A high resolution set up devoted to the measurement of the Bidirectional Reflectance Distribution Function around the specular peak, at LNE-CNAM

Ouarets, Shiraz; Leroux, Thierry; Rougié, B.; Razet, Annick; Obein, Gaël

doi:10.1051/metrology/201314008

Cited by 14 publications

(14 citation statements)

References 2 publications

(1 reference statement)

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“…We used our Conoscopic Device for Optical Reflectometry (ConDOR) [Ouarets, 2013]. ConDOR is a goniospectrophotometer composed of a mobile illumination system embedded on a 2 m diameter ring, a 6-axis robot as sample holder and an immobile detection (figure 2).…”

Section: Measurement Devicementioning

confidence: 99%

What Is the True Width and Height of the Specular Peak According the Level of Gloss?

Rabal¹,

Ged²,

Obein³

2019

PROCEEDINGS OF the 29th Quadrennial Session of the CIE

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When evaluating the gloss of a surface, observers always look in and around the specular direction. Thus, the specular peak contains information connected with gloss. In order to progress in the comprehension and measurement of gloss, it could be therefore useful to study it. But this peak is narrow and not all measurement devices have the proper optical settings to access the peak. Using a dedicated goniospectrophotometer, we have measured the specular peak of a commercial gloss scale with samples varying from matt to full glossy. From these traceable and metrological measurements, we clarified the settings requested to access a reliable BRDF of the surface in the specular direction, according to its gloss level measured with a classical glossmeter. For gloss values higher than 60 GU, the angular resolution of the measurement setup should be lower than 0.05° to ensure proper BRDF measurement.

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Section: Measurement Devicementioning

confidence: 99%

What Is the True Width and Height of the Specular Peak According the Level of Gloss?

Rabal¹,

Ged²,

Obein³

2019

PROCEEDINGS OF the 29th Quadrennial Session of the CIE

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“…The photo series below gives an overview of the variety of the different set-ups and measurement concepts. The facilities (a) to (d) are robot-based set-ups where the device under test is mounted to the robotic-hand of small industrial robots, giving the flexibility for arbitrary orientation in three-dimensional space [18][19][20]. Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 11/6/2018 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use The facilities (e) to (g) are built by mounting different rotation and translation stages together in order to realize the required degrees of freedom for the measurement of the devices under test [21,22].…”

Section: Inter-laboratory Comparison Of Standard Goniometric Geometriesmentioning

confidence: 99%

"Multidimensional reflectometry for industry" (xD-Reflect) an European research project

et al. 2014

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The European Metrology Research Program (EMRP) is a metrology-focused program of coordinated Research & Development (R&D) funded by the European Commission and participating countries within the European Association of National Metrology Institutes (EURAMET). It supports and ensures research collaboration between them by launching and managing different types of project calls. Within the EMRP Call 2012 "Metrology for Industry", the joint research project (JRP) entitled "Multidimensional Reflectometry for Industry" (xD-Reflect) was submitted by a consortium of 8 National Metrology Institutes (NMIs) and 2 universities and was subsequently funded. The general objective of xD-Reflect is to meet the demands from industry to describe the overall macroscopic appearance of modern surfaces by developing and improving methods for optical measurements which correlate with the visual sensation being evoked. In particular, the project deals with the "Goniochromatism", "Gloss" and "Fluorescence" properties of dedicated artifacts, which will be investigated in three main work packages (WP). Two additional transversal WP reinforce the structure: "Modelling and Data Analysis" with the objective to give an irreducible set of calibration schemes and handling methods and "Visual Perception", which will produce perception scales for the different visual attributes. Multidimensional reflectometry involves the enhancement of spectral and spatial resolution of reference gonioreflectometers for BRDF measurements using modern detectors, conoscopic optical designs, CCD cameras, line scan cameras, and modern light sources in order to describe new effects like sparkle and graininess/coarseness. More information and updated news concerning the project can be found on the xD-Reflect website http://www.xdreflect.eu/.

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“…At the highest level, most of the National Metrological Institutes (NMIs) are equipped today with primary goniospectrophotometers to ensure the traceability of BRDF measurements [3][4][5][6][7][8][9][10][11]. Comparisons of BRDF scales between NMIs is an actual work in progress, in order to ensure that the BRDF, as a quantity, is well defined.…”

Section: Introductionmentioning

confidence: 99%

Metrological issues related to BRDF measurements around the specular direction in the particular case of glossy surfaces

et al. 2015

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Among the complete bidirectional reflectance distribution function (BRDF), visual gloss is principally related to physical reflection characteristics located around the specular reflection direction. This particular part of the BRDF is usually referred to as the specular peak. A good starting point for the physical description of gloss could be to measure the reflection properties around this specular peak. Unfortunately, such a characterization is not trivial, since for glossy surfaces the width of the specular peak can become very narrow (typically a full width at half maximum inferior to 0.5° is encountered). In result, new BRDF measurement devices with a very small solid angle of detection are being introduced. Yet, differences in the optical design of BRDF measurement instruments engender different measurement results for the same specimen, complicating direct comparison of the measurement results.This issue is addressed in this paper. By way of example, BRDF measurement results of two samples, one being matte and the other one glossy, obtained by use of two high level goniospectrophotometers with a different optical design, are described. Important discrepancies in the results of the glossy sample are discussed. Finally, luminance maps obtained from renderings with the acquired BRDF data are presented, exemplifying the large visual differences that might be obtained. This stresses the metrological aspects that must be known for using BRDF data. Indeed, the comprehension of parameters affecting the measurement results is an inevitable step towards progress in the metrology of surface gloss, and thus towards a better metrology of appearance in general.

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A high resolution set up devoted to the measurement of the Bidirectional Reflectance Distribution Function around the specular peak, at LNE-CNAM

Cited by 14 publications

References 2 publications

What Is the True Width and Height of the Specular Peak According the Level of Gloss?

What Is the True Width and Height of the Specular Peak According the Level of Gloss?

"Multidimensional reflectometry for industry" (xD-Reflect) an European research project

Metrological issues related to BRDF measurements around the specular direction in the particular case of glossy surfaces

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