CN105512714B - A kind of fingerprint Identification sensor and its induction region - Google Patents
A kind of fingerprint Identification sensor and its induction region Download PDFInfo
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- CN105512714B CN105512714B CN201410505507.2A CN201410505507A CN105512714B CN 105512714 B CN105512714 B CN 105512714B CN 201410505507 A CN201410505507 A CN 201410505507A CN 105512714 B CN105512714 B CN 105512714B
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Abstract
The present invention relates to fingerprint identification technology field, a kind of fingerprint Identification sensor and its induction region are disclosed.In the present invention, the induction region of fingerprint Identification sensor includes several sensing units, and each sensing unit top layer includes at least the first pole plate and the second pole plate, and the area of the top layer pattern of the first pole plate is greater than the area of the top layer pattern of the second pole plate；When touching, finger and the first pole plate form the first hand capacity C1, form the second hand capacity C2 with the second pole plate, form feedback capacity Cf between the first pole plate and the second pole plate.The size of capacitance C1, C2 and Cf relevant to each pole plate is adjusted by the pattern of each pole plate in optimization induction region in each sensing unit in embodiments of the present invention, so that these parameters be made to be more conducive to the raising of system sensitivity.
Description
Technical field
The present invention relates to fingerprint identification technology field, in particular to a kind of fingerprint Identification sensor and its induction region.
Background technique
Fingerprint identification technology is a kind of new and high technology having recently been developed.Fingerprint recognition be using human body uniqueness with
Constant the features of sex physiology, using fingerprint as one kind " identity card living " of human body or a portable special seal come into
A kind of technology of row identification.
Existing fingerprint recognition is usually realized by fingerprint Identification sensor.Fingerprint Identification sensor is built-in with fingerprint biography
Sensor array, for acquiring finger print information.When carrying out fingerprint detection, user's finger is covered on fingerprint sensor array, with shape
At a pole of capacitor (or resistance), and due to the pole plate of fingerprint median ridge and paddy and each sensing unit of fingerprint sensor array it
Between laminating degree it is different so that capacitor (or resistance) numerical value formed at each sensing unit is different, fingerprint Identification sensor
Processor collected different numerical value are summarized, just complete the acquisition of fingerprint.
The penetration depth of capacitance type fingerprint identification sensor and some parasitic capacitances of sensing unit top layer and induction region
The electrology characteristic of the protective layer of upper covering is related.Before the electrology characteristic of these parasitic capacitance values and protective layer directly determines system
The size of the actual induction signal of grade, to determine the sensitivity of whole system.To reach higher sensitivity, condenser type is passed
Sensor is solved two problems firstly the need of from source: first is that how to optimize parameters, to cover induction region top layer thicker
Protective layer, second is which type of protective layer induction region top layer covers.
Summary of the invention
The purpose of the present invention is to provide a kind of fingerprint Identification sensor and its induction regions, so that fingerprint Identification sensor
Sensitivity be improved.
In order to solve the above technical problems, embodiments of the present invention provide a kind of induction zone of fingerprint Identification sensor
Domain, the induction region include several sensing units, and each sensing unit top layer includes at least the first pole plate and the second pole plate, and
And first pole plate top layer pattern area be greater than the second pole plate top layer pattern area；
When touching, finger and the first pole plate form the first hand capacity C1, form the second hand capacity with the second pole plate
C2 forms feedback capacity Cf between the first pole plate and the second pole plate.
Embodiments of the present invention additionally provide a kind of fingerprint Identification sensor, the sense comprising above-mentioned fingerprint Identification sensor
Answer region.
In terms of existing technologies, the induction region of the fingerprint Identification sensor of embodiment of the present invention includes several
Sensing unit, each sensing unit top layer include at least the first pole plate and the second pole plate, and the top layer pattern of the first pole plate
Area is greater than the area of the top layer pattern of the second pole plate；When touching, finger and the first pole plate form the first hand capacity C1, with
Second pole plate forms the second hand capacity C2, and feedback capacity Cf is formed between the first pole plate and the second pole plate.Implementation of the invention
Capacitance relevant to each pole plate is adjusted by the pattern of each pole plate in each sensing unit in optimization induction region in mode
The size of C1, C2 and Cf, so that these parameters be made to be more conducive to the raising of system sensitivity.
In addition, the area of the top layer pattern of the first pole plate be greater than sensing unit area half, the area of C1 it is more big more
Good, the area of C2 is the smaller the better.By increasing the area of the top layer pattern of the first pole plate, detection accuracy can be improved；Subtract simultaneously
The area of the top layer pattern of small second pole plate can be accelerated to detect speed.
In addition, the top layer pattern of first pole plate and second pole plate is respectively rectangle, and adjacent edge is aligned, and can be use up
The value of Cf may be increased.
In addition, the top layer pattern of second pole plate is rectangle, the top layer pattern of first pole plate is straight-flanked ring, described
Second pole plate is located within first pole plate；Alternatively, the top layer pattern of second pole plate is circle, first pole plate
Top layer pattern is annulus, and second pole plate is located within first pole plate.By the way that the second pole plate is placed in the first pole plate,
The length of adjacent edge between two pole plates can be further increased, to increase the value of Cf.
In addition, being equipped with free electrode between first pole plate and second pole plate, the free electrode is in hanging
State.The free electrode is matched with the spacing between the first pole plate and the second pole plate, can increase Cf, so that Cf variation is more equal
It is even, to improve detection accuracy.
In addition, the fingerprint Identification sensor includes: metal edge frame and external emission source；
The metal edge frame surround and is set to around the induction region；
The external emission source emits the first input signal Vin1 to the metal edge frame；
Each sensing unit separately includes an internal emission source and charging capacitor Cin；The internal emission source is to right
The Cin answered emits the second input signal Vin2, charges to the Cin；
Wherein, the Vin2 is the square wave with the Vin1 opposite in phase, for offsetting the direct current carried in the Vin1
Big signal.
In addition to emitting the second input signal (Vin2) using charging capacitor (Cin) of the internal emission source into sensing unit,
It charges to it, it is also defeated to emitting first around the metal edge frame being set to around sensing unit array using external emission source
Enter signal (Vin1), charge to it, since Vin1 is square wave with Vin2 opposite in phase, can offset and be carried in Vin1
To the useless big signal of direct current is detected, specific gravity of the useful signal in resultant signal is increased, the front end of fingerprint Identification sensor is made
Have high-gain ability, improve signal-to-noise ratio, the sensitivity of fingerprint Identification sensor detection is finally improved, so that fingerprint be made to know
Individual sensor surface can cover thicker protective layer.
In addition, each sensing unit also includes amplifier and reset switch；The input node of the amplifier is distinguished
It is connected with the first port of first pole plate, the reset switch, the output node of the amplifier is respectively with described second
Pole plate, the second port of the reset switch are connected；The third port of the reset switch is for inputting reset signal.In addition,
Each sensing unit also includes a phase inverter；The phase inverter is connected with the third port of the reset switch.In this way,
Phase inverter can increase the ability of output driving.
In addition, the amplifier includes: the first P-channel metal-oxide semiconductor fieldeffect transistor PMOS, second
PMOS, the first N-channel metal-oxide semiconductor fieldeffect transistor NMOS and the 2nd NMOS；
The grid of first PMOS is used for input service voltage VDD, leakage for inputting the first bias voltage Vbp1, source electrode
Pole is connected with the source electrode of the 2nd PMOS；
The grid of 2nd PMOS is for inputting the second bias voltage Vbp2, the drain electrode phase to drain with the first NMOS
Connect, and the output node as the amplifier；
The grid of first NMOS is for inputting third bias voltage Vbn1, the drain electrode phase of source electrode and the 2nd NMOS
Even；
The grid of 2nd NMOS is the input node of the amplifier, source electrode ground connection.
The amplifier is inverter structure amplifier, and structure is simple, and occupied area is small, can be placed in fingerprint Identification sensor
In in a limited areal extent of sensing unit, ensure that the feasibility of embodiment of the present invention.
In addition, the induction region surface covers matcoveredn, the protective layer is jewel cover board or ceramic cover plate, can be with
It realizes the functions such as antistatic, wear-resisting, and can guarantee sensitivity.
In addition, jewel cover board or ceramic cover plate are round or rectangle cover board.In addition, the fingerprint Identification sensor is located at electricity
The front or the back side of sub- product.These flexible settings provide multiple choices for electronics manufacturer, are conducive to fingerprint recognition
The popularization and application of sensor.
Detailed description of the invention
Fig. 1 is the top layer pattern signal of the induction region of the fingerprint Identification sensor of first embodiment according to the present invention
Figure；
Fig. 2 is the sensing unit and finger of the induction region of the fingerprint Identification sensor of first embodiment according to the present invention
Contact forms capacitor schematic diagram；
Fig. 3 is the top layer pattern signal of the induction region of the fingerprint Identification sensor of second embodiment according to the present invention
Figure；
Fig. 4, which is that the top layer pattern of the induction region of the fingerprint Identification sensor of second embodiment according to the present invention is another, to be shown
It is intended to；
Fig. 5 is the top layer pattern signal of the induction region of the fingerprint Identification sensor of third embodiment according to the present invention
Figure；
Fig. 6 is the induction region schematic diagram of the fingerprint Identification sensor of the 4th embodiment according to the present invention；
Fig. 7 is the sensing unit operation principle schematic diagram of the fingerprint Identification sensor of the 4th embodiment according to the present invention；
Fig. 8 is the schematic diagram that passivation protective layer is applied on existing induction region；
Fig. 9 is the signal of the induction region protective mulch of the fingerprint Identification sensor of the 5th embodiment according to the present invention
Figure；
Figure 10 is that the fingerprint Identification sensor of the 5th embodiment according to the present invention is located at the positive schematic diagram of electronic product；
Figure 11 is that the fingerprint Identification sensor of the 5th embodiment according to the present invention is located at the schematic diagram at the electronic product back side.
Specific embodiment
To make the object, technical solutions and advantages of the present invention clearer, below in conjunction with attached drawing to each reality of the invention
The mode of applying is explained in detail.However, it will be understood by those skilled in the art that in each embodiment of the present invention,
In order to make the reader understand this application better, many technical details are proposed.But even if without these technical details and base
In the various changes and modifications of following embodiment, each claim of the application technical side claimed also may be implemented
Case.
The first embodiment of the present invention is related to a kind of induction regions of fingerprint Identification sensor, if the induction region includes
Dry sensing unit, each sensing unit top layer include at least the first pole plate and the second pole plate, and the top level diagram of the first pole plate
The area of case is greater than the area of the top layer pattern of the second pole plate, as shown in Figure 1.When touching, finger and the first pole plate formation the
One hand capacity C1 forms the second hand capacity C2 with the second pole plate, forms feedback capacity between the first pole plate and the second pole plate
Cf, as shown in Figure 2.When finger different zones and sensing unit contact, it is different to be formed by capacitance, for example, paddy and
It is different from the capacitance that the pole plate in sensing unit is formed when ridge part and sensing unit contact, by detecting these capacitances
Difference, valley and a ridge can be distinguished, it is final to realize identification fingerprint.
When finger contacts some sensing unit, the relevant capacitor of the unit is caused to change: C1 increases, and C2 reduces,
Cf reduces.On the one hand, after a charge and discharge, the output variable quantity of fingerprint Identification sensor increases with the increase of C1, with Cf's
Reduce and increases；On the other hand, the minimum value of C1 and Cf will limit the detection accuracy of fingerprint Identification sensor, can be according to reality
Situation selects.And C2 will affect the stabilization time of amplifier in each sensing unit, pass to will limit entire fingerprint recognition
The working frequency of sensor.C2 is smaller, and the stabilization time of amplifier is shorter, and therefore, the value of C1, C2 and Cf can be single by design induction
The top layer pattern of electrode in member is adjusted.
In the prior art, the basic phase of area of the top layer pattern of the first pole plate in a sensing unit and the second pole plate
Deng respectively accounting for the half or so of entire sensing unit area.Since the value of C1 and C2 depends primarily on the area of top layer pattern, and Cf
Value depend primarily on the area of spacing between the first pole plate and the second pole plate, the length of adjacent edge and each pole plate, therefore,
In general, the area of C1 is the bigger the better, and the area of C2 is the smaller the better；But, it is contemplated that the value of Cf, C2 can not be without limitations
Ground reduces.In the present embodiment, the area of the top layer pattern of the first pole plate is mainly increased, the face of sensing unit is larger than
Long-pending half, can be improved detection accuracy；The area for reducing the top layer pattern of the second pole plate simultaneously can be accelerated to detect speed.
In addition, the top layer pattern of the explanation of value, the first pole plate and the second pole plate is respectively rectangle, and adjacent edge pair
Together.Since the value of Cf increases as the dielectric constant between the length of adjacent edge, two-plate increases, between two-plate
Distance reduces and increases, and the adjacent edge alignment of the top layer pattern of the first pole plate and the second pole plate can increase the value of Cf as far as possible.
Second embodiment of the present invention is related to a kind of induction region of fingerprint Identification sensor.Second embodiment and the
One embodiment is roughly the same, is in place of the main distinction: in the first embodiment, the top layer pattern of two-plate is rectangle,
First pole plate and the second pole plate are set side by side and adjacent edge is aligned.And in second embodiment of the invention, the first pole plate is ring
Shape, the second pole plate are located in the first pole plate, the length of adjacent edge between two pole plates can be further increased, to increase Cf's
Value.
Specifically, the top layer pattern of the second pole plate can be rectangle, the top layer pattern of the first pole plate can be straight-flanked ring, second
Pole plate is located within the first pole plate, as shown in Figure 3.Alternatively, the top layer pattern of the second pole plate is circle, the top level diagram of the first pole plate
Case is annulus, and the second pole plate is located within the first pole plate, as shown in Figure 4.
Third embodiment of the present invention is related to a kind of induction region of fingerprint Identification sensor.Third embodiment is
One or second embodiment on the basis of be further improved, mainly the improvement is that: increasing between the first pole plate and the second pole plate
Add free electrode, so that capacitor Cf changes more evenly, to improve detection accuracy between two electrodes.
Specifically, the top layer pattern of the first pole plate is rectangle as shown in figure 5, the top layer pattern of the second pole plate is rectangle
Ring is equipped with free electrode between two electrodes, which is in vacant state.The free electrode and the first pole plate and the second pole
Spacing between plate matches, and can increase Cf, to improve detection accuracy.
It is worth noting that only giving a kind of common example in Fig. 5, the equal of other situations can be between two pieces of pole plates
Increase free electrode, also, the number of the free electrode between two pieces of pole plates is also not necessarily limited to one, can be multiple, as long as with the
Spacing between one pole plate and the second pole plate matches, numerous to list herein.
Four embodiment of the invention is related to a kind of fingerprint Identification sensor, which includes: above-mentioned
One into third embodiment any one fingerprint Identification sensor induction region.By the top layer pattern for increasing the first pole plate
Area, reduce the second pole plate top layer pattern area, be adjusted capacitance C1, C2 and Cf relevant to each pole plate it is big
It is small, so that these parameters be made to be more conducive to the raising of system sensitivity.
In the present embodiment, fingerprint Identification sensor can also eliminate the big letter of useless direct current of input by double emission sources
Number, increase specific gravity of the useful signal in resultant signal, the front end of fingerprint Identification sensor is made to have high-gain ability, improves noise
Than the final sensitivity for improving fingerprint Identification sensor detection, so that it is thicker to cover fingerprint Identification sensor surface
Protective layer.
In order to realize that double emission sources eliminate the big signal of useless direct current of input, metal edges can be set around induction region 1
Frame 2, as shown in Figure 6.Third capacitor C3 is formed between finger and metal edge frame, and when finger contacts metal edge frame, C3 is silent
Think short circuit.External emission source can emit the first input signal (Vin1) by the metal edge frame, and each sensing unit point
Not Bao Han internal emission source and charging capacitor (Cin), which emits the second input signal to corresponding (Cin)
(Vin2), it charges to Cin, as shown in Figure 7.Also, Vin2 is the square wave with Vin1 opposite in phase, for offsetting in Vin1
The big signal of the direct current of carrying.
In addition, the explanation of value, induction region may include the sensing unit 11 of M row, N column, i.e. N*M sensing unit
11, wherein N, M are positive integer.Each 11 top layer of sensing unit may include two pieces of pole plates or muti-piece pole plate.When finger difference
When region and sensing unit 11 contact, it is formed by that capacitance is different, for example, the valley and a ridge part of fingerprint and sensing unit
It is different from the capacitance that the pole plate in sensing unit 11 is formed when 11 contact, by detecting the difference of these capacitances, to distinguish
Valley and a ridge, it is final to realize identification fingerprint.
As shown in Fig. 1,3,4,5, each 11 top layer of sensing unit includes at least two pieces of pole plates, and surround and be set to first
Ground wire (VSS) around pole plate and the second pole plate.When finger touches, finger and the first pole plate form the first hand capacity
(C1), the second hand capacity (C2) is formed with the second pole plate, forms feedback capacity (Cf) between the first pole plate and the second pole plate.?
When finger touches, the voltage signal in feedback capacity changes, and the variable quantity of the voltage signal carries finger print information.
In the present embodiment, each sensing unit 11 also separately includes amplifier, phase inverter and reset switch.Amplification
The input node of device is connected with the first port of the first pole plate, reset switch respectively, and the output node of amplifier is respectively with second
Pole plate, the second port of reset switch are connected；The third port of reset switch is connected with phase inverter.Wherein, phase inverter can increase
The ability of strong output driving.
Amplifier exports after amplifying the voltage signal on feedback capacity Cf.Specifically, amplifier includes: first
PMOS (M1), the 2nd PMOS (M2), the first NMOS (M3) and the 2nd NMOS (M4).Wherein, the grid of M1 is for inputting first partially
Voltage Vbp1 is set, drain electrode of the source electrode for input service voltage VDD, M1 is connected with the source electrode of M2；The grid of M2 is for inputting the
The drain electrode of two bias voltage Vbp2, M2 is connected with the drain electrode of M3, and the output node as amplifier；The grid of M3 is for inputting
The source electrode of third bias voltage Vbn1, M3 are connected with the drain electrode of M4；The grid of M4 is the input node of amplifier, and the source electrode of M4 connects
Ground.The amplifier is inverter structure amplifier, and structure is simple, and occupied area is small, can be placed in one in fingerprint Identification sensor
In a limited areal extent of sensing unit, the feasibility of embodiment of the present invention ensure that.
Moreover, in the present embodiment, a line sense of work can be selected from sensing unit array by controlling Vbp1
Unit is answered, selects a column sensing unit of work from sensing unit array by controlling Vbp2；Wherein, appoint in Vbp1 and Vbp2
When anticipating one more than or equal to operating voltage VDD, amplifier is closed.Row selection function is realized by control Vbp1, is led to
It crosses control Vbp2 and realizes column selection function.In this way, only selecting a line sensing unit and one to arrange induction by control Vbp1 and Vbp2
When cell operation, then only the row and the column intersect sensing unit work, i.e. entire sensing unit array scanning when it is each
Only open a sensing unit.By controlling Vbp1 or Vbp2, the reasonable selection to the sensing unit of work may be implemented, after being
Continuous processing of circuit is laid a good foundation.
Reset switch resets feedback capacity for inputting reset signal.In reset state, reset switch
First port (input node) is connected with second port (output node), establishes an operating point for amplifier.Specifically, multiple
Bit switch can be third NMOS；The drain electrode of 3rd NMOS is the first port of reset switch, and source electrode is second port, and grid is
Third port.
The fingerprint Identification sensor of present embodiment uses charge transfer mode, its working principles are as follows:
It is primary to charging capacitor Cin charging, then the charge being charged into is moved on Cf.After a charge and discharge,
The output of the output node of amplifier reaches an a reference value VoBenchmark, for making reference value.Wherein,
The a reference value is in reasonable operating point, which may insure that system works in maximum dynamic range.
When finger is close, C1 and C2 will increase, while reducing Cf.When finger contacts some sensing unit and metal simultaneously
When frame, capacitor relevant to the unit is caused to change, i.e. the variable quantity that C1 increases is △ C1, and the variable quantity that C2 increases is
△ C2, the variable quantity that Cf reduces are △ Cf, wherein C3 is defaulted as short circuit.Therefore, the output of the output node of amplifier is caused to change
Become Vo, wherein
Output Vo is relative to a reference value VoBenchmarkVariable quantity △ Vo be
It when the thickness of the protective layer on sensing unit surface is very thick, for example is 100-500 μm, the value very little of △ Cf, relatively
Can be ignored for other variable quantities, then above formula can simplify for
It only include useful signal in above formula, the direct current big signal unrelated with detection has been cancelled.
In addition, it is necessary to explanation, in practical application, metal edge frame can also be circle, sensing unit can be circle
Shape, or rectangle；The present invention is not limited thereto, can select different shapes according to actual needs.
Fifth embodiment of the invention is related to a kind of fingerprint Identification sensor.5th embodiment is in the 4th embodiment base
Be further improved on plinth, mainly the improvement is that: in the 5th embodiment, induction region surface is covered with protection
Layer, and protective layer is jewel cover board or ceramic cover plate, the functions such as antistatic, wear-resisting may be implemented, and can guarantee sensitivity, moreover it is possible to
Play beauty function.
Fingerprint Identification sensor may be touched often in use, therefore need to be had antistatic, wear-resisting, corresponding
The basic functions such as electrology characteristic.Major part fingerprint recognition chip is by applying passivation protective layer on induction region come real at present
These existing functions, as shown in Figure 8.When the application of fingerprint recognition chip accumulates unconfined field over there, induction region area ratio
It is larger, it can detecte more characteristic points in induction region, when algorithm process is less high to noise, sensitivity requirement, therefore
It is required to reach antistatic, wear-resisting etc., protective layer thickness can be increased, this is realized using sacrificing sensitivity as cost certainly
's.When fingerprint recognition chip is applied in portable electronic products such as mobile phone, tablet computers, area cannot be too big, chip induction
Region area accordingly also can be smaller, and the characteristic point in induction region is fewer, therefore algorithm compares noise, sensitivity requirement
It is high.If still applying very thick protective layer on induction region surface at this time, it will sensitivity is reduced, and limited characteristic point is in low spirit
It cannot achieve fingerprint identification function in the case of sensitivity.
Present embodiment is above-mentioned to make using the other materials for having the features such as electrostatic, wear-resisting, corresponding electrology characteristic
Protective layer, be not only able to achieve the basic functions such as antistatic, wear-resisting, but also can guarantee sensitivity, moreover it is possible to play beauty function.This implementation
Mode will be provided with ceramic and various jewels of individual features etc. and apply in fingerprint identification device as cover board, be covered on induction zone
Field surface, as shown in Figure 9.Wherein, jewel include jasper, sapphire, green agate, emerald, carnelian, ruby, Huang Bixi,
The diamond materials such as sight of beryl, red wall imperial or royal seal, emerald, lavender agate, amethyst.These jewels and ceramics can be natural, be also possible to
It is made.
Since in the present invention, the area of the top layer pattern by increasing the first pole plate reduces the top layer pattern of the second pole plate
Area, be adjusted capacitance C1, C2 and Cf relevant to each pole plate size, so that it is sensitive so that these parameters is more conducive to system
The raising of degree；The big signal of useless direct current that input can be eliminated by double emission sources again, increases useful signal in resultant signal
Specific gravity makes the front end of fingerprint Identification sensor have high-gain ability, improves signal-to-noise ratio, final to improve fingerprint Identification sensor inspection
The sensitivity of survey；Therefore, can be made using jewel cover board or ceramic cover plate coated than originally passivation protective layer come it is thick, again
It can guarantee the sensitivity of fingerprint Identification sensor detection.
In addition, it is worth noting that, jewel cover board or ceramic cover plate are round or rectangle cover board, can be placed on home key
(Home key is Microsoft's Windows operating system, apple iOS operating system, has the function of in Google's Android operation system to return
Key), it can also be placed at other keys.Also, fingerprint Identification sensor can be located at the front or the back side of electronic product, such as Figure 10 and
Shown in 11, wherein face is front where the display area of electronic product, and another side is the back side.These settings are selected as electronic product
Manufacturer provides multiple choices, is conducive to the popularization and application of fingerprint Identification sensor.
It will be understood by those skilled in the art that the respective embodiments described above are to realize specific embodiments of the present invention,
And in practical applications, can to it, various changes can be made in the form and details, without departing from the spirit and scope of the present invention.
Claims (12)
1. a kind of fingerprint Identification sensor, which is characterized in that the induction region comprising fingerprint Identification sensor, the induction region
Comprising several sensing units, each sensing unit top layer includes at least the first pole plate and the second pole plate, and the first pole plate
The area of top layer pattern is greater than the area of the top layer pattern of the second pole plate；When touching, finger forms first with the first pole plate and connects
C1 is held in electric shock, forms the second hand capacity C2 with the second pole plate, forms feedback capacity Cf between the first pole plate and the second pole plate；
Metal edge frame and external emission source；
The metal edge frame surround and is set to around the induction region；
The external emission source emits the first input signal Vin1 to the metal edge frame；
Each sensing unit separately includes an internal emission source and charging capacitor Cin；The internal emission source is to corresponding
Cin emits the second input signal Vin2, charges to the Cin；
Wherein, the Vin2 is the square wave with the Vin1 opposite in phase, for offsetting the big letter of direct current carried in the Vin1
Number；
Each sensing unit also includes amplifier and reset switch；
The input node of the amplifier is connected with the first port of first pole plate, the reset switch respectively, described to put
The output node of big device is connected with the second port of second pole plate, the reset switch respectively；
The third port of the reset switch is for inputting reset signal；
The amplifier includes: the first P-channel metal-oxide semiconductor fieldeffect transistor PMOS, the 2nd PMOS, the first N
Channel metal-oxide-semiconductor field effect transistor NMOS and the 2nd NMOS；
The grid of first PMOS for input the first bias voltage Vbp1, source electrode be used for input service voltage VDD, drain electrode with
The source electrode of 2nd PMOS is connected；
The grid of 2nd PMOS is connected for inputting the second bias voltage Vbp2, drain electrode with the drain electrode of the first NMOS,
And the output node as the amplifier；
For inputting third bias voltage Vbn1, source electrode is connected the grid of first NMOS with the drain electrode of the 2nd NMOS；
The grid of 2nd NMOS is the input node of the amplifier, source electrode ground connection.
2. fingerprint Identification sensor according to claim 1, which is characterized in that the face of the top layer pattern of first pole plate
Product is greater than the half of the area of sensing unit.
3. fingerprint Identification sensor according to claim 1, it is characterised in that first pole plate and second pole plate
Top layer pattern be respectively rectangle, the first pole plate and the second pole plate are set side by side and adjacent edge is aligned.
4. fingerprint Identification sensor according to claim 1, it is characterised in that the top layer pattern of second pole plate is square
The top layer pattern of shape, first pole plate is straight-flanked ring, and second pole plate is located within first pole plate.
5. fingerprint Identification sensor according to claim 1, which is characterized in that the top layer pattern of second pole plate is circle
The top layer pattern of shape, first pole plate is annulus, and second pole plate is located within first pole plate.
6. fingerprint Identification sensor according to claim 1, which is characterized in that first pole plate and second pole plate
Between be equipped with free electrode, the free electrode is in vacant state.
7. fingerprint Identification sensor according to claim 1, which is characterized in that the reset switch is the 3rd NMOS；
The drain electrode of 3rd NMOS is the first port of the reset switch, and source electrode is the second port of the reset switch,
Grid is the third port of the reset switch.
8. fingerprint Identification sensor according to claim 1, which is characterized in that each sensing unit also includes one
Phase inverter；
The phase inverter is connected with the third port of the reset switch.
9. fingerprint Identification sensor according to claim 1, which is characterized in that the metal edge frame is rectangle, the sense
Answering region is rectangle or border circular areas；Or
The metal edge frame is circle, and the induction region is round or rectangular area.
10. fingerprint Identification sensor according to claim 1, which is characterized in that the induction region surface is covered with guarantor
Sheath, the protective layer are jewel cover board or ceramic cover plate.
11. fingerprint Identification sensor according to claim 10, which is characterized in that jewel cover board or ceramic cover plate are circle
Or rectangle cover board.
12. fingerprint Identification sensor according to claim 1, which is characterized in that the fingerprint Identification sensor is located at electricity
The front or the back side of sub- product.
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