Fingerprint sensing control method and control circuit

Abstract

A fingerprint sensing control method and control circuit are disclosed. The fingerprint sensing control method includes the following steps: In a pre-scan mode, multiple first fingerprint brightness codes are received. The first fingerprint brightness codes are detected with reference to a ramp count variable that varies over a full range. An initial code is generated based on the distribution of the first fingerprint brightness codes. In a normal scanning mode, the initial code is applied to the ramp count variable, and multiple second fingerprint brightness codes are detected with reference to the ramp count variable that varies over a local range. A boundary of the local range is determined based on the initial code. A control circuit is also disclosed. In the normal scanning mode, a ramp voltage signal that varies over a local range is used to detect the fingerprint brightness code, thereby saving time.

Description

Technical Field

[0001] The present disclosure relates to a fingerprint sensing control method and a control circuit, and more particularly to a fingerprint sensing control method and a control circuit involving a ramp counting method. Background Art

[0002] For optical fingerprint sensors integrated into LCD panels (such as so-called under-display fingerprint sensors), light generated by a light source strikes a human finger, generating reflected light. This reflected light is received by the optical sensor and converted into multiple input voltage signals. A readout circuit then converts the input voltage signals into digital signals and transmits them to a processor for subsequent image processing.

[0003] This readout circuit can convert the input voltage signal into a digital signal using a ramp voltage that repeatedly varies across its full range. However, in most cases, the voltage levels of multiple input voltage signals are concentrated within a specific voltage range (for example, within the 20% to 40% range relative to the full range). Therefore, ramp voltage changes outside of this specific voltage range are generally unnecessary. In other words, using a ramp voltage that repeatedly varies across its full range is relatively inefficient in terms of detection time. Summary of the Invention

[0004] One aspect of the present disclosure relates to a fingerprint sensing control method comprising the following steps: In a pre-scan mode, a plurality of first fingerprint brightness codes are received, wherein the first fingerprint brightness codes are detected with reference to a ramp count variable that varies over a full range. An initial code is generated based on the distribution of the first fingerprint brightness codes. In a normal scan mode, the initial code is applied to the ramp count variable, and a plurality of second fingerprint brightness codes are detected with reference to the ramp count variable that varies over a local range, wherein a boundary of the local range is determined based on the initial code.

[0005] In one embodiment, the first fingerprint brightness codes are detected by: using a digital counter to count the ramp count variable in ascending order from a zero scale toward a full scale; generating a first ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable; and comparing a plurality of optical sensing voltage signals with the first ramp voltage signal to detect the first fingerprint brightness codes.

[0006] In one embodiment, the initial code is generated according to a minimum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

[0007] In one embodiment, applying the initial code to the ramp count variable includes: counting the ramp count variable by the digital counter in ascending order from the initial code toward the full scale; and generating a second ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable, wherein the plurality of second fingerprint brightness codes are detected by comparing the plurality of optical sensing voltage signals with the second ramp voltage signal.

[0008] In one embodiment, the first fingerprint brightness codes are detected by: using a digital counter to count a ramp count variable in descending order from a full scale toward a zero scale; generating a first ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable; and comparing a plurality of optical sensing voltage signals with the first ramp voltage signal to detect the first fingerprint brightness codes.

[0009] In one embodiment, the initial code is generated according to a maximum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

[0010] In one embodiment, applying the initial code to the ramp count variable includes: counting the ramp count variable by the digital counter in descending order from the initial code toward the zero scale; and generating a second ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable, wherein the plurality of second fingerprint brightness codes are detected by comparing the plurality of optical sensing voltage signals with the second ramp voltage signal.

[0011] In one embodiment, each of a plurality of consecutive readout frames includes the pre-scan mode and the normal scan mode, and the initial code generated in the pre-scan mode of one of the plurality of consecutive readout frames is used to determine the local range in the normal scan mode of the same readout frame.

[0012] In one embodiment, a first readout frame among a plurality of consecutive readout frames includes the pre-scan mode and the normal scan mode, and the initial code generated in the pre-scan mode of the first readout frame is used to determine the local range in the normal scan mode of each of the plurality of consecutive readout frames.

[0013] Another aspect of the present disclosure relates to a fingerprint sensing control method, comprising the following steps: In a pre-scan mode, a plurality of first fingerprint brightness codes are received, wherein the plurality of first fingerprint brightness codes are detected with reference to a ramp count variable that varies at a first clock frequency over a full range. An initial code is generated based on the distribution of the plurality of first fingerprint brightness codes detected in the pre-scan mode. In a normal scan mode, the ramp count variable is set to a plurality of different clock frequencies based on the initial code, and a plurality of second fingerprint brightness codes are detected with reference to the ramp count variable, wherein a first portion of the ramp count variable within the full range preceding the initial code varies at a second clock frequency, and a second portion of the ramp count variable within the full range following the initial code varies at the first clock frequency, wherein the second clock frequency is higher than the first clock frequency.

[0014] In one embodiment, the first fingerprint brightness codes are detected by: using a digital counter to count the ramp count variable in ascending order from a zero scale toward a full scale at the first clock frequency; generating a first ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable; and comparing a plurality of optical sensing voltage signals with the first ramp voltage signal to detect the first fingerprint brightness codes.

[0015] In one embodiment, the initial code is generated according to a minimum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

[0016] In one embodiment, setting the ramp count variable in the normal scanning mode includes: counting the ramp count variable by the digital counter in the ascending order from the zero scale toward the initial code at the second clock frequency, and counting the ramp count variable in the ascending order from the initial code toward the full scale at the first clock frequency; and generating a second ramp voltage signal whose voltage level varies in a positive correlation with the ramp count variable, wherein the plurality of second fingerprint brightness codes are detected by comparing the plurality of optical sensing voltage signals with the second ramp voltage signal.

[0017] In one embodiment, the first fingerprint brightness codes are detected by: using a digital counter to count the ramp count variable in descending order from full scale toward zero scale at the first clock frequency; generating a first ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable; and comparing a plurality of optical sensing voltage signals with the first ramp voltage signal to detect the first fingerprint brightness codes.

[0018] In one embodiment, the initial code is generated according to a maximum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

[0019] In one embodiment, setting the ramp count variable in the normal scanning mode includes: counting the ramp count variable by the digital counter in descending order from the full scale toward the initial code at the second clock frequency, and counting the ramp count variable in descending order from the initial code toward the zero scale at the first clock frequency; and generating a second ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable, wherein the plurality of second fingerprint brightness codes are detected by comparing the plurality of optical sensing voltage signals with the second ramp voltage signal.

[0020] In one embodiment, each of a plurality of consecutive readout frames includes the pre-scan mode and the normal scan mode, and the initial code generated in the pre-scan mode of one of the plurality of consecutive readout frames is used to determine the boundary between the first portion and the second portion in the normal scan mode in the same readout frame.

[0021] In one embodiment, a first readout frame among a plurality of consecutive readout frames includes the pre-scan mode and the normal scan mode, and the initial code generated in the pre-scan mode of the first readout frame is used to determine the boundary between the first part and the second part in the normal scan mode of each of the plurality of consecutive readout frames.

[0022] Another aspect of the present disclosure relates to a control circuit for an electronic device comprising a plurality of optical sensors and a readout circuit. The plurality of optical sensors are configured to generate a plurality of optical sensing voltage signals. The readout circuit is configured to compare the plurality of optical sensing voltage signals with a ramp voltage signal to detect a plurality of fingerprint brightness codes. The control circuit comprises a digital counter, a ramp converter, and a controller. The digital counter is configured to count a ramp count variable. The ramp converter is coupled to the digital counter and is configured to generate the ramp voltage signal, the voltage level of which varies in direct correlation with the ramp count variable. The controller is coupled to the digital counter and the ramp converter.

[0023] In some embodiments, the controller is configured to trigger the digital counter to count the ramp count variable within a full range in a pre-scan mode. The controller is configured to receive a plurality of first fingerprint brightness codes from the readout circuit, wherein the plurality of first fingerprint brightness codes are detected with reference to the ramp count variable that varies within the full range. The controller is configured to generate an initial code based on the distribution of the plurality of first fingerprint brightness codes detected in the pre-scan mode. The controller is configured to trigger the digital counter to count the ramp count variable within a local range in a normal scan mode, wherein a boundary of the local range is determined based on the initial code. In the normal scan mode, the controller is configured to receive a plurality of second fingerprint brightness codes from the readout circuit, wherein the plurality of second fingerprint brightness codes are detected with reference to the ramp count variable that varies within the local range.

[0024] Another aspect of the present disclosure relates to a control circuit for an electronic device comprising a plurality of optical sensors and a readout circuit. The plurality of optical sensors are configured to generate a plurality of optical sensing voltage signals. The readout circuit is configured to compare the plurality of optical sensing voltage signals with a ramp voltage signal to detect a plurality of fingerprint brightness codes. The control circuit comprises a digital counter, a ramp converter, and a controller. The digital counter is configured to count a ramp count variable. The ramp converter is coupled to the digital counter and is configured to generate the ramp voltage signal, the voltage level of which varies in direct correlation with the ramp count variable. The controller is coupled to the digital counter and the ramp converter.

[0025] In some embodiments, the controller is configured to trigger the digital counter to count the ramp count variable at a first clock frequency over a full range in a pre-scan mode. The controller is configured to receive a plurality of first fingerprint brightness codes from the readout circuit, with the detection of the plurality of first fingerprint brightness codes being based on the ramp count variable varying over the full range. The controller is configured to generate an initial code based on the distribution of the plurality of first fingerprint brightness codes detected in the pre-scan mode. The controller is configured to trigger the digital counter to count the ramp count variable at a second clock frequency over a first portion of the full range preceding the initial code in a normal scan mode, and to count the ramp count variable at the first clock frequency over a second portion of the full range following the initial code in the normal scan mode. In the normal scan mode, the controller is configured to receive a plurality of second fingerprint brightness codes from the readout circuit, with the detection of the plurality of second fingerprint brightness codes being based on the ramp count variable.

[0026] In some embodiments, this disclosure proposes that, in normal scanning mode, a second ramp voltage signal that varies locally can be used to improve time efficiency. A control device and control method can determine an initial code based on the distribution of multiple first fingerprint brightness codes in pre-scan mode. This allows the initial code to be dynamically detected in pre-scan mode based on the current user and context. This allows the control method to quickly and accurately generate a second fingerprint brightness code for different users and contexts. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram illustrating a control circuit according to some embodiments of the present disclosure is shown;

[0028] Figure 2 A flow chart illustrating a control method according to some embodiments of the present disclosure is shown;

[0029] Figure 3A FIG2 is a schematic diagram illustrating a first ramp voltage signal generated in a pre-scan mode with reference to a ramp count variable varying within a full range according to some embodiments of the present disclosure;

[0030] Figure 3B FIG. 1 shows a schematic diagram of a method for referring to a scan file in a pre-scan mode according to some embodiments of the present disclosure. Figure 3A A schematic diagram of a first fingerprint brightness code generated by a first ramp voltage signal in FIG;

[0031] Figure 4A A schematic diagram illustrating a second ramp voltage signal generated in a normal scan mode with reference to a ramp count variable varying within a local range according to some embodiments of the present disclosure;

[0032] Figure 4B FIG. 1 shows a diagram of some embodiments of the present disclosure in a normal scanning mode. Figure 4A A schematic diagram of a second fingerprint brightness code generated by a second ramp voltage signal in ;

[0033] Figure 5A A schematic diagram illustrating a first ramp voltage signal generated in a pre-scan mode with reference to a ramp count variable that changes in descending order within a full range according to some embodiments of the present disclosure;

[0034] Figure 5B FIG. 1 shows a schematic diagram of a method for referring to a scan file in a pre-scan mode according to some embodiments of the present disclosure. Figure 5A A schematic diagram of a first fingerprint brightness code generated by a first ramp voltage signal in FIG;

[0035] Figure 6AA schematic diagram illustrating a second ramp voltage signal generated in a normal scan mode with reference to a ramp count variable varying within a local range according to some embodiments of the present disclosure;

[0036] Figure 6B FIG. 1 shows a diagram of some embodiments of the present disclosure in a normal scanning mode. Figure 6A A schematic diagram of a second fingerprint brightness code generated by a second ramp voltage signal in ;

[0037] Figure 7A A schematic diagram illustrating a timing sequence of performing a display function and a fingerprint sensing function on an electronic device according to some embodiments of the present disclosure is shown;

[0038] Figure 7B A schematic diagram illustrating a timing sequence of performing a display function and a fingerprint sensing function on an electronic device according to some embodiments of the present disclosure is shown;

[0039] Figure 8 Schematic diagrams illustrating control circuits according to other embodiments of the present disclosure;

[0040] Figure 9 A flow chart illustrating a control method according to some embodiments of the present disclosure is shown;

[0041] Figure 10A A schematic diagram illustrating a first ramp voltage signal generated in a pre-scan mode with reference to a ramp count variable varying in accordance with a first clock frequency within a full range according to some embodiments of the present disclosure;

[0042] Figure 10B FIG. 1 shows a schematic diagram of a method for referring to a scan file in a pre-scan mode according to some embodiments of the present disclosure. Figure 10A A schematic diagram of a first fingerprint brightness code generated by a first ramp voltage signal in FIG;

[0043] Figure 11A A schematic diagram illustrating a second ramp voltage signal generated in a normal scan mode with reference to ramp count variables having different clock frequencies according to some embodiments of the present disclosure; and

[0044] Figure 11B FIG2 is a schematic diagram illustrating a second fingerprint brightness code generated in a normal scanning mode according to some embodiments of the present disclosure.

[0045]

Explanation of symbols

[0046] 100,300: Electronic devices

[0047] 120,320: Control circuit

[0048] 122,322: Digital counter

[0049] 124,324: Ramp Converter

[0050] 126,326:Controller

[0051] 128,328: Oscillator

[0052] 140,340: Pixel array

[0053] 141,341: Optical sensor

[0054] 160,360: Readout circuit

[0055] 161,361: Comparator

[0056] 162,362: latch

[0057] 200,400: Fingerprint sensing control method

[0058] Vramp: ramp voltage signal

[0059] Vramp1, Vramp1d: first ramp voltage signal

[0060] Vramp2, Vramp2d: second ramp voltage signal

[0061] FS: Full scale

[0062] ZS: Zero scale

[0063] CDi: Initial Code

[0064] RC: Ramp counting variable

[0065] CLK, F1, F2: clock frequency

[0066] Scol1~Scoln: Optical sensing voltage signal

[0067] BC: Fingerprint Brightness Code

[0068] BC1: First fingerprint brightness code

[0069] BC2: Second fingerprint brightness code

[0070] BUFF: buffer interval

[0071] DIST: distribution

[0072] BC1max: Maximum code

[0073] BC1min: Minimum code

[0074] Rf: Full range

[0075] Rp1, Rp2: local range

[0076] T1, T2: single cycle time

[0077] DF1, DF2, DF3: Display frame

[0078] RF1, RF2, RF3: read frame

[0079] PRE1, PRE2, PRE3: Pre-scan mode

[0080] NOR1, NOR2, NOR3: Normal scan mode DETAILED DESCRIPTION

[0081] The following embodiments are disclosed along with accompanying drawings illustrating implementations. For clarity, many implementation details are explained in the following description. However, it should be understood that these implementation details are not intended to limit the present disclosure. In other words, these implementation details are not essential to the embodiments of the present disclosure. Furthermore, to simplify the figures, some conventional structures and components are illustrated schematically.

[0082] Figure 1 A schematic diagram of a control circuit 120 according to some embodiments of the present disclosure is shown. In some embodiments, the control circuit 120 is applicable to an electronic device 100 capable of sensing fingerprint images. For example, the electronic device 100 may be a mobile phone, a smartphone, a tablet computer, a personal digital assistant (PDA), a computer, or other equivalent device with fingerprint sensing capabilities.

[0083] like Figure 1 In the embodiment shown, the electronic device 100 includes a pixel array 140 and a readout circuit 160. The pixel array 140 includes a plurality of optical sensors 141 arranged in different rows. These optical sensors 141 are used to generate a plurality of optical sensing voltage signals Scol1, Scol2...Scoln. Figure 1 In the illustrated embodiment, the pixel array 140 includes n different columns, where n is a positive integer greater than 1. For example, n can be 20, 40, 120, 360, 480, 720, 1080, or any other suitable number of columns. This disclosure is not limited to a particular number of columns.

[0084] To detect fingerprints on pixel array 140, a light source (e.g., a light emitter in pixel array 140) can generate light that can be reflected by a user's finger. The reflected light from the user's finger can then be sensed by optical sensor 141, which generates optical sensing voltage signals Scol1, Scol2, ..., Scoln in response to the reflected light.

[0085] like Figure 1 As shown, the readout circuit 160 is coupled to the optical sensor 141 in the pixel array 140. The readout circuit 160 is used to compare the optical sensing voltage signals Scol1, Scol2 . . . Scolen with a ramp voltage signal Vramp to detect a plurality of fingerprint brightness codes BC.

[0086] In some embodiments, the ramp voltage signal Vramp serves as a reference signal to determine the brightness levels of the optical sensing voltage signals Scol1, Scol2, ..., Scoln to generate the fingerprint brightness code BC. In some embodiments, the ramp voltage signal Vramp can be an upward step-like signal whose voltage level gradually increases in ascending order, or a downward step-like signal whose voltage level gradually decreases in descending order.

[0087] like Figure 1 In the illustrated embodiment, the control circuit 120 is configured to generate a ramp voltage signal Vramp and provide the ramp voltage signal Vramp to the readout circuit 160 . The control circuit 120 includes a digital counter 122 , a ramp converter 124 , a controller 126 , and an oscillator 128 .

[0088] The digital counter 122 is configured to count the ramp count variable RC according to the clock frequency CLK generated by the oscillator 128. In some embodiments, the clock frequency CLK has a fixed period. The digital counter 122 is configured to increment or decrement the ramp count variable RC.

[0089] For example, assuming that the digital counter 122 is an 8-bit up-counter, by default, the ramp count variable RC may start at zero scale, i.e., 0, and then increment by 1, 2, 3, 4, and so on, until the ramp count variable RC reaches full scale. For an 8-bit up-counter, the full scale is 255. Assuming that the digital counter 122 is an 8-bit down-counter, by default, the ramp count variable RC may start at full scale, i.e., 255, and then increment by 254, 253, 252, and so on, until the ramp count variable RC reaches zero scale, i.e., 0.

[0090] The ramp converter 124 is coupled to the digital counter 122. The ramp converter 124 is configured to generate a ramp voltage signal Vramp whose voltage level varies in direct correlation with the ramp count variable RC. For example, as the ramp count variable RC increases, the ramp voltage signal Vramp has a higher voltage level; and as the ramp count variable RC decreases, the ramp voltage signal Vramp has a lower voltage level. In some embodiments, the ramp converter 124 is a digital-to-analog converter (DAC) configured to convert the digital count value (i.e., the ramp count variable RC) into an analog voltage signal (i.e., the ramp voltage signal Vramp).

[0091] In one example, the ramp counting variable RC counts over a full range (e.g., from 0, 1, 2, 3, 4, etc. to full scale). Consequently, the generated ramp voltage signal Vramp also varies from a minimum voltage level to a maximum voltage level within the full range. This ramp voltage signal Vramp serves as a reference signal for detecting the fingerprint brightness code BC. In most cases, the fingerprint brightness code BC does not extend over the full range; instead, the detected fingerprint brightness code BC typically falls within a local range (e.g., 75 to 150) within the full range (e.g., 0 to 255). Using a ramp counting variable RC that varies over the full range to detect the fingerprint brightness code BC is relatively time-inefficient.

[0092] In some embodiments, the controller 126 is configured to generate a start code CDi and trigger the digital counter 122 to count the ramp count variable RC in a local range based on the start code CDi. In this case, the controller 126 can increase the processing speed of the fingerprint brightness code BC detected by the electronic device 100. Details regarding how to generate the start code CDi and count the ramp count variable RC in a local range will be discussed in further detail in the following sections.

[0093] Please also refer to Figure 2 , which illustrates a method flow chart of a control method 200 according to some embodiments of the present disclosure. The control method 200 may be Figure 1 Executed by the control circuit 120 in.

[0094] According to control method 200 , the readout frame used to detect fingerprint brightness code BC may include a pre-scan mode and a normal scan mode following the pre-scan mode. In the pre-scan mode, step S210 is performed, where controller 126 receives a plurality of first fingerprint brightness codes in the pre-scan mode. These first fingerprint brightness codes are detected by reference to a ramp count variable RC that varies over a full range.

[0095] Please also refer to Figure 3A , which is a schematic diagram illustrating a first ramp voltage signal Vramp1 generated in a pre-scan mode with reference to a ramp count variable RC varying within a full range Rf according to some embodiments of the present disclosure.

[0096] In the pre-scan mode, the controller 126 triggers the digital counter 122 to count the ramp count variable RC within the full range Rf. Figure 3A In the embodiment of the present invention, the digital counter 122 counts the ramp count variable RC from zero scale "0" to full scale FS in ascending order. For example, full scale FS can be 15, 31, 63, 127, 255, etc. The value of full scale FS depends on the resolution of brightness grayscale in fingerprint sensing. For simplicity of explanation, it is assumed that full scale FS is set to 255. The digital counter 122 provides the ramp count variable RC to the ramp converter 124. The ramp converter 124 generates Figure 3A The voltage level of the first ramp voltage signal Vramp1 shown in FIGURE 1 varies in direct correlation with the ramp count variable RC over the full range Rf. In this case, the first ramp voltage signal Vramp1 also varies over the full range. The ramp converter 124 provides the first ramp voltage signal Vramp1 to the readout circuit 160. The multiple comparators 161 in the readout circuit 160 are used to compare the optical sensing voltage signals Scol1, Scol2, ..., Scoln with the first ramp voltage signal Vramp1, and store the comparison results in the multiple latches 162 to generate the first fingerprint brightness code BC1.

[0097] Please also refer to Figure 3B , which illustrates a method of referring to a scan pattern in a pre-scan mode according to some embodiments of the present disclosure. Figure 3A Schematic diagram of a first fingerprint brightness code BC1 generated by the first ramp voltage signal Vramp1 in .

[0098] like Figure 3B As shown, although the plurality of first fingerprint brightness codes BC1 are generated with reference to the first ramp voltage signal Vramp1 that changes within the full range Rf, the plurality of first fingerprint brightness codes BC1 are not evenly distributed at all positions within the full range Rf. Figure 3B As shown, according to the distribution DIST of the plurality of first fingerprint brightness codes BC1, the maximum code BC1max and the minimum code BC1min can be found from the plurality of first fingerprint brightness codes BC1.

[0099] Since the first fingerprint brightness codes BC1 are between the minimum code BC1min and the maximum code BC1max, it means that in the normal scanning mode, if a ramp voltage signal that varies within a local range is used to detect the fingerprint brightness code, time can be saved.

[0100] like Figure 1 、 Figure 2 as well as Figure 3B As shown, the control circuit 120 executes step S220 , and after receiving the plurality of first fingerprint brightness codes BC1 , the controller 126 generates an initial code CDi according to the distribution DIST of the plurality of first fingerprint brightness codes BC1 .

[0101] exist Figure 3B In the embodiment, the ramp counting variable RC is counted in ascending order, and the initial code CDi can be generated according to the minimum code BC1min. Figure 3B As shown, the minimum code BC1min can be set to the minimum code BC1min minus the buffer interval BUFF. In some other embodiments, the initial code CDi can also be equal to the minimum code BC1min.

[0102] like Figure 1 as well as Figure 2 As shown, the control circuit 120 executes step S230. In the normal scanning mode, the control circuit 120 applies the initial code CDi to the ramp count variable RC, thereby detecting a plurality of second fingerprint brightness codes BC2 with reference to the ramp count variable RC that varies in a local range.

[0103] Please also refer to Figure 4A , which is a schematic diagram illustrating a second ramp voltage signal Vramp2 generated by referring to a ramp count variable RC varying within a local range Rp1 in a normal scan mode according to some embodiments of the present disclosure.

[0104] In the normal scanning mode, the controller 126 triggers the digital counter 122 to count the ramp count variable RC within the local range Rp1. Figure 4A In the embodiment, one of the boundaries (hereinafter referred to as the boundary) of the local range Rp1 is determined according to the initial code CDi. In other words, the digital counter 122 starts counting the ramp count variable RC from the initial code CDi, rather than from the zero scale ZS.

[0105] The digital counter 122 provides the ramp count variable RC that changes within the local range Rp1 to the ramp converter 124. The ramp converter 124 generates Figure 4AThe voltage level of the second ramp voltage signal Vramp2 shown in FIGURE 1 varies in direct correlation with the ramp count variable RC within the local range Rp1. The ramp converter 124 provides the second ramp voltage signal Vramp2 to the readout circuit 160. The plurality of comparators 161 within the readout circuit 160 compare the optical sensing voltage signals Scol1, Scol2, ..., Scoln with the second ramp voltage signal Vramp2, respectively, and stores the comparison results in the plurality of latches 162 to generate the second fingerprint brightness code BC2. Figure 4B In some embodiments of the present disclosure, reference is made to the Figure 4A Schematic diagram of a second fingerprint brightness code BC2 generated by the second ramp voltage signal Vramp2 in .

[0106] In some embodiments, in normal scan mode, the ramp count variable RC starts counting from the initial code CDi instead of from the zero scale ZS. Figure 4A The single cycle time T2 required for the second ramp voltage signal Vramp2 to change within the local range Rp1 is shorter than Figure 3A The first ramp voltage signal Vramp1 shown in FIG. 1 takes a single cycle time T1 to change within the full range Rf. Therefore, in the normal scanning mode, using the second ramp voltage signal Vramp2 that changes within the partial range Rp1 helps improve time efficiency.

[0107] Starting the ramp count variable RC from the initial code CDi helps save single cycle time. However, if the initial code CDi is not set to an appropriate value, the ramp voltage signal may be set to an inappropriate range, which will damage the accuracy of the fingerprint brightness code.

[0108] In one example, different users' fingers may have different characteristics. For example, the fingerprint brightness codes sensed by different users' fingers may be distributed in different ranges. In another example, in different usage scenarios, users may touch the electronic device 100 in different ways, which may also cause the detected fingerprint brightness codes to be distributed in different ranges. If the initial code CDi is set to a fixed value regardless of the user or the usage scenario, the generated fingerprint brightness code may be invalid due to an inappropriate reference standard.

[0109] In the above embodiment of the present disclosure, the initial code CDi is generated in step S220 according to the distribution DIST of the plurality of first fingerprint brightness codes BC1 in the pre-scan mode, such as Figure 3BTherefore, the initial code CDi is dynamically determined based on the current context and current user detected by the pre-scan mode. In this way, the control method 200 can quickly and accurately generate the second fingerprint brightness code BC2 in step S230.

[0110] In the above Figure 3A 、 Figure 3B 、 Figure 4A as well as Figure 4B In the illustrated embodiment, the ramp counting variable RC is counted in ascending order, and the initial code CDi is determined according to the minimum code BC1min among the plurality of first fingerprint brightness codes BC1, but the present disclosure is not limited thereto.

[0111] In some other embodiments, the control method 200 may count the ramp counting variable RC in descending order. Figure 5A as well as Figure 5B , Figure 5A FIG. 1 is a schematic diagram illustrating a first ramp voltage signal Vramp1d generated in a pre-scan mode with reference to a ramp count variable RC that changes in descending order within a full range Rf according to some embodiments of the present disclosure. Figure 5B FIG. 1 shows a schematic diagram of a method for referring to a scan file in a pre-scan mode according to some embodiments of the present disclosure. Figure 5A Schematic diagram of a first fingerprint brightness code BC1 generated by the first ramp voltage signal Vramp1d in FIG.

[0112] like Figure 5A As shown, the controller 126 triggers the digital counter 122 to count the ramp count variable RC from full scale FS to zero scale ZS in descending order within the full range Rf. The ramp converter 124 generates a first ramp voltage signal Vramp1d, whose voltage level changes in direct correlation with the ramp count variable RC. The readout circuit 160 compares the optical sensing voltage signals Scol1, Scol2...Scoln with the first ramp voltage signal Vramp1d to generate a first fingerprint brightness code BC1, as shown in FIG. Figure 5B shown.

[0113] like Figure 5B As shown in FIG, the initial code CDi is generated according to the maximum code BC1max among the plurality of first fingerprint brightness codes BC1 in the pre-scan mode. Figure 5B As shown, the initial code CDi can be set to the maximum code BC1max plus the buffer interval BUFF. In some other embodiments, the initial code CDi can also be equal to the maximum code BC1max.

[0114] Please also refer to Figure 6A, which is a schematic diagram illustrating a second ramp voltage signal Vramp2d generated in a normal scan mode with reference to a ramp count variable RC varying within a local range Rp2 according to some embodiments of the present disclosure.

[0115] like Figure 6A As shown, in normal scan mode, the digital counter 122 counts the ramp count variable RC in descending order within the local range Rp2, starting from the initial code CDi and moving toward the zero scale ZS. The ramp converter 124 generates a second ramp voltage signal Vramp2d, whose voltage level varies in direct correlation with the ramp count variable RC, wherein the ramp count variable RC counts in descending order within the local range Rp2.

[0116] The ramp converter 124 provides the second ramp voltage signal Vramp2d to the readout circuit 160. The readout circuit 160 is used to compare the optical sensing voltage signals Scol1, Scol2 . . . Scolen with the second ramp voltage signal Vramp2d to generate a second fingerprint brightness code BC2. Figure 6B FIG. 1 shows a diagram of some embodiments of the present disclosure in a normal scanning mode. Figure 6A Schematic diagram of a second fingerprint brightness code BC2 generated by the second ramp voltage signal Vramp2d in .

[0117] In some embodiments, in normal scan mode, the ramp count variable RC starts counting from the initial code CDi instead of the full scale FS. Figure 6A The single cycle time T2 required for the second ramp voltage signal Vramp2d to change within the local range Rp2 is shorter than Figure 5A The single cycle time T1 required for the first ramp voltage signal Vramp1d to change within the full range Rf is shown. Therefore, in the normal scanning mode, using the second ramp voltage signal Vramp2d that changes within the partial range Rp2 helps improve time efficiency.

[0118] In some embodiments, the pixel matrix 140 in the electronic device 100 may be a touch display panel that integrates fingerprint sensing and display functions. In some embodiments, the pixel matrix 140 may alternately perform display and fingerprint sensing functions in different time periods. Figure 7A It illustrates a timing diagram of the display function and the fingerprint sensing function performed on the electronic device 100 according to some embodiments of the present disclosure. Figure 7A In the embodiment, there are multiple display frames (DF1, DF2 and DF3) and multiple readout frames (RF1, RF2 and RF3), which are alternately executed on the electronic device 100. Figure 7AAs shown in the embodiment, readout frames RF1, RF2, and RF3 each include a pre-scan mode and a normal scan mode. For example, readout frame RF1 includes a pre-scan mode PRE1 and a normal scan mode NOR1; readout frame RF2 includes a pre-scan mode PRE2 and a normal scan mode NOR2; and readout frame RF3 includes a pre-scan mode PRE3 and a normal scan mode NOR3.

[0119] In some embodiments, the initial code generated in the pre-scan mode of one of a plurality of consecutive readout frames is used to determine a local range in the normal scan mode within the same readout frame. For example, the initial code CD1 generated in the pre-scan mode PRE1 is used to determine a local range in the normal scan mode NOR1. The initial code CD2 generated in the pre-scan mode PRE2 is used to determine a local range in the normal scan mode NOR2. The initial code CD3 generated in the pre-scan mode PRE3 is used to determine a local range in the normal scan mode NOR3.

[0120] Please also refer to Figure 7B , which illustrates a timing diagram of performing display function and fingerprint sensing function on the electronic device 100 according to some embodiments of the present disclosure. Figure 7B In the embodiment, there are multiple display frames (DF1, DF2 and DF3) and multiple readout frames (RF1, RF2 and RF3), which are alternately executed on the electronic device 100. Figure 7B In the embodiment shown in FIG. 1 , readout frame RF1 includes a pre-scan pattern and a normal scan pattern, while subsequent readout frames RF2 and RF3 include a normal scan pattern and do not include a pre-scan pattern. For example, readout frame RF1 includes a pre-scan pattern PRE1 and a normal scan pattern NOR1; readout frame RF2 includes a normal scan pattern NOR2; and readout frame RF3 includes a normal scan pattern NOR3.

[0121] In some embodiments, the initial code detected in the pre-scanning mode PRE1 can be used to determine the local range used by the normal scanning modes NOR1-NOR3 in the plurality of readout frames RF1-RF3. In other words, the normal scanning modes NOR1-NOR3 share the initial code generated in the pre-scanning mode PRE1.

[0122] In the above embodiment, in the normal scanning mode, in a local range (such as Rp1 or Rp2 in Figure 4A), Figure 6A The ramp count variable RC, which changes in Rp2 (in the example), is counted starting from the start code CDi to increase the speed of fingerprint sensing. However, this disclosure is not limited to this. In other embodiments, the ramp count variable RC can be counted at different clock frequencies in different segments within the full range to increase the speed of fingerprint sensing.

[0123] Figure 8 FIG. 3 is a schematic diagram of a control circuit 320 according to some other embodiments of the present disclosure. In some embodiments, the control circuit 320 is applicable to an electronic device 300 capable of sensing fingerprint images.

[0124] like Figure 8 In the embodiment shown, the electronic device 300 includes a pixel array 340 and a readout circuit 360. The pixel array 340 includes a plurality of optical sensors 341 arranged in different columns. These optical sensors 341 are used to generate a plurality of optical sensing voltage signals Scol1, Scol2...Scoln. The readout circuit 360 is used to compare the optical sensing voltage signals Scol1, Scol2...Scoln with a ramp voltage signal Vramp to detect a plurality of fingerprint brightness codes BC. Figure 8 Some details of the pixel array 340 and the readout circuit 360 in the embodiment are similar to Figure 1 In the embodiment of the present invention, the pixel array 140 and the readout circuit 160 are similar and are not described in detail herein.

[0125] like Figure 8 In the illustrated embodiment, the control circuit 320 is configured to generate a ramp voltage signal Vramp and provide the ramp voltage signal Vramp to the readout circuit 360. The control circuit 320 includes a digital counter 322, a ramp converter 324, a controller 326, and an oscillator 328.

[0126] The digital counter 322 is used to count the ramp count variable RC according to the clock frequency CLK generated by the oscillator 328. Figure 8 In the embodiment, the controller 326 can adjust the clock frequency CLK to different clock frequencies, such as a clock frequency F1 and another clock frequency F2. The digital counter 322 can count the ramp count variable RC in an increasing or decreasing manner.

[0127] The ramp converter 324 is coupled to the digital counter 322. The ramp converter 324 is configured to generate a ramp voltage signal Vramp whose voltage level varies in direct correlation with the ramp count variable RC. For example, as the ramp count variable RC increases, the ramp voltage signal Vramp has a higher voltage level; and as the ramp count variable RC decreases, the ramp voltage signal Vramp has a lower voltage level. In some embodiments, the ramp converter 324 is a digital-to-analog converter (DAC) configured to convert a digital count value (i.e., the ramp count variable RC) into an analog voltage signal (i.e., the ramp voltage signal Vramp).

[0128] In one example, the ramp counting variable RC counts over a full range (e.g., from 0, 1, 2, 3, 4, etc. to full scale). Consequently, the generated ramp voltage signal Vramp also varies from a minimum voltage level to a maximum voltage level within the full range. This ramp voltage signal Vramp serves as a reference signal for detecting the fingerprint brightness code BC. In most cases, the fingerprint brightness code BC does not extend over the full range; instead, the detected fingerprint brightness code BC typically falls within a local range (e.g., 75 to 150) within the full range (e.g., 0 to 255). Using a ramp counting variable RC that varies at the same temporal frequency over the full range to detect the fingerprint brightness code BC is a relatively time-inefficient approach.

[0129] In some embodiments, the controller 326 is configured to generate a start code CDi and trigger the digital counter 122 to count the ramp count variable RC at different clock frequencies (i.e., clock frequency F1 or clock frequency F2) based on the start code CDi. In this manner, the controller 326 can increase the processing speed of the fingerprint brightness code BC detected by the electronic device 300. Details regarding how to generate the start code CDi and how to count the ramp count variable RC at different clock frequencies based on the start code CDi will be discussed in further detail in subsequent sections.

[0130] See also Figure 9 , which illustrates a flow chart of a control method 400 according to some embodiments of the present disclosure. The control method 400 may be Figure 8 Executed by the control circuit 320 in.

[0131] According to control method 400 , the readout frame used to detect fingerprint brightness code BC may include a pre-scan mode and a normal scan mode following the pre-scan mode. In the pre-scan mode, step S410 is performed, where controller 326 receives a plurality of first fingerprint brightness codes. These first fingerprint brightness codes are detected by reference to a ramp count variable RC that varies within a full range according to a first clock frequency.

[0132] Please also refer to Figure 10A , which is a schematic diagram illustrating a first ramp voltage signal Vramp1 generated in a pre-scan mode with reference to a ramp count variable RC varying in accordance with a first clock frequency F1 within a full range Rf according to some embodiments of the present disclosure.

[0133] In the pre-scan mode, the controller 326 triggers the digital counter 322 to count the ramp count variable RC according to the first clock frequency F1 within the full range Rf. Figure 10AIn the embodiment of the present invention, the digital counter 322 counts the ramp count variable RC from zero scale “0” to full scale FS in ascending order. The digital counter 322 provides the ramp count variable RC to the ramp converter 324. The ramp converter 324 generates Figure 10A The voltage level of the first ramp voltage signal Vramp1 shown in FIGURE 1 varies in direct correlation with the ramp count variable RC over the full range Rf. The ramp converter 324 provides the first ramp voltage signal Vramp1 to the readout circuit 360. The multiple comparators 361 in the readout circuit 360 compare the optical sensing voltage signals Scol1, Scol2, ..., Scoln with the first ramp voltage signal Vramp1, respectively, and store the comparison results in the multiple latches 362 to generate the first fingerprint brightness code BC1.

[0134] Please also refer to Figure 10B , which illustrates a method of referring to a scan pattern in a pre-scan mode according to some embodiments of the present disclosure. Figure 10A Schematic diagram of a first fingerprint brightness code BC1 generated by the first ramp voltage signal Vramp1 in .

[0135] like Figure 8 、 Figure 9 as well as Figure 10B As shown, the control circuit 320 executes step S420. After receiving the plurality of first fingerprint brightness codes BC1, the controller 326 generates the initial code CDi according to the distribution DIST of the plurality of first fingerprint brightness codes BC1. Figure 10B The detailed method of generating the initial code CDi according to the distribution DIST is the same as that in the previous embodiment. Figure 3B The embodiment shown in FIG is similar to that shown in FIG, and will not be described in detail here.

[0136] like Figure 8 as well as Figure 9 As shown, the control circuit 320 executes step S430. In the normal scanning mode, the control circuit 320 applies the initial code CDi to the ramp counting variable RC, thereby detecting multiple second fingerprint brightness codes BC2 with reference to the ramp counting variable RC with different clock frequencies F1 and F2. Figure 11A , which is a schematic diagram illustrating a second ramp voltage signal Vramp2 generated by referring to a ramp count variable RC with different clock frequencies F1 and F2 in a normal scan mode according to some embodiments of the present disclosure.

[0137] The ramp count variable RC varies at the second clock frequency F2 in a first portion P1 before the initial code CDi within the full range Rf. The ramp count variable RC varies at the first clock frequency F1 in a second portion P2 after the initial code CDi within the full range Rf. The second clock frequency F2 is higher than the first clock frequency F1.

[0138] like Figure 11A As shown, the boundary between the first portion P1 and the second portion P2 is determined by the initial code CDi. In other words, the digital counter 322 counts the ramp count variable RC at a higher frequency (i.e., the second clock frequency F2) before the initial code CDi. After the initial code CDi, the digital counter 322 counts the ramp count variable RC at a lower frequency (i.e., the first clock frequency F1) until full scale.

[0139] The digital counter 322 provides the ramp count variable RC to the ramp converter 324. The ramp converter 124 generates Figure 11A The second ramp voltage signal Vramp2 shown in FIG. has a voltage level that varies in direct correlation with a ramp counter variable RC having two clock frequencies. The ramp converter 324 provides the second ramp voltage signal Vramp2 to the readout circuit 360. The readout circuit 360 compares the optical sensing voltage signals Scol1, Scol2, ..., Scoln with the second ramp voltage signal Vramp2 and stores the comparison results in a plurality of latches 362 to generate a second fingerprint brightness code BC2.

[0140] In some embodiments, in the normal scanning mode, the ramp counting variable RC is counted at a higher frequency (i.e., the second clock frequency F2) before the initial code CDi, and the ramp counting variable RC is counted at the normal standard frequency (i.e., the first clock frequency F1) after the initial code CDi to the full scale. In this example, Figure 11A The single cycle time T2 required by the second ramp voltage signal Vramp2 is shorter than Figure 10A The first ramp voltage signal Vramp1 requires a single cycle time T1. Therefore, in the normal scan mode, using the second ramp voltage signal Vramp2 with two clock frequencies F1 and F2 helps improve time efficiency. Figure 11B FIG2 is a schematic diagram illustrating a second fingerprint brightness code BC2 generated in a normal scanning mode according to some embodiments of the present disclosure.

[0141] exist Figures 10A to 11BIn the embodiment of the present disclosure, the ramp counting variable RC is counted in ascending order, but the present disclosure is not limited thereto. In other embodiments, the ramp counting variable RC can be counted in descending order. How to change the counting from ascending order to descending order has been previously described. Figures 3A to 4B Examples and Figures 5A to 6B A full description of the comparison between the two embodiments is provided in the accompanying figures. Similarly, the descending order can also be applied to ramp count variables RC with different clock frequencies, which will not be further described here. Thus, counting the ramp count variable RC with different clock frequencies in different portions P1 and P2 of the full range Rf can improve the processing speed of fingerprint sensing.

[0142] In summary, this disclosure proposes a control device and method that determine an initial code CDi based on the distribution DIST of multiple first fingerprint brightness codes BC1 during a pre-scan mode. This allows the initial code CDi to be dynamically detected during the pre-scan mode based on the current user and context. This control method can quickly and accurately generate a second fingerprint brightness code for different users and contexts.

[0143] Although specific embodiments of the present disclosure have been disclosed with respect to the above-described embodiments, these embodiments are not intended to limit the present disclosure. Various substitutions and modifications may be made by those skilled in the relevant art without departing from the principles and spirit of the present disclosure. Therefore, the scope of protection of the present disclosure is determined by the appended claims.

Claims

1. A fingerprint sensing control method, characterized in that: Include: receiving a plurality of first fingerprint brightness codes in a pre-scan mode, wherein the plurality of first fingerprint brightness codes are detected with reference to a ramp count variable that varies over a full range; generating an initial code according to a minimum code or a maximum code among the plurality of first fingerprint brightness codes; as well as The initial code is applied to the slope count variable in a normal scanning mode, and a plurality of second fingerprint brightness codes are detected by referring to the slope count variable that changes within a local range, wherein a boundary of the local range is determined according to the initial code.

2. The fingerprint sensing control method according to claim 1, characterized in that: The first plurality of fingerprint brightness codes are detected by: A digital counter counts the ramp count variable in ascending order from a zero scale toward a full scale; generating a first ramp voltage signal, the voltage level of which changes in direct correlation with the ramp count variable; and The plurality of optical sensing voltage signals are compared with the first ramp voltage signal to detect the plurality of first fingerprint brightness codes.

3. The fingerprint sensing control method according to claim 2, characterized in that: The initial code is generated according to the minimum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

4. The fingerprint sensing control method according to claim 3, characterized in that: Applying the initialization code to the ramp count variable includes: counting the ramp count variable by the digital counter in the ascending order, starting from the initial code toward the full scale; and Generate a second ramp voltage signal whose voltage level changes in direct correlation with the ramp count variable. The second fingerprint brightness codes are detected by comparing the optical sensing voltage signals with the second ramp voltage signal.

5. The fingerprint sensing control method according to claim 1, characterized in that: The first plurality of fingerprint brightness codes are detected by: A digital counter counts the ramp count variable in a descending order from a full scale toward a zero scale; generating a first ramp voltage signal, the voltage level of which changes in direct correlation with the ramp count variable; and The plurality of optical sensing voltage signals are compared with the first ramp voltage signal to detect the plurality of first fingerprint brightness codes.

6. The fingerprint sensing control method according to claim 5, characterized in that: The initial code is generated according to a maximum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

7. The fingerprint sensing control method according to claim 6, characterized in that: Applying the initialization code to the ramp count variable includes: Counting the ramp count variable by the digital counter in the descending order starting from the initial code toward the zero scale; and Generate a second ramp voltage signal, the voltage level of which changes in direct correlation with the ramp count variable. The second fingerprint brightness codes are detected by comparing the optical sensing voltage signals with the second ramp voltage signal.

8. The fingerprint sensing control method according to claim 1, characterized in that: Each of a plurality of consecutive readout frames includes the pre-scan mode and the normal scan mode. The initial code generated in the pre-scan mode of one of the plurality of consecutive readout frames is used to determine the local range in the normal scan mode of the same readout frame.

9. The fingerprint sensing control method according to claim 1, characterized in that: A first readout frame among a plurality of consecutive readout frames includes the pre-scan mode and the normal scan mode. The initial code generated in the pre-scan mode of the first readout frame is used to determine the local range in the normal scan mode of each of the plurality of consecutive readout frames.

10. A fingerprint sensing control method, characterized in that: Include: receiving a plurality of first fingerprint brightness codes in a pre-scan mode, wherein the plurality of first fingerprint brightness codes are detected with reference to a ramp count variable that varies at a first clock frequency over a full range; generating an initial code according to a minimum code or a maximum code among the plurality of first fingerprint brightness codes detected in the pre-scan mode; as well as In a normal scanning mode, the ramp count variable is set to a plurality of different clock frequencies according to the initial code, and a plurality of second fingerprint brightness codes are detected with reference to the ramp count variable, wherein a first portion of the ramp count variable within the full range and before the initial code varies at a second clock frequency, and a second portion of the ramp count variable within the full range and after the initial code varies at the first clock frequency, wherein the second clock frequency is higher than the first clock frequency.

11. The fingerprint sensing control method according to claim 10, characterized in that: The first plurality of fingerprint brightness codes are detected by: Counting the ramp count variable at the first clock frequency by a digital counter in ascending order from a zero scale toward a full scale; generating a first ramp voltage signal whose voltage level varies in direct correlation with the ramp count variable; and The plurality of optical sensing voltage signals are compared with the first ramp voltage signal to detect the plurality of first fingerprint brightness codes.

12. The fingerprint sensing control method according to claim 11, characterized in that: The initial code is generated according to the minimum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

13. The fingerprint sensing control method according to claim 12, characterized in that: Setting the ramp count variable in the normal scan mode includes: Counting the ramp count variable by the digital counter in the ascending order from the zero scale toward the initial code at the second clock frequency, and counting the ramp count variable in the ascending order from the initial code toward the full scale at the first clock frequency; and Generate a second ramp voltage signal whose voltage level changes in direct correlation with the ramp count variable. The second fingerprint brightness codes are detected by comparing the optical sensing voltage signals with the second ramp voltage signal.

14. The fingerprint sensing control method according to claim 10, characterized in that: The first plurality of fingerprint brightness codes are detected by: Counting the ramp count variable at the first clock frequency by a digital counter in a descending order from a full scale toward a zero scale; generating a first ramp voltage signal, the voltage level of which changes in direct correlation with the ramp count variable; and The plurality of optical sensing voltage signals are compared with the first ramp voltage signal to detect the plurality of first fingerprint brightness codes.

15. The fingerprint sensing control method according to claim 14, characterized in that: The initial code is generated according to a maximum code among the plurality of first fingerprint brightness codes in the pre-scan mode.

16. The fingerprint sensing control method according to claim 15, characterized in that: Setting the ramp count variable in the normal scan mode includes: Counting the ramp count variable by the digital counter in the descending order from the full scale toward the initial code at the second clock frequency, and counting the ramp count variable in the descending order from the initial code toward the zero scale at the first clock frequency; and Generate a second ramp voltage signal whose voltage level changes in direct correlation with the ramp count variable. The second fingerprint brightness codes are detected by comparing the optical sensing voltage signals with the second ramp voltage signal.

17. The fingerprint sensing control method according to claim 10, characterized in that: Each of the consecutive readout frames includes the pre-scan mode and the normal scan mode. The initial code generated in the pre-scan mode of one of the consecutive readout frames is used to determine the boundary between the first portion and the second portion in the normal scan mode in the same readout frame.

18. The fingerprint sensing control method according to claim 10, characterized in that: A first readout frame among a plurality of consecutive readout frames includes the pre-scan mode and the normal scan mode, and the initial code generated in the pre-scan mode of the first readout frame is used to determine the boundary between the first part and the second part in the normal scan mode of each of the plurality of consecutive readout frames.

19. A control circuit, characterized in that: The control circuit is applicable to an electronic device comprising a plurality of optical sensors and a readout circuit. The plurality of optical sensors are used to generate a plurality of optical sensing voltage signals. The readout circuit is used to compare the plurality of optical sensing voltage signals with a ramp voltage signal to detect a plurality of fingerprint brightness codes. The control circuit comprises: a digital counter for counting a ramp counting variable; a ramp converter coupled to the digital counter, the ramp converter being configured to generate the ramp voltage signal, the voltage level of which varies in direct correlation with the ramp count variable; a controller coupled to the digital counter and the ramp converter, the controller being configured to: triggering the digital counter to count the ramp count variable over a full range in a pre-scan mode; receiving a plurality of first fingerprint brightness codes from the readout circuit, wherein the plurality of first fingerprint brightness codes are detected with reference to the ramp count variable that varies within the full range; generating an initial code according to a minimum code or a maximum code among the plurality of first fingerprint brightness codes detected in the pre-scan mode; as well as triggering the digital counter to count the ramp count variable in a local range in a normal scanning mode, wherein a boundary of the local range is determined according to the initial code; In the normal scanning mode, a plurality of second fingerprint brightness codes are received from the readout circuit. The plurality of second fingerprint brightness codes are detected with reference to the slope count variable that changes within the local range.

20. A control circuit, characterized in that: The control circuit is applicable to an electronic device comprising a plurality of optical sensors and a readout circuit. The plurality of optical sensors are used to generate a plurality of optical sensing voltage signals. The readout circuit is used to compare the plurality of optical sensing voltage signals with a ramp voltage signal to detect a plurality of fingerprint brightness codes. The control circuit comprises: a digital counter for counting a ramp counting variable; a ramp converter coupled to the digital counter, the ramp converter being configured to generate the ramp voltage signal, the voltage level of which varies in direct correlation with the ramp count variable; a controller coupled to the digital counter and the ramp converter, the controller being configured to: triggering the digital counter to count the ramp count variable at a first clock frequency within a full range in a pre-scan mode; receiving a plurality of first fingerprint brightness codes from the readout circuit, wherein the plurality of first fingerprint brightness codes are detected with reference to the ramp count variable that varies within the full range; generating an initial code according to a minimum code or a maximum code among the plurality of first fingerprint brightness codes detected in the pre-scan mode; as well as triggering the digital counter to count the ramp count variable at a second clock frequency in a first portion of the full range before the initial code in a normal scan mode, and to count the ramp count variable at the first clock frequency in a second portion of the full range after the initial code in the normal scan mode; In the normal scanning mode, a plurality of second fingerprint brightness codes are received from the readout circuit, and the plurality of second fingerprint brightness codes are detected with reference to the ramp count variable.

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