of transmit electrodes disposed in a first direction in a sensing region of the touch screen device, a plurality of receive electrodes disposed in a second direction in the sensing region of the touch screen device, the second direction substantially orthogonal to the first direction, wherein the plurality of receive electrodes is fixed relative to the plurality of transmit electrodes, and wherein the plurality of transmit electrodes and the plurality of receive electrodes are configured for capacitive sensing; and

a controller coupled to the plurality of transmit electrodes and the plurality of receive electrodes, the controller configured to;

simultaneously apply a first modulation signal to a first transmit electrode of the plurality of transmit electrodes and a second modulation signal to a second transmit electrode of the plurality of transmit electrodes, wherein the first modulation signal comprises a carrier signal modulated according to a first distinct digital code of a plurality of distinct digital codes and the second modulation signal comprises the carrier signal modulated according to a second distinct digital code of the plurality of distinct digital codes, wherein the carrier signal has a periodically varying voltage;

receive a plurality of resultant signals from the plurality of receive electrodes, wherein a first resultant signal of the plurality of resultant signals is received with a first receive electrode of the plurality of receive electrodes and a second resultant signal of the plurality of resultant signals is

received with a second receive electrode of the plurality of receive electrodes, and

wherein the first resultant signal comprises first electrical effects associated with at least the first modulation signal, and the second modulation signal and the second resultant signal comprises second electrical effects associated with at least the first modulation signal and the second modulation signal;

demodulate the first resultant signal and the second resultant signal to obtain the first electrical effects and the second electrical effects by removing the carrier signal and then removing effects of the first distinct digital code and second distinct digital code;

define a multi-dimensional image using at least the first electrical effects and the second electrical effects;

determine the positions of the plurality of input objects at least partially based on the multi-dimensional image; and

adjust a frequency of the carrier signal in response to electrical noise.

2. The touch screen device of claim 1, wherein the first resultant signal and the second resultant signal are simultaneously received.

3. The touch screen device of claim 1, wherein the at least one receive electrode of the plurality of receive electrodes at least partially physically overlaps at least one transmit electrode of the plurality of transmit electrodes.

4. The touch screen device of claim 1, wherein the controller is further configured to perform, in response to determining the positions of the plurality of input objects, an action selected from a group of actions consisting of:

a scrolling action and a mode selection action.

5. The touch screen device of claim 1 further comprising a plurality of signal paths, wherein the controller is separately coupled to each transmit electrode of the plurality of transmitter electrodes via a respective one of the plurality of signal paths.

6. The touch screen device of claim 1, wherein each input object of the plurality of input objects is selected from a group consisting of:

a finger and a stylus.

7. A controller for a touch screen configured to detect a plurality of input objects in a sensing region, the controller comprising:

drive circuitry configured to simultaneously apply a first modulation signal to a first transmit electrode of a plurality of transmit electrodes and a second modulation signal to a second transmit electrode of the plurality of transmit electrodes, wherein the first modulation signal comprises a carrier signal modulated according to a first distinct digital code of a plurality of distinct digital codes and the second modulation signal comprises the carrier signal modulated according to a second distinct digital code of the plurality of distinct digital codes, and

wherein the carrier signal has a periodically varying voltage;

receive circuitry configured to receive a first resultant signal with a first receive electrode of a plurality of receive electrodes and a second resultant signal with a second receive electrode of the plurality of receive electrodes, wherein the first resultant signal comprises first electrical effects associated with the first modulation signal and the second modulation signal, and the second resultant signal comprises second electrical effects associated with the first modulation signal and the second modulation signal, wherein the plurality of transmit electrodes is disposed in a first direction in the sensing region and the plurality of receive electrodes is disposed in a second direction in the sensing region, and

wherein the second direction is substantially orthogonal to the first direction;

a demodulator configured to demodulate the first resultant signal and the second resultant signal to obtain the first electrical effects and the second electrical effects by removing the carrier signal and then removing effects of the first distinct digital code and second distinct digital code; and

a memory device comprising instructions executable by the controller to;

determine a position of a first input object of the plurality input objects and a position of a second input object of the plurality of input objects with respect to the sensing region using at least the first electrical effects and the second electrical effects; and

report the position of the first input object as first object coordinates and the position of the second input object as second object coordinates.

8. The controller of claim 7, wherein the memory device further comprises instructions executable by the controller to define a multi-dimensional image based on the first electrical effects and the second electrical effects.

9. The controller of claim 7, wherein the memory device further comprises instructions executable by the controller to further adjust a frequency of the carrier signal in response to electrical noise.

10. The controller of claim 7, further comprising a demodulation filter coupled to the demodulator, the demodulation filter selected from a group consisting of:

a low-pass filter and a band-pass filter.

11. The controller of claim 7, wherein the controller is further configured to compare the first electrical effects and the second electrical effects to a plurality of baseline values.

12. The controller of claim 11, wherein the plurality of baseline values comprises values selected from a group consisting of:

empirically determined values, values averaged over time, and values based on a previous observation.

13. The controller of claim 11, wherein the plurality of transmit electrodes and the plurality of receive electrodes form a plurality of sensing channels and wherein the plurality of baseline values comprises baseline values each corresponding to one sensing channel of the plurality of sensing channels.

14. The controller of claim 7, wherein the first modulation signal comprises the carrier signal phase modulated according to the first distinct digital code and the second modulation signal comprises the carrier signal phase modulated according to the second distinct digital code.

15. The controller of claim 7, wherein the first modulation signal comprises the carrier signal amplitude modulated according to the first distinct digital code and the second modulation signal comprises the carrier signal amplitude modulated according to the second distinct digital code.

16. The controller of claim 7, wherein a first virtual capacitor is formed between the first transmit electrode and the first receive electrode and a second virtual capacitor is formed between the second transmit electrode and the first receive electrode, and wherein the first electrical effects are based on at least the first virtual capacitor and the second virtual capacitor.

17. The controller of claim 7, wherein the memory device stores at least a portion of the plurality of distinct digital codes.

18. The controller of claim 7, wherein the second distinct digital code of the plurality of distinct digital codes is a shifted version of the first distinct digital code of the plurality of distinct digital codes.

19. A method for operating a touch screen, the method comprising:

simultaneously applying a first modulation signal to a first transmit electrode of a plurality of transmit electrodes and a second modulation signal to a second transmit electrode of the plurality a transmit electrodes, wherein the first modulation signal comprises a carrier signal modulated according to a first distinct digital code of a plurality of distinct digital codes and the second modulation signal comprises the carrier signal modulated according to a second distinct digital code of the plurality of distinct digital codes, wherein the carrier signal has a periodically varying voltage;

receiving a first resultant signal with a first receive electrode of a plurality of receive electrodes and a second resultant signal with a second receive electrode of a plurality of receive electrodes,

wherein the first resultant signal comprises first electrical effects associated with the first modulation signal and the second modulation signal and the second resultant signal comprises second electrical effects associated with the first modulation signal and the second modulation signal, wherein the plurality of transmit electrodes is disposed in a first direction of a sensing region of the touch screen and the plurality of receive electrodes is disposed in a second direction of the sensing region of the touch screen, and

wherein the second direction is substantially orthogonal to the first direction;

demodulating the first resultant signal and the second resultant signal to obtain the first electrical effects and the second electrical effects by removing the carrier signal and then removing effects of the first distinct digital code and second distinct digital code;

defining a multi-dimensional image using at least the first electrical effects and the second electrical effects;

determining a first position of a first object and a second position of a second object with respect to the sensing region of the touch screen using the multi-dimensional image;

and adjusting a frequency of the carrier signal in response to electrical noise.

20. The method of claim 19, wherein the first modulation signal comprises the carrier signal phase modulated according to the first distinct digital code and the second modulation signal comprises the carrier signal phase modulated according to the second distinct digital code.

21. The method of claim 19, further comprising reporting the position of the first object as first object coordinates and the position of the second object as second object coordinates.

22. The method of claim 19, wherein a first virtual capacitor is formed between the first transmit electrode and the first receive electrode and a second virtual capacitor is formed between the second transmit electrode and the first receive electrode, and wherein the first electrical effects are based on at least the first virtual capacitor and the second virtual capacitor.