Every so often, internet news aggregator
sites run a story about a research group that put an LED into a contact lens,
then inserted it into a rabbit's eye. I
figured that I would try the same thing, but put the lens into my own eye. I
accomplished this by laminating a coil of wire and an 0402 surface-mount LED
between two ordinary soft contact lenses. I was hoping the lenses would stick
to each other, but they did not, so I ended up fixing the edges together by
pinching the plastic together with hot tweezers. This held well enough to
capture a minute of video with the LED
illuminated in my eye. For video purposes, I mounted the LED facing
outward. An actual VR/AR display would
have the LED facing inward.
I powered the LED by using a very
primitive spark-gap transmitter built from a mechanical relay to send RF energy
into a larger coil held near my eye. The large coil coupled the energy into the
contact lens coil and pulsed the LED.
oh my god it's an
LED in a contact lens
I think VR displays are right around the
corner hey everyone Ben here it seems
every so often on the Internet this
story comes up with about the contact
lens with an LED in it and I think the
group that did this put it into a
rabbit's eye so I thought I'd one-up
them and put it into my own eye so let
me show you how I did it I started by
winding 40 turns of number 40 wire on a
form this is just an aluminum rod that's
5/16 of an inch in diameter and I
soldered the ends of the magnet wire to
a very small Oh 402 led and this is a
low profile
Oh 402 led so that when I put this into
the contact lens it won't poke out so
much the total height of this whole
thing is under a millimeter is very hard
to measure because the coils kind of
overlap and make it difficult anyway so
that so the way that I plan to power the
circuit is just through plain inductive
coupling I originally wanted to do a
tuned circuit and have a capacitor
inside the contact lens as well so the
best way of transferring power through a
large airspace is with a a resonant
inductive circuit unfortunately there's
just so little room inside the contact
lens I went with just a straight coil so
the coils connected directly to the LED
and for half the cycle power won't flow
because the LED is blocking it and
through the other half of the cycle a
power will flow through the LED and
we'll get some light out of it so I
tried a few different drivers I was
hoping to switch the power on and off
through the transmitter coil which is
about 80 turns of number 32 wire and
didn't have much luck with that so I
ended up sort of making a spark-gap
transmitter I know this is pretty silly
but I had a relay laying around and I
noticed that when I just engaged the
relay and sent power through the
transmit coil I would get a flash out of
the led
and I tried doing this with
semiconductors switching elements and
couldn't get it to work it really had he
was actually using the spark as the
transmitting element so it's dumping you
know broadband noise into the coil and
eventually some frequency propagated
well enough through the system to
actually light the LED up so I figured I
would just turn the relay on and off
over and over again and make myself a
little strange spark-gap kind of
transmitter here so that's what I did I
used my frequency generator and a simple
low power switching transistor just to
open and close the relay and that dumps
power through the transmit coil you know
a few times a second so I tested it out
on the bench and put the small 40 turn
receiver coil inside the transmit coil
which has a diameter of about an inch
and a quarter and it was really you know
it was reliable I could get the led to
flash pretty well so then I proceeded
with the construction of the contact
lens itself I started with a soft
contact lens this is a Seba vision toric
focus focus
toric I think air optics I don't know
they keep changing the brand on me I'm
not sure anymore but I've been wearing
contact lenses for quite a while
probably over 10 years or something and
I'm pretty familiar with putting them in
my eyes so I started with the contact
lens and put the 40 turn receiver coil
onto it and started to dry the lens out
oh I stood out I soaked these lenses in
distilled water for a while I was
following the directions that I found
online that a research group put
together for doing search coils inside
contact lenses so a search coil is a way
to do eye tracking by embedding a coil
into a contact lens and the research
group was nice enough to publish some
construction details in their paper
unfortunately it didn't quite pan out so
I soaked the lens in distilled water and
kind of laminated the receiver coil
between that lens and another lens which
I also soak them distilled water but it
didn't take it was you know that the
lenses didn't stick together well enough
so I ended up doing was heating up a
pair of tweezers and then pinching the
two lenses at the periphery to sort of
melt the plastic together and this
worked okay it actually did stitch the
two lenses together well enough
unfortunately it was even less
comfortable in my eye with this strange
kind of burned you know twisted plastic
edge on there I wouldn't say it was
extremely painful that it was definitely
not something you'd want to keep going
for a long time good to make a video but
not good to wear throughout the day but
I will add when I had the contact lens
just what might be my initial try where
I just had the two lenses cemented
together without any of this you know
how tweeze are burning if it actually
was you know reasonably comfortable I
mean the front and back services are
both smooth it was a little bulky in my
eye but it was definitely smooth and I
could blink and move my eye around and
it seemed to just fine so if any of you
have any tips about gluing contact
lenses together let me know I've tried
superglue in the past for other contact
lens projects and that really doesn't
work very well because the superglue
fogs the contact lens causes it to turn
milky and it's very difficult to get the
thing in the right place before the glue
sets so take a look here's some more
footage of the lens of the LED flashing
in my eye
and now of course I did this for your
benefit so the LED is facing outward if
I are gonna make a a real VR display
with this thing obviously the LED you
have to face inward which I also tried
off-camera and the light is unfocused so
one of the problems with building a
display in a contact lens is that there
needs to be a lens letour a small lens
between the light source and the edge of
the contacts otherwise the light just
sprays out into your eye and covers the
entire retina if you actually want to
make an image from something that's
being projected from the surface of the
eye you have to get some additional
optics in there and if you want to do an
entire two dimensional display you have
to have an optical element for
essentially every pixel so there's a lot
of
technical issues that are going to
prevent contact lens displays from
happening anytime soon but you know the
future is a long way off right okay see
you next time guys bye
s
Posts
No comments:
Post a Comment