The last decades a variety of portable or wearable navigation systems have been developed to assist visually impaired people during navigation in known or unknown, indoor or outdoor environments. There are three main categories of these systems: Electronic travel aids (ETAs), electronic orientation aids (EOAs), and position locator devices (PLDs). This paper presents a comparative survey among portable/wearable obstacle detection/avoidance systems (a subcategory of ETAs) in an effort to inform the research community and users about the capabilities of these systems and about the progress in assistive technology for visually impaired people. The survey is based on various features and performance parameters of the systems that classify them in categories, giving qualitative-quantitative measures. Finally, it offers a ranking, which will serve only as a reference point and not as a critique on these systems.

This paper deals with the design, simulation and implementation of a 2D vibration array used as a major component of an assistive wearable navigation device for visual impaired. The 2D vibration array consists of 16 (4x4) miniature vibrators connected to a portable computer, which is the main computing component of the entire wearable navigation system, called Tyflos. Tyflos consists of two miniature cameras (attached to a pair of dark glasses), a microphone, an ear speaker, the 2D vibration array, and a portable computer. The cameras capture images from the surrounding environment and after appropriate processing 3D representations are created. These 3D space representations are projected on the 2D array, which vibrates in various levels corresponding to the distances of the surrounding obstacles. The 2D array is attached to the user's chest in order to provide the appropriate sensation (via vibrations) of the distances from the surroundings.

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This paper presents several important issues related with the preservation and analysis of important image information needed by a visually impaired individual for safe navigation in an indoor environment. The image information is provided to a visually impaired individual, via a 2D Vibration Array (VA), which is part of the Tyflos navigation system and is attached on the individual's abdomen. The system is also consisted of two micro-cameras (hidden in a pair of dark glasses), headphone, microphone and a portable computer. The cameras capture video from the 3D surrounding environment and after stereo vision processing 3D representations are created. These representations are projected on the VA whose 4×4 vibration elements vibrate in various levels corresponding to the distances of the surrounding objects. During this projection appropriate high-to-low resolution algorithms are used in order to make the image mapping onto the VA.