Combining Confocal Imaging and Descattering

Christian Fuchs¹           Michael Heinz¹           Marc Levoy²
Hans-Peter Seidel¹           Hendrik P. A. Lensch¹

¹MPI Informatik      ²Stanford University

Example Images

EGSR (Eurographics Symposium on Rendering) 2008 Paper

Full Paper (PDF, full-res, 19 MB)

About the Method

(a)

In translucent objects, light paths are affected by multiple scattering, which is polluting any observation. Confocal imaging (a) reduces the influence of such global illumination effects by carefully focusing illumination and viewing rays from a large aperture to a specific location within the object volume. However, the selected light paths still contain some global scattering contributions.
Descattering based on high frequency illumination serves the same purpose. It allows for a separation of the incident light into direct reflections and global components for observed light paths.
We demonstrate that confocal imaging and descattering are orthogonal and propose a novel descattering protocol that analyzes the light transport in a neighborhood of light transport paths. In combination with confocal imaging, our descattering method achieves optical sectioning in translucent media with higher contrast and better resolution.

Measurement setup

Our measurement setup consists of several geometrically and photometrically calibrated cameras and projectors. The cameras record high dynamic range image sequences, while the projectors send out high frequency illumination patterns, for example single line stripes that are swiped over the object's surface.

Data acquisition

The video below shows a typical acquisition image sequence in which a line pattern is swiped over the target object by 3 projectors individually. Each illumination condition is captured using 3 different cameras.

Results

The first two images on the right show the original island scene and a photograph under floodlight illumination when the island is immersed in dilute milk.

The next image shows the reconstruction using synthetic aperture confocal imaging. Although most of the multiple scattering from the milk is gone, some objects (like the red parrot or most of the palm tree) in the background are not visible. The bottom image shows our reconstruction result using a combination of confocal imaging and descattering. Objects in the background become visible.

Result videos


This video shows a run through the acquired volume of the island scene from front to back. Note how objects in the background become visible while objects in the foreground disappear.	In this video, the acquired volume is rendered from novel viewpoints.

Bibliography

Christian Fuchs, Michael Heinz, Marc Levoy, Hans-Peter Seidel, Hendrik P. A. Lensch, "Combining Confocal Imaging and Descattering" , Computer Graphics Forum, Special Issue for the Eurographics Symposium on Rendering 2008, Volume 27, Issue 4 (June 2008).

BibTeX entry

@article{Fuchs:2008:CCD,
    title = "Combining Confocal Imaging and Descattering",
    author = "Christian Fuchs and Michael Heinz and Marc Levoy and Hans-Peter Seidel and
        Hendrik P. A. Lensch",
    journal = "Computer Graphics Forum, Special Issue for the Eurographics Symposium on Rendering 2008",
    volume = 27,
    number = 4,
    month = June, 
    year = 2008,
    pages = "1245--1253",
  }