WO2016049984A1 - 指纹识别装置和方法 - Google Patents

指纹识别装置和方法 Download PDF

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Publication number
WO2016049984A1
WO2016049984A1 PCT/CN2014/094725 CN2014094725W WO2016049984A1 WO 2016049984 A1 WO2016049984 A1 WO 2016049984A1 CN 2014094725 W CN2014094725 W CN 2014094725W WO 2016049984 A1 WO2016049984 A1 WO 2016049984A1
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Prior art keywords
fingerprint
analog
digital conversion
signal
conversion module
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PCT/CN2014/094725
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English (en)
French (fr)
Inventor
陈松涛
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深圳市汇顶科技股份有限公司
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Priority to KR1020167022319A priority Critical patent/KR20160108527A/ko
Priority to EP14902933.2A priority patent/EP3203409A4/en
Publication of WO2016049984A1 publication Critical patent/WO2016049984A1/zh
Priority to US15/248,479 priority patent/US20160364597A1/en

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/12—Fingerprints or palmprints
    • G06V40/13—Sensors therefor
    • G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/20—Image preprocessing
    • G06V10/28—Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/96—Touch switches
    • H03K17/962—Capacitive touch switches

Definitions

  • the present invention relates to the field of communications technologies, and in particular, to a fingerprint identification apparatus and method.
  • the convex part is called “ridge” and the concave part is called “valley”.
  • the capacitive fingerprint recognition device uses different sizes of the sensing capacitors corresponding to the "peak” and the “valley” contained in the fingerprint, so the amplitude of the output signal is different under the excitation of the same AC signal, and the "peak” and “valley” are The image information is converted into a corresponding electrical signal.
  • the fingerprint sensing unit extracts the capacitive coupling signal of each pixel point, and then sends it to other parts of the fingerprint identification device for amplification, analog-to-digital conversion, image stitching, etc., and extracts Valid fingerprint information.
  • a non-conductive thick dielectric layer is placed on the surface of the sensor, so the coupling capacitance of the finger to the fingerprint sensing unit is small; The depth is shallow, so the capacitance difference between “peak” and “valley” is also small. This part of the difference information usually only accounts for 1%-3% of the fingerprint information.
  • Chinese Patent Application No. 200510063872.3 discloses a method of implementing a fingerprint sensor using a charge amplifier.
  • the plate of the fingerprint sensing unit needs to adopt a strained film material, and the relative capacitance change of the two films is obtained by using the pressure of the fingerprint depth when touched.
  • strained film materials are costly in process manufacturing and are difficult to implement.
  • the main object of the present invention is to provide a fingerprint identification method and apparatus, which aim to increase the contrast of a fingerprint image at a lower cost, thereby improving the recognition rate of fingerprint recognition.
  • the present invention provides a fingerprint identification apparatus, including a fingerprint acquisition module, an analog-to-digital conversion module, and a control module, which are sequentially connected, and the analog-to-digital conversion module includes a quantized voltage generator that generates a quantized voltage, and the fingerprint
  • the acquisition module is configured to collect fingerprint information
  • the analog-to-digital conversion module is configured to perform analog-to-digital conversion on the fingerprint information and output the quantized fingerprint information data
  • the control module is configured to use the distribution range of the fingerprint information data.
  • the quantization voltage generator is controlled to adjust an output range of the quantized voltage to increase a distribution range of the quantized fingerprint information data.
  • the fingerprint identification device further comprises a common mode voltage generating circuit respectively connected to the fingerprint collecting module and the analog to digital conversion module, wherein the common mode voltage generating circuit is used for coordinating the common mode of the output signal of the fingerprint collecting module.
  • the common mode level of the input signal of the level and analog to digital conversion module is used for coordinating the common mode of the output signal of the fingerprint collecting module.
  • the fingerprint collection module comprises a fingerprint sensing unit, a signal amplifier and a signal enhancement unit connected in sequence, and the signal enhancement unit is connected to the analog to digital conversion module.
  • the analog to digital converter is a ramp analog to digital converter
  • the quantized voltage generator is a ramp generator
  • the signal output by the quantized voltage generator is a single-ended signal or a differential signal.
  • the analog to digital converter is a pipeline analog to digital converter or a successive approximation analog to digital converter.
  • the invention also proposes a fingerprint identification method, comprising the steps of:
  • the fingerprint collection module collects fingerprint information, and outputs the fingerprint information to an analog-to-digital conversion module;
  • the analog-to-digital conversion module generates a quantized voltage to perform analog-to-digital conversion on the fingerprint information, and outputs the quantized fingerprint information data to the control module;
  • the control module sends a quantized voltage adjustment signal to the analog-to-digital conversion module according to the distribution range of the fingerprint information data;
  • the analog to digital conversion module adjusts an output range of the quantized voltage according to the quantized voltage adjustment signal.
  • the fingerprint collection module outputs the fingerprint information to the analog-to-digital conversion module, and further includes:
  • the common mode voltage generating circuit coordinates the common mode level of the output signal of the fingerprint acquisition module and the common mode level of the input signal of the analog to digital conversion module.
  • the analog to digital conversion module generates a quantized voltage by a quantized voltage generator.
  • the analog to digital conversion module is a ramp analog to digital converter, a pipelined analog to digital converter or a successive approximation analog to digital converter.
  • the fingerprint identification device adjusts the quantization voltage range of the analog-to-digital converter according to the distribution range of the currently received fingerprint information data, thereby increasing the distribution range of the subsequent fingerprint information data, and realizing the contrast of the fingerprint image. Dynamic adjustment. By improving the resolution of the fingerprint information analog-to-digital conversion, the contrast and signal-to-noise ratio of the grayscale information of the fingerprint image are improved.
  • the common mode voltage generating circuit coordinates the common mode level of the output signal of the signal enhancement unit of the fingerprint acquisition module and the common mode level of the input signal of the analog to digital conversion module, so that the swing of the fingerprint detection signal reaches the maximum signal pendulum.
  • the amplitude, and the signal swing does not exceed but is closest to the size of the adjusted quantization window, so that the analog to digital conversion module operates in an optimal state.
  • the fingerprint identification device of the invention increases the proportion of the difference information between the "peak” and the "valley” in the fingerprint information quantitative data, that is, enhances the contrast of the "peak” and “valley” images, and significantly improves the imaging. Quality ultimately improves the recognition rate of subsequent fingerprint recognition.
  • the fingerprint identification device of the invention has the following advantages: the circuit is simple, the implementation cost is low, and the imaging consistency is ensured because the implementation form and the working state of the fingerprint sensing unit are not involved, and the medium layer without special performance is improved.
  • the adaptability of the sensor the adjustment of the quantized voltage and the distribution of the fingerprint information data can be dynamically adjusted, the adjustment is quite flexible, and the interference of common mode information between “peak” and “valley” can be avoided to the greatest extent; any analog to digital conversion
  • the device structure can be realized, so the adaptability is good; the processing speed is fast, and the imaging frame rate of the fingerprint recognition device is not reduced.
  • FIG. 1 is a block diagram showing the structure of a first embodiment of a fingerprint identification device of the present invention
  • FIG. 2 is a structural block diagram of a fingerprint collection module in an embodiment of the present invention.
  • FIG. 3 is a schematic circuit diagram of the fingerprint identification device of FIG. 1;
  • Figure 5 is a block diagram showing the structure of a second embodiment of the fingerprint identification device of the present invention.
  • FIG. 6 is a schematic circuit diagram of the fingerprint identification device of FIG. 5;
  • FIG. 7 is a flow chart of a first embodiment of a fingerprint identification method of the present invention.
  • Figure 8 is a flow chart of a second embodiment of the fingerprint identification method of the present invention.
  • the fingerprint identification apparatus includes a fingerprint collection module, an analog-to-digital conversion module, and a control module that are sequentially connected.
  • the fingerprint collection module is configured to collect fingerprint information, as shown in FIG. 2, which includes a fingerprint sensing unit, a signal amplifier, and a signal enhancement unit (or a noise shaping and signal enhancement unit) connected in sequence, and the fingerprint sensing unit is configured to collect fingerprints.
  • the signal amplifier is used to amplify the collected fingerprint information
  • the signal enhancement unit is used for performing noise shaping and signal-to-noise ratio improvement on the fingerprint information
  • the signal enhancement unit includes but is not limited to the following common functional circuits: variable gain amplifier , integrators, low pass filters, and sample and hold circuits, and the signal links they make up.
  • the analog-to-digital conversion module is configured to perform analog-to-digital conversion on the fingerprint information, convert the fingerprint information from the analog signal into a digital signal, the analog-to-digital conversion process is a quantization process, and the analog-to-digital conversion module sends the quantized fingerprint information data to the control module;
  • the analog-to-digital conversion module includes a quantized voltage generator for generating a quantized voltage for analog-to-digital conversion of the fingerprint information, and the signal output by the quantized voltage generator may be a single-ended signal or a differential signal.
  • the type of the analog-to-digital conversion module is not limited, and may be a pipeline analog-to-digital converter, a successive approximation analog-to-digital converter, etc., preferably a ramp analog-to-digital converter, and the quantized voltage generator corresponds to a ramp generator.
  • the ramp analog-to-digital converter has a small area, simple implementation, and good linearity.
  • the control module may be an MCU (Micro Control Unit) for performing certain algorithm processing on the quantized fingerprint information, and finally implementing functions such as fingerprint recognition or detection.
  • the control module of the present invention further controls the quantization voltage generator to adjust the output range of the quantized voltage according to the distribution range of the currently received fingerprint information data, so as to increase the distribution range of the quantized fingerprint information data, thereby improving the contrast of the fingerprint image.
  • the control module outputs a control signal to the quantized voltage generator according to the distribution characteristics of the currently received fingerprint information data, such as a distribution range, and controls the generated quantized reference voltage to adjust the quantized voltage.
  • the output range according to which can dynamically change the FS and LSB of the analog-to-digital converter, and finally realize the dynamic adjustment function of the fingerprint image contrast in the fingerprint recognition device.
  • FS is the effective full-swing input signal amplitude of the analog-to-digital converter
  • LSB is the least significant bit of the quantized output of the analog-to-digital converter, and its value is equal to FS/2 N , where N represents the number of bits of the analog-to-digital converter .
  • the circuit connection diagram of the fingerprint identification device of this embodiment is shown in FIG. 3, wherein the fingerprint sense The unit, the signal amplifier, the signal enhancement unit, the analog-to-digital conversion module and the control module are sequentially connected, wherein the quantization voltage generator in the control module and the analog-to-digital conversion module constitutes a contrast dynamic adjustment loop.
  • the fingerprint sensing unit When the finger touches the sensor surface of the fingerprint identification device, the fingerprint sensing unit outputs sampling information of the fingerprint path information, that is, fingerprint information, and then the fingerprint information is amplified by the signal amplifier and output to a subsequent signal enhancement unit for further noise suppression and The signal-to-noise ratio is improved, and the common mode level of the signal is transformed as needed to facilitate subsequent processing.
  • the fingerprint signal enhanced by the signal enhancement unit is transmitted to the analog-to-digital conversion module, and after the analog-to-digital conversion, the digital codeword signal ADC_OUT ⁇ N:1> is output, and the quantized fingerprint information is obtained, and finally the fingerprint information is performed by the control module.
  • a certain algorithm is processed to finally realize functions such as fingerprint recognition or detection.
  • the control module may generate the quantized voltage adjustment signal according to the range of the fingerprint information data distribution of the previous frame, thereby changing the output range of the quantized voltage of the quantized voltage generator inside the analog-to-digital conversion module, and then controlling Under the control of the module, the sampling of the next frame of fingerprint information is started for the same finger part.
  • the initial analog-to-digital conversion reference voltage of the analog-to-digital conversion module is V1
  • its corresponding quantization window is [V0-V1, V0+V1]
  • the fingerprint information voltage distributed in the quantization window range will be quantized to a range of 0 ⁇ .
  • the increment of "1" for the quantized data corresponds to an increase of the original signal voltage before conversion (2 ⁇ V1)/10000.
  • the fingerprint information data distribution range is 5500-7000 after quantization; the voltage corresponding to the original fingerprint information, that is, the quantized voltage signal range is:
  • the quantization window Before quantizing the fingerprint information collected again in the same part of the finger, the quantization window can be adjusted to [V0, V0+0.5*V1], that is, the electric signal voltage distribution range corresponding to the actual fingerprint information is slightly larger. Because the following two relationships are established:
  • the distribution of fingerprint information data after quantization is 2000-8000, that is, the distribution range of the second quantized data of the same fingerprint information is increased to 4 times before the adjustment.
  • the range of the quantized voltage is negatively correlated with the distribution range of the fingerprint information data, and the distribution range of the fingerprint information data can be improved by reducing the range of the quantized voltage, thereby improving the contrast of the fingerprint image.
  • the quantized voltage output range of the quantized voltage generator inside the analog-to-digital conversion module is reduced to 1/X of the original range, the contrast of the obtained second frame fingerprint information is increased to the log 2 of the contrast of the first frame fingerprint information. (X) times, in general, the signal-to-noise ratio is also increased to log 2 (X) times of the first frame, so the image quality will be greatly optimized.
  • the fingerprint information sensed by the subsequent signal amplification and enhancement processing is recorded as V INXB , and the fingerprint information sensed by the fingerprint sensing unit B is simulated .
  • the digital code word obtained after the number conversion is ADC_OUT 1B , then there are:
  • the fingerprint information obtained by the two adjacent fingerprint sensing units A and B can be quantized and the digital code word difference is
  • the quantized voltage output range of the ramp generator inside the ramp analog-to-digital converter is adjusted to ⁇ V SET2 , then the fingerprint information sensed by the fingerprint sensing unit A is followed.
  • the signal after signal amplification and enhancement processing should still be V INXA .
  • the digital code word obtained by analog-to-digital conversion of the fingerprint sensing information sensed by the fingerprint sensing unit A is ADC_OUT 2A , then:
  • the fingerprint information sensed by the subsequent signal amplification and enhancement processing is recorded as V INXB , and the fingerprint information sensed by the fingerprint sensing unit B is simulated .
  • the digital code word obtained after the number conversion is ADC_OUT 2B , then there are:
  • the fingerprint information obtained by the two adjacent fingerprint sensing units A and B can be quantized and the digital code word difference is
  • FIG. 5 and FIG. 6 a second embodiment of the fingerprint identification device of the present invention is presented.
  • This embodiment and the An embodiment differs in that a common mode voltage generating circuit is added.
  • the common mode voltage generating circuit is respectively connected to a fingerprint collecting module and an analog to digital conversion module for coordinating the common mode level and analog to digital conversion module of the output signal of the fingerprint collecting module.
  • the circuit diagram of the fingerprint identification device of this embodiment is shown in FIG. 6 , wherein the fingerprint sensing unit, the signal amplifier, the signal enhancement unit, the analog-to-digital conversion module and the control module are sequentially connected, and the common mode voltage generating circuit is respectively connected to the fingerprint collection module.
  • Signal enhancement unit and analog to digital conversion module are sequentially connected, and the common mode voltage generating circuit is respectively connected to the fingerprint collection module.
  • the fingerprint identification device adjusts the quantized voltage range of the analog-to-digital converter according to the distribution range of the current frame fingerprint information data, thereby further increasing the distribution range of the fingerprint information data of the next frame.
  • a dynamic adjustment of the contrast of the fingerprint image is achieved.
  • the common mode voltage generating circuit coordinates the common mode level of the output signal of the signal enhancement unit of the fingerprint acquisition module and the common mode level of the input signal of the analog to digital conversion module, so that the swing of the fingerprint detection signal reaches the maximum signal pendulum.
  • the amplitude, and the signal swing does not exceed but is closest to the size of the adjusted quantization window, so that the analog to digital conversion module operates in an optimal state.
  • the fingerprint identification device of the invention increases the proportion of the difference information between the "peak” and the "valley” in the fingerprint information quantitative data, that is, enhances the contrast of the "peak” and “valley” images, and significantly improves the imaging. Quality ultimately improves the recognition rate of subsequent fingerprint recognition.
  • the circuit is simple, the implementation cost is low, and the imaging consistency is ensured because the implementation form and the working state of the fingerprint sensing unit are not involved;
  • the adjustment of the quantization voltage is related to the distribution of the fingerprint information data, so that the dynamic adjustment is quite flexible, and the interference of the common mode information between the “peak” and the “valley” can be avoided to the greatest extent;
  • the processing speed is fast, and the imaging frame rate of the fingerprint recognition device is not reduced.
  • the fingerprint identification method includes the following steps:
  • Step S101 The fingerprint collection module collects fingerprint information and outputs the same to the analog-to-digital conversion module.
  • the fingerprint collection module includes a fingerprint sensing unit, a signal amplification unit and a signal enhancement unit (or a noise shaping and signal enhancement unit) connected in sequence, the fingerprint sensing unit collects fingerprint information, and the signal amplifier amplifies the collected fingerprint information, and the signal is enhanced.
  • the unit performs noise shaping and signal-to-noise ratio improvement on the fingerprint information, and outputs the processed fingerprint information to the analog-to-digital conversion module.
  • Step S102 The analog-to-digital conversion module generates a quantized voltage to perform analog-to-digital conversion on the fingerprint information, and outputs the quantized fingerprint information data to the control module.
  • the analog-to-digital conversion module generates a quantized voltage by a quantized voltage generator, and the analog-to-digital conversion process is a quantization process, and the signal output by the quantized voltage generator can be a single-ended signal or a differential signal.
  • the analog to digital conversion module can be a ramp analog to digital converter, a pipelined analog to digital converter, or a successive approximation analog to digital converter.
  • a ramp analog-to-digital converter is preferred, in which case the quantized voltage generator is correspondingly a ramp generator, the ramp analog-to-digital converter has a small area, is simple to implement, and has good linearity.
  • Step S103 The control module sends the quantized voltage adjustment signal to the analog-to-digital conversion module according to the distribution range of the fingerprint information data.
  • control module outputs a control signal to the quantized voltage generator of the analog-to-digital conversion module after performing certain algorithm processing according to the distribution characteristics of the currently received fingerprint information data, such as a distribution range.
  • Step S104 The analog-to-digital conversion module adjusts the output range of the quantized voltage according to the quantized voltage adjustment signal.
  • the quantized voltage generator of the analog-to-digital conversion module generates a corresponding quantized reference voltage according to the control signal, and adjusts an output range of the quantized voltage, thereby dynamically changing the FS and LSB of the analog-to-digital converter, and finally implementing the fingerprint identification device. Dynamic adjustment of fingerprint image contrast.
  • FS is the effective full-swing input signal amplitude of the analog-to-digital converter
  • LSB is the least significant bit of the quantized output of the analog-to-digital converter, and its value is equal to FS/2 N , where N represents the number of bits of the analog-to-digital converter .
  • the distribution range of the fingerprint information data can be improved by reducing the range of the quantized voltage by a certain amplitude, thereby improving the contrast of the fingerprint image. If the quantized voltage output range of the quantized voltage generator inside the analog-to-digital conversion module is reduced to 1/X of the original range, the contrast of the obtained second frame fingerprint information is increased to the log 2 of the contrast of the first frame fingerprint information. (X) times, in general, the signal-to-noise ratio is also increased to log 2 (X) times of the first frame, so the image quality will be greatly optimized.
  • the fingerprint identification method of the present invention the proportion of the difference information between the “peak” and the “valley” in the fingerprint information quantized data is increased, that is, the contrast of the “peak” and “valley” images is enhanced, and the contrast is significantly improved.
  • the imaging quality ultimately improves the recognition rate of subsequent fingerprint recognition.
  • the fingerprint identification method includes the following steps:
  • Step S201 The fingerprint collection module collects fingerprint information and outputs the same to the analog-to-digital conversion module.
  • Step S202 The common mode voltage generating circuit coordinates the common mode level of the output signal of the fingerprint acquisition module and the common mode level of the input signal of the analog to digital conversion module.
  • a common mode voltage generating circuit is added, and the common mode voltage generating circuit is respectively connected to the signal enhancement unit and the analog to digital conversion module of the fingerprint acquisition module. Coordinating the reference voltage signal outputted by the common mode voltage generating circuit, the common mode level Vcmo of the fingerprint detecting signal output by the signal enhancing unit and the common mode level Vcmi of the input signal of the analog to digital converting module are substantially equal, thereby The amplitude of the fingerprint detection signal output by the signal enhancement unit can reach the maximum signal swing, and the signal swing does not exceed the size of the quantization window of the quantized voltage adjusted by the analog-to-digital conversion module, thereby enabling analog-to-digital conversion.
  • the module works at its best.
  • Step S203 The analog-to-digital conversion module generates a quantized voltage to perform analog-to-digital conversion on the fingerprint information, and outputs the quantized fingerprint information data to the control module.
  • Step S204 The control module sends the quantized voltage adjustment signal to the analog-to-digital conversion module according to the distribution range of the fingerprint information data.
  • Step S205 The analog-to-digital conversion module adjusts the output range of the quantized voltage according to the quantized voltage adjustment signal.
  • the quantization voltage range of the analog-to-digital converter is adjusted according to the distribution range of the current frame fingerprint information data, thereby further increasing the distribution of the fingerprint information data of the next frame.
  • the range realizes the dynamic adjustment of the fingerprint image contrast.
  • the common mode voltage generating circuit coordinates the common mode level of the output signal of the signal enhancement unit of the fingerprint acquisition module and the common mode level of the input signal of the analog to digital conversion module, so that the fingerprint detection
  • the swing of the measured signal reaches the maximum signal swing, and the swing of the signal does not exceed but is closest to the size of the adjusted quantization window, so that the analog-to-digital conversion module works optimally.
  • the fingerprint identification method of the invention increases the proportion of the difference information between the "peak” and the “valley” in the fingerprint information quantitative data, that is, enhances the contrast of the "peak” and “valley” images, and significantly improves the imaging. Quality ultimately improves the recognition rate of subsequent fingerprint recognition.
  • fingerprint identification method and the fingerprint identification device provided by the foregoing embodiments are in the same concept, and the technical features in the device embodiments are applicable in the method embodiments, and details are not described herein again.
  • the invention provides a fingerprint identification device and method, which adjusts the quantization voltage range of the analog-to-digital converter according to the distribution range of the currently received fingerprint information data, thereby further increasing the distribution range of the subsequent fingerprint information data and realizing the fingerprint. Dynamic adjustment of image contrast. By improving the resolution of the fingerprint information analog-to-digital conversion, the contrast and signal-to-noise ratio of the grayscale information of the fingerprint image are improved.
  • the common mode voltage generating circuit coordinates the common mode level of the output signal of the signal enhancement unit of the fingerprint acquisition module and the common mode level of the input signal of the analog to digital conversion module, so that the swing of the fingerprint detection signal reaches the maximum signal pendulum.
  • the amplitude, and the signal swing does not exceed but is closest to the size of the adjusted quantization window, so that the analog to digital conversion module operates in an optimal state.
  • the fingerprint identification device of the invention increases the proportion of the difference information between the "peak” and the "valley” in the fingerprint information quantitative data, that is, enhances the contrast of the "peak” and “valley” images, and significantly improves the imaging. Quality ultimately improves the recognition rate of subsequent fingerprint recognition.
  • the fingerprint identification device of the invention has the following advantages: the circuit is simple, the implementation cost is low, and the imaging consistency is ensured because the implementation form and the working state of the fingerprint sensing unit are not involved. It is not necessary to use a special performance medium layer to improve the adaptability of the sensor; the adjustment of the quantization voltage and the distribution of the fingerprint information data can realize dynamic adjustment, the adjustment is quite flexible, and the "peak” and "valley” can be avoided to the greatest extent. Interference between common mode information; any analog-to-digital converter structure can be realized, so the adaptability is good; the processing speed is fast, and the imaging frame rate of the fingerprint recognition device is not reduced.

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Abstract

本发明公开了一种指纹识别装置和方法，所述指纹识别装置包括依次连接的指纹采集模块、模数转换模块和控制模块，所述模数转换模块包括一产生量化电压的量化电压发生器，所述指纹采集模块用于采集指纹信息，所述模数转换模块用于对所述指纹信息进行模数转换并输出量化后的指纹信息数据，所述控制模块用于根据所述指纹信息数据的分布范围，来控制所述量化电压发生器调整量化电压的输出范围，以增大量化后的指纹信息数据的分布范围。从而，以简单的电路、较低的成本实现了指纹图像对比度的动态调节。通过提高指纹信息模数转换分辨率，实现了指纹图像灰度信息对比度和信噪比的提高，最终提高了后续的指纹识别的识别率。

Description

指纹识别装置和方法 技术领域
本发明涉及通信技术领域，尤其是涉及一种指纹识别装置和方法。
背景技术
人的手指纹路有深度差异，凸的地方称为“峰(ridge)”，凹的地方称为“谷(valley)”。电容式指纹识别装置利用指纹上包含的“峰”和“谷”对应的感应电容大小不同，所以在同样的交流信号激励下输出信号的幅度也不同的原理，将“峰”和“谷”的图像信息转化为相应的电信号。
对于采用指纹感应单元作为基本单元的电容式指纹识别装置，指纹感应单元提取每个像素点的电容耦合信号，再送入指纹识别装置的其他部分进行放大、模数转换、图像拼接等操作，提取出有效的指纹信息。为防止反复触摸过程对指纹识别装置的传感器的静电损伤，以及提高机械强度，需在传感器表面放置不导电的厚介质层(cover)，因此手指到指纹感应单元的耦合电容很小；另外由于指纹深度较浅，因此“峰”“谷”对应的电容差异也很小，这部分差异信息通常只占到指纹信息量化数据的1％-3％。
因此，如何增大指纹信息数据的分布范围，进而增大“峰”和“谷”之间的差异信息在指纹信息量化数据中的占比，即增强“峰”和“谷”图像的对比度，是提高指纹识别的识别率的关键所在。
申请号为200510063872.3的中国专利公开了一种采用电荷放大器来实现指纹传感器的方法。该专利中指纹感应单元的极板需采用应变薄膜材料，利用触摸时指纹深度的压力，来获得两层薄膜的相对电容变化。然而应变薄膜材料在工艺制造上成本较高，实现难度大。
发明内容
本发明的主要目的在于提供一种指纹识别方法和装置，旨在以较低的成本实现增大指纹图像的对比度，进而提高指纹识别的识别率。
为达以上目的，本发明提出一种指纹识别装置，包括依次连接的指纹采集模块、模数转换模块和控制模块，所述模数转换模块包括一产生量化电压的量化电压发生器，所述指纹采集模块用于采集指纹信息，所述模数转换模块用于对所述指纹信息进行模数转换并输出量化后的指纹信息数据，所述控制模块用于根据所述指纹信息数据的分布范围，来控制所述量化电压发生器调整量化电压的输出范围，以增大量化后的指纹信息数据的分布范围。
优选地，所述指纹识别装置还包括分别连接所述指纹采集模块和模数转换模块的共模电压产生电路，所述共模电压产生电路用于协调所述指纹采集模块的输出信号的共模电平和模数转换模块的输入信号的共模电平。
优选地，所述指纹采集模块包括依次连接的指纹感应单元、信号放大器和信号增强单元，所述信号增强单元连接所述模数转换模块。
优选地，所述模数转换器为斜坡模数转换器，所述量化电压发生器为斜坡发生器。
优选地，所述量化电压发生器输出的信号为单端信号或差分信号。
优选地，所述模数转换器为流水线模数转换器或逐次逼近模数转换器。
本发明同时提出一种指纹识别方法，包括步骤：
指纹采集模块采集指纹信息，并输出所述指纹信息至模数转换模块；
模数转换模块产生量化电压对所述指纹信息进行模数转换，并输出量化后的指纹信息数据至控制模块；
控制模块根据所述指纹信息数据的分布范围，向所述模数转换模块发送量化电压调整信号；
模数转换模块根据所述量化电压调整信号，调整所述量化电压的输出范围。
优选地，所述指纹采集模块输出所述指纹信息至模数转换模块的同时还包括：
共模电压产生电路协调指纹采集模块的输出信号的共模电平和模数转换模块的输入信号的共模电平。
优选地，所述模数转换模块通过量化电压发生器产生量化电压。
优选地，所述模数转换模块为斜坡模数转换器、流水线模数转换器或逐次逼近模数转换器。
本发明所提供的一种指纹识别装置，根据当前接收到的指纹信息数据的分布范围来调整模数转换器的量化电压范围，进而实现增大后续指纹信息数据的分布范围，实现了指纹图像对比度的动态调节。通过提高指纹信息模数转换分辨率，实现了指纹图像灰度信息对比度和信噪比的提高。此外，通过共模电压产生电路协调指纹采集模块的信号增强单元的输出信号的共模电平和模数转换模块的输入信号的共模电平，使得指纹侦测信号的摆幅达到最大的信号摆幅，且该信号摆幅不超过但最接近调整后的量化窗口的大小，使得模数转换模块工作在最佳状态。本发明的指纹识别装置，增大了“峰”和“谷”之间的差异信息在指纹信息量化数据中的占比，即增强了“峰”和“谷”图像的对比度，显著提高了成像质量，最终提高了后续的指纹识别的识别率。
本发明指纹识别装置具有以下优势：电路简单，实现成本低，且因为不涉及到指纹感应单元的实现形式和工作状态的改变，所以成像一致性得以保证；无需使用特殊性能的介质层，提高了传感器的适应性；量化电压的调整和指纹信息数据分布相关，可以实现动态调整，调整相当灵活，且可最大程度上避免“峰”和“谷”之间共模信息的干扰；任何模数转换器结构均可实现，因此适应性很好；处理速度快，不会降低指纹识别装置的成像帧率。
附图说明
图1是本发明的指纹识别装置第一实施例的结构框图；
图2是本发明实施例中指纹采集模块的结构框图；
图3是图1中的指纹识别装置的电路连接示意图；
图4是本发明实施例的原理示意图；
图5是本发明的指纹识别装置第二实施例的结构框图；
图6是图5中的指纹识别装置的电路连接示意图；
图7是本发明的指纹识别方法第一实施例的流程图；
图8是本发明的指纹识别方法第二实施例的流程图。
本发明目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
参见图1-图3，提出本发明的指纹识别装置第一实施例，所述指纹识别装置包括依次连接的指纹采集模块、模数转换模块和控制模块。
指纹采集模块用于采集指纹信息，如图2所示，其包括依次连接的指纹感应单元、信号发大器和信号增强单元(或称噪声整形和信号增强单元)，指纹感应单元用于采集指纹信息，信号放大器用于对采集的指纹信息进行放大处理，信号增强单元用于对指纹信息进行噪声整形和信噪比提升等处理，信号增强单元包括但不限于以下常见功能电路：可变增益放大器、积分器、低通滤波器和采样保持电路，以及它们组成的信号链路。
模数转换模块用于对指纹信息进行模数转换，将指纹信息由模拟信号转换为数字信号，模数转换过程即为量化过程，模数转换模块将量化后的指纹信息数据发送给控制模块；模数转换模块包括一量化电压发生器，该量化电压发生器用于产生量化电压对指纹信息进行模数转换，量化电压发生器输出的信号可以是单端信号，也可以是差分信号。模数转换模块的类型不限，可以是流水线模数转换器、逐次逼近模数转换器等，优选斜坡模数转换器，量化电压发生器对应的为斜坡发生器。斜坡模数转换器面积小，实施简单，且线性度好。
控制模块可以是MCU(Micro Control Unit，微控制单元)，用于对量化后的指纹信息进行一定的算法处理，最终实现指纹识别或检测等功能。本发明的控制模块还根据当前接收到的指纹信息数据的分布范围，来控制量化电压发生器调整量化电压的输出范围，以增大量化后的指纹信息数据的分布范围，进而提高指纹图像的对比度。具体来说，控制模块根据当前接收到的指纹信息数据的分布特点如分布范围等，进行一定的算法处理后输出控制信号到量化电压发生器，并控制其产生不同的量化参考电压，调整量化电压的输出范围，据此可以动态改变模数转换器的FS和LSB，最终实现指纹识别装置中指纹图像对比度的动态调节功能。其中，FS是指模数转换器有效的满摆幅输入信号幅度；LSB是指模数转换器量化输出的最低有效位，其数值等于FS/2N，其中N表示模数转换器的位数。
本实施例的指纹识别装置的电路连接示意图如图3所示，其中，指纹感 应单元、信号放大器、信号增强单元、模数转换模块和控制模块依次连接，其中控制模块和模数转换模块中的量化电压发生器构成对比度动态调节回路。当手指接触到指纹识别装置的传感器表面时，指纹感应单元输出手指纹路信息的采样信息，即指纹信息，然后该指纹信息经信号放大器放大后输出到后续的信号增强单元，进行进一步的噪声抑制和信噪比提升等处理，并且根据需要对信号的共模电平进行变换以方便后续处理。经信号增强单元增强处理后的指纹信号传输给模数转换模块，经模数转换后输出数字码字信号ADC_OUT<N:1>，即得到量化后的指纹信息，最后由控制模块对指纹信息进行一定的算法处理，最终实现指纹识别或检测等功能。
本发明中，为了达到足够的分辨率DPI(dots per inch)，通常由指纹感应单元构成的m*k阵列对手指纹路信息进行感应，所有m*k数量的指纹感应单元的输出均完成一次量化后得到的数据阵列称之为一帧指纹信息。在本发明提供的方案中，控制模块可以根据前一帧指纹信息数据分布的范围来产生量化电压调整信号，从而改变模数转换模块内部的量化电压发生器的量化电压的输出范围，然后在控制模块的控制下对同一个手指部位开始下一帧指纹信息的采样。
举例而言：
假设模数转换模块初始的模数转换参考电压为V1，其对应的量化窗口为[V0-V1,V0+V1]，分布在量化窗口范围内的指纹信息电压将会被量化为范围为0～10000的数据，即从最低可转换电压“V0-V1”开始，量化后的数据每增加“1”对应着转换前的原始信号电压增加(2·V1)/10000。假设对于某次手指按压后采集的指纹信息，进行量化后指纹信息数据分布范围为5500～7000；其原始指纹信息对应的电压——即被量化的电压信号范围为:
Figure PCTCN2014094725-appb-000001
上述结果可简化为：
Figure PCTCN2014094725-appb-000002
对手指同一部位再次采集的指纹信息进行量化之前，可将量化窗口调整为[V0,V0+0.5*V1]，即比实际指纹信息对应的电信号电压分布范围稍大即可。因为有下述两关系成立：
Figure PCTCN2014094725-appb-000003
所以此时量化后指纹信息数据分布范 围则为2000～8000，即对于同一幅指纹信息其第二次量化数据分布范围增大为调整前的4倍。
由此可见，量化电压的范围与指纹信息数据的分布范围呈负相关关系，可以通过减小量化电压的范围一定幅度来提高指纹信息数据的分布范围，进而提高指纹图像的对比度。如果减小模数转换模块内部的量化电压发生器的量化电压输出范围为原有范围的1/X，那么得到的第二帧指纹信息的对比度将提高为第一帧指纹信息的对比度的log2(X)倍，通常情况下，信噪比也会随之提高为第一帧的log2(X)倍，因此，成像质量将得到大幅度优化。
下面结合图4说明实现上述对比度提高的理论依据。以模数转换模块为斜坡模数转换器，其量化电压发生器为斜坡发生器为例，假设第一帧指纹信息采集过程中，斜坡模数转换器内部的斜坡发生器的量化电压输出范围为ΔVSET1，那么对于指纹感应单元A感应到的指纹信息经后续信号放大和增强处理后的信号记为VINXA，另记该指纹感应单元A感应的指纹信息经模数转换后得到的数字码字为ADC_OUT1A，slope为斜率，则有：
Figure PCTCN2014094725-appb-000004
此外，对于与指纹感应单元A相邻的指纹感应单元B，其感应到的指纹信息经后续信号放大和增强处理后的信号记为VINXB，另记该指纹感应单元B感应的指纹信息经模数转换后得到的数字码字为ADC_OUT1B,则有：
Figure PCTCN2014094725-appb-000005
由上述关系式(1)和(2)可得相邻的指纹感应单元A、B两处位置感应到的指纹信息量化后数字码字差值为
Figure PCTCN2014094725-appb-000006
假设第二帧指纹信息采集过程中，手指按压情况未发生改变；斜坡模数转换器内部的斜坡发生器的量化电压输出范围调整为ΔVSET2，那么对于指纹感应单元A感应到的指纹信息经后续信号放大和增强处理后的信号应该仍为VINXA，另记该指纹感应单元A感应的指纹感应信息经模数转换后得到的数字码字为ADC_OUT2A,则有：
Figure PCTCN2014094725-appb-000007
此外，对于与指纹感应单元A相邻的指纹感应单元B，其感应到的指纹信息经后续信号放大和增强处理后的信号记为VINXB，另记该指纹感应单元B感应的指纹信息经模数转换后得到的数字码字为ADC_OUT2B,则有：
Figure PCTCN2014094725-appb-000008
由上述关系式(3)和(4)可得相邻的指纹感应单元A、B两处位置感应到的指纹信息量化后数字码字差值为
Figure PCTCN2014094725-appb-000009
假定存在关系式ΔVSET1＝4ΔVSET2(7)
则根据式(3)、(6)和(7)可知，
Figure PCTCN2014094725-appb-000010
即经过斜坡发生器的量化电压范围后，可以显著提升指纹图像的模数转换量化分辨率，进而提高指纹灰度信息的对比度。
参见图5、图6，提出本发明的指纹识别装置第二实施例，本实施例与第 一实施例的区别是增加了一共模电压产生电路，该共模电压产生电路分别连接指纹采集模块和模数转换模块，其用于协调指纹采集模块的输出信号的共模电平和模数转换模块的输入信号的共模电平，从而使模数转换模块工作在最佳状态。
本实施例的指纹识别装置的电路示意图如图6所示，其中，指纹感应单元、信号放大器、信号增强单元、模数转换模块和控制模块依次连接，共模电压产生电路分别连接指纹采集模块的信号增强单元和模数转换模块。在共模电压产生电路输出的参考电压信号的协调下，使得信号增强单元输出的指纹侦测信号的共模电平Vcmo和模数转换模块的输入信号的共模电平Vcmi基本相等，从而使得信号增强单元输出的指纹侦测信号的摆幅可以达到最大的信号摆幅，且该信号摆幅不超过但最接近模数转换模块调整后的量化电压的量化窗口的大小。
本发明的指纹识别装置，在指纹信息感应或检测过程中，根据当前帧指纹信息数据的分布范围来调整模数转换器的量化电压范围，进而实现增大下一帧指纹信息数据的分布范围，实现了指纹图像对比度的动态调节。通过提高指纹信息模数转换分辨率，实现了指纹图像灰度信息对比度和信噪比的提高。此外，通过共模电压产生电路协调指纹采集模块的信号增强单元的输出信号的共模电平和模数转换模块的输入信号的共模电平，使得指纹侦测信号的摆幅达到最大的信号摆幅，且该信号摆幅不超过但最接近调整后的量化窗口的大小，使得模数转换模块工作在最佳状态。本发明的指纹识别装置，增大了“峰”和“谷”之间的差异信息在指纹信息量化数据中的占比，即增强了“峰”和“谷”图像的对比度，显著提高了成像质量，最终提高了后续的指纹识别的识别率。
本发明的指纹识别装置具有以下优势：
第一、电路简单，实现成本低，且因为不涉及到指纹感应单元的实现形式和工作状态的改变，所以成像一致性得以保证；
第二、无需使用特殊性能的介质层，提高了传感器的适应性；
第三、量化电压的调整和指纹信息数据分布相关，从而使得动态调整相当灵活，且可最大程度上避免“峰”和“谷”之间共模信息的干扰；
第四、任何模数转换器结构均可实现，因此适应性很好；
第五、处理速度快，不会降低指纹识别装置的成像帧率。
参见图7，提出本发明的指纹识别方法第一实施例，所述指纹识别方法包括以下步骤：
步骤S101：指纹采集模块采集指纹信息并输出至模数转换模块
指纹采集模块包括依次连接的指纹感应单元、信号发大器和信号增强单元(或称噪声整形和信号增强单元)，指纹感应单元采集指纹信息，信号放大器对采集的指纹信息进行放大处理，信号增强单元对指纹信息进行噪声整形和信噪比提升等处理，并将处理后的指纹信息输出至模数转换模块。
步骤S102：模数转换模块产生量化电压对指纹信息进行模数转换，并输出量化后的指纹信息数据至控制模块
模数转换模块通过量化电压发生器产生量化电压，其模数转换过程即为量化过程，量化电压发生器输出的信号可以是单端信号，也可以是差分信号。模数转换模块可以为斜坡模数转换器、流水线模数转换器或逐次逼近模数转换器。优选斜坡模数转换器，此时量化电压发生器相应的为斜坡发生器，斜坡模数转换器面积小，实施简单，且线性度好。
步骤S103：控制模块根据指纹信息数据的分布范围，向模数转换模块发送量化电压调整信号
具体来说，控制模块根据当前接收到的指纹信息数据的分布特点如分布范围等，进行一定的算法处理后输出控制信号到模数转换模块的量化电压发生器。
步骤S104：模数转换模块根据量化电压调整信号，调整量化电压的输出范围
具体的，模数转换模块的量化电压发生器根据控制信号，产生相应的量化参考电压，调整量化电压的输出范围，据此可以动态改变模数转换器的FS和LSB，最终实现指纹识别装置中指纹图像对比度的动态调节功能。其中，FS是指模数转换器有效的满摆幅输入信号幅度；LSB是指模数转换器量化输出的最低有效位，其数值等于FS/2N，其中N表示模数转换器的位数。
由于量化电压的范围与指纹信息数据的分布范围呈负相关关系，因此可以通过以一定幅度减小量化电压的范围来提高指纹信息数据的分布范围，进而提高指纹图像的对比度。如果减小模数转换模块内部的量化电压发生器的 量化电压输出范围为原有范围的1/X，那么得到的第二帧指纹信息的对比度将提高为第一帧指纹信息的对比度的log2(X)倍，通常情况下，信噪比也会随之提高为第一帧的log2(X)倍，因此，成像质量将得到大幅度优化。
从而通过本发明的指纹识别方法，增大了“峰”和“谷”之间的差异信息在指纹信息量化数据中的占比，即增强了“峰”和“谷”图像的对比度，显著提高了成像质量，最终提高了后续的指纹识别的识别率。
参见图8，提出本发明的指纹识别方法第二实施例，所述指纹识别方法包括以下步骤：
步骤S201：指纹采集模块采集指纹信息并输出至模数转换模块
步骤S202：共模电压产生电路协调指纹采集模块的输出信号的共模电平和模数转换模块的输入信号的共模电平
本实施例增设了一共模电压产生电路，该共模电压产生电路分别连接指纹采集模块的信号增强单元和模数转换模块。在共模电压产生电路输出的参考电压信号的协调下，使得信号增强单元输出的指纹侦测信号的共模电平Vcmo和模数转换模块的输入信号的共模电平Vcmi基本相等，从而使得信号增强单元输出的指纹侦测信号的摆幅可以达到最大的信号摆幅，且该信号摆幅不超过但最接近模数转换模块调整后的量化电压的量化窗口的大小，从而使得模数转换模块工作在最佳状态。
步骤S203：模数转换模块产生量化电压对指纹信息进行模数转换，并输出量化后的指纹信息数据至控制模块
步骤S204：控制模块根据指纹信息数据的分布范围，向模数转换模块发送量化电压调整信号
步骤S205：模数转换模块根据量化电压调整信号，调整量化电压的输出范围
从而，本发明的指纹识别方法，在指纹信息感应或检测过程中，根据当前帧指纹信息数据的分布范围来调整模数转换器的量化电压范围，进而实现增大下一帧指纹信息数据的分布范围，实现了指纹图像对比度的动态调节。通过提高指纹信息模数转换分辨率，实现了指纹图像灰度信息对比度和信噪比的提高。此外，通过共模电压产生电路协调指纹采集模块的信号增强单元的输出信号的共模电平和模数转换模块的输入信号的共模电平，使得指纹侦 测信号的摆幅达到最大的信号摆幅，且该信号摆幅不超过但最接近调整后的量化窗口的大小，使得模数转换模块工作在最佳状态。
本发明的指纹识别方法，增大了“峰”和“谷”之间的差异信息在指纹信息量化数据中的占比，即增强了“峰”和“谷”图像的对比度，显著提高了成像质量，最终提高了后续的指纹识别的识别率。
需要说明的是：上述实施例提供的指纹识别方法与指纹识别装置实施例属于同一构思，装置实施例中的技术特征在方法实施例中均对应适用，这里不再赘述。
本领域普通技术人员可以理解,实现上述实施例方法中的全部或部分步骤可以通过程序来控制相关的硬件完成，所述的程序可以存储于一计算机可读取存储介质中，所述的存储介质可以是ROM/RAM、磁盘、光盘等。
应当理解的是，以上仅为本发明的优选实施例，不能因此限制本发明的专利范围，凡是利用本发明说明书及附图内容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本发明的专利保护范围内。
工业实用性
本发明所提供的一种指纹识别装置和方法，根据当前接收到的指纹信息数据的分布范围来调整模数转换器的量化电压范围，进而实现增大后续指纹信息数据的分布范围，实现了指纹图像对比度的动态调节。通过提高指纹信息模数转换分辨率，实现了指纹图像灰度信息对比度和信噪比的提高。此外，通过共模电压产生电路协调指纹采集模块的信号增强单元的输出信号的共模电平和模数转换模块的输入信号的共模电平，使得指纹侦测信号的摆幅达到最大的信号摆幅，且该信号摆幅不超过但最接近调整后的量化窗口的大小，使得模数转换模块工作在最佳状态。本发明的指纹识别装置，增大了“峰”和“谷”之间的差异信息在指纹信息量化数据中的占比，即增强了“峰”和“谷”图像的对比度，显著提高了成像质量，最终提高了后续的指纹识别的识别率。
本发明指纹识别装置具有以下优势：电路简单，实现成本低，且因为不涉及到指纹感应单元的实现形式和工作状态的改变，所以成像一致性得以保 证；无需使用特殊性能的介质层，提高了传感器的适应性；量化电压的调整和指纹信息数据分布相关，可以实现动态调整，调整相当灵活，且可最大程度上避免“峰”和“谷”之间共模信息的干扰；任何模数转换器结构均可实现，因此适应性很好；处理速度快，不会降低指纹识别装置的成像帧率。

Claims (10)

  1. 一种指纹识别装置，包括依次连接的指纹采集模块、模数转换模块和控制模块，所述模数转换模块包括一产生量化电压的量化电压发生器，所述指纹采集模块用于采集指纹信息，所述模数转换模块用于对所述指纹信息进行模数转换并输出量化后的指纹信息数据，其特征在于，所述控制模块用于根据所述指纹信息数据的分布范围，来控制所述量化电压发生器调整量化电压的输出范围，以增大量化后的指纹信息数据的分布范围。
  2. 根据权利要求1所述的指纹识别装置，其特征在于，所述指纹识别装置还包括分别连接所述指纹采集模块和模数转换模块的共模电压产生电路，所述共模电压产生电路用于协调所述指纹采集模块的输出信号的共模电平和模数转换模块的输入信号的共模电平。
  3. 根据权利要求1或2所述的指纹识别装置，其特征在于，所述指纹采集模块包括依次连接的指纹感应单元、信号放大器和信号增强单元，所述信号增强单元连接所述模数转换模块。
  4. 根据权利要求1或2所述的指纹识别装置，其特征在于，所述模数转换器为斜坡模数转换器，所述量化电压发生器为斜坡发生器。
  5. 根据权利要求1或2所述的指纹识别装置，其特征在于，所述量化电压发生器输出的信号为单端信号或差分信号。
  6. 根据权利要求1或2所述的指纹识别装置，其特征在于，所述模数转换器为流水线模数转换器或逐次逼近模数转换器。
  7. 一种指纹识别方法，其特征在于，包括步骤：
    指纹采集模块采集指纹信息，并输出所述指纹信息至模数转换模块；
    模数转换模块产生量化电压对所述指纹信息进行模数转换，并输出量化后的指纹信息数据至控制模块；
    控制模块根据所述指纹信息数据的分布范围，向所述模数转换模块发送量化电压调整信号；
    模数转换模块根据所述量化电压调整信号，调整所述量化电压的输出范围。
  8. 根据权利要求7所述的指纹识别方法，其特征在于，所述指纹采集模 块输出所述指纹信息至模数转换模块的同时还包括：
    共模电压产生电路协调指纹采集模块的输出信号的共模电平和模数转换模块的输入信号的共模电平。
  9. 根据权利要求7或8所述的指纹识别方法，其特征在于，所述模数转换模块通过量化电压发生器产生量化电压。
  10. 根据权利要求7或8所述的指纹识别方法，其特征在于，所述模数转换模块为斜坡模数转换器、流水线模数转换器或逐次逼近模数转换器。
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