Patent Publication Number: US-11380130-B2

Title: Face authentication device having database with small storage capacity

Description:
The present application is a continuation application of U.S. patent application Ser. No. 15/933,723 filed on Mar. 23, 2018, which claims the benefit of priority from Japanese Patent Application 2017-060863 filed on Mar. 27, 2017, the disclosures of all of which are incorporated in their entirety by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to a face authentication device, a face authentication method, and a face authentication program. 
     Description of the Related Art 
     In order to achieve a high authentication accuracy in a face authentication technology, it is required to photograph a face from a position as close to the front of the face as possible. However, in particular, a camera for monitoring is installed in the vicinity of a ceiling in many cases, and hence it is difficult for the camera to capture the face from the front. 
     The authentication accuracy can be expected to be improved by setting an angle, distance, height, or the like of a camera with respect to an object as recommended. However, when a camera is installed in, for example, a narrow floor or passage, there is a case in which the angle, distance, height, or the like of a camera cannot be set as recommended depending on the environment in which the camera is installed and it is consequently difficult to perform face authentication. 
     Meanwhile, in order to solve such a problem, there have been proposed various face authentication technologies that use a mirror. There have been known, as such face authentication technologies that use a mirror, for example, a technology requiring a front face image, a reflected face image, and a reflected side image to be registered with a database in advance, and a technology involving performing authentication processing without distinguishing between a real image and a reflected image. However, with such face authentication technologies that use a mirror, there is a fear that a person whose face image is similar to the laterally-inverted face image may be erroneously authenticated. 
     For example, in Japanese Unexamined Patent Application Publication (JP-A) No. 2014-106816, there is disclosed a technology involving installing a front mirror and a mirror that is inclined at a small angle with respect to the front mirror, and picking up a reflected front image and a reflected side image with a camera, to thereby improve an accuracy of face authentication for entry and exit of a room. 
     In Japanese Unexamined Patent Application Publication (JP-A) No. 2007-011456, there is disclosed a technology involving picking up a front image of a face and right and left side images thereof, which are reflected by two mirrors, with a wide-angle camera, and determining whether a person to be authenticated is successfully authenticated through use of those picked-up images. Also in Japanese Unexamined Patent Application Publication (JP-A) No. 2007-011456, in the same manner as in Japanese Unexamined Patent Application Publication (JP-A) No. 2014-106816, a front image of a face of a person to be authenticated and right and left side images thereof are registered with a storage as registered information. 
     In Japanese Unexamined Patent Application Publication (JP-A) No. 2006-099615, there is disclosed a technology involving using only a face image reflected by a mirror for authentication. 
     In Japanese Unexamined Patent Application Publication (JP-A) No. 2007-206834, there is disclosed a technology involving extracting a face image in which a person to be authenticated faces the front from among face images of the person to be authenticated, which are acquired through reflection from a plurality of mirrors, to thereby perform face authentication of the person to be authenticated. 
     Meanwhile, in Japanese Unexamined Patent Application Publication (JP-A) No. 2000-250116, there is disclosed a technology involving laterally inverting image data on a person image (image data on a person image containing a person laterally inverted by a reflection mirror), which is generated by an image pickup camera, with an image inversion processor, to thereby convert the image into an original image. 
     However, the above-mentioned technologies disclosed in Japanese Unexamined Patent Application Publication (JP-A) Nos. 2014-106816, 2007-011456, 2006-099615, 2007-206834, and 2000-250116 have the following problems. 
     In the technology disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. 2014-106816, the reflected front image and the reflected side image as well as the real front image are registered with the database for face authentication, and hence three face images are required to be registered for each person to be authenticated. This increases the storage capacity of the database threefold. In addition, in Japanese Unexamined Patent Application Publication (JP-A) No. 2014-106816, there is no definition of a method of detecting a mirror, and image correction suited to an angle and distortion of the mirror is not performed. Moreover, in the technology disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. 2014-106816, there is a fear that, when a person to be authenticated does not stand still, the reflected front image and the reflected side image cannot be distinguished from each other. 
     Also in the technology disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. 2007-011456, the front image of the face of the person to be authenticated and the right and left side images thereof are registered with the storage as the registered information, and hence the storage capacity of the database is increased threefold. 
     In the technologies disclosed in Japanese Unexamined Patent Application Publication (JP-A) Nos. 2006-099615 and 2007-206834, there is a fear that a person whose face image is similar to the laterally-inverted face image may be erroneously authenticated. 
     In Japanese Unexamined Patent Application Publication (JP-A) No. 2000-250116, there is merely disclosed the technology involving inverting again a picked-up image containing a person laterally inverted by the reflection mirror to convert the image into the original image. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention is to provide a face authentication device, a face authentication method, and a non-transitory computer readable recording medium storing a face authentication program, which are capable of solving the above-mentioned problems. 
     One example embodiment according to this invention is a face authentication device, which is configured to perform face authentication based on an input image picked up by an image pickup device, the input image including a mirror region reflected by a mirror. The face authentication device comprises: a database with which, for each face of a person to be authenticated, only one real front image is to be registered as a reference face image; a mirror image processing circuitry configured to detect the mirror region from the input image and to subject a detected mirror region to lateral inversion processing to produce a processed image; a face detection processing circuitry configured to detect a face image from the processed image to generate a detected face image; and a face authentication processing circuitry configured to compare the detected face image with the reference face image, to thereby perform face authentication. 
     In addition, another example embodiment according to this invention is a face authentication method for performing face authentication based on an input image including a mirror region reflected by a mirror. The face authentication method comprising: registering, for each face of a person to be authenticated, only one real front image with a database as a reference face image; subjecting the mirror region of the input image to lateral inversion processing to produce a processed image; detecting a face region from the processed image to generate a detected face image; and comparing the detected face image with the reference face image, to thereby perform face authentication. 
     Furthermore, another example embodiment according to this invention is a non-transitory computer readable recording medium storing a face authentication program for causing a computer to execute face authentication based on an input image including a mirror region reflected by a mirror. The face authentication program causing the computer to execute: a registration procedure of registering, for each face of a person to be authenticated, only one real front image with a database as a reference face image; a mirror image processing procedure of subjecting the mirror region of the input image to lateral inversion processing to produce a processed image; a face detection processing procedure of detecting a face region from the processed image to generate a detected face image; and a face authentication processing procedure of comparing the detected face image with the reference face image, to thereby perform face authentication. 
     According to this invention, the face authentication can easily be performed based on the input image including the mirror region reflected by the mirror without increasing the storage capacity of the database. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  and  FIG. 1B  are each an explanatory diagram of a camera arrangement in face authentication; 
         FIG. 2  is a block diagram of a face authentication system including a face authentication device according to an embodiment of this invention; 
         FIG. 3  is a flowchart for illustrating an operation of the face authentication device illustrated in  FIG. 2 ; 
         FIG. 4  is an explanatory diagram of a camera arrangement that uses a mirror; 
         FIG. 5  is an explanatory diagram of a camera arrangement that uses a mirror and allows face authentication to be performed from a plurality of directions; 
         FIG. 6  is an explanatory diagram of an application example of a camera arrangement that uses a mirror; 
         FIG. 7  is a block diagram of a face authentication system in one embodiment of this invention; 
         FIG. 8  is a block diagram of a mirror region determination unit to be used in the face authentication system illustrated in  FIG. 7 ; 
         FIG. 9  is a flowchart of face authentication to be performed in the face authentication system illustrated in  FIG. 7  to which this invention is applied; 
         FIG. 10  is a flowchart of mirror region detection; and 
         FIG. 11  is a diagram for illustrating an example of an image for correction. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Related Art 
     In order to facilitate understanding of this invention, the related art will be described first. 
     In order to achieve a high authentication accuracy in a face authentication technology, it is required to photograph a face from a position as close to the front as possible. However, in particular, a camera for monitoring is installed in the vicinity of a ceiling in many cases, and hence it is difficult for the camera to capture the face from the front. 
     The authentication accuracy can be expected to be improved by setting an angle, distance, height, or the like of a camera with respect to an object as recommended. However, when a camera is installed in, for example, a narrow floor or passage, there is a case in which the angle, distance, height, or the like of a camera cannot be set as recommended depending on the environment in which the camera is installed and it is consequently difficult to perform face authentication. 
     For example, such camera arrangements as illustrated in  FIG. 1A  and  FIG. 1B  to be used in face authentication are considered.  FIG. 1A  is an aerial view, and  FIG. 1B  is a side view. 
     A case is considered in which, in monitoring performed in such a narrow floor as illustrated in the aerial view of  FIG. 1A , a camera  11   a  is installed so as to be aligned with a flow line direction of a person. When a person to be photographed  12  is to be photographed from the position of the camera  11   a , a distance between the camera  11   a  and the person to be photographed  12  (hereinafter referred to as “photographing distance”) is not sufficient, and hence the person to be photographed  12  cannot be photographed at a recommended angle of the camera  11   a  with respect to an object. 
     In other words, in order to achieve recommended settings for the camera  11   a  illustrated in the side view of  FIG. 1B , a certain distance, for example, the distance between a camera  11   b  and the person to be photographed  12 , is required. 
     Now, an example embodiment of this invention will be described with reference to the drawings. It is to be understood that the technical scope of this invention is not limited to the example embodiment, and is to be interpreted based on the description of the appended claims. 
     Example Embodiment 
     Next, the example embodiment of this invention will be described. 
     In order to increase the accuracy of the face authentication in such a narrow floor as illustrated in  FIG. 1A , it is required to increase the photographing distance. Thus, in this example embodiment, the following method is adopted: a camera is arranged so as to face a mirror, and a person to be photographed reflected by the mirror is photographed with the camera, to thereby increase the photographing distance. 
     It is assumed in this example embodiment that a face authentication system is for monitoring, and is thus also applicable to a case in which faces of a plurality of persons on a mirror are detected. 
     When a real image and a reflected image are acquired at the same time, in this example embodiment, a mirror region is automatically detected to determine whether or not a face image is required to be subjected to correction and inversion processing. With this, images for which a plurality of angles are specified, such as a reflected front image and a reflected side image, are not required, and hence it is only required to register one front face image for each face of a person to be photographed with a database for face authentication. 
     Next, features of the example embodiment of this invention will be described. 
     In this example embodiment, through use of reflection by a mirror, it is possible to increase a face authentication accuracy and also increase a degree of freedom of a position at which the camera is installed. In particular, a feature of this example embodiment resides in that a logic of determining whether or not face image inversion processing is required when a real image and a reflected image are acquired at the same time is introduced. 
     Referring to  FIG. 2 , a description will be given of a face authentication system including a face authentication device according to the example embodiment of this invention. 
     The face authentication system comprises an image pickup device  100 , a face authentication device  200 , and a result output device  300 . 
     The image pickup device  100  picks up an input image including a mirror region reflected by a mirror. The face authentication device  200  receives the input image picked up by the image pickup device  100 , and supplies an authenticated result to the result output unit  300 . 
     The face authentication device  200  includes a processing unit  210  and a storage unit  220 . 
     The storage unit  220  comprises a storage device including, for example, a hard disk drive or a non-volatile memory. The storage unit  220  serves as a database with which, for each face of a person to be authenticated, only one real front image is to be registered as a reference face image. 
     The processing unit  210  comprises a mirror image processing unit  212 , a face detection processing unit  214 , and a face authentication processing unit  216 . 
     The mirror image processing unit  212  detects the mirror region in the input image, and subjects a detected mirror region to lateral inversion processing to produce a processed image. 
     The face detection processing unit  214  detects a face image from the processed image to generate a detected face image. 
     The face authentication processing unit  216  compares the detected face image with the reference face image stored in the storage unit  200 , to thereby perform face authentication. 
     Next, referring to  FIG. 3 , a description will be given of an operation of the face authentication device  200  illustrated in  FIG. 2 . 
     First, in the face authentication device  200 , for each face of a person to be authenticated, only one real front image is registered with the storage unit  220  in advance as a reference face image (Step S 101 ). 
     Next, the mirror image processing unit  212  detects the mirror region in the input image picked up by the image pickup device  100 , and subjects the detected mirror region to lateral inversion processing to produce the processed image (Step S 102 ). 
     The face detection processing unit  214  detects a face image from the processed image to generate the detected face image (Step S 103 ). 
     Then, the face authentication processor  216  compares the detected face image with the reference face image stored in the storage unit  200 , to thereby perform face authentication (Step S 104 ). 
     The face authentication device  200  configured as described above produces the following effect. 
     Specifically, the effect of this example embodiment is as follows: the face authentication can easily be performed based on the input image including the mirror region without increasing the storage capacity of the database. This is because the mirror region is subjected to the lateral inversion processing, which eliminates the necessity to register a face image subjected to lateral inversion with the database. 
     The respective components of the face authentication device  200  are only required to be implemented through use of a combination of hardware and software. In a mode in which hardware and software are combined, a face authentication program is loaded onto a random access memory (RAM), and a control unit (central processing unit (CPU)) and other hardware are caused to operate based on the face authentication program, to thereby implement each component as corresponding means. Further, the face authentication program may be recorded in a recording medium for distribution. The face authentication program recorded in the recording medium is read into a memory in a wired or wireless manner, or via the recording medium itself, to cause the control unit and the like to operate. Examples of the recording medium include an optical disc, a magnetic disk, a semiconductor memory device, and a hard disk. 
     When the above-mentioned example embodiment is described in another expression, the example embodiment can be implemented by causing a computer, which is to be caused to operate as the face authentication device  200 , to operate as the mirror image processing unit  212 , the face detection processing unit  214 , and the face authentication processing unit  216  based on the face authentication program loaded on the RAM. 
     First Example 
     Now, referring to the accompanying drawings, a first example of this invention will be described. 
       FIG. 4  to  FIG. 6  are each a diagram for illustrating a camera arrangement that uses a mirror. 
       FIG. 4  is a diagram for illustrating an example in which an image pickup range of a camera  21  is limited to a mirror  23  so that the camera  21  receives light reflected by the mirror  23  to photograph the person to be photographed  22 . 
       FIG. 5  is a diagram for illustrating an example in which a wide range including a mirror  33  is photographed from a camera  31 . In other words,  FIG. 5  is an explanatory diagram for illustrating a camera arrangement that uses the mirror  33  and allows face authentication to be performed from a plurality of directions. 
       FIG. 6  is a diagram for illustrating an example in which a triangular mirror  43  is used to allow a camera  41  to photograph persons to be photographed  42  existing on both sides of the mirror  43 . In other words,  FIG. 6  is an explanatory diagram of an application example of a camera arrangement that uses the mirror  43 . 
       FIG. 7  is a block diagram for illustrating a configuration of a face authentication system  500  in the first example of this invention. The face authentication system  500  illustrated in  FIG. 7  comprises an image pickup device  501 , a face authentication device  502 , and a result output device  512 . 
     The face authentication device  502  is implemented by adding a mirror image processing module  504  to a general face authentication device. 
     To describe more specifically, the face authentication device  502  includes an image input unit  503 , the mirror image processing module  504 , a face detection processing unit  508 , a facial feature point detection processing unit  509 , a comparison processing unit  510 , and a feature point database  511 . 
     In the face authentication device  502 , first, the image input unit  503  receives, as an input image, an image picked up by the image pickup device  501 . The mirror image processing module  504  reads the input image received by the image input unit  503 . After the input image is processed by the mirror image processing module  504 , the face detection processing unit  508  cuts out a face image from the processed image. The facial feature point detection processing unit  509  extracts a feature point of the cut-out face image. The comparison processing unit  510  compares the extracted feature point with a reference feature point registered with the feature point database  511 . The comparison processing unit  510  then produces a result of the face authentication to the result output device  512 . 
     The mirror image processing module  504  includes a mirror region decision unit  505 , a distortion correction unit  506 , and an image inversion processing unit  507 . 
     As illustrated in  FIG. 8 , the mirror region decision unit  505  includes any one of a mirror frame detection unit  513  and a wavelength detection unit  514 . The mirror region decision unit  505  further includes a storage unit  515 . The storage unit  515  stores settings for detection and the mirror region. 
     Next, referring to  FIG. 9  and  FIG. 10 , a description will be given of an operation of the face authentication system  500  illustrated in  FIG. 7  and  FIG. 8 .  FIG. 9  is a flowchart of face authentication, and  FIG. 10  is a flowchart of mirror region detection. 
     First, the image input unit  503  acquires from the image pickup device  501  an image signal of an image (still image) or a moving image (Step S 61 ). The mirror region decision unit  505  extracts a mirror region from the acquired image signal of the image (still image) or the moving image (Step S 62 ). 
     Referring to  FIG. 10 , decision of a mirror region (detection of a mirror region) will be described. The mirror region decision (mirror region detection) in the mirror region decision unit  505  is performed by any one of the mirror frame detection unit  513  and the wavelength detection unit  514 . 
     The mirror region decision unit  505  specifies in advance a detection method to be used (Step S 71 ). 
     When the mirror frame detection unit  513  is to be used, it is required to mount a frame to the mirror in advance. 
     It is assumed that the mirror region decision unit  505  determines in Step S 71  that the mirror frame detection unit  513  is to be used. In this case, the mirror frame detection unit  513  reads from the storage unit  515  a feature, for example, a color, of the mirror frame (Step S 72 ) to detect the inside of the frame as a mirror region (Step S 73 ). The mirror frame detection unit  513  stores the detected mirror region into the storage unit  515  (Step S 74 ), and passes the region to the distortion correction unit  506 . 
     When the wavelength detection unit  514  is to be used, a filter that does not reflect a specific wavelength, for example, an infrared cut film, is attached to the mirror, and a camera capable of capturing a specific wavelength, for example, a visible light-infrared camera, is used. A portion in which the cut film is attached does not emit light having the specific wavelength. 
     It is assumed that the mirror region decision unit  505  determines in Step S 71  that the wavelength detection unit  514  is to be used. In this case, the wavelength detection unit  514  detects from the picked-up image a portion from which light having the specific wavelength is not emitted (Step S 75 ), and stores the detected portion into the storage unit  515  as a mirror region (Step S 74 ). After that, the wavelength detection unit  514  cuts out the mirror region from an input image picked up by a visible light camera, and passes the cut-out mirror region to the distortion correction unit  506 . 
     Referring back to  FIG. 9 , the mirror region decision unit  505  decides whether or not a relevant region is the mirror region (Step S 63 ). 
     When the mirror region decision unit  505  decides that the relevant region is the mirror region (Yes in Step S 63 ), the mirror image processing module  504  determines whether or not correction of distortion or expansion is required to be performed on a region detected as the mirror region (Step S 64 ). When it is determined that correction is required (Yes in Step S 64 ), the distortion correction unit  506  corrects the mirror image (Step S 65 ). Whether or not to perform correction is determined based on whether or not a distortion correction value is set in advance in the storage unit  515 . Distortion correction is not performed in normal cases, but is performed mainly when an angle of a camera with respect to a mirror is small or when a special mirror, for example, a convex mirror, is used. 
     The distortion correction value is determined before the face authentication flow of  FIG. 9 . Next, the determination of the distortion correction value will be described. 
     Before the face authentication, such an image for correction as illustrated in  FIG. 11  is enlarged, and is reflected by the entire mirror. The camera picks up the reflected image of the image for correction, and a processing device (not shown) compares the reflected image with the original image and performs reverse calculation, to thereby calculate a correction parameter representative of a deformation difference from the original image. The processing device stores the correction parameter into the storage unit  515 , and distorts an image based on the correction parameter when correcting distortion of the image. 
     Referring back to  FIG. 9 , after the processing by the distortion correction unit  506 , the image inversion processing unit  507  performs lateral inversion processing (Step S 66 ). After that, a combination of the face detection processing unit  508 , the facial feature point detection processing unit  509 , and the comparison processing unit  510  performs face authentication processing on a region decided by the mirror region decision unit  505  as a region other than the mirror and on the region processed by the mirror image processing module  504  (Step S 67 ). Finally, the comparison processing unit  510  produces a result of the authentication to the result output device  512 . 
     Therefore, the combination of the face detection processing unit  508 , the facial feature point detection processing unit  509 , and the comparison processing unit  510  serves as the face authentication processing unit  216  (see  FIG. 2 ) configured to perform face authentication processing. 
     Next, effects of the first example will be described. 
     In a case of normal face authentication, a camera is installed at the position of the mirror  23  ( FIG. 4 ), and hence an angular difference between the person to be photographed  22  and the camera in a vertical direction is disadvantageously increased. 
     In contrast, in the first example, the distance between the camera  21  and the mirror  23  is added to the distance between the person to be photographed  22  and the mirror  23 . As a result, the distance between the camera  21  and the person to be photographed  22  (photographing distance) is increased, and hence it is possible to reduce the angular difference in the vertical direction. 
     Further, in the case of such an installation as illustrated in  FIG. 5  in which the mirror is contained in the image picked up by the camera  31 , a normal camera image is subjected to a normal face authentication process, whereas an automatically detected mirror region is subjected to the face authentication after being subjected to distortion correction and lateral inversion processing. This consequently enables face authentication processing from a plurality of points to be performed in a manner close to the actual processing from a plurality of points, and hence a probability of capturing a front image of a face increases. With this, increase in detection rate is expected in face authentication for monitoring, for example, detection of a suspicious person. Further, a mirror region is subjected to lateral inversion processing, which eliminates the necessity to register a laterally-inverted face image with the feature point database  511  for face images. It is therefore possible to reduce the storage capacity of the database. 
     Through installation of a special mirror such as the triangular mirror  43  or a convex mirror as illustrated in  FIG. 6 , the camera  41  is allowed to pick up images in a plurality of directions. It is therefore possible to implement face authentication for monitoring in a narrow floor or passage in which the camera cannot be installed. 
     The respective components of the face authentication device  502  are only required to be implemented through use of a combination of hardware and software. In a mode in which hardware and software are combined, a face authentication program is loaded onto a random access memory (RAM), and a control unit (central processing unit (CPU)) and other hardware are caused to operate based on the face authentication program, to thereby implement each component as corresponding means. Further, the face authentication program may be recorded in a recording medium for distribution. The face authentication program recorded in the recording medium is read into a memory in a wired or wireless manner, or via the recording medium itself, to cause the control unit and the like to operate. Examples of the recording medium include an optical disc, a magnetic disk, a semiconductor memory device, and a hard disk. 
     When the above-mentioned example is described in another expression, the example can be implemented by causing a computer, which is to be caused to operate as the face authentication device  502 , to operate as the image input unit  503 , the mirror image processing module  504 , the face detection processing unit  508 , the facial feature point detection processing unit  509 , and the comparison processing unit  510  based on the face authentication program loaded on the RAM. 
     Next, other examples of this invention will be described. 
     In such a case as illustrated in  FIG. 4 , a filter configured to transmit only a specific wavelength therethrough, for example, an infrared transmission filter, may be attached to the mirror  23 , and the camera  21  configured to capture the specific wavelength may be used. With this, visible light is cut off, which inhibits the person to be photographed  22  from recognizing the camera  21  reflected by the mirror  23 . It is therefore possible to reduce a psychological stress on the person to be photographed  22 . 
     In the mirror region detection, a mirror may be subjected to surface treatment to be formed into, for example, a Chinese magic mirror, and a region subjected to the surface treatment may be detected as a mirror region. 
     In the mirror region detection, a polarization filter may be attached to a mirror to polarize reflected light so that a region of polarized light may be detected as a mirror region. 
     The mirror region detection and distortion correction may be set manually as well as automatically. 
     The mirror region detection and distortion correction may be set automatically through use of machine learning. 
     In such a camera arrangement as illustrated in  FIG. 5 , when the distance between a real image and a mirror reflected image that are picked up by the camera  31  is too large, a case in which one of the images is out of focus is conceivable. In this case, a function of adjusting focus may be added to the mirror in order to adjust focus, or a camera capable of adjusting focus after photographing, such as a light-field camera or a lensless camera, may be used to acquire an image. 
     In the image picked up by the camera, only the mirror region may be subjected to face authentication. 
     In the above, the example embodiment and the examples of this invention are described in detail with reference to the drawings. It is to be noted, however, that a person skilled in the art can employ other similar example embodiments and examples, and can perform change or addition of modes as appropriate without departing from this invention. 
     The whole or part of the example embodiments and the examples described above can be described as, but not limited to, the following supplementary notes. 
     Supplementary Note 1 
     A face authentication device, which is configured to perform face authentication based on an input image picked up by an image pickup device, the input image including a mirror region reflected by a mirror, 
     the face authentication device comprising:
         a database with which, for each face of a person to be authenticated, only one real front image is to be registered as a reference face image;   a mirror image processing circuitry configured to detect the mirror region from the input image and to subject a detected mirror region to lateral inversion processing to produce a processed image;   a face detection processing circuitry configured to detect a face image from the processed image to generate a detected face image; and   a face authentication processing circuitry configured to compare the detected face image with the reference face image, to thereby perform face authentication.       

     Supplementary Note 2 
     The face authentication device according to Supplementary Note 1, wherein the mirror image processing circuitry includes a mirror region decision circuitry configured to decide the mirror region from the input image. 
     Supplementary Note 3 
     The face authentication device according to Supplementary Note 2, 
     wherein the mirror has a mirror frame mounted thereto in advance, and 
     wherein the mirror region decision circuitry includes:
         a storage configured to store a feature of the mirror frame as a stored feature; and   a mirror frame detection circuitry configured to detect the mirror region from the input image based on the stored feature.       

     Supplementary Note 4 
     The face authentication device according to Supplementary Note 2, 
     wherein the mirror has attached thereto a cut film configured to avoid reflecting a specific wavelength, and 
     wherein the mirror region decision circuitry includes a wavelength detection circuitry configured to detect from the input image, as the mirror region, a portion in which light having the specific wavelength is inhibited from being reflected. 
     Supplementary Note 5 
     The face authentication device according to any one of Supplementary Notes 1 to 4, wherein the mirror image processing circuitry further includes a distortion correction circuitry configured to correct distortion of the mirror region. 
     Supplementary Note 6 
     A face authentication method for performing face authentication based on an input image including a mirror region reflected by a mirror, 
     the face authentication method comprising:
         registering, for each face of a person to be authenticated, only one real front image with a database as a reference face image;   subjecting the mirror region of the input image to lateral inversion processing to produce a processed image;   detecting a face region from the processed image to generate a detected face image; and   comparing the detected face image with the reference face image, to thereby perform face authentication.       

     Supplementary Note 7 
     The face authentication method according to Supplementary Note 6, wherein the subjecting the mirror region of the input image to lateral inversion processing includes deciding the mirror region from the input image. 
     Supplementary Note 8 
     The face authentication method according to Supplementary Note 7, 
     wherein the mirror has a mirror frame mounted thereto in advance, and 
     wherein the deciding includes:
         storing a feature of the mirror frame in a storage as a stored feature; and   detecting the mirror region from the input image based on the stored feature.       

     Supplementary Note 9 
     The face authentication method according to Supplementary Note 7, 
     wherein the mirror has attached thereto a cut film configured to avoid reflecting a specific wavelength, and 
     wherein the deciding includes detecting from the input image, as the mirror region, a portion in which light having the specific wavelength is inhibited from being reflected. 
     Supplementary Note 10 
     The face authentication method according to any one of Supplementary Notes 6 to 9, wherein the subjecting the mirror region of the input image to lateral inversion processing further includes correcting distortion of the mirror region. 
     Supplementary Note 11 
     A non-transitory computer readable recoding medium storing a face authentication program for causing a computer to execute face authentication based on an input image including a mirror region reflected by a mirror, the face authentication program causing the computer to execute: 
     a registration procedure of registering, for each face of a person to be authenticated, only one real front image with a database as a reference face image; 
     a mirror image processing procedure of subjecting the mirror region of the input image to lateral inversion processing to produce a processed image; 
     a face detection processing procedure of detecting a face region from the processed image to generate a detected face image; and 
     a face authentication processing procedure of comparing the detected face image with the reference face image, to thereby perform face authentication. 
     Supplementary Note 12 
     The non-transitory computer readable recording medium according to Supplementary Note 11, wherein the mirror image processing procedure includes a mirror region decision procedure of causing the computer to decide the mirror region from the input image. 
     Supplementary Note 13 
     The non-transitory computer readable recording medium according to Supplementary Note 12, 
     in which the mirror has a mirror frame mounted thereto in advance, and 
     in which the mirror region determination procedure includes:
         a procedure of causing the computer to store a feature of the mirror frame in a storage; and   a mirror frame detection procedure of causing the computer to detect the mirror region from the input image based on the stored feature of the mirror frame.       

     Supplementary Note 14 
     The non-transitory computer readable recording medium according to Supplementary Note 12, 
     in which the mirror has attached thereto a cut film configured to avoid reflecting a specific wavelength, and 
     in which the mirror region determination procedure includes a wavelength detection procedure of causing the computer to detect from the input image a portion in which light having the specific wavelength is inhibited from being reflected as the mirror region. 
     Supplementary Note 15 
     The non-transitory computer readable recording medium according to any one of Supplementary Notes 11 to 14, in which the mirror image processing procedure further includes a distortion correction procedure of causing the computer to correct distortion of the mirror region.