A System-Prototype Representing 3D Space via Alternative-Sensing for Visually Impaired Navigation

Offering an alternative mode of interaction with the surrounding 3-D space to the visually impaired for collision free navigation is a goal of great significance that includes several key challenges. In this paper, we study the alternative 3-D space sensation that is interpreted by our computer vision prototype system and transferred to the user via a vibration array. There are two main tasks for conducting such a study. The first task is to detect obstacles in close proximity, and motion patterns in image sequences, both important issues for a safe navigation in a 3-D dynamic space. To achieve this task, the images from the left and right cameras are acquired to produce new stereo images, followed by video stabilization as a preprocessing stage, a nonlinear spatio-temporal diffusion and kernel based density estimation method to assess the motion activity, and finally watershed-based detection of moving regions (or obstacles) of interest. The second task is to efficiently represent the information of the captured static and dynamic visual scenes as 3-D detectable patterns of vibrations applied on the human body to create a 3-D sensation of the space during navigation. To accomplish this task, considering the current limitations imposed by the technology, we create a high-to-low (H-L) image resolution representation scheme to facilitate the mapping onto a low-resolution 2-D array of vibrators. The H-L scheme uses pyramidal modeling to obtain low-resolution images of interest-preserving motion and obstacles-that are mapped onto a vibration array. These patterns are utilized to train and test the performance of the users in free space navigation. Thus, in this paper we study the synergy of these two important schemes to offer an alternative sensation of the 3-D space to the visually impaired via an array of vibrators. Particularly, the motion component is employed as an element for the identification of visual information of interest to be retained during the H-L transformation. The role of the array vibrators is to create a small-scale front representation of the space via various levels of vibrations. Thus, 3-D vibrations applied on the user's body (chest, abdomen) offer a 3-D sensation of the surrounding space and the motion in it. In addition, we present experimental results that indicate the efficiency of this navigation scheme in creating low-resolution 3-D views of the free navigation space and detecting obstacles and moving areas.