DIY TSA Backscatter Body Scanner

[Ben Krasnow] built his own version of the TSA’s body scanner. The device works by firing a beam of x-rays at at target. Some of the beam will go through the target, some will be absorbed by the target, and some will reflect back. These reflected x-rays are called ‘backscatter‘, and they are captured to create an image.

In [Ben]‘s setup a rotating disk focuses x-rays into beams that travel in arcs across the X-axis. The disk is moved along the Y-axis to fill in the scan. On the disk assembly, there is a potentometer to measure the y-axis position of the beam, and an optical sensor to trigger an oscilloscope, aligning the left and right sides of the image. Using these two sensors, the scope can reconstruct an X-Y plot of the scan.

To detect the x-rays, a phosphorous screen turns the backscattered x-rays into visible light, and a photo-multiplier amplifies the light source. A simple amplifier circuit connects the photo-multiplier to a scope, controlling the brightness at each point.

The result is very similar to the TSA version, and [Ben] managed to learn a lot about the system from a patent. This isn’t the first body scanner we’ve seen though: [Jeri Ellsworth] built a microwave version a couple years ago.

The impressive build does a great job of teaching the fundamentals of backscatter imaging. [Ben] will be talking about the project at EHSM, which you should check out if you’re in Berlin from December 28th to the 30th. After the break, watch [Ben]‘s machine scan a turkey in a Christmas sweater.

Comments

  1. Peter says:

    Hacking is fine, hacking with X-rays strikes me as a bit over the edge…in the sense that if you don’t know what you’re doing, you could end up hurting people other than yourself.

    X-rays and radioactive stuff are further than I care to go at home.

    • Wizzard says:

      As a guy with both radioactive substances and dangerous UV experiments running at home… Safety is all relative.

      • vpoko says:

        I’m not sure what “safety is all relative” means. If you mean, some things are relatively less safe than others, then I agree, but from the context you seem to be minimizing safety concerns. Someone playing with microcontrollers and electronics at 5V would need a freak event of biblical proportions to be harmed. Not so with x-rays, radioactivity, dangerous chemicals, lasers, or various other things. I’m not saying people shouldn’t hack with them, but I would hope those people have had some training and aren’t learning as they go.

    • asgposjdg says:

      No! Go go go, as far as you can.

  2. john says:

    Don’t play with X-rays.

  3. Chris C. says:

    Very impressive! Given:

    1) The size of the phosphorescent screen, of which the entire area acts as a detector at all times
    2) The use of a photomultiplier
    3) The scanned and focused x-ray source

    The actual x-ray exposure *might* be very low, just like the real thing. And I don’t expect [Ben] will point it at himself too often. So I’m not going to jump on the safety bandwagon this time.

  4. IthinkIunderstand says:

    I’ve watched all of Ben’s videos. The guy builds things that are so over my head I don’t know where to start. I’m not sure what I like more, the fact he built a body scanner in his garage, or that he dressed a turkey in a sweater to test it. Classic…

  5. Ptolom says:

    God damn that was fast. It seems like only two or three weeks since he put up the video about getting the x-ray tube driver working.

  6. CoolMod says:

    My mom forbid me to play with X-rays…

  7. Steve says:

    Hey, this is _exactly_ how the Mechanical TV transmitter works at the Early Television Museum:

    http://www.earlytelevision.org/mechanical.html

    I didn’t find a description of the TV camera, but they projected a scanning light in a dark room, and had one huge “back scatter” detector. I guess one big difference is, most light back scattered or absorbed, not much light went through…

  8. Robot says:

    What a bunch of safety dorks. Be informed and cautious, not fearful.

    This is a remarkable hack! I am most impressed. It would be interested to see this paired with some sort of computer vision.

    • ka1axy says:

      Remember three things:
      – Marie Curie died of cancer(?) due to radiation poisoning
      – Radioactive Boy Scout
      – It’s not what you know, it’s what you don’t know that will get you (and others) hurt or killed

      Have fun and be safe.

      • John says:

        I think I’m one of the ‘Safety Freaks’ that people are complaining about.
        But please keep in mind that X-ray radiation driven by a vacuum tube is a lot different than having radioactive dust all over your house.

        And this is Ben we are talking about. I am sure that the man will die in a fireball, but given that he’s still alive he must know what he’s doing.

      • Robot says:

        That maxim “It’s what you don’t know. . . ” is like trying to prove a negative.

  9. I forgot to mention that you shouldn’t try this unless you know what your doing in the post, and a few people brought it up, so I’ll say it now: don’t try this unless you know what you’re doing. Be safe!

  10. echodelta says:

    After watching the video,the scan is quite clear. It’s a terrorist turkey with an Allen wrench! Nice drumsticks!
    The target object hidden under the garment should have been a carving tool or scissors something more recognizable, maybe a toy gun.

  11. wretch says:

    What happened to the turkey after being bombarded with X-Ray? Did it come alive and become Hulkey?

  12. Tyler says:

    So, as someone who has a hobby with X rays, it would be wise of this fellow to have any instrumentation whatsoever that would give him an idea of whether or not he was getting cooked…like an ionization meter (Victoreen 470A, etc.)…

  13. jpnorair says:

    Sorry to be pedantic, but don’t the airport scanners use mm wave? X-ray wavelength is on the nm scale.

  14. jpnorair says:

    What I forgot to mention in my last post is how great I find this project. This is hack-a-day, not nanny-a-day. Haters, stop being jealous — this project should be in the list for hack-of-the-year.

  15. Murray says:

    Good build.
    Yes X ray safety is an issue, instead of scaring the young ones, lets spell out the dangers. Every single X ray photon is a form of ionizing radiation. If it hits the right spot on your DNA it can alter it, and cause cancer. You can not reduce the energy of the photons, only the amount of them. Most X-rays pass right through you, some don’t and the chances of a single photon hitting just the right spot is very small indead. That being said, there is NO SAFE LIMIT. It is purely a statistical game, twice the exposure = twice the risk of cancer.
    On medical X ray danger see

    http://www.newscientist.com/article/dn4621-medical-xrays-cause-thousands-of-cancers.html

  16. Reader says:

    I remember long ago seeing an ancient book of “electronics projects for boys.” The last project featured homemade x-rays with a bare x-ray tube, powered by an induction coil described as an earlier project in the book. Just clamp the tube in a test-tube holder, stick your hand between the tube and a piece of film and off you go. Pretty scary.

  17. A voice of reason says:

    And I’ll add that instead of complaining, the safety monitors should be educating. That’s what Tyler did, and I learned something helpful, and maybe even applicable.

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