Deep Photometric Stereo Network with Multi-Scale Feature Aggregation

Abstract

We present photometric stereo algorithms robust to non-Lambertian reflection, which are based on a convolutional neural network in which surface normals of objects with complex geometry and surface reflectance are estimated from a given set of an arbitrary number of images. These images are taken from the same viewpoint under different directional illumination conditions. The proposed method focuses on surface normal estimation, where multi-scale feature aggregation is proposed to obtain a more accurate surface normal, and max pooling is adopted to obtain an intermediate order-agnostic representation in the photometric stereo scenario. The proposed multi-scale feature aggregation scheme using feature concatenation is easily incorporated into existing photometric stereo network architectures. Our experiments were performed with a DiLiGent photometric stereo benchmark dataset consisting of ten real objects, and they demonstrated that the accuracies of our calibrated and uncalibrated photometric stereo approaches were improved over those of baseline methods. In particular, our experiments also demonstrated that our uncalibrated photometric stereo outperformed the state-of-the-art method. Our work is the first to consider the multi-scale feature aggregation in photometric stereo, and we showed that our proposed multi-scale fusion scheme estimated the surface normal accurately and was beneficial to improving performance.

Comparison of Chest Radiograph Interpretations by Artificial Intelligence Algorithm vs Radiology Residents

“…Specifically VGGNet (16 layers) and ResNet (50 layers) were used as the initial feature extractors, which were trained on several million images from ImageNet . Dilated blocks composed of multiscale features and skip connections were used to improve convergence while spatial dropout was used to reduce overfitting. Group normalization (16 groups) was used, along with Rectified Linear Unit as activation function.…”