Active-illumination extension to the Priest and Meier pBRDF.

This paper develops a 3D vector solution for the scattering of partially coherent laser-beam illumination from statistically rough surfaces. Such a solution enables a rigorous comparison to the well-known Priest and Meier polarimetric bidirectional reflectance distribution function (pBRDF) [Opt. Eng.

Solar cell BRDF measurement and modeling with out-of-plane data.

In this work, a CCD-augmented complete angle scatter instrument (CASI) with a visible red laser source was used to measure the BRDF of a commercially available solar cell designed for small satellites, simultaneously capturing both in-plane and out-of-plane data with high angular resolution surrounding the specular direction. The measurements exhibited three distinct scatter features: a central specular peak, an offset specular peak, and a diffraction pattern. The two peaks were caused by different material surfaces with slightly different normal directions, and the diffraction pattern arose from periodically-spaced metal conducting bars running in one direction across the solar cell surface.

Use of a novel infrared wavelength-tunable laser Mueller-matrix polarimetric scatterometer to measure nanostructured optical materials.

Nanostructured optical materials, for example, metamaterials, have unique spectral, directional, and polarimetric properties. Samples designed and fabricated for infrared (IR) wavelengths have been characterized using broadband instruments to measure specular polarimetric transmittance or reflectance as in ellipsometry or integrated hemisphere transmittance or reflectance. We have developed a wavelength-tunable IR Mueller-matrix (Mm) polarimetric scatterometer which uses tunable external-cavity quantum-cascade lasers (EC-QCLs) to tune onto and off of the narrowband spectral resonances of nanostructured optical materials and performed full polarimeteric and directional evaluation to more fully characterize their behavior.

Three-dimensional imaging of trapped cold atoms with a light field microscope.

This research images trapped atoms in three dimensions, utilizing light field imaging. Such a system is of interest in the development of atom interferometer accelerometers in dynamic systems where strictly defined focal planes may be impractical. In this research, a light field microscope was constructed utilizing a Lytro Development Kit micro lens array and sensor.

Comparison of microfacet BRDF model to modified Beckmann-Kirchhoff BRDF model for rough and smooth surfaces.

A popular class of BRDF models is the microfacet models, where geometric optics is assumed. In contrast, more complex physical optics models may more accurately predict the BRDF, but the calculation is more resource intensive. These seemingly disparate approaches are compared in detail for the rough and smooth surface approximations of the modified Beckmann-Kirchhoff BRDF model, assuming Gaussian surface statistics.

Effects of a measurement floor on Mueller matrix measurements in a dual rotating retarder polarimeter bidirectional scatter distribution function system.

Since a measurement of the bidirectional scatter distribution function (BSDF) of a material is proportional to the intensity of the scattered light, a BSDF measurement system with the addition of a dual rotating retarder polarimeter can be used to calculate the Mueller matrix of a scatterer. One advantage of a BSDF system using a laser source is its large dynamic range, which allows the measurement of scattered light both near to and away from the specular region. As BSDF measurements move away from the specular region and into a more diffuse-scatter region, the measured signal decreases and may approach the system's measurement floor.

Experimental analysis of bidirectional reflectance distribution function cross section conversion term in direction cosine space.

Of the many classes of bidirectional reflectance distribution function (BRDF) models, two popular classes of models are the microfacet model and the linear systems diffraction model. The microfacet model has the benefit of speed and simplicity, as it uses geometric optics approximations, while linear systems theory uses a diffraction approach to compute the BRDF, at the expense of greater computational complexity. In this Letter, nongrazing BRDF measurements of rough and polished surface-reflecting materials at multiple incident angles are scaled by the microfacet cross section conversion term, but in the linear systems direction cosine space, resulting in great alignment of BRDF data at various incident angles in this space.

Design considerations regarding ellipsoidal mirror based reflectometers.

Hemi-ellipsoidal mirrors are used in reflection-based measurements due to their ability to collect light scattered from one focal point at the other. In this paper, a radiometric model of this energy transfer is derived for arbitrary mirror and detector geometries. This model is used to examine the imaging characteristics of the mirror away from focus for both diffuse and specular light.

Path-averaged Cn2 estimation using a laser-and-corner-cube system.

As a finite cross-section laser beam propagates through the atmosphere, the beam spreads due to both diffraction and atmospheric turbulence effects. Using turbulence theory valid in both weak and strong optical turbulence regimes, a relationship between atmospheric beam spread and the resulting return power for an optical system and the refractive-index structure parameter or Cn2 can be established. A technique for estimating the path-averaged Cn2 using a laser-and-corner-cube system based on this relationship is described.