Transforming a Fluorescent Glare Into a Guiding Light

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October 11, 2001

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Transforming a Fluorescent Glare Into a Guiding Light

By ANNE EISENBERG

THEY were once the hallmark of institutional monotony. No more, though: the
drab fluorescent tube has been rehabilitated.

A professor at the Massachusetts Institute of Technology has figured out a
way to transform the ubiquitous fixtures in the ceilings of airports,
museums,
offices and factories into inexpensive data transmitters. Pass under one
these revamped fluorescent lights at the airport, and it may send out not
just
its characteristic cold glow, but also a message that flashes on your hand-
held computer screen saying: "Turn left at the next corridor for Gate A.
There's
a cash machine just as you reach the intersection."

To create fluorescent tubes that can communicate, their inventor, Dr. Steven
Leeb, has modified ordinary fluorescent fixtures so that they beam data as
well as illumination. Dr. Leeb, who teaches circuit design and other
subjects at M.I.T., does this by changing one component in the fixture to
produce
fluctuations in the light that can be read as a digital signal. These
fluctuations, imperceptible to the eye, are easily detected by light sensors
that
pick up the signals and pass them to processors and software that produce
voice, music or text messages. The lights may be linked to create
inexpensive
data networks.

Passers-by in subways and shopping malls may one day use messages
transmitted by such lights to guide them. Some blind and brain-damaged
people have already
tried out the fluorescent devices as an aid in navigating unfamiliar
corridors in office buildings and hospitals.

Dr. Leeb has formed a company, Talking Lights, based in Boston, to market
the new device. He sometimes demonstrates his product by turning on a
circular
fluorescent fixture and watching their faces as Handel's "Messiah" streams
out of loudspeakers connected to the photodetector and processor. "Then
people
get the idea," he said.

The process of using the lights to transmit data starts with a ballast, the
component of fluorescent tubes that controls the current needed to create
the
light. The ballast causes the vapor inside the tube to ionize many times a
second, creating the imperceptible flicker. Dr. Leeb has modified the
ballast
to modulate the number of times per second that the light flickers.

"The ballast is what makes the magic happen," Dr. Leeb said. "We drop it in,
just as we would replace a bulb."

If, for instance, the light is flickering at 40 kilohertz, or 40,000 times
per second, which is standard for modern fluorescent fixtures using
electronic
ballasts, the modified ballast might alter the frequency slightly to create
a digital 1, and then alter it slightly differently to create a digital 0,
thus producing a binary datastream.

"The trick is that our ballast moves the frequency around in such a way that
the light doesn't flicker visibly," Dr. Leeb said.

Inexpensive photocells on hand-held computers or earphones, for instance,
pick up the change in flicker and pass this signal on for conversion to
graphics,
music, written messages or speech. The entire receiver packet of photocell,
circuits, and processing chips runs about half the size of a pack of
cigarettes,
said Dr. Neil Lupton, president of Talking Lights.

The information can get to the lights in many ways, Dr. Lupton explained. If
people are using the lights to broadcast information, for example, they
might
use a microphone to create the signal and a wire to carry the information to
each light. Or a chip could be equipped with a continual audio signal
repeating,
for instance, the location of a restroom at an airport. Users would hear the
announcement only when they came near the lights and their receivers locked
on the signal. When the lights are wired together in a network, the
information can be changed by reprogramming.

Dr. David Burke, an assistant professor at Harvard Medical School and
director of the brain injury unit at Spaulding Rehabilitation Hospital in
Boston,
is heading a project to see if Talking Lights technology can be effective in
helping patients with brain injuries. The project is financed by the
National
Institutes of Health.

"The brain-injured can walk around, but they can't organize schedules or
remember when to do things," he said. To see if the lights could alleviate
these
problems, Dr. Burke's group equipped the patients with hand-held computers
in holsters tucked next to the patients' bodies.

There is a series of talking lights on the hospital floor, each emitting a
different digital signal. Before the patients start their day, their
hand-held
computers are programmed with that day's schedule, along with information
about the locations and signals of the lights that the patients should pass
at
specific times. As a patient passes each talking light, the hand-held
computer recognizes the unique signal from each light and matches the
patient's projected
schedules with actual whereabouts.

For example, Dr. Burke said, if a patient turns up as expected at a nursing
station, the hand-held device recognizes the signal from a nearby light as
the
correct one. But if another patient who is due someplace else shows up at
the nursing station, the hand- held device recognizes that the light signal
is
incorrect and instructs the patient by voice prompt to go somewhere else.

At the end of the day, the staff downloads the data into a PC to analyze,
for instance, how often patients need to be reminded and when the reminders
tend
to fail so that they can fine-tune the program. Results of the pilot phase
of the project were published in the June edition of the Journal of Head
Trauma
Rehabilitation. The data showed that patients using the system relied less
on directions from people in the hospital and got to their appointments more
promptly than those without.

Dr. Burke would like to apply talking lights technology beyond the hospital,
in office buildings and homes, for example. "Sometimes we can rehabilitate
head-injury patients so that they can leave," he said, but they still need
help. "Devices like this could remind them to take their medications, make
them
more independent and keep them free from institutional environments for
longer periods of time."

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