JP2015185042A - Information processing device, authentication device and methods thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a feature amount which is low dimensional and suitable to pattern recognition by learning a conversion parameter for converting a bit string into a scalar value when converting a bit string composed of a plurality of elements into a scalar value to generate a feature amount.SOLUTION: An arithmetic processing part 105 respectively uses a plurality of pieces of data near target data within a processing object area 108 in input data 101 to perform arithmetic processing. A binarization processing part 106 performs binarization processing of an arithmetic processing result 102 corresponding to each of the plurality of pieces of data. A feature data generation part 107 uses a conversion parameter to generate feature data 104 to the target data from a binarization processing result 103 corresponding to each of the plurality of pieces of data. A learning part 109 learns the conversion parameter such that distance between feature data generated from input data of the same class is small and that distance between feature data generated from input data of different classes is large.

Description

  The present invention relates to information processing for extracting feature values suitable for pattern identification.

  As a feature quantity effective for pattern identification such as face authentication, local binary pattern (LBP, local binary pattern) described in Non-Patent Document 1 has been proposed. An outline of LBP extraction processing will be described with reference to FIG.

The LBP of the coordinates (x, y) is _expressed by an equation (8) using the center pixel (x, y) in the 3 × 3 pixel region as the target pixel and eight reference pixels (x + x _n , y + y _n ) adjacent to the target pixel. Calculated by 1).
t _n (x, y) = i (x + x _n , y + y _n )-i (x, y);
if (t _n (x, y) ≥ 0)
s (t _n (x, y)) = '1';
else
s (t _n (x, y)) = '0';
LBP (x, y) = Σ _{n = 0} ⁷ {s (t _n (x, y)) · 2 ⁿ };… (1)
Where i (x, y) is the pixel value of the target pixel,
i (x + x _n , y + y _n ) is the pixel value of the nth reference pixel,
x _n = {-1, 0, 1}, y _n = {-1, 0, 1}, x _n ² + y _n ² ≠ 0.

That is, LBP is an 8-bit feature quantity obtained as a scalar value obtained by multiplying each element of the bit string obtained from the difference between the value of the target pixel and each reference pixel by 2 ⁿ .

In the example shown in FIG. 1, the pixel adjacent to the left of the target pixel is (x ₀ , y ₀ ), and (x ₁ , y ₁ ), (x ₂ , y ₂ ), , (X ₇ , y ₇ ). In other words, in the example shown in FIG. 1, the bit string “00111010” is obtained by arranging the bits in the order of the dashed arrows, and the value of the LBP is “58”.

  Patent Document 1 proposes a technique in which a bit string before encoding in LBP is used as a feature amount. Non-Patent Document 1 has an LBP of 8 bits and a one-dimensional feature value (58 in the example of FIG. 1), whereas Patent Document 1 has a 1-bit feature value and an eight-dimensional feature value (in the example of FIG. 00111010 ′).

  Patent Document 2 proposes a method for determining a bit string conversion method by learning. In this method, a conversion method for reducing the Euclidean distance between bit strings obtained from 3 × 3 pixel regions having similar pixel patterns is determined by learning. Specifically, a conversion formula for projecting a bit string to a P-dimensional (P <8) space expressing the similarity of pixel patterns in a 3 × 3 pixel region is learned. According to this method, it is possible to generate a relatively low-dimensional feature amount that represents the similarity of original data.

  LBP is widely used as an effective feature amount for pattern identification. Since LBP was originally designed on the assumption that it is used as an LBP histogram, the value of LBP is merely an index, and the magnitude relationship between the values is meaningless. When detailed texture information is effective for identification, such as face authentication, in pattern identification, it is preferable to use data before histogram formation as it is as a feature quantity. However, since the size of the LBP has no meaning in itself, the similarity between the original data cannot be appropriately expressed by the distance between the LBPs.

  On the other hand, according to the method of Patent Document 1, it is possible to express the similarity between the original data by calculating the distance for each bit. However, since the dimension of the feature amount is eight times that of the original data, the calculation time in the subsequent processing increases.

  Further, according to the method of Patent Document 2, it is possible to express the similarity between original data with a relatively low-dimensional feature amount. However, this method learns a conversion method capable of expressing the similarity of original data, and does not learn a conversion method suitable for identifying an object. Therefore, the conversion method obtained by learning is not necessarily suitable for pattern identification.

JP 2009-86926 JP 2011-08631 A

T. Ojala, M. Pietikainen, D. Harwood "A Comparative Study of Texture Measures with Classification Based on Featured Distributions" Pattern Recognition, Vol. 29, pp. 51-59, 1996 S. Chopra, R. Hadsell, Y. LeCun “Learning a similarity metric discriminatively, with application to face verification” Proc. IEEE Conference on Computer Vision and Pattern Recognition, pp. 539-546, 2005

  An object of the present invention is to obtain a feature quantity suitable for a low-dimensional pattern identification target when generating a feature quantity by converting a bit string composed of a plurality of elements into a scalar value.

  The present invention has the following configuration as one means for achieving the above object.

  The information processing according to the present invention performs arithmetic processing using each of a plurality of data near the target data in the processing target area in the input data, binarizes the arithmetic processing result corresponding to each of the plurality of data, and converts Using the parameters, feature data for the data of interest is generated from the binarization processing result corresponding to each of the plurality of data, and the distance between the feature data generated from the input data of the same class is small, and the input of different classes The conversion parameter is learned so that the distance between the feature data generated from the data is increased.

  According to the present invention, when learning a conversion parameter for converting a bit string into a scalar value, a bit string composed of a plurality of elements is converted into a scalar value to generate a feature quantity, the object of low-dimensional pattern identification is obtained. A suitable feature amount can be obtained.

The figure explaining the outline | summary of the extraction process of LBP. FIG. 2 is a block diagram illustrating a configuration example of a signal processing unit according to the first embodiment. The figure explaining the relationship between input image data and a process target area. The figure which shows an example of the positional relationship of an attention pixel and a reference pixel. The block diagram explaining the structural example of a learning part. The block diagram which shows the structural example of the information processing apparatus of an Example. The flowchart explaining the face authentication process of an Example. The figure which shows an example of the memory storage format of the information regarding a process target area | region, the relative position of a reference pixel, and a weighting coefficient group. The flowchart explaining a learning process. The flowchart explaining an identification process. The figure which shows the example of an output of a face authentication result. The flowchart explaining a registration process. FIG. 6 is a block diagram illustrating a signal processing unit according to the second embodiment. The figure explaining a binary tree process. The figure explaining the example of a setting of a some process target area | region. The figure which shows the example which compares two reference pixels.

  Hereinafter, information processing according to an embodiment of the present invention will be described in detail with reference to the drawings.

  In the following, the signal processing and learning method of the embodiment will be described, and an information processing apparatus and method for applying the signal processing and learning method of the embodiment to pattern identification will be described. The signal processing of the embodiment is used to extract a feature amount used for pattern identification from an input data group. The input data group is a set of data composed of a plurality of elements, for example, image data.

  Hereinafter, an example in which the signal processing of the embodiment is used to extract a feature amount suitable for face authentication from a face image will be described. In face authentication, a feature quantity is extracted from an input face image, and an individual is specified by comparing the extracted feature quantity with a previously created and registered feature quantity. In the embodiment, an example in which the present invention is applied to feature extraction in face authentication will be described, but the present invention can also be applied to feature extraction in other pattern identification.

[Signal processing section]
A configuration example of the signal processing unit in the first embodiment will be described with reference to the block diagram of FIG.

  A processing target area 108 is set in advance in the input image data 101. The relationship between the input image data 101 and the processing target area 108 will be described with reference to FIG. A region including a part that well represents facial features such as eyes, nose, and mouth is set as the processing target region 108.

The arithmetic processing units 105a to 105c perform local arithmetic processing on the image data of the processing target area 108, and generate local arithmetic processing results 102a to 102c of two-dimensional data. The local calculation process is a calculation process using a plurality of data existing in a predetermined neighborhood area. Processing unit 105a-105c are shown in the following equation, it calculates a difference r _n of the pixel values between the pre-specified reference pixel and the pixel of interest as a local operation result.
r _n (x, y) = i (x + x _n , y + y _n )-i (x, y)… (2)
Here, r _n (x, y) is the pixel value of the local calculation processing result corresponding to the nth reference pixel,
i (x, y) is the pixel value of the target pixel,
i (x + x _n , y + y _n ) is the pixel value of the nth reference pixel,
(x _n , y _n ) is the relative position of the nth reference pixel with respect to the target pixel.

FIG. 4 shows an example of the positional relationship between the target pixel and the reference pixel. The relative positions (x _n , y _n ) are, for example, in the order of FIGS. 4 (a) (b) (c), (x ₀ , y ₀ ) = (0, −1), (x ₁ , y ₁ ) = (-1, 0), (x ₂ , y ₂ ) = (1, 1).

The binarization processing units 106a-106c perform binarization processing on the local calculation processing results 102a-102c, and generate binarization processing results 103a-103c of two-dimensional data. For example, the binarization processing units 106a to 106c perform step function processing of the following equation for binarization processing.
if (r _n (x, y) ≥ 0)
b _n (x, y) = '1';
else
b _n (x, y) = '0';… (3)
Here, b _n (x, y) is a pixel value of the binarization processing result corresponding to the nth reference pixel.

The feature data generation unit 107 multiplies each of the binarization processing results 103a-103c by the multipliers 107a-107c by the weighting coefficient w ₀ -w ₂ and adds the multiplication result by the adder 107d to perform the feature processing of the two-dimensional data. A generation process for generating data 104 is performed. Hereinafter, the set of weighting factors w ₀ -w ₂ used for the processing target area 108 is referred to as a “weighting factor group”. The following formula is a calculation formula for generating the feature data 104 from the binarization processing results 103a-103c.
v (x, y) = Σ _{n = 0} ^N-1 {b _n (x, y) ・ w _n }… (4)
Where v (x, y) is the pixel value of the feature data 104,
w _n is a weighting factor of the binary processing result corresponding to the nth reference pixel,
N is the number of binarization processing results.

The signal processing unit illustrated in FIG. 2 is an example of N = 3, and b ₀ (x, y) to b ₂ (x, y) are pixel values of the binarization processing results 103a to 103c.

Although details will be described later, the learning unit 109 determines a weighting coefficient group w ₀ -w ₂ suitable for the target of pattern identification through learning.

LBP multiplies each bit of the bit string by 2 ^N to obtain a scalar value. In the signal processing unit of the embodiment, the binarization processing results 103a to 103c are equivalent to a bit string before encoding processing in LBP. Then, the weight coefficient group w ₀ -w ₂ learned so as to match the object of pattern identification and the multiplication result of each bit are added to obtain feature data 104 as a scalar value. That is, the weight coefficient group w ₀ -w ₂ corresponds to a conversion parameter for converting a bit string into a scalar value.

[Learning Department]
The learning unit 109 determines the weight coefficient group w ₀ -w ₂ by learning so that the feature data 104, which is the output of the signal processing unit shown in FIG.

  A configuration example of the learning unit 109 will be described with reference to the block diagram of FIG. The learning unit 109 has a basic configuration of a Siamese learner (see Non-Patent Document 2). The Siamese learner reduces the distance between feature data based on the pair of input data and the label information indicating the class of those data, and increases the distance for the same class of data. Learn the conversion parameters.

  The database (DB) 406 stores a face authentication data group including a face image and a person ID corresponding to the face image. The person ID is identification information for specifying a person corresponding to the face image, and is represented by an integer value, for example. For example, values 0, 1, 2,... Are set as person IDs in the order of persons registered in the DB 406, for example. Furthermore, it is preferable to associate character string data such as a name and a nickname with the person ID.

  The face image registered in the DB 406 is preferably an image obtained by converting the images so that both eyes are arranged horizontally and have a predetermined size. Furthermore, the face image includes various variations in the tilt, facial expression, lighting conditions, etc. of the face in the pan direction and tilt direction so that a robust feature amount can be obtained as a signal processing output. It is desirable.

  The image pair selection unit 407 selects a face image pair to be used for learning from the DB 406. A pair of face images is randomly selected from every face image stored in the DB 406 each time. The image data 401a and 401b of the selected face image are input to the feature extraction units 408a and 408b, respectively. Further, the image pair selection unit 407 sets a label 405 having a value of 0 when the person IDs of the selected face images are the same, and a value of 1 when they are different. The label 405 is used when the loss is calculated in the loss calculation unit 404.

  The feature extraction units 408a and 408b perform the same processing as the signal processing unit shown in FIG. 2 on the input face images 401a and 401b to generate the feature data 104. Since the feature extraction units 408a and 408b have the same configuration and share the weight coefficient group 402, the same feature data can be obtained if the input face images are the same.

The distance calculation unit 403 calculates the distance between the two feature data generated by the feature extraction units 408a and 408b. In this embodiment, an L1 norm between vectors when feature data is a vector is used as a distance scale. For example, if the feature data size is W × H, the vector dimension is W × H. The following equation is a calculation equation for calculating the L1 norm between the feature data generated by the feature extraction processing 408a and 408b.
E (w) = ‖v ₁ (w)-v ₂ (w) ‖ ₁ … (5)
Where E (w) is the L1 norm between feature data,
w is a group of weight coefficients,
v _m (w) is feature data generated from the input image m,
m is the index in the image pair.

In Equation (5), the weighting factor group w is a vector having the weighting factors in the signal processing of this embodiment as elements. The feature data v and the L1 norm E are expressed as functions of w because the values change depending on the weighting coefficient. The feature data v ₁ (w) and v ₂ (w) are feature data generated from the face images 401a and 401b. That is, according to Equation (5), a one-dimensional vector in which the elements of the first feature data v ₁ (w) are arranged and a one-dimensional vector in which the elements of the second feature data v ₂ (w) are arranged. The L1 norm between is calculated.

  The distance scale is not limited to the L1 norm between vectors, and other distance scales such as Euclidean distance and cosine distance may be used.

The loss calculation unit 404 calculates a loss based on the L1 norm calculated by the distance calculation unit 403 and the label 405 generated by the image pair selection unit 407. The following formula is a formula for calculating the loss L (w) from the L1 norm and the label 405.
L (w) = (1-Y) 2 / Q ・ E (w) ² + Y ・ 2Q ・ exp {-2.77E (w) / Q}… (6)
Where Y is label 405 (value 0 is the same person ID, value 1 is the different person ID),
Q is the upper limit (set value) of L1 norm E (w).

  If the face images 401a and 401b have the same person ID, the label 405 is Y = 0, and the loss L (w) is small if the L1 norm E (w) is small, and if the L1 norm E (w) is large. Large value (distance and loss are proportional). In other words, for the same person's face image, the smaller the distance between the feature data, the smaller the loss L (w).

  Further, when the person IDs of the face images 401a and 401b are different, the label 405 is Y = 1, the loss L (w) is a large value if the L1 norm E (w) is small, and the L1 norm E (w) is The larger the value, the smaller the value (distance and loss are inversely related). That is, for face images of different persons, it means that the loss L (w) becomes smaller as the distance between the feature data is larger.

  When the loss L (w) is calculated from the pair of face images, the coefficient updating unit 409 updates the weighting coefficient group 402 using the gradient descent method based on the loss L (w). Note that the weighting coefficient group 402 needs to be initialized before starting learning, and the coefficient updating unit 409 initializes the weighting coefficient group 402 using random numbers, or a weighting coefficient group obtained by previous learning. w is set to the initial value of the weighting coefficient group 402, and additional relearning is performed.

The following expression is an expression indicating the update of the i-th element of the weight coefficient group w by the gradient descent method.
w ' _i = w _i -ρ ・ ∂L (w) / ∂w _i … (7)
Where w _i is the i-th element before update,
w ' _i is the i-th element after the update,
ρ is an update coefficient.

In order to update w _i by equation (7), it is necessary to obtain (L (w) / ∂w _i . Since the loss L (w) depends on w _i only through the L1 norm E (w), the partial differential chain law is applied to transform ∂L (w) / ∂w _i as shown in the following equation.
∂L (w) / ∂w _i = ∂L (w) / ∂E (w) ・ ∂E (w) / ∂w _i … (8)

In equation (8), ∂L (w) / ∂E (w) is obtained by partial differentiation of equation (6) with respect to L1 norm E (w). Further, ∂E (w) / ∂w _i, as in the case of decomposing ∂L (w) / ∂w _i, can be transformed into the following equation.
∂E (w) / ∂w _i = Σ _j {∂L (w) / ∂v _j・ ∂v _j / ∂w _i }… (9)
Here, v _j is the j-th element of the feature data v (w).

In Equation (9), ∂E (w) / ∂v _j is obtained by partial differentiation of Equation (5) with respect to v _j . However, ∂E (w) / ∂v _j is calculated for v _j, respectively v _j included in the feature data v ₂ (w) of the face image 401b included in the feature data v ₁ (w) of the face image 401a There is a need. Equation (9) sums the results of decomposition for each element v _j of the feature data v (w). This is because the L1 norm E (w) depends on w _i through all elements v _{j of the} feature data v (w).

Further, in the equation _{(9), ∂v j / ∂w} i is obtained by equation (4) is partially differentiated for w _i. The thus obtained ∂L (w) / using ∂w _i, and updates the w _i by the equation (7).

Note that ∂E (w) / ∂v _j includes those calculated from the feature data v ₁ (w) and those calculated from the feature data v ₂ (w). Weight coefficient group w, after being updated using the former ∂E (w) / ∂v _j, it shall be updated using the latter ∂E (w) / ∂v _j.

  The updating of the weight coefficient group w by the gradient descent method described above is executed once for each pair of face images. For example, when M pairs (M ≧ 1) are selected, the updating of the weighting coefficient w by Expression (7) is executed M times.

[Configuration of information processing device]
A block diagram of FIG. 6 shows a configuration example of the information processing apparatus of the embodiment.

  The CPU 503 uses the RAM 505 as a work memory, executes an OS and various programs stored in the ROM 504 and the data storage unit 501, controls a configuration described later via the system bus 509, and executes a function described later. The data storage unit 501 includes a hard disk drive (HDD), a disk drive, a memory card, a USB memory, and the like, and holds image data, programs, and other data on a recording medium. The programs stored in the data storage unit 501 include programs and data for realizing the signal processing unit and the learning unit 109 described above, and programs and data for executing face authentication described later.

  The display unit 507 includes a video card and a monitor. The CPU 503 displays images before and after image processing, a graphics user interface (GUI), and the like.

  The input unit 506 includes a keyboard, a pointing device, a touch panel superimposed on the monitor of the display unit 507, and the like, and inputs user instructions. When the information processing apparatus according to the embodiment is applied to a device such as a digital camera or a printer, the input unit 506 corresponds to a button, a dial, a numeric keypad, a touch panel, or the like. Of course, a configuration in which a software keyboard is displayed on a monitor and a user instruction is input by operating the touch panel is also possible.

  The communication unit 502 is an interface for performing communication between devices via a wired or wireless network.

  The CPU 503 inputs face authentication target image data from an external imaging device via, for example, a serial interface such as USB provided in the input unit 506. Alternatively, face authentication target image data may be input from an imaging device, an information processing device, or a server device on the network via the communication unit 502. 5 is stored in the data storage unit 501 or a server device on the network.

  The information processing apparatus according to the embodiment can be realized by supplying the above-described signal processing unit and learning unit, and a program for realizing face authentication processing described later to a general-purpose computer device.

[Face recognition processing]
The face authentication process of the embodiment will be described with reference to the flowchart of FIG. Note that the processing shown in FIG.

  When the face authentication process is started, the CPU 503 loads the information on the processing target area 108 used for the above-described signal processing, the relative position of the reference pixel, the weighting coefficient group, a later-described transformation matrix, and the like into a predetermined area of the RAM 505. Is executed (S601).

FIG. 8 shows an example of a memory storage format of information on the processing target area 108, the relative position of the reference pixel, and the weighting coefficient group. The RAM 505 stores the following information. As information of the processing target area, coordinates (Xlt, Ylt) and (Xrb, Yrb) of two vertices on the diagonal line of the processing target area 108 are stored. Subsequently, the number N of reference pixels corresponding to the number of local calculation processing results is stored. Subsequently, (x ₀ , y ₀ ), (x ₁ , y ₁ ),..., (X _N−1 , y _N−1 ) are stored as the relative positions of the reference pixels corresponding to the reference pixel number N. Further, w ₀ , w ₁ ,..., W _N−1 are stored as weight coefficient groups corresponding to the number of reference pixels N.

  As the weight coefficient group, for example, a random number or a weight coefficient group obtained by previous learning is set as an initial value. Note that the storage format of information regarding the processing target area 108, the relative position of the reference pixel, and the weighting coefficient group illustrated in FIG. 8 is an example, and any storage method may be used as long as the CPU 503 can identify the information.

  Next, the CPU 503 determines whether or not an operation mode instruction has been input via the input unit 506 (S602). When the operation mode instruction is input, the process branches according to the instructed operation mode (S603). When the process according to the instructed operation mode is completed, the process returns to step 601.

  There are three operation modes in the embodiment: (a) learning mode, (b) identification mode, and (c) registration mode. In the learning mode, the above-described learning process (S604) is executed. In the identification mode, face authentication processing (S605) is executed using the signal processing described above. In the registration mode, registration data creation processing (S606) used for face authentication is executed using the signal processing described above.

  Further, it is assumed that the face image used for the learning process is created according to the following procedure prior to the learning process and stored in the DB 406 assigned to the data storage unit 501 or the like in association with the person ID.

  The CPU 503 loads the image data of the face image to be learned from the data storage unit 501 or the like to a predetermined area of the RAM 505, and converts the loaded image data into an 8-bit unsigned luminance image. Then, using a face detection method, a face area is detected from the image data, and the image data of the face image resized to a predetermined size is stored in the DB 406 in association with the person ID.

  In addition, the position of the eyes, nose, mouth, and other parts are detected using a dynamic appearance model, a dynamic shape model, etc., and the eyes are horizontally arranged based on the detected positions, and the face image has a predetermined size. It is preferable to convert the image so that Furthermore, the face image includes various variations in the tilt, facial expression, lighting conditions, etc. of the face in the pan direction and tilt direction so that a robust feature amount can be obtained as a signal processing output. It is desirable.

  It should be noted that the preparatory work for creating the face image used for the learning process can also be executed by an external image processing device or the like. In this case, the CPU 503 inputs an externally created face image and person ID via a network or a recording medium, and stores the face image and person ID in the DB 406.

Learning Mode The learning process (S604) will be described with reference to the flowchart of FIG.

  When the learning mode is instructed, the CPU 503 initializes a counter p for determining completion of learning to p = 0 (S611), and a predetermined number of repetitions K (≧ 1) based on the count value of the counter p. It is determined whether learning has been completed (S612). That is, if p <K, learning is determined to be incomplete, and the process proceeds to step S613. If p = K, learning is determined to be complete, and the process returns to step S602 to wait for an operation mode instruction input.

  If the learning has not been completed, the CPU 503 randomly selects the first face image to be used for learning from the DB 406, and loads the image data 401a of the selected face image and the person ID of the face image into a predetermined area of the RAM 505. (S613). Then, feature data is extracted from the image data 401a of the first face image by the signal processing described above (S614).

  Next, the CPU 503 selects a second face image to be used for learning from the DB 406, and loads the image data 401b of the selected face image and the person ID of the face image into a predetermined area of the RAM 505 (S615). The second face image is randomly selected from the face images excluding the first face image. Then, feature data is extracted from the image data 401b of the second face image by the signal processing described above (S616).

  Next, the CPU 503 determines whether the person ID of the first face image matches the person ID of the second face image, and generates a label 405 (S617). As described above, the label Y = 0 is generated if the person IDs match, and the label Y = 1 is generated if they do not match.

  Next, the CPU 503 calculates the loss L (w) using the two feature data and the label Y (S618), and uses the loss L (w) to calculate the weight coefficient group stored in the RAM 505 by the gradient descent method. Update (S619). Then, the counter p is incremented (S620), and the process returns to step S612.

Identification Mode The identification process (S605) will be described with reference to the flowchart of FIG.

  When the identification mode is instructed, the CPU 503 loads face authentication target image data into a predetermined area of the RAM 505 (S631), and extracts a face image from the image data (S632). When the face authentication target image data includes a plurality of person face images, a plurality of face images are extracted.

  Next, the CPU 503 detects the positions of the eyes, nose, mouth, and other parts from the extracted face image using a dynamic appearance model, a dynamic shape model, etc., and horizontally arranges both eyes based on the detected position, In addition, image conversion for converting the face image into a predetermined size is performed as preprocessing (S633).

  Next, the CPU 503 extracts feature data from the image data of the face image (single image data if a plurality of face images are extracted) by the signal processing described above (S634), and reduces the dimension of the feature data ( S635). Hereinafter, feature data after dimension reduction is referred to as a “projection vector”.

  The dimension reduction is processing for extracting only information effective for identification from feature data and reducing the amount of calculation in the subsequent processing. The dimension reduction may be performed using a predetermined transformation matrix such as principal component analysis or locality preserving projection.

  The transformation matrix is an arrangement of base vectors that define a vector space after dimension reduction. Using the transformation matrix, the feature vector in which the feature data is arranged in a line is projected from the original space to the space defined by the base vector. The conversion matrix is stored in the ROM 504 and the data storage unit 501, or is provided as a part of the program, and is loaded into the RAM 505 in the initialization process (S601).

  Next, the CPU 503 executes an identification process for collating the projection vector with the registration data stored in the DB 406 (S636). The registered data is, for example, data having a projection vector (hereinafter referred to as a registered vector) of image data of a registered face image and a person ID of the face image, and is verification data for identification processing. In association with the person ID, character string data such as the name and nickname of the person and image data of the face image are registered in the DB 406.

  In the identification process, the person ID of the face image to be identified is specified based on the similarity between the projection vector and the registered vector and a predetermined threshold. Here, the similarity is described as the Euclidean distance between vectors in the feature space after dimension reduction. In this case, it can be determined that the projection vector and the registration vector are similar as the distance is small, and the face image corresponding to the registration vector with a small distance is determined to be similar to the face image to be identified.

  The CPU 503 calculates the distance between the projection vector and all the registered vectors, and sorts the registered vectors in ascending order of the distance. After sorting, the distance (minimum distance) between the first registered vector and the projection vector is calculated, and the minimum distance Dmin is compared with a predetermined threshold value Dth. If the minimum distance is equal to or smaller than the threshold (Dmin ≦ Dth), the face image to be identified matches the person ID corresponding to the first registered vector and is determined to be a registered face image. On the other hand, when the minimum distance is larger than the threshold (Dmin> Dth), it is determined that the face image to be identified is not registered. In the case of an unregistered face image, for example, a predetermined ID value corresponding to an unregistered person is set as the person ID of the face image to be identified.

  Next, the CPU 503 stores the person ID obtained by the identification process in the RAM 505 in association with the face image to be identified (S637). The face image stored in the RAM 505 is associated with information for displaying the face authentication result (for example, the position and size of the face image in the face authentication target image data) and stored.

  The CPU 503 repeats the processing from step S634 to S637 until the identification processing for all face images extracted from the face authentication target image data is completed by the determination in step S638. When the identification process is completed for all the face images, the identification result is output as a face authentication result (S639), the process returns to step S602, and an operation mode instruction input is awaited.

  FIG. 11 shows an output example of the face authentication result. Based on the face authentication target image data stored in the RAM 505, the position and size of each face image, and the person ID of the face image, an image showing the face authentication result as shown in FIG. 11 is generated and displayed on the display unit 507. To do. FIG. 11 shows an output example in which each face image area in the face authentication target image data is represented by a rectangular frame, and a character string related to the face image is displayed above the rectangular frame.

  The output of the face authentication result is not limited to display on the display unit 507, but may be stored in the data storage unit 501 in association with the image data to be authenticated, the position and size of the face image, the person ID of the face image, and the like. . Further, the face authentication result may be transmitted to an external device via the communication unit 502.

  Further, the example in which the face authentication result is output after the identification process is completed for all the face images extracted from the image data to be face-authenticated has been described, but each time the identification process for each face image is completed, the face authentication result is It may be output.

  Further, an example has been described in which image conversion is performed in which both eyes are horizontally arranged and have a predetermined size in the preprocessing (S623) in order to increase the identification accuracy. However, for example, the accuracy may be slightly reduced, but the preprocessing (S623) may be omitted when there is a system requirement for improving the face authentication speed or reducing the resources of the face authentication process.

Registration Mode As described above, registration data is data having, for example, a projection vector (registration vector) of image data of a registered face image and a person ID of the face image. Preferably, character string data such as a name and a nickname is registered in association with the person ID.

  The registration process (S606) will be described with reference to the flowchart of FIG.

  When the registration mode is instructed, the CPU 503 loads the image data of the face image to be registered into a predetermined area of the RAM 505 (S651), extracts the face image from the image data (S652), and extracts the extracted face image as a rectangle. The image surrounded by the frame is displayed on the display unit 507 (S653). Note that when the registration target image data includes face images of a plurality of persons, a plurality of face images are extracted.

  The user refers to the display image and operates the input unit 506 to select a face image to be registered (S654). At that time, the user can select a plurality of face images. If there is no face image to be registered, it is possible to instruct input of image data of the next face image.

  Next, the CPU 503 performs preprocessing on the image data of the face image selected by the user in the same manner as the processing in steps S633 to S635 in the identification mode (S655). Then, feature data is extracted from the image data of the face image (single image data when a plurality of face images are selected) (S656), and a projection vector in which the dimension of the feature data is reduced is generated (S657).

  Next, the CPU 503 displays the registered person ID (or character string data associated with the person ID) on the display unit 507 (S658). Preferably, a face image corresponding to the person ID (or character string data) is also displayed. The user refers to the display and operates the input unit 506 to specify a person ID (or character string data) that seems to correspond to the selected face image, or a person ID (or character that corresponds to the selected face image). (Column data) is entered (S659).

  The CPU 503 determines whether or not a person ID has been designated (S660). If it is input that no corresponding person ID exists in the selected face image, a new person ID is issued (S661). Then, the registration data in which the projection vector is associated with the designated person ID or the issued person ID is stored in the DB 406 (S662).

  The CPU 503 repeats the processing from step S656 to S662 until the registration processing for all the face images selected by the user is completed according to the determination in step S663. When the identification process is completed for all the face images, the process returns to step S602 to wait for an operation mode instruction input.

  In the above description, an example in which the learning process, the identification process, and the registration process are executed by a single device or program has been described as a preferable example in which the difference between the flows of the learning process and the face authentication process can be understood. However, a configuration is also possible in which a weighting coefficient group is prepared by prior learning processing, and identification processing and registration processing are performed by referring to the weighting coefficient group.

  In this way, by learning the parameters (weighting coefficient group) used for conversion to scalar values in the feature values generated by converting bit strings representing the magnitude relationship between pixels such as LBP to values, It is possible to extract a feature quantity suitable for a dimension and pattern identification target.

  The information processing according to the second embodiment of the present invention will be described below. Note that the same reference numerals in the second embodiment denote the same parts as in the first embodiment, and a detailed description thereof will be omitted.

  The signal processing unit according to the second embodiment will be described with reference to the block diagram of FIG.

The binary tree processing unit 901 performs binary tree processing on the processing target area 108 to generate two-dimensional data binarization processing results 902a to 902c. The feature data generation unit 107 multiplies each of the binarization processing results 902a-902c by the weight coefficient group w ₀ -w ₂ and adds the multiplication results to generate the feature data 104 of two-dimensional data. Note that the processing for generating the feature data 104 from the binarization processing results 902a to 902c and the learning method for the weighting coefficient group are the same as in the first embodiment.

  The binary tree process will be described with reference to FIG. Example 2 uses a complete binary tree where all nodes have leaves or two children and all leaves are the same depth. The binary tree shown in FIG. 14 is a complete binary tree having a depth of “3” and a number of leaves of “8”.

  In the binary tree processing, it is determined which of the two child nodes is branched in order until the input data reaches the leaf nodes 1004a-1004h from the root node 1001. In the second embodiment, the relative position of the reference pixel in Expression (2) is set in advance for each node (1001, 1002a-1002b, 1003a-1003d) having child nodes.

When data is input, for each target pixel (x, y), calculates a difference r _n between the reference pixel and the pixel of interest by the formula (2) (local processing). Then, based on the result of the step function processing shown in Expression (3), a branch destination is determined (that is, binarization processing for determining which child node to branch to). In the example shown in FIG. 14, when the result of the step function processing is “0”, the process proceeds to the left child node, and when it is “1”, the process proceeds to the right child node.

  When the leaf node 1004a-1004h is reached, a binary string in which all the determination results are arranged is generated. In the example indicated by the dashed arrow in FIG. 14, the binary string is “001”. Then, each element of the generated binary string is set as a pixel value at the coordinates (x, y) of the binarization processing results 902a-902c shown in FIG.

  In this way, by learning the weights for the branch determination results in each hierarchy of the binary tree, it is possible to extract a feature quantity suitable for a low-dimensional pattern identification target.

[Modification]
In the above, an example in which the above-described signal processing is applied to two-dimensional image data has been described. However, the present invention is also applied to three-dimensional data or one-dimensional data such as an audio signal. Can be applied. In other words, the above-described signal processing may be applied by performing arithmetic processing using a plurality of data in the vicinity of the data of interest in the processing target area in input data of various dimensions.

  In the above, an example in which there is one processing target area has been described. However, the number of processing target areas is not limited to one, a plurality of processing target areas are set, and different weight coefficient groups are set for each processing target area. Also good.

  An example of setting a plurality of processing target areas will be described with reference to FIG. FIG. 15 shows an example in which four processing target areas, that is, a left eye area 1201, a right eye area 1202, a nose area 1203, and a mouth area 1204 are set. By applying the learning method described above to these four processing target areas, it is possible to determine an appropriate weighting coefficient group for each processing target area. However, for regions having similar characteristics, such as the left eye region 1201 and the right eye region 1202, a weighting factor group may be learned without distinguishing them, and the obtained weighting factor group may be applied to these regions.

In the above, an example in which the step function shown in Expression (3) is used as the binarization process has been described, but the pulse function shown in the following expression may be used as the binarization process.
if (| t | ≧ Th)
p (t) = '1';
else
p (t) = '0';… (10)
Where t is the result of local operation,
Th is a predetermined threshold.

  In the case of using a step function, “1” if the local calculation result ≧ 0, and “0” if the local calculation result <0. That is, as described in the first and second embodiments, when the local calculation is a size comparison between the target pixel and the reference pixel, '1' if the reference pixel value ≧ the target pixel value, and the reference pixel value <the target pixel value. If there is, it will be '0'.

  On the other hand, when the pulse function is used, the absolute value of the local calculation result ≧ 1 is set to ‘1’, and the absolute value <threshold is set to ‘0’. That is, the absolute value of the difference between the target pixel value and the reference pixel value is “1” if it is greater than or equal to the threshold, and “0” if it is less than the threshold. For this reason, the use of a pulse function is effective when focusing on the difference in pixel values rather than the magnitude relationship between pixel values.

  Further, as a local calculation process, a ratio of two pixel values may be calculated and binarized using a pulse function. Even if the level of the value of the entire image data changes (for example, increase or decrease in brightness), the ratio of the pixel values does not change. There is an advantage that a processing result can be obtained.

  Moreover, although the example which compares the pixel value of the attention pixel and reference pixel of input image data as local calculation processing was demonstrated above, it is not restricted to this. Two reference pixels at a predetermined position with respect to the target pixel may be compared without using the target pixel. FIG. 16 shows an example in which two reference pixels are compared. Alternatively, four arithmetic operations (addition, subtraction, multiplication, and division) of the pixel value of the target pixel and the reference pixel and a predetermined fixed value may be executed. Further, the absolute values of the pixel values of the target pixel and the reference pixel may be calculated.

  In the above description, an example in which the pixel value of the input image data is compared in the local calculation process has been described. Good.

[Other Examples]
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

105a-105c ... arithmetic processing unit, 106a-106c ... binarization processing unit, 107 ... feature data generation unit, 109 ... learning unit

Claims (22)

Arithmetic means for performing arithmetic processing using a plurality of data in the vicinity of the data of interest in the processing target area in the input data,
Binarization means for binarizing the arithmetic processing result corresponding to each of the plurality of data;
Generation means for performing generation processing for generating feature data for the attention data from a binarization processing result corresponding to each of the plurality of data using a conversion parameter;
Learning means for learning the conversion parameter so as to reduce the distance between feature data generated from input data of the same class and increase the distance between feature data generated from input data of different classes; Information processing apparatus.   2. The information processing apparatus according to claim 1, wherein the calculation unit calculates a difference between the attention data and each of the plurality of data having a predetermined positional relationship with respect to the attention data.   2. The information processing apparatus according to claim 1, wherein the calculation unit calculates a difference between the plurality of pieces of data having a predetermined positional relationship with respect to the attention data. The computing means calculates a difference between the attention data and one of the plurality of data in a predetermined positional relationship with respect to the attention data at each node of the binary tree,
2. The information processing apparatus according to claim 1, wherein the binarization unit determines a branch destination as the binarization process based on the difference at each node of the binary tree.   5. The information processing apparatus according to claim 1, wherein the binarization unit performs the binarization process using a step function.   5. The information processing apparatus according to claim 1, wherein the binarization unit performs the binarization process using a pulse function.   7. The information processing apparatus according to claim 1, wherein the generation unit performs multiplication of the binarization processing result and the conversion parameter, and adds the multiplication results as the generation processing. .   7. The information processing apparatus according to claim 1, wherein there are a plurality of processing target areas, and the generation unit applies the same conversion parameter or different conversion parameters to the plurality of processing target areas.   9. The information processing apparatus according to claim 8, wherein the generation unit applies the same conversion parameter to a region having similar characteristics among the plurality of processing target regions.   10. The information processing apparatus according to claim 1, wherein the conversion parameter is a weighting factor corresponding to each of the plurality of data. The learning means includes
Randomly select first data and second data different from the first data from a plurality of data, and generate label information indicating a relationship between the class of the first data and the class of the second data A selection means;
Means for generating first feature data from the first data and generating second feature data from the second data by the arithmetic processing, the binarization processing and the generation processing;
Distance calculating means for calculating a distance between the first feature data and the second feature data;
A loss calculating means for calculating a loss based on the distance and the label information;
11. The information processing apparatus according to claim 1, further comprising an update unit that updates the conversion parameter based on the loss.   The selection unit generates the label information indicating the same class when the identification information of the first and second data is the same, and indicates a different class when the identification information of the first and second data is different. 12. The information processing apparatus according to claim 11, wherein the label information is generated.   The distance calculation means calculates a norm between a one-dimensional vector in which the elements of the first feature data are arranged and a one-dimensional vector in which the elements of the second feature data are arranged as the distance. 13. An information processing apparatus according to claim 11 or claim 12.   The loss calculating means calculates a loss indicating a proportional relationship with the distance when the label information indicates the same class, and calculates a loss indicating an inverse proportional relationship with the distance when the label information indicates a different class. 14. The information processing device according to any one of claims 11 to 13.   15. The information processing apparatus according to claim 11, wherein the update unit updates the conversion parameter using the loss and gradient descent method. An information processing method for an information processing apparatus having a calculation means, a binarization means, a generation means, and a learning means,
The arithmetic means performs arithmetic processing using each of a plurality of data in the vicinity of the data of interest in the processing target area in the input data,
The binarization means binarizes the calculation processing result corresponding to each of the plurality of data,
The generation unit generates feature data for the attention data from a binarization processing result corresponding to each of the plurality of data using a conversion parameter;
The learning means learns the conversion parameter so as to reduce the distance between feature data generated from input data of the same class and increase the distance between feature data generated from input data of different classes. Information processing method.   16. An authentication device that performs face authentication processing using the information processing device according to any one of claims 1 to 15. The authentication apparatus includes a storage unit that stores image data and collation data of a face image associated with identification information, an input unit that inputs a user instruction and image data, and an authentication unit, and the authentication unit includes:
When a user instruction indicating a learning mode is input, the conversion parameter is updated based on the image data stored in the storage unit using the information processing apparatus,
When a user instruction indicating a registration mode is input, a face image included in the input image data is extracted, feature data is extracted from the image data of the face image using the information processing device, and the feature data The collation data with reduced dimensions and the image data of the face image are associated with identification information and registered in the storage means,
When a user instruction indicating an identification mode is input, a face image included in the input image data is extracted, feature data is extracted from the image data of the face image using the information processing device, and the feature data 18. The authentication apparatus according to claim 17, wherein the face authentication process is performed using data with reduced dimensions and collation data stored in the storage unit. 16. The storage device according to claim 1, further comprising: a storage unit that stores image data and collation data of a face image associated with the identification information; an input unit that inputs a user instruction and image data; and an authentication unit. An authentication processing method of an authentication device that performs face authentication processing using the information processing device according to claim 1, wherein the authentication unit includes:
When a user instruction indicating a learning mode is input, the conversion parameter is updated based on the image data stored in the storage unit using the information processing apparatus,
When a user instruction indicating a registration mode is input, a face image included in the input image data is extracted, feature data is extracted from the image data of the face image using the information processing device, and the feature data The collation data with reduced dimensions and the image data of the face image are associated with identification information and registered in the storage means,
When a user instruction indicating an identification mode is input, a face image included in the input image data is extracted, feature data is extracted from the image data of the face image using the information processing device, and the feature data An authentication processing method for performing the face authentication processing using data with reduced dimensions and collation data stored in the storage means.   16. A program for causing a computer to function as each unit of the information processing apparatus according to any one of claims 1 to 15.   19. A program for causing a computer to function as each unit of the authentication device according to claim 17 or 18.   A computer-readable recording medium on which the program according to claim 20 or 21 is recorded.

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