Researchers have developed a laser test for measuring the effectiveness of a facemask. The mask-testing setup is much simpler than those commonly seen in typical laser labs: it consists only of a laser, a lens, and a camera. Specifically, a laser is shone through a cylindrical lens to create an elliptical beam profile, which then passes through a slit into a 30×30×35-cm black box, creating a light sheet within the box.
To put a mask to the test using the setup, a person wearing the mask speaks into a hole cut in the front of the box; through another hole in the back, a mobile phone records video as the laser test light scatters off of droplets coming from the speaker’s mouth. The video file is then piped to a computer algorithm, which counts the droplets recorded in the light scattering.
The team used one of the scientific – a 2-W, 532-nm model. But the researchers say the setup should work equally well with cheap, commercially available lasers retailing for less than US$100. They believe that the whole setup should be achievable for a total spend of less than US$200 and that it can easily be built and operated by non-experts.