Kind: captions
Language: en
it was here at MIT in the early 1960s
that Professor Harold ederson pushed the
boundaries of high-speed photography he
was my uncle Harold when I was a kid he
used to show me the coolest pictures
like this famous example a 2,000 mph
bullet rendered seemingly
motionless well 60 years later a team of
scientists here at MIT have outdone my
uncle Harold
this is actually inspiration for our own
work the only difference is that ederon
used a bullet made of copper and Lead
whereas we use bullets of light they've
created a camera so fast it slows to a
crawl the fastest moving thing in the
universe light the camera has a
resolution of a trillionth of a frame
per second and so we can actually
observe light as it goes through this
scene a trillion frames per second mhm
at that speed a flash of light on a
still life is transformed into a journey
we'll see light coming coming in By Its
Reflection off the floor oh wow as the
light wave propagates it'll hit the
surface of the fruit and will see that
light
up and then only after delay will you
see the light hit the wall behind it and
only after another delay will you
actually see the shadow behind it wait
so the shadow doesn't appear
instantaneously that's right because the
wall is farther away it takes light
longer time to reach it that's
crazy so let me show you another example
it may seem unremarkable at first a soda
bottle filled with water but then a
flash so you see the pulse of light
entering from the left this pulse is
actually a packet of photons particles
of light and we can see its energy front
sweeping across the bottle from left to
right and eventually the pulse will hit
the cap and emit a bright flash just
think how fast it was traveling about
600 million mph and how long did that
event take in real life took a billionth
of a second for light to go from one end
to the other so an event that took a
nanc it has been stretched to about 20
seconds 20 seconds so that's that's a
lot of stretching this is super slow
motion put another way if you were to
film that iconic apple with this camera
and made a movie of the bullet entering
the picture going through the apple and
out the other side it would take about a
year to watch this entire movie this
would take a year to watch that's right
yes oh I recognize this setup so how
exactly does this super fast camera slow
things down we shine laser light uh
inside the bottle you can actually see
the beam it looks like a continuous ray
of light but it's not the laser light
emits a train of pulses very fast the
object is to capture just one of these
pulses as it enters the bottle to get
this image they actually have to take
500 separate pictures each just
photographing a narrow slice of the
scene the camera looks at the scene
through this mirror system which rotates
and as the uh mirror moves record a
different slice of the bottle out of
time so in order to get a complete
picture you'd need 500 slices of it
exactly but how do you capture a single
burst of light if you have to film it
500 times what we do is we don't shine
just one laser pulse we rely on the fact
that the laser is shooting out pulses
periodically in time over and over again
for each laser pulse the camera records
one line of the scene at a time and and
the fact that each pulse looks the same
as the last that's why the finished
movie looks like it's just one pulse yes
we stitch it all together taking it a
step further so for example if when you
combine the camera this fast with
information processing by this wall it
opens up some interesting possibilities
this camera over here can somehow see
around the corner precisely how does
that work well what we do is we take our
laser beam and we shine it onto another
wall that light boun off the wall and
scatters in all different directions
some of that light hits the mannequin
because the camera camera is so fast it
can record the difference in time it
takes for this path or this path each of
the billions of Paths of bounced light
that reach it so based on the fact that
we know how fast light travels we can
build computer software to actually
place all the light back where it came
from on the object digitally
reconstructing it after the
Reconstruction it actually looks like an
image of our
object like
this and with more processing a 3D image
it's similar to sonar where an image is
reconstructed from reflected sound waves
it's similar but in sonar the object or
the ground floor that you want to look
at still has to be in the direct line of
view of the camera in this case you no
longer have that restriction so it has
potential use for fire and rescue and
for automobiles to detect approaching
vehicles around corners or in medicine
to visualize the inside of a person's
body I think Uncle Harold would be proud