Acoustic wave touch detection circuit and method
First Claim
Patent Images
1. A method of detecting a touch on a touch responsive area comprising:
- generating an acoustic wave in the touch responsive area;
determining a value representing the time that the acoustic wave in the touch responsive area decays to a predetermined level in the absence of a touch to provide a reference;
generating a subsequent acoustic wave in the touch responsive area;
determining a subsequent value representing the time that the subsequent acoustic wave decays to the predetermined level;
comparing the subsequent value to the reference to determine whether the subsequent value represents a touch on the touch responsive area.
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Abstract
A circuit for an acoustic wave switch or sensor having a resonant acoustic wave cavity detects a touch or sensed event using a time domain approach. The circuit includes a controller that drives an acoustic wave transducer to generate a resonant acoustic wave in the acoustic wave cavity during a first portion of a sampling cycle. In a second portion of the sampling cycle, the controller monitors the time that it takes for the acoustic wave signal from the transducer to decay to a predetermined level. Based on the decay time, the controller detects a sensed event, such as a touch on the acoustic wave switch/sensor.
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Citations
20 Claims
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1. A method of detecting a touch on a touch responsive area comprising:
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generating an acoustic wave in the touch responsive area; determining a value representing the time that the acoustic wave in the touch responsive area decays to a predetermined level in the absence of a touch to provide a reference; generating a subsequent acoustic wave in the touch responsive area; determining a subsequent value representing the time that the subsequent acoustic wave decays to the predetermined level; comparing the subsequent value to the reference to determine whether the subsequent value represents a touch on the touch responsive area. - View Dependent Claims (2, 3)
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4. A method of detecting a touch on a touch responsive area comprising:
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generating an acoustic wave in the touch responsive area; determining a value representing the time that the acoustic wave in the touch responsive area decays to a predetermined level in the absence of a touch to provide a reference; generating a subsequent acoustic wave in the touch responsive area of the device; determining a subsequent value representing the time that the subsequent acoustic wave decays to the predetermined level; comparing the subsequent value to the reference to determine whether the subsequent value represents a touch on the touch responsive area; and updating the reference based on the comparison of the subsequent value to the reference. - View Dependent Claims (5, 6)
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7. A method of detecting a touch on a touch responsive area comprising:
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generating an acoustic wave in the touch responsive area; providing a signal representing the acoustic wave in the touch responsive area, the acoustic wave signal, in the absence of a touch on the touch responsive area, decaying to a predetermined level over a period of time and the acoustic wave signal, in the presence of a touch on the touch responsive area, decaying to the predetermined level over a shorter period of time; determining a value representing the period of time that the acoustic wave signal decays to the predetermined value; and
comparing the determined value to a reference to detect a touch on the touch responsive area. - View Dependent Claims (8, 9, 10, 11)
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12. A method of detecting a touch on a touch responsive area comprising:
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generating an acoustic wave in the touch responsive area; providing a signal representing the acoustic wave in the touch responsive area, the acoustic wave signal, in the absence of a touch on the touch responsive area, decaying to a predetermined level over a number of cycles of the signal and the acoustic wave signal, in the presence of a touch on the touch responsive area, decaying to the predetermined level over a smaller number of cycles; counting the number of cycles of the signal having an amplitude above the predetermined level to provide a count; and
comparing the count to a reference to detect a touch on the touch responsive area. - View Dependent Claims (13, 14, 15)
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16. A method of detecting a touch on a touch responsive area comprising:
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generating an acoustic wave in the touch responsive area; providing a signal representing the acoustic wave in the touch responsive area in a sampling cycle, the acoustic wave signal for a sampling cycle, in the absence of a touch on the touch responsive area, decaying to a predetermined level over a period of time and the acoustic wave signal for a sampling cycle, in the presence of a touch on the touch responsive area, decaying to the predetermined level over a shorter period of time; comparing the acoustic wave signal for a sampling cycle to the predetermined level to generate a pulse when the amplitude of the signal is greater than the predetermined level; counting a number of the pulses generated to provide a count for a sampling cycle; and comparing the count for a sampling cycle to a reference to detect a touch. - View Dependent Claims (17, 18, 19, 20)
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Specification