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Proceedings Paper

Adaptive time-sequential binary sensing for high dynamic range imaging
Author(s): Chenhui Hu; Yue M. Lu
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Paper Abstract

We present a novel image sensor for high dynamic range imaging. The sensor performs an adaptive one-bit quantization at each pixel, with the pixel output switched from 0 to 1 only if the number of photons reaching that pixel is greater than or equal to a quantization threshold. With an oracle knowledge of the incident light intensity, one can pick an optimal threshold (for that light intensity) and the corresponding Fisher information contained in the output sequence follows closely that of an ideal unquantized sensor over a wide range of intensity values. This observation suggests the potential gains one may achieve by adaptively updating the quantization thresholds. As the main contribution of this work, we propose a time-sequential threshold-updating rule that asymptotically approaches the performance of the oracle scheme. With every threshold mapped to a number of ordered states, the dynamics of the proposed scheme can be modeled as a parametric Markov chain. We show that the frequencies of different thresholds converge to a steady-state distribution that is concentrated around the optimal choice. Moreover, numerical experiments show that the theoretical performance measures (Fisher information and Cram´er-Rao bounds) can be achieved by a maximum likelihood estimator, which is guaranteed to find globally optimal solution due to the concavity of the log-likelihood functions. Compared with conventional image sensors and the strategy that utilizes a constant single-photon threshold considered in previous work, the proposed scheme attains orders of magnitude improvement in terms of sensor dynamic ranges.

Paper Details

Date Published: 19 May 2012
PDF: 11 pages
Proc. SPIE 8375, Advanced Photon Counting Techniques VI, 83750A (19 May 2012); doi: 10.1117/12.919597
Show Author Affiliations
Chenhui Hu, Harvard School of Engineering and Applied Sciences (United States)
Yue M. Lu, Harvard School of Engineering and Applied Sciences (United States)

Published in SPIE Proceedings Vol. 8375:
Advanced Photon Counting Techniques VI
Mark A. Itzler, Editor(s)

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