Here we outline the specific hardware items used. Some can be sourced from Adafruit. Other items are from external vendors.
Camera
A Raspberry Pi Zero W with a V2 camera module was used for all video capture. You could use any other model Pi as well. But since we only used the Pi for video capture, and all Pi's have a good GPU, the Pi Zero W is plenty good.
You can get these items separately:
Or you can get them as a kit:
You'll also want one of these to help focus the camera lens:
NOTE: One drawback to using a Pi Zero W is the smaller and more delicate camera connector on the Pi. The "regular" sized Pi boards all have a larger and generally more durable camera connector that may prove more robust in an educational setting. We mainly wanted to show that this experiment is possible on the cheapest Pi available. Any model Pi will work.
Laser and Optics
Here are the links to the laser, batteries, and line generating optics used:
- THOR H Series Laser Pointer, in 520nm (green)
- CR123A Batteries (2x) and Charger
- CR123A (2x) Spare Batteries
- 20deg Divergence Lens (CL007), for generating laser sheet
Yep, the optics were more expensive than the laser itself. But we got a very nice laser sheet as a result.
The Box
We used a left over cardboard shipping box lined with black poster board. Any other suitable box with similar dimensions should be fine.
This is the side where the Pi Zero W and Pi Camera are attached. A small hole is cut for the camera module.
The Pi Zero W and Pi Camera module are put in place. Make sure the camera module is pointing through the hole.
Attach the various cables. At a minimum, you need power. Here we show additional connections for audio and a button.
And here's the final setup, with the addition of the audio cue and the Go button. The mask tester sits in front of the box and places their mouth into the mask test hole. When ready, they can then press the Go button. An audio cue plays to let them know to start speaking. After the video is done, another audio cue plays to let them know it's over.
Here's an example with the laser on and spraying in some water from above through the open box top. Even with the room lights on, the particles are clearly visible in the light sheet.
Note that the box used here does not have an exit slot for the laser, which the box in the original paper did. This did produce a noticeable amount of back scattered light into the closed box, as observed through the mask hole. However, it was minimal enough that it did not seem to affect the simple threshold based analysis done here (details later).
