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8 págs.; 7 figs., The spectral bidirectional reflectance distribution function (BRDF) is the key quantity to specify the spectral reflectance of materials for any condition of irradiation and detection, and its characterization is quite important for surfaces with a high dependence on these conditions, such as iridescent coatings. In order to evaluate the calibration and measurement capabilities (CMC) of National Metrology Institutes with the ability to measure the spectral BRDF, a case study interlaboratory comparison is in progress. Spectral BRDF has both spectral and geometric dependence, and this multidimensionality must be treated in the comparison to provide useful information to the participants about their CMCs. A data analysis method for the comparison is presented in this work, which was tested by simulations for different scenarios. The proposed method assesses whether the experimental data from each participant are consistent with those from the others. Finally, one-dimensional and multidimensional degrees of equivalence are defined, which should allow systematic deviations of spectral and geometric nature to be identified., This report was compiled within the EMRP IND52 Project xD-Reflect ‘Multidimensional reflectometry for industry’. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. Part of the authors (Instituto de Óptica ‘Daza de Valdés’, Agencia Estatal CSIC) are also grateful to Comunidad de Madrid for funding the project SINFOTON-CM: S2013/MIT-2790.

Coatings and plastics that contain special effect pigments show angular-dependent reflection characteristics. Interference pigments, for instance, exhibit a color impression (“appearance”) that changes with the directions of illumination and observation. It is currently an open question how the appearance of such coatings can be best characterized without extensive measurements of the spectral radiance factor. In this paper, a simple and efficient approach is presented on how to characterize the appearance of surfaces composed of metallic and interference pigments. Based on the rotational symmetry of the pigment distribution around the surface normal, it is demonstrated how the appearance at any configuration of illumination and observation can be estimated from a set of in-plane measurements. For practical applications, it is shown that a rather small number of geometries (e.g., 10) are sufficient. The presented methodology is an alternative to a recent principal components analysis-based procedure and offers the advantage of being based directly on an extensible physical model while having at least the same prediction accuracy.

The basis for the description of diffuse reflecting materials is the concept of the radiance factor ?, or as a quite similar depiction, the bidirectional reflectance distribution function fr. Both characterizations use the concept of the perfectly reflecting diffuser (PRD), which reflects, by definition, the incoming radiation loss-free, completely diffuse and with Lambertian direction characteristics. The PRD is a theoretical concept only, which cannot be realized materially. Since there is no material with these characteristics, the realization is carried out with physical methods, i.e. by the measuring apparatus itself, in the context of an absolute measurement. For practical purposes, radiance factor measurements are predominantly accomplished relative to commercially available reflection standards. In the present investigation, different widely used diffuse reflection materials were measured for the first time in a multi-geometry configuration with the robot-based gonioreflectometer of the Physikalisch-Technische Bundesanstalt (PTB) in order to characterize their three-dimensional reflection behaviour. For a set of four distinct incident angles, the full hemispherical reflection indicatrix was determined at a wavelength of 550?nm.The angle-resolved reflection data are an important reference for manufacturers, providers and users of radiometric and photometric products. This paper attempts to give users in research and industry an overview of the strongly non-Lambertian reflection behaviour of standard reflection materials, because it is a widespread false assumption that commonly used standard reflection materials have only minor deviations from the ideal specification of the PRD.

Versatile applications in radiometry and photometry require uniform light source systems with a highly Lambertian radiance/luminance output. Examples for this kind of requirements include different applications such as calibration of photometers and radiometers, testing of electronic imaging devices like CCDs or similar array detectors or the use as a homogenous light source in, for instance, gonioreflectometric measurements. At the Physikalisch-Technische Bundesanstalt (PTB) a homogenous sphere radiator consisting of a medium sized integrating sphere (ϕ = 150 mm) with an internal reflector in the equatorial plane was developed. In its first stage of development it was equipped with an internal 250 W quartz tungsten halogen lamp. This sphere radiator had a radiance homogeneity of 99.8% of the emitted radiation measured in the plane of the limiting aperture (ϕ = 40 mm) at the output of the device. In the latest design of the system the radiative output power could be increased by a factor of about 3 by the use of an internal 400 W quartz tungsten halogen lamp while nearly maintaining homogeneity.

The effects of goniochromatism and sparkle are gaining more and more interest for surface refinement applications driven by demanding requirements from such different branches as automotive, cosmetics, printing and packaging industry. The common background and intention in all of these implementations is improvement of the visual appearance of the related commercial products. Goniochromatic materials show strong angular-dependent reflection characteristics and hence a color impression depending on the effective spatial arrangement of illumination and observation relative to the surface of the artifact. Sparkle is a texture related effect giving a surface which is irradiated directionally, like direct sun light, a bright glittering effect, similar to twinkling stars at the night sky. The prototype for this new effect is the Xirallic® pigment of MERCK KGaA, Germany. The same pigment shows in diffuse irradiation, like on a cloudy day, a different visual effect called graininess (coarseness) which appears as a granular structure of the surface. Both effects were studied on especially manufactured samples of a dilution series in pigment concentration and a tonality series with carbon black. The experiments were carried out with the robot-based gonioreflectometer and integrating sphere facilities at Physikalisch-Technische Bundesanstalt (PTB) in multidimensional configurations of directional and diffuse irradiation. The research is part of the European Metrology Research Program (EMRP), which 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). More information and updated news concerning the project can be found on the xD-Reflect website http://www.xdreflect.eu/.

11 pags., The European Metrology Research Program (EMRP) is a metrology-focused program of coordinated Research and Development (RD) 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/.

We describe a new, easy-to-use reagent, Cyto-Chex (Streck Laboratories, Omaha, Neb), that preserves fresh whole blood in a non-cross-linking, nonformalin manner. Target values assigned to fresh blood were essentially met after preservation and storage of up to 31 days. Respective mean analytic inaccuracies and short-term intra-assay coefficients of variation (n = 30) were as follows: WBCs, 6.7% and 1.99%; RBCs, 0.7% and 0.76%; hemoglobin, -1.8% and 0.79%; hematocrit, -0.3% and 0.75%; mean corpuscular volume, -1.0% and 0.78%; and platelets, 6.9% and 3.12%. Linearity of dilution-sensitive analytes was satisfactory over a wide range of dilutions after preservation of blood samples. Ten independent laboratories using 10 different instruments determined day-to-day interassay imprecision during four 7-day periods after blood preservation. Mean interassay coefficients of variation for participating laboratories were WBC, 1.92%; RBC, 1.00%; hemoglobin, 1.29%; hematocrit, 2.00%; and platelets 3.29%. Cyto-Chex enables long-term monitoring of instrument accuracy and precision with retained blood specimens of healthy persons. Blood from patient cohorts with various hematologic disorders and with a wide range of numeric abnormalities and/or parameter aberrations can be preserved satisfactorily with this reagent. The reanalysis of preserved patient blood samples is an important adjunct to the use of commercial control material in quality control programs of multichannel hematology analyzers.

This chapter describes the basic terms of diffuse reflectance and transmission measurements. The focus will be on diffuse reflectance of the highest technical quality. Measurements of spectral diffuse reflectance have been used for more than 75 years as a tool in the measurement of color. As of October 2013, the CMC-Database (Calibration and Measurement Capabilities Database) of the BIPM (International Bureau of Weights and Measures) has 18 entries by different NMI´s (National Metrology Institutes) for spectral diffuse reflectance, compared to only 5 entries for spectral diffuse transmittance. Reflectometry is a subdivision of the radiometry and photometry and is responsible for the realization, maintenance, and dissemination of the scales of diffuse reflection. This is done by the measurement of absolute spectral reflection values in the desired geometries. For practical applications, these measurements are predominantly accomplished relative to commercially available reflection standards. Unlike the measurement of specular reflection, where the angle of incidence equals the angle of reflection, in the case of diffuse reflection, the incoming radiation is spread over the half-space above the surface, with a certain distribution specific to the surface or material under test. The integrating sphere as a measurement device becomes important, with its ability to collect all of the diffusely reflected and transmitted radiation and making methods available to measure these quantities.

A comparison between the absolute gonioreflectometric scales at the Helsinki University of Technology (TKK) and the Physikalisch-Technische Bundesanstalt (PTB) has been accomplished. Six different reflection standards were measured for their 0:45 spectral radiance factor between 250 and 1650 nm in 10 nm intervals. Also, the 0:d reflectance factor between 400 and 1600 nm in 100 nm intervals was determined from goniometric reflectance measurements over polar angles with subsequent integration within the hemisphere above the sample. Goniometric comparisons covering such an extensive wavelength range and also several different sample materials are rarely implemented. For all but one sample, the difference between the results obtained at the TKK and the PTB was, with the exception of a couple of measurement points, within the expanded uncertainty (k = 2) of the comparison at least up to a wavelength of 1400 nm. All differences between the measurement results can be understood, except for one translucent sample in the visible wavelength range. The effect of sample translucency was found to be significant in the NIR wavelength region. Also, a general tendency of an increase of the TKK values relative to the PTB values in the UV region was observed. Possible causes for this phenomenon are discussed.

Interlaboratory comparisons, referred to as key comparisons, are completed for many metrological units within the framework of the mutual recognition arrangement of the Bureau International des Poids et Mesures. These comparisons are the responsibility of consultative committees of the different metrological areas. In the case of the Consultative Committee for Photometry and Radiometry, there are currently about 20 key comparisons for various measurands. While interest in the field of bidirectional reflectance has been growing in recent years among users in industry and research and development, there is currently no dedicated key comparison to demonstrate scale conformity. This is the basis of the comparison of the bidirectional reflectance scales between the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). Measurements of two distinct sets of white diffuse reflectance standards, two sintered polytetrafluoroethylene samples and two matte ceramic samples, were performed using the common and widely used 0∶45 geometry. The wavelength range of the comparison spans the ultraviolet (λ≥330 nm) to the near infrared (λ≤1150 nm), a technically important region. In total, five different facilities participated in this bilateral investigation. The results of the comparison show good agreement within the combined uncertainties.

We used a flow cytometer together with an intensified CCD camera to record spatially resolved light scattering from micrometer-sized single particles and single oriented particle agglomerates. Experimental differential cross sections of an oriented dumbbell made from two identical polystyrene spheres were compared with theoretical values calculated within the discrete dipole approximation, and good agreement was achieved. Furthermore, characteristic two-dimensional patterns of the scattered-light intensity were recorded for single blood cells, yielding information on the cells' shape and volume. Besides flow cytometry, we observed and analyzed differential light scatter of particle clusters of known size, shape, and orientation located within an optical trap.

Laser-induced fluorescence as well as forward and orthogonal Ught scatter, integrated over the acceptance angles of the detectors used, is routinely employed in a flow cytometer to detect, differentiate and count (blood) cells. In this contribution we report measurements of the angular distribution of laser radiation scattered by single blood cells, microspheres and their agglomerates

At the Physikalisch-Technische Bundesanstalt, the National Metrology Institute of Germany, a new facility for measuring visual appearance-related quantities has been built up. The acronym ARGon(3) stands for "3D appearance robot-based gonioreflectometer". Compared to standard gonioreflectometers, there are two main new features within this setup. First, a photometric luminance camera with a spatial resolution of 28 μm on the device under test (DUT) enables spatially high-resolved measurements of luminance and color coordinates. Second, a line-scan CCD-camera mounted to a spectrometer provides measurements of the radiance factor, respectively the bidirectional reflectance distribution function, in full V(λ)-range (360 nm-830 nm) with arbitrary angles of irradiation and detection relative to the surface normal, on a time scale of about 2 min. First goniometric measurements of diffuse reflection within 3D-space above the DUT with subsequent colorimetric representation of the obtained data of special effect pigments based on the interference effect are presented.

Homogeneity measurements in a gold-coated integrating sphere at eight wavelengths in the range from 400 to 2000 nm are presented and discussed. The inner sphere wall was scanned with a mirror-based internal sphere scanner at 288 different positions. The spatially resolved measurements show the transition from poor reflectivity, associated with large inhomogeneities at 400 nm, to high reflectivity in the infrared region at 2000 nm, associated with only small deviations. From the measurements the spectrally dependent relative uncertainty of the radiance of the inner sphere wall was deduced. A spectrally dependent sphere homogeneity correction factor F(lambda) relative to a specific point within the sphere wall was also derived.