Application of stereovision in a navigation aid for blind people

A "Navigation Aid for Visually Impaired" (NAVI) system has been developed in UMS in 2001 and improved in 2002. The NAVI system comprises of 3-part functioning units namely a digital video camera, a single board computer and a headphone. The single camera limitation in providing the depth information, which is critical for navigation purposes, has prompted the extension into a stereovision system by using two cameras. This stereovision system also uses the fuzzy-based segmentation procedure as an image preprocessing package that was developed for the single camera NAVI but with an additional adaptive loop. The segmented images undergo a rule-based stereo matching procedure. From the matching features, the disparity is computed. The disparity in combination with information of focal length as well as the space between two cameras provides the information on the distance between cameras and object. This distance information is incorporated into the final processed image as four gray levels such as white, light gray, dark gray and black. The size and location of object in the visual plane is then conveyed to the blind individual by means of a structured coded sound. The distance information is represented by means of verbal sound. Preliminary experimental analysis reveals a promising new approach for developing a navigational aid for blinds through the transformation of stereo image to stereo sound.