272 research outputs found
3D Computational Ghost Imaging
Computational ghost imaging retrieves the spatial information of a scene
using a single pixel detector. By projecting a series of known random patterns
and measuring the back reflected intensity for each one, it is possible to
reconstruct a 2D image of the scene. In this work we overcome previous
limitations of computational ghost imaging and capture the 3D spatial form of
an object by using several single pixel detectors in different locations. From
each detector we derive a 2D image of the object that appears to be illuminated
from a different direction, using only a single digital projector as
illumination. Comparing the shading of the images allows the surface gradient
and hence the 3D form of the object to be reconstructed. We compare our result
to that obtained from a stereo- photogrammetric system utilizing multiple high
resolution cameras. Our low cost approach is compatible with consumer
applications and can readily be extended to non-visible wavebands.Comment: 13pages, 4figure
Machine learning and advanced data analytics automating the exploitation of Raman spectroscopy: From micro-scale to large-scale operation
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Simultaneous real-time visible and infrared video with single-pixel detectors
Conventional cameras rely upon a pixelated sensor to provide spatial resolution. An alternative approach replaces the sensor with a pixelated transmission mask encoded with a series of binary patterns. Combining knowledge of the series of patterns and the associated filtered intensities, measured by single-pixel detectors, allows an image to be deduced through data inversion. In this work we extend the concept of a ‘single-pixel camera’ to provide continuous real-time video at 10 Hz , simultaneously in the visible and short-wave infrared, using an efficient computer algorithm. We demonstrate our camera for imaging through smoke, through a tinted screen, whilst performing compressive sampling and recovering high-resolution detail by arbitrarily controlling the pixel-binning of the masks. We anticipate real-time single-pixel video cameras to have considerable importance where pixelated sensors are limited, allowing for low-cost, non-visible imaging systems in applications such as night-vision, gas sensing and medical diagnostics
Normalized ghost imaging
We present an experimental comparison between different iterative ghost imaging algorithms. Our experimental setup utilizes a spatial light modulator for generating known random light fields to illuminate a partially-transmissive object. We adapt the weighting factor used in the traditional ghost imaging algorithm to account for changes in the efficiency of the generated light field. We show that our normalized weighting algorithm can match the performance of differential ghost imaging
Fast full-color computational imaging with single-pixel detectors
Single-pixel detectors can be used as imaging devices by making use of structured illumination. These systems work by correlating a changing incident light field with signals measured on a photodiode to derive an image of an object. In this work we demonstrate a system that utilizes a digital light projector to illuminate a scene with approximately 1300 different light patterns every second and correlate these with the back scattered light measured by three spectrally-filtered single-pixel photodetectors to produce a full-color high-quality image in a few seconds of data acquisition. We utilize a differential light projection method to self normalize the measured signals, improving the reconstruction quality whilst making the system robust to external sources of noise. This technique can readily be extended for imaging applications at non-visible wavebands
Bipartite partial duals and circuits in medial graphs
It is well known that a plane graph is Eulerian if and only if its geometric
dual is bipartite. We extend this result to partial duals of plane graphs. We
then characterize all bipartite partial duals of a plane graph in terms of
oriented circuits in its medial graph.Comment: v2: minor changes. To appear in Combinatoric
Astro2020 Project White Paper: The Cosmic Accelerometer
We propose an experiment, the Cosmic Accelerometer, designed to yield
velocity precision of cm/s with measurement stability over years to
decades. The first-phase Cosmic Accelerometer, which is at the scale of the
Astro2020 Small programs, will be ideal for precision radial velocity
measurements of terrestrial exoplanets in the Habitable Zone of Sun-like stars.
At the same time, this experiment will serve as the technical pathfinder and
facility core for a second-phase larger facility at the Medium scale, which can
provide a significant detection of cosmological redshift drift on a 6-year
timescale. This larger facility will naturally provide further detection/study
of Earth twin planet systems as part of its external calibration process. This
experiment is fundamentally enabled by a novel low-cost telescope technology
called PolyOculus, which harnesses recent advances in commercial off the shelf
equipment (telescopes, CCD cameras, and control computers) combined with a
novel optical architecture to produce telescope collecting areas equivalent to
standard telescopes with large mirror diameters. Combining a PolyOculus array
with an actively-stabilized high-precision radial velocity spectrograph
provides a unique facility with novel calibration features to achieve the
performance requirements for the Cosmic Accelerometer
Kepler Mission Stellar and Instrument Noise Properties
Kepler Mission results are rapidly contributing to fundamentally new
discoveries in both the exoplanet and asteroseismology fields. The data
returned from Kepler are unique in terms of the number of stars observed,
precision of photometry for time series observations, and the temporal extent
of high duty cycle observations. As the first mission to provide extensive time
series measurements on thousands of stars over months to years at a level
hitherto possible only for the Sun, the results from Kepler will vastly
increase our knowledge of stellar variability for quiet solar-type stars. Here
we report on the stellar noise inferred on the timescale of a few hours of most
interest for detection of exoplanets via transits. By design the data from
moderately bright Kepler stars are expected to have roughly comparable levels
of noise intrinsic to the stars and arising from a combination of fundamental
limitations such as Poisson statistics and any instrument noise. The noise
levels attained by Kepler on-orbit exceed by some 50% the target levels for
solar-type, quiet stars. We provide a decomposition of observed noise for an
ensemble of 12th magnitude stars arising from fundamental terms (Poisson and
readout noise), added noise due to the instrument and that intrinsic to the
stars. The largest factor in the modestly higher than anticipated noise follows
from intrinsic stellar noise. We show that using stellar parameters from
galactic stellar synthesis models, and projections to stellar rotation,
activity and hence noise levels reproduces the primary intrinsic stellar noise
features.Comment: Accepted by ApJ; 26 pages, 20 figure
Solution fibre spinning technique for the fabrication of tuneable decellularised matrix-laden fibres and fibrous micromembranes.
UNLABELLED: Recreating tissue-specific microenvironments of the extracellular matrix (ECM) in vitro is of broad interest for the fields of tissue engineering and organ-on-a-chip. Here, we present biofunctional ECM protein fibres and suspended membranes, with tuneable biochemical, mechanical and topographical properties. This soft and entirely biologic membrane scaffold, formed by micro-nano-fibres using low voltage electrospinning, displays three unique characteristics for potential cell culture applications: high-content of key ECM proteins, single-layered mesh membrane, and flexibility for in situ integration into a range of device setups. Extracellular matrix (ECM) powder derived from urinary bladder, was used to fabricate the ECM-laden fibres and membranes. The highest ECM concentration in the dry protein fibre was 50 wt%, with the rest consisting of gelatin. Key ECM proteins, including collagen IV, laminin, and fibronectin, were shown to be preserved post the biofabrication process. The single fibre tensile Young's modulus can be tuned for over two orders of magnitude between ∼600 kPa and 50 MPa depending on the ECM content. Combining the fibre mesh printing with 3D printed or microfabricated structures, culture devices were constructed for endothelial layer formation, and a trans-membrane co-culture formed by glomerular cell types of podocytes and glomerular endothelial cells, demonstrating feasibility of the membrane culture. Our cell culture observation points to the importance of membrane mechanical property and re-modelling ability as a factor for soft membrane-based cell cultures. The ECM-laden fibres and membranes presented here would see potential applications in in vitro assays, and tailoring structure and biological functions of tissue engineering scaffolds. STATEMENT OF SIGNIFICANCE: Recreating tissue-specific microenvironments of the extracellular matrix (ECM) is of broad interest for the fields of tissue engineering and organ-on-a-chip. Both the biochemical and biophysical signatures of the engineered ECM interplay to affect cell response. Currently, there are limited biomaterials processing methods which allow to design ECM membrane properties flexibly and rapidly. Solvents and additives used in many existing processes also induced unwanted ECM protein degradation and toxic residues. This paper presents a solution fibre spinning technique, where careful selection of the solution combination led to well-preserved ECM proteins with tuneable composition. This technique also provides a highly versatile approach to fabricate ECM fibres and membranes, leading to designable fibre Young's modulus for over two orders of magnitude.This work is supported by the Engineering and Physical Sciences Research Council (EPSRC) UK (EP/M018989/1) and European Research Council (ERC-StG, 758865). The authors thank the studentship and funding supports from the EPSRC DTA (Z.L.), the WD Armstrong Trust (I.M.L), the Swiss National Science Foundation (P300P2_171219) and the Centre for Misfolding Disease of the University of Cambridge (F.S.R.)
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