- This is a polo mint, the British equivalent
of a Life Saver under a microscope,
except it's a really weird microscope.
Honestly, I'm not sure
that you could even call it a microscope.
I just don't know how to characterize this thing.
Look, here's a Lego brick,
and what about this thing?
What is this?
I'll tell you at the end
of the video if you want to have a guess in the meantime.
What's weird about these images is
that there's no color information
or transparency information.
What we're seeing is just the shape.
In that way it's kind of reminiscent
of what you see under an electron microscope,
but actually this is a normal sized Lego brick
and this microscope uses touch
and I got to play with one thanks
to the Sempre Group who said I could come round
and have a play.
They're are distributor of precision measurement instruments
in the UK, link to what they do in the description.
They're not paying me to make this video
neither is the manufacturer of the device.
I just saw it out the corner of my eye when I was walking
around the advanced engineering expo
and I went up to them and said, can I make a YouTube video?
So thank you for saying yes.
It's a handheld device.
It's called Gel Site because
at the end there's this gel pad.
The gel is especially formulated so
that when you push an object into it
the gel deforms so that it can get
into all the tiny nooks and crannies of the object.
Just behind the gel, there's a camera pointing at it
and crucially, there is a ring of six lights.
What you see in the preview image
on the screen is just what the camera sees when
only one of those lights is switched on.
And you can see how the image changes as we cycle
through the six lights.
By illuminating the deformed gel in this way,
the human visual system can discern the shape
of the object using cues about light and shade
and shadows and highlights.
It's a bit like whitewashing the object because by doing so
you are removing all information
about color and transparency.
And you might think, well
what's the point of a microscope that removes information?
Why don't we just stick with a light-based microscope
and then we don't lose any information?
Well, it turns out that with some clever mathematics
we can actually gain information that we would never
have had access to with a regular microscope.
And it's all to do
with those six lights arranged around the gel pad,
like in the preview image where only one light is turned on.
The human eye can discern things like, well
this area is higher up than this area.
This area slopes down to the left.
This area slopes down to the right and so on.
But could a computer brain do the same thing?
Well, it turns out that
if you present the computer brain with six images,
one taken with each of the six different light sources
you can use a clever algorithm to analyze those six images
and come up with a 3D model
of that object accurate to plus or minus four microns
in the case of this device
which is way better than the human brain can do.
It's called the photometric stereo technique
and there are publicly available papers on the subject
and then there's some proprietary stuff on top
in the case of this device, and you can see why
it would be desirable to remove information
about color and transparency from the object
before trying to run the algorithm on the six images.
By removing all color information
we can say with certainty that this region
of the image is bright because it's facing the light source.
This region of the image is dark because it's facing away
from the light source, but real life objects have light
and dark regions unrelated to the lighting of the thing.
In principle, the algorithm should be able to cope
with objects that have light and dark regions
because after all, it's only looking
at the differences that it perceives
from the six different images at each point on the object
unless part of the object is jet black
in which case it's jet black regardless
of what direction it's lit from.
But perhaps the most challenging thing
for the algorithm is transparency, reflection, and glare
and the gel pad removes all of those things.
I think there's an interesting distinction here
between human brains and computer brains.
Like human brains can discern 3D information
from flat images of things, even when color, glare,
and transparency haven't been removed from the object.
That's because the human brain can draw on experience.
Like your brain recognizes this flat image
of a Lego minifigure head as a Lego minifigure head,
your brain doesn't think, oh this region is dark
because it's facing away from the light source.
You know that it's the eyeball.
Perhaps one day with the addition of machine learning
an algorithm like the one used
by Gel Site could discern 3D information
from objects that haven't had color glare
transparency and reflection removed
by training the neural network on everyday objects
in the same way that our brains have been trained
through our lives to recognize objects.
There's an interesting side note here
about the way human brains perceive depth.
Like the human brain perceives depth
in lots of different ways.
For example, by having two eyeballs, the slight difference
in the two images that each eyeball gets can be
used to extract information about depth.
Another example is parallax.
There's loads of different ways we perceive depth
but one way that's relevant
to this video is using light cues.
We don't need to take six different images
of an object with a light source in six different locations.
We can do it with just a single light source.
But to do that, your brain has to make an assumption
and every time your brain makes an assumption
it can be tricked.
It can be tricked with an optical illusion.
Take this image, for example.
It looks like a mountain of some kind
but if I turn it 180 degrees, you can now see it's a crater.
It's called the crater illusion.
Your brain is tricked in this orientation
because it assumes the scene is lit
from the top down, and that's a sensible assumption
given our every day experience.
Light typically comes from above us.
And the cool thing is you can see the crater illusion
with these images.
Like here, the lettering looks like it's sticking out
but that's only because it's being lit from below.
By switching to the light at the top
you can see that the lettering is in fact indented.
And of course, the crater illusion disappears.
Where there are other depth clues available
like no one would see this face as concave
even though it's lit from below, because our experience
of faces gives us overriding information about depth.
So what's this device actually used for?
Well, using the software that comes with it
you can take actual measurements.
So you can see that the lettering
on this coin is raised by 70 microns
and this is really what the device is all about.
It's handheld.
You can take it around with you
press it into things, and as a manufacturer, let's say
you can figure out the tolerances
of the things you are making in your factory.
You can also characterize a surface and say how rough it is.
Another scenario is an aircraft has a scratch
on the surface
and you need to characterize the scratch to figure
out whether the aircraft can still fly.
Traditionally, you would create a cast
of the scratch and then measure the cast in a lab, but
with this handheld device, you can do it in a few minutes.
I asked them about drape because presumably there are parts
of the object that the gel won't be able to get into.
So how does that affect the use of the device?
- So we need the depth to not be wider than the mark.
- Oh, okay.
- Say that was one millimeter here and that was two.
What we would have is the effect is we probably
get that deep.
We wouldn't get the corner.
But normally what the operator's looking
for is that value as opposed to the the value of this area.
- So in terms of the application
- That's the important bit.
- Yeah, like the important bit
for me is, ooh, that looks pretty.
- That looks cool.
- Yeah yeah.
Here's some other cool things that we put
under the microscope.
This is some woven fabric under the microscope.
This is a UK driver's license
and you can see there's a slight emboss here
which you can't see with the naked eye.
This is a button battery, and what I like
about this shot is that there's a bit of hair
and dust stuck to the gel, so you can see how the gel moves
and warps around the object as you press into it.
Here's a phone speaker under a microscope, and you can see
that the screen protector isn't quite lined up.
Here's a chip and pin from a credit card.
This is interesting.
It's a part that I had 3D printed
and you can see how the printhead must have moved
as it was printing the thing.
It goes around the edge
and then it fills in in this kind of zigzag motion.
How cool is that?
Can you guess what this one is?
It's my stubble.
Sorry about that.
This is a love heart,
and this is the take home message of the video by the way,
just be you.
The gel pads get sticky over time and need to
be replaced periodically, but when it's a little bit sticky
the visuals are really interesting.
I really think this needs a sound effect.
You know what I mean?
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I hope you enjoyed this video.
If you did, don't forget to hit subscribe.
Oh, and that thing from the beginning
it's the inside of a quartz analog watch.
(upbeat music)