CN203964928U - For the capacitance detecting device of fingerprint recognition with there is its fingerprint identification device - Google Patents
For the capacitance detecting device of fingerprint recognition with there is its fingerprint identification device Download PDFInfo
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- CN203964928U CN203964928U CN201320871000.XU CN201320871000U CN203964928U CN 203964928 U CN203964928 U CN 203964928U CN 201320871000 U CN201320871000 U CN 201320871000U CN 203964928 U CN203964928 U CN 203964928U
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Abstract
The utility model discloses a kind of capacitance detecting device for fingerprint recognition, comprise: detect screen and conductor frame, detect screen and comprise a plurality of detecting units, each detecting unit comprises first to fourth conductor layer, the finger that the first conductor layer and touch detect screen forms inductance capacitance, between the first and second conductor layers, form feedback capacity, between the third and fourth conductor layer, form integrating capacitor, when finger contacts with detection screen, finger is electrically connected to conductor frame; Pick-up unit, for inductance capacitance and feedback capacity being charged in sample phase, and in integration phase, measure the electric charge of controlling in inductance capacitance and feedback capacity and shift to integrating capacitor, measure integrating capacitor at the voltage variety of integration phase simultaneously, and calculate inductance capacitance according to voltage variety.Capacitance detecting device of the present utility model has improved fingerprint detection precision, effectively reduces circuit noise simultaneously, and has reduced power consumption and the area of circuit.The invention also discloses a kind of fingerprint identification device.
Description
Technical field
The utility model relates to electronic technology field, particularly a kind of capacitance detecting device for fingerprint recognition and a kind ofly have this for the fingerprint identification device of the capacitance detecting device of fingerprint recognition.
Background technology
At present in carrying out the process of fingerprint recognition, mainly adopted fingerprint sensor and the finger contact part of capacitive transducer technology also to detect panel, detecting panel consists of a plurality of small detecting units, a detecting unit can be described as a pixel, wherein, fingerprint detection pixel can be Two dimensional Distribution.When carrying out fingerprint recognition, finger is placed on and detects on panel, reason due to finger lines, line peak directly touches detection panel, line paddy has a bit of distance with detection panel, and this distance is deeply corresponding with the paddy of line paddy, if this distance can be identified, just can tell line peak and the line paddy of fingerprint, also just obtain the feature of fingerprint; Another kind of mode is to change by finger the Electric Field Distribution that fingerprint recognition detects panel surface, and then detects fingerprint characteristic.
Detection fingerprint method above-mentioned can be realized by capacitance detecting mode.The existing multiple implementation of fingerprint detection method based on this principle, wherein a kind of detection mode is: by detection, point and the electric capacity that is positioned at the top-level metallic electrode formation that detects panel below, structurally, conventionally detect each detection pixel correspondence on panel and a metal polar plate, Two dimensional Distribution in the direction that these metal polar plates are expert at row, forms two-dimensional detection matrix and a pole plate during as fingerprint detection; Simultaneously because the conductor feature of finger, when finger is placed on detection panel, finger has just formed another pole plate corresponding with the pole plate of fingerprint two-dimensional detection matrix, the electric capacity that these pole plates form is corresponding one by one with the surface characteristics of fingerprint, the polar plate spacing that line peak is corresponding is larger from little inductance capacitance, line paddy is contrary, by detecting this inductance capacitance, just can determine fingerprint surface characteristics; Another kind of detection mode is: each detects pixel packets containing two pole plates, alternative arrangement being positioned on different metal layer between pole plate, between them, just formed fixed capacity, while carrying out fingerprint detection, when finger is positioned over, detect on panel, the Electric Field Distribution between pole plate will change, and then change the fixed capacity between them, line peak and line paddy are different on the impact of electric field, therefore also just can differentiate branching peak and line paddy.
In the fingerprint sensor of realizing with semiconductor inductance capacitance at present, its superstructure towards finger comprises the conductor layer that multilayer consists of metal conventionally, between these conductor layers, also comprise corresponding separation layer, the conductor layer of the superiors is fingerprint detection pole plates corresponding with finger, the electric capacity that the electric capacity forming between each conductor layer or conduct are used for processing top layer fingerprint signal that Detection capacitance detects is as integrating capacitor or as stray capacitance, but, if stray capacitance will affect fingerprint detection precision.
Yet stray capacitance does not exist only between each conductor layer, at each adjacent top layer detecting electrode, each conductor layer to also there being stray capacitance between ground.Stray capacitance on the impact of accuracy of detection mainly from two aspects: on the one hand, conventionally between these stray capacitances and Detection capacitance, be relation in parallel, for example, existence due to stray capacitance Cp, input signal becomes Vin*Cf/ (Cf+Cp) from Vin, stray capacitance Cp is greater than the capacitor C f that fingerprint forms conventionally, can significantly reduce like this precision of fingerprint detection; On the other hand, stray capacitance conventionally by the noise coupling from substrate to Detection capacitance, reduced the precision of fingerprint detection.
Utility model content
The purpose of this utility model is intended at least one of solve the problems of the technologies described above.
For this reason, first object of the present utility model is to propose a kind of capacitance detecting device for fingerprint recognition.This capacitance detecting device has improved fingerprint detection precision, effectively reduces circuit noise simultaneously, and has significantly reduced power consumption and the area of circuit.
Second object of the present utility model is to propose a kind of fingerprint identification device.
To achieve these goals, the capacitance detecting device for fingerprint recognition that the utility model first aspect embodiment proposes, comprise: detect screen and conductor frame, described detection screen comprises a plurality of detecting units, described in each, detecting unit comprises: the first conductor layer to the four conductor layers, wherein, the finger of the described detection screen of described the first conductor layer and touch forms inductance capacitance, between described the first conductor layer and the second conductor layer, form feedback capacity, between described the 3rd conductor layer and the 4th conductor layer, form integrating capacitor, described in when described finger contacts with described detection screen, point and be electrically connected to described conductor frame, pick-up unit, described pick-up unit is for charging to described inductance capacitance and feedback capacity in sample phase, and in integration phase, measure the electric charge of controlling in described inductance capacitance and feedback capacity and shift to described integrating capacitor, measure described integrating capacitor at the voltage variety of described integration phase simultaneously, and calculate described inductance capacitance according to described voltage variety.
According to the capacitance detecting device for fingerprint recognition of the utility model embodiment, can in sample phase, to inductance capacitance and feedback capacity, charge by pick-up unit, and in integration phase, measure the electric charge of controlling in inductance capacitance and feedback capacity and shift to integrating capacitor, measure integrating capacitor at the voltage variety of integration phase simultaneously, and calculate inductance capacitance according to this voltage variety, to realize the identification of fingerprint, at least have the following advantages: (1) is passed through the electric capacity digitizing of fingerprint signal, avoided the front-end detection part in general fingerprint detection, circuit scale is significantly reduced, less circuit scale has lower circuit noise and power consumption, thereby there is higher fingerprint detection precision and lower energy consumption, (2) by operational amplifier, stray capacitance is remained on to fixing current potential, make in circuit working stray capacitance not have the transfer of electric charge, eliminate the impact of stray capacitance on input signal, and eliminated the impact of switching device on accuracy of detection, thereby improved accuracy of detection.
To achieve these goals, the fingerprint identification device that the utility model second aspect embodiment proposes, comprising: the capacitance detecting device for fingerprint recognition described in the utility model first aspect embodiment.
According to the fingerprint identification device of the utility model embodiment, can be by the pick-up unit of the capacitance detecting device for fingerprint recognition, in sample phase, inductance capacitance and feedback capacity are charged, and in integration phase, measure the electric charge of controlling in inductance capacitance and feedback capacity and shift to integrating capacitor, measure integrating capacitor at the voltage variety of integration phase simultaneously, and calculate inductance capacitance according to this voltage variety, to realize the identification of fingerprint, at least have the following advantages: (1) is passed through the electric capacity digitizing of fingerprint signal, avoided the front-end detection part in general fingerprint detection, circuit scale is significantly reduced, less circuit scale has lower circuit noise and power consumption, thereby there is higher fingerprint detection precision and lower energy consumption, (2) by operational amplifier, stray capacitance is remained on to fixing current potential, make in circuit working stray capacitance not have the transfer of electric charge, eliminate the impact of stray capacitance on input signal, and eliminated the impact of switching device on accuracy of detection, thereby improved accuracy of detection.
The aspect that the utility model is additional and advantage in the following description part provide, and part will become obviously from the following description, or recognize by practice of the present utility model.
Accompanying drawing explanation
Above-mentioned and/or the additional aspect of the utility model and advantage will become from the following description of the accompanying drawings of embodiments and obviously and easily understand, wherein:
Fig. 1 is according to the structural representation of the capacitance detecting device for fingerprint recognition of an embodiment of the utility model;
Fig. 2 is according to the schematic diagram of the capacitance detecting device for fingerprint recognition of an embodiment of the utility model;
Fig. 3 is the fingerprint detection schematic diagram of a detecting unit in Fig. 2; And
Fig. 4 is the fingerprint detection schematic diagram according to the capacitance detecting device for fingerprint recognition of a specific embodiment of the utility model.
Drawing reference numeral:
100: detect screen; 110 detecting units; 111: the first conductor layers; 112: the second conductor layers;
113: the three conductor layers; 114: the four conductor layers; 115: the five conductor layers; 200: conductor frame;
300: pick-up unit; 310: reference voltage provides module; 320: amplification module;
330 voltage detection module; 340: switching controls module; 4: detection arrays; 5: finger.
Embodiment
Describe embodiment of the present utility model below in detail, the example of described embodiment is shown in the drawings, and wherein same or similar label represents same or similar element or has the element of identical or similar functions from start to finish.Below by the embodiment being described with reference to the drawings, be exemplary, only for explaining the utility model, and can not be interpreted as restriction of the present utility model.
Disclosing below provides many different embodiment or example to be used for realizing different structure of the present utility model.Of the present utility model open in order to simplify, hereinafter the parts of specific examples and setting are described.Certainly, they are only example, and object does not lie in restriction the utility model.In addition, the utility model can be in different examples repeat reference numerals and/or letter.This repetition is in order to simplify and object clearly, itself do not indicate the relation between discussed various embodiment and/or setting.In addition, the various specific technique that the utility model provides and the example of material, but those of ordinary skills can recognize the property of can be applicable to of other techniques and/or the use of other materials.In addition, First Characteristic described below Second Characteristic it " on " structure can comprise that the first and second Characteristics creations are for the direct embodiment of contact, also can comprise the embodiment of other Characteristics creation between the first and second features, such the first and second features may not be direct contacts.
In description of the present utility model, it should be noted that, unless otherwise prescribed and limit, term " installation ", " being connected ", " connection " should be interpreted broadly, for example, can be mechanical connection or electrical connection, also can be the connection of two element internals, can be to be directly connected, and also can indirectly be connected by intermediary, for the ordinary skill in the art, can understand as the case may be the concrete meaning of above-mentioned term.
With reference to description and accompanying drawing below, by these and other aspects of clear embodiment of the present utility model.In these descriptions and accompanying drawing, specifically disclose some specific implementations in embodiment of the present utility model, represent to implement some modes of the principle of embodiment of the present utility model, but should be appreciated that the scope of embodiment of the present utility model is not limited.On the contrary, embodiment of the present utility model comprises spirit and all changes within the scope of intension, modification and the equivalent that falls into additional claims.
The capacitance detecting device for fingerprint recognition proposing according to the utility model first aspect embodiment is described below with reference to Fig. 1 to Fig. 4.
As shown in Figure 1, should can comprise for the capacitance detecting device of fingerprint recognition and detect screen 100, metallic conductor frame 200 and pick-up unit 300.Wherein, detect screen 100 and can comprise a plurality of detecting units 110, as shown in Figure 4, each detecting unit 110 can comprise the first conductor layer 111, the second conductor layer 112, the 3rd conductor layer 113 and the 4th conductor layer 114.Wherein, the finger 5 that the first conductor layer 111 and touch detect screen 100 forms inductance capacitance Cf, between the first conductor layer 111 and the second conductor layer 112, form feedback capacity Cm, between the 3rd conductor layer 113 and the 4th conductor layer 114, form integrating capacitor Ci, when finger 5 contacts with detection screen 100, finger 5 is electrically connected to metallic conductor frame 200.Wherein, metallic conductor frame 200 can conduct electricity, and when finger 5 contacts with detection screen 100, metallic conductor frame 200 can be electrically connected to finger 5.
Further, in embodiment of the present utility model, as shown in Figure 4, the first conductor layer 111, the second conductor layer 112, the 3rd conductor layer 113 and the 4th conductor layer 114 all parallel with the detection plane that detects screen 100.Wherein, detection plane can be regarded as the plane that detects screen 100 places.That is to say, the first conductor layer 111, the second conductor layer 112, the 3rd conductor layer 113 and the 4th conductor layer 114 can be arranged under the overlay successively, and all shield the plane parallel at 100 places with detection.
And, in embodiment of the present utility model, metallic conductor frame 200 is different from the internal conductor layers such as first to fourth conductor layer in detecting unit 110, the first conductor layer 111, the second conductor layer 112, the 3rd conductor layer 113 and the 4th conductor layer 114 can be positioned at and detect screen 100 inside, insulate with the external world, and metallic conductor frame 200 is positioned at the outside of detecting screen 100, and metallic conductor frame 200 can be the metallic conductor frame that is surrounded on detection screen 100 surroundings.Because finger 5 is also conductor, therefore, when finger 5 is positioned on detection screen 100, finger 5 can be realized and being electrically connected to this metallic conductor frame 200, can to finger 5, transmit by this metallic conductor frame 200.Should be appreciated that for finger 5 fully contact, metallic conductor frame 200 conventionally with respect to detect screen 100 rat some.
That is to say, in embodiment of the present utility model, as shown in Figure 2, a plurality of detecting units 110 can be by rearranging two-dimensional detection array 4, metallic conductor frame 200 can be looped around detection arrays 4 around, and can provide reference signal by pointing 5 when fingerprint detection.When finger 5 is positioned on detection screen 100, metallic conductor frame 200 can be realized and being electrically connected to finger 5, and metallic conductor frame 200 provides reference signal and complete the collection to fingerprint graph together with detection arrays 4 by pointing 5.Wherein, the size that is the inductance capacitance Cf of the formation between the first conductor layer 111 and finger 5 due to the top conductors layer at detecting unit 110 has represented the line peak of fingerprint or the feature of line paddy, so the inductance capacitance Cf of all detecting units 110 of detection arrays 4 and finger 5 formation have just represented the feature of fingerprint graph.
According to an embodiment of the present utility model, as shown in Figure 4, detect screen 100 and can also comprise that the 5th conductor layer 115, the five conductor layers 115 that are formed between the second conductor layer 112 and the 3rd conductor layer 113 can be used for as the separation layer between the second conductor layer 112 and the 3rd conductor layer 113.Wherein, in embodiment of the present utility model, the 5th conductor layer 115 ground connection or be connected to set potential, and the 5th conductor layer 115 can be metal or polysilicon.That is to say, in embodiment of the present utility model, because the second conductor layer 112 is not a static current potential, the second conductor layer 112 can switch between different current potentials, so, for fear of the potential change of the second conductor layer 112, other circuit are caused to interference, can below the second conductor layer 112, place one deck the 5th conductor layer 115 as separation layer, the 5th conductor layer 115 is connected to earth potential or other set potentials, and the 5th conductor layer 115 can consist of metal or polysilicon.
According to an embodiment of the present utility model, detect screen 100 and can also comprise and be formed on the first conductor layer 111 to the multilayer dielectric layer between the 4th conductor layer 114.That is to say, as shown in Figure 4, detecting screen 100 can also comprise the insulation course 11 that is formed between the first conductor layer 111 and the second conductor layer 112, is formed on insulation course 12 between the second conductor layer 112 and the 5th conductor layer 115, is formed on insulation course 14 between the 5th conductor layer 115 and the 3rd conductor layer 113, is formed on the insulation course 15 between the 3rd conductor layer 113 and the 4th conductor layer 114.Wherein, as shown in Figure 4,16 can comprise other conductor layers, can be used for electrical connection, other are active or the connection of passive device, electric shield etc.
Wherein, in embodiment of the present utility model, the size of the feedback capacity Cm forming between the first conductor layer 111 and the second conductor layer 112, can be by regulating the thickness of insulation course 11 to realize; The size of the integrating capacitor Ci forming between the 3rd conductor layer 113 and the 4th conductor layer 114, can be by regulating the thickness of insulation course 15 to realize.
According to an embodiment of the present utility model, detect screen 100 and can also comprise the protective seam that covers the first conductor layer 111.For example, as shown in Figure 4, the first conductor layer 111 tops have covered one deck insulator 10, and this insulator 10 can be used as the encapsulating structure of fingerprint sensor and provides protection for inner detection architecture.
As shown in Figure 1, pick-up unit 300 is used in sample phase inductance capacitance Cf and feedback capacity Cm is charged, and in integration phase, measure the electric charge of controlling in inductance capacitance Cf and feedback capacity Cm and shift to integration capacitor C i, measure integrating capacitor Ci at the voltage variety of integration phase simultaneously, and calculate inductance capacitance Cf according to voltage variety.
According to an embodiment of the present utility model, as shown in Figure 1, pick-up unit 300 can comprise that reference voltage provides module 310, amplification module 320, voltage detection module 330 and switching controls module 340.
Wherein, in embodiment of the present utility model, reference voltage provides module 310 to can be used for providing the first reference voltage to the four reference voltages.Amplification module 320 can be used for the voltage of integrating capacitor Ci to amplify.Voltage detection module 330 is connected with amplification module 320, and voltage detection module 330 can be used for detecting the voltage of integrating capacitor.When switching controls module 340 is used in sample phase, the first reference voltage is provided to finger 5 by metallic conductor frame 200, and provide respectively the second reference voltage to the first conductor layer 111 and the second conductor layer 112, and when integration phase, the second reference voltage is provided to finger 5 by metallic conductor frame 200, and the first conductor layer 111 is connected to the 4th conductor layer 114, to the second conductor layer 112, provide the 3rd reference voltage or the 4th reference voltage simultaneously.Wherein, in embodiment of the present utility model, the first input end of amplification module 320 is connected with the 4th conductor layer 114, and the second input end of amplification module 320 is connected with the second reference voltage, and the output terminal of amplification module 320 is connected with the 3rd conductor layer 113.For example, as shown in Figure 4, amplification module 320 can be operational amplifier 6, and the first input end of amplification module 320 is the negative input end of operational amplifier 6, and the second input end of amplification module 320 is the positive input terminal of operational amplifier 6.In addition, voltage detection module 330 can comprise quantizer and modulator etc.
In embodiment of the present utility model, as shown in Figure 4, pick-up unit 300 can also comprise reset switch S0, and one end of reset switch S0 is connected with the 3rd conductor layer 113, and the other end of reset switch S0 is connected with the 4th conductor layer 114.
In embodiment of the present utility model, as shown in Figure 4, switching controls module 340 can comprise the first switch S 1, second switch S2, the 3rd switch S 3, the 4th switch S 4 and controller 341.Wherein, the first end of the first switch S 1 is connected with metallic conductor frame 200, and the second end of the first switch S 1 is connected with the first reference voltage Vref, and the 3rd end of the first switch S 1 is connected with the second reference voltage VCM.The first end of second switch S2 is connected with the first conductor layer 111, and the second end of second switch S2 is connected with the first input end of amplification module 320.The first end of the 3rd switch S 3 is connected with the first conductor layer 111, and the second end of the 3rd switch S 3 is connected with the second reference voltage VCM.The first end of the 4th switch S 4 is connected with the second conductor layer 112, and the second end to the four ends of the 4th switch S 4 are connected with the second reference voltage VCM with three reference voltage Vref _ H, four reference voltage Vref _ L respectively.Controller 341 can be used for controlling respectively disconnection and the closure of the first switch S 1, second switch S2, the 3rd switch S 3 and the 4th switch S 4.
That is to say, for each detecting unit 110, its top conductors layer i.e. the first conductor layer 111 conducts and the surperficial detecting electrodes that form fingerprint inductance capacitance Cf of finger 5, the first conductor layer 111 can be connected with the first input end of operational amplifier 6 by second switch S2, maybe can be connected with set potential (i.e. the second reference voltage VCM) by the 3rd switch S 3, the second input end of operational amplifier 6 is connected to set potential (i.e. the second reference voltage VCM), like this, can pass through the short characteristic of void of operational amplifier 6 positive-negative input end mouths, make detecting unit 110 can remain on set potential VCM always, thereby can eliminate the impact that stray capacitance is brought.
And, in embodiment of the present utility model, as shown in Figure 1, controller 341 is connected with voltage detection module 330, and controller 341 can select three reference voltage Vref _ H or four reference voltage Vref _ L to provide to the second conductor layer 112 according to the Output rusults of voltage detection module 330.
In order to make advantage of the present utility model more obvious, below in conjunction with Fig. 3, detecting unit 110 is elaborated.
For example, shown in Fig. 3, in Fig. 32 is that the top conductors layer of detecting unit 110 in Fig. 4 is the first conductor layer 111, after finger the 5 and first conductor layer 111 forms inductance capacitance Cf, finger 5 can be connected to different reference voltages by the first switch S 1, the first conductor layer 111 can be connected with the negative input end of operational amplifier 6 by second switch S2, or is connected with a fixed voltage VCM by the 3rd switch S 3; Between the negative input end of operational amplifier 6 and output terminal, be connected integrating capacitor Ci, and have a reset switch S0 in parallel with integrating capacitor Ci with reset integrating capacitor Ci; Feedback capacity Cm completes the subtraction function of modulator, and its one end is connected with the first conductor layer 111, and the other end is connected to different reference voltages according to the output of modulator; The output terminal of operational amplifier 6 is connected to the input end of quantizer 7, and quantizer 7 completes the thick quantification of operational amplifier 6 output signals and the output signal of modulator is provided in modulator work; The output of quantizer 7 can be connected to time-sequence control module 9 on the one hand so that the clock signal of S1 ~ S4 to be provided, the thick quantized signal that can be used as on the other hand modulator output offers DSP(Digital Signal Processing, digital signal processing) module 8 is processed, to obtain the size of capacitor C f.
As shown in Figure 3, when carrying out fingerprint detection, can be divided into sample phase and integration phase.In sample phase, can by metallic conductor frame 200 with point 5 be electrically connected to, the first switch S 1 is connected to the first reference voltage Vref, second switch S2 disconnects simultaneously, the 3rd switch S 3 closures, the 4th switch S 4 is connected to the second reference voltage VCM, and the electrically charged amount of capacitor C f that the surface of finger 5 and the first conductor layer 111 form is: (Vref-VCM) * Cf, in integration phase, the first switch S 1 is connected to the second reference voltage VCM, second switch S2 is closed, the 3rd switch S 3 disconnects, the 4th switch S 4 can be connected to three reference voltage Vref _ H or four reference voltage Vref _ L according to the output of quantizer 7, as, when quantizer 7 is output as when high, the 4th switch S 4 can be connected to three reference voltage Vref _ H, when quantizer 7 is output as when low, the 4th switch S 4 can be connected to four reference voltage Vref _ L, because the input end void of operational amplifier 6 is short, the voltage of negative input end A and positive input terminal B remains the second reference voltage VCM, at this moment inductance capacitance Cf both end voltage equates, electrically charged amount (Vref-VCM) the * Cf of inductance capacitance Cf institute in sample phase has been transferred on integrating capacitor Ci, simultaneously in integration phase, feedback capacity Cm need to complete subtraction function, wherein the charge transfer quantity of feedback capacity Cm is: (Vref_H/L – VCM) * Cm, the charge variation amount of integrating capacitor Ci is: (Vref-VCM) * Cf-(Vref_H/L-VCM) * Cm.Like this, through once complete sampling integral process, the output voltage variable quantity of operational amplifier 6 is: Δ V=[(Vref-VCM) * Cf-(Vref_H/L-VCM) * Cm]/Ci, can find out, in the item relevant to Δ V, only having Cf is variable, so Δ V is the function of Cf, the output that is also modulator is the function of Cf, thereby realizes the detection to Cf.Wherein, it should be noted that, the quantizer 7 in Fig. 3 can be realized by the comparator configuration of known type, and the sequential that time-sequence control module 9 provides can be used for bottomplanksampling and integration control, so normally not overlapping sequential.What modulator was modulated rear output to fingerprint signal Cf is slightly to quantize digital signal, need to process the digitized result that just can obtain Cf through DSP module.
It should be noted that, in the sampling and integration phase of pick-up unit 300, all by operational amplifier 6, realize, operational amplifier 6 is realized based on CMOS technique, the reset switch S0 that is connected to operational amplifier 6 negative input ends and output terminal is used for realizing the input end of operational amplifier 6 is fixed on to the DC level of, to guarantee the state of operational amplifier 6 in normally working.Reset switch S0 makes operational amplifier 6 very effective in normal bias voltage state for realization, and when the positive input terminal of operational amplifier 6 is fixed on current potential VCM, the current potential of negative input end also will remain on the electricity of VCM according to the short characteristic of void.Thus, guaranteed normally carrying out of sampling and integration phase.
Also it should be noted that, each detecting unit 110 can comprise independently operational amplifier 6, and for realizing the modulation function to input signal, in order to reduce the area of integrated circuit, operational amplifier 6 must be realized by simple structure.Because the utility model adopts oversampling technique, low with respect to other detection schemes to the performance requirement of operational amplifier 6, so be also easier to realize the simplification to operational amplifier 6.
In sum, in switching capacity over-sampling detects, can, by the voltage of input or current signal are maintained to fixed value, using the size of sampling capacitance as variable, can detect the relative variation of this electric capacity.Because fingerprint detection is the detection to electric capacity, can utilize above-mentioned principle, just can realize the direct quantification to fingerprint capacitor, without independent front-end detection circuit, simplified circuit structure, reduce the noise of circuit, and then improved the precision of fingerprint detection.
According to the capacitance detecting device for fingerprint recognition of the utility model embodiment, can in sample phase, to inductance capacitance and feedback capacity, charge by pick-up unit, and in integration phase, measure the electric charge of controlling in inductance capacitance and feedback capacity and shift to integrating capacitor, measure integrating capacitor at the voltage variety of integration phase simultaneously, and calculate inductance capacitance according to this voltage variety, to realize the identification of fingerprint, at least have the following advantages: (1) is passed through the electric capacity digitizing of fingerprint signal, avoided the front-end detection part in general fingerprint detection, circuit scale is significantly reduced, less circuit scale has lower circuit noise and power consumption, thereby there is higher fingerprint detection precision and lower energy consumption, (2) by operational amplifier, stray capacitance is remained on to fixing current potential, make in circuit working stray capacitance not have the transfer of electric charge, eliminate the impact of stray capacitance on input signal, and eliminated the impact of switching device on accuracy of detection, thereby improved accuracy of detection.
In addition, embodiment of the present utility model has also proposed a kind of fingerprint identification device, and it comprises the above-mentioned capacitance detecting device for fingerprint recognition.
According to the fingerprint identification device of the utility model embodiment, can be by the pick-up unit of the capacitance detecting device for fingerprint recognition, in sample phase, inductance capacitance and feedback capacity are charged, and in integration phase, measure the electric charge of controlling in inductance capacitance and feedback capacity and shift to integrating capacitor, measure integrating capacitor at the voltage variety of integration phase simultaneously, and calculate inductance capacitance according to this voltage variety, to realize the identification of fingerprint, at least have the following advantages: (1) is passed through the electric capacity digitizing of fingerprint signal, avoided the front-end detection part in general fingerprint detection, circuit scale is significantly reduced, less circuit scale has lower circuit noise and power consumption, thereby there is higher fingerprint detection precision and lower energy consumption, (2) by operational amplifier, stray capacitance is remained on to fixing current potential, make in circuit working stray capacitance not have the transfer of electric charge, eliminate the impact of stray capacitance on input signal, and eliminated the impact of switching device on accuracy of detection, thereby improved accuracy of detection.
In the description of this instructions, the description of reference term " embodiment ", " some embodiment ", " example ", " concrete example " or " some examples " etc. means to be contained at least one embodiment of the present utility model or example in conjunction with specific features, structure, material or the feature of this embodiment or example description.In this manual, the schematic statement of above-mentioned term is not necessarily referred to identical embodiment or example.And the specific features of description, structure, material or feature can be with suitable mode combinations in any one or more embodiment or example.
Although illustrated and described embodiment of the present utility model, for the ordinary skill in the art, be appreciated that in the situation that not departing from principle of the present utility model and spirit and can carry out multiple variation, modification, replacement and modification to these embodiment, scope of the present utility model is by claims and be equal to and limit.
Claims (11)
1. for a capacitance detecting device for fingerprint recognition, it is characterized in that, comprising:
Detect screen and conductor frame, described detection screen comprises a plurality of detecting units, and described in each, detecting unit comprises:
The first conductor layer to the four conductor layers, wherein, the finger of the described detection screen of described the first conductor layer and touch forms inductance capacitance, between described the first conductor layer and the second conductor layer, form feedback capacity, between described the 3rd conductor layer and the 4th conductor layer, form integrating capacitor, point described in when described finger and described detection screen contact and be electrically connected to described conductor frame;
Pick-up unit, described pick-up unit is for charging to described inductance capacitance and feedback capacity in sample phase, and in integration phase, measure the electric charge of controlling in described inductance capacitance and feedback capacity and shift to described integrating capacitor, measure described integrating capacitor at the voltage variety of described integration phase simultaneously, and calculate described inductance capacitance according to described voltage variety.
2. the capacitance detecting device for fingerprint recognition as claimed in claim 1, is characterized in that, described the first conductor layer to the four conductor layers all parallel with the detection plane of described detection screen.
3. the capacitance detecting device for fingerprint recognition as claimed in claim 1, is characterized in that, described detection screen also comprises:
Be formed on the 5th conductor layer between described the second conductor layer and described the 3rd conductor layer, described the 5th conductor layer is used for as the separation layer between described the second conductor layer and described the 3rd conductor layer.
4. the capacitance detecting device for fingerprint recognition as claimed in claim 3, is characterized in that, described the 5th conductor layer ground connection or be connected to set potential, and described the 5th conductor layer is metal or polysilicon.
5. the capacitance detecting device for fingerprint recognition as claimed in claim 1, is characterized in that, described detection screen also comprises:
Be formed on the multilayer dielectric layer between described the first conductor layer to the four conductor layers.
6. the capacitance detecting device for fingerprint recognition as claimed in claim 1, is characterized in that, described detection screen also comprises:
Cover the protective seam of described the first conductor layer.
7. the capacitance detecting device for fingerprint recognition as claimed in claim 1, is characterized in that, described pick-up unit comprises:
Reference voltage provides module, and described reference voltage provides module for the first reference voltage to the four reference voltages are provided;
Amplification module, described amplification module is for amplifying the voltage of described integrating capacitor, the first input end of described amplification module is connected with described the 4th conductor layer, the second input end of described amplification module is connected with described the second reference voltage, and the output terminal of described amplification module is connected with described the 3rd conductor layer;
Voltage detection module, described voltage detection module is connected with described amplification module, and described voltage detection module is for detection of the voltage of described integrating capacitor;
Switching controls module, described switching controls module for providing described the first reference voltage to described finger by described conductor frame when sample phase, and provide respectively described the second reference voltage to described the first conductor layer and the second conductor layer, and when integration phase, described the second reference voltage is provided to described finger by described conductor frame, and described the first conductor layer is connected to described the 4th conductor layer, to described the second conductor layer, provide the 3rd reference voltage or the 4th reference voltage simultaneously.
8. the capacitance detecting device for fingerprint recognition as claimed in claim 7, is characterized in that, described pick-up unit also comprises:
Reset switch, one end of described reset switch is connected with described the 3rd conductor layer, and the other end of described reset switch is connected with described the 4th conductor layer.
9. the capacitance detecting device for fingerprint recognition as claimed in claim 7, is characterized in that, described switching controls module comprises:
The first switch, the first end of described the first switch is connected with described conductor frame, and the second end of described the first switch is connected with described the first reference voltage, and the 3rd end of described the first switch is connected with described the second reference voltage;
Second switch, the first end of described second switch is connected with described the first conductor layer, and the second end of described second switch is connected with the first input end of described amplification module;
The 3rd switch, the first end of described the 3rd switch is connected with described the first conductor layer, and the second end of described the 3rd switch is connected with described the second reference voltage;
The 4th switch, the first end of described the 4th switch is connected with described the second conductor layer, and the second end to the four ends of described the 4th switch are connected with described the 3rd reference voltage, the 4th reference voltage and described the second reference voltage respectively;
Control described the first switch to the controller of described the 4th switch.
10. the capacitance detecting device for fingerprint recognition as claimed in claim 9, it is characterized in that, described controller is connected with described voltage detection module, and described controller selects the 3rd reference voltage or the 4th reference voltage to provide to described the second conductor layer according to the Output rusults of described voltage detection module.
11. 1 kinds of fingerprint identification devices, is characterized in that, comprise the capacitance detecting device for fingerprint recognition as described in claim 1-10 any one.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201320871000.XU CN203964928U (en) | 2013-12-27 | 2013-12-27 | For the capacitance detecting device of fingerprint recognition with there is its fingerprint identification device |
| KR1020167020384A KR101816002B1 (en) | 2013-12-27 | 2014-12-26 | Capacitance detecting device for fingerprint identification and fingerprint identification apparatus comprising the same |
| EP14874728.0A EP3087349A4 (en) | 2013-12-27 | 2014-12-26 | Capacitance detecting device for fingerprint identification and fingerprint identification apparatus comprising the same |
| PCT/CN2014/095134 WO2015096807A1 (en) | 2013-12-27 | 2014-12-26 | Capacitance detecting device for fingerprint identification and fingerprint identification apparatus comprising the same |
| US15/192,807 US9679186B2 (en) | 2013-12-27 | 2016-06-24 | Capacitance detecting device for fingerprint identification and fingerprint identification apparatus comprising the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201320871000.XU CN203964928U (en) | 2013-12-27 | 2013-12-27 | For the capacitance detecting device of fingerprint recognition with there is its fingerprint identification device |
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| Publication Number | Publication Date |
|---|---|
| CN203964928U true CN203964928U (en) | 2014-11-26 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201320871000.XU Withdrawn - After Issue CN203964928U (en) | 2013-12-27 | 2013-12-27 | For the capacitance detecting device of fingerprint recognition with there is its fingerprint identification device |
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| Country | Link |
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| CN (1) | CN203964928U (en) |
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