Combining Confocal Imaging and Descattering

Abstract

Figure 1: Reconstructed volume of a 3D scene in a fish tank with diluted milk. While in the floodlit image (b) only the front objects are recognizable, confocal imaging (c) partially removes the haze. Using our novel descattering algorithm combined with confocal imaging more global scattering is removed and objects at even larger distances become visible (d). The image is sharper and features more saturated colors. In (e), the recovered 3D structure is visualized for a different view. Images (c)-(e) have been created by computing a confocal or descattered confocal volume followed by maximum intensity projection. AbstractIn translucent objects, light paths are affected by multiple scattering, which is polluting any observation. Confocal imaging 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. The selected light paths still contain some global scattering contributions, though. Descattering based on high frequency illumination serves the same purpose. It removes the global component from 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.

Spaceborne underwater imaging

“…The satellite in orbit forms a huge, planet-sized light field camera, which over time captures a 3D subspace of the 5D spatiotemporal light field. Interestingly, the light field concept has recently evolved [9] to treat short distance descattering problems using active illumination. In a sense, multiangular (light field) sensing performs a set of tomographic projections of a multilayered scene.…”

Primal-dual coding to probe light transport

“…We use p = 0.5 in our experiments because it maximizes the magnitude of the probing matrix. Fuchs et al [2008] describe an approach for imaging through scattering media that combines confocal imaging and de-scattering. It requires scanning a line across the scene and capturing, storing and analyzing many photos.…”

“…These methods are a special case of primal-dual coding where the primaland dual-domain patterns are binary, and either coincide or are complements of each other. To our knowledge, they have not been used for one-shot imaging in standard photography settings, although "synthetic" implementations of aperture correlation have been demonstrated by Levoy and colleagues [Levoy et al 2004;Fuchs et al 2008]. These implementations keep optical processing to a minimum and rely on substantial image acquisition and computational processing to synthesize individual photos.…”

Hemispherical Confocal Imaging Using Turtleback Reflector

“…Treibitz and Schechner [21] used polarizer under water. Assuming that only single scattering is observed in optically thin media, Narasimhan et al [18] Recently, Fuchs et al [5] combined confocal imaging with descattering which utilize the fact that scattering components have low frequency. The principle of our hemispherical confocal imaging is similar to this approach.…”