A significant proportion of the population is visually impaired or blind. Navigation through unfamiliar environments is a challenge for people with visual impairments that is often ameliorated by the use of canes and/or the assistance of guide dogs. Various attempts have been made to utilize technology to provide additional assistance from simple devices such as ultrasonic canes to more complex devices that attempt to provide navigation guidance.
A number of head-mounted devices, such as headsets and headbands, have been developed for reading and travel assistance for the blind. Head-mounted devices possess the advantage that the ears, which are the only sensory organ responsible for hearing and the main substitution pathway for the blind, are located on the head. An early head-mounted navigation aid was the Binaural Sonic Aid (SonicGuide), which included an ultrasonic wide-beam range sensor mounted on spectacle lenses as shown in FIG. 1. Signals reflected back from real world objects were presented to the user as audio indicating the presence of an obstacle and its approximate distance to the user. Over the years, SonicGuide has been improved and the latest version of the system called KASPA creates an auditory representation of the objects ahead of the user. With sufficient training, KASPA enables users to distinguish different objects and even different surfaces in the environment.
The Sonic PathFinder, developed by Perceptual Alternatives, is a head-mounted system that employs five ultrasonic transducers to measure distance to objects. The system uses the notes of a musical scale to provide warning of objects, where the musical scale descends with each note representing a distance of approximately 0.3 m. Objects picked up from the left or right of the user are heard in the left and right ears respectively. Those straight ahead are heard in both ears simultaneously.
Another approach involved the use of optical sensing to capture environmental information. The vOICe Learning Edition video sonification software available at www.seeingwithsound.com enables the rendering of video images into auditory sound scapes.
The Intelligent Glasses (IG) is a combined head-mounted display and tactile display system developed at Paris 6 University in France. The IG provides tactile maps of visual spaces and allows users to deduce possible paths for navigation through these spaces. The IG includes a pair of stereo-cameras mounted on a glasses frame. The input image data is provided to vision algorithms that identify obstacles in the scene. The locations of the objects is then communicated via a tactile display. The resulting tactile map is a simple edge-like representation of the obstacles' locations in the scene.
A number of GPS based navigation systems have been developed. GPS-based navigation systems are a true orientation aid, as the satellites provide constantly updated position information. A limitation of GPS based navigation systems is that they typically cannot be used to reliably perform indoor navigation.
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