Abstract:
A security device for identifying a person makes two images of a person to detect spoofing. The first image is a conventional visible image and the second image is an infrared image. Both images are analyzed to determine whether they represent a real person or not. If a placard or active display device is presented to the security device to spoof the real person, the infrared image of the placard or display device is recognized not to have the same characteristics as the infrared image of a real person.

Description:
BACKGROUND 
       [0001]    A. Field 
         [0002]    This disclosure pertains to a system for identifying a person using face recognition, and more particularly, to a system and method in which, in addition to a standard image of the person&#39;s face, an infra-red (IR) image is also obtained for confirmation. 
         [0003]    B. Description of the Prior Art 
         [0004]    There are many instances in which it is necessary and important to identify a person using an automated device. For example, ATMs must be able to determine that a person using a debit or credit card is really a customer authorized to access a bank account or not. An airline ticket dispenser at an airport must be able to verify that a person trying to obtain or confirm an airline ticket is the identified traveler, or not. Some entities, such as banks, use automated doors or other gateways that provide access to certain rooms or premises only to authorized personnel. The standard means of identifying persons by such automated devices has been to provide such persons with some kind of electronic card. In order to activate the device (e.g., gain access to an account, obtain a ticket, gain entry through a door, etc.) a person had to insert the card into a card reader. Over time, it was found that the electronic card could be duplicated or otherwise compromised and a secondary authentication means was also provided. For example, the person had to enter a secret code on a keyboard and/or place a finger on a fingerprint reader, etc. 
         [0005]    However, none of the systems described above are foolproof and therefore other authentication means have been proposed, many of which relied on biometrics. For example, devices have been provided with a camera for taking a standard, visible image of a person trying to activate a device. The visible image was then analyzed using face recognition techniques and compared to a reference image previously taken of the person. (The term “image” is used herein to refer to both still pictures and videos). Of course, this technique can be circumvented by an imposter displaying an image of the person. 
         [0006]    Alternatively, a system captures a video of a person and then performs facial motion analysis on the video to test for a live face. However, such security systems can be similarly compromised by an unauthorized user presenting the camera with a video of the person having the desired authorization. Moreover, algorithms for detecting live faces in a video are fairly complex. 
       SUMMARY 
       [0007]    The present disclosure provides a system and method that prevents spoofing. In one example, two images are taken. The first image is a standard image taken in the visible light range. The second image is an IR image. The two images are either taken with the same camera using different filters or by using two different cameras, one being sensitive to visible light and the second being sensitive to radiation in the IR range. The second image is analyzed first to determine if there is a real person standing in front of the camera. This can be done, for example, by determining whether the IR image has a signature generally characteristic of human faces in general. If the IR image is consistent with the IR images of human faces in general then the first image is analyzed using conventional algorithms. In an alternate example, certain predetermined features of the person&#39;s face are compared in the two images to determine if there is a correlation, thereby providing further authentication of the person. 
         [0008]    In an alternate example, the IR image is analyzed to confirm that has the characteristics associated with human faces. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]      FIG. 1  shows a diagrammatic side view of a device constructed in accordance with this disclosure and being used by a genuine person; 
           [0010]      FIG. 2  shows a similar diagrammatic side view of a device constructed in accordance with this disclosure and being used by an unauthorized person; 
           [0011]      FIGS. 3A ,  3 B  3 C shows images obtained by the devices of  FIGS. 1 and 2 ; 
           [0012]      FIG. 4  shows a block diagram of a camera used for the device of  FIGS. 1 and 2 ; and 
           [0013]      FIG. 5  shows a flow chart for the operation of the device of  FIGS. 1-4 ; and 
           [0014]      FIG. 6  shows a flow chart of an alternate implementation of the device. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring now to  FIG. 1 , an authentication device  10  in accordance with this disclosure is stationed and is part of a security system used to control access to a restricted area of a facility. The facility is conventionally a part of a private or governmental entity that must assure that only authorized personnel enters the area. However, the present disclosure may also be used to provide access for the general public to venues requiring an entrance fee, such as a sports stadium, a theater, etc. The device  10  includes a housing  12  with a front face  14 , a camera  16  and several interfacing components that provide an interface with a person P. This interface includes, for example, a card reader  18  used to read a card or other authorization member (not shown), a keyboard  20 , etc. The device  10  further includes a microprocessor  22  and a memory  24 . 
         [0016]    It should be understood that the camera  16 , microprocessor  22  and memory  24  may but need not be disposed in the same housing  12  as the interfacing components. The camera  16  must be directed so that its optical element  16 A is directed at the person P (preferably his or her face) and images are obtained of the person, such as images shown in  FIGS. 3A-3C  described more fully below. 
         [0017]    Preferably, the camera  16  is used to obtain a normal image (e.g., an image generated using light in the visible range) and an IR image (e.g., an image generated using electromagnetic radiation in the infrared range). Optionally, other types of electromagnetic radiation may be used to generate images as well. Conventional cameras, especially digital cameras, are made with sensors that are sensitive to radiation in the range that extends beyond the visible light, including at least a substantial portion of the IR range. It has been found that using images obtained from such sensors creates various undesirable effects, such as undesirable color artifacts. Therefore, it is very common to provide such cameras with filters that restrict the range of the sensors to the visible light range. 
         [0018]    For example, as shown in  FIG. 4 , camera  16  is frequently provided with an IR filter  16 C that passes visible light but blocks IR radiation. In the present disclosure, camera  16  is used with filter  16 C blocks IR radiation and is substantially transparent to visible light. Filter  16 C is used in front of the optical element  16 A. To take an IR image, the IR filter  16 C is shifted to position  16 C′ away from the field of view of element  16 A, and a visible light filter  16 D is shifted to position  16 D′ as shown. Filter  16 D blocks visible light and is substantially transparent to IR radiation. Of course, it should be understood that alternatively optical filters  16 C,  16 D, can be implemented electronically by performing data processing on the output of the camera  16 . 
         [0019]    Referring now to  FIGS. 1-5 , a person P uses the device  10  as follows. In step  100 , he approaches the device  10  and positions himself in the field of view of camera  16 . In step  102  the device  10  is activated. This activation may take place automatically, for example by detecting the presence of person P either through the camera  16 , or through other means such as a proximity sensor (not shown) or a mechanical switch (not shown). The activation may also occur manually, with the person P either inserting an authorization card into card reader  18 , by activating a switch on the keyboard  20 , by entering a code on the keyboard  20 , etc. 
         [0020]    In step  104  a visible image is taken by camera  16  and the visible image is sent for processing to the microprocessor  22 . In step  106  the visible image is analyzed using well known face recognition techniques.  FIG. 3A  shows (diagrammatically) a visible image  36  of person P.  FIG. 3B  shows an IR image  38  of the person P. As can be seen in these figures, the visible image  36  includes several well-known characteristic features such as the eyes  30 , nose  32 , mouth  34 , etc. The image  38  also includes several characteristic features having very definite shapes, such as the eyes  40 , nose  42 , mouth  44  or cheeks  46  disposed close to the nose  42 . While some of the features match the visible features, others do not. The various features characterizing the visible image  36  are determined in step  106 . 
         [0021]    In step  108  a decision is made as to whether the visible image  36  is accepted or not. This step can be accomplished in many different ways. For example, a plurality of reference images of acceptable or authorized people may be stored in memory  24  and, in step  108  a known optical recognition algorithm is used to compare the images from memory  24  with the visible image of P, using features  30 ,  32 ,  34 . Alternatively, when a person has an identification card, a reference Image may be stored in the identification card and provided to microprocessor  22  by the card reader  16 . Many other methods for identifying or authenticating the person P from his image  36  can be used as well. 
         [0022]    If the image  36  is not recognized, then an alarm or some other audible, visual signal is generated and/or a message is sent to a remote location indicating this event. 
         [0023]    If the visible image is recognized in step  108  then a validation process is performed as follows. In step  112  an IR image of the person standing in front of camera  16  is taken. In one implementation of the disclosure this is accomplished by having filters  16 C and  16 D automatically shift to positions  16 C′ and  16 D′ respectively (if necessary). The IR image is also sent to the microprocessor  22  for processing to identify some characteristic features, such as zones  40 ,  42 ,  44  and  46 . If no optical filters  16 C,  16 D are used, then IR image  38  is obtained by the microprocessor (or by other digital signal processing equipment) from the raw image obtained from the camera  16 . 
         [0024]    As previously mentioned, step  108  can be defeated by a person S who is masquerading as person P. For example, when person S is positioned in the field of view of camera  16 , he may hold up or hide before a placard  50  with an image  52  of person P. In this situation, when the microprocessor  22  analyzes the image  52 , it will most likely erroneously recognize it as a true image  36  of person P. In an alternate implementation of the disclosure, instead of a placard with an image  52 , the person S may hold up a portable screen on which either a still image  52  or a short video clip is presented to camera  16 . The camera  16  may use either a still image of P as the reference or a video clip. 
         [0025]    In yet another, more elaborate example, if conditions permit, person S may hold up a blank screen and the fake image  52  or video clip can be projected on the screen by an image projector (not shown) or by directly presenting the security camera with a display screen. 
         [0026]    In any case, when camera  16  takes an IR picture of the placard  50 , the resulting IR image is either blank or consists of some indeterminate shape  48  ( FIG. 3C ) that looks nothing like the image  36 . 
         [0027]    The IR image obtained by camera  16  is analyzed in step  112 . This step can be implemented in several different ways. In one implementation, the IR image recorded by camera  16  (e.g., either  38  or  48 ) is analyzed to determine whether it is an actual IR image of a person or not. This may be done in the crudest sense by determining whether the IR image (if any) includes a shape having the dimensions similar to a typical human head or by determining if the color (or shade) of the IR image is in predetermined range, since this color is related to the temperature of the object being imaged. 
         [0028]    A more substantive test includes looking for and detecting various other known features of a human face. For example, because of temperature variations, the image of human face may include several zones (See  FIG. 3B ), such as zone  40  corresponding to the location of the eyes, zone  42  corresponding to the nose, zone  44  corresponding to the mouth, or zone  46  corresponding to the cheeks. In one example, the sizes, positions and/or colors or shades (especially for a monochromatic image) are determined and compared to known characteristics of a standard human face. 
         [0029]    In another example, instead of comparing zones of image  36  to standard human faces, specific characteristics of the image  36  are compared to known characteristics of person P&#39;s face as recorded in memory  24  or on the authorization card inserted into card reader  18 . If the characteristics match, image  38  is considered genuine. 
         [0030]    The test for detecting an IR image of an actual person P as opposed to a spoofing person S is performed in step  114 . If the IR image is recognized, then the person is accepted as person P. If the IR image is not recognized then an alarm is generated in step  110 . 
         [0031]    As discussed above, most digital cameras have a wide responsive range that covers the visible light and IR range. Therefore a single camera  16  can be used to obtain images  36 ,  38 ,  48  using either analog or digital filtering. Alternatively, two different cameras  16 ,  16 R may be used to record the images of  FIGS. 3A ,  3 B,  3 C. 
         [0032]    Depending on various considerations, the visible and IR images may be taken and/or analyzed in the reverse order to the one described above, or even simultaneously. For example, in the implementation of  FIG. 6 , a person stands in front of the camera (step  200 ) causing the device to be activated (step  202 ), the visible and IR images are taken (steps  204 ,  206 ). The IR image is checked (step  208 ) and only if it is acceptable, is the visible image checked (steps  210 ,  212 ). If both images pass the inspection (steps  208 ,  212 ) the person is accepted as P, otherwise an alarm is generated (step  214 ). 
         [0033]    Numerous modifications may be made to the disclosure without departing from its scope as defined in the appended claims.