2,439 research outputs found
Robust Bayesian target detection algorithm for depth imaging from sparse single-photon data
This paper presents a new Bayesian model and associated algorithm for depth
and intensity profiling using full waveforms from time-correlated single-photon
counting (TCSPC) measurements in the limit of very low photon counts (i.e.,
typically less than 20 photons per pixel). The model represents each Lidar
waveform as an unknown constant background level, which is combined in the
presence of a target, to a known impulse response weighted by the target
intensity and finally corrupted by Poisson noise. The joint target detection
and depth imaging problem is expressed as a pixel-wise model selection and
estimation problem which is solved using Bayesian inference. Prior knowledge
about the problem is embedded in a hierarchical model that describes the
dependence structure between the model parameters while accounting for their
constraints. In particular, Markov random fields (MRFs) are used to model the
joint distribution of the background levels and of the target presence labels,
which are both expected to exhibit significant spatial correlations. An
adaptive Markov chain Monte Carlo algorithm including reversible-jump updates
is then proposed to compute the Bayesian estimates of interest. This algorithm
is equipped with a stochastic optimization adaptation mechanism that
automatically adjusts the parameters of the MRFs by maximum marginal likelihood
estimation. Finally, the benefits of the proposed methodology are demonstrated
through a series of experiments using real data.Comment: arXiv admin note: text overlap with arXiv:1507.0251
Quantum-inspired computational imaging
Computational imaging combines measurement and computational methods with the aim of forming images even when the measurement conditions are weak, few in number, or highly indirect. The recent surge in quantum-inspired imaging sensors, together with a new wave of algorithms allowing on-chip, scalable and robust data processing, has induced an increase of activity with notable results in the domain of low-light flux imaging and sensing. We provide an overview of the major challenges encountered in low-illumination (e.g., ultrafast) imaging and how these problems have recently been addressed for imaging applications in extreme conditions. These methods provide examples of the future imaging solutions to be developed, for which the best results are expected to arise from an efficient codesign of the sensors and data analysis tools.Y.A. acknowledges support from the UK Royal Academy of Engineering under the Research Fellowship Scheme (RF201617/16/31). S.McL. acknowledges financial support from the UK Engineering and Physical Sciences Research Council (grant EP/J015180/1). V.G. acknowledges support from the U.S. Defense Advanced Research Projects Agency (DARPA) InPho program through U.S. Army Research Office award W911NF-10-1-0404, the U.S. DARPA REVEAL program through contract HR0011-16-C-0030, and U.S. National Science Foundation through grants 1161413 and 1422034. A.H. acknowledges support from U.S. Army Research Office award W911NF-15-1-0479, U.S. Department of the Air Force grant FA8650-15-D-1845, and U.S. Department of Energy National Nuclear Security Administration grant DE-NA0002534. D.F. acknowledges financial support from the UK Engineering and Physical Sciences Research Council (grants EP/M006514/1 and EP/M01326X/1). (RF201617/16/31 - UK Royal Academy of Engineering; EP/J015180/1 - UK Engineering and Physical Sciences Research Council; EP/M006514/1 - UK Engineering and Physical Sciences Research Council; EP/M01326X/1 - UK Engineering and Physical Sciences Research Council; W911NF-10-1-0404 - U.S. Defense Advanced Research Projects Agency (DARPA) InPho program through U.S. Army Research Office; HR0011-16-C-0030 - U.S. DARPA REVEAL program; 1161413 - U.S. National Science Foundation; 1422034 - U.S. National Science Foundation; W911NF-15-1-0479 - U.S. Army Research Office; FA8650-15-D-1845 - U.S. Department of the Air Force; DE-NA0002534 - U.S. Department of Energy National Nuclear Security Administration)Accepted manuscrip
3D Target Detection and Spectral Classification for Single-photon LiDAR Data
3D single-photon LiDAR imaging has an important role in many applications.
However, full deployment of this modality will require the analysis of low
signal to noise ratio target returns and a very high volume of data. This is
particularly evident when imaging through obscurants or in high ambient
background light conditions. This paper proposes a multiscale approach for 3D
surface detection from the photon timing histogram to permit a significant
reduction in data volume. The resulting surfaces are background-free and can be
used to infer depth and reflectivity information about the target. We
demonstrate this by proposing a hierarchical Bayesian model for 3D
reconstruction and spectral classification of multispectral single-photon LiDAR
data. The reconstruction method promotes spatial correlation between
point-cloud estimates and uses a coordinate gradient descent algorithm for
parameter estimation. Results on simulated and real data show the benefits of
the proposed target detection and reconstruction approaches when compared to
state-of-the-art processing algorithm
Lidar waveform based analysis of depth images constructed using sparse single-photon data
This paper presents a new Bayesian model and algorithm used for depth and
intensity profiling using full waveforms from the time-correlated single photon
counting (TCSPC) measurement in the limit of very low photon counts. The model
proposed represents each Lidar waveform as a combination of a known impulse
response, weighted by the target intensity, and an unknown constant background,
corrupted by Poisson noise. Prior knowledge about the problem is embedded in a
hierarchical model that describes the dependence structure between the model
parameters and their constraints. In particular, a gamma Markov random field
(MRF) is used to model the joint distribution of the target intensity, and a
second MRF is used to model the distribution of the target depth, which are
both expected to exhibit significant spatial correlations. An adaptive Markov
chain Monte Carlo algorithm is then proposed to compute the Bayesian estimates
of interest and perform Bayesian inference. This algorithm is equipped with a
stochastic optimization adaptation mechanism that automatically adjusts the
parameters of the MRFs by maximum marginal likelihood estimation. Finally, the
benefits of the proposed methodology are demonstrated through a serie of
experiments using real data
Robust 3D Reconstruction of Dynamic Scenes From Single-Photon Lidar Using Beta-Divergences
In this paper, we present a new algorithm for fast, online 3D reconstruction
of dynamic scenes using times of arrival of photons recorded by single-photon
detector arrays. One of the main challenges in 3D imaging using single-photon
lidar in practical applications is the presence of strong ambient illumination
which corrupts the data and can jeopardize the detection of peaks/surface in
the signals. This background noise not only complicates the observation model
classically used for 3D reconstruction but also the estimation procedure which
requires iterative methods. In this work, we consider a new similarity measure
for robust depth estimation, which allows us to use a simple observation model
and a non-iterative estimation procedure while being robust to
mis-specification of the background illumination model. This choice leads to a
computationally attractive depth estimation procedure without significant
degradation of the reconstruction performance. This new depth estimation
procedure is coupled with a spatio-temporal model to capture the natural
correlation between neighboring pixels and successive frames for dynamic scene
analysis. The resulting online inference process is scalable and well suited
for parallel implementation. The benefits of the proposed method are
demonstrated through a series of experiments conducted with simulated and real
single-photon lidar videos, allowing the analysis of dynamic scenes at 325 m
observed under extreme ambient illumination conditions.Comment: 12 page
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