Computer-Vision-Based Vibration Tracking Using a Digital Camera: A Sparse-Optical-Flow-Based Target Tracking Method.

Computer-vision-based target tracking is a technology applied to a wide range of research areas, including structural vibration monitoring. However, current target tracking methods suffer from noise in digital image processing. In this paper, a new target tracking method based on the sparse optical flow technique is introduced for improving the accuracy in tracking the target, especially when the target has a large displacement. The proposed method utilizes the Oriented FAST and Rotated BRIEF (ORB) technique which is based on FAST (Features from Accelerated Segment Test), a feature detector, and BRIEF (Binary Robust Independent Elementary Features), a binary descriptor. ORB maintains a variety of keypoints and combines the multi-level strategy with an optical flow algorithm to search the keypoints with a large motion vector for tracking. Then, an outlier removal method based on Hamming distance and interquartile range (IQR) score is introduced to minimize the error. The proposed target tracking method is verified through a lab experiment-a three-story shear building structure subjected to various harmonic excitations. It is compared with existing sparse-optical-flow-based target tracking methods and target tracking methods based on three other types of techniques, i.e., feature matching, dense optical flow, and template matching. The results show that the performance of target tracking is greatly improved through the use of a multi-level strategy and the proposed outlier removal method. The proposed sparse-optical-flow-based target tracking method achieves the best accuracy compared to other existing target tracking methods.

DNA: Deeply Supervised Nonlinear Aggregation for Salient Object Detection.

Recent progress on salient object detection mainly aims at exploiting how to effectively integrate multiscale convolutional features in convolutional neural networks (CNNs). Many popular methods impose deep supervision to perform side-output predictions that are linearly aggregated for final saliency prediction. In this article, we theoretically and experimentally demonstrate that linear aggregation of side-output predictions is suboptimal, and it only makes limited use of the side-output information obtained by deep supervision. To solve this problem, we propose deeply supervised nonlinear aggregation (DNA) for better leveraging the complementary information of various side-outputs. Compared with existing methods, it: 1) aggregates side-output features rather than predictions and 2) adopts nonlinear instead of linear transformations. Experiments demonstrate that DNA can successfully break through the bottleneck of the current linear approaches. Specifically, the proposed saliency detector, a modified U-Net architecture with DNA, performs favorably against state-of-the-art methods on various datasets and evaluation metrics without bells and whistles.

Analysis on Mitigation of Visually Induced Motion Sickness by Applying Dynamical Blurring on a User's Retina.

Visually induced motion sickness (MS) experienced in a 3D immersive virtual environment (VE) limits the widespread use of virtual reality (VR). This paper studies the effects of a saliency detection-based approach on the reduction of MS when the display on a user's retina is dynamic blurred. In the experiment, forty participants were exposed to a VR experience under a control condition without applying dynamic blurring, and an experimental condition applying dynamic blurring. The experimental results show that the participants under the experimental condition report a statistically significant reduction in the severity of MS symptoms on average during the VR experience compared to those under the control condition, which demonstrates that the proposed approach may alleviate visually induced MS in VR and enable users to remain in a VE for a longer period of time.