Imaging through obscurants using time-correlated single-photon counting in the short-wave infrared

Single-photon time-of-flight (ToF) light detection and ranging (LiDAR) systems have emerged in recent years as a candidate technology for high-resolution depth imaging in challenging environments, such as long-range imaging and imaging in scattering media. This Thesis investigates the potential of two ToF single-photon depth imaging systems based on the time-correlated single-photon (TCSPC) technique for imaging targets in highly scattering environments. The high sensitivity and picosecond timing resolution afforded by the TCSPC technique offers high-resolution depth profiling of remote targets while maintaining low optical power levels. Both systems comprised a pulsed picosecond laser source with an operating wavelength of 1550 nm, and employed InGaAs/InP SPAD detectors. The main benefits of operating in the shortwave infrared (SWIR) band include improved atmospheric transmission, reduced solar background, as well as increased laser eye-safety thresholds over visible band sensors. Firstly, a monostatic scanning transceiver unit was used in conjunction with a single-element Peltier-cooled InGaAs/InP SPAD detector to attain sub-centimetre resolution three-dimensional images of long-range targets obscured by camouflage netting or in high levels of scattering media. Secondly, a bistatic system, which employed a 32 × 32 pixel format InGaAs/InP SPAD array was used to obtain rapid depth profiles of targets which were flood-illuminated by a higher power pulsed laser source. The performance of this system was assessed in indoor and outdoor scenarios in the presence of obscurants and high ambient background levels. Bespoke image processing algorithms were developed to reconstruct both the depth and intensity images for data with very low signal returns and short data acquisition times, illustrating the practicality of TCSPC-based LiDAR systems for real-time image acquisition in the SWIR wavelength region - even in the photon-starved regime.The Defence Science and Technology Laboratory ( Dstl) National PhD Schem

DARIUS I IN EGYPT: ACHAEMENID AUTHORITY AND EGYPTIAN CONTINUITY

ABSTRACT Rachael Tobin-Dodd: Darius I in Egypt: Achaemenid Authority and Egyptian Continuity (Under the direction of Jennifer Gates-Foster) The ideological systems of the Persian Great King and the Egyptian Pharaoh were inherently in conflict. The Egyptian Pharaoh was responsible for defeating foreign enemies, including Achaemenid Persians, while the Persian Great King was the ruler of a universal empire. The Persian king, Darius I, had to embody both roles in order to maintain his rule over Egypt. By examining three Egyptian artifacts that depict Darius and originate from different socio-political spheres, I assess the different ways he was portrayed and consider the ways these images navigated the inherent ideological conflict between the Great King and the Egyptian Pharaoh. This analysis reveals a pattern in which Darius was presented to an Egyptian audience as an Egyptian Pharaoh that has taken on visual attributes of the Achaemenid Great King, but to a Persian audience, Darius was presented as an entirely Achaemenid conqueror.Master of Art

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

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

The Hurricane Sandy Place Report: Evacuation Decisions, Housing Issues and Sense of Community

Hurricane Sandy was one of the largest storms on record, sweeping through the eastern seaboard of the United States with a massive diameter twice the size of Hurricane Katrina. Although wind speeds did not match those of Katrina, the combination of high tide at landfall and the lunar phase resulted in exceptionally high storm surges. Catastrophic storms such as Hurricane Sandy can have devastating effects on many aspects of human life and the environment, undermining economic activity, crippling critical infrastructure, and disrupting hundreds of thousands of lives for weeks, months, or even years. The Sandy Child and Family Health (S-CAFH) Study was designed to describe and analyze the impacts of the storm on the residents of New Jersey, identifying those needs which emerged and those which are still pressing. The research team – a partnership of faculty and research staff from Rutgers University, New York University, Columbia University, and Colorado State University – randomly selected and surveyed 1,000 residents of New Jersey’s “Disaster Footprint,” representing the experiences of 1 million New Jersey residents living in or near those coastal areas of the state most directly exposed to the storm. The primary focus of this Briefing Report, the first in a series of four thematic reports, is to document the storm’s impact on PLACE in New Jersey residents’ lives, with a particular emphasis on Sandy’s effect on people’s homes and housing decisions

The Hurricane Sandy Person Report: Disaster Exposure, Health Impacts, Economic Burden, and Social Well-Being

The impact a disaster has on the health of a population can be described as having a “dose-response” relationship: the larger the “dose” of the disaster, the greater the health impact or “response” among those individuals and communities exposed. This PERSON Briefing Report describes the impact of Hurricane Sandy (the dose) on the health and well-being of adults and children exposed to the storm (the response). Data for the report are drawn from the baseline survey of the Sandy Child and Family Health (S-CAFH) Study, an observational cohort study of nearly 1,000 randomly-selected New Jersey residents who were living in areas of the state exposed to the storm in 2012. Participants in the study represent over 1 million people living in Sandy’s “Disaster Footprint,” the hurricane-exposed portions of the state. This report describes and examines several critical aspects of individual health and well-being that may be associated with the storm, including: 1. Physical health of adults; 2. Psychological and emotional health of adults; 3. Social and economic health of adults; 4. Health and well-being of children; and 5. The association between disaster exposure and individual outcomes