# Analysis of Feature Extraction and Anti-Interference of Face Image under Deep Reconstruction Network Algorithm

Authors: Jin Yang; Yuxuan Zhao; Shihao Yang; Xinxin Kang; Xinyan Cao; Xixin Cao
Journal: Complexity
 (2021)

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## Abstract

In face recognition systems, highly robust facial feature representation and good classification algorithm performance can affect the effect of face recognition under unrestricted conditions. To explore the anti-interference performance of convolutional neural network (CNN) reconstructed by deep learning (DL) framework in face image feature extraction (FE) and recognition, in the paper, first, the inception structure in the GoogleNet network and the residual error in the ResNet network structure are combined to construct a new deep reconstruction network algorithm, with the random gradient descent (SGD) and triplet loss functions as the model optimizer and classifier, respectively, and it is applied to the face recognition in Labeled Faces in the Wild (LFW) face database. Then, the portrait pyramid segmentation and local feature point segmentation are applied to extract the features of face images, and the matching of face feature points is achieved using Euclidean distance and joint Bayesian method. Finally, Matlab software is used to simulate the algorithm proposed in this paper and compare it with other algorithms. The results show that the proposed algorithm has the best face recognition effect when the learning rate is 0.0004, the attenuation coefficient is 0.0001, the training method is SGD, and dropout is 0.1 (accuracy: 99.03%, loss: 0.0047, training time: 352 s, and overfitting rate: 1.006), and the algorithm proposed in this paper has the largest mean average precision compared to other CNN algorithms. The correct rate of face feature matching of the algorithm proposed in this paper is 84.72%, which is higher than LetNet-5, VGG-16, and VGG-19 algorithms, the correct rates of which are 6.94%, 2.5%, and 1.11%, respectively, but lower than GoogleNet, AlexNet, and ResNet algorithms. At the same time, the algorithm proposed in this paper has a faster matching time (206.44 s) and a higher correct matching rate (88.75%) than the joint Bayesian method, indicating that the deep reconstruction network algorithm proposed in this paper can be used in face image recognition, FE, and matching, and it has strong anti-interference.


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## Body

## 1. Introduction

FR technology has been extensively adopted in identity recognition, but it is mainly used to detect biological features in the face for recognition, with strong uniqueness and security [1]. However, the dataset made up of face images is one that presents a highly nonlinear distribution, and if simple classification method is applied, higher classification errors will occur due to individual differences [2]. Moreover, the face image will be disturbed by lighting, decorations, scenes, and other factors during the shooting, which makes FR extremely difficult. At present, the methods commonly used for face detection include principal component analysis, support vector machine, CNN, and active deformation model [3].Depth model has been applied in many fields, and its application in image recognition is the first to be concerned. Moreover, the depth model is used for FE in the image, which is far better than manual FE, and can be effectively applied in the field where manual FE is not perfect [4]. The common feature of DL and most machine learning is the ability to extract features. In DL, multilayer network structure is mostly applied, which can fuse the bottom features in the image to form the top features [5]. ImageNet’s annual ImageNet Large-Scale Visual Recognition Challenge is the largest and most advanced image recognition competition in the world. Since 2012, AlexNET used DCNN to reduce the recognition error rate of the top 5 to 16.4%, and DCNN algorithm has been adopted in the subsequent champion recognition models [6, 7].The rest of the paper is organized as follows. Section2 discusses the related work of the DCNN network and image FE technology. Then, in Section 3, a deep reconstruction network is proposed, and the face recognition and facial FE algorithm is constructed based on the optimized deep reconstruction network. Section 4 carries out the verification of face recognition and FE and matching algorithms proposed in this paper and compares them with other DCNN algorithms. Section 5 discusses and analyzes the results obtained in this paper, and the results of the paper were compared with other people’s relevant research results. Section 6 concludes the paper with summary and points out the future research directions.


## 2. Related Work

NN is a common computer model, which is mainly based on the traditional statistical modeling of complex relationships to explore the relationship between different datasets. The NN structure in different application fields is different, but the NN structure with the largest application in image-related fields is CNN. Seeliger et al. applied DCNN to the detection of magnetoencephalogram signal map and reconstructed the cerebral cortex activity model based on the extracted resolution source [8]. Hoang and Kang proposed a method for fault diagnosis of rolling axis based on CNN and vibration images based on the depth structure and found that this method does not need FE technology and has high diagnostic accuracy and robustness under noisy environment [9]. At present, deep learning has been widely used in the field of image analysis, especially in facial image recognition, which has obtained excellent results. Zhang et al. proposed a convolutional neural network model based on three-stage filtering and HOG, which was applied to the recognition of color face images and obtained excellent effect [10]. Goswami et al. proposed a framework for face recognition based on deep neural networks and used a characteristic anomaly filter to detect singularities. Finally, after verification with public data, it was found that the model built by it had strong face recognition robustness [11]. Isogawa et al. indicated that there was no denoising method capable of parameter adjustment in the DCNN model.They used the proportional coefficient of soft shrinkage threshold to optimize DCNN, which was found to be applicable to noise removal in the image [12]. Nakazawa and Kulkarni proposed a method to detect and segment abnormal defect patterns using the NN architecture of deep convolutional encoder-decoder and finally found that these models could detect invisible defect patterns from real images [13].The basic principle of image FE is to use a computer to extract the information in the image and then judge whether the differences in the image are one of the features in the image. An and Zhou proposed an image FE algorithm based on two-dimensional empirical mode decomposition and scale-invariant feature change. After verification, they found that it could effectively improve the speed and accuracy of FE [14]. Xu et al. proposed a model for automatically extracting noise level perception features based on the CNN model and feature vectors and found that the proposed algorithm had high extraction speed and accuracy at different noise levels [15]. Fieldin et al. used enhanced adaptive particle swarm optimization to conduct deep CNN evolution, and after training and verification, they found that the extraction error rate was 4.78% [16].To sum up, it is evident that DCNN is widely used in image recognition. The improved DCNN can effectively extract the features in the image. However, there are few research studies on the anti-interference of DCNN in face image recognition. Therefore, a DCNN based on Caffe depth framework is proposed. Matlab simulation software is used to explore the influence of different parameter settings on the performance of FR by constructing the DCNN model. Then, the LFW database and the self-constructed face database in this paper are combined to explore the anti-interference performance of the DCNN model constructed in this paper for face image recognition in different scenarios. The results of this paper are intended to lay a foundation for improving the efficiency of FR.


## 3. Methodology

### 3.1. Design of Deep Reconstruction Network Structure

Existing studies have shown that, with the gradual deepening of the CNN structure, the CNN training results become better, but while improving the results, it will also increase the amount of network computation [17]. Therefore, an inception network structure is proposed in the GoogleNet network, which can make full use of the features extracted by each layer of the network, and the structure can increase the depth and complexity of the network while ensuring the network computing complexity. In the paper, some network parameter adjustments are proposed for the basic structure of the GoogleNet network: (1) the size of the feature map of the input network should be slowly reduced in the network to avoid the bottleneck of the feature representation in the image; (2) high-dimensional features are easier to obtain than low-dimensional features and can accelerate the training speed of the model; (3) the adjacent neurons in the network have close correlations and can be integrated into spatial relations in low-dimensional spaces.In the convolutional neural network, the 5∗ 5 size convolution kernel is 25/9 times the size of 3 ∗ 3 convolution. If the larger convolution kernel can be replaced with the superposition of multiple 3 ∗ 3 size convolution kernels, then it can make the network have fewer parameters in the same field of view. Therefore, a hypothesis is proposed in the study. First, a 3 ∗ 3 size convolution filter is adopted to process a 5 ∗ 5 size block to obtain a 3 ∗ 3 size output feature map. After the convolution with a 3 ∗ 3 size convolution kernel, 1 ∗ 1 size output is obtained. At this time, the final calculation amount is about 18/25 of the direct use of the 5 ∗ 5 size convolution kernel, which saves 28% of the calculation amount, but the network also needs to use the ReLu activation function to correct the output. After that, the 2 ∗ 2 size convolution kernel is adopted to replace the 3 ∗ 3 size convolution kernel, which can save 11% of the calculation, but the use of an asymmetric convolution kernel is better. Therefore, in the study, 1 ∗ 3 and 3 ∗ 1 size cascaded convolution kernels are used to replace 3 ∗ 3 size convolution kernels to save 33% of the calculation, so the larger size convolution kernel can be decomposed in the same way. Based on this, an improved Inception structure is obtained, as shown in Figure 1.Figure 1
Improved inception structure.The structure of ResNet can have up to 152 layers [18]. This model adds an identical high-speed channel to a simple stacked shallow network, as shown in Figure 2. On the left is the ordinary network, and its output value is H(x), which represents any ideal feature transformation. The residual network output value on the right is H(x) = F(x) + x, and what needs to be fitted in the network is the residual F(x). Adding an identical shortcut connection in the network Europe can make the input mapping and input of the network overlap. The output formula of the residual unit is y = F(x,{Wi}) + x, where x represents the input and y represents the output, and the function F(x,{Wi}) is the residual mapping obtained by learning. Theoretically, the following two networks can approximate any function. But if the optimal solution of the network is close to the identity mapping, it is easier to optimize using the residual network; if the convolution branch appears as gradient dispersion, the features and gradients in the network can also flow in the branches of the identity mapping, which ensures the reliability of information transmission.Figure 2
Differences s in the structure of different networks. The left is an ordinary network, and the right is a residual network in ResNet.The convolution layer in the convolution branchF(x,{Wi}) of the residual unit can be composed of multiple layers, and the residual unit can also be modified by scaling of the mapping branch, convolution kernel size, dropout, and the activation function location. Therefore, a new DCNN network structure is constructed based on the inception structure in the GoogleNet network and the residual structure in the ResNet network, to improve the network’s computational efficiency and information circulation effect. The combined new network structure is shown in Figure 3.Figure 3
(a) ResNet-Inception-1 structure; (b) ResNet-Inception-2 structure; (c) ResNet-Inception-3 structure.
(a)(b)(c)The basic parameters of the deep reconstruction network constructed in this paper are shown in Table1, where the dropout parameter is x, and the subsequent continuous adjustment of the parameters is required to select the optimal dropout value for the final test.Table 1
Basic parameters of ResNet-Inception network structure.
StructureParameterOutput image sizeConv-13∗ 3147∗ 147 ∗ 32Conv-23∗ 3145∗ 145 ∗ 32Conv-33∗ 3145∗ 145 ∗ 64Pool-1—73∗ 73 ∗ 64Conv-41∗ 173∗ 73 ∗ 80Conv-53∗ 370∗ 70 ∗ 190Conv-63∗ 333∗ 33 ∗ 256ResNet-Inception-1533∗ 33 ∗ 256Reduction-1—16∗ 16 ∗ 512ResNet-Inception-21016∗ 16 ∗ 512Reduction-2—8∗ 8 ∗ 1024ResNet-Inception-358∗ 8 ∗ 1024Pool-2—1792Dropoutx1792Deep neural networks often use Softmax as a classifier, and the triplet loss function is a classifier function proposed by Google for face recognition CNNs. Studies have also shown that its recognition rate on the LFW dataset has reached 99.63%, and the recognition rate on the YouTube dataset has also reached 95.12% [19]. Therefore, the impact of different classifiers on the model’s face recognition rate is analyzed. In this paper, triplets are composed of a reference (anchor) of random samples in the training set, a reference sample (positive), and a sample of different categories (negative). Assuming that the sample features obtained by extracting each sample in triplets are fx1, fx2, and fx3, respectively, then the goal of optimization is as follows:(1)fx1i−fx2i22+α<fx1i−fx3i22,∀x1i,x2i,x3i∈τ,in which α is the Euclidean distance between sample features of the same category or the minimum interval of Euclidean distance between sample features of different categories.At this time, the mathematical expression of triplet loss is as follows:(2)L=∑iNfx1i−fx2i22−fx1i−fx3i22+α.In the training process of the neural network, the gradient equation corresponding to each parameter is as follows:(3)∂L∂fx1i=2fx3i−fx2i,(4)∂L∂fx2i=2fx2i−fx1i,(5)∂L∂fx3i=2fx1i−fx3i.In order to improve the optimization efficiency of the model, the online method is used to select the combination of triplets. At the same time, in order to prevent the model from falling into the local optimal solution state,α is removed when selecting the negative sample, so xni only needs to satisfy(6)fx1i−fx3i22<fx1i−fxni22.Center loss can ensure the separation of samples of different categories during the training process and also ensure the aggregation characteristics between samples of the same category [20]. Center loss can be defined as follows: in which cyi is the feature center of the i-th category.(7)LC=12∑i=1mxi−cyi22,where LC is the center loss. Cyi is the feature center of i-th category. xi is the feature before full connection layer, and m is the size of the mini-batch.Therefore, the equation expects the smaller the sum of the distances between the characteristics and the feature center of each sample in the batch, that is, the smaller the distance within the class, the better the performance is.Thecyi is updated to update the sample set in the input network, and the update rule is as follows:(8)cuv+1=cuv−∑i=1nδyi=u⋅cyi−xi1+∑i=1nδyi=u,in which δ belongs to 0 or 1.Then, the error function in the network can be defined as follows:(9)LOSS=LOSSs+λLOSSc,in which λ is the weight in the loss function. When λ is 0, the classifier in the network is Softmax.


### 3.2. Face Fe and Matching Based on Deep Reconstruction Network

In the process of taking photos, people may not fully expose their faces due to the camera angle, light, mood, and equipment. In order to detect faces in different positions or different angles in the image, it needs to first change the scale of the sliding window or the input image. The sliding window also needs to scan the input image according to a certain step size (w); as w increases, the quantity of judgment windows and the amount of computation in the model network will decrease geometrically. When the image is input into the DCNN, there is no need to preprocess the image. However, in order to better detect faces of different sizes, the subacquisition rate of the original input image is scaled at different scales, and then, the image pyramid is obtained, as shown in Figure 4.Figure 4
Flow chart of face detection in face image.In this paper, DCNN is used to process each face image located in the image pyramid according to the input order, and the potential regions in the detected face image are marked at the same time. The coordinate points and size of the specific area of the face in the image are recorded. After all images are processed, all regions of response points in the detected images are reversely mapped to the original face image input in the input layer. Then, the overlapping areas of the image are fused to obtain the final result. Subsequently, face straightening is performed at the stage of no face alignment, and the face features in different poses are extracted, mainly partial images around the eyes, corners of the mouth, and the tip of the nose in the face image, as shown in Figure5.Figure 5
Extraction of face feature points and subfigures of each area.Subsequently, the Euclidean distance [21] and the learning feature matching algorithm are applied to feature matching in the face image, and the matching process is shown in Figure 6.Figure 6
Matching process of face feature points.In the first step, it is necessary to quickly judge the sample that is easy to judge in matching face image samples. The Euclidean distance is used for the similarity between samples, and then, the absolute distance between two points in space is calculated as follows:(10)du,v=∑i=1nui−vi2.In the second step, on the premise of ensuring the feature recognition rate in the face image, a learning algorithm with a higher recognition rate is used to model the features in the face image, and the similarity of the complete face features is matched to realize the refined judgment of the sample. It is evident from Figure5 that it is needed to extract five local value features in the face image and obtain a total of six 160-dimensional feature vectors, which are spliced into 960-dimensional facial feature vectors. Then, the feature image is reduced to 160 dimensions again by PCA dimension reduction.Besides, in the second step, joint Bayesian is used to calculate the similarity between samples. Assuming that the two faces are the joint distribution ofx1 and x2, respectively, and both obey the Gaussian distribution feature of 0 mean, then the mathematical expression of the covariance between these two face images is as follows:(11)covui,vj=covμi,μj+covεi,εj,in which μ is the identity of the character and ε is the difference between the face itself (light, expression, and posture).


### 3.3. Evaluation Indexes for the Testing and Identification of Deep Reconstruction Network Algorithm

In this paper, Matlab software is used to simulate the deep reconstruction network, and LFW dataset is used for training and testing. In this paper, the following experiments are carried out on TensorFlow platform with Linux as the operating system and 2∗ TITAN X as the GPU. The LFW dataset has a total of 13233 face images, each of which gives the corresponding name, there are a total of 5749 people, and most people have only one picture. The size of each image is 250 × 250, most of which are color images, but there are also a few black and white face pictures. In this paper, the face images in the dataset are randomly divided into a training set and a verification set. The training set contains 10,000 face images, and the verification set contains 3233 face images. When training the model, first the effects of different parameter settings (learning rate η, attenuation coefficient λ, training optimization algorithm, and dropout) on the training effect of the model are analyzed, and the loss value, accuracy value, overfitting rate, and training time are adopted for evaluation of the training effect. Based on the model with the optimal parameter settings, it is applied to the verification set, and the mean average precision (mAP) value is used to evaluate the model recognition effect.In order to evaluate the effect of the proposed algorithm on face FE, 10140 images of 1150 people from the LFW dataset are selected, and 180 pairs of positive face samples and 180 pairs of negative face samples are randomly selected as test sample pairs. Then, the construction network is used to perform face FE, and the simplest Euclidean distance is used to match feature similarity. Finally, classification accuracy and matching accuracy are used to evaluate the effectiveness of face FE. Subsequently, these 10140 images are used to continue segmentation. Images of 1050 people are selected for facial feature matching algorithm training. For the remaining 100 images of individuals, 200 pairs of positive samples and 200 pairs of negative samples are randomly selected to verify. The recognition accuracy rate, positive sample error rate, negative sample error rate, pairing correct rate, and pairing average time are used to evaluate the matching effect of face features.In the field of target recognition and detection and recognition, mAP is often used to evaluate the effect of algorithm detection and recognition [22]. In the paper, basic concepts such as error rate, accuracy, precision, recall, and average precision are first introduced. The error rate and accuracy rate are the most commonly used measurement terms in classification evaluation, where the error rate is the ratio of error samples to the total sample, and the accuracy rate is the ratio of correct sample to the total sample. Assuming that the sample dataset is S, the sample is defined as ui, the type of the sample is vi, the algorithm’s prediction result is f(ui), and then the calculation equations of error rate and accuracy rate are as follows:(12)Errorf;S=1m∑i=1mIfui≠vi,(13)Accf;S=1m∑i=1mIfui=vi=1−Errorf;S.The calculation equations for the precision rate (Pre) and the recall rate (Recall) are as follows:(14)Pre=TPTP+FP,(15)Recall=TPTP+FN,where TP is the true positive, FP is the false positive, and FN is the false negative.Using the precision rate as the vertical axis and the recall rate as the horizontal axis, a P-R curve is obtained. The area under the P-R curve is average precision (AP), and mAP is the average of AP indicators in each type of classification task. In addition, the overfitting ratio (OR) is used to evaluate the algorithm. The calculation equation of OR is as follows:(16)OR=TrainAccValAcc,in which TrainAcc is the training accuracy rate and ValAcc is the verification accuracy rate.


## 3.1. Design of Deep Reconstruction Network Structure

Existing studies have shown that, with the gradual deepening of the CNN structure, the CNN training results become better, but while improving the results, it will also increase the amount of network computation [17]. Therefore, an inception network structure is proposed in the GoogleNet network, which can make full use of the features extracted by each layer of the network, and the structure can increase the depth and complexity of the network while ensuring the network computing complexity. In the paper, some network parameter adjustments are proposed for the basic structure of the GoogleNet network: (1) the size of the feature map of the input network should be slowly reduced in the network to avoid the bottleneck of the feature representation in the image; (2) high-dimensional features are easier to obtain than low-dimensional features and can accelerate the training speed of the model; (3) the adjacent neurons in the network have close correlations and can be integrated into spatial relations in low-dimensional spaces.In the convolutional neural network, the 5∗ 5 size convolution kernel is 25/9 times the size of 3 ∗ 3 convolution. If the larger convolution kernel can be replaced with the superposition of multiple 3 ∗ 3 size convolution kernels, then it can make the network have fewer parameters in the same field of view. Therefore, a hypothesis is proposed in the study. First, a 3 ∗ 3 size convolution filter is adopted to process a 5 ∗ 5 size block to obtain a 3 ∗ 3 size output feature map. After the convolution with a 3 ∗ 3 size convolution kernel, 1 ∗ 1 size output is obtained. At this time, the final calculation amount is about 18/25 of the direct use of the 5 ∗ 5 size convolution kernel, which saves 28% of the calculation amount, but the network also needs to use the ReLu activation function to correct the output. After that, the 2 ∗ 2 size convolution kernel is adopted to replace the 3 ∗ 3 size convolution kernel, which can save 11% of the calculation, but the use of an asymmetric convolution kernel is better. Therefore, in the study, 1 ∗ 3 and 3 ∗ 1 size cascaded convolution kernels are used to replace 3 ∗ 3 size convolution kernels to save 33% of the calculation, so the larger size convolution kernel can be decomposed in the same way. Based on this, an improved Inception structure is obtained, as shown in Figure 1.Figure 1
Improved inception structure.The structure of ResNet can have up to 152 layers [18]. This model adds an identical high-speed channel to a simple stacked shallow network, as shown in Figure 2. On the left is the ordinary network, and its output value is H(x), which represents any ideal feature transformation. The residual network output value on the right is H(x) = F(x) + x, and what needs to be fitted in the network is the residual F(x). Adding an identical shortcut connection in the network Europe can make the input mapping and input of the network overlap. The output formula of the residual unit is y = F(x,{Wi}) + x, where x represents the input and y represents the output, and the function F(x,{Wi}) is the residual mapping obtained by learning. Theoretically, the following two networks can approximate any function. But if the optimal solution of the network is close to the identity mapping, it is easier to optimize using the residual network; if the convolution branch appears as gradient dispersion, the features and gradients in the network can also flow in the branches of the identity mapping, which ensures the reliability of information transmission.Figure 2
Differences s in the structure of different networks. The left is an ordinary network, and the right is a residual network in ResNet.The convolution layer in the convolution branchF(x,{Wi}) of the residual unit can be composed of multiple layers, and the residual unit can also be modified by scaling of the mapping branch, convolution kernel size, dropout, and the activation function location. Therefore, a new DCNN network structure is constructed based on the inception structure in the GoogleNet network and the residual structure in the ResNet network, to improve the network’s computational efficiency and information circulation effect. The combined new network structure is shown in Figure 3.Figure 3
(a) ResNet-Inception-1 structure; (b) ResNet-Inception-2 structure; (c) ResNet-Inception-3 structure.
(a)(b)(c)The basic parameters of the deep reconstruction network constructed in this paper are shown in Table1, where the dropout parameter is x, and the subsequent continuous adjustment of the parameters is required to select the optimal dropout value for the final test.Table 1
Basic parameters of ResNet-Inception network structure.
StructureParameterOutput image sizeConv-13∗ 3147∗ 147 ∗ 32Conv-23∗ 3145∗ 145 ∗ 32Conv-33∗ 3145∗ 145 ∗ 64Pool-1—73∗ 73 ∗ 64Conv-41∗ 173∗ 73 ∗ 80Conv-53∗ 370∗ 70 ∗ 190Conv-63∗ 333∗ 33 ∗ 256ResNet-Inception-1533∗ 33 ∗ 256Reduction-1—16∗ 16 ∗ 512ResNet-Inception-21016∗ 16 ∗ 512Reduction-2—8∗ 8 ∗ 1024ResNet-Inception-358∗ 8 ∗ 1024Pool-2—1792Dropoutx1792Deep neural networks often use Softmax as a classifier, and the triplet loss function is a classifier function proposed by Google for face recognition CNNs. Studies have also shown that its recognition rate on the LFW dataset has reached 99.63%, and the recognition rate on the YouTube dataset has also reached 95.12% [19]. Therefore, the impact of different classifiers on the model’s face recognition rate is analyzed. In this paper, triplets are composed of a reference (anchor) of random samples in the training set, a reference sample (positive), and a sample of different categories (negative). Assuming that the sample features obtained by extracting each sample in triplets are fx1, fx2, and fx3, respectively, then the goal of optimization is as follows:(1)fx1i−fx2i22+α<fx1i−fx3i22,∀x1i,x2i,x3i∈τ,in which α is the Euclidean distance between sample features of the same category or the minimum interval of Euclidean distance between sample features of different categories.At this time, the mathematical expression of triplet loss is as follows:(2)L=∑iNfx1i−fx2i22−fx1i−fx3i22+α.In the training process of the neural network, the gradient equation corresponding to each parameter is as follows:(3)∂L∂fx1i=2fx3i−fx2i,(4)∂L∂fx2i=2fx2i−fx1i,(5)∂L∂fx3i=2fx1i−fx3i.In order to improve the optimization efficiency of the model, the online method is used to select the combination of triplets. At the same time, in order to prevent the model from falling into the local optimal solution state,α is removed when selecting the negative sample, so xni only needs to satisfy(6)fx1i−fx3i22<fx1i−fxni22.Center loss can ensure the separation of samples of different categories during the training process and also ensure the aggregation characteristics between samples of the same category [20]. Center loss can be defined as follows: in which cyi is the feature center of the i-th category.(7)LC=12∑i=1mxi−cyi22,where LC is the center loss. Cyi is the feature center of i-th category. xi is the feature before full connection layer, and m is the size of the mini-batch.Therefore, the equation expects the smaller the sum of the distances between the characteristics and the feature center of each sample in the batch, that is, the smaller the distance within the class, the better the performance is.Thecyi is updated to update the sample set in the input network, and the update rule is as follows:(8)cuv+1=cuv−∑i=1nδyi=u⋅cyi−xi1+∑i=1nδyi=u,in which δ belongs to 0 or 1.Then, the error function in the network can be defined as follows:(9)LOSS=LOSSs+λLOSSc,in which λ is the weight in the loss function. When λ is 0, the classifier in the network is Softmax.


## 3.2. Face Fe and Matching Based on Deep Reconstruction Network

In the process of taking photos, people may not fully expose their faces due to the camera angle, light, mood, and equipment. In order to detect faces in different positions or different angles in the image, it needs to first change the scale of the sliding window or the input image. The sliding window also needs to scan the input image according to a certain step size (w); as w increases, the quantity of judgment windows and the amount of computation in the model network will decrease geometrically. When the image is input into the DCNN, there is no need to preprocess the image. However, in order to better detect faces of different sizes, the subacquisition rate of the original input image is scaled at different scales, and then, the image pyramid is obtained, as shown in Figure 4.Figure 4
Flow chart of face detection in face image.In this paper, DCNN is used to process each face image located in the image pyramid according to the input order, and the potential regions in the detected face image are marked at the same time. The coordinate points and size of the specific area of the face in the image are recorded. After all images are processed, all regions of response points in the detected images are reversely mapped to the original face image input in the input layer. Then, the overlapping areas of the image are fused to obtain the final result. Subsequently, face straightening is performed at the stage of no face alignment, and the face features in different poses are extracted, mainly partial images around the eyes, corners of the mouth, and the tip of the nose in the face image, as shown in Figure5.Figure 5
Extraction of face feature points and subfigures of each area.Subsequently, the Euclidean distance [21] and the learning feature matching algorithm are applied to feature matching in the face image, and the matching process is shown in Figure 6.Figure 6
Matching process of face feature points.In the first step, it is necessary to quickly judge the sample that is easy to judge in matching face image samples. The Euclidean distance is used for the similarity between samples, and then, the absolute distance between two points in space is calculated as follows:(10)du,v=∑i=1nui−vi2.In the second step, on the premise of ensuring the feature recognition rate in the face image, a learning algorithm with a higher recognition rate is used to model the features in the face image, and the similarity of the complete face features is matched to realize the refined judgment of the sample. It is evident from Figure5 that it is needed to extract five local value features in the face image and obtain a total of six 160-dimensional feature vectors, which are spliced into 960-dimensional facial feature vectors. Then, the feature image is reduced to 160 dimensions again by PCA dimension reduction.Besides, in the second step, joint Bayesian is used to calculate the similarity between samples. Assuming that the two faces are the joint distribution ofx1 and x2, respectively, and both obey the Gaussian distribution feature of 0 mean, then the mathematical expression of the covariance between these two face images is as follows:(11)covui,vj=covμi,μj+covεi,εj,in which μ is the identity of the character and ε is the difference between the face itself (light, expression, and posture).


## 3.3. Evaluation Indexes for the Testing and Identification of Deep Reconstruction Network Algorithm

In this paper, Matlab software is used to simulate the deep reconstruction network, and LFW dataset is used for training and testing. In this paper, the following experiments are carried out on TensorFlow platform with Linux as the operating system and 2∗ TITAN X as the GPU. The LFW dataset has a total of 13233 face images, each of which gives the corresponding name, there are a total of 5749 people, and most people have only one picture. The size of each image is 250 × 250, most of which are color images, but there are also a few black and white face pictures. In this paper, the face images in the dataset are randomly divided into a training set and a verification set. The training set contains 10,000 face images, and the verification set contains 3233 face images. When training the model, first the effects of different parameter settings (learning rate η, attenuation coefficient λ, training optimization algorithm, and dropout) on the training effect of the model are analyzed, and the loss value, accuracy value, overfitting rate, and training time are adopted for evaluation of the training effect. Based on the model with the optimal parameter settings, it is applied to the verification set, and the mean average precision (mAP) value is used to evaluate the model recognition effect.In order to evaluate the effect of the proposed algorithm on face FE, 10140 images of 1150 people from the LFW dataset are selected, and 180 pairs of positive face samples and 180 pairs of negative face samples are randomly selected as test sample pairs. Then, the construction network is used to perform face FE, and the simplest Euclidean distance is used to match feature similarity. Finally, classification accuracy and matching accuracy are used to evaluate the effectiveness of face FE. Subsequently, these 10140 images are used to continue segmentation. Images of 1050 people are selected for facial feature matching algorithm training. For the remaining 100 images of individuals, 200 pairs of positive samples and 200 pairs of negative samples are randomly selected to verify. The recognition accuracy rate, positive sample error rate, negative sample error rate, pairing correct rate, and pairing average time are used to evaluate the matching effect of face features.In the field of target recognition and detection and recognition, mAP is often used to evaluate the effect of algorithm detection and recognition [22]. In the paper, basic concepts such as error rate, accuracy, precision, recall, and average precision are first introduced. The error rate and accuracy rate are the most commonly used measurement terms in classification evaluation, where the error rate is the ratio of error samples to the total sample, and the accuracy rate is the ratio of correct sample to the total sample. Assuming that the sample dataset is S, the sample is defined as ui, the type of the sample is vi, the algorithm’s prediction result is f(ui), and then the calculation equations of error rate and accuracy rate are as follows:(12)Errorf;S=1m∑i=1mIfui≠vi,(13)Accf;S=1m∑i=1mIfui=vi=1−Errorf;S.The calculation equations for the precision rate (Pre) and the recall rate (Recall) are as follows:(14)Pre=TPTP+FP,(15)Recall=TPTP+FN,where TP is the true positive, FP is the false positive, and FN is the false negative.Using the precision rate as the vertical axis and the recall rate as the horizontal axis, a P-R curve is obtained. The area under the P-R curve is average precision (AP), and mAP is the average of AP indicators in each type of classification task. In addition, the overfitting ratio (OR) is used to evaluate the algorithm. The calculation equation of OR is as follows:(16)OR=TrainAccValAcc,in which TrainAcc is the training accuracy rate and ValAcc is the verification accuracy rate.


## 4. Results

### 4.1. Comparison of Recognition Rate Based on Deep Reconstruction Network Algorithm

By adjusting the learning rateη, attenuation coefficient λ, training method, and dropout, the impact of different parameters on the accuracy of DCNN model recognition is explored, the database is used to train the DCNN model, and the maximum number of iterations is set to 1000. In the experiment, the activation function in the network is always kept as ReLU. First, the effects of different learning rates η on the model recognition rate are compared. The results are shown in Figures 7 and 8. It is evident from Figure 7 that when η = 0.0004, the recognition accuracy of the algorithm is the highest; when η = 0.001, the recognition accuracy of the algorithm is the lowest. It is evident from Figure 8 that when η = 0.0004, the loss value of the algorithm is the smallest, and when η = 0.001, the loss value of the algorithm is the largest. With the gradual increase in η, the accuracy value gradually decreases and the loss value gradually increases.Figure 7
Comparison of recognition accuracy of different learning rates.Figure 8
Comparison of training loss value of different learning rates.Then, the effects of different learning rates on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table2 that when η = 0.0004, the algorithm has the largest accuracy value (99.03%), the smallest loss value (0.047), and the shortest training time (352 s). When η = 0.0007, the algorithm has the lowest overfitting rate (1.005). In summary, when η = 0.0004, the performance of the algorithm is the best, so follow-up tests are conducted based on this.Table 2
Effects of different learning rates on the training effect of deep reconstruction network algorithm.
ηAcc (%)LossTraining time (s)Overfitting rate0.000499.030.0473521.0060.000596.740.0593541.0060.000693.150.0623681.0820.000790.310.1203701.0050.000888.070.1154001.0110.000986.410.1703981.0260.00185.050.2064051.058The effect of different attenuation coefficientsλ on the model recognition rate is compared. The results are shown in Figures 9 and 10. It is evident from Figure 9 that when λ = 0.0001, the recognition accuracy of the algorithm is the highest; when λ = 0.09, the recognition accuracy of the algorithm is the lowest. It is evident from Figure 10 that when λ = 0.0001, the loss value of the algorithm is the smallest; when λ = 0.09, the loss value of the algorithm is the largest. With the gradual increase in λ, the accuracy value gradually decreases and the loss value gradually increases.Figure 9
Comparison of recognition accuracy of different attenuation coefficients.Figure 10
Comparison of training loss value of different attenuation coefficients.Then, the effects of different attenuation coefficients on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table3 that when λ = 0.0001, the accuracy value of the algorithm is the largest (99.03%), and the loss value is the smallest (0.047). When λ = 0.0007, the training time of the algorithm is the shortest (342 s). When λ = 0.0001 and 0.0009, the overfitting rate of the algorithm is the smallest (1.006). In summary, when λ = 0.0001, the performance of the algorithm is the best, so follow-up tests are conducted based on this, and the classifier used in this model is determined to be the triplet loss function.Table 3
Influence of different attenuation coefficients on the training effect of deep reconstruction network algorithm.
λAcc (%)LossTraining time (s)Overfitting rate0.000199.030.0473521.0060.000997.630.0483421.0060.00195.170.1023581.037After comparing the effects of different training methods on the model recognition rate, the results are shown in Figures11 and 12. It is evident from Figure 11 that when the training method is SGD, the recognition accuracy of the algorithm is the highest; when the training method is Adagrad, the recognition accuracy of the algorithm is the lowest. It is evident from Figure 12 that when the training method is SGD, the loss value of the algorithm is the smallest; when the training method is Adagrad, the loss value of the algorithm is the largest.Figure 11
Comparison of recognition accuracy of six training methods.Figure 12
Comparison of training loss value of six training methods.Then, the effects of different training methods on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table4 that when the training method is SGD, the algorithm has the largest Acc value (99.03%), the smallest loss value (0.047), and the lowest overfitting rate (1.006). When the training method is RMSprop, the training time of the algorithm is the shortest (351 s). In summary, when the training method is SGD, the performance of the algorithm is the best, so follow-up tests are performed based on this.Table 4
Influence of different training methods on the training effect of deep reconstruction network algorithm.
Training methodAcc (%)LossTraining time (s)Overfitting rateAdadelta97.450.0623571.010Adam97.050.0873881.012Nadam96.870.1324381.016RMSprop96.140.1473511.129SGD99.030.0473521.006Adagrad94.910.1874221.158Finally, the impact of different dropout values on the model recognition rate is compared. The results are shown in Figures13 and 14. It is evident from Figure 13 that when dropout = 0.1, the algorithm has the highest recognition accuracy; when dropout = 0.6, the algorithm has the lowest recognition accuracy. It is evident from Figure 14 that when dropout = 0.1, the loss value of the algorithm is the smallest, and when dropout = 0.6, the loss value of the algorithm is the largest. With the gradual increase in the dropout value, the accuracy value of the algorithm gradually decreases, and the loss value gradually increases.Figure 13
Comparison of recognition accuracy with different dropout values.Figure 14
Comparison of training loss value with different dropout values.Then, the effects of different dropout values on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table5 that when dropout = 0.1, the algorithm has the largest Acc value (99.03%), the smallest loss value (0.047), and the lowest overfitting rate with dropout = 0.2 (1.006). When dropout = 0.6, the training time of the algorithm is the shortest (337 s). In summary, when dropout = 0.1, the performance of the algorithm is the best, so follow-up tests are conducted based on this.Table 5
Effect of different dropout values on the training effect of deep reconstruction network algorithm.
DropoutAcc (%)LossTraining time (s)Overfitting rate0.199.030.0473521.0060.298.830.0573471.0060.397.200.0873481.0090.497.050.1123511.0170.596.230.1273401.0270.695.930.1533371.518It is set thatη = 0.0004 and λ = 0.0001 in the construction of the deep reconstruction network, SGD is selected as the training method, and dropout = 0.1. Then, the effects of different activation functions on the model recognition rate are compared, as shown in Figures 15 and 16. It is evident from Figure 15 that the recognition accuracy rate is the highest when the activation function is ReLu, and the recognition accuracy rate is the lowest when the activation function is sigmoid. From Figure 16, it is evident that the loss value is the lowest when the activation function is ReLu, and the loss value is the highest when the activation function is sigmoid.Figure 15
Comparison of accuracy of behavior recognition of six activation functions.Figure 16
Comparison of behavior training loss of six activation functions.Then, the effects of different activation functions on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table6 that when the activation function is ReLu, the Acc value of this algorithm is the largest (99.03%), the loss value is the smallest (0.047), and the overfitting rate is the lowest (1.006). When the activation function is Tanh, the training time of this algorithm is the shortest (341 s). In summary, when the activation function is ReLu, the performance of the algorithm is the best, so follow-up tests are carried out on the basis.Table 6
Influence of different activation functions on the training effect of deep reconstruction network algorithm.
Activation functionAcc (%)LossTraining time (s)Overfitting rateSigmoid95.170.0913821.007ReLu99.030.0473521.006Tanh98.520.0533411.007LeakyReLu97.110.0733501.006ELU96.780.0873491.007MaxOut97.450.0823671.006Based on the results obtained above, in the deep reconstruction network constructed in this paper,η = 0.0004, λ = 0.0001, the training method is set to SGD, and dropout = 0.1 for face recognition verification, and the recognition effect is compared with LetNet-5, GoogleNet, AlexNet, VGG-16, VGG-19, and ResNet network. It is evident from Figure 17 that the area under the P-R curve of the algorithm constructed in this paper is the largest; that is, the mAP value is the largest. The mAP values of different models are ranked, and the result is the algorithm proposed in the paper > ResNet > AlexNet > VGG-19>GoogleNet > VGG-16>LetNet-5.Figure 17
Comparison of P-R curves of face recognition performance of different models.


### 4.2. Face Fe and Matching Verification Based on Deep Reconstruction Network Algorithm

The face recognition and FE algorithm proposed in this paper is applied to the LFW dataset to extract and match face features. The results are shown in Figure18. It is evident that the algorithm proposed in this paper can effectively extract the features in the face image and can complete the matching of the same features and then realize the recognition and detection of the same face.Figure 18
Face image FE and matching. Different colored circles in the same picture indicate different extracted features, and the same color in different pictures in the same group indicates matching similar features.Then, the deep reconstruction network algorithm constructed in this paper is applied to FE and feature matching in face images, and the performance is compared with other models. It is evident from Table7 that when the construction method of this paper is trained, the classification accuracy rate on the training set is 97.94%, and it is higher than the LetNet-5, VGG-16, and VGG-19 algorithms, the accuracy rates of which are 2.1%, 0.94%, and 1.16%, respectively, but lower than GoogleNet, AlexNet, ResNet algorithm, the accuracy rates of which are 0.14%, 0.58%, and 0.46%, respectively. In the verification set, the correct matching rate of the algorithm constructed in this paper is 84.72%, and it is higher than the LetNet-5, VGG-16, and VGG-19 algorithms, the correct matching rates of which are 6.94%, 2.5%, and 1.11%, but lower than the GoogleNet, AlexNet, and ResNet algorithms, the correct matching rates of which are 0.56%, 1.39%, and 1.95%, respectively.Table 7
Comparison of facial FE performance of different models.
AlgorithmCorrect number of training classificationsTraining classification accuracy (%)Verify correct logVerification correct match rate (%)LetNet-5902895.8428077.78VGG-16911796.7829682.22VGG-19913797.0030183.61GoogleNet923998.0830785.28AlexNet928198.5231086.11ResNet926998.4031286.67Our method922697.9430584.72LetNet-5902895.8428077.78The matching effect of the features extracted from the face image is compared. The comparison results of the total recognition rate are shown in Table8. It is evident that, after the joint Bayesian method is used in the algorithm proposed in this paper, the correct recognition log rate in the verification set is the highest (88.75%), and it is higher than LetNet-5, GoogleNet, AlexNet, VGG-16, VGG-19, and ResNet algorithms, the correct recognition rates of which are 4%, 1.25%, 0.75%, 3.75%, 3.25%, and 0.25%, respectively.Table 8
Comparison of total recognition rates of facial features of different models.
AlgorithmIdentify the correct logarithmRecognition correct log rate (%)Log error rate of positive samples (%)Logarithmic error rate of negative samples (%)LetNet-533984.7513.517VGG-163408514.515.5VGG-1934285.51514GoogleNet35087.51411AlexNet3528811.512.5ResNet35488.510.512.5Our method35588.751111.5The effects of using only the joint Bayesian method and the algorithm in this paper on the matching effect of face features are compared, and the results are shown in Table9. It is evident that the algorithm proposed in this paper has a faster matching time (206.44 s) and a higher correct matching rate (88.75%) than the joint Bayesian method.Table 9
Comparison of total recognition rates of facial features of different models.
AlgorithmMatching time (s)Match log correctlyCorrect match rate (%)United Bayes240.1535087.5Our method206.4435588.75


## 4.1. Comparison of Recognition Rate Based on Deep Reconstruction Network Algorithm

By adjusting the learning rateη, attenuation coefficient λ, training method, and dropout, the impact of different parameters on the accuracy of DCNN model recognition is explored, the database is used to train the DCNN model, and the maximum number of iterations is set to 1000. In the experiment, the activation function in the network is always kept as ReLU. First, the effects of different learning rates η on the model recognition rate are compared. The results are shown in Figures 7 and 8. It is evident from Figure 7 that when η = 0.0004, the recognition accuracy of the algorithm is the highest; when η = 0.001, the recognition accuracy of the algorithm is the lowest. It is evident from Figure 8 that when η = 0.0004, the loss value of the algorithm is the smallest, and when η = 0.001, the loss value of the algorithm is the largest. With the gradual increase in η, the accuracy value gradually decreases and the loss value gradually increases.Figure 7
Comparison of recognition accuracy of different learning rates.Figure 8
Comparison of training loss value of different learning rates.Then, the effects of different learning rates on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table2 that when η = 0.0004, the algorithm has the largest accuracy value (99.03%), the smallest loss value (0.047), and the shortest training time (352 s). When η = 0.0007, the algorithm has the lowest overfitting rate (1.005). In summary, when η = 0.0004, the performance of the algorithm is the best, so follow-up tests are conducted based on this.Table 2
Effects of different learning rates on the training effect of deep reconstruction network algorithm.
ηAcc (%)LossTraining time (s)Overfitting rate0.000499.030.0473521.0060.000596.740.0593541.0060.000693.150.0623681.0820.000790.310.1203701.0050.000888.070.1154001.0110.000986.410.1703981.0260.00185.050.2064051.058The effect of different attenuation coefficientsλ on the model recognition rate is compared. The results are shown in Figures 9 and 10. It is evident from Figure 9 that when λ = 0.0001, the recognition accuracy of the algorithm is the highest; when λ = 0.09, the recognition accuracy of the algorithm is the lowest. It is evident from Figure 10 that when λ = 0.0001, the loss value of the algorithm is the smallest; when λ = 0.09, the loss value of the algorithm is the largest. With the gradual increase in λ, the accuracy value gradually decreases and the loss value gradually increases.Figure 9
Comparison of recognition accuracy of different attenuation coefficients.Figure 10
Comparison of training loss value of different attenuation coefficients.Then, the effects of different attenuation coefficients on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table3 that when λ = 0.0001, the accuracy value of the algorithm is the largest (99.03%), and the loss value is the smallest (0.047). When λ = 0.0007, the training time of the algorithm is the shortest (342 s). When λ = 0.0001 and 0.0009, the overfitting rate of the algorithm is the smallest (1.006). In summary, when λ = 0.0001, the performance of the algorithm is the best, so follow-up tests are conducted based on this, and the classifier used in this model is determined to be the triplet loss function.Table 3
Influence of different attenuation coefficients on the training effect of deep reconstruction network algorithm.
λAcc (%)LossTraining time (s)Overfitting rate0.000199.030.0473521.0060.000997.630.0483421.0060.00195.170.1023581.037After comparing the effects of different training methods on the model recognition rate, the results are shown in Figures11 and 12. It is evident from Figure 11 that when the training method is SGD, the recognition accuracy of the algorithm is the highest; when the training method is Adagrad, the recognition accuracy of the algorithm is the lowest. It is evident from Figure 12 that when the training method is SGD, the loss value of the algorithm is the smallest; when the training method is Adagrad, the loss value of the algorithm is the largest.Figure 11
Comparison of recognition accuracy of six training methods.Figure 12
Comparison of training loss value of six training methods.Then, the effects of different training methods on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table4 that when the training method is SGD, the algorithm has the largest Acc value (99.03%), the smallest loss value (0.047), and the lowest overfitting rate (1.006). When the training method is RMSprop, the training time of the algorithm is the shortest (351 s). In summary, when the training method is SGD, the performance of the algorithm is the best, so follow-up tests are performed based on this.Table 4
Influence of different training methods on the training effect of deep reconstruction network algorithm.
Training methodAcc (%)LossTraining time (s)Overfitting rateAdadelta97.450.0623571.010Adam97.050.0873881.012Nadam96.870.1324381.016RMSprop96.140.1473511.129SGD99.030.0473521.006Adagrad94.910.1874221.158Finally, the impact of different dropout values on the model recognition rate is compared. The results are shown in Figures13 and 14. It is evident from Figure 13 that when dropout = 0.1, the algorithm has the highest recognition accuracy; when dropout = 0.6, the algorithm has the lowest recognition accuracy. It is evident from Figure 14 that when dropout = 0.1, the loss value of the algorithm is the smallest, and when dropout = 0.6, the loss value of the algorithm is the largest. With the gradual increase in the dropout value, the accuracy value of the algorithm gradually decreases, and the loss value gradually increases.Figure 13
Comparison of recognition accuracy with different dropout values.Figure 14
Comparison of training loss value with different dropout values.Then, the effects of different dropout values on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table5 that when dropout = 0.1, the algorithm has the largest Acc value (99.03%), the smallest loss value (0.047), and the lowest overfitting rate with dropout = 0.2 (1.006). When dropout = 0.6, the training time of the algorithm is the shortest (337 s). In summary, when dropout = 0.1, the performance of the algorithm is the best, so follow-up tests are conducted based on this.Table 5
Effect of different dropout values on the training effect of deep reconstruction network algorithm.
DropoutAcc (%)LossTraining time (s)Overfitting rate0.199.030.0473521.0060.298.830.0573471.0060.397.200.0873481.0090.497.050.1123511.0170.596.230.1273401.0270.695.930.1533371.518It is set thatη = 0.0004 and λ = 0.0001 in the construction of the deep reconstruction network, SGD is selected as the training method, and dropout = 0.1. Then, the effects of different activation functions on the model recognition rate are compared, as shown in Figures 15 and 16. It is evident from Figure 15 that the recognition accuracy rate is the highest when the activation function is ReLu, and the recognition accuracy rate is the lowest when the activation function is sigmoid. From Figure 16, it is evident that the loss value is the lowest when the activation function is ReLu, and the loss value is the highest when the activation function is sigmoid.Figure 15
Comparison of accuracy of behavior recognition of six activation functions.Figure 16
Comparison of behavior training loss of six activation functions.Then, the effects of different activation functions on the face recognition performance of the algorithm are quantitatively compared. It is evident from Table6 that when the activation function is ReLu, the Acc value of this algorithm is the largest (99.03%), the loss value is the smallest (0.047), and the overfitting rate is the lowest (1.006). When the activation function is Tanh, the training time of this algorithm is the shortest (341 s). In summary, when the activation function is ReLu, the performance of the algorithm is the best, so follow-up tests are carried out on the basis.Table 6
Influence of different activation functions on the training effect of deep reconstruction network algorithm.
Activation functionAcc (%)LossTraining time (s)Overfitting rateSigmoid95.170.0913821.007ReLu99.030.0473521.006Tanh98.520.0533411.007LeakyReLu97.110.0733501.006ELU96.780.0873491.007MaxOut97.450.0823671.006Based on the results obtained above, in the deep reconstruction network constructed in this paper,η = 0.0004, λ = 0.0001, the training method is set to SGD, and dropout = 0.1 for face recognition verification, and the recognition effect is compared with LetNet-5, GoogleNet, AlexNet, VGG-16, VGG-19, and ResNet network. It is evident from Figure 17 that the area under the P-R curve of the algorithm constructed in this paper is the largest; that is, the mAP value is the largest. The mAP values of different models are ranked, and the result is the algorithm proposed in the paper > ResNet > AlexNet > VGG-19>GoogleNet > VGG-16>LetNet-5.Figure 17
Comparison of P-R curves of face recognition performance of different models.


## 4.2. Face Fe and Matching Verification Based on Deep Reconstruction Network Algorithm

The face recognition and FE algorithm proposed in this paper is applied to the LFW dataset to extract and match face features. The results are shown in Figure18. It is evident that the algorithm proposed in this paper can effectively extract the features in the face image and can complete the matching of the same features and then realize the recognition and detection of the same face.Figure 18
Face image FE and matching. Different colored circles in the same picture indicate different extracted features, and the same color in different pictures in the same group indicates matching similar features.Then, the deep reconstruction network algorithm constructed in this paper is applied to FE and feature matching in face images, and the performance is compared with other models. It is evident from Table7 that when the construction method of this paper is trained, the classification accuracy rate on the training set is 97.94%, and it is higher than the LetNet-5, VGG-16, and VGG-19 algorithms, the accuracy rates of which are 2.1%, 0.94%, and 1.16%, respectively, but lower than GoogleNet, AlexNet, ResNet algorithm, the accuracy rates of which are 0.14%, 0.58%, and 0.46%, respectively. In the verification set, the correct matching rate of the algorithm constructed in this paper is 84.72%, and it is higher than the LetNet-5, VGG-16, and VGG-19 algorithms, the correct matching rates of which are 6.94%, 2.5%, and 1.11%, but lower than the GoogleNet, AlexNet, and ResNet algorithms, the correct matching rates of which are 0.56%, 1.39%, and 1.95%, respectively.Table 7
Comparison of facial FE performance of different models.
AlgorithmCorrect number of training classificationsTraining classification accuracy (%)Verify correct logVerification correct match rate (%)LetNet-5902895.8428077.78VGG-16911796.7829682.22VGG-19913797.0030183.61GoogleNet923998.0830785.28AlexNet928198.5231086.11ResNet926998.4031286.67Our method922697.9430584.72LetNet-5902895.8428077.78The matching effect of the features extracted from the face image is compared. The comparison results of the total recognition rate are shown in Table8. It is evident that, after the joint Bayesian method is used in the algorithm proposed in this paper, the correct recognition log rate in the verification set is the highest (88.75%), and it is higher than LetNet-5, GoogleNet, AlexNet, VGG-16, VGG-19, and ResNet algorithms, the correct recognition rates of which are 4%, 1.25%, 0.75%, 3.75%, 3.25%, and 0.25%, respectively.Table 8
Comparison of total recognition rates of facial features of different models.
AlgorithmIdentify the correct logarithmRecognition correct log rate (%)Log error rate of positive samples (%)Logarithmic error rate of negative samples (%)LetNet-533984.7513.517VGG-163408514.515.5VGG-1934285.51514GoogleNet35087.51411AlexNet3528811.512.5ResNet35488.510.512.5Our method35588.751111.5The effects of using only the joint Bayesian method and the algorithm in this paper on the matching effect of face features are compared, and the results are shown in Table9. It is evident that the algorithm proposed in this paper has a faster matching time (206.44 s) and a higher correct matching rate (88.75%) than the joint Bayesian method.Table 9
Comparison of total recognition rates of facial features of different models.
AlgorithmMatching time (s)Match log correctlyCorrect match rate (%)United Bayes240.1535087.5Our method206.4435588.75


## 5. Discussion

Previous studies have shown that different parameter settings will have a certain impact on the recognition rate of the DCNN model. In this paper, the effects of different learning rates, training methods, attenuation coefficients, and dropout on the recognition performance of the algorithm are compared. Studies have shown that too large learning rate will cause the algorithm to appear unstable during the learning process, which in turn affects the performance of the algorithm [23], which is consistent with the results of this paper that the learning rate is negatively correlated with the performance of the algorithm proposed in this paper. Then, the effects of different training methods on the recognition rate of the DCNN model are compared. The RMSprop-based network training method will increase the probability of overfitting, and the madam-based network training method will increase the momentum parameter of Nesterov, so the training will take more time. Previous studies have shown that adjusting dropout discarding rate in many network parameters can solve the problem of overfitting in the model, but excessively increasing dropout discarding rate will reduce the RA of image classification, and the overfitting probability will increase [24], which is basically consistent with the results in this paper that the dropout is negatively correlated with the recognition performance of the constructed face recognition algorithm. At the same time, the effect of different attenuation coefficient settings on the recognition performance of the proposed algorithm is compared. It is found that the attenuation coefficient is negatively correlated with the recognition rate of the proposed algorithm. This is because excessive weight attenuation coefficient will destroy the stability of the algorithm in the learning process, so choosing the smallest possible attenuation coefficient can ensure the stability of the face recognition algorithm [25].Facial features are mainly divided into color (skin color), contour (ellipse), illumination (hair, eyes, and jaw), template (mean and variance), transformation domain (feature representation), structure (facial symmetry), inlay (mosaic rule), and histogram features (grey distribution) [26]. In the process of face feature detection, because of factors such as highly nonlinear distribution (such as facial expression and color difference), ornaments (beard, glasses, and hats), the expression (facial muscle movement), light (brightness and angles), image quality (resolution), and a complex scenario (face number and gap), classification errors are caused [27]. Xu et al. proposed a semisupervised method for FR in LFW and YTF databases and found that the recognition rate of the algorithm was 98.63% and 91.76%, respectively [28]. In this paper, the constructed deep reconstruction network is applied to the FE of face images in LFW data; after the proposed algorithm is compared to LetNet-5 [29], VGG-16 [30], and VGG-19 [31] algorithms, it is found that it has a higher matching accuracy rate but slightly lower than GoogleNet [32], AlexNet [33], and ResNet [34] algorithms. However, the algorithm proposed in this paper can reduce the complexity of model generation, while preventing the occurrence of overfitting. Finally, the Bayesian method [35] is used to match face features. It is found that the accuracy rate of the proposed algorithm for face features matching is higher than LetNet-5, VGG-16, VGG-19, GoogleNet, AlexNet, and ResNet. At the same time, compared with the joint Bayes method alone, it can reduce the time consumption of feature matching [36] and improve the matching accuracy [37], indicating that the algorithm proposed in this paper can quickly perform large-scale face image feature matching and has certain advantages compared with other DCNN models.


## 6. Conclusion

In this paper, a new deep reconstruction network is constructed using the Inception structure in the GoogleNet network and the residual structure in the ResNet network, and it is applied to face recognition for optimal parameter selection of the algorithm. Based on this algorithm, face pyramid and local feature segmentation are applied to construct a face FE algorithm. It is found that it has a better FE effect than the general DCNN model. Finally, based on the algorithm, the face feature matching is achieved using the joint Bayesian method, and the results are verified. The results show that the model constructed in this paper can effectively identify face images with different interference factors. However, the model is trained and verified only through the images in the database. A specific FR system needs to be developed to explore its application effect in video portrait recognition. In conclusion, the results help for the subsequent development of FR system based on DCNN and the improvement of the efficiency of FR.



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*Source: 8391973-2021-03-20.xml*