The Four-Color Matrix method (FCM) was developed to improve the accuracy of chromaticity measurements of various
display colors. The method is valid for each type of display having similar spectra. To develop the Four-Color
correction matrix, spectral measurements of primary red, green, blue, and white colors of a display are needed.
Consequently, a calibration facility should be equipped with a number of different displays. This is very inconvenient
and expensive. A spectrally tunable light source (STS) that can mimic different display spectral distributions would
eliminate the need for maintaining a wide variety of displays and would enable a colorimeter to be calibrated for a
number of different displays using the same setup. Simulations show that an STS that can create red, green, blue and
white distributions that are close to the real spectral power distribution (SPD) of a display works well with the FCM for
the calibration of colorimeters.
A spectrally tunable light source using a large number of LEDs and an integrating sphere has been designed and is being constructed at the National Institute of Standards and Technology. The source is designed to have a capability of producing any spectral distribution, mimicking various light sources in the visible region by feedback control of individual LEDs. The output spectral irradiance or radiance of the source will be calibrated by a reference instrument, and the source will be used as a spectroradiometric as well as a photometric and colorimetric standard. A series of simulations have been conducted to predict the performance of the designed tunable source when used for calibration of display colorimeters. The results indicate that the errors can be reduced by an order of magnitude when the tunable source is used to calibrate the colorimeters, compared with measurement errors when the colorimeters are calibrated against Illuminant A. The source can also approximate various CIE daylight illuminants and common lamp spectral distributions for other photometric and colorimetric applications.
A spectrally tunable light source using an integrating sphere with a large number of LEDs has been designed and constructed at the National Institute of Standards and Technology (NIST). The source is designed to have a capability of producing any visible spectral distribution, mimicking various light sources in the visible region by feedback control of the radiant power emitted by individual LEDs. The spectral irradiance or radiance of the source is measured by a standard reference instrument; the source will be used as a transfer standard for colorimetric, photometric and radiometric applications. A series of simulations have been conducted to predict the performance of the designed tunable source and source distributions have been realized for a number of target distributions.
A spectrally tunable light source using a large number of LEDs and an integrating sphere has been designed and being developed at NIST. The source is designed to have a capability of producing any spectral distributions mimicking various light sources in the visible region by feedback control of individual LEDs. The output spectral irradiance or radiance of the source will be calibrated by a reference instrument, and the source will be used as a spectroradiometric as well as photometric and colorimetric standard. The use of the tunable source mimicking spectra of display colors, for example, rather than a traditional incandescent standard lamp for calibration of colorimeters, can reduce the spectral mismatch errors of the colorimeter measuring displays significantly. A series of simulations have been conducted to predict the performance of the designed tunable source when used for calibration of colorimeters. The results indicate that the errors can be reduced by an order of magnitude compared with those when the colorimeters are calibrated against Illuminant A. Stray light errors of a spectroradiometer can also be effectively reduced by using the tunable source producing a blackbody spectrum at higher temperature (e.g., 9000 K). The source can also approximate various CIE daylight illuminants and common lamp spectral distributions for other photometric and colorimetric applications.
In practice, the problem of vision discomfort appears at a number of different work-stands. Among others, it concerns people like drivers or people working with screen monitors. As a result of extensive research into appropriate illumination, a number of recommendations have been produced in order to ensure comfort of vision at work-stands. It is assumed that if the work-stand is provided with sufficiently high level of illuminance, and if the luminance distribution is uniform, and there is no glare, then we have comfort of vision and the eye fatigue is acceptable. Currently, to measure luminance distribution in order to assess the quality of illumination, it is necessary to carry out a large number of point measurements by using the luminance meter. Another way of determining the luminance distribution coming from the sources lying in a relatively small solid angle is the application of luminance meter built by using a CCD camera. Measurements of this type require, however, a great number of exposures to determine luminance distribution coming from light sources located in a large solid angle (e.g. a halfspace). This paper presents a design model of luminance distribution meter which makes it possible to obtain data about the distribution of luminance coming from light sources located in the whole halfspace only by a single measurement. Furthermore, the meter enables simultaneous determination of all the parameters on the work-stand illumination quality.
There is a large number of elements used for spatial correction of the luxmeter photometric head. However, none of them, as yet, ensures perfect correction. As a result, research work into this type of correction has been playing a crucial role in the measurement of photometric quantities. In this paper an original model of a luxmeter photometric head created on the basis of optical fibers has been presented. This photometric head operates on the principle of measurement of the spatial distribution of luminous flux.
The paper presents a design model of a photometric head of luminance distribution meter. For the construction of this model optical fibers and CCD array were used. Such a photometric head makes it possible to obtain data about the distribution of optical radiation coming from the light sources located in a very large solid angle (even in the whole halfspace) only by a single measurement.
In this study it was shown that when the measurement of luminance distributions are made by means of a CCD array spectrally corrected by a set of absorption filters positioned behind the lens, the measurement accuracy depends, among other factors, on the size of the diaphragm at which the measurements are made. The distributions of the spectral correction error on the surface of the spectrally corrected CCD matrix in relation to the angle of view of the lens and the diaphragm used during the measurements are also presented.
This paper considers the spectral characteristics of photometric illuminance meter, consisting of a diffusing scren, spectral correction filters, and Si photodetector. Measured spectral characteristics of the diffuser are used. It is shown that a selective characteristic of the transmittance of the diffusing element affects the quality of the spectral correction. Calculated results for spectral correction errors are presented for a range of light sources and varying angles of incidence.
In the paper one of the basic parameters of silicon optical measuring photovoltaic cells is discussed. The method of testing the quality of the transducer and the results of measurements made on a photovoltaic cell BPYP 07 chosen as an example are also given.
In this paper the results of measurements of the spectral sensitivity of a silicon detector fitted with a filter for spectral correction are presented. The measurements were made at various angles of incidence of a monochromatic luminous flux on the same surface of the spectral correction filter. The effect of the luminous flux angle of incidence on the spectral sensitivity of the system, detector -- correction filter, was studied. In addition, the errors resulting from changes in spectral sensitivity were determined quantitatively.
In this paper methods of a spatial correction of a luxmeter photometric head are presented. It was found that a transparent element may be used in a luxmeter photometric head for its spatial correction. Furthermore the luminous efficiency of this type of photometric head is 4.3 times higher than that of photometric head used at present. Thus high photometric efficiency of this kind of the photometric head enables measurement of very low illuminance.
The measurement error of calorimetric heads, precisely corrected for light falling from a half-space of uniform luminance, caused by the improper geometry of the incidence of light beams on their active surface was calculated.
A method of spectral correction of detectors used in illuminance meter heads is discussed. An equation is presented by means of which it is possible to determine the monochromatic transmittance (tau) (lambda ) of the filter set which should be used in order that the photometric head be spectrally corrected for the luminous flux falling from the half-space. The spectral characteristics of the filter set for spectral correction of a silicon detector are given for cases in which the luminous flux measured comes from a half-space of uniform luminance distribution. For a head so corrected, the measurement errors due to an inappropriate geometry of the light beams falling on its active surface were calculated. A relation between the magnitude of errors f1 and f1' and the luminous flux incidence on the active surface of the luxmeter head was found.
A new procedure for depositing three-layer structures [doped metal oxide/metal/metal oxide (In2O3/Ag/TiO2)] on a glass substrate by applying different methods of film deposition was developed. To obtain the first film -- In2O3:Sn, the spray hydrolysis method was employed and for the second, a thin Ag film, the vacuum evaporation technique was used. The third film -- TiO2 was obtained by the organic oxide compound polymerization method. The electrical and optical properties of the films and the multilayer structure thus obtained were investigated. The studies showed that the three-layer structure could be used as a broad-band infrared filter.
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