Dynamic Schlieren Imaging Using a Pulsed LED

We have constructed a Schlieren imaging system which uses a pulsed LED to synchronize the light source to the dynamic refractive index changes. In this system, a point source LED broadly illuminates a parabolic mirror which then refocuses the light onto a razor blade aperture. A video camera immediately behind the aperture reconstructs the image. When disturbances near the mirror surface slightly modify the index of refraction and redirect the wavefront, the camera is able to see these interactions in real time. Synchronization of the pulsed LED and the disturbance (for instance, sound waves) allows the camera to capture dynamic distortions in a static image, making this system suitable for both instructional demonstrations and laboratory experiments.