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Open AccessArticle

Action Recognition Using Single-Pixel Time-of-Flight Detection

iCv Lab, Institute of Technology, University of Tartu, 50411 Tartu, Estonia
University of Barcelona, 08007 Barcelona, Spain
Institute of Physics, University of Tartu, 50411 Tartu, Estonia
The Computer Vision Centre, 08193 Barcelona, Spain
Trinity College Dublin, Dublin 2, Ireland
Department of Electrical and Electronic Engineering, Hasan Kalyoncu University, Gaziantep 27000, Turkey
Institute of Digital Technologies, Loughborough University London, London E15 2GZ, UK
Author to whom correspondence should be addressed.
All authors contributed equally to this work.
Entropy 2019, 21(4), 414;
Received: 14 January 2019 / Revised: 15 April 2019 / Accepted: 15 April 2019 / Published: 18 April 2019
(This article belongs to the Special Issue Statistical Machine Learning for Human Behaviour Analysis)
Action recognition is a challenging task that plays an important role in many robotic systems, which highly depend on visual input feeds. However, due to privacy concerns, it is important to find a method which can recognise actions without using visual feed. In this paper, we propose a concept for detecting actions while preserving the test subject’s privacy. Our proposed method relies only on recording the temporal evolution of light pulses scattered back from the scene. Such data trace to record one action contains a sequence of one-dimensional arrays of voltage values acquired by a single-pixel detector at 1 GHz repetition rate. Information about both the distance to the object and its shape are embedded in the traces. We apply machine learning in the form of recurrent neural networks for data analysis and demonstrate successful action recognition. The experimental results show that our proposed method could achieve on average 96.47 % accuracy on the actions walking forward, walking backwards, sitting down, standing up and waving hand, using recurrent neural network. View Full-Text
Keywords: single pixel single photon image acquisition; time-of-flight; action recognition single pixel single photon image acquisition; time-of-flight; action recognition
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Ofodile, I.; Helmi, A.; Clapés, A.; Avots, E.; Peensoo, K.M.; Valdma, S.-M.; Valdmann, A.; Valtna-Lukner, H.; Omelkov, S.; Escalera, S.; Ozcinar, C.; Anbarjafari, G. Action Recognition Using Single-Pixel Time-of-Flight Detection. Entropy 2019, 21, 414.

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