  Depth information has been proven useful for face recognition. However,
existing depth-image-based face recognition methods still suffer from noisy
depth values and varying poses and expressions. In this paper, we propose a
novel method for normalizing facial depth images to frontal pose and neutral
expression and extracting robust features from the normalized depth images. The
method is implemented via two deep convolutional neural networks (DCNN),
normalization network ($Net_{N}$) and feature extraction network ($Net_{F}$).
Given a facial depth image, $Net_{N}$ first converts it to an HHA image, from
which the 3D face is reconstructed via a DCNN. $Net_{N}$ then generates a
pose-and-expression normalized (PEN) depth image from the reconstructed 3D
face. The PEN depth image is finally passed to $Net_{F}$, which extracts a
robust feature representation via another DCNN for face recognition. Our
preliminary evaluation results demonstrate the superiority of the proposed
method in recognizing faces of arbitrary poses and expressions with depth
images.
