CN103778420A - Fingerprint detection system having automatic gain control function and automatic gain control method thereof - Google Patents
Fingerprint detection system having automatic gain control function and automatic gain control method thereof Download PDFInfo
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Abstract
The invention relates to a fingerprint detection system having an automatic gain control function. The fingerprint detection system comprises a fingerprint sensor which comprises a fingerprint sensing unit array comprising a plurality of sensing units, a rapid scanning control circuit for selecting at least a part of the sensing units in the fingerprint sensing unit array as effective sensing units, a gain control circuit which comprises an ADC (Analog to Digital Converter) array and is used for converting an electric signal into digital fingerprint image information, an image gray value counting unit for counting the gray level distribution information of a fingerprint image, and an adaptive judging circuit for defining the type of the fingerprint image according to the gray level distribution information of the fingerprint image, wherein the gain control circuit is further used for receiving the output of the adaptive judging circuit and adjusting the gain of each effective sensing unit according to the type of the fingerprint image in order to correct the digital fingerprint image information and outputting the corrected information. The fingerprint detection system is wide in application range, high in stability and consistence and low in power consumption.
Description
Technical field
The present invention relates to fingerprint collecting technical field.Especially, the present invention relates to a kind of fingerprint detection system and auto gain control method thereof with automatic gain control.
Background technology
Along with people are more and more higher to the requirement of information security, the authentication of living body biological feature and identification more and more apply in daily life.Finger print identifying, as have very high reliability and cost performance in biological characteristic authentication, has become the main flow of current biological identification.Meanwhile, also high speed development of fingerprint collecting technology, more low cost, more the fingerprint sensor of small size, more low-power consumption and high dynamic range will capture huge market, the fingerprint sensor therefore with above-mentioned advantage becomes the emphasis of current research, and wherein capacitive fingerprint sensing device becomes one of current main product.
Along with the maturation gradually of fingerprint sensing technology, advanced fingerprint sensing technology is applied in cell phone and other electronic products gradually, and Chinese third generation I.D. need to be registered finger print information, fingerprint identification technology can be applied to our daily life very soon and widely, meanwhile, more and more higher to the requirement of fingerprint sensor.A good fingerprint recognition decorum, not only should solve the deficiency that software in fingerprint sensor or hardware aspect exist, more should in the time being applied to special occasions or in the time that special finger occurs, fingerprint image clearly can both be collected, and the deception of prosthetic finger can be effectively refused.
Existing domestic fingerprint sensor, as a kind of prior art scheme only provides a kind of capacitance type fingerprint reading manner, but it is in the time of the fingerprint in the face of dissimilar, its shortcoming is very significant, though the gathering algorithm for dissimilar fingerprint can be embedded to host computer, but this can waste the resource that host computer is very large, improve host computer and used threshold.In other prior art schemes, though thereby have and mention the dissimilar fingerprint of reference voltage self-adaptation of adjusting comparer by adaptive algorithm, not mentioned adaptive algorithm, or setting range is limited.Existing external fingerprint sensor, has though realize the fingerprint collecting that automatic gain changes, gain when it only can adjust analog to digital conversion, and same setting range is limited, and still not good to some specific type fingerprint collecting and recognition effect.
As illustrated in fig. 1 and 2, Fig. 1 illustrates the structure of its sensing cell to the fingerprint sensor that a kind of prior art provides.Sensing cell 10 structures comprise: a sense capacitance 11, is formed with sensing electrode by finger 1; One edge capacitance 12, is formed by the output electrode of sensing electrode and amplifier 13; One amplifier 13, one input ends are connected between sense capacitance 11 and edge capacitance 12, an input end grounding, and output terminal connects edge capacitance 12 other ends; This sensing cell 10 by detect sent by radiofrequency signal 14 through pointing the radiofrequency signal of 1 reflection, this signal after capacitance integral amplifying circuit by the processing of subsequent conditioning circuit (not shown), the radiofrequency signal of different amplitudes detected according to the difference of sense capacitance value, thereby realize fingerprint collecting, this system is because each sensing cell 10 uses an amplifier 13, and its power consumption is very large.
Fig. 2 illustrates the automative interest increasing controlling circuit of above-mentioned sensing cell, and automative interest increasing controlling circuit 2 comprises: multiple sensing cells 10; One scan controller 20; Multiple analog to digital converters (ADC) 21 and digital to analog converter (ADC) 22; One gain process circuit 23; Wherein scanning monitor 20 is read the electric signal that sensing cell 10 is exported continuously, multiple analog to digital converters 21 convert the electrical signal to fingerprint image gray-scale value, the histogram of gain process circuit 23 statistical picture gray-scale values, and according to the output of the multiple digital to analog converters 22 of statistical conditions control of histogram, thereby regulate gain VOFFSET and the direct current biasing VREF of multiple analog to digital converters 21.The method is owing to only controlling the gain of ADC21, and its range of adjustment is limited, can not distinguish paddy and the ridge of fingerprint in some application scenario.
In the personal identification of fingerprint and a lot of application of identification, expect to have larger progress, however unfortunately current fingerprint sensor and the circuit relevant to them too large and expensive, brought instability to fingerprint recognition on the one hand; On the other hand, the fingerprint image that conventional fingerprint sensor collects is along with the difference of individual fingerprint and gather the difference of environment, changes also very greatly, and recognizer is had to harsh requirement; In addition, the variation of manufacturing process also causes the inconsistency of the sensor of producing.
Therefore, those skilled in the art expect to obtain a kind of applied widely, good stability and high conformity, fingerprint detection system low in energy consumption.
Summary of the invention
One object of the present invention is to provide a kind of applied widely, good stability and high conformity, fingerprint detection system low in energy consumption.
For achieving the above object, the invention provides a kind of technical scheme as follows:
A fingerprint detection system with automatic gain control, comprising: fingerprint sensor, and it comprises fingerprint sensing cell array, fingerprint sensing cell array comprises multiple sensing cells; Rapid scanning control circuit, for selecting at least a portion sensing cell of fingerprint sensing cell array as effective feeling measurement unit, for sensing finger fingerprint and be converted to electric signal; Gain control circuit, it comprises an ADC array, for converting the electrical signal to digital information in fingerprint; Gradation of image Data-Statistics unit, for adding up the intensity profile information of fingerprint image; Adaptive judgement circuit, it receives the output of gradation of image Data-Statistics unit, for according to the type of this fingerprint image of intensity profile information definition of fingerprint image; Wherein, gain control circuit is also received from the output that adapts to decision circuitry, and according to the gain of the each effective feeling measurement unit of the type adjustment of fingerprint image, digital information in fingerprint is revised and output subsequently.
Preferably, it also comprises a digital reference voltage source, and it provides the reference voltage level of different range according to the type of fingerprint image to ADC array, to regulate the digital information in fingerprint of ADC array output.
Preferably, each sensing cell at least comprises: a sensing electrode, at least one gain electrode, at least one reference electrode pair, on-off circuit and sensing cell control circuit, at least one reference electrode is to being formed as respectively two electrodes of at least one reference capacitance, sensing electrode with press on finger type on sensing electrode and become two electrodes of a sense capacitance, sensing electrode and at least one gain electrode are formed as respectively two electrodes of at least one gain capacitances, sensing cell control circuit by on-off circuit control following any or appoint the charge/discharge state of multiple electric capacity: sense capacitance, at least one reference capacitance, and, at least one gain capacitances.
Preferably, gain control circuit also comprises reference capacitance sequential control circuit and gain capacitances sequential control circuit, reference capacitance sequential control circuit sends the first timing control signal to the sensing cell control circuit of each effective feeling measurement unit respectively, with by the charge/discharge state of on-off circuit control reference capacitance; Gain capacitances sequential control circuit sends the second timing control signal to the sensing cell control circuit of each effective feeling measurement unit respectively, to pass through the charge/discharge state of on-off circuit ride gain electric capacity.
Preferably, gain electrode is multiple, wherein, some gains electrode in multiple gain electrodes is connected with a set potential, all the other gain electrodes in multiple gain electrodes connect respectively the sensing cell control circuit of each effective feeling measurement unit, sensing cell control circuit receives the second timing control signal, and the number that is connected and fixed current potential or is connected the gain electrode of sensing cell control circuit by change regulates the gain of sensing cell.
Another object of the present invention is to provide a kind of auto gain control method of fingerprint detection system, its applied widely, good stability.
For achieving the above object, the invention provides another technical scheme as follows:
A kind of auto gain control method of fingerprint detection system, for information in fingerprint is revised, information in fingerprint is obtained by fingerprint detection system sensing finger fingerprint, the method comprises the steps: a), passes through multiple sensing cells continuously by finger print information switching electrical signals, converts electrical signals to fingerprint image with ADC array; B), the intensity profile information of statistics fingerprint image; C), according to the type of the intensity profile information definition fingerprint image of fingerprint image; D), according to the reference voltage level of the gain of the each sensing cell of type adjustment of fingerprint image and/or input ADC array, information in fingerprint is revised and output subsequently.
Fingerprint detection system and the auto gain control method thereof with automatic gain control provided by the invention, can be by analyzing the half-tone information of fingerprint image, and correspondingly control the charge/discharge state of sense capacitance, reference capacitance and/or gain capacitances, and then regulating the gain of each effective feeling measurement unit, the scope that its self-adaptation is adjusted is larger; In different environment, under the input of dissimilar fingerprint and different preparation technology, collection and the recognition effect of this fingerprint detection system to fingerprint image is good, this fingerprint detection system is applied widely, good stability and high conformity, low in energy consumption, and that this auto gain control method is implemented is simple, be adapted at applying in this area.
Accompanying drawing explanation
Fig. 1 illustrates the structural representation of the sensing cell of a fingerprint sensor in prior art;
Fig. 2 illustrates the circuit diagram of the automative interest increasing controlling circuit of above-mentioned fingerprint sensor;
Fig. 3 illustrates the structural representation of the fingerprint sensor of one embodiment of the invention;
Fig. 4 illustrates the structural representation of sensing cell in above-described embodiment;
Fig. 5 illustrates the circuit diagram of automative interest increasing controlling circuit in above-described embodiment;
Fig. 6 A illustrates the dry finger print image collecting while closing automatic gain control;
Fig. 6 B illustrates the dry finger print image collecting while opening automatic gain control;
Fig. 6 C illustrates the wet finger print image collecting while closing automatic gain control;
Fig. 6 D illustrates the wet finger print image collecting while opening automatic gain control.
Embodiment
In the following detailed description, the preferred embodiments of the present invention have only been described by reference to the accompanying drawings.But should be understood that in the situation that not departing from inventive concept and can make various deformation designs.
A kind of fingerprint detection system with automatic gain control that one embodiment of the invention provides, comprises as lower module: fingerprint sensor, rapid scanning control circuit, gain control circuit, gradation of image Data-Statistics unit and adaptive judgement circuit.Wherein, fingerprint sensor comprises fingerprint sensing cell array, and fingerprint sensing cell array comprises multiple sensing cells; Rapid scanning control circuit is for selecting at least a portion sensing cell of fingerprint sensing cell array as effective feeling measurement unit, for sensing finger fingerprint and be converted to electric signal; Gain control circuit comprises an ADC array, for converting the electrical signal to digital information in fingerprint; The intensity profile information of gradation of image Data-Statistics unit for adding up fingerprint image; Adaptive judgement circuit receives the output of gradation of image Data-Statistics unit, for according to the type of this fingerprint image of intensity profile information definition of fingerprint image; Wherein, gain control circuit also receives the output of gradation of image Data-Statistics unit, and according to the gain of the each effective feeling measurement unit of the type adjustment of fingerprint image, digital information in fingerprint is revised and output subsequently.
According to a kind of embodiment of this embodiment, as shown in Figure 3, fingerprint sensor comprises antenna metal frame 33, and its transmitting gathers the required radiofrequency signal of fingerprint and this fingerprint detection system being integrated on a chip carried out to esd protection simultaneously; One prosthetic finger detecting electrode 31, for detection of prosthetic finger, prevents prosthetic finger fraud system; The megohmite insulant 32 of isolated antennas metal frame 33 and prosthetic finger detecting electrode 31; One fingerprint sensing cell array 35, it comprises multiple sensing cells 351; Sensor surface megohmite insulant 34, is formed as finger contact face; And other fingerprint collecting interlock circuit (not shown).The version providing in other prior aries can also be provided fingerprint sensor.
According to this embodiment, as shown in Figure 4, in fingerprint sensing cell array, each sensing cell 351 comprises: the sensing electrode 401 that formed by the top-level metallic of integrated circuit technology, by the layer of metal of other level of integrated circuit technology or multiple gain electrodes 41 that multiple layer metal forms, a reference electrode to, multiple on-off circuit 421,422,423,424 and sensing cell control circuit and radio-frequency (RF) driver circuit 45.Wherein, reference electrode to and electrode pair in the middle of insulation course be formed as reference capacitance 43; Sensing electrode 401 tops are equipped with sense capacitance insulation course, passivation insulation on its top-level metallic that comprises integrated circuit technology and polyester complexes insulation course, sensing electrode 401 is formed as sense capacitance 40 with finger and the sense capacitance insulation course pressed thereon; Gain electrode 41 is multiple, wherein, a part of gain electrode is connected with a set potential, all the other gain electrodes connect respectively the sensing cell control circuit of each sensing cell 351, sensing cell control circuit receives the second timing control signal, and the number that is connected and fixed current potential or is connected the gain electrode of sensing cell control circuit by change regulates the gain of sensing cell 351.
Further, gain electrode 41 is five, be respectively first, second, the 3rd, the the 4th and the 5th gain electrode, first, second, the 3rd, the the 4th and the 5th gain electrode is formed as first with sensing electrode respectively, second, the 3rd, two electrodes of the 4th and the 5th gain capacitances, wherein, the first gain electrode is connected with direct voltage source 441 positive poles, the second gain electrode is connected with these direct voltage source 441 negative poles, the 3rd, the clock signal that the 4th and the 5th gain electrode transmits according to sensing cell control circuit 45 respectively changes corresponding gain capacitances 413, 414, 415 charge/discharge state, and then change the 3rd, the the 4th and the 5th gain capacitances 413, 414, 415 capacitance.On-off circuit 422,424 is connected with direct voltage source 442,443 respectively, to control the charge/discharge of corresponding capacitance.
The insulation course of sensing electrode 401 respectively and between first, second, third, fourth and fifth gain electrode and corresponding two electrodes is formed as five gain capacitances 411,412,413,414,415, by changing the control sequential of the plurality of gain electrode, can realize the sensing cell 351 of gain programmable; Multiple on-off circuits 421,422,423,424 ride gain electric capacity 411,412,413,414,415 discriminably, and the charge/discharge state of sense capacitance 40 and/or reference capacitance 43.Opening/closing of on-off circuit 421,422,423,424 moved by the control of sensing cell control circuit, the transmitting of radio-frequency (RF) driver circuit control radiofrequency signal 14.
In the time that finger 1 is placed on sensing cell array 35, input the first pulse signal to sensing cell array 35, this pulse signal charges to the programmable reference capacitance 43 in each sensing cell 351 selected in this sensing cell array 35 during pulse width, make these reference capacitance 43 two ends accumulate certain quantity of electric charge, input afterwards the second pulse signal to sensing cell array 35, sensing electrode 401 in this each selected sensing cell 351 of this pulse enable signal is charged to a certain fixed voltage, make the gain electrode 41 in this each selected sensing cell 351 discharge into a certain fixed voltage, launch a radio-frequency (RF) pulse signal 14 with this while antenna metal frame 33, it is even zero that sensing electrode 401 is reduced with the quantity of electric charge at finger 1 electrode two ends, then input the 3rd pulse signal to sensing cell array 35, fractionated gain electrode 41 in this each selected sensing cell 351 of this pulse enable signal is charged to a certain voltage, make reference capacitance 43 and sense capacitance 40 and gain capacitances 411 in this each selected sensing cell 351 simultaneously, 412, 413, 414, 415 carry out equalizing charge, the quantity of electric charge at these reference capacitance 43 two ends is reduced, then input the second pulse signal of fixed cycles number of times and the 3rd pulse signal to sensing cell array 35, the voltage difference at reference capacitance 43 two ends in this each selected sensing cell 351 is successively reduced, after circulation finishes, the voltage difference at these reference capacitance 43 two ends is locked and output to ADC array, ADC array converts this voltage differential signal to fingerprint image gray-scale value, this fingerprint image gray-scale value is input in shift LD impact damper.
As shown in Figure 5, according to this embodiment, the circuit of automative interest increasing controlling circuit comprises: a gradation of image Data-Statistics unit 50, an adaptive judgement circuit 51, digital reference voltage source 54, a programmable gain control circuit and a buffer unit 56, a rapid scanning control circuit 57, fingerprint sensing cell array 35.Gain control circuit at least comprises ADC array 55, and it converts the electrical signal to digital information in fingerprint.
Wherein, rapid scanning control circuit 57 selects the K(K of two-dimentional fingerprint sensing cell array 35 to be greater than 0 positive integer) go as the effective surveyed area in automatic gain control process, effectively the capable sensing cell 351 of K converts sensing electrode 401 and sensing 40 electric capacity that finger 1 forms to electric signal, and invalid (not selected) sensing cell 351 will be in off working state.Wherein effectively surveyed area can be made up of by capable sensing cell continuous K, also can be made up of the capable sensing cell of the K being interrupted.
Wherein, the intensity profile information of the fingerprint image in buffer unit 56 is added up in gradation of image Data-Statistics unit 50, and offers adaptive judgement circuit 51, and adaptive judgement circuit 51 is according to the type of this fingerprint image of intensity profile information definition of fingerprint image.Digital reference voltage source 54 is able to programme, and it provides the reference voltage level of different range according to the type of fingerprint image to ADC array 55, thus the digital information in fingerprint of adjustable ADC array 55 final outputs.
It should be noted that, in the present invention, the type of fingerprint image includes but not limited to: wet fingerprint image, dry fingerprint image.
According to this embodiment, gain control circuit is also received from the output that adapts to decision circuitry 51, according to the gain of the each effective feeling measurement unit 351 of the type adjustment of fingerprint image, digital information in fingerprint is revised and exported external data interface to by ADC array 55 subsequently.
Particularly, except ADC array 55, gain control circuit also comprises reference capacitance sequential control circuit 52, gain capacitances sequential control circuit 53.Reference capacitance sequential control circuit 52 sends the first timing control signal to the sensing cell control circuit of each effective feeling measurement unit 351 respectively, to control the charge/discharge state of reference capacitance 43 by on-off circuit 421,422,423,424; Gain capacitances sequential control circuit 52 sends the second timing control signal to the sensing cell control circuit of each effective feeling measurement unit 351 respectively, to pass through the charge/discharge state of on-off circuit 421,422,423,424 ride gain electric capacity 411,412,413,414,415.The gain of sensing cell 351 is determined jointly by reference capacitance value and gain capacitances value.
Further, the digital information in fingerprint that buffer unit 56 buffer memory ADC arrays 55 are exported first, and offer gradation of image Data-Statistics circuit 50, after gain correction at gain control circuit to each effective feeling measurement unit 351 locking, more finally exported through revised digital information in fingerprint to external data interface by ADC array 55.
Further, fingerprint image gray-scale value statistical circuit 50 comprises: the capable fingerprint image gray-scale value of a statistics K is greater than or less than the statistical circuit of the number of a certain specific gray value; The capable fingerprint image gray-scale value of one statistics K is greater than or less than the statistical circuit of the summation of all fingerprint image gray-scale values of a certain specific gray value; The statistical circuit of the standard variance of the capable fingerprint image gray-scale value of one statistics K; The information of these 3 kinds of statistical circuit gained will send adaptive judgement circuit 51 in the lump to, for the type that defines or judge fingerprint image.
In above-described embodiment, gain control circuit is realized gain capacitances 411,412,413,414,415, and comprehensive control of the charge/discharge state of sense capacitance 40 and/or reference capacitance 43, and then can regulate the gain of each sensing cell 351 on a large scale.Wherein, each sensing cell 351 does not use amplifier, thereby has reduced the power consumption of fingerprint detection system.
Fig. 6 A, Fig. 6 B illustrate respectively the dry finger print image collecting while closing and open automatic gain control; Fig. 6 C, Fig. 6 D illustrate respectively the wet finger print image collecting while closing and open automatic gain control.
Visible, in different environment, under the input of dissimilar fingerprint and different preparation technology, the collection of this fingerprint detection system with automatic gain control to fingerprint image and recognition effect is good, applied widely, good stability and high conformity.
Another embodiment of the present invention provides a kind of auto gain control method of fingerprint detection system, and for information in fingerprint is revised, information in fingerprint is obtained by fingerprint detection system sensing finger fingerprint, and the method comprises the steps:
A), by multiple sensing cells continuously by finger print information switching electrical signals, convert electrical signals to fingerprint image with ADC array;
B), the intensity profile information of statistics fingerprint image;
C), according to the type of the intensity profile information definition fingerprint image of fingerprint image;
D), according to the reference voltage level of the gain of the each sensing cell of type adjustment of fingerprint image and/or input ADC array, information in fingerprint is revised and output subsequently.
Wherein, step b) can specifically comprise: in statistics fingerprint image, gray-scale value is greater than or less than the number of pixels of first threshold; In statistics fingerprint image, gray-scale value is greater than or less than the gray-scale value sum of the pixel of Second Threshold; The pixel standard variance of statistics fingerprint image.Wherein, described first, second threshold value is set by host computer by user.
Further, in this embodiment, according to the judged result of adaptive judgement circuit 51, if the fingerprint image half-tone information of current statistics is in a certain state, define fingerprint image and belong to the first kind, the now gain of locking pin to each sensing cell the reference voltage level of locking input ADC array, thereby the output of locking gain control circuit, then exit gain control process, output information in fingerprint, if fingerprint image half-tone information is in being different from another state of above-mentioned state, define fingerprint image and belong to Second Type, now first regulate the input reference voltage value of ADC array 55 by digital reference voltage source 54, make the input reference voltage value of ADC array 55 increase X step-length or reduce X step-length, in the time that the input reference voltage value of ADC array 55 is adjusted to its maximum set value or minimum setting value, start by reference to electric capacity sequential control circuit 52, gain capacitances sequential control circuit 53 regulates the gain of effective feeling measurement unit 351, make the gain of sensing cell 351 increase Y step-length or reduce Y step-length, in the time that being adjusted to its maximum set value or minimum setting value, sensing cell gain locks the output of gain control circuit, then exit gain control process, output information in fingerprint.Wherein X, Y is more than or equal to 1 integer.
This auto gain control method, by analyzing the half-tone information of fingerprint image, and correspondingly control the charge/discharge state of sense capacitance, reference capacitance and/or gain capacitances, and then regulate the gain of each effective feeling measurement unit, the scope that its self-adaptation is adjusted is larger, thereby make fingerprint detection system be suitable for using in multiple environment, occasion, and it is implemented simply, is adapted at applying in this area.
Although shown in the present invention preferred embodiment, those of ordinary skill in the art can understand, and based on thought of the present invention, can make various interchangeable and/or equivalent deformation designs, and not deviate from scope of the present invention.
Claims (10)
1. a fingerprint detection system with automatic gain control, comprising:
Fingerprint sensor, it comprises fingerprint sensing cell array, described fingerprint sensing cell array comprises multiple sensing cells;
Rapid scanning control circuit, for selecting at least a portion sensing cell of described fingerprint sensing cell array as effective feeling measurement unit, for finger print described in sensing and be converted to electric signal;
Gain control circuit, it comprises an ADC array, for converting described electric signal to digital information in fingerprint;
Gradation of image Data-Statistics unit, for adding up the intensity profile information of described fingerprint image;
Adaptive judgement circuit, it receives the output of described gradation of image Data-Statistics unit, for according to the type of this fingerprint image of intensity profile information definition of described fingerprint image;
Wherein, described gain control circuit also receives the output of described adaptive judgement circuit, and according to the gain of the each described effective feeling measurement unit of the type adjustment of described fingerprint image, described digital information in fingerprint is revised and output subsequently.
2. fingerprint detection system according to claim 1, it is characterized in that, it also comprises a digital reference voltage source, and it is according to the type of described fingerprint image, provide the reference voltage level of different range to described ADC array, to regulate the digital information in fingerprint of described ADC array output.
3. fingerprint detection system according to claim 1, it is characterized in that, described each sensing cell at least comprises: a sensing electrode, at least one gain electrode, at least one reference electrode pair, on-off circuit and sensing cell control circuit, described at least one reference electrode is to being formed as respectively two electrodes of at least one reference capacitance, described sensing electrode with press on finger type on described sensing electrode and become two electrodes of a sense capacitance, described sensing electrode and at least one gain electrode are formed as respectively two electrodes of at least one gain capacitances, described sensing cell control circuit is by the charge/discharge state of the following multiple electric capacity of described on-off circuit control:
Described sense capacitance;
At least one described reference capacitance; And,
At least one described gain capacitances.
4. fingerprint detection system according to claim 3, it is characterized in that, described gain control circuit also comprises reference capacitance sequential control circuit and gain capacitances sequential control circuit, described reference capacitance sequential control circuit sends the first timing control signal to the sensing cell control circuit of each described effective feeling measurement unit respectively, with by the charge/discharge state of reference capacitance described in described on-off circuit control; Described gain capacitances sequential control circuit sends the second timing control signal to the sensing cell control circuit of each described effective feeling measurement unit respectively, with by the charge/discharge state of gain capacitances described in described on-off circuit control.
5. fingerprint detection system according to claim 4, it is characterized in that, described gain electrode is multiple, wherein, some gains electrode in described multiple gain electrode is connected with a set potential, all the other gain electrodes in described multiple gain electrode connect respectively the sensing cell control circuit of each described effective feeling measurement unit, described sensing cell control circuit receives described the second timing control signal, and the number that is connected described set potential or connected the described gain electrode of described sensing cell control circuit by change regulates the gain of described sensing cell.
6. fingerprint detection system according to claim 1, it is characterized in that, it also comprises a buffer unit, the digital information in fingerprint of exporting first for ADC array described in buffer memory, and offer described gradation of image Data-Statistics unit, after gain correction at described gain control circuit to described sensing cell locking, described ADC array is exported through revised described digital information in fingerprint.
7. fingerprint detection system according to claim 1, is characterized in that, described gradation of image Data-Statistics unit comprises:
The first statistical circuit, it adds up the number of pixels that gray-scale value in described fingerprint image is greater than or less than first threshold;
The second statistical circuit, it adds up the gray-scale value sum that gray-scale value in described fingerprint image is greater than or less than the pixel of Second Threshold;
The 3rd statistical circuit, it adds up the pixel standard variance of described fingerprint image.
8. an auto gain control method for fingerprint detection system, for information in fingerprint is revised, described information in fingerprint is obtained by described fingerprint detection system sensing finger fingerprint, and described method comprises the steps:
A), by multiple sensing cells continuously by finger print information switching electrical signals, with ADC array, described electric signal is converted to described fingerprint image;
B), add up the intensity profile information of described fingerprint image;
C), according to the type of fingerprint image described in the intensity profile information definition of described fingerprint image;
D), according to the gain of the each described sensing cell of type adjustment of described fingerprint image and/or input the reference voltage level of described ADC array, described information in fingerprint is revised and output subsequently.
9. method according to claim 8, is characterized in that, described step b) specifically comprises:
Add up gray-scale value in described fingerprint image and be greater than or less than the number of pixels of first threshold;
Add up gray-scale value in described fingerprint image and be greater than or less than the gray-scale value sum of the pixel of Second Threshold;
Add up the pixel standard variance of described fingerprint image;
Wherein, described first, second threshold value is set by host computer by user.
10. method according to claim 8 or claim 9, is characterized in that described steps d) specifically comprise:
If the fingerprint image that described step obtains in c) belongs to the first kind, the gain of locking pin to each described sensing cell and input the reference voltage level of described ADC array, then exports described information in fingerprint;
If the fingerprint image that described step obtains in c) belongs to Second Type, first regulate the reference voltage level of the described ADC array of input, make described reference voltage level increase X step-length or reduce X step-length, when described reference voltage level is adjusted to maximal value that user sets or when minimum value, start the gain of metering needle to each described sensing cell, make described gain increase Y step-length or reduce Y step-length, in the time that described gain is adjusted to maximal value or minimum value, lock the value of described gain, then export described information in fingerprint; Wherein X, Y is more than or equal to 1 integer.
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Cited By (26)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104318222A (en) * | 2014-11-14 | 2015-01-28 | 深圳市汇顶科技股份有限公司 | Detection method and device used for detecting fingerprints |
| CN105205440A (en) * | 2015-02-13 | 2015-12-30 | 比亚迪股份有限公司 | Data processing method for fingerprint sensor and electronic device |
| CN105335739A (en) * | 2015-12-08 | 2016-02-17 | 北京集创北方科技有限公司 | Fingerprint image optimization method |
| CN105335707A (en) * | 2015-10-19 | 2016-02-17 | 广东欧珀移动通信有限公司 | Method and apparatus for acquiring fingerprint image to be identified, and mobile terminal |
| WO2016029346A1 (en) * | 2014-08-25 | 2016-03-03 | 华为技术有限公司 | Fingerprint extraction method and apparatus |
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