Reducing display noise in an electronic device

• US 10,394,359 B2
• Filed: 08/04/2017
• Issued: 08/27/2019
• Est. Priority Date: 12/20/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Agarwal, Manu, Klaassen, Erno H., Bae, Hopil, Brahma, Kingsuk
• Primary Examiner(s): Khan, Ibrahim A
• Application Number:
  US15/669,869
• Publication Number:
  US 20170351368A1
• Time in Patent Office: Days
• CPC Class Codes: G01R 31/001 Measuring interference from external sources to, or emission from, the device under test, e.g. EMC, EMI, EMP or ESD testing measuring electromagnetic fields G01R29/08; circuits for generating HV pulses in dielectric strength testing G01R31/14
• CPC Class Codes: G02B 5/201 in the form of arrays
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/133334 Electromagnetic shields
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 1/1626 with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]
• CPC Class Codes: G06F 1/1637 Details related to the display arrangement, including those related to the mounting of the display in the housing
• CPC Class Codes: G06F 1/1643 the display being associated to a digitizer, e.g. laptops that can be used as penpads details related to the relative motion of the display enclosure with respect to the body enclosure, e.g. to move between laptop and tablet PC configuration G06F1/1615
• CPC Class Codes: G06F 1/1671 Special purpose buttons or auxiliary keyboards, e.g. retractable mini keypads, keypads or buttons that remain accessible at closed laptop G06F1/1666 takes precedence
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

A sensing device can be included in a display of an electronic device. Various techniques can be used to reduce display noise in the signals output from the sensing device. The techniques include the use of a filtering layer in a display stack, the use of a non-uniform sampling scheme, averaging together noise signal samples sampled over multiple display frames, and inverting a phase of the sampling of the noise signal over multiple display frames.

Claims

1. A method of non-uniform sampling to mitigate display noise in a sensing device, wherein the sensing device is included in a display of an electronic device, the method comprising:

sampling a signal produced by the sensing device for a first time period, wherein the signal includes noise produced by the display and the sampled noise has a first polarity for the first given time period;

when the signal is sampled for the first time period, switching a polarity of the sampled noise; and

sampling the signal produced by the sensing device for a second time period, wherein the sampled noise has an opposite second polarity for the second time period such that noise samples having the opposite second polarity substantially cancel the noise samples having the first polarity.

2. The method of claim 1, wherein switching a polarity of the sampled noise comprises skipping a sampling of the noise during a line refresh period.

3. The method of claim 2, further comprising skipping at least one other sampling of the noise during a display frame refresh period.

4. The method of claim 3, wherein a location of each skipping of the sampling of the noise is random within the display frame refresh period.

5. The method of claim 1, wherein switching a polarity of the sampled noise comprises skipping three samplings of the noise during a line refresh period.

6. The method of claim 5, wherein locations of each skipping of the sampling of the noise are equally spaced within the line refresh period.

7. The method of claim 1, wherein the sampling the signal produced by the sensing device for the first time period is performed responsive to an excitation signal being applied to the sensing device.

8. The method of claim 1, wherein:

the sensing device comprises a capacitive sensing element and;

sampling a signal produced by the sensing device for a first time period comprises measuring a capacitance of the capacitive sensing element.

9. A method of reducing display noise in a sensing device, wherein the sensing device is included in a display of an electronic device, the method comprising:

sampling a display noise signal and averaging the display noise samples for each display frame refresh period of a set of display frame refresh periods; and

averaging the display noise samples from a set of consecutive display frame refresh periods together, wherein the set of consecutive display frame refresh periods comprises at least two display frame refresh periods.

10. The method of claim 9, wherein averaging the display noise samples from the set of consecutive display frame refresh periods together comprises averaging the display noise samples from four consecutive display frame refresh periods together.

11. The method of claim 9, wherein:

the set of consecutive display frame refresh periods is a first set of consecutive display frame refresh periods;

the method further comprises averaging a second set of consecutive display frame refresh periods; and

the second set of consecutive display frame refresh periods comprises at least one display frame refresh period that is not in the first set of consecutive display frame refresh periods.

12. The method of claim 11, wherein the first and second sets of consecutive display frame refresh periods each comprise four consecutive display frame refresh periods.

13. The method of claim 11, wherein exactly one display frame refresh period of the second set of consecutive display frame refresh periods is not in the first set of consecutive display frame refresh periods.

14. The method of claim 11, wherein each display frame refresh period of the second set of consecutive display frame refresh periods is not in the first set of consecutive display frame refresh periods.

15. A method of reducing display noise in a sensing device, wherein the sensing device is included in a display of an electronic device, the method comprising:

sampling a display noise signal and averaging the display noise samples for a first display frame refresh period;

inverting a phase of the sampling;

sampling the display noise signal and averaging the display noise samples for a second display frame refresh period; and

averaging the display noise samples from the first and second display frame refresh periods.

16. The method of claim 15, further comprising:

inverting the phase of the sampling;

sampling the display noise signal and averaging the display noise samples for a third display frame refresh period;

inverting the phase of the sampling;

sampling the display noise signal and averaging the display noise samples for a fourth display frame refresh period; and

averaging the display noise samples from the third and fourth display frame refresh periods.

17. The method of claim 16, further comprising averaging the averaged display noise samples associated with the first, second, third, and fourth display frame refresh periods together.

18. The method of claim 16, further comprising:

inverting the phase of the sampling;

sampling the display noise signal and averaging the display noise samples for a fifth display frame refresh period; and

averaging the display noise samples from the fifth display frame refresh period.

19. The method of claim 18, further comprising:

averaging the averaged display noise samples associated with the second, third, fourth, and fifth display frame refresh periods together.

20. The method of claim 16, further comprising:

inverting the phase of the sampling;

sampling the display noise signal and averaging the display noise samples for a sixth display frame refresh period;

averaging the display noise samples from the sixth display frame refresh period; and

averaging the averaged display noise samples associated with the third, fourth, fifth, and sixth display frame refresh periods together.