Abstract: The present invention relates to a fingerprint sensing device for sensing a fingerprint pattern of a finger, the fingerprint sensing device comprising at least a first sensing structure and a second sensing structure; and at least a first charge amplifier and a second charge amplifier. Each charge amplifier comprises: a first input; a second input; an output; and at least one amplifier stage between the first and second inputs, and the output. The output is capacitively coupled to the first input. The first input of the first charge amplifier is connected to the first sensing structure; the first input of the second charge amplifier is connected to the second sensing structure; and the output of the first charge amplifier is capacitively coupled to the first input of the second charge amplifier to suppress the common mode component.

Abstract: A fingerprint sensing system comprises a sensor array with a plurality of sensing structures and read-out circuitry connectable to each of the sensing structures, and power supply circuitry arranged to provide to the read-out circuitry a substantially constant supply voltage being a difference between a high potential and a low potential. The fingerprint sensing system is configured in such a way that the low potential and the high potential are variable while substantially maintaining the supply voltage, and the read-out circuitry is connectable to each of the sensing structures in such a way that a variation in the low potential and the high potential while substantially maintaining the supply voltage results in a change of the charge carried by a sensing structure connected to the read-out circuitry. The change in charge is indicative of a capacitive coupling between the sensing structure and the finger.

Abstract: The present invention relates to a fingerprint sensing device for sensing a fingerprint pattern of a finger, the fingerprint sensing device comprising at least a first sensing structure and a second sensing structure; and at least a first charge amplifier and a second charge amplifier. Each charge amplifier comprises: a first input; a second input; an output; and at least one amplifier stage between the first and second inputs, and the output. The output is capacitively coupled to the first input. The first input of the first charge amplifier is connected to the first sensing structure; the first input of the second charge amplifier is connected to the second sensing structure; and the output of the first charge amplifier is capacitively coupled to the first input of the second charge amplifier to suppress the common mode component.

Abstract: The present invention relates to a capacitive fingerprint sensing device comprising a plurality of sensing elements. Each sensing element includes a protective dielectric top layer to be touched by a finger; an electrically conductive sensing structure arranged underneath the top layer; a charge amplifier connected to the sensing structure for providing a sensing voltage signal indicative of a change of a charge carried by the sensing structure resulting from a change in a potential difference between the finger and the sensing structure; and a voltage-to-current converter for converting the sensing voltage signal to a sensing current signal indicative of the change of charge carried by the sensing structure. Hereby, accurate sensing as well as faster operation of the sensing elements can be achieved without a corresponding increase in power consumption.

Abstract: There is provided a capacitive fingerprint sensing device comprising a plurality of sensing elements, sensing circuitry for providing an analog sensing signal, drive signal circuitry providing a drive signal comprising a drive pulse having a maximum level and a minimum level, providing a change in potential difference between the finger and the sensing structure, analog sampling circuitry comprising at least three analog sample and hold circuits arranged to sample the sensing signal, and a sampling control unit for individually controlling the sample and hold circuits to capture a sample at a specified time, wherein the samples comprises one sample captured when the drive signal is at a first voltage level V1 and one sample captured when the drive signal is at a second voltage level V2, different from V1; and an analog-to-digital converter, ADC, configured to convert a combination of the samples into a digital signal, wherein the three samples are captured times such that a noise component is suppressed from

Abstract: The present invention relates to a method of sensing a fingerprint pattern of a finger using a fingerprint sensing device comprising an array of sensing elements; an electrically conductive finger detecting structure; and finger detecting circuitry connected to the finger detecting structure for providing a finger detection signal indicative of a capacitive coupling between the finger detecting structure and the finger. The method comprises the steps of: comparing the finger detection signal with a first threshold value indicating a first capacitive coupling, and a second threshold value indicating a second capacitive coupling stronger than the first capacitive coupling; and activating at least a subset of the sensing elements when the finger detection signal changes from a first value indicating a capacitive coupling weaker than the first capacitive coupling to a second value indicating a capacitive coupling stronger than the second capacitive coupling.

Abstract: The present invention relates to an electronic device comprising a fingerprint sensing system including a plurality of sensing elements, each being configured to capacitively couple to a finger arranged adjacent to the sensing element and to provide a sensing signal indicative of a response to a time-varying finger excitation signal provided to the finger; and an electrically conducting housing at least partly enclosing an interior of the electronic device. The electronic device further comprises housing connection circuitry connected to the electrically conducting housing, and arranged and configured to at least intermittently allow a potential of the electrically conducting housing to follow the finger excitation signal. Hereby the housing can be used to enhance the functionality of the fingerprint sensing system.

Abstract: A capacitive fingerprint sensing system includes excitation signal providing circuitry and a plurality of sensing elements. Each sensing element includes a protective dielectric top layer, an electrically conductive sensing structure coupled to the excitation signal for providing a sensing signal indicative of a change of a charge carried by the sensing structure resulting from a change in potential difference between the finger and the sensing structure, and demodulation circuitry connected to the sensing circuitry for combining the sensing signal and a demodulation signal being timing-related to the excitation signal to provide a combined signal including a DC signal component indicating the change of the charge carried by the sensing structure. The fingerprint sensing system further includes readout circuitry connected to each of the sensing elements for providing a representation of the fingerprint pattern based on the DC signal component from each of the sensing elements.

Abstract: A fingerprint sensing system comprises a sensor array with a plurality of sensing structures and read-out circuitry connectable to each of the sensing structures, and power supply circuitry arranged to provide to the read-out circuitry a substantially constant supply voltage being a difference between a high potential and a low potential. The fingerprint sensing system is configured in such a way that the low potential and the high potential are variable while substantially maintaining the supply voltage, and the read-out circuitry is connectable to each of the sensing structures in such a way that a variation in the low potential and the high potential while substantially maintaining the supply voltage results in a change of the charge carried by a sensing structure connected to the read-out circuitry. The change in charge is indicative of a capacitive coupling between the sensing structure and the finger.

Abstract: The present invention relates to a capacitive fingerprint sensing device for sensing a fingerprint pattern of a finger, the capacitive fingerprint sensor comprising a plurality of sensing elements, each including: a protective dielectric top layer to be touched by the finger; an electrically conductive sensing structure arranged underneath the top layer; charge measuring circuitry connected to the sensing structure for sequentially transitioning between at least a first measurement state and a second measurement state to perform a measurement sequence resulting in an output signal from the charge measuring circuitry being indicative of a change of a charge carried by the sensing structure resulting from a change in a potential difference between the finger and the sensing structure; and timing circuitry connected to the charge measuring circuitry for controlling a timing of at least one of the measurement states.

Abstract: The present invention relates to a capacitive fingerprint sensing device comprising a plurality of sensing elements. Each sensing element includes a protective dielectric top layer to be touched by a finger; an electrically conductive sensing structure arranged underneath the top layer; a charge amplifier connected to the sensing structure for providing a sensing voltage signal indicative of a change of a charge carried by the sensing structure resulting from a change in a potential difference between the finger and the sensing structure; and a voltage-to-current converter for converting the sensing voltage signal to a sensing current signal indicative of the change of charge carried by the sensing structure. Hereby, accurate sensing as well as faster operation of the sensing elements can be achieved without a corresponding increase in power consumption.

Abstract: A fingerprint sensing system comprises a sensor array with a plurality of sensing structures and read-out circuitry connectable to each of the sensing structures, and power supply circuitry arranged to provide to the read-out circuitry a substantially constant supply voltage being a difference between a high potential and a low potential. The fingerprint sensing system is configured in such a way that the low potential and the high potential are variable while substantially maintaining the supply voltage, and the read-out circuitry is connectable to each of the sensing structures in such a way that a variation in the low potential and the high potential while substantially maintaining the supply voltage results in a change of the charge carried by a sensing structure connected to the read-out circuitry. The change in charge is indicative of a capacitive coupling between the sensing structure and the finger.

Abstract: The present invention relates to a capacitive fingerprint sensing system comprising excitation signal providing circuitry and a plurality of sensing elements. Each sensing element includes a protective dielectric top layer, an electrically conductive sensing structure coupled to the excitation signal for providing a sensing signal indicative of a change of a charge carried by the sensing structure resulting from a change in potential difference between the finger and the sensing structure, and demodulation circuitry connected to the sensing circuitry for combining the sensing signal and a demodulation signal being timing-related to the excitation signal to provide a combined signal including a DC signal component indicating the change of the charge carried by the sensing structure.

Abstract: The present invention relates to a capacitive fingerprint sensing device for sensing a fingerprint pattern of a finger, the capacitive fingerprint sensor comprising a plurality of sensing elements, each including: a protective dielectric top layer to be touched by the finger; an electrically conductive sensing structure arranged underneath the top layer; charge measuring circuitry connected to the sensing structure for sequentially transitioning between at least a first measurement state and a second measurement state to perform a measurement sequence resulting in an output signal from the charge measuring circuitry being indicative of a change of a charge carried by the sensing structure resulting from a change in a potential difference between the finger and the sensing structure; and timing circuitry connected to the charge measuring circuitry for controlling a timing of at least one of the measurement states.

Abstract: The present invention relates to a method of determining a representation of a fingerprint pattern. The method comprises the steps of acquiring a reference signal indicative of an electric coupling between a hand surface having friction ridges and a reference sensing structure extending across a plurality of the friction ridges; and determining the representation of the fingerprint pattern based on the reference signal and a capacitive coupling between the finger and each of a plurality of sensing elements. The acquired reference signal can, for example, be used for controlling the sensing elements so that the sensing performed by the sensing elements is carried out using favorable timing, when the signal quality is good. Alternatively, or in combination, the acquired reference signal may be used for post-processing, whereby the signals/signal values obtained by the sensing elements are modified depending on the corresponding values of the reference signal.

Abstract: The present invention relates to an electronic device comprising a fingerprint sensing system including a plurality of sensing elements, each being configured to capacitively couple to a finger arranged adjacent to the sensing element and to provide a sensing signal indicative of a response to a time-varying finger excitation signal provided to the finger; and an electrically conducting housing at least partly enclosing an interior of the electronic device. The electronic device further comprises housing connection circuitry connected to the electrically conducting housing, and arranged and configured to at least intermittently allow a potential of the electrically conducting housing to follow the finger excitation signal. Hereby the housing can be used to enhance the functionality of the fingerprint sensing system.

Abstract: The present invention relates to a capacitive fingerprint sensing device comprising a semiconductor substrate; and an array of sensing elements formed on the semiconductor substrate. Each of the sensing elements comprises a protective dielectric top layer; a sensing structure arranged underneath the top layer; and a charge amplifier connected to the sensing structure. The charge amplifier comprises a negative input connected to the sensing structure; a positive input; an output providing a sensing signal; a feedback capacitor; and a sense transistor having a gate constituting the negative input. The sense transistor is formed in an insulated well in the semiconductor substrate. The fingerprint sensing device further comprises excitation signal providing circuitry connected to the positive input of the charge amplifier and the well for changing electric potentials of the sensing structure and the well, to thereby reduce the influence of parasitic capacitances in the sensing element.

Abstract: The present invention relates to a capacitive fingerprint sensing device comprising a semiconductor substrate; and an array of sensing elements formed on the semiconductor substrate. Each of the sensing elements comprises a protective dielectric top layer; a sensing structure arranged underneath the top layer; and a charge amplifier connected to the sensing structure. The charge amplifier comprises a negative input connected to the sensing structure; a positive input; an output providing a sensing signal; a feedback capacitor; and a sense transistor having a gate constituting the negative input. The sense transistor is formed in an insulated well in the semiconductor substrate. The fingerprint sensing device further comprises excitation signal providing circuitry connected to the positive input of the charge amplifier and the well for changing electric potentials of the sensing structure and the well, to thereby reduce the influence of parasitic capacitances in the sensing element.

Abstract: The present invention relates to a method of determining a representation of a fingerprint pattern. The method comprises the steps of acquiring a reference signal indicative of an electric coupling between a hand surface having friction ridges and a reference sensing structure extending across a plurality of the friction ridges; and determining the representation of the fingerprint pattern based on the reference signal and a capacitive coupling between the finger and each of a plurality of sensing elements. The acquired reference signal can, for example, be used for controlling the sensing elements so that the sensing performed by the sensing elements is carried out using favorable timing, when the signal quality is good. Alternatively, or in combination, the acquired reference signal may be used for post-processing, whereby the signals/signal values obtained by the sensing elements are modified depending on the corresponding values of the reference signal.

Abstract: The present invention relates to a fingerprint sensing system comprising a sensor array with a plurality of sensing structures and read-out circuitry connectable to each of the sensing structures, and power supply circuitry arranged to provide to the read-out circuitry a substantially constant supply voltage being a difference between a high potential and a low potential. The fingerprint sensing system is configured in such a way that the low potential and the high potential are variable while substantially maintaining the supply voltage, and the read-out circuitry is connectable to each of the sensing structures in such a way that a variation in the low potential and the high potential while substantially maintaining the supply voltage results in a change of the charge carried by a sensing structure connected to the read-out circuitry. The change in charge is indicative of a capacitive coupling between the sensing structure and the finger.