Time-of-Travel Methods for Measuring Optical Flow on Board a Micro Flying Robot
Aix-Marseille Université, CNRS, ISM UMR7287, 13288 Marseille Cedex 09, France
Author to whom correspondence should be addressed.
Academic Editors: Felipe Gonzalez Toro and Antonios Tsourdos
Received: 30 December 2016 / Revised: 8 March 2017 / Accepted: 9 March 2017 / Published: 11 March 2017
For use in autonomous micro air vehicles, visual sensors must not only be small, lightweight and insensitive to light variations; on-board autopilots also require fast and accurate optical flow measurements over a wide range of speeds. Using an auto-adaptive bio-inspired Michaelis–Menten Auto-adaptive Pixel (M
APix) analog silicon retina, in this article, we present comparative tests of two optical flow calculation algorithms operating under lighting conditions from
(i.e., from 0.2 to 12,000 lux for human vision). Contrast “time of travel” between two adjacent light-sensitive pixels was determined by thresholding and by cross-correlating the two pixels’ signals, with measurement frequency up to 5 kHz for the 10 local motion sensors of the M
APix sensor. While both algorithms adequately measured optical flow between 25
/s and 1000
/s, thresholding gave rise to a lower precision, especially due to a larger number of outliers at higher speeds. Compared to thresholding, cross-correlation also allowed for a higher rate of optical flow output (99 Hz and 1195 Hz, respectively) but required substantially more computational resources.
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Vanhoutte, E.; Mafrica, S.; Ruffier, F.; Bootsma, R.J.; Serres, J. Time-of-Travel Methods for Measuring Optical Flow on Board a Micro Flying Robot. Sensors 2017, 17, 571.
Vanhoutte E, Mafrica S, Ruffier F, Bootsma RJ, Serres J. Time-of-Travel Methods for Measuring Optical Flow on Board a Micro Flying Robot. Sensors. 2017; 17(3):571.
Vanhoutte, Erik; Mafrica, Stefano; Ruffier, Franck; Bootsma, Reinoud J.; Serres, Julien. 2017. "Time-of-Travel Methods for Measuring Optical Flow on Board a Micro Flying Robot." Sensors 17, no. 3: 571.
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