U.S. patent application number 16/961561 was filed with the patent office on 2021-11-04 for face authentication apparatus.
This patent application is currently assigned to NEC CORPORATION. The applicant listed for this patent is NEC CORPORATION. Invention is credited to Taketo KOCHI, Kenji SAITO.
Application Number | 20210343099 16/961561 |
Document ID | / |
Family ID | 1000005721601 |
Filed Date | 2021-11-04 |
United States Patent
Application |
20210343099 |
Kind Code |
A1 |
KOCHI; Taketo ; et
al. |
November 4, 2021 |
FACE AUTHENTICATION APPARATUS
Abstract
A face authentication apparatus includes a face image
acquisition unit, a collation unit, a time measurement unit, and a
threshold change unit. The face image acquisition unit acquires a
face image of an authentication target. The collation unit performs
face authentication on the face image of the authentication target
on the basis of a threshold. The time measurement unit measures the
elapsed time from the time of starting operation of the face
authentication apparatus. The threshold change unit restricts
changing of the threshold to a value larger than a value determined
depending on the measured elapsed time.
Inventors: |
KOCHI; Taketo; (Tokyo,
JP) ; SAITO; Kenji; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEC CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
NEC CORPORATION
Tokyo
JP
|
Family ID: |
1000005721601 |
Appl. No.: |
16/961561 |
Filed: |
December 20, 2018 |
PCT Filed: |
December 20, 2018 |
PCT NO: |
PCT/JP2018/047066 |
371 Date: |
July 10, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G07C 9/37 20200101; G07C
2209/08 20130101; G06F 21/32 20130101; G06K 9/00288 20130101 |
International
Class: |
G07C 9/37 20060101
G07C009/37; G06K 9/00 20060101 G06K009/00; G06F 21/32 20060101
G06F021/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 12, 2018 |
JP |
2018-003233 |
Claims
1. A face authentication apparatus comprising: a memory containing
program instructions; and a processor coupled to the memory,
wherein the processor is configured to execute the program
instructions to: acquire a face image of an authentication target;
perform face authentication on the face image of the authentication
target on a basis of a threshold; measure elapsed time from a time
of starting operation of the face authentication apparatus; and
restrict changing of the threshold to a value larger than a value
determined depending on the elapsed time measured.
2. The face authentication apparatus according to claim 1, wherein
the changing of the threshold includes setting the threshold to be
smaller relative to a target value at the time of starting the
operation of the face authentication apparatus.
3. The face authentication apparatus according to claim 1, wherein
the changing of the threshold includes, before changing the
threshold in accordance with a request from a user, checking
whether or not a value of the threshold after the change is larger
than the value determined depending on the elapsed time measured,
and if the value is larger, rejecting the request.
4. The face authentication apparatus according to claim 1, wherein
the changing of the threshold includes gradually incrementing the
threshold until the threshold reaches a target value in accordance
with the value determined depending on the elapsed time
measured.
5. The face authentication apparatus according to claim 1, further
comprising a threshold changing schedule that is a schedule of
changing the threshold after the time of starting the operation of
the face authentication apparatus and in which a value of the
threshold after the change becomes larger as the elapsed time from
the time of starting the operation is longer, wherein the changing
of the threshold includes calculating the value determined
depending on the elapsed time measured, on a basis of the threshold
changing schedule and the elapsed time measured.
6. The face authentication apparatus according to claim 5, further
comprising a plurality of types of the threshold changing
schedules, wherein the changing of the threshold includes
selecting, from the plurality of the types of the threshold
changing schedules, a threshold changing schedule to be used for
calculating the value determined depending on the elapsed time
measured, on a basis of a history of face authentication
success.
7. The face authentication apparatus according to claim 1, wherein
the processor is configured to further execute the program
instructions to: output a result of the face authentication.
8. The face authentication apparatus according to claim 7, wherein
the acquiring the face image includes acquiring a face image of a
user who passes through a gate apparatus as the face image of the
authentication target, and the outputting includes outputting, to
the gate apparatus, a result of the face authentication for
controlling open and close operation of the gate apparatus.
9. The face authentication apparatus according to claim 1, wherein
in the face authentication, a feature amount of a face extracted
from the face image of the authentication target and a feature
amount of a face extracted from a reference face image of each
registered user are collated with each other, and similarly between
the face image of the authentication target and the reference face
image is calculated.
10. A face authentication method performed by a face authentication
apparatus, the method comprising: acquiring a face image of an
authentication target; performing face authentication on the face
image of the authentication target on a basis of a threshold;
measuring elapsed time from a time of starting operation of the
face authentication apparatus; and restricting changing of the
threshold to a value larger than a value determined depending on
the elapsed time measured.
11. The face authentication method according to claim 10, wherein
the threshold is set to be smaller relative to a target value at
the time of starting the operation of the face authentication
apparatus.
12. The face authentication method according to claim 10, wherein
the restricting the changing of the threshold includes, before
changing the threshold in accordance with a request from a user,
checking whether or not a value of the threshold after the change
is larger than the value determined depending on the elapsed time
measured, and if the value is larger, rejecting the request.
13. The face authentication method according to any of claim 10,
further comprising gradually incrementing the threshold until the
threshold reaches a target value in accordance with the value
determined depending on the elapsed time measured.
14. The face authentication method according to claim 10, wherein
the face authentication apparatus includes a threshold changing
schedule that is a schedule of changing the threshold after the
time of starting the operation of the face authentication apparatus
and in which a value of the threshold after the change becomes
larger as the elapsed time from the time of starting the operation
is longer, and the method further comprises calculating the value
determined depending on the elapsed time measured, on a basis of
the threshold changing schedule and the elapsed time measured.
15. The face authentication method according to claim 14, wherein
the face authentication apparatus includes a plurality of types of
the threshold changing schedules, and the method further comprises
selecting, from the plurality of the types of the threshold
changing schedules, a threshold changing schedule to be used for
calculating the value determined depending on the elapsed time
measured, on a basis of a history of face authentication
success.
16. The face authentication method according to claim 10, further
comprising outputting a result of the face authentication.
17. The face authentication method according to claim 16, wherein
the acquiring the face image includes acquiring a face image of a
user who passes through a gate apparatus as the face image of the
authentication target, and the outputting the result of the face
authentication includes outputting, to the gate apparatus, a result
of the face authentication for controlling open and close operation
of the gate apparatus.
18. The face authentication method according to claim 10, wherein
in the face authentication, a feature amount of a face extracted
from the face image of the authentication target and a feature
amount of a face extracted from a reference face image of each
registered user are collated with each other, and similarly between
the face image of the authentication target and the reference face
image is calculated.
19. A non-transitory computer-readable medium storing a program
comprising instructions for causing a computer to perform
processing to: acquire a face image of an authentication target;
perform face authentication on the face image of the authentication
target on a basis of a threshold; measure elapsed time from a time
of starting operation of the face authentication apparatus; and
restrict chanting of the threshold to a value larger than a value
determined depending on the elapsed time measured.
Description
TECHNICAL FIELD
[0001] The present invention relates to a face authentication
apparatus, a face authentication method, and a recording
medium.
BACKGROUND ART
[0002] Conventionally, in various systems such as an access
monitoring system and an attendance management system, personal
authentication by means of face authentication is performed on a
user who passes through a gate or the like.
[0003] For example, Patent Literatures 1 to 3 disclose a face
authentication apparatus that performs personal authentication by
acquiring a face image of an authentication target by a camera,
calculating similarity between the face image of the authentication
target and a reference face image of a person that is previously
registered, and comparing it with a threshold, thereby collating
the face image of the authentication target and the reference face
image.
[0004] Further, a face authentication apparatus of this type
employs a configuration of automatically changing a threshold to be
used for collation.
[0005] For example, in Patent Literature 1, a threshold is
determined based on the false rejection rate. In Patent Literature
2, a threshold is changed based on an authentication result after
the start of operation. In Patent Literature 3, a threshold is
changed according to a used condition such as a period of time in
which the frequency of use is high.
[0006] Patent Literature 1: JP 2016-118977 A
[0007] Patent Literature 2: JP 2013-117876 A
[0008] Patent Literature 3: JP 2002-183734 A
SUMMARY
[0009] At the time of starting operation of a face authentication
apparatus, since a user is not used to use it, there is a tendency
that a high-quality face image cannot be obtained. For example,
when a face authentication apparatus is provided to an existing or
new gate and face authentication is performed on users who pass
through the gate, a user may look down when passing through the
gate or a user may attempt to pass through the gate with a mask so
that a part of the face is hidden, in the beginning of the
operation. As a result, the quality of a face image tends to be
lowered. On the other hand, when a certain period of time has
passed from the start of operation, users are used to use face
authentication. Therefore, acts of lowering the quality of a face
image as described above are decreased. However, Patent Literatures
1 to 3 do not pay attention to such acts of users as described
above. Therefore, there is a case where a large threshold value
that can achieve target security strength is set from the beginning
of the operation so that the frequency of failure in face
authentication is high. There is also a case where although a small
threshold value is set at the beginning of the operation, the
threshold value may be incremented easily so that the frequency of
failure in face authentication becomes high. As a result,
convenience of a face authentication apparatus in the beginning of
the operation is lowered.
[0010] An exemplary object of the present invention is to provide a
face authentication apparatus that solves the aforementioned
problem.
[0011] A face authentication apparatus according to one aspect of
the present invention is a face authentication apparatus
including
[0012] a face image acquisition unit that acquires a face image of
an authentication target,
[0013] a collation unit that performs face authentication on the
face image of the authentication target on the basis of a
threshold,
[0014] a time measurement unit that measures elapsed time from the
time of starting operation of the face authentication apparatus,
and
[0015] a threshold change unit that restricts changing of the
threshold to a value larger than a value determined depending on
the elapsed time measured.
[0016] A face authentication method according to another aspect of
the present invention is a face authentication method performed by
a face authentication apparatus. The method includes
[0017] acquiring a face image of an authentication target,
[0018] performing face authentication on the face image of the
authentication target on the basis of a threshold,
[0019] measuring elapsed time from the time of starting operation
of the face authentication apparatus, and
[0020] restricting changing of the threshold to a value larger than
a value determined depending on the elapsed time measured.
[0021] A computer-readable medium according to another aspect of
the present invention stores a program for causing a computer
constituting a face authentication apparatus to function as
[0022] a face image acquisition unit that acquires a face image of
an authentication target,
[0023] a collation unit that performs face authentication on the
face image of the authentication target on the basis of a
threshold,
[0024] a time measurement unit that measures elapsed time from the
time of starting operation of the face authentication apparatus,
and
[0025] a threshold change unit that restrict changing of the
threshold to a value larger than a value determined depending on
the elapsed time measured.
[0026] With the configurations described above, the present
invention is able to prevent deterioration in convenience of a face
authentication apparatus in the beginning of operation.
BRIEF DESCRIPTION OF DRAWINGS
[0027] FIG. 1 is a block diagram of a face authentication apparatus
according to a first exemplary embodiment of the present
invention.
[0028] FIG. 2 is a schematic diagram of an access management system
including the face authentication apparatus according to the first
exemplary embodiment of the present invention.
[0029] FIG. 3 illustrates an example of a threshold changing
schedule in the face authentication apparatus according to the
first exemplary embodiment of the present invention.
[0030] FIG. 4 is a flowchart illustrating the overall operation of
the face authentication apparatus according to the first exemplary
embodiment of the present invention.
[0031] FIG. 5 is a flowchart illustrating an exemplary operation of
a threshold change unit in the face authentication apparatus
according to the first exemplary embodiment of the present
invention.
[0032] FIG. 6 is a flowchart illustrating another exemplary
operation of the threshold change unit in the face authentication
apparatus according to the first exemplary embodiment of the
present invention.
[0033] FIG. 7 illustrates an example of a collation threshold
setting screen displayed by the threshold change unit in the face
authentication apparatus according to the first exemplary
embodiment of the present invention.
[0034] FIG. 8 illustrates examples of threshold changing schedules
in a face authentication apparatus according to a second exemplary
embodiment of the present invention.
[0035] FIG. 9 is a block diagram of a face authentication apparatus
according to a third exemplary embodiment of the present
invention.
EXEMPLARY EMBODIMENTS
[0036] Next, exemplary embodiments of the present invention will be
described in detail with reference to the drawings.
First Exemplary Embodiment
[0037] FIG. 1 is a block diagram of a face authentication apparatus
100 according to a first exemplary embodiment of the present
invention. FIG. 2 is a schematic diagram of an access management
system including the face authentication apparatus 100 according to
the present embodiment. Referring to FIG. 1, the face
authentication apparatus 100 of the present embodiment includes an
interface 111 with a camera unit 141, an interface 112 with a gate
apparatus 142, a communication interface 113, an operation input
unit 114, a screen display unit 115, a storage unit 120, and an
arithmetic processing unit 130.
[0038] The interface 111 is configured to transmit and receive
signals with the camera unit 141 that images a face of a person who
is an authentication target. Transmission and reception of signals
may be performed via wired or wireless communication. As
illustrated in FIG. 2, the camera unit 141 is set at a position
with an image angle where the camera unit 141 can image a face
portion of a user 143 who passes through the gate apparatus 142.
The camera unit 141 is an imaging device configured of a Charge
Coupled Device (CCD), a Complementary Metal-Oxide Semiconductor
(CMOS) device, or the like that outputs image data captured by
imaging a face of a person who is a collation target to the
arithmetic processing unit 130 via the interface 111. The image
data captured by the camera unit 141 is, for example, a
black-and-white gradation image of 256 gradations but may be a
color image.
[0039] The interface 112 is configured to transmit and receive
signals such as results of face authentication to and from the gate
apparatus 142. Transmission and reception of signals may be
performed via wired or wireless communication. The gate apparatus
142 performs predetermined operation according to the received
result of the face authentication. Predetermined operation may
include various types of operation. For example, the gate apparatus
142 automatically performs open/close operation of a door attached
to the gate apparatus 142 according to the result of face
authentication. The gate apparatus 142 may include a gate bar that
is manually openable/closable, and release lock of the gate bar for
a certain period only when face authentication has succeeded. The
gate apparatus 142 may output a message of passage propriety
visually or by sound from an alarm provided to the gate apparatus
142 according to the result of face authentication. The gate
apparatus 142 may be a stationary type, or a portable type that can
be moved. The gate apparatus 142 may be an apparatus independent of
the face authentication apparatus 100, or an apparatus integrated
with the face authentication apparatus 100.
[0040] The communication interface 113 is a communication device
that performs data communication with an external device such as a
terminal. The communication system may be wired or wireless
communication.
[0041] The operation input unit 114 includes an input device such
as a keyboard and numeric keys, and is configured to detect an
operation by an operator and output it to the arithmetic processing
unit 130.
[0042] The screen display unit 115 is a screen display device such
as a liquid crystal display (LCD) or a plasma display panel (PDP).
The screen display unit 115 is configured to display various types
of information such as an authentication result on a screen
according to an instruction from the arithmetic processing unit
130.
[0043] The storage unit 120 is a storage device such as a hard disk
or a memory. The storage unit 120 is configured to store therein
processing information and a program 121 necessary for various
types of processing to be performed in the arithmetic processing
unit 130.
[0044] The program 121 implements various processing units by being
read into the arithmetic processing unit 130 and executed. The
program 121 is read, in advance, from an external device (not
illustrated) or a storage medium (not illustrated) via a data
input/output function such as the communication interface 113, and
is stored in the storage unit 120.
[0045] Main processing information stored in the storage unit 120
includes reference face image data 122, a collation threshold 123,
elapsed time 124, and a threshold changing schedule 125.
[0046] The reference face image data 122 is data in which a face
image, serving as a reference to be used when face authentication
is performed, and a user ID are associated with each other. In the
reference face image data 122, at least one face image of a person
having a user ID may be associated with the user ID as a reference
face image. Alternatively, in the reference face image data 122,
the feature amount of a face extracted from a face image of a
person having a user ID may be associated with the user ID as
reference face information. Here, the feature amount of a face is a
numerical value representing a feature of each part in a face image
for recognizing the positional relationship or shape of each part
such as eye, nose, mouth, eyebrow, or the like constituting the
face, and is used for similarity determination or the like between
images.
[0047] The collation threshold 123 is a threshold to be used for
performing face authentication. In the case of the present
embodiment, the collation threshold 123 is shared by every user
ID.
[0048] The elapsed time 124 is data showing elapsed time from the
start of operation of the face authentication apparatus 100.
[0049] The threshold changing schedule 125 is data showing a
schedule of changing the collation threshold 123. In the threshold
changing schedule 125, values of the collation threshold at the
time of starting operation of the face authentication apparatus 100
and values of the collation threshold after the change to be used
at a plurality of points of time after the start of operation are
defined. Further, in the threshold changing schedule 125, the value
of the collation threshold after the change is larger as the
elapsed time from the start of operation of the face authentication
apparatus 100 is longer.
[0050] FIG. 3 shows an example of the threshold changing schedule
125. The threshold changing schedule 125 of this example includes a
plurality of rows, each of which is configured of stage No.,
period, and collation threshold value. The stage No. is a number of
identifying each state when a section from a point of time of
starting operation until a point of time of setting the collation
threshold to be a target value is divided into a plurality of
stages. The period is time information defining the section of the
stage. The collation threshold value is a value of the collation
threshold used in the stage. For example, the stage of the stage
No. 1 is a period in which the operation start time is the start
and a point of time at which time T1 elapses is the end, and the
collation threshold value is TH1. The stage of the stage No. 2 is a
period in which the point of time at which time T1 elapses from the
start of operation is the start and the point of time at which time
T2 elapses from the start of operation is the end, and the
collation threshold value is TH2. The stage of the stage No. 3 is a
period in which the point of time at which time T2 elapses from the
start of operation is the start and the point of time at which time
T3 elapses from the start of operation is the end, and the
collation threshold value is TH3. The stage of the stage No. 4 is a
period in which the point of time at which time T3 elapses from the
start of operation is the start, and the collation threshold value
is TH4. Here, TH1<TH2<TH3<TH4 is established. TH1 is also
referred to as an initial value of the collation threshold, TH4 is
also referred to as a target value, and TH2 and TH3 are also
referred to as intermediate values of the collation threshold.
While the threshold changing schedule 125 is configured of four
stages in this example, any number of stages is acceptable if it is
plural.
[0051] The arithmetic processing unit 130 is an arithmetic
processing unit having a microprocessor such as an MPU and its
peripheral circuits. The arithmetic processing unit 130 is
configured to read the program 121 from the storage unit 120 and
executes it to thereby allow the hardware and the program 121 to
operate in cooperation with each other to implement various
processing units. The processing units implemented by the
arithmetic processing unit 130 includes the input unit 131, the
face image acquisition unit 132, the collation unit 133, the time
measurement unit 134, the threshold change unit 135, and the output
unit 136.
[0052] The input unit 131 is configured to receive the reference
face image data 122 and the threshold changing schedule 125 input
from the outside via the communication interface 113 or the
operation input unit 114, and store them in the storage unit
120.
[0053] The face image acquisition unit 132 is configured to receive
image data of a person to be collated, captured by the camera unit
141 and input via the interface 111, and acquire (detect) a face
image of the person to be collated from the image data. The face
image acquisition unit 132 performs matching between a template
representing a general face contour of a person and image data to
thereby acquire a face image existing in the image data. Besides
template matching, various publicly-known face detection algorithms
may be used. The face image acquisition unit 132 is configured to
transmit the acquired face image to the collation unit 133.
[0054] The collation unit 133 is configured to read the reference
face image data 122 and the collation threshold 123 from the
storage unit 120, calculates, for each user ID, similarity between
the reference face image included in the reference face image data
122 and a face image acquired by the face image acquisition unit
132, and based on the result of comparing the calculated similarity
for each user ID with the collation threshold 123, determine
whether or not the face image of the collation target matches a
reference face image of any user ID included in the reference face
image data 152. As an example of similarity, a cross-correlation
coefficient between face images may be used. In that case, the
similarity is lowered when a face portion of the same person is
included in the two face images. As similarity between face images,
besides the cross-correlation coefficient, publicly-known
similarity calculation technique may be used. For example, the
collation unit 133 may be configured to extract a feature amount
from the face image of the collation target, collate the feature
amount of the face extracted from the face image with the feature
amount of the reference face included in the reference face image
data 122, and calculate the similarity between the reference face
image and the face image to be collated.
[0055] The collation unit 133 is also configured to generate an
authentication result representing face authentication failure when
there is no reference face image of a user ID in which the
similarity with the face image of the collation target acquired by
the face image acquisition unit 132 is equal to or larger than the
collation threshold 123. The collation unit 133 is also configured
to, when there is at least one reference face image in which the
similarity with the face image of the collation target acquired by
the face image acquisition unit 132 is equal to or larger than the
collation threshold 123, generate an authentication result
representing face authentication success including the user ID of
the maximum similarity. The collation unit 133 is also configured
to transmit the authentication result to the output unit 136.
[0056] The time measurement unit 134 is configured to measure the
elapsed time from the start of operation of the face authentication
apparatus 100 and store it as the elapsed time 124 in the storage
unit 120. For example, the time measurement unit 134 is configured
to measure the elapsed time from the point of time when a command
instructing to start operation is input from the operation input
unit 114 as the elapsed time from the start of operation of the
face authentication apparatus 100. Alternatively, the time
measurement unit 134 may be configured to measure the time obtained
by subtracting the time during which the gate apparatus 142 is
closed or released from the elapsed time, as the elapsed time from
the start of operation of the face authentication apparatus 100.
Here, "closed" means a state where the gate apparatus 142 is
physically blocked to prevent a user from passing through. Further,
"released" means a state where a user can freely pass through the
gate apparatus 142 without face authentication. A minimum unit of
the elapsed time may be a minute, an hour, or a day. Note that in
the case where the gate apparatus 142 is a portable type that can
be moved, when it is moved to another place and if it is operated
first time at that place, the operating time at the previous place
may be canceled.
[0057] The threshold change unit 135 is configured to read the
elapsed time 124 and the threshold changing schedule 125 from the
storage unit 120, and based on them, set and change the collation
threshold 123. Specifically, at the time of starting operation of
the face authentication apparatus 100, the threshold change unit
135 sets a smaller value, relative to the target value, to the
collation threshold 123. After the start of operation of the face
authentication apparatus 100, the threshold change unit 135
automatically changes the collation threshold 123 to a larger value
gradually until it reaches the target value. The threshold change
unit 135 also changes the collation threshold 123 in accordance
with a request from a user. At that time, before changing the value
of the collation threshold 123 in accordance with the request from
the user, the threshold change unit 135 checks whether or not the
value of the collation threshold after the change becomes larger
than a value that is determined depending on the elapsed time from
the start of operation of the face authentication apparatus 100,
and if it is larger, rejects the request.
[0058] The output unit 136 is configured to transmit an
authentication result of the collation unit 133 to the gate
apparatus 142 via the interface 112. The output unit 136 may be
configured to display the authentication result of the collation
unit 133 on the screen display unit 115, and/or transmit it to an
external device via the communication interface 113.
[0059] FIG. 4 is a flowchart illustrating the overall operation of
the face authentication apparatus 100. Referring to FIG. 4, first,
the input unit 131 of the face authentication apparatus 100
receives the reference face image data 122 input from the outside,
and stores it in the storage unit 120 (step S1). Then, the input
unit 131 receives the threshold changing rule 125 input from the
outside, and stores it in the storage unit 120 (step S2). Then, the
time measurement unit 134 of the face authentication apparatus 100
waits for an input of a command instructing the operation start
from the operator via the operation input unit 114 (step S3). Then,
when a command instructing the operation start is input, the time
measurement unit 134 stores the elapsed time 124 having a value 0
in the storage unit 120, and starts measurement of the elapsed time
(step S4). Then, the time measurement unit 134 stores the collation
threshold 123 having the initial value in the storage unit 120
(step S5). That is, since the value of the elapsed time 124 is 0,
the time measurement unit 134 sets, to the collation threshold 123,
the value TH1 of the collation threshold of the stage of the stage
No. 1 in the threshold changing schedule 125 illustrated in FIG. 3.
The processing of steps S1 to S5 described above is performed only
once when operation of the face authentication apparatus 100 is
started. Note that after the start of operation of the face
authentication apparatus 100, it is possible to add new reference
face image data 122 to the reference face image data 122 stored in
the storage unit 120 or delete part of the stored reference face
image data 122.
[0060] During operation, the face authentication apparatus 100
operates as described below. First, the face image acquisition unit
132 of the face authentication apparatus 100 receives image data
obtained by capturing a collation target, input from the camera
unit 141, and acquires the face image of the collation target from
the image data (step S6). Then, the collation unit 133 of the face
authentication apparatus 100 calculates similarity between each
reference face image included in the reference face image data 122
and the face image of the collation target acquired by the face
image acquisition unit 132 and compares the similarity with the
collation threshold 123 to thereby perform face authentication
(step S7).
[0061] Next, the output unit 136 of the face authentication
apparatus 100 outputs the result of face authentication to the gate
apparatus 142 via the interface 112 (step S8). Then, the face
authentication apparatus 100 returns to step S6 and repeats the
same processes as those described above.
[0062] The face authentication apparatus 100 is also configured to
perform processing illustrated in FIG. 5 parallel to the processing
illustrated in FIG. 4. Referring to FIG. 5, the threshold change
unit 135 of the face authentication apparatus 100 initializes the
noticed stage No. i to 1 (step S11), and monitors that the elapsed
time 124 stored in the storage unit 120 exceeds the end of the
stage No. i, that is, the end T1 of the stage No. 1 (step S12).
Then, when the elapsed time 124 exceeds T1, the threshold change
unit 135 changes the collation threshold 123 stored in the storage
unit 120 to the value of the collation threshold used in the stage
of the stage No. i+1, that is, TH2. Then, the threshold change unit
135 increments the stage No. i to 2, and determines whether or not
the stage number i is equal to or larger than the maximum value (in
the case of the threshold changing schedule of FIG. 3, the maximum
value is 4) (step S15). Then, if the stage number i does not exceed
the maximum value, the threshold change unit 135 returns to step
S12 and repeats the same processes as those described above.
Thereby, whether or not the elapsed time 124 exceeds the end T2 of
the stage number 2 is monitored, and at the point of time when it
is exceeded, the collation threshold 123 is changed to TH3.
Similarly, when the elapsed time 124 exceeds the end T3 of the
stage No. 3, the collation threshold 123 is changed to TH4. Then,
when the internal variable i becomes the maximum value or larger,
the threshold change unit 135 ends the processing of FIG. 5.
[0063] Since the threshold change unit 135 performs the processing
illustrated in FIG. 5 as described above, the collation threshold
123 that is initially set to have the value TH1 in the storage unit
120 is automatically changed from TH1 to TH2 when the elapsed time
from the start of operation exceeds T1. Also, when the elapsed time
from the start of operation exceeds T2, the collation threshold is
automatically changed from TH2 to TH3. Then, when the elapsed time
from the start of operation exceeds T3, the collation threshold is
automatically changed from TH3 to TH4 that is the target value. In
this way, the threshold change unit 135 changes the collation
threshold 123 to a larger value gradually until it reaches the
target value.
[0064] The face authentication apparatus 100 is also configured to
perform processing illustrated in FIG. 6 parallel to the processing
illustrated in FIGS. 4 and 5. The face authentication apparatus 100
starts processing illustrated in FIG. 6 when, for example, a
command requesting a change of a collation threshold is input from
the operator via the operation input unit 114.
[0065] Referring to FIG. 6, the threshold change unit 135 of the
face authentication apparatus 100 first displays a collation
threshold setting screen on the screen display unit 115 (step S21).
FIG. 7 illustrates an example of a collation threshold setting
screen. The collation threshold setting screen of this example
includes a slide bar for designating the value of a collation
threshold, an OK button, and a cancel button.
[0066] Then, the threshold change unit 135 calculates an allowable
maximum value THmax of the collation threshold on the basis of the
elapsed time 124 and the threshold changing schedule 125 stored in
the storage unit 120 (step S22). That is, in the stage where the
elapsed time from the start of operation does not exceed T1 (stage
No. 1), the allowable maximum value THmax of the collation
threshold is TH1. In the stage where the elapsed time from the
start of operation does not exceed T2 (stage No. 2), the maximum
value THmax is TH2. In the stage where the elapsed time from the
start of operation does not exceed T3 (stage No. 3), the maximum
value THmax is TH3. Meanwhile, in the stage where the elapsed time
from the start of operation exceeds T3 (stage No. 4), the maximum
value THmax is TH4 or TH4+.alpha.. Here, .alpha. is a predetermined
value.
[0067] Next, the threshold change unit 135 receives a collation
threshold input from the user (step S23). In the collation
threshold setting screen of FIG. 7, the user designates the
collation threshold by moving the position of the knob of the slide
bar to left or right. Then, when the OK button is clicked, the
threshold change unit 135 executes processing of steps S24 and
after of FIG. 6. When the cancel button is clicked, the processing
of FIG. 6 ends.
[0068] At step S24, the threshold change unit 135 determines
whether or not the value of the input collation threshold is larger
than the maximum value THmax calculated at step S22. When the value
of the input collation threshold is not larger than the maximum
value THmax, the threshold change unit 135 changes the collation
threshold 123 stored in the storage unit 120 to the value of the
input collation threshold (step S25). Then, the threshold change
unit 135 ends the processing of FIG. 6.
[0069] On the other hand, when the value of the input collation
threshold is larger than the maximum value THmax, the threshold
change unit 135 rejects the change, and displays a message urging
input of a collation threshold equal to or smaller than THmax on
the screen display unit 115 (step S26). Then, the threshold change
unit 135 returns to step S23 and receives input of a collation
threshold again.
[0070] Since the threshold change unit 135 performs the processing
as illustrated in FIG. 6, it is possible to prevent a situation in
which a user easily changes the collation threshold 123 to a large
value in the beginning of the operation so that failure in face
authentication frequently occurs.
[0071] As described above, according to the present embodiment, the
threshold change unit 135 is configured to set the collation
threshold 123 to be smaller relative to the target value at the
time of starting operation of the face authentication apparatus
100, and prohibit a change of the collation threshold to a value
larger than a value that is determined depending on the elapsed
time from the start of the operation. Therefore, it is possible to
prevent deterioration in the convenience of the face authentication
apparatus 100 in the beginning of the operation.
[0072] Further, according to the present embodiment, the threshold
change unit 135 is configured to automatically change the collation
threshold 123 to a larger value gradually according to the elapsed
time from the start of operation of the face authentication
apparatus 100. Therefore, it is possible to finally set the
collation threshold to the target value without impairing the
convenience of the face authentication apparatus 100 and without
placing a load on the administrator.
Second Exemplary Embodiment
[0073] Next, a second exemplary embodiment of the present invention
will be described. A face authentication apparatus 200 of the
present embodiment differs from that of the first exemplary
embodiment in that the face authentication apparatus 200 includes a
plurality of types of threshold changing schedules 125.
[0074] FIG. 8 shows an example of a plurality of types of threshold
changing schedules 125. Each of the threshold changing schedules is
configured of a row describing schedule No., a row describing a
selection condition, and rows each describing a set of stage No,
period, and a collation threshold value. In the three threshold
changing schedules illustrated in FIG. 8, the initial values and
the target values of the collation thresholds are the same, but the
intermediate values and the numbers thereof are different from each
other. That is, a threshold changing schedule 125-1 of schedule No.
1 is the same as the threshold changing schedule 125 illustrated in
FIG. 3. The collation threshold is changed from the initial value
TH1 to the target value TH4 via the two intermediate values TH2 and
TH3, and the elapsed time up to the target value TH4 is T3. In a
threshold changing schedule 125-2 of schedule No. 2, the collation
threshold is changed from the initial value TH1 to the target value
TH4 via an intermediate value (TH2+TH3)/2, and the elapsed time up
to the target value TH4 is T2 that is shorter than T3. In a
threshold changing schedule 125-3 of schedule No. 3, the collation
threshold is changed from the initial value TH1 to the target value
TH4 via five intermediate values (TH1+TH2)/2, TH2, (TH2+TH3)/2,
TH3, and (TH3/TH4)/2, and the elapsed time up to the target value
TH4 is T4 that is longer than T3. In short, in the threshold
changing schedule 125-2, the collation threshold reaches the target
value in a shorter period, and the changing width per change is
larger. On the other hand, in the threshold changing schedule
125-3, the collation threshold reaches the target value with a
longer period, and the changing width per change is smaller. The
threshold changing schedule 125-1 has an intermediate
characteristic between the threshold changing schedule 125-2 and
the threshold changing schedule 125-3.
[0075] In the present embodiment, the threshold change unit 135 is
configured to select a threshold changing schedule to be used from
a plurality of types of threshold changing schedules 125, based on
the history of similarity on face authentication success.
Specifically, as an index of selecting a threshold changing
schedule, the threshold change unit 135 uses an average value of
the similarity when authentication performed by the collation unit
133 succeeded during the period from the point of starting
operation until time T1 elapsed. The threshold change unit 135 is
configured to select a threshold changing schedule that is
scheduled to reach the target value TH4 in a shorter period as the
average value of the similarity on face authentication success is
larger. For example, when the average value of the similarity on
face authentication success is equal to or smaller than a value A
set in advance, the threshold change unit 135 selects the threshold
changing schedule 125-3. When the average value of the similarity
on face authentication success is larger than the value A and equal
to or smaller than a value B set in advance, the threshold change
unit 135 selects the threshold changing schedule 125-1. Here,
B>A is established. When the average value of the similarity on
face authentication success is larger than the value B, the
threshold change unit 135 selects the threshold changing schedule
125-2. However, the index for selecting a threshold changing
schedule is not limited to those described above. For example, it
may be a minimum value, a maximum value, or a median value of the
similarity on face authentication success during the period from
the point of starting operation until time T1 elapsed.
Alternatively, it is possible to divide a period from the point of
starting operation until time T1 elapsed into a plurality of
sections, and an inclination of a line segment linking average
values of the similarity on face authentication success in the
respective sections may be used as an index.
[0076] Next, operation of the face authentication apparatus 200
according to the present embodiment will be described by focusing
on the differences from the operation of the face authentication
apparatus 100 according to the first exemplary embodiment.
[0077] First, at step S5 of FIG. 4, the threshold change unit 135
selects the threshold changing schedule 125-3 as a threshold
changing schedule to be actually used, from among the three
threshold changing schedules 125 illustrated in FIG. 8. This is
because the threshold changing schedule 125-3, among the three
threshold changing schedules, gently increments the collation
threshold from the initial value TH1 taking the longest time, so
that it has the smallest possibility of impairing the
convenience.
[0078] When the face authentication succeeded at step S7 of FIG. 4,
the threshold change unit 135 acquires the similarity on face
authentication success from the collation unit 133, and stores it
as a history. Then, the threshold change unit 135 calculates an
average value of the accumulated similarity on the face
authentication success in a period from the point of starting
operation until immediately before time T1 elapses, and compares it
with the value A and the value B. Then, when the average value of
the similarity on face authentication success is equal to or
smaller than the value A, the threshold change unit 135 maintains
the state of selecting the threshold changing schedule 125-3. When
the average value of the similarity on face authentication success
is larger than the value A and equal to or smaller than the value
B, the threshold change unit 135 selects the threshold changing
schedule 125-1 in place of the threshold changing schedule 125-3.
When the average value of the similarity on face authentication
success is larger than the value B, the threshold change unit 135
selects the threshold changing schedule 125-2 in place of the
threshold changing schedule 125-3. Then, the threshold change unit
135 performs the processing illustrated in FIGS. 5 and 6 on the
basis of the selected threshold changing schedule.
[0079] In the present embodiment, the threshold change unit 135
selects and uses a threshold changing schedule suitable for the
actual operating environment from a plurality of types of threshold
changing schedules, based on the history of the similarity on face
authentication success. As described above, by using the threshold
changing schedule suitable for the actual operation environment, it
is possible to further prevent deterioration in convenience of the
face authentication apparatus in the beginning of the operation,
and to set the collation threshold to a target value in a shorter
period of time.
Third Exemplary Embodiment
[0080] Next, a third exemplary embodiment of the present invention
will be described. FIG. 9 is a block diagram of a face
authentication apparatus 300 according to the present embodiment.
Referring to FIG. 9, the face authentication apparatus 300 of the
present embodiment includes a face image acquisition unit 301, a
collation unit 302, a time measurement unit 303, and a threshold
change unit 304.
[0081] The face image acquisition unit 301 is configured to acquire
a face image of an authentication target with use of a camera or
the like. The face image acquisition unit 301 may have a
configuration similar to that of the face image acquisition unit
132 of FIG. 1, but it is not limited thereto. The collation unit
302 is configured to perform face authentication on the face image
of the authentication target on the basis of a threshold. The
collation unit 302 may have a configuration similar to that of the
collation unit 133 of FIG. 1, but it is not limited thereto. The
time measurement unit 303 is configured to measure the elapsed time
from the start of operation of the face authentication apparatus
300. The time measurement unit 303 may have a configuration similar
to that of the time measurement unit 134 of FIG. 1, but it is not
limited thereto. The threshold change unit 304 is configured to
restrict changing of the threshold to a value larger than a value
that is determined depending on the measured elapsed time. The
threshold change unit 304 may have a configuration similar to that
of the threshold change unit 135 of FIG. 1, but it is not limited
thereto.
[0082] The face authentication apparatus 300 according to the
present embodiment configured as described above operates as
described below. First, the face image acquisition unit 301
acquires a face image of an authentication target. Then, the
collation unit 302 performs face authentication on the face image
of the authentication target on the basis of a threshold. The time
measurement unit 303 measures the elapsed time from the start of
operation of the face authentication apparatus 300. Then, the
threshold change unit 304 restricts changing of the threshold to a
value larger than a value that is determined depending on the
measured elapsed time.
[0083] As described above, according to the present embodiment, it
is possible to prevent deterioration in convenience of the face
authentication apparatus in the beginning of the operation. This is
because the threshold change unit 304 restricts changing of the
threshold to a value larger than a value that is determined
depending on the measured elapsed time.
[0084] While the present invention has been described with
reference to the exemplary embodiments described above, the present
invention is not limited to the above-described embodiments. The
form and details of the present invention can be changed within the
scope of the present invention in various manners that can be
understood by those skilled in the art.
[0085] For example, in the second exemplary embodiment, a threshold
changing schedule suitable for the actual operating environment is
selected from a plurality of types of threshold changing schedules,
based on the history of the similarity on face authentication
success. However, the period of the threshold changing schedule may
be changed based on the history of the similarity on face
authentication success. For example, in the case of using the
threshold changing schedule illustrated in FIG. 3, if the average
value of the similarity on face authentication success in a period
from the start of operation until time T1 elapsed is smaller than
the predetermined value A, the period of the stage is extended.
That is, T1 is changed to T1+.DELTA.t, T2 is changed to
T2+2.DELTA.t, and T3 is changed to T3+3.DELTA.t, for example. Here,
.DELTA.t represents a period of time having a predetermined length.
Further, if the average value of the similarity on face
authentication success is equal to or larger than the predetermined
value B (>A), the period of the stage is shortened. That is, T2
is changed to T2-2.DELTA.t, and T3 is changed to T3-2.DELTA.t, for
example.
[0086] Further, the collation threshold may be set for each user
ID. In that case, the collation threshold for each user ID may be
changed with use of a threshold changing schedule common to the
user IDs. Alternatively, it is possible to use a threshold changing
schedule for each user ID and change the collation threshold for
each user ID in accordance with the corresponding threshold
changing schedule. Moreover, if the passage rate of the gate is
lowered due to a change in the collation threshold, flexible
operation such as temporarily decrementing the collation threshold
may be adopted.
[0087] The present application is based upon and claims the benefit
of priority from Japanese patent application No. 2018-003233, filed
on Jan. 12, 2018, the disclosure of which is incorporated herein in
its entirety by reference.
INDUSTRIAL APPLICABILITY
[0088] The present invention is applicable to an access monitoring
system, an attendance management system, and the like, and in
particular, suitable for the case of improving convenience and
security by automatically correcting the threshold used for
collation appropriately without placing a burden on the users.
[0089] The whole or part of the exemplary embodiments disclosed
above can be described as, but not limited to, the following
supplementary notes.
(Supplementary Note 1)
[0090] A face authentication apparatus comprising:
[0091] a face image acquisition unit that acquires a face image of
an authentication target;
[0092] a collation unit that performs face authentication on the
face image of the authentication target on a basis of a
threshold;
[0093] a time measurement unit that measures elapsed time from a
time of starting operation of the face authentication apparatus;
and
[0094] a threshold change unit that restricts changing of the
threshold to a value larger than a value determined depending on
the elapsed time measured.
(Supplementary Note 2)
[0095] The face authentication apparatus according to supplementary
note 1, wherein the threshold change unit sets the threshold to be
smaller relative to a target value at the time of starting the
operation of the face authentication apparatus.
(Supplementary Note 3)
[0096] The face authentication apparatus according to supplementary
note 1 or 2, wherein
[0097] before changing the threshold in accordance with a request
from a user, the threshold change unit checks whether or not a
value of the threshold after the change is larger than the value
determined depending on the elapsed time measured, and if the value
is larger, the threshold change unit rejects the request.
(Supplementary Note 4)
[0098] The face authentication apparatus according to any of
supplementary notes 1 to 3, wherein
[0099] the threshold change unit gradually increments the threshold
until the threshold reaches a target value in accordance with the
value determined depending on the elapsed time measured.
(Supplementary Note 5)
[0100] The face authentication apparatus according to any of
supplementary notes 1 to 4, further comprising
[0101] a threshold changing schedule that is a schedule of changing
the threshold after the time of starting the operation of the face
authentication apparatus and in which a value of the threshold
after the change becomes larger as the elapsed time from the time
of starting the operation is longer, wherein
[0102] the threshold change unit calculates the value determined
depending on the elapsed time measured, on a basis of the threshold
changing schedule and the elapsed time measured.
(Supplementary Note 6)
[0103] The face authentication apparatus according to supplementary
note 5, further comprising
[0104] a plurality of types of the threshold changing schedules,
wherein
[0105] the threshold change unit selects, from the plurality of the
types of the threshold changing schedules, a threshold changing
schedule to be used for calculating the value determined depending
on the elapsed time measured, on a basis of a history of face
authentication success.
(Supplementary Note 7)
[0106] The face authentication apparatus according to any of
supplementary notes 1 to 6, further comprising
[0107] an output unit that outputs a result of the face
authentication.
(Supplementary Note 8)
[0108] The face authentication apparatus according to supplementary
note 7, wherein
[0109] the face image acquisition unit acquires a face image of a
user who passes through a gate apparatus as the face image of the
authentication target, and
[0110] the output unit outputs, to the gate apparatus, a result of
the face authentication for controlling open and close operation of
the gate apparatus.
(Supplementary Note 9)
[0111] The face authentication apparatus according to any of
supplementary notes 1 to 8, wherein
[0112] in the face authentication, a feature amount of a face
extracted from the face image of the authentication target and a
feature amount of a face extracted from a reference face image of
each registered user are collated with each other, and similarly
between the face image of the authentication target and the
reference face image is calculated.
(Supplementary Note 10)
[0113] A face authentication method performed by a face
authentication apparatus, the method comprising:
[0114] acquiring a face image of an authentication target;
[0115] performing face authentication on the face image of the
authentication target on a basis of a threshold;
[0116] measuring elapsed time from a time of starting operation of
the face authentication apparatus; and
[0117] restricting changing of the threshold to a value larger than
a value determined depending on the elapsed time measured.
(Supplementary Note 11)
[0118] The face authentication method according to supplementary
note 10, wherein the threshold is set to be smaller relative to a
target value at the time of starting the operation of the face
authentication apparatus.
(Supplementary Note 12)
[0119] The face authentication method according to supplementary
note 10 or 11, wherein the restricting the changing of the
threshold includes, before changing the threshold in accordance
with a request from a user, checking whether or not a value of the
threshold after the change is larger than the value determined
depending on the elapsed time measured, and if the value is larger,
rejecting the request.
(Supplementary Note 13)
[0120] The face authentication method according to any of
supplementary notes 10 to 12, further comprising
[0121] gradually incrementing the threshold until the threshold
reaches a target value in accordance with the value determined
depending on the elapsed time measured.
(Supplementary Note 14)
[0122] The face authentication method according to any of
supplementary notes 10 to 13, wherein
[0123] the face authentication apparatus includes a threshold
changing schedule that is a schedule of changing the threshold
after the time of starting the operation of the face authentication
apparatus and in which a value of the threshold after the change
becomes larger as the elapsed time from the time of starting the
operation is longer, and
[0124] the method further comprises calculating the value
determined depending on the elapsed time measured, on a basis of
the threshold changing schedule and the elapsed time measured.
(Supplementary Note 15)
[0125] The face authentication method according to supplementary
note 14, wherein
[0126] the face authentication apparatus includes a plurality of
types of the threshold changing schedules, and
[0127] the method further comprises selecting, from the plurality
of the types of the threshold changing schedules, a threshold
changing schedule to be used for calculating the value determined
depending on the elapsed time measured, on a basis of a history of
face authentication success.
(Supplementary Note 16)
[0128] The face authentication method according to any of
supplementary notes 10 to 15, further comprising
[0129] outputting a result of the face authentication.
(Supplementary Note 17)
[0130] The face authentication method according to supplementary
note 16, wherein
[0131] the acquiring the face image includes acquiring a face image
of a user who passes through a gate apparatus as the face image of
the authentication target, and
[0132] the outputting the result of the face authentication
includes outputting, to the gate apparatus, a result of the face
authentication for controlling open and close operation of the gate
apparatus.
(Supplementary Note 18)
[0133] The face authentication method according to any of
supplementary notes 10 to 17, wherein
[0134] in the face authentication, a feature amount of a face
extracted from the face image of the authentication target and a
feature amount of a face extracted from a reference face image of
each registered user are collated with each other, and similarly
between the face image of the authentication target and the
reference face image is calculated.
(Supplementary Note 19)
[0135] A computer-readable medium storing a program for causing a
computer constituting a face authentication apparatus to function
as:
[0136] a face image acquisition unit that acquires a face image of
an authentication target;
[0137] a collation unit that performs face authentication on the
face image of the authentication target on a basis of a
threshold;
[0138] a time measurement unit that measures elapsed time from a
time of starting operation of the face authentication apparatus;
and
[0139] a threshold change unit that operates to change the
threshold to a value larger than a value determined depending on
the elapsed time measured.
(Supplementary Note 20)
[0140] The face authentication apparatus, the face authentication
method, or the computer-readable medium storing the program
according to any of supplementary notes 1 to 19, wherein
[0141] the threshold change unit gradually increments the threshold
until the threshold reaches a target value in accordance with the
elapsed time measured and a history of the similarity when the face
authentication succeeded.
(Supplementary Note 21)
[0142] The face authentication apparatus, the face authentication
method, or the computer-readable medium storing the program,
according to any of supplementary notes 1 to 20, wherein
[0143] the threshold change unit changes the period of the
threshold changing schedule on the basis of a history of the
similarity when the face authentication succeeded.
REFERENCE SIGNS LIST
[0144] 100 face authentication apparatus [0145] 111 interface
[0146] 112 interface [0147] 113 communication interface [0148] 114
operation input unit [0149] 115 screen display unit [0150] 120
storage unit [0151] 121 program [0152] 122 reference face image
data [0153] 123 collation threshold [0154] 124 elapsed time [0155]
125 threshold changing schedule [0156] 130 arithmetic processing
unit [0157] 131 input unit [0158] 132 face image acquisition unit
[0159] 133 collation unit [0160] 134 time measurement unit [0161]
135 threshold change unit [0162] 136 output unit [0163] 141 camera
unit [0164] 142 gate apparatus [0165] 143 user [0166] 200 face
authentication apparatus [0167] 300 face authentication apparatus
[0168] 301 face image acquisition unit [0169] 302 collation unit
[0170] 303 time measurement unit [0171] 304 threshold change
unit
* * * * *