WO2019061477A1

WO2019061477A1 - Sensing pixel unit and optical fingerprint sensor

Info

Publication number: WO2019061477A1
Application number: PCT/CN2017/104941
Authority: WO
Inventors: 赵维民
Original assignee: 深圳市汇顶科技股份有限公司
Priority date: 2017-09-30
Filing date: 2017-09-30
Publication date: 2019-04-04
Also published as: CN107820618A; CN107820618B

Abstract

A sensing pixel unit (30). The sensing pixel unit (30) comprises a pixel light sensing unit (32), multiple reference elements, and an integration unit (34). The pixel light sensing unit (32) comprises multiple light sensing elements used for receiving light illumination and outputting multiple light-sensing sub-pixel values corresponding to the multiple light sensing elements. Each light-sensing sub-pixel value corresponds to a first light-sensing area. The multiple reference elements output multiple reference sub-pixel values corresponding to the multiple reference elements. Each reference sub-pixel value corresponds to a second light sensing area, and the second light sensing area is smaller than the first light sensing area. The integration unit (34) is in coupled connection with the multiple light sensing elements and the multiple reference elements, and is used for outputting a pixel value corresponding to the sensing pixel unit (30) according to the multiple light-sensing sub-pixel values and the multiple reference sub-pixel values.

Description

Sensing pixel unit and optical fingerprint sensor

Technical field

The present application relates to a sensing pixel unit and an optical fingerprint sensor, and more particularly to a sensing pixel unit and an optical fingerprint sensor that improve temperature and cause image inconsistency.

Background technique

With the rapid development of technology, more and more portable electronic devices such as mobile phones, digital cameras, tablet computers, and notebook computers have become essential tools in people's lives. Since portable electronic devices are generally used by individuals and have certain privacy, their internally stored data, such as phone books, photos, personal information, etc., are privately owned. If the electronic device is lost, the data may be used by others and cause unnecessary losses. Although password protection has been used to prevent electronic devices from being used by others, passwords are easily leaked or cracked, and have low security. Moreover, the user needs to remember the password in order to use the electronic device, and if the password is forgotten, it will bring a lot of inconvenience to the user. Therefore, the use of personal fingerprint identification systems to achieve identity authentication has been developed to improve data security.

On the other hand, with the advancement of fingerprint identification technology, Invisible Fingerprint Sensor (IFS) has gradually been favored by consumers. In the invisible fingerprint sensing technology, the optical fingerprint sensor can be disposed under the display screen, that is, the Under Display fingerprint sensing. in other words, The user can perform fingerprint recognition by pressing the display screen. However, due to process factors, the sensing pixel unit in the fingerprint identification sensor may be contaminated by metal and have different sensitivity to temperature, resulting in output of multiple sensing pixel units of the optical fingerprint sensor when the temperature is higher. Inconsistent or non-uniformity of multiple pixel values may be serious. For example, in the case of no illumination, a plurality of pixel values output by the plurality of sensing pixel units are at 25 ° C, 37 ° C, 41 ° C, The standard deviation (Standard Deviation, STD) at 55 ° C is 1.3, 1.9, 2.7, and 9.9 unit values, respectively. In the actual Under Display application, since the optical fingerprint sensor is disposed below the display screen, it will be exposed to the heat emitted by the display screen, so that the inconsistency or unevenness of the fingerprint image will be more serious, affecting the fingerprint interpretation. accuracy. Therefore, the prior art is in need of improvement.

Summary of the invention

Accordingly, it is an object of some embodiments of the present application to provide a sensing pixel unit and an optical fingerprint sensor that improve temperature resulting in image inconsistency to improve the disadvantages of the prior art.

In order to solve the above technical problem, the embodiment of the present application provides a sensing pixel unit, which is applied to an optical fingerprint sensor, where the sensing pixel unit outputs a pixel value corresponding to the sensing pixel unit, and the sensing pixel The unit includes a pixel photosensitive unit, and includes a plurality of photosensitive elements for receiving illumination and outputting a plurality of photosensitive sub-pixel values corresponding to the plurality of photosensitive elements, wherein each of the photosensitive sub-pixel values corresponds to a first photosensitive area; Reference elements, outputting a plurality of reference sub-pixel values corresponding to the plurality of reference elements, wherein each reference sub-pixel value corresponds to a second photosensitive area, the second photosensitive area is smaller than the first photosensitive area; And an integration unit coupled to the plurality of photosensitive elements and the plurality of reference elements for inputting according to the plurality of photosensitive sub-pixel values and the plurality of reference sub-pixel values The pixel value corresponding to the sensing pixel unit is output.

For example, one of the plurality of reference elements includes a photodiode having a photosensitive region; and a light blocking layer disposed over the photosensitive region of the photodiode in the reference element.

For example, the light blocking layer completely covers the photosensitive area, and the second photosensitive area is zero.

For example, the light blocking layer partially covers the photosensitive area.

For example, the light blocking layer is a metal layer in an integrated circuit layout.

For example, the integration unit includes a reference statistics unit for calculating a reference statistic of the plurality of reference sub-pixel values; a reference averaging unit, receiving a reference threshold, and according to the reference threshold and the reference a statistic, a reference average value corresponding to the plurality of reference sub-pixel values; a sensation statistic unit for calculating a sensation statistic of the plurality of photoreceptor pixel values; a table lookup unit for responsive to the sensitization a statistic quantity, a sensation limit value; a sensation averaging unit configured to calculate a sensitized average value corresponding to the plurality of photoreceptor pixel values according to the sensation threshold value and the sensation statistic amount; and a subtraction unit And the reference averaging unit and the sensitization averaging unit are configured to output the pixel value as a subtraction result of the photographic average value and the reference average value.

For example, the reference averaging unit is configured to perform the following steps to calculate the reference average value according to the reference threshold and the reference statistic: according to the reference statistic and the reference 临 a limit value, a plurality of normal reference sub-pixel values of the plurality of reference sub-pixel values, wherein a difference between each normal reference sub-pixel value and the reference statistic is less than or equal to the reference threshold; and a calculation The reference average is the average of the plurality of normal reference sub-pixel values.

For example, the reference statistic is one of a minimum, a median or an average of the plurality of reference sub-pixel values.

For example, the photosensitive averaging unit is configured to perform the following steps to calculate the sensible average value according to the sensation visit limit value and the sensation statistic amount: according to the sensible statistic amount and the sensation visit limit value, a plurality of normal photosensitive sub-pixel values of the plurality of photosensitive sub-pixel values, wherein a difference between each normal photo-sensing sub-pixel value and the sensible statistic is less than or equal to the sensation limit value; and calculating the photographic average value Is the average of the plurality of normal photoreceptor sub-pixel values.

For example, the sensation statistic is one of a minimum, a median or an average of the plurality of photoreceptor pixel values.

For example, the sensing pixel unit further includes an analog to digital converter coupled between the plurality of photosensitive elements and the plurality of reference elements and the integrated unit.

In order to solve the above technical problem, an embodiment of the present application further provides an optical fingerprint sensor, including a plurality of sensing pixel units, for outputting a plurality of pixel values corresponding to a plurality of sensing pixel units, wherein each sensing pixel The sensing pixel unit of the unit, the plurality of pixels of the plurality of sensing pixel units are sensitive The cells are arranged in an array.

For example, the optical fingerprint sensor is disposed under the display of the electronic device.

For example, the optical fingerprint sensor is coupled to the fingerprint recognition unit, and the fingerprint recognition unit is configured to determine a fingerprint of the user according to the plurality of pixel values corresponding to the plurality of sensing pixel units.

The embodiment of the present application utilizes a plurality of photosensitive elements and a plurality of reference elements to form a sensing pixel unit; the reference sub-pixel generated by the light-insensitive reference element is used to eliminate or compensate a temperature-affected signal component of the photosensitive sub-pixel; Use integrated units to eliminate temperature-sensitive components and eliminate noise. The present application improves the inconsistency or unevenness caused by temperature in the prior art, and is applied in the field of optical fingerprint identification. The present application enhances the accuracy of fingerprint recognition.

DRAWINGS

1 is a schematic cross-sectional view of an electronic device according to an embodiment of the present application;

2 is a functional block diagram of the electronic device of FIG. 1;

3 is a schematic diagram of a sensing pixel unit according to an embodiment of the present application;

4 is a schematic view of a photosensitive element and a reference element according to an embodiment of the present application;

FIG. 5 is a schematic diagram of an integration unit according to an embodiment of the present application.

Detailed ways

In order to make the objects, technical solutions and advantages of the present application more clear, the following The application is further described in detail in the application. It is understood that the specific embodiments described herein are merely illustrative of the application and are not intended to be limiting.

1 is a schematic cross-sectional view of an electronic device 10 according to an embodiment of the present application, FIG. 2 is a functional block diagram of an electronic device 10 according to an embodiment of the present application, and FIG. 3 is a sensing pixel unit according to an embodiment of the present application. Schematic diagram of 30. For convenience of explanation, FIGS. 1 to 3 only show elements related to the features of the present invention, and omit irrelevant elements. The electronic device 10 includes a display screen 12, an optical fingerprint sensor 14 and a fingerprint identification unit 16. The optical fingerprint sensor 14 is disposed under the display screen 12 (ie, under the screen) and coupled to the fingerprint identification unit. 16. The optical fingerprint sensor 14 includes a plurality of sensing pixel units 30, and the plurality of sensing pixel units 30 respectively output a plurality of pixel values PX_out to the fingerprint recognition unit 16 (ie, each sensing pixel unit 30 outputs its corresponding pixel value PX_out to The fingerprint identification unit 16) can determine the fingerprint of the user according to the plurality of pixel values PX_out corresponding to the plurality of sensing pixel units 30. The photosensitive area of each sensing pixel unit 30 can be approximately 50×50 μm ² , so that the optical fingerprint sensor 14 can have a resolution of at least 508 Dots Per Inch (DPI), which is sufficient to accurately recognize the fingerprint.

In detail, each of the sensing pixel units 30 includes a pixel photosensitive unit 32, an analog-to-digital converter ADC, and an integrating unit 34, and the plurality of pixel photosensitive units 32 of the plurality of sensing pixel units 30 are arranged in a plane. The array in which the area of the pixel photosensitive unit 32 is approximately 50 × 50 μm ² . The pixel photosensitive unit 32 includes a plurality of photosensitive elements AP and a plurality of reference elements OBP. In the embodiment illustrated in FIG. 3, the sensing pixel unit 30 includes 12 photosensitive elements AP and 4 reference elements OBP (ie, N=12). And K = 4), not limited to this. The plurality of photosensitive elements AP and the plurality of reference elements OBP may be further arranged in an array in a region where the pixel photosensitive unit 32 is located, and the plurality of photosensitive elements AP may output a plurality of photosensitive sub-pixel values LSP ₁ corresponding to the plurality of photosensitive elements AP. LSP _N , the plurality of reference elements OBP may output a plurality of reference sub-pixel values RP ₁ -RP _K corresponding to the plurality of reference elements OBP. In addition, the plurality of photosensitive elements AP and the plurality of reference elements OBP are coupled to the integrating unit 34 through the analog-to-digital converter ADC. In other words, the analog-to-digital converter ADC will simulate the photosensitive sub-pixel values LSP ₁ LSP _N and reference. The sub-pixel values RP ₁ to RP _{K are} converted into digital photo sub-pixel values LSP ₁ to LSP _N and reference sub-pixel values RP ₁ to RP _K , and the integration unit 34 can perform digital photo sub-pixel values LSP ₁ to LSP _N and The calculation and processing are performed with reference to the sub-pixel values RP ₁ to RP _K to generate pixel values PX_out corresponding to the sensing pixel unit 30.

The photosensitive element AP is used to actually receive illumination and thereby generate photoelectrons or photocurrents (which can be regarded as active Pixels), which are highly sensitive to light. However, the photosensitive element AP may have different sensitivity to temperature due to process factors. Therefore, in order to reduce/eliminate the influence of temperature on the pixel value PX_out, the sensing pixel unit 30 uses the light-insensitive reference component OBP to eliminate/compensate for the influence of temperature, and the reference component OBP can be regarded as an optical black pixel (Optical Black Pixel). ).

In detail, please refer to FIG. 4. FIG. 4 is a schematic top view of the photosensitive element AP, the reference component OBP1, and the reference component OBP2 according to an embodiment of the present invention. Both the reference element OBP1 and the reference element OBP2 can be used to implement the reference element OBP in the pixel photosensitive unit 32. The photosensitive element AP, the reference element OBP1, and the reference element OBP2 each include a photodiode having the same photosensitive area/area, wherein the photosensitive diode has a photosensitive area LSA and a non-photosensitive area NSA, and the photosensitive area LSA has a photosensitive area A1. The photosensitive element AP is simply a photodiode, that is, the photosensitive element AP has a photosensitive area LSA and a non-photosensitive area NSA, and the area of the photosensitive area LSA is a photosensitive area A1. On the other hand, unlike the photosensitive element AP, the reference element OBP includes a light blocking layer LBL in addition to the photodiode, and the light blocking layer LBL may be a metal layer (Metal) in an integrated circuit layout (IC Layout). It is placed above the photosensitive area of the photodiode. LBL optical barrier layer to reduce the area of the reference photosensitive element OBP photosensitive diode, i.e., to reduce sensitivity to light OBP reference element, the photosensitive element corresponding to the reference area A2 of OBP A2 = A1-Δ _A, where Δ _A The projected area of the light-blocking layer LBL on the photosensitive region of the photosensitive diode, that is, the photosensitive area A2 of the reference element OBP is smaller than the photosensitive area A1 of the photosensitive element AP. In short, the sensitivity of the reference element OBP to light is smaller than the sensitivity of the photosensitive element AP to light compared to the photosensitive element AP.

In an embodiment, the light blocking layer LBL completely covers the photosensitive area of the photodiode in the reference component OBP, that is, the photosensitive area A2 of the reference component OBP is zero, as shown in the reference component OBP1 of FIG. 4, and the reference output by the reference component OBP1. The sub-pixels are unaffected by the illumination and are only affected by temperature, which can be used to cancel/compensate for temperature-affected signal components in the pixel value PX_out.

Further, in another embodiment, the light blocking layer LBL partially covers the photosensitive region of the photodiode in the reference component OBP, as shown in the reference component OBP2 of FIG. 4, and the reference subpixel output by the reference component OBP2 is slightly illuminated. Influence and temperature effects, which can be used to eliminate/compensate for signal components in the pixel value PX_out that are affected by temperature and background light.

In short, the reference sub-pixel values RP ₁ ～ RP _K generated by the reference element OBP are less affected by the illumination of the photosensitive element AP (even completely unaffected by illumination, such as the reference element OBP1), and the reference element OBP The degree of influence of the temperature on the photosensitive element AP is the same. Therefore, the integration unit 34 detects and excludes the hot pixel (Hot Pixel, or white pixel point) caused by the process factor of the photosensitive element AP or the reference element OBP. (White Pixel)), and the reference sub-pixel values RP ₁ to RP _K generated by the reference component OBP are used to compensate the photoreceptor sub-pixel values LSP ₁ to LSP _N generated by the photosensitive element AP.

For details, please refer to FIG. 5. FIG. 5 is a schematic diagram of an integration unit 34 according to an embodiment of the present application. The integration unit 34 includes a sensation statistic unit 50, a lookup unit 52, a sensation averaging unit 54, a reference statistic unit 56, and a reference averaging unit 58. And a subtraction unit SUB. Reference counting unit 56 for calculating a reference value of the sub-pixel ₁ to the reference statistics RP _K RP RP _M, wherein the reference statistical quantity RP _M may be a reference sub-pixel values of the RP RP _K ₁ to the minimum, average or median one of them. The reference averaging unit 58 receives the reference statistic RP _M and a reference threshold D_th, and calculates a reference average RP corresponding to the reference sub-pixel values RP ₁ RP RP _K based on the reference threshold D_th and the reference statistic RP _M . _AVE , where the reference threshold D_th can be set by the production staff before leaving the factory. Similarly, the photosensitive unit 50 for calculating the statistical photosensitive sub-pixel values LSP ₁ ~ photosensitive statistics of LSP _M LSP _N, photosensitive statistics LSP _M may be the minimum value of the LSP ₁ ~ LSP _N photosensitive subpixel, median, or One of the averages. The sensitization averaging unit 54 receives the sensation statistic LSP _M and the sensation visit limit value L_th, and calculates a sensible average LSP corresponding to the photoreceptor sub-pixel values LSP ₁ LSP _N from the sensation limit value L_th and the sensation statistic LSP _M . _AVE , where the sense of the limit value L_th can be obtained by looking up the table. The subtraction unit SUB is coupled to the sensitization unit 54 and the reference averaging unit 58 for subtracting the sensitized average value LSP _AVE from the reference average value RP _AVE to output the pixel value PX_out as the sensible average value LSP _AVE and the reference average value RP _AVE The result of the subtraction, such as PX_out = LSP _{AVE -} RP _AVE , the subtraction unit SUB is used to perform a common-ternal rejection (Common-tern Rejection) operation. In addition, the lookup unit 52 can store the correspondence between the sensible statistic LSP _M and the sensible visit limit L_th, and the corresponding relationship can be established in advance in the calibration phase of the electronic device 10t. Therefore, when the electronic device 10 performs During normal operation, the look-up table unit 52 can output its corresponding sense visit limit value L_th according to the light-sensing statistic LSP _M.

The details of calculating the reference average RP _AVE by the reference averaging unit 58 are detailed below. The reference averaging unit 58 examines one by one whether the difference between the reference sub-pixel values RP ₁ RP RP _K and the reference statistic RP _M is greater than the reference threshold D_th, wherein the difference may be any of the reference sub-pixel values RP ₁ ～RP _K The absolute value of the subtraction result of the sub-pixel value RP _k and the reference statistic RP _M , that is, |RP _k -RP _M |. If the difference |RP _k -RP _M | is greater than the reference threshold D_th, the reference element OBP corresponding to the reference sub-pixel value RP _k is highly susceptible to temperature, so the reference averaging unit 58 rejects the reference sub-pixel value RP _k , i.e. not used in calculating the difference between the reference average value RP _AVE | RP _k -RP _M | D_th greater than a reference threshold value of the reference sub-pixel RP _k. On the other hand, if the difference |RP _k -RP _M | of the reference sub-pixel value RP _k and the reference statistic RP _M is less than or equal to the reference threshold D_th, the representative reference sub-pixel value RP _k is a normal reference sub-pixel value, reference averaging unit 58 in calculating the average value of the reference sub-pixel RP _AVE reference value RP _k into account in calculating the reference average value RP _AVE. In an embodiment, for each reference sub-pixel value RP _k (k=1, . . . , K), when the difference |RP _k -RP _M | is greater than the reference threshold D_th, the reference averaging unit 58 The weight w _k corresponding to the reference sub-pixel value RP _k is set to 0; when the difference |RP _k -RP _M | is less than or equal to the reference threshold D_th, the reference averaging unit 58 will correspond to the weight w of the reference sub-pixel value RP _k _{k is} set to 1; thus, the reference averaging unit 58 can calculate the reference average RP _AVE as RP _AVE = (Σ _k w _k * RP _k ) / (Σ _k w _k ) (Equation 1). In other words, the reference averaging unit 58 first selects a plurality of normal reference sub-pixel values from the reference sub-pixel values RP ₁ ～RP _K (where the difference between each normal reference sub-pixel value and the reference statistic RP _M is less than or equal to the reference Threshold D_th), and then calculate the reference average RP _AVE as the average of a plurality of normal reference sub-pixel values.

Similarly, the photosensitive unit 54 one by one to view the photosensitive average sub-pixel value difference LSP _N LSP ₁ ~ and the photosensitive statistics LSP _M is greater than a limit value L_th presence sensing, wherein the difference value of the LSP ₁ ~ LSP _N as photosensitive subpixel The absolute value of the subtraction result of any photosensitive sub-pixel value LSP _n and the photosensitive statistic LSP _M , that is, |LSP _{n -} LSP _M |. If the difference | LSP _{n -} LSP _M | is greater than the sense limit value L_th, the photosensitive element AP corresponding to the photoreceptor sub-pixel value LSP _n is highly susceptible to temperature, so the photosensitive averaging unit 54 rejects the photoreceptor sub-pixel value LSP _n . That is, when the photosensitive average value LSP _AVE is calculated, the difference | LSP _{n -} LSP _M | is larger than the photosensitive sub-pixel value LSP _{n of the} sense limit value L_th. On the other hand, if the difference |LSP _n -LSP _M | of the photoreceptor sub-pixel value LSP _n and the photosensitive statistic LSP _M is less than or equal to the sense limit value L_th, the photoreceptor sub-pixel value LSP _n is a normal photo sub-pixel value, when the photosensitive averaging unit 54 calculates average LSP _AVE photosensitive photosensitive LSP _n subpixel values into consideration when calculating the average of the photosensitive LSP _AVE. In an embodiment, for each photo sub-pixel value LSP _n (n=1, . . . , N), when the difference |LSP _n -LSP _M | is greater than the sense limit value L_th, the sensation averaging unit 54 The weight c _n corresponding to the photoreceptor sub-pixel value LSP _n is set to 0; when the difference | LSP _{n -} LSP _M | is less than or equal to the sense limit value L_th, the photosensitive averaging unit 54 will assign a weight c corresponding to the photoreceptor sub-pixel value LSP _n _{n is} set to 1; thus, the photosensitive averaging unit 54 can calculate the photosensitive average value LSP _AVE as LSP _AVE = (Σ _n c _n * LSP _n ) / (Σ _n c _n ) (Equation 2). In other words, the sensitization unit 54 first selects a plurality of normal photo sub-pixel values from the photo sub-pixel values LSP ₁ LSP _N (the difference between each normal photo sub-pixel value and the sensation statistic LSP _M is less than or equal to the sense At the limit value L_th), the sensitivities LSP _AVE are calculated as an average of a plurality of normal photoreceptor sub-pixel values.

From another point of view, the reference averaging unit 58 can not only reject the reference sub-pixel values generated by the temperature-sensitive reference element OBP, but also utilize the averaging operation of Equation 1, the reference averaging unit 58 can also eliminate noise; likewise, Photosensitive averaging unit 54 can remove not only temperature sensitive photosensitive elements The reference sub-pixel value generated by the AP, using the averaging operation of Equation 2, the sensitization unit 54 can also eliminate noise. In addition, with the subtraction unit SUB, the components affected by the temperature of the sensing pixel unit 30 can be eliminated (or compensated back).

In this way, the present application can greatly reduce the inconsistency or unevenness of the plurality of pixel values PX_out output by the plurality of sensing pixel units 30. Specifically, when the temperatures are 25° C., 37° C., 41° C., and 55° C., the standard deviations (Standard Deviations, STD) of the plurality of pixel values PX_out output by the plurality of sensing pixel units 30 are 0.7 and 0.9, respectively. 1.0, 1.4 unit values. Especially in the case of high temperature, the degree of standard deviation is particularly significant. When the temperature is 41 ° C, 55 ° C, the standard deviation decreases by 2.7, 7.0 times.

The integration unit is not limited to being implemented in a specific manner, and may be implemented by a digital circuit such as a Register-Transfer Level (RTL) circuit or an Application-Specific Integrated Circuit (ASIC), and may even utilize a digital signal. The processor (Digital Signal Processor, DSP) is implemented.

In summary, the present application utilizes a plurality of photosensitive elements and a plurality of reference elements to form a sensing pixel unit; the reference sub-pixels generated by the light-insensitive reference elements are used to eliminate or compensate for temperature-dependent effects in the photosensitive sub-pixels. Signal components; use integrated units to eliminate temperature-sensitive components and eliminate noise. The present application improves the inconsistency or unevenness caused by temperature in the prior art, and is applied in the field of optical fingerprint identification. The present application enhances the accuracy of fingerprint recognition.

The above is only a part of the embodiments of the present application, and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application are included in the scope of protection of the present application. within.

Claims

A sensing pixel unit is applied to an optical fingerprint sensor, and the sensing pixel unit outputs a pixel value corresponding to the sensing pixel unit, wherein the sensing pixel unit comprises:

The pixel photosensitive unit includes:

a plurality of photosensitive elements for receiving illumination and outputting a plurality of photosensitive sub-pixel values corresponding to the plurality of photosensitive elements, wherein each of the photosensitive sub-pixel values corresponds to a first photosensitive area;

a plurality of reference elements, outputting a plurality of reference sub-pixel values corresponding to the plurality of reference elements, wherein each of the reference sub-pixel values corresponds to a second photosensitive area, and the second photosensitive area is smaller than the first photosensitive area ;as well as

An integrating unit, coupled to the plurality of photosensitive elements and the plurality of reference elements, for outputting corresponding to the sensing pixel unit according to the plurality of photosensitive sub-pixel values and the plurality of reference sub-pixel values The pixel value.
The sensing pixel unit of claim 1 wherein one of the plurality of reference elements comprises:

a photodiode having a photosensitive area;

a light blocking layer disposed over the photosensitive region of the photodiode in the reference component.
The sensing pixel unit of claim 2 wherein said light blocking layer completely covers said photosensitive area and said second photosensitive area is zero.
The sensing pixel unit of claim 2 wherein said light blocking layer partially covers said photosensitive region.
The sensing pixel unit of claim 2 wherein said light blocking layer is a metal layer in an integrated circuit layout.
The sensing pixel unit of claim 1 wherein said integrating unit comprises:

a reference statistic unit, configured to calculate a reference statistic of the plurality of reference sub-pixel values;

Referring to the averaging unit, receiving a reference threshold, and calculating a reference average corresponding to the plurality of reference sub-pixel values according to the reference threshold and the reference statistic;

a sensation statistical unit, configured to calculate a sensation statistic of the plurality of photoreceptor pixel values;

a look-up unit for outputting a sense of presence limit according to the sensation statistic;

a photosensitive averaging unit configured to calculate a sensitized average value corresponding to the plurality of photoreceptor pixel values according to the sensation threshold value and the sensation statistic amount;

And a subtraction unit coupled to the reference averaging unit and the sensitization averaging unit for outputting the pixel value as a subtraction result of the photographic average value and the reference average value.
The sensing pixel unit of claim 6 wherein said reference averaging unit is operative to perform the step of calculating said reference average based on said reference threshold and said reference statistic:

Determining, according to the reference statistic and the reference threshold, a plurality of normal reference sub-pixel values of the plurality of reference sub-pixel values, wherein a difference between each normal reference sub-pixel value and the reference statistic is less than or Equal to the reference threshold; and

The reference average is calculated as an average of the plurality of normal reference sub-pixel values.
The sensing pixel unit of claim 6 wherein said reference statistic is one of a minimum, a median or an average of said plurality of reference sub-pixel values.
The sensing pixel unit of claim 6, wherein the photosensitive averaging unit is configured to perform the step of calculating the sensitized average value according to the sensation threshold and the sensation statistic:

Determining, according to the sensation statistic and the sensation limit value, a plurality of normal photo sub-pixel values of the plurality of photo sub-pixel values, wherein a difference between each normal photo sub-pixel value and the sensation statistic is less than or Equal to the sense of presence limit; and

The average of the photosensitivity is calculated as an average of the plurality of normal photoreceptor sub-pixel values.
The sensing pixel unit of claim 6 wherein said sensitivity statistic is one of a minimum, a median or an average of said plurality of photoreceptive pixel values.
The sensing pixel unit of claim 1 further comprising:

An analog to digital converter coupled between the plurality of photosensitive elements and the plurality of reference elements and the integrated unit.
An optical fingerprint sensor, comprising:

a plurality of sensing pixel units for outputting a plurality of pixel values corresponding to the plurality of sensing pixel units, wherein each sensing pixel unit is the sensing pixel unit according to any one of claims 1-11, A plurality of pixel photosensitive cells of the plurality of sensing pixel units are arranged in an array.
The optical fingerprint sensor of claim 12 wherein said optical fingerprint sensor is disposed below a display of the electronic device.
The optical fingerprint sensor according to claim 12, wherein the optical fingerprint sensor is coupled to a fingerprint recognition unit, and the fingerprint recognition unit is configured to be configured according to the plurality of sensing pixel units The pixel value determines the fingerprint of the user.