Computational Schlieren Photography with Light Field Probes

Abstract

We introduce a new approach to capturing refraction in transparent media, which we call light field background oriented Schlieren photography. By optically coding the locations and directions of light rays emerging from a light field probe, we can capture changes of the refractive index field between the probe and a camera or an observer. Our prototype capture setup consists of inexpensive off-the-shelf hardware, including inkjet-printed transparencies, lenslet arrays, and a conventional camera. By carefully encoding the color and intensity variations of 4D light field probes, we show how to code both spatial and angular information of refractive phenomena. Such coding schemes are demonstrated to allow for a new, single image approach to reconstructing transparent surfaces, such as thin solids or surfaces of fluids. The captured visual information is used to reconstruct refractive surface normals and a sparse set of control points independently from a single photograph.

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Notes

  1. 1.

    The connection between Snell’s law and the ray equation of geometric optics (Eq. 1) is well-known in physics, see e.g. http://en.wikibooks.org/wiki/Introduction_to_Mathematical_Physics/Electromagnetism/Optics,_particular_case_of_electromagnetism.

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Acknowledgments

Gordon Wetzstein was supported by an NSERC Postdoctoral Fellowship. Ramesh Raskar was supported by an Alfred P. Sloan Research Fellowship and a DARPA Young Faculty Award.

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Correspondence to Gordon Wetzstein.

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Wetzstein, G., Heidrich, W. & Raskar, R. Computational Schlieren Photography with Light Field Probes. Int J Comput Vis 110, 113–127 (2014). https://doi.org/10.1007/s11263-013-0652-x

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Keywords

  • Computational photography
  • Light transport
  • Fluid imaging
  • Shape from x