Reducing noise in a force signal in an electronic device
First Claim
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1. A method of operating a force sensing device incorporated with a display of an electronic device, the method comprising:
- dividing a scanning period for a frame of the display into a plurality of sub scan time periods; and
within each sub scan time period, sampling force signals only during a scan period and not sampling force signals during a delay period, wherein the scan and delay periods are offset from one another within a sub scan time period;
wherein;
a time period between the scan periods in only every other sub scan time period is set to a value that reduces background noise in the force signals.
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Abstract
A force sensing device can be included in a display. Noise produced by various sources can be injected into the force signals produced by the force sensing device. Example noise sources include, but are not limited to, the display, Johnson or Thermal noise from the force sensing device, system noise, and magnetically-coupled or background noise produced by ambient light sources. A sampling scheme that includes one or more noise cancelling techniques can be employed to reduce the amount of noise in the force signals.
90 Citations
17 Claims
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1. A method of operating a force sensing device incorporated with a display of an electronic device, the method comprising:
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dividing a scanning period for a frame of the display into a plurality of sub scan time periods; and within each sub scan time period, sampling force signals only during a scan period and not sampling force signals during a delay period, wherein the scan and delay periods are offset from one another within a sub scan time period;
wherein;a time period between the scan periods in only every other sub scan time period is set to a value that reduces background noise in the force signals. - View Dependent Claims (2, 3, 4, 5)
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6. An electronic device, comprising:
- a display stack for a display, comprising;
a cover glass; and a strain sensing structure positioned below the cover glass, the strain sensing structure comprising a substrate, a first set of strain sensitive films positioned on a first surface of the substrate, and a second set of strain sensitive films positioned on a second surface of the substrate and aligned vertically with the first set of strain sensitive films, wherein a strain sensitive film in the first set and a vertically aligned strain sensing film in the second set together form a strain sensing element;
wherein a strain sensitive film in the first set and a vertically aligned strain sensing film in the second set together from a strain sensing element;sense circuitry operably connected to each strain sensing element; and a controller operably connected to the sense circuitry and configured to cause force signals to be sampled from one or more strain sensing elements multiple times during a frame scanning period of the display, wherein the force signals are sampled only during multiple scan periods in the frame scanning period and the scan periods are offset from one another by a delay period;
wherein;a time period between only every other scan period is set to a value that reduces background noise in the force signals. - View Dependent Claims (7, 8, 9, 10, 11)
- a display stack for a display, comprising;
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12. A method of operating a force sensing device incorporated with a display of an electronic device, wherein the force sensing device comprises a strain sensing element, the method comprising:
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dividing a scanning period for a frame of the display into a plurality of sub scan time periods; within each sub scan time period, sampling force signals only during a scan period and not sampling force signals during a delay period, wherein the scan and delay periods are offset from one another within each sub scan time period; and flipping a first reference voltage and a second reference voltage between first and second nodes of the strain sensing element when a force signal not sampled from the strain sensing element;
wherein;a time period between the scan periods in only every other sub scan time period Is set to a value that reduces background noise in the force signals. - View Dependent Claims (13, 14, 15)
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16. A method of operating a force sensing device incorporated with a display of an electronic device, wherein the force sensing device comprises a strain sensing element, the method comprising:
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sampling a force signal from the strain sensing element during a scan period in at least one sub scan time period, wherein a plurality of sub scan time periods occur during a scanning period for a frame of the display and the scan period is offset from a signal instability produced by a VCOM signal in the display transitioning between two signal levels;
wherein;a time period between the scan periods in only every other sub scan time period is set to a value that reduces background noise in the force signals. - View Dependent Claims (17)
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Specification