Structured Light Scanners, or ‘SLS’ are something you may have seen ghost hunters use when looking for the ‘physical embodiment of spirits’. While they command a high price on the internet, the chances are, you can pick up the important pieces from eBay or a local charity shop for not much outlay. You just need to know what to look for, and how to hook up them up with the right software. You’ll be surprised just how easy this is. Firstly, what do we mean by ‘structured light’?
By using tiny dots of infra-red (IR) light laid out in a specific pattern, an IR-sensitive camera can measure the distortion to the pattern, and perceive the aspects of an environment in three dimensions. What does this look like? If you look at the image below, you can see that my face and room are covered in the pattern of dots, when seen through a simple IR camera.1
However, merely seeing the pattern of dots isn’t where the power lies. By using an appropriate algorithm, software can map the 3D environment and recognise the likely physical shape of a human. By measuring the distorted pattern of dots, it can estimate where the gross morphology of the body is. In other words, the software can map a crude stick figure onto where it thinks a person is standing. It can even successfully map two people within a scene. Sounds clever, but why would someone go to great lengths to do this?
It started with entertainment company, Nintendo. Their Wii console swept the market from 2006 with its innovative human-computer interface, making gaming accessible to an audience that didn’t want to sit still and use a traditional handheld controller. Your physical movements of the Wii remote (or ‘Wiimote’) were the principal means of controlling your game avatar. Rather than ignoring this hugely popular market, in 2010 Microsoft launched their new innovation in response to the Wii: the Kinect camera system for its Xbox 360 console.
Reception and market share of the Kinect was moderate, including awards, but never gained the traction that Nintendo achieved. incidentally, neither of Sony’s 2003 ‘EyeToy’ nor 2010 ‘Move’ systems made any significant impact in the arena of this type of gaming, and were considered disappointing. To boost the uptake of its innovation, Microsoft openly released the software development kits (SDK) for people using its Windows operating system, encouraging creation of new uses for the Kinect system. You could code your own software, suited to your purposes. To demonstrate possible uses, the SDK features presets, meaning you can plug in your 360 Kinect, and the software algorithms will recognise a person in view of the camera, depicting them as stick figures, just as happens behind the software you played on your Xbox.
However, the first version of the Kinect equipment, designed for the Xbox 360 isn’t perfect; certainly not as good as the second iteration, the ‘Kinect v2’, which has more checks and balances in assessing the environment it is looking at. Given either dim light, reflections, or glimpses of daylight, the sensor may see an element of a body where one does not exist. The algorithm makes assumptions and looks for where the other limbs may be. You can probably see where this is going, from a ghost hunter’s perspective.
An example can be seen above. A wet, grassy floor, in the darkness, and the Kinect thinks it can see a human form lying on the ground, where there is no physical form. Is it a ghost? No, it’s the result of a poor environmental conditions, well outside the limits of the intended use. The software is merely guessing, desperately searching for what it expects: a human form.
Incidentally, the above set up is my machine. The unaltered Kinect is mounted on top of a small rig frame, and powered by the battery described below and kept in my backpack, which also houses the laptop the software runs on. The small screen also mounted on the small rig is merely fed by the HDMI output of the laptop. Sure, it would be more compact to use a Windows tablet, but this is kit I’ve assembled myself for not much cash, rather than the £400 being asked by SpiritShack, linked in the first paragraph.
Anyway, this intriguing error of judgement lead to the Kinect being adopted by ghost hunters, and popularised when it became a principal cinematic feature of the 2012 film, ‘Paranormal Activity 4‘. In that film, the Kinect SLS dominated scenes filmed with IR cameras, providing an atmospheric combination of darkness and dots, heightening the ‘otherworldliness’ of the subject; A clever and innovative cinematic technique for a frankly terrible movie. This, being a movie that would appeal to the paranormal investigators, ensured that there was a focus on the Kinect used solely for the purposes of ghost hunting. By 2014, Bill Chappell was selling them on his Digital Dowsing website for $1250, complete with a tablet and compact 3D-printed case that rehoused the essentials of the Kinect. It subsequently appeared on the show he provided tech innovation for, Ghost Adventures, and the rest is history.
But no amount of argument is going to prevent ghost hunters from perceiving this erroneous, algorithmic phenomena as anything other than compelling evidence of the paranormal. If you want an in-depth look at more specific investigations behind how the Kinect works, and how it is fooled, check out the report by Ken Biddle in the Skeptical Inquirer. I’m certainly not going to argue. Instead, I’m happy to tell you how to make your own setup. Refer to the previous posts if you want to see why.
The Shopping List
You don’t need an Xbox 360, just a version 1 Kinect sensor. It’s the one that has rounded edges on the front, rather than the second version, which looks more square. Search eBay for them and don’t pay a lot. I’ve even seen them on sale for £6 at CEX, complete with a power supply.
Yes, you need the power supply for it, as you won’t be plugging it into an Xbox. You can go with the usual mains plug which has two leads attached. One is the USB, which will plug into your laptop, and the other is the specialist lead for the Kinect. Before you click ‘buy now’, read the next paragraph.
If you want to go mobile, you’ll need a battery power supply. This needs to be 12 volts, and at least 1 amp. I bought this one, which was way more expensive than anything else I ever needed to go ghost hunting, but it is a very portable beast of a rechargeable power supply. You will also still need a Kinect power supply as above, but will cut off the end of the adaptor at the mains plug end. On this end you need to solder a plug that will interface nicely with your battery’s output socket. That may take different forms, depending on your battery, but make sure the polarity is correct!
The Software End
Finally, you’ll need a laptop running Microsoft Windows. There’s some free software to download, which is only available for these machines. I’m sure somebody will have got it running in a virtual machine on a Mac, but for now, just go with the nearest Windows laptop you can find. It’s not even essential for it to be an x64 machine. The software was happily running on everything from Windows 7 onwards. The software needs to be installed once, and in the correct order to get you up and running:
- Ensure the Kinect is not connected to the laptop.
- Download and install the Kinect for Windows SDK v1.8 from here.
- Download and install the Kinect for Windows Developer Toolkit v1.8 from here.
- Download and install the Kinect for Windows Runtime v1.8 from here.
- Choose, download and install an appropriate version of OpenNI v2.2 from here. If you have an 64-bit laptop, go for that one, else download the x86 version.
- Download and install NiTE v2.2. If you have an 64-bit laptop, get it from here, else download the x86 version from here.
- Now you can plug in your Kinect and wait for a minute while Windows sorts out the drivers and what not.
Using it.
You’ll likely only use two programs, for which you can create desktop shortcuts for, from the suite of stuff you’ve just installed:
- The NiTE application, where the camera shows in dark mode and overlays green stick figures over bodies it detects, and found either in either:
- C:\Program Files\PrimeSense\NiTE2\Samples\Bin\UserViewer.exe
- C:\Program Files (x86) \PrimeSense\NiTE2\Samples\Bin\UserViewer.exe
- The standard Kinect mode, which you will find in the
Start Menu, Programme, Kinect for Windows SDK v1.8, opening theToolstab, and selecting ‘Kinect Explorer-D2D‘ from the available options. You might want to then change the one view so that you can see the IR view, rather than it overlayed by the RGB colours.
You should be able to find either .exe application in the program files and create shortcuts to place on the desktop. This makes it easy to get to them later.
So now, you can go and find a ghost… allegedly. The first time I tried it, there were multiple forms sketched out in my living room, which is not haunted at all. One tried to climb bookcase, while the other did some breakdancing on my lovely rug. It won’t take long to find yours; try changing the lighting conditions, angle of the camera, or maybe select a place in the camera frame that is completely blank, like the side of a cupboard.
In this session, you’re more likely to learn a little about computer systems, and how to solder connectors safely and securely, rather than discover ghosts, but it looks very cool for your mates. The challenge here is get them to explain why they think the scanner sometimes sees a form. Is it the shape of a chair, a reflection from a secondary source of IR light, or a glimpse of daylight? All the same, it doesn’t stop ghost hunters from using them.
- Note that you cannot usually see the dots with your normal vision, as humans don’t see infra-red light. But using an IR camera, like discussed in an earlier post, you can capture the structured pattern of dots. ↩︎