CN107368773A - A kind of fingerprint sensor and apply its smart machine - Google Patents
A kind of fingerprint sensor and apply its smart machine Download PDFInfo
- Publication number
- CN107368773A CN107368773A CN201610321626.1A CN201610321626A CN107368773A CN 107368773 A CN107368773 A CN 107368773A CN 201610321626 A CN201610321626 A CN 201610321626A CN 107368773 A CN107368773 A CN 107368773A
- Authority
- CN
- China
- Prior art keywords
- feedback
- sensing
- circuit
- signal
- output
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000002463 transducing effect Effects 0.000 claims abstract description 126
- 230000006698 induction Effects 0.000 claims abstract description 123
- 238000005259 measurement Methods 0.000 claims description 54
- 239000003990 capacitor Substances 0.000 claims description 31
- 230000005611 electricity Effects 0.000 claims description 31
- 238000006243 chemical reaction Methods 0.000 claims description 27
- 238000012545 processing Methods 0.000 claims description 6
- 206010016256 fatigue Diseases 0.000 claims description 2
- 230000035945 sensitivity Effects 0.000 abstract description 5
- 230000008859 change Effects 0.000 description 11
- 230000003321 amplification Effects 0.000 description 9
- 238000003199 nucleic acid amplification method Methods 0.000 description 9
- 230000001186 cumulative effect Effects 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 7
- 238000000034 method Methods 0.000 description 6
- 102220062248 rs568171603 Human genes 0.000 description 6
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000003989 dielectric material Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000004422 calculation algorithm Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000009514 concussion Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000007850 degeneration Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 235000013399 edible fruits Nutrition 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000009916 joint effect Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000013215 result calculation Methods 0.000 description 1
- 230000000392 somatic effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/13—Sensors therefor
- G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F21/00—Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
- G06F21/30—Authentication, i.e. establishing the identity or authorisation of security principals
- G06F21/31—User authentication
- G06F21/32—User authentication using biometric data, e.g. fingerprints, iris scans or voiceprints
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/1347—Preprocessing; Feature extraction
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
- G06F2218/02—Preprocessing
- G06F2218/04—Denoising
Landscapes
- Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- Computer Security & Cryptography (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Software Systems (AREA)
- General Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Human Computer Interaction (AREA)
- Multimedia (AREA)
- Computer Vision & Pattern Recognition (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
- Image Input (AREA)
Abstract
The present invention provides a kind of fingerprint sensor, including：Multiple induction electrodes, circuit occurs for sensing and transducing circuit and feedback, the multiple induction electrode is connected with the input of the sensing and transducing circuit, the input that with the feedback circuit occurs for the output end of the sensing and transducing circuit is connected, and the output end that circuit occurs for the feedback is connected with the input of the sensing and transducing circuit.Wherein, the multiple induction electrode is used to obtain multiple inductance capacitances；The sensing and transducing circuit is used to the multiple inductance capacitance and feedback signal being converted to multiple output signals and finally obtains multiple fingerprint peak valley difference in height signals, and the feedback occurs circuit and obtains feedback signal according to the multiple output signal and feed back.The present invention improves the sensitivity of fingerprint sensor, reduces noise, fingerprint sensor is obtained clearly fingerprint image, or under identical dielectric thickness through thicker dielectric, using the teaching of the invention it is possible to provide higher, the apparent fingerprint image of signal to noise ratio.
Description
Technical field
The present invention relates to sensor technical field, more particularly to a kind of capacitive fingerprint sensing device and application should
The smart machine of sensor.
Background technology
Somatic fingerprint identification has been the technology of comparative maturity, and fingerprint recognition is mainly made up of two technologies：
The collection of fingerprint image and the recognizer of fingerprint.The technology that the collection of wherein fingerprint image is conventional has：Light
Learn fingerprint sensor and (refer to conventional art, commercial application has been for many years；Shortcoming：Volume can not be small-sized
Change, it is impossible to be used in mobile phone)；Ultrasonic fingerprint sensor (has just been developed, it is necessary to MEMS technology system
Sensor is made, manufacturing process is special, and threshold is high, it is also necessary to carry out 3-dimensional Digital Image Processing, it is necessary to floating
Points digital signal processing chip, chip power-consumption is high, and signal processing chip design complexities are also high, therefore
Cost is also high)；Pressure sensitive fingerprint sensor (does not have industrialization)；Thermoinduction fingerprint sensor is (integrated
On chip, once industrialization, but superseded at present)；Capacitive sensing fingerprint sensor.
In recent years with the popularization and application of smart mobile phone, due to the small volume of capacitive sensing fingerprint sensor,
Cost is low, small power consumption, reliability are also preferable, is widely applied on smart mobile phone.But at present
The sensitivity of widely used capacitive sensing fingerprint sensor and signal to noise ratio are limited on smart mobile phone, finger
Distance between induction electrode can not be too big, the electrode for the capacitive sensing fingerprint sensor that volume production uses
Dielectric thickness between finger can accomplish 200um, it is said that it can accomplish dielectric thickness
400um technology, but currently without volume production.And high sensitivity, the product of heavy insulation medium need to rise
Volt circuit, cost and power consumption all increased.In the case of below dielectric thickness 400um, it is impossible to
Directly capacitive sensing fingerprint sensor is arranged under mobile phone screen protective glass, it is necessary to be protected in mobile phone screen
Perforate installation capacitive sensing fingerprint sensor, complex process on glass are protected, also influences the freedom of appearance design
Degree.The typical thickness of mobile phone screen protective glass is 0.7mm, current capacitive sensing fingerprint sensor without
Dielectric collection fingerprint image of the method through 0.7mm.
The operation principle of capacitive sensing fingerprint sensor is as follows：The finger lines of people has depth difference, convex
Place is referred to as " peak (ridge) ", and recessed place is referred to as " paddy (valley) ".On fingerprint " peak " and
" paddy " is different from the distance of induction electrode, and corresponding inductance capacitance is of different sizes；It is connected with induction electrode
Inductance capacitance on " peak " and " paddy " counter electrode is converted into corresponding voltage by capacitance measurement circuit to be believed
Number output, so as to obtain the image of fingerprint " peak " and " paddy ".Typical capacitive sensing fingerprint sensor
It is made up of multiple capacitive sensing electrodes and corresponding capacitance measurement circuit, each capacitive sensing electrode pair answers one
One pixel of individual fingerprint image.Capacitance measurement circuit is by measuring between capacitive sensing electrode and finger
Capacitance obtains the information at corresponding " peak " and " paddy ".The sense of typical capacitive sensing fingerprint sensor
It is equidistant ranks array arrangement to answer electrode, and line space is equal with column pitch, the size shape of electrode
Identical, the area of each electrode is also identical, it can be considered that the electrical characteristic parameter of each electrode is identical
's.According to capacity plate antenna principle, if finger does not have " peak " and " paddy ", finger is very smooth, hand
Refer to identical with the distance of each electrode, then the electric capacity of each electrode also can be identical.It is but actual
Finger have the presence of " peak " and " paddy ", " peak " and " paddy " is different from the distance of each electrode,
Thus the electric capacity of " peak " and " paddy " between the induction electrode of correspondence position will be different, if measurement
The difference change of electric capacity between induction electrode and finger, the finger at " peak " and " paddy " with regard to finger can be obtained
Line frame.Therefore the induced electricity tolerance between different induction electrodes, it is only final useful fingerprint letter
Breath, and identification of the average capacitance of induction electrode to fingerprint is useless.When induction electrode and finger away from
When close, when minimum distance is much smaller than the difference in height at " peak " and " paddy ", " peak " and " paddy " is right
Answer the difference of inductance capacitance relative to the percentage of maximum capacitor with regard to larger, and when induction electrode and finger
Apart from it is far when, when minimum distance is far longer than the difference in height at " peak " and " paddy ", " peak " and " paddy "
The difference of corresponding inductance capacitance is relative to the percentage of maximum capacitor with regard to very little.Such as when minimum distance connects
When nearly 0, the difference of " peak " and " paddy " corresponding electric capacity approaches relative to the change percentage of maximum capacitor
100%.And when distance is more than 400um, the difference of " peak " and " paddy " corresponding electric capacity is relative to maximum electricity
The percentage of appearance only has a few percent, even less than 1 percent.Capacitance measurement circuit holds inductance capacitance
Value is converted to corresponding voltage and amplifies suitable multiple, the output voltage after amplification, it is desirable to it is the bigger the better,
But can not saturation distortion.Capacitance measurement circuit is converted to induced electricity capacity in voltage and amplification process,
The percentage of the capacitance difference relative maximum capacitance at " peak " and " paddy " is constant, therefore works as finger and sense
When answering interelectrode dielectric thicker, output voltage difference corresponding to " peak " and " paddy " only accounts for maximum
Seldom part of output voltage.And the maximum of output voltage is limited to the working power voltage of measuring circuit,
Therefore it is limited.Typical capacitance measurement circuit supply voltage is 3V, the electricity of capacitance measurement circuit output
Pressure also needs to be converted to data signal by analog-digital converter, gives algorithm for recognizing fingerprint module and carries out numeral
Change is handled.And analog-to-digital conversion is that have certain resolution ratio digit, when analog-to-digital conversion digitizes, if
The difference portion percentage of useful signal is too small, and the difference portion digital amplitude after analog-to-digital conversion will
Too small, the signal quality of fingerprint signal live part will be very poor.Although point of analog-to-digital conversion can be improved
Resolution digit, but due to various noises be present, when resolution ratio is less than noise, then improve resolution ratio
With regard to useless, too high analog-to-digital conversion definition digit, it can also increase the cost and power consumption of circuit.
In order to improve ratio of the difference portion of finger peak valley in output voltage signal, in the prior art,
The method for subtracting reference capacitance is taken, subtracts a part for average capacitance, or subtracts output average voltage
A part, output signal are just not easy saturation distortion, so as to which the multiplication factor of signal is improved, most
Ratio of the useful signal in output voltage signal is improved eventually.Chinese invention patent, the patent No.
" 201410105847.6 ", the patent document of entitled " capacitive fingerprint sensor circuit and inductor ",
A kind of capacitive fingerprint sensor circuit and inductor are disclosed, sensor circuit includes cancellation module and feedback amplifier,
The first input end of cancellation module is connected with the first external driving source, and the second input of cancellation module passes through
The finger for being pressed against the input is connected with the second external driving source, and output end and the feedback of cancellation module are put
The signal of the input connection of big device, the first external driving source and the second external driving source output is anti-phase each other,
First external driving source is linked into the signal of cancellation module and the second external driving source is coupled to cancellation module
Signal produces counteracting, obtains the fingerprint induced signal related to fingerprint depth, so as to realize the useful letter of increase
Number ratio, and then the multiplication factor of useful signal can be improved.But this scheme has two shortcomings：The
First, a part of average capacitance can only be offset, it is impossible to the noise signal sensed on finger is offset, it is flat when offsetting
After equal electric capacity, multiplication factor can be improved, still, when improving multiplication factor, the noise that senses on finger
Signal is also exaggerated, and when particularly multiplication factor is larger, the noise signal sensed on finger cannot neglect
Slightly, therefore during useful " peak " and " paddy " difference electric capacity accounting very little, the noise letter sensed on finger
Number have a strong impact on the quality of fingerprint image.Secondth, the size offset must be pre-set, and circuit can not
Autobalance offsets condenser paper average, so, due to temperature, power supply, dielectric thickness change, mill
When damage etc. a variety of causes causes average value drift, otherwise need to reset cancellation after remeasuring,
Sufficiently large tolerance can only be left, it is allowed to a range of change, can not perfectly offset in a word flat
Average, additionally, due to finger human body (finger and human body are same conductors, can regard same object as)
Electric capacity between the ground of sensor circuit is a uncertain capacitance, with different applicable cases,
It may change a lot, and the capacitance size between finger human body and circuit ground, it can also influence most
Whole average eguivalent capacitance.So the scheme in the patent does not accomplish automatic maximization useful signal
Accounting, so as to which best fingerprint image can not be collected.
The content of the invention
For above-mentioned the deficiencies in the prior art, it is a primary object of the present invention to provide one kind to lift electricity
Hold the sensitivity of sensing fingerprint sensor while noise can be reduced, so that capacitive sensing refers to
Line sensor obtains clearly fingerprint image, or in identical dielectric thickness through thicker dielectric
Under, using the teaching of the invention it is possible to provide signal to noise ratio is higher, the electric capacity sense of the automatic elimination average capacitance of apparent fingerprint image
Answer fingerprint sensor.
To achieve these goals, the present invention uses following technical scheme：
A kind of fingerprint sensor, including：Circuit occurs for multiple induction electrodes, sensing and transducing circuit and feedback,
The multiple induction electrode is connected with the input of the sensing and transducing circuit, the sensing and transducing circuit
The input that with the feedback circuit occurs for output end is connected, and output end and the institute of circuit occur for the feedback
The input connection of sensing and transducing circuit is stated, wherein, the multiple induction electrode, for gathering Fingers
Multiple inductance capacitances of line generation；The sensing and transducing circuit is more for multiple induction electrodes to be generated
Individual inductance capacitance and feedback signal, which are converted to multiple output signals and exported to the feedback, occurs circuit；
Circuit occurs for the feedback, for multiple output signals of the sensing and transducing circuit output to be added up
Enhanced processing obtains feedback signal, and the input by the feedback signal back to the sensing and transducing circuit
End；The sensing and transducing circuit, it is additionally operable to be obtained according to the multiple inductance capacitance and the feedback signal
Multiple fingerprint peak valley difference in height signals.
Preferably, the sensing and transducing circuit, specifically for generating the output signal by below equation
V8, and the output signal V8 is exported by output end：
V8=Kc6_v8*C6+Kv10_v8*V10+Kv12_v8*V12*C6.
Wherein, C6 is the inductance capacitance being connected with sensing and transducing circuit input end, and V12 is that finger sensing is made an uproar
Sound, V10 are feedback signal；Kc6_v8 is converted to the conversion coefficient of output signal, Kv10_v8 for inductance capacitance
The conversion coefficient of output signal is converted to for feedback signal, Kv12_v8 is that finger induced noise is converted to output
The conversion coefficient of signal.
Preferably, when finger induced noise V12 is 0, the sensing and transducing circuit, specifically for logical
Cross below equation and generate the fingerprint peak valley difference in height signal, and the fingerprint peak valley is exported by output end
Height difference signal V8 [i]：V8 [i]=Kc6_v8*C6i/ (1-K)+Kc6_v8*Cdet [i].
Wherein, C6i is average inductance capacitance, and Cdet [i] is the inductance capacitance of each measurement induction electrode with putting down
The difference of equal inductance capacitance, Kc6_v8 are the conversion coefficient that inductance capacitance is converted to output signal, and K is to open
Ring multiplication factor.
Preferably, feedback element, it is connected to the feedback and the output end of circuit and the sensing and transducing occurs
Between the input of circuit, the feedback signal for the feedback into circuit output to occur is sent to the biography
Feel change-over circuit.
Preferably, it is provided with and the one-to-one feedback canceller electrode of the induction electrode, the feedback member
Part is arranged to the feedback coupled capacitor by being formed between feedback canceller electrode and corresponding induction electrode.
Preferably, the feedback element includes resistance or electric capacity or the wire of FBN feedback network or short circuit.
Preferably, circuit, which occurs, for the feedback includes accumulator U5 and feedback amplifier U6, the accumulator
U5 is provided with multiple inputs, each input of the accumulator U5 respectively with a sensing and transducing
The output end of circuit is corresponding to be connected, and the output end of the accumulator U5 is defeated with the feedback amplifier U6's
Enter end to be connected, the output end of the feedback amplifier U6 is connected with the input of sensing and transducing circuit..
Preferably, the sensing and transducing circuit includes the first sensing and transducing unit 22 and signal source V1, described
First sensing and transducing unit 22 includes the first operational amplifier U1, the second operational amplifier U2, phase inverter
U4, the first electric capacity C1, first resistor R1, second resistance R2 and 3rd resistor R3；First computing
Amplifier U1 inverting input is connected with one end of the induction electrode, feedback element, first fortune
Calculate amplifier U1 homophase input termination signal source V1, the first operational amplifier U1 output termination
First electric capacity C1 one end, first resistor R1 one end；Another termination first of the first electric capacity C1
Operational amplifier U1 inverting input；The input termination signal source V1 of the phase inverter U4 is described anti-
Phase device U4 output termination second resistance R2 one end；The other end of the first resistor R1, described
The two resistance R2 other end connects the inverting input of the second operational amplifier U2；Second fortune
Calculate amplifier U2 in-phase input ends ground connection, the output termination 3rd resistor of the second operational amplifier U2
R3 one end, the second operational amplifier of another termination U2 of 3rd resistor R3 inverting input,
The output end of the second operational amplifier U2 connects the input of feedback amplifier, first electricity simultaneously
It is equal with second resistance R2 to hinder R1.
Preferably, the sensing and transducing circuit includes the second sensing and transducing unit 23 and signal source V2；It is described
Second sensing and transducing unit 23 includes the 3rd operational amplifier U3 and the second electric capacity C2, the 3rd computing
Amplifier U3 inverting input is connected with one end of induction electrode, feedback element, while the signal source
V2 is connected by inductance capacitance with the 3rd operational amplifier U3 inverting input；3rd operation amplifier
Device U3 in-phase input end ground connection, output end and second electric capacity of the 3rd operational amplifier U3
C2 one end is connected, the other end of the second electric capacity C2 and the 3rd operational amplifier U3 anti-phase input
End is connected, and the output end of the 3rd operational amplifier U3 connects the input of feedback amplifier simultaneously.
A kind of smart machine, including above-described fingerprint sensor.
Compared to prior art, by being provided with feedback circuit, feedback occur for fingerprint sensor of the invention
Occur circuit by the output signal of sensing and transducing circuit it is accumulated, amplification after feed back to sensing and transducing circuit
Input, the signal after signal after making feedback signal converted is converted with inductance capacitance are added, and are eliminated
After average signal after inductance capacitance is converted, the peak valley height difference signal of multiple finger prints is finally obtained,
So that accounting ratio of the capacitance useful signal of finger print peak valley difference in height relative to peak-peak signal
Maximize.Finger induced noise can be also produced while finger produces inductance capacitance with induction electrode simultaneously,
Feedback signal can be added the average value signal for eliminating finger induced noise with finger induced noise signal simultaneously,
The sensitivity of fingerprint sensor of the present invention is improved, reduces noise, makes fingerprint sensor of the present invention can be with
Clearly fingerprint image, or under identical dielectric thickness is obtained through thicker dielectric, can
There is provided signal to noise ratio higher, apparent fingerprint image, improve the accuracy of fingerprint recognition comparison, reduce
The accuracy of system identification that fingerprint recognition compares.
Brief description of the drawings
Fig. 1 is inventive sensor circuit block diagram；
Fig. 2 is inventive sensor circuit theory diagrams；
Fig. 3 is the sensor circuit schematic diagram of the embodiment of the present invention 1；
Fig. 4 is the sensing and transducing circuit theory diagrams of the embodiment of the present invention 1；
Fig. 5 is the induction electrode of the embodiment of the present invention 1 and the structural representation of feedback canceller electrode；
Fig. 6 is the induction electrode of another embodiment of the present invention and the structural representation of feedback canceller electrode；
Fig. 7 is the induction electrode of the embodiment of the present invention 1 and the planar structure schematic diagram of feedback canceller electrode；
Fig. 8 shows for the plane of the induction electrode of the embodiment of the present invention 2, feedback canceller electrode and emission electrode
It is intended to；
Fig. 9 is the sensor circuit schematic diagram of the embodiment of the present invention 2；
Figure 10 is the sensing and transducing circuit theory diagrams of the embodiment of the present invention 2；
In figure, 1, induction electrode；2nd, circuit occurs for sensing and transducing circuit, 3, feedback；4th, feed back
Element；41st, feedback canceller electrode；22nd, the first sensing and transducing unit；23rd, the second sensing and transducing unit.
Embodiment
In order to make the purpose , technical scheme and advantage of the present invention be clearer, below in conjunction with accompanying drawing and
Embodiment, the present invention will be described in further detail.It should be appreciated that specific implementation described herein
Example is not intended to limit the present invention only to explain the present invention.
Embodiment 1
Capacitive sensing fingerprint sensor includes multiple capacitive sensing electrodes, and induction electrode is distributed in same
In plane, there is one layer of dielectric between sensed finger, dielectric thickness is uniform.Measurement sensing refers to
During line, the peak of fingerprint lines contacts dielectric, contacts the peak and induced electricity of the fingerprint lines of dielectric
The distance of pole is defined in a constant distance value by dielectric in uniform thickness, and induction electrode is used to feel
Should with the distance of finger print peaks or valleys, so as to obtain fingerprint image.Induction electrode and finger lines distance
Difference, the inductance capacitance that induction electrode senses is just different, and the inductance capacitance that induction electrode is sensed turns
Sensor output voltage signal is changed to, sensor output voltage signal can be obtained by by follow-up processing
The fingerprint image signal related to fingerprint lines peak valley.
As shown in figure 1, the capacitive sensing fingerprint sensor of the present invention includes induction electrode 1, sensing and transducing electricity
Circuit 3 and feedback element 4 occur for road 2, feedback.The input of sensing and transducing circuit 2 and induction electrode 1
Connection, the input that circuit 3 occurs for feedback are connected with the output end of sensing and transducing circuit 2, and feedback occurs
The output end of circuit 3 is connected by feedback element 4 with the input of sensing and transducing circuit 2；Induction electrode 1
It is used for for acquisition and inductance capacitance, sensing and transducing circuit 2 caused by finger print sensing by inductance capacitance
And feedback signal is converted to multiple output signals, circuit occurs for feedback by the multiple defeated of sensing and transducing circuit 2
Go out that signal is accumulated, obtains feedback signal and by the feedback signal through feedback element 4 after the suitable multiple of amplification
Send to the input of sensing and transducing circuit 2, the signal after making feedback signal converted passes through with inductance capacitance
Average signal after conversion offsets, and makes there was only fingerprint peakses in the signal of the final output of sensing and transducing circuit 2
There was only the signal of fingerprint peak valley difference in height in the signal of paddy difference in height, i.e. sensor output signal so that refer to
The useful signal of line peak valley difference value relative to peak-peak signal accounting highest percentage.Feedback letter simultaneously
The finger sensing average noise signal received on induction electrode number can also be offset, it is therefore, of the invention
Sensor also has stronger anti-noise ability.
Connect as shown in Fig. 2 being provided with multiple induction electrodes 1 and being corresponded respectively with each induction electrode 1
The sensing and transducing circuit 2 connect, the view data of the induced electricity capacitance of all induction electrodes corresponding to fingerprint peak valley
Obtained by one-shot measurement；The induction electrode for participating in measurement finger print data is referred to as measuring induction electrode.Each
The input that circuit 3 occurs with feedback respectively for the output end of sensing and transducing circuit 2 is connected, feedback hair
The output end of raw circuit 3 passes through the feedback element 4 of connection corresponding with the input of each sensing and transducing circuit 2
The input with each sensing and transducing circuit 2 is connected respectively.Sense between finger and measurement induction electrode 1
Answer electric capacity to be set to C6, be not directly connected between finger and circuit ground, but arrived in the presence of an about 1pF
Between 100pF or bigger inductance capacitance C11；Inductance capacitance C11 between finger and circuit ground is long-range
Inductance capacitance C6 between finger and measurement induction electrode 1, according to Circuit theory, can derive sensing
Equivalent capacity between electrode 1 and circuit ground is approximately equal to inductance capacitance C6, therefore can in simple equivalent circuit
To think that electric capacity C11 is short circuit between finger and circuit ground.Sensing and transducing circuit 2 turns inductance capacitance C6
It is changed to a part of component of the output voltage signal of its output end；Meanwhile sensing and transducing circuit 2 also will be from
The output electricity that the feedback signal that circuit 3 is fed back is converted to the output end of sensing and transducing circuit 2 occurs for feedback
Press another part component of signal；If there is finger induced noise signal, sensing and transducing circuit 2 will also
Finger induced noise signal is converted to a part of component of the output end output voltage signal of sensing and transducing circuit 2；
The voltage signal that then sensing and transducing circuit 2 exports is at least inductance capacitance C6, feedback occurs circuit 3 and produced
Feedback signal, finger induced noise signal these three signals export after the conversion of sensing and transducing circuit 2
The linear superposition of voltage electric signal joint effect.It is assumed that the voltage of the output end of sensing and transducing circuit 2 output
Signal is V8, and finger induced noise signal is V12, feedback signal V10, is expressed then using mathematical formulae
For：
V8=Kc6_v8*C6+Kv10_v8*V10+Kv12_v8*V12*C6 (formula 1)
Wherein, Kc6_v8 is inductance capacitance C6 to the output end output voltage signal V8 of sensing and transducing circuit 2
Influence coefficient；Kv10_v8 is that feedback signal V10 brings out end output voltage signal to sensing and transducing circuit 2
V8 influence coefficient；Kv12_v8 finger induced noise V12 bring out output electricity to sensing and transducing circuit 2
Signal V8 influence coefficient is pressed, because finger induced noise V12 is to sensing output voltage signal V8 shadow
Sound is also directly proportional to inductance capacitance C6, so Kv12_v8*V12*C6 is only V12 pairs of finger induced noise
The output voltage signal V8 of sensing and transducing circuit 2 influence component.
In another embodiment, a sensing and transducing circuit can be connected with multiple induction electrodes simultaneously,
Only an induction electrode participates in surveying every time in the multiple induction electrodes being connected with same sensing and transducing circuit
Amount, every time in measurement, the induction electrode for participating in measurement finger print data is referred to as measuring induction electrode, fingerprint peakses
The view data of the induced electricity capacitance of all induction electrodes corresponding to paddy obtains through repeatedly measurement.
Circuit 3, which occurs, for feedback includes accumulator U5 and feedback amplifier U6, and accumulator U5 is provided with multiple
Input, each of which input are connected with an output end of sensing and transducing circuit 2 respectively, accumulator U5
Output end be connected with feedback amplifier U6 input, feedback amplifier U6 output end pass through with it is each
The feedback element 4 of the corresponding connection of the input of sensing and transducing circuit 2 respectively with each sensing and transducing circuit 2
Input be connected.Obtained after voltage signal that accumulator U5 exports sensing and transducing circuit 2 is accumulated
Cumulative signal sends feedback amplifier U6 to, and cumulative signal is amplified suitable multiple by feedback amplifier U6
Output feedback signal and the input of sensing and transducing circuit 2 is fed back to by feedback element 4 afterwards.Make feedback
The average-voltage signal that voltage signal of the signal after the conversion of sensing and transducing circuit 2 comes with inductance capacitance conversion
And the finger sensing average noise signal received on induction electrode offsets.
The suitable multiplication factor requirement of feedback amplifier is that multiplication factor is as big as possible, but to ensure closed loop
Circuit after feedback will not control oneself concussion, there is enough closed-loop stability.Multiplication factor it is positive and negative
Polarity is correct, and to make feedback signal is negative-feedback signal, it is impossible to and it is positive feedback signal, positive feedback signal
Circuit can be shaken.The multiplication factor of open loop is bigger, and the average inductance capacitance balanced out is more, but closed loop
After work, circuit is more unstable.The determination of specific feedback amplifier multiplication factor and setting for stabilizing circuit
Meter, can be realized as using existing amplifier and feedback loop design technology, is described again here.
And the relation of average induced electricity capacitance of the feedback amplifier multiplication factor with that can offset then is pushed away by following
Leading to draw, it is assumed that during open loop, the feedback signal that is applied to feedback element 4 is V10, feedback signal
V10 is coupled to the input of sensing and transducing circuit 2 by feedback element 4, is changed through sensing and transducing circuit 2
The voltage signal exported afterwards is V8_1, and the conversion coefficient that signal is converted to V8_1 from V10 is assumed to
Kv10_v8, then there is V8_1=Kv10_v8*V10.It is assumed that shared N=999 induction electrode participates in fingerprint
Measurement, the signal of accumulator U5 outputs is V9, then the signal of accumulator U5 outputs then has：
V9=V8_1*N=Kv10_v8*V10*N；(formula 2)
It is assumed that feedback amplifier U6 multiplication factor is AMP, the open loop exported after feedback amplifier amplifies
Voltage signal is V10_1, then has：
V10_1=V9*AMP=Kv10_v8*V10*N*AMP (formula 3)
That is the open loop of input signal V10 to feedback amplifier U6 output ends puts multiple and is：
K=V10_1/V10=Kv10_v8*N*AMP (formula 4)
It is assumed that finger induced noise V12 is 0V, then after closed loop, had by formula 1：
V8=Kc6_v8*C6+Kv10_v8*V10+Kv12_v8*V12*C6
=Kc6_v8*C6+Kv10_v8*V10 (formula 5)
And V10=V10_1=AMP*N*V8, V8 replace with Kc6_v8*C6+Kv10_v8*V10, then：
V10=AMP*N* (Kc6_v8*C6+Kv10_v8*V10) (formula 6)
Then have：
V10=AMP*N*Kc6_v8*C6/ (1-AMP*N*Kv10_v8)
=AMP*N*Kc6_v8*C6/ (1-K) (formula 7)
By V10=AMP*N*V8, V8=V10/ (AMP*N) is obtained, formula 7 is substituted into, then：
V8=Kc6_v8*C6/ (1-K) (formula 8)
It can be seen from amplifier circuit knowwhy, after closed loop feedback, stable negative-feedback circuit is formed,
Kv10_v8*N*AMP is necessary for negative.Therefore have in AMP and Kv10_v8 and only one is negative.
It is assumed that Kv10_v8 is -1, AMP=1, then Open loop gain cofficient K=-999；It is assumed that during open loop, hand
Refer to inductance capacitance average value, the voltage signal V8_1 exported after the conversion of sensing and transducing several piece 2 is equal to 1V
(Kc6_v8*C6=1V), analysis can show that after closed loop feedback, sensing and transducing circuit 2 is defeated more than
Component caused by inductance capacitance go out, average is about 1V/ (1-K)=1mV, i.e. closed-loop averagely senses
Electric capacity output is reduced to original (1-K) divides one.
It can be seen that K absolute value is bigger, the average inductance capacitance of the output end output of sensing and transducing circuit 2 draws
The nubbin voltage risen is smaller.Under closed-loop case, the output of the output end of sensing and transducing circuit 2,
The output component of inductance capacitance average value can reduce (1-K) times, but related to each measurement induction electrode
Fingerprint peak valley caused by output voltage part will not be influenceed by closed loop feedback.It is because each
The output signal of individual sensing and transducing circuit is Kc6_v8*C6+Kv10_v8*V10, it is seen that single sensing and transducing electricity
The output on road part and feedback signal V10 as caused by the inductance capacitance C6 of this measurement induction electrode draw
Part this two parts composition risen.And the feedback signal V10's and all C6 of the stabilization ultimately produced is cumulative
And correlation.The average inductance capacitance C6i of all measurement induction electrodes variable quantity, the influence to V10 are
N times of the C6 of single measurement induction electrode variable quantity influence.N is the number of induction electrode.It is because single
Influences of the inductance capacitance C6 of individual induction electrode to the summation of all inductance capacitances is a influence, and
Influence of the average inductance capacitance to the summation of final all inductance capacitances is N times.
Analytical conclusions above are, it is assumed that the inductance capacitance of all measurement induction electrodes is all equal and is equal to
During C6,1/ (1-K) that is exported when the output of each sensing and transducing circuit is no feedback control loop during closed loop.
If the inductance capacitance C6 of certain two measurement induction electrodes is relative to average inductance capacitance C6i, an increasing
Add Cdet [i], one reduces Cdet [i], then, the inductance capacitance C6 of all measurement induction electrodes it
With it is constant, so V10 now is identical with original V10, so, the two measurement induced electricities
The output of the sensing and transducing circuit of other induction electrodes outside pole is still constant, is still what open loop exported
1/(1-K).Kc6_v8*Cdet [i] occurs for the output signal of the only two measurement induction electrodes changed
Variable quantity.It can be seen that the output signal of the sensing and transducing circuit of the two measurement induction electrodes is eventually equal to
Kc6_v8*Cdet [i]+(Kc6_v8*C6i/ (1-K)) and-Kc6_v8*Cdet [i]+(Kc6_v8*
C6i/(1-K))。
Make further popularization, the inductance capacitance C6 of all measurement induction electrodes is not equal to average measurement sense
When answering electric capacity, the output of its sensing and transducing circuit also complies with above formula, i.e. the output of sensing and transducing circuit is equal to
Kc6_v8*Cdet [i]+(Kc6_v8*C6i/ (1-K)), wherein Cdet [i] are the induced electricities of the induction electrode
Hold the difference with average inductance capacitance.
Can so it consider：1st, feedback signal V10 is decided by the sum of all measurement inductance capacitances.2nd, it is anti-
Due to be present feedback cycle in feedback signal V10, it will offset in the output signal of each sensing and transducing circuit
Part only with all measurement inductance capacitances and relevant, although the inductance capacitance of single measurement sensing can shadow
Ring the sum of all measurement inductance capacitances, but the final sum for being also embodied in inductance capacitance.3rd, it is so-called average
Electric capacity is N/mono- of inductance capacitance sum.So the effect of the sum of average capacitance and inductance capacitance is
Equivalent.4th, what is V10 influenceed is inductance capacitance and (i.e. average capacitance), due to the final work of feedback
With so that (1-K) that average capacitance becomes when not feeding back in the output of sensing and transducing circuit divides it
One.But the difference portion of the inductance capacitance and average capacitance for single measurement induction electrode, it is for passing
Feeling the contribution part of the output voltage signal of change-over circuit will not be removed by (1-K).
It is also possible that considering, feedback causes in the output component of each sensing and transducing circuit, is supported by feedback
Influence part disappeared, inductance capacitance sum, if the change of average capacitance turns to Cdet [i], due to every
Individual inductance capacitance has all changed Cdet [i], and its influence to final inductance capacitance summation is N*Cdet [i],
And the change Cdet [i] of single inductance capacitance, only influence the Cdet [i] of final inductance capacitance summation, it is seen that
The capacitance variations of single induction electrode, output, the feedback canceller of sensing and transducing circuit are not interfered with substantially
Partial output.The capacitance variations of i.e. single induction electrode are still existed with Kc6_v8*Cdet [i] variable quantity
Reflected in the output of this sensing and transducing circuit.
Although the capacitance variations Cdet [i] of single induction electrode has an impact to inductance capacitance summation, it influences
Part, Cdet [i]/N of average capacitance influence of the variable quantity to inductance capacitance summation is equivalent to, and
This influence of the capacitance variations of single induction electrode, has actually been presented as average capacitance, so
Have been contemplated that into average capacitance.
Same conclusion is also applied for finger induced noise.In case of a closed loop, sensing and transducing circuit 2
Output end output, finger sensing caused by average noise voltage, (1-K) only under open loop case
/ mono-, i.e. average noise reduces (1-K) times, only the one of residual (1-K) point.
First analyze all inductance capacitances it is identical when, output when stable, then to analyze inductance capacitance not
Situation when identical.When it is assumed that inductance capacitance is identical, i.e. when C6 is equal to average value, all sensings turn
The output voltage for changing circuit is identical, it is assumed that is V8, then, feedback signal V10=V8*N*AMP.Such as
Fruit stabilizes, and necessarily has V8=Kc6_v8*C6+Kv10_v8*V10, then：V8=Kc6_v8*C6/ (1-K),
Wherein K=Kv10_v8*N*AMP.If the electric capacity of each electrode is C6i+Cdet [i], C6i is flat
Equal electric capacity, Cdet [i] they are part of the inductance capacitance of each measurement induction electrode more than average capacitance, and respectively
The Cdet [i] of individual induction electrode and when differing, the output electricity of the sensing and transducing circuit of this measurement induction electrode
Pressure is equal to when stable：
V8 [i]=Kc6_v8*C6i/ (1-K)+Kc6_v8*Cdet [i].
Average inductance capacitance C6i can be extrapolated so, it is assumed that M induction electrode be shared, by k times
Measurement, the inductance capacitance of jth time measurement N [j] individual induction electrode, wherein j=1,2,3....k, induction electrode is total
NumberWhen the inductance capacitance of the individual measurement induction electrodes of jth time measurement N [j], this N [j] individual sense
Electric capacity is answered to be referred to as measuring inductance capacitance.When in jth time measuring section, to sharing the individual measurement induced electricities of N [j]
When the inductance capacitance of pole measures, the inductance capacitance of each of which measurement induction electrode is respectively
C6 [h], wherein h=1,2,3 ... N [j].The average value for further assuming that N [j] individual inductance capacitance is C6i, then
If the finger induced noise V12 of human body sensing on finger be present, finger induced noise V12 passes through
Inductance capacitance C6 inputs to sensing and transducing circuit 2, is embodied in sensor output voltage signal, but
It is due to the presence of close loop negative feedback loop, it will the average back of this noise is balanced out, fed back
The multiplication factor of amplifier is bigger, it will the noise average balanced out is more, if peak valley induction electrode
Induced electricity tolerance it is smaller, the noise balanced out is more, it is impossible to the noise section and induced electricity balanced out
Tolerance is directly proportional.As a result, signal to noise ratio caused by finger induced noise V12 will not diminish because of capacitance difference
And diminish, signal to noise ratio will not be deteriorated, therefore even if through thicker dielectric, remain able to obtain compared with
Clearly fingerprint image.It could be fed back the common mode part (average inductance capacitance) of only noise and inductance capacitance
Signal cancellation is fallen, and the peak valley difference section of inductance capacitance will not be canceled out, and difference portion still can be
Embodied in sensor output voltage signal.
For example first consider the situation of only two measurement induction electrodes, i.e. N=2 situation, more measurements
It is identical with the conclusion of two measurement induction electrodes during induction electrode, it is not repeated.For an induction electrode
When, it is assumed that inductance capacitance C6 is converted to voltage signal V8 by inductance capacitance C6, sensing and transducing circuit 2
The open loop conversion coefficient of output is Kc6_v8, then V8=Kc6_v8*C6；The signal of sensing and transducing circuit 2
Input is assumed to be the inverting input of operational amplifier, is virtual earth end, it is assumed that finger induced voltage noise
For V12, then inductance capacitance C6 noise current Inoise=V12/Xc is flowed through, wherein, Inoise is stream
Inductance capacitance C6 noise current is crossed, Xc is inductance capacitance C6 capacitive reactance Xc=1/2 π fC6, wherein f
It is the frequency of noise signal.It is assumed that the noise voltage that sensing and transducing circuit 2 exports is Voutnoise, sensing
The noise voltage Voutnoise that the input noise electric current Inoise of change-over circuit 2 exports with sensing and transducing circuit 2
Open loop conversion coefficient be Knoise, then Voutnoise=Inoise*Knoise=Knoise*V12/Xc=
Knoise*V12*2πfC6.When measuring induction electrode for only two, it is assumed that two inductance capacitances are averaged
It is worth for C, the difference with average inductance capacitance is cdet, i.e. two inductance capacitances are respectively C+cdet and C-cdet,
So two measurement induction electrodes 1 open loops output useful signal voltage be respectively：Kc6_v8*C+
Kc6_v8*cdet and Kc6_v8*C-Kc6_v8*cdet, the noise of two measurement sense electrode open loop output
Voltage is respectively：Knoise*V12*2 π fC+Knoise*V12*2 π fcdet and Knoise*V12*2 π fC-
Knoise*V12*2πfcdet.After closed loop feedback by the present invention, it is assumed that the multiplication factor of feedback amplifier
It is sufficiently large, the substantially all portion for balancing out, not being canceled out of average value part in output voltage signal
Divide the output component much smaller than induced electricity capacity difference, i.e. the averagely voltage signal portion meeting of inductance capacitance output
Fallen by feedback canceller, average output noise signal section is also substantially fed back caused by finger induced noise
Balance out.So, after closed loop feedback, in the signal that sensing and transducing circuit 2 exports, inductance capacitance C+cdet
Output useful voltage signal be about Kc6_v8*cdet, output noise voltage is about Knoise*
The useful voltage signal of V12*2 π fcdet, inductance capacitance C-cdet outputs is about-Kc6_v8*cdet, is exported
Noise is about-Knoise*V12*2 π fcdet, and their signal to noise ratio is all Kc6_v8/Knoise*V12*2 π f.
It can be seen that signal to noise ratio caused by finger induced noise is unrelated with average induced electricity capacitance, the electric capacity with fingerprint peak valley
Difference is also unrelated.That is signal to noise ratio caused by finger induced noise, with the capacitive differential peace of peak valley
Equal induced electricity capacitance is all unrelated, that is to say, that signal to noise ratio is unrelated with the thickness of dielectric, even if finger with
Measure in larger distance, the difference in height very little of fingerprint peak valley of induction electrode, letter caused by finger induced noise
Make an uproar than will not also become.When the thickness of dielectric is constant, if the difference in height of fingerprint peak valley reduces,
Although output useful signal amplitude can reduce, output noise caused by finger induced noise also can be simultaneously
Reduce.
As shown in Figure 3, Figure 4, in the present embodiment, feedback element 4 is arranged to feed back coupled capacitor, instead
Feedback coupled capacitor is the Space Coupling by being formed between at least one feedback canceller electrode 41 and measurement induction electrode
Electric capacity.Feedback canceller electrode 41 forms a feedback coupled capacitor between each measurement induction electrode 1 respectively
C7, feedback coupled capacitor C7 one end is exactly to measure induction electrode 1, and measurement induction electrode 1 turns with sensing
The input connection of circuit 2 is changed, so feedback coupled capacitor C7 this one end and sensing and transducing circuit 2
Input connects, and the feedback coupled capacitor C7 other end is feedback canceller electrode 41, feedback canceller electrode
41 are connected with feedback amplifier U6 output end, so the feedback coupled capacitor C7 other end is put with feedback
Big device U6 output end is connected.And in another embodiment, feedback element 4 may be arranged as one
Resistance or an electric capacity or a FBN feedback network or other modules.If sensing and transducing circuit 2 has Special reverse
Feedback signal input, feedback element 4 is it can also be provided that the wire of a short circuit, the work(of feedback element 4
It is able to can be realized by the other elements inside sensing and transducing circuit 2.
In the present embodiment, feedback canceller electrode 41 is designed to form coupled capacitor between finger, and feedback is supported
Electric eliminating pole 41 forms feedback coupled capacitor C7 also between induction electrode 1 simultaneously.As shown in figure 5, feedback
Offset electrode 41 and induction electrode 1 arranges in the same plane there is one layer of dielectric between finger.Instead
Feedback signal V10 is coupled to finger by finger coupled capacitor, can offset a part of noise of finger sensing
Signal.The feedback signal V10 being applied on feedback canceller electrode 41 is also by feeding back coupled capacitor C7 couplings
Close on induction electrode 1.
And in another embodiment, feedback canceller electrode 41 is designed to form feedback between induction electrode 1
Coupled capacitor C7.As shown in fig. 6, the side of induction electrode 1 is the insulating dielectric materials with finger insulation,
Feedback canceller electrode 41 is arranged on the opposite side of induction electrode 1, and feedback canceller electricity is shielded by induction electrode 1
Pole 41 couples with the signal between finger.The feedback signal V10 being applied on feedback canceller electrode 41 passes through
Feedback coupled capacitor C7 is coupled on induction electrode 1.
If finger is identical with the distance of induction electrode 1, inductance capacitance C6 is with regard to identical, if feedback coupling
Electric capacity C7 is also identical, and feedback signal V10 can just be offset with finger on identical induction electrode 1
Fall identical average capacitance value, can also balance out identical finger induced noise signal.
In order that the electrical characteristic parameter of each induction electrode is identical consistent, induction electrode is equidistant with ranks
The mode of matrix arrange, the row distance of adjacent induction electrode 1 is identical at once, arranges adjacent induced electricity
The column distance of pole 1 is identical.The shape size of each induction electrode 1 is identical.All induction electrodes 1 arrange
In approximately the same plane.Between induction electrode 1 and finger, the side of induction electrode 1 is equal covered with thickness
Even insulating dielectric materials, keep finger consistent with the distance of induction electrode 1 when being easy to implement finger pressing
Property.As shown in fig. 7, induction electrode 1 and feedback canceller electrode 41 are arranged in approximately the same plane, feedback
Offset electrode 41 and a unitary electrode is connected into by latticed metal, induction electrode 1 is area equation
Square electrode, separated by feedback canceller electrode 41.
, can be with when analyzing sensing and transducing circuit 2 inductance capacitance C6 being converted into voltage signal V8 outputs
By finger induced noise V12 as the voltage source V12 that output voltage is 0.Again due to finger and circuit
Between electric capacity C11 be much larger than inductance capacitance C6, electric capacity C11 is to inductance capacitance C6's between finger and circuit ground
Influence can be ignored, and electric capacity C11 between finger and circuit ground can be regarded as the element of a short circuit, letter
Equivalent circuit after change is as shown in Figure 4.Sensing and transducing circuit 2 includes the first sensing and transducing unit 22 and letter
Number source V1, wherein, the first sensing and transducing unit 22 includes the first operational amplifier U1, the second computing is put
Big device U2, phase inverter U4, the first electric capacity C1, first resistor R1, second resistance R2 and 3rd resistor R3.
First operational amplifier U1 inverting input is connected with induction electrode 1, and Equivalent conjunction is in inductance capacitance C6
One end, the inductance capacitance C6 other end is connected with finger induced noise voltage source V12, and finger sensing is made an uproar
Acoustic-electric potential source V12 other end ground connection；The first operational amplifier U1 inverting input is also attached to simultaneously
Coupled capacitor C7 one end is fed back, the feedback coupled capacitor C7 other end is feedback canceller electrode 41, i.e.,
The feedback coupled capacitor C7 other end is connected with feedback amplifier U6 output end.First operational amplifier
U1 homophase input termination signal source V1 one end, source source V1 other end ground connection；First computing is put
Big device U1 the first electric capacity C1 of output termination one end；The first electric capacity C1 other end is put with the first computing
Big device U1 inverting input is connected；First operational amplifier U1 output end meets first resistor R1 simultaneously
One end；The first resistor R1 other end is connected with the second operational amplifier U2 inverting input；Instead
Phase device U4 input termination signal source V1, phase inverter U4 output termination second resistance R2 one end；The
Two resistance R2 the second operational amplifier of another termination U2 inverting input；Second operational amplifier U2
In-phase input end is grounded, the second operational amplifier U2 output end output transducer output voltage signal；Together
When the second operational amplifier U2 output termination 3rd resistor R3 one end, the 3rd resistor R3 other end
Connect the second operational amplifier U2 inverting input.
In the present embodiment, first resistor R1 is equal with second resistance R2 resistance, according to Circuit theory
Principle, it can release, when being not connected to feedback signal V10, feedback coupled capacitor C7 is equivalent to open circuit,
It is equivalent to open loop.It is assumed that finger induced noise V12 is 0, during open loop, C7 open circuits do not connect, and believe
Number source V1 signal frequency is f, magnitude of voltage V1, now, the first operational amplifier U1 and induced electricity
Hold C6, the first electric capacity of negative-feedback C1, signal source V1 composition in-phase amplifiers, inverting input is to ground resistance
Anti- XC6=-j/2 π fC6, degeneration impedance are XC1=-j/2 π fC1, the output voltage of negative-feedback in-phase amplifier
V3=V1* (1+XC1/XC6)=V1* (1+C6/C1).According to Circuit theory, it is not difficult to derive, the second computing
The sensor output voltage signal of amplifier U2 outputsPass
Feel conversion coefficient of the change-over circuit 2 to inductance capacitance C6Sensing and transducing circuit 2
To finger induced noise V12 conversion coefficientThen V8=V12*Kv12_v8*
C6+C6*Kc6_v8.Second operational amplifier U2 output end and an accumulator U5 input
Connection, accumulator U5 export tired from output end after the input signal V8 inputted from all inputs is added up
Plus signal V9, accumulator U5 output end are connected with feedback amplifier U6 input, feedback amplification
Device U6 is by the output end output feedback signal after the cumulative signal V9 of input amplification from feedback amplifier U6
V10.Feedback amplifier U6 output end is connected with feedback canceller electrode 41, then forms feedback loop
Amplifier, it can be caused so as to form one with the average value of automotive resistance inductance capacitance and finger induced noise
Average noise output valve circuit arrangement.Accumulator U5 and feedback amplifier U6 can be merged into one
Feedback signal generator, feedback signal generator realize cumulative and feedback amplification function simultaneously.More than
Deriving analysis result, drawn after some conditions are simplified, if not simplifying these conditions, its point
It is also identical to analyse conclusion, and simplified complicated analysis process is not described again here.
Embodiment 2
The present embodiment difference from Example 1 is sensing and transducing circuit 2, the sensing and transducing of the present embodiment
Circuit includes signal source V2 and sensing and transducing unit 23.Signal source V2 is produced by emitter stage 5, such as Fig. 8
Shown, feedback canceller electrode 41 and induction electrode 1 are arranged in the same plane, feedback canceller electrode 41,
There is the uniform dielectric of a layer thickness between induction electrode 1 and finger.Emission electrode 5 is ring electrode,
Induction electrode 1, the surrounding of feedback canceller electrode 41 are arranged in, by induction electrode 1 and feedback canceller electrode 41
It is enclosed in the inside of ring.There is no insulating dielectric layer or only very thin insulating barrier between emission electrode 5 and finger
Medium, there is a larger coupled capacitor C15 of a capacitance between finger and emission electrode 5, or finger with
Directly connected between emission electrode 5, be equivalent to the infinitely great electric capacity that electric capacity C15 is short circuit.Feedback canceller
Feedback coupled capacitor C7 is formed between electrode 41 and induction electrode 1.Feedback signal V10 passes through feedback canceller
Finger coupled capacitor between electrode 41 and finger is coupled to finger, and the part that can offset finger sensing is made an uproar
Acoustical signal, but due between finger and circuit ground electric capacity C11 be much larger than finger coupled capacitor, and electric capacity
A part of noise signal that C15 is offset also much larger than finger coupled capacitor, by finger coupled capacitor can be with
Ignore.
Fig. 9 is the overall structure composition figure of the present embodiment, when analysis sensing and transducing circuit 2 is by inductance capacitance
When C6 is converted to the voltage signal V8 of the output end of sensing and transducing circuit 2 output, finger can be sensed and made an uproar
Sound V12 is as the voltage source V12 that output voltage is 0.And because electric capacity C11 is remote between finger and circuit ground
More than measurement inductance capacitance C6, and electric capacity C15 is also much larger than measurement inductance capacitance C6, finger and electricity
Influences of the electric capacity C11 to equivalent inductance capacitance C6 can be neglected between the ground of road, and electric capacity C15 is to equivalent induced electricity
Holding C6 influence can also ignore.According to Circuit theory, can obtain after sensing and transducing circuit 2 simplifies
Equivalent circuit is as shown in Figure 10, equivalent finger induced noise voltage source V12 and equivalent transmitting letter in Figure 10
Number source V2 be it is equivalent after magnitude of voltage, its numerical value and finger induced noise voltage source V12 and hair in Fig. 9
The value for penetrating signal source V2 is differed, and the mutual conversion between them can be determined according to basic Circuit theory
Relation, the derivation of conversion relation and result calculation formula are described again here.
Second sensing and transducing unit 23 includes the 3rd operational amplifier U3 and the second electric capacity C2, the 3rd computing
Amplifier U3 inverting input is connected with induction electrode 1, Equivalent conjunction in inductance capacitance C6 one end,
The inductance capacitance C6 other end concatenates two equivalent voltage source (i.e. equivalent finger induced noise voltage source V12
With equivalent transmiting signal source V2) it is grounded afterwards, while the 3rd operational amplifier U3 inverting input is also connected with
In feedback coupled capacitor C7 one end, the feedback coupled capacitor C7 other end is feedback canceller electrode 41；
Feed back coupled capacitor C7 other end connection feedback amplifier U6 output end；3rd operational amplifier
U3 in-phase input end ground connection, the 3rd operational amplifier U3 output end and the second electric capacity C2 one end phase
Even, the second electric capacity C2 other end is connected with the 3rd operational amplifier U3 inverting input, the 3rd fortune
Calculate amplifier U3 output end output transducer output voltage signal.
It according to existing Circuit theory knowledge, can release, when being not connected to feedback signal V10, feed back coupling
Close electric capacity C7 and be equivalent to open circuit, that is, be equivalent to open loop, at this moment, according to Circuit theory, be not difficult to derive,
The sensor output voltage signal of 3rd operational amplifier U3 outputsPass
Feel conversion coefficient of the change-over circuit 2 to inductance capacitanceSensing and transducing circuit 2 is to equivalent hand
Refer to induced noise V12 conversion coefficientThen V8=V12*Kv12_v8*C6+C6*
Kc6_v8.3rd operational amplifier U3 output end is connected with accumulator U5 one of input, is tired out
Device U5 is added to be exported after the sensing output voltage signal V8 come from all inputs is added up from output end cumulative
Signal V9, accumulator U5 output end are connected with feedback amplifier U6 input, feedback amplifier U6
By the output end output feedback signal V10 after the cumulative signal V9 amplifications of input from feedback amplifier U6.Instead
Feedback amplifier U6 output end is connected with feedback canceller electrode 41, then forms feedback loop amplifier, from
And forming one can be measured caused by average value and the equivalent finger induced noise of inductance capacitance with automotive resistance
The circuit arrangement of average noise output valve.Accumulator U5 and feedback amplifier U6 can be merged into same anti-
Feedback signal generator, feedback signal generator realize cumulative and feedback amplification function simultaneously.The above pushes away
Analysis result is led, is drawn after some conditions are simplified, if not simplifying these conditions, it is analyzed
Conclusion is also identical, and simplified complicated analysis process is not described again here.
The foregoing is only a preferred embodiment of the present invention, but protection scope of the present invention not
Be confined to this, any one skilled in the art the invention discloses technical scope in, can
The change or replacement readily occurred in, it should all be included within the scope of the present invention.Therefore, it is of the invention
Protection domain should be defined by scope of the claims.
Claims (10)
- A kind of 1. fingerprint sensor, it is characterised in that including：Multiple induction electrodes, sensing and transducing circuit and Circuit occurs for feedback, and the multiple induction electrode is connected with the input of the sensing and transducing circuit, the biography The output end for feeling change-over circuit is connected with the input that circuit occurs for the feedback, and circuit occurs for the feedback Output end is connected with the input of the sensing and transducing circuit, wherein,The multiple induction electrode, for gathering multiple inductance capacitances of finger print generation；The sensing and transducing circuit, for the multiple inductance capacitances and feedback letter for generating multiple induction electrodes Number be converted to multiple output signals and export to the feedback and circuit occurs；Circuit occurs for the feedback, for multiple output signals of the sensing and transducing circuit output to be tired out Enhanced processing is added to obtain feedback signal, and the input by the feedback signal back to the sensing and transducing circuit End；The sensing and transducing circuit, it is additionally operable to be obtained according to the multiple inductance capacitance and the feedback signal more Individual fingerprint peak valley difference in height signal.
- 2. fingerprint sensor according to claim 1, it is characterised in that the sensing and transducing circuit, Specifically for generating the output signal V8 by below equation, and the output signal is exported by output end V8：V8=Kc6_v8*C6+Kv10_v8*V10+Kv12_v8*V12*C6；Wherein, C6 is the inductance capacitance being connected with sensing and transducing circuit input end, and V12 is finger induced noise, V10 is feedback signal；Kc6_v8 is the conversion coefficient that inductance capacitance is converted to output signal, and Kv10_v8 is anti- Feedback signal is converted to the conversion coefficient of output signal, and Kv12_v8 is that finger induced noise is converted to output signal Conversion coefficient.
- 3. fingerprint sensor according to claim 2, it is characterised in that as finger induced noise V12 For 0 when, the sensing and transducing circuit, specifically for generating the fingerprint peak valley difference in height by below equation Signal, and the fingerprint peak valley difference in height signal V8 [i] is exported by output end：V8 [i]=Kc6_v8*C6i/ (1-K)+Kc6_v8*Cdet [i]Wherein, C6i is average inductance capacitance, and Cdet [i] is the inductance capacitance of each measurement induction electrode with being averaged The difference of inductance capacitance, Kc6_v8 are the conversion coefficient that inductance capacitance is converted to output signal, and K is put for open loop Big multiple.
- 4. fingerprint sensor according to claim 1, it is characterised in that also include：Feedback element, it is connected to the feedback and the output end of circuit and the input of the sensing and transducing circuit occurs Between end, the feedback signal for the feedback into circuit output to occur is sent to the sensing and transducing circuit.
- 5. fingerprint sensor according to claim 4, it is characterised in that be provided with and the induced electricity Extremely one-to-one feedback canceller electrode, the feedback element are arranged to by feedback canceller electrode and corresponding sensing The feedback coupled capacitor formed between electrode.
- 6. fingerprint sensor according to claim 4, it is characterised in that the feedback element includes electricity Resistance or electric capacity or the wire of FBN feedback network or short circuit.
- 7. fingerprint sensor according to claim 1, it is characterised in that circuit bag occurs for the feedback Include accumulator U5 and feedback amplifier U6, the accumulator U5 are provided with multiple inputs, the accumulator U5 each input is corresponding with the output end of a sensing and transducing circuit respectively to be connected, the accumulator U5 output end is connected with the input of the feedback amplifier U6, the output end of the feedback amplifier U6 It is connected with the input of sensing and transducing circuit.
- 8. fingerprint sensor according to claim 4, it is characterised in that the sensing and transducing circuit bag Include：First sensing and transducing unit 22 and signal source V1, the first sensing and transducing unit 22 include the first fortune Calculate amplifier U1, the second operational amplifier U2, phase inverter U4, the first electric capacity C1, first resistor R1, the Two resistance R2 and 3rd resistor R3；The inverting input of the first operational amplifier U1 and the induced electricity Pole, one end of feedback element are connected, the homophase input termination signal source V1 of the first operational amplifier U1, The first electric capacity C1 of output termination of first operational amplifier U1 one end, first resistor R1 one end； The first operational amplifier of another termination U1 of first electric capacity C1 inverting input；The phase inverter U4 Input termination signal source V1, the phase inverter U4 output termination second resistance R2 one end；Described The one resistance R1 other end, the other end of the second resistance R2 connect the second operational amplifier U2's Inverting input；The second operational amplifier U2 in-phase input ends ground connection, the second operational amplifier U2 Output termination 3rd resistor R3 one end, the operational amplifier of another termination second of the 3rd resistor R3 U2 inverting input, the output end of the second operational amplifier U2 connect the input of feedback amplifier simultaneously End, the first resistor R1 are equal with second resistance R2.
- 9. fingerprint sensor according to claim 4, it is characterised in that the sensing and transducing circuit bag Include the second sensing and transducing unit 23 and signal source V2；The second sensing and transducing unit 23 includes the 3rd computing Amplifier U3 and the second electric capacity C2, the 3rd operational amplifier U3 inverting input and induction electrode, One end of feedback element is connected, while the signal source V2 passes through inductance capacitance and the 3rd operational amplifier U3 Inverting input be connected；The in-phase input end ground connection of the 3rd operational amplifier U3, the 3rd computing Amplifier U3 output end is connected with one end of the second electric capacity C2, the other end of the second electric capacity C2 It is connected with the 3rd operational amplifier U3 inverting input, the output end of the 3rd operational amplifier U3 is same When connect the input of feedback amplifier.
- 10. a kind of smart machine, it is characterised in that including described in any one of the claims 1 to 9 Fingerprint sensor.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610321626.1A CN107368773A (en) | 2016-05-12 | 2016-05-12 | A kind of fingerprint sensor and apply its smart machine |
| PCT/CN2017/079931 WO2017193744A1 (en) | 2016-05-12 | 2017-04-10 | Fingerprint sensor and intelligent device using same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610321626.1A CN107368773A (en) | 2016-05-12 | 2016-05-12 | A kind of fingerprint sensor and apply its smart machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN107368773A true CN107368773A (en) | 2017-11-21 |
Family
ID=60266439
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201610321626.1A Pending CN107368773A (en) | 2016-05-12 | 2016-05-12 | A kind of fingerprint sensor and apply its smart machine |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN107368773A (en) |
| WO (1) | WO2017193744A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111428702A (en) * | 2020-06-12 | 2020-07-17 | 深圳市汇顶科技股份有限公司 | Ultrasonic sensor, fingerprint identification module and electronic equipment |
| WO2021128204A1 (en) * | 2019-12-26 | 2021-07-01 | 深圳市汇顶科技股份有限公司 | Capacitance measurement circuit, touch chip, and electronic device |
Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103607599A (en) * | 2013-11-08 | 2014-02-26 | 四川长虹电器股份有限公司 | Television user registration system and method based on fingerprint identification |
| CN104268530A (en) * | 2014-09-29 | 2015-01-07 | 深圳市汇顶科技股份有限公司 | Fingerprint detection circuit, capacitance type finger sensor comprising same, and mobile terminal |
| US20150030217A1 (en) * | 2010-10-28 | 2015-01-29 | Synaptics Incorporated | Signal strength enhancement in a biometric sensor array |
| CN105046194A (en) * | 2015-06-08 | 2015-11-11 | 苏州迈瑞微电子有限公司 | Capacitance fingerprint sensor comprising integrator |
| CN105095855A (en) * | 2015-06-26 | 2015-11-25 | 京东方科技集团股份有限公司 | Fingerprint identification member, touch control panel, input device and fingerprint identification method |
| CN105138986A (en) * | 2015-08-25 | 2015-12-09 | 敦泰电子有限公司 | Fingerprint detection circuit, fingerprint detection device and touch panel |
| SE1451084A1 (en) * | 2014-09-16 | 2016-03-17 | Fingerprint Cards Ab | Method and fingerprint sensing system for authenticating a candidate fingerprint |
| CN105512714A (en) * | 2014-09-26 | 2016-04-20 | 上海思立微电子科技有限公司 | Fingerprint identification sensor and sensing area thereof |
| CN105574520A (en) * | 2016-02-23 | 2016-05-11 | 北京集创北方科技股份有限公司 | Signal processing circuit and method for fingerprint sensor |
| CN205665714U (en) * | 2016-05-12 | 2016-10-26 | 戴孟军 | Fingerprint sensor and use its smart machine |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8115497B2 (en) * | 2007-11-13 | 2012-02-14 | Authentec, Inc. | Pixel sensing circuit with common mode cancellation |
| CN111382711B (en) * | 2014-03-12 | 2024-01-26 | 艾迪克斯生物识别普通股份公司 | Fingerprint detection device and driving method thereof |
| CN104217193B (en) * | 2014-03-20 | 2017-12-19 | 深圳市汇顶科技股份有限公司 | Capacitive fingerprint sensor circuit and inductor |
| CN105447434B (en) * | 2014-09-26 | 2019-02-15 | 上海思立微电子科技有限公司 | Current-mode fingerprint Identification sensor |
| CN205139939U (en) * | 2015-09-25 | 2016-04-06 | 上海思立微电子科技有限公司 | Fingerprint detection circuit |
-
2016
- 2016-05-12 CN CN201610321626.1A patent/CN107368773A/en active Pending
-
2017
- 2017-04-10 WO PCT/CN2017/079931 patent/WO2017193744A1/en active Application Filing
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20150030217A1 (en) * | 2010-10-28 | 2015-01-29 | Synaptics Incorporated | Signal strength enhancement in a biometric sensor array |
| CN103607599A (en) * | 2013-11-08 | 2014-02-26 | 四川长虹电器股份有限公司 | Television user registration system and method based on fingerprint identification |
| SE1451084A1 (en) * | 2014-09-16 | 2016-03-17 | Fingerprint Cards Ab | Method and fingerprint sensing system for authenticating a candidate fingerprint |
| CN105512714A (en) * | 2014-09-26 | 2016-04-20 | 上海思立微电子科技有限公司 | Fingerprint identification sensor and sensing area thereof |
| CN104268530A (en) * | 2014-09-29 | 2015-01-07 | 深圳市汇顶科技股份有限公司 | Fingerprint detection circuit, capacitance type finger sensor comprising same, and mobile terminal |
| CN105046194A (en) * | 2015-06-08 | 2015-11-11 | 苏州迈瑞微电子有限公司 | Capacitance fingerprint sensor comprising integrator |
| CN105095855A (en) * | 2015-06-26 | 2015-11-25 | 京东方科技集团股份有限公司 | Fingerprint identification member, touch control panel, input device and fingerprint identification method |
| CN105138986A (en) * | 2015-08-25 | 2015-12-09 | 敦泰电子有限公司 | Fingerprint detection circuit, fingerprint detection device and touch panel |
| CN105574520A (en) * | 2016-02-23 | 2016-05-11 | 北京集创北方科技股份有限公司 | Signal processing circuit and method for fingerprint sensor |
| CN205665714U (en) * | 2016-05-12 | 2016-10-26 | 戴孟军 | Fingerprint sensor and use its smart machine |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2021128204A1 (en) * | 2019-12-26 | 2021-07-01 | 深圳市汇顶科技股份有限公司 | Capacitance measurement circuit, touch chip, and electronic device |
| US11275468B2 (en) | 2019-12-26 | 2022-03-15 | Shenzhen GOODIX Technology Co., Ltd. | Capacitance detection circuit, touch control chip and electronic device |
| CN111428702A (en) * | 2020-06-12 | 2020-07-17 | 深圳市汇顶科技股份有限公司 | Ultrasonic sensor, fingerprint identification module and electronic equipment |
| CN111428702B (en) * | 2020-06-12 | 2020-11-13 | 深圳市汇顶科技股份有限公司 | Ultrasonic sensor, fingerprint identification module and electronic equipment |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2017193744A1 (en) | 2017-11-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN205665714U (en) | Fingerprint sensor and use its smart machine | |
| CN104217193A (en) | Capacitance fingerprint sensing circuit and sensor | |
| KR102028243B1 (en) | Fingerprint detection circuit and capacitive fingerprint sensor thereof, and mobile terminal | |
| TWI441087B (en) | Finger sensing device including differential measurement circuitry and related methods | |
| CN105574520B (en) | Signal processing circuit and method for fingerprint sensor | |
| US20130193988A1 (en) | Electronic Imager Using an Impedance Sensor Grid Array and Method of Making | |
| CN103679163A (en) | Novel capacitance type fingerprint image acquisition system | |
| CN202815746U (en) | Touch pen for capacitance screen | |
| CN107368773A (en) | A kind of fingerprint sensor and apply its smart machine | |
| CN105512650A (en) | Capacitive fingerprint detection circuit, sensor and device | |
| WO2012073116A3 (en) | Electric field signature detection using exciter-sensor arrays | |
| CN103824093A (en) | SAR (Synthetic Aperture Radar) image target characteristic extraction and identification method based on KFDA (Kernel Fisher Discriminant Analysis) and SVM (Support Vector Machine) | |
| CN104252621A (en) | Fingerprint identification device and fingerprint identification method | |
| CN202815747U (en) | Touch pen for capacitance screen | |
| KR20170020737A (en) | Processing method and system for fingerprint sensing signal and fingerprint recognition terminal | |
| CN107167673A (en) | A kind of sensor of detectable charge variation feature | |
| CN205507799U (en) | A processing circuit for fingerprint sensor | |
| CN104834423A (en) | Touch panel array | |
| CN1278270C (en) | Semiconductor acquisition element for fingerprint | |
| CN108345870B (en) | High-precision fingerprint sensor capable of preventing influence of parasitic capacitance | |
| TWI730183B (en) | Fingerprint sensing with different capacitive configurations | |
| Serra et al. | Human step detection from a piezoelectric polymer floor sensor using normalization algorithms | |
| CN102521795A (en) | Cross matching fingerprint image scaling method based on global ridge distance | |
| CN105447434B (en) | Current-mode fingerprint Identification sensor | |
| CN109871793A (en) | Fingerprint detection method, fingerprint sensor, finger print detection device and mobile terminal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| AD01 | Patent right deemed abandoned |
Effective date of abandoning: 20240524 |
|
| AD01 | Patent right deemed abandoned |