A Smartphone-based Haptic Vision Substitution system for the blind

Haptic Vision Substitution is a relatively new Human-Machine Interface (HMI) designed to help the blind to `see' through touch. This paper documents the implementation and design of a Smartphone-based vibrotactile system that uses Catadioptric stereo imaging to increase the spatial awareness of a visually impaired individual. The system computes a disparity map, where distance from an object is inversely proportional to the intensity, using Computer Vision techniques. This information is then compressed and sent to a microcontroller via Bluetooth to be actuated on an 8×8 matrix of shaftless coin vibration motors composing the vibrotactile interface. The interface is built into a wearable vest, where actuation occurs on the upper back region. The upper back was chosen as it is a relatively unused area of the body, providing minimal contraction, and has the somatosensory neuron resolution to accommodate an 8×8 vibrotactile array. This study also includes research on the effectiveness of the haptic transduction and methods of enhancing the tactile sensation to provide a more seamless user experience. It also builds the basis for a programmable tactile interface that would open the doors to a variety of applications for the blind.

I. INTRODUCTION

Vision or visual perception is a complex sensory system of a human organism that interprets light reflected off objects onto the retina of an eye. Special receptor cells in the retina, rods and cones, convert the light intensity and color of the light into electrical signals sent to the brain via the optical nerve. Visually impaired and blind individuals have this process obstructed either physiologically or neurologically. The World Health Organization estimated in May 2009 that about 314 million people are visually impaired worldwide, and 45 million of them are blind. Although 85% can be cured through modem clinical treatment, for the other 15%, hope of a complete awareness of their surroundings lies with modem technology and innovation. They can avoid collisions through the use of a walking stick or a trained dog, but this doesn't give 3D perception. They can also feel textures using their hands, but this is time consuming. The blind tend to use the sense of touch as a substitution for vision so a proper technological solution would use this property to its advantage.