For Kids

Every day, kids are killed or injured by landmines.  Landmines are little bombs hidden in the ground during war and left there.  They can lie there for years, ready to be stepped on.  Exactly how many people are in danger is hard to say, but they are all over the world.  And, it’s not just people - many animals are also victims of mines.  Even worse, most of the casualties are innocent farmers.  Many are also children who might find a landmine and play with it until KABOOM!

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For The Very Young

PMN-2 landmine

There are millions of landmines, of many types, buried all over the world; South America, Europe, the Middle East, Asia...  In 1997, most countries agreed to never make or use landmines again, but some countries did not agree and sadly, landmines are still made and used in some places.

Please click to see the original from Landmine Monitor

Click on the map to see the countries that have a landmine problem

Landmines are cheap to make – about 3 US dollars each.  But once they are in the ground, it may cost up to 1000 dollars to get just one back out again.  It is expensive because de-miners have to look for them very slowly and carefully, and a lot of what they find is just pieces of trash.  So, time and money that could be spent destroying dangerous landmines are used to dig up soda cans, tin foil, and CD’s.

The current best methods for finding buried mines are metal detectors and probing spikes.  But metal detectors can’t find plastic mines, and careful poking with a spike can’t tell the difference between a mine and a piece of trash.

Wouldn’t it be nice if there were a way to “see” into the ground to spot what’s a landmine and what’s not?

That’s where holographic radar comes in.  It makes holograms of hidden objects that we can’t see with just our eyes.  A hologram is a special kind of picture, a little bit like a photograph.  Photographs record patterns of visible light on photographic film or a digital memory stick.  Our eyes recognize these light patterns as books, elephants, waterfalls, and such.  However, a photo is only 2-dimensional or flat, while a hologram tricks our brain into thinking that it sees a 3-dimensional object.  It does this by capturing an interference pattern

Photo by Mila Zinkova

This is an interference pattern made by ripples on a pond running into each other.

Imagine you are standing on a bridge over a pond.  When you drop a pebble into the water, it forms waves that spread in a circle.  Now imagine that you drop two pebbles into the pond.  Both will make waves that will spread and meet.  Where they meet, you might say they interfere with each other.  The pattern of waves that is made when the two waves meet is called an interference pattern.

This doesn’t only happen in water – light is a wave too.  When light waves bounce off the objects all around you, the waves mix to create interference patterns in your eye that your brain recognizes as everything in our world.  These interference patterns are special because they don’t just record color and outline like a photograph – when you record an interference pattern on a clear photographic plate, you can shine light back through the pattern, and it will get bent and mixed to make a phantom 3-dimensional image of the original object - a hologram!

Holographic radar makes interference patterns too – but instead of visible light, it uses radar or microwaves.  These are the same microwaves you make popcorn with.  Microwaves are really just a different type of light, but it is light that we humans cannot see.  You don’t see the microwaves when you’re making popcorn do you?  But, light and microwaves are the same stuff - electromagnetic waves.  They are just waves that vibrate more slowly than light.

Diagram by NASA

The special thing about microwaves is that they go right through many things that we can’t “see through” with our eyes.  So, holograms made with microwaves can show things hidden in walls or buried in the ground.  In a way, a microwave hologram is kind of like Superman’s X-Ray vision!  We can shine microwaves into the ground, and record the interference pattern from buried objects that reflect the waves.

With light, we could then shine light through the interference pattern and make a phantom 3-D image of the object.  But, here’s where we run into a problem.  Human eyes can’t see microwaves.  So, even if we did shine microwaves through the radar interference pattern to make the 3-D phantom, it would be completely invisible to us humans.  So, our holographic radar has to “translate” or shift the interference pattern from one portion of the electromagnetic spectrum to another – into the portion that we can see.  To do that, it does “color by numbers” – assigning a color (usually a shade of gray) to each different value in the interference pattern, and “voila!”, now we can see the interference pattern!

However, we still can’t shine light through the interference pattern to see the 3-D phantom (because we did not use light in the first place).  But because of the way that microwaves behave in the ground - some are “lost” or converted to heat (just like in the popcorn) - the interference pattern itself looks a lot like the buried object, even without reconstructing the phantom image.  You can see for yourself in these pictures.

  Here are photos of some objects before they are hidden:




 And here are holograms taken right through the dirt or walls that hid them:




So, holographic radar pictures are clear enough to show the locations of objects and their shapes - even to people who are not radar experts!  We hope that this can be used to detect buried landmines and tell the dangerous landmines from harmless pieces of trash.  This could save time and money - and most importantly kids’ limbs and lives.

Photo from Landmine Monitor

Looking for Landmines with Holographic Radar

Try it yourself on our Virtual Demining page

Have you ever seen a Real Minefield?

Please visit our Gallery of Radar Holograms

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