COMMENTS ON FEEL-A-VISION
By
Robert S. Jaquiss Jr.
August 16, 1995
This letter is to the blind, their friends and other
interested persons. Recently, David A Harrell has issued articles
on the Internet and has been in correspondence with the Research
and Development (R&D) committee of the National Federation of the
Blind. The R&D committee has carefully reviewed Mr. Harrell's
articles and correspondence. Because there has been discussion of
Mr. Harrell's proposal on the Internet, the R&D committee is
responding publicly.
Mr. Harrell proposes that a system can be constructed which
will obtain an image, process that image and "display" it on the
skin of a person using an array of stimulators. The manner of
stimulation could be electrical, mechanical (tickling or pressure)
or thermal (using a laser). One of the premises used is that a
large number of stimulating elements would be used (100,000) in the
array. There are some fundamental problems with this proposed
device. These are:
1. In order for a stimulator to work, there must be a nerve
ending to be stimulated. There must, in fact, be a nerve
ending of the proper type for each of the stimulators. The
density of nerve endings varies from place to place on the
human body. The fingertips, hands and face have the greatest
density of tactile nerve endings per square inch; while the
back has fewer tactile nerve endings per square inch. There
are far fewer heat sensor nerves than tactile sensor nerves.
A high resolution display is of no use unless it can be
perceived. A simple experiment can be done as a proof for
this argument. Feel the fur of a dog or cat with a bare hand,
then put a thick glove on the same hand and again feel the
fur. The surface of the fur is a very high resolution image.
Notice the difference, you cannot feel the fur as well (if at
all) with the gloved hand. The resolution of the image has
not changed but your ability to perceive it has. This same
experiment can be tried on various surfaces such as a hair
brush, highly textured apholstery or even a doormat.
2. The second problem occurs, with the use of a two dimensional
array to observe a three dimensional world. Humans have
stereoscopic vision and binaural hearing. We see three
dimensional objects because our eyes are set apart. The brain
receives two slightly different views of the same object. The
difference is used to provide depth perception. People with
only one eye have no depth perception. Our ears provide two
slightly different sound images. These allow people to
aurally locate sources of sound in all three dimensions. It
is very difficult to convert a three dimensional image into
two dimensions. This is why artists draw in perspective.
Drawing in perspective allows an artist to make lifelike
pictures. One answer is to have the array of stimulators give
variable amounts of stimulation. This greatly complicates the
construction of the array and its associated processor.
3. The third problem is that of constructing such a complicated
device. 100,000 stimulators will each have (Depending on
the type.) several components. This makes the component
count very high. A machine of this complexity would have
nearly as many components as a commercial jet airplane.
The problems of manufacturing and maintenance are
enormous. There is also the problem of power
consumption. If each of 100,000 stimulators required .01
watt to operate, the user would need a power source of
one kilowatt. This is more power than used by a full
sized microwave oven, coffee maker, iron or hair dryer.
Carrying enough batteries for several hours of use would
be difficult to say the least.
In conclusion, the Research and Development committee of the
National Federation of the Blind does not consider the device
proposed by David Harrell to be possible, or practical. We do not
recommend that funds be sought or provided for this kind of
research. For those readers not familiar with the National
Federation of the Blind, we are an organization of blind people
working to obtain security, opportunity and equality for all
persons who are blind throughout the world. The National
Federation of the Blind has and will continue to change that it
means to be blind.
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