October 29, 2008
Schlieren photography can help understanding how diseases spread
The New England Journal of Medicine has published an image that shows a man coughing which was created by Schlieren photography. Schlieren photography involves shining collimated light past a knife edge onto a target, and variations in the refractive index of moving air create “shadows” of a sort in the image captured on film, and it’s most often used to solve aeronautical air-flow problems, or weapons in action. To map a cough, a virus expert from Singapore appointed a healthy student to cough. The expelled air, traveling at 18 miles per hour, mixed with cooler surrounding air and produced “temperature differences that bend light rays by different amounts.
The aim of the photograph was to study the dynamics of how diseases spread when people surround an infected person. The technique was used to explore how coughs spread diseases like SARS and the flu.