Method of producing a fingerprint image and a fingerprint sensor

Abstract

Disclosed is a method of generating a fingerprint image, including: determining an amount of charge to be removed from each of a plurality of detection circuits connected to a fingerprint sensor based on an amplifier characteristic of each of the plurality of detection circuits; and obtaining a second amount of electricity by removing the amount of charge from a first amount of electricity input to each of the plurality of detection circuits; integrating the second amount of electricity to obtain an integrated value; and generating the fingerprint image based on a comparison between the integrated value of the second amount of electricity and a predetermined threshold value.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2019-0133271, filed on October 24, 2019, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The apparatus and method according to the example embodiments involve generating fingerprint images and fingerprint sensors. Background Technology

[0004] The demand for personal authentication using unique human characteristics (such as fingerprints, voice, face, hand, or iris scans) has been steadily increasing. Personal authentication features are primarily used in banking devices, access control devices, mobile devices, or laptops. More recently, with the widespread deployment of mobile phones such as smartphones, fingerprint recognition devices for personal authentication are being used to protect much of the security information stored in smartphones. Summary of the Invention

[0005] The example embodiment provides a method for generating a fingerprint image, a fingerprint sensor, and a computer-readable recording medium thereon having a program for performing the method. The technical problem to be solved is not limited to the above-described technical problem, and other technical problems may exist.

[0006] Additional aspects will be set forth in part in the description which follows, and will also be apparent in part from the description, or may be learned by practicing the embodiments presented in this disclosure.

[0007] According to one aspect of an example embodiment, a method for generating a fingerprint image is provided, comprising: determining an amount of charge to be removed from each of a plurality of detection circuits connected to a fingerprint sensor based on amplifier characteristics of each of the plurality of detection circuits; obtaining a second charge by removing the charge from a first charge input to each of the plurality of detection circuits; integrating the second charge to obtain an integral value; and generating a fingerprint image based on a comparison between the integral value of the second charge and a predetermined threshold.

[0008] Each of the multiple detection circuits may include a current source and a switch, the switch being configured to connect the current source to the multiple detection circuits according to a control signal. Determining the amount of charge may include determining the amount of charge based on the amount of current generated from the current source included in each of the multiple detection circuits and the on-time of the switch.

[0009] The predetermined threshold can correspond to the input offset voltage of the amplifier included in each of the multiple detection circuits.

[0010] The method may further include: determining the input offset voltage of the amplifier based on the output value of the analog-to-digital converter (ADC) included in each of the plurality of detection circuits.

[0011] Determining the charge quantity may include determining the charge quantity such that a first component of the first charge is not less than the input offset voltage of the amplifier.

[0012] The method may further include: determining the maximum on-time of the switch by increasing the maximum on-time of the switch while fixing the current generated from the current source; determining the maximum on-time of the switch such that a first component of the first charge is not less than the input offset voltage of the amplifier included in each of the plurality of detection circuits; and determining the maximum current of the current source such that the first component is not less than the input offset voltage of the amplifier by adjusting the on-time of the switch and the current generated from the current source, wherein obtaining the second charge may include: determining the charge based on the maximum on-time and the maximum current, and obtaining the second charge by removing the determined charge from the first charge.

[0013] The method may further include: determining, by increasing the current generated from the current source while fixing the on-time of the switch, that a first component of the first charge is not less than the maximum current of the current source of the amplifier included in each of the plurality of detection circuits, and by adjusting the on-time of the switch and the current generated from the current source, that the first component is not less than the input offset voltage; and determining, by adjusting the on-time of the switch and the current generated from the current source, the maximum on-time of the switch, that the first component is not less than the input offset voltage, wherein obtaining the second charge may include: determining the charge based on the maximum current and the maximum on-time, and obtaining the second charge by removing the charge from the first charge.

[0014] The method may further include: determining the charge quantity and integrating the second charge quantity at least once based on the integral value being greater than or equal to a predetermined threshold.

[0015] A predetermined threshold can represent the signal-to-noise ratio of each of the multiple detection circuits.

[0016] According to one aspect of another example embodiment, a non-transitory computer-readable recording medium having thereon recorded a program for performing a method of generating a fingerprint image is provided.

[0017] According to one aspect of another example embodiment, an apparatus is provided, comprising: a fingerprint sensor including a plurality of driving electrodes and a plurality of detection electrodes; a plurality of detection circuits connected to the fingerprint sensor; and at least one processor configured to: determine an amount of charge to be removed from each of the plurality of detection circuits based on amplifier characteristics of each of the plurality of detection circuits; obtain a second charge by removing the amount of charge from a first charge input to each of the plurality of detection circuits; integrate the second charge to obtain an integral value; and generate a fingerprint image based on a comparison between the integral value of the second charge and a predetermined threshold.

[0018] Each of the plurality of detection circuits may include a current source and a switch, the switch being configured to connect the current source to the plurality of detection circuits according to a control signal. The at least one processor may also be configured to determine a charge amount based on the amount of current generated from the current source included in each of the detection circuits and the on-time of the switch.

[0019] Each of the plurality of detection circuits may include an amplifier. A predetermined threshold may correspond to the input offset voltage of the amplifier included in each of the plurality of detection circuits.

[0020] The at least one processor can also be configured to determine the amplifier's input offset voltage based on the output value of the analog-to-digital converter (ADC) included in each of the plurality of detection circuits.

[0021] The at least one processor may also be configured to determine the amount of charge such that a first component of the first charge is not less than the input offset voltage of the amplifier.

[0022] The at least one processor may also be configured to: determine the maximum on-time of the switch such that a first component of the first charge is not less than the input offset voltage of the amplifier included in each of the plurality of detection circuits by increasing the on-time of the switch while fixing the amount of current generated from the current source; determine the maximum amount of current from the current source such that the first component is not less than the input offset voltage of the amplifier by adjusting the on-time and the amount of current generated from the current source; and obtain a second charge by determining the charge based on the maximum on-time and the maximum current and by removing the determined charge from the first charge.

[0023] The at least one processor may also be configured to: determine a first component of the first charge that is not less than the maximum current of the current source of the amplifier included in each of the plurality of detection circuits, by increasing the current generated from the current source when the on-time of the fixed switch is fixed; determine a maximum on-time of the switch where the first component is not less than the input offset voltage by adjusting the on-time of the switch and the current generated from the current source; and obtain a second charge by determining the charge based on the maximum current and the maximum on-time, and by removing the charge from the first charge.

[0024] The at least one processor may also be configured to repeat the operation of determining the charge amount and the operation of integrating the second charge amount at least once, based on the integral value being greater than or equal to a predetermined threshold.

[0025] A predetermined threshold can represent the signal-to-noise ratio of each of the multiple detection circuits.

[0026] According to one aspect of another example embodiment, an electronic device is provided, comprising: a fingerprint sensor including a plurality of driving electrodes and a plurality of detection electrodes; a plurality of detection circuits configured to receive a first electrical charge from the plurality of detection electrodes of the fingerprint sensor, the plurality of detection circuits including an analog-to-digital converter (ADC), a current source, and a switch configured to connect the current source to the ADC; and at least one processor configured to: determine, based on the output voltage of the ADC, a candidate charge amount to be removed from each of the plurality of detection circuits; perform a first integral on a second electrical charge obtained by removing the candidate charge amount from the first electrical charge until the first electrical charge becomes less than a predetermined threshold; and determine, based on the integral value of the second electrical charge, a final charge amount to be removed from each of the plurality of detection circuits, the integral value of the second electrical charge being obtained by performing a second integral on the second electrical charge, the second number being less than the first number; and generate a fingerprint image by removing the final charge amount from the plurality of detection circuits. Attached Figure Description

[0027] The above and / or other aspects will become clearer from the description of certain exemplary embodiments with reference to the accompanying drawings, in which:

[0028] Figure 1 An example of an apparatus for generating a fingerprint image according to an exemplary embodiment is shown;

[0029] Figure 2 The concept of mutual capacitance corresponding to each node in the sensor is illustrated according to an example embodiment;

[0030] Figure 3 An example of a detection circuit included in a receiving circuit according to an exemplary embodiment is shown;

[0031] Figure 4 This is a flowchart illustrating an example of a method for generating a fingerprint image according to an exemplary embodiment;

[0032] Figure 5 This is a flowchart illustrating an example of a processor determining the amount of charge according to an example embodiment;

[0033] Figure 6 An example is shown where the processor determines the final charge amount according to an example embodiment;

[0034] Figure 7 This is a flowchart illustrating an example of a processor setting the amount of candidate charge according to an example embodiment;

[0035] Figure 8 A detailed illustration is provided according to the example embodiment. Figure 7 The method described in the flowchart;

[0036] Figure 9 This is a flowchart of another example of setting the candidate charge amount by the processor according to the example embodiment;

[0037] Figure 10 Another example of a detection circuit included in a receiving circuit according to an example embodiment is shown; and

[0038] Figure 11 A fingerprint image according to an example embodiment and a fingerprint image according to a comparison example are shown. Detailed Implementation

[0039] In consideration of the functions described herein, the terms used herein have been selected from currently widely used, general terminology. However, these terms may vary depending on the intent of a person skilled in the art, precedent, and the emergence of new technologies. Furthermore, for specific cases, the meanings of the terms chosen by the applicant are described in detail in the descriptive section. Therefore, the terms used herein are defined based on their meaning in relation to the content discussed throughout the specification, rather than by their simplistic meaning.

[0040] Unless otherwise specified, when a component may “include” a particular constituent element, it shall not be construed as excluding another constituent element, but rather as including other constituent elements. Furthermore, terms such as “~part,” “~unit,” and “~module” used in the specification may refer to a unit for performing at least one function or operation, and such unit may be embodied in hardware, software, or a combination of hardware and software.

[0041] When a phrase such as "at least one of..." precedes a list of components, it modifies the entire list of components, rather than individual components within the list. For example, the phrase "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or any variations of the above examples.

[0042] In the following, the preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the present disclosure is not limited thereto, and it will be understood that various changes in form and detail may be made therein.

[0043] In the following description, exemplary embodiments are described in detail with reference to the accompanying drawings.

[0044] Figure 1 An example of a device 100 for generating a fingerprint image according to an exemplary embodiment is shown. The device 100 may also be referred to as a fingerprint reader or a fingerprint scanner.

[0045] refer to Figure 1 The device 100 may include a sensor 110, electronic circuitry 120, a processor 123, a memory 124, and a display 125. Furthermore, the electronic circuitry 120 may include a transmitting circuit 121 and a receiving circuit 122. Although... Figure 1 Only the components related to device 100 are shown, but those skilled in the art will understand that other general components may also be included.

[0046] Processor 123 may be implemented as an array of multiple logic gates or a combination of a general-purpose microprocessor and a memory storing a program executable on the microprocessor. Furthermore, those skilled in the art will understand that processor 123 may be implemented in different forms of hardware.

[0047] Sensor 110 may include multiple driving electrodes Tx and multiple detection electrodes Rx arranged in a direction intersecting the driving electrodes Tx. Although Figure 1 The number of driving electrodes Tx and the number of detection electrodes Rx are shown to be 10, but this disclosure is not limited thereto.

[0048] The transmitting circuit 121 can apply a driving signal to the driving electrode Tx, and the receiving circuit 122 can measure the electrical signal from the detection electrode Rx.

[0049] The driving electrode Tx and the detection electrode Rx of sensor 110 can be arranged in directions that intersect each other. Although Figure 1The illustration shows the driving electrode Tx and the detection electrode Rx arranged orthogonally to each other, but this disclosure is not limited thereto. In other words, the angle between the direction in which the driving electrode Tx is arranged and the direction in which the detection electrode Rx is arranged may not be 90°.

[0050] When a user's finger approaches the sensor 110, the mutual capacitance between each of the driving electrodes Tx and each of the detection electrodes Rx in the sensor 110 can change. For example, the mutual capacitance at each node where the driving electrodes Tx and detection electrodes Rx in the sensor 110 intersect each other can vary according to the user's fingerprint pattern. As the spacing between the driving electrodes Tx and the spacing between the detection electrodes Rx decreases, the resolution of the fingerprint sensor can be increased. A passivation layer for protecting the driving electrodes Tx and detection electrodes Rx may also be included in the sensor 110.

[0051] For example, the driving electrode Tx and the detection electrode Rx may include line electrodes. Furthermore, each of the driving electrodes Tx may also include certain patterns disposed between nodes where the driving electrode Tx and the detection electrode Rx intersect each other. These patterns can have various shapes, such as polygons or circles. Similarly, each of the detection electrodes Rx may also include certain patterns disposed between the aforementioned nodes.

[0052] The transmitting circuit 121 can apply a driving signal to the driving electrode Tx. For example, the transmitting circuit 121 can apply a voltage pulse to each of the driving electrodes Tx. The receiving circuit 122 can measure the electrical signal from the detection electrode Rx. As an example, the receiving circuit 122 can measure the current flowing in each of the detection electrodes Rx. As another example, the receiving circuit 122 can measure the potential of each of the detection electrodes Rx.

[0053] Processor 123 typically controls the operation of the transmitting circuit 121 and receiving circuit 122 included in device 100. For example, processor 123 can control the amplitude and duration of voltage pulses applied by transmitting circuit 121 to each of the drive electrodes Tx. Furthermore, processor 123 can control transmitting circuit 121 such that voltage pulses can be selectively applied to some of the drive electrodes Tx.

[0054] The processor 123 can use the current or potential received by the receiving circuit 122 to generate and process fingerprint-related data. For example, the processor 123 can use the current or potential received by the receiving circuit 122 to generate data corresponding to a fingerprint image, and can use the pixel values ​​included in the data to generate a fingerprint image.

[0055] Figure 2 The concept of mutual capacitance corresponding to each node of sensor 110 according to an example embodiment is shown.

[0056] refer to Figure 2 The mutual capacitance between the driving electrode Tx and the detection electrode Rx can correspond to the node where the driving electrode Tx and the detection electrode Rx intersect each other.

[0057] For example, the mutual capacitance C11 between the first driving electrode Tx1 and the first detection electrode Rx1 can be detected from node N11 where they intersect. Similarly, the mutual capacitance Cmn between the m-th driving electrode Txm and the n-th detection electrode Rxn can be detected from node Nmn where they intersect. Here, "m" and "n" represent natural numbers. In the following description, the mutual capacitance at node Nmn refers to the mutual capacitance between the m-th driving electrode Txm and the n-th detection electrode Rxn.

[0058] Multiple channels of sensor 110 can be defined by driving electrode Tx and detection electrode Rx. For example, multiple channels can each correspond to multiple nodes formed at the intersection of driving electrode Tx and detection electrode Rx. For example, channel CHl1 can correspond to node N11.

[0059] For example, to measure the mutual capacitance at each of multiple nodes, the transmitting circuit 121 can sequentially apply different driving signals to the corresponding driving electrodes Tx. Furthermore, the receiving circuit 122 can measure the individual electrical signal from each of the detection electrodes Rx. For example, when measuring the mutual capacitance C11, a driving signal can be applied to the first driving electrode Tx1, and the electrical signal from the first detection electrode Rx1 can be measured. Similarly, when measuring the mutual capacitance Cmn, a driving signal can be applied to the m-th driving electrode Txm, and the electrical signal from the n-th detection electrode Rxn can be measured.

[0060] The receiving circuit 122 may include detection circuits respectively connected to the detection electrode Rx. See below for reference. Figure 3 An example detection circuit is described.

[0061] Figure 3 An example of a detection circuit 300 included in a receiving circuit 122 according to an exemplary embodiment is shown.

[0062] refer to Figure 3 The detection circuit 300 may include a first portion 310 and a second portion 320. Although only the portion shown is related to... Figure 3 The components related to the detection circuit 300 are as follows, but those skilled in the art will understand that other general components may also be included.

[0063] The first part 310 can process an input electrical signal received from one of the detection electrodes Rx and may include at least one amplifier AMP and a feedback capacitor Cf. The at least one amplifier AMP may be implemented as an operational amplifier. The input electrical signal received from the detection electrode Rx may be represented as an indication of the electrical quantity of the object detected by the sensor 110. In this case, the electrical quantity can be used to describe some electrical characteristic, parameter, or property that can be quantified by some measurement. For example, the electrical quantity may include charge, current, voltage, impedance, capacitance (mutual capacitance), or resistance. When assuming that the object detected by the sensor 110 is a fingerprint, the electrical quantity output from the detection electrode Rx may be represented as the voltage difference between the voltage corresponding to the ridges and the voltage corresponding to the valleys of the fingerprint, or the capacitance difference between the ridges and valleys, i.e., the capacitance difference ΔCm between the mutual capacitance corresponding to the ridges and the mutual capacitance corresponding to the valleys.

[0064] The second part 320 can generate the amount of charge to be removed from the electrical quantity input to the first part 310, and may include a current source Tdc and a switch SW. The charge Q is generated by the current I supplied from the current source Id and the switching connection time (or switching on time) t during which the switch SW is turned on. The charge Q can be equal to the product of the current I and the switching connection time (i.e., Q = I × t). The charge supplied from the detection circuit 300 can be reduced by the same amount as the charge generated by the second part 320. In other words, the charge generated by the second part 320 is removed from the electrical quantity input to the first part 310, and the result of this removal is output to the output terminal Vout via the first part 310. Therefore, as the closing time of the switch SW increases, the amount of charge generated from the second part 320 can increase, and the total amount of charge generated from the detection circuit 300 can decrease. Furthermore, as the current generated by the current source Tdc increases, the amount of charge removed from the electrical quantity generated by the first part 310 increases.

[0065] The input terminal Vin of the detection circuit 300 can be connected to any one of the detection electrodes Rx included in the sensor 110. In other words, assuming that the sensor 110 includes n detection electrodes Rx, the receiving circuit 122 can include n detection circuits 300.

[0066] As referenced above Figure 1 As described, a passivation layer can be deposited on sensor 110. Typically, in systems employing capacitive sensors, obtaining high-quality images can become more difficult as the sensor thickness increases. When a capacitive sensor system detects a user's fingerprint, the mutual capacitance ΔCm, corresponding to the capacitance difference between the ridges and valleys of the fingerprint, is inversely proportional to the square of the passivation thickness. Therefore, when the passivation thickness is greater than or equal to certain conditions, it may be difficult to detect the mutual capacitance ΔCm corresponding to the capacitance difference between the ridges and valleys of the fingerprint.

[0067] The quality of a fingerprint image is proportional to the mutual capacitance ΔCm, which corresponds to the capacitance difference between the ridges and valleys of the fingerprint. Therefore, as the mutual capacitance ΔCm, corresponding to the capacitance difference between the ridges and valleys of the fingerprint, decreases, the quality of the fingerprint image deteriorates.

[0068] Therefore, systems that typically employ capacitive sensors measure the input to... Figure 3 The signal from the input terminal Vin (i.e., the signal from the detection electrode Rx) is integrated several to hundreds of times to accumulate the mutual capacitance ΔCm corresponding to the capacitance difference between the ridges and valleys of the fingerprint.

[0069] Since there is a maximum usable voltage Vdd for the first part 310, the number of integrations described above can be limited. In other words, the integration can be repeated until the output Vout, based on the amount of charge obtained through integration, becomes greater than or equal to the maximum usable voltage Vdd for the first part 310, or until the amount of charge obtained through integration becomes equal to the capacitance Cf of the feedback capacitor Cf of the first part 310. Generally, as the number of integrations increases, the signal-to-noise ratio of the signal output from the output terminal Vout improves. However, as mentioned above, since the number of integrations is limited by the maximum voltage Vdd, as much unnecessary charge as possible can be removed from the amount of charge obtained through integration or the mutual capacitance ΔCm.

[0070] The detection circuit 300 according to the example embodiment may include a second portion 320, and when the switch SW of the second portion 320 is closed, the charge from the current source Idc to the first portion 310 is removed, thereby reducing the charge input to the first portion 310. Therefore, even when integration is repeatedly performed by the first portion 310, the amount of charge obtained through integration may not exceed the integration limit. Thus, the number of integrations to be performed increases, resulting in an improvement in the quality of the fingerprint image. In the following description, for ease of explanation, the reduction in charge input to the first portion 310 is represented as the removal of charge input to the first portion 310.

[0071] Specifically, the second portion 320 of the detection circuit 300 is individually connected to the first portion 310. In other words, although a single second portion is not connected to multiple first portions, each second portion 320 is connected to each first portion 310. Therefore, even when the specifications and / or parameters of the detection circuits 300 connected to the sensor 110 are different from each other, an optimal amount of charge can be removed for each of the detection circuits 300.

[0072] refer to Figures 4 to 10An example is described whereby the device 100 generates an image of the object detected by the sensor 110 as each of the optimal charge amounts removed from the detection circuit 300, and integrates the charge amount from which unnecessary charge has been removed.

[0073] Figure 4 This is a flowchart of an example method for generating a fingerprint image according to an exemplary embodiment.

[0074] refer to Figure 4 The method for generating a fingerprint image may include using... Figures 1 to 3 The device 100, sensor 110, and electronic circuit 120 shown operate in a chronological order. Therefore, it can be seen that, although the following description is omitted, the above presentation of information regarding... Figures 1 to 3 The description of the device 100, sensor 110, and electronic circuit 120 shown also applies to Figure 4 Image generation methods.

[0075] In operation 410, processor 123 may determine the amount of charge detected by each detection circuit 300 based on the specifications and / or parameters of the detection circuits 300 included in electronic circuit 120. For example, the specifications and parameters of the detection circuits 300 may include, but are not limited to, the phase margin, gain margin, differential voltage gain, input capacitance, and input offset voltage of the amplifier in each of the detection circuits 300.

[0076] For example, processor 123 can determine the amount of charge based on an offset of detection circuit 300 (e.g., the input offset voltage of an amplifier in detection circuit 300). The offset can be determined by the output value of an analog-to-digital converter (ADC) at the rear end of detection circuit 300. For example, processor 123 can determine the amount of charge such that a first component of the first electrical quantity input to detection circuit 300 is not less than the offset of detection circuit 300. For example, assuming sensor 110 is a sensor for detecting fingerprints, the first component could be a voltage corresponding to the ridges of the fingerprint, but this disclosure is not limited thereto.

[0077] Processor 123 adjusts the amount of current generated in the current source Idc included in the detection circuit 300 and the operating time of the switch SW connected to the current source Idc to correspond to a determined amount of charge. For example, processor 123 calculates the amount of charge by adjusting the amount of current generated in the current source Idc and the operating time of the switch SW. For example, the amount of charge Q can be determined by multiplying the amount of current I by the time T in which the current flows. Therefore, processor 123 can calculate the amount of charge based on the amount of current generated in the current source Idc and the operating time of the switch SW.

[0078] The operating time of switch SW refers to the time it takes for switch SW to close and then change to the ON state. For example, refer to... Figure 3 The detection circuit 300 determines the current to be removed from the first part 310 based on the duration of the closing of the period switch SW.

[0079] The following is for reference. Figures 5 to 9 This describes an example of how processor 123 determines the amount of charge corresponding to detection circuit 300 and adjusts the current of current source Idc and the operating time of switch SW to correspond to the determined amount of charge.

[0080] In operation 420, processor 123 integrates a second charge obtained by removing the charge determined in operation 410 from a first charge obtained from each of the input to the detection circuits 300.

[0081] For example, when sensor 110 is a sensor for detecting fingerprints, the first electrical quantity can be the difference between the voltage corresponding to the ridge of the fingerprint and the voltage corresponding to the valley of the fingerprint, or the capacitance difference between the ridge and the valley, that is, the difference ΔCm between the mutual capacitance corresponding to the ridge and the mutual capacitance corresponding to the valley.

[0082] Processor 123 removes the charge determined in operation 410 from the first charge. Processor 123 integrates the second charge obtained by removing some charge from the first charge. Therefore, the mutual capacitance ΔCm corresponding to the difference between the ridges and valleys of the fingerprint may increase.

[0083] As referenced above Figure 3 As described, the limit value for integration exit can limit the amount of integration available. However, as the processor 123 integrates the second electrical charge, the amount of integration available increases. Therefore, at least because the mutual capacitance of each node of the sensor 110 is removed by an amount adjusted for each of the detection circuits 300 according to specifications / parameters (e.g., the input offset voltage of the amplifier in each of the detection circuits 300), the quality of the image generated by the processor 123 is improved.

[0084] In operation 430, processor 123 generates an image corresponding to the detection of sensor 110 connected to electronic circuit 120 based on whether the integration result of operation 420 meets specific conditions.

[0085] For example, processor 123 may generate an image corresponding to the detection of sensor 110 only if the integration result of operation 420 meets a specific condition. This specific condition may be a specific signal-to-noise ratio, such as 10 dB or greater. However, the specific condition is not limited to the description above.

[0086] When the integration result of operation 420 does not meet a specific condition, processor 123 may repeat operations 410 and 420 at least once. For example, when the integration result does not meet a specific signal-to-noise ratio, processor 123 re-determines the charge quantity based on the third charge quantity obtained by integrating the second charge quantity. In other words, processor 123 re-determines the charge quantity such that the first component of the third charge quantity is not less than the offset of detection circuit 300.

[0087] The processor 123 readjusts the amount of current generated in the current source Idc included in the detection circuit 300 and the operating time of the switch SW connected to the current source Idc to correspond to the redefined amount of charge.

[0088] The processor 123 re-integrates the fourth charge obtained by removing the redetermined charge from the third charge. The processor 123 generates an image corresponding to the detection of the sensor 110 only if the result of the re-integration meets a specific condition. If the result of the re-integration does not meet the specific condition, the above-described process of determining the charge, removing the charge, and integrating the charge is repeated.

[0089] The processor 123 can generate a high-quality image representing the object detected by the sensor 110 through the above processing.

[0090] Figure 5 This is a flowchart illustrating an example of a processor determining the amount of charge according to an example embodiment.

[0091] In operation 510, processor 123 examines the offset of each of the detection circuits 300. For example, when integration of electrical quantity is not performed, processor 123 may determine the offset as the output value of the ADC included in the detection circuit 300.

[0092] In operation 520, processor 123 examines a first component among the various inputs of detection circuit 300. For example, processor 123 may examine the first component from the electrical quantities input to detection circuit 300. When sensor 110 is a sensor for detecting fingerprints, the first component may be a voltage corresponding to the ridges of the fingerprint, but this disclosure is not limited thereto.

[0093] In operation 530, processor 123 sets the candidate charge amount. For example, processor 123 can set the candidate charge amount by adjusting the parameters of the current source Idc and the switch SW in the second part 320 of the detection circuit 300. Specifically, processor 123 can set the candidate charge amount by increasing the current of the current source Idc and the operating time of the switch SW by a certain amount.

[0094] In operation 540, processor 123 determines whether the amount of the first component of the candidate charge removed is less than an offset. For example, when the first component is the voltage corresponding to the ridge of the fingerprint, processor 123 determines whether the amount of voltage corresponding to the ridge of the fingerprint with the candidate charge removed is less than the offset. If the amount of the first component of the candidate charge removed is less than the offset, the process proceeds to operation 550; otherwise, the process proceeds to operation 530, thereby resetting the candidate charge.

[0095] In operation 550, processor 123 determines the final charge amount. Processor 123 can determine the final charge amount such that the amount by which the first component of the charge amount has been removed is not less than an offset. For example, processor 123 can determine the candidate charge amount as the final charge amount before the amount by which the first component of the candidate charge has been removed is less than the offset.

[0096] Although processor 123 repeatedly executes operations 530 and 540 until the amount of the first component of the charge removed is not less than the offset, processor 123 can store each of the candidate charge quantities in memory 124 and assign a reference number to each candidate charge quantity in the order in which the candidate charge quantities were applied in operation 530. The reference number can indicate the number of times each operation in operations 530 and 540 is executed. When processor 123 determines that the condition of operation 540 is satisfied in the nth operation of operation 540, processor 123 can retrieve the candidate charge quantity set in the (n-1)th operation of operation 530 based on the reference number n-1 associated with the (n-1)th operation of operation 530. For example, processor 127 can control memory 124 to store the following data:

[0097]

[0098]

[0099] The following is for reference. Figure 6 A detailed description of an example of how processor 123 determines the final charge amount.

[0100] Figure 6 An example is shown where the processor determines the final charge amount according to an example embodiment.

[0101] First, the processor 123 determines the output value of the ADC of the detection circuit 300 as offset 610. Then, the processor 123 checks the first component 620 from the electrical quantity input to the detection circuit 300.

[0102] The processor 123 sets the candidate charge quantity by adjusting the current quantity of the current source Idc of the detection circuit 300 and the operating time of the switch SW. For example, the processor 123 can increase the candidate charge quantity by increasing the current quantity and the operating time by a certain amount.

[0103] Processor 123 checks whether the results 631, 632, and 633 obtained by removing candidate charge amounts from the first component 620 are less than offset 610. Processor 123 performs the process of setting candidate charge amounts m times, where m is a natural number, and checks whether the results 631, 632, and 633 obtained by removing candidate charge amounts from the first component 620 are less than offset 610.

[0104] For example, when the result 631 of removing the first candidate charge from the first component 620 is greater than the offset 610, the processor 123 sets a second candidate charge and repeats the above process. In this way, when the result 633 of removing the (n+1)th candidate charge from the first component 620 is less than the offset 610 for the first time (where n is a natural number), the processor 123 determines the nth candidate charge as the final charge. In other words, when the result 632 of removing the nth candidate charge from the first component 620 is closest to exceeding the offset 610, the processor 123 determines the nth candidate charge as the final charge.

[0105] The candidate charge quantity can be set to the current quantity of the current source Idc of the detection circuit 300, and the operating time of the switch SW can be adjusted. For example, the processor 123 can set the candidate charge quantity by performing a two-step adjustment process.

[0106] As an example, when the current of the current source Idc is fixed, the processor 123 can perform the first step of the adjustment process by increasing the operating time of the switch SW to determine the maximum operating time of the switch SW. The processor 123 can then perform the second step of the adjustment process to determine the maximum current load of the current source Idc by adjusting the overall current of the current source Idc and the operating time of the switch SW.

[0107] As another example, when the operating time of switch SW is fixed, processor 123 can perform a first-step adjustment process to determine the maximum current of current source Idc by increasing the current amount of current source Idc. Processor 123 can then perform a second-step adjustment process to determine the maximum operating time of switch SW by adjusting the overall current amount of current source Idc and the operating time of switch SW.

[0108] The following is for reference. Figure 7 , Figure 8 and Figure 9 This section provides a detailed example of how the processor sets the candidate charge amount by performing a two-step adjustment process.

[0109] Figure 7 This is a flowchart illustrating an example of setting candidate charge quantities by processor 1123 according to an example embodiment.

[0110] refer to Figure 7The first step of the adjustment process may include operations 710 to 740. Furthermore, the second step of the adjustment process may include operations 750 to 770.

[0111] In operation 710, the processor 123 fixes the amount of current supplied from the current source Idc to a specific value. For example, the specific value can be the default value of the device 100 and can be adaptively changed according to the number of objects or integrals detected by the sensor 110. In addition, the specific value can be changed by the user.

[0112] In operation 720, processor 123 increases the operating time of switch SW. In other words, processor 123 increases the time during which switch SW is closed and then turns on.

[0113] In operation 730, processor 123 determines whether the amount of the first component of the first candidate charge removed is less than an offset. For example, processor 123 can calculate the first candidate charge by multiplying the amount of current supplied from current source Idc by the operating time of switch SW. If the amount of the first component of the first candidate charge removed is greater than the offset, the process proceeds to operation 720; otherwise, the process proceeds to operation 740.

[0114] In operation 740, processor 123 determines the maximum operating time of switch SW. For example, processor 123 selects a candidate charge amount before the amount of the first component of the first candidate charge removed is first less than the offset. Processor 123 determines the computation time used to calculate the selected candidate charge amount as the maximum computation time. (See above reference...) Figure 5 and Figure 6 The process of selecting candidate charge quantities by processor 123 is described.

[0115] In summary, in operation 710, the amount of current supplied from the current source Idc is determined, and in operation 740, the operating time of the switch SW is determined. However, the current amount and operating time determined when performing operations 710 to 740 may not be optimal results. This is because, in operation 710, it is assumed that the current amount is fixed at a specific value. Therefore, the processor 123 can determine the optimal current amount and optimal operating time by performing coarse adjustment through the first step of the adjustment process and fine adjustment through the second step of the adjustment process.

[0116] In operation 750, processor 123 adjusts the operating time of switch SW and the amount of current supplied from current source Idc. In operation 760, processor 123 determines whether the amount of the first component of the second candidate charge removed is less than an offset. For example, processor 123 can calculate the second candidate charge by multiplying the amount of current adjusted in operation 750 by the operating time. When the amount of the first component of the first candidate charge removed is greater than the offset, processing proceeds to operation 750; otherwise, processing proceeds to operation 770.

[0117] In operation 770, processor 123 determines the maximum current amount of current source Idc. For example, processor 123 selects a candidate charge amount before the amount of the first component after removing the second candidate charge is first less than the offset. Processor 123 determines the current amount used to calculate the selected candidate charge amount as the maximum current amount. (Refer to above) Figure 5 and Figure 6 The process of selecting candidate charge quantities by processor 123 is described.

[0118] Figure 8 The following is a detailed illustration of an example embodiment. Figure 7 The method described in the flowchart.

[0119] Figure 8 An example table is shown, consisting of the current I of the current source Idc, the operating time T of the switch SW, and the charge Q. The charge Q is calculated by multiplying the current I by the operating time T.

[0120] Assume the operating time T can be changed from 1 to 20 in increments of 1, and the current I can be changed from 1 to 20 in increments of 1. Furthermore, assume the range from 1 to 20 indicates the relative amounts of operating time T and current I from their respective minimum to maximum values. In this case, the total number of combinations of [operating time T, current I] to be selected by processor 123 is 400. Therefore, a large amount of computation may be required to determine the optimal operating time T and optimal current I. The computational load required to determine the optimal operating time T and optimal current I can be reduced when processor 123 performs the first and second adjustment steps.

[0121] Processor 123 can perform the first step of adjustment by increasing one of the current I and the operating time T, while keeping the other fixed at a specific value. For example, processor 123 can perform the first step of adjustment in which the amount of current I is increased while the amount of operating time T is fixed at 14. Figure 8 The maximum operating time T is determined to be 12 based on the first step adjustment.

[0122] exist Figure 8In this process, since the current I is assumed to be fixed at 14 in the first adjustment step, the charge Q of 6.72C as a result of the first adjustment step may not be the optimal charge. In other words, the optimal charge Q can be any value in the range of 6.72C to 7.28C, so the optimal charge Q does not have to be fixed at 6.72C.

[0123] The processor 123 can perform the second step of adjustment by regulating the current I and the operating time T. Figure 8 In the process of performing the second step of adjustment, the optimal charge Q can be checked to be 7.2C, and therefore the maximum operating time T can be determined to be 12, and the maximum current I can be determined to be 15.

[0124] Based on the above reference Figure 7 and Figure 8 As described above, processor 123 can perform the first step of regulation while fixing the amount of current I supplied from current source Idc, but this disclosure is not limited thereto.

[0125] The following is for reference. Figure 9 This describes an example of the processor 123 performing the first step of adjustment while the operation time T of the fixed switch SW is being described.

[0126] Figure 9 This is a flowchart of another example of setting the candidate charge amount by the processor according to the example embodiment.

[0127] refer to Figure 9 The first step of the adjustment process may include operations 910 to 940. Furthermore, the second step of the adjustment process may include operations 950 to 970.

[0128] In operation 910, the processor 123 fixes the operating time of the switch SW to a specific value. For example, the specific value can be the default value of the device 100, or it can be adaptively changed according to the number of objects or integrals detected by the sensor 110. In addition, the specific value can be changed by the user.

[0129] In operation 920, processor 123 increases the current of current source Idc. In operation 930, processor 123 determines whether the amount of the first component of the third candidate charge removed is less than the offset. If the amount of the first component of the third candidate charge removed is greater than the offset, the process proceeds to operation 920; otherwise, the process proceeds to operation 940.

[0130] In operation 940, processor 123 determines the maximum current amount of current source Idc. For example, processor 123 selects a candidate charge amount before the amount of the first component of the first candidate charge removed is first less than an offset. Processor 123 determines the current amount used to calculate the selected candidate charge amount as the maximum current amount. (Refer to above) Figure 5 and Figure 6 The process of selecting candidate charge quantities by processor 123 is described.

[0131] In operation 950, processor 123 adjusts the operating time of switch SW and the amount of current supplied from current source Idc. In operation 960, processor 123 determines whether the amount of the first component of the fourth candidate charge removed is less than an offset. If the amount of the first component of the fourth candidate charge removed is greater than the offset, the process proceeds to operation 950; otherwise, the process proceeds to operation 970.

[0132] In operation 970, processor 123 determines the maximum operating time of switch SW. For example, processor 123 selects a candidate charge amount before the amount of the first component of the second candidate charge removed is first less than the offset. Processor 123 determines the computation time used to calculate the selected candidate charge amount as the maximum computation time. (See above reference...) Figure 5 and Figure 6 The process of selecting candidate charge quantities by processor 123 is described.

[0133] Figure 10 Another example of a detection circuit 1000 included in a receiving circuit according to an example embodiment is shown.

[0134] Figure 10 An example of a detection circuit 1000 is shown. When... Figure 3 The detection circuit 300 and Figure 10 When the detection circuits 1000 compare with each other, the first part 310 may correspond to the first part 1010, and the second part 320 may correspond to the second part 1020. The first part 1010 may also include an ADC.

[0135] The detection circuit 1000 may include a third part 1030, and the third part 1030 may control the operating time of the switch included in the second part 1020 and the current amount of the current source. Although Figure 10 The third part 1030 is shown to include a separate processor 1033, which controls the operating time of the switch and the current of the current source; however, this disclosure is not limited thereto. When the processor 1033 is omitted in the third part 1030, the above-described functions of the processor 1033 can be performed by the processor 123.

[0136] The third part 1030 may include a first register 1031 corresponding to a switch and a second register 1032 corresponding to a current source. (See reference) Figures 3 to 9The operating time of the switch can be set in register 1031, and the current amount of the current source can be set in the second register 1032. Furthermore, both the first register 1031 and the second register 1032 can be included as a single configuration in the third part 1030.

[0137] Based on the above description, device 100 can determine an optimal charge amount for each detection circuit and set the current of the current source and the operating time of the switch according to the determined charge amount. Therefore, without the limitation of an integration limit, device 100 can perform a sufficient number of integrations relative to the effective charge amount required to generate the image. Thus, device 100 can generate a high-quality image of the object detected by the sensor.

[0138] Figure 11 A fingerprint image according to an example embodiment and a fingerprint image according to a comparison example are shown.

[0139] According to an example embodiment, the amount of charge to be removed from each of the plurality of detection circuits 300 is optimized for each of the plurality of detection circuits 300 based on the amplifier characteristics (e.g., input amplifier offset voltage) of each of the plurality of detection circuits 300.

[0140] According to Comparative Example 1, no charge was removed from the multiple detection circuits 300. According to Comparative Example 2, the same amount of charge was removed from each of the multiple detection circuits 300 without optimization.

[0141] Referring to the graph of the relationship between the number of integration indicators and the output voltages VOUT1 to VOUT4 respectively output from the plurality of detection circuits 300, more integration can be performed compared to Comparative Examples 1 and 2. Therefore, a higher quality fingerprint image can be generated according to the exemplary embodiment compared to Comparative Examples 1 and 2.

[0142] Moreover, such as Figure 11 As shown, the fingerprint image A generated and displayed on the display 125 of the device 100 according to the example embodiment has a higher resolution than the fingerprint images B and C generated and displayed according to Comparative Examples 1 and 2.

[0143] The methods described above can be programmed into a computer program and implemented in a general-purpose digital computer that executes the program using a computer-readable recording medium. Furthermore, the data structures used in the methods described above can be recorded on a computer-readable recording medium by various means. Examples of computer-readable recording media include magnetic storage media (e.g., ROM, floppy disk, hard disk, etc.), optical recording media (e.g., CD-ROM or DVD), etc.

[0144] It should be understood that the exemplary embodiments described herein are to be considered descriptive only and not for limiting purposes. The description of features or aspects in each exemplary embodiment should be typically considered as other similar features or aspects that may be used in other exemplary embodiments. Although one or more exemplary embodiments have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope defined by the appended claims.

Claims

1. A method for generating a fingerprint image, the method comprising: Based on the amplifier characteristics of each of a plurality of detection circuits connected to a fingerprint sensor, an amount of charge to be removed from each of the plurality of detection circuits is determined, wherein each of the plurality of detection circuits includes: a current source; and a switch configured to connect the current source to the plurality of detection circuits according to a control signal; a second amount of charge is obtained by removing the amount of charge from a first amount of charge input to each of the plurality of detection circuits, wherein obtaining the second amount of charge includes: determining a maximum on-time of the switch and a maximum current of the current source, respectively; determining the amount of charge by adjusting the current generated by the current source and the on-time of the switch based on the maximum on-time and the maximum current; and obtaining the second amount of charge by removing the determined amount of charge from the first amount of charge; Integrate the second electrical quantity to obtain an integral value; and The fingerprint image is generated based on a comparison between the integral value of the second electrical charge and a predetermined threshold.

2. The method of claim 1, wherein the predetermined threshold corresponds to the input offset voltage of the amplifier included in each of the plurality of detection circuits.

3. The method according to claim 2, further comprising: The input offset voltage of the amplifier is determined based on the output value of the analog-to-digital converter (ADC) included in each of the plurality of detection circuits.

4. The method of claim 2, wherein determining the amount of charge comprises: The charge quantity is determined such that a first component of the first charge quantity is not less than the input offset voltage of the amplifier.

5. The method according to claim 1, wherein determining the maximum on-time of the switch and the maximum current of the current source comprises: By increasing the on-time of the switch while keeping the amount of current generated from the current source constant, the maximum on-time of the switch is determined to be such that a first component of the first electrical quantity is not less than the input offset voltage of the amplifier included in each of the plurality of detection circuits. as well as By adjusting the on-time of the switch and the amount of current generated from the current source, the maximum current of the current source whose first component is not less than the input offset voltage of the amplifier is determined.

6. The method according to claim 1, wherein determining the maximum on-time of the switch and the maximum current of the current source comprises: By increasing the amount of current generated from the current source while fixing the on-time of the switch, it is determined that the first component of the first electrical quantity is not less than the maximum current of the current source of the amplifier included in each of the plurality of detection circuits, which is not less than the input offset voltage of the amplifier included in each of the plurality of detection circuits. as well as The maximum on-time of the switch is determined by adjusting the on-time of the switch and the amount of current generated from the current source, such that the first component is not less than the input offset voltage.

7. The method according to claim 1, further comprising: Based on the integral value being greater than or equal to the predetermined threshold, the charge quantity is determined at least once and the second charge quantity is integrated.

8. The method of claim 1, wherein the predetermined threshold represents the signal-to-noise ratio of each of the plurality of detection circuits.

9. A non-transitory computer-readable recording medium having a program recorded thereon for performing the method according to claim 1.

10. An apparatus comprising: A fingerprint sensor includes multiple driving electrodes and multiple detection electrodes; Multiple detection circuits are connected to the fingerprint sensor, wherein each of the multiple detection circuits includes a current source and a switch, the switch being configured to connect the current source to the multiple detection circuits according to a control signal; as well as At least one processor is configured as follows: Based on the amplifier characteristics of each of the plurality of detection circuits, the amount of charge to be removed from each of the plurality of detection circuits is determined; A second charge is obtained by removing the charge from a first charge input to each of the plurality of detection circuits, wherein obtaining the second charge includes: determining the maximum on-time of the switch and the maximum current of the current source, respectively; determining the charge by adjusting the current generated by the current source and the on-time of the switch based on the maximum on-time and the maximum current; and obtaining the second charge by removing the determined charge from the first charge. Integrate the second electrical quantity to obtain an integral value; and A fingerprint image is generated based on a comparison between the integral value of the second electrical charge and a predetermined threshold.

11. The apparatus of claim 10, wherein each of the plurality of detection circuits comprises an amplifier, and The predetermined threshold corresponds to the input offset voltage of the amplifier included in each of the plurality of detection circuits.

12. The apparatus of claim 11, wherein the at least one processor is further configured to determine the input offset voltage of the amplifier based on the output value of the analog-to-digital converter (ADC) included in each of the plurality of detection circuits.

13. The apparatus of claim 11, wherein the at least one processor is further configured to determine the amount of charge such that a first component of the first amount of charge is not less than the input offset voltage of the amplifier.

14. The apparatus of claim 10, wherein determining the maximum on-time of the switch and the maximum current of the current source comprises: By increasing the on-time of the switch while keeping the amount of current generated from the current source constant, the maximum on-time of the switch is determined to be such that a first component of the first electrical quantity is not less than the input offset voltage of the amplifier included in each of the plurality of detection circuits. as well as By adjusting the on-time and the amount of current generated from the current source, the maximum current of the current source whose first component is not less than the input offset voltage of the amplifier is determined.

15. The apparatus of claim 10, wherein determining the maximum on-time of the switch and the maximum current of the current source comprises: By increasing the amount of current generated from the current source while fixing the on-time of the switch, it is determined that the first component of the first electrical quantity is not less than the maximum current of the current source of the amplifier included in each of the plurality of detection circuits, which is not less than the input offset voltage of the amplifier included in each of the plurality of detection circuits. as well as The maximum on-time of the switch is determined by adjusting the on-time of the switch and the amount of current generated from the current source, such that the first component is not less than the input offset voltage.

16. The apparatus of claim 10, wherein the at least one processor is further configured to repeat the operation of determining the charge quantity and the operation of integrating the second charge quantity at least once based on the integral value being greater than or equal to the predetermined threshold.

17. The apparatus of claim 10, wherein the predetermined threshold represents the signal-to-noise ratio of each of the plurality of detection circuits.

18. An electronic device comprising: A fingerprint sensor includes multiple driving electrodes and multiple detection electrodes; Multiple detection circuits are configured to receive a first electrical charge from the multiple detection electrodes of the fingerprint sensor, the multiple detection circuits including an analog-to-digital converter (ADC), a current source, and a switch configured to connect the current source to the ADC; as well as At least one processor is configured as follows: Based on the output voltage of the ADC, determine the amount of candidate charge to be removed from each of the plurality of detection circuits; The second electrical quantity, obtained by removing the candidate charge from the first electrical quantity, is subjected to a first integral until the first electrical quantity becomes less than a predetermined threshold. Obtaining the second electrical quantity includes: determining the maximum on-time of the switch and the maximum current of the current source; determining the candidate charge by adjusting the current generated by the current source and the on-time of the switch based on the maximum on-time and the maximum current; and obtaining the second electrical quantity by removing the determined candidate charge from the first electrical quantity. Based on the integral value of the second charge, the final amount of charge to be removed from each of the plurality of detection circuits is determined, wherein the integral value of the second charge is obtained by performing a second integral on the second charge, the second number being less than the first number; and A fingerprint image is generated by removing the final charge from the plurality of detection circuits.

Images