TWI831017B - Capacitive fingerprint collection module, fingerprint identification device and information processing device - Google Patents

Abstract

The present invention mainly discloses a capacitive fingerprint collection module, which has a capacitive sensing array and a signal processing circuit. The signal processing circuit includes an analog front-end unit, an analog-to-digital conversion unit and a micro control unit, and the capacitive sensor The surface of the measuring array is covered with a coating. Among them, the surface and bottom of the coating are a curved surface and a flat surface respectively, and the signal processing circuit of the capacitive fingerprint acquisition module further includes a compensation unit to adjust the analog front-end unit so that the analog front-end unit Receive a first fingerprint collection signal from a central area of the sensing range of the capacitive sensing array with a first gain, and enable the analog front-end unit to sense from the second gain. Areas on both sides of the range receive a second fingerprint collection signal. The micro control unit obtains a first collection image and a second collection image after performing signal processing on the first fingerprint collection signal and the second fingerprint collection signal, and finally combines the first collection image and the second collection image. The images are stitched into a fingerprint image.

Description

Capacitive fingerprint collection module, fingerprint identification device and information processing device

The present invention relates to the field of fingerprint identification devices, and in particular, to a capacitive fingerprint collection module used in side fingerprint identification.

It is known that capacitive fingerprint recognition devices have been widely used in various electronic products. FIG. 1 shows a perspective view of a conventional smart phone with a fingerprint recognition function, and FIG. 2 shows a perspective view of a conventional capacitive fingerprint recognition device. Further, FIG. 3 shows a side cross-sectional view of a conventional capacitive fingerprint identification device. As shown in Figures 1, 2 and 3, the capacitive fingerprint identification device 2a is a fingerprint identification solution currently widely used in smart phones 1a. Its basic composition includes: a housing frame 21a with an opening 211a; A substrate 22a is provided in the accommodation frame 21a, a capacitive sensing array 23a is provided on the surface of the substrate 22a, a micro control chip 25a is provided on the bottom surface of the substrate 22a, and a microcontroller chip 25a is connected to the substrate 22a. Electrical connector 26a.

As shown in FIG. 3 and FIG. 1 , the opening 211a of the capacitive fingerprint recognition device 2a is usually exposed outside the front panel or the back panel of the smart phone 1a. Therefore, in order to prevent external contaminants from falling onto the capacitive sensing array 23a and thereby affecting its sensing accuracy, the surface of the capacitive sensing array 23a of the capacitive fingerprint identification device 2a is usually covered with a uniform coating 24a. . The coating 24a is not only waterproof, but also prevents fingerprints from remaining.

Figure 4 shows a side view of an existing full-screen smartphone. In some applications, as shown in Figure 4, for a capacitive fingerprint recognition device 2a used in a full-screen smartphone 3a, its opening 211a is exposed on the side of the full-screen smartphone 3a, realizing the so-called side fingerprint recognition. Figure 5 is a side cross-sectional view of the capacitive sensing array 23a. As shown in FIGS. 4 and 5 , in the application scenario of side fingerprint recognition, the surface of the coating 24 a is usually made to have a curvature, so that the user experience of side fingerprint recognition can be improved. Unfortunately, practical experience points out that the thickness of the coating 24a with a curved surface is laterally unevenly distributed, resulting in uneven fingerprint signal intensity in the capacitive sensing array 23a below when performing fingerprint sensing. Love affair.

From the above description, it can be seen that a new type of capacitive fingerprint collection module is urgently needed in this field.

The main purpose of the present invention is to provide a capacitive fingerprint acquisition module, which has a capacitive sensing array and a signal processing circuit. The signal processing circuit includes an analog front-end unit, an analog-to-digital conversion unit and a micro-control unit, and The surface of the capacitive sensing array is covered with a coating. Among them, the surface and bottom of the coating are a curved surface and a flat surface respectively, and the signal processing circuit of the capacitive fingerprint acquisition module further includes a compensation unit to adjust the analog front-end unit so that the analog front-end unit Receive a first fingerprint collection signal from a central area of the sensing range of the capacitive sensing array with a first gain, and enable the analog front-end unit to sense from the second gain. Areas on both sides of the range receive a second fingerprint collection signal. The micro control unit obtains a first collection image and a second collection image after performing signal processing on the first fingerprint collection signal and the second fingerprint collection signal, and finally combines the first collection image and the second collection image. The images are stitched into a fingerprint image.

In this way, since the analog front-end unit collects the first fingerprint collection signal and the second fingerprint collection signal with different gain values, it plays an important role in solving the lateral unevenness of the fingerprint collection signal intensity caused by the uneven lateral thickness of the coating. compensation effect.

To achieve the above object, the present invention proposes an embodiment of the capacitive fingerprint acquisition module, which has a capacitive sensing array and a signal processing circuit including an analog front-end unit, an analog-to-digital conversion unit and a micro-control unit. , wherein the surface of the capacitive sensing array is covered with a coating, and the surface and bottom of the coating are a curved surface and a flat surface respectively; it is characterized in that the capacitive fingerprint acquisition module further includes:

a compensation unit coupled to the microcontrol unit and the analog front-end unit;

Wherein, the capacitive sensing array has a sensing range including a central area, a first side area and a second side area;

Wherein, according to the control of the micro control unit, the compensation unit adjusts the gain of the analog front-end unit to a first gain, so that the analog front-end unit receives a first gain from the central area with the first gain. a fingerprint collection signal; and

Wherein, according to the control of the micro control unit, the compensation unit adjusts the gain of the analog front-end unit to a second gain, so that the analog front-end unit switches from the first side area and the second gain when having the second gain. The second side area receives a second fingerprint collection signal.

In one embodiment, the compensation unit is a control register.

In one embodiment, the compensation unit is a variable capacitance controller.

In one embodiment, the first gain is greater than the second gain.

Furthermore, in order to achieve the above object, the present invention also proposes another embodiment of the capacitive fingerprint acquisition module, which has a capacitive sensing array and an analog front-end unit, an analog-to-digital conversion unit and a micro-control unit. A signal processing circuit, in which the surface of the capacitive sensing array is covered with a coating, and the surface and bottom surface of the coating are a curved surface and a flat surface respectively; it is characterized in that the capacitive fingerprint acquisition module further includes:

a compensation unit coupled to the micro control unit;

Wherein, the capacitive sensing array has a sensing range including a central area, a first side area and a second side area, and the analog front-end unit receives a first fingerprint collection signal from the central area, and from the The first side area and the second side area receive a second fingerprint collection signal;

Wherein, the analog-to-digital conversion unit converts the first fingerprint collection signal and the second fingerprint collection signal into a first digital signal and a second digital signal, and the compensation unit provides a first compensation parameter and a second compensation parameter. The micro control unit is configured to perform a compensation process on the first digital signal and the second digital signal based on the first compensation parameter and the second compensation parameter.

In one embodiment, the compensation unit is any one selected from the group consisting of a register and a parameter storage.

In one embodiment, the compensation process is a subtraction process and/or an addition process.

Moreover, the present invention also provides an information processing device, which has a fingerprint identification device, and the fingerprint identification device includes the capacitive fingerprint collection module of the present invention as mentioned above.

In a feasible embodiment, the information processing device is selected from the group consisting of smart TVs, smart phones, smart watches, smart bracelets, tablet computers, notebook computers, all-in-one computers, access control devices, and electronic door locks. An electronic device among the group consisting of an automatic teller machine and a fingerprint punch card machine.

In order to enable the review committee to further understand the structure, characteristics, purpose, and advantages of the present invention, drawings and detailed descriptions of preferred embodiments are attached below.

First embodiment

Figure 6 shows a side view of a smartphone with a fingerprint recognition function, Figure 7 shows a perspective view of a fingerprint recognition device including a capacitive fingerprint collection module of the present invention, and Figure 8 is the fingerprint recognition device shown in Figure 7 side cross-section view. As shown in Figures 6, 7 and 8, the present invention proposes a capacitive fingerprint collection module CF, which is used in a fingerprint identification device 2 and includes: a capacitive sensing array 23 and an analog front-end unit 251. A signal processing circuit 25 of an analog-to-digital conversion unit 252 and a micro-control unit 253. To explain in more detail, the fingerprint identification device 2 also includes: a receiving frame 21 having an opening 211 , a substrate 22 provided in the receiving frame 21 , and an electrical connector 26 . The capacitive sensing array 23 is disposed on the surface of the substrate 22 , the signal processing circuit 25 is disposed on the bottom surface of the substrate 22 , and the electrical connector 26 is connected to the substrate 22 .

It is worth noting that the surface of the capacitive sensing array 23 is covered with a coating 24, and the surface and bottom of the coating 24 are a curved surface and a flat surface respectively. It should be understood that the thickness of the coating 24 with a curved surface is laterally unevenly distributed, so that the capacitive sensing array 23 located below the coating 24 will generate a fingerprint collection signal when performing a fingerprint sensing operation. The phenomenon of uneven lateral strength. In other words, the intensity of the fingerprint collection signal will be affected by the thickness of the coating 24 .

FIG. 9 is a first block diagram of the signal processing circuit 25 and the capacitive sensing array 23 shown in FIG. 8 . As shown in FIG. 9 , the capacitive sensing array 23 includes M×N sensing pixels 231 , and the M×N sensing pixels 231 have a sensing range. For example, the capacitive sensing array 23 shown in FIG. 9 includes 8×8 sensing pixels 231. On the other hand, the signal processing circuit 25 includes an analog front-end unit 251 , an analog-to-digital conversion unit 252 and a micro control unit 253 .

In particular, as shown in FIG. 9 , the present invention adds a compensation unit 254 in the signal processing circuit 25 , which is coupled to the micro control unit 253 and the analog front-end unit 251 . When using the signal processing circuit 25 to drive the capacitive sensing array 23 to perform fingerprint sensing, the micro control unit 253 will divide (or customize) a sensing range of the capacitive sensing array 23 into a central area and two side areas. For example, as shown in FIG. 9 , the sensing range is divided into a central area 23C, a right area 23R, and a left area 23L. Further, according to the control of the micro control unit 253, the compensation unit 254 adjusts the gain of the analog front-end unit 251 to a first gain (gain 1), so that the analog front-end unit 251 has the first gain. A first fingerprint collection signal is received from the central area 23C. Moreover, according to the control of the micro control unit 253, the compensation unit 254 adjusts the gain of the analog front-end unit 251 to a second gain (gain 2), so that the analog front-end unit 251 has the second gain. A second fingerprint collection signal is received from the two side areas (ie, the right area 23R + the left area 23L).

FIG. 10 is a circuit topology diagram of the analog front-end unit 251 shown in FIG. 9 . As shown in FIGS. 9 and 10 , since the capacitive sensing array 23 includes M×N sensing pixels 231 , M×N signal amplifying circuits are correspondingly provided inside the analog front-end unit 251 . Each of the signal amplification circuits includes: a current source 2511, an operational amplifier 2512, a variable capacitor 2513, and a switching element 2514. The first end of the current source 2511 is coupled to one of the sensing pixels 231, and the first end is coupled to a ground end. Furthermore, the positive input terminal and the negative input terminal of the operational amplifier 2512 are respectively coupled to the first terminal of the current source 2511 and a reference voltage V _REF .

To explain in more detail, the first terminal of the variable capacitor 2513 is coupled to the positive input terminal of the operational amplifier 2512, and the second terminal thereof is coupled to the output terminal of the operational amplifier 2512. Furthermore, the switching element 2514 is connected in parallel with the variable capacitor 2513 . In a possible embodiment, the compensation unit 254 is a control register. Electronic engineers who are familiar with computer science must know that control registers are generally used to control and determine the operating mode of a microcontroller. In the present invention, the compensation unit 254 is composed of a control register and is used to output a gain adjustment signal S _CA according to the control of the micro control unit 253 (for example, using a clock signal). As shown in FIGS. 9 and 10 , the gain adjustment signal S _CA is a bias voltage signal, which is transmitted to the first end of the variable capacitor 2513 to change (adjust) the first end of the variable capacitor 2513 . The terminal voltage at one end changes (adjusts) the capacitance value of the variable capacitor 2513 in this manner to achieve gain adjustment of the analog front-end unit 251.

As can be seen from the foregoing description, in a feasible embodiment, the compensation unit 254 may also be a variable capacitance control circuit, such as a bias voltage signal generator.

It should be added that the intensity of the fingerprint collection signal generated by the capacitive sensing array 23 after fingerprint sensing is negatively correlated with the thickness of the coating 24 . In other words, the intensity of the fingerprint collection signal collected in the central area 23C corresponding to the high-thickness portion of the coating 24 will be lower than the intensity of the fingerprint collection signal collected in the two side areas corresponding to the low-thickness portion of the coating 24 . Therefore, when the bias voltage adjusts the gain of the analog front-end unit 251, it is required that the first gain be greater than the second gain. In other words, the first gain corresponding to the central area 23C is greater than the second gain corresponding to the two side areas (ie, the right area 23R + the left area 23L).

To further explain, as shown in Figures 9 and 10, the analog-to-digital conversion unit 252 receives the first fingerprint collection signal and the second fingerprint collection signal that have been amplified by the analog front-end unit 251, and then compares the first fingerprint collection signal and the second fingerprint collection signal. The second fingerprint collection signal undergoes an analog-to-digital conversion process, thereby outputting a first digital signal and a second digital signal to the micro control unit 253 . Finally, after using an algorithm to process the first digital signal and the second digital signal into a first captured image and a second captured image, the micro control unit 253 combines the first captured image with the third captured image. The two collected images are spliced into one fingerprint image. It should be noted that the micro-control unit 253 implements fingerprint identification by comparing the characteristics of the fingerprint image with a pre-recorded fingerprint template.

Second embodiment

Continuing to refer to FIGS. 7 and 8 , please also refer to FIG. 11 , which is a second block diagram of the signal processing circuit 25 and the capacitive sensing array 23 shown in FIG. 8 . In the second embodiment, the capacitive fingerprint capture module CF of the present invention also includes a capacitive sensing array 23 and a signal processing circuit 25, and the signal processing circuit 25 also includes an analog front-end unit 251 and an analog-to-digital conversion. unit 252, a micro control unit 253 and a compensation unit 254. Different from the aforementioned first embodiment, as shown in FIG. 11 , the compensation unit 254 is coupled to the micro control unit 253 to provide a first compensation parameter and a second compensation parameter to the micro control unit 253 .

When using the signal processing circuit 25 to drive the capacitive sensing array 23 to perform fingerprint sensing, the micro control unit 253 will divide (or customize) a sensing range of the capacitive sensing array 23 into a central area 23C and two side areas. (Right area 23R + left area 23L). Then, the analog front-end unit 251 receives a first fingerprint collection signal from the central area 23C, and receives a second fingerprint collection signal from both side areas (right area 23R + left area 23L).

To further explain, as shown in Figure 11, the analog-to-digital conversion unit 252 receives the first fingerprint collection signal and the second fingerprint collection signal that have been amplified by the analog front-end unit 251, and then converts the first fingerprint collection signal and the second fingerprint The collected signal undergoes an analog-to-digital conversion process, thereby outputting a first digital signal and a second digital signal to the micro control unit 253 . At this time, the compensation unit 254 provides a first compensation parameter and a second compensation parameter to the micro control unit 253, so that the micro control unit 253 calculates the first digital signal according to the first compensation parameter and the second compensation parameter. Perform a compensation process with the second digital signal. Finally, after using an algorithm to process the first digital signal and the second digital signal that have completed the compensation process into a first acquisition image and a second acquisition image, the micro control unit 253 converts the first acquisition image The fingerprint image is spliced with the second collected image to form a fingerprint image.

The compensation unit 254 is a register or a parameter storage for storing the first compensation parameter corresponding to the central area 23C and the second compensation parameter corresponding to the two side areas (ie, the right area 23R + the left area 23L). In one embodiment, the compensation process is an addition process or an addition process. For example, the compensation process causes the second digital signal corresponding to the two side areas (23R+23L) to be added with a smaller value (ie, the second compensation parameter), while the first digital signal corresponding to the central area 23C is Subtract a smaller value (i.e., the first compensation parameter). Alternatively, the compensation process causes the second digital signal corresponding to the two side areas (23R+23L) to be subtracted by a larger value (ie, the second compensation parameter), while the first digital signal corresponding to the central area 23C is added A larger value (i.e., the first compensation parameter).

And, it is further added that when performing the compensation process, a compensation is performed on the first digital signal and the second digital signal in accordance with the column order of the capacitive sensing array 23 (ie, the 1st column to the Mth column). handle.

According to the above description, the capacitive fingerprint acquisition module of the present invention can be generalized as: a capacitive fingerprint acquisition module, which has a capacitive sensing array and a signal processing circuit, and is characterized in that: the surface of the capacitive sensing array Covered with a curved surface coating; and the signal processing circuit has a compensation unit to enable an analog front-end unit to use different gains for multiple areas of the capacitive sensing array corresponding to the curved surface coating The sensing element performs an amplification operation or performs different compensation processing on signals received by an analog front-end unit from multiple sensing elements of the capacitive sensing array corresponding to multiple different areas of the curved coating.

In this way, the above has completely and clearly explained a capacitive fingerprint collection module of the present invention; and from the above, it can be known that the present invention has the following advantages:

(1) The present invention discloses a capacitive fingerprint collection module, which has a capacitive sensing array and a signal processing circuit. The signal processing circuit includes an analog front-end unit, an analog-to-digital conversion unit and a micro-control unit, and the signal processing circuit The surface of the capacitive sensing array is covered with a coating. Among them, the surface and bottom of the coating are a curved surface and a flat surface respectively, and the signal processing circuit of the capacitive fingerprint acquisition module further includes a compensation unit to adjust the analog front-end unit so that the analog front-end unit Receive a first fingerprint collection signal from a central area of the sensing range of the capacitive sensing array with a first gain, and enable the analog front-end unit to sense from the second gain. Areas on both sides of the range receive a second fingerprint collection signal. The micro control unit obtains a first collection image and a second collection image after performing signal processing on the first fingerprint collection signal and the second fingerprint collection signal, and finally combines the first collection image and the second collection image. The images are stitched into a fingerprint image.

(2) In this way, since the analog front-end unit collects the first fingerprint collection signal and the second fingerprint collection signal with different gain values, the fingerprint collection signal intensity is laterally inconsistent due to uneven lateral thickness of the coating. Uniform compensation effect.

(3) The present invention also provides an information processing device, which has a fingerprint identification device, and the fingerprint identification device includes the capacitive fingerprint collection module of the present invention as described above. In a feasible embodiment, the information processing device is selected from the group consisting of smart TVs, smart phones, smart watches, smart bracelets, tablet computers, notebook computers, all-in-one computers, access control devices, and electronic door locks. An electronic device among the group consisting of an automatic teller machine and a fingerprint punch card machine.

It must be emphasized that the foregoing disclosed in this case are preferred embodiments. Any partial changes or modifications derived from the technical ideas of this case and easily inferred by those familiar with the art do not deviate from the patent of this case. category of rights.

To sum up, regardless of the purpose, means and effects of this case, it shows that it is completely different from the conventional technology, and that the invention is practical first, and indeed meets the patent requirements for inventions. I sincerely ask the review committee to take a clear look and grant the patent as soon as possible for your benefit. Society is a prayer for the Supreme Being.

1a:Smartphone 2a: Capacitive fingerprint identification device 21a: Accommodation frame 211a: Open your mouth 22a:Substrate 23a: Capacitive sensing array 24a:Coating 25a:Micro control chip 26a: Electrical connector 3a: Full screen smartphone 3:Smartphone CF: Capacitive fingerprint collection module 2:Fingerprint identification device 20:Circuit board 21: Accommodation frame 211:Open your mouth 22:Substrate 23: Capacitive sensing array 23C:Central area 23L: Left area 23R:Right area 231: Sensing pixel 24:Coating 25:Signal processing circuit 251: Analog front-end unit 2511:Current source 2512: Operational amplifier 2512 2513:Variable capacitor 2514:Switching element 252:Analog to digital conversion unit 253:Micro control unit 254: Compensation unit 26: Electrical connectors

Figure 1 is a three-dimensional view of a conventional smart phone with a fingerprint recognition function; Figure 2 is a perspective view of a conventional capacitive fingerprint identification device; Figure 3 is a side cross-sectional view of a conventional capacitive fingerprint identification device; Figure 4 is a side view of an existing full-screen smartphone; Figure 5 is a side cross-sectional view of the capacitive sensing array; Figure 6 is a side view of a smartphone with fingerprint recognition function; Figure 7 is a perspective view of a fingerprint identification device including a capacitive fingerprint collection module of the present invention; Figure 8 is a side cross-sectional view of the fingerprint identification device shown in Figure 7; Figure 9 is a first block diagram of the signal processing circuit and capacitive sensing array shown in Figure 8; Figure 10 is a circuit topology diagram of the analog front-end unit shown in Figure 9 and FIG. 11 is a second block diagram of the signal processing circuit and capacitive sensing array shown in FIG. 8 .

23: Capacitive sensing array

23C:Central area

23L:Left area

23R:Right area

231: Sensing pixel

25:Signal processing circuit

251: Analog front-end unit

252:Analog to digital conversion unit

253:Micro control unit

254: Compensation unit

Claims (5)

A capacitive fingerprint acquisition module, which has a capacitive sensing array and a signal processing circuit including an analog front-end unit, an analog-to-digital conversion unit and a micro control unit, wherein the surface of the capacitive sensing array is covered with a coating , and the surface and bottom surface of the coating are an arc surface and a flat surface respectively; it is characterized in that the capacitive fingerprint acquisition module further includes: a compensation unit coupled to the micro control unit and the analog front-end unit, and It is a control register or a variable capacitance controller; wherein, the capacitance sensing array has a sensing range including a central area, a first side area and a second side area; wherein, according to the micro control unit Controlled, the compensation unit adjusts the gain of the analog front-end unit to a first gain, so that the analog front-end unit receives a first fingerprint acquisition signal from the central area with the first gain; and wherein , according to the control of the micro control unit, the compensation unit adjusts the gain of the analog front-end unit to a second gain, so that the analog front-end unit switches from the first side area and the second gain when having the second gain. The second side area receives a second fingerprint collection signal, wherein the first gain is greater than the second gain. A capacitive fingerprint acquisition module, which has a capacitive sensing array and a signal processing circuit including an analog front-end unit, an analog-to-digital conversion unit and a micro control unit, wherein the surface of the capacitive sensing array is covered with a coating , and the surface and bottom of the coating are an arc surface and a flat surface respectively; it is characterized in that the capacitive fingerprint collection module further includes: a compensation unit, which is coupled to the micro control unit, and which is a register or A parameter storage; wherein the capacitive sensing array has a sensing range including a central area, a first side area and a second side area, and the analog front-end unit receives a first fingerprint collection from the central area signal, and receives a second fingerprint collection signal from the first side area and the second side area; wherein the analog-to-digital conversion unit converts the first fingerprint collection signal and the second fingerprint collection signal into a first digital signal and a second digital signal, and the compensation unit provides a first compensation parameter and A second compensation parameter is given to the micro control unit, so that the micro control unit performs a compensation process on the first digital signal and the second digital signal based on the first compensation parameter and the second compensation parameter; wherein, the compensation process It is used to perform an addition operation on the first digital signal and the first compensation parameter to increase the value of the first digital signal, and perform a subtraction operation on the second digital signal and the second compensation parameter to reduce the value of the first digital signal. The numerical value of a two-digit signal. A capacitive fingerprint collection module, which has a capacitive sensing array and a signal processing circuit, is characterized in that: the surface of the capacitive sensing array is covered with a curved coating, and it has a central sensing area and a plurality of The side sensing area; and the signal processing circuit has a compensation unit to enable an analog front-end unit to use different gains for the capacitance corresponding to the central sensing area of the curved surface coating and the side sensing areas. The sensing signals of the multiple sensing elements of the sensing array are subjected to an amplification operation, wherein the gain corresponding to the central sensing area is greater than the gains corresponding to the side sensing areas; or for an analog front-end unit Compensation processing is performed on the sensing signals received from the plurality of sensing elements of the capacitive sensing array corresponding to the central sensing area and the side sensing areas of the arc surface coating, wherein the compensation processing is performed using An addition operation is performed on the sensing signal of the central sensing area and a first compensation parameter to increase the value of the sensing signal of the central sensing area, and on the side sensing areas The sensing signal and a second compensation parameter are subjected to a subtraction operation to reduce the value of the sensing signal in the side sensing areas. An information processing device includes a fingerprint identification device, and the fingerprint identification device includes the capacitive fingerprint acquisition module as described in any one of claims 1 to 3. The information processing device as described in claim 4, wherein the information processing device is selected from the group consisting of smart TVs, smart phones, smart watches, smart bracelets, tablet computers, notebook computers, all-in-one computers, access control An electronic device among the group consisting of an electronic door lock, an automatic teller machine, and a fingerprint punch card machine.

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