AUDIO DISPLAY FOR THE BLIND (1976):

Patterns, shapes are presented to the blind person in the form of sound through ear-phones.
Listeners imagine a dot of sound moving in front of them. The vertical loaction of the dot was directly rellated to the pitch of the sound (since for tones below 7kHz a higher pitch is perceived as coming from a higher vertical position), and the horizontal position through the use of binaural hearing.
With little training, patterns and shapes can be correctly determined.
This idea was later modified allowing a camera to obtain an image which was then scanned. When thwe scan is on the desired object, the methods above are used to convey the information to the subject.
Simple and complex shapes, as well as patterns were successfully determined.

CONTOUR PERCEPTION SYSTEM (KONWA) (1988):

Prototype mobility aid to allow for better orientation and object recognition.
User moves an optical sensor which reduces an object to its outlines (which is the essential information necessary for object recognition). the contour informationis transferred to the forearm of the user via electrical pulses. Two weak pulses signal a contour line and its direction. Two stimuli indicate the direction of the contour.
By moving the forearm, the contour can be tracked (through the presence of the stimuli), allowing a mental image of the figure to be developed which may be rocognised by the user depending on past experiences.

Covert visual informnation obtained through a camera into a pattern on a matrix of stimulators which are in contact with the skin. The stimulators aither vibrate or release electric current creating a sensation on the skin.
Not very promising for mobility uses.

TVSS (TACTILE VISUAL SUBSTITUTION SYSTEM) (1969):

Converts visual information obtained with a camera into a pattern of vibrations or electrical stimulations on a matrix in contact with the user's back or abdomen.
Experimented with a staionary camera (yielding poor results), hand held and spectacle mounted camera.
When an object is introduced for the first time the user is told what it is in hopes of being able to recognise the same object in the future.
Can learn to scan the object in order to find distinct features as cues to identification.
After several hours of practice, subjects were able to identify reliably, randomly presented objects (from a set of 25), in an average of 10s.

PATTERN RECOGNITION ON THE FOREHEAD: ELECTRIC SCAN SYSTEM

Cutaneous and auditory modalities can process information serially better.
Same idea as the TVSS, however a 10 * 10 matrix was used on the forehead (since the back and abdomen have poor 'two-point' descrimination and the area on the fingertips is too small to provide efficiency), incorporating the above three considerations.
Serial stimulation achieved by activating the appropriate stimulators of each row in a left to right manner starting from the top row.
Provided better results than the TVSS.

MODIFIED OPTACON:

Camera with 144 cells (6 * 24), which are directly connected to the stimulators (vibrotactile array finger pad).
Any pattern on the camera's array is immediately transfered to the finger pad (in contacct with the user's finger).
Camera is head mounted allowing the user to scan for objects.

64 SOLENOID, FOUR LEVEL FINGERTIP SEARCH DISPLAY FOR THE THE BLIND (1986):

Information of a camera image is conveyed to the finger through varying stimulations taking advantage of the blind person's skill of exploring with their fingertips.
Goal of the device:

Used an 8 * 8 array of dc solenoids allowing for four different heights (each height corresponding to a level on the grey scale).
The PC obtains the image from the camera (or the image may be stored in memory), and passes an 8 * 8 portion of the image to the display.
user uses the mouse to select the portion of the image they wish to examine.

CORTICAL STIMULATION:

Generation of light flash sensations by electrically stimulating the visual cortex through an implanted array of stimulators corresponding to the image picked up by the camera.
Although several implants have been performed, this field requires much research. Several implants performed during the 70s were very long and complicating. The devices usually malfunctioned with time.
See IEEE Spectrum May 1996 for a thorough description of some current work in this field

TALKING SIGNS

Conveys printed sign information (used by the sighted population to aid in orientation), in the form of audio (speech).
"Talking Signs do for print- handicapped persons what printed signs do for those able to read them. They are small, inexpensive voice-modulated infrared transmitters whose message is heard by means of a pocket-size receiver which speaks the Signs' messages and indicates the direction of their source. ". (The Smith-Kettlewell Eye Research Institute)

'Bracons' which continuously transmit audible (speeh) messages are placed in public places (e.g. bus and train stations),.
A user within this environment with a receiver will receive this message which gives information regarding the environment and direction.
Messges are transmitted in four different languages and the user may choose either.
The messages conveyed by the beacons can easily be changed (e.g. the beacons are networked allowing any one beacon to be accessed from a central control location).