Active sensing element for acoustic imaging systems
First Claim
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1. An acoustic imaging sensor comprising:
- a piezoelectric element operable in a drive mode and a sense mode;
a sense circuit coupled to the piezoelectric element and configured to obtain a voltage signal from the piezoelectric element when in the sense mode, the voltage signal corresponding to at least a portion of a pixel of an acoustic image; and
a ground-shifting controller configured to increase a ground and a source of the sense circuit approximately to a drive voltage when in the drive mode.
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Abstract
An acoustic fingerprint imaging system having a plurality of acoustic elements, each acoustic element including a transducer, and independent drive and sense circuitry is disclosed. Drive circuitry may require higher voltage than low voltage sense circuitry. Many embodiments described herein include a ground shifting controller to apply a voltage bias to the low voltage sense circuitry during a drive operation, in order to prevent electrical damage to the sense circuitry.
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Citations
20 Claims
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1. An acoustic imaging sensor comprising:
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a piezoelectric element operable in a drive mode and a sense mode; a sense circuit coupled to the piezoelectric element and configured to obtain a voltage signal from the piezoelectric element when in the sense mode, the voltage signal corresponding to at least a portion of a pixel of an acoustic image; and a ground-shifting controller configured to increase a ground and a source of the sense circuit approximately to a drive voltage when in the drive mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of operating an acoustic sensor element in a drive mode, the method comprising:
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increasing a ground of a low-voltage sense circuit coupled to the acoustic sensor element to a voltage approximately equal to a high-voltage drive signal; increasing a source of the low-voltage sense circuit such that a potential difference between the source and the ground of the low-voltage sense circuit does not exceed a selected low-voltage threshold; and after increasing the ground and source of the low-voltage sense circuit, applying the high-voltage drive signal to the acoustic sensor element. - View Dependent Claims (13, 14, 15, 16)
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17. A method of operating an acoustic imaging sensor, the method comprising:
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operating in a drive mode by; increasing a ground of a low-voltage sense circuit coupled to an acoustic sensor element array to a voltage approximately equal to a high-voltage drive signal; increasing a source of the low-voltage sense circuit such that a potential difference between the source and the ground of the low-voltage sense circuit does not exceed a selected threshold; and applying the high-voltage drive signal to at least one acoustic sensor element of the acoustic sensor element array; and operating in a sense mode, after applying the high-voltage drive signal to the at least one acoustic sensor element, by; decreasing the ground of the low-voltage sense circuit; decreasing the source of the low-voltage sense circuit such that the potential difference between the source and the ground does not exceed the selected threshold; and obtaining at least one voltage signal from the at least one acoustic sensor element. - View Dependent Claims (18, 19, 20)
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Specification