Holography Video Lecture - Civil Engineering (CE)

so that's how you make a still hologram
but can we then apply this to
holographic movies so 3d movies are
massive right now two big blockbusters
at the moment The Hobbit
and Life of Pi except the way that 3ds
currently done called stereoscopic 3d
doesn't actually give you the full 3d
experience it gives you that sense of
depth but it doesn't give you what's
called parallax that means if you move
your head around the view doesn't
actually change with a 3d movie now
there is a way of doing this and that's
using Holograms Holograms were actually
invented in the 1940s by Dennis Gaber it
earned him the Nobel Prize in 1971 but
it wasn't actually until the 60s that
they started doing Holograms with light
previously it was with electrons and
that's because the laser hadn't been
invented yet so how does a hologram
actually work well if we go right back
to basics and think of a photograph to
start with how do you make one of those
well you have an object the subject of
your photograph and light bounces or
scatters off of it now that light's
probably from the Sun or the flash in
your camera now that scattered light is
then going to go through a lens in your
camera and then hit the CCD if you've
got a digital one or if you're
old-school a photographic plate then
encoded on that photographic plate you
have the intensity of the light that
bounced off of that object now there's
actually one property of the light that
we have missed it's called the phase and
that's actually related to the distance
the light has traveled from the object
we can't capture that in a photograph
but in a hologram you can because the
setup is slightly different if you start
off with a laser you take the laser beam
and you split it into two one of those
we're going to use as a reference beam
and the second one we're going to bounce
off our object so just like with a
photograph you have light bouncing off
an object which then hits a photographic
plate great what you need to do now
which is different from a photograph is
reflect that reference beam into that
plate what that's going to give you is
an interference pattern between the two
beams and
that is what allows you to capture the
face and there you go you've made a
hologram except if you look at it with
your naked eye it's it's not going to
look like what you expect because what
you need to take is your original laser
again or at least an identical one and
showing it into the plate that you've
made what that allows you to do is
actually reverse the whole process you
can recreate the light that originally
bounced off of the object and that's why
when you look at a hologram it looks
like it's actually there in full 3d
because you're recreating light that
previously hid it so that's how you make
a still hologram but can we then apply
this to holographic movies well it's
actually our technical limitations right
at the moment it's not as easy as you
might think but not entirely impossible
a group of scientists at MIT for
instance have been able to recreate the
famous Princess Leia scene you know help
me obi-wan Kenobi you're my only hope
except it was kind of blurry and also it
was only at 15 frames a second now if
you think about normal movies we do 24
frames a second and Peter Jackson's a
bit fancy and does 48 frames a second on
The Hobbit we're a bit of a way off to
be able to make a convincing holographic
movie but it's certainly in my opinion
the future of 3d if you'd like to see
some other really cool stuff like a
woman trying to do a home made light
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