Laser Sees Through Keyhole

Those guys at Stanford must be watching a lot of James Bond movies. Their latest invention is a laser that can image an entire room through a keyhole. We imagine that will show up in a number of spy movies real soon now. You can see the code or watch the video below.

The technique is called NLOS or non-line-of-sight imaging. Previous approaches require scanning a large area to find indirect light from hidden objects. This new approach uses a laser to find objects that are moving. The indirect data changes based on the movement and an algorithm can reverse the measurements to determine the characteristics of the object.

If you are worried about the neighborhood peeping Tom, you can probably relax. The recovered images are amazing, but not particularly high-quality. Still, considering they were made indirectly, they are great, but you are not going to make out fine details.

As you might expect, the work is computationally intensive. The GitHub repository has Python code as well as data you can use if you don’t want to build your own laser setup. You can use CUDA to speed up the computations if you have a GPU with enough memory.

NLOS imaging isn’t exactly new, but there are still new ways to do it waiting to be found. We love novel uses of lasers. We’ve seen laser logic gates. We still want to try the laser oven.

23 thoughts on “Laser Sees Through Keyhole

  1. Cool!
    That should bring in the government funding!
    So… is the beam continous? That would make it difficult to read the reflection, I imagine the 3rd reflection is many orders of magnitude less than the transmitted beam. But if it was quickly pulsed, Time of Flight measurements would be useful in determining the reflections.

  2. Interesting I guess, but where are these locks that you can see through? My front door has a keyhole on the outside and the deadbolt knob on the inside.

    Anyway, if you find such a lock, easily defeated with a piece of duct tape. Or better yet a mirror.

    1. Yeah… I was wondering why they were saying “keyhole” as if we still used skeleton key locks. I’d imagine it would be used with a hole bored in a wall or ceiling, not an existing peephole.

    2. Lived in Italy for five years, most people had skeleton key locks there, the opening was large enough that you would feel a considerable draft coming from it. As Americans living over there we all thought having a skeleton key for our entry lock was cool and stupid at the same time.

      1. “Skeleton Keys” refer typically to warded locks, where there is no specific locking mechanism, but simply a cam that must be turned. The shape of the key-way (ward) prevents other keys from being used.
        A “Skeleton Key” would be a cut down version of a key that attempts to bypass the wards.

        Warded locks still exist today, but they are typically low security (think: cheap padlocks) – and are not found on houses.

        The Italian style “Skeleton Keys” you’re describing that are popular in Italy (Brands such as Cisa, etc) are lever locks: When the key is inserted, the differing heights on the key interact with levers. The levers must be simultaneously lifted to the correct height for the cam bar to engage and open the lock.

        Lever locks are quite difficult to pick / manipulate – which is why most large safes use lever locks.
        The reason that these locks are less used in the rest of Europe / rest of the world is because they don’t fit into a standard Euro cylinder profile, so ‘standard’ door hardware isn’t adapted to them.

        Definitely a cool lock to have on the door, and definitely not stupid. In comparison to standard US Schlage / Yale 5 pin tumbler locks – Italian lever locks are vastly more secure.

      1. Some home insurance companies require both before they’ll cover you. Good pin-tumbler (Yale) locks are pretty secure and hard to pick but the cheap ones can be bump picked in about half a second, very little torque is required to rotate the tumbler. Even cheap mortice locks take a bit of effort and knowledge to pick and good ones are pretty secure (assuming you don’t leave the key in the lock on the inside!).

    3. You know drills exist, right?

      The excellent book on CIA spycraft & gadgets mentions they even developed a silent drill that uses air circulating abrasive to silently drill pinholes through walls or ceilings to place microphones, so it’s easy to imagine a very similar scenario here for the nefarious operator.

      I can imagine a lot of “civilan” uses for this too though.

  3. I remember a similar article from several years back, possibly also featured here on HaD, in which they were imaging around corners. I’m guessing the technology might have moved on a bit since then.

    1. yeah, I remember some demonstration here (HaD) which detected what was on the other side of a bus at a bus stop, IIRC, it compared the scene before and during the bus arrival?

    1. Or pretty much anything that might cause rays to scatter or be absorbed in a way other than what they’re expecting. Even an opaque cup glued to the wall would bring everything to a halt. Personally, I just don’t use locks with keyholes that allow people to look into a room. The video didn’t actually use a keyhole as it was in the middle of the door and looked more like a peephole. You could also just use one of those peepholes that has the metal cover that falls into place when you’re not actively looking through it. These types of demos are interesting for sure, but almost always based on doing pointless things. If you can see through the peephole, and the subject is moving, why not just wait for them to move into view? Yes, you can probably think of ways my idea wouldn’t work, and I could think of new ways it would. My point is, the same result can be had much simpler.

      1. Oh yeah… and if it’s not IR light, people will notice that bright laser spot on the wall. If you’re lucky they cover the hole. If you’re not, they shoot a bunch of bullets at you through the door.

      2. Even better, stick a little small-scale “room” in a little box on the wall where the spot comes in, and they will be imaging what you want them to image. Perhaps a little blackboard in the corner with “CIA/Mossad/MI6 are idiots” written on it?

    2. I agree, but there is nothing preventing the lessons learned from being applied at a lower resolution using a Maser (microwave amplification by stimulated emission of radiation) or a ?Taser?/?Tlaser? (terahertz light amplification by stimulated emission of radiation) which would not need a keyhole.

  4. I wonder if this can be replicated with ultrasonic waves to some extend. Creating a 3D sonar image. You could take advantage of the Doppler effect with ultrasonic waves and potentially measure speed.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.