CN105469067B - Fingerprint identification dynamic range adjusting method and equipment - Google Patents
Fingerprint identification dynamic range adjusting method and equipment Download PDFInfo
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- CN105469067B CN105469067B CN201510890658.9A CN201510890658A CN105469067B CN 105469067 B CN105469067 B CN 105469067B CN 201510890658 A CN201510890658 A CN 201510890658A CN 105469067 B CN105469067 B CN 105469067B
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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
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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
- G06V40/1347—Preprocessing; Feature extraction
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Abstract
The invention provides a dynamic range adjusting method of an analog-digital converter of fingerprint identification sensing equipment and a realizing circuit thereof. The method has the advantages that the system dynamic range can be utilized to the maximum limit through respectively and independently adjusting the gain of a front-end amplifier, and the gain and the offset of the analog-digital converter, so that the contrast of fingerprint images is increased and the identification performance of fingerprint identification is increased. The invention also discloses a gain adjusting method of the analog-digital converter, wherein the gain adjustment is realized through simultaneously and synchronously adjusting the reference voltage of the analog-digital converter. By adopting the method, the dynamic optimization of the input range of the analog-digital converter is realized; the quality of the fingerprint images is improved; the gain adjustment and the offset adjustment of the analog-digital converter are independent of each other and can be respectively and independently realized; and therefore, the adjustment iterations is reduced and the detection time of the fingerprint identification is shortened.
Description
Technical field
The present invention relates to fingerprint recognition and process field, and in particular to a kind of method and apparatus of fingerprint detection identification.
Background technology
Fingerprint detection and technology of identification are a kind of reliable and wide variety of personal identification verification technologies.CMOS fingerprints are known
Individual sensor has the advantages that small volume, low in energy consumption, module are frivolous, disclosure satisfy that field of mobile terminals to miniaturization, low-power consumption
Requirement, therefore be widely used in portable mobile apparatus, such as mobile phone, tablet device, PAD etc..Capacitance type fingerprint identification is passed
Sensor has the fingerprint sensing pixel electrode array being made up of multiple electrodes, and it can respond the drive signal of drive circuit, and
Change based on electrode capacitance produces induced signal, at finger touching sensor surface, induction electrode and Fingers wrinkle ridge and
The electric capacity formed between fingerprint valley is different.Electric capacity between each pixel finger sensing of sensor circuit and induction electrode
Variable quantity, is translated into the variable quantity of the signal of telecommunication, and is converted to the numeral containing half-tone information through analog-digital converter (ADC)
Signal, fingerprint image is formed Jing after subsequent treatment.
The size of the capacitance that fingerprint ridge and fingerprint valley and induction electrode are formed depends on medium between finger and sensor
Thickness and dielectric constant.The electric capacity is less than 1fF, therefore fingerprint ridge and fingerprint valley and induction electrode shape in the case of being normally applied
Into capacitance change can be less.This means that fingerprint Identification sensor needs that the very little signal of difference is amplified and distinguished
Out, and system need have higher output signal dynamic range.Sensor output data possesses higher dynamic range,
The fingerprint image that recovery is obtained possesses higher contrast, and fingerprint identification method is easier matching identification, with higher identification
Precision.
Generally speaking input signal (capacitance corresponding to being formed between the finger and induction electrode) Jing of sensor is sensed
Output signal range after device amplifying circuit can be much smaller than the input dynamic range of the analog-digital converter of rear class, it is impossible to fully sharp
With the full range of analog-digital converter.If do not process be adjusted to dynamic range, the fingerprint image of collection occurs
The defect of poor contrast, causes to affect the reduction of fingerprint recognition accuracy rate.
Therefore, existing fingerprint Identification sensor needs to do optimization processing to Dynamic Range, by adjusting parameter, to the greatest extent
Input signal may be caused to reach the full scale of analog-digital converter.Make full use of the input dynamic model of system and analog-digital converter
Enclose, improve the total quality of collection image.
Existing analog-digital converter has the disadvantage that：Generally for the common mode inhibition of the system of raising, analog-digital converter
(ADC) differential architecture is typically adopted, the reference voltage of such as analog-digital converter is VREFH, then analog-digital converter (ADC) it is defeated
Enter dynamic range for [- VREFH, 0] and [0, VREFH].Fingerprint recognition sensing equipment is exported after front-end amplifier amplification
Signal to analog-digital converter is on the occasion of therefore for fingerprint equipment itself, it is only necessary to analog-digital converter (ADC) it is positive defeated
Enter scope [0, VREFH].Therefore when the picture quality of the GTG of system requirements 256, ADC needs the precision of 9-bit.Should be noted
, this specification form of " [lower limit, the upper limit] " represents a certain scope, and the scope includes endpoint value.
The multiple parameters of existing fingerprint sensor apparatus circuit all can dynamic range generation impact.Such as frontend amplifying circuit
The gain of (one-level is multistage), the gain of analog-digital converter and side-play amount.There is dependence in the adjustment of these variables.
Fig. 1 is that analog-digital converter of the prior art (ADC) input signal with output digital code (i.e. believe by numeral output
Number) between transformational relation.Transformation curve can be understood as table below up to formula：
Code=Aadc(Vin+Soffset)；
Wherein code is the numeral output of the lower ADC of different inputs, AadcFor the gain of analog-digital converter, VinRepresent that ADC's is defeated
Enter component, Soffset is side-play amount.The gain A of analog-digital converteradcChange the slope of transformation curve, offset parameter
Soffset translates curve.
It will be seen from figure 1 that in the case where side-play amount is 0, the intersection point of the transformation curve under different gains adjustment is defeated
Enter the position that signal is 0.The input dynamic range of analog-digital converter (ADC) is [- VREFH, 0] and [0, VREFH]。
By taking the gain of analog-digital converter and side-play amount adjustment as an example, when only using positive input range [0, VREFH] when,
As shown in figure 1, the gain of digital to analog converter can affect the slope of transformation curve, and side-play amount understands the relative position of influence curve.
When there is constant offset amount, the intersection point of the transformation curve under different gains adjustment is no longer in the position that input signal is 0.Skew
The impact measured to exporting is closely related with the gain of analog-digital converter.When the gain of system digital to analog converter changes, partially
Shifting amount also can change with the change of gain.Therefore, in existing fingerprint sensing identification equipment, analog-digital converter dynamic model
The adjustment enclosed is present needs repeated multiple times iteration adjustment, causes inefficiency, or the problem that cannot find optimal setting.
The content of the invention
The present invention for existing fingerprint recognition sensing equipment exist defect, it is proposed that a kind of fingerprint recognition sensing equipment and
Dynamic range method of adjustment, the method for adjustment and concrete grammar that can simplify dynamic range realizes process, reduces and changes repeatedly
The number of times in generation, so as to improve the response speed and identification performance of fingerprint recognition.
The fingerprint recognition sensing equipment includes a fingerprint sensing pixel electrode array, and for driving the array
Drive circuit, and front end input amplifier (AMP), it is used to receiving and amplifying the mould of fingerprint sensing pixel electrode array output
Intend signal, and send the signal after amplification to analog-digital converter.
Fingerprint recognition sensing equipment proposed by the present invention, also includes the analog-digital converter with scalable dynamic range
(ADC), the analog-digital converter is used to for the signal after front-end processing to be converted to a range of digital signal.
The present invention proposes a kind of fingerprint recognition sensing equipment dynamic range method of adjustment and related realization circuit.The method
By the design to analog-digital converter, respectively the gain to analog-digital converter and side-play amount carry out independent adjustment.
The present invention is proposed in a kind of fingerprint recognition sensing equipment dynamic range method of adjustment, and analog-digital converter has reference
Voltage, the adjustment of gain realizes that analog-digital converter includes a comparator, the tune of side-play amount by adjusting its reference voltage level
The whole common mode reference voltage by adjusting comparator differential input end is realized.
The present invention propose for fingerprint recognition sensing equipment dynamic range method of adjustment, can adjust front end input put
The gain of big device.
The present invention proposes a kind of fingerprint recognition sensing equipment dynamic range adjustment circuit, and it includes front-end amplifier, mould
Number converter, data processing module and dynamic range adjustment module.
Dynamic range method of adjustment proposed by the present invention, is carried out solely by the Gain tuning and side-play amount to analog-digital converter
Vertical adjustment, it is possible to use offset parameter and Gain tuning parameter are input into dynamic model using analog-digital converter ADC to greatest extent
Enclose, according to different fingerprints and the dynamics real-time regulating system parameter of pressing, obtain optimum picture quality.This method eliminates
Dependence in prior art between analog-digital converter gain and side-play amount, after offset parameter has been adjusted, gain parameter
Change do not interfere with the meansigma methodss of image output, so as to without the need for carrying out readjusting for offset parameter again, reduce method
Iterationses, shorten the time of system fingerprint detection.
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 operation principle of fingerprint recognition sensing equipment proposed by the present invention.
Fig. 3 shown in fingerprint recognition sensing equipment dynamic range method of adjustment proposed by the present invention, the adjustment of ADC gains
Method.
Principle when Fig. 4 shows that fingerprint recognition sensing equipment proposed by the present invention is applied to suppression system common-mode noise
Figure.
Fig. 5 shows that the method for fingerprint recognition sensing equipment dynamic range adjustment proposed by the present invention realizes flow process.
Specific embodiment
The detailed content of the present invention will in the examples below combine accompanying drawing and be described in detail.However, the present invention has
Various different implementations, it should not be seen as limited by several embodiments cited below.Hereinafter preferably implement
Example is provided for explaining, clarifies invention.
Fig. 2 shows one embodiment of fingerprint recognition sensing circuit proposed by the present invention, and it includes amplifier AMP, mould
Number converter ADC, data processing module and dynamic range adjustment module, amplifier AMP is front end input amplifier, realizes electricity
Hold the conversion of the signal of telecommunication, and signal is amplified.AMP can be single-stage, it is also possible to be formed by multi-stage cascade.ADC is mould
Number converter, completes the conversion of analog electrical signal to digital component.Data processing module is used to for ADC output signal to be converted to one
Fixed luma data, by the output data to ADC appropriate dynamic adjustment is carried out, and is shown with the GTG of adaptive system and is required.
The output data of dynamic range method of adjustment module receiving data processing module go forward side by side Mobile state scope adjustment, the increasing to amplifier
Beneficial Aamp, the gain A of analog-digital converteradc, offseting Soffset carries out independent adjustment.In general fingerprint recognition application, the essence of ADC
Spend for 8-10bit.As shown in figure 1, abscissa is input analogue signal, abscissa is most for the transformation curve of analog-digital converter ADC
Little value-VREFHWith maximum VREFHRepresent the maximum magnitude of input signal.Vertical coordinate is digital defeated for representative simulation semaphore size
Go out code, vertical coordinate minima is 0, and maximum is the maximum that ADC conversion accuracies are allowed, and such as 8bit precision corresponds to 256, correspondence
Coding is represented by 0000...00～code_max (1111...11).Concrete he number is relevant with precision.Transformation curve is oblique
The adjustment of rate means the change of picture contrast.General fingerprint identified input signal scope very little, the increasing to front-end amplifier
Benefit, ADC transformation curve slopes are adjusted the input range that can make full use of ADC, improve overall image quality.
In order to increase the motility of system, the circuit can simultaneously realize gain and the adjustment of side-play amount.It is defeated in identical
In the case of entering, the change in gain corresponding conversion slope of a curve of ADC changes；The side-play amount adjustment corresponding conversion curve of ADC
Translated with fixed slope.Because when Gain tuning is carried out, overall data may be not up to optimum in data dynamic range
When there is data one direction saturation, in such a case, it is possible to pass through adjust analog-digital converter offset parameter translation conversion
Curve, so as to eliminate the phenomenon of data saturation.
ADC Gain tunings and the circuit implementations of side-play amount adjustment will be tied in practice in view of specific adc circuit
Structure, for different adc circuits, the implementation of ADC Gain tunings and side-play amount adjustment difference.The modulus of common ADC
All there is sampling hold circuit in change-over circuit, sampling hold circuit includes sampling capacitance, and circuit will be input into by sampling capacitance
Analog signal sampling keeps, and circuit afterwards carries out quantification treatment to the sampled signal of sampling hold circuit, rather than real
When analogue signal.
Below so that capacitor array electric charge redistributes formula successive approximation analog to digital C (SAR ADC) circuit as an example, illustrate that ADC offsets
The implementation of amount adjustment.Reference voltage defines the input reference signal of ADC.The gain of ADC can be by its reference of adjustment
Voltage realizing, the side-play amount adjustment of ADC can by adjusting ADC in comparator differential input end common mode reference voltage come
Realize.
Fig. 3 is one embodiment of ADC gain adjusting methods proposed by the present invention.ADC has in technical solution of the present invention
Two reference voltage VREFHAnd VREFL, VREFHLevel is higher than VREFL.ADC input reference signals are defined by described two reference voltages.
From figure 3, it can be seen that working as VREFH-VREFLBecome hour, the gain of ADC conversions becomes big；Otherwise the gain of ADC conversions diminishes.Therefore originally
The dynamic range method of adjustment that invention is proposed is by controlling VREFHAnd VREFLValue adjusting the gain of ADC.The method is in adjustment
During ADC gains, to VREFHAnd VREFLIt is simultaneously synchronous to carry out identical step-length, and rightabout adjustment.If i.e. VREFH-VREFLNeed
Reduce voltage variety absolute value delta, the method is designed as：VREFHChange turns to VREFH- Δ/2, VREFLChange turns to VREFL+Δ/2。
From figure 3, it can be seen that by such design, (VREFH+VREFL)/2 remain constant, i.e., under the conditions of different gains, Suo Youzhuan
It is (V that curve is changed in inputREFH+VREFLThe point of)/2 intersects.
By taking 10-bit ADC quantified precisions as an example, it is ten in digital output code that the transformation curve of ADC is positive under different gains
The position of system number 768 is intersected, and negative sense intersects in the position of decimal number 256.Therefore when system finally intercepts positive input model
After exporting after enclosing and by data zooming to 8-bit, all gain adjustment curves will be at the midpoint of out-put dynamic range
The point of decimal number 128 intersects.
Reference voltage VREFHAnd VREFLCan be produced by various modes, such as the mode of electric resistance partial pressure.Producing circuit needs to protect
Both step footpaths of adjustment of card are identical.The adjustment of gain can be set by the control word of depositor.
ADC also includes a comparator, and the adjustment of side-play amount Soffset can pass through adjustment comparator differential input end
Common mode reference voltage is realizing.Comparator differential input end applies different common mode reference voltages, and its pressure reduction is Δ, corresponding number
Word is output as：
Code=((Vin-Δ)/Vrange)*code_max；
Code for analog-digital converter ADC digital output code, wherein V corresponding with digital output signalrangeFor ADC
Input maximum, code_max is numeral output maximum.As can be seen from the above equation, in VrangeIn the case of certain, Δ can make
Whole transformation curve is translated.Common mode reference voltage can be adopted similar to generation VREFHAnd VREFLBleeder circuit, its adjustment
Can be set by the control word of depositor.
With reference to above-mentioned ADC gains and side-play amount adjustment circuit, corresponding Dynamic Range adjustment side proposed by the present invention
Method, 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 increasing of ADC
Benefit is Aadc, side-play amount is adjusted to Soffset, and method is by adjusting Aamp、AadcAnd Soffset is realizing Dynamic Range
Optimization.
Used as one kind application of system detectio, fingerprint recognition testing equipment can also be by way of copped wave to system common-mode
Noise is suppressed, and the embodiment is as shown in Figure 4.System switches the positive V of modulus device for interchanging at the T1 momentINPWith negative sense VINNIt is defeated
Enter, later moment in time T1 and the analog-digital converter of previous moment T0 are exported into poor, then final output is obtained divided by 2.T1 and T0 it
Between be Fixed Time Interval, it to be chosen suppressed according to analog-digital converter framework and system noise and depending on frequency, is typically chosen at
Between the μ s of 100ns～2.In this application, the common mode reference voltage for adjusting side-play amount also carries out positive negative input at the T1 moment
End exchanges.Switch common mode reference voltage to realize the change in the same direction of side-play amount and input signal by positive negative sense simultaneously.By this
The method of kind, the setting of side-play amount is retained in data handling, so as to complete the adjustment function of side-play amount.
Used as a kind of embodiment in actually used, for the method for saving time, method of adjustment can choose certain area
The image in domain is processed, without choosing view picture fingerprint image.
Fig. 5 shows a specific embodiment of dynamic range adjustment side method.Method in Fig. 5 includes following step
Suddenly：
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.Initial value is selected
The maximum parameter setting of Dynamic Range is taken, setting principle is the saturation that data are occurred without when first image acquisition is carried out.
Then, method carries out the adjustment of front-end amplifier gain, and by way of traversal front-end amplifier gain is selected
Optimal value.Collection image, the maximum D of statistical picture dataMAX, minima DMINAnd meansigma methodss Davg, and calculate Range=
DMAX-DMIN, final amplifier gain control word choose that view data scope is maximum and data maximums and minima not less than
The gain of preset threshold range [DL_set, DH_set] is arranged.
Used as another kind of implementation of the present invention, front-end amplifier gain optimal value also can be calculated or tabled look-up by search
Mode obtain.Three of the above implementation traversal, search are calculated and tabled look-up and can be used alone, and also can arbitrarily be combined with each other makes
With..
Subsequently carry out the adjustment of side-play amount.Collection image, the maximum D of statistical picture dataMAX, minima DMINAnd it is flat
Average Davg, by the data of statistics gatherer image the meansigma methodss of image are tried to achieve, by taking 256 gray scale images as an example, method of adjustment
Target is the meansigma methodss of image to be adjusted near the midpoint of data output i.e. decimal number 128.In practical application, can be with
Certain nearby sphere [Davg_H, Davg_L] is chosen centered on point value as adjustment target.If meansigma methodss Davvg ＜
Davg_L, then side-play amount Soffset+1, if meansigma methodss Davg ＞ Davg_H, side-play amount Soffest-1, finally, will be average
Value Davg is adjusted in target zone (Davg_L≤Davg≤Davg_H), i.e., in [Davg_H, Davg_L].
Adjustment equally can be using tabling look-up and/or searching method is carried out.
Finally carry out ADC gain AsadcAdjustment.Adjustment can be using tabling look-up or searching method is carried out.
AadcView data scope is maximum to choose for adjustment target, and this scope can reach the bound of adc data conversion.
Data maximums and minima are arranged not less than the gain of preset threshold range [DL_set, DH_set].Collection image, statistics
The maximum D of view dataMAX, minima DMINAnd meansigma methodss Davg, if DMAX＞ DH_set, or DMIN＜ DLset, then increase
Beneficial Aadc+ 1, final target is to make data maximums DMAXWith minima DMINNot less than threshold range [DL_set, DH_
set]。
Implementing from above example, in dynamic range method of adjustment proposed by the present invention, ADC gain Asadc,
Side-play amount Soffset of ADC and the gain A of amplifierampAdjustment there is the independence on realizing, each other without direct
Affect, it is to avoid in prior art, the adjustment of each circuit parameter variable has the defect of dependence.
After finishing so as to the side-play amount Soffset adjustment that ADC in a particular application, can be worked as, then carry out ADC gain Asadc
And/or the gain A of amplifierampAdjustment, so as to avoid prior art in side-play amount arrange Dynamic Range is born
Face rings, and simplifies adjustment process, improves the response speed and identification performance of fingerprint recognition sensing equipment.
By said method, the gain A of amplifieramp, ADC gain AsadcThe amplification or contracting of Dynamic Range can be realized
It is little, it is actually used in can be by AampCoarse adjustment is set to, by AadcIt is set to fine tuning, it is also possible to by AampFine tuning is set to, by AadcIt is set to thick
Adjust, the two can individually be adjusted or cooperate, so as to obtain to obtain larger range of intense adjustment.
Used as other preferred embodiments of the present invention, the analog-digital converter ADC can be pipeline-ADC, flash
ADC etc., and it is not limited to above type.
Claims (10)
1. the analog-digital converter dynamic range method of adjustment of a kind of fingerprint recognition sensing equipment, can be to the analog-digital converter
The gain A of ADCadcEnter Mobile state adjustment；
The fingerprint recognition sensing equipment includes the analog-digital converter ADC and dynamic range adjustment module of adjustable gain, mould
Number converter ADC is used to for signal after front-end processing to be converted to a range of digital signal, and the analog-digital converter ADC has
Reference voltage, it is used to define the scope of input signal；The method comprises the steps：
First, front-end amplifier gain A is initializedampAnd side-play amount Soffset；
Secondly, front-end amplifier gain A is adjustedamp；
Secondly, analog-digital converter side-play amount Soffset is adjusted according to the meansigma methodss of fingerprint image data, until fingerprint image data
Preset threshold range of the meansigma methodss near the midpoint that adc data is exported in；
After side-play amount Soffset adjustment is finished, the gain A of analog-digital converter is adjustedadc。
2. analog-digital converter dynamic range method of adjustment as claimed in claim 1, the reference voltage includes two, i.e. VREFHWith
VREFL, VREFHWith VREFLThe gain A of difference and analog-digital converteradcInto inverse change, by being adjusted with identical step-length simultaneously
VREFHAnd VREFLValue carry out adjust gain Aadc。
3. analog-digital converter dynamic range method of adjustment as claimed in claim 1, the gain A of the analog-digital converter ADCadc's
Adjustment target is so that chooses the bound that view data scope reaches adc data conversion, maximum DMAXWith minima DMIN
Not less than preset threshold range；The gain A of analog-digital converter ADCadcInitial value setting principle for image acquisition first when do not go out
Existing data saturation.
4. analog-digital converter dynamic range method of adjustment as claimed in claim 1, the gain of the adjustment front-end amplifier AMP
AampThe step of in, calculate and/or select gain A by way of tabling look-up traveling through and/or searching foramp, the front-end amplifier AMP
For amplifying and sending to the analog-digital converter ADC by the analogue signal that fingerprint sensing pixel electrode array is exported.
5. analog-digital converter dynamic range method of adjustment as claimed in claim 1, the change of side-play amount Soffset and input signal
In the same direction.
6. the analog-digital converter dynamic range method of adjustment as described in any one of Claims 1 to 5, the gain A of amplifierampAnd/or
ADC gain AsadcMake coarse adjustment or fine tuning realizes that Dynamic Range is zoomed in or out.
7. a kind of fingerprint recognition sensing equipment, including the analog-digital converter of front-end amplifier AMP, adjustable gain and side-play amount
ADC, data processing module and dynamic range adjustment module, analog-digital converter ADC is used for after front-end amplifier AMP process
Signal is converted to a range of digital signal, and analog-digital converter ADC has reference voltage, and it is used to define input signal
Scope；
The data processing module is used to for analog-digital converter ADC output signal to be converted to fingerprint image data；
The dynamic range adjustment module is used to adjust analog-digital converter side-play amount according to the meansigma methodss of fingerprint image data
Soffset, in the preset threshold range of the meansigma methodss near the midpoint that adc data is exported of fingerprint image data, and
After the side-play amount Soffset adjustment is finished, realize adjusting the gain of analog-digital converter by adjusting the reference voltage level
Aadc。
8. fingerprint recognition sensing equipment as claimed in claim 7, the front end input amplifier AMP is used to receive and amplify to refer to
The analogue signal of stricture of vagina sensing pixels electrod-array output, and send the signal after amplification to analog-digital converter.
9. fingerprint recognition sensing equipment as claimed in claim 7 or 8, the data processing module is used for ADC output signal
Luma data is converted to, Mobile state adjustment is entered to the output data of ADC.
10. fingerprint recognition sensing equipment as claimed in claim 7 or 8, the dynamic range adjustment module can put to front end
The gain A of big device AMPamp, the gain A of analog-digital converteradcIndependent adjustment is carried out respectively with side-play amount Soffset.
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| CN106022271B (en) * | 2016-03-31 | 2020-04-10 | 深圳市奔凯安全技术股份有限公司 | Fingerprint acquisition method |
| CN106355145A (en) * | 2016-08-26 | 2017-01-25 | 广东欧珀移动通信有限公司 | Fingerprint identification method, device and mobile terminal |
| CN109657656B (en) * | 2019-01-31 | 2021-04-09 | 北京集创北方科技股份有限公司 | Fingerprint detection method, fingerprint detection device and mobile terminal |
| CN112580597B (en) * | 2020-12-29 | 2022-10-14 | 深圳贝特莱电子科技股份有限公司 | Device and method for automatically adjusting fingerprint image brightness |
| TWI774196B (en) * | 2021-01-18 | 2022-08-11 | 瑞昱半導體股份有限公司 | Analog front-end circuit capable of dynamically adjusting gain |
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| CN101657969A (en) * | 2007-04-17 | 2010-02-24 | 密克罗奇普技术公司 | Analog-to-digital converter offset and gain calibration using internal voltage references |
| CN102279924A (en) * | 2010-06-11 | 2011-12-14 | 金鹏科技有限公司 | Fingerprint identification system and testing device |
| US8587464B2 (en) * | 2012-01-09 | 2013-11-19 | International Business Machines Corporation | Off-line gain calibration in a time-interleaved analog-to-digital converter |
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