3D Density Field Measurements Using a Plenoptic Camera and Background Oriented Schlieren Imaging

  • Student:  Abhishek Bichal

This project investigates the use of a plenoptic camera and Background Oriented Schlieren (BOS) imaging to tomographically reconstruct a 3D density field.  BOS is a line-of-sight technique that measures deflections of light rays as they pass through an inhomogeneous index-of-refraction field.  The image below shows a random background placed behind a Mach 2.0 flow over a cone model.  By determining the displacement of the random background image relative to a no-flow reference image, the deflection of light rays passing through the flow can be measured.  This is shown on the right hand image where the presence of the shock wave and subsequent expansion are clear.  Evidence of the boundary layer formed on the side of the model and additional shock waves formed by fins on the aft portion of the model are also clear.

Raw image of a random background Measured deflection for a cone model

Raw image of a random background and the measured deflection for a cone model placed in a Mach 2.0 wind tunnel.

A plenoptic camera provides the unique ability to computationally render images with different viewpoints from a single snapshot.  This capability is shown in the video below where the light-field data captured by the plenoptic camera is interpolated to create the different viewpoints.  The present work is focused on merging the plenoptic camera concept with BOS to reconstruct the 3D density field using tomographic algorithms.  In this case, the plenoptic camera will be used to collect, in a single snapshot, a collection of views through the flow field.  As the observed BOS image is dependent on the path through the flow, the views collected by the camera represent different paths through the flow.

Last Updated: Aug 09, 2013