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The Candela and Photometric and Radiometric Measurements.

A C Parr1

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Summary
This summary is machine-generated.

The national measurement system now uses advanced optical detector technology, traceable to cryogenic radiometers, for photometric and radiometric quantities. This shift, driven by the 1979 candela redefinition, enhances measurement accuracy and methodology.

Keywords:
cryogenic radiometerlaser powerphotodiodesphotometryradiation temperatureradiometrystandards

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Area of Science:

  • Metrology
  • Optical Physics
  • Radiometry

Background:

  • The national measurement system for photometric and radiometric quantities historically relied on cryogenic radiometers for traceability.
  • The 1979 redefinition of the candela enabled a shift towards optical detector technology for photometric measurements.

Purpose of the Study:

  • To review the implementation of technical changes following the 1979 candela redefinition.
  • To assess the impact of these changes on the maintenance and dissemination of optical radiation measurements at NIST.

Main Methods:

  • Review of historical measurement techniques and traceability chains.
  • Analysis of advancements in cryogenic radiometer performance and photodetector technology.
  • Evaluation of the NIST's adoption of detector-based photometry.

Main Results:

  • The 1979 redefinition facilitated the transition to absolute detector-based photometry.
  • Improvements in cryogenic radiometers and photodetectors have significantly impacted radiometric measurement methodologies.
  • NIST has implemented technical changes for maintaining and disseminating optical radiation measurements.

Conclusions:

  • The adoption of detector-based technology aligns with the 1979 candela redefinition, enhancing photometric measurements.
  • Advancements in optical detectors have broadly improved radiometric measurement practices.
  • The NIST's implementation ensures accurate and reliable dissemination of optical radiation standards.