11,553 research outputs found
Prototype of the SST-1M Telescope Structure for the Cherenkov Telescope Array
A single-mirror small-size (SST-1M) Davies-Cotton telescope with a dish
diameter of 4 m has been built by a consortium of Polish and Swiss institutions
as a prototype for one of the proposed small-size telescopes for the southern
observatory of the Cherenkov Telescope Array (CTA). The design represents a
very simple, reliable, and cheap solution. The mechanical structure prototype
with its drive system is now being tested at the Institute of Nuclear Physics
PAS in Krakow. Here we present the design of the prototype and results of the
performance tests of the structure and the drive and control system.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Imaging With Nature: Compressive Imaging Using a Multiply Scattering Medium
The recent theory of compressive sensing leverages upon the structure of
signals to acquire them with much fewer measurements than was previously
thought necessary, and certainly well below the traditional Nyquist-Shannon
sampling rate. However, most implementations developed to take advantage of
this framework revolve around controlling the measurements with carefully
engineered material or acquisition sequences. Instead, we use the natural
randomness of wave propagation through multiply scattering media as an optimal
and instantaneous compressive imaging mechanism. Waves reflected from an object
are detected after propagation through a well-characterized complex medium.
Each local measurement thus contains global information about the object,
yielding a purely analog compressive sensing method. We experimentally
demonstrate the effectiveness of the proposed approach for optical imaging by
using a 300-micrometer thick layer of white paint as the compressive imaging
device. Scattering media are thus promising candidates for designing efficient
and compact compressive imagers.Comment: 17 pages, 8 figure
Understanding and ameliorating non-linear phase and amplitude responses in AMCW Lidar
Amplitude modulated continuous wave (AMCW) lidar systems commonly suffer from non-linear phase and amplitude responses due to a number of known factors such as aliasing and multipath inteference. In order to produce useful range and intensity information it is necessary to remove these perturbations from the measurements. We review the known causes of non-linearity, namely aliasing, temporal variation in correlation waveform shape and mixed pixels/multipath inteference. We also introduce other sources of non-linearity, including crosstalk, modulation waveform envelope decay and non-circularly symmetric noise statistics, that have been ignored in the literature. An experimental study is conducted to evaluate techniques for mitigation of non-linearity, and it is found that harmonic cancellation provides a significant improvement in phase and amplitude linearity
Visibility Constrained Generative Model for Depth-based 3D Facial Pose Tracking
In this paper, we propose a generative framework that unifies depth-based 3D
facial pose tracking and face model adaptation on-the-fly, in the unconstrained
scenarios with heavy occlusions and arbitrary facial expression variations.
Specifically, we introduce a statistical 3D morphable model that flexibly
describes the distribution of points on the surface of the face model, with an
efficient switchable online adaptation that gradually captures the identity of
the tracked subject and rapidly constructs a suitable face model when the
subject changes. Moreover, unlike prior art that employed ICP-based facial pose
estimation, to improve robustness to occlusions, we propose a ray visibility
constraint that regularizes the pose based on the face model's visibility with
respect to the input point cloud. Ablation studies and experimental results on
Biwi and ICT-3DHP datasets demonstrate that the proposed framework is effective
and outperforms completing state-of-the-art depth-based methods
Laser Based Mid-Infrared Spectroscopic Imaging – Exploring a Novel Method for Application in Cancer Diagnosis
A number of biomedical studies have shown that mid-infrared spectroscopic images can provide
both morphological and biochemical information that can be used for the diagnosis of cancer. Whilst
this technique has shown great potential it has yet to be employed by the medical profession. By
replacing the conventional broadband thermal source employed in modern FTIR spectrometers with
high-brightness, broadly tuneable laser based sources (QCLs and OPGs) we aim to solve one of the
main obstacles to the transfer of this technology to the medical arena; namely poor signal to noise
ratios at high spatial resolutions and short image acquisition times. In this thesis we take the first
steps towards developing the optimum experimental configuration, the data processing algorithms
and the spectroscopic image contrast and enhancement methods needed to utilise these high
intensity laser based sources. We show that a QCL system is better suited to providing numerical
absorbance values (biochemical information) than an OPG system primarily due to the QCL pulse
stability. We also discuss practical protocols for the application of spectroscopic imaging to cancer
diagnosis and present our spectroscopic imaging results from our laser based spectroscopic imaging
experiments of oesophageal cancer tissue
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