Creation and validation of Spectralon PTFE BRDF targets and standards

Durell, Christopher; Scharpf, Dan; McKee, Greg; L'Heureux, Michelle; Georgiev, G.; Obein, Gaël; Cooksey, Catherine C.

doi:10.1117/12.2195503

Cited by 4 publications

(3 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Likewise, the basic supervised vicarious calibration (SVC) method [138] does not consider the anisotropic nature of the hemispherical downwelling irradiance composed of the combined direct solar and anisotropic diffuse sky downwelling irradiance. It is well established that under theoretical conditions, with the solar zenith angle from near nadir (90 • ) to slightly off-nadir (60 • ), the biconical reflectance factor (BCRF) provides radiance that can be corrected by a reflectance factor measured upon a reflectance panel, e.g., SpectralonTM [139]. A part of the BCRF is a hemispherical-conical reflectance factors (HCRF) characterization of flat panel samples using an integrating sphere, which is a well-established technique from Nicodemus et al [140] All theoretical/laboratory approaches rely on the goniometric system and suggest applying a common ratio between HCRF (0 • ) and BCRF (45 • ), which was reported as a linear relationship by [141].…”

Section: Radiometric Processingmentioning

confidence: 99%

Current Practices in UAS-based Environmental Monitoring

et al. 2020

View full text Add to dashboard Cite

With the increasing role that unmanned aerial systems (UAS) are playing in data collection for environmental studies, two key challenges relate to harmonizing and providing standardized guidance for data collection, and also establishing protocols that are applicable across a broad range of environments and conditions. In this context, a network of scientists are cooperating within the framework of the Harmonious Project to develop and promote harmonized mapping strategies and disseminate operational guidance to ensure best practice for data collection and interpretation. The culmination of these efforts is summarized in the present manuscript. Through this synthesis study, we identify the many interdependencies of each step in the collection and processing chain, and outline approaches to formalize and ensure a successful workflow and product development. Given the number of environmental conditions, constraints, and variables that could possibly be explored from UAS platforms, it is impractical to provide protocols that can be applied universally under all scenarios. However, it is possible to collate and systematically order the fragmented knowledge on UAS collection and analysis to identify the best practices that can best ensure the streamlined and rigorous development of scientific products.

show abstract

Section: Radiometric Processingmentioning

confidence: 99%

Current Practices in UAS-based Environmental Monitoring

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The device is calibrated with a relative calibration method using Spectralon and the associated reference BRDF provided by Durell et al. [DSM*15]. We acquired the in‐plane BRDF of all samples with a sampling resolution of 10° in the incident domain (

\theta _{\text{in}}

) and dynamic resolution in the reflection domain (

\theta _{\text{out}}

).…”

Section: Methodsmentioning

confidence: 99%

Investigation and Simulation of Diffraction on Rough Surfaces

Clausen

Chen

Fuhrmann

et al. 2022

Computer Graphics Forum

View full text Add to dashboard Cite

Simulating light-matter interaction is a fundamental problem in computer graphics. A particular challenge is the simulation of light interaction with rough surfaces due to diffraction and multiple scattering phenomena. To properly model these phenomena, wave-optics have to be considered. Nevertheless, the most accurate BRDF models, including wave-optics, are computationally expensive, and the resulting renderings have not been systematically compared to real-world measurements. This work sheds more light on reflectance variations due to surface roughness. More specifically, we look at wavelength shifts that lead to reddish and blueish appearances. These wavelength shifts have been scarcely reported in the literature, and, in this paper, we provide the first thorough analysis from precise measured data. We measured the spectral in-plane BRDF of aluminium samples with varying roughness and further acquired the surface topography with a confocal microscope. The measurements show that the rough samples have, on average, a reddish and blueish appearance in the forward and back-scattering, respectively. Our investigations conclude that this is a diffraction-based effect that dominates the overall appearance of the samples. Simulations using a virtual gonioreflectometer further confirm our claims. We propose a linear model that can closely fit such phenomena, where the slope of the wavelength shifts depends on the incident and reflection direction. Based on these insights, we developed a simple BRDF model based on the Cook-Torrance model that considers such wavelength shifts.

show abstract

“…The QE Pro has a signal‐to‐noise ratio of 1000:1 and a maximal non‐linearity of 0.5%. The calibration is done with a relative calibration method using a Spectralon diffuse reflectance standard in combination with reference BRDF measurements by Durell et al [DSM*15]. The BRDF acquired by the calibrated spectrometer deviates from the reference BRDF in averaged by 0.7%.…”

Section: Implementation Error Pathmentioning

confidence: 99%

Acquisition and Validation of Spectral Ground Truth Data for Predictive Rendering of Rough Surfaces

Clausen

Marroquim

Fuhrmann

2018

Computer Graphics Forum

View full text Add to dashboard Cite

Physically based rendering uses principles of physics to model the interaction of light with matter. Even though it is possible to achieve photorealistic renderings, it often fails to be predictive. There are two major issues: first, there is no analytic material model that considers all appearance critical characteristics; second, light is in many cases described by only 3 RGB‐samples. This leads to the problem that there are different models for different material types and that wavelength dependent phenomena are only approximated. In order to be able to analyze the influence of both problems on the appearance of real world materials, an accurate comparison between rendering and reality is necessary. Therefore, in this work, we acquired a set of precisely and spectrally resolved ground truth data. It consists of the precise description of a new developed reference scene including isotropic BRDFs of 24 color patches, as well as the reference measurements of all patches under 13 different angles inside the reference scene. Our reference data covers rough materials with many different spectral distributions and various illumination situations, from direct light to indirect light dominated situations.

show abstract

Creation and validation of Spectralon PTFE BRDF targets and standards

Cited by 4 publications

References 2 publications

Current Practices in UAS-based Environmental Monitoring

Current Practices in UAS-based Environmental Monitoring

Investigation and Simulation of Diffraction on Rough Surfaces

Acquisition and Validation of Spectral Ground Truth Data for Predictive Rendering of Rough Surfaces

Contact Info

Product

Resources

About