Deep feature mining in weakly supervised perception

Abstract

Convolutional neural networks (CNNs or ConvNets) provide a powerful end-to-end framework to learn features or representations directly from raw data in a hierarchical manner. Mining the features of a pre-trained CNN helps us understand the workings of CNNs and eases the burden of data acquisition and annotation in deep learning. This thesis focuses on mining the hidden features of a deep CNN trained as a classifier to obtain finer levels of perception results, and applying them in autonomous driving. We first develop a CNN-based method for fine-grained categorization where the training data are limited and the differences between the classes are very subtle. By extracting and interpreting the hierarchical hidden layer features learned by a CNN, our method obtains robust object and part detection when only the class labels are provided in training, then leverages these detection results to boost the classification results. Recently, weakly supervised semantic segmentation has aroused interest, since pixel-wise labels are expensive to obtain. This thesis secondly proposes a novel weakly-supervised semantic segmentation method using image-level labels only. The class-specific activation maps from the well-trained classifiers are used as cues to train a segmentation network. We use super-pixels to refine the cues, and fuse the cues extracted from both a color-image-trained classifier and a gray-image-trained classifier to compensate for their incompleteness. Lastly, we use our weakly-supervised semantic segmentation method to modify a visual simultaneous localization and mapping (vSLAM) system so that the movable objects in the environment are not used as landmarks for camera pose estimation. Experimental results demonstrate the superiority of our proposed method over the state-of-the-art.

Date of Award	2019
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology