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The NIST Detector-Based Luminous Intensity Scale.

C L Cromer1, G Eppeldauer1, J E Hardis1

  • 1National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.

Journal of Research of the National Institute of Standards and Technology
|January 1, 1996
PubMed
Summary
This summary is machine-generated.

New photometry methods using absolute detectors improve luminous intensity calibration uncertainty by nearly 50%. This advancement enhances the accuracy of the candela, the SI base unit for photometry, benefiting scientific measurements.

Keywords:
calibrationcandelailluminancelumenluminous intensityluxmeasurementphotometerphotometryscalestandardsunits

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Area of Science:

  • Metrology
  • Photometry
  • Optical Physics

Background:

  • The Système International des Unités (SI) base unit for photometry is the candela.
  • Traditional realization of the candela relied on absolute sources, presenting limitations in calibration accuracy.
  • Improved methods are crucial for precise luminous intensity measurements in scientific and industrial applications.

Purpose of the Study:

  • To implement a novel method for realizing the candela using absolute detectors.
  • To enhance the accuracy of luminous intensity calibrations for standard lamps.
  • To develop and characterize reference photometers for improved photometric measurements.

Main Methods:

  • Realization of the candela using absolute detectors instead of absolute sources.
  • Construction of eight reference photometers utilizing silicon photodiodes matched with filters.
  • Mimicking the spectral luminous efficiency function for photopic vision with photometer filters.

Main Results:

  • Achieved a relative expanded uncertainty of 0.46% (k=2) for luminous intensity calibrations, a near two-fold improvement.
  • Developed wide dynamic range photometers with carefully selected components to minimize errors and study aging.
  • Determined that yearly recalibration of the reference photometers is necessary based on periodic remeasurements.

Conclusions:

  • The use of absolute detectors offers a significant advancement in candela realization and photometric calibration.
  • The developed reference photometers provide a reliable and accurate tool for luminous intensity measurements.
  • This improved methodology contributes to higher precision in fundamental photometric standards.