Device and method for fingerprint sensing

Abstract

The application provides a device for fingerprint sensing. The device comprises a Code Division Multiple (CDM) driver for acquiring multiple sets of raw data by using a set of CDM codes multiple times, and a data processor for combining the multiple sets of raw data to reconstruct high-resolution image data. The application improves the sensing distance while maintaining high resolution.

Description

TECHNICAL FIELD

[0001] The present application relates to an apparatus and method for fingerprint sensing. BACKGROUND

[0002] In a capacitive finger print sensor (FPS), horizontal Tx lines are driven line by line. For example, a rectangular wave is applied to each Tx line, and the current according to the finger-induced capacitance flows in each vertical Rx line, and this operation is repeated from the top Tx line to the bottom Tx line. The capacitive FPS has a distance limit of less than 0.2mm or 0.3mm because the electric field generated by the FPS is very weak due to a high-resolution sensor. Therefore, it is difficult to use it in a smartphone because it is easily broken by a thinner cover glass.

[0003] In a bundled drive, a rectangular wave is applied to Tx lines, for example, in three consecutive lines, which allows to increase the sensing distance. This technique is applied to hovering detection, etc. Therefore, it allows to detect information of a more distant object.

[0004] In a Code Division Multiplex (CDM) drive, a waveform corresponding to a CDM code is applied and detected at a predetermined number of consecutive lines and a predetermined time point, and it allows to improve the signal level by generating a strong electric field. The strength and quality of the signal are proportional to the number of CDM codes. But the positive and negative voltages are randomly mixed with the minimum sensor pitch, and the electric fields partially cancel each other out. So the electric field cannot reach a long distance. SUMMARY

[0005] The present application provides an apparatus and method for fingerprint sensing to increase the sensing distance while maintaining high resolution, for example, by combining a bundled shift CDM drive and a super-resolution method, it is possible to perform fingerprint detection using a thicker cover glass.

[0006] According to a first aspect, there is provided an apparatus for fingerprint sensing, wherein the apparatus comprises: a Code Division Multiple (CDM) driver for acquiring a plurality of sets of raw data by using a set of CDM codes a plurality of times; and a data processor for combining the plurality of sets of raw data to reconstruct high-resolution image data.

[0007] In one possible implementation, the CDM driver comprises: a plurality of scanners for providing a CDM waveform to each line according to a CDM waveform pattern; and a random sequencer for sequentially selecting the scanners.

[0008] In one possible implementation, the frequency of the clock provided to the scanners is different from the frequency of the clock provided to the sequencer.

[0009] In one possible implementation, the CDM driver comprises a plurality of scanners for providing CDM waveforms to the lines according to a CDM waveform pattern, a start selector for setting a start position of selecting the scanners, a random sequencer for successively selecting every Mth scanner, and an output selector for connecting the scanners to the corresponding line and the subsequent (M-1) lines.

[0010] In one possible implementation, the CDM waveform pattern is for NM lines and NM time points, and it is generated from a CDM waveform pattern for N lines and N time points by repeating each waveform M times in each column and adding (M-1) columns after each column (M-1) times.

[0011] In one possible implementation, the CDM driver comprises a random sequencer for successively selecting each other scanner, an odd line driver comprising scanners for driving corresponding odd lines, an even line driver comprising scanners for driving corresponding even lines, and a switch for connecting the odd lines to corresponding scanners in the odd line driver and the even lines to VGL when driving the odd lines, and connecting the even lines to corresponding scanners in the even line driver and the odd lines to VGL when driving the even lines.

[0012] In one possible implementation, the CDM code is an m-sequence code.

[0013] According to a second aspect, there is provided a method for fingerprint sensing, wherein the method comprises: acquiring, by a code division multiplexing (CDM) driver, a plurality of groups of raw data by using a set of CDM codes a plurality of times; and combining, by a data processor, the plurality of groups of raw data to reconstruct high resolution image data. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0015] Figure 1 A flow chart of a method for fingerprint sensing according to an embodiment of the present application is shown;

[0016] Figure 2 A simplified structural diagram of a detection area of an apparatus is shown;

[0017] Figure 3 A simplified structural diagram of a detection area is shown;

[0018] Figure 4 A diagram illustrating CDM driving is shown;

[0019] Figure 5 An example of a waveform pattern to be applied is shown;

[0020] Figure 6 A process of generating high resolution image data from raw data of a frame is shown;

[0021] Figure 7 A process of calculating three sets of low resolution image data after all raw data is acquired is shown;

[0022] Figure 8 A process of calculating sets of low resolution image data after partial raw data is acquired is shown.

[0023] Figure 9 A block diagram of a CDM driver for bundled CDM driving according to an embodiment of the present application is shown;

[0024] Figure 10 A clock signal provided to a random sequencer and a scanner is shown;

[0025] Figure 11 A waveform used in a random sequencer is shown;

[0026] Figure 12 A block diagram of another CDM driver for bundled CDM driving according to an embodiment of the present application is shown;

[0027] Figure 13 A process of Figure 12 Operation of the CDM driver for bundled CDM driving shown is shown;

[0028] Figure 14 A circuit example of a sensor for detecting electric field intensity detected by an RX line is shown;

[0029] Figure 15 How ΔCm is acquired is shown;

[0030] Figure 16 A relationship between the number of Tx lines and capacitance is shown;

[0031] Figure 17 Measurement results of SNR of TDM, CDM128, CDM256, and CDM512 driving schemes are shown;

[0032] Figure 18 Measurement results of signal levels are shown;

[0033] Figure 19Measurement results of SNR are shown.

[0034] Figure 20 Waveform patterns used in a random sequencer are shown.

[0035] Figure 21 Relationships between Tx lines for generating electric fields and Rx lines for detecting electric fields are shown.

[0036] Figure 22 Relationships between Tx lines for generating electric fields and Rx lines for detecting electric fields are shown.

[0037] Figure 23 Relationships between Tx lines for generating electric fields and Rx lines for detecting electric fields are shown.

[0038] Figure 24 A two-dimensional (2D) CDM scheme according to an embodiment of the present application is shown.

[0039] Figure 25 A voltage forming method according to an embodiment of the present application is shown.

[0040] Figure 26 A voltage forming and CDM driving scheme according to an embodiment of the present application is shown.

[0041] Figure 27 (a) shows an application scenario of an embodiment of the present application.

[0042] Figure 27 (b) shows an application scenario of an embodiment of the present application; and

[0043] Figure 27 (c) shows an application scenario of an embodiment of the present application. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. The described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0045] Figure 1 A flow chart of a method for fingerprint sensing according to an embodiment of the present application is shown. In step S1, raw data of a frame is acquired by using a bundled CDM driving. The bundled CDM driving performs CDM driving using a set of lines. First, refer to Figures 2 to 4 CDM driving is explained. Electric fields are generated by horizontal Tx lines (hereinafter, Tx lines are also referred to as “lines” simply) and detected by vertical Rx lines. To simplify the description, Figure 3Only Tx1 to Tx4 lines are shown. The same rectangular wave is applied on each line, while the waveform is detected in all Rx lines.

[0046] In this example, the application of the rectangular wave and the detection of the waveform are performed at four time points, as Figure 4 indicated. Figure 3 The object is shown on the Tx2 line. Figure 4 The level detected in one Rx line over time is shown, specifically, at the intersection of the Rx line and the Tx1 to Tx4 lines in Figure 3 The current depending on the capacitance caused by the object flows in each Rx line. As Figure 4 indicated, since the object is on the Tx2 line, the level detected in the Tx2 line is 20% lower than the levels detected in the Tx1, Tx3, and Tx4 lines.

[0047] The detected levels are summed at each time point indicated by the dotted arrows in Figure 4 . Assuming that the level detected from low to high is 1 without the object, and the level detected from high to low is -1 without the object, the level detected from low to high is 0.8 with the object, and the level detected from high to low is -0.8 with the object, the summed levels are shown below the corresponding dotted arrows. These values are multiplied by a matrix corresponding to the CDM code, and then subtracted from values corresponding to the number of lines. The value depending on the object is 0.8 in the TX2 line, and 0 in the other lines. In this way, the signal of one Rx line can be acquired. The signal of one frame can be acquired by acquiring the signal of each Rx line. In this way, the raw data of one frame can be acquired.

[0048] In the embodiment of the present invention, 21 lines are CDM driven. However, the number of lines is not limited. Figure 5 An example of a waveform pattern to be applied to lines 1 to 21 and 21 time points is shown. "P" indicates that the level is applied from low to high, and "N" indicates that the level is applied from high to low. For Figure 5 The raw data in each Rx line is acquired for each time point in Figure 5 By acquiring the raw data of 21 time points using the waveform pattern in

[0049] Returning to Figure 1 , in step S2, a plurality of sets of low-resolution image data are generated from the one-frame bundled CDM driving data by sorting and calculation. The raw data of one frame includes the raw data of 21 time points. As Figure 6As shown, the raw data of one frame is divided into three groups of raw data by ordering in a predetermined time sequence. The first group includes the raw data of the 1st, 4th, 7th, 10th, 13th, 16th and 19th time points, i.e. the raw data of every third time point starting from the 1st time point. The second group includes the raw data of the 2nd, 5th, 8th, 11th, 14th, 17th and 20th time points, i.e. the raw data of every third time point starting from the 2nd time point. The third group includes the raw data of the 3rd, 6th, 9th, 12th, 15th, 18th and 21st time points, i.e. the raw data of every third time point starting from the 3rd time point.

[0050] Then, the first, second and third groups of raw data including 21 lines and 7 time points of raw data are subjected to CDM decoding process. For example, by using the raw data of the 1st to 7th lines and 7 time points, the signals of the 1st to 7th lines in each Rx line can be calculated in the same way as explained with reference to Figure 4

[0051]

[0052] In this embodiment, the sensing distance can be improved from 200umCG (micron cover glass) to 400umCG, the signal level can be improved up to 1000 times, and the high resolution can be maintained up to 300ppi (pixels per inch).

[0053] In this embodiment, after obtaining the raw data of the 1st to 21st time points and ordering the raw data, three groups of low resolution image data are calculated as shown in Figure 7 Figure 8 Figure 6 ​​​​The time-sequential acquisition of raw data is shown on the right. In this way, after the acquisition of raw data at time points 1 to 7, a first set of low-resolution image data can be computed immediately, after the acquisition of raw data at time points 8 to 14, a second set of low-resolution image data can be computed immediately, and after the acquisition of raw data at time points 15 to 21, a third set of low-resolution image data can be computed immediately, as shown in Figure 8 The CDM decoding process takes a long time. This structure enables pipelining of data sensing and code decoding, thus increasing the sensing and computation speed.

[0054] The following describes a circuit for fingerprint sensing according to an embodiment of the present application.

[0055] Figure 9 A block diagram of a CDM driver for bundled CDM driving according to an embodiment of the present application is shown. The combination of bundled driving and CDM driving is achieved by a simple circuit configuration using a simple scanner and a randomizer (e.g., m-sequence). This circuit allows a stronger electric field to be generated by bundled CDM driving. Step S1 is performed by the CDM driver, and steps S2 and S3 are performed by the data processor.

[0056] Scanners 1 to 21 (scanners 10 to 21 are not shown in Figure 9 are driven by different frequencies clk1 and clk2 in Figure 10 , clk1 is used for scanners 1 to 21, and clk2 is used for randomizer 30. Randomizer 30 uses Figure 11 a waveform pattern of 7 lines and 7 time points in

[0057] First, randomizer 30 generates the CDM code "P", "N", "N", "P", "P", "P", "N" shown in the leftmost column of the waveform pattern in Figure 11 in synchronization with clk2, and the generated CDM code is stored in each scanner in synchronization with clk1. Similarly, randomizer 30 stores the "P" waveform in scanners 1 to 3, the "N" waveform in scanners 4 to 6, and the waveform in scanners 7 to 21. After all the CDM codes are stored in scanners 1 to 21, scanners 1 to 21 drive the Tx lines according to the stored codes and detect the waveforms in the Tx lines in each Rx line.

[0058] Next, randomizer 30 generates the CDM code "P", "N", "N", "P", "P", "P", "N" shown in the leftmost column of the waveform pattern in Figure 11The CDM code "N", "P", "N", "N", "P", "P", "P" shown in the second column on the left of the middle wave pattern and the generated CDM code is stored in each scanner in synchronization with clk1. Similarly, the random sequencer 30 stores "N" waveforms in scanners 1 to 3, "P" waveforms in scanners 4 to 6, and waveforms in scanners 7 to 21. After storing all the CDM codes in scanners 1 to 21, the scanners 1 to 21 drive the Tx lines according to the stored codes and detect the waveforms in the Tx lines in each Rx line.

[0059] The subsequent steps are similarly performed and the raw data corresponding to the waveforms at the 4th to 21st time points in the middle are obtained. Figure 4

[0060] A block diagram of another CDM driver for bundled CDM driving according to an embodiment of the present application is shown. The combination of bundled driving and CDM driving is achieved by using a simple circuit configuration of block scanners, a random sequencer (e.g. m-sequence) and a sensing block selector. This circuit allows faster generation of a fingerprint image. Figure 12 The circuit includes scanners 1 to 21 (scanners 10 to 21 are not shown), a random sequencer 30, a start selector 40 and output selectors 101 to 121 (output selectors 110 to 121 are not shown). The start selector 40 sets the start position of the selection of the scanners and the random sequencer 30 selects every third scanner in turn. Each output selector connects a scanner to a corresponding line and two subsequent lines, for example, when scanner 1 is selected, the output selector 101 connects scanner 1 to the first to third lines.

[0061]

[0062] The operation of the CDM driver for bundled CDM driving shown is shown. Figure 13 The wave pattern shown on the right is applied to these lines. Figure 12 The left, middle and right parts of Figure 6 show the operation of obtaining the raw data for the first, second and third images in Figure 13 The wave pattern of 7 lines and 7 time points in Figure 7 Figure 11 First, referring to the left part of the start selector 40 opens the left switch in response to the signal sel1 and thereby drives scanners 1, 4, 7, 10, 13, 16 and 19 in that order, i.e. every third scanner starting from scanner 1. The output selectors 101 to 121 open the upper switches in response to the signal sel1. The random sequencer 30 uses the wave pattern of 7 lines and 7 time points in

[0063] Figure 13 Figure 11 ​​The waveforms are shown in the leftmost column. Therefore, scanner 1 outputs a "P" waveform on lines 1 to 3, scanner 4 outputs an "N" waveform on lines 4 to 6, scanner 7 outputs an "N" waveform on lines 7 to 9, scanner 10 outputs a "P" waveform on lines 10 to 12, scanner 13 outputs a "P" waveform on lines 13 to 15, scanner 16 outputs a "P" waveform on lines 16 to 18, and scanner 19 outputs an "N" waveform on lines 19 to 21. The waveform on each Rx line is detected.

[0064] Then, the random sequencer 30 uses Figure 11 The waveforms in the second column from the left are detected, and the same scanner is driven. Therefore, scanner 1 outputs an "N" waveform on lines 1 to 3, scanner 4 outputs a "P" waveform on lines 4 to 6, scanner 7 outputs an "N" waveform on lines 7 to 9, scanner 10 outputs an "N" waveform on lines 10 to 12, scanner 13 outputs a "P" waveform on lines 13 to 15, scanner 16 outputs a "P" waveform on lines 16 to 18, and scanner 19 outputs a "P" waveform on lines 19 to 21. The waveform on each Rx line is detected.

[0065] Random sequencer 30 is used sequentially Figure 11 The waveforms in columns three through seven from the left are output online by the same scanner, and the waveforms on each Rx line are detected. This obtains the raw data for the first image.

[0066] Secondly, refer to Figure 13 The intermediate image is processed, and selector 40 activates the intermediate switch in response to signal sel2, thereby driving scanners 2, 5, 8, 11, 14, 17, and 20 in that order, i.e., driving every third scanner starting with scanner 2. Output selectors 101 to 121 activate the intermediate switches in response to signal sel2. Random sequencer 30 uses... Figure 11 The waveforms are shown in the leftmost column. Therefore, line 1 is connected to VGL (the voltage corresponding to the gate driver's turn-off voltage). Scanner 2 outputs "P" waveforms on lines 2 through 4, scanner 5 outputs "N" waveforms on lines 5 through 7, scanner 8 outputs "N" waveforms on lines 8 through 10, scanner 11 outputs "P" waveforms on lines 11 through 13, scanner 14 outputs "P" waveforms on lines 14 through 16, scanner 17 outputs "P" waveforms on lines 17 through 19, and scanner 20 outputs "N" waveforms on lines 20 through 21. The waveform on each Rx line is detected.

[0067] Random sequencer 30 is used sequentially Figure 11The waveforms from the second to seventh columns from the left are obtained by scanning the same waveforms on the lines and detecting the waveforms on each Rx line. This process yields the raw data for the second image.

[0068] Third, see Figure 13 On the right side, selector 40 activates the right switch in response to signal sel3, thereby driving scanners 3, 6, 9, 12, 15, 18, and 21 in that order, starting with scanner 3 and driving every third scanner. Output selectors 101 to 121 activate the lower switch in response to signal sel3. Random sequencer 30 uses... Figure 11 The waveforms are shown in the leftmost column. Therefore, lines 1 and 2 are connected to VGL. Scanner 3 outputs "P" waveforms on lines 3 through 5, scanner 6 outputs "N" waveforms on lines 6 through 8, scanner 9 outputs "N" waveforms on lines 9 through 11, scanner 12 outputs "P" waveforms on lines 12 through 14, scanner 15 outputs "P" waveforms on lines 15 through 17, scanner 18 outputs "P" waveforms on lines 18 through 20, and scanner 21 outputs "N" waveforms on line 21. The waveforms on each Rx line are detected.

[0069] Random sequencer 30 is used sequentially Figure 11 The waveforms from the second to seventh columns from the left are obtained by scanning the same waveforms on the lines, detecting the waveforms on each Rx line. This process yields the raw data for the third image.

[0070] Here, an example of a readout circuit connected to the RX line will be described. Figure 14 An example circuit of a sensor for detecting the electric field strength detected by the RX line is shown. Figure 14 On the left side of the circuit shown, a 20V rectangular waveform is applied to the Tx line. The sensor capacitance ΔCm is calculated using the formula ΔCm = Cm ridge - Cm valley. Figure 15 As shown. Cm represents the Tx-Rx mutual capacitance. The capacitance when performing CDM using four Tx lines is greater than the capacitance between one Tx line and one Rx line, as shown. Figure 16 As shown. The ridge (Cm) is the capacitance when the ridge of the finger surface is above the Tx and Rx lines, and the valley (Cm) is the capacitance when the valley of the finger surface is above the Tx and Rx lines. The current, depending on ΔCm, flows from the sensor output to the analog front end (AFE). The AFE includes an integrator, a gain amplifier (gain AMP), and an analog-to-digital converter (ADC). The integrated waveform output from the integrator is amplified and converted into a digital signal.

[0071] In an embodiment according to the present invention, a high-order CDM driving scheme can achieve a high SNR. Figure 17 The measurement results of the SNR of the TDM, CDM128, CDM256, and CDM512 driving schemes are shown. A 60-μm sensor pitch and a 500-μm tester pitch were used. Figure 18 The measurement results of the signal level are shown, and Figure 19 the measurement results of the SNR are shown. The measured signal level and SNR increase approximately proportionally to the CDM order.

[0072] Next, refer to Figures 20 to 23 to describe another embodiment of the CDM driving scheme. In Figures 21 to 23 , the number of scanners is 32, and the waveform pattern shown in Figure 20 is used.

[0073] Before explaining the actual operation, for easier understanding, how to obtain the signal only for the first Rx output is explained below. The first Rx output is enabled by the switch (SW) of the first Rx output.

[0074] Refer to Figure 21 , and the operations at the 1st and 4th time points are described as follows: <000023​​​​​​​​​​​​​​​​​​​​​In the "second column", the Rx line bundles 2, 3, 6, and 8 of the number of rows of "N" are driven by an "N" waveform, and the electric fields detected by the first Rx output are summed to a negative value. The sum of the positive and negative values is the Rx output at the 4th time point.

[0077] Reference Figure 22 , the operations at the 2nd and 5th time points are described as follows:

[0078] At the 2nd time point, in " Figure 22 ", the Rx line bundles 3, 4, 6, 8, 9, and 10 corresponding to the number of rows of "P" in the " Figure 20 " in the "first column" are driven by a "P" waveform, and the electric fields detected by the first Rx output are summed to a positive value. After that, in " Figure 22 ", the Rx line bundles 1, 2, 5, and 7 corresponding to the number of rows of "N" in the " Figure 20 " in the "first column" are driven by an "N" waveform, and the electric fields detected by the first Rx output are summed to a negative value. The sum of the positive and negative values is the Rx output at the 2nd time point.

[0079] At the 5th time point, in " Figure 22 ", the Rx line bundles 1, 4, 5, 7, 9, and 10 corresponding to the number of rows of "P" in the " Figure 20 " in the "second column" are driven by a "P" waveform, and the electric fields detected by the first Rx output are summed to a positive value. After that, in " Figure 22 ", the Rx line bundles 2, 3, 6, and 8 corresponding to the number of rows of "N" in the " Figure 20 " in the "second column" are driven by an "N" waveform, and the electric fields detected by the first Rx output are summed to a negative value. The sum of the positive and negative values is the Rx output at the 5th time point.

[0080] Reference Figure 23 , the operations at the 3rd and 6th time points are described as follows:

[0081] At the 3rd time point, in " Figure 23 ", the Rx line bundles 3, 4, 6, 8, 9, and 10 corresponding to the number of rows of "P" in the " Figure 20 " in the "first column" are driven by a "P" waveform, and the electric fields detected by the first Rx output are summed to a positive value. After that, in " Figure 23 ", the Rx line bundles 1, 2, 5, and 7 corresponding to the number of rows of "N" in the " Figure 20 " in the "first column" are driven by an "N" waveform, and the electric fields detected by the first Rx output are summed to a negative value. The sum of the positive and negative values is the Rx output at the 3rd time point.

[0082] At the 6th time point, in " Figure 23 ", the Rx line bundles corresponding to...Figure 20 The Rx line bundles 1, 4, 5, 7, 9, and 10 in the row of "P" in the "second column" are driven with the "P" waveform, and the electric field detected by the first Rx output is summed as a positive value. After that, the Rx line bundles 2, 3, 6, and 8 in the row of "N" in the "second column" are driven with the "N" waveform, and the electric field detected by the first Rx output is summed as a negative value. The sum of the positive value and the negative value is the Rx output at the 6th time point. Figure 23 Figure 20 The Rx line bundles 2, 3, 6, and 8 in the row of "N" in the "second column" are driven with the "N" waveform, and the electric field detected by the first Rx output is summed as a negative value. The sum of the positive value and the negative value is the Rx output at the 6th time point.

[0083] By repeating the above steps for the 3rd to 11th columns in Figure 20 , the Rx outputs at the 7th to 33rd time points can be obtained.

[0084] Figure 24 A two-dimensional (2D) CDM scheme according to an embodiment of the present application is shown. In this embodiment, four Tx lines and four Rx outputs are used, however, the scheme can be applied to any number of Tx lines and Rx outputs. In Figure 24 , the intersection positions of the four Tx lines and the four Rx outputs are numbered from 1 to 16, and these positions are referred to as points 1 to 16. In the following description, for example, it is assumed that read(+, ij) (i = 1, 2, 3, and 4, and j = 1, 2, 3, and 4) and read(-, ij) (i = 2, 3, and 4, and j = 2, 3, and 4) are storage areas in which detection values are stored.

[0085] At time tl, the Tx1 to Tx4 lines are driven with the "P" waveform, and the electric field is detected by the Rx1 to Rx4 lines. At time tl 1, the sum of the detection values by the Rx1 to Rx4 lines is obtained as read(+, 11), the value 0 is obtained as read(-, 11), and read(+, 11) - read(-, 11) is output as the Rx output at time tl 1. At time tl 2, the sum of the detection values by the Rx1 and Rx3 lines is obtained as read(+, 12), the sum of the detection values by the Rx2 and Rx4 lines is obtained as read(-, 12), and read(+, 12) - read(-, 12) is output as the Rx output at time tl 2. At time tl 3, the sum of the detection values by the Rx1 and Rx2 lines is obtained as read(+, 13), the sum of the detection values by the Rx3 and Rx4 lines is obtained as read(-, 13), and read(+, 13) - read(-, 13) is output as the Rx output at time tl 3. At time tl 4, the sum of the detection values by the Rx1 and Rx4 lines is obtained as read(+, 14), the sum of the detection values by the Rx2 and Rx3 lines is obtained as read(-, 14), and read(+, 14) - read(-, 14) is output as the Rx output at time tl 4.

[0086] ​At time t2, the Tx1 and Tx3 lines are driven with the "P" waveform, the Tx2 and Tx4 lines are driven with the "N" waveform, and the electric field is detected by the Rx1 to Rx4 lines. At time t21, the sum of the detected values by the Rx1 to Rx4 lines is taken as the read (+, 21), the value 0 is taken as the read (-, 21), and the read (+, 21) - read (-, 21) is output as the Rx output at time t21. At time t22, the sum of the detected values by the Rx1 and Rx3 lines is taken as the read (+, 22), the sum of the detected values by the Rx2 and Rx4 lines is taken as the read (-, 22), and the read (+, 22) - read (-, 22) is output as the Rx output at time t22. At time t23, the sum of the detected values by the Rx1 and Rx2 lines is taken as the read (+, 23), the sum of the detected values by the Rx3 and Rx4 lines is taken as the read (-, 23), and the read (+, 23) - read (-, 23) is output as the Rx output at time t23. At time t24, the sum of the detected values by the Rx1 and Rx4 lines is taken as the read (+, 24), the sum of the detected values by the Rx2 and Rx3 lines is taken as the read (-, 24), and the read (+, 24) - read (-, 24) is output as the Rx output at time t24.

[0087] At time t3, the Tx1 and Tx2 lines are driven with the "P" waveform, the Tx3 and Tx4 lines are driven with the "N" waveform, and the electric field is detected by the Rx1 to Rx4 lines. At time t31, the sum of the detected values by the Rx1 to Rx4 lines is taken as the read (+, 31), the value 0 is taken as the read (-, 31), and the read (+, 31) - read (-, 31) is output as the Rx output at time t31. At time t32, the sum of the detected values by the Rx1 and Rx3 lines is taken as the read (+, 32), the sum of the detected values by the Rx2 and Rx4 lines is taken as the read (-, 32), and the read (+, 32) - read (-, 32) is output as the Rx output at time t32. At time t33, the sum of the detected values by the Rx1 and Rx2 lines is taken as the read (+, 33), the sum of the detected values by the Rx3 and Rx4 lines is taken as the read (-, 33), and the read (+, 33) - read (-, 33) is output as the Rx output at time t33. At time t34, the sum of the detected values by the Rx1 and Rx4 lines is taken as the read (+, 34), the sum of the detected values by the Rx2 and Rx3 lines is taken as the read (-, 34), and the read (+, 34) - read (-, 34) is output as the Rx output at time t34.

[0088] At time t4, the Tx1 and Tx4 lines are driven with the "P" waveform, the Tx2 and Tx3 lines are driven with the "N" waveform, and the electric field is detected by the Rx1 to Rx4 lines. At time t41, the sum of the detected values by the Rx1 to Rx4 lines is taken as the read (+, 41), the value 0 is taken as the read (-, 41), and the read (+, 41) - read (-, 41) is output as the Rx output at time t41. At time t42, the sum of the detected values by the Rx1 and Rx3 lines is taken as the read (+, 42), the sum of the detected values by the Rx2 and Rx4 lines is taken as the read (-, 42), and the read (+, 42) - read (-, 42) is output as the Rx output at time t42. At time t43, the sum of the detected values by the Rx1 and Rx2 lines is taken as the read (+, 43), the sum of the detected values by the Rx3 and Rx4 lines is taken as the read (-, 43), and the read (+, 43) - read (-, 43) is output as the Rx output at time t43. At time t44, the sum of the detected values by the Rx1 and Rx4 lines is taken as the read (+, 44), the sum of the detected values by the Rx2 and Rx3 lines is taken as the read (-, 44), and the read (+, 44) - read (-, 44) is output as the Rx output at time t44.

[0089] The signals of the points 1 to 16 (hereinafter referred to as s1 to s16) can be calculated using the following equations (1) and (2), i.e., the right side matrix of equation (1), which is the data after Rx CDM decoding, can be obtained by calculating the left side multiplication, and the right side matrix of equation (2), which is the data after Tx CDM decoding, can be obtained by calculating the left side multiplication:

[0090]

[0091]

[0092] Figure 25 A voltage forming method according to an embodiment of the present application is shown. Figure 25 The upper half of FIG. 1 shows a cross-sectional view perpendicular to the Tx lines. Every other line is used as an Fx line. For example, the even Tx lines are used for AC driving, and a negative voltage is applied to the odd Tx lines (Fx lines). This negative voltage can be a direct current voltage, or can be a reverse voltage close to the left or right Tx lines (Fx lines), as shown in FIG. 1. Figure 25

[0093] Figure 26 ​A voltage forming and CDM driving scheme according to an embodiment of the present application is shown. The combination of voltage forming and CDM driving is achieved by a simple circuit configuration including even / odd line CDM drivers and a random sequencer (e.g. m-sequence). Each odd line is connected to a scanner in the odd line CDM driver 51 through a switch, and to VGL through another switch. Each even line is connected to a scanner in the even line CDM driver 52 through a switch, and to VGL through another switch. In Figure 26 In the middle, the left and right halves are not connected with a solid line because their scales are different.

[0094] When odd line CDM is performed, in response to the signal odd sel, the odd lines are connected to the corresponding scanners in the odd line CDM driver 51, and the even lines are connected to VGL. The random sequencer 30 drives the scanners in the odd line CDM driver 51 to output waveforms according to a waveform pattern. The raw data acquired from the odd lines are used to calculate a fingerprint image. When even line CDM is performed, in response to the signal even sel, the even lines are connected to the corresponding scanners in the even line CDM driver 52, and the odd lines are connected to VGL. The random sequencer 30 drives the scanners in the even line CDM driver 52 to output waveforms according to a waveform pattern. The raw data acquired from the even lines are used to calculate a fingerprint image. After the fingerprint images are acquired from the odd and even lines, a complete fingerprint image is generated from these fingerprint images using a Super-Resolution (SR) technique.

[0095] Figure 27 An application scenario of an embodiment of the present application is shown. By applying this technology to global FPS, it is possible to provide a smooth user interface and enhance security. Figure 27 (a) shows seamless screen unlocking by touching any area of its display, Figure 27 (b) shows App direct login by authenticating by touching an icon, Figure 27 (c) shows high security payment by multi-finger authentication.

[0096] In an embodiment according to the present application, the combination of bundled CDM driving and Super-Resolution method allows to increase the sensing distance while maintaining high resolution. Fingerprint can be detected with thicker cover glass. The present application is applicable to a global FPS solution for in-cell PD (photodiode manufactured in display device) without the need for in-pixel amplifier system for in-cell PD. The same method as for capacitive sensor is also applicable to optical sensor. When photodiode is used for fingerprint sensing, the amount of current is weak. However, the signal can be enhanced without using an amplifier by the driving method of the present application.

[0097] The above disclosed are only exemplary embodiments of the present application, and certainly cannot limit the protection scope of the present application. Those skilled in the art can understand that the implementation of all or part of the processes of the above embodiments and the equivalent changes made according to the claims of the present application still belong to the scope covered by the present application.

Claims

1. An apparatus for fingerprint sensing, the apparatus comprising: comprising: a code division multiplexing (CDM) driver for obtaining a plurality of sets of raw data by using a set of CDM codes a plurality of times; and a data processor for generating a plurality of sets of low resolution image data by sorting and calculating the plurality of sets of raw data; and for generating high resolution image data from the plurality of sets of low resolution image data by reconstruction.

2. The apparatus of claim 1, wherein, The CDM driver comprises: a plurality of scanners for providing CDM waveforms to lines according to a CDM waveform pattern; and a random sequencer for successively selecting the scanners.

3. The apparatus of claim 2, wherein, The frequency of the clock provided to the scanners is different from the frequency of the clock provided to the sequencer.

4. The apparatus of claim 1, wherein, The CDM driver further comprises: a plurality of scanners for providing CDM waveforms to lines according to a CDM waveform pattern; a start selector for setting a start position of selecting scanners; a random sequencer for successively selecting every Mth scanner; and an output selector for connecting the scanners to corresponding lines and subsequent (M-1) lines.

5. The apparatus of claim 4, wherein, The CDM waveform pattern is for NM lines and NM time points, and is generated from a CDM waveform pattern for N lines and N time points by repeating each waveform M times in each column and adding (M-1) columns after each column (M-1) times.

6. The apparatus of claim 1, wherein, The CDM driver comprises: a random sequencer for successively selecting every other scanner; and an odd line driver comprising scanners for driving corresponding odd lines; an even line driver comprising scanners for driving corresponding even lines; and a switch for connecting the odd lines to corresponding scanners in the odd line driver and the even lines to VGL when driving the odd lines, and connecting the even lines to corresponding scanners in the even line driver and the odd lines to the VGL when driving the even lines.

7. The apparatus of any one of claims 1 to 6, wherein, The CDM codes are m-sequence codes.

8. A method for fingerprint sensing, characterized by, comprising: obtaining a plurality of sets of raw data by using a set of CDM codes a plurality of times by a code division multiplexing (CDM) driver; and sorting and calculating the plurality of sets of raw data by a data processor to obtain a plurality of sets of low resolution image data; and generating high resolution image data from the plurality of sets of low resolution image data by the data processor by reconstruction from the plurality of sets of low resolution image data.

Images