LMFNet: a lightweight multiscale fusion network with hierarchical structure for low-quality 3-D face recognition

Three-dimensional (3-D) face recognition (FR) can improve the usability and user-friendliness of human–machine interaction. In general, 3-D FR can be divided into high-quality and low-quality 3-D FR according to different interaction scenarios. The low-quality data can be easily obtained, so its application prospect is more extensive. However, the challenge is how to balance the trade-offs between data accuracy and real-time performance. To solve this problem, we propose a lightweight multiscale fusion network (LMFNet) with a hierarchical structure based on single-mode data for low-quality 3-D FR. First, we design a backbone network with only five feature extraction blocks to reduce computational complexity and improve the inference speed. Second, we devise a mid-low adjacent layer with a multiscale feature fusion (ML-MSFF) module to extract the facial texture and contour information, and a mid-high adjacent layer with a multiscale feature fusion (MH-MSFF) module to obtain the discriminative information in high-level features. Then, a hierarchical multiscale feature fusion (HMSFF) module is formed by combining these two modules mentioned above to acquire the local information of different scales. Finally, we enhance the expression of features by integrating HMSFF with a global convolutional neural network for improving recognition accuracy. Experiments on Lock3DFace, KinectFaceDB, and IIIT-D datasets demonstrate that our proposed LMFNet can achieve superior performance on low-quality datasets. Furthermore, experiments on the cross-quality database based on Bosphorus and the different intensity noise low-quality datasets based on UMB-DB and Bosphorus show that our network is robust and has a high generalization ability. It satisfies the real-time requirement, which lays a foundation for a smooth and user-friendly interactive experience.