Wednesday, November 27, 2013

Coded Time of Flight Cameras: Sparse Deconvolution to Address Multipath Interference and Recover Time Profiles

Achuta Kadambi just let me know of a different ToF camera than the UBC effort  featured in the previous blog entrythe project page is here; wow.

Time of flight cameras produce real-time range maps at a relatively low cost using continuous wave amplitude modulation and demodulation. However, they are geared to measure range (or phase) for a single reflected bounce of light and suffer from systematic errors due to multipath interference.

We re-purpose the conventional time of flight device for a new goal: to recover per-pixel sparse time profiles expressed as a sequence of impulses. With this modification, we show that we can not only address multipath interference but also enable new applications such as recovering depth of near-transparent surfaces, looking through diffusers and creating time-profile movies of sweeping light.

Our key idea is to formulate the forward amplitude modulated light propagation as a convolution with custom codes, record samples by introducing a simple sequence of electronic time delays, and perform sparse deconvolution to recover sequences of Diracs that correspond to multipath returns. Applications to computer vision include ranging of near-transparent objects and subsurface imaging through diffusers. Our low cost prototype may lead to new insights regarding forward and inverse problems in light transport.

I note the good performance of the greedy solver.

I also note the very interesting item in the project page

Reproducible Experiments
Newer components are available to build an improved version of the prototype detailed in a paper. It is also cheaper due to the reduced cost of components in today's market. Please contact us if you would like to build the nanophotography setup.
For technical details contact: Achuta Kadambi:

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