Colloquium: Gary Settles

    Thursday, April 7, 2016 - 3:30pm - 5:00pm
    Meinel 307

    Schlieren and Shadowgraph Optical Instruments


    The schlieren technique is basically a Fourier optical processor lookingat phase distortions caused by transparent phenomena.  By spatiallyfiltering the Fourier spectrum (most often by a Hilbert transform),gradients of phase become amplitude images that can be photographed andanalyzed.  Shadowgraphy is even simpler, with no spatial filtering.Instead, the warped optical wavefront is allowed to cast a pattern ofcaustics on a screen.  Invented before their time by Robert Hooke, thesemethods first became lab instruments 150 years ago.  They have since ledto many important scientific discoveries by allowing one to see andmeasure the invisible.  To illustrate this, the talk will include manystill images and video clips.  Finally, the newest approach is called"background-oriented schlieren," in which sub-pixel distortions of apatterned background and digital processing can yield pseudo-schlierenimages without large, expensive optical elements.

    Speaker Bio(s): 

    Dr. Gary Settles grew up on a farm in Tennessee, and earned his Bachelor's degree in Aerospace Engineering at the University of Tennessee. He received a PhD degree from Princeton Engineering faculty at Penn State, retiring last summer with the title of Distinguished Professor Emeritus.  At Penn State he established the Gas Dynamics Laboratory, known for research in supersonic flows, optical flow diagnostics, materials processing and homeland security.  He educated 20 PhD students and many MS and undergraduate students at Penn State.  He was the 2004 ASME Freeman Scholar, is a Fellow of ASME and Associate Fellow of AIAA, and is the author of a book entitled "Schlieren and Shadowgraph Techniques." Science Citation Index recognizes 115 journal publications authored by Prof. Settles and his students and colleagues.