WO2012024961A1 - 人脸识别方法和系统及红外背光补偿方法和系统 - Google Patents

人脸识别方法和系统及红外背光补偿方法和系统 Download PDF

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Publication number
WO2012024961A1
WO2012024961A1 PCT/CN2011/075670 CN2011075670W WO2012024961A1 WO 2012024961 A1 WO2012024961 A1 WO 2012024961A1 CN 2011075670 W CN2011075670 W CN 2011075670W WO 2012024961 A1 WO2012024961 A1 WO 2012024961A1
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Prior art keywords
infrared
frequency pulse
pulse signal
face
high frequency
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PCT/CN2011/075670
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English (en)
French (fr)
Inventor
袁军涛
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汉王科技股份有限公司
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Application filed by 汉王科技股份有限公司 filed Critical 汉王科技股份有限公司
Priority to US13/818,442 priority Critical patent/US9245174B2/en
Priority to EP11819336.6A priority patent/EP2610779A4/en
Publication of WO2012024961A1 publication Critical patent/WO2012024961A1/zh

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • 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
    • G06V40/16—Human faces, e.g. facial parts, sketches or expressions
    • G06V40/161—Detection; Localisation; Normalisation
    • G06V40/166—Detection; Localisation; Normalisation using acquisition arrangements
    • 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
    • G06V40/16—Human faces, e.g. facial parts, sketches or expressions
    • G06V40/172—Classification, e.g. identification
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/042—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means

Definitions

  • the present invention relates to pattern recognition technology, and in particular to a face recognition method and system and an infrared backlight compensation method and system. Background technique
  • Face recognition is a new biometric recognition technology that has emerged in recent years with the rapid advancement of computer technology, image processing technology, and pattern recognition technology. It is based on a person's facial features, which compares the entered face image with known face data to identify the identity of each face.
  • Face recognition has been successfully applied in the fields of access control, attendance, security monitoring, etc.
  • common products are mainly used under indoor environmental conditions.
  • the inventors have found that face recognition under outdoor conditions is easily disturbed by ambient light, thereby affecting the accuracy of face recognition in an outdoor environment. Summary of the invention
  • Embodiments of the present invention provide a face recognition method and system, which can improve the accuracy of face recognition in an outdoor environment.
  • a face recognition method includes:
  • the infrared light group is driven by the high frequency pulse signal to generate an infrared backlight; the recognized face feature located under the infrared backlight is collected; and the collected recognized face feature is compared with the face template to complete the face recognition.
  • a face recognition system includes a face collection device, a face recognition device, and an infrared backlight compensation system, wherein
  • the infrared backlight compensation device includes an infrared backlight driver and an infrared light group disposed on the infrared backlight board, wherein the infrared backlight driver generates a high frequency pulse signal, and the infrared light group on the infrared backlight board is used
  • the high-frequency pulse signal is driven to provide the required infrared backlight for the face collecting device;
  • the face gathering device is configured to collect the recognized face feature located under the infrared backlight;
  • the face recognition method and system can generate an infrared backlight by using a high-frequency pulse signal to drive an infrared light group, so that the infrared light group on the infrared backlight board can generate high-current high-frequency lighting in a short time. And this short-time high-current state is continuously repeated, so that an infrared backlight with high luminous intensity can be obtained. Then, by collecting the recognized facial features under the infrared backlight illumination, and comparing the recognized facial features collected by the pupils with the face templates to complete the face recognition, thereby providing the recognized facial features A sufficient light source helps the face recognition algorithm to quickly locate the face. Compared with the prior art, the face recognition can be improved in the outdoor environment by reducing the influence of outdoor light changes on the recognized face features. accuracy.
  • Embodiments of the present invention provide an infrared backlight compensation method and system, which can improve the brightness intensity of an infrared backlight.
  • An infrared backlight compensation method includes: generating a high frequency pulse signal; and driving the infrared light group on the infrared backlight panel with the high frequency pulse signal.
  • An infrared backlight compensation system includes an infrared backlight driver and an infrared light group disposed on the infrared backlight board, wherein the infrared backlight driver is configured to generate a high frequency pulse signal, and the infrared light group on the infrared backlight board The high frequency pulse signal is used for driving.
  • the infrared backlight compensation method and system according to the embodiment of the present invention can drive a high-frequency pulse of a large current in a short time by driving a high-frequency pulse signal on an infrared lamp group on an infrared backlight panel, and This short-time, high-current state is constantly being repeated, thus increasing the brightness of the infrared backlight.
  • FIG. 1 is a flowchart of a method for recognizing a face according to an embodiment of the present invention
  • FIG. 2 is a schematic diagram of the generation of a high frequency pulse signal according to the present invention.
  • FIG. 3 is a flow chart of the high frequency pulse signal driving infrared lamp group of the present invention.
  • FIG. 4 is a schematic diagram of a high frequency pulse signal for driving an infrared lamp group according to the present invention.
  • FIG. 5 is a flowchart of a method for controlling synchronization of a high frequency pulse signal and an exposure synchronization signal according to an embodiment of the present invention
  • FIG. 6 is a schematic diagram of driving signals of an infrared light group after synchronization according to an embodiment of the present invention
  • FIG. 7 is a structural diagram of a face recognition system according to an embodiment of the present invention. detailed description
  • a method for recognizing a face includes:
  • Step 11 using a high frequency pulse signal to drive the infrared light group to generate an infrared backlight.
  • Step 12 Acquire an identified facial feature under the infrared backlight illumination.
  • the infrared light source used in the existing infrared backlight is an infrared light group composed of an 850 nm infrared light emitting diode, and the infrared light group is disposed on the infrared backlight board.
  • the infrared light unit is controlled by a DSP (Digital Signal Processor) light-on signal, which can continuously and stably operate at 20mA to obtain 6.5mW/sr light intensity.
  • DSP Digital Signal Processor
  • the embodiment of the present invention uses the high-frequency pulse signal to perform the infrared light group on the infrared backlight board. Driven, the frequency of the high frequency pulse signal is 100 Hz to 10 kHz. Under the high-frequency pulse driving, the infrared lamp group can instantaneously pass the current of up to 1000mA, and obtain an average light intensity of 300mW/sr. Compared with the continuous and stable current of 20mA, the luminous power of the infrared lamp group can be 6.5mW from 20mA.
  • the infrared light group starts to close the infrared light group until the face recognition ends, thereby greatly improving the brightness intensity of the infrared backlight, and thus can provide sufficient light source for the recognized face feature, which helps the face recognition algorithm to quickly locate the face.
  • Recognizing face recognition by concentrating the recognized face features under the infrared backlight illumination, and comparing the recognized face features collected by the ⁇ with the face template to complete face recognition, due to a large current occurring in a short time
  • High-frequency lighting improves the brightness of the infrared backlight, thereby reducing the influence of outdoor light changes on the recognized face features, thus improving the accuracy of face recognition in outdoor environments.
  • the high-frequency pulse signal generation process is shown in Figure 2.
  • the active crystal generates a 24MHz clock signal, which can be internally used by CPLD (Complex Programmable Logic Device).
  • the programming program divides the input clock signal. By adjusting the division factor, the 24MHz clock signal frequency can be reduced to the high-frequency pulse signal required to drive the infrared lamp group.
  • the flow of the high frequency pulse signal to drive the infrared lamp group is shown in Figure 3.
  • the high-frequency pulse signal is high, the infrared light group is turned on, and the light-on timer is reset and started, the light-on timer is turned on until the light-on timer overflows;
  • the high-frequency pulse signal is low, the infrared light group is turned off, and at the same time Reset and start the light-off timer, turn off the light timer until the light-off timer overflows.
  • the infrared lamp group driving signal is valid
  • the above-mentioned infrared lamp group is turned on and off until the infrared lamp group driving signal is invalid, and the infrared lamp group is turned off.
  • the high frequency pulse signal that drives the infrared lamp group is shown in Figure 4.
  • the infrared light group lights up in T1 time, turns off in T2 time, and repeats this process to realize pulse lighting.
  • T driving period
  • T-T1+T2 driving period
  • different pulse frequencies can be obtained; when T is constant, different infrared backlight brightness can be obtained by adjusting the lighting time T1 of the infrared lamp group.
  • the pulse frequency of the infrared light group driven by the embodiment of the present invention is very high, the infrared light group driven by the high frequency pulse seems to be continuously lit, so the CCD (Charge Coupled Device) is collected when the recognized face feature is collected. , Charge coupled device) The image captured by the camera will not flicker.
  • CCD Charge Coupled Device
  • the lighting time T1 in the driving period T of the lamp group should be determined according to the specification of the selected infrared light emitting diode. Too long, usually within 100 microseconds. If the lighting time T1 is too long, the infrared lamp group will be overheated, and the infrared lamp group will be accelerated or even burned.
  • the number of infrared light-emitting diodes in the embodiments of the present invention can be adjusted to meet the illumination requirements of the outdoor application, and the number of infrared light-emitting diodes can be increased from the existing ten to one hundred, or even more. .
  • the face recognition method provided by the embodiment of the present invention can also turn on the driving output enable signal of the infrared light group when the exposure time of the recognized face feature is collected, so as to drive the infrared light group.
  • the high-frequency pulse signal is synchronized with the exposure synchronization signal of the CCD camera at the time of face acquisition, that is, the control infrared light group is turned on during the exposure, and is turned off after the exposure ends.
  • the infrared light group By receiving the exposure synchronization signal when the recognized face feature is collected, and then controlling the high frequency pulse signal for driving the infrared light group to be synchronized with the exposure synchronization signal, the infrared light group can be controlled to be turned on during the exposure period and turned off after the exposure is completed.
  • a method flow for controlling synchronization of the high frequency pulse signal with the exposure synchronization signal is as shown in FIG. When the face recognition system starts working, turn on the DSP turn-on signal, and the DSP turn-on signal is valid.
  • the driving output of the infrared light group is set to be enabled, and the high-frequency pulse signal is generated to drive the infrared light group; At any time, set the drive output of the infrared light group to be disabled.
  • the driving signals of the synchronized infrared lamp group are as shown in FIG. 5.
  • the embodiment of the present invention synchronizes the driving signal of the infrared lamp group with the exposure synchronization signal of the CCD camera, thereby realizing that the infrared lamp group is illuminated during the CCD exposure, and is turned off immediately after the exposure ends.
  • the CCD camera outputs a standard TV signal, which completes 50 image acquisitions per second with a period of 20ms per field.
  • the field blanking time of each field is about 1.5ms.
  • the CCD camera exposure time is in the field blanking time of each field.
  • the driving of the infrared lamp group is synchronized with the field blanking signal of the CCD camera.
  • the infrared light group is turned on during the entire blanking time, and the rest of the time is turned off, so the driving duty ratio of the infrared light group is 7.5%, thereby effectively improving the working efficiency of the infrared light group and reducing the infrared light group.
  • the infrared lamp group drive and the CCD camera field blanking signal can also illuminate the target ahead of the exposure point for a period of time, so that the CCD camera can obtain better results when exposed.
  • the embodiment of the present invention can adopt the CPLD as the main controller of the infrared light group driving circuit.
  • the CPLD's signal response time is 10ns, which is programmed to ensure that the IR light group is illuminated accurately during the exposure of the CCD camera.
  • the face recognition method of the embodiment of the invention provides an infrared backlight by using an infrared light group on the infrared backlight board by using a high-frequency pulse signal, thereby achieving not only greater illumination intensity, but also meeting the need for face recognition to work outdoors.
  • the target can be illuminated in advance of the exposure point for a better image. Set the effect.
  • the embodiment of the present invention may also filter the ambient visible light when the recognized facial features are collected.
  • an infrared filter to the front end of the video recognition device for face recognition, it is possible to reflect and attenuate visible light well, and only through infrared light, thereby minimizing the impact of ambient light on face recognition. Ring, to ensure the accuracy of outdoor face recognition.
  • the embodiment of the present invention performs face recognition under the infrared backlight which is driven by the high-frequency pulse signal to ensure sufficient intensity. It is ensured that the infrared light passing through the filter still has sufficient strength, so that the accuracy of face recognition in an outdoor environment is not affected.
  • a face recognition system includes a face collection device 61, a face recognition device 62, and an infrared backlight compensation device.
  • the infrared backlight compensation device includes an infrared backlight driver 601 and an infrared light group (not shown) disposed on the infrared backlight panel 602.
  • the infrared backlight driver 601 generates a high frequency pulse signal, and the infrared backlight is
  • the infrared light group on the board 602 is driven by the high frequency pulse signal to provide the required infrared backlight for the face gathering device 61;
  • the face collecting device 61 is configured to collect the recognized face features located under the infrared backlight; the face recognition device 62 is configured to collect the recognized person by the face collecting device 61 Face features are compared with face templates to complete face recognition.
  • the face recognition system of the embodiment of the invention provides an infrared backlight by using an infrared backlight driver to drive an infrared light group on the infrared backlight board by using a high-frequency pulse signal, so that the infrared light group on the infrared backlight board can occur in a short time.
  • High-frequency high-frequency lighting, and this short-time high-current state is continuously repeated, so that an infrared backlight with high luminous intensity can be obtained, providing sufficient light source for the recognized facial features, which contributes to face recognition.
  • the algorithm quickly locates the face. Compared with the prior art, the accuracy of the face recognition in the outdoor environment can be improved by reducing the influence of the outdoor light change on the recognized face features.
  • the infrared backlight driver 601 is further configured to receive an exposure synchronization signal sent by the face collection device 61, and control the generated high frequency pulse signal to be synchronized with the exposure synchronization signal.
  • the time of opening the infrared lamp group can be shortened, the heat emitted by the infrared lamp group during operation can be effectively controlled, and the infrared diode can be extended.
  • the working life is beneficial to the long-term stable operation of the system; on the other hand, the target can be illuminated in advance of the exposure point for a better image acquisition effect.
  • an infrared filter 63 may be disposed at the front end of the face gathering device 61 for collecting ambient visible light when the face collecting device is configured to recognize the face feature. Filtering is performed to minimize the influence of ambient light on face recognition, and to ensure the accuracy of outdoor face recognition.
  • an embodiment of the present invention further provides an infrared backlight compensation method, including: generating a high frequency pulse signal, and driving the infrared light emitting diode on the infrared backlight panel by using the high frequency pulse signal.
  • the infrared backlight compensation method of the embodiment of the present invention may further receive an exposure synchronization signal sent when the recognized object is acquired, and control the high frequency pulse signal to be synchronized with the exposure synchronization signal.
  • an embodiment of the present invention further provides an infrared backlight compensation system, including an external backlight driver and an infrared light emitting diode disposed on the infrared backlight panel, wherein the infrared backlight driver is configured to generate a high frequency pulse signal The infrared light emitting diode on the infrared backlight panel is driven by the high frequency pulse signal.
  • the infrared backlight driver is further configured to receive an exposure synchronization signal emitted when the recognized object is collected, and control the generated high frequency pulse signal to be synchronized with the exposure synchronization signal.
  • the infrared backlight compensation method and system can drive the high-frequency pulse of a large current in a short time by driving the infrared lamp group on the infrared backlight panel with a high-frequency pulse signal. Moreover, this short-time high current state is continuously repeated, thus continuously increasing the brightness intensity of the infrared backlight.
  • the time of opening the infrared light group can be shortened, the heat emitted by the infrared light group during operation can be effectively controlled, and the operation of the infrared diode can be prolonged. The longevity is beneficial to the long-term stable operation of the system; on the other hand, the target can be illuminated for a period of time in advance to obtain a better image acquisition effect.
  • the infrared backlight compensation method and system of the embodiments of the present invention can be applied to object recognition other than face recognition that requires infrared backlight, and can provide sufficient light source for the recognized object to reduce ambient light changes.
  • the impact on the identified object improves the accuracy of object recognition in an outdoor environment.

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Description

人脸识别方法和系统及红外背光补偿方法和系统 技术领域
本发明涉及模式识别技术， 尤其涉及一种人脸识别方法和系统及红外背光补 偿方法和系统。 背景技术
人脸识别是近年来随着计算机技术、 图像处理技术、 模式识别技术等技术的 快速进步而出现的一种崭新的生物特征识别技术。 它是基于人的脸部特征， 将输 入的人脸图像与已知的人脸数据进行对比， 从而识别出每个人脸的身份。
人脸识别已经成功地应用于门禁、 考勤、 安全监控等领域， 目前常见的产品 都主要是基于室内的环境条件下使用。 在实现本发明的过程中发明人发现， 室外 条件下的人脸识别容易被环境光线干扰， 从而影响了人脸识别在室外环境下工作 的准确性。 发明内容
本发明实施例提供一种人脸识别方法和系统， 能够提高人脸识别在室外环境 下工作的准确性。
本发明实施例采用如下技术方案：
一种人脸识别方法， 包括：
采用高频脉冲信号驱动红外灯组生成红外背光； 采集位于所述红外背光照射 下的被识别人脸特征； 将所述采集到的被识别人脸特征与人脸模板进行对比完成 人脸识别。
一种人脸识别系统， 包括人脸采集装置、 人脸识别装置和红外背光补偿系统， 其中，
所述红外背光补偿装置， 包括红外背光驱动器和设置在红外背光灯板上的红 外灯组， 所述红外背光驱动器生成高频脉冲信号， 对所述红外背光灯板上的红外 灯组采用所述高频脉冲信号进行驱动，为所述人脸采集装置提供需要的红外背光； 所述人脸釆集装置， 用于采集位于所述红外背光照射下的被识别人脸特征； 所述 人脸识别装置， 用于将所述人脸采集装置釆集到的被识别人脸特征与人脸模板进 行对比完成人脸识别。
本发明实施例的人脸识别方法和系统， 通过釆用高频脉冲信号驱动红外灯组 生成红外背光， 可使红外背光灯板上的红外灯组在短时间内发生大电流的高频点 亮， 而且这种短时间大电流状态是在不断重复的， 从而可以获得高光亮强度的红 外背光。 然后通过采集位于所述红外背光照射下的被识别人脸特征， 并将所述釆 集到的被识别人脸特征与人脸模板进行对比完成人脸识别， 因此能够为被识别人 脸特征提供充足的光源， 有助于人脸识别算法迅速定位人脸， 与现有技术相比， 由于降低了室外光线变化对被识别人脸特征的影响， 因此能够提高人脸识别在室 外环境下工作的准确性。
本发明实施例提供一种红外背光补偿方法和系统， 能够提高红外背光的光亮 强度。
本发明实施例采用如下技术方案：
一种红外背光补偿方法， 包括： 生成高频脉冲信号； 对红外背光灯板上的红 外灯组釆用所述高频脉冲信号进行驱动。
一种红外背光补偿系统， 包括红外背光驱动器和设置在红外背光灯板上的红 外灯组， 所述红外背光驱动器， 用于生成高频脉冲信号， 对所述红外背光灯板上 的红外灯组采用所述高频脉冲信号进行驱动。
本发明实施例的红外背光补偿方法和系统， 通过对红外背光灯板上的红外灯 组采用高频脉冲信号进行驱动，可使红外灯组在短时间内发生大电流的高频点亮， 而且这种短时间大电流状态是在不断重复的， 因此提高了红外背光的光亮强度。 附图说明
为了更清楚地说明本发明实施例的技术方案， 下面将对实施例描述中所需要 使用的附图作一简单地介绍。
图 1为本发明实施例提供的一种人脸识别方法的流程图；
图 2为本发明的高频脉冲信号产生示意图；
图 3为本发明的高频脉冲信号驱动红外灯组的流程图；
图 4为本发明驱动红外灯组的高频脉冲信号示意图；
图 5为本发明实施例控制高频脉冲信号与曝光同步信号同步的方法流程图； 图 6为本发明实施例同步后的红外灯组的驱动信号示意图； 图 7为本发明实施例提供的一种人脸识别系统的结构图。 具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、 完整地描述。
如图 1所示， 本发明实施例提供的一种人脸识别方法， 包括：
步骤 11， 采用高频脉冲信号驱动红外灯组生成红外背光。
步骤 12， 采集位于所述红外背光照射下的被识别人脸特征。
步骤 13，将所述釆集到的被识别人脸特征与人脸模板进行对比完成人脸识别。 现有的红外背光所使用的红外光源是由 850nm红外发光二极管组成的红外灯 组， 该红外灯组设置在红外背光灯板上。 红外灯组受控于 DSP ( Digital Signal Processor, 数字信号处理器） 开灯信号， 可以连续、 稳定地工作在 20mA电流下， 获得 6.5mW/sr的光照强度。 DSP在识别人脸时给出开灯信号打开红外灯组， 识别 完成后关闭， 在整个识别过程中红外灯组一直处于开启状态。
由于室外环境光线复杂， 需要人脸识别技术更快、 更准确地响应环境光线的 变换， 以消除环境光线的影响， 本发明实施例采用高频脉冲信号对红外背光灯板 上的红外灯组进行驱动， 该高频脉冲信号的频率为 100Hz〜10KHz。 在高频脉冲驱 动下， 红外灯组可以瞬间通过高达 1000mA的电流， 获得平均 300mW/sr的光照 强度， 相比于连续稳定地通过 20mA电流， 红外灯组的发光功率可从 20mA时的 6.5mW/sr 增加到 300mW/sr， 在短时间内发生大电流的高频点亮， 而且在人脸采 集过程中， 这种短时间大电流状态是在不断重复的， 从 DSP给出开灯信号打开红 外灯组开始， 直至人脸识别结束关闭红外灯组， 从而大大提高了红外背光的光亮 强度， 因此能够为被识别人脸特征提供充足的光源， 有助于人脸识别算法迅速定 位人脸。
通过釆集位于所述红外背光照射下的被识别人脸特征， 并将所述釆集到的被 识别人脸特征与人脸模板进行对比完成人脸识别， 由于在短时间内发生大电流的 高频点亮， 提高了红外背光的光亮强度， 从而降低了室外光线变化对被识别人脸 特征的影响， 因此提高了人脸识别在室外环境下工作的准确性。
高频脉冲信号的产生过程如图 2所示， 有源晶体生成 24MHz的时钟信号， 通 过 CPLD ( Complex Programmable Logic Device, 复杂可编程逻辑器件） 的内部可 编程程序， 对输入的时钟信号进行分频， 通过调整分频系数， 可以将 24MHz的时 钟信号频率降低至驱动红外灯组所需的高频脉冲信号。
高频脉冲信号驱动红外灯组的流程如图 3所示。 在高频脉冲信号高电平时， 打开红外灯组， 同时复位并启动开灯计时器， 开灯计时器计时直至开灯计时器溢 出； 在高频脉冲信号低电平时， 关闭红外灯组， 同时复位并启动关灯计时器， 关 灯计时器计时直至关灯计时器溢出。 在红外灯组驱动信号有效期间， 重复上述红 外灯组的打开和关闭， 直至红外灯组驱动信号无效， 关闭红外灯组。
驱动红外灯组的高频脉冲信号如图 4所示。 红外灯组在 T1 时间内点亮， 在 T2时间内关闭， 重复这个过程来实现脉冲点亮。 通过调整红外灯组的驱动周期 T ( T-T1+T2 ) ， 可以获得不同的脉冲频率； 当 T一定时， 通过调整红外灯组的点 亮时间 T1 , 可以获得不同的红外背光亮度。
需要说明的是， 由于本发明实施例驱动红外灯组的脉冲频率非常高， 使得高 频脉冲驱动下的红外灯组看起来就是连续点亮， 因此采集被识别人脸特征时 CCD ( Charge Coupled Device, 电荷耦合器件）摄像头采集到的图像就不会发生闪烁现 象。
还需要说明的是， 由于本发明实施例大幅度提高了红外发光二极管的工作电 路， 最高达 ΙΟΟΟπιΑ, 因此灯组驱动周期 T内的点亮时间 T1应该依据选用的红外 发光二极管规格书要求， 不能太长， 一般在 100微秒内。 如果点亮时间 T1过长， 会引起红外灯组过热， 加速红外灯组的老化甚至烧毁。
可以理解的是， 为了满足室外应用的光照需要， 本发明实施例的红外发光二 极管的数量可以进行调整， 可以将红外发光二极管的数量由现有的十几个增加至 一百个， 甚至更多。
为了进一步提高红外灯组的工作效率， 本发明实施例提供的人脸识别方法还 可以在采集被识别人脸特征时的曝光时刻， 打开红外灯组的驱动输出使能信号， 使得驱动红外灯组的高频脉冲信号与人脸采集时的 CCD 摄像头的曝光同步信号 同步， 也即是说， 控制红外灯组在曝光期间幵启， 在曝光结束后关闭。
通过接收釆集被识别人脸特征时的曝光同步信号， 然后控制驱动红外灯组的 高频脉冲信号与该曝光同步信号同步， 可以控制红外灯组在曝光期间开启， 在曝 光结束后关闭。 控制所述高频脉冲信号与所述曝光同步信号同步的方法流程如图 5所示。 在人脸识别系统开始工作时， 打开 DSP开灯信号， 在 DSP开灯信号有效 期间， 判断采集被识别人脸特征的 CCD摄像头是否处于曝光期间， 并在 CCD摄 像头处于曝光期间， 设置红外灯组的驱动输出使能， 生成高频脉冲信号驱动红外 灯组； 在曝光期间外的任一时间内， 设置红外灯组的驱动输出禁止。 同步后的红 外灯组的驱动信号如图 5所示。
需要说明的是， CCD摄像头在工作过程中并非一直处于曝光状态， 而是曝光 获取一场图像信号， 然后输出采集到的图像数据， 在数据输出过程中外界光线对 CCD摄像头没有任何影响， 而且曝光时间要远远小于输出图像数据的时间。 鉴于 这个特点，本发明实施例将红外灯组的驱动信号与 CCD摄像头的曝光同步信号进 行了同步， 从而实现了红外灯组在 CCD曝光期间点亮， 曝光结束后立即关闭。
CCD摄像头输出的是标准电视信号， 每秒完成 50场图像采集， 周期为 20ms 每场， 每一场的场消隐时间为 1.5ms左右， CCD摄像头曝光时刻位于每场的场消 隐时间内。 实际操作中红外灯组的驱动是与 CCD 摄像头的场消隐信号进行了同 步。 红外灯组在整个场消隐时间内打开， 其余的时间都处于关闭状态， 因此红外 灯组的驱动占空比为 7.5%， 从而有效提高了红外灯组的工作效率， 减小了红外灯 组开启时产生的热量。 另外， 红外灯组驱动与 CCD摄像头场消隐信号同步还可以 提前于曝光点一段时间把目标照亮， 使得 CCD摄像头曝光时获得更好的效果。
进一步地， 为控制驱动红外灯组的高频脉冲信号与曝光同步信号严格同步， 本发明实施例可以采用 CPLD作为红外灯组驱动电路的主控制器。 CPLD 的信号 响应时间为 10ns， 通过程序设计可以保证红外灯组准确无误地在 CCD摄像头的 曝光期间进行点亮。
本发明实施例的人脸识别方法， 通过采用高频脉冲信号驱动红外背光灯板上 的红外灯组来提供红外背光， 不仅实现了更大的光照强度， 满足人脸识别在室外 工作的需要， 提高人脸识别在室外环境下工作的准确性； 而且通过控制红外灯组 的高频脉冲驱动信号与采集被识别人脸特征时的曝光同步信号同步， 一方面可以 缩短红外灯组开启的时间， 有效地控制红外灯组在工作中散发的热量， 延长红外 二极管的工作寿命， 有利于系统长期稳定地工作； 另一方面， 可以提前于曝光点 一段的时间把目标照亮， 获得更好的图像釆集效果。
更进一步地， 本发明实施例还可以对釆集被识别人脸特征时的环境可见光进 行过滤。 通过在人脸识别的视频釆集设备前端添加红外滤光片， 可以很好地反射 和衰减可见光， 只通过红外光线， 从而最大程度地降低环境光线对人脸识别的影 响， 保证室外人脸识别的准确性。
需要说明的是， 虽然红外滤光片在一定程度上会同时衰减通过的红外光线， 但由于本发明实施例是在通过高频脉冲信号驱动保证足够强度的红外背光下进行 人脸识别， 因此可以保证通过滤光片后的红外光线仍有足够的强度， 从而不会影 响到人脸识别在室外环境下工作的准确性。
参见图 7 , 本发明实施例提供的一种人脸识别系统， 包括人脸采集装置 61、 人脸识别装置 62和红外背光补偿装置， 其中，
所述红外背光补偿装置，包括红外背光驱动器 601和设置在红外背光灯板 602 上的红外灯组 （图中未示出） ， 该红外背光驱动器 601生成高频脉冲信号， 对所 述红外背光灯板 602上的红外灯组釆用所述高频脉冲信号进行驱动， 从而为所述 人脸釆集装置 61提供需要的红外背光；
所述人脸采集装置 61，用于釆集位于所述红外背光照射下的被识别人脸特征； 所述人脸识别装置 62 , 用于将所述人脸采集装置 61 采集到的被识别人脸特征与 人脸模板进行对比完成人脸识别。
本发明实施例的人脸识别系统， 通过红外背光驱动器采用高频脉冲信号驱动 红外背光灯板上的红外灯组来提供红外背光， 可使红外背光灯板上的红外灯组在 短时间内发生大电流的高频点亮， 而且这种短时间大电流状态是在不断重复的， 从而可以获得高光亮强度的红外背光， 为被识别的人脸特征提供充足的光源， 有 助于人脸识别算法迅速定位人脸， 与现有技术相比， 由于降低了室外光线变化对 被识别人脸特征的影响， 因此能够提高人脸识别在室外环境下工作的准确性。
进一步地， 所述红外背光驱动器 601， 还用于接收所述人脸采集装置 61发出 的曝光同步信号， 并控制生成的高频脉冲信号与所述曝光同步信号同步。
通过控制驱动红外灯组的高频脉冲信号与人脸采集装置的曝光同步信号同 步， 一方面可以缩短红外灯组开启的时间， 有效地控制红外灯组在工作中散发的 热量， 延长红外二极管的工作寿命， 有利于系统长期稳定地工作； 另一方面， 可 以提前于曝光点一段的时间把目标照亮， 获得更好的图像采集效果。
更进一步地， 本发明实施例的人脸识别系统， 还可以在人脸釆集装置 61前端 设置红外滤光片 63 , 用于对所述人脸采集装置采集被识别人脸特征时的环境可见 光进行过滤， 从而最大程度地降低环境光线对人脸识别的影响， 保证室外人脸识 别的准确性。 最后， 本发明实施例还提供一种红外背光补偿方法， 包括： 生成高频脉冲信 号， 对红外背光灯板上的红外发光二极管采用所述高频脉冲信号进行驱动。
进一步地， 本发明实施例的红外背光补偿方法还可以接收采集被识别对象时 发出的曝光同步信号， 并控制所述高频脉冲信号与所述曝光同步信号同步。
相应该红外背光补偿方法， 本发明实施例还提供一种红外背光补偿系统， 包 括外背光驱动器和设置在红外背光灯板上的红外发光二极管， 所述红外背光驱动 器， 用于生成高频脉冲信号， 对所述红外背光灯板上的红外发光二极管采用所述 高频脉冲信号进行驱动。
进一步地， 所述红外背光驱动器， 还用于接收釆集被识别对象时发出的曝光 同步信号， 并控制生成的高频脉冲信号与所述曝光同步信号同步。
本发明实施例的红外背光补偿方法和系统， 通过对红外背光灯板上的红外灯 组釆用高频脉冲信号进行驱动，可使红外灯组在短时间内发生大电流的高频点亮， 而且这种短时间大电流状态是在不断重复的， 因此持续地提高了红外背光的光亮 强度。 另外通过控制生成的高频脉冲信号与采集被识别对象时的曝光同步信号同 步， 一方面可以缩短红外灯组开启的时间， 有效地控制红外灯组在工作中散发的 热量， 延长红外二极管的工作寿命， 有利于系统长期稳定地工作； 另一方面， 可 以提前一段的时间把目标照亮， 获得更好的图像采集效果。
容易理解的是， 本发明实施例的红外背光补偿方法和系统， 可以应用到除人 脸识别之外的任何需要红外背光的对象识别上， 能够为被识别对象提供充足的光 源， 降低环境光线变化对被识别对象的影响， 提高对象识别在室外环境下工作的 准确性。
上述具体实施例并不用以限制本发明， 对红外背光灯板上的多个 （如两个） 红外灯组， 可以部分采用高频脉冲信号进行驱动， 部分仍采用现有的连续稳定地 小电流进行驱动， 对于本技术领域的普通技术人员来说， 凡在不脱离本发明原理 的前提下， 所作的任何修改、 等同替换、 改进等， 均应包含在本发明的保护范围 之内。

Claims

权 利 要 求
1、 一种人脸识别方法， 其特征在于， 包括- 采用高频脉冲信号驱动红外灯组生成红外背光；
釆集位于所述红外背光照射下的被识别人脸特征；
将所述采集到的被识别人脸特征与人脸模板进行对比完成人脸识别。
2、 根据权利要求 1所述的人脸识别方法， 其特征在于， 在所述釆用高频脉冲 信号驱动红外灯组生成红外背光之前， 还包括： 生成高频脉冲信号；
所述生成高频脉冲信号的方法包括：
有源晶体生成时钟信号， 对所述时钟信号进行分频生成高频脉冲信号。
3、 根据权利要求 1所述的人脸识别方法， 其特征在于， 所述采用高频脉冲信 号驱动红外灯组生成红外背光包括：
在高频脉冲信号高电平时， 打开红外灯组；
复位并启动开灯计时器， 开灯计时器计时直至开灯计时器溢出；
在高频脉冲信号低电平时， 关闭红外灯组；
复位并启动关灯计时器， 关灯计时器计时直至关灯计时器溢出；
在红外灯组驱动信号有效期间， 重复所述红外灯组的打开和关闭， 直至红外 灯组驱动信号无效， 关闭红外灯组。
4、 根据权利要求 1所述的人脸识别方法， 其特征在于， 在所述高频脉冲信号 驱动周期一定时， 通过调整红外灯组的点亮时间来获得不同的红外背光亮度。
5、 根据权利要求 1 -4任一所述的人脸识别方法， 其特征在于， 还包括- 接收采集被识别人脸特征时发出的曝光同步信号；
控制所述高频脉冲信号与所述曝光同步信号同步。
6、 根据权利要求 5所述的人脸识别方法， 其特征在于， 还包括：
对釆集被识别人脸特征时的环境可见光进行过滤。
7、 一种人脸识别系统， 其特征在于， 包括人脸采集装置、 人脸识别装置和红 外背光补偿装置， 其中，
所述红外背光补偿装置， 包括红外背光驱动器和设置在红外背光灯板上的红 外灯组， 所述红外背光驱动器生成高频脉冲信号， 对所述红外背光灯板上的红外 灯组采用所述高频脉冲信号进行驱动，为所述人脸采集装置提供需要的红外背光； 所述人脸采集装置， 用于采集位于所述红外背光照射下的被识别人脸特征； 所述人脸识别装置， 用于将所述人脸采集装置采集到的被识别人脸特征与人 脸模板进行对比完成人脸识别。
8、 根据权利要求 7所述的人脸识别系统， 其特征在于，
所述红外背光驱动器， 还用于接收所述人脸采集装置发出的曝光同步信号， 并控制生成的高频脉冲信号与所述曝光同步信号同步。
9、 根据权利要求 7或 8所述的人脸识别系统， 其特征在于， 还包括： 红外滤光片， 用于对所述人脸采集装置采集被识别人脸特征时的环境可见光 进行过滤。
10、 一种红外背光补偿方法， 其特征在于， 包括：
生成高频脉冲信号；
对红外背光灯板上的红外灯组采用所述高频脉冲信号进行驱动。
1 1、 根据权利要求 10所述的方法， 其特征在于， 还包括：
接收采集被识别对象时发出的曝光同步信号；
控制所述高频脉冲信号与所述曝光同步信号同步。
12、 一种红外背光补偿系统， 其特征在于， 包括红外背光驱动器和设置在红 外背光灯板上的红外灯组，
所述红外背光驱动器， 用于生成高频脉冲信号， 对所述红外背光灯板上的红 外灯组采用所述高频脉冲信号进行驱动。
13、 根据权利要求 12所述的红外背光补偿系统， 其特征在于，
所述红外背光驱动器， 还用于接收采集被识别对象时发出的曝光同步信号， 并控制所述高频脉冲信号与所述曝光同步信号同步。
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