1,477 research outputs found
Simultaneous multiplane imaging with reverberation multiphoton microscopy
Multiphoton microscopy (MPM) has gained enormous popularity over the years for its capacity to provide high resolution images from deep within scattering samples1. However, MPM is generally based on single-point laser-focus scanning, which is intrinsically slow. While imaging speeds as fast as video rate have become routine for 2D planar imaging, such speeds have so far been unattainable for 3D volumetric imaging without severely compromising microscope performance. We demonstrate here 3D volumetric (multiplane) imaging at the same speed as 2D planar (single plane) imaging, with minimal compromise in performance. Specifically, multiple planes are acquired by near-instantaneous axial scanning while maintaining 3D micron-scale resolution. Our technique, called reverberation MPM, is well adapted for large-scale imaging in scattering media with low repetition-rate lasers, and can be implemented with conventional MPM as a simple add-on.Accepted manuscrip
Optical patterning of trapped charge in nitrogen-doped diamond
The nitrogen-vacancy (NV) centre in diamond is emerging as a promising
platform for solid-state quantum information processing and nanoscale
metrology. Of interest in these applications is the manipulation of the NV
charge, which can be attained by optical excitation. Here we use two-color
optical microscopy to investigate the dynamics of NV photo-ionization, charge
diffusion, and trapping in type-1b diamond. We combine fixed-point laser
excitation and scanning fluorescence imaging to locally alter the concentration
of negatively charged NVs, and to subsequently probe the corresponding
redistribution of charge. We uncover the formation of spatial patterns of
trapped charge, which we qualitatively reproduce via a model of the interplay
between photo-excited carriers and atomic defects. Further, by using the NV as
a probe, we map the relative fraction of positively charged nitrogen upon
localized optical excitation. These observations may prove important to
transporting quantum information between NVs or to developing
three-dimensional, charge-based memories
A high-resolution full-field range imaging system
There exist a number of applications where the range to all objects in a field of view needs to be obtained. Specific examples include obstacle avoidance for autonomous mobile robots, process automation in assembly factories, surface profiling for shape analysis, and surveying. Ranging systems can be typically characterized as being either laser scanning systems where a laser point is sequentially scanned over a scene or a full-field acquisition where the range to every point in the image is simultaneously obtained. The former offers advantages in terms of range resolution, while the latter tend to be faster and involve no moving parts. We present a system for determining the range to any object within a camera's field of view, at the speed of a full-field system and the range resolution of some point laser scans. Initial results obtained have a centimeter range resolution for a 10 second acquisition time. Modifications to the existing system are discussed that should provide faster results with submillimeter resolution
AZIMUTH ORIENTATION CALIBRATION FOR HIGH PRECISION AUTONOMOUS DEVICES
A calibration technique that aligns the azimuth of a high-precision,
autonomous device uses a point laser for each wheel and a target template to adjust the
azimuth laser of the device
Automatic Road Survey by Using Vehicle Mounted Point Laser for Local Road Management
In most countries local roads (i.e., urban and rural) form over 80% of the entire road network and constitute the country's largest asset value. In order for local roads to remain fit for purpose and maintain their value, they require periodic maintenance. To make the best use of scarce maintenance resources, road maintenance needs to be preventative which requires the condition of the road to be assessed periodically. Traditional road surveys suffer from the lack of repeatability and reproducibility, are high cost and time consuming. This work proposes a vehicle mounted point laser system for the automated, rapid and inexpensive measurement of a major mode of local road deterioration, namely fretting. Compared to other technologies such as Ground Penetrating Radar (GPR), visual sensors and the Mobile Laser Scanning (MLS) system, the point laser requires less computational power, is less sensitive to the surrounding environment and is of comparatively low cost. A robust approach is proposed which consists of a number of pre-processing algorithms to deal with noise and the effects of the vehicles dynamic motion, and a signal processing algorithm which analyses histograms of the distance from the road surface measured by the laser to account for changes in road texture. Road fretting measured by the proposed system on a variety of roads is compared with fretting determined using a standard visual assessment process. The results indicate that the proposed system can measure road fretting to the levels of detail which are suitable for planning, programming and preparations road management functions
Single-channel laser Doppler vibrometers integrated on silicon-on-insulator (SOI)
Multi-location velocity measurements of a vibrating surface are of interest recently. By scanning the laser beam of a single-point laser Doppler vibrometer (LDV) across the surface of interest, one can realize the multi-location vibration measurement. However, the recovered velocity values of different locations are not obtained at the same time. In many applications, such as measuring the aortic pulse wave velocity, simultaneous velocity measurements for different locations are required. Multi-channel LDVs can be used in this case, in which multiple laser beams are generated and sent to the surface of interest simultaneously. However, the complexity of realizing the multiple interferometers in a bulk LDV system will increase as the number of channels increases, and thus it is very hard to realize a bulk LDV with many channels
We propose to use the silicon-on-insulator (SOI) chip as a platform of the multi-channel interferometers. With the help of silicon photonics and CMOS technology, multiple interferometers can be miniaturized and fabricated on SOI chips. Laser beams are sent into or out of the chip through optimized on-chip grating couplers, with the coupling insertion loss of less than 2 dB per coupler. The total footprint of the integrated multiple interferometers can be very small (several square of millimetres) compared to a bulk LDV system. The cost of the chips will be dramatically decreased for mass production. Additionally, the stability of the integrated interferometers is much better than that of the interferometer built with discrete optical components
Overview of Solid Target Studies for a Neutrino Factory
The UK programme of high power target developments for a Neutrino Factory is centred on the study of high-Z materials (tungsten, tantalum). A description of lifetime shock tests on candidate materials is given as part of the research into a solid target solution. A fast high current pulse is applied to a thin wire of the sample material and the lifetime measured from the number of pulses before failure. These measurements are made at temperatures up to ~2000 K. The stress on the wire is calculated using the LS-DYNA code and compared to the stress expected in the real Neutrino Factory target. It has been found that tantalum is too weak to sustain prolonged stress at these temperatures but a tungsten wire has reached over 26 million pulses (equivalent to more than ten years of operation at the Neutrino Factory). An account is given of the optimisation of secondary pion production from the target and the issues related to mounting the target in the muon capture solenoid and target station are discussed
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