120 research outputs found
Challenges in using GPUs for the real-time reconstruction of digital hologram images
This is the pre-print version of the final published paper that is available from the link below.In-line holography has recently made the transition from silver-halide based recording media, with laser reconstruction, to recording with large-area pixel detectors and computer-based reconstruction. This form of holographic imaging is an established technique for the study of fine particulates, such as cloud or fuel droplets, marine plankton and alluvial sediments, and enables a true 3D object field to be recorded at high resolution over a considerable depth.
The move to digital holography promises rapid, if not instantaneous, feedback as it avoids the need for the time-consuming chemical development of plates or film film and a dedicated replay system, but with the growing use of video-rate holographic recording, and the desire to reconstruct fully every frame, the computational challenge becomes considerable. To replay a digital hologram a 2D FFT must be calculated for every depth slice desired in the replayed image volume. A typical hologram of ~100 μm particles over a depth of a few hundred millimetres will require O(10^3) 2D FFT operations to be performed on a hologram of typically a few million pixels.
In this paper we discuss the technical challenges in converting our existing reconstruction code to make efficient use of NVIDIA CUDA-based GPU cards and show how near real-time video slice reconstruction can be obtained with holograms as large as 4096 by 4096 pixels. Our performance to date for a number of different NVIDIA GPU running under both Linux and Microsoft Windows is presented. The recent availability of GPU on portable computers is discussed and a new code for interactive replay of digital holograms is presented
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POMPOMs: Cost-efficient polarity sensors for the MICE muon beamline
Copyright @ 2011 The AuthorsThe cooling effect in MICE (Muon Ionisation Cooling Experiment) will be studied with both positive and negative muons, reversing the electrical input to the magnets by physically swapping over the power leads. Ensuring the actual operating polarity of the beamline is correctly recorded is a manual step and at risk of error or omission. We have deployed a simple system for monitoring the operating polarity of the two bending magnets by placing in each dipole bore a Honeywell LOHET-II Hall-effect sensor that operates past saturation at nominal field strengths, and thus return one of two well-defined voltages corresponding to the two possible polarities of the magnet. The environment in the experimental hall is monitored by an AKCP securityProbe 5E system integrated into our EPICS-based controls and monitoring system. We read out the beamline polarity sensors using a voltmeter module, and translate the output voltage into a polarity (or alarm) state within EPICS whence it can be accessed by the operators and stored in the output datastream. Initial tests of the LOHET-II sensors indicate they will still be able to indicate beamline polarity after radiation doses of 900 Gy (Co60)
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GRID
Presentation at 39th MICE Collaboration Meeting (CM39), 25th-28th June 2014. https://indico.cern.ch/event/321200/timetable/ (Slides titled "Grid Status", updated 27th June 2014
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Data Extraction for Underwater Particle Holography
Presentation to ECE dept
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GRID Status
Presentation at 44th MICE Collaboration Meeting (CM44), 30th March - 1st April 2016. https://indico.cern.ch/event/485764/timetable/ (Slides titled "Grid Status"
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Status and Plans for Applications Monitoring
Talk at the UK CMS Collaboration Meeting 2004, University of Bristol, Bristol, UK; 1st-2nd July 200
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GRID Status
Presentation at 40th MICE Collaboration Meeting (CM40), 26th-29th October 2014. https://indico.cern.ch/event/331481/timetable/ Slides titled "Grid Status"
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Using the EVO Videoconferencing Workstation
User instructions for the EVO Videoconferencing Workstation in the BITlab Boardroo
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Underwater Particle Holography and Grid Middleware
Presentation to ECE dept
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A data extraction system for underwater particle holography
Pulsed laser holography is an extremely powerful technique for the study of particle fields as it allows instantaneous, noninvasive high-resolution recording of substantial volumes. By replaying the real image one can obtain the size, shape,
position and - if multiple exposures are made - velocity of every object in the recorded field. Manual analysis of large volumes containing thousands of particles is, however, an enormous and time-consuming task, with operator fatigue an
unpredictable source of errors. Clearly the value of holographic measurements also depends crucially on the quality of the reconstructed image: not only will poor resolution degrade size and shape measurements, but aberrations such as coma and astigmatism can change the perceived centroid of a particle, affecting position and velocity measurements.
For large-scale applications of particle field holography, specifically the in situ recording of marine plankton with 'HoloCam,' we have developed an automated data extraction system that can be readily switched between the in-line and off-axis geometries and provides optimised reconstruction from holograms recorded underwater. As a videocamera is automatically stepped through the 200 by 200 by 1000mm sample volume, image processing and object tracking routines locate and extract particle images for further classification by a separate software module
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