Directional Reflectance Measurements Research Articles

Polarized light diffuse reflectance FT-NIR MEMS spectrometer enabling the detection of powder samples through a thin plastic layer.

Polarized scattered light Fourier transform infrared (FTIR) spectroscopy is used for measuring the absorbance of highly scattering materials overcoming the multiple scattering effect. It has been reported for in vivo for biomedical applications and in-field for agricultural and for environmental monitoring. In this paper, we report a polarized light microelectromechanical system (MEMS)-based FTIR in the extended near infrared (NIR) that utilizes a bistate polarizer in a diffuse reflectance measurement setup. The spectrometer is capable of distinguishing between single backscattering from the uppermost layer and multiple scattering from the deep layers. The spectrometer has a spectral resolution of 64c m -1 (about 16nm at a wavelength of 1550nm) and operates in the spectral range of 4347c m -1 to 7692c m -1 (1300nm to 2300nm). The technique implies de-embedding of the MEMS spectrometer polarization response by normalizing its effect; this is applied on three different samples: milk powder, sugar, and flour in plastic bags. The technique is examined on different scattering size particles. The scattering particles diameter's range is expected to vary from 10µm to 400µm. The absorbance spectra of the samples are extracted and compared to the direct diffuse reflectance measurements of the samples, showing good agreement. By using the proposed technique, the calculated error for the flour was decreased from 43.2% to 2.9% at 1935nm wavelength. The wavelength error dependence is also reduced.

Model to subtract contributions of scattered radiation from measured direct transmittance and specular reflectance by light diffusing materials.

The formalism of the Lorenz-Mie (LM) theory is used to estimate the contributions of radiation being scattered into the detector acceptance angle of spectrophotometers (with or without an integrating sphere) to the apparent direct transmittance and specular reflectance measurements. These contributions are subtracted from the measurements before doing the inversion to obtain the spectral variation of the scattering and absorption (S&A) coefficients of optically particulate liquid samples, decoupling the contribution to extinction from these two mechanisms. The method is applied to transmittance spectra of Pickering emulsions of dodecane oil (DO) and DO micelles with saturated dissolved Nile red dye, stabilized with anatase (T i O 2) in water. What we believe to be novel expressions are given to estimate the forward and backward average path-length parameters of propagating diffuse radiation from its equivalent quantities defined within the formalism of the LM theory and to relate these single particle average path-length parameters with the forward scattering ratio, asymmetry parameter, and higher-order coefficients in the expansion of the LM phase function. This novel approach makes it possible to avoid the underestimation of the S&A coefficients, which arises when the correction is not made by subtracting that contribution due to scattered radiation that is reaching the detectors from the directional reflectance and transmittance measurements.

"Dead" Exciton Layer and Exciton Anisotropy of Bulk MoS2 Extracted from Optical Measurements.

Excitons (electron-hole pairs bound by the Coulomb potential) play an important role in optical and electronic properties of layered materials. They can be used to modulate light with high frequencies due to the optical Pauli blocking. The properties of excitons in 2D materials are extremely anisotropic. However, due to nanometre sizes of excitons and their short life times, reliable tools to study this anisotropy are lacking. Here, we show how direct optical reflection measurements can be used to evaluate anisotropy of excitons in transition metal dichalcogenides MoS2. Using focused beam spectroscopic ellipsometry, we have measured the polarized optical reflection of bulk MoS2 for two crystal orientations: c-axis being perpendicular to the surface from which reflection is measured and c-axis being parallel to the surface from which reflection is measured. We found that for the parallel configuration the optical reflection near excitonic transitions is strongly affected by the presence of the exciton "dead" layer such that the excitonic reflection peaks become the excitonic dips due to light interference. At the same time, the optical reflection for the perpendicular orientation is not significantly altered by the exciton "dead" layer due to large anisotropy of exciton properties. Performing simultaneous Fresnel fitting for both geometries, we were able to evaluate exciton anisotropy in layered materials from simple optical measurements.

Two-color pyrometry for backface temperature and emissivity measurement of burning materials

Two-color (2C) pyrometry has long been used for flame temperature and soot concentration studies and is now becoming more widely used to measure backface temperatures of burning materials. With the obvious advantage of being a contact-free method that requires only minimal optical access, 2C pyrometry combined with high-speed acquisition is a promising diagnostic tool to obtain exceptional temporal and spatial resolution of thermally degrading samples. However, its conceptual simplicity relies on a set of basic assumptions that when violated can result in large errors. In this work, we used an experimental configuration representative for fire resistance testing for aerospace and naval applications to analyze the impact of camera parameters and test setup on the accuracy of the surface temperature results obtained. Two types of fiber reinforced polymer composites and a steel plate are used to investigate material specific aspects that affect the measurements. An improved workflow for camera calibration is presented that takes into account the actual experimental setup. The temperature and emissivity mapping obtained through in-situ IR measurements is compared to data acquired through thermocouples and post-fire hemispherical directional reflectance measurements at room temperature. Excellent agreement is found for post-processed 2C pyrometry measurements and TC probe measurements with an uncertainty of 30 °C at 500 °C. In-situ emissivity mappings of burnt specimens are consistent with data from the literature for degraded composite samples and oxidized steel plates. Our results remind the importance of proper post-processing and demonstrate the potentials of 2C pyrometry for fire testing applications. We also present a detailed error budget and suggestions for calibration measurements to improve measurement accuracy.

Laboratory intercomparison of solar absorptance and thermal emittance measurements at room temperature

Solar thermal absorber coatings play an important role in the opto-thermal efficiency of receivers in Concentrated Solar Power (CSP). Two standard figures of merit are the solar absorptance αsol and thermal emittance εth, derived from spectral directional hemispherical reflectance measurements at room temperature. These two figures of merit allow comparing coating formulations in terms of performance and durability. In this study, a black coating and a solar selective coating are optically characterized by different laboratories to compare spectral datasets, solar absorptance αsol and thermal emittance εth calculations. The comparison includes various benchtop spectrophotometers operating in the UV-VIS-NIR and Infrared spectral ranges as well as three commercial portable reflectometers/emissometers. A good agreement is found between the nine parties participating in this intercomparison campaign. The black coating αsol value is 96.6 ± 0.2%, while the solar selective coating αsol value is 94.5 ± 0.4%. For the thermal emittance, spectral data is concatenated and integrated from 0.3 to 16 μm. The black coating εth value calculated at 650 °C is 80.8 ± 3.8%, while the solar selective coating εth value calculated at 650 °C is 25.0 ± 0.5%.

Determination of Spectral and Broadband Albedos in Visible-near Infrared Bands for Different Phenophases of Wheat Using Hemispherical Directional Reflectance Measurements

Albedo is an important parameter in radiation balance, energy balance, atmospheric correction of remote sensing data and weather forecasting models. The values of albedo of agricultural area vary with changes in biophysical parameters at different phenophases of the crop. Spectral and broadband albedo of visible-infrared bands for wheat canopy was estimated with numerical and spectral integration of hemispherical directional reflectance factors (HDRFs). The HDRF measurements on wheat were acquired at 54 view angles (6 azimuthal planes × 9 view zenith angles) to cover the hemispheric span up to 60° view zenith at 7-8 days’ interval during early growth stages to physiological maturity. Canopy and atmospheric parameters were measured parallel to HDRFs of the crop. The spectral and broadband albedo of wheat varies in decreasing pattern with advancement of growth stages. Visible-infrared albedo of crop was maximum at early growth stages (tillering and booting; 0.23) and minimum at late growth stages (late milking and dough; 0.15). The albedo values retrieved from HDRF in this investigation can be useful for phenophase specific applications in cropland fluxes algorithms, crop phenotyping, regional climate modeling and other remote sensing studies.

In-Situ and Aircraft Reflectance Measurement Effectiveness for CAL/VAL Activities: A Study over Railroad Valley

This paper aims to assess the relationship between the surface reflectance derived from ground based and aircraft measurements. The parameters of the Rahman–Pinty–Verstraete (RPV) and Ross Thick-LiSparse (RTLS) kernel based bi-directional reflectance distribution functions (BRDF), have been derived using actual measurements of the hemispherical-directional reflectance factor (HDRF), collected during different campaigns over the Railroad Valley Playa. The effect of the atmosphere, including that of the diffuse radiation on bi-directional reflectance factor (BRF) parameter retrievals, assessed using 6S model simulations, was negligible for the low turbidity conditions of the site under investigation (τ550≤0.05). It was also shown that the effects of the diffuse radiation on RPV spectral parameters retrieval is linear for the isotropic parameter ρ0 and the scattering parameter Θ, and can be described with a second order polynomial for the k-Minnaert parameter. In order to overcome the lack of temporal collocations between aircraft and in-situ measurements, Monte Carlo 3-D radiative transfer simulations mimicking in-situ and remote sensing techniques were performed on a synthetic parametric meshed scene defined by merging Landsat and Multianglhe Imaging Spectroradiometer (MISR) remote sensing reflectance data. We simulated directional reflectance measurements made at different heights for PARABOLA and CAR, and analyzed them according to practices adopted for real measurements, consisting of the inversion of BRF functions and the calculation of the bi-hemispherical reflectance (BHR). The difference of retrievals against the known benchmarks of kernel parameters and BHR is presented. We associated an uncertainty of up to 2% with the retrieval of area averaged BHR, independently of flight altitudes and the BRF model used for the inversion. As expected, the local nature of PARABOLA data is revealed by the difference of the anisotropic kernel parameters with the corresponding parameters retrieved from aircraft loops. The uncertainty of the resultant BHR fell within ±3%.

Distinguishing multicellular life on exoplanets by testing Earth as an exoplanet

AbstractCan multicellular life be distinguished from single cellular life on an exoplanet? We hypothesize that abundant upright photosynthetic multicellular life (trees) will cast shadows at high sun angles that will distinguish them from single cellular life and test this using Earth as an exoplanet. We first test the concept using unmanned aerial vehicles at a replica moon-landing site near Flagstaff, Arizona and show trees have both a distinctive reflectance signature (red edge) and geometric signature (shadows at high sun angles) that can distinguish them from replica moon craters. Next, we calculate reflectance signatures for Earth at several phase angles with POLDER (Polarization and Directionality of Earth's reflectance) satellite directional reflectance measurements and then reduce Earth to a single pixel. We compare Earth to other planetary bodies (Mars, the Moon, Venus and Uranus) and hypothesize that Earth's directional reflectance will be between strongly backscattering rocky bodies with no weathering (like Mars and the Moon) and cloudy bodies with more isotropic scattering (like Venus and Uranus). Our modelling results put Earth in line with strongly backscattering Mars, while our empirical results put Earth in line with more isotropic scattering Venus. We identify potential weaknesses in both the modelled and empirical results and suggest additional steps to determine whether this technique could distinguish upright multicellular life on exoplanets.

Realization of photonic charge-2 Dirac point by engineering super-modes in topological superlattices

Quite recently, an unconventional variety of fourfold linear band degeneracy points has been discovered in certain condensed-matter systems. Contrary to standard 3-D Dirac monopoles, these quadruple points known as the charge-2 Dirac points are characterized by nonzero topological charges, which can be exploited to delve into hitherto unknown realms of topological physics. Here, we report on the experimental realization of a charge-2 Dirac point by deliberately engineering hybrid topological states, called super-modes, in a 1-D optical superlattice system with synthetic dimensions. Utilizing direct reflection and transmission measurements, we propose the existence of the synthetic charge-2 Dirac point in the visible region. We also show an experimental approach to manipulating two spawned Weyl points possessing equal charge. Topological end modes resulting from the charge-2 Dirac point can be delicately controlled within truncated superlattices, opening a pathway to rationally engineer local fields with intense enhancement.

Parameter estimation and evaluation of Ross-Li and RPV models for wheat phenophases using hemispherical directional reflectance measurements

ABSTRACT Hemispherical directional reflectance factor (HDRF) measurements of wheat crop acquired with field goniometer system are used to estimate parameters and evaluate anisotropic reflectance models. The HDRFs were sampled at 54 view angles (6 azimuthal planes × 9 view zenith angles) to cover the hemispheric span up to 60° zenith. The observations were made at 7–8 days’ interval during different phenophases of the crop. Biophysical parameters were also measured parallel to HDRF. Kernel driven Ross-Li variants and RPV (Rehman Pinty Verstrate) models parameters are generated by fitting HDRF data. RossThin-H/LiSparse-R model was fitted best for all visible-near infrared bands in early phenophases while the RossThick-H/LiSparse-R model was best fitted for heading and flowering phases in most cases. In late grain development phases (Late milking and Dough) of the wheat, HDRFs of visible bands were best fitted with RossThin-H/LiDense-R model in most instances. The HDRF simulation of wheat by RPV models is identical to Ross-Li models. Both models are adequate to account reflectance anisotropy of wheat canopy. Phenophase specific model parameters can be used to reconstruct reflectance anisotropy of wheat for different applications.

Large-area surface topography analysis of additively manufactured metallic materials using directional reflectance microscopy

The surface topography of additively manufactured metals carries valuable information about the mechanisms involved during materials formation. As such, it may be used as an indirect measure of materials quality, both during and after production. Standard surface analysis techniques, however, are characterized by narrow field of view and low data acquisition rate, making them unsuited to rapidly characterize large areas. In this work, we describe a novel method to quantify the three-dimensional surface topography of a 1 cm3 metal sample produced by selective laser melting. The method relies on directional reflectance microscopy—an optical technique that quantifies surface reflectance as a function of the illumination angle. By fitting the directional reflectance measurements with a reflection model, we map the surface normal orientation and microscopic surface roughness over the entire sample surface at a spatial resolution of ~5.3μm. We also discuss the possibility of integrating our method within the additive process by reducing the number of measurements required to reconstruct surface topography. Because of the inexpensive equipment employed, the large field of view measurements, and rapid data acquisition speed, we believe that our method is a competitive alternative for analysing the surface topography—and thus the quality—of additively manufactured metals both during and after production.

METHODOLOGY FOR DIRECT REFLECTANCE MEASUREMENT FROM A DRONE: SYSTEM DESCRIPTION, RADIOMETRIC CALIBRATION AND LATEST RESULTS

Abstract. We study and analyse performance of a system for direct reflectance measurements from a drone. Key instruments of the system are upwards looking irradiance sensor and downwards looking imaging spectrometer. Requirement for both instruments is that they are radiometrically calibrated, the irradiance sensor has to be horizontally stabilized, and the sensors needs to be accurately synchronized. In our system, irradiance measurements are done with FGI Aerial Image Reference System (FGI AIRS), which uses novel optical levelling methodology and can compensate sensor tilting up to 15°. We performed SI-traceable spectral and radiance calibration of FPI hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). After the calibration, the radiance accuracy of different channels was between ±4 % when evaluated with independent test data. Sensors response to radiance proved to be highly linear and was on average 0.9994 for all channels. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI and highlighted the importance of accurate calibration. The drone-based direct reflectance measurement system showed promising results with imagery collected over Jokioinen agricultural grass test site, Finland. AIRS-based image- and band wise image adjustment provided homogenous and seamless image mosaics even under varying illumination conditions and under clouds.

Direct Reflectance Measurements from Drones: Sensor Absolute Radiometric Calibration and System Tests for Forest Reflectance Characterization.

Drone-based remote sensing has evolved rapidly in recent years. Miniaturized hyperspectral imaging sensors are becoming more common as they provide more abundant information of the object compared to traditional cameras. Reflectance is a physically defined object property and therefore often preferred output of the remote sensing data capture to be used in the further processes. Absolute calibration of the sensor provides a possibility for physical modelling of the imaging process and enables efficient procedures for reflectance correction. Our objective is to develop a method for direct reflectance measurements for drone-based remote sensing. It is based on an imaging spectrometer and irradiance spectrometer. This approach is highly attractive for many practical applications as it does not require in situ reflectance panels for converting the sensor radiance to ground reflectance factors. We performed SI-traceable spectral and radiance calibration of a tuneable Fabry-Pérot Interferometer -based (FPI) hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). The camera represents novel technology by collecting 2D format hyperspectral image cubes using time sequential spectral scanning principle. The radiance accuracy of different channels varied between ±4% when evaluated using independent test data, and linearity of the camera response was on average 0.9994. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI. The drone-based direct reflectance measurement system showed promising results with imagery collected over Wytham Forest (Oxford, UK).

Comparative study of radiometric and calorimetric methods for total hemispherical emissivity measurements

Accurate knowledge of infrared emissivity is important in applications such as surface temperature measurements by infrared thermography or thermal balance for building walls. A comparison of total hemispherical emissivity measurement was performed by two laboratories: the Laboratoire National de Metrologie et d’Essais (LNE) and the Centre d’Etudes et de Recherche en Thermique, Environnement et Systemes (CERTES). Both laboratories performed emissivity measurements on four samples, chosen to cover a large range of emissivity values and angular reflectance behaviors. The samples were polished aluminum (highly specular, low emissivity), bulk PVC (slightly specular, high emissivity), sandblasted aluminum (diffuse surface, medium emissivity), and aluminum paint (slightly specular surface, medium emissivity). Results obtained using five measurement techniques were compared. LNE used a calorimetric method for direct total hemispherical emissivity measurement [1], an absolute reflectometric measurement method [2], and a relative reflectometric measurement method. CERTES used two total hemispherical directional reflectometric measurement methods [3, 4]. For indirect techniques by reflectance measurements, the total hemispherical emissivity values were calculated from directional hemispherical reflectance measurement results using spectral integration when required and directional to hemispherical extrapolation. Results were compared, taking into account measurement uncertainties; an added uncertainty was introduced to account for heterogeneity over the surfaces of the samples and between samples. All techniques gave large relative uncertainties for a low emissive and very specular material (polished aluminum), and results were quite scattered. All the indirect techniques by reflectance measurement gave results within ±0.01 for a high emissivity material. A commercial aluminum paint appears to be a good candidate for producing samples with medium level of emissivity (about 0.4) and with good uniformity of emissivity values (within ±0.015).

The Use of Directional Reflectance Measurement for in vivo Assessment of Protective Properties of Cosmetics in the Infrared Radiation Range.

Photoprotection of skin is now focused on UV radiation. The aim of this study was to evaluate in vivo cosmetic products in terms of protection against infrared radiation (IR) and propose a methodology for conducting such measurements. The directional reflectance (DR) of 12 UV filters, six care creams and two preparations containing fumed silica applied on the forearm of 36 volunteers was examined in six spectral bands for two angles of incidence. SOC-410 Directional Hemispherical Reflectometer was used to measure DR. There is very little change in DR for all spectral bands for both incident angles for both UV filters, care creams and preparations containing fumed silica. For example, for 15% of fumed silica in glycerin for the spectral band of 0.9-1.1 μm and the incident angle of 20°, skin DR prior to application was 0.543; 5 min after application was 0.533 and 30 min after application was 0.559. Both UV filters, care creams and fumed silica do not protect skin against IR. The proposed method of in vivo measurements is superior to in vitro studies which have been conducted so far because it takes into account both the refractive index at the tissue/air interface and the absorption of IR by adipose tissue.

Estimation of FAPAR over Croplands Using MISR Data and the Earth Observation Land Data Assimilation System (EO-LDAS)

The Fraction of Absorbed Photosynthetically-Active Radiation (FAPAR) is an important parameter in climate and carbon cycle studies. In this paper, we use the Earth Observation Land Data Assimilation System (EO-LDAS) framework to retrieve FAPAR from observations of directional surface reflectance measurements from the Multi-angle Imaging SpectroRadiometer(MISR) instrument. The procedure works by interpreting the reflectance data via the semi-discrete Radiative Transfer (RT) model, supported by a prior parameter distribution and a dynamic regularisation model and resulting in an inference of land surface parameters, such as effective Leaf Area Index (LAI), leaf chlorophyll concentration and fraction of senescent leaves, with full uncertainty quantification. The method is demonstrated over three agricultural FLUXNET sites, and the EO-LDAS results are compared with eight years of in situ measurements of FAPAR and LAI, resulting in a total of 24 site years. We additionally compare three other widely-used EO FAPAR products, namely the MEdium Resolution Imaging Spectrometer (MERIS) Full Resolution, the MISR High Resolution (HR) Joint Research Centre Two-stream Inversion Package (JRC-TIP) and MODIS MCD15 FAPAR products. The EO-LDAS MISR FAPAR retrievals show a high correlation with the ground measurements ( r 2 > 0.8), as well as the lowest average R M S E (0.14), in line with the MODIS product. As the EO-LDAS solution is effectively interpolated, if only measurements that are coincident with MISR observations are considered, the correlation increases ( r 2 > 0.85); the R M S E is lower by 4–5%; and the bias is 2% and 7%. The EO-LDAS MISR LAI estimates show a strong correlation with ground-based LAI (average r 2 = 0.76), but an underestimate of LAI for optically-thick canopies due to saturation (average R M S E = 2.23). These results suggest that the EO-LDAS approach is successful in retrieving both FAPAR and other land surface parameters. A large part of this success is based on the use of a dynamic regularisation model that counteracts the poor temporal sampling from the MISR instrument.

Lidar reflectance from snow at 2.05 μm wavelength as measured by the JPL Airborne Laser Absorption Spectrometer.

We report airborne measurements of lidar directional reflectance (backscatter) from land surfaces at a wavelength in the 2.05 μm CO₂ absorption band, with emphasis on snow-covered surfaces in various natural environments. Lidar backscatter measurements using this instrument provide insight into the capabilities of lidar for both airborne and future global-scale CO₂ measurements from low Earth orbit pertinent to the NASA Active Sensing of CO₂ Emissions over Nights, Days, and Seasons mission. Lidar measurement capability is particularly useful when the use of solar scattering spectroscopy is not feasible for high-accuracy atmospheric CO₂ measurements. Consequently, performance in high-latitude and winter season environments is an emphasis. Snow-covered surfaces are known to be dark in the CO₂ band spectral regions. The quantitative backscatter data from these field measurements help to elucidate the range of backscatter values that can be expected in natural environments.

Caractérisation radiative de liquides volatils semi-transparents dans le domaine infrarouge

The LNE has developed a technique to measure infrared radiative properties of volatile liquids. LNE uses a homemade reflectometer for the measurement of the spectral directional hemispherical reflectance from 0.8 μm to 14 μm and a Fourier transform spectrometer for the measurement of the regular spectral transmittance from 1 μm to 25 μm. For volatile liquids, a tight cell with two infrared windows was constructed. Optical models were developed to calculate the spectral complex refractive index of the liquid from reflectance and transmittance results. Results were validated for water by comparison to data found in literature.

Dynamics of spectral bio-indicators and their correlations with light use efficiency using directional observations at a Douglas-fir forest

The carbon science community must rely on satellite remote sensing to obtain global estimates of photosynthetic activity, typically expressed as net primary production (NPP), gross primary production (GPP) or light use efficiency (LUE). The photochemical reflectance index (PRI), calculated as a normalized difference reflectance index using a physiologically active green band (∼531 nm) and another physiologically insensitive green reference band (∼570 nm), denoted as PRI(570), has been confirmed in many studies as being strongly related to LUE. Here, we examined the potential of utilizing PRI(570) observations under different illumination conditions for canopy LUE estimation of a forest. In order to evaluate this, directional hyperspectral reflectance measurements were collected continuously throughout the daytime periods using an automated spectroradiometer in conjunction with tower-based eddy covariance fluxes and environmental measurements at a coastal conifer forest in British Columbia, Canada throughout the 2006 growing season. A parameter calculated as the PRI(570) difference (dPRI(570)) between shaded versus sunlit canopy foliage sectors showed a strong correlation to tower-based LUE. The seasonal pattern for this correlation produced a dramatic change from high negative (r ∼ −0.80) values in the springtime and early fall to high positive values (r ∼ 0.80) during the summer months, which could represent the seasonality of physiological characteristics and environmental factors. Although the PRI(570) successfully tracked canopy LUE, one or both of its green bands (∼531 and 570 nm) used to calculate the PRI are unavailable on most existing and planned near-term satellites. Therefore, we examined the potential to use 24 other spectral indexes for LUE monitoring that might be correlated to PRI, and thereby a substitute for it. We also continued our previous investigations into the influence of illumination conditions on the observed PRI(570) and other indexes. Among the 24 indexes examined, three PRI indexes using different reference bands (488, 551 and 705 nm) showed high correlations to the traditional PRI(570), especially PRI(551) and PRI(705). This indicates three additional PRI variations for LUE monitoring if the traditional reference band at 570 nm is not available but the 531 nm band is available. Five other indexes also yielded high correlations to PRI(570): Dmax and DM705, two indexes calculated from derivative reflectance spectra; a simple ratio of reflectance values at 685 nm and 655 nm (SR685_655); and a double-peak optical index (DPI). The diurnal and seasonal dynamics of these eight indexes and PRI(570) were explored. All of these indexes except DPI expressed linear dependence on available sunlight and more strongly expressed diurnal dynamics in April than in August during summer drought. The differences for shaded versus sunlit canopy foliage sectors were also calculated for the eight indexes, and their correlations to canopy LUE across the season were examined. The performances were similar for the most successful and seasonally stable indexes: dPRI(551), dPRI(705) and dPRI(570). The other five indexes showed good correlation to LUE in some but not all the months, and the months with high correlations varied among them.

Evaluation of the ARKRAY AUTION Eleven® reflectometer in detecting microalbuminuria with AUTION Screen® test strips and proteinuria with AUTION Sticks 10PA® strips

Objective. Albumin/creatinine and protein/creatinine ratios were measured with the ARKRAY AUTION Eleven reflectometer using AUTION Screen and AUTION Sticks 10PA strips, respectively, against quantitative Siemens Advia reference procedures from 368 patient urines, as an evaluation of their applicability for use in points‐of‐care and small laboratories. Material and methods. Direct reflectance measurements were utilized to estimate imprecision, as well as to suggest reclassification of ordinal scale categories into normoalbuminuria, microalbuminuria and macroalbuminuria groups (3.4 g/mol and 34 g/mol cut‐off limits, corresponding to 30 mg/g and 300 mg/g creatinine in conventional units). Results. Analytically, ordinal scale albumin/creatinine ratios agreed in 86 % of cases with those obtained from Advia measurements, resulting in a kappa coefficient of 0.79. Protein/creatinine ratios of the AUTION Sticks 10PA strip were classified into three groups at limits of 11.3 g/mol and 56.6 g/mol (100 mg/g and 500 mg/g in conventional units), with an agreement of 77 % and a kappa coefficient of 0.65 against Advia procedures. To optimize clinical outcomes, cut‐off reflectances of ordinal scale categories of AUTION Eleven were adjusted. The clinical specificity of detecting an increased albumin/creatinine ratio was then increased from 81 % to 95 %, with clinical sensitivity kept at 88 % at the 3.4 g/mol limit of the reference procedure. Clinical specificity of the albuminuria field alone (at a clinical sensitivity of 88 %) was only 73 %. Adjustments to cut‐off reflectances of the reported categories for protein/creatinine ratios increased clinical specificity from 54 % to 94 %, while losing clinical sensitivity from 97 % to 89 % only, with an improved concordance of 83 % and a kappa coefficient of 0.75 against Advia measurements. The combination to creatinine measurements improved clinical specificity compared to 50 % by the protein field alone. In economic terms, it is estimated that population screening for microalbuminuria using the AUTION Eleven reflectometer is cheaper than by quantitative albumin/creatinine measurements alone, based on the incidence of end‐stage renal disease of 90 patients/million/year at the Northern Ostrobothnia Hospital District.