CN105512650A - Capacitive fingerprint detection circuit, sensor and device - Google Patents
Capacitive fingerprint detection circuit, sensor and device Download PDFInfo
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- CN105512650A CN105512650A CN201610051330.2A CN201610051330A CN105512650A CN 105512650 A CN105512650 A CN 105512650A CN 201610051330 A CN201610051330 A CN 201610051330A CN 105512650 A CN105512650 A CN 105512650A
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- fingerprint
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- testing circuit
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- 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
Abstract
The invention provides a capacitive fingerprint detection circuit, a sensor and a device. The detection circuit comprises a precharge voltage source, a voltage buffer, a detection element, an integrator and a detection circuit board. The detection element is connected with the precharge voltage source, the voltage buffer and the integrator respectively to receive voltage transmitted by the precharge voltage source and the voltage buffer and to transmit fingerprint electric charge to the integrator. The integrator receives the fingerprint electric charge transmitted by the detection element, generates fingerprint signals according to fingerprint charge integration, and outputs the fingerprint signals. The precharge voltage source, the voltage buffer, the detection element and the integrator are all installed on the detection circuit board. According to the capacitive fingerprint detection circuit, excitation signals do not need to be connected to a finger of a user through external electrodes, so that when the detection circuit is combined with other devices, the integration technology becomes simple, and application scenarios of the capacitive fingerprint detection circuit are increased.
Description
Technical field
The present invention relates to integrated circuit (IC) design and fingerprinting detection technique field, in particular to a kind of capacitance type fingerprint testing circuit, sensor and equipment.
Background technology
The requirement of present people to information security is more and more higher, all need the identity being determined user by identification, and fingerprint recognition is current application the most a kind of identification mode in fields such as gate inhibition, work attendance and mobile devices.
At present, mostly adopt capacitance type fingerprint pick-up unit to carry out fingerprint detection, capacitance type fingerprint pick-up unit comprises detection chip and outer electrode, pumping signal is connected on the finger of user by outer electrode, form fingerprint detection loop with the circuit in detection chip again, thus realize carrying out fingerprint detection to user.
But need in prior art by outer electrode, pumping signal to be connected on the finger of user, outer electrode is in the outside of detection chip, making capacitance type fingerprint pick-up unit integrated process technical sophistication when being combined with other equipment, greatly limit the application scenarios of capacitance type detector.
Summary of the invention
In view of this, the invention provides a kind of capacitance type fingerprint testing circuit, sensor and equipment, the finger of user is needed pumping signal to be connected to by outer electrode for solving existing capacitance type fingerprint pick-up unit, making capacitance type fingerprint pick-up unit integrated process technical sophistication when being combined with other equipment, greatly limit the problem of the application scenarios of capacitance type detector.
First aspect, embodiments provides a kind of capacitance type fingerprint testing circuit, comprising: precharge potential source, voltage buffer, detecting element, integrator and testing circuit plate;
Described detecting element is connected with described precharge potential source, described voltage buffer and described integrator respectively, receive the voltage of described precharge potential source and the transmission of described voltage buffer, and transmission fingerprint electric charge gives described integrator;
Described integrator receives the Charge fingerprint of described detecting element transmission, produces fingerprint signal, and export described fingerprint signal according to described Charge fingerprint integration;
Described precharge potential source, described voltage buffer, described detecting element and described integrator are installed on described testing circuit plate.
In conjunction with first aspect, embodiments provide the first possible implementation of above-mentioned first aspect, wherein, described detecting element comprises: detecting electrode and isolated electrode;
Described isolated electrode is connected by the first switch with described precharge potential source respectively, is connected by second switch with described voltage buffer, receives the first voltage of described precharge potential source transmission and receives the second voltage of described voltage buffer transmission;
Described detecting electrode is connected by the 3rd switch with described isolated electrode respectively, be connected by the 4th switch with described integrator.
In conjunction with the first possible implementation of first aspect, embodiments provide the implementation that the second of above-mentioned first aspect is possible, wherein, described integrator comprises operational amplifier, integrating condenser and the 5th switch;
The inverting input of described operational amplifier is connected with one end of described integrating condenser, one end of described 5th switch respectively, and is connected with described detecting electrode by described 4th switch;
The output terminal of described operational amplifier is connected with the other end of described integrating condenser and the other end of described 5th switch respectively;
The in-phase input end of described operational amplifier is connected with reference voltage source, receives the reference voltage of described reference voltage source transmission.
In conjunction with the implementation that the second of first aspect is possible, embodiments provide the third possible implementation of above-mentioned first aspect, wherein, described testing circuit also comprises A/D converter;
Described A/D converter is connected with the output terminal of described operational amplifier, the fingerprint signal that the output terminal receiving described operational amplifier exports, and converts described fingerprint signal to fingerprint digital signal.
In conjunction with the first possible implementation of first aspect, embodiments provide the 4th kind of possible implementation of above-mentioned first aspect, wherein, described detecting electrode is the metal electrode that the top-level metallic in described testing circuit plate is formed.
In conjunction with the first possible implementation of first aspect, embodiments provide the 5th kind of possible implementation of above-mentioned first aspect, wherein, described isolated electrode is the metal electrode that in described testing circuit plate, time top-level metallic is formed, and described isolated electrode is U-shaped, described detecting electrode is wrapped up.
In conjunction with first aspect, embodiments provide the 6th kind of possible implementation of above-mentioned first aspect, wherein, described precharge potential source comprises the low noise voltage source of external voltage source or the generation of described testing circuit intralamellar part.
Second aspect, embodiments provides a kind of capacitance type fingerprint detecting sensor, comprising: multiple pixel sensing element and the capacitance type fingerprint testing circuit described in multiple above-mentioned first aspect, pixel sensing element and capacitance type fingerprint testing circuit one_to_one corresponding;
The capacitance type fingerprint testing circuit that pixel sensing element is corresponding with it respectively connects, and transmission fingerprint induced signal gives the capacitance type fingerprint testing circuit of its correspondence.
In conjunction with second aspect, embodiments provide the first possible implementation of above-mentioned second aspect, wherein, described pixel sensing element comprises multiple fingerprint inductor, multiple CMOS (Complementary Metal Oxide Semiconductor) cmos switch and emulation bus, fingerprint inductor and cmos switch one_to_one corresponding;
Fingerprint inductor is connected in described emulation bus by the cmos switch corresponding with it;
The described emulation bus capacitance type fingerprint testing circuit corresponding with described pixel sensing element connects.
The third aspect, embodiments provides a kind of capacitance type fingerprint checkout equipment, comprises and detects panel, processor, shell and the capacitance type fingerprint detecting sensor described in above-mentioned second aspect;
Described capacitance type fingerprint detecting sensor is embedded on described detection panel, and described detection panel and described processor are installed on described shell;
Described capacitance type fingerprint detecting sensor is connected with described processor, and transmission fingerprint digital signal gives described processor.
Capacitance type fingerprint testing circuit provided by the invention, sensor and equipment, do not need by outer electrode, pumping signal to be connected on the finger of user, make above-mentioned capacitance type fingerprint testing circuit with other equipment in conjunction with time integrated process become simple, and add the application scenarios of capacitance type fingerprint testing circuit.
For making above-mentioned purpose of the present invention, feature and advantage become apparent, preferred embodiment cited below particularly, and coordinate appended accompanying drawing, be described in detail below.
Accompanying drawing explanation
In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, be briefly described to the accompanying drawing used required in embodiment below, be to be understood that, the following drawings illustrate only some embodiment of the present invention, therefore the restriction to scope should be counted as, for those of ordinary skill in the art, under the prerequisite not paying creative work, other relevant accompanying drawings can also be obtained according to these accompanying drawings.
Fig. 1 shows the structural representation of a kind of capacitance type fingerprint testing circuit that the embodiment of the present invention 1 provides;
Fig. 2 shows the structural representation of the detecting element in a kind of capacitance type fingerprint testing circuit that the embodiment of the present invention 1 provides;
Fig. 3 shows the structural representation of the integrator in a kind of capacitance type fingerprint detecting sensor that the embodiment of the present invention 1 provides;
Fig. 4 shows the circuit diagram of a kind of capacitance type fingerprint testing circuit that the embodiment of the present invention 1 provides;
Fig. 5 shows the structural representation of a kind of capacitance type fingerprint detecting sensor that the embodiment of the present invention 2 provides;
Fig. 6 shows the structural representation of a kind of capacitance type fingerprint checkout equipment that the embodiment of the present invention 3 provides.
Fig. 4 description of reference numerals is as follows:
Detecting electrode 131, isolated electrode 132, the first switch 401, second switch the 402, three switch 403, the 4th switch 404, the 5th switch 143, operational amplifier 141, integrating condenser 142, reference voltage source 406, voltage buffer 120 and precharge potential source 110.
Embodiment
Below in conjunction with accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only a part of embodiment of the present invention, instead of whole embodiments.The assembly of the embodiment of the present invention describing and illustrate in usual accompanying drawing herein can be arranged with various different configuration and design.Therefore, below to the detailed description of the embodiments of the invention provided in the accompanying drawings and the claimed scope of the present invention of not intended to be limiting, but selected embodiment of the present invention is only represented.Based on embodiments of the invention, the every other embodiment that those skilled in the art obtain under the prerequisite not making creative work, all belongs to the scope of protection of the invention.
Consider that pumping signal need be connected on the finger of user by outer electrode by capacitance type fingerprint pick-up unit of the prior art, outer electrode is in the outside of detection chip, making capacitance type fingerprint pick-up unit integrated process technical sophistication when being combined with other equipment like this, greatly limit the application scenarios of capacitance type detector.Based on this, embodiments provide a kind of capacitance type fingerprint testing circuit, sensor and equipment.Be described below by embodiment.
Embodiment 1
Embodiments provide a kind of capacitance type fingerprint testing circuit.This fingerprint detection circuit does not need finger pumping signal being connected to user by outer electrode, and the collection of fingerprint signal all completes in this testing circuit inside.
As shown in Figure 1, the capacitance type fingerprint testing circuit that the embodiment of the present invention provides, comprising: precharge potential source 110, voltage buffer 120, detecting element 130, integrator 140 and testing circuit plate 150;
Detecting element 130 is connected with precharge potential source 110, voltage buffer 120 and integrator 140 respectively, receive the voltage of precharge potential source 110 and voltage buffer 120 transmission, and transmission fingerprint electric charge is to integrator 140;
Integrator 140 receives the Charge fingerprint that detecting element 130 transmits, and produces fingerprint signal, and export this fingerprint signal according to this Charge fingerprint integration;
Precharge potential source 110, voltage buffer 120, detecting element 130 and integrator 140 are installed on testing circuit plate 150.
Wherein, above-mentioned precharge potential source 110 can be external voltage source, it can also be the low noise voltage source that testing circuit plate 150 inside produces, and low noise voltage source is the voltage source that a kind of noise figure is very low, if above-mentioned precharge potential source 110 is external voltage source, then above-mentioned precharge potential source 110 can be battery on this capacitance type fingerprint testing circuit place equipment or electric battery.
The slow device 120 of voltage punching is voltage sources, can outside transmission voltage, and in embodiments of the present invention, voltage buffer 120 is to detecting element 130 transmission voltage.
Above-mentioned testing circuit plate 150 can be PCB (PrintedCircuitBoard, printed circuit board) plate.
In embodiments of the present invention, the finger of people contacts with detecting element 130, a fingerprint capacitor can be produced, precharge potential source 110 is connected with detecting element 130, transmission voltage is to detecting element 130, voltage precharge potential source 110 being transferred to detecting element 130 is designated as the first voltage, voltage buffer 120 is also connected with detecting element 130, and transmission voltage is to detecting element 130, voltage voltage buffer 120 being transferred to detecting element 130 is designated as the second voltage, wherein, above-mentioned first voltage can be greater than the second voltage, detecting element 130 receives the first voltage that precharge potential source 110 transmits respectively, and the second voltage that receiver voltage impact damper 120 transmits, the first voltage that detecting element 130 will receive, second voltage and fingerprint capacitor, generate Charge fingerprint, and this Charge fingerprint is transferred to integrator 140, after integrator 140 receives the Charge fingerprint of detecting element 130 transmission, integral operation is carried out to this Charge fingerprint, produce a fingerprint signal, this fingerprint signal is a fingerprint simulating signal, and export this fingerprint signal.
Wherein, above-mentioned precharge potential source 110, voltage buffer 120, detecting element 130 and integrator 140 are installed on testing circuit plate 150, above-mentioned precharge potential source 110, voltage buffer 120, detecting element 130 and integrator 140 are all integrated on testing circuit plate 150, form a complete fingerprint detection circuit, this fingerprint detection circuit can complete the generation of the collection of fingerprint capacitor, the transmission of voltage and fingerprint signal, does not need external electrode pumping signal to be connected on the finger of user.
Wherein, as an embodiment, as shown in Figure 2, above-mentioned detecting element 130 comprises:
Detecting electrode 131 and isolated electrode 132.
Isolated electrode 132 is connected by the first switch with precharge potential source 110 respectively, be connected by second switch with voltage buffer 120, receives the second voltage that the first voltage of above-mentioned precharge potential source 110 transmission and receiver voltage impact damper 120 transmit;
Detecting electrode 131 is connected by the 3rd switch with isolated electrode 132 respectively, be connected by the 4th switch with integrator 140.
In embodiments of the present invention, isolated electrode 132 is connected by the first switch with precharge potential source 110, when above-mentioned first switch disconnects, disconnect between isolated electrode 132 and precharge potential source 110, isolated electrode 132 cannot receive the first voltage that precharge potential source 110 transmits, after above-mentioned first switch is closed, connect between isolated electrode 132 and precharge potential source 110, at this moment, isolated electrode 132 can receive the first voltage that precharge potential source 110 transmits, isolated electrode 132 is also connected by second switch with voltage buffer 120, when second switch disconnects, disconnect between isolated electrode 132 and voltage buffer 120, at this moment isolated electrode 132 cannot receive the second voltage that voltage buffer 120 transmits, after above-mentioned second switch is closed, connect between isolated electrode 132 and voltage buffer 120, at this moment isolated electrode 132 can receiver voltage impact damper 120 transmit the second voltage.
Connected by the 3rd switch between above-mentioned detecting electrode 131 and isolated electrode 132, when above-mentioned 3rd switch disconnects, disconnect between detecting electrode 131 and isolated electrode 132, at this moment the first voltage that the precharge potential source 110 that isolated electrode 132 receives transmits, and the second voltage that the voltage buffer 120 received transmits cannot be transferred to detecting electrode 131, after above-mentioned 3rd switch is closed, connect between detecting electrode 131 and isolated electrode 132, at this moment isolated electrode 132 can by the voltage transmission that receives to detecting electrode 131, this voltage is the first voltage or the second voltage.Above-mentioned detecting electrode 131 is also connected by the 4th switch with integrator 140, when above-mentioned 4th switch disconnects, disconnect between above-mentioned detecting electrode 131 sum-product intergrator 140, integrator 140 is the Charge fingerprints that cannot receive detecting electrode 131 transmission, after above-mentioned 4th switch is closed, connect between detecting electrode 131 sum-product intergrator 140, at this moment the Charge fingerprint of generation can be transferred to integrator 140 by detecting electrode 131.
In the above-described embodiments, the finger of people contacts with detecting electrode 131, can produce measured capacitance, namely a fingerprint capacitor between the finger of people and detecting electrode 131, voltage on this fingerprint capacitor and detecting electrode 131 forms Charge fingerprint, and this Charge fingerprint is transferred to integrator 140.
Wherein, as an embodiment, above-mentioned detecting electrode 131 is the metal electrode that the top-level metallic in above-mentioned testing circuit plate 150 is formed; Above-mentioned isolated electrode 132 is the metal electrode that in above-mentioned testing circuit plate 150, time top-level metallic is formed, and isolated electrode 132 is in U-shaped, is wrapped up by described detecting electrode 131.
In embodiments of the present invention, detecting electrode 131 and isolated electrode 132 are all that the metal on testing circuit plate 150 is formed, wherein, detecting electrode 131 is metal electrodes that the top-level metallic on testing circuit plate 150 is formed, and isolated electrode 132 is the secondary top layers on testing circuit plate 150, the namely metal electrode of second layer metal formation, and, isolated electrode 132 is U-shaped, detecting electrode 131 is yi word pattern, detecting electrode 131 is at the top of the U-shaped of isolated electrode 132, like this, detecting electrode 131 wraps by isolated electrode 132, detecting electrode 131 is isolated from the outside.
Wherein, as an embodiment, as shown in Figure 3, integrator 140 comprises:
Operational amplifier 141, integrating condenser 142 and the 5th switch 143.
The inverting input of operational amplifier 141 is connected with one end of integrating condenser 142, one end of the 5th switch 143 respectively, and is connected with detecting electrode 131 by the 4th switch;
The output terminal of operational amplifier 141 is connected with the other end of integrating condenser 142 and the other end of the 5th switch 143 respectively;
The in-phase input end of operational amplifier 141 is connected with reference voltage source, receives the reference voltage of reference voltage source transmission.
Wherein, above-mentioned operational amplifier 141 comprises two input ends, an output terminal, and two input ends are respectively in-phase input end and inverting input.
In embodiments of the present invention, the inverting input of operational amplifier 141 is connected with detecting electrode 131 by the 4th switch, when the 4th switch disconnects, do not connect between operational amplifier 141 and detecting electrode 131, at this moment operational amplifier 141 is the Charge fingerprints that cannot receive detecting electrode 131 transmission, after above-mentioned 4th switch is closed, connect between operational amplifier 141 and detecting electrode 131, at this moment, the Charge fingerprint of generation can be transferred to operational amplifier 141 by detecting electrode 131.The inverting input of operational amplifier 141 is also connected with one end of integrating condenser 142 and one end of the 5th switch 143, and the output terminal of operational amplifier 141 is connected with the other end of integrating condenser 142 and the other end of the 5th switch 143 respectively, after operational amplifier 141 receives the Charge fingerprint of detecting electrode 131 transmission, integration can be carried out to this Charge fingerprint, generate fingerprint signal, and by the output terminal of operational amplifier 141, this fingerprint signal is exported.
The in-phase input end of operational amplifier 141 is connected with reference voltage source, receives the reference voltage of reference voltage source transmission.
Wherein, when above-mentioned 5th switch 143 disconnects, integrating condenser 142 can carry out the accumulation of electric charge, after above-mentioned 5th switch 143 is closed, electric charge on integrating condenser 142 will reset, further, the inverting input of operational amplifier 141 and the voltage of output terminal also can be initialized as said reference voltage.
In order to convert the fingerprint signal that above-mentioned integrator 140 exports to fingerprint digital signal, above-mentioned capacitance type fingerprint testing circuit also comprises A/D converter;
A/D converter is connected with the output terminal of operational amplifier 141, the fingerprint signal that the output terminal receiving operational amplifier 141 exports, and converts this fingerprint signal to fingerprint digital signal.
In embodiments of the present invention, the inverting input of operational amplifier 141 is connected with detecting electrode 131, receive the Charge fingerprint that detecting electrode 131 transmits, and integration is carried out to this Charge fingerprint, generate fingerprint signal, this fingerprint signal is fingerprint simulating signal, the output terminal of operational amplifier 141 is connected with A/D converter, the fingerprint signal of generation is transferred to A/D converter, after A/D converter receives the fingerprint signal of operational amplifier 141 transmission, convert this fingerprint signal to fingerprint digital signal, and this fingerprint digital signal is exported.
In order to introduce the annexation in capacitance type fingerprint testing circuit that the embodiment of the present invention provides between each components and parts in more detail, the circuit diagram of the capacitance type fingerprint testing circuit provided below in conjunction with the embodiment of the present invention is introduced this testing circuit and the method that uses this testing circuit to carry out fingerprint detection, and the circuit diagram of the capacitance type fingerprint testing circuit that the embodiment of the present invention provides as shown in Figure 4.
In embodiments of the present invention, isolated electrode 132 is connected with precharge potential source 110 by the first switch 401, be connected with voltage buffer 120 by second switch 402, detecting electrode 131 is connected by the 3rd switch 403 with isolated electrode 132, finger contacts with detecting electrode 131, produce Detection capacitance, i.e. fingerprint capacitor, the inverting input of operational amplifier 141 is connected with detecting electrode 131 by the 4th switch 404, the inverting input of operational amplifier 141 is also connected with one end of integrating condenser 142 and one end of the 5th switch 143 respectively, the output terminal of operational amplifier 141 is connected with the other end of integrating condenser 142 and the other end of the 5th switch 143 respectively, the in-phase input end of operational amplifier 141 is connected with reference voltage source 406, receive the reference voltage that reference voltage source 406 transmits.
Adopt above-mentioned capacitance type fingerprint testing circuit to carry out fingerprint detection to comprise the steps:
Closed 5th switch 143, resets the electric charge of accumulation on integrating condenser 142, simultaneously because the in-phase input end of operational amplifier 141 is connected with reference voltage source 406, receives the reference voltage V that reference voltage source 406 transmits
3, now, the reversed-phase output of operational amplifier 141 and the voltage of output terminal are also initialized as reference voltage V
3, the reseting stage in fingerprint detection that Here it is, after reseting stage completes, then entering signal acquisition phase.
Wherein, signal acquisition stage comprises following three steps:
Preliminary filling, signal compensation and signal integration.
Closed 3rd switch 403 and the first switch 401, connects between such detecting electrode 131 and isolated electrode 132, connects between isolated electrode 132 and precharge potential source 110, and namely isolated electrode 132 receives the first voltage V that precharge potential source 110 transmits
1, and by this first voltage V
1be transferred to detecting electrode 131, at this moment, the voltage in detecting electrode 131 and isolated electrode 132 is all charged to the first voltage V in advance
1.
For convenience of description, suppose human body grounding, the voltage of such human body is 0, because the voltage on detecting electrode 131 is V
1, there is voltage difference between the finger of people and detecting electrode 131, therefore, when the finger of people contacts with above-mentioned detecting electrode 131, can measured capacitance C be produced
f, i.e. fingerprint capacitor C
f, and voltage now in detecting electrode 131 and isolated electrode 132 is equal, the stray capacitance C therefore formed between detecting electrode 131 and isolated electrode 132
botbe zero, at this moment, the total amount of electric charge that detecting electrode 131 stores is: Q
0=V
1c
f, this stored charge is exactly Charge fingerprint, preliminary filling process that Here it is.
After preliminary filling completes, then closed second switch 402, at this moment, connects between isolated electrode 132 and voltage buffer 120, the second voltage V of isolated electrode 132 receiver voltage impact damper 120 transmission
2, now, the voltage in isolated electrode 132 is from V
1drop to V
2, wherein, the first voltage V
1be greater than the second voltage V
2, and, be originally stored in the Charge fingerprint Q on detecting electrode 131
0detecting electrode 131 and isolated electrode 132 redistribute, but the total amount of Charge fingerprint remains unchanged, this process is then signal compensation process, and after signal compensation terminates, the voltage in isolated electrode 132 is the second voltage V
2.
After signal compensation process completes, then closed 4th switch 404, at this moment, connect between the inverting input of detecting electrode 131 and operational amplifier 141, Charge fingerprint on detecting electrode 131 can be transferred to operational amplifier 141, is transferred on integrating condenser 142 by the Charge fingerprint received by operational amplifier 141, and, in this stage, detecting electrode 131 also receives the reference voltage V of operational amplifier 141 inverting input transmission
3, therefore, the voltage on detecting electrode 131 is reference voltage V
3, and the voltage in isolated electrode 132 is V
2, at this moment, between detecting electrode 131 and isolated electrode 132, there is voltage difference, therefore, the stray capacitance C between detecting electrode 131 and isolated electrode 132
botnon-vanishing, at this moment, the net charge that detecting electrode 131 stores is
:q
1=V
3c
f+(V
3-V
2) C
bot, wherein, C
botfor the stray capacitance produced between detecting electrode 131 and isolated electrode 132, therefore, by the charge Q of accumulation on detecting electrode 131 in preliminary filling process
0and the charge Q that this process detecting electrode 131 stores
1the quantity of electric charge Δ Q=Q transferred on integrating condenser 142 can be calculated
0-Q
1, i.e. Δ Q=(V
1-V
3) C
f-(V
3-V
2) C
bot, wherein, Δ Q transfers to the quantity of electric charge on integrating condenser 142, and this process is then signal integration process, now, then completes once complete signals collecting.
Wherein, in the computing formula of above-mentioned Δ Q, reference voltage V
3with the second voltage V that voltage buffer 120 produces
2unequal, can be reference voltage V
3be greater than the second voltage V
2, also can be reference voltage V
3be less than the second voltage V
2, such reference voltage V
3with the second voltage V
2between have a voltage difference, therefore can produce (a V to tested charge signal
3-V
2) C
botcharge signal compensate, it can be positive charge signal compensation that this charge signal compensates, also can be negative charge signal compensation, the basal signal existed between the fingerprint paddy of fingerprint and fingerprint ridge can be compensated like this, only select to carry out integration sampling to the difference signal between fingerprint paddy and fingerprint ridge, thus a very wide fingerprint paddy/ridge signal sampling dynamic range can be obtained.
In order to a small-signal being converted into a large-signal being easy to measure, can repeat N time last time signal acquisition process, wherein, N is a positive integer being greater than zero, if repeat N above-mentioned signal acquisition process, total then transfer on integrating condenser 142 the quantity of electric charge be N Δ Q, this total quantity of electric charge is exactly the semaphore that operational amplifier 141 obtains, this semaphore, after operational amplifier 141 carries out Integral Processing, obtains a N (Δ Q/C at the output terminal of operational amplifier 141
int) voltage swing, wherein, C
intthe integrating capacitor that integrating condenser 142 produces, as can be seen from above-mentioned formula, the integrating capacitor C that the size of the times N value gathered by regulating repeating signal and integrating condenser 142 produce
intsize, a small-signal can be converted into one be easy to measure large-signal, so both can reduce the accuracy requirement to A/D converter, the signal to noise ratio (S/N ratio) of the fingerprint signal obtained can also have been improved.
After signal acquisition stage completes, then enter measuring phases, the output terminal of operational amplifier 141 produces a N (Δ Q/C by integration
int) voltage swing, namely fingerprint signal, but this fingerprint signal is fingerprint simulating signal, therefore, this fingerprint signal is transferred to A/D converter by the output terminal of operational amplifier 141, after A/D converter receives the fingerprint signal of output terminal transmission of operational amplifier 141, then convert this fingerprint signal to fingerprint digital signal, and export this fingerprint digital signal.
Above-described embodiment, that the circuit diagram of the capacitance type fingerprint testing circuit that the embodiment of the present invention provides and using method are illustrated, also can after often completing a signals collecting and measurement, will reset by foregoing circuit, such next time is when carrying out fingerprint detection, directly from signal acquisition stage, certain the present invention does not limit the concrete using method step of above-mentioned capacitance type fingerprint testing circuit.
The first switch 401 in the embodiment of the present invention, second switch 402, the 3rd switch 403, the 4th switch 404 and the 5th switch 143 can be electromagnetic relay.
Capacitance type fingerprint testing circuit provided by the invention, do not need by outer electrode, pumping signal to be connected on the finger of user, make above-mentioned capacitance type fingerprint testing circuit with other equipment in conjunction with time integrated process become simple, and add the application scenarios of capacitance type fingerprint testing circuit.
Embodiment 2
Embodiments provide a kind of capacitance type fingerprint detecting sensor.
As shown in Figure 5, the capacitance type fingerprint detecting sensor that the embodiment of the present invention provides comprises:
The capacitance type fingerprint testing circuit 520 that multiple pixel sensing element 510 and above-described embodiment 1 provide;
Pixel sensing element 510 and capacitance type fingerprint testing circuit 520 one_to_one corresponding;
The capacitance type fingerprint testing circuit 520 that pixel sensing element 510 is corresponding with it respectively connects, and transmission fingerprint induced signal gives the capacitance type fingerprint testing circuit 520 of its correspondence.
Wherein, above-mentioned pixel sensing element 510 is a kind of elements can experiencing the fingerprint signal of the finger of people.
In embodiments of the present invention, when carrying out fingerprint detection, the finger of people contacts with above-mentioned pixel sensing element 510, when carrying out fingerprint detection at every turn, the finger of people may contact with one or several pixel sensing elements 510 in above-mentioned multiple pixel sensing element 510, and pixel sensing element 510 can sense the fingerprint on the finger of people, and generate a fingerprint induced signal, and this fingerprint induced signal is transferred to the capacitance type fingerprint testing circuit 520 corresponding with it, when condenser type is after fingerprint detection circuit 520 receives the fingerprint induced signal of above-mentioned pixel sensing element 510 transmission, detecting electrode 131 in capacitance type fingerprint testing circuit 520 can generate fingerprint capacitor, the accumulation of electric charge can be carried out in this fingerprint capacitor, generate Charge fingerprint, by integrator 140, Integral Processing is carried out to this Charge fingerprint, obtain fingerprint signal, and export after converting this fingerprint signal to fingerprint digital signal by A/D converter.
Wherein, as an embodiment, each pixel sensing element 510 in above-mentioned multiple pixel sensing element comprises:
Multiple fingerprint inductor, multiple CMOS (ComplementaryMetalOxideSemiconductor, complementary metal oxide semiconductor (CMOS)) switch and emulation bus, fingerprint inductor and cmos switch one_to_one corresponding;
Fingerprint inductor is connected in above-mentioned emulation bus by the cmos switch corresponding with it;
The above-mentioned emulation bus capacitance type fingerprint testing circuit 520 corresponding with above-mentioned pixel sensing element 510 connects.
Wherein, each fingerprint inductor in above-mentioned multiple fingerprint inductor is provided with a cmos switch, a row fingerprint inductor can be comprised in above-mentioned each pixel sensing element 510, like this, when the multiple pixel sensing elements 510 of above-mentioned condenser type in fingerprint detection sensor are arranged in rows, fingerprint inductor in this capacitance type fingerprint detecting sensor is then two-dimensional array arrangement, in the embodiment of the present invention, each fingerprint inductor in a row fingerprint inductor in each pixel sensing element 510 is connected in same emulation bus by cmos switch, this cmos switch is for controlling connection between above-mentioned fingerprint inductor and cmos switch and disconnection.
In embodiments of the present invention, the fingerprint signal of the finger of fingerprint inductor induction people, produce a fingerprint induced signal, and by above-mentioned emulation bus, this fingerprint induced signal is transferred to capacitance type fingerprint testing circuit 520, when condenser type is after fingerprint detection circuit 520 receives the fingerprint induced signal of above-mentioned emulation bus transmission, detecting electrode 131 in capacitance type fingerprint testing circuit 520 can generate fingerprint capacitor, the accumulation of electric charge can be carried out in this fingerprint capacitor, a Charge fingerprint can be generated, by integrator 140, Integral Processing is carried out to this Charge fingerprint, obtain fingerprint signal, and export after converting this fingerprint signal to fingerprint digital signal by A/D converter.
Capacitance type fingerprint detecting sensor provided by the invention, do not need by outer electrode, pumping signal to be connected on the finger of user, make above-mentioned capacitance type fingerprint testing circuit with other equipment in conjunction with time integrated process become simple, and add the application scenarios of capacitance type fingerprint testing circuit.
Embodiment 3
Embodiments provide a kind of capacitance type fingerprint checkout equipment.
As shown in Figure 6, the capacitance type fingerprint checkout equipment that the embodiment of the present invention provides comprises:
Detect the capacitance type fingerprint detecting sensor 640 that panel 610, processor 620, shell 630 and above-described embodiment 2 provide;
Capacitance type fingerprint detecting sensor 640 is embedded on above-mentioned detection panel 610, and this detection panel 610 and processor 620 are installed on above-mentioned shell 630;
Capacitance type fingerprint detecting sensor 640 is connected with above-mentioned processor 620, and transmission fingerprint digital signal gives above-mentioned processor 620.
In embodiments of the present invention, when carrying out fingerprint detection, the finger of people contacts with above-mentioned capacitance type fingerprint detecting sensor 640, this capacitance type fingerprint detecting sensor 640 can gather the fingerprint signal of the finger of people, produce fingerprint induced signal, this fingerprint induced signal is processed, finally obtain a fingerprint digital signal, and by this fingerprint digital data transmission to processor 620, after processor 620 receives the fingerprint digital signal of capacitance type fingerprint detecting sensor 640 transmission, can compare with the fingerprint digital signal of the identity of mark people that stores in this processor 620, carry out authentication, if the fingerprint digital signal that processor 620 receives is consistent with the fingerprint signal of its storage, authentication success is then described, if the fingerprint signal stored in the fingerprint digital signal that processor 620 receives and processor 620 is inconsistent, then illustrate that authentication is unsuccessful.
Capacitance type fingerprint checkout equipment provided by the invention, do not need by outer electrode, pumping signal to be connected on the finger of user, make capacitance type fingerprint testing circuit with other equipment in conjunction with time integrated process become simple, and add the application scenarios of capacitance type fingerprint testing circuit.
The above; be only the specific embodiment of the present invention, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; change can be expected easily or replace, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of described claim.
Claims (10)
1. a capacitance type fingerprint testing circuit, is characterized in that, comprising: precharge potential source, voltage buffer, detecting element, integrator and testing circuit plate;
Described detecting element is connected with described precharge potential source, described voltage buffer and described integrator respectively, receive the voltage of described precharge potential source and the transmission of described voltage buffer, and transmission fingerprint electric charge gives described integrator;
Described integrator receives the Charge fingerprint of described detecting element transmission, produces fingerprint signal, and export described fingerprint signal according to described Charge fingerprint integration;
Described precharge potential source, described voltage buffer, described detecting element and described integrator are installed on described testing circuit plate.
2. capacitance type fingerprint testing circuit according to claim 1, is characterized in that, described detecting element comprises: detecting electrode and isolated electrode;
Described isolated electrode is connected by the first switch with described precharge potential source respectively, is connected by second switch with described voltage buffer, receives the first voltage of described precharge potential source transmission and receives the second voltage of described voltage buffer transmission;
Described detecting electrode is connected by the 3rd switch with described isolated electrode respectively, be connected by the 4th switch with described integrator.
3. capacitance type fingerprint testing circuit according to claim 2, is characterized in that, described integrator comprises operational amplifier, integrating condenser and the 5th switch;
The inverting input of described operational amplifier is connected with one end of described integrating condenser, one end of described 5th switch respectively, and is connected with described detecting electrode by described 4th switch;
The output terminal of described operational amplifier is connected with the other end of described integrating condenser and the other end of described 5th switch respectively;
The in-phase input end of described operational amplifier is connected with reference voltage source, receives the reference voltage of described reference voltage source transmission.
4. capacitance type fingerprint testing circuit according to claim 3, is characterized in that, described testing circuit also comprises A/D converter;
Described A/D converter is connected with the output terminal of described operational amplifier, the fingerprint signal that the output terminal receiving described operational amplifier exports, and converts described fingerprint signal to fingerprint digital signal.
5. capacitance type fingerprint testing circuit according to claim 2, is characterized in that, described detecting electrode is the metal electrode that the top-level metallic in described testing circuit plate is formed.
6. capacitance type fingerprint testing circuit according to claim 2, is characterized in that, described isolated electrode is the metal electrode that in described testing circuit plate, time top-level metallic is formed, and described isolated electrode is U-shaped, is wrapped up by described detecting electrode.
7. capacitance type fingerprint testing circuit according to claim 1, is characterized in that, described precharge potential source comprises the low noise voltage source of external voltage source or the generation of described testing circuit intralamellar part.
8. a capacitance type fingerprint detecting sensor, is characterized in that, comprises multiple pixel sensing element and multiple capacitance type fingerprint testing circuit as described in any one of claim 1 ~ 7, pixel sensing element and capacitance type fingerprint testing circuit one_to_one corresponding;
The capacitance type fingerprint testing circuit that pixel sensing element is corresponding with it respectively connects, and transmission fingerprint induced signal gives the capacitance type fingerprint testing circuit of its correspondence.
9. capacitance type fingerprint detecting sensor according to claim 8, is characterized in that, described pixel sensing element comprises multiple fingerprint inductor, multiple CMOS (Complementary Metal Oxide Semiconductor) cmos switch and emulation bus, fingerprint inductor and cmos switch one_to_one corresponding;
Fingerprint inductor is connected in described emulation bus by the cmos switch corresponding with it;
The described emulation bus capacitance type fingerprint testing circuit corresponding with described pixel sensing element connects.
10. a capacitance type fingerprint checkout equipment, is characterized in that, comprises the capacitance type fingerprint detecting sensor detected described in panel, processor, shell and claim 8 or 9;
Described capacitance type fingerprint detecting sensor is embedded on described detection panel, and described detection panel and described processor are installed on described shell;
Described capacitance type fingerprint detecting sensor is connected with described processor, and transmission fingerprint digital signal gives described processor.
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