Temperature compensating transparent force sensor having a compliant layer
First Claim
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1. An electronic device comprising:
- a touch-sensitive surface;
a force sensor positioned below the touch-sensitive surface and comprising;
a first strain-sensitive element;
a compliant layer disposed below the first strain-sensitive element; and
a second strain-sensitive element below the compliant layer and electrically coupled to the first-strain sensitive element; and
a sensor circuit configured to obtain a differential measurement between a first strain of the first strain-sensitive element and a second strain of the second strain-sensitive element;
whereinthe differential measurement changes in response to a force applied to the touch-sensitive surface; and
the sensor circuit compensates for a difference in temperature between the first and second strain-sensitive elements in response to the differential measurement.
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Abstract
An optically transparent force sensor that may compensate for environmental effects, including, for example, variations in temperature of the device or the surroundings. In some examples, two force-sensitive layers are separated by a compliant layer. The relative electrical response of the two force-sensitive layers may be used to compute an estimate of the force of a touch that reduces the effect of variations in temperature. In some examples, piezoelectric films having anisotropic strain properties are used to reduce the effects of temperature.
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Citations
13 Claims
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1. An electronic device comprising:
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a touch-sensitive surface; a force sensor positioned below the touch-sensitive surface and comprising; a first strain-sensitive element; a compliant layer disposed below the first strain-sensitive element; and a second strain-sensitive element below the compliant layer and electrically coupled to the first-strain sensitive element; and a sensor circuit configured to obtain a differential measurement between a first strain of the first strain-sensitive element and a second strain of the second strain-sensitive element;
whereinthe differential measurement changes in response to a force applied to the touch-sensitive surface; and the sensor circuit compensates for a difference in temperature between the first and second strain-sensitive elements in response to the differential measurement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An electronic device comprising:
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a cover defining a touch-sensitive surface; a force sensor positioned below the cover and comprising a strain-sensitive element configured to deform in response to a force applied to the touch-sensitive surface; and a sensor circuit configured to obtain a differential measurement between a strain response of the strain-sensitive element and an electrical response of a resistive element, the resistive element electrically coupled to the strain-sensitive element;
whereinthe resistive element is formed from the same material as the strain-sensitive element; and the resistive element is thermally coupled to the strain-sensitive element such that the electronic device is configured to reduce a difference in temperature between the resistive element and the strain-sensitive element in response to the differential measurement. - View Dependent Claims (12, 13)
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Specification