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.

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).

Example

Here's a short clip showing the resulting video.