ever since setting up this electron
microscope in my shop I've wanted to
make animations with it showing video
taken through the microscope and I've
also been thinking about different
recording media lately so I put the two
together this weekend and came up with
this this is an animation that shows a
phonograph needle riding in an LP groove
so in this video I'm going to talk about
how I made this and some other recording
technologies the first step is to head
down to the local music store and pick
out a few LPS from the dollar bin and of
course the electron microscope chamber
is so small I can't fit the whole record
in there so I cut off a small section
the next problem is that the electron
microscope cannot image things that are
electrical insulators and the reason is
that the microscope works by firing
electrons at the object that you want to
inspect and if the object is an
insulator those electrons get trapped
inside the object because it's an
insulator and eventually if enough
electrons get trapped their future
electrons coming in will be repelled
because like charges repel each other so
the way to solve this problem is to coat
the object in something conductive in
this case I mounted the pieces of record
to a glass microscope slide and then
loaded the slide into a vacuum chamber
and evaporated some silver metal onto
the pieces of LP normally this is done
with a machine called a sputter coder
but my sputter coder needs some work so
I'm using physical vapor deposition so
this is enough to image the record by
itself and I needed to prepare a stylus
so that we could see the dynamics I
really wanted to see the animation of
the needle flowing in the LP groove so I
also got a cheap stylus and cartridge
from the same music store of course from
the used needles bin and most of it is
plastic and even worse there's a couple
magnets inside there so the way this
works is that the stylus vibrates
because of the grooves in the LP and it
moves the magnets near a coil and that's
what generates the electricity that gets
amplified into the audio signal also
unfortunately if we put this directly in
the electron microscope those magnets
would deflect the electron path and
distort the image so I pulled the
magnets off of the stylus next I needed
to make us
sort of primitive tonearm that I could
put inside the electron microscope
chamber so that there would be some
amount of tracking allowed like a little
bit of compliance so that I could push
the needle into the record without it
you know destroying the record but still
have it follow the groove so I just used
a piece of copper wire and melted it
into the side of the stylus and then cut
away all the excess plastic so this is
what I was left with I also noticed that
there's sort of a rubber suspension on
here so that the actual stylus arm is
electrically isolated from everything
else on the stylus like the plastic and
everything so I added a tiny copper wire
and then use conductive carbon glue to
make sure that the stylus arm itself was
grounded or at least electrically
connected to everything else
this particular electron microscope has
two separate stages inside with their
own motion controls so this allowed me
to put the needle with its you know sort
of makeshift tone arm onto one stage and
then put the piece of LP that's been
coated with silver onto another stage
and then I could move both of them
independently so that I could arrange it
to make an aesthetically pleasing image
after getting everything aligned it
turned on you can see the video image
that the electron microscope creates so
it is possible to get real-time imagery
this is running even at close to 60
fields per second but the resolution in
this mode is quite poor and so is the
contrast the signal is very low in order
to make a decent image the scanning
electron microscope requires about 10
seconds per frame to scan it out so what
I did was use the micrometers the
controls on the emotion controls on the
stage to move the record by a very very
tiny amount about 50 microns and then
take a still frame and I'm using my
Tektronix MDO oscilloscope to store the
data so the procedure you know I kind of
got in the rhythm of doing it so it's
moved 50 microns take a frame save it to
the USB stick moved by 50 microns take a
frame you know saved at the stick and so
I eventually ended up with 60 frames
each spaced about 50 microns apart I
used a couple felt tip marks on the CRT
on the scanning electron microscope to
for as reference points so since the
position of the LP is not perfectly 90
degrees to the scope or perfectly 90
degrees to the movement axes I was
actually moving in two axes and then
using those marks on the screen to sort
of maintain a the rough the rough
position of that needle would stay about
the same I processed the data from the
oscilloscope in octave which is a an
open source MATLAB alternative and then
took the images from that and processed
them in Photoshop using batch processing
and then used Photoshop to create the
animated gif the playback speed of that
animated gif is about one four hundredth
actual speed if the record we're playing
as you can see the stylus doesn't move
up and down or side to side in the
record groove since this is a stereo
record it actually has two channels of
audio information encoded in one groove
so diagonal movements sort of bottom
left to top right is one channel and
bottom right to top left is the other
channel so depending how the magnets
move based on the vibrations picked up
by that needle tip you can get different
signals sent to each channel so then I
thought well this is cool maybe there's
some other interesting recording formats
I can take a look at and yeah just in
the last week or two my friends at evil
mad scientist laboratories reminded me
or showed me this for the first time
this is a capacitance electronic disk a
very unusual video format that was
developed by RCA that was sort of a
commercial failure so they're kind of
hard to find the disc comes in this
plastic caddy and you put this whole
caddy in the machine and the machine
would open it up and pull out this
basically video phonograph it's it's an
analog device it's basically it has a
track just like audio LPS do it's just
that the information density is so much
higher the track spacing is really tight
so you can actually see the light
diffraction patterns in this device so
here it is under the sound and I've put
it next to the phonograph needle tip
just for comparison as you can see the
track densities incredibly tighter and
the method of storage is not quite the
same whereas on an audio record the
needle is actually vibrated by physical
cuts in the track on this capacitance
electronic disk it's actually the depth
of the track that makes the signal and
the needle doesn't really move
and down so much as the capacitance
between the needle and the disk changes
interestingly this this capacitive
electronic disk is somewhat conductive
and the capacitance between it and the
needle is measured and as it spins
around the track thickness varies or the
trench depth almost the varies so as it
spins you get this signal correlated
with the capacitance change as it goes
around it sounds incredibly difficult to
do technically and indeed it took RCA
from the late 60s all the way to the
early 80s to get this out and by that
time VHS beta and even laserdisc had
pretty much you know toasted it so this
format was dead on arrival and RCA lost
apparently hundreds of millions of
dollars I also wanted to take a look at
a cd-rom and these are read with a laser
of course that we can't just put this in
the electron microscope either even
though the the metal is aluminum it's
behind plastic so on this side it's just
polycarbonate on the surface and on this
side it's this protective lacquer label
so if we put this into the SEM either
side up all we'd see is a smooth surface
if anything because there's actually no
bumps on the surface that's that's good
because it protects the media so I spent
a long time trying to figure out how to
expose the aluminum part at first I cut
off a small bit and put this into
methylene chloride and that dissolves
the polycarbonate base really well and
you're left with this very thin almost
falling apart piece of aluminum that has
the the pattern printed into it but I
had problems with a trace amount of
plastic being left on the surface and it
was just so curled up it didn't work
anyway I tried a bunch of other things
and then I found out the thing that
works best is just double stick tape
just get some really strong double stick
tape and stick it down to the top of the
disc and pull it off and now we have a
really fresh sample of aluminum here and
so if you come in with a multimeter this
is actually quite conducted this is bare
aluminum exposed so here's what the
cd-rom looks like and of course this is
a digital format so instead of having a
track vary in width or depth the track
is predefined and then there's pits and
lands carved into it
of course the width of this is even
smaller than the redic
this capacitive electronic disk we're
down to about a 500 nanometer wide pit
and I think the track spacing is about
1.6 micron of course I also wanted to
take a look at a DVD and so unlike a
cd-rom that has the aluminum layer and a
protective lacquer on one side the DVD
is built sort of like a sandwich where
it's got a polycarbonate discs on the
top and the bottom and the aluminum
information layer is in the middle so to
get at the aluminum we just separate the
two parts and then that exposes the raw
aluminum surface the tracks facing on
this DVD is only about 700 something
nanometers and this is getting near the
limit of the resolution that I can pull
out of my scanning electron microscope
in its current condition at least okay
see you next time bye