New scanning gonio-photometer for extended BRTF measurements

Apian-Bennewitz, Peter

doi:10.1117/12.860889

Cited by 27 publications

(18 citation statements)

References 9 publications

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“…A more comprehensive description of the directional distribution of retro-reflected light can be expressed by the Bidirectional Scattering distribution function (BSDF), describing the radiative flux between any pair of incident and outgoing scattered direction [17][18][19][20]. However, such directionally resolved characterization of retro-reflection employing gonio-photometers is a particular challenge, since light source and detector occlude each other if incident and outgoing direction are close to equal (Fig.…”

Section: Measurement Techniquesmentioning

confidence: 99%

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Characterization and data-driven modeling of a retro-reflective coating in Radiance

Grobe

2018

Energy and Buildings

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a b s t r a c tRetro-reflective coatings applied to blinds of reduced geometric complexity promise to provide view to the outside while effectively controlling solar gains and glare. To characterize the reflection characteristics of such coatings over the entire solar spectrum, a novel extension to a scanning gonio-photometer is developed. The extended instrument is tested and applied to measure a coating's Bidirectional Reflection Distribution Function including the region of the retro-reflected peak. The measured datasets are compiled into a data-driven reflection model for the daylight simulation software Radiance. This model is applied to illustrate the coating's effect in a comparison to purely diffuse and specular surface finishes on geometrically identical, flat blinds. Daylight supply, the probability of glare, and solar gains are assessed for an exemplary, South-oriented office under sunny sky conditions. The results indicate the potential of the coating to effectively shade direct sunlight even if applied on blinds with minimalistic geometries. The modeling technique is shown to be a general means to replicate the irregular optical properties of the coating, which cannot be represented by the standard models in daylight simulation software.

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Section: Measurement Techniquesmentioning

confidence: 99%

“…Second, under identical illumination conditions, light scattered by a sample introduced into the beam is recorded by the detector as irradiance E at direction (Â i , i , Â s , s ). BSDF and differential scattering function (DSF) are calculated [19] as:…”

Section: Measurement Of the Bsdfmentioning

confidence: 99%

Characterization and data-driven modeling of a retro-reflective coating in Radiance

Grobe

2018

Energy and Buildings

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“…Only two devices, also based on scanning methods, allow fenestration systems to be characterized spectrally, described in (Breitenbach, et al, 2001) and (Apian-Bennewitz, 2007), with a possibility to extend the wavelength to NIR for the latter. Because scanning cannot avoid the risk of missing transmission or reflection features between measured points, this approach often requires refinements in resolution for high light gradients and can thus become a time-consuming process.…”

Section: Us Energy Consumption (Us Department Of Energy 2006)mentioning

confidence: 99%

Using digital imaging to assess spectral solar-optical properties of complex fenestration materials: A new approach in video–goniophotometry

et al. 2010

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A large variety of angularly selective fenestration systems has been developed in the past two decades and shows great potential in improving visual comfort while reducing energy consumption, especially when combined with spectrally selective properties. Such systems include light-redirecting glazing, shading, film coatings, reflectors and others. To assess the potential of these systems accurately and reliably, one needs to be able to predict in detail how they modify the energy, direction, and spectral make-up of solar radiation. For this assessment, spectral (wavelength-dependent) Bidirectional Transmission or Reflection Distribution Functions are used, usually referred to as BTDFs or BRDFs, or more generally BSDFs for Scattering Functions.To enable a faster, cheaper, and continuous investigation of these properties over most of the solar spectrum (400 to 1700 nm), an innovative goniospectrometric instrument has been created, relying on digital imaging, on light collection by an ellipsoidal half-transparent mirror, and on a filtering method in the visible range to generate spectral radiometric BSDFs. This so-called Heliodome instrument is described in this paper. It enables the performance of new fenestration technologies to be assessed in terms of lighting and solar gains management potential. The rotating table also serves as a heliodon, an architectural design tool for visualizing sunlight distribution inside a scale model and performing analyses on appropriate sun control strategies. The Heliodome's major innovations compared to other devices are to enable an analysis of both the visible and the near-infrared portions of the solar spectrum, to provide * Corresponding author: Prof.

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“…Not only TIR/TIT (Total Integrated Reflectance / Transmittance) [2] but also BRDF/BTDF (Bidirectional Reflection / Transmission Distribution Function) [3] is mainly measured in the scattering measurements.…”

Section: Introductionmentioning

confidence: 99%

“…Traditionally, BRDF/BTDF measurements are performed using goniometric systems [1] [3], which involve tilting and rotating a sample and/or a detector around the sample center in order to measure the BRDF/BTDF at selected points on the sphere around the sample, but these systems are relatively slow, potentially requiring hours to measure the sample. Nominally TIR/TIT measurements are made by integrating the BRDF/BTDF over a portion of the sphere around the sample, but actually they are measured using an integrating sphere [1] [2].…”

Section: Introductionmentioning

confidence: 99%

New Scatterometer for Spatial Distribution Measurements of Light Scattering from Materials

Kawate

Hain²

2012

Measurement Science Review

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A new scatterometer is composed of two ellipsoidal mirrors of revolution and an optical detection system. It enables us to absolutely measure diffuse reflectance and transmittance and to measure the spatial distribution of light scattering from almost all materials. The optical detection system has been developed both to measure total photo-intensity using a photodiode and to capture the imaging data using a CCD camera. This results in faster, more complete and often more accurate measurements than can be achieved with traditional goniometric methods and integrated sphere methods. The absolute total integrated reflectance and transmittance of well-known samples were measured and the spatial distribution of light scattering from a diffraction grating was captured and evaluated.

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New scanning gonio-photometer for extended BRTF measurements

Cited by 27 publications

References 9 publications

Characterization and data-driven modeling of a retro-reflective coating in Radiance

Characterization and data-driven modeling of a retro-reflective coating in Radiance

Using digital imaging to assess spectral solar-optical properties of complex fenestration materials: A new approach in video–goniophotometry

New Scatterometer for Spatial Distribution Measurements of Light Scattering from Materials

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