Physics Project Abstract
DEVELOPING AND CALIBRATING A LASER SCHLIEREN VIDEO SYSTEM FOR IMAGING AND DETECTING AIR DENSITY GRADIENTS
Presenter:
Chris Chrobak, Illinois Mathematics and Science Academy, 1500 W. Sullivan Road, Aurora, IL 60506
Mentor:
William A. Ellingson, Ph.D., Argonne National Laboratory, Energy Technology Division, 9700 South Cass Avenue, Bldg. 212, Argonne, IL 60439; 630-252-5068
Abstract:
A schlieren system is an arrangement of optical devices that uses the principle of refraction to detect density gradients in gases or liquids within the testing area. Density gradients can be caused by temperature differences or turbulence. The schlieren system constructed will be eventually used for the purpose of characterizing transmitted ultrasound waves through air at frequencies in excess of 400 kHz. Ultrasound waves propagating through air create small density gradients. A high level of sensitivity is required to view such small density gradients. Therefore, a large amount of testing and calibrating was required to achieve this high level of detection sensitivity. The light sources used in this project were first a laser pointer and then a 20mw helium-neon. Laser light has its benefits over traditional broad-spectrum white light, but poses certain problems such as speckling because of its coherence. A significant part of the research involved evaluating one-dimensional and two-dimensional optical stops to determine which gave the best results. The resulting image data were processed through a digital image subtraction program created in Labview. This reduced noise and generated image data that was used for quantitative analysis.