If you're buying a used Oculus Rift or HTC Vive (or even a new one), one of the things you ought to check for is that all the infrared lights work. Here's how.
The Oculus Rift uses outside-in tracking, which means an external camera tracks infrared lights from the headset (they aren't sensors but emitters). The HTC Vive uses inside-out tracking, where the headset's sensors track the lasers and infrared lights from the base stations. To ensure that your headset can track properly, you need to check if these lights are working.
Modern digital cameras have infrared filters to improve image quality, so you probably can't see the infrared lights with a high-end digital camera. However, there are several cameras that you can use to see the infrared lights:
1. The front-facing camera on a smartphone (like in the shot above, from the front-facing camera of an iPhone 6).
2. A toy digital camera
3. The camera from an old cell phone or old smartphone (iPhone 3 or older).
4. A webcam (as in the shot below),
5. A nanny cam or security camera
|From a webcam|