Qualitative Real-Time Schlieren and Shadowgraph Imaging of Human Exhaled Airflows: An Aid to Aerosol Infection Control
Figure 2
Camera and light source set-up.
The LED light source is shaped into a vertical slit positioned just in front of the camera lens. When the subject is in focus, the knife edge (or razor blade painted white as shown here) is moved carefully into the path of the LED beam, cutting off part of its lateral aspect, to give the schlieren or shadowgraph effect.