19-12-2009, 07:10 PM
Blind since old age have been using walking stick and also walking dogs for their mobility purposes. many different types of electronic travel aid are available: These use either ultrasound or laser beam. One of such devices is the laser cane that is similar to a long cane with built-in laser ranging facilities.Most use ultrasound for functioning.These use the reflectance property of the high frequency ultrasound and are available in different
models like:
1.Sonic torch
a hand held device and operates on the principle of transmitting ultrasound in the forward direction and receiving the reflected beam from a nearby object.
2.Mowat sensor
It detects object by sending high frequency ultrasound in pulses and receiving the reflected beam from any nearby object.distance of the object can be identified by the rate of vibration produced by the device.
3.Sonic pathfinder
a sonic pathfinder is fitted on the head of the user. The audio output from the sonic pathfinder is made up of notes of a musical scale which produce a familiar tonal progression as the user approaches an object,which is then fed to the user through earphones.
A novel device
The device transmits radio frequency signals having different carrier frequencies. Each path to a certain destination (like main office, library, canteen, toilet) from the user's room, carries a specific radio frequency signal.The information may be square wave pulses that can be used to produce tactile vibration.each path is identified by its carrier.
Its parts are:
1.Transmitter
Each individual antenna carries a specific radio frequency
signal.radio frequency signals are transmitted using different
transmitting antennas that start from the user's room to the
respective destination. Antenna is a single ended electrical
wire that runs from the user's room to the destination.
2. Receiver
A small ferrite rod placed at the top of the walking
stick will act as the receiving antenna. It maybe AM
or FM depending on the type of the transmitter.The frequency
tuning circuit tune the receiver at the require carrier
frequency.
3. Output devices
audio signal that fed to
the user through earphoneswhich guide
the user from his room to the require destination.
detailed seminar report download:
[attachment=665]