90,805 research outputs found
Light-sheet microscopy: a tutorial
This paper is intended to give a comprehensive review of light-sheet (LS) microscopy from an optics perspective. As such, emphasis is placed on the advantages that LS microscope configurations present, given the degree of freedom gained by uncoupling the excitation and detection arms. The new imaging properties are first highlighted in terms of optical parameters and how these have enabled several biomedical applications. Then, the basics are presented for understanding how a LS microscope works. This is followed by a presentation of a tutorial for LS microscope designs, each working at different resolutions and for different applications. Then, based on a numerical Fourier analysis and given the multiple possibilities for generating the LS in the microscope (using Gaussian, Bessel, and Airy beams in the linear and nonlinear regimes), a systematic comparison of their optical performance is presented. Finally, based on advances in optics and photonics, the novel optical implementations possible in a LS microscope are highlighted.Peer ReviewedPostprint (published version
Adaptive Optics for Astronomy
Adaptive Optics is a prime example of how progress in observational astronomy
can be driven by technological developments. At many observatories it is now
considered to be part of a standard instrumentation suite, enabling
ground-based telescopes to reach the diffraction limit and thus providing
spatial resolution superior to that achievable from space with current or
planned satellites. In this review we consider adaptive optics from the
astrophysical perspective. We show that adaptive optics has led to important
advances in our understanding of a multitude of astrophysical processes, and
describe how the requirements from science applications are now driving the
development of the next generation of novel adaptive optics techniques.Comment: to appear in ARA&A vol 50, 201
Precision near-infrared radial velocity instrumentation II: Non-Circular Core Fiber Scrambler
We have built and commissioned a prototype agitated non-circular core fiber
scrambler for precision spectroscopic radial velocity measurements in the
near-infrared H band. We have collected the first on-sky performance and modal
noise tests of these novel fibers in the near-infrared at H and K bands using
the CSHELL spectrograph at the NASA InfraRed Telescope Facility (IRTF). We
discuss the design behind our novel reverse injection of a red laser for
co-alignment of star-light with the fiber tip via a corner cube and visible
camera. We summarize the practical details involved in the construction of the
fiber scrambler, and the mechanical agitation of the fiber at the telescope. We
present radial velocity measurements of a bright standard star taken with and
without the fiber scrambler to quantify the relative improvement in the
obtainable blaze function stability, the line spread function stability, and
the resulting radial velocity precision. We assess the feasibility of applying
this illumination stabilization technique to the next generation of
near-infrared spectrographs such as iSHELL on IRTF and an upgraded NIRSPEC at
Keck. Our results may also be applied in the visible for smaller core diameter
fibers where fiber modal noise is a significant factor, such as behind an
adaptive optics system or on a small < 1 meter class telescope such as is being
pursued by the MINERVA and LCOGT collaborations.Comment: Proceedings of the SPIE Optics and Photonics Conference "Techniques
and Instrumentation for Detection of Exoplanets VI" held in San Diego, CA,
August 25-29, 201
Tightly Coupled GNSS and Vision Navigation for Unmanned Air Vehicle Applications
This paper explores the unique benefits that can be obtained from a tight integration of a GNSS sensor and a forward-looking vision sensor. The motivation of this research is the belief that both GNSS and vision will be integral features of future UAV avionics architectures, GNSS for basic aircraft navigation and vision for obstacle-aircraft collision avoidance. The paper will show that utilising basic single-antenna GNSS measurements and observables, along with aircraft information derived from optical flow techniques creates unique synergies. Results of the accuracy of attitude estimates will be presented, based a comprehensive Matlab® Simulink® model which re-creates an optical flow stream based on the flight of an aircraft. This paper establishes the viability of this novel integrated GNSS/Vision approach for use as the complete UAV sensor package, or as a backup sensor for an inertial navigation system
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