Fisheye camera method for spatial non-uniformity corrections in luminous flux measurements with integrating spheres

Alexander Kokka, Tomi Pulli, Tuomas Poikonen, Janne Askola, Erkki Ikonen

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)

Abstract

This paper presents a fisheye camera method for determining spatial non-uniformity corrections in luminous flux measurements with integrating spheres. Using a fisheye camera installed into a port of an integrating sphere, the relative angular intensity distribution of the lamp under test is determined. This angular distribution is used for calculating the spatial non-uniformity correction for the lamp when combined with the spatial responsivity data of the sphere. The method was validated by comparing it to a traditional goniophotometric approach when determining spatial correction factors for 13 LED lamps with different angular spreads. The deviations between the spatial correction factors obtained using the two methods ranged from $-0.15$ % to 0.15%. The mean magnitude of the deviations was 0.06%. For a typical LED lamp, the expanded uncertainty ($k = 2$ ) for the spatial non-uniformity correction factor was evaluated to be 0.28%. The fisheye camera method removes the need for goniophotometric measurements in determining spatial non-uniformity corrections, thus resulting in considerable system simplification. Generally, no permanent modifications to existing integrating spheres are required.
Original languageEnglish
Pages (from-to)577-583
Number of pages7
JournalMetrologia
Volume54
Issue number4
DOIs
Publication statusPublished - 24 Jul 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • angular intensity distribution
  • fisheye camera
  • integrating sphere
  • luminous flux
  • measurement uncertainty
  • photometry
  • spatial correction

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