Consultative Committee For Photometry And Radiometry Research Articles

The outcomes of Ukraine’s participation within the CIPM

The article is devoted to the 108th meeting of the International Committee for Weights and Measures (CIPM) and the meetings of the Consultative Committee for Acoustics, Ultrasound and Vibration (CCAUV), the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM), the Consultative Committee for Photometry and Radiometry (CCPR), and the Consultative Committee for Units (CCU). The meetings were held in 2019 at the International Bureau of Weights and Weight (BIPM), in the city of Sevres, France. The specialists from NSC “Institute of Metrology”, SE “Ukrmetrteststandard” and DP NDI “Systema” took part in the meetings, which was made possible due to the accession of Ukraine to the Metre Convention on August 7, 2018.The purpose of the article is to analyse the results of Ukraine’s activities in the work of the CIPM and the results of the participation in the meetings of the Consultative Committees.The CIPM supervises all work in the field of metrology, the joint implementation of which was decided by Member States. In accordance with the Metric Convention, the CIPM is endowed with the authority of exclusive direction and supervision over the BIPM activities.For the time being, the CIPM consists of eighteen members. Each member represents a certain Member State and is appointed by the General Conference on Weights and Measures (CGPM). General Director of the National Scientific Centre “Institute of Metrology”, Prof. P. Neyezhmakov was elected as a member of the International Committee for Weights and Measures for the first time since the signing of the Metric Convention. It was a very important event from the point of view of the recognition of the Ukrainian metrological system at the international level (especially its scientific component).The CIPM has ten Consultative Committees (CCs). Each CC is presided by the CIPM Member. The operation of the CCs is an integral part of the mechanism to implement the most important decisions of the highest international metrology bodies. ССs perform the work related with the collaboration between the researchers from different NMIs, which ensures the best results of international comparisons as well as calibration and measurement capabilities of NMIs.The CIPM Subcommittees, Working Groups and Task Groups play an important role in the development and preparation of the CIPM Resolutions and draft working documents on various metrological activities, which are carried out world-wide.

Mise en pratique for the definition of the candela and associated derived units for photometric and radiometric quantities in the International System of Units (SI)

The purpose of this mise en pratique, prepared by the Consultative Committee for Photometry and Radiometry (CCPR) of the International Committee for Weights and Measures (CIPM) and formally adopted by the CIPM, is to provide guidance on how the candela and related units used in photometry and radiometry can be realized in practice. The scope of the mise en pratique recognizes the fact that the two fields of photometry and radiometry and their units are closely related through the current definition of the SI base unit for the photometric quantity, luminous intensity: the candela.The previous version of the mise en pratique was applied only to the candela whereas this updated version covers the realization of the candela and other related units used for photometric and radiometric quantities. Recent advances in the generation and manipulation of individual photons show great promise of producing radiant fluxes with a well-established number of photons. Thus, this mise en pratique also includes information on the practical realization of units for photometric and radiometric quantities using photon-number-based techniques. In the following, for units used for photometric and radiometric quantities, the shorter term, photometric and radiometric units, is generally used.Section 1 describes the definition of the candela which introduces a close relationship between photometric and radiometric units. Sections 2 and 3 describe the practical realization of radiometric and photon-number-based units, respectively. Section 4.1 explains how, in general, photometric units are derived from radiometric units. Sections 4.2–4.5 deal with the particular geometric conditions for the specific photometric units. Section 5 deals very briefly with the topic of determination of measurement uncertainties in photometry.

International comparisons of the CCPR-S1 units of spectral radiance at wavelengths of 220–2500 nm

The Consultative Committee for Photometry and Radiometry (CCPR) has organized international comparisons of the CCPR-S1 units of spectral radiance at wavelengths of 220–2500 nm with participation by the BNM-INM (France), NIST (USA), NRC (Canada), PTB (Germany), and VNIIOFI (Russia), with the latter as the pilot laboratory. The methods and equipment for these measurements, as well as the results of the comparisons, are discussed. The comparisons showed that the discrepancies between the spectral radiance scales were basically within ±1.5%. This discrepancy decreases to ±1.0% if the data from highly unstable transfer standards are eliminated from the analysis.

Final report on the bilateral supplementary comparison of cryogenic radiometers CCPR-S3 between the NPL and the NMC-A*STAR

Following the decisions of the 1994 meeting of the Consultative Committee for Photometry and Radiometry (CCPR), BIPM acted as pilot laboratory for an international comparison of cryogenic radiometers, later designated as a supplementary comparison CCPR-S3, carried out using silicon trap detectors as transfer devices. This comparison was completed in February 1999.After the completion of this comparison and the publication of the final report, the National Metrology Centre of the Agency for Science, Technology and Research (NMC-A*STAR) of Singapore expressed a wish to demonstrate its primary spectral responsivity measurement capabilities, in support of its CMC claims, through linkage to the CCPR-S3 comparison. NPL offered to organize a bilateral comparison with NMC-A*STAR following a similar protocol to that used in the original comparison.The comparison was carried out by using three silicon trap detectors as transfer devices, to be calibrated at a number of laser wavelengths at NPL and NMC-A*STAR from 2005 to 2007.The results of the comparison demonstrate agreement between NMC-A*STAR and CCPR-S3 comparison reference values, in the selected wavelength range, to better than 6.8 parts in 104 with a combined uncertainty (k = 1) of 2.2 parts in 104 or better.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Final report on the key comparison CCPR-K2.a-2003: Spectral responsivity in the range of 900 nm to 1600 nm

An international comparison of spectral responsivity in the near infrared region, 900 nm to 1600 nm, designated CCPR-K2.a, has been conducted under the Consultative Committee for Photometry and Radiometry (CCPR) as one of the key comparisons to support the Mutual Recognition Arrangement (MRA). This comparison was participated in by 15 laboratories and was piloted by National Institute of Standards and Technology (NIST). The comparison was carried out through calibration of a group of transfer standard detectors, which were indium gallium arsenide (InGaAs) photodiodes with sapphire windows, mounted with a thermistor. The comparison was organized in a star pattern, and conducted in four groups of participants. The report describes in detail the measurements made at NIST and summarizes the reports submitted by the participants. Key comparison reference values and degrees of equivalence have been determined from the comparison results.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Spectral irradiance calibrations at the National Research Council of Canada (NRC)

The basis of accurate photometric evaluations of light sources is provided by accurate spectral measurements under specified geometric conditions. This accuracy is ensured by traceable, internationally recognized absolute spectroradiometric scales. National Metrology Institutes (NMIs) develop primary-level spectroradiometric facilities and verify these absolute optical measurements through international comparisons with other NMIs. This paper describes the NRC facilities, standards and the results of recent international CCPR (Consultative Committee for Photometry and Radiometry) key comparisons of spectral irradiance measurements. It concludes with a brief update on our plans for using our new high-temperature blackbody as the basis for a new spectroradiometric scale.

CCPR-S1 Supplementary comparison for spectral radiance in the range of 220 nm to 2500 nm

In 1997, the Consultative Committee for Photometry and Radiometry (CCPR) initiated a supplementary comparison of spectral radiance in the wavelength range from 220 nm to 2500 nm (CCPR-S1) using tungsten strip-filament lamps as transfer standards. Five national metrology institutes (NMIs) took part in the comparison: BNM/INM (France), NIST (USA), NRC (Canada), PTB (Germany) and VNIIOFI (Russia), with VNIIOFI as the pilot laboratory. Each NMI provided the transfer lamps that were used to transfer their measurements to the pilot laboratory. The intercomparison sequence began with the participant measurements, then the pilot measurements, followed by a second set of measurements by the participant laboratory. The measurements were carried out from 1998 to 2002, with the final report completed in 2008. This paper presents the descriptions of measurement facilities and uncertainties of the participants, as well as the comparison results that were analysed in accordance with the Guidelines for CCPR Comparisons Report Preparation, and a re-evaluation of the results taking into account the instability of some of the transfer lamps. Excluding a few wavelengths, all participants agree with each other within ±1.5%. The disagreement decreases to approximately ±1.0% when the anomalous data are excluded from the analysis.

Report on the comparison CCPR-K2.b of spectral responsivity measurements in the range 300 nm to 1000 nm

At its meeting in March 1997, the Consultative Committee for Photometry and Radiometry (CCPR) identified several key comparisons in the field of optical radiation metrology, one of which concerns spectral responsivity. The present report concerns the key comparison CCPR-K2.b, international comparison of spectral responsivity measurements in the wavelength range 300 nm to 1000 nm, piloted by the BIPM.The comparison was carried out through the calibration of a group of transfer detectors, single silicon photodiodes and trap detectors, by the 17 participating national metrology institutes. It was organized in a star form, in two phases with two groups of participants.The report describes in detail the measurements made at the BIPM and summarizes the reports submitted by the participants. A key comparison reference value and degrees of equivalence have been determined from the calibration results.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the Mutual Recognition Arrangement (MRA).

Final Report on the International Comparison of Luminous Responsivity CCPR-K3.b

During its 13th meeting in 1994 the Consultative Committee for Photometry and Radiometry (CCPR) decided to carry out a comparison of luminous responsivity to be organized by the BIPM. This comparison was classified as a key comparison by the 14th CCPR in 1997 and subsequently named CCPR-K3.b.Fifteen laboratories took part in this comparison by sending calibrated photometers to the BIPM. The photometers were compared with a common set of reference photometers to deduce the relative differences between the calibrations made in the participating laboratories.In this report the details of the procedure and the results are presented.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the Mutual Recognition Arrangement (MRA).

Final report on the subsequent bilateral comparison of cryogenic radiometers CCPR-S3 between the BIPM and the IEN

In 1994 the Consultative Committee for Photometry and Radiometry (CCPR) decided to start an international comparison of cryogenic radiometers. The BIPM acted as pilot laboratory. Following the publication of the results of this comparison in 2000, the Istituto Elettrotecnico Nazionale (IEN, Italy) expressed the wish to repeat the comparison. The report describes the results of this subsequent bilateral comparison between the BIPM and the IEN.The comparison was carried out by using silicon trap detectors as transfer instruments, to be calibrated at a number of laser wavelengths at the IEN and the BIPM.The results obtained by the IEN in the subsequent comparison are in much better agreement with the BIPM results than in the previous comparison. The BIPM providing a link to the previous large-scale comparison, this leads also to a considerably better agreement between the IEN and the other participants of the first comparison.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by CCPR, according to theprovisions of the Mutual Recognition Arrangement (MRA).

Combined result and associated uncertainty from interlaboratory evaluations based on the ISO Guide

We address the problem of determining the combined result and its associated uncertainty in the measurement of a common measurand by a group of competent laboratories. Most data analyses of interlaboratory evaluations are based on the assumption that the expected values of the individual laboratory results are all equal to the value of the common measurand. This means that the laboratory results are subject to random effects only with respect to the value of the measurand. This assumption is frequently unjustified. We use the more realistic assumption that the laboratory results are subject to both random and systematic effects with respect to the value of the measurand. In this case, the value of the measurand may fall anywhere within the range of results. Therefore, a combined result and its associated standard uncertainty that place a non-negligible fraction of the results outside the 2-standard-uncertainty interval are unsatisfactory representations of the value of the common measurand provided by the set of laboratory results. The more realistic assumption requires us to deal with the uncertainty arising from possible systematic effects in the laboratory results. Following the approach of the ISO Guide to deal with systematic effects, we propose a three-step method to determine a combined result and its associated standard uncertainty such that the 2-standard-uncertainty interval would include a sufficiently large fraction of the results. When the interlaboratory evaluation is an International Committee for Weights and Measures (CIPM) key comparison, we suggest that the combined result and its associated standard uncertainty determined by the three-step method be identified with the key comparison reference value and its associated standard uncertainty. These quantities can then be used to specify the degree of equivalence of the individual laboratory results. We illustrate the three-step method by applying it to the results of an international comparison of cryogenic radiometers recently organized by the Consultative Committee for Photometry and Radiometry (CCPR).

Summary of high-accuracy aperture-area measurement capabilities at the NIST

The determination of the geometrical and effective area for optical-quality apertures is one of the fundamental sources of uncertainty in many radiometric and photometric measurements. The National Institute of Standards and Technology (NIST) has developed two non-contact instruments for measuring the area of these optical apertures. Some details of the instruments and their capabilities are presented. Both instruments can be used to measure the area of apertures with diameters ranging from 3.5 mm to 25 mm. The measurements using the absolute instrument result in k = 2 relative uncertainties ranging from 3 × 10−5 for 25 mm diameter apertures 5 × 10−5 for 3.5 mm diameter apertures. The uncertainty depends to some extent on the quality of the edge and the diameter of the aperture. The measurements using the relative instrument result in k = 2 relative uncertainties ranging from 2 × 10−4 for 25 mm diameter apertures to 3 × 10−4 for 3.5 mm diameter apertures, assuming adequate optical-edge quality. For apertures with an edge of very poor quality, the difference between geometrical and effective area can be as high as 0.3 %. The increased uncertainty largely arises from scattering from the edge. Both instruments play a major role in the Consultative Committee for Photometry and Radiometry (CCPR) key comparison on aperture area, which began in 1999.

New spectral radiance scale from 220 nm to 2500 nm

The Physikalisch-Technische Bundesanstalt (PTB) has developed a spectral comparator facility for accurate spectral radiance measurements. As a primary standard source, a high-temperature black body (HTBB) is operated in the temperature range 1500 K to 3200 K. The black-body temperature is determined by two methods: monochromatic radiation thermometry relative to the freezing point of gold; and absolute radiometry with filter radiometers calibrated against a cryogenic radiometer. For these purposes, the HTBB is operated in radiance and irradiance modes at the same time. This paper presents an uncertainty analysis of the new spectral radiance scale embodied by gas-filled tungsten strip lamps from 220 nm to 2500 nm. Such lamps are currently used as transfer standards for the Consultative Committee for Photometry and Radiometry (CCPR) comparison of spectral radiance (CCPR-S1).

Measurements using two types of transfer radiometer developed for a monochromator-based cryogenic radiometer facility

A facility for the monochromator-based calibration of transfer standard detectors using a cryogenic radiometer has been set up at the National Research Council of Canada (NRC). A brief status report is given on this facility, which has undergone some modifications since it was first set up in 1994. Measurements so far have concentrated on the spectral range 450 nm to 700 nm. The wavelength calibration of the monochromator used with this facility is discussed in detail. Two types of transfer radiometer have been developed for use with the cryogenic radiometer. The original radiometers use a single photodiode and incorporate a quartz window. The second type of radiometer is a windowless three-detector trap using special 18 mm properties of these two types of transfer radiometer are compared: spectral responsivity, uniformity, polarization sensitivity, and linearity. Results of calibrations of these radiometers over one to two years are presented. These measurements suggest that the long-term reproducibility of the calibrations is approximately 0.025% for a single radiometer, but close to 0.01% for a group of radiometers. The transfer radiometers can be used to calibrate accurately other detectors using auxiliary apparatus. Measurements are presented which suggest that the transfer uncertainty is close to 0.01% on average. The accuracy of the cryogenic-radiometer-based calibrations can be estimated by linking them to the international comparison of spectral-responsivity scales carried out at the Bureau International des Poids et Mesures in 1994 under the auspices of the Consultative Committee for Photometry and Radiometry (CCPR). From this comparison, it is estimated that the overall accuracy of the cryogenic radiometer calibrations is better than 0.05% in the range 450 nm to 700 nm.

Approximation function of spectral irradiance of standard lamps

Band filter radiometry has recently become popular. Its application for detector-based spectral-irradiance measurements requires improved characterization of standard lamps. This paper presents an approximation function for the spectral irradiance of NPL/GEC and FEL lamp data, reported in the 1990 international comparison measurements of the Consultative Committee for Photometry and Radiometry (CCPR). Characterization with a minimum number of parameters, applicable within the visible spectral range, is attempted. Since the spectral emissivity of tungsten is nearly linear in the spectral range from 400 nm to 900 nm, the irradiance of the standard lamps was approximated with three parameters, representing a linear polynomial multiplied by the Planck function. The same linear polynomial was used for each lamp of the same type, and was fitted only for temperature and intensity. The average difference between the measured and the approximated data was found to be less than 0.085 % for the NPL/GEC lamps and less than 0.095 % for the FEL lamps. This means that the relative spectral emissivity of each lamp of the same type is practically the same. The temperature fitting was characterized by the average difference between the measured and approximated data in the ultraviolet and infrared spectral ranges.

International intercomparisons of photometric base units

In order to evaluate the worldwide consistency of practical implementations of the 1979 redefinition of the candela, the Consultative Committee for Photometry and Radiometry (CCPR) has conducted an international intercomparison of photometric base units. The intercomparison showed 0.8% agreement (one standard deviation) of independent luminous-intensity scale realizations by 15 national laboratories, and 0.6% agreement of luminous-flux scale realizations by 11 laboratories. The NBS candela and lumen agreed with the world mean within quoted uncertainty limits, and were shown to be consistent with one another within 0.5%.