5,654 research outputs found
Optically gated beating-heart imaging
The constant motion of the beating heart presents an obstacle to clear optical imaging, especially 3D imaging, in small animals where direct optical imaging would otherwise be possible. Gating techniques exploit the periodic motion of the heart to computationally "freeze" this movement and overcome motion artefacts. Optically gated imaging represents a recent development of this, where image analysis is used to synchronize acquisition with the heartbeat in a completely non-invasive manner. This article will explain the concept of optical gating, discuss a range of different implementation strategies and their strengths and weaknesses. Finally we will illustrate the usefulness of the technique by discussing applications where optical gating has facilitated novel biological findings by allowing 3D in vivo imaging of cardiac myocytes in their natural environment of the beating heart
3D + time blood flow mapping using SPIM-microPIV in the developing zebrafish heart
We present SPIM-μPIV as a flow imaging system, capable of measuring in vivo flow information with 3D micron-scale resolution. Our system was validated using a phantom experiment consisting of a flow of beads in a 50 μm diameter FEP tube. Then, with the help of optical gating techniques, we obtained 3D + time flow fields throughout the full heartbeat in a ∼3 day old zebrafish larva using fluorescent red blood cells as tracer particles. From this we were able to recover 3D flow fields at 31 separate phases in the heartbeat. From our measurements of this specimen, we found the net pumped blood volume through the atrium to be 0.239 nL per beat. SPIM-μPIV enables high quality in vivo measurements of flow fields that will be valuable for studies of heart function and fluid-structure interaction in a range of small-animal models
Multi-purpose SLM-light-sheet microscope
By integrating a phase-only Spatial Light Modulator (SLM) into the
illumination arm of a cylindrical-lens-based Selective Plane Illumination
Microscope (SPIM), we have created a versatile system able to deliver high
quality images by operating in a wide variety of different imaging modalities.
When placed in a Fourier plane, the SLM permits modulation of the microscope's
light-sheet to implement imaging techniques such as structured illumination,
tiling, pivoting, autofocusing and pencil beam scanning. Previous publications
on dedicated microscope setups have shown how these techniques can deliver
improved image quality by rejecting out-offocus light (structured illumination
and pencil beam scanning), reducing shadowing (light-sheet pivoting), and
obtaining a more uniform illumination by moving the highest-resolution region
of the light-sheet across the imaging Field of View (tiling). Our SLM-SPIM
configuration is easy to build and use, and has been designed to allow all of
these techniques to be employed on one optical setup compatible with the
OpenSPIM design. It also offers the possibility to choose between three
different light-sheets, in thickness and height, which can be selected
according to the characteristics of the sample and the imaging technique to be
applied. We demonstrate the flexibility and performance of the system with
results obtained by applying a variety of different imaging techniques on
samples of fluorescent beads, Zebrafish embryos, and optically cleared whole
mouse brain samples. Thus our approach allows easy implementation of advanced
imaging techniques while retaining the simplicity of a cylindrical-lens-based
light-sheet microscope
Adaptive foveated single-pixel imaging with dynamic super-sampling
As an alternative to conventional multi-pixel cameras, single-pixel cameras
enable images to be recorded using a single detector that measures the
correlations between the scene and a set of patterns. However, to fully sample
a scene in this way requires at least the same number of correlation
measurements as there are pixels in the reconstructed image. Therefore
single-pixel imaging systems typically exhibit low frame-rates. To mitigate
this, a range of compressive sensing techniques have been developed which rely
on a priori knowledge of the scene to reconstruct images from an under-sampled
set of measurements. In this work we take a different approach and adopt a
strategy inspired by the foveated vision systems found in the animal kingdom -
a framework that exploits the spatio-temporal redundancy present in many
dynamic scenes. In our single-pixel imaging system a high-resolution foveal
region follows motion within the scene, but unlike a simple zoom, every frame
delivers new spatial information from across the entire field-of-view. Using
this approach we demonstrate a four-fold reduction in the time taken to record
the detail of rapidly evolving features, whilst simultaneously accumulating
detail of more slowly evolving regions over several consecutive frames. This
tiered super-sampling technique enables the reconstruction of video streams in
which both the resolution and the effective exposure-time spatially vary and
adapt dynamically in response to the evolution of the scene. The methods
described here can complement existing compressive sensing approaches and may
be applied to enhance a variety of computational imagers that rely on
sequential correlation measurements.Comment: 13 pages, 5 figure
Feasibility of a trapped atom interferometer with accelerating optical traps
In order to increase the measured phase of an atom interferometer and improve
its sensitivity, researchers attempt to increase the enclosed space-time area
using two methods: creating larger separations between the interferometer arms
and having longer evolution times. However, increasing the evolution time
reduces the bandwidth that can be sampled, whereas decreasing the evolution
time worsens the sensitivity. In this paper, we attempt to address this by
proposing a setup for high-bandwidth applications, with improved overall
sensitivity. This is realized by accelerating and holding the atoms using
optical dipole traps. We find that accelerations of up to -
m/s can be achieved using acousto-optic deflectors (AODs) to move the
traps. By comparing the sensitivity of our approach to acceleration as a
baseline to traditional atom interferometry, we find a substantial improvement
to the state of the art. In the limit of appropriate beam and optics
stabilization, sensitivities approaching 10 (m/s)/
may be achievable at 1 Hz, while detection at 1 kHz with a sensitivity an order
of magnitude better than traditional free-fall atom interferometers is possible
with today's systems.Comment: 25 pages. 9 figures. New subsection on achievable sensitivities
added. Some corrections of factors of 2 and \pi. Numerics update
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