نتایج جستجو برای: radiance
تعداد نتایج: 3741 فیلتر نتایج به سال:
Improved measurements of the foreign-broadened continuum of water vapor in the 6.3 μm band at -30 °C
Atmospheric emission in the 2 band of water vapor by the foreign-broadened continuum (1300-2000 cm -1 ) is important for retrievals of upper tropospheric water vapor. Previous work reported continuum coefficients retrieved from two downwelling emission measurements made with the Polar Atmospheric Emitted Radiance Interferometer (PAERI) at temperatures characteristic of the upper troposphere (be...
Using hyperspectral measurements made in the field, we show that the effective sea-surface reflectance ρ (defined as the ratio of the surface-reflected radiance at the specular direction corresponding to the downwelling sky radiance from one direction) varies not only for different measurement scans, but also can differ by a factor of 8 between 400 nm and 800 nm for the same scan. This means th...
We report on super-radiance obtained from the TAU FEM just above waveguide cutoff and near grazing intersection. Grazing intersection (or ‘‘Zero Slippage’’) is defined as the point at which the two synchronous frequencies merge to one frequency. In this case, the radiated power frequency can be tuned over a very wide band by change of the premodulation frequency. Near the lower synchronous freq...
An analysis is performed to determine the accuracy with which an ac heterodyne lateral shear interferometer can measure wavefront aberrations if a white light extended source is used with the interferometer, and shot noise is the predominate noise source. The analysis shows that for uniform circular or square sources larger than a derived minimum size, the wavefront measurement accuracy depends...
We present a framework for progressive and interactive rendering with soft shadows and indirect illumination of a triangulated scene. Our method is a multi-pass algorithm that separates the rendering of each main component of radiance in order to update the image as fast as new samples are computed. Those radiance samples are computed at the vertices of multiple recursively subdivided meshes, a...
We propose a novel remote sensing technique that infers the three-dimensional wave form and radiance of oceanic sea states via a variational stereo imagery formulation. In this setting, the shape and radiance of the wave surface are minimizers of a composite cost functional which combines a data fidelity term and smoothness priors on the unknowns. The solution of a system of coupled partial dif...
The Parallel Virtual Machine (PVM) tool has been used for a distributed implementation of Greg Ward’s Radiance code. In order to generate exactly the same primary rays with both the sequential and the parallel codes, the quincunx sampling technique used in Radiance for the reduction of the number of primary rays by interpolation, must be left untouched in the parallel implementation. The octree...
Since radiance in a vacuum remains constant along rays, the radiance in a scene’s free space can be represented as a real function over the space of maximal segments. This space is four dimensional and organized by the visibility complex. To date only the 0-D and 1-D cells of the visibility complex have been constructed and implemented. In order to use this topological space to support radiance...
Comparison of atmospheric spectral radiance measurements from five independently calibrated systems.
A variety of instruments have been developed over the past 50 years to measure spectral radiance in absolute units at UV and visible wavelengths with high spectral resolution. While there is considerable experience in the measurement of spectral irradiance, less emphasis has been given to the reliable measurement of spectral radiance from ground observations. We discuss the methodology and cali...
Forward and adjoint Monte Carlo (MC) models of radiance are proposed for use in model-based quantitative photoacoustic tomography. A two-dimensional (2-D) radiance MC model using a harmonic angular basis is introduced and validated against analytic solutions for the radiance in heterogeneous media. A gradient-based optimization scheme is then used to recover 2-D absorption and scattering coeffi...
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