Imaging Components, Systems, and Processing

Resolving multiple propagation paths in time of flight range cameras using direct and global separation methods

[+] Author Affiliations
Refael Whyte, Lee Streeter, Michael J. Cree, Adrian A. Dorrington

University of Waikato, School of Engineering, Private Bag 3105, Hamilton 3240, New Zealand

Opt. Eng. 54(11), 113109 (Nov 24, 2015). doi:10.1117/1.OE.54.11.113109
History: Received July 22, 2015; Accepted October 26, 2015
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Abstract.  Time of flight (ToF) range cameras illuminate the scene with an amplitude-modulated continuous wave light source and measure the returning modulation envelopes: phase and amplitude. The phase change of the modulation envelope encodes the distance travelled. This technology suffers from measurement errors caused by multiple propagation paths from the light source to the receiving pixel. The multiple paths can be represented as the summation of a direct return, which is the return from the shortest path length, and a global return, which includes all other returns. We develop the use of a sinusoidal pattern from which a closed form solution for the direct and global returns can be computed in nine frames with the constraint that the global return is a spatially lower frequency than the illuminated pattern. In a demonstration on a scene constructed to have strong multipath interference, we find the direct return is not significantly different from the ground truth in 33/136pixels tested; where for the full-field measurement, it is significantly different for every pixel tested. The variance in the estimated direct phase and amplitude increases by a factor of eight compared with the standard time of flight range camera technique.

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© 2015 Society of Photo-Optical Instrumentation Engineers

Topics

Cameras

Citation

Refael Whyte ; Lee Streeter ; Michael J. Cree and Adrian A. Dorrington
"Resolving multiple propagation paths in time of flight range cameras using direct and global separation methods", Opt. Eng. 54(11), 113109 (Nov 24, 2015). ; http://dx.doi.org/10.1117/1.OE.54.11.113109


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