Abstract: Concerning low accuracy of age classification of face images under unrestricted conditions, a new method of face age classification under unconstrained conditions based on deep Residual Networks (ResNets) and large dataset pre-training was proposed. Firstly, the deep residual networks were used as the basis convolutional neural network model to deal with the problem of face age classification. Secondly, the deep residual networks were trained on the ImageNet dataset to learn the expression of basic image features. Thirdly, the large-scale face age images IMDB-WIKI was cleaned, and the IMDB-WIKI-8 dataset was established for fine-tuning the deep residual networks, and migration learning from the general object image to face age image was achieved to make the model adapt to the distribution of the age group and improve the network learning capability. Finally, the fine-tuned network model was trained and tested on the unconstrained Adience dataset, and the age classification accuracy was obtained by the cross-validation method. Through the comparison of 34/50/101/152-layer residual networks, it could be seen that the more layers of the network have the higher accuracy of age classification. And the best state-of-the-art age classification result on Adience dataset with the accuracy of 65.01% was achieved by using the 152-layer residual network. The experimental results show that the combination of deeper residual network and large dataset pretraining can effectively improve the accuracy of face age classification.

Key words: unconstrained face age classification, deep Residual Networks (ResNets), migrate learning, ImageNet

摘要： 针对非受限条件下人脸图像年龄分类准确度较低的问题，提出了一种基于深度残差网络（ResNets）和大数据集微调的非受限条件下人脸年龄分类方法。首先，选用深度残差网络作为基础卷积神经网络模型处理人脸年龄分类问题；其次，在ImageNet数据集上对深度残差网络预训练，学习基本图像特征的表达；然后，对大规模人脸年龄图像数据集IMDB-WIKI清洗，并建立了IMDB-WIKI-8数据集用于微调深度残差网络，实现一般物体图像到人脸年龄图像的迁移学习，使模型适应于年龄段的分布并提高网络学习能力；最后，在非受限人脸数据集Adience上对微调后的网络模型进行训练和测试，并采用交叉验证方法获取年龄分类准确度。通过34/50/101/152层残差网络对比可知，随着网络层数越深年龄分类准确度越高，并利用152层残差网络获得了Adience数据集上人脸图像年龄分类的最高准确度65.01%。实验结果表明，结合更深层残差网络和大数据集微调，能有效提高人脸图像年龄分类准确度。

关键词: 非受限人脸年龄分类, 深度残差网络, 迁移学习, ImageNet