Vision Substitution Systems
Although visual pattern recognition is rapidly evolving, most of the attempts to allow the blind "to see" or "perceive" use sound. There is an entire profession (or groups of professions) working on sonification. Refer to the 
Sonification Report prepared by the National Science Foundation in the United States.
A bio-acoustic "vision prothesis" called KASPA was developed by Dr. Leslie Kay in New Zealand. Dr. Kay is a world renown inventor and expert in the field of electronic travel aid technology. KASPA is a completed product with successful users all over the world. It is especially valuable for use with blind children as they develop spatial concepts. Earlier versions of KASPA were called "the Trisensor", and later the "Sonic Guide".
Dr. Peter Meijer, a researcher at Philips Research Labs in the Netherlands, invented The vOICe; an experimental system for auditory image representation (real time conversion of auditory images into soundscapes). Video images are digitalized and converted into sound by a computer. Peter Meijer is one of the most articulate and tireless scientists working in the field today.
The work of David Dewhurst is similar to that of Peter Meijer. His system is called "Vuphonics". David concentrates on pre-processing and interpreting more of an image before conveying it to the user. The approach also tends towards only
conveying a small part of an image at any time. In David's words " more recently I've been concentrating on using speech-like sounds and "telling" the user more. I am not concentrating on systematic scanning (although I use it to some extent), as Peter and Phil are doing a lot of excellent work in that area and I would just be duplicating it if I did. I suppose the general approach I am now using is to attempt to reproduce in sound and tactile effects certain aspects of visual perception "
Dr. Phil Picton at Nene College in England is working on a sonification system similar to that of Peter Meijer and David Dewhurst called the Optophone.
Also in England, Manchester scientist Professor Cronly-Dillon (an optometrist) has found a way to transform shapes into music. Professor Cronly-Dillon uses basically the same kind of mapping as the vOICe, left-to-right scanning, with pitch depending on elevation, and with a vertical line segment resulting in a chord with all tones sounding simultaneously.