CN205302320U - Fingerprint identification device - Google Patents
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- CN205302320U CN205302320U CN201521004137.0U CN201521004137U CN205302320U CN 205302320 U CN205302320 U CN 205302320U CN 201521004137 U CN201521004137 U CN 201521004137U CN 205302320 U CN205302320 U CN 205302320U
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Abstract
The utility model provides a fingerprint identification sensing equipment's adc dynamic adjustment module and circuit. Through the gain of independently adjusting the front end amplifier respectively, adc's gain and offset, can furthest utilize the system Dynamics scope, improve the fingerprint image like the contrast, improve fingerprint identification's identifiability ability. The utility model provides a fingerprint identification device, through the application adc improves fingerprint image quality, has reduced adjustment "Iterations", has shortened fingerprint identification check -out time.
Description
Technical field
The utility model relates to fingerprint recognition and process field, is specifically related to a kind of fingerprint detection recognition device.
Background technology
Fingerprint detection and recognition technology are a kind of personal identification verification technology of reliable and extensive use. CMOS fingerprint Identification sensor has the advantages such as volume is little, low in energy consumption, module is frivolous, can meet the requirement of field of mobile terminals to miniaturization, low-power consumption, be therefore widely used in portable mobile apparatus, and as mobile phone, tablet device, PAD etc. Capacitance type fingerprint identification sensor has the fingerprint sensing pixel electrode array being made up of multiple electrodes, it can respond the driving signal of drive circuit, and produce induced signal based on the variation of electrode capacitance, in the time of finger contact sensor surface, the electric capacity difference forming between induction electrode and Fingers wrinkle ridge and fingerprint paddy. Capacitance change between each pixel finger sensing and the induction electrode of sensor circuit, be translated into the variable quantity of the signal of telecommunication, and be converted to through analog-digital converter (ADC) data signal that contains half-tone information, after subsequent treatment, form fingerprint image.
The size of the capacitance that fingerprint ridge and fingerprint paddy and induction electrode form depends on thickness and the dielectric constant of medium between finger and sensor. Under general applicable cases, this electric capacity is less than 1fF, and the capacitance change that therefore fingerprint ridge and fingerprint paddy and induction electrode form can be less. This just means that fingerprint Identification sensor need to amplify signal very little difference distinguish, and system need to have higher output signal dynamic range. Sensor output data has higher dynamic range, and the fingerprint image that recovers to obtain has higher contrast, and the easier matching identification of fingerprint identification method, has higher identification precision.
Generally speaking the output signal range of the input signal of sensor (corresponding to the capacitance forming between finger and induction electrode) after sensor amplifier circuit can, much smaller than the input dynamic range of the analog-digital converter of rear class, cannot make full use of the full range of analog-digital converter. If do not process dynamic range is adjusted, the fingerprint image of collection there will be the defect of poor contrast, causes affecting the reduction of fingerprint recognition accuracy rate.
Therefore, existing fingerprint Identification sensor need to do optimization process to Dynamic Range, by adjusting parameter, makes as far as possible input signal reach the full scale of analog-digital converter. Make full use of the input dynamic range of system and analog-digital converter, improve the total quality that gathers image.
Existing analog-digital converter has following defect: in order to improve the common mode inhibition of system, analog-digital converter (ADC) generally adopts differential architecture conventionally, and the reference voltage of for example analog-digital converter is VREFH, the input dynamic range of analog-digital converter (ADC) is [V soREFH, 0] and [0, VREFH]. After fingerprint recognition sensing equipment amplifies through front-end amplifier, the signal that exports analog-digital converter to be on the occasion of, therefore for fingerprint equipment itself, only need forward input range [0, the V of analog-digital converter (ADC)REFH]. Therefore in the time of the picture quality of system requirements 256 GTGs, ADC needs the precision of 9-bit. It should be noted that this description form of " [lower limit, the upper limit] " represents a certain scope, and this scope comprises endpoint value.
Multiple parameters of existing fingerprint sensor apparatus circuit all can dynamic range exert an influence. Such as the gain of frontend amplifying circuit (one-level or multistage), the gain of analog-digital converter and side-play amount. The adjustment Existence dependency relationship of these variablees.
Fig. 1 is the transformational relation between analog-digital converter of the prior art (ADC) input signal and output digital code (being digital output signal). Transformation curve can be understood as expression formula below:
code＝Aadc(Vin+Soffset)；
Wherein code is the numeral output of the lower ADC of different inputs, AadcFor the gain of analog-digital converter, VinThe input component that represents ADC, Soffset is side-play amount. The gain A of analog-digital converteradcThe slope that changes transformation curve, offset parameter Soffset makes curve generation translation.
As can be seen from Figure 1, in the situation that side-play amount is 0, the position that the intersection point of the transformation curve under different gains adjustment is 0 at input signal. The input dynamic range of analog-digital converter (ADC) is [VREFH, 0] and [0, VREFH]。
Gain and side-play amount with analog-digital converter are adjusted into example, when only utilizing input range [0, the V of forwardREFH] time, as shown in Figure 1, the gain of digital to analog converter can affect the slope of transformation curve, and the relative position of side-play amount meeting influence curve. In the time there is constant offset amount, the position that the intersection point of the transformation curve under different gains adjustment is no longer 0 at input signal. Side-play amount is closely related on the gain of the impact of exporting and analog-digital converter. In the time that the gain of system digital to analog converter changes, side-play amount also can be along with the variation of gain changes. Therefore, in existing fingerprint sensing identification equipment, the adjustment of analog-digital converter dynamic range exists needs repeated multiple times iteration adjustment, causes inefficiency, or cannot find the optimum problem arranging.
Summary of the invention
The defect that the utility model exists for existing fingerprint recognition sensing equipment, a kind of fingerprint recognition sensing equipment and dynamic range method of adjustment have been proposed, method of adjustment and the concrete grammar implementation procedure of dynamic range can be simplified, reduce the number of times iterating, thereby improved response speed and the identification performance of fingerprint recognition.
This fingerprint recognition sensing equipment comprises a fingerprint sensing pixel electrode array, and for driving the drive circuit of described array, and front end input amplifier (AMP), it is for receiving and amplify the analog signal of fingerprint sensing pixel electrode array output, and sends the signal after amplifying to analog-digital converter.
The fingerprint recognition sensing equipment the utility model proposes, also comprises the analog-digital converter (ADC) with adjustable dynamic scope, and described analog-digital converter is for being converted to the signal after front-end processing the data signal of certain limit.
The utility model proposes a kind of fingerprint recognition sensing equipment dynamic range method of adjustment and related realization circuit. The method is by the design to analog-digital converter, and the gain to analog-digital converter and side-play amount are carried out independent adjustment respectively.
The utility model proposes in a kind of fingerprint recognition sensing equipment dynamic range method of adjustment, analog-digital converter has reference voltage, the adjustment of gain realizes by adjusting its reference voltage level, analog-digital converter comprises a comparator, and the adjustment of side-play amount realizes by the common mode reference voltage of adjusting comparator differential input end.
The utility model proposes for fingerprint recognition sensing equipment dynamic range method of adjustment, can adjust the gain of front end input amplifier.
The utility model proposes a kind of fingerprint recognition sensing equipment dynamic range Circuit tuning, it comprises front-end amplifier, analog-digital converter, data processing module and dynamic range adjustment module.
The utility model proposes a kind of fingerprint identification device, comprise described analog-digital converter, data processing module and control module etc.
The dynamic range method of adjustment the utility model proposes, carry out independent adjustment by the gain adjustment to analog-digital converter and side-play amount, can use offset parameter and gain to adjust parameter and utilize to greatest extent analog-digital converter ADC input dynamic range, according to different fingerprints and the dynamics real-time regulating system parameter of pressing, obtain optimum picture quality. The method has been eliminated the dependence between analog-digital converter gain and side-play amount in prior art, adjusting after offset parameter, the variation of gain parameter can not affect the mean value of image output, thereby without carrying out again readjusting of offset parameter, reduce method iterations, shortened the time that system fingerprint detects.
Brief description of the drawings
Fig. 1 shows the transformation curve of the analog-digital converter of existing fingerprint recognition sensing equipment.
Fig. 2 shows the circuit working principle of the fingerprint recognition sensing equipment the utility model proposes.
Fig. 3 shows in the fingerprint recognition sensing equipment dynamic range method of adjustment the utility model proposes, the method for adjustment of ADC gain.
Schematic diagram when Fig. 4 shows the fingerprint recognition sensing equipment the utility model proposes and is applied to inhibition system common-mode noise.
Fig. 5 shows the method realization flow of the fingerprint recognition sensing equipment dynamic range adjustment the utility model proposes.
Fig. 6 shows an embodiment of the fingerprint recognition sensing device the utility model proposes.
Detailed description of the invention
Detailed content of the present utility model will be described in detail by reference to the accompanying drawings in following examples. But, the utlity model has multiple different implementation, it should not be regarded as only limiting to several embodiment cited below. Following preferred embodiment is provided for explaining, clarify summary of the invention.
Fig. 2 shows an embodiment of the fingerprint recognition sensing circuit the utility model proposes, it comprises amplifier AMP, analog-digital converter ADC, data processing module and dynamic range adjustment module, amplifier AMP is front end input amplifier, realize the conversion of electric capacity to the signal of telecommunication, and signal is amplified. AMP can be single-stage, also can be formed by multi-stage cascade. ADC is analog-digital converter, completes the conversion of analog electrical signal to digital component. Data processing module, for ADC output signal is converted to certain luma data, carries out suitable dynamic adjustment by the output data to ADC, shows requirement with the GTG of adaptive system. Dynamic range method of adjustment module receives the Mobile state scope adjustment of going forward side by side of the output data of data processing module, to the gain A of amplifieramp, the gain A of analog-digital converteradc, skew Soffset carries out independent adjustment. In general fingerprint recognition application, the precision of ADC is 8-10bit. As shown in Figure 1, abscissa is input analog signal, the minimum of a value-V of abscissa to the transformation curve of analog-digital converter ADCREFHWith maximum VREFHRepresent the maximum magnitude of input signal. Ordinate is the digital output code of representative simulation semaphore size, ordinate minimum of a value is 0, maximum is the maximum that ADC conversion accuracy allows, and as 8bit precision corresponds to 256, corresponding coding can be expressed as 0000...00～code_max (1111...11). Concrete code element number is relevant with precision. The adjustment of transformation curve slope means the variation of picture contrast. General fingerprint recognition input reference signal is very little, and gain, ADC transformation curve slope to front-end amplifier are adjusted the input range that can make full use of ADC, improves overall image quality.
In order to increase the flexibility of system, this circuit can be realized the adjustment of gain and side-play amount simultaneously. Under identical input condition, the change in gain corresponding conversion slope of a curve of ADC changes; The side-play amount of ADC is adjusted corresponding conversion curve and is carried out translation with the slope of fixing. Because data sheet Direction saturation may appear in overall data in the time gaining adjustment in the time that Data Dynamic scope does not reach optimum, in this case, can pass through to adjust the offset parameter translation transformation curve of analog-digital converter, thereby eliminate the saturated phenomenon of data.
ADC gain is adjusted and the circuit implementation of side-play amount adjustment will be considered concrete adc circuit structure in practice, for different adc circuits, and the implementation difference to some extent that ADC gain is adjusted and side-play amount is adjusted. In the analog to digital conversion circuit of common ADC, all there is sampling hold circuit, sampling hold circuit comprises sampling capacitance, circuit will be inputted analog signal sampling by sampling capacitance and keep, and circuit afterwards carries out quantification treatment to the sampled signal of sampling hold circuit, instead of real-time analog signal.
Redistribute formula successive approximation analog to digital C (SARADC) circuit as example taking capacitor array electric charge below, the implementation that ADC side-play amount is adjusted is described. Reference voltage has defined the input reference signal of ADC. The gain of ADC can realize by adjusting its reference voltage, and the side-play amount adjustment of ADC can realize by the common mode reference voltage of adjusting the comparator differential input end in ADC.
Fig. 3 is an embodiment of the ADC gain adjusting method that the utility model proposes. In technical solutions of the utility model, ADC has two reference voltage VREFHAnd VREFL，VREFHLevel is higher than VREFL. ADC input reference signal is defined by described two reference voltages. As can be seen from Figure 3, work as VREFH-VREFLWhile diminishing, the gain of ADC conversion becomes large; Otherwise the gain of ADC conversion diminishes. Therefore the dynamic range method of adjustment the utility model proposes is by controlling VREFHAnd VREFLValue adjust the gain of ADC. The method is in the time adjusting ADC gain, to VREFHAnd VREFLSynchronously carry out identical step-length simultaneously, and rightabout adjustment. If i.e. VREFH-VREFLNeed to reduce voltage variety absolute value delta, the method is designed to: VREFHBe changed to VREFH-Δ/2，VREFLBe changed to VREFL+ Δ/2. As can be seen from Figure 3, by such design, (VREFH+VREFL)/2 remain constant, and, under different gains condition, all transformation curves are being input as (VREFH+VREFLThe point of)/2 intersects.
Taking 10-bitADC quantified precision as example, intersect the position that under different gains, the transformation curve forward of ADC is decimal number 768 at digital output code, and negative sense intersects in the position of decimal number 256. Therefore after system finally intercepts forward input range and by data zooming to 8-bit output, all gains are adjusted curves the point that is decimal number 128 at the mid point of out-put dynamic range are intersected.
Reference voltage VREFHAnd VREFLCan produce by variety of way, as the mode of electric resistance partial pressure. Produce the step footpath that circuit need to ensure that both adjust identical. The adjustment of gain can be set by the control word of register.
ADC also comprises a comparator, and the adjustment of side-play amount Soffset can realize by the common mode reference voltage of adjusting comparator differential input end. Comparator differential input end applies different common mode reference voltage, and its pressure reduction is Δ, and corresponding numeral is output as:
code＝((Vin-Δ)/Vrange)*code_max；
Code is the digital output code of analog-digital converter ADC, corresponding with digital output signal, wherein VrangeFor ADC input maximum, code_max is numeral output maximum. As can be seen from the above equation, at VrangeIn certain situation, Δ can make whole transformation curve generation translation. Common mode reference voltage can adopt to be similar to and produce VREFHAnd VREFLBleeder circuit, its adjustment can be set by the control word of register.
In conjunction with above-mentioned ADC gain and side-play amount Circuit tuning, the corresponding Dynamic Range method of adjustment that the invention proposes, it is realized by the dynamic range adjustment module in Fig. 2. As shown in Figure 3, the gain of front-end amplifier is Aamp, the gain of ADC is Aadc, side-play amount is adjusted into Soffset, and method is by adjusting Aamp、AadcAnd Soffset realizes the optimization of Dynamic Range.
The one application detecting as system, fingerprint recognition checkout equipment can also suppress system common-mode noise by the mode of copped wave, and this embodiment is as shown in Figure 4. System is switched the forward V of modulus device for interchanging in the T1 momentINPWith negative sense VINNInput, by poor the analog-digital converter output of a rear moment T1 and previous moment T0, is more finally exported divided by 2. Between T1 and T0, be Fixed Time Interval, it is chosen according to analog-digital converter framework and system noise blanketing frequency and determines, and is generally chosen between the μ s of 100ns～2. In this application, also carry out positive-negative input end exchange in the T1 moment for the common mode reference voltage of adjusting side-play amount. Realize the variation in the same way of side-play amount and input signal by simultaneously positive negative sense switching common mode reference voltage. By this method, the Data processing that is arranged on of side-play amount is retained, thereby completes the adjustment function of side-play amount.
A kind of embodiment in using as reality, in order to save time, method of adjustment can be chosen the image of certain area and process, and needn't choose view picture fingerprint image.
Fig. 5 shows a specific embodiment of dynamic range method of adjustment. Method in Fig. 5 comprises the steps:
A initializes Aamp、AadcAnd Soffset;
B adjusts front-end amplifier gain Aamp；
C adjusts analog-digital converter side-play amount Soffset;
D adjusts analog-digital converter gain Aadc。
Aamp、AadcAnd the initial value of Soffset is set as Aamp_init，Aadc_initAnd Soffset_init. The setting parameter of initial value selecting system dynamic range maximum, setting principle is in the time carrying out first IMAQ, not occur the saturated of data.
Then, carry out the adjustment of front-end amplifier gain, select the optimal value of front-end amplifier gain by the mode of traversal. Gather image, the maximum D of statistical picture dataMAX, minimum of a value DMINAnd mean value Davg, and calculate Range=DMAX-DMIN, final amplifier gain control word is chosen the gain setting that view data scope maximum and data maximum and minimum of a value all do not exceed predetermined threshold value scope [DL_set, DH_set].
As the another kind of implementation of the invention, front-end amplifier gain optimal value also can be calculated or the mode of tabling look-up obtains by search. Above three kinds of implementations traversal, search are calculated and are tabled look-up and can be used alone, and use also can mutually combine arbitrarily.
Carry out subsequently the adjustment of side-play amount. Gather image, the maximum D of statistical picture dataMAX, minimum of a value DMINAnd mean value Davg, try to achieve the mean value of image by the data of statistics gatherer image, taking 256 gray scale images as example, the target of method of adjustment is that the mid point that the mean value of image is adjusted to data output is near decimal number 128.
Adjust can adopt equally table look-up and or searching method carry out.
Finally carry out ADC gain AadcAdjustment. Adjustment can adopt tables look-up or searching method carries out.
AadcAdjustment aim is for choosing view data scope maximum, and this scope can reach the bound of adc data conversion. Data maximum and minimum of a value all do not exceed the gain setting of predetermined threshold value scope [DL_set, DH_set].
From the specific implementation of above embodiment, in the dynamic range method of adjustment that the invention proposes, ADC gain Aadc, the side-play amount Soffset of ADC and the gain A of amplifierampAdjustment there is the independence in realization, each other without directly impact, avoided in prior art the defect of the adjustment Existence dependency relationship of each circuit parameter variable.
Thereby in concrete application, after can working as the side-play amount Soffset adjustment of ADC, then carry out ADC gain AadcAnd/or the gain A of amplifierampAdjustment, thereby avoided side-play amount in prior art that the negative effect to Dynamic Range is set, simplified adjustment process, improved response speed and the identification performance of fingerprint recognition sensing equipment.
By said method, the gain A of amplifieramp, ADC gain AadcCan realize zooming in or out of Dynamic Range, can be by A in actual useampBe made as coarse adjustment, by AadcBe made as fine tuning, also can be by AampBe made as fine tuning, by AadcBe made as coarse adjustment, the two can be adjusted separately or cooperatively interact, thus the intense adjustment that obtains widerly.
As other preferred embodiment of the present utility model, described analog-digital converter ADC can be pipeline-ADC, flashADC etc., and be not limited to above type.
Fig. 6 shows a kind of fingerprint identification device embodiment that comprises described ADC.
This sensing device application Low-Power CMOS technology, is used coating or cover plate technique; Can be encapsulated as single-chip or be combined with other circuit module. In the time being encapsulated as single-chip, can select to install additional becket.
Specifically, comprise electrod-array, analog-digital converter ADC, data processing module, communication module, control module etc. Wherein, electrod-array can sensing fingerprint, and fingerprint ridge line and valley line are converted to respective electrical capacitance. Analog-digital converter can be converted to the signal after front-end processing the data signal of certain limit. Data processing module can be converted to ADC output signal certain luma data, carries out suitable dynamic adjustment by the output data to ADC, shows requirement with the GTG of adaptive system. It is mutual that communication module can be realized controling and data signal of or wired interconnecting unit wireless with other. Control module can be controlled the mode of operation of described device, and selects sensing region under different working modes, can also control fingerprint arousal function under the execution of fingerprint detection function and low power consumpting state.
Alternatively, described dynamic range adjustment module can embed among control module, thereby control module also can realize the adjustment to described ADC gain and side-play amount.
Alternatively, described device can also comprise clock module, power module and reseting module etc.
Described fingerprint identification device can use jointly with bridging chip, forms module; Bridging chip can be the power supply of fingerprint sensing device, and assists fingerprint sensing device and Master Communications. Under this application scenarios, becket is can arrangement. Do not use becket can simplify system, use becket to need to make its ground connection, contribute to reduce system noise and disturb, strengthen ESD performance.
Claims (10)
1. a fingerprint recognition sensing equipment, comprise analog-digital converter ADC and the dynamic range adjustment module of adjustable gain, analog-digital converter ADC is for being converted to the signal after front-end processing the data signal of certain limit, this analog-digital converter ADC has reference voltage, and it is for defining the scope of input signal; Described dynamic range adjustment module is adjusted this reference voltage level and is realized adjustment gain A adc.
2. fingerprint recognition sensing equipment as claimed in claim 1, comprises front end input amplifier AMP, receives and amplify the analog signal of fingerprint sensing pixel electrode array output, and sends the signal after amplifying to analog-digital converter.
3. fingerprint recognition sensing equipment as claimed in claim 1, comprises data processing module, and ADC output signal is converted to luma data, and the output data of ADC are dynamically adjusted.
4. fingerprint recognition sensing equipment as claimed in claim 1, described dynamic range adjustment module can be to the gain A amp of front-end amplifier AMP, and the gain A adc of analog-digital converter and side-play amount Soffset carry out respectively independent adjustment.
5. a fingerprint identification device, comprises electrod-array, analog-digital converter ADC, data processing module, communication module, control module; Described electrod-array can sensing fingerprint, and fingerprint ridge line and valley line are converted to respective electrical capacitance; Described analog-digital converter can be converted to the signal after front-end processing the data signal of certain limit; Described data processing module can be converted to ADC output signal certain luma data; Described communication module can be realized with controling and data signal of wireless or wired interconnecting unit mutual; Described control module can be controlled the mode of operation of described device, and selects sensing region under different working modes, controls fingerprint under the execution of fingerprint detection function and low power consumpting state and wakes up; Dynamic range adjustment module embeds among described control module.
6. fingerprint identification device as claimed in claim 5, comprises clock module, power module and reseting module.
7. fingerprint identification device as described in claim 5 or 6, described dynamic range adjustment module is adjusted described ADC gain and side-play amount.
8. fingerprint identification device as described in claim 5 or 6, uses Low-Power CMOS technology, coating or cover plate technique.
9. fingerprint identification device as described in claim 5 or 6, is encapsulated as single-chip or is combined with other circuit module.
10. fingerprint identification device as claimed in claim 5, uses jointly with bridging chip, forms module; Bridging chip can be the power supply of fingerprint sensing device, and assists fingerprint sensing device and Master Communications.
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| CN201521004137.0U CN205302320U (en) | 2015-12-08 | 2015-12-08 | Fingerprint identification device |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106127174A (en) * | 2016-06-30 | 2016-11-16 | 北京小米移动软件有限公司 | fingerprint identification method and device |
| CN106203301A (en) * | 2016-06-30 | 2016-12-07 | 北京小米移动软件有限公司 | Terminal unit, fingerprint identification method and device |
| CN106250883A (en) * | 2016-08-26 | 2016-12-21 | 广东欧珀移动通信有限公司 | Pressure fingerprint identification method, device and terminal unit |
| CN107578242A (en) * | 2016-07-05 | 2018-01-12 | 恩智浦有限公司 | Fingerprint sensing system and method |
| US10565423B2 (en) | 2017-09-26 | 2020-02-18 | Chipons Technology (Beijing) Co., Ltd. | Detection method and device used in fingerprint identification system |
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2015
- 2015-12-08 CN CN201521004137.0U patent/CN205302320U/en active Active
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106127174A (en) * | 2016-06-30 | 2016-11-16 | 北京小米移动软件有限公司 | fingerprint identification method and device |
| CN106203301A (en) * | 2016-06-30 | 2016-12-07 | 北京小米移动软件有限公司 | Terminal unit, fingerprint identification method and device |
| CN106127174B (en) * | 2016-06-30 | 2019-06-11 | 北京小米移动软件有限公司 | Fingerprint identification method and device |
| CN107578242A (en) * | 2016-07-05 | 2018-01-12 | 恩智浦有限公司 | Fingerprint sensing system and method |
| CN107578242B (en) * | 2016-07-05 | 2023-07-25 | 恩智浦有限公司 | Fingerprint sensing system and method |
| CN106250883A (en) * | 2016-08-26 | 2016-12-21 | 广东欧珀移动通信有限公司 | Pressure fingerprint identification method, device and terminal unit |
| US10565423B2 (en) | 2017-09-26 | 2020-02-18 | Chipons Technology (Beijing) Co., Ltd. | Detection method and device used in fingerprint identification system |
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