共查询到20条相似文献,搜索用时 36 毫秒
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In the development, production control, quality assurance and during the selection of appropriate LEDs for very different
applications, it is essential to know their photometric and colorimetric quantities very precisely. The calibration of the
measuring devices required for this purpose is performed via LED transfer standards. These LED standards transfer photometric,
spectroradiometric and colorimetric units and characteristics, from the National Metrology Institute (NMI) to the user. Finally,
LED standards serve as references for the user. Usually a set of LED reference standards consists of at least four different
LED colours (blue, green, red and white), sometimes even more. Further more it is very often necessary to have more than only
one set of reference standards as a backup. This generally causes a large number of calibrations. To handle this work load,
a special reference standard and a compact goniophotometer prove to be a considerable advantage. PTB developed a special LED
transfer standard which operates under controlled conditions: a controlled LED chip temperature and a controlled chip current
help to keep the photometric and colorimetric properties constant. On the other hand, a compact goniophotometer was designed
to measure luminous flux, luminous intensity and colorimetric quantities of LED transfer standards in a relatively short time
with low measurement uncertainties. 相似文献
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Z. Yuan 《International Journal of Thermophysics》2009,30(1):220-226
Demands for accurate temperature measurement and calibration are increasing along with the wider use of radiation thermometry
in industry. However, the deviation of a ‘blackbody’ radiator emissivity from the emissivity of an ideal blackbody remains
one of the main uncertainty contributions in the calibration of radiation thermometers, although the performance of blackbody
radiators has been continually improving. Nevertheless, the influence of this deviation was often ignored due to the complexity
of the correction. In this paper, general methods to evaluate the influence of the emissivity deviation of a blackbody radiator
from unity for typical radiation thermometer models are described. An approximate practical method for wide-band radiation
thermometers is proposed. Moreover, the concept of equivalent wavelength and the corresponding calculation method are introduced
to simplify the mathematical model. The calculation result and a mathematical expression for the equivalent wavelength applicable
to most popular radiation thermometers with a spectral range of 8–14 μm are given. The analysis and calculation show that
the influence of blackbody radiator emissivity on longer working-wavelength radiation thermometer calibrations at mid or high
temperatures cannot be ignored. 相似文献
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S. A. Ogarev V. I. Sapritskii N. A. Parfent'ev G. N. Tolstykh A. V. Sharoshkin 《Measurement Techniques》2005,48(11):1090-1095
The article is devoted to the state primary standard of the luminous intensity unit (candela) and luminous flux unit (lumen)
of continuous and pulsed radiation GET 5-03 created at VNIIOFI and also the contemporary state of providing uniformity of
light quantity measurements based on a new edition of the state verification scheme GOST 8.023-2003.
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Translated from Izmeritel'naya Tekhnika, No. 11, pp. 34–37, November, 2005. 相似文献
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当微光物镜系统中产生杂散光后,将会降低物像的对比度,从而使系统分辨率降低、像质变坏。本文将从理论上加以分析,将杂光系数这一因子,引入于以A·ROSE理论为基础建立的探测方程式之中,并就荣光系数对系统分辨率的影响作了估算,再对有关资料数据进行分析处理,以期使理论与实际结合起来说明问题。 相似文献
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Role of error in spectral measurements in the photometry of thermal and quasimonochromatic radiation
L. S. Lovinskii 《Measurement Techniques》1998,41(9):797-805
A metrological analysis of the influence of errors in spectral measurements on the error of light calibrations of thermal
and quasimonochromatic radiation sources and photometers is presented. It is shown that quasimonochromatic light-emitting
diodes, rather than thermal filament lamps, should be used as primary sources in order to maintain low errors in the measurement
of the luminous quantities of quasimonochromatic radiation.
Translated from Izmeritel'yana Tekhnika. No. 9, pp. 9–14, September, 1998. 相似文献
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An approach for the optimization of near-infrared (NIR) spectroscopic process monitoring at low signal-to-noise ratio is presented. It compromises the combined adjustment of different measurement variables and data pretreatments considering the prediction error, economic aspects of the application, and process constraints. The integration time, light intensity, and number of averaged spectra were varied; their mutual influence on the prediction error of partial least squares (PLS) models (i.e., root-mean-square error of cross-validation (RMSECV)) was evaluated in the laboratory. At low signal levels, the spectral uncertainty had a strong impact on the prediction error. It leveled off with increasing values of all three parameters and was finally dominated by other sources of uncertainty. The experimental findings could be characterized and explained by a mathematical equation, which was deduced from theoretical principles. The knowledge about the interaction of the measurement variables allowed their combined adjustment resulting in a reduced impact of spectral uncertainty on the prediction error (i.e., root-mean-square error of prediction (RMSEP)) without additional costs or process modifications. Moreover, a convenient procedure to compensate the stray light caused by strongly absorbing windows was developed. The whole approach was successfully applied to a challenging process, namely, the NIR inline monitoring of the liquid content of two model substances in a rotating suspension dryer. 相似文献
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A method of combined determination of thermophysical characteristics (TPC) of heat-insulating materials that is based on solving
the inverse heat-conduction problem is discussed. The influence of the parameters of the calculation algorithm and the uncertainty
in specifying the parameters of the measuring device on the TPC measurement error is analyzed. It is shown that the measurement
error considerably exceeds the scatter of the results of repeated measurements of the same sample without disassembling the
measuring device.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 1, pp. 106–111, January–February, 1998. 相似文献
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The NIST 10 V Compact Josephson Voltage Standard (CJVS) and 2.5 V Programmable Josephson Voltage Standard (PJVS) were directly
compared at 1.018 V and 2.511 V in February 2007. The difference between the two systems at 1.018 V (CJVS — PJVS) was −0.09
nV with an expanded uncertainty of 4.72 nV or a relative uncertainty of 4.64×10−9 at the 95 % confidence level where as the difference between the two systems at 2.511 V was 0.00 nV with an expanded uncertainty
of 4.04 nV or a relative uncertainty of 1.61×10−9 at the 95 % confidence level. These intercomparison results demonstrated the satisfactory performance of the CJVS system
handling minor trapped flux in the array and the effectiveness of the “NISTVolt software” to manage step jumps in the measurements. 相似文献
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医用内窥镜光能传递效率的评价方法 总被引:1,自引:0,他引:1
建立医用硬性内窥镜光能传递效率的评价方法.通过影响光能传递效率的原因分析并结合光能传递效率的实际应用意义,提出了有效光度率定义和表达式,以表示医用硬性内窥镜的光能传递效率.运用光度学原理导出有效光度率测量的应用公式,并通过对相关的模拟视场面与光度量关系的理论推导,得出有效光度率测量的应用公式与模拟视场形状无关的结果,并进一步采用几个典型视场面下的实际测量,验证了该应用公式的通用性.此方法可用于医用硬性内窥镜光能传递效率的评价,便于实际测量应用. 相似文献
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At the National Institute of Metrology of China (NIM), silicon photodiode-based narrow-band interference filter radiometers (FRs) have been designed for the radiometric determination of the thermodynamic temperature. The FR calibrations were performed on a new spectral comparator with a trap detector which was calibrated against the cryogenic radiometer at several discrete laser lines. The new spectral comparator is constructed from two grating monochromators assembled to give lower stray light and higher transmitted flux. Applying a transmittance measurement of the filter in the out-of-band region and careful control of the temperature, the irradiance responsivity of a 633 nm centered FR has been obtained over a dynamic range of nearly eight decades in the wavelength range from 450 nm to 1200 nm. The relative standard uncertainty of the responsivity is also analyzed and estimated to be less than 7 × 10?4 at the 1 ?? level. 相似文献
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In this paper a method for separate measurement of the extinction of optical thin films is presented. The method combines a laser calorimetric technique and a light-scattering goniophotometer. As an example, the spectral extinction properties of r.f. reactively sputtered TiO2 films were measured. Under certain conditions absorption indices of 10-5 or less can be achieved. Thus light scattering, rather than absorption, is the dominant optical loss mechanism in sputtered TiO2 films. 相似文献
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Giovanni A. Longo 《International Journal of Thermophysics》2008,29(2):664-677
This paper presents a steady-state apparatus to measure the thermal conductivity of solids based on the use of heat flux sensors.
The uncertainty assessment of the experimental apparatus is performed in accordance with the ISO “Guide to the Expression
of Uncertainty in Measurement” (GUM): the combined standard uncertainty (k = 1) with reference to the properties of Pyrex Glass CRM 039 at 20°C is ±1.9%. The standard uncertainty has also been assessed
in the measurement range from 0.1 to 10W · m−1 · K−1. The experimental apparatus has been used to measure the certified reference material Pyrex Glass CRM 039 in the temperature
range from 3.1 to 60.3°C: the standard deviation (k = 1) between the experimental measurements and the certified values is ±1.1% with a maximum deviation of 2.4%. Reasonable
agreement is found between the uncertainty assessment and the experimental validation. 相似文献
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Ping Huang Beiying Zhou Qi Zheng Yuan Tian Mengmeng Wang Lianjun Wang Jianlin Li Wan Jiang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(1):1905951
Replacing traditional luminous silicone or resins with phosphor in ceramics (PiCs) as color converters has been proposed as an efficient way to improve thermal stability of high-power white light-emitting diodes (WLEDs). However, excessive light scattering in existing PiCs results in enormous phosphor-converted light losses, which makes the luminosity of current PiCs color converters less efficient and means that they can only be used in devices working in reflective mode. By introducing nano wave plate structuring and Rayleigh scattering, luminous hydroxyapatite (HA)-YAG: Ce ceramics are prepared from mesoporous HA nanorods and YAG: Ce phosphors at 850 °C, enabling for the first time WLEDs equipped with PiC color converters in transmission mode. With low-temperature sintering and a highly transparent matrix, the quantum yield of HA-YAG: Ce retains ≈90% of the raw phosphor, and WLEDs with the color converters exhibit a record luminous efficiency of 170 lm W−1 and a correlated color temperature below 4500 K. A facile and practical strategy of using nano structural modulation to eliminate birefringence-induced light scattering for fabricating high-performance ceramic converters suitable for multiple mode luminaires is demonstrated. 相似文献