Baselining techniques in force-based touch panel systems
First Claim
Patent Images
1. A method for determining a touch location of a touch on a touch screen, comprising:
- developing a first reference level for a force responsive touch signal;
developing a second reference level for the force responsive touch signal; and
determining the touch location by calculating a difference between the touch signal and at least one of the first and second reference levels;
wherein developing the second reference level comprises using an extrapolated value as the second reference level, and wherein using an extrapolated value as the second reference level comprises;
acquiring a first touch signal sample during a quiescent period;
acquiring a second touch signal sample during the quiescent period, the second touch signal sample acquired a predetermined number of sample times after the first touch signal sample;
determining a rate of change of the touch signal during the quiescent period using the first and the second touch signal samples;
extrapolating a value of the touch signal based on the first touch signal sample, the second touch signal sample and the rate of change of the touch signal; and
using the extrapolated value as the second reference level.
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Abstract
In connection with establishing a touch location on a touch screen, a number of reference levels are developed. One or more of the reference levels may be used to determine a differential change in the touch signal between a zero touch force condition and a touch event. In one approach, one or more reference levels are selected to compensate for various conditions affecting the touch screen at the time a touch is applied. Using one or more reference levels to compensate for conditions affecting the touch signal at the time touch location information is obtained can provide improved accuracy in determining touch location.
122 Citations
13 Claims
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1. A method for determining a touch location of a touch on a touch screen, comprising:
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developing a first reference level for a force responsive touch signal; developing a second reference level for the force responsive touch signal; and determining the touch location by calculating a difference between the touch signal and at least one of the first and second reference levels; wherein developing the second reference level comprises using an extrapolated value as the second reference level, and wherein using an extrapolated value as the second reference level comprises; acquiring a first touch signal sample during a quiescent period; acquiring a second touch signal sample during the quiescent period, the second touch signal sample acquired a predetermined number of sample times after the first touch signal sample; determining a rate of change of the touch signal during the quiescent period using the first and the second touch signal samples; extrapolating a value of the touch signal based on the first touch signal sample, the second touch signal sample and the rate of change of the touch signal; and using the extrapolated value as the second reference level.
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2. A method for determining a touch location of a touch on a touch screen, comprising:
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developing the first reference level for a force responsive touch signal; developing a second reference level for the force responsive touch signal; and determining the touch location by calculating a difference between the touch signal and at least one of the first and second reference levels; wherein developing the second reference level comprises using an interpolated value as the second reference level, wherein using an interpolated value as the second reference level comprises; acquiring a first touch signal sample during a quiescent period; acquiring a second touch signal sample when the touch signal returns to a quiescent state following application of a touch; determining a rate of change of the touch signal between the first touch signal sample and the second touch signal sample; interpolating a value of the touch signal based on the first touch signal sample, the second touch signal sample and the rate of change of the touch signal; and using the interpolated value as the second reference level.
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3. A method for determining a touch location of a touch on a touch screen, comprising:
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developing a first reference level for a force responsive touch signal; developing a second reference level for a force responsive touch signal; and determining the touch location by calculating a difference between the touch signal and at least one of the first and second reference levels; wherein determining the touch location includes transitioning from using the first reference level to using the second reference level, wherein transitioning from using the first reference level to using the second reference level comprises calculating X and Y touch location coordinates as;
X=WXref2+(1−
W)Xref1,
Y=WYref2+(1−
W)Yref1,where; W is a weighting factor, Xref1 and Yref2 are touch location coordinates calculated using the second reference level, and Xref1 and Yref1 are touch location coordinates calculated using the first reference level. - View Dependent Claims (4, 5, 6, 7, 8, 9)
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10. A method of establishing a reference level for a touch signal, comprising:
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sensing a quiescent touch signal prior to an application of a touch force; detecting a touch signal responsive to the application of the touch force; and establishing a reference level for the touch signal based on one or more values of the touch signal acquired contemporaneously with the detection of the touch force, the reference level representing a zero applied force reference condition, wherein a difference calculated between the reference level and the touch signal is used to determine a location of the touch force; wherein establishing the reference level comprises establishing the reference level based on a particular time at which touch location information is obtained, wherein establishing the reference level comprises; detecting a first quiescent touch signal, the first quiescent touch signal representing the force responsive touch signal before the touch is applied to the touch screen; detecting a second quiescent touch signal, the second quiescent touch signal representing the force responsive touch signal after the touch is removed from the touch screen; determining an interpolated touch signal between the first and the second quiescent touch signals; and using a value of the interpolated touch signal at the particular time at which the touch location is determined as the reference level. - View Dependent Claims (11, 12, 13)
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Specification