Spectral Radiance Factor Research Articles

Colorimetry and its accuracy in the measurement of fluorescent materials by the two‐monochromator method

AbstractThe fundamental procedure involved in the two‐monochromator method for determining the spectral radiance factors of fluorescent materials is described, and some measured results are presented. The colorimetric accuracy of the method was confirmed by comparing two sets of tristimulus values: (1) those based on the two‐monochromator method and calculated from the reflected and the fluorescent spectral radiance factors and the spectral power distributions of a tungsten‐halogen lamp and a xenon lamp (which were determined separately); and (2) those calculated from the total radiance factors obtained from the measurement under polychromatic illumination, where the fluorescent materials were irradiated with the tungsten and the xenon lamp. The color differences between these sets of tristimulus values in CIE‐LUV color space were estimated to be less than 1.0 unit, irrespective of the illuminant or the source.

Monte‐carlo study of errors in the tristimulus colorimetry of white papers

AbstractA computational method with pseudorandom numbers was used to determine the spectral radiance factors of various dyed or fluorescent white samples, designed to be statistically similar to those evaluated by direct measurements. Colorimetric parameters were then computed and compared with direct readings from a tristimulus colorimeter for various practical conditions. Also obtained were evaluations of errors, comparison between CIE 2° and CIE 10° observers, comparisons among actual filters used, and comparisons with different sources. A number of practical conclusions that are difficult to obtain from direct experimental methods can be deduced from this study.

Errors in spectrophotometry and colorimetry of fluorescent samples caused by polarization of the measuring system

AbstractThis article describes a method for the prediction of the reflected and the fluorescent spectral radiance factor which are expected to be measured by use of a measuring system with polarizing properties, and a method for the estimation of the spectrophotometric errors in the predicted radiance factors. Polarization properties are described for the measuring system, the white standard surface, and the two kinds of fluorescent samples used in the two‐monochromator method of the present study. In this method, the spectrophotometric errors in the reflected spectral radiance factor are estimated to be not less than 1% at some wavelengths. However, the error of the fluorescent spectral radiance factor is relatively small. Colorimetric errors of fluorescent samples due to polarization are estimated for the one‐ and two‐monochromator methods. The errors expressed as CIELUV color differences are estimated to be less than 1.0 unit and are negligibly small.

On analytical versus numerical integration in tristimulus calculations

AbstractIf one assumes that the CIE recommendations for linear interpolation of illuminant and observer data between unit nanometers define these data as analytical functions, and accepts similar linear interpolation of the spectral radiance factor, an analytical equation can be derived for calculating tristimulus values. This article shows that, even in extreme cases, use of this more complex equation gives results that are not significantly different from those obtained by simple summation.

The Determination of Weights for Use in Calculating Tristimulus Values

AbstractMultiplication of weights by spectral radiance factors and summation is the usual method of calculating tristimulus values. The spectral‐radiance‐factor data may vary in abridgement (omission of intermediate data), truncation (omission of data at the extremes of the visual range), and in the case of fluorescent‐lamp illuminants, omission of mercury‐line data. This article sets forth recommendations for the calculation of weights for any set of spectral‐radiance‐factor data.

A New Look at the Calculation of Tristimulus Values

AbstractThe method of calculating tristimulus values currently recommended by the International Commission on Illumination (CIE) consists of summing, over the visible region, terms which involve an approximation over the wavelength interval 1, 5, or 10 nm for which data from standard tables are multiplied by measured spectral radiance factors. It is suggested that this approximation be carried out by integration. Integration can be carried out if the standard data are considered as points on a curve subject to interpolation between listed values and if the spectral radiance factor can be determined by interpolation between measured values. Adoption of this suggestion would lead to more accurate determination of tristimulus values and improved agreement among laboratories.

Whiteness: assessment of tint

The tint of 431 white textile samples is visually assessed by 6 colorists. Tristimulus values based on measured spectral radiance factors of the samples are calculated for the CIE 1931 standard colorimetric observer and the CIE 1964 supplementary standard colorimetric observer. The parameters of colorimetric tint formulas are evaluated for both standard observers.

CIE提案簡易けい光測色法の測色精度

The accuracy of CIE proposed one monochromator method was studied on the basis of the two monochromator method regarding the Colorimetry of fluorescent materials. In all the experiments, the fluorescent materials were always illuminated normally and viewed at 45° from the normal.The results studied are summarized as follows:(1) A theoretical account is given to estimate the accuracy of the CIE proposed method on the basis of the measurement by use of the two-monochromator method. The accuracy is discussed on the total, the reflected, and the fluorescent spectral radiance factor (SRF), respectively.(2) It is confirmed that the CIE proposed method is able to give the total SRF's of fluorescent materials under D65 within an average deviation of 1 % from those measured and estimated by the two-monochromator method. This average deviation of the total SRF's corresponds to the color difference less than 1 CIE LUV unit. In the overlapping region by excitation and luminescence, however, the deviation of the reflected SRF shows an error from 2 to 4 % in some fluorescent materials, and the error of Q (μ) function (fluorescence radiant efficiency) is also significant.(3) A simplified procedure is given for estimating Q (μ) function without using the spectral characteristic of the light receiver to be used. This simplification in the CIE proposed method is used provided that the colorimetric accuracy is allowed within the color difference of 1.5 CIE LUV unit.

Calculation of the Spectral Radiance Factors of Luminescent Samples

AbstractIt is often desirable to calculate the spectral radiance factor (SRF, the sum of the reflected and fluorescent radiances) which a photoluminescent—commonly called a fluorescent—sample would exhibit if it were irradiated by a standard illuminant, such as CIE D65, which is not available as a source for direct measurement. Several methods described in the literature for calculating the desired SRF from measurements made using available sources are tested experimentally using measurements made on commonly available one‐monochromator integrating‐sphere spectrophotometers. The choice of the calculation method is shown to be less important than the closeness of the match of the spectral distribution of irradiance on the sample to that from the standard illuminant. This is influenced by both the selection of the experimental source and the effects of the integrating sphere. With all variables properly controlled, comparison of calculated and directly measured SRFs leads to color differences less than one CIELAB unit.

けい光材料の分光測光および測色における偏光の影響

Some specific properties of polarization are found in the grating-type monochromators which are generally used in the colorimetry of fluorescent samples. The present paper describes the errors in their spectrophotometry andcolorimetry caused by the presence of polarization properties in the measuring system. The results reported are as follows.(1) A method is suggested in order to predict the reflected and the fluorescent spectral radiance factor which are expected to be measured by use of a measuring system with polarization properties. A method is further givenwhich estimates the spectrophotometric errors in the predicted radiance factors.(2) The properties of polarization are described on the measuring system of two-monochromator method, the whitestandard surface, and the fluorescent samples used in the present study.(3) Spectrophotometric errors in the reflected and the fluorescent radiance factor are estimated to the twokinds of fluorescent samples by use of the methods given in (1) and of the measured characteristics of polarizationin (2) necessary in the computation. In the two-monochromator method used, the error of the reflected spectral radiance factor is estimated not to be less than 19 at some wavelengths. However, the error of the fluorescent spectral radiance factor is relatively small and is estimated to be less than 0.006%.(4) Colorimetric errors of fluorescent samples due to polarization are estimated in the cases of one-and two-monochromator method. The errors are given by the color difference in the CIE LAB unit, which are estimated to be less than 1.0 units and found to be negligibly small.

Proceedings of the Inter‐Society Color Council Technical Conference “Instrumental Colorant Formulation 1976” Williamsburg, Virginia. III Problems of Fluorescence in Colorant Formulation

AbstractThe presence of fluorescence in samples to be matched and in dyes to be used for matching requires precautions in measurement and in computation. Measurement of conventional reflectance may cause serious errors of formulation. Standard procedures for calculating matches are usually based on the additivity of the K/S values. In contrast, contributions of fluorescence have to be added to the spectral radiance factors. Specifications for a rigorous procedure are presented. Merits and shortcomings of currently used methods are discussed. An approximation making use of negative Kubelka‐Munk coefficients is set forth. It is valid only for applications of a single fluorescent colorant which may be shaded slightly by minor additions of other colorants.

Color Changes of Dyeings in Spectrophotometers Using Heterochromatic Illumination

In Spectrophotometers using heterochromatic illumination (so-called reversed optics), total spectral radiance factor curves of textile dyeings showed marked changes on repeated measurements, approaching equilibrium after 15–20 min. For reactive dyes on cotton, color differences as large as 5 Adams-Nickerson (AN) units were observed between the first and last measurements; for disperse dyes on polyester, the differences were below 2 AN units. They result from evaporation of water from the substrate— hence, “hygrochromism” —and place a principal limit on measurement accuracy of hygroscopic fabrics when using polychromatic illumination.

Spectroradiometric and Radiation Temparature Measurements for Ground Objects at Different Flight Heights

Spectroradiometric and radiation temperature measurements were made at different flight heights (200m, 400m, 600m, 800m, 1000m) for various ground objects. The dependence of the spectral radiance factor β (λ) and radiation temperature on flight heights was investigated. As a result, it was found that the increase of the spectral radiance factor β (λ) in the wavelength range from 400nm to 450nm was caused by the path radiance of atmosphere. Also, the rate of radiation temperature decrease was 1.8°c/km over reeds and 2.4°c/km over the river.

Requirements for Reflection Standards and the Measurement of Their Reflection Values

The standards necessary for transferring the reflection scale must meet certain requirements. First, the present paper discusses the question of how far these requirements are met by the materials now used for realizing the reflection standards. Then the instrumentation is described that was developed in the Physikalisch-Technische Bundesanstalt for measuring the spectral radiance factor beta(lambda) for the d/O and 45/0 geometries and in principle also for the inverse geometries. How these measurements are made so that the values obtained for a material standard are related to the perfect reflecting diffuser as the primary standard is discussed.

Measurement of Fluorescent Colors

Four chromatic daylight fluorscent colors (lumino-tape, fluorescent safety colors) were measured by the following four method and compared: I, complete matrix method, II, simulated matrix method III, two-mode method and, IV, sharp-cut filter method. Two instruments were used for these experiments. they were, Model MPF-4 spectrofiuorophotometer for methods I and II, and Model 307 recording spectrophotometer for Methods III and IV.For all samples and for all methods, spectral radiance factor distributions of true reflection, fluorescence and total reflection for illuminant P 3100 K and xenon lamp were obtained, then tristimulus values and chromaticity coordinates were calculated.Of these four samples, shapes of the fluorescence spectra were changeable with the excitation wavelength, and crossover region between excitation and emission spectra was rather wide, therefore, the deviations of colorimetric values from the true values, which were obtained by method I, were estimated for each methods.

Separation of the Spectral Radiance Factor Curve of Fluorescent Substances into Reflected and Fluoresced Components

When a spectrophotometer with the correct optical configuration is used to measure a fluorescent sample, the resulting spectral radiance factor curve consists of the sum of a reflected and a fluoresced portion. The true reflectance curve can be obtained by direct measurement below the emission region and also above the absorption region by the use of a fluorescence-killing filter. Between these two limits, in the region of simultaneous absorption and emission (the crossover region), the true reflectance curve can be. obtained by calculation from two different spectral radiance factor curves and a single reading through the fluorescence-killing filter.

In Situ Measurements of the Photometric Properties of an Area on the Lunar Surface*

A preliminary determination has been made of the photometric properties of the lunar surface from high–resolution pictures received from the Surveyor I spacecraft. Several target areas were chosen at selected locations around the spacecraft, and photometric measurements were taken with the television camera throughout the lunar day. Surveyor I data agree within ±20% with the terrestrially observed photometric properties. Initial examination of the data indicates no anomalies of the photometric properties of homogeneous areas on scales greater than 6 cm in diameter. Luminance factors were estimated from the observed data and ranged from 7.0% to 7.5% for more than 91% of the area; however, values of 5% to 25% were recorded in some locations. The chromaticity coordinates of the disturbed area near one of the footpads were found to be very close to natural sunlight on a gray paint. A preliminary estimate of the spectral radiance factor of this area is given, using an eigenvector-analysis technique. The spacecraft characteristics, viewing geometry, and ground-recording techniques are included, along with a brief description of errors.

Propagation of Errors in Tristimulus Colorimetry

The uncertainty ellipse equation is developed for the general case of propagation of errors in tristimulus colorimetry, where spectral tristimulus values as well as spectral radiance factors are deemed uncertain. Two applications are presented as special cases. In the first, uncertainty in chromaticity coordinates for spectrum colors, uncertainties of spectral tristimulus values are based on the CIE standard observer system and the 2°- and 10°-field systems derived from Stiles’ data by Judd and Kelly. In the second, uncertainties in chromaticity coordinates of fluorescent light sources, uncertainties in spectral emittances are based on five sets of data for one source. It is important that an international standard-observer system be specified not only by mean tristimulus values of the spectrum but also by their variances; otherwise the significance of the departure of an individual experimental datum from that by the standard observer cannot be assessed.